1
AU - Sinha MK
AU - Opentanova I
AU - Ohannesian JP
AU - Kolaczynski JW
AU - Heiman ML
AU - Hale J
AU - Becker GW
AU - Bowsher RR
AU - Stephens TW
AU - Caro JFTI - Evidence of free and bound leptin in human circulation.Studies in lean and obese subjects and during short-term fasting.AB - Little is known about leptin's interaction with other circulating proteins which could be important for its biological effects.Sephadex G-100 gel filtration elution profiles of 125I-leptin-serum complex demonstrated 125I-leptin eluting in significant proportion associated with macromolecules. The 125I-leptin binding to circulating macromolecules was specific, reversible, and displaceable with unlabeled leptin (ED50: 0.73 +/- 0.09 nM, mean +/- SEM, n = 3). Several putative leptin binding proteins were detected by leptin-affinity chromatography of which either 80- or 100-kD proteins could be the soluble leptin receptor as approximately 10%of the bound 125I-leptin was immunoprecipitable with leptin receptor antibodies. Significantly higher (P < 0.001) proportions of total leptin circulate in the bound form in lean (46.5 +/- 6.6%) compared with obese (21.4 +/- 3.4%) subjects.In lean subjects with 21% or less body fat, 60-98% of the total leptin was in the bound form. Short-term fasting significantly decreased basal leptin levels in three lean (P < 0.0005) and three obese (P < 0.005) subjects while refeeding restored it to basal levels. The effects of fasting on free leptin levels were more pronounced in lean subjects (basal vs. 24-h fasting: 19.6 +/- 1.9 vs. 1.3 +/- 0.4 ng/ml) compared with those in obese subjects (28.3 +/- 9.8 vs. 14.7 +/- 5.3). No significant (P > 0.05) decrease was observed in bound leptin in either group. These studies suggest that in obese individuals the majority of leptin circulates in free form, presumably bioactive protein, and thus obese subjects are resistant to free leptin. In lean subjects with relatively low adipose tissue, the majority of circulating leptin is in the bound form and thus may not be available to brain receptors for its inhibitory effects on food intake both under normal and food deprivation states.MH - Carrier Proteins|*AN/*MEMH - Proteins|*AN/*ME/PHSO - J Clin Invest 1996 Sep; 98(6):1277-82DP - 1996 SepTA - J Clin InvestPG - 1277-82IP - 6VI - 98UI - 964205932
AU - Baumann H
AU - Morella KK
AU - White DW
AU - Dembski M
AU - Bailon PS
AU - Kim H
AU - Lai CF
AU - Tartaglia LATI - The full-length leptin receptor has signaling capabilities of interleukin 6-type cytokine receptors.AB - The leptin receptor (OB-R) is a single membrane-spanning protein that mediates the weight regulatory effects of leptin (OB protein). The mutant allele (db) of the OB-R gene encodes a protein with a truncated cytoplasmic domain that is predicted to be functionally inactive. Several mRNA splice variants encoding OB-Rs with different length cytoplasmic domains have been detected in various tissues.Here we demonstrate that the full-length OB-R (predominantly expressed in the hypothalamus), but not a major naturally occurring truncated form or a mutant from found in db/db mice, can mediate activation of signal transducer and activator of transcription (STAT) proteins and stimulate transcription through interleukin 6 responsive gene elements. Reconstitution experiments suggest that, although OB-R mediates intracellular signals with a specificity similar to interleukin 6-type cytokine receptors, signaling appears to be independent of the gp130 signal transducing component of the interleukin 6-type cytokine receptors.MH - Antigens, CD|*PHMH - Carrier Proteins|*PHMH - Receptors, Interleukin|*PHSO - Proc Natl Acad Sci U S A 1996 Aug; 93(16):8374-8DP - 1996 AugTA - Proc Natl Acad Sci U S APG - 8374-8IP - 16VI - 93UI - 963232293
AU - Campfield LA
AU - Smith FJ
AU - Burn PTI - The OB protein (leptin) pathway--a link between adipose tissue mass and central neural networks.AB - OB protein (also known as leptin), a previously unknown protein signal, is secreted from adipose tissue, circulates in the blood, probably bound to a family of binding proteins,and acts on central neural networks that regulate ingestive behavior and energy balance. OB protein provides a communication link from fat tissue and the brain. Rapidly accumulating evidence suggests that OB protein appears to play a major role in the control of body fat stores through coordinated regulation of feeding behavior, metabolism, autonomic nervous system and body energy balance in rodents, primates and humans. The field has rapidly moved from cloning of the ob gene to demonstration of complex regulation of ob gene expression in adipose tissue in rats and humans, and then the demonstration of potent biological activity of OB protein in ob/ob, diet-induced, and lean mice as well as obese and lean rats but not in db/db obese mice. A significant milestone was our demonstration that central administration of OB protein lead to reductions in food intake, body weight and alterations in metabolism consistent with activation of the autonomic nervous system. These findings were followed by the identification of a central binding site for labelled OB protein in the choroid plexus in ob/ob, db/db and lean mice as well as lean and obese Zucker rats. The expression cloning of a central receptor, OB-R, from the mouse choroid plexus soon followed. The OB-R receptor was found to be expressed in the choroid plexus, the hypothalamus as well as several peripheral tissues. OB-R exists in multiple forms; the two major forms are a short form (with a truncated intracellular domain) and long form (with the complete intracellular domain). The long form is thought to be the form that signals and mediates the biological effects of OB protein. Initial in situ hybridization studies have demonstrated the mRNA for the long form OB-R receptor to be localized to the hypothalamus as well as peripheral sites. Recently, it was demonstrated that the db gene encodes the OB-R receptor. Evidence has been provided for a specific transport system for OB protein to cross the blood-brain-barrier and enter the brain of mice, rats and humans. The rate of transport can be decreased by high plasma concentrations of OB protein. Thus, reduced entry of OB protein to the brain may be one of the mechanisms of reduced sensitivity of the OB protein pathway in obese individuals. OB protein appears to also play a role in the important neuroendocrine adaptive responses to fasting and in the control of reproduction.Therapeutic approaches to the treatment of obesity based on OB protein ranging from OB protein by injection to OB-R receptor agonists and to upregulation of OB signalling pathways are under intense investigation.MH - Adipose Tissue|*MH - Neural Pathways|*MH - Obesity|*/ET/THMH - Proteins|GE/*PHSO - Horm Metab Res 1996 Dec; 28(12):619-32DP - 1996 DecTA - Horm Metab ResPG - 619-32IP - 12VI - 28UI - 971658384
AU - Mercer JG
AU - Hoggard N
AU - Williams LM
AU - Lawrence CB
AU - Hannah LT
AU - Morgan PJ
AU - Trayhurn PTI - Coexpression of leptin receptor and preproneuropeptide Y mRNA in arcuate nucleus of mouse hypothalamus.AB - Leptin, the protein product of the adipose tissue-specific ob (obese) gene (1), reduces the body weight, adiposity and food intake of obese ob/ob mice on peripheral or central injection (2, 3, 4). [125I]leptin binding has been detected in mouse choroid plexus (5), from which a leptin receptor gene was expression cloned (5). The gene has at least 6 splice variants (6, 7). Leptin receptor mRNA was localized in the hypothalamus by in situ hybridization being particularly abundantly expressed in the arcuate nucleus (8). There is evidence linking the physiological effects of injected leptin with hypothalamic neuropeptide Y (9, 10) (NPY), which has potent central effects on food intake and energy balance (11), and is also expressed in the arcuate nucleus.Here we report dual in situ hybridization studies for leptin receptor and NPY gene expression in the mouse arcuate nucleus,where the majority of cells examined expressed both genes.This provides the first direct evidence that leptin acts on cells that express NPY mRNA.MH - Arcuate Nucleus|*ME/ULMH - Carrier Proteins|*BI/GEMH - Neuropeptide Y|*BI/GEMH - Protein Precursors|*BI/GEMH - RNA, Messenger|GE/*MESO - J Neuroendocrinol 1996 Oct; 8(10):733-5DP - 1996 OctTA - J NeuroendocrinolPG - 733-5IP - 10VI - 8UI - 970673885
AU - Vaisse C
AU - Halaas JL
AU - Horvath CM
AU - Darnell JE Jr
AU - Stoffel M
AU - Friedman JMTI - Leptin activation of Stat3 in the hypothalamus of wild-type and ob/ob mice but not db/db mice.AB - Leptin, a hormone secreted by adipocytes, regulates the size of the adipose tissue mass through effects on satiety and energy metabolism. Leptin's precise sites of action are not known. The leptin receptor (Ob-R) is found in many tissues in several alternatively spliced forms raising the possibility that leptin exerts effects on many tissues including the hypothalamus. Ob-R is a member of the gp130 family of cytokine receptors which are known to stimulate gene transcription via activation of cytosolic STAT proteins.In order to identify the sites of leptin action in vivo,we assayed for activation of STAT proteins in mice treated with leptin. The STAT proteins bind to phosphotyrosine residues in the cytoplasmic domain of the ligand-activated receptor where they are phosphorylated. The activated STAT proteins dimerize and translocate to the nucleus where they bind DNA and activate transcription. The activation of STAT proteins in response to leptin was assayed in a variety of mouse tissues known to express Ob-R. Leptin injection activated Stat3 but no other STAT protein in the hypothalamus of ob/ob and wild-type mice but not db/db mice, mutants that lack an isoform of the leptin receptor.Leptin did not induce STAT activation in any of the other tissues tested. Activation of Stat3 by leptin was dose dependent and first observed after 15 minutes and maximal at 30 minutes. Our data indicate the hypothalamus is a direct target of leptin action and that this activation is critically dependent on the gp-130-like leptin receptor isoform missing in C57BLKS/J db/db mice. This is the first in vivo demonstration of leptin signal transduction.MH - DNA-Binding Proteins|*MEMH - Hypothalamus|*MEMH - Proteins|*PHMH - Trans-Activators|*MESO - Nat Genet 1996 Sep; 14(1):95-7DP - 1996 SepTA - Nat GenetPG - 95-7IP - 1VI - 14UI - 963769786
AU - Imagawa K
AU - Numata Y
AU - Katsuura G
AU - Sakaguchi I
AU - Morita A
AU - Kikuoka S
AU - Matumoto Y
AU - Tsuji T
AU - Tamaki M
AU - Sasakura K
AU - Teraoka H
AU - Hosoda
AU - K
AU - Ogawa Y
AU - Nakao KTI - Structure-function studies of human leptin.AB - To elucidate the structural requirement of human leptin for its functions, the wild-type, mutant-type, C-terminal deletion, and N-terminal deletion were expressed in Escherichia coli and purified in soluble forms. These leptin analogs were intracerebroventrically injected into C57BL/6J ob/ob mice, and their in vivo biological activities were evaluated.The mutant-type leptin lacking a C-terminal disulfide bond reduced food intake at doses of more than 15 pmol/mouse,which was as effective as the wild-type leptin. C-terminal deletion without the loop structure, also significantly,but to a lesser extent, reduced food intake at doses of more than 90 pmol/mouse. However, N-terminal deletions showed no effect on food intake. We also evaluated the effects of the leptin analogs on radiolabeled leptin binding to its receptor in the choroid plexus using autoradiography.An excess of unlabeled mutant-type leptin as well as wild-type leptin led to complete inhibition of binding. C-terminal deletions led to weak inhibitory activity, whereas N-terminal deletions caused no inhibitory activity. These results clearly demonstrate that the N-terminal region of leptin is essential for both its biological and receptor binding activities. The amino acid sequence of the C-terminal loop structure is also important for enhancing these actions,whereas the C-terminal disulfide bond is not needed.MH - Carrier Proteins|*MEMH - Obesity|*MEMH - Proteins|GE/*PDAD - Research and Development Diagnostic Science DivisionAD - Osaka 566-0022AD - Japan.SO - J Biol Chem 1998 Dec 25; 273(52):35245-9DP - 1998 Dec 25TA - J Biol ChemPG - 35245-9IP - 52VI - 273UI - 990743097
AU - da Silva BA
AU - Bjçrbaek C
AU - Uotani S
AU - Flier JSTI - Functional properties of leptin receptor isoforms containing the gln-->pro extracellular domain mutation of the fatty rat [see comments]AB - Mutations of the leptin receptor have been found to cause obesity in rodents. The fa mutation that is responsible for obesity in Zucker rats is a missense mutation (269 gln-->pro) in the extracellular domain of the leptin receptor.We have characterized the effects of this mutation on the two major isoforms of the leptin receptor, Ob-Rb and Ob-Ra, by studying cell-surface expression, leptin binding affinity, signaling capacity, and receptor-mediated internalization and degradation of leptin in transfected mammalian cell lines. Both Ob-Rb(269 gln-->pro) and Ob-Ra(269 gln-->pro)have decreased cell-surface expression and decreased leptin binding affinity. Ob-Rb(269 gln-->pro) was shown to have defective signaling to the JAK-STAT pathway and markedly diminished ability to activate transcription of the egr-1 promoter. Constitutive ligand-independent activation of Ob-Rb(269 gln-->pro) was observed for activation of egr-1-luc but only under conditions when JAK2 was coexpressed with Ob-Rb(269 gln-->pro), Finally, Ob-Ra(269 gln-->pro)has an increased ability to internalize leptin but is less efficient at degrading leptin, as compared with Ob-Ra. In conclusion, both Ob-Ra(269 gln-->pro) and Ob-Rb(269 gln-->pro) have multiple functional defects.MH - Carrier Proteins|*GE/ME/*PHMH - Mutation|*PHMH - Obesity|*GE/*PPMH - Rats, Zucker|*GE/*PHSO - Endocrinology 1998 Sep; 139(9):3681-90DP - 1998 SepTA - EndocrinologyPG - 3681-90IP - 9VI - 139UI - 983894118
AU - Golden PL
AU - Maccagnan TJ
AU - Pardridge WMTI - Human blood-brain barrier leptin receptor. Binding and endocytosis in isolated human brain microvessels.AB - The peripheral production of leptin by adipose tissue and its putative effect as a signal of satiety in the central nervous system suggest that leptin gains access to the regions of the brain regulating energy balance by crossing the brain capillary endothelium, which constitutes the blood-brain barrier in vivo. The present experiments characterize the binding and internalization of mouse recombinant leptin in isolated human brain capillaries, an in vitro model of the human blood-brain barrier. Incubation of 125I-leptin with isolated human brain capillaries resulted in temperature-dependent binding: at 37 degrees C, approximately 65% of radiolabeled leptin was bound per milligram of capillary protein. Two-thirds of the bound radioactivity was resistant to removal by acid wash, demonstrating endocytosis of 125I-leptin into capillary cells. At 4 degrees C, binding to isolated capillaries was reduced to approximately 23%/mg of protein, the majority of which was acid wash resistant.Binding of 125I-leptin to brain capillary endothelial plasma membranes was saturable, described by a two-site binding model with a high-affinity dissociation constant of 5.1+/-2.8 nM and maximal binding capacity of 0.34+/-0.16 pmol/mg of membrane protein. Addition of porcine insulin or insulin-like growth factor at a final concentration of 100 nM had a negligible effect on leptin binding. These results provide evidence for a leptin receptor that mediates saturable, specific, temperature-dependent binding and endocytosis of leptin at the human blood-brain barrier.MH - Blood-Brain Barrier|*PHMH - Carrier Proteins|*PHMH - Endocytosis|*SO - J Clin Invest 1997 Jan; 99(1):14-8DP - 1997 JanTA - J Clin InvestPG - 14-8IP - 1VI - 99UI - 971487659
AU - Kieffer TJ
AU - Heller RS
AU - Habener JFTI - Leptin receptors expressed on pancreatic beta-cells.AB - Leptin (Ob protein) is a recently isolated hormone produced by adipocytes and is a powerful regulator of satiety centers in the brain. A defect in either leptin production or transmission of the leptin signal in animal models, i.e. ob/ob and db/db mice, respectively, results in a syndrome of obesity and diabetes which closely resembles that which occurs in humans. Leptin release is regulated in part by nutritional status and its expression in adipose tissue is up-regulated by insulin. Since hyperinsulinemia is a primary defect in ob/ob and db/db mice which manifests early in the disease,we postulated that leptin may also regulate insulin release as part of a "adipoinsular' feedback loop. We demonstrate the expression of leptin receptor mRNA in primary rat pancreatic islets and in the insulinoma cell line beta TC-3. Furthermore,we find binding of 125I-leptin to beta TC-3 cells which is significantly displaced by leptin. These findings suggest the possibility that the binding of leptin to its receptor in beta-cells may modulate insulin expression in a negative feedback loop, and thereby may have an anti-obesity effect.MH - Carrier Proteins|*BI/MEMH - Islets of Langerhans|*MEMH - Proteins|*MESO - Biochem Biophys Res Commun 1996 Jul; 224(2):522-7DP - 1996 JulTA - Biochem Biophys Res CommunPG - 522-7IP - 2VI - 224UI - 9629552010
AU - Ghilardi N
AU - Ziegler S
AU - Wiestner A
AU - Stoffel R
AU - Heim MH
AU - Skoda RCTI - Defective STAT signaling by the leptin receptor in diabetic mice.AB - Leptin and its receptor, obese receptor (OB-R), comprise an important signaling system for the regulation of body weight. Splice variants of OB-R mRNA encode proteins that differ in the length of their cytoplasmic domains. We cloned a long isoform of the wild-type leptin receptor that is preferentially expressed in the hypothalamus and show that it can activate signal transducers and activators of transcription (STAT)-3, STAT-5, and STAT-6. A point mutation within the OB-R gene of diabetic (db) mice generates a new splice donor site that dramatically reduces expression of this long isoform in homozygous db/db mice. In contrast, an OB-R protein with a shorter cytoplasmic domain is present in both db/db and wild-type mice. We show that this short isoform is unable to activate the STAT pathway. These data provide further evidence that the mutation in OB-R causes the db/db phenotype and identify three STAT proteins as potential mediators of the anti-obesity effects of leptin.MH - Carrier Proteins|GE/*PHMH - Diabetes Mellitus, Experimental|*MEMH - DNA-Binding Proteins|*MEMH - Signal Transduction|*GEMH - Trans-Activators|*MESO - Proc Natl Acad Sci U S A 1996 Jun; 93(13):6231-5DP - 1996 JunTA - Proc Natl Acad Sci U S APG - 6231-5IP - 13VI - 93UI - 9627052011
AU - Antczak M
AU - Van Blerkom JTI - Oocyte influences on early development: the regulatory proteins leptin and STAT3 are polarized in mouse and human oocytes and differentially distributed within the cells of the preimplantation stage embryo.AB - Unique protein domains, concentration gradients, and asymmetric protein distributions or polarities are principle forces establishing the identity and fate of individual cells during early development in lower vertebrates and invertebrates.Here, we present evidence that these same forces exist during mammalian development in the form of two representative regulatory proteins, leptin and STAT3. Leptin, the 16 kDa cytokine product of the obese gene (ob) is involved in the activation of STAT3, a member of the signal transducer and activation of transcription family of proteins. We examined the temporal and spatial aspects of leptin and STAT3 immunofluorescence in mouse and human oocytes and preimplantation stage embryos. The findings demonstrate that both leptin and STAT3 are polarized in the oocyte and, as a consequence of their location and the position of the cleavage planes with respect to these protein domains:(i) differences in allocation of these proteins between blastomeres occur at the first cell division such that by the 8-cell stage; (ii) unique cellular domains consisting of leptin/STAT3 rich and leptin/STAT3 poor populations of cells are generated. By the morula stage, a cell-borne concentration gradient of these proteins extending along the surface of the embryo is observed. A potential role of these proteins in early development is indicated at the morula stage where the 'inner' cells consist of blastomeres that contain little, if any, leptin/STAT3 while 'outer'cells contain both leptin/STAT3 rich and poor cells. This pattern persists through the hatched blastocyst stage with little, if any, leptin/STAT3 detected in the inner cell mass and populations of leptin/STAT3 rich and poor cells forming the trophoblast. We have examined oocytes from mutant C57BL/6J ob/ob mice which are both obese and infertile (although fertility can be restored by the exogenous provision of leptin) and have found STAT3 and the mutant (truncated)leptin protein to be present and polarized, suggesting the possibility that the truncated leptin protein may still contain operational domains which are functional during oocyte development and early embryogenesis. Furthermore,analysis of leptin and STAT3 in intact ovarian follicles suggests that these proteins may be maternally derived and in particular, that a subpopulation of follicle cells may be partly responsible for the establishment of their polarized distribution in the oocyte. The results are discussed with respect to the proposition that leptin and STAT3 have critical roles in early mammalian development, and may be involved in the determination of the animal pole of the oocyte and in the establishment of the inner cell mass and trophoblast in the preimplantation stage embryo.MH - Cell Polarity|*PHMH - DNA-Binding Proteins|IP/*ME/PHMH - Fetal Development|*PHMH - Oocytes|ME/*PHMH - Preimplantation Phase|*PHMH - Proteins|IP/*ME/PHMH - Trans-Activators|IP/*ME/PHSO - Mol Hum Reprod 1997 Dec; 3(12):1067-86DP - 1997 DecTA - Mol Hum ReprodPG - 1067-86IP - 12VI - 3UI - 9812449912
AU - Campbell FM
AU - Gordon MJ
AU - Hoggard N
AU - Dutta Roy AKTI - Interaction of free fatty acids with human leptin.AB - Relatively high concentrations of leptin are present in plasma and it is thought to play a major role in lipid homeostasis. Leptin is reported to lower tissue triglyceride content by increasing intracellular oxidation of free fatty acids (FFA). However very little is known regarding the interaction between leptin and plasma FFA. We studied the interaction of FFA with leptin using a direct radiolabelled fatty acid binding assay, a fluorescence assay, electrophoretic mobility and autoradiobinding. All these data indicate that binding of FFA with leptin is reversible and shows a positive co-operativity. The binding of FFA to leptin produces a change in the pI value of the leptin and also increased the electrophoretic mobility of the protein in native polyacrylamide gels. The change in leptin's electrophoretic mobility depends on the chain length and the number of double bonds of the fatty acid, as stearic acid, 18:0, had no effect whereas oleic acid, 18:1n-9, linoleic acid,18:2n-6, arachidonic acid, 20:4n-6, and docosahexaneoic acid, 22:6n-3, affected leptin's mobility to different degrees. The physiological implication of leptin-FFA interaction is not known, however the interaction may depend on the plasma FFA composition and concentration which are known to vary in different pathological/physiological conditions.MH - Fatty Acids|*MEMH - Proteins|*MESO - Biochem Biophys Res Commun 1998 Jun; 247(3):654-8DP - 1998 JunTA - Biochem Biophys Res CommunPG - 654-8IP - 3VI - 247UI - 9832118213
AU - Siegrist Kaiser CA
AU - Pauli V
AU - Juge Aubry CE
AU - Boss O
AU - Pernin A
AU - Chin WW
AU - Cusin I
AU - Rohner Jeanrenaud F
AU - Burger AG
AU - Zapf J
AU - Meier CATI - Direct effects of leptin on brown and white adipose tissue.AB - Leptin is thought to exert its actions on energy homeostasis through the long form of the leptin receptor (OB-Rb), which is present in the hypothalamus and in certain peripheral organs, including adipose tissue. In this study, we examined whether leptin has direct effects on the function of brown and white adipose tissue (BAT and WAT, respectively) at the metabolic and molecular levels. The chronic peripheral intravenous administration of leptin in vivo for 4 d resulted in a 1.6-fold increase in the in vivo glucose utilization index of BAT, whereas no significant change was found after intracerebroventricular administration compared with pair-fed control rats, compatible with a direct effect of leptin on BAT. The effect of leptin on WAT fat pads from lean Zucker Fa/ fa rats was assessed ex vivo, where a 9- and 16-fold increase in the rate of lipolysis was observed after 2 h of exposure to 0.1 and 10 nM leptin, respectively.In contrast, no increase in lipolysis was observed in the fat pads from obese fa/fa rats, which harbor an inactivating mutation in the OB-Rb. At the level of gene expression,leptin treatment for 24 h increased malic enzyme and lipoprotein lipase RNA 1.8+/-0.17 and 1.9+/-0.14-fold, respectively,while aP2 mRNA levels were unaltered in primary cultures of brown adipocytes from lean Fa/fa rats. Importantly, however, no significant effect of leptin was observed on these genes in brown adipocytes from obese fa/fa animals.The presence of OB-Rb receptors in adipose tissue was substantiated by the detection of its transcripts by RT-PCR, and leptin treatment in vivo and in vitro activated the specific STATs implicated in the signaling pathway of the OB-Rb. Taken together, our data strongly suggest that leptin has direct effects on BAT and WAT, resulting in the activation of the Jak/STAT pathway and the increased expression of certain target genes, which may partially account for the observed increase in glucose utilization and lipolysis in leptin-treated adipose tissue.MH - Adipose Tissue|*DE/MEMH - Brown Fat|*DE/MEMH - Proteins|*PDSO - J Clin Invest 1997 Dec; 100(11):2858-64DP - 1997 DecTA - J Clin InvestPG - 2858-64IP - 11VI - 100UI - 9805259014
AU - Gavrilova O
AU - Barr V
AU - Marcus Samuels B
AU - Reitman MTI - Hyperleptinemia of pregnancy associated with the appearance of a circulating form of the leptin receptor.AB - Leptin is a hormone produced in adipose cells that regulates energy expenditure, food intake, and adiposity. In mice,we observed that circulating leptin levels increase 20-40-fold during pregnancy. Pregnant ob/ob females had no detectable serum leptin, demonstrating that the heterozygous conceptus was not the source of the leptin. However, leptin RNA and protein levels in maternal adipose tissue were not elevated. The circulating leptin was in a high molecular weight complex, suggesting that the rise in leptin was due to expression of a binding protein. Indeed, quantitative assays of serum leptin binding capacity revealed a 40-fold increase, coincident with the rise in serum leptin. Leptin binding activity reached a capacity of 207 +/- 15 nmol/liter of serum at day 18 of gestation, and half-maximal binding was observed with approximately 3 nM leptin. The binding protein was purified and partially sequenced, revealing sequence identity to the extracellular domain of the leptin receptor. We found that the placenta produces large amounts of the OB-Re isoform of leptin receptor mRNA, which encodes a soluble binding protein. Thus, the extreme hyperleptinemia of late pregnancy is attributable to binding of the leptin by a secreted form of the leptin receptor made by the placenta.MH - Carrier Proteins|CH/*MEMH - Mice, Obese|*BLMH - Proteins|*MESO - J Biol Chem 1997 Nov; 272(48):30546-51DP - 1997 NovTA - J Biol ChemPG - 30546-51IP - 48VI - 272UI - 9804376415
AU - Yamashita T
AU - Murakami T
AU - Otani S
AU - Kuwajima M
AU - Shima KTI - Leptin receptor signal transduction: OBRa and OBRb of fa type.AB - We report herein the characterization of activities of signal transduction for three types of leptin receptors (OBRs) from rats, the OBRa, OBRb, and OBRb with fa mutation (OBRb-fa), by measurement of the levels of tyrosine phosphorylation of STAT3 (signal transducers and activators of transcription 3) and MAPK (mitogen-activated protein kinase), which are induced by leptin stimulation of CHO cells stably expressing the OBR (CHO-OBRb, CHO-OBRa, or CHO-OBRb-fa cells). As the result of leptin stimulation, enhanced levels of tyrosine phosphorylation of STAT3 and MAPK were detected in CHO-OBRb cells. In CHO-OBRb-fa cells, enhancement levels for both were lower than those in CHO-OBRb cells. In CHO-OBRa cells, only the phosphorylation of MAPK was detected. These data suggest that these reduced signaling activities cause obesity in fa/fa rats and that OBRa, which has been generally thought to be inactive at signaling, actually transmits signals through the MAPK pathway.MH - Carrier Proteins|CL/GE/*MEMH - Proteins|*MEMH - Receptors, Cytokine|CL/GE/*MESO - Biochem Biophys Res Commun 1998 May; 246(3):752-9DP - 1998 MayTA - Biochem Biophys Res CommunPG - 752-9IP - 3VI - 246UI - 9828960316
AU - Diamond FB Jr
AU - Eichler DC
AU - Duckett G
AU - Jorgensen EV
AU - Shulman D
AU - Root AWTI - Demonstration of a leptin binding factor in human serum.AB - Serum leptin levels are elevated in subjects with exogenous obesity, indicating that obesity is associated with leptin resistance. Since in man no abnormalities have yet been found in either the genes for leptin or its receptor, the mechanism of leptin resistance in obesity remains unknown.To determine if resistance might be related to leptin binding by a serum component, we assessed the carrier status of leptin in serum. The presence of a specific leptin binding factor in human serum has been established by (1) demonstrating [125I]-leptin binding to a serum component that is saturable and specifically displaceable only by unlabeled leptin and not by human growth hormone, pork insulin, insulin-like growth factors I and II, luteinizing or follicle stimulating hormones, transforming growth factor-beta 1, interleukin-6, or leukemia inhibiting factor; (2) fractionating the leptin bound serum complex and the serum leptin binding component on a molecular sieving column revealing a mass of approximately 450 kDa; and (3) identifying an inverse correlation between the concentration of serum leptin and the quantity of the leptin binding component. It is suggested that binding of leptin by this serum component may influence the physiologic response to leptin.MH - Carrier Proteins|*BL/CH/IPMH - Proteins|*MESO - Biochem Biophys Res Commun 1997 Apr; 233(3):818-22DP - 1997 AprTA - Biochem Biophys Res CommunPG - 818-22IP - 3VI - 233UI - 9731249917
AU - Birkenmeier G
AU - Kmpfer I
AU - Kratzsch J
AU - Schellenberger WTI - Human leptin forms complexes with alpha 2-macroglobulin which are recognized by the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein.AB - OBJECTIVE: To identify binding proteins of leptin in human plasma. METHODS: Binding was evaluated by electrophoresis,size exclusion chromatography (SEC), Western blotting, and radioisotope labeling. Quantification of leptin and the different forms of alpha2-macroglobulin (alpha2-M) was performed by ELISA. RESULTS: Leptin interacts with the proteinase inhibitor, alpha2-M. 125I-labeled leptin specifically binds to the transformed inhibitor, which arises by reaction with proteinases or with reactive primary amines. No leptin binding was observed to the native alpha2-M, which abundantly occurs in plasma. The complex formation between leptin and alpha2-M was found to proceed within minutes and was stable, as it resisted separation by SEC and electrophoresis. The Kd of the complex was 2.14 +/-0.78 micromol/l. Complex formation with transformed alpha2-M did not interfere with the immunological determination of leptin in plasma. The leptin-alpha2-M complex was found to be recognized by the alpha2-M receptor/low density lipoprotein receptor-related protein. By computer analysis, a simple model is presented showing that the degree of transformation of alpha2-M may significantly influence the leptin concentration in blood. CONCLUSIONS: The proteinase inhibitor, alpha2-M, may act as a leptin-binding protein in human plasma.Binding of leptin to transformed alpha2-M and its rapid clearance by the alpha2-M receptor may significantly influence the bioavailability of leptin in human plasma.MH - alpha-Macroglobulins|*MEMH - Proteins|*MEMH - Receptors, Immunologic|*BLMH - Receptors, LDL|*BLSO - Eur J Endocrinol 1998 Aug; 139(2):224-30DP - 1998 AugTA - Eur J EndocrinolPG - 224-30IP - 2VI - 139UI - 9838947418
AU - Carpenter LR
AU - Farruggella TJ
AU - Symes A
AU - Karow ML
AU - Yancopoulos GD
AU - Stahl NTI - Enhancing leptin response by preventing SH2-containing phosphatase 2 interaction with Ob receptor.AB - Leptin is an adipocyte-derived cytokine that regulates food intake and body weight via interaction with its Ob receptor (ObR). Serum leptin levels are chronically elevated in obese humans, suggesting that obesity may be associated with leptin resistance and the inability to generate an adequate ObR response. Evidence suggests that transcriptional activation of target genes by STAT3 (signal transducer and activator of transcription) in the hypothalamus is a critical pathway that mediates leptin's action. Herein we report that activation of ObR induces the tyrosine phosphorylation of the tyrosine phosphatase SH2-containing phosphatase 2 (SHP-2) and demonstrate that Tyr986 within the ObR cytoplasmic domain is essential to mediate phosphorylation of SHP-2 and binding of SHP-2 to ObR. Surprisingly, mutation of Tyr986 to Phe, which abrogates SHP-2 phosphorylation and binding to the receptor, dramatically increases gene induction mediated by STAT3. Our findings indicate that SHP-2 is a negative regulator of STAT3-mediated gene induction after activation of ObR and raise the possibility that blocking the interaction of SHP-2 with ObR could overcome leptin resistance by boosting leptin's weight-reducing effects in obese individuals.MH - Carrier Proteins|GE/*MEMH - DNA-Binding Proteins|*MEMH - Protein-Tyrosine-Phosphatase|*MEMH - Proteins|*MEMH - Signal Transduction|*MH - Trans-Activators|*MESO - Proc Natl Acad Sci U S A 1998 May; 95(11):6061-6DP - 1998 MayTA - Proc Natl Acad Sci U S APG - 6061-6IP - 11VI - 95UI - 9826330819
AU - Quinton ND
AU - Smith RF
AU - Clayton PE
AU - Gill MS
AU - Shalet S
AU - Justice SK
AU - Simon SA
AU - Walters S
AU - Postel Vinay MC
AU - Blakemore AI
AU - Ross RJTI - Leptin binding activity changes with age: the link between leptin and puberty.AB - The timing of the physical transition from child to adult is determined by a biological clock that switches off the pituitary gonadal axis during infancy until puberty. Body composition (and in particular, fat mass), through leptin,are critical signals to this clock. However, no direct relationship between leptin and puberty has been demonstrated.Leptin is bound in the circulation by a high-affinity binding protein, which has been identified as a soluble leptin receptor. We found circulating levels of leptin binding activity (LBA) to be low at birth, to be high in the prepubertal years, to fall through puberty, and then to remain stable during adult life. LBA correlated with pubertal status in both boys and girls. We postulate that the fall in LBA,associated with increasing age and puberty, reflects a reduction in expression of truncated leptin receptors, and leptin is then available to the full-length receptor,which transmits the biological signal for leptin. The high levels of LBA occur during the years when the pituitary gonadal axis is quiescent. Thus, the change in LBA could explain how leptin regulates puberty.MH - Aging|*PHMH - Proteins|*ME/PHMH - Puberty|*PHSO - J Clin Endocrinol Metab 1999 Jul; 84(7):2336-41DP - 1999 JulTA - J Clin Endocrinol MetabPG - 2336-41IP - 7VI - 84UI - 9933168520
AU - Liu C
AU - Liu XJ
AU - Barry G
AU - Ling N
AU - Maki RA
AU - De Souza EBTI - Expression and characterization of a putative high affinity human soluble leptin receptor.AB - Leptin, a circulating 16-kDa protein secreted by adipocytes,decreases body weight by reducing food intake and enhancing energy utilization. Leptin receptors that share homology to the glycoprotein gp130 have been recently cloned. In addition, differentially spliced leptin receptor messenger RNAs have been identified. Functional mutations in either the leptin or leptin receptor gene cause obesity. In the present study, expression of the full length human leptin receptor complementary DNA encoding the long cytoplasmic domain of leptin receptor in COS7 cells resulted in high affinity membrane binding of 125I-leptin (Ki approximately 200 pM); no detectable binding was present in the medium.In addition, we expressed the extracellular domain of human leptin receptor in COS7 cells and identified a soluble leptin receptor in the conditioned medium that binds human and mouse leptin with high affinity comparable with the full length membrane receptor. Transfected COS7 cells expressing the soluble leptin receptor also demonstrated modest specific 125I-leptin binding in whole cells, presumably due to association of the soluble leptin receptor to cell membrane proteins.Data from cross-linking studies identified two specific bands in the 125I-leptin/soluble leptin receptor complex with molecular masses of approximately 130-150 kDa and 300 kDa. The 130-150 kDa molecular mass was confirmed in Western blot analysis and Coomassie staining of the purified soluble receptor and probably represents the glycosylated form of the receptor. The 300-kDa band most likely represents a homodimer of the soluble leptin receptor complex because HPLC gel filtration analysis of the 125I-leptin/soluble leptin receptor complex identified a single peak corresponding to a molecular mass of approximately 340 kDa. The soluble leptin receptor antagonized 125I-leptin binding to the membrane receptor, suggesting its potential utility as a functional tool for determining the role of endogenous leptin.MH - Carrier Proteins|*BI/*GE/MESO - Endocrinology 1997 Aug; 138(8):3548-54DP - 1997 AugTA - EndocrinologyPG - 3548-54IP - 8VI - 138UI - 9737549321
AU - Nakashima K
AU - Narazaki M
AU - Taga TTI - Leptin receptor (OB-R) oligomerizes with itself but not with its closely related cytokine signal transducer gp130.AB - Leptin (OB) exerts weight-reducing effects in mice. The structure of the receptor for this factor, OB-R, is considerably similar to those of gp130, the common signal transducing receptor component for the interleukin-6 (IL-6) family of cytokines, and leukemia inhibitory factor receptor (LIFR). Since the IL-6 family of cytokines signal through gp130 homodimer or gp130/LIFR heterodimer, we have examined in this study the possible involvement of gp130 and LIFR in leptin signaling through OB-R. Leptin stimulation induces tyrosine phosphorylation of neither gp130 nor LIFR, while LIF stimulation does both. As examined by using two differently epitope-tagged OB-R molecules, the spontaneous homo-oligomerization of OB-R has been elucidated. Ba/F3 cells, which do not express gp130, are non-responsive to leptin and exhibit increased DNA synthesis in response to leptin after transfection of OB-R cDNA alone. OB-R appears to transduce the signal via its homo-oligomerization without interaction with gp130 or LIFR.MH - Antigens, CD|CH/*MEMH - Carrier Proteins|*CH/GE/*MEMH - Membrane Glycoproteins|CH/*MEMH - Receptors, Cytokine|*MESO - FEBS Lett 1997 Feb; 403(1):79-82DP - 1997 FebTA - FEBS LettPG - 79-82IP - 1VI - 403UI - 9719020922
AU - Barr VA
AU - Lane K
AU - Taylor SITI - Subcellular localization and internalization of the four human leptin receptor isoforms.AB - There are four known isoforms of the human leptin receptor (HLR) with different C-terminal cytoplasmic domains (designated by the number of unique C-terminal amino acids). In cells expressing HLR-5, -15, or -274, 15-25% of the leptin binding sites were located at the plasma membrane. In contrast,in cells expressing HLR-67, only 5% of the total binding sites were at the plasma membrane. Immunofluorescent microscopy showed that all four isoforms partially co-localized with calnexin and beta-COP, markers of the endoplasmic reticulum and the Golgi, respectively. All isoforms were also detected in an unidentified punctate compartment. All isoforms were internalized via clathrin-mediated endocytosis, but at different rates. After 20 min at 37 degrees C, 45% of a bound cohort of labeled ligand had been internalized by HLR-15, 30% by HLR-67, 25% by HLR-274, and 15% by HLR-5.Degradation of internalized leptin occurred in lysosomes.Overnight exposure to leptin down-regulated all isoforms,but to a variable extent. HLR-274 displayed the greatest down-regulation and also appeared to reach lysosomes more quickly than the other isoforms. The faster degradation of HLR-274 may help to terminate leptin signaling.MH - Carrier Proteins|GE/*MESO - J Biol Chem 1999 Jul; 274(30):21416-24DP - 1999 JulTA - J Biol ChemPG - 21416-24IP - 30VI - 274UI - 9934008623
AU - Combatsiaris TP
AU - Charron MJTI - Downregulation of uncoupling protein 2 mRNA in white adipose tissue and uncoupling protein 3 mRNA in skeletal muscle during the early stages of leptin treatment.AB - The mechanisms underlying the increase in energy expenditure during leptin treatment are not clear. We recently showed that a 5-h intravenous or intracerebroventricular infusion of leptin elevated basal glucose uptake in skeletal muscle (SM) and brown adipose tissue and increased whole-body glucose turnover in C57Bl/6J mice (Kamohara S, Burcelin R, Halaas JL, Friedman JM, Charron MJ: Acute stimulation of glucose metabolism in mice by leptin treatment. Nature 389:374-377, 1997). We extended the previous study by measuring steady-state levels of uncoupling protein (UCP)-2 mRNA and UCP-3 mRNA in white adipose tissue (WAT) and SM. Leptin by intravenous or intracerebroventricular infusion for 5 h was associated with a decrease in UCP-2 mRNA in WAT (47-52%) and UCP-3 mRNA in SM (33-37%). Because overexpression of UCP-2 or UCP-3 can depolarize the inner mitochondrial membrane, suppression of UCP-2 mRNA and UCP-3 mRNA may in fact lower respiratory demands in WAT and SM. This is consistent with the parallel suppression of cytochrome oxidase subunit IV (COX-IV) mRNA in WAT (35-39%) after leptin infusion. COX-IV mRNA in SM did not respond to acute leptin treatment. Mitochondrial inorganic phosphate carrier (P1C) mRNA was also suppressed in WAT (33-35%) by either method of leptin infusion, but only intravenous infusion of leptin reduced P1C mRNA in SM (40%). Denervation suppressed mRNA levels for UCP-2 (49%), UCP-3 (36%), and COX-IV (59%) and eliminated the acute response to leptin in SM. The comparable response to leptin under intravenous or intracerebroventricular infusion and the loss of responsiveness after denervation strongly suggest that the acute effects of leptin involve central signaling pathways.MH - Adipose Tissue|*MEMH - Carrier Proteins|*GEMH - Muscle, Skeletal|*MEMH - Proteins|*GE/*PDMH - RNA, Messenger|*MEAD - Department of BiochemistryAD - Albert Einstein College of MedicineAD - BronxAD - New York 10461AD - USA.SO - Diabetes 1999 Jan; 48(1):128-33DP - 1999 JanTA - DiabetesPG - 128-33IP - 1VI - 48UI - 9910725124
AU - Wang MY
AU - Koyama K
AU - Shimabukuro M
AU - Mangelsdorf D
AU - Newgard CB
AU - Unger RHTI - Overexpression of leptin receptors in pancreatic islets of Zucker diabetic fatty rats restores GLUT-2, glucokinase,and glucose-stimulated insulin secretion.AB - The high-Km glucose transporter, GLUT-2, and the high-Km hexokinase of beta cells, glucokinase (GK), are required for glucose-stimulated insulin secretion (GSIS). GLUT-2 expression in beta cells of Zucker diabetic fatty (ZDF)rats is profoundly reduced at the onset of beta-cell dysfunction of diabetes. Because ZDF rats are homozygous for a mutation in their leptin receptor (OB-R) gene and are therefore leptin-insensitive, we expressed the wild-type OB-R gene in diabetic islets by infusing a recombinant adenovirus (AdCMV-OB-Rb) to determine whether this reversed the abnormalities.Leptin induced a rise in phosphorylated STAT3, indicating that the transferred wild-type OB-R was functional. GLUT-2 protein rose 17-fold in AdCMV-OB-Rb-treated ZDF islets without leptin, and leptin caused no further rise. GK protein rose 7-fold without and 12-fold with leptin. Preproinsulin mRNA increased 64% without leptin and rose no further with leptin, but leptin was required to restore GSIS. Clofibrate and 9-cis-retinoic acid, the partner ligands for binding to peroxisome proliferator-activator receptor alpha (PPARalpha)and retinoid X receptor, up-regulated GLUT-2 expression in islets of normal rats, but not in ZDF rats, in which PPARalpha is very low. Because the fat content of islets of diabetic ZDF rats remains high unless they are treated with leptin, it appears that restoration of GSIS requires normalization of intracellular nutrient homeostasis, whereas up-regulation of GLUT-2 and GK is leptin-independent, requiring only high expression of OB-Rb.MH - Carrier Proteins|*GEMH - Diabetes Mellitus, Non-Insulin-Dependent|*GE/*PPMH - Islets of Langerhans|DE/*ME/PHMH - Obesity|*GE/*PPSO - Proc Natl Acad Sci U S A 1998 Sep; 95(20):11921-6DP - 1998 SepTA - Proc Natl Acad Sci U S APG - 11921-6IP - 20VI - 95UI - 9842625425
AU - Zhang Y
AU - Olsen DR
AU - Nguyen KB
AU - Olson PS
AU - Rhodes ET
AU - Mascarenhas DTI - Expression of eukaryotic proteins in soluble form in Escherichia coli.AB - At the optimum temperature for its growth (37 degrees C), Escherichia coli tends to accumulate heterologous proteins in insoluble form. Fusion protein technology has been used to increase the solubility of overexpressed proteins in this organism, but with variable degrees of success. Fusion to a mutant form of DsbA (DsbAmut) confers higher levels of solubility to heterologous proteins in a reproducible way, even when E. coli is grown at 37 degrees C. We have shown this to be true with a diverse sample of eukaryotic proteins: IGF-I, IGFBP-3, 3C proteinase, TGF beta-2, sTGF beta-RII, BDNF, GDNF, mEGFBP, leptin, and GFP. In addition,we have investigated the effects of charge average and proline content on the solubility of DsbAmut fusions. Coexpression of a protein prolyl isomerase [cyclophilin (L-)] and modification of selected asparagine residues to aspartic acid appear to have beneficial effects on the accumulation of soluble heterologous proteins.MH - Escherichia coli|GE/*MEMH - Gene Expression Regulation, Bacterial|*GEMH - Recombinant Fusion Proteins|*BI/CH/GESO - Protein Expr Purif 1998 Mar; 12(2):159-65DP - 1998 MarTA - Protein Expr PurifPG - 159-65IP - 2VI - 12UI - 9819187626
AU - Shimizu H
AU - Ohtani K
AU - Tsuchiya T
AU - Takahashi H
AU - Uehara Y
AU - Sato N
AU - Mori MTI - Leptin stimulates insulin secretion and synthesis in HIT-T 15 cells.AB - Leptin, an ob gene product, corrects hyperinsulinemia in ob/ob mice. The leptin receptor may exist in pancreatic islets. The present studies were undertaken to determine the direct effect of 1-100 ng/ml recombinant leptin on insulin secretion and synthesis in HIT-T 15 cells by using static culture system. The addition of recombinant leptin significantly increased insulin secretion for 20 min at the highest concentration (100 ng/ml). The addition of recombinant leptin dose-dependently increased insulin secretion for 24 h in the 7 mM glucose-containing F-12 K medium. The incubation with recombinant leptin for 24 h increased preproinsulin mRNA expression, assessed with reverse transcription-polymerase chain reaction (RT-PCR) method. It was furthermore demonstrated that HIT-T 15 cells possessed the specific binding site for [125I]-labeled leptin. The present study demonstrated the existence of the leptin-specific binding sites that mediate its stimulatory effect on insulin secretion and synthesis in HIT-T 15 cells.MH - Insulin|BI/*SEMH - Islets of Langerhans|ME/*SEMH - Proteins|ME/*PDSO - Peptides 1997; 18(8):1263-6DP - 1997TA - PeptidesPG - 1263-6IP - 8VI - 18UI - 9805785327
AU - Albertsson Wikland K
AU - Boguszewski M
AU - Karlberg JTI - Children born small-for-gestational age: postnatal growth and hormonal status.AB - It is generally recognized that children born small-for-gestational age (SGA) have a 5-7 times higher risk of short stature than children born at normal size. It has been suggested that the programming of the endocrine axes occurs during critical phases of fetal development and is affected by intrauterine growth retardation. This study was undertaken to characterize the postnatal growth pattern and the final height of children born SGA, as part of a population- based study (n = 3,650), from birth to final height, and to evaluate the hormonal status in another group of prepubertal children born SGA (n = 134) without postnatal catch-up growth. The majority (88%) of 'healthy' full-term singleton SGA infants achieved catch-up growth during the first 2 years of life,and most of the increase in height occurred by 2 months of age. The SGA children who remained short at 2 years of age had a higher risk of short stature later in life.The risk of having a short final height (<-2 SDS) was five times higher for children with a low birth weight and seven times higher for those with a low birth length in comparison with children with a normal birth size. Moreover, about 20% of all children of short stature were born SGA. As a group, children born SGA will have a final height, expressed in SDS, as they had during the prepubertal years. This is in contrast to children, who became short postnatally.During puberty, these short children will have a mean height gain of 0.6 SDS for girls and 0.7 SDS for boys. The mean estimated secretion rate for growth hormone (GH) was lower in the short children born SGA compared with the reference groups born at an appropriate size for gestational age,of either short (p < 0.05) or normal stature (p < 0.001). Moreover, in the youngest children born SGA (2-6 years of age) a different pattern of GH secretion was found, with a high basal GH level, low peak amplitude, and high peak frequency. The majority of the children born SGA had levels of GH-binding protein within the range previously reported for normal children. However, the levels of insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3) and leptin were significantly reduced compared with the reference values (p < 0.001, p < 0.01 and p < 0.001,respectively). In conclusion, the low spontaneous GH secretion rate and a disturbed GH secretion pattern, together with low serum levels of IGF-I, IGFBP-3 and leptin, might contribute to the reduced postnatal growth in some of the subgroup of children born SGA who remained short during childhood.MH - Infant, Small for Gestational Age|BL/*GDSO - Horm Res 1998; 49 Suppl 2():7-13DP - 1998TA - Horm ResPG - 7-13VI - 49 Suppl 2UI - 9840250028
AU - Eichler DC
AU - Root AW
AU - Duckett G
AU - Moore KL
AU - Diamond FBTI - A spun-column assay for determination of leptin binding in serum.AB - Serum collected from 27 patients was assayed simultaneously using a spun-column assay (SPC) and a traditional exclusion gel-filtration assay (GFC) to determine specific leptin binding. The levels of serum leptin binding determined by either assay correlated inversely with serum leptin levels (SPC, r = 0.63, P < 0.001; GFC, r = 0.79, P < 0.0001). Although specific leptin binding as determined by the traditional exclusion gel-filtration assay was generally higher than that obtained by the spun-column assay (mean = 18.3% vs 14.0%, P < 0. 02, respectively); the values obtained between the two assay methods were highly correlative (r = 0.89, P < 0.0001). By varying either the amount of 125I-leptin or the amount of competitor, analysis was carried out using the spun-column assay to determine the intrinsic properties of serum leptin binding. Results yielded a Kd = 0.3 nM, where each variable amount of leptin or competitor was carried out in duplicate. The complete analysis was carried out in the time that it typically takes for a single sample determination by the traditional exclusion gel-filtration assay. We conclude that the "spun-column" assay is a useful method for rapid and accurate quantification of leptin binding in serum. Copyright 1999 Academic Press.MH - Blood Chemical Analysis|*MTMH - Chromatography, Gel|*MTMH - Proteins|*MESO - Anal Biochem 1999 Feb; 267(1):100-3DP - 1999 FebTA - Anal BiochemPG - 100-3IP - 1VI - 267UI - 9911928129
AU - Chung CD
AU - Liao J
AU - Liu B
AU - Rao X
AU - Jay P
AU - Berta P
AU - Shuai KTI - Specific inhibition of Stat3 signal transduction by PIAS3.AB - The signal transducer and activator of transcription-3 (Stat3) protein is activated by the interleukin 6 (IL-6)family of cytokines, epidermal growth factor, and leptin.A protein named PIAS3 (protein inhibitor of activated STAT)that binds to Stat3 was isolated and characterized. The association of PIAS3 with Stat3 in vivo was only observed in cells stimulated with ligands that cause the activation of Stat3. PIAS3 blocked the DNA-binding activity of Stat3 and inhibited Stat3-mediated gene activation. Although Stat1 is also phosphorylated in response to IL-6, PIAS3 did not interact with Stat1 or affect its DNA-binding or transcriptional activity. The results indicate that PIAS3 is a specific inhibitor of Stat3.MH - Carrier Proteins|CH/GE/*ME/PDMH - DNA-Binding Proteins|GE/*MEMH - Signal Transduction|*MH - Trans-Activators|*MESO - Science 1997 Dec; 278(5344):1803-5DP - 1997 DecTA - SciencePG - 1803-5IP - 5344VI - 278UI - 9804961530
AU - Seufert J
AU - Kieffer TJ
AU - Leech CA
AU - Holz GG
AU - Moritz W
AU - Ricordi C
AU - Habener JFTI - Leptin suppression of insulin secretion and gene expression in human pancreatic islets: implications for the development of adipogenic diabetes mellitus.AB - Previously we demonstrated the expression of the long form of the leptin receptor in rodent pancreatic beta-cells and an inhibition of insulin secretion by leptin via activation of ATP-sensitive potassium channels. Here we examine pancreatic islets isolated from pancreata of human donors for their responses to leptin. The presence of leptin receptors on islet beta-cells was demonstrated by double fluorescence confocal microscopy after binding of a fluorescent derivative of human leptin (Cy3-leptin). Leptin (6.25 nM) suppressed insulin secretion of normal islets by 20% at 5.6 mM glucose.Intracellular calcium responses to 16.7 mM glucose were rapidly reduced by leptin. Proinsulin messenger ribonucleic acid expression in islets was inhibited by leptin at 11.1 mM, but not at 5.6 mM glucose. Leptin also reduced proinsulin messenger ribonucleic acid levels that were increased in islets by treatment with 10 nM glucagon-like peptide-1 in the presence of either 5.6 or 11.1 mM glucose. These findings demonstrate direct suppressive effects of leptin on insulin-producing beta-cells in human islets at the levels of both stimulus-secretion coupling and gene expression.The findings also further indicate the existence of an adipoinsular axis in humans in which insulin stimulates leptin production in adipocytes and leptin inhibits the production of insulin in beta-cells. We suggest that dysregulation of the adipoinsular axis in obese individuals due to defective leptin reception by beta-cells may result in chronic hyperinsulinemia and may contribute to the pathogenesis of adipogenic diabetes.MH - Gene Expression|*DEMH - Insulin|*SEMH - Islets of Langerhans|CH/DE/*MEMH - Obesity in Diabetes|*MEMH - Proinsulin|*GEMH - Proteins|*PDAD - Laboratory of Molecular EndocrinologyAD - Massachusetts General HospitalAD - Howard Hughes Medical InstituteAD - Harvard Medical SchoolAD - Boston 02114AD - USA.SO - J Clin Endocrinol Metab 1999 Feb; 84(2):670-6DP - 1999 FebTA - J Clin Endocrinol MetabPG - 670-6IP - 2VI - 84UI - 9914503431
AU - Bjçrbaek C
AU - Uotani S
AU - da Silva B
AU - Flier JSTI - Divergent signaling capacities of the long and short isoforms of the leptin receptor.AB - Leptin receptors include a long form (OBRl) with 302 cytoplasmic residues that is presumed to mediate most or all of leptins signaling, and several short forms, including one (OBRs)that has 34 cytoplasmic residues, is widely expressed, and is presumed not to signal but to mediate transport or clearance of leptin. We studied the abilities of these two receptor isoforms to mediate signaling in transfected cells. In response to leptin, OBRl, but not OBRs, underwent tyrosine phosphorylation that was enhanced by co-expression with JAK2. In cells expressing receptors and JAK2, both OBRs and OBRl mediated leptin-dependent tyrosine phosphorylation of JAK2, and this was abolished with OBRs when the Box 1 motif was mutated. In cells expressing receptors, JAK2 and IRS-1, leptin induced tyrosine phosphorylation of IRS-1 through OBRs and OBRl. In COS cells expressing hemagglutinin-ERK1 and receptors, leptin increased ERK1 kinase activity through OBRl, with the magnitude increased by co-expression of JAK1 or JAK2, and to a lesser degree through OBRs, despite greater receptor expression. In stable Chinese hamster ovary cell lines expressing OBRs or OBRl, leptin stimulated endogenous ERK2 phosphorylation. Whereas leptin stimulated tyrosine phosphorylation of hemagglutinin-STAT3 and induction of a c-fos luciferase reporter plasmid through OBRl, OBRs was without effect in these assays. In conclusion, OBRl is capable of signaling to IRS-1 and mitogen-activated protein kinase via JAK, in addition to activating STAT pathways. Although substantially weaker than OBRl, OBRs is capable of mediating signal transduction via JAK, but these activities are of as yet unknown significance for leptin biology in vivo.MH - Carrier Proteins|CH/GE/*MEMH - Signal Transduction|*SO - J Biol Chem 1997 Dec; 272(51):32686-95DP - 1997 DecTA - J Biol ChemPG - 32686-95IP - 51VI - 272UI - 9807045332
AU - Chance WT
AU - Sheriff S
AU - Moore J
AU - Peng F
AU - Balasubramaniam ATI - Reciprocal changes in hypothalamic receptor binding and circulating leptin in anorectic tumor-bearing rats.AB - Although reduced biological activity of the obese gene product, leptin, has been associated with obesity, little information is available concerning leptin alterations during anorexia. Therefore, we measured circulating leptin concentrations and hypothalamic leptin binding in anorectic tumor-bearing and pair-fed control rats. Plasma concentrations of leptin decreased in tumor-bearing rats early in the course of tumor growth, and fell to nearly non-detectable levels during severe anorexia. The pair-fed control rats that ate the same amount of food as did the anorectic tumor-bearing rats exhibited a 50% decrease in plasma leptin concentration. Concentrations of free fatty acids were elevated in both tumor-bearing and pair-fed groups, while circulating levels of triglycerides were increased only in anorectic tumor-bearing rats. Leptin receptor density was doubled in the hypothalamus of tumor bearing rats, while binding affinity was decreased by 50%. These results suggest that peripheral leptin production is down-regulated,perhaps due to increased lipolysis in tumor-bearing rats.It appears that hypothalamic leptin systems up-regulate receptor numbers in response to decreased blood leptin level, however, the decrease in binding affinity may compensate for these alterations. Therefore, the influence of leptin on hypothalamic neuropeptide Y feeding systems may be minimal in anorectic tumor-bearing rats. Copyright 1998 Published by Elsevier Science B.V.MH - Anorexia|BL/*MEMH - Carrier Proteins|*MEMH - Hypothalamus|*ME/PHMH - Proteins|*MEMH - Sarcoma, Experimental|BL/*MESO - Brain Res 1998 Aug; 803(1-2):27-33DP - 1998 AugTA - Brain ResPG - 27-33IP - 1-2VI - 803UI - 9839837733
AU - Matsuoka T
AU - Tahara M
AU - Yokoi T
AU - Masumoto N
AU - Takeda T
AU - Yamaguchi M
AU - Tasaka K
AU - Kurachi H
AU - Murata YTI - Tyrosine phosphorylation of STAT3 by leptin through leptin receptor in mouse metaphase 2 stage oocyte.AB - Leptin is the product of the obese gene (ob), and is secreted in plasma from mature adipocytes. It has been recently reported that leptin is synthesized in granulosa and cumulus cells within the follicle of the ovary, and is present in mature human oocytes, suggesting possible roles of leptin in several aspects of pre- and post-ovulatory follicular development. On the other hand, STAT (Signal Transducer and Activator of Transcription) transcription factors are involved in leptin-associated signal transduction. In this report, we studied the expression of leptin receptor and STAT3 activation by leptin in metaphase 2 stage (M2) oocytes.Reverse transcriptase-polymerase chain reaction (RT-PCR)and immunoblotting showed that mRNA and protein of leptin receptor were expressed in M2 stage oocyte. Leptin at 15 ng/ml, the concentration observed in follicular fluid, caused tyrosine phosphorylation of STAT3 in mouse M2 stage oocytes. These results suggest possible roles of leptin in several aspects during oocyte maturation by activating the STAT signal transduction pathway. Copyright 1999 Academic Press.MH - Carrier Proteins|GE/*MEMH - DNA-Binding Proteins|*MEMH - Oocytes|*DE/GD/MEMH - Phosphotyrosine|*MEMH - Proteins|GE/PD/*PHMH - Trans-Activators|*MESO - Biochem Biophys Res Commun 1999 Mar; 256(3):480-4DP - 1999 MarTA - Biochem Biophys Res CommunPG - 480-4IP - 3VI - 256UI - 9918231534
AU - Ghilardi N
AU - Skoda RCTI - The leptin receptor activates janus kinase 2 and signals for proliferation in a factor-dependent cell line.AB - The antiobesity effects of leptin are mediated by the obese receptor (OB-R), a member of the cytokine receptor superfamily.Several isoforms of OB-R that differ in the length of the cytoplasmic domain have been described. An isoform with a long cytoplasmic domain of 302 amino acids, termed OB-Rb, contains the conserved box 1 and box 2 motifs and is likely to be responsible for leptin-induced signaling. A point mutation in the OB-R gene of diabetes (db) mice generates a new splice donor that interferes with the correct splicing of the OB-Rb mRNA and is predicted to cause absence of the OB-Rb protein in db/db mice. Here we examined the signaling potential of the long isoform, OB-Rb, and of a short isoform, OB-Ra, in BaF3 cells, a factor-dependent hematopoietic cell line. The long isoform was able to generate a proliferative signal and upon leptin binding, activated janus kinase 2 (Jak2). Consistently, antibodies directed against the extracellular domain of OB-R coprecipitated Jak2. The short isoform, OB-Ra, was inactive in both proliferation and Jak activation. These results provide further support for the long isoform, OB-Rb, being the principal mediator of the effects of leptin and help to explain why db/db mice are resistant to leptin, despite the presence of the short OB-R isoforms.MH - Carrier Proteins|GE/*MEMH - Protein-Tyrosine Kinase|*MEMH - Receptors, Cytokine|GE/*MEMH - Signal Transduction|*SO - Mol Endocrinol 1997 Apr; 11(4):393-9DP - 1997 AprTA - Mol EndocrinolPG - 393-9IP - 4VI - 11UI - 9724655335
AU - Li C
AU - Friedman JMTI - Leptin receptor activation of SH2 domain containing protein tyrosine phosphatase 2 modulates Ob receptor signal transduction.AB - Leptin exerts its weight-reducing effects by binding to its receptor and activating signal transduction in hypothalamic neurons and other cell types. To identify the components of the leptin signal transduction pathway, an approach was developed in which bacterially expressed phosphorylated fragments of Ob receptor b (Ob-Rb) were used as affinity agents. Leptin binding to the Ob-Rb form of the leptin receptor leads to tyrosyl phosphorylation of the cytoplasmic domain of its receptor. Two of the three cytoplasmic tyrosines of Ob-Rb, at positions 985 and 1138, are phosphorylated after leptin treatment. Affinity chromatography using a tyrosine-phosphorylated fragment spanning Tyr 985 of Ob-Rb was used to identify proteins that bind to this site.The SH2 domain containing protein tyrosine phosphatase 2 (SHP-2) was isolated from bovine and mouse hypothalamus by using this method. After cotransfection of Ob-Rb, Janus kinase 2 (JAK2), and SHP-2 into 293T cells, leptin results in direct binding of SHP-2 to the phosphorylated Tyr 985.The bound SHP-2 is itself tyrosine phosphorylated after leptin treatment. SHP-2 is not phosphorylated after leptin treatment when a Y-->F 985 receptor mutant is cotransfected.In the absence of SHP-2 phosphorylation, the level of JAK2 phosphorylation was increased. Tyrosyl phosphorylation of the leptin receptor and signal transducer and activater of transcription 3 (STAT3) are not affected by phosphorylation of SHP-2. These data suggest that activation of SHP-2 by the leptin receptor results in a decreased phosphorylation of JAK2 and may act to attenuate leptin signal transduction.The method used in this report can in principle be used to isolate additional components of the leptin, or other,signal transduction pathway.MH - Carrier Proteins|*MEMH - Obesity|*PPMH - Protein-Tyrosine-Phosphatase|*MEMH - Signal Transduction|*SO - Proc Natl Acad Sci U S A 1999 Aug; 96(17):9677-82DP - 1999 AugTA - Proc Natl Acad Sci U S APG - 9677-82IP - 17VI - 96UI - 9938057836
AU - Haft CR
AU - de la Luz Sierra M
AU - Barr VA
AU - Haft DH
AU - Taylor SITI - Identification of a family of sorting nexin molecules and characterization of their association with receptors.AB - Sorting nexin 1 (SNX1) is a protein that binds to the epidermal growth factor (EGF) receptor and is proposed to play a role in directing EGF receptors to lysosomes for degradation (R. C. Kurten, D. L. Cadena, and G. N. Gill, Science 272:1008-1010, 1996). We have obtained full-length cDNAs and deduced the amino acid sequences of three novel homologous proteins, which were denoted human sorting nexins (SNX2,SNX3, and SNX4). In addition, we identified a presumed splice variant isoform of SNX1 (SNX1A). These molecules contain a conserved domain of approximately 100 amino acids,which was termed the phox homology (PX) domain. Human SNX1 (522 amino acids), SNX1A (457 amino acids), SNX2 (519 amino acids), SNX3 (162 amino acids), and SNX4 (450 amino acids)are part of a larger family of hydrophilic molecules including proteins identified in Caenorhabditis elegans and Saccharomyces cerevisiae. Despite their hydrophilic nature, the sorting nexins are found partially associated with cellular membranes.They are widely expressed, although the tissue distribution of each sorting nexin mRNA varies. When expressed in COS7 cells, epitope-tagged sorting nexins SNX1, SNX1A, SNX2,and SNX4 coimmunoprecipitated with receptor tyrosine kinases for EGF, platelet-derived growth factor, and insulin. These sorting nexins also associated with the long isoform of the leptin receptor but not with the short and medium isoforms.Interestingly, endogenous COS7 transferrin receptors associated exclusively with SNX1 and SNX1A, while SNX3 was not found to associate with any of the receptors studied. Our demonstration of a large conserved family of sorting nexins that interact with a variety of receptor types suggests that these proteins may be involved in several stages of intracellular trafficking in mammalian cells.MH - Carrier Proteins|*CH/PHMH - Receptors, Epidermal Growth Factor-Urogastrone|*MESO - Mol Cell Biol 1998 Dec; 18(12):7278-87DP - 1998 DecTA - Mol Cell BiolPG - 7278-87IP - 12VI - 18UI - 9903823237
AU - Crouse JA
AU - Elliott GE
AU - Burgess TL
AU - Chiu L
AU - Bennett L
AU - Moore J
AU - Nicolson M
AU - Pacifici RETI - Altered cell surface expression and signaling of leptin receptors containing the fatty mutation.AB - Leptin and the leptin receptor are key players in the regulation of body weight. In an attempt to dissect the molecular mechanism of the Zucker fatty rat leptin receptor mutation (Gln269 --> Pro) we analyzed the effects of this mutation on leptin receptor signaling and expression in three different expression systems: 1) 32D cells expressing leptin/erythropoietin receptor chimeras, 2) COS-7 cells expressing a leptin receptor short form, and 3) 293 cells expressing soluble receptor forms. To determine if the Gln269 --> Pro mutation is critical for the observed phenotype, we made a similar Gln --> Pro mutation at a vicinal residue two amino acids upstream of the fatty mutation to see if it would have similar effects.Incorporation of either of the Gln --> Pro mutations into wild type receptor forms did not interfere with leptin binding, but it resulted in a signaling-incompetent receptor.In addition, the majority of the mutant receptor protein was localized intracellularly. Our results suggest that the obese phenotype resulting from the Gln269 --> Pro mutation in the leptin receptor of the Zucker fatty rat may be due not only to a reduced cell surface expression of this form of the leptin receptor, but also to a post-leptin binding malfunction of the receptor that interferes with subsequent signal transduction.MH - Carrier Proteins|*GE/MEMH - Signal Transduction|*/GESO - J Biol Chem 1998 Jul; 273(29):18365-73DP - 1998 JulTA - J Biol ChemPG - 18365-73IP - 29VI - 273UI - 9832504738
AU - Serradeil Le Gal C
AU - Raufaste D
AU - Brossard G
AU - Pouzet B
AU - Marty E
AU - Maffrand JP
AU - Le Fur GTI - Characterization and localization of leptin receptors in the rat kidney.AB - Characterization and localization of leptin binding sites were investigated in rat kidneys using [125I]leptin as a ligand. [125I]Leptin specific binding was found in high amounts in rat renomedullary membranes. This binding was specific, saturable, time-dependent (K(obs) = 0.055 +/-0.008 min(-1)) and the dissociation of receptor-bound ligand was slowly reversible (K(-1) = 0.048 +/- 0.013 min(-1)). From saturation experiments, a single class of high-affinity binding sites for leptin was identified with an apparent K(d) of 0.57 +/- 0.14 nM and a B(max) of 45 +/- 10 fmol/mg protein. [125I]Leptin binding was inhibited in a dose-dependent manner by cold leptin and was highly selective since not displaceable by a number of other hormones or peptides. Autoradiographic experiments performed on adult rat kidney sections showed the intense presence of [125I]leptin receptors only in specific areas of the renal inner medulla and also consistent labeling associated with vascular structures in the corticomedullary region. The study of the postnatal developmental expression of leptin receptors in the kidney showed very low expression during the early postnatal period (8-21 days). Full expression of leptin sites was achieved at about 30 days and remained stable throughout adulthood (60 days and upwards). Moreover, in vivo administration of leptin (0.5 mg/kg i.p.) induced a significant and rapid diuretic effect in normally hydrated conscious rats. Thus, these data constitute the first characterization and mapping of [125I]leptin specific binding sites in the rat kidney and raise the possibility of a renal control by leptin.MH - Aging|*MEMH - Carrier Proteins|*MEMH - Diuresis|*DEMH - Kidney|GD/*MEMH - Proteins|*ME/PDSO - FEBS Lett 1997 Mar; 404(2-3):185-91DP - 1997 MarTA - FEBS LettPG - 185-91IP - 2-3VI - 404UI - 9722794439
AU - Haniu M
AU - Arakawa T
AU - Bures EJ
AU - Young Y
AU - Hui JO
AU - Rohde MF
AU - Welcher AA
AU - Horan TTI - Human leptin receptor. Determination of disulfide structure and N-glycosylation sites of the extracellular domain.AB - The leptin receptor (OB-R) is a member of the class I cytokine receptor family and mediates the weight regulatory effects of its ligand through interaction with cytoplasmic kinases.The extracellular domain of this receptor is comprised of two immunoglobulin-like and cytokine-receptor homology domains each and type III fibronectin domains. The extracellular domain of human leptin receptor was expressed in and purified from Chinese hamster ovary cells and was found to contain extensive N-glycosylation (approximately 36% of the total protein). The purified protein had a molecular weight of approximately 145,000 and exhibited ligand binding ability as evidenced by formation of ligand-receptor complex, followed by chemical cross-linking. The determined disulfide motif of the soluble leptin receptor contained several distinct cystine knots as well as 10 free cysteines. The N-glycosylation analysis revealed that Asn624 of the WSXWS motif (residues 622-626) within the C-terminal cytokine receptor homology domain was glycosylated, indicating that this region is solvent-exposed. On the other hand, the N-terminal WSXWS motif was not glycosylated.MH - Carrier Proteins|CH/IP/*MEMH - Disulfides|*CHSO - J Biol Chem 1998 Oct; 273(44):28691-9DP - 1998 OctTA - J Biol ChemPG - 28691-9IP - 44VI - 273UI - 9900321140
AU - Devos R
AU - Guisez Y
AU - Van der Heyden J
AU - White DW
AU - Kalai M
AU - Fountoulakis M
AU - Plaetinck GTI - Ligand-independent dimerization of the extracellular domain of the leptin receptor and determination of the stoichiometry of leptin binding.AB - The leptin receptor is a class I transmembrane protein with either a short or a long cytoplasmic domain. Using chemical cross-linking we have analyzed the binding of leptin to its receptor. Cross-linking of radiolabeled leptin to different isoforms of the leptin receptor expressed on COS-1 cells reveals leptin receptor monomer, homodimer,and oligomer complexes. Cotransfection of the long and short form of the leptin receptor did not provide any evidence for the formation of heterodimer complexes. Soluble forms consisting of either the entire extracellular domain or the two cytokine receptor homologous domains of the leptin receptor were purified to homogeneity from recombinant baculovirus-infected insect cells by leptin affinity chromatography.Gel filtration chromatography showed that these proteins exist in a dimeric form. Analysis of the complex formed between soluble leptin receptor and leptin by native polyacrylamide gel electrophoresis, and data obtained from the amino acid composition of the complex provide direct evidence that the extracellular domain of the leptin receptor binds leptin in a 1:1 ratio.MH - Carrier Proteins|*CH/*MEMH - Proteins|*MESO - J Biol Chem 1997 Jul; 272(29):18304-10DP - 1997 JulTA - J Biol ChemPG - 18304-10IP - 29VI - 272UI - 9736476041
AU - Laron Z
AU - Silbergeld A
AU - Lilos P
AU - Blum FWTI - Serum leptin in obese patients with Laron syndrome before and during IGF-I treatment.AB - Fifteen patients with primary GH resistance (Laron syndrome,LS) were studied before and during 6 months of daily replacement treatment with IGF-I. The main findings were that patients with LS and normal or high serum GH binding protein (GHBP)were less obese than those with a negative GHBP, and that serum leptin levels varied with body mass as in other types of obesity.MH - Insulin-Like Growth Factor I|AN/DF/*TUMH - Mutation|*MH - Obesity|*BL/DT/*GEMH - Proteins|*ANMH - Receptors, Somatotropin|*GEAD - Endocrine & Diabetes Research UnitAD - Schneider Children's Medical Center of IsraelAD - Petah TikvaAD - Israel.SO - J Pediatr Endocrinol Metab 1998 Sep-Oct; 11(5):653-6DP - 1998 Sep-OctTA - J Pediatr Endocrinol MetabPG - 653-6IP - 5VI - 11UI - 9904665742
AU - Commins SP
AU - Marsh DJ
AU - Thomas SA
AU - Watson PM
AU - Padgett MA
AU - Palmiter R
AU - Gettys TWTI - Norepinephrine is required for leptin effects on gene expression in brown and white adipose tissue.AB - Exogenous leptin enhances energy utilization in ob/ob mice by binding its hypothalamic receptor and selectively increasing peripheral fat oxidation. Leptin also increases uncoupling protein 1 (UCP1) expression in brown adipose tissue (BAT), but the neurotransmitter that mediates this effect has not been established. The present experiments sought to determine whether leptin regulates UCP1 expression in BAT and its own expression in white adipose tissue (WAT) through the long or short forms of leptin receptor and modulation of norepinephrine release. Mice lacking dopamine beta-hydroxylase (Dbh-/-), the enzyme responsible for synthesizing norepinephrine and epinephrine from dopamine, were treated with leptin (20 microg/g body weight/day) for 3 days before they were euthanized. UCP1 messenger RNA (mRNA) and protein expression were 5-fold higher in BAT from control (Dbh+/-) compared with Dbh-/- mice. Leptin produced a 4-fold increase in UCP1 mRNA levels in Dbh+/- mice but had no effect on UCP1 expression in Dbh-/-. The beta3-adrenergic agonist, CL-316,243 increased UCP1 expression and established that BAT from both groups of mice was capable of responding to beta-adrenergic stimulation. Similarly, exogenous leptin reduced leptin mRNA in WAT from Dbh+/- but not Dbh-/- mice.In separate experiments, leptin produced comparable reductions in food intake in both Dbh+/- and Dbh-/- mice, illustrating that norepinephrine is not required for leptin's effect on food intake. Lastly, db/db mice lacking the long form of the leptin receptor failed to increase UCP1 mRNA in response to exogenous leptin but increased UCP1 mRNA in response to CL-316,243. These studies establish that norepinephrine is required for leptin to regulate its own expression in WAT and UCP1 expression in BAT and indicate that these effects are likely mediated through the centrally expressed long form of the leptin receptor.MH - Adipose Tissue|*PHMH - Brown Fat|*PHMH - Carrier Proteins|*MEMH - Gene Expression|*PHMH - Membrane Proteins|*MEMH - Norepinephrine|*PHMH - Proteins|GE/PD/*PHSO - Endocrinology 1999 Oct; 140(10):4772-8DP - 1999 OctTA - EndocrinologyPG - 4772-8IP - 10VI - 140UI - 9942788343
AU - Florkowski CM
AU - Barnard R
AU - Livesey JH
AU - Veveris T
AU - Espiner EA
AU - Donald RATI - Growth hormone binding protein correlates strongly with leptin and percentage body fat in GH-deficient adults, is increased by GH replacement but does not predict IGF-I response.AB - GH-binding protein (GHBP) corresponds to the extracellular domain of the GH receptor (GHR) and has been shown to be closely related to body fat. This study aimed to examine the inter-relationship between GHBP, leptin and body fat,and to test the hypothesis that GHBP is modified by GH replacement in GH-deficient adults and predicts IGF-I response.Twenty adults, mean age 47 years (range 20-69) with proven GH deficiency were randomly allocated to either GH (up to 0.25 U/kg/week in daily doses) or placebo for 3 months before cross-over to the opposite treatment. Plasma GHBP and leptin were measured at baseline and 2, 4, 8 and 12 weeks after each treatment. Whole body composition was measured at baseline by dual-energy X-ray absorptiometry (DEXA). There was a strong correlation between baseline leptin and GHBP (r = 0.88, P < 0.0001) and between baseline GHBP and percentage body fat, (r = 0.83, P < 0.0001). Mean GHBP levels were higher on GH compared with placebo, 1.53 +/- 0.28 vs 1.41 +/- 0.25nM, P = 0.049. There was no correlation between baseline IGF-I and GHBP (r = -0.049,P = 0.84), and GHBP did not predict IGF-I response to GH replacement. The close inter-relationship between GHBP,leptin and body fat suggests a possible role for GHBP in the regulation of body composition. GHBP is increased by GH replacement in GH-deficient adults, but does not predict biochemical response to GH replacement.MH - Adipose Tissue|*AHMH - Body Composition|*MH - Carrier Proteins|*BLMH - Hormone Replacement Therapy|*MH - Hypopituitarism|ET/PA/*PP/THMH - Insulin-Like Growth Factor I|*ME/SEMH - Proteins|*ME/SEMH - Somatropin|*DF/*TUSO - Growth Horm IGF Res 1999 Feb; 9(1):35-40DP - 1999 FebTA - Growth Horm IGF ResPG - 35-40IP - 1VI - 9UI - 9922391344
AU - Igel M
AU - Becker W
AU - Herberg L
AU - Joost HGTI - Hyperleptinemia, leptin resistance, and polymorphic leptin receptor in the New Zealand obese mouse.AB - New Zealand Obese (NZO) mice exhibit a polygenic syndrome of hyperphagia, obesity, hyperinsulinemia, and hyperglycemia similar to that observed in young diabetes mutant mice on the C57BLKS/J background (C57BLKS/J-Lepr(db)/Lepr(db)). Here we show that in NZO this syndrome is accompanied by a marked elevation of the leptin protein in adipose tissue and serum. The promoter region and the complementary DNA of the ob gene of NZO mice, including its 5'-untranslated region, are identical with the wild-type sequence (C57BL,BALB/c), except that the transcription start is located 5 bp upstream of the reported site. In contrast to C57BLKS/J+/+ and C57BL/6J-Lep(ob)/Lep(ob) mice, NZO mice failed to respond to recombinant leptin (7.2 microg/g) with a reduction of food intake. Leptin receptor messenger RNA as detected by PCR appears as abundant in hypothalamic tissue of NZO mice as in tissue from lean mice. Ten nucleotide polymorphisms are found in the complementary DNA of the leptin receptor, resulting in two conservative substitutions (V541I and V651I) in the extracellular part of the receptor and one nonconservative substitution (T1044I) in the intracellular domain between the presumed Jak and STAT binding boxes.However, these mutations are also present in the related lean New Zealand Black strain (body fat at 9 weeks: New Zealand Black, 6.2 +/- 1.3%; NZO, 17.0 +/- 1.7%). Thus,the polymorphic leptin receptor seems to play only a minor,if any, role in the obesity and hyperleptinemia of the NZO mouse. It is suggested that the main defect in NZO is located distal from the leptin receptor or at the level of leptin transport into the central nervous system.MH - Carrier Proteins|AN/GE/*MEMH - Obesity|*ME/PPMH - Polymorphism (Genetics)|*MH - Proteins|GE/*ME/*PDSO - Endocrinology 1997 Oct; 138(10):4234-9DP - 1997 OctTA - EndocrinologyPG - 4234-9IP - 10VI - 138UI - 9746270845
AU - Llopis MA
AU - Granada ML
AU - Cuatrecasas G
AU - Formiguera X
AU - Sßnchez Planell L
AU - Sanmart A
AU - Alastru A
AU - Rull M
AU - Corominas A
AU - Foz MTI - Growth hormone-binding protein directly depends on serum leptin levels in adults with different nutritional status.AB - The aim of this work was to assess the relationship between GH-binding protein (GHBP) and leptin. Both peptides are nutritionally regulated, but the recent implication of a role for leptin in the GH axis requires further study.To avoid the sexual dimorphism in leptin values, we performed leptin standardization according to gender (SD score-leptin). The relationship between SD score-leptin and GHBP was studied in 128 adults with different nutritional status [8 groups according to body mass index (BMI)], ranging from severely underweight anorexia nervosa to highly morbid obesity. Both GHBP and SD score-leptin significantly increased according to BMI within the range from 18-27 kg/m2, whereas no significant differences were found among underweight groups (BMI, < 18 kg/m2) or among obesity grades (BMI, > 27 kg/m2). We found a strong correlation between GHBP and SD score-leptin (r = 0.8; P < 0.0001). Multiple regression analysis revealed SD score-leptin to be a significant determinant of GHBP, accounting for 64% of the variation, whereas BMI did not contribute further to explaining changes in GHBP.This suggests a physiological pathway involving both GHBP (the soluble fraction of GH receptor) and leptin. Thus,we might speculate that leptin could be the signal that induces the related nutritional changes observed in GHBP/GH receptor expression.MH - Carrier Proteins|*MEMH - Nutritional Status|*MH - Proteins|*MESO - J Clin Endocrinol Metab 1998 Jun; 83(6):2006-11DP - 1998 JunTA - J Clin Endocrinol MetabPG - 2006-11IP - 6VI - 83UI - 9828937246
AU - Bjarnason R
AU - Boguszewski M
AU - Dahlgren J
AU - Gelander L
AU - Kristr÷m B
AU - Rosberg S
AU - Carlsson B
AU - Albertsson Wikland K
AU - Carlsson LMTI - Leptin levels are strongly correlated with those of GH-binding protein in prepubertal children.AB - OBJECTIVE: Nutritional status is an important determinant of growth, and previous studies have indicated that this is due, at least in part, to an increased target-tissue sensitivity to GH. An attractive candidate for mediating this effect is leptin, a hormone secreted by the adipose tissue. The aim of this study was to investigate if there was a connection between GH-binding protein (GHBP) and leptin. DESIGN AND METHODS: We investigated the relationship between serum levels of leptin and those of GHBP in 229 prepubertal children. These included 107 healthy children with normal GH secretion, 55 GH-deficient (GHD) children and 55 children born small for gestational age (SGA) sampled on one occasion for GHBP and leptin, and 12 healthy children followed longitudinally at monthly interval for 1 year.RESULTS: In the healthy children and in those born SGA,the serum concentration of GHBP was positively correlated with that of leptin (r = 0.65, P < 0.001; r = 0.74, P <0.001 respectively). There was no correlation between GHBP and leptin in the group of children with GHD (r = 0.27,not significant). This means that leptin alone explained 42% of the variation of GHBP in the healthy group and 55%in the SGA group. The correlation remained after adjustment for body mass index and age in the healthy children (r = 0.57, P < 0.0001, r2 = 0.33) and for children born SGA (r = 0.74, P < 0.0001, r2 = 0.55). There was a positive correlation between the intra-individual monthly changes in GHBP and changes in leptin respectively, in the 12 healthy children followed longitudinally, the mean of the correlation coefficients was 0.38 (median = 0.29; range 0.03 to 0.86;P < 0.05). CONCLUSIONS: There was a highly significant correlation between serum levels of leptin and those of GHBP, except in children with GHD. The possibility that leptin could mediate the effects of body fat mass on GH sensitivity, therefore, merits further investigation.MH - Carrier Proteins|*BLMH - Proteins|*MESO - Eur J Endocrinol 1997 Jul; 137(1):68-73DP - 1997 JulTA - Eur J EndocrinolPG - 68-73IP - 1VI - 137UI - 9738622047
AU - Schffler A
AU - Palitzsch KD
AU - Watzlawek E
AU - Drobnik W
AU - Schwer H
AU - Sch÷lmerich J
AU - Schmitz GTI - Frequency and significance of the A-->G (-3826) polymorphism in the promoter of the gene for uncoupling protein-1 with regard to metabolic parameters and adipocyte transcription factor binding in a large population-based Caucasian cohort.AB - BACKGROUND: The recently described A-->G (-3826) point mutation within the distal region of the UCP-1 promoter is possibly involved in the development of obesity, diabetes and related metabolic disorders. It was the aim of this study to examine the allelic frequency and the prevalence of the three UCP-1 genotypes in a broad caucasian cohort and to investigate the significance of this polymorphism for obesity and diabetes. METHODS: 1020 subjects were randomly chosen from 6450 participants in the Diabetomobile Study.The UCP-1 genotype was determined by genomic PCR and Bcl-I-RFLP analysis in 1020 subjects and tested for association with a variety of metabolic parameters. In addition, the influence of this mutation on adipocyte nuclear factor binding was investigated by electrophoretic mobility shift assays (EMSA). RESULTS: The genotype frequencies in 1020 subjects were: AA genotype, 57.0%; AG genotype, 35.4%; GG genotype, 7.6%; with allelic frequencies of 0.75 for allele A and 0.25 for allele G. No significant differences between the genotypes and age, gender, BMI, leptin, glucose,fasting insulin, C-peptide, HbA1c, diabetes manifestation,total cholesterol, and HDL cholesterol were found. Analysis of the Trp64Arg polymorphism of the beta3-adrenergic receptor in a subgroup of 343 subjects revealed no additive effect to the UCP-1 polymorphism. An yet unknown adipocyte-specific factor of nuclear extracts from 3T3-L1 adipocytes during differentiation is able to bind specifically to the distal UCP-1 promoter region and this binding ability can not be abolished by the mutation. CONCLUSIONS: We determined the genotype and allelic frequency of the UCP-1 promoter polymorphism in the largest known population-based study.The results from genotyping demonstrate clearly that this polymorphism does not play a major role in the pathogenesis obesity and diabetes. A yet unknown adipocyte derived and differentiation-dependent regulated transcription factor is able to bind to the distal UCP-1 promoter surrounding -3826 bp. This binding is not affected by presence of the mutation.MH - Carrier Proteins|*GEMH - Caucasoid Race|*GEMH - Diabetes Mellitus, Non-Insulin-Dependent|*GEMH - Membrane Proteins|*GEMH - Obesity|*GEMH - Polymorphism (Genetics)|*SO - Eur J Clin Invest 1999 Sep; 29(9):770-9DP - 1999 SepTA - Eur J Clin InvestPG - 770-9IP - 9VI - 29UI - 9939836748
AU - Cao GY
AU - Considine RV
AU - Lynn RBTI - Leptin receptors in the adrenal medulla of the rat.AB - Leptin is the protein product of the recently cloned obesity gene. Leptin receptor mRNA is found in a number of central and peripheral locations. The hypothalamus is a presumed site of action. However, little is known about the specific locations of the receptor in peripheral organs. Epinephrine has potent anorectic effects and can cause weight loss by a variety of mechanisms. Excretion of epinephrine is reduced in the ob/ob mouse, which lacks leptin, suggesting an effect by leptin on the adrenal medulla. In the current study, the presence of the leptin receptor was identified on epinephrine-secreting cells in the adrenal medulla. Immunohistochemical studies found dense leptin receptor-like immunoreactivity in the adrenal medulla with no labeling in the adrenal cortex. Double immunofluorescent labeling confirmed that the leptin receptor was present on cells that were phenylethanolamine N-methyltransferase-like immunoreactive and therefore were epinephrine-secreting cells. Leptin receptor mRNA in the adrenal medulla was detected by reverse transcriptase-polymerase chain reaction, with the majority of the mRNA coding for the short isoform (Ob-Ra) of the receptor. Finally, autoradiography was performed using 125I-labeled leptin; specific binding was found in the adrenal medulla, with no specific binding in the adrenal cortex. These results suggest that leptin may have a direct effect on epinephrine-secreting cells in the adrenal medulla.Epinephrine may play a role in mediating the effects of leptin to reduce body weight.MH - Adrenal Medulla|*MEMH - Carrier Proteins|GE/*MESO - Am J Physiol 1997 Aug; 273(2 Pt 1):E448-52DP - 1997 AugTA - Am J PhysiolPG - E448-52IP - 2 Pt 1VI - 273UI - 9742345849
AU - Ceddia RB
AU - William WN Jr
AU - Lima FB
AU - Carpinelli AR
AU - Curi RTI - Pivotal role of leptin in insulin effects.AB - The OB protein, also known as leptin, is secreted by adipose tissue, circulates in the blood, probably bound to a family of binding proteins, and acts on central neural networks regulating ingestive behavior and energy balance. The two forms of leptin receptors (long and short forms) have been identified in various peripheral tissues, a fact that makes them possible target sites for a direct action of leptin.It has been shown that the OB protein interferes with insulin secretion from pancreatic islets, reduces insulin-stimulated glucose transport in adipocytes, and increases glucose transport, glycogen synthesis and fatty acid oxidation in skeletal muscle. Under normoglycemic and normoinsulinemic conditions, leptin seems to shift the flux of metabolites from adipose tissue to skeletal muscle. This may function as a peripheral mechanism that helps control body weight and prevents obesity. Data that substantiate this hypothesis are presented in this review.MH - Adipose Tissue|*MEMH - Insulin|*SEMH - Islets of Langerhans|*MEMH - Muscle, Skeletal|*MEMH - Proteins|*PHSO - Braz J Med Biol Res 1998 Jun; 31(6):715-22DP - 1998 JunTA - Braz J Med Biol ResPG - 715-22IP - 6VI - 31UI - 9836397150
AU - Saito K
AU - Tobe T
AU - Minoshima S
AU - Asakawa S
AU - Sumiya J
AU - Yoda M
AU - Nakano Y
AU - Shimizu N
AU - Tomita MTI - Organization of the gene for gelatin-binding protein (GBP28).AB - GBP28 is a novel human plasma gelatin-binding protein that is encoded by apM1 mRNA, expressed specifically in adipose tissue. Three overlapping clones (two lambda clones and one BAC clone) containing the human plasma gelatin-binding protein (GBP28) gene were isolated and characterized. The GBP28 gene spans 16kb and is composed of three exons from 18bp to 4277bp in size with consensus splice sites. The sizes of the two introns were 0.8 and 12kb, respectively.The gene's regulatory sequences contain putative promoter elements, but no typical TATA box.The third exon of this gene contains a long 3'-untranslated sequence containing three Alu repeats. The exon-intron organization of this gene was very similar to that of obese gene, encoding leptin.We also report the chromosome mapping of this gene by fluorescence in situ hybridization (FISH) using a genomic DNA fragment as a probe. The GBP28 gene was located on human chromosome 3q27. The nucleotide sequence data reported in this paper will appear in the DDBJ/EMBL/GenBank nucleotide sequence databases with the accession numbers ABO12163, ABO12164 or ABO12165.MH - Carrier Proteins|*GESO - Gene 1999 Mar; 229(1-2):67-73DP - 1999 MarTA - GenePG - 67-73IP - 1-2VI - 229UI - 9919698451
AU - Kratzsch J
AU - Dehmel B
AU - Pulzer F
AU - Keller E
AU - Englaro P
AU - Blum WF
AU - Wabitsch MTI - Increased serum GHBP levels in obese pubertal children and adolescents: relationship to body composition, leptin and indicators of metabolic disturbances.AB - OBJECTIVE: The serum concentration of the high-affinity growth hormone-binding protein (GHBP) is increased in obesity but the mechanisms are poorly understood. This study assessed the physiological mechanisms involved in the regulation of GHBP in adiposity. SUBJECTS AND MEASUREMENTS: We tested a number of obesity specific parameters for their association with GHBP. In this study, 199 normal or overweight children and adolescents (101 boys, 98 girls, aged (mean +/- s.d.): 13.7 +/- 2.3 y) underwent an anthropometric evaluation (circumference measurements and bioimpedance analysis) combined with blood withdrawal for the measurement of insulin-like growth factor-I (IGF-I), insulin, leptin and GHBP (by specific RIA), uric acid, triglycerides and cholesterol.RESULTS: By linear regression analysis GHBP correlated significantly (P < 0.001) with percent body fat mass (r = 0.71), waist (r = 0.73) and hip (r = 0.69) circumference,weight (r = 0.61) waist hip ratio (WHR) (r = 0.54), as well as with the serum concentrations of leptin (r = 0.64), uric acid (r = 0.54), insulin (r = 0.45), LDL-cholesterol (r = 0.43), cholesterol (r =0.33), LDL/HDL ratio (r = 0.47), triglycerides (r = 0.30) and with height standard deviations scores (SDS) (r = 0.23). Age, gender and pubertal stage had no impact on GHBP. In a multiple regression analysis containing age and gender, as well as the anthropometric variables, percent fat mass and waist circumference, as independent variables, associations between GHBP and leptin (P < 0.001), cholesterol (P < 0.01), LDL-cholesterol (P = 0.01), LDL/HDL ratio (P = 0.02), triglycerides (P = 0.01) remained significant. In a final model using the stepwise analysis involving age, gender and all the independent predictors of GHBP, waist circumference (P < 0.001), accounted for 49.5% of the 60.0% total variability in GHBP, while the implication of leptin (P < 0.001), age (P < 0.01) and cholesterol (P < 0.05) increased the predicted variability for 7.5%, 1.9%, and 1.0%, respectively. Serum GHBP was significantly reduced in a subgroup of 104 overweight or obese patients during a diet-induced weight loss programme,the coefficient of correlation between GHBP and leptin after (r = 0.45, P < 0.001) and before weight reduction (r = 0.41, P < 0.001) were comparable. CONCLUSION: Waist circumference, an indicator of abdominal body fat mass,is a major determinant of GHBP levels during childhood,while leptin may be one candidate for a signal linking adipocytes to the growth hormone receptor related GHBP release. Additionally, elevated serum levels of GHBP may reflect metabolic disturbances of adiposity.MH - Aging|*BL/ME/PHMH - Body Composition|*MH - Carrier Proteins|*BLMH - Obesity|*BL/ME/PPMH - Proteins|*MEMH - Puberty|*BL/ME/PHSO - Int J Obes Relat Metab Disord 1997 Dec; 21(12):1130-6DP - 1997 DecTA - Int J Obes Relat Metab DisordPG - 1130-6IP - 12VI - 21UI - 9808776052
AU - Williams LM
AU - Adam CL
AU - Mercer JG
AU - Moar KM
AU - Slater D
AU - Hunter L
AU - Findlay PA
AU - Hoggard NTI - Leptin receptor and neuropeptide Y gene expression in the sheep brain.AB - Leptin, a protein secretory product of adipocytes, is important in appetite control, energy balance and reproduction. In rodents, the physiological effects of leptin are centrally mediated, in part via the neuropeptide Y (NPY) system in the hypothalamus. The role of leptin in ruminants, where appropriate nutrition and reproductive status are of major economic concern, is largely unknown. To elucidate the function of leptin in sheep we have investigated putative sites of action for leptin in the brain and pituitary gland using both in-situ hybridization to detect expression of the signalling form of the leptin receptor (OB-Rb) and in-vitro autoradiography using (125I)leptin to detect sites of specific leptin binding. OB-Rb gene expression occurred in the hippocampus, cerebral cortex, preoptic area, stria terminalis and choroid plexus, and within the hypothalamus in the paraventricular (PVN), ventromedial (VHM) and arcuate (ARC) nuclei. OB-Rb gene expression in the ovine pituitary gland was not detected by in-situ hybridization. Sites of OB-Rb and NPY gene expression were compared using both in-situ hybridization on adjacent sections containing the arcuate and ventromedial nuclei, and dual in-situ hybridization on sections containing these areas. In serial sections,OB-Rb expression was found to correspond closely with that of NPY over the arcuate nuclei. Using dual in-situ hybridization,NPY expressing neurones in the arcuate nuclei were also positive for OB-Rb gene expression. Therefore, it appears that leptin may partly act via OB-Rb located on NPY neurones in the sheep hypothalamus as in the rodent.MH - Brain|*MEMH - Carrier Proteins|*GEMH - Gene Expression|*MH - Neuropeptide Y|*GESO - J Neuroendocrinol 1999 Mar; 11(3):165-9DP - 1999 MarTA - J NeuroendocrinolPG - 165-9IP - 3VI - 11UI - 9921599453
AU - Rosenblum CI
AU - Tota M
AU - Cully D
AU - Smith T
AU - Collum R
AU - Qureshi S
AU - Hess JF
AU - Phillips MS
AU - Hey PJ
AU - Vongs A
AU - Fong TM
AU - Xu L
AU - Chen HY
AU - Smith RG
AU - Schindler C
AU - Van der Ploeg LHTI - Functional STAT 1 and 3 signaling by the leptin receptor (OB-R); reduced expression of the rat fatty leptin receptor in transfected cells.AB - The leptin receptor (OB-R) bears homology to members of the class I cytokine receptor family. We demonstrate that leptin binding to OB-R stimulates formation of STAT-1 and STAT-3 complexes, thereby defining transcriptional motifs for genes that are under leptin control. Transfected fa OB-R bound leptin with equal affinity to that of wild type OB-R. fa OB-R abundance was about 7 fold reduced compared to control cells. Surprisingly, the low level of fa OB-R is fully capable of activating the STAT signal transduction pathway. We discuss plausible explanations for the obese phenotype in Zucker fatty rats.MH - Carrier Proteins|*BI/*PHMH - DNA-Binding Proteins|*MEMH - Signal Transduction|*MH - Trans-Activators|*MESO - Endocrinology 1996 Nov; 137(11):5178-81DP - 1996 NovTA - EndocrinologyPG - 5178-81IP - 11VI - 137UI - 9705066854
AU - Hamann A
AU - Matthaei STI - Regulation of energy balance by leptin.AB - The high prevalence of obesity and its well documented association with the cardiovascular risk factors diabetes mellitus, dyslipidemia and hypertension represents a major problem for the general health status of industrialized societies. Although numerous studies have shown that genetic factors have a major influence on the regulation of energy homeostasis and the susceptibility to obesity, the genes and predisposing mutations involved are insufficiently understood. Among several known rodent models of obesity due to single gene mutations, mice homozygous for the obese (ob) gene exhibit massive early-onset obesity, hyperphagia,non-insulin-dependent diabetes mellitus, defective thermoregulation and infertility. Recently the ob gene was identified by positional cloning and shown to be mutated in ob/ob mice.Leptin, the product of the ob gene, is a 167-amino acid secreted protein that is synthesized exclusively in adipose tissue. With the exception of ob/ob mice, circulating plasma leptin is elevated in obesity. Administration of recombinant leptin to ob/ob mice reduces fat mass, food intake, hyperglycemia and hyperinsulinemia. The various effects of the hormone are mediated by leptin receptors expressed at high levels in the hypothalamus, but also in several other non-neuronal tissues. A mutation in the leptin receptor gene is responsible for the obese phenotype of db/db mice. Plasma leptin in humans is positively correlated with body fat mass, suggesting that leptin resistance rather than leptin deficiency is a common feature of human obesity. This review briefly summarizes the current status of the rapidly growing evidence that leptin plays an important role in the regulation of body weight and fat deposition.MH - Adipocytes|*MEMH - Carrier Proteins|GE/*MEMH - Energy Metabolism|*PHMH - Obesity|*ET/GE/MEMH - Proteins|AD/BI/*MESO - Exp Clin Endocrinol Diabetes 1996; 104(4):293-300DP - 1996TA - Exp Clin Endocrinol DiabetesPG - 293-300IP - 4VI - 104UI - 9704147455
AU - Cohen B
AU - Novick D
AU - Rubinstein MTI - Modulation of insulin activities by leptin [see comments]AB - Leptin mediates its effects on food intake through the hypothalamic form of its receptor OB-R. Variants of OB-R are found in other tissues, but their function is unknown.Here, an OB-R variant was found in human hepatic cells.Exposure of these cells to leptin, at concentrations comparable with those present in obese individuals, caused attenuation of several insulin-induced activities, including tyrosine phosphorylation of the insulin receptor substrate-1 (IRS-1), association of the adapter molecule growth factor receptor-bound protein 2 with IRS-1, and down-regulation of gluconeogenesis.In contrast, leptin increased the activity of IRS-1-associated phosphatidylinositol 3-kinase. These in vitro studies raise the possibility that leptin modulates insulin activities in obese individuals.MH - Insulin|*PDMH - Proteins|ME/*PDSO - Science 1996 Nov; 274(5290):1185-8DP - 1996 NovTA - SciencePG - 1185-8IP - 5290VI - 274UI - 9705360456
AU - Schwartz MW
AU - Seeley RJ
AU - Campfield LA
AU - Burn P
AU - Baskin DGTI - Identification of targets of leptin action in rat hypothalamus.AB - The hypothesis that leptin (OB protein) acts in the hypothalamus to reduce food intake and body weight is based primarily on evidence from leptin-deficient, ob/ob mice. To investigate whether leptin exerts similar effects in normal animals,we administered leptin intracerebroventricularly (icv) to Long-Evans rats. Leptin administration (3.5 microg icv)at the onset of nocturnal feeding reduced food intake by 50% at 1 h and by 42% at 4 h, as compared with vehicle-treated controls (both P < 0.05). To investigate the basis for this effect, we used in situ hybridization (ISH) to determine whether leptin alters expression of hypothalamic neuropeptides involved in energy homeostasis. Two injections of leptin (3.5 microg icv) during a 40 h fast significantly decreased levels of mRNA for neuropeptide Y (NPY, which stimulates food intake) in the arcuate nucleus (-24%) and increased levels of mRNA for corticotrophin releasing hormone (CRH, an inhibitor of food intake) in the paraventricular nucleus (by 38%) (both P < 0.05 vs. vehicle-treated controls). To investigate the anatomic basis for these effects, we measured leptin receptor gene expression in rat brain by ISH using a probe complementary to mRNA for all leptin receptor splice variants. Leptin receptor mRNA was densely concentrated in the arcuate nucleus, with lower levels present in the ventromedial and dorsomedial hypothalamic nuclei and other brain areas involved in energy balance.These findings suggest that leptin action in rat hypothalamus involves altered expression of key neuropeptide genes, and implicate leptin in the hypothalamic response to fasting.MH - Corticotropin-Releasing Hormone|GE/*MEMH - Eating|*DEMH - Gene Expression Regulation|*DEMH - Hypothalamus|AH/*DE/MEMH - Neuropeptide Y|GE/*MEMH - Proteins|*PDSO - J Clin Invest 1996 Sep; 98(5):1101-6DP - 1996 SepTA - J Clin InvestPG - 1101-6IP - 5VI - 98UI - 9637965857
AU - Considine RV
AU - Caro JFTI - Leptin: genes, concepts and clinical perspective.AB - Obesity is a complex disease which results from the interaction of multiple genes and the environment. The recently discovered genes for leptin (ob gene) and the leptin receptor appear to play a major regulatory role in body energy balance and adipose tissue deposition. Furthermore, defects in the ob gene and leptin receptor gene have been demonstrated to be the cause of obesity in several rodent models. These observations raise the possibility that human obesity may also be due to defects in the leptin signal system. This review will summarize the current findings on the ob gene,leptin and the leptin receptor in both animals and humans.These observations will be discussed in the context of potential defects in the system and the possibility that these defects result in obesity in humans.MH - Carrier Proteins|*MEMH - Obesity|*/BL/GE/MEMH - Proteins|*/AN/GE/MEMH - Receptors, Cytokine|*MESO - Horm Res 1996; 46(6):249-56DP - 1996TA - Horm ResPG - 249-56IP - 6VI - 46UI - 9713739758
AU - Bennett BD
AU - Solar GP
AU - Yuan JQ
AU - Mathias J
AU - Thomas GR
AU - Matthews WTI - A role for leptin and its cognate receptor in hematopoiesis.AB - BACKGROUND. Hematopoiesis entails the production of multiple blood cell lineages throughout the lifespan of the organism.This is accomplished by the regulated expansion and differentiation of hematopoietic precursors that originate from self-renewing hematopoietic stem cells. Studies of lineage commitment and proliferation have shown that the cytokine family of growth factors plays an important role in hematopoietic differentiation. However, in hematopoiesis, as in most self-renewing biological systems, the molecules that regulate the stem cells directly remain largely unknown. In this study, we have undertaken a search for novel cytokines that may influence the fate of hematopoietic stem cells.RESULTS. We have cloned three splice variants of a novel cytokine receptor from human hematopoietic stem cells expressing the CD34 antigen, one of which is identical to the leptin receptor. Expression analysis revealed that the leptin receptor is expressed in both human and murine hematopoietic stem cell populations, and that leptin is expressed by hematopoietic stroma. We show that leptin provides a proliferative signal in hematopoietic cells. Importantly, we demonstrate that leptin provides a proliferative signal in BAF-3 cells and increases the proliferation of hematopoietic stem cell populations. The proliferative effects of leptin seem to be at the level of a multilineage progenitor, as shown by increased myelopoiesis, erythropoiesis and lymphopoiesis.Analysis of db/db mice, in which the leptin receptor is truncated, revealed that the steady-state levels of peripheral blood B cells and CD4-expressing T cells were dramatically reduced, demonstrating that the leptin pathway plays an essential role in lymphopoiesis. Colony assays performed using marrow from db/db and wild-type mice indicated that db/db marrow has a deficit in lymphopoietic progenitors;furthermore, db/db mice are unable to fully recover the lymphopoietic population following irradiation insult, and although the levels of peripheral blood erythrocytes are normal in db/db mice, spleen erythrocyte production is severely compromized. CONCLUSIONS. We have discovered that leptin and its cognate receptor constitute a novel hematopoietic pathway that is required for normal lymphopoiesis.This pathway seems to act at the level of the hematopoietic stem/progenitor cell, and may well also impact upon erythropoiesis,particularly in anemic states that may require output from the spleen. These findings offer a new perspective on the role of the fat cell in hematopoiesis.MH - Carrier Proteins|GE/*PHMH - Hematopoiesis|*PHMH - Proteins|*PHSO - Curr Biol 1996 Sep; 6(9):1170-80DP - 1996 SepTA - Curr BiolPG - 1170-80IP - 9VI - 6UI - 9639896859
AU - Gainsford T
AU - Willson TA
AU - Metcalf D
AU - Handman E
AU - McFarlane C
AU - Ng A
AU - Nicola NA
AU - Alexander WS
AU - Hilton DJTI - Leptin can induce proliferation, differentiation, and functional activation of hemopoietic cells.AB - Many cytokines exert their biological effect through members of the hemopoietin receptor family. Using degenerate oligonucleotides to the common WSXWS motif, we have cloned from human hemopoietic cell cDNA libraries various forms of the receptor that was recently shown to bind the obesity hormone, leptin.mRNAs encoding long and short forms of the human leptin receptor were found to be coexpressed in a range of human and murine hemopoietic organs, and a subset of cells from these tissues bound leptin at the cell surface. Ectopic expression in murine Ba/F3 and M1 cell lines revealed that the long, but not the short, form of the leptin receptor can signal proliferation and differentiation, respectively.In cultures of murine or human marrow cells, human leptin exhibited no capacity to stimulate cell survival or proliferation,but it enhanced cytokine production and phagocytosis of Leishmania parasites by murine peritoneal macrophages. Our data provide evidence that, in addition to its role in fat regulation, leptin may also be able to regulate aspects of hemopoiesis and macrophage function.MH - Carrier Proteins|GE/*MEMH - Hematopoietic Stem Cells|*CY/DE/MEMH - Proteins|*PDSO - Proc Natl Acad Sci U S A 1996 Dec; 93(25):14564-8DP - 1996 DecTA - Proc Natl Acad Sci U S APG - 14564-8IP - 25VI - 93UI - 9712142660
AU - Caro JF
AU - Kolaczynski JW
AU - Nyce MR
AU - Ohannesian JP
AU - Opentanova I
AU - Goldman WH
AU - Lynn RB
AU - Zhang PL
AU - Sinha MK
AU - Considine RVTI - Decreased cerebrospinal-fluid/serum leptin ratio in obesity:a possible mechanism for leptin resistance [see comments]AB - BACKGROUND: A receptor for leptin has been cloned from the choroid plexus, the site of cerebrospinal-fluid (CSF)production and the location of the blood/cerebrospinal-fluid barrier. Thus, this receptor might serve as a transporter for leptin. We have studied leptin concentrations in serum and (CSF). METHODS AND FINDINGS: We demonstrated by radioimmunoassay and western blot the presence of leptin in human CSF. We then measured leptin in CSF and serum in 31 individuals with a wide range of bodyweight. Mean serum leptin was 318% higher in 8 obese (40.2 [SE 8.6] ng/mL) than in 23 lean individuals (9.6 [1.5] ng/mL, p < 0.0005). However,the CSF leptin concentration in obese individuals (0.337 [0.04] ng/mL) was only 30% higher than in lean people (0.259 [0.26] ng/mL, p < 0.1). Consequently, the leptin CSF/serum ratio in lean individuals (0.047 [0.010]) was 4.3-fold higher than that in obese individuals (0.011 [0.002], p < 0.05). The relation between CSF leptin and serum leptin was best described by a logarithmic function (r = 0 x 52, p < 0.01). INTERPRETATION: Our data suggest that leptin enters the brain by a saturable transport system.The capacity of leptin transport is lower in obese individuals,and may provide a mechanism for leptin resistance.MH - Obesity|*MEMH - Proteins|*ME/PHSO - Lancet 1996 Jul; 348(9021):159-61DP - 1996 JulTA - LancetPG - 159-61IP - 9021VI - 348UI - 9629529761
AU - Malik KF
AU - Young WS 3rdTI - Localization of binding sites in the central nervous system for leptin (OB protein) in normal, obese (ob/ob), and diabetic (db/db) C57BL/6J mice.AB - Leptin (OB protein) fused to the FLAG epitope and a kinase recognition site was expressed in bacteria, immunopurified,and phosphorylated using [gamma-(33)P] ATP. The resulting probe was used to characterize the distribution of leptin binding sites within brain sections of normal, ob/ob, and db/db C57BL/6J male mice. Leptin binding sites were found in leptomeninges and choroid plexus. Leptin binding within the choroid plexus is slightly elevated in ob/ob mice when compared to normal males (p<0.05). Binding of leptin by the choroid plexus of db/db male mice is lower than in normal males (p<0.05), but normally distributed. Based on the association and dissociation rates of leptin binding on tissue sections, we estimate the K(D) of the choroid plexus site at 0.25X10(-9) M. From our results, we hypothesize that the binding of leptin to its site may cause the release or transport of uncharacterized factor(s) into the cerebral spinal fluid (CSF) to affect neuronal populations controlling feeding and metabolism.MH - Central Nervous System|CH/*MEMH - Diabetes Mellitus|GE/*MEMH - Mice, Obese|*MEMH - Obesity|GE/*MEMH - Proteins|*MESO - Endocrinology 1996 Apr; 137(4):1497-500DP - 1996 AprTA - EndocrinologyPG - 1497-500IP - 4VI - 137UI - 9617859062
AU - Houseknecht KL
AU - Mantzoros CS
AU - Kuliawat R
AU - Hadro E
AU - Flier JS
AU - Kahn BBTI - Evidence for leptin binding to proteins in serum of rodents and humans: modulation with obesity.AB - Many hormones circulate bound to serum proteins that modulate ligand bioactivity and bioavailability. To understand the biology of leptin action, we investigated the presence of leptin binding proteins in serum. 125I-labeled leptin binds competitively to at least three serum macromolecules with molecular masses of approximately 85, approximately 176, and approximately 240 kDa in rodents and approximately 176 and approximately 240 kDa in humans. The ability to bind appears to involve sulfhydryl/disulfide interactions because it is inhibited under reducing conditions. When serum is added to recombinant 125I-leptin, there is a shift in sedimentation of 125I-leptin as analyzed by sucrose gradient centrifugation from approximately S1.9 to approximately S4.3. This shift is markedly attenuated in serum from obese mice (ob/ob, db/db, brown-fat ablated, gold-thioglucose treated, high-fat fed) compared with that from nonobese controls. The size distribution of endogenous serum leptin as determined by radioimmunoassay (RIA) after sucrose gradient centrifugation is also consistent with saturation of binding in hyperleptinemic obesity. In humans, free leptin increases with BMI. Thus, in lean rodents and humans a large proportion of leptin circulates bound to several serum proteins. Free leptin is increased in serum of obese subjects, which may alter leptin bioactivity, transport, and/or clearance.MH - Blood Proteins|IP/*MEMH - Obesity|*BLMH - Proteins|IP/*MESO - Diabetes 1996 Nov; 45(11):1638-43DP - 1996 NovTA - DiabetesPG - 1638-43IP - 11VI - 45UI - 9702018863
AU - Igel M
AU - Becker W
AU - Herberg L
AU - Joost HGTI - Evidence that reduced leptin levels, but not an aberrant sequence of leptin or its receptor, contribute to the obesity syndrome in NON mice.AB - NON mice exhibit a polygenic syndrome of mild obesity which is less pronounced than that of the ob and db strains. Here, we have shown that the syndrome is accompanied by a rise in leptin mRNA levels in adipose tissue, corresponding with the increase in adipose tissue mass. Surprisingly,levels of the leptin protein in adipose tissue and serum were comparable to those of lean control animals (BL57/Ksj-+/+), and markedly lower than those in db/db-mice. The coding regions of the cDNA sequences of both leptin and the leptin receptor from NON mice were identical with those of the wild-type sequences. We suggested that low levels of leptin in adipose tissue and serum contribute to the obesity of NON mice.MH - Carrier Proteins|*GE/*MEMH - Obesity|*GE/MEMH - Proteins|*GE/*MESO - Horm Metab Res 1996 Dec; 28(12):669-73DP - 1996 DecTA - Horm Metab ResPG - 669-73IP - 12VI - 28UI - 9716584664
AU - Leclercq Meyer V
AU - Considine RV
AU - Sener A
AU - Malaisse WJTI - Do leptin receptors play a functional role in the endocrine pancreas?AB - It was recently speculated that leptin may exert a direct inhibitory effect upon insulin release from the pancreatic B-cell. This proposal meets, however, with two objections.First, although the message for leptin receptors is indeed detected in rat pancreatic islets, the short form of this receptor, for which no signalling function is known, represents the major species present in islet cells. Second, in the isolated perfused rat pancreas, leptin (1.0 nM) fails to affect the release of either insulin or glucagon.MH - Carrier Proteins|GE/*MEMH - Insulin|*SEMH - Pancreas|*MEMH - Proteins|*MESO - Biochem Biophys Res Commun 1996 Dec; 229(3):794-8DP - 1996 DecTA - Biochem Biophys Res CommunPG - 794-8IP - 3VI - 229UI - 9711565965
AU - Kallen CB
AU - Lazar MATI - Antidiabetic thiazolidinediones inhibit leptin (ob) gene expression in 3T3-L1 adipocytes.AB - Lack of leptin (ob) protein causes obesity in mice. The leptin gene product is important for normal regulation of appetite and metabolic rate and is produced exclusively by adipocytes. Leptin mRNA was induced during the adipose conversion of 3T3-L1 cells, which are useful for studying adipocyte differentiation and function under controlled conditions. We studied leptin regulation by antidiabetic thiazolidinedione compounds, which are ligands for the adipocyte-specific nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) that regulates the transcription of other adipocyte-specific genes. Remarkably,leptin gene expression was dramatically repressed within a few hours after thiazolidinedione treatment. The ED50 for inhibition of leptin expression by the thiazolidinedione BRL49653 was between 5 and 50 nM, similar to its Kd for binding to PPARgamma. The relatively weak, nonthiazolidinedione PPAR activator WY 14,643 also inhibited leptin expression,but was approximately 1000 times less potent than BRL49653.These results indicate that antidiabetic thiazolidinediones down-regulate leptin gene expression with potencies that correlate with their abilities to bind and activate PPARgamma.MH - Adipocytes|*DE/MEMH - Gene Expression Regulation|*DEMH - Hypoglycemic Agents|ME/*PDMH - Obesity|*GEMH - Proteins|*GEMH - Pyrimidines|ME/*PDMH - Thiazoles|ME/*PDSO - Proc Natl Acad Sci U S A 1996 Jun; 93(12):5793-6DP - 1996 JunTA - Proc Natl Acad Sci U S APG - 5793-6IP - 12VI - 93UI - 9623404266
AU - Iida M
AU - Murakami T
AU - Ishida K
AU - Mizuno A
AU - Kuwajima M
AU - Shima KTI - Substitution at codon 269 (glutamine --> proline) of the leptin receptor (OB-R) cDNA is the only mutation found in the Zucker fatty (fa/fa) rat.AB - We recently cloned one of spliced variant forms of rat leptin receptor (OB-R), which contains a short intracellular domain, and found obese-phenotype-linked nucleotide alteration in the extracellular domain of the cDNA from the Zucker (fa/fa) rat, which results in a glutamine269 to proline269 amino acid substitution. Reported herein are the cloning and sequencing of another spliced variant forms of rat OB-R cDNA with a long intracellular domain. Both forms of OB-R cDNA share the same extracellular domain. In the Zucker (fa/fa) rat, no changes in either the gene structure nor in the nucleotide sequence of the long intracellular domain were observed. However, the expression level of OB-R mRNA in the brain of Zucker (fa/fa) rat was higher than for lean littermates. These facts suggest that the substitution at codon 269 of the OB-R cDNA represents the crucial mutation which results in the obese phenotype of Zucker (fa/fa) rat.MH - Carrier Proteins|CH/*GEMH - Glutamine|*MH - Obesity|*GEMH - Point Mutation|*MH - Proline|*MH - Rats, Zucker|*GESO - Biochem Biophys Res Commun 1996 Jul; 224(2):597-604DP - 1996 JulTA - Biochem Biophys Res CommunPG - 597-604IP - 2VI - 224UI - 9629553167
AU - Mercer JG
AU - Hoggard N
AU - Williams LM
AU - Lawrence CB
AU - Hannah LT
AU - Trayhurn PTI - Localization of leptin receptor mRNA and the long form splice variant (Ob-Rb) in mouse hypothalamus and adjacent brain regions by in situ hybridization.AB - Expression of the leptin receptor gene has been examined in mouse hypothalamus and other brain regions by in situ hybridization. With a probe recognizing all the known splice variants, receptor mRNA was evident in several brain regions (cortex, hippocampus, thalamus), with strong expression in the hypothalamus (arcuate, ventromedial, paraventricular and ventral premammillary nuclei), choroid plexus and leptomeninges.A probe specific to the long splice variant of the leptin receptor (Ob-Rb), containing the putative intracellular signaling domain, again revealed strong expression in the hypothalamus; there was, however, minimal hybridization to choroid plexus and leptomeninges. These results indicate that the hypothalamus is a key site of leptin action, although other brain regions are also targeted.MH - Alternative Splicing|*MH - Brain|*MEMH - Carrier Proteins|BI/*GEMH - Hypothalamus|*MESO - FEBS Lett 1996 Jun; 387(2-3):113-6DP - 1996 JunTA - FEBS LettPG - 113-6IP - 2-3VI - 387UI - 9624450568
AU - Lynn RB
AU - Cao GY
AU - Considine RV
AU - Hyde TM
AU - Caro JFTI - Autoradiographic localization of leptin binding in the choroid plexus of ob/ob and db/db mice.AB - The obese gene product, leptin, is synthesized in adipose tissue and is a circulating factor regulating body weight.To identify the location of leptin receptors in the brain we have performed an autoradiographic study of the binding of [(125)I]leptin to frozen sections of mouse brain. Dense specific binding of [(125)I]leptin was found only in the choroid plexus which is located in the dorsal part of the third ventricle and lateral ventricles. Specific binding of [(125)I]leptin was found the ob/ob and db/db mice. These findings further our understanding of the sites and mechanism of action of leptin on brain centers regulating body weight.MH - Brain|*MEMH - Carrier Proteins|*MEMH - Obesity|*GE/*MEMH - Obesity in Diabetes|GE/*MEMH - Proteins|*MESO - Biochem Biophys Res Commun 1996 Feb; 219(3):884-9DP - 1996 FebTA - Biochem Biophys Res CommunPG - 884-9IP - 3VI - 219UI - 9621674569
AU - Tartaglia LA
AU - Dembski M
AU - Weng X
AU - Deng N
AU - Culpepper J
AU - Devos R
AU - Richards GJ
AU - Campfield LA
AU - Clark FT
AU - Deeds J
AU - et alTI - Identification and expression cloning of a leptin receptor,OB-R.AB - The ob gene product, leptin, is an important circulating signal for the regulation of body weight. To identify high affinity leptin-binding sites, we generated a series of leptin-alkaline phosphatase (AP) fusion proteins as well as [125I]leptin. After a binding survey of cell lines and tissues, we identified leptin-binding sites in the mouse choroid plexus. A cDNA expression library was prepared from mouse choroid plexus and screened with a leptin-AP fusion protein to identify a leptin receptor (OB-R). OB-R is a single membrane-spanning receptor most related to the gp130 signal-transducing component of the IL-6 receptor,the G-CSF receptor, and the LIF receptor. OB-R mRNA is expressed not only in choroid plexus, but also in several other tissues, including hypothalamus. Genetic mapping of the gene encoding OB-R shows that it is within the 5.1 cM interval of mouse chromosome 4 that contains the db locus.MH - Obesity|*GE/MEMH - Proteins|*GE/IP/MESO - Cell 1995 Dec; 83(7):1263-71DP - 1995 DecTA - CellPG - 1263-71IP - 7VI - 83UI - 9612812970
AU - Considine RV
AU - Considine EL
AU - Williams CJ
AU - Hyde TM
AU - Caro JFTI - The hypothalamic leptin receptor in humans: identification of incidental sequence polymorphisms and absence of the db/db mouse and fa/fa rat mutations.AB - Leptin-receptor gene expression in hypothalamic tissue from lean and obese humans was examined. The full-length leptin receptor, that is believed to transmit the leptin signal, is expressed in human hypothalamus. There was no difference in the amount of leptin-receptor mRNA In seven lean (BMI 23.3 +/- 0.9 kg/m2) and eight obese (BMI 36.9 +/- 1.5) subjects as determined by reverse transcription-polymerase chain reaction. A sequence polymorphism (A-->G) was detected at position 668 of the leptin receptor cDNA. This second base substitution changed a glutamine to an arginine at position 223 of the leptin receptor protein.Of 15 subjects analyzed, 11 were heterozygous for this base change and 3 were homozygous. The occurrence [correction of occurance] of the polymorphic allele(s) did not correlate with BMI in the population studied. The mutation responsible for the defect in the leptin receptor in db/db mice was not detected in any obese human, nor was the fa/fa rat mutation. These results provide evidence that the leptin resistance observed in obese humans is not due to a defect in the leptin receptor.MH - Carrier Proteins|*BI/*GEMH - Hypothalamus|*MEMH - Polymorphism (Genetics)|*SO - Diabetes 1996 Jul; 45(7):992-4DP - 1996 JulTA - DiabetesPG - 992-4IP - 7VI - 45UI - 9627048971
AU - Chua SC Jr
AU - White DW
AU - Wu Peng XS
AU - Liu SM
AU - Okada N
AU - Kershaw EE
AU - Chung WK
AU - Power Kehoe L
AU - Chua M
AU - Tartaglia LA
AU - Leibel RLTI - Phenotype of fatty due to Gln269Pro mutation in the leptin receptor (Lepr).AB - The rat fatty (fa) mutation produces profound obesity of early onset caused by hyperphagia, defective nonshivering thermogenesis, and preferential deposition of energy into adipose tissue. Genetic mapping studies indicate that fa and diabetes (db) are homologous loci in the rat and mouse genomes, respectively. It has been shown that db alleles carry mutations in the Lepr (leptin receptor) gene. This paper describes a point mutation in the fatty allele of Lepr. A nucleotide substitution at position 880 (A-->C)causes an amino acid substitution at position 269 (Gln-->Pro). The mutation generates a novel Msp I site that cosegregates with fa in 1,028 meioses examined in obese F2 progeny from two crosses (Bnx13M and WKYx13M) and is still segregating in three rat colonies. PCR-based mutagenesis was used to introduce the fa mutation into the mouse Lepr cDNA. Transient transfection studies indicate that the mutant Lepr cDNA has greatly reduced binding of leptin (Lep) at the cell surface. These data are strong evidence that the single nucleotide substitution in the fa allele of Lepr (Leprfa) is responsible for the obese phenotype.MH - Carrier Proteins|*GEMH - Obesity|*GEMH - Receptors, Cytokine|*MESO - Diabetes 1996 Aug; 45(8):1141-3DP - 1996 AugTA - DiabetesPG - 1141-3IP - 8VI - 45UI - 9631432972
AU - White DW
AU - Tartaglia LATI - Leptin and OB-R: body weight regulation by a cytokine receptor.AB - There has been intense recent interest in the molecules and pathways governing mammalian body weight regulation.Leptin (OB), an ancestral member of the cytokine family,is an adipocyte-secreted circulating hormone exhibiting weight regulatory properties. Recently, the leptin receptor (OB-R) was identified and shown to exhibit sequence homology and functional similarity to members of the class I cytokine receptor family. The mechanisms governing OB-R triggering and signal transduction have begun to be elucidated, providing new insight into the pathways controlling mammalian body weight homeostasis.MH - Body Weight|*MH - Carrier Proteins|*PHMH - Proteins|*PHSO - Cytokine Growth Factor Rev 1996 Dec; 7(4):303-9DP - 1996 DecTA - Cytokine Growth Factor RevPG - 303-9IP - 4VI - 7UI - 9717539573
AU - Hkansson ML
AU - Hulting AL
AU - Meister BTI - Expression of leptin receptor mRNA in the hypothalamic arcuate nucleus--relationship with NPY neurones.AB - The obese phentotype of ob/ob mice is linked to a mutation in the ob gene that results in expression of a truncated inactive protein. The ob gene product, leptin, is synthesized in adipose tissue and is a circulating factor that regulates body weight. Leptin receptors were recently cloned and a mutation in the leptin receptor gene in obese db/db mice was identified. Leptin receptor mRNA has been detected in brain, including hypothalamus, but the cellular localization has so far not been clarified. Here we report on the cellular localization of leptin receptor mRNA in the mouse brain using in situ hybridization. Strong hybridization was observed in the choroid plexus and hypothalamic arcuate nucleus.Weaker hybridization was detected in the hippocampal formation and in the cerebral cortex. Within the arcuate nucleus,cell bodies expressing leptin receptor mRNA were distributed in its ventromedial subdivision. Hybridization of semiadjacent sections with a probe to neuropeptide Y (NPY) showed a co-distribution of labelled cell bodies, suggesting the presence of leptin receptors on NPY-containing neurones.MH - Arcuate Nucleus|CY/*MEMH - Carrier Proteins|*BIMH - Neurons|*MEMH - Neuropeptide Y|*BIMH - Receptors, Cytokine|*BIMH - RNA, Messenger|*BISO - Neuroreport 1996 Nov; 7(18):3087-92DP - 1996 NovTA - NeuroreportPG - 3087-92IP - 18VI - 7UI - 9716639574
AU - Chua SC Jr
AU - Chung WK
AU - Wu Peng XS
AU - Zhang Y
AU - Liu SM
AU - Tartaglia L
AU - Leibel RLTI - Phenotypes of mouse diabetes and rat fatty due to mutations in the OB (leptin) receptor [see comments]AB - Mice harboring mutations in the obese (ob) and diabetes (db) genes display similar phenotypes, and it has been proposed that these genes encode the ligand and receptor,respectively, for a physiologic pathway that regulates body weight. The cloning of ob, and the demonstration that it encodes a secreted protein (leptin) that binds specifically to a receptor (OB-R) in the brain, have validated critical aspects of this hypothesis. Here it is shown by genetic mapping and genomic analysis that mouse db, rat fatty (a homolog of db), and the gene encoding the OB-R are the same gene.MH - Carrier Proteins|*GEMH - Diabetes Mellitus|*GEMH - Obesity|*GEMH - Receptors, Cytokine|*GESO - Science 1996 Feb; 271(5251):994-6DP - 1996 FebTA - SciencePG - 994-6IP - 5251VI - 271UI - 9617236075
AU - Cioffi JA
AU - Shafer AW
AU - Zupancic TJ
AU - Smith Gbur J
AU - Mikhail A
AU - Platika D
AU - Snodgrass HRTI - Novel B219/OB receptor isoforms: possible role of leptin in hematopoiesis and reproduction.AB - Hematopoietic development is a complex process that involves a large number of growth factors and cytokines. Many cytokines are known to act on more mature, lineage-restricted cells of the hematopoietic system. However, no specific factors have yet been identified that induce the expansion of the most primitive hematopoietic cells without also inducing differentiation. To search for such factors, we isolated novel cell lines from the yolk sac in order to identify genes important in early hematopoietic and endothelial development. This approach led to the discovery of B219,a sequence that is expressed in at least four isoforms in very primitive hematopoietic cell populations and which may represent a novel hemopoietin receptor. The recently published receptor for the obesity (ob) gene product (leptin)is an isoform of B219 with a nearly identical ligand binding domain. B219/obr is expressed in the yolk sac, early fetal liver, enriched hematopoietic stem cells and in a variety of lymphohematopoietic cell lines. B219/obr is also expressed at high levels in adult reproductive organs. B219/obr maps to human chromosome 1p32, a region syntenic with the recently reported location of obr on murine chromosome 4 (ref. 5).MH - Carrier Proteins|BI/*GEMH - Gonads|*PHMH - Hematopoietic Stem Cells|*PHMH - Receptors, Cytokine|BI/*GESO - Nat Med 1996 May; 2(5):585-9DP - 1996 MayTA - Nat MedPG - 585-9IP - 5VI - 2UI - 9620628676
AU - Chen H
AU - Charlat O
AU - Tartaglia LA
AU - Woolf EA
AU - Weng X
AU - Ellis SJ
AU - Lakey ND
AU - Culpepper J
AU - Moore KJ
AU - Breitbart RE
AU - Duyk GM
AU - Tepper RI
AU - Morgenstern JPTI - Evidence that the diabetes gene encodes the leptin receptor:identification of a mutation in the leptin receptor gene in db/db mice.AB - OB-R is a high affinity receptor for leptin, an important circulating signal for the regulation of body weight. We identified an alternatively spliced transcript that encodes a form of mouse OB-R with a long intracellular domain. db/db mice also produce this alternatively spliced transcript,but with a 106 nt insertion that prematurely terminates the intracellular domain. We further identified G --> T point mutation in the genomic OB-R sequence in db/db mice.This mutation generates a donor splice site that converts the 106 nt region to a novel exon retained in the OB-R transcript. We predict that the long intracellular domain form of OB-R is crucial for initiating intracellular signal transduction, and as a corollary, the inability to produce this form of OB-R leads to the severe obese phenotype found in db/db mice.MH - Carrier Proteins|*GEMH - Diabetes Mellitus, Insulin-Dependent|*GE/*MEMH - Point Mutation|*MH - Proteins|*MEMH - Receptors, Cytokine|*GESO - Cell 1996 Feb; 84(3):491-5DP - 1996 FebTA - CellPG - 491-5IP - 3VI - 84UI - 9619081677
AU - Huang XF
AU - Koutcherov I
AU - Lin S
AU - Wang HQ
AU - Storlien LTI - Localization of leptin receptor mRNA expression in mouse brain.AB - The distribution of the leptin receptor in the brain of C57 mice was investigated using a non-radioactive in situ hybridization method. Leptin receptor mRNA expression was highest in the arcuate nucleus and median eminence of the hypothalamus, but it was also abundant in hippocampus, primarily in the dentate gyrus and CA1, and was detected at low levels in piriform cortex and the medial margin of the medial habenular nucleus. The localization of leptin receptor-containing neurones in the present study indicates the possibility that the leptin receptor is expressed on neuropeptide Y-containing neurones.MH - Brain|*MEMH - Carrier Proteins|*MESO - Neuroreport 1996 Nov; 7(15-17):2635-8DP - 1996 NovTA - NeuroreportPG - 2635-8IP - 15-17VI - 7UI - 9713590078
AU - Lee GH
AU - Proenca R
AU - Montez JM
AU - Carroll KM
AU - Darvishzadeh JG
AU - Lee JI
AU - Friedman JMTI - Abnormal splicing of the leptin receptor in diabetic mice.AB - Mutations in the mouse diabetes (db) gene result in obesity and diabetes in a syndrome resembling morbid human obesity.Previous data suggest that the db gene encodes the receptor for the obese (ob) gene product, leptin. A leptin receptor was recently cloned from choroid plexus and shown to map to the same 6-cM interval on mouse chromosome 4 as db. This receptor maps to the same 300-kilobase interval as db, and has at least six alternatively spliced forms. One of these splice variants is expressed at a high level in the hypothalamus, and is abnormally spliced in C57BL/Ks db/db mice. The mutant protein is missing the cytoplasmic region, and is likely to be defective in signal transduction.This suggests that the weight-reducing effects of leptin may be mediated by signal transduction through a leptin receptor in the hypothalamus.MH - Alternative Splicing|*GEMH - Carrier Proteins|*GEMH - Diabetes Mellitus, Experimental|*GEMH - Mutation|*MH - Proteins|*SO - Nature 1996 Feb; 379(6566):632-5DP - 1996 FebTA - NaturePG - 632-5IP - 6566VI - 379UI - 9623199779
AU - Iida M
AU - Murakami T
AU - Ishida K
AU - Mizuno A
AU - Kuwajima M
AU - Shima KTI - Phenotype-linked amino acid alteration in leptin receptor cDNA from Zucker fatty (fa/fa) rat.AB - The mouse obese (ob) gene product (leptin), expressed specifically in adipose cells, regulates energy balance in mice. Both mouse diabetes (db) and rat fatty (fa) gene products are thought to play major roles in leptin signaling pathways in the hypothalamic area. Mutations of these genes in murines result in marked obesity and type II diabetes as part of a syndrome that resembles morbid obesity in humans. Reported herein are the cloning and sequencing of one of spliced variant forms of rat leptin receptor (OB-R) cDNA with a short intracellular domain. In the Zucker (fa/fa) rat, no changes in either the gene structure or the expression levels were observed. However phenotype-linked nucleotide alteration exists in the cDNA from Zucker (fa/fa) rat, which results in an amino acid substitution.MH - Carrier Proteins|*GEMH - Obesity|*GEMH - Rats, Zucker|*GESO - Biochem Biophys Res Commun 1996 May; 222(1):19-26DP - 1996 MayTA - Biochem Biophys Res CommunPG - 19-26IP - 1VI - 222UI - 9621290680
AU - Grgoire Nyomba BL
AU - Johnson M
AU - Berard L
AU - Murphy LJTI - Relationship between serum leptin and the insulin-like growth factor-I system in humans.AB - The growth hormone (GH)/insulin-like growth factor-I (IGF-I) system and leptin both play an important role in the regulation of body composition. Although the regulation of these two hormonal systems by insulin has been under intense investigation, the physiologic interactions between leptin and the GH/IGF-I system remain unknown. In this study, we examined the relationships among circulating leptin and key elements of the IGF-I system in 60 subjects (27 nondiabetic lean, 21 nondiabetic obese, and 12 type 1 diabetic subjects) with a wide range of insulin secretory capacity. Leptin, glucose, insulin, free IGF-I, total IGF-I, IGF-binding protein-1 (IGFBP-1), and IGFBP-3 levels were measured in the basal state after an overnight fast,and the acute insulin response to glucose (AIRG) was determined after intravenous glucose injection. AIRG was significantly higher (P < .01) in the obese (3,365+/-562 pmol/L x min)versus lean subjects (1,624+/-155 pmol/L x min). In simple regression analysis, the serum leptin concentration was positively correlated with the body mass index ([BMI] men,r = .51, P = .005; women, r = .71, P < .001), IGFBP-3 (men, r = .20, P = nonsignificant; women, r = .41, P < .025), and AIRG (men, r = .73, P < .001; women, r = .62,P < .01). There was a nonlinear correlation between leptin and IGFBP-1, but there was no correlation between leptin and free or total IGF-I. In multiple regression analysis with leptin as the dependent variable, gender, BMI, and IGFBP-3 entered the equations at a statistically significant level. The correlation of leptin with IGFBP-3 was independent of obesity and persisted after correction for AIRG, suggesting a link between leptin and GH action.MH - Diabetes Mellitus, Insulin-Dependent|BL/*MEMH - Insulin-Like Growth Factor I|*ANMH - Obesity|*BL/PAMH - Proteins|*ANSO - Metabolism 1999 Jul; 48(7):840-4DP - 1999 JulTA - MetabolismPG - 840-4IP - 7VI - 48UI - 9934759081
AU - Attia N
AU - Caprio S
AU - Jones TW
AU - Heptulla R
AU - Holcombe J
AU - Silver D
AU - Sherwin RS
AU - Tamborlane WVTI - Changes in free insulin-like growth factor-1 and leptin concentrations during acute metabolic decompensation in insulin withdrawn patients with type 1 diabetes.AB - To determine the effect of acute insulin withdrawal and its subsequent replacement on components of the insulin-like growth factor (IGF)-1 binding protein system and on circulating leptin levels in patients with type 1 diabetes.Seventeen patients (age 31 yr +/-10) with type 1 diabetes treated with continuous subcutaneous insulin infusion (HbA1c 7.6% +/-1.0) were studied. The protocol consisted of two phases: acute insulin withdrawal of up to 8 h followed by a further 2-h period of insulin replacement. For the first phase the basal insulin infusion was stopped (at 0300 h), and for the second a single dose of either regular human or insulin lispro was given subcutaneously (0.2 U/kg). Plasma insulin, glucose, growth hormone, glucagon,IGF-1, free IGF-1, IGFBP-1, -2, -3 and leptin were measured.Results: After interruption of the basal insulin infusion,plasma free insulin levels fell from 60+/-12.0 pmol/L to 10.8+/-4.2 pmol/L, and plasma glucose rose from 5.6+/-0.4 mmol/L to 14.8+/-1.2 mmol/L (P< 0.01). During insulin withdrawal, IGFBP-1 increased by more than 6-fold (from 32+/-8 to 205+/-17 ng/mL, P<0.001), IGFBP-3 increased significantly (from 2631+/-118 to 3053+/-101 ng/mL, P<0.001), and total IGF-1 levels declined modestly (from 226+/-33 to 182+/-26 ng/mL, P<0.001). In contrast, free IGF-1 concentrations (0.72+/-0.22 ng/mL at baseline) were markedly suppressed during insulin withdrawal to values below the detection limit of the assay (0.08 ng/mL) in 15 of the 17 patients (P<0.001). Circulating plasma leptin declined markedly in females from 20+/-3 ng/mL to 11+/-2 ng/mL (P<0.0001)and in males from 10+/-2 ng/mL to 7+/-2 ng/mL (P<0.02).Within 2 h of insulin replacement, the changes in circulating concentrations of IGFBP-1 and IGFBP-3 were partially reversed,and free IGF-1 levels rebounded to 0.54+/-0.22 ng/mL (P<0.1 vs. insulin withdrawal). Growth hormone, glucagon, and IGFBP-2 levels did not change significantly throughout the study. Despite the rapid restoration of plasma insulin and substrate levels, circulating leptin levels continued to fall in the 2-h period after insulin replacement in both females and males. The marked reduction in circulating free IGF-1 after insulin withdrawal and its increase after insulin administration suggest that acute changes in IGFBP concentrations induced by insulin are important regulators of IGF-1 bioavailability in patients with type 1 diabetes.In both males and females, the rapid induction of severe insulin deficiency is associated with a consistent fall in plasma leptin levels.MH - Diabetes Mellitus, Insulin-Dependent|*BL/DTMH - Insulin|*AD/BL/TUMH - Insulin-Like Growth Factor I|*MEMH - Proteins|*MESO - J Clin Endocrinol Metab 1999 Jul; 84(7):2324-8DP - 1999 JulTA - J Clin Endocrinol MetabPG - 2324-8IP - 7VI - 84UI - 9933168382
AU - Gill MS
AU - Toogood AA
AU - Jones J
AU - Clayton PE
AU - Shalet SMTI - Serum leptin response to the acute and chronic administration of growth hormone (GH) to elderly subjects with GH deficiency.AB - In human studies, the principal determinant of serum leptin concentrations is fat mass (FM), but lean mass (LM) also has a significant negative influence. GH treatment in GH deficiency (GHD) alters body composition, increasing LM and decreasing FM, and thus would be expected to alter leptin concentrations. We have therefore examined the acute and chronic effects of GH on serum leptin in 12 elderly GHD subjects (ages 62-85 yr; 3 women and 9 men). FM (kilograms)and LM (kilograms) were determined by dual energy x-ray absortiometry. Leptin, insulin, insulin-like growth factor I (IGF-I), IGF-II, IGF-binding protein-1 (IGFBP-1), IGFBP-2, and IGFBP-3 were measured by specific immunoassays. Leptin, insulin, and IGFBP-1 concentrations were log10 transformed, and data were expressed as the geometric mean (-1, +1 tolerance factor). All other data are presented as the mean +/- SD. In the acute study, patients received a single bolus dose of GH (0.1 mg/kg BW) at time zero, with blood samples drawn at 0, 12, 24, 48, and 72 h and 1 and 2 weeks. There was a significant rise in leptin, insulin, and IGF-I at a median time of 24 h, followed by a significant fall, and nadir concentrations were reached at a median time of 1.5 weeks (leptin) or 2 weeks (insulin and IGF-I). IGFBP-3 concentrations were also significantly increased, but peak concentrations were not achieved until 48 h. IGF-II, IGFBP-1, and IGFBP-2 exhibited transient decreases before returning to baseline levels. There was no relationship between increased leptin concentrations and either insulin or IGF-I concentrations. In the chronic study, patients received daily GH treatment at doses of 0.17, 0.33, and 0.5 mg/day, each for 3 months (total time on GH, 9 months), and were then followed off GH for a further 3 months. Dual energy x-ray absortiometry was undertaken at 0, 3, 6, 9, and 12 months, and blood samples were drawn at these time points. Over 9 months on GH there was a significant fall in FM and a significant rise in LM, but no change in leptin. There were also significant increments in insulin,IGF-I, and IGFBP-3, whereas IGF-II, IGFBP-1, and IGFBP-2 did not change over 9 months of GH treatment. After 3 months off GH, there was a significant rise in FM and leptin.High dose single bolus GH led to an increase in serum leptin within 24 h apparently independent of changes in insulin or IGF-I. Despite the changes in body composition during chronic GH treatment, there was no change in leptin. However,discontinuation of GH led to a rapid reversal of the favorable body composition and a rise in serum leptin.MH - Proteins|*ANMH - Somatropin|*AD/*DFSO - J Clin Endocrinol Metab 1999 Apr; 84(4):1288-95DP - 1999 AprTA - J Clin Endocrinol MetabPG - 1288-95IP - 4VI - 84UI - 9921386183
AU - Audi L
AU - Mantzoros CS
AU - Vidal-Puig A
AU - Vargas D
AU - Gussinye M
AU - Carrascosa ATI - Leptin in relation to resumption of menses in women with anorexia nervosa [see comments]AB - Serum levels of leptin are decreased in underweight AN patients and increase with weight restoration. To assess the relationship of decreased leptin levels with other hormonal abnormalities in AN and to evaluate the possible role of increasing leptin levels, alone or in combination with other hormones, in the resumption of menses that accompanies weight gain, we studied cross-sectionally sixty-five consecutively enrolled AN patients. Subjects were divided in three groups:(I) underweight and amenorrheic; (II) weight-recovered but still amenorrheic; and (III) weight-recovered and eumenorrheic women. Patients in group I had decreased BMI, serum leptin,estradiol (E2), insulin-like growth factor 1 (IGF-1) and urinary growth hormone (GH) levels and increased sex hormone-binding globulin (SHBG) levels, compared to AN patients in groups II and III. Moreover, although no differences in leptin levels or BMI were observed between amenorrheic and eumenorrheic weight-recovered patients (groups II and III), free E2 and GH levels were higher (P<0.02) in weight-recovered, eumenorrheic women. Thus, it appears that leptin is a necessary, but not a sufficient, factor for the resumption of menses in AN patients.MH - Amenorrhea|*ETMH - Anorexia Nervosa|BL/*PP/URMH - Menstrual Cycle|*PHMH - Proteins|*MEAD - Hospital Materno Infantil Vall' HebronAD - BarcelonaAD - Spain.SO - Mol Psychiatry 1998 Nov; 3(6):544-7DP - 1998 NovTA - Mol PsychiatryPG - 544-7IP - 6VI - 3UI - 9907369384
AU - He Y
AU - Chen H
AU - Quon MJ
AU - Reitman MTI - The mouse obese gene. Genomic organization, promoter activity,and activation by CCAAT/enhancer-binding protein alpha.AB - The obese gene product, leptin, regulates adiposity. Mice homozygous for a nonfunctional obese gene become massively obese and develop diabetes mellitus due to overeating and increased metabolic efficiency. The cDNA sequence of obese was recently reported (Zhang, Y., Proenca, R., Maffei, M., Barone, M., Leopold, L., and Friedman, J. L. (1994)Nature 372, 425-432; Correction: (1995 Nature 374, 479). We have determined the genomic organization of the 5'end of the mouse obese gene. The coding sequence is in exons 2 and 3. A single TATA-containing promoter was found upstream of exon 1. A minority (probably approximately 5%) of the obese mRNA contained an extra, untranslated exon between exons 1 and 2. Transcription of the obese gene was detected only in adipose cells. A 762-base pair obese gene promoter driving a luciferase gene yielded abundant activity in transiently transfected rat adipose cells in primary culture. The obese promoter was inactive in erythroid K562 cells. Deletion of bases from -762 downstream to -161 did not affect promoter activity in transfected adipose cells. The -161 minimal promoter contained consensus Sp1 and CCAAT/enhancer-binding protein (C/EBP) motifs. Cotransfection with C/EBP alpha (a transcription factor important in adipose cell differentiation) caused 23-fold activation. These data suggest that the obese promoter is a natural target of C/EBP alpha.MH - DNA-Binding Proteins|*MEMH - Nuclear Proteins|*MEMH - Obesity|*GEMH - Promoter Regions (Genetics)|*MH - Proteins|*GE/MESO - J Biol Chem 1995 Dec; 270(48):28887-91DP - 1995 DecTA - J Biol ChemPG - 28887-91IP - 48VI - 270UI - 9608195885
AU - Nakata M
AU - Yada T
AU - Soejima N
AU - Maruyama ITI - Leptin promotes aggregation of human platelets via the long form of its receptor.AB - Plasma leptin levels are elevated in most obese individuals,and obesity is accompanied by a high incidence of cardiovascular disease. Therefore, leptin could be involved in the pathogenesis of cardiovascular disease. In the present study, the role of leptin was explored in the regulation of platelet function.The expression of the long form of the leptin receptor was detected in human platelets. At 50 ng/ml, human leptin induced phosphorylation of several proteins of platelets at the tyrosine residue. Neither leptin at concentrations < or = 100 ng/ml nor ADP at concentrations > or = 1 micromol/l affected platelet aggregation. However, after pretreatment with 100 ng/ml leptin for 5 min, 1 micromol/l ADP caused aggregation. Thus, leptin and ADP acted synergistically.At a concentration of 2 micromol/l, ADP induced platelet aggregation, which was markedly enhanced by 30-100 ng/ml leptin in a concentration-dependent manner. This concentration range corresponds to that of plasma leptin levels in obese individuals. At the lower concentrations (< 10 ng/ml) that are observed in normal individuals, leptin had no effect on platelet aggregation. In conclusion, leptin at high concentrations has the novel function of promoting platelet aggregation, which may be a key coupling factor between obesity and the cardiovascular disease associated with syndrome X and diabetes.MH - Carrier Proteins|BL/CH/*PHMH - Platelet Aggregation|*DEMH - Proteins|*PDSO - Diabetes 1999 Feb; 48(2):426-9DP - 1999 FebTA - DiabetesPG - 426-9IP - 2VI - 48UI - 9926549586
AU - Raver N
AU - Taouis M
AU - Dridi S
AU - Derouet M
AU - Simon J
AU - Robinzon B
AU - Djiane J
AU - Gertler ATI - Large-scale preparation of biologically active recombinant chicken obese protein (leptin).AB - Prokaryotic expression vector pMON3401 encoding full size A(-1) chicken leptin (AF012727) was prepared by PCR of previously described cDNA. Escherichia coli cells transformed with this vector overexpressed large amounts of chicken leptin upon induction with nalidixic acid. The expressed protein found in the inclusion bodies was refolded and purified to homogeneity on a Q-Sepharose column, yielding two electrophoretically pure fractions (leptin-1 and leptin-2), eluted from the column by 100 and 125 mM NaCl. Both fractions showed a single band of the expected molecular mass of 16 kDa and were composed of over 95% of monomeric protein. The biological activity of both fractions, resulting from proper renaturation, was further evidenced by their ability to stimulate proliferation of leptin-sensitive BAF/3 cells transfected with a long form of human leptin-receptor construct and by lowering the food intake of starved chicken following intravenous or intraperitoneal injections.Copyright 1998 Academic Press.MH - Chickens|*MEMH - Proteins|AD/BI/GE/*IP/PDAD - Institute of BiochemistryAD - Food Science and NutritionAD - Faculty of AgriculturalAD - Food and Environmental Quality SciencesAD - RehovotAD - 76100AD - Israel.SO - Protein Expr Purif 1998 Dec; 14(3):403-8DP - 1998 DecTA - Protein Expr PurifPG - 403-8IP - 3VI - 14UI - 9910277487
AU - Mantzoros CS
AU - Bolhke K
AU - Moschos S
AU - Cramer DWTI - Leptin in relation to carcinoma in situ of the breast: a study of pre-menopausal cases and controls.AB - Leptin reflects the amount of energy stores, regulates energy balance and is associated with circulating levels of reproductive hormones and insulin-like growth factor-I (IGF-I). Breast cancer has also been associated with obesity, reproductive hormones and circulating IGF-I levels.To determine whether leptin is involved in the etiology of breast cancer, we compared serum leptin levels in 83 cases of pre-menopausal carcinoma in situ of the breast and 69 healthy controls recruited in Massachusetts. Serum leptin levels were 13.69 + 1.3 ng/ml in cases and 16.03 + 1.7 ng/ml in controls. Data were also analyzed using multiple logistic regression with adjustment for known risk factors for the development of breast cancer as well as anthropometric, demographic and hormonal variables, including estradiol, prolactin, IGF-I and IGF-binding protein-3. Odds ratios were 1.75 (95% CI, 0.73-4.21) for the second control-defined tertile and 1.54 (0.46-5.16) for the third control-defined tertile relative to the first. Thus, leptin does not appear to increase the risk of pre-menopausal breast cancer in situ substantially.MH - Biological Markers|*BLMH - Breast Neoplasms|*BL/ETMH - Carcinoma in Situ|*BL/ETMH - Carcinoma, Infiltrating Duct|*BL/ETMH - Premenopause|*BLMH - Proteins|*ANAD - Division of EndocrinologyAD - Beth Israel Deaconess Medical CenterAD - Harvard Medical SchoolAD - BostonAD - MA 02215AD - USA. cmantzor@bidmc.harvard.eduSO - Int J Cancer 1999 Feb 9; 80(4):523-6DP - 1999 Feb 9TA - Int J CancerPG - 523-6IP - 4VI - 80UI - 9913185088
AU - Lord GM
AU - Matarese G
AU - Howard JK
AU - Baker RJ
AU - Bloom SR
AU - Lechler RITI - Leptin modulates the T-cell immune response and reverses starvation-induced immunosuppression.AB - Nutritional deprivation suppresses immune function. The cloning of the obese gene and identification of its protein product leptin has provided fundamental insight into the hypothalamic regulation of body weight. Circulating levels of this adipocyte-derived hormone are proportional to fat mass but maybe lowered rapidly by fasting or increased by inflammatory mediators. The impaired T-cell immunity of mice now known to be defective in leptin (ob/ob) or its receptor (db/db), has never been explained. Impaired cell-mediated immunity and reduced levels of leptin are both features of low body weight in humans. Indeed, malnutrition predisposes to death from infectious diseases. We report here that leptin has a specific effect on T-lymphocyte responses, differentially regulating the proliferation of naive and memory T cells. Leptin increased Th1 and suppressed Th2 cytokine production. Administration of leptin to mice reversed the immunosuppressive effects of acute starvation.Our findings suggest a new role for leptin in linking nutritional status to cognate cellular immune function, and provide a molecular mechanism to account for the immune dysfunction observed in starvation.MH - Immune Tolerance|*MH - Proteins|*IMMH - Starvation|*IMMH - T-Lymphocytes|*IMAD - Imperial College School of MedicineAD - Department of ImmunologyAD - The Hammersmith HospitalAD - LondonAD - UK.SO - Nature 1998 Aug 27; 394(6696):897-901DP - 1998 Aug 27TA - NaturePG - 897-901IP - 6696VI - 394UI - 9840170989
AU - Marsh DJ
AU - Hollopeter G
AU - Huszar D
AU - Laufer R
AU - Yagaloff KA
AU - Fisher SL
AU - Burn P
AU - Palmiter RDTI - Response of melanocortin-4 receptor-deficient mice to anorectic and orexigenic peptides.AB - Mutations reducing the functional activity of leptin, the leptin receptor, alpha-melanocyte stimulating hormones (alpha-MSH) and the melanocortin-4 receptor (Mc4r) all lead to obesity in mammals. Moreover, mutant mice that ectopically express either agouti (Ay/a mice) or agouti-related protein (Agrp), antagonists of melanocortin signalling,become obese. These data suggest that alpha-MSH signalling transduced by Mc4r tonically inhibits feeding; however,it is not known to what extent this pathway mediates leptin signalling. We show here that Mc4r-deficient (Mc4r-/-) mice do not respond to the anorectic actions of MTII, an MSH-like agonist, suggesting that alpha-MSH inhibits feeding primarily by activating Mc4r. Obese Mc4r-/-mice do not respond significantly to the inhibitory effects of leptin on feeding, whereas non-obese Mc4r-/- mice do. These data demonstrate that melanocortin signalling transduced by Mc4r is not an exclusive target of leptin action and that factors resulting from obesity contribute to leptin resistance.Leptin resistance of obese Mc4r-/- mice does not prevent their response to the anorectic actions of ciliary neurotrophic factor (CNTF), corticotropin releasing factor (CRF), or urocortin; or the orexigenic actions of neuropeptide Y (NPY) or peptide YY (PYY), indicating that these neuromodulators act independently or downstream of Mc4r signalling.MH - Carrier Proteins|ME/*PDMH - Neuropeptides|ME/*PDMH - Oligopeptides|ME/*PDMH - Receptors, Corticotropin|GE/*PHMH - Signal Transduction|*AD - Howard Hughes Medical Institute and Department of BiochemistryAD - University of WashingtonAD - Seattle 98195AD - USA.SO - Nat Genet 1999 Jan; 21(1):119-22DP - 1999 JanTA - Nat GenetPG - 119-22IP - 1VI - 21UI - 9911384290
AU - Li C
AU - Ioffe E
AU - Fidahusein N
AU - Connolly E
AU - Friedman JMTI - Absence of soluble leptin receptor in plasma from dbPas/dbPas and other db/db mice.AB - The leptin receptor (Ob-R) is alternatively spliced into at least five different RNAs designated Ob-R(a-e). Ob-R(a-d) predict receptors with a single transmembrane domain,and Ob-Re predicts a secreted form of the receptor. The presence of an approximately 120-kDa soluble leptin receptor in mouse plasma was confirmed by precipitation with leptin-Sepharose beads followed by immunobloting with anti-leptin receptor antibodies. The soluble leptin receptor is larger than that predicted by the primary sequence. Deglycosylation of the receptor with peptide N:glycosidase F results in a decrease in molecular mass to a size consistent with that of the primary sequence. The secreted receptor was present in plasma from wild type mice but was truncated in plasma from db3J/db3J and absent in dbPas/dbPas plasma.Although db3J/db3J mice are known to have a frameshift mutation at amino acid 625, the basis for the mutation in dbPas/dbPas mice was not known. Further studies indicated that dbPas/dbPas mice carry a duplication of exons 4 and 5 of Ob-R. This mutation introduces a premature stop codon into the protein at amino acid 281. The absence of Ob-R in db3J/db3J and dbPas/dbPas mice confirm the identify of the 120-kDa plasma protein as Ob-Re.MH - Carrier Proteins|*BL/*GE/IPMH - Exons|*MH - Hypothalamus|*MEMH - Mice, Mutant Strains|*GEMH - Proteins|IP/*MESO - J Biol Chem 1998 Apr; 273(16):10078-82DP - 1998 AprTA - J Biol ChemPG - 10078-82IP - 16VI - 273UI - 9821205291
AU - Seck T
AU - Englaro P
AU - Blum WF
AU - Scheidt Nave C
AU - Rascher W
AU - Ziegler R
AU - Pfeilschifter JTI - Leptin concentrations in serum from a randomly recruited sample of 50- to 80-year-old men and women: positive association with plasma insulin-like growth factors (IGFs) and IGF-binding protein-3 in lean, but not in obese, individuals.AB - OBJECTIVE: The GH/IGF axis is thought to play an important role in the regulation of body composition throughout life.Changes in body fat stores also affect the activity of the GH/IGF axis, but the mechanisms whereby body fat status is signaled to the GH/IGF axis are poorly understood. The newly discovered protein leptin is exclusively produced by adipocytes, and circulating concentrations of leptin closely reflect body fat stores. DESIGN: We here examined whether leptin might be associated with the activity of the GH/IGF axis in a population-based sample. PATIENTS AND METHODS: Circulating concentrations of leptin, IGF-I, IGF-II, and insulin-like growth factor-binding protein-3 (IGFBP-3) were measured in a population-based sample of 50- to 80-year-old men (n=217) and women (n=198) by specific RIA. RESULTS: All three IGF components were significantly positively correlated with leptin in lean women (body mass index (BMI) <25 kg/m2). IGF-II was also positively correlated with leptin in lean men, and positive correlation of leptin with IGF-I in lean men was of borderline statistical significance.In contrast, no correlation was observed in moderately overweight (BMI 25-30kg/m2) and obese individuals (BMI >30 kg/m2). CONCLUSION: Our study shows that serum leptin concentrations are significantly associated with circulating IGF components in lean elderly subjects. The precise mechanism of this interaction between leptin and the GH/IGF system remains to be determined.MH - Insulin-Like Growth Factor Binding Protein 3|*BLMH - Obesity|*BL/PAMH - Proteins|*ANMH - Somatomedins|*ANSO - Eur J Endocrinol 1998 Jan; 138(1):70-5DP - 1998 JanTA - Eur J EndocrinolPG - 70-5IP - 1VI - 138UI - 9812121792
AU - Tanizawa Y
AU - Okuya S
AU - Ishihara H
AU - Asano T
AU - Yada T
AU - Oka YTI - Direct stimulation of basal insulin secretion by physiological concentrations of leptin in pancreatic beta cells.AB - We examined a possible mechanism underlying the link between obesity and hyperinsulinemia, focusing on leptin, a peptide released from adipocytes which affects the satiety center in the brain. The leptin receptor isoforms, Ob-Ra and Ob-Rb, are present in the pancreatic beta cell line MIN6 and in rat pancreatic islets, based on RT-PCR. A 2 hr, but not a 30 min, incubation with 1 nM recombinant mouse leptin,the concentration observed in obese subjects, stimulated basal (at 5 mM glucose) insulin secretion by approximately 40% in both MIN6 and rat islets. Stimulatory effects were not observed without glucose or when the incubation medium containing 1 nM leptin had been preincubated with the immobilized leptin antibody. In contrast to the stimulatory effects on basal insulin secretion at 1 nM, the maximally stimulated insulin secretion at 25 mM glucose was not significantly changed by 1 nM leptin in isolated rat islets. In addition,10 and 100 nM leptin exerted small but significant inhibitory effects on 16.7 mM glucose-stimulated insulin secretion.Thus, leptin acts directly on pancreatic beta cells, and stimulation of basal insulin secretion by physiological concentrations of leptin may account in part for the fasting hyperinsulinemia observed in obese subjects.MH - Insulin|*SEMH - Islets of Langerhans|CY/PH/*SEMH - Proteins|*PD/PHSO - Endocrinology 1997 Oct; 138(10):4513-6DP - 1997 OctTA - EndocrinologyPG - 4513-6IP - 10VI - 138UI - 9746274893
AU - Pearson SL
AU - Cawthorne MA
AU - Clapham JC
AU - Dunmore SJ
AU - Holmes SD
AU - Moore GB
AU - Smith SA
AU - Tadayyon MTI - The thiazolidinedione insulin sensitiser, BRL 49653, increases the expression of PPAR-gamma and aP2 in adipose tissue of high-fat-fed rats.AB - The effects of the thiazolidinedione insulin sensitiser BRL 49653 on plasma leptin concentrations and on epididymal fat OB, PPAR-gamma and aP2 mRNA expression were examined in high-fat-fed and high-carbohydrate-fed adult Wistar rats. Diets were given for 4 weeks, with BRL 49653 (10 micromol/kg/day) administered by oral gavage for the last 4 days. Treatment with BRL 49653 reduced plasma leptin concentrations in high-fat-fed rats from 2.34 +/- 0.19 (n=9) to 1.42 +/- 0.09 (n=9) ng/ml (p<0.001). Plasma leptin was unaffected by BRL 49653 in the high-carbohydrate-fed rats. There was no difference in OB mRNA expression between high-fat-fed and high-carbohydrate-fed rats, with or without treatment. PPAR-gamma and aP2 mRNA expression were significantly increased in the high-fat-fed rats treated with BRL 49653 (p < 0.01 and p < 0.001 respectively), but not in carbohydrate-fed rats.MH - Adipose Tissue|*MEMH - Carrier Proteins|*BIMH - Dietary Fats|*ADMH - Hypoglycemic Agents|*PDMH - Myelin P2 Protein|*BIMH - Receptors, Cytoplasmic and Nuclear|*BIMH - Thiazoles|*PDMH - Transcription Factors|*BISO - Biochem Biophys Res Commun 1996 Dec; 229(3):752-7DP - 1996 DecTA - Biochem Biophys Res CommunPG - 752-7IP - 3VI - 229UI - 9711565394
AU - Takaya K
AU - Ogawa Y
AU - Isse N
AU - Okazaki T
AU - Satoh N
AU - Masuzaki H
AU - Mori K
AU - Tamura N
AU - Hosoda K
AU - Nakao KTI - Molecular cloning of rat leptin receptor isoform complementary DNAs--identification of a missense mutation in Zucker fatty (fa/fa) rats.AB - We cloned the full-length rat leptin receptor (Ob-R) isoform complementary DNAs (cDNAs) and examined the gene expression in rats. We also identified a mutation in Ob-R in Zucker fatty (fa/fa) rats. Three alternatively spliced isoforms (Ob-Ra, Ob-Rb, and Ob-Re) have been identified, which are closely related to the gp130 signal-transduction component of class I cytokine receptors. Rat Ob-Ra and Ob-Rb were single transmembrane proteins, which differ in the C-terminal amino acid sequences. On the other hand, Ob-Re had no transmembrane domain and was a soluble form of the receptor. Reverse transcription-polymerase chain reaction analysis revealed that Ob-R isoform messenger RNAs (mRNAs) are expressed in a wide variety of rat tissues in tissue-specific manners.A missense mutation (an A to C conversion at nucleotide position 806) was found in the extracellular domain of all the isoforms in Zucker fatty (fa/fa) rats, which resulted in an amino acid change from Gln to Pro at + 269 (the Gln269Pro mutation). These Ob-R isoform mRNAs were present in the brain from Zucker fatty (fa/fa) rats at comparable amounts to those in their lean littermates. The present study provides new insight into the molecular mechanisms for Ob-R.MH - Carrier Proteins|*BI/*GEMH - Obesity|*GEMH - Point Mutation|*MH - Rats, Zucker|*GESO - Biochem Biophys Res Commun 1996 Aug; 225(1):75-83DP - 1996 AugTA - Biochem Biophys Res CommunPG - 75-83IP - 1VI - 225UI - 9633240895
AU - Gainsford T
AU - Alexander WSTI - A role for leptin in hemopoieses?AB - The recent discovery of leptin as a major controller of appetite has led to a detailed analysis of its specific actions in this process as well as any potential role in the etiology of obesity. It has also emerged that leptin has a wider spectrum of biological activities and has been strongly implicated in fertility and reproduction. The structural similarity between leptin and its receptor and cytokine-receptor systems that control hemopoiesis has also prompted investigation of the potential for this hormone to influence blood cell formation. Recent studies have shown that the leptin receptor is expressed on a diverse range of hemopoietic cells. Leptin itself appears to enhance proliferation of hemopoietic cells in vitro, particularly in combination with other cytokines and may augment some mature hemopoietic cell functions. Although only relatively minor hemopoietic deficiencies have been reported in mice lacking leptin or its receptor, these emerging studies suggest that further analysis of leptin actions in hemopoiesis may be warranted.MH - Hematopoiesis|*PHMH - Proteins|GE/PD/*PHSO - Mol Biotechnol 1999 Apr; 11(2):149-58DP - 1999 AprTA - Mol BiotechnolPG - 149-58IP - 2VI - 11UI - 9939403596
AU - Uotani S
AU - Bjçrbaek C
AU - Tornçe J
AU - Flier JSTI - Functional properties of leptin receptor isoforms: internalization and degradation of leptin and ligand-induced receptor downregulation.AB - Long (ObRb) and short (ObRa) leptin receptor isoforms are thought to play essential roles in mediating leptin signaling and the transport and degradation of leptin, respectively.Although the capacity of these cloned receptor species to mediate signal transduction has been reported, there is no information on the ability of individual receptor species to mediate leptin internalization and degradation or to undergo ligand-induced downregulation. We therefore studied these parameters in Chinese hamster ovary (CHO)cells stably expressing either ObRa or ObRb isoforms of the leptin receptor. We determined that both ObRa and ObRb mediated internalization of 125I-labeled leptin by a temperature-and coated pit-dependent mechanism. Both ObRa and ObRb also mediated degradation of 125I-leptin by a lysosomal mechanism, and this was more efficiently mediated by ObRa in these cells. Neither leptin internalization nor degradation by ObRa was affected by mutation of the conserved Box 1 motif. By studying deletion mutants of ObRa, we found that efficient internalization was dependent on a motif located between amino acids 8 and 29 of the intracellular domain of ObRa. Exposure of cells expressing ObRa or ObRb to unlabeled leptin for 90 min at 37 degrees C produced downregulation of available surface receptors, and this effect was of greater magnitude in cells expressing ObRb. Whereas CHO cells expressing the growth hormone receptor showed marked downregulation of ligand binding after exposure to dexamethasone (DEX) or phorbol myristic acid (PMA), PMA had no effect on expression of ObRa or ObRb, and DEX reduced binding to cells expressing ObRb by 15%. Thus, the two leptin receptor isoforms, ObRa and ObRb, mediate leptin internalization by a coated pit-dependent mechanism, leptin degradation by a lysosomal pathway, and ligand-induced receptor downregulation.The differential capacity of the two receptor isoforms may relate to the different roles of the receptor isoforms in the biology of leptin.MH - Carrier Proteins|DE/GE/*MEMH - Down-Regulation (Physiology)|*PHSO - Diabetes 1999 Feb; 48(2):279-86DP - 1999 FebTA - DiabetesPG - 279-86IP - 2VI - 48UI - 9926547197
AU - Steppan CM
AU - Swick AGTI - A role for leptin in brain development.AB - Leptin, the product of the obese gene, is a circulating hormone involved in feeding behavior and energy homeostasis.Ob/ob mice which are leptin deficient have many phenotypic abnormalities including brains that are smaller in both weight and cortical volume. To this end, we monitored the effects of leptin administration on brain growth. Intraperitoneal administration of leptin for 2 weeks daily to 4-week-old ob/ob mice resulted in a maximal 10% increase in both wet and dry brain weights. This increase appears to be partially the result of increased cell number as indicated by a 19%increase in total brain DNA. In summary, our data suggest that the decreased brain size of the ob/ob mouse is due to a developmental defect that can be corrected upon leptin administration and therefore leptin plays a role in brain growth and development. Copyright 1999 Academic Press.MH - Brain|DE/*GDMH - Proteins|AD/GE/PD/*PHSO - Biochem Biophys Res Commun 1999 Mar; 256(3):600-2DP - 1999 MarTA - Biochem Biophys Res CommunPG - 600-2IP - 3VI - 256UI - 9918233698
AU - Thomas T
AU - Gori F
AU - Khosla S
AU - Jensen MD
AU - Burguera B
AU - Riggs BLTI - Leptin acts on human marrow stromal cells to enhance differentiation to osteoblasts and to inhibit differentiation to adipocytes.AB - Both bone mass and serum leptin levels are increased in obesity. Because osteoblasts and adipocytes arise from a common precursor in bone marrow, we assessed the effects of human recombinant leptin on a conditionally immortalized human marrow stromal cell line, hMS2-12, with the potential to differentiate to either the osteoblast or adipocyte phenotypes. By RT-PCR and Western immunoblot analysis, the hMS2-12 cells expressed messenger RNA (mRNA) and protein for the leptin receptor. Leptin did not affect hMS2-12 cell proliferation, but resulted in dose- and time-dependent increases in mRNA and protein levels of alkaline phosphatase,type I collagen, and osteocalcin, and in a 59% increase in mineralized matrix. Leptin increased mRNA levels of lipoprotein lipase at 3 days, but decreased mRNA levels of adipsin and leptin at 9 days and decreased lipid droplet formation by 50%. Leptin did not affect the expression of Cbfa1 or peroxisome proliferator-activated receptor-gamma2, transcription factors involved in commitment to the osteoblast and adipocyte pathways, respectively. Thus,leptin acts on human marrow stromal cells to enhance osteoblast differentiation and to inhibit adipocyte differentiation.Our data support the hypothesis that leptin is a previously unrecognized, physiological regulator of these two differentiation pathways, acting primarily on maturation of stromal cells into both lineages.MH - Adipocytes|*CYMH - Bone Marrow Cells|*CYMH - Cell Differentiation|*MH - Osteoblasts|*CYMH - Proteins|ME/*PDMH - Stromal Cells|*CYSO - Endocrinology 1999 Apr; 140(4):1630-8DP - 1999 AprTA - EndocrinologyPG - 1630-8IP - 4VI - 140UI - 9919613399
AU - Sivitz WI
AU - Fink BD
AU - Donohoue PATI - Fasting and leptin modulate adipose and muscle uncoupling protein: divergent effects between messenger ribonucleic acid and protein expression.AB - Leptin is believed to act through hypothalamic centers to decrease appetite and increase energy utilization, in part through enhanced thermogenesis. In this study, we examined the effects of fasting for 2 days and exogenous s.c. leptin, 200 microg every 8 h for 2 days, on the regulation of uncoupling protein (UCP) subtypes in brown adipose tissue (BAT) and gastrocnemius muscle. Northern blot analysis (UCP-1) and ribonuclease protection (UCP-2 and 3) were used for quantitative messenger RNA (mRNA) analysis, and specific antibodies were used to measure UCP-1 and UCP-3 total protein expression. Leptin, compared with vehicle,did not alter BAT UCP-1 or UCP-3 mRNA or protein expression when administered to normal ad libitum fed rats. Fasting significantly decreased BAT UCP-1 and UCP-3 mRNA expression,to 31% and 30% of ad libitum fed controls, respectively,effects which were prevented by administration of leptin to fasted rats. Fasting also significantly decreased BAT UCP-1 protein expression, to 67% of control; however, that effect was not prevented by leptin treatment. Fasting also decreased BAT UCP-3 protein, to 85% of control, an effect that was not statistically significant. Fasting, with or without leptin administration, did not affect BAT UCP-2 mRNA; however, leptin administration to ad libitum fed rats significantly increased BAT UCP-2 mRNA, to 138% of control. Fasting significantly enhanced gastrocnemius muscle UCP-3 mRNA (411% of control) and protein expression (168%of control), whereas leptin administration to fasted rats did not alter either of these effects. In summary, UCP subtype mRNA and protein are regulated in tissue- and subtype-specific fashion by leptin and food restriction. Under certain conditions, the effects of these perturbations on UCP mRNA and protein are discordant.MH - Adipose Tissue|*CHMH - Fasting|*PHMH - Gene Expression|*MH - Muscle, Skeletal|*CHMH - Proteins|AD/AN/GE/*PDMH - Uncoupling Agents|*ANSO - Endocrinology 1999 Apr; 140(4):1511-9DP - 1999 AprTA - EndocrinologyPG - 1511-9IP - 4VI - 140UI - 99196118100
AU - Seufert J
AU - Kieffer TJ
AU - Habener JFTI - Leptin inhibits insulin gene transcription and reverses hyperinsulinemia in leptin-deficient ob/ob mice.AB - Leptin controls feeding behavior and insulin secretion from pancreatic beta-cells. Insulin stimulates the production of leptin, thereby establishing an adipoinsular axis. Earlier we identified leptin receptors on pancreatic beta-cells and showed leptin-mediated inhibition of insulin secretion by activation of ATP-sensitive potassium channels. Here we examine transcriptional effects of leptin on the promoter of the rat insulin I gene in rodent beta-cells. A fall in levels of preproinsulin mRNA is detected in vivo in islets of ob/ob mice 24 h after a single injection of leptin,in isolated ob/ob islets treated with leptin in vitro and in the beta-cell line INS-1 on leptin exposure when preproinsulin mRNA expression is stimulated by 25 mM glucose or 10 nM glucagon-like peptide 1. Under these conditions, transcriptional activity of -410 bp of the rat insulin I promoter is inhibited by leptin, whereas transactivation of a 5'-deleted promoter (-307 bp) is not. The -307 sequence contains the known glucose-responsive control elements (E2:A3/4). Constitutive activation of ATP-sensitive potassium channels by diazoxide does not alter leptin inhibition of preproinsulin mRNA levels. Distinct protein-DNA complexes appear on the rat insulin I promoter sequences located between -307 and -410 with nuclear extracts from ob/ob islets in response to leptin, including a signal transducer and activator of transcription (STAT)5b binding site. These results indicate that leptin inhibits transcription of the preproinsulin gene by altering transcription factor binding to sequences upstream from the elements (307 bp) that confer glucose responsivity to the rat insulin I gene promoter. Thus leptin exerts inhibitory effects on both insulin secretion and insulin gene expression in pancreatic beta-cells, but by different cellular mechanisms.MH - Hyperinsulinemia|*THMH - Insulin|*GEMH - Islets of Langerhans|*DEMH - Proteins|*PDMH - Transcription, Genetic|*DE/GESO - Proc Natl Acad Sci U S A 1999 Jan; 96(2):674-9DP - 1999 JanTA - Proc Natl Acad Sci U S APG - 674-9IP - 2VI - 96UI - 99110949101
AU - Houseknecht KL
AU - Portocarrero CPTI - Leptin and its receptors: regulators of whole-body energy homeostasis.AB - Leptin is the adipocyte-specific product of the ob gene.Expression of leptin in fully fed animals reflects adipocyte size and body-fat mass. Leptin signals the status of body energy stores to the brain, where signals emanate to regulate food intake and whole-body energy expenditure. The leptin gene was identified in the leptin-deficient, obese ob/ob mouse by positional cloning techniques. Recently, leptin has been cloned in domestic species including pigs, cattle,and chickens. The leptin receptor has at least five splice variants; the long form of the receptor is primarily expressed in the hypothalamus and is thought to be the predominant signaling isoform. Leptin receptors are members of the cytokine family of receptors and signal via janus-activated kinases (JAK)/signal transducers and activators of transcription (STAT) and mitogen-activated protein kinase (MAPK) pathways.Mutations in the leptin or leptin receptor genes results in morbid obesity, infertility, and insulin resistance in rodents and humans. Leptin regulates food intake and energy expenditure via central and peripheral mechanisms.Leptin receptors are expressed in most tissues, and in vitro evidence suggests that leptin may have direct effects on some tissues such as adipose tissue, the adrenal cortex,and the pancreatic beta-cell. Leptin is thought to influence whole-body glucose homeostasis and insulin action. Studies are underway to determine the role that leptin plays in the biology of domestic animals.MH - Carrier Proteins|CH/GE/*PHMH - Energy Metabolism|*MH - Homeostasis|*MH - Proteins|GE/*PHSO - Domest Anim Endocrinol 1998 Nov; 15(6):457-75DP - 1998 NovTA - Domest Anim EndocrinolPG - 457-75IP - 6VI - 15UI - 99078531102
AU - Takahashi N
AU - Waelput W
AU - Guisez YTI - Leptin is an endogenous protective protein against the toxicity exerted by tumor necrosis factor.AB - Tumor necrosis factor (TNF) is a central mediator of a number of important pathologies such as the systemic inflammatory response syndrome. Administration of high TNF doses induces acute anorexia, metabolic derangement, inflammation, and eventually shock and death. The in vivo effects of TNF are largely mediated by a complex network of TNF-induced cytokines and hormones acting together or antagonistically.Since TNF also induces leptin, a hormone secreted by adipocytes that modulates food intake and metabolism, we questioned the role of leptin in TNF-induced pathology. To address this question, we tested mouse strains that were defective either in leptin gene (ob/ob) or in functional leptin receptor gene (db/db), and made use of a receptor antagonist of leptin. Ob/ob and db/db mice, as well as normal mice treated with antagonist, exhibited increased sensitivity to the lethal effect of TNF. Exogenous leptin afforded protection to TNF in ob/ob mice, but failed to enhance the protective effect of endogenous leptin in normal mice. We conclude that leptin is involved in the protective mechanisms that allow an organism to cope with the potentially autoaggressive effects of its immune system.MH - Carrier Proteins|*AIMH - Proteins|*MEMH - Tumor Necrosis Factor|IM/*TOAD - Molecular Pathophysiology and Experimental Therapy UnitAD - Department of Molecular BiologyAD - Flanders Interuniversity Institute for TechnologyAD - University of GhentAD - B-9000 GhentAD - Belgium. nozomi.takahashi@dumb.rug.ac.beSO - J Exp Med 1999 Jan 4; 189(1):207-12DP - 1999 Jan 4TA - J Exp MedPG - 207-12IP - 1VI - 189UI - 99093439103
AU - Ishizuka T
AU - Ernsberger P
AU - Liu S
AU - Bedol D
AU - Lehman TM
AU - Koletsky RJ
AU - Friedman JETI - Phenotypic consequences of a nonsense mutation in the leptin receptor gene (fak) in obese spontaneously hypertensive Koletsky rats (SHROB).AB - The genetically obese Koletsky rat (SHROB, fak) has a novel point mutation of the leptin receptor at amino acid +763,resulting in a premature stop codon in the leptin receptor extracellular domain. This implies that all leptin receptor isoforms should be absent in this model. We examined the phenotypic consequences of this mutation on leptin and leptin receptor mRNA in hypothalamus and peripheral tissues from SHROB and their lean SHR littermates. Despite the mutation, mRNA for both the long (ObRa) and the short (ObRb) form were expressed at comparable levels in SHROB and SHR in brain and throughout peripheral tissues. Adipose tissue mRNA for leptin was two to three times greater in SHROB compared to SHR (P < 0.01), while circulating leptin concentration was 170 times greater than SHR littermates (P < 0.01), suggesting extreme leptin resistance in SHROB.Leptin was also detected in the cerebrospinal fluid (CSF)of SHR and SHROB (13.8 and 27.2 pmol/L, respectively); however, the CSF/plasma ratio for leptin was 32-fold greater in SHR than in SHROB. To assess the putative action of leptin and leptin receptors on insulin-mediated glucose transport, muscles from SHR and SHROB were incubated in vitro with recombinant human leptin. Leptin directly suppressed insulin-mediated glucose transport by 50% in skeletal muscle from SHR but not in obese SHROB rats lacking all forms of the leptin receptor. These results suggest that the natural leptin receptor knockout in the SHROB represents a unique rat model to define the functional role(s) of leptin in central and peripheral energy metabolism.MH - Carrier Proteins|*GEMH - Obesity|*GE/MEMH - Point Mutation|*MH - Proteins|GE/*ME/PDAD - Departments of NutritionAD - Case Western Reserve University School of MedicineAD - ClevelandAD - OH 44106AD - USA.SO - J Nutr 1998 Dec; 128(12):2299-306DP - 1998 DecTA - J NutrPG - 2299-306IP - 12VI - 128UI - 99091713104
AU - Scarpace PJ
AU - Nicolson M
AU - Matheny MTI - UCP2, UCP3 and leptin gene expression: modulation by food restriction and leptin.AB - To determine the effects of food restriction and leptin administration on several transcripts involved in energy homeostasis, we examined leptin, uncoupling proteins (UCP)1, 2 and 3, lipoprotein lipase (LPL), beta3-adrenergic receptors (beta3AR) and hormone-sensitive lipase (HSL) mRNA levels in brown adipose tissue (BAT) and epididymal (EWAT) and perirenal (PWAT) white adipose tissue in three groups of rats. The groups were administered leptin for 1 week, or had food restricted to the amount of food consumed by the leptin-treated animals, or had free access to food.Leptin administration increased serum leptin concentrations 50-fold and decreased food consumption by 43%, whereas serum insulin and corticosterone concentrations were unchanged.Leptin increased LPL mRNA by 80%, UCP1 mRNA twofold, and UCP3 mRNA levels by 62% in BAT, and increased UCP2 mRNA levels twofold in EWAT. In contrast, UCP2 mRNA levels were unchanged in PWAT and BAT. In WAT from food-restricted rats, leptin gene expression was diminished by 40% compared with those fed ad libitum. With leptin administration, there was a further 50% decrease in leptin expression. LPL mRNA levels were decreased by food restriction but not by leptin in WAT, whereas beta3AR and HSL mRNA levels were unchanged with either food restriction or leptin treatment.The present study indicates that leptin increases the gene expression of UCP2 in EWAT and that of UCP1, UCP3 and LPL in BAT, whereas reduced food consumption but not leptin,decreases LPL expression in WAT. In addition, with leptin administration there is a decrease in leptin gene expression in WAT, independent of food intake and serum insulin and corticosterone concentrations.MH - Adipose Tissue|*MEMH - Carrier Proteins|*GEMH - Food Deprivation|*PHMH - Gene Expression Regulation|*DEMH - Proteins|*GE/*PDMH - Uncoupling Agents|*AD - Geriatric ResearchAD - Education and Clinical CenterAD - Department of Veterans Affairs Medical CenterAD - GainesvilleAD - Florida 32608-1197AD - USA.SO - J Endocrinol 1998 Nov; 159(2):349-57DP - 1998 NovTA - J EndocrinolPG - 349-57IP - 2VI - 159UI - 99069541105
AU - Commins SP
AU - Watson PM
AU - Padgett MA
AU - Dudley A
AU - Argyropoulos G
AU - Gettys TWTI - Induction of uncoupling protein expression in brown and white adipose tissue by leptin.AB - Deposition of excess body fat occurs when energy intake chronically exceeds energy expenditure. In ob/ob mice, the absence of leptin affects both components of the energy balance equation, and the mice become morbidly obese after weaning. Treatment of ob/ob mice with exogenous leptin reduces body weight by decreasing food intake and stimulating energy utilization, but even when saline- and leptin-injected ob/ob mice are pair-fed, mice receiving leptin lose significantly more weight. Therefore, the purpose of the present study was to test the hypotheses that uncoupling protein-1 (UCP1)expression is reduced in adipose tissue from ob/ob mice and is restored by treatment with exogenous leptin. Lean and ob/ob mice (5-6 weeks old) were housed at 23 C and treated with leptin (20 microg/g BW x day) for 3 days before they were killed. Compared with levels in lean littermates,UCP1 messenger RNA (mRNA) and protein levels were lower in brown adipose tissue (BAT) and retroperitoneal white adipose tissue (WAT) from ob/ob mice. Treatment of ob/ob mice with leptin reduced body weight and produced a 4- to 5-fold increase in UCP1 mRNA levels in both interscapular BAT and retroperitoneal WAT. The increases in UCP1 mRNA were accompanied by comparable increases in UCP1 protein in mitochondrial preparations from each tissue. Given that the sole known function of UCP1 is to uncouple oxidative phosphorylation, the present results are consistent with the conclusion that leptin stimulates energy utilization in ob/ob mice by increasing thermogenic activity and capacity (UCP1). In addition, the present results suggest that decreased UCP1 expression in BAT and WAT of ob/ob mice is in part responsible for their increased metabolic efficiency and propensity to become obese.MH - Adipose Tissue|DE/*MEMH - Brown Fat|DE/*MEMH - Carrier Proteins|*BIMH - Membrane Proteins|*BIMH - Proteins|*BI/*PDAD - Department of MedicineAD - Medical University of South CarolinaAD - Charleston 29425AD - USA.SO - Endocrinology 1999 Jan; 140(1):292-300DP - 1999 JanTA - EndocrinologyPG - 292-300IP - 1VI - 140UI - 99101953106
AU - Glasow A
AU - Haidan A
AU - Hilbers U
AU - Breidert M
AU - Gillespie J
AU - Scherbaum WA
AU - Chrousos GP
AU - Bornstein SRTI - Expression of Ob receptor in normal human adrenals: differential regulation of adrenocortical and adrenomedullary function by leptin.AB - The major effects of leptin, an adipostatic hormone produced in fat tissue, are exerted through the hypothalamic-pituitary-adrenal axis and the systemic sympathetic/adrenomedullary system at the level of the central nervous system. Here,we examined the direct effects of leptin on the adrenal gland, a peripheral end organ of both the hypothalamic-pituitary-adrenal axis and the sympathetic/adrenomedullary system. As cortical and chromaffin tissues are intermingled in the human adrenal, we employed the novel technique of laser capture microdissection to analyze these systems separately. Functional full-length leptin receptor messenger ribonucleic acid and all human isoforms Ob219.1-3 were demonstrated by RT-PCR in both cortical and medullary tissue.Immunohistochemical staining of leptin receptor protein,however, demonstrated a strong signal only in the adrenal cortex, whereas there was weak positive staining in the medulla. Corticotropin (ACTH)-induced adrenal aldosterone,cortisol, and dehydroepiandrosterone secretion was inhibited by leptin in a concentration-dependent manner, whereas this hormone had no significant effect on catecholamine release by primary cultures of human adrenal chromaffin cells. Leptin itself was not expressed in human adrenal tissue, excluding a local paracrine or autocrine function of this peptide. In conclusion, this is the first report identifying functional leptin receptor in human adrenal tissue and showing a differential action of leptin on human adrenocortical and chromaffin hormone production. This peripheral action of leptin on the adrenal gland provides an additional important link between the human stress response and body weight regulation.MH - Adrenal Cortex|*PHMH - Adrenal Glands|CY/DE/*ME/SEMH - Adrenal Medulla|*PHMH - Carrier Proteins|GE/*MEMH - Proteins|GE/ME/PD/*PHSO - J Clin Endocrinol Metab 1998 Dec; 83(12):4459-66DP - 1998 DecTA - J Clin Endocrinol MetabPG - 4459-66IP - 12VI - 83UI - 99067119107
AU - Cancello R
AU - Zingaretti MC
AU - Sarzani R
AU - Ricquier D
AU - Cinti STI - Leptin and UCP1 genes are reciprocally regulated in brown adipose tissue.AB - In a previous work we showed that only unilocular brown adipocytes express leptin. In order to investigate the relationship between leptin gene expression, brown adipocyte activity (UCP1) and morphology, we studied brown adipose tissues of mice (C57BL, female, 7 weeks old) acclimated at different temperatures (19 degrees C and 28 degrees C). Northern blot analysis revealed higher leptin and lower UCP1 mRNA levels in mice exposed to 28 degrees C than in the group acclimated at 19 degrees C. Also protein expression (immunohistochemistry) differed in the two groups: at 28 degrees C brown adipocytes were positive for leptin and only weakly positive for UCP1, while at 19 degrees C they were leptin-negative and UCP1-positive. In the former group the morphology was mainly unilocular. Our data suggest that in brown adipocytes of warm-acclimated mice leptin expression is closely related to their hypoactive functional stage, as evidenced by their low level of UCP1 synthesis and the morphological rearrangement of the lipid content (unilocularity).MH - Brown Fat|*PHMH - Carrier Proteins|*BI/GEMH - Membrane Proteins|*BI/GEMH - Proteins|*BI/GESO - Endocrinology 1998 Nov; 139(11):4747-50DP - 1998 NovTA - EndocrinologyPG - 4747-50IP - 11VI - 139UI - 99008620108
AU - Rauch F
AU - Westermann F
AU - Englaro P
AU - Blum WF
AU - Sch÷n
AU ETI - Serum leptin is suppressed by growth hormone therapy in growth hormone-deficient children.AB - Leptin is a hormone which is exclusively synthesized and secreted by adipocytes. As of yet, little is known about the complex interplay of hormones in the modulation of circulating leptin levels. To investigate the effect of growth hormone (GH) therapy on leptin, leptin serum concentrations were measured by a specific radioimmunoassay in 29 children with GH deficiency (21 boys, 8 girls; age range 3-14 years)before and after 1, 3 and 6 months of treatment with recombinant human GH. At baseline, serum leptin levels were identical to those of healthy children. Serum leptin correlated with body mass index (BMI; r=0.60, p < 0.001) and weight (r=0.48, p=0.004), but not with height, age, insulinlike growth factor 1, or insulinlike growth factor-binding protein 3, and there was no sex difference (p > 0.05). After 1 month of treatment, the leptin levels had decreased to 73+/-(SEM) 13% of individual pretreatment levels (p=0.002)and remained constant thereafter. While the correlation between leptin, BMI, and weight persisted throughout the study period, the changes in leptin concentrations during treatment were not associated with changes in BMI, weight,height, insulinlike growth factor 1, and insulinlike growth factor binding protein 3. In conclusion, this preliminary study demonstrates that serum leptin decreases during GH treatment in children with GH deficiency.MH - Proteins|*MEMH - Somatropin|*AE/*DF/TUSO - Horm Res 1998; 50(1):18-21DP - 1998TA - Horm ResPG - 18-21IP - 1VI - 50UI - 98359231109
AU - Sierra Honigmann MR
AU - Nath AK
AU - Murakami C
AU - Garca Carde±a G
AU - Papapetropoulos A
AU - Sessa WC
AU - Madge LA
AU - Schechner JS
AU - Schwabb MB
AU - Polverini PJ
AU - Flores Riveros JRTI - Biological action of leptin as an angiogenic factor [see comments]AB - Leptin is a hormone that regulates food intake, and its receptor (OB-Rb) is expressed primarily in the hypothalamus.Here, it is shown that OB-Rb is also expressed in human vasculature and in primary cultures of human endothelial cells. In vitro and in vivo assays revealed that leptin has angiogenic activity. In vivo, leptin induced neovascularization in corneas from normal rats but not in corneas from fa/fa Zucker rats, which lack functional leptin receptors.These observations indicate that the vascular endothelium is a target for leptin and suggest a physiological mechanism whereby leptin-induced angiogenesis may facilitate increased energy expenditure.MH - Carrier Proteins|AN/*PHMH - Endothelium, Vascular|CH/CY/*PHMH - Neovascularization, Physiologic|*MH - Proteins|PD/*PHSO - Science 1998 Sep; 281(5383):1683-6DP - 1998 SepTA - SciencePG - 1683-6IP - 5383VI - 281UI - 98404276110
AU - Van den Berghe G
AU - Wouters P
AU - Carlsson L
AU - Baxter RC
AU - Bouillon R
AU - Bowers CYTI - Leptin levels in protracted critical illness: effects of growth hormone-secretagogues and thyrotropin-releasing hormone.AB - Prolonged critical illness is characterized by feeding-resistant wasting of protein, whereas reesterification,instead of oxidation of fatty acids, allows fat stores to accrue and associate with a low-activity status of the somatotropic and thyrotropic axis, which seems to be partly of hypothalamic origin. To further unravel this paradoxical metabolic condition, and in search of potential therapeutic strategies, we measured serum concentrations of leptin;studied the relationship with body mass index, insulin,cortisol, thyroid hormones, and somatomedins; and documented the effects of hypothalamic releasing factors, in particular,GH-secretagogues and TRH. Twenty adults, critically ill for several weeks and supported with normocaloric, continuously administered parenteral and/or enteral feeding, were studied for 45 h. They had been randomized to receive one of three combinations of peptide infusions, in random order: TRH (one day) and placebo (other day); TRH + GH-releasing peptide (GHRP)-2 and GHRP-2; TRH + GHRH + GHRP-2 and GHRH + GHRP-2. Peptide infusions were started after a 1-microgram/kg bolus at 0900 h and infused (1 microgram/kg.h) until 0600 h the next morning. Serum concentrations of leptin, insulin,cortisol, T4, T3, insulin-like growth factor (IGF)-I, IGF-binding protein-3 and the acid-labile subunit (ALS) were measured at 0900 h, 2100 h, and 0600 h on each of the 2 study days. Baseline leptin levels (mean +/- SEM: 12.4 +/- 2.1 micrograms/L) were independent of body mass index (25 +/- 1 kg/m2), insulin (18.6 +/- 2.9 microIU/mL), cortisol (504 +/- 43 mmol/L), and thyroid hormones (T4: 63 +/- 5 nmol/L, T3: 0.72 +/- 0.08 nmol/L) but correlated positively with circulating levels of IGF-I [86 +/- 6 micrograms/L,determination coefficient (R2) = 0.25] and ALS (7.2 +/-0.6 mg/L, R2 = 0.32). Infusion of placebo or TRH had no effect on leptin. In contrast, GH-secretagogues elevated leptin levels within 12 h. Infusion of GHRP-2 alone induced a maximal leptin increase of +87% after 24 h, whereas GHRH + GHRP-2 elevated leptin by up to +157% after 24 h. The increase in leptin within 12 h was related (R2 = 0.58) to the substantial rise in insulin. After 45 h, and having reached a plateau, leptin was related to the increased IGF-I (R2 = 0.37). In conclusion, circulating leptin levels during protracted critical illness were linked to the activity state of the GH/IGF-I axis. Stimulating the GH/IGF-I axis with GH-secretagogues increased leptin levels within 12 h. Because leptin may stimulate oxidation of fatty acids,and because GH, IGF-I, and insulin have a protein-sparing effect, GH-secretagogue administration may be expected to result in increased utilization of fat as preferential substrate and to restore protein content in vital tissues and, consequently, has potential as a strategy to reverse the paradoxical metabolic condition of protracted critical illness.MH - Critical Illness|*MH - Proteins|*MEMH - Protirelin|*TUMH - Somatotropin-Releasing Hormone|*TUMH - Somatropin|*SESO - J Clin Endocrinol Metab 1998 Sep; 83(9):3062-70DP - 1998 SepTA - J Clin Endocrinol MetabPG - 3062-70IP - 9VI - 83UI - 98417926111
AU - Kotz CM
AU - Briggs JE
AU - Pomonis JD
AU - Grace MK
AU - Levine AS
AU - Billington CJTI - Neural site of leptin influence on neuropeptide Y signaling pathways altering feeding and uncoupling protein.AB - Inhibition of a signal that produces positive energy balance involving neuropeptide Y (NPY) projection from arcuate nucleus (Arc; site of NPY synthesis) to paraventricular nucleus (PVN; site of NPY release) is one potential mechanism of leptin action. NPY in the PVN increases feeding and decreases uncoupling protein (UCP) activity in brown fat,whereas leptin decreases NPY biosynthesis in the Arc, which presumably decreases PVN NPY. It is hypothesized that decreased NPY activity is necessary for the satiety and thermogenic effects of leptin. To test this, we first determined the effect of leptin on feeding in two paradigms: satiated rats and food-deprived rats. Leptin was effective in decreasing feeding in the satiated rats but ineffective in the food-deprived rats. Next, we determined that leptin decreases NPY and increases UCP gene expression. Finally, we injected leptin intracerebroventricularly before specific PVN NPY microinjection. We found that repletion of NPY in PVN by specific NPY microinjection reverses the feeding-inhibitory and thermogenic effects of centrally administered leptin,the first functional evidence indicating that leptin acts on the Arc-PVN feeding-regulatory pathway.MH - Arcuate Nucleus|DE/*PHMH - Carrier Proteins|BI/*GEMH - Cerebral Ventricles|DE/*PHMH - Feeding Behavior|DE/*PHMH - Gene Expression Regulation|*DEMH - Membrane Proteins|BI/*GEMH - Neuropeptide Y|BI/*GE/*PHMH - Paraventricular Hypothalamic Nucleus|DE/*PHMH - Proteins|AD/*PD/PHSO - Am J Physiol 1998 Aug; 275(2 Pt 2):R478-84DP - 1998 AugTA - Am J PhysiolPG - R478-84IP - 2 Pt 2VI - 275UI - 98355977112
AU - Scarpace PJ
AU - Matheny MTI - Leptin induction of UCP1 gene expression is dependent on sympathetic innervation.AB - We previously demonstrated that leptin increases uncoupling protein 1 (UCP1) and lipoprotein lipase (LPL) gene expression in brown adipose tissue (BAT) of rats. To determine whether the induction of these transcripts is dependent on sympathetic innervation of BAT, we unilaterally surgically denervated interscapular BAT in both pair-fed and leptin (0.9 mg/day by infusion)-treated rats. In pair-fed rats, the level of UCP1 mRNA in the denervated BAT pad was 30-47% less than in the innervated pad. In the intact BAT pad, leptin administration increased UCP1 mRNA levels by nearly 2.5-fold compared with pair-fed rats. In contrast, in the denervated BAT pad, there was no increase in UCP1 gene expression.When LPL mRNA was examined in pair-fed rats, there was no difference between innervated and denervated BAT pads.With leptin administration, LPL gene expression increased by 75% in both the innervated and denervated BAT pads. beta3-Adrenergic receptor mRNA was unaffected by either denervation or leptin, whereas uncoupling protein 2 mRNA levels were increased in epididymal white adipose tissue (WAT) but not in perirenal WAT. CGP-12177, a specific beta3-adrenergic receptor agonist, induced nearly a fourfold increase in UCP1 and a twofold increase in LPL gene expression in both the innervated and denervated BAT pads. These data indicate that the leptin induction of UCP1 gene expression in BAT is dependent on sympathetic innervation but that the leptin induction of LPL gene expression is not.MH - Adipose Tissue|*MEMH - Brown Fat|*IR/*MEMH - Carrier Proteins|BI/*GEMH - Gene Expression Regulation|*/DEMH - Membrane Proteins|BI/*GEMH - Proteins|AD/GE/*PD/PHSO - Am J Physiol 1998 Aug; 275(2 Pt 1):E259-64DP - 1998 AugTA - Am J PhysiolPG - E259-64IP - 2 Pt 1VI - 275UI - 98365316113
AU - Gertler A
AU - Simmons J
AU - Keisler DHTI - Large-scale preparation of biologically active recombinant ovine obese protein (leptin).AB - Prokaryotic expression vector pMON3401 encoding full size A(-1) ovine leptin was prepared by polymerase chain reaction (PCR) of previously described cDNA. E. coli cells transformed with this vector overexpressed large amounts of ovine leptin upon induction with nalidixic acid. The expressed protein found in the inclusion bodies was refolded and purified to homogeneity on Q-Sepharose and SP-Sepharose columns,yielding two electrophoretically pure fractions (leptin-Q and leptin-SP), composed respectively of 90 and 95% of monomeric protein of the expected molecular mass of 16 kDa. The purified protein was capable of interacting with antibodies raised against (GST-ovine leptin and to bind specifically to ventromedial hypothalamus of ewes. The biological activity of both fractions resulting from proper renaturation was further evidenced by their ability to stimulate DNA synthesis in leptin-sensitive BAF/3 cells transfected with a long form of human leptin receptor construct.MH - Cloning, Molecular|*MTMH - Proteins|*BI/CH/*PDSO - FEBS Lett 1998 Jan; 422(2):137-40DP - 1998 JanTA - FEBS LettPG - 137-40IP - 2VI - 422UI - 98149636114
AU - Guerre Millo MTI - Regulation of ob gene and overexpression in obesity.AB - The ob gene product, called leptin, is a recently discovered hormone secreted by the adipose cells. By acting as a satiety factor and increasing energy expenditure, leptin plays a major role in body weight homeostasis in mice. Ob gene and leptin production by the adipose cells are under the control of various hormonal and metabolic factors. Ob mRNA levels are markedly reduced by fasting and restored to normal by refeeding. High-fat feeding increases ob gene and plasma leptin, and induces a state of resistance to leptin. Two hormones, insulin and corticosterone, increase leptin production in rodent and human adipose cells. In contrast, the activity of the sympathetic nervous system exerts an opposite effect, mainly through activation of the adipose beta 3-adrenergic receptors. Leptin synthesis is also decreased by thiazolidinediones, a new class of antidiabetic drugs. The obese Zucker fa/fa rats bear a mutation in the leptin receptor gene (OB-R) and are leptin resistant. In these rats, ob mRNA levels are increased early in life and are not reduced by fasting. This suggests that functional OB-Rs are required for the generation of the signal(s) that downregulates ob gene expression in the adipose cell. The extent to which this is relevant to human obesities, which are characterized by increased leptin levels, remains to be determined.MH - Gene Expression Regulation|*MH - Obesity|*GESO - Biomed Pharmacother 1997; 51(8):318-23DP - 1997TA - Biomed PharmacotherPG - 318-23IP - 8VI - 51UI - 98099108115
AU - Fehmann HC
AU - Peiser C
AU - Bode HP
AU - Stamm M
AU - Staats P
AU - Hedetoft C
AU - Lang RE
AU - G÷ke BTI - Leptin: a potent inhibitor of insulin secretion.AB - The hormone leptin is expressed and secreted by the adipose tissue and impacts on the central nervous system. Leptin is involved in the regulation of energy balance, satiety,and body composition. The lack of active leptin results in obesity, high food intake, hyperglycemia, and hyperinsulinemia.We present data supporting effects of leptin on the endocrine pancreas. We found the leptin receptor to be expressed in insulin- and glucagon-secretin cells derived from mouse,hamster, and rat pancreas. In the isolated perfused rat pancreas leptin is a potent inhibitor of basal and glucose-induced insulin secretion, especially during the first phase of the insulin response. At isolated mouse islets and insulin-secreting INS-1 cells leptin reduced promptly and persistently the intracellular Ca2+ levels. Cytoplasmic Ca2+ oscillation amplitude was decreased and the oscillation frequency increased. These findings suggest functional active receptors for leptin on insulin-secreting B-cells.Therefore, leptin is a metabolic hormone and not only a signal to the brain indicating filled fat stores. Our data suggest that leptin is also a signal back to the endocrine pancreas that no more insulin is required to replenish fat stores. Thus, an "adipo-insular axis" operating with two arms exists: insulin and glucagon are signals to the adipocyte. This releases leptin, which could be the mediator of the respective feedback to the pancreas. A defective leptin suppression of insulin secretion could contribute to hyperinsulinemia and disturbances of glucose metabolism.MH - Insulin|*SEMH - Islets of Langerhans|ME/*SEMH - Proteins|PD/*PHSO - Peptides 1997; 18(8):1267-73DP - 1997TA - PeptidesPG - 1267-73IP - 8VI - 18UI - 98057854116
AU - Frhbeck G
AU - Aguado M
AU - Martnez JATI - In vitro lipolytic effect of leptin on mouse adipocytes:evidence for a possible autocrine/paracrine role of leptin.AB - The present study has examined the effects of the adipocyte-derived hormone, leptin, on lipolysis in fat cells of different types of mice. Exposure to leptin (1.25.10(-6) M to 1.25.10(-12) M) increased (P < 0.01) the lipolytic activity of fat cells obtained from lean mice. A greater stimulation was observed when adipocytes from ob/ob mice were examined.Throughout the concentrations tested, the leptin-induced lipolysis observed in fat cells of lean animals was smaller than that obtained in ob/ob mice. The maximal lipolytic effect in obese animals was observed with 10(-8) M of OB protein. The lipolytic activity following the addition of 1.25.10(-10) M to 1.25.10(-6) M was significantly increased (P < 0.01) in ob/ob mice compared to lean animals. Adipocytes from ob/ob mice responded in a dose-dependent manner to the OB protein, while the leptin-induced lipolysis observed in lean animals was dose-independent. In contrast to lean and ob/ob mice, leptin did not stimulate lipolysis in adipocytes from db/db mice, which have a mutation in the leptin receptor gene. These in vitro studies suggest an autocrine/paracrine action of leptin on white fat cells and envisages the involvement of the OB protein, not only in centrally mediated pathways,but also in physiological functions which take place peripherally.MH - Adipocytes|DE/*MEMH - Lipolysis|*DEMH - Proteins|GE/ME/*PDSO - Biochem Biophys Res Commun 1997 Nov; 240(3):590-4DP - 1997 NovTA - Biochem Biophys Res CommunPG - 590-4IP - 3VI - 240UI - 98063281117
AU - Wang Y
AU - Kuropatwinski KK
AU - White DW
AU - Hawley TS
AU - Hawley RG
AU - Tartaglia LA
AU - Baumann HTI - Leptin receptor action in hepatic cells.AB - Leptin, an adipocyte-secreted hormone, is one of the central regulators of body weight homeostasis. In humans and rodents,two major forms of leptin receptors (OB-R) are expressed.The short form (OB-RS), considered to lack signaling capability,is detected in many organs. In contrast, OB-R long form (OB-RL) predominates in the hypothalamus, but is also present at low levels in peripheral tissues. Transient transfection experiments have demonstrated that OB-RL transduces an intracellular signaling similar to interleukin (IL)-6 type-cytokine receptors. To define the specificity by which OB-R induces genes and cooperates with signal transduction pathways utilized by other hormones and cytokines, rat and human hepatoma cell lines were generated which stably express human OB-RL. Hepatoma cell lines selected for appreciable levels of OB-RL mRNA display enhanced leptin binding and responded to leptin with an IL-6 receptor-like signaling that includes the activation of STAT proteins, induction of acute-phase plasma proteins, and synergism with IL-1 and tumor necrosis factor-alpha. A leptin-mediated recruitment of phosphatidylinositol 3-kinase to insulin receptor substrate-2 was also detected. However, no significant tyrosine phosphorylation of insulin receptor substrate-2 and modulation of the immediate cell response to insulin were observed. The data suggest that OB-RL action in hepatic cells is equivalent to that of IL-6 receptor. However, leptin does not play a specific role in muting insulin action on hepatoma cells and therefore may not contribute to the diabetic symptoms associated with obesity.MH - Antigens, CD|*PHMH - Carrier Proteins|GE/*PHMH - Liver|*MEMH - Receptors, Interleukin|*PHSO - J Biol Chem 1997 Jun; 272(26):16216-23DP - 1997 JunTA - J Biol ChemPG - 16216-23IP - 26VI - 272UI - 97341153118
AU - Koyama K
AU - Chen G
AU - Wang MY
AU - Lee Y
AU - Shimabukuro M
AU - Newgard CB
AU - Unger RHTI - beta-cell function in normal rats made chronically hyperleptinemic by adenovirus-leptin gene therapy.AB - Leptin was overexpressed in the liver of normal Wistar rats by infusing recombinant adenovirus containing the cDNA encoding leptin. Plasma leptin levels rose to 12-24 ng/ml (vs. <2 ng/ml in control rats), and food intake and body weight fell. Visible fat disappeared within 7 days.Plasma insulin fell to <50% of normal in association with hypoglycemia, suggesting enhanced insulin sensitivity. Although beta-cells appeared histologically normal, the pancreases were unresponsive to perfusion with stimulatory levels of glucose and arginine. Since islet triglyceride content was 0, compared with 14 ng/islet in pair-fed control rats, we coperfused a 2:1 oleate:palmitate mixture (0.5 mmol/l). This restored insulin responses to supranormal levels. When normal islets were cultured with 20 ng/ml of leptin, they too became triglyceride-depleted and failed to respond when perifused with glucose or arginine. Perifusion of fatty acids restored both responses. We conclude that in normal rats, hyperleptinemia for 2 weeks causes reversible beta-cell dysfunction by depleting tissue lipids, thereby depriving beta-cells of a lipid-derived signal required for the insulin response to other fuels.MH - Adenoviridae|*GEMH - Gene Therapy|*MH - Islets of Langerhans|CY/*MEMH - Pancreas|CY/*MEMH - Proteins|*AN/*GE/MESO - Diabetes 1997 Aug; 46(8):1276-80DP - 1997 AugTA - DiabetesPG - 1276-80IP - 8VI - 46UI - 97375334119
AU - Gloaguen I
AU - Costa P
AU - Demartis A
AU - Lazzaro D
AU - Di Marco A
AU - Graziani R
AU - Paonessa G
AU - Chen F
AU - Rosenblum CI
AU - Van der Ploeg LH
AU - Cortese R
AU - Ciliberto G
AU - Laufer RTI - Ciliary neurotrophic factor corrects obesity and diabetes associated with leptin deficiency and resistance.AB - Receptor subunits for the neurocytokine ciliary neurotrophic factor (CNTF) share sequence similarity with the receptor for leptin, an adipocyte-derived cytokine involved in body weight homeostasis. We report here that CNTF and leptin activate a similar pattern of STAT factors in neuronal cells, and that mRNAs for CNTF receptor subunits, similarly to the mRNA of leptin receptor, are localized in mouse hypothalamic nuclei involved in the regulation of energy balance. Systemic administration of CNTF or leptin led to rapid induction of the tis-11 primary response gene in the arcuate nucleus, suggesting that both cytokines can signal to hypothalamic satiety centers. Consistent with this idea, CNTF treatment of ob/ob mice, which lack functional leptin, was found to reduce the adiposity, hyperphagia,and hyperinsulinemia associated with leptin deficiency.Unlike leptin, CNTF also reduced obesity-related phenotypes in db/db mice, which lack functional leptin receptor, and in mice with diet-induced obesity, which are partially resistant to the actions of leptin. The identification of a cytokine-mediated anti-obesity mechanism that acts independently of the leptin system may help to develop strategies for the treatment of obesity associated with leptin resistance.MH - Diabetes Mellitus, Non-Insulin-Dependent|PP/*THMH - DNA-Binding Proteins|*MEMH - Nerve Growth Factors|*PDMH - Nerve Tissue Proteins|*PDMH - Obesity|*DT/GE/PPMH - Proteins|GE/*PD/PHSO - Proc Natl Acad Sci U S A 1997 Jun; 94(12):6456-61DP - 1997 JunTA - Proc Natl Acad Sci U S APG - 6456-61IP - 12VI - 94UI - 97322394120
AU - Wolf G
AU - Hamann A
AU - Han DC
AU - Helmchen U
AU - Thaiss F
AU - Ziyadeh FN
AU - Stahl RATI - Leptin stimulates proliferation and TGF-beta expression in renal glomerular endothelial cells: potential role in glomerulosclerosis [seecomments]AB - BACKGROUND: Leptin inhibits food intake and increases energy expenditure. Although the kidney expresses abundant transcripts of the short form of the leptin receptor (Ob-Ra), a role for this hormone in renal function remains unclear. Because individuals with massive obesity who may exhibit increased leptin serum concentrations develop renal glomerulosclerosis,we studied whether leptin can influence renal growth and profibrogenic processes. METHODS: The effects of recombinant leptin on proliferation and synthesis of transforming growth factor-beta1 (TGF-beta1) was investigated in cultured glomerular endothelial cells of the rat (GERs) and syngeneic mesangial cells. Furthermore, leptin receptor expression and potential signal transduction pathways were evaluated in GERs. In addition, leptin was also infused for different time periods (72 hr and 3 weeks) into naive rats. RESULTS: Recombinant mouse leptin induced proliferation of GERs, but not of syngeneic mesangial cells. Coincubation with angiotensin II and leptin exerts additive proliferative effects in GERs. An antileptin-receptor antibody totally abolished this proliferation but did not influence serum-induced proliferation. GER expressed high affinity receptors of the Ob-Ra type (Kd, 4 nM; Bmax, 9700 receptors/cell). Leptin also stimulated phosphorylation of STAT1alpha, and kinase inhibitors attenuated proliferation, suggesting a pivotal role of phosphorylation in this process. Incubation of GERs with leptin also induced mRNA expression of TGF-beta1 and enhanced secretion of this profibrogenic cytokine. Short-term leptin infusion (72 hr) into naive rats induced a significant proliferation, mainly restricted to glomerular endothelial cells, and enhanced glomerular TGF-beta1 mRNA levels. In rats continuously infused for three weeks with leptin, glomerular TGF-beta1 expression was still enhanced,and an additional increase in glomerular collagen type IV mRNA and protein expression was detected. These animals revealed an increase in proteinuria compared with control-infused rats. CONCLUSION: Our findings are the first in vitro and in vivo demonstration that leptin is a renal growth and profibrogenic factor. These results may be an important contribution to our understanding of how leptin can contribute to renal damage, characterized by endocapillary proliferation and subsequent development of glomerulosclerosis,in pathophysiological situations with high circulating levels such as in diabetics or obese individuals. Although the effects of leptin itself are moderate, growth-promoting and profibrogenic effects may be enhanced in concert with other factors such as angiotensin II.MH - Glomerulosclerosis, Focal|*ETMH - Kidney Glomerulus|*CY/*DE/MEMH - Proteins|AD/*PDMH - Transforming Growth Factor beta|*BI/*GESO - Kidney Int 1999 Sep; 56(3):860-72DP - 1999 SepTA - Kidney IntPG - 860-72IP - 3VI - 56UI - 99398516121
AU - Patel N
AU - Brinkman Van der Linden EC
AU - Altmann SW
AU - Gish K
AU - Balasubramanian S
AU - Timans JC
AU - Peterson D
AU - Bell MP
AU - Bazan JF
AU - Varki A
AU - Kastelein RATI - OB-BP1/Siglec-6. a leptin- and sialic acid-binding protein of the immunoglobulin superfamily.AB - We report the expression cloning of a novel leptin-binding protein of the immunoglobulin superfamily (OB-BP1) and a cross-hybridizing clone (OB-BP2) that is identical to a recently described sialic acid-binding I-type lectin called Siglec-5. Comparisons to other known Siglec family members (CD22, CD33, myelin-associated glycoprotein, and sialoadhesin) show that OB-BP1, OB-BP2/Siglec-5, and CD33/Siglec-3 constitute a unique related subgroup with a high level of overall amino acid identity: OB-BP1 versus Siglec-5 (59%), OB-BP1 versus CD33 (63%), and OB-BP2/Siglec-5 versus CD33 (56%). The cytoplasmic domains are not as highly conserved, but display novel motifs which are putative sites of tyrosine phosphorylation, including an immunoreceptor tyrosine kinase inhibitory motif and a motif found in SLAM and SLAM-like proteins. Human tissues showed high levels of OB-BP1 mRNA in placenta and moderate expression in spleen,peripheral blood leukocytes, and small intestine. OB-BP2/Siglec-5 mRNA was detected in peripheral blood leukocytes,lung, spleen, and placenta. A monoclonal antibody specific for OB-BP1 confirmed high expression in the cyto- and syncytiotrophoblasts of the placenta. Using this antibody on peripheral blood leukocytes showed an almost exclusive expression pattern on B cells. Recombinant forms of the extracellular domains of OB-BP1, OB-BP2/Siglec-5, and CD33/Siglec-3 were assayed for specific binding of leptin. While OB-BP1 exhibited tight binding (K(d) 91 nM), the other two showed weak binding with K(d) values in the 1-2 microM range. Studies with sialylated ligands indicated that OB-BP1 selectively bound Neu5Acalpha2-6GalNAcalpha (sialyl-Tn) allowing its formal designation as Siglec-6. The identification of OB-BP1/Siglec-6 as a Siglec family member, coupled with its restricted expression pattern, suggests that it may mediate cell-cell recognition events by interacting with sialylated glycoprotein ligands expressed on specific cell populations. We also propose a role for OB-BP1 in leptin physiology, as a molecular sink to regulate leptin serum levels.MH - Antigens, CD|GE/IP/*MEMH - Antigens, Differentiation, Myelomonocytic|GE/IP/*MEMH - Immunoglobulins|*GEMH - Multigene Family|*MH - N-Acetylneuraminic Acid|*MEMH - Proteins|*MESO - J Biol Chem 1999 Aug; 274(32):22729-38DP - 1999 AugTA - J Biol ChemPG - 22729-38IP - 32VI - 274UI - 99357812122
AU - Jin L
AU - Burguera BG
AU - Couce ME
AU - Scheithauer BW
AU - Lamsan J
AU - Eberhardt NL
AU - Kulig E
AU - Lloyd RVTI - Leptin and leptin receptor expression in normal and neoplastic human pituitary: evidence of a regulatory role for leptin on pituitary cell proliferation.AB - Leptin is a circulating hormone secreted by adipose and a few other tissues. The leptin receptor consists of a single transmembrane-spanning polypeptide that is present as a long physiologically important form as well as in several short isoforms. Recent studies have suggested that the anterior pituitary may have a role in the regulatory effects of leptin in animal models. To test this possibility in human pituitaries, we examined the expression of leptin and OB-R in normal and neoplastic pituitaries, and the possible functions of leptin in the pituitary were also analyzed. Leptin was present in 20-25% of anterior pituitary cells and was expressed in most normal anterior pituitary cells, including ACTH (70% of ACTH cells), GH (21%), FSH (33%), LH (29%), TSH (32%), and folliculo-stellate cells (64%), but was colocalized with very few PRL cells (3%), as detected by double labeling immunohistochemistry with two different antileptin antibodies. In addition, leptin expression was detected by RT-PCR in some pituitary tumors,including ACTH (three of four), GH (one of four), null cells (two of four), and gonadotroph (one of four) tumors as well as in normal pituitary. Immunohistochemical staining showed greater immunoreactivity for leptin in normal pituitaries compared to adenomas. Treatment of an immortalized cultured anterior pituitary cell line, HP75, with leptin stimulated pancreastatin secretion in vitro. Leptin also inhibited cell growth in the human HP75 and in the rat pituitary GH3 cell lines. Both long (OB-Rb) and common (OB-Ra) forms of the leptin receptor messenger ribonucleic acid and leptin receptor protein were expressed in normal and neoplastic anterior pituitary cells. These findings show for the first time that leptin is expressed by most human anterior pituitary cell types and that there is decreased leptin protein immunoreactivity in pituitary adenomas compared to that in normal pituitary tissues. We also show that OB-Rb is widely expressed by normal and neoplastic anterior pituitary cells, implicating an autocrine/paracrine loop in the production and regulation of leptin in the pituitary.MH - Carrier Proteins|*AN/GEMH - Pituitary Gland|*CH/CYMH - Pituitary Neoplasms|*CHMH - Proteins|AN/GE/*PHSO - J Clin Endocrinol Metab 1999 Aug; 84(8):2903-11DP - 1999 AugTA - J Clin Endocrinol MetabPG - 2903-11IP - 8VI - 84UI - 99371298123
AU - Gmez Ambrosi J
AU - Frhbeck G
AU - Martnez JATI - Leptin, but not a beta 3-adrenergic agonist, upregulates muscle uncoupling protein-3 messenger RNA expression: short-term thermogenic interactions.AB - The short-term effects of leptin and a beta 3-adrenoceptor agonist on thermogenesis and expression of uncoupling proteins (UCPs) in brown adipose tissue (BAT) and muscle and their possible interactions were assessed. One hour after administration of the beta 3-adrenoceptor agonist Trecadrine, a statistically significant increase in UCP1 messenger RNA (mRNA) expression in BAT was observed, whereas UCP2 and UCP3 in both BAT and gastrocnemius muscle were unaffected. Leptin induced an upregulation of UCP3 mRNA in muscle, with no changes in BAT UCP1 mRNA. A statistical interaction was found between leptin and Trecadrine in rectal temperature. The present study provides evidence, for the first time, of the induction of UCP3 mRNA expression in skeletal muscle by leptin in nongenetically obese animals.MH - Adrenergic beta-Agonists|*PDMH - Benzyl Alcohols|*PDMH - Body Temperature Regulation|*DEMH - Carrier Proteins|*BI/GEMH - Gene Expression Regulation|*DEMH - Muscle Proteins|*BI/GEMH - Proteins|BI/GE/*PHMH - Receptors, Adrenergic, beta|*DE/PHSO - Cell Mol Life Sci 1999 Jun; 55(6-7):992-7DP - 1999 JunTA - Cell Mol Life SciPG - 992-7IP - 6-7VI - 55UI - 99340887124
AU - Tsuchiya T
AU - Shimizu H
AU - Horie T
AU - Mori MTI - Expression of leptin receptor in lung: leptin as a growth factor.AB - Leptin receptors are expressed in various tissues in rodents but their function is not clear. The present studies were undertaken to investigate the function of the leptin receptor in mouse and human lungs. Cell proliferation, assessed with [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT), was significantly less in primary cultures of tracheal epithelial cells of db/db mice than in those of their lean littermates. Mouse recombinant leptin significantly increased cell proliferation only in lean mice, but not in db/db mice. Reverse transcription-polymerase chain reaction (RT-PCR) study demonstrated the existence of a long form,OB-Rb type leptin receptor in both human lung tissue and lung squamous cell line (SQ-5). Cell proliferation, assessed with MTT, was dose-dependently increased in SQ-5 cells incubated with 10-1000 ng/ml human recombinant leptin for 6 h. The 5-bromo-2'-deoxyuridine (BrdU) uptake into SQ-5 cells was also increased by the addition of 10-100 ng/ml human recombinant leptin. Mitogen-activated protein (MAP) kinase activity was significantly increased by 10 and 100 ng/ml human recombinant leptin in SQ-5 cells. MAP kinase kinase (MEK)-1-specific inhibitor, (2-[2-amino-3-methoxyphenyl]-4H-1-benzopyran-4-one) (PD98059), blocked the increase in BrdU uptake into SQ-5 cells caused by human recombinant leptin. In conclusion, leptin (OB-Rb) receptors exist in human lung tissue and leptin may have stimulatory effects on the proliferation of cells of a human cell line and mouse tracheal epithelial cells through its specific leptin receptor.MH - Carrier Proteins|*ME/PHMH - Obesity|*GEMH - Proteins|*PDSO - Eur J Pharmacol 1999 Jan; 365(2-3):273-9DP - 1999 JanTA - Eur J PharmacolPG - 273-9IP - 2-3VI - 365UI - 99140611125
AU - Shimabukuro M
AU - Wang MY
AU - Zhou YT
AU - Newgard CB
AU - Unger RHTI - Protection against lipoapoptosis of beta cells through leptin-dependent maintenance of Bcl-2 expression.AB - Obesity causes its complications through functional and morphologic damage to remotely situated tissues via undetermined mechanisms. In one rodent model of obesity, the Zucker diabetic fatty fa/fa rat, overaccumulation of triglycerides in the pancreatic islets may be responsible for a gradual depletion of beta cells, leading to the most common complication of obesity, non-insulin-dependent diabetes mellitus. At the onset of non-insulin-dependent diabetes mellitus, the islets from fa/fa rats contain up to 100 times the fat content of islets from normal lean rats. Ultimately, about 75% of the beta cells disappear from these fat-laden islets as a consequence of apoptosis induced by long-chain fatty acids (FA). Here we quantify Bcl-2, the anti-apoptosis factor in these islets, and find that Bcl-2 mRNA and protein are, respectively, 85% and 70% below controls. In normal islets cultured in 1 mM FA, Bcl-2 mRNA declined by 68% and completely disappeared in fa/fa islets cultured in FA. In both groups, suppression was completely blocked by the fatty acyl-CoA synthetase inhibitor, triacsin C,evidence of its mediation by fatty acyl-CoA. To determine whether leptin action blocked FA-induced apoptosis, we cultured normal and fa/fa islets in 1 mM FA with or without leptin. Leptin completely blocked FA-induced Bcl-2 suppression in normal islets but had no effect on islets from fa/fa rats, which are unresponsive to leptin because of a mutation in their leptin receptors (OB-R). However, when wild-type OB-R is overexpressed in fa/fa islets, leptin completely prevented FA-induced Bcl-2 suppression and DNA fragmentation.MH - Apoptosis|*/*PHMH - Gene Expression Regulation|*PHMH - Islets of Langerhans|*PAMH - Proteins|*PHMH - Proto-Oncogene Proteins c-bcl-2|*GESO - Proc Natl Acad Sci U S A 1998 Aug; 95(16):9558-61DP - 1998 AugTA - Proc Natl Acad Sci U S APG - 9558-61IP - 16VI - 95UI - 98356196126
AU - Yarnell DO
AU - Knight DS
AU - Hamilton K
AU - Tulp O
AU - Tso PTI - Localization of leptin receptor immunoreactivity in the lean and obese Zucker rat brain.AB - Leptin, a product of the obese (ob) gene, is secreted by adipocytes and appears to act as a hormone to regulate food intake, metabolism and body weight. Subcutaneous administration of leptin causes reductions in food intake and body and fat-depot weights in both lean and genetically obese (ob/ob) mice, and leptin infusion into the lateral cerebral ventricles decreases feeding with short latency, suggesting a central site of action. A gene defect in the Zucker obese rat causes an amino acid substitution in the leptin receptor and reduced leptin binding at the cell surface. An antiserum to a portion of the mouse leptin receptor (AA 877-894) located within the intracellular domain was used to label Zucker lean (Fa/?) and obese (fa/fa) rat brain sections.At optimal dilution (1:8000), only cells in the basal forebrain,preoptic area, hypothalamus and brainstem were moderately or intensely labeled. The most intensely-labeled nuclei,the anterior commissural, magnocellular paraventricular,supraoptic, circularis in the anterior hypothalamus and fornical in the lateral hypothalamus contain large neurons that synthesize and secrete vasopressin or oxytocin and their respective neurophysins. Diminished leptin transport into the central nervous system or defective signal transduction in Zucker obese rats may sufficiently compromise leptin regulation of the HPA axis, NPY-immunoreactive neurons or other hypothalamic elements to cause obesity. Copyright 1998 Elsevier Science B.V.MH - Brain|CY/*ME/PAMH - Carrier Proteins|AN/GE/*MEMH - Obesity|GE/*ME/PAMH - Proteins|*PDSO - Brain Res 1998 Feb; 785(1):80-90DP - 1998 FebTA - Brain ResPG - 80-90IP - 1VI - 785UI - 98195333127
AU - Stephens TW
AU - Caro JFTI - To be lean or not to be lean. Is leptin the answer?AB - Leptin and the leptin receptor genes have been identified as the site of mutations in the peripheral adipocyte hormone pathway responsible for obesity in the ob/ob mouse (Zhang et al., 1994) and the db/db mouse (Chen et al., 1996). In obese humans, ob/ob like mutations in leptin are rare but confirm a role for leptin (Montague et al., 1997), and db/db like mutations in the leptin receptor have not been found (Considine et al., 1996a); however, the increased understanding of the molecular basis for obesity has generated tremendous interest among scientists and patients alike.The new knowledge could be the base for intelligent drugs for the treatment of obesity. Herein we will put in perspective a) the physiological background that led to the discovery of leptin, b) leptin biosynthesis, c) leptin action and d) the clinical issues related to leptin as a drug for the treatment of obesity.MH - Carrier Proteins|GE/*PHMH - Obesity|DT/*PPMH - Proteins|GE/*PH/TUSO - Exp Clin Endocrinol Diabetes 1998; 106(1):1-15DP - 1998TA - Exp Clin Endocrinol DiabetesPG - 1-15IP - 1VI - 106UI - 98175809128
AU - Loffreda S
AU - Yang SQ
AU - Lin HZ
AU - Karp CL
AU - Brengman ML
AU - Wang DJ
AU - Klein AS
AU - Bulkley GB
AU - Bao C
AU - Noble PW
AU - Lane MD
AU - Diehl AMTI - Leptin regulates proinflammatory immune responses.AB - Obesity is associated with an increased incidence of infection,diabetes, and cardiovascular disease, which together account for most obesity-related morbidity and mortality. Decreased expression of leptin or of functional leptin receptors results in hyperphagia, decreased energy expenditure, and obesity. It is unclear, however, whether defective leptin-dependent signal transduction directly promotes any of the conditions that frequently complicate obesity. Abnormalities in tumor necrosis factor alpha expression have been noted in each of the above comorbid conditions, so leptin deficiency could promote these complications if leptin had immunoregulatory activity. Studies of rodents with genetic abnormalities in leptin or leptin receptors revealed obesity-related deficits in macrophage phagocytosis and the expression of proinflammatory cytokines both in vivo and in vitro.Exogenous leptin up-regulated both phagocytosis and the production of proinflammatory cytokines. These results identify an important and novel function for leptin: up-regulation of inflammatory immune responses, which may provide a common pathogenetic mechanism that contributes to several of the major complications of obesity.MH - Cytokines|*BI/GEMH - Macrophages|DE/*IMMH - Phagocytosis|*PHMH - Proteins|*PHSO - FASEB J 1998 Jan; 12(1):57-65DP - 1998 JanTA - FASEB JPG - 57-65IP - 1VI - 12UI - 98099248129
AU - Kulkarni RN
AU - Wang ZL
AU - Wang RM
AU - Hurley JD
AU - Smith DM
AU - Ghatei MA
AU - Withers DJ
AU - Gardiner JV
AU - Bailey CJ
AU - Bloom SRTI - Leptin rapidly suppresses insulin release from insulinoma cells, rat and human islets and, in vivo, in mice.AB - Obesity is associated with diabetes, and leptin is known to be elevated in obesity. To investigate whether leptin has a direct effect on insulin secretion, isolated rat and human islets and cultured insulinoma cells were studied.In all cases, mouse leptin inhibited insulin secretion at concentrations within the plasma range reported in humans.Insulin mRNA expression was also suppressed in the cultured cells and rat islets. The long form of the leptin receptor (OB-Rb) mRNA was present in the islets and insulinoma cell lines. To determine the significance of these findings in vivo, normal fed mice were injected with two doses of leptin. A significant decrease in plasma insulin and associated rise in glucose concentration were observed. Fasted normal and leptin receptor-deficient db/db mice showed no response to leptin. A dose of leptin, which mimicked that found in normal mice, was administered to leptin-deficient, hyperinsulinemic ob/ob mice. This caused a marked lowering of plasma insulin concentration and a doubling of plasma glucose. Thus, leptin has a powerful acute inhibitory effect on insulin secretion.These results suggest that the action of leptin may be one mechanism by which excess adipose tissue could acutely impair carbohydrate metabolism.MH - Insulin|*SEMH - Islets of Langerhans|CY/*MEMH - Obesity|*MH - Proteins|ME/*PHSO - J Clin Invest 1997 Dec; 100(11):2729-36DP - 1997 DecTA - J Clin InvestPG - 2729-36IP - 11VI - 100UI - 98052574130
AU - Goldstone AP
AU - Mercer JG
AU - Gunn I
AU - Moar KM
AU - Edwards CM
AU - Rossi M
AU - Howard JK
AU - Rasheed S
AU - Turton MD
AU - Small C
AU - Heath MM
AU - OShea D
AU - Steere J
AU - Meeran K
AU - Ghatei MA
AU - Hoggard N
AU - Bloom SRTI - Leptin interacts with glucagon-like peptide-1 neurons to reduce food intake and body weight in rodents.AB - The adipose tissue hormone, leptin, and the neuropeptide glucagon-like peptide-1 (7-36) amide (GLP-1) both reduce food intake and body weight in rodents. Using dual in situ hybridization, long isoform leptin receptor (OB-Rb) was localized to GLP-1 neurons originating in the nucleus of the solitary tract. ICV injection of the specific GLP-1 receptor antagonist, exendin(9-39), at the onset of dark phase, did not affect feeding in saline pre-treated controls,but blocked the reduction in food intake and body weight of leptin pre-treated rats. These findings suggest that GLP-1 neurons are a potential target for leptin in its control of feeding.MH - Eating|*/DEMH - Glucagon|AN/GE/*MEMH - Neurons|CH/*MEMH - Peptide Fragments|*ME/PDMH - Protein Precursors|AN/GE/*MEMH - Proteins|AI/*ME/PDMH - Solitary Nucleus|*CY/MESO - FEBS Lett 1997 Sep; 415(2):134-8DP - 1997 SepTA - FEBS LettPG - 134-8IP - 2VI - 415UI - 98010466131
AU - Cheung CC
AU - Clifton DK
AU - Steiner RATI - Proopiomelanocortin neurons are direct targets for leptin in the hypothalamus.AB - Leptin is a protein product of the obese (ob) gene, which is secreted by adipocytes and functions as a satiety factor to regulate food intake. The expression of the leptin receptor in several hypothalamic nuclei suggests that multiple neuronal subtypes are targets for leptin's action. Products of the proopiomelanocortin (POMC) gene are known to affect feeding behavior, and POMC neurons share a similar distribution with leptin receptor mRNA in the arcuate nucleus. We used double label in situ hybridization and computerized image analysis to test the hypothesis that POMC neurons coexpress the leptin receptor. Quantitative analysis confirmed that POMC neurons in the hypothalamus express leptin receptor mRNA. Based on this observation, we infer that POMC neurons and the products of the POMC gene may be part of the signaling pathway mediating leptin's action on feeding and perhaps other physiological functions.MH - Hypothalamus|*CY/DEMH - Neurons|*CH/*DE/ULMH - Pro-Opiomelanocortin|*AN/GE/PHMH - Proteins|*PD/PHSO - Endocrinology 1997 Oct; 138(10):4489-92DP - 1997 OctTA - EndocrinologyPG - 4489-92IP - 10VI - 138UI - 97462742132
AU - Liu YL
AU - Emilsson V
AU - Cawthorne MATI - Leptin inhibits glycogen synthesis in the isolated soleus muscle of obese (ob/ob) mice.AB - The ob gene product, leptin, causes significant and dose-dependent inhibition of basal and insulin-stimulated glycogen synthesis in isolated soleus muscle from ob/ob mice, and a smaller, non-significant inhibition in muscle from wild-type mice. Leptin had no inhibitory effect on glycogen synthesis in soleus muscle from the diabetic (db/db) mice,which lack the functional leptin receptor. The full-length leptin receptor (Ob-Rb), is expressed in soleus muscle of both ob/ob and wild-type mice, however with no detectable differences in expression level. These results suggest that hyperleptinaemia may attenuate insulin action on glucose storage in skeletal muscle.MH - Glycogen|*BI/MEMH - Muscle, Skeletal|*MEMH - Obesity|*MEMH - Proteins|*PDSO - FEBS Lett 1997 Jul; 411(2-3):351-5DP - 1997 JulTA - FEBS LettPG - 351-5IP - 2-3VI - 411UI - 97415435133
AU - Kieffer TJ
AU - Heller RS
AU - Leech CA
AU - Holz GG
AU - Habener JFTI - Leptin suppression of insulin secretion by the activation of ATP-sensitive K+ channels in pancreatic beta-cells.AB - In the genetic mutant mouse models ob/ob or db/db, leptin deficiency or resistance, respectively, results in severe obesity and the development of a syndrome resembling NIDDM.One of the earliest manifestations in these mutant mice is hyperinsulinemia, suggesting that leptin may normally directly suppress the secretion of insulin. Here, we show that pancreatic islets express a long (signal-transducing)form of leptin-receptor mRNA and that beta-cells bind a fluorescent derivative of leptin (Cy3-leptin). The expression of leptin receptors on insulin-secreting beta-cells was also visualized utilizing antisera generated against an extracellular epitope of the receptor. A functional role for the beta-cell leptin receptor is indicated by our observation that leptin (100 ng/ml) suppressed the secretion of insulin from islets isolated from ob/ob mice. Furthermore, leptin produced a marked lowering of [Ca2+]i in ob/ob beta-cells,which was accompanied by cellular hyperpolarization and increased membrane conductance. Cell-attached patch measurements of ob/ob beta-cells demonstrated that leptin activated ATP-sensitive potassium channels (K(ATP)) by increasing the open channel probability, while exerting no effect on mean open time. These effects were reversed by the sulfonylurea tolbutamide, a specific inhibitor of K(ATP). Taken together,these observations indicate an important physiological role for leptin as an inhibitor of insulin secretion and lead us to propose that the failure of leptin to inhibit insulin secretion from the beta-cells of ob/ob and db/db mice may explain, in part, the development of hyperinsulinemia,insulin resistance, and the progression to NIDDM.MH - Adenosine Triphosphate|*PDMH - Carrier Proteins|AN/BI/*GEMH - Insulin|*SEMH - Islets of Langerhans|CH/*PH/ULMH - Potassium Channels|*MEMH - Proteins|*PHSO - Diabetes 1997 Jun; 46(6):1087-93DP - 1997 JunTA - DiabetesPG - 1087-93IP - 6VI - 46UI - 97309270134
AU - Yamashita T
AU - Murakami T
AU - Iida M
AU - Kuwajima M
AU - Shima KTI - Leptin receptor of Zucker fatty rat performs reduced signal transduction.AB - Zucker fatty (fa/fa) rats exhibit overt obesity, hypercholesterolemia,hyperlipidemia, and hyperglycemia as recessive traits. The fa mutation has been determined to be a missense mutation in the extracellular domain of the leptin receptor. We report herein the construction of CHO cells that stably express the fa-type leptin receptor and the characterization of this receptor using mRNA expression levels of the immediate early genes, c-fos, c-jun, and jun-B, which are induced by leptin as a criterion of signal transduction. The fa-type receptor not only exhibits a slightly reduced leptin-binding affinity, but also performs reduced signal transduction.MH - Carrier Proteins|GE/*MEMH - Gene Expression Regulation|*GEMH - Genes, Immediate-Early|*GEMH - Proteins|AN/*ME/*PDMH - Signal Transduction|*SO - Diabetes 1997 Jun; 46(6):1077-80DP - 1997 JunTA - DiabetesPG - 1077-80IP - 6VI - 46UI - 97309268135
AU - Murakami T
AU - Yamashita T
AU - Iida M
AU - Kuwajima M
AU - Shima KTI - A short form of leptin receptor performs signal transduction.AB - The obese (ob) gene product, leptin, a peptide hormone,which is synthesized in adipocytes, is a satiety factor and is involved in the control of body weight via the regulation of energy homeostasis. Several alternate spliced isoforms (a-e, as well as others) of the leptin receptor (OBR) have been cloned, all of which, except for OBRe (soluble form), contain a single transmembrane domain. They share the same extracellular domain, with homology to the class I cytokine receptor family. The OBRb, which has longest cytoplasmic domain, is expressed in high levels in the hypothalamus and is thought to be the only isoform capable of signal transmission. Herein, we report the mRNA expression of immediate early genes, c-fos, c-jun and jun-B, which are induced by leptin addition, not only in CHO cells expressing the OBRb, but also in cells expressing one of the short form receptors, OBRa.MH - Carrier Proteins|CH/GE/*MEMH - Gene Expression Regulation|*MH - Genes, Immediate-Early|*MH - Proteins|ME/*PDMH - Receptors, Cytokine|CH/GE/*MEMH - Signal Transduction|*SO - Biochem Biophys Res Commun 1997 Feb; 231(1):26-9DP - 1997 FebTA - Biochem Biophys Res CommunPG - 26-9IP - 1VI - 231UI - 97223392136
AU - Deuschle M
AU - Blum WF
AU - Englaro P
AU - Schweiger U
AU - Weber B
AU - Pflaum CD
AU - Heuser ITI - Plasma leptin in depressed patients and healthy controls.AB - Leptin is known to regulate food intake and energy expenditure.Since loss of appetite and bodyweight are important signs and symptoms of major depression we studied leptin plasma concentrations in both depressed patients (n = 24) suffering from loss of appetite and a healthy control group (n = 33). To rule out the possibility of inferences with other endocrine parameters known to be changed in depression or suspected to be related to leptin, we also studied cortisol,insulin, growth hormone (GH) and GH-binding protein (GHBP). We found that leptin plasma concentrations did not differ between depressed patients and healthy controls. However,leptin was positively associated with female gender, body mass index (BMI) and morning insulin. 24-hour mean cortisol was not related to leptin. Also, GH and GHBP were not related to leptin when controlled for BMI in an ANCOVA model. We conclude that leptin plasma concentrations are unchanged in depression and that there is no evidence for leptin playing a major role in loss of appetite and body weight in depressed patients.MH - Depression|*BLMH - Proteins|*MESO - Horm Metab Res 1996 Dec; 28(12):714-7DP - 1996 DecTA - Horm Metab ResPG - 714-7IP - 12VI - 28UI - 97165856137
AU - Wang MY
AU - Zhou YT
AU - Newgard CB
AU - Unger RHTI - A novel leptin receptor isoform in rat.AB - Five mouse and human leptin receptors (Ob-R) have recently been identified, a long isoform (Ob-Rb), preferentially expressed in hypothalamus, and 4 short isoforms, Ob-Ra,Ob-Rc, Ob-Rd, and Ob-Re. We have identified a new short isoform in the rat, r-OB-Rf, with 6 C-terminal amino acids and a 3' untranslated region without homology to other Ob-R isoforms. Its higher expression in rat liver and spleen compared to brain, stomach, kidney, thymus, heart, lung and hypothalamus, contrasts with Ob-Ra and Ob-Rb homologues and raises possibilities of as yet unidentified roles for members of the growing Ob-R gene family.MH - Carrier Proteins|*GEMH - Receptors, Cytokine|*GESO - FEBS Lett 1996 Aug; 392(2):87-90DP - 1996 AugTA - FEBS LettPG - 87-90IP - 2VI - 392UI - 96368027138
AU - Lepercq J
AU - Lahlou N
AU - Timsit J
AU - Girard J
AU - Mouzon SHTI - Macrosomia revisited: ponderal index and leptin delineate subtypes of fetal overgrowth.AB - OBJECTIVES: We sought to reanalyze the concept of fetal macrosomia with regard to the ponderal index and to investigate the role of insulin, insulinlike growth factor I, leptin,and maternal factors on birth size in a population of infants with nondiabetic mothers. STUDY DESIGN: Venous cord blood levels of insulin, insulinlike growth factor I, insulinlike growth factor binding protein 3, and leptin were measured in 28 large-for-gestational-age and 21 appropriate-for-gestational-age newborns. RESULTS: Large-for-gestational-age newborns can be divided into symmetric and asymmetric subtypes according to the ponderal index. Mean leptin concentrations in cord blood were significantly higher in asymmetric than in symmetric large-for-gestational-age newborns (P =.01). A positive correlation was observed between leptin and the ponderal index (r = 0.53, P =.001) and between leptin and insulin concentrations in cord blood (r = 0.53, P =.008). CONCLUSION: Our results strongly suggest that macrosomia should not be classified on the basis of birth weight and gestational age alone. We also show that asymmetric macrosomic infants with nondiabetic mothers have abnormal leptin and insulin concentrations.MH - Fetal Development|*MH - Fetal Macrosomia|*PPMH - Proteins|*MESO - Am J Obstet Gynecol 1999 Sep; 181(3):621-5DP - 1999 SepTA - Am J Obstet GynecolPG - 621-5IP - 3VI - 181UI - 99417448139
AU - Bernard A
AU - Cohen R
AU - Khuth ST
AU - Vedrine B
AU - Verlaeten O
AU - Akaoka H
AU - Giraudon P
AU - Belin MFTI - Alteration of the leptin network in late morbid obesity induced in mice by brain infection with canine distemper virus.AB - Viruses can induce progressive neurologic disorders associated with diverse pathological manifestations, and therefore,viral infection of the brain can impair differentiated neural functions, depending on the initial viral tropism.We have previously reported that canine distemper virus (CDV) targets certain mouse brain structures, including the hypothalamus, early and selectively. Infected mice exhibit acute encephalitis, with late disease, characterized by motor impairment or obesity syndrome, appearing in some of the surviving mice several months after the initial viral replication. In the present study, we show viral persistence in the hypothalami of obese mice, as demonstrated by low, but still significant, levels of CDV nucleoprotein transcripts, associated with a dramatic decrease in F gene mRNAs. Given the pivotal role of the hypothalamus in obesity (eating behavior, energy consumption, and neuroendocrine function) and that of leptin, the adipose tissue-derived satiety factor acting through hypothalamic receptors, we analyzed the leptin networks in both obese and nonobese mice. The discrepancy found between the chronic and dramatic increase in blood leptin levels and the occurrence of obesity may be due to leptin resistance in the brain. In fact, expression of the long leptin receptor isoform, representing the functional leptin receptor, was specifically downregulated in the hypothalami of obese mice, explaining their inability to generate an adequate response to leptin in the brain.Intriguingly, during the acute phase of infection, its expression was increased in CDV-targeted structures in all infected mice and remained high in obese mice in all CDV-targeted structures, except for the hypothalamus. The biphasic change in hypothalamic leptin receptor expression seen during the progression of CDV-induced obesity provides a new paradigm for understanding mechanisms of neuroendocrinological,virus-induced abnormalities.MH - Brain|*ME/PA/PPMH - Distemper Virus, Canine|*PHMH - Obesity, Morbid|*ME/PA/PP/VIMH - Proteins|*MESO - J Virol 1999 Sep; 73(9):7317-27DP - 1999 SepTA - J VirolPG - 7317-27IP - 9VI - 73UI - 99370174140
AU - Rouru J
AU - Cusin I
AU - Zakrzewska KE
AU - Jeanrenaud B
AU - Rohner Jeanrenaud FTI - Effects of intravenously infused leptin on insulin sensitivity and on the expression of uncoupling proteins in brown adipose tissue.AB - Centrally administered leptin has been shown to increase insulin-stimulated glucose utilization and to favor the expression of uncoupling proteins (UCPs). To study if leptin also has direct peripherally mediated effects on these processes, this hormone (1 mg/day) or its vehicle was infused i.v. for 4 days to lean rats and insulin-stimulated glucose utilization in skeletal muscle and adipose tissue as well as the expression of UCP messenger RNAs (mRNAs) in brown adipose tissue were measured. I.v. leptin administration resulted in decreases in food intake (31%), body weight gain, and plasma insulin levels (45%), in increases in overall (23%) as well as brown adipose tissue and muscle glucose utilization, and in decreases in white adipose tissue glucose uptake. Most of these changes were mimicked,in control rats, by giving them the same amount of food as that consumed by the leptin-infused group (pair-feeding). I.v. leptin infusion also favored the expression of UCPs in brown adipose tissue, either by increasing their expression or preventing the fall occurring during the pair-feeding regimen. Relative UCP expression levels were 100, 104, and 33 for UCP1, 100, 191, and 125 for UCP2 and 100, 107,and 29 for UCP3 in ad libitum fed control rats, in leptin-treated rats and in pair-fed control rats, respectively.These results suggest that the overall effect of leptin on glucose utilization and on the expression of UCPs may be mediated through central mechanism.MH - Glucose|*MEMH - Insulin|AD/BL/*PDMH - Proteins|AD/GE/*PDSO - Endocrinology 1999 Aug; 140(8):3688-92DP - 1999 AugTA - EndocrinologyPG - 3688-92IP - 8VI - 140UI - 99360610141
AU - Agarwal SK
AU - Vogel K
AU - Weitsman SR
AU - Magoffin DATI - Leptin antagonizes the insulin-like growth factor-I augmentation of steroidogenesis in granulosa and theca cells of the human ovary.AB - There is increasing evidence that leptin is a physiological link between obesity and infertility. Although leptin receptors have been demonstrated in human ovaries, there is no information regarding the effects of leptin on cells from developing ovarian follicles. To test the direct effects of leptin on human ovarian cells, granulosa cells (GC) and theca cells were isolated from the ovaries of regularly cycling women. Serum was obtained at the time of surgery, and follicular fluid was aspirated from the follicles before isolation of the ovarian cells. Leptin concentrations were similar in follicular fluid and serum. RT-PCR analysis demonstrated that the long, signaling form of the leptin receptor was expressed in both theca and GC. In cultured GC, leptin had no effect on estradiol production, alone or in the presence of FSH, but caused a concentration-related inhibition of the insulin-like growth factor I (IGF-I) augmentation of FSH-stimulated estradiol production. The effect of leptin was specific, because there was no effect on progesterone production. In cultured theca cells, leptin did not alter androstenedione production, alone or in the presence of LH. Leptin caused a concentration-related inhibition of the IGF-I augmentation of LH-stimulated androstenedione production. These data demonstrate that leptin can directly inhibit IGF-I action in ovarian theca and GC at concentrations commonly present in obese women.MH - Granulosa Cells|*MEMH - Insulin-Like Growth Factor I|PD/*PHMH - Ovary|CY/*MEMH - Proteins|AN/PD/*PHMH - Steroids|*AI/BIMH - Theca Cells|*MESO - J Clin Endocrinol Metab 1999 Mar; 84(3):1072-6DP - 1999 MarTA - J Clin Endocrinol MetabPG - 1072-6IP - 3VI - 84UI - 99182088142
AU - Igel M
AU - Taylor BA
AU - Phillips SJ
AU - Becker W
AU - Herberg L
AU - Joost HGTI - Hyperleptinemia and leptin receptor variant Asp600Asn in the obese, hyperinsulinemic KK mouse strain.AB - KK obese mice exhibit a multigenic syndrome of moderate obesity, hyperinsulinemia and hyperglycemia. Here we show that the syndrome is accompanied by a marked elevation of leptin protein in adipose tissue, as well as leptin levels in serum, which corresponds with the degree of obesity.The cDNA sequence of leptin is normal in KK mice, whereas three nucleotide polymorphisms were found in the cDNA of the leptin receptor, one of them resulting in exchange of an aspartate residue for asparagine (Asp600Asn) in a highly conserved part of the second extracellular cytokine-receptor homology module. In female (but not male) F2 mice of a C57BL/6JxKK intercross, the weight of gonadal, retroperitoneal and mesenteric adipose tissue was positively correlated with the number of alleles inherited from the KK parental strain at a microsatellite marker (D4Mit175) which maps close (0.7 centimorgan proximal) to the leptin receptor gene. It is suggested that the Asp600Asn leptin receptor variant contributes to the obesity syndrome in KK female mice, but that its contribution is only a part of the multigenic syndrome.MH - Carrier Proteins|*GEMH - Insulin|*BLMH - Proteins|*MEAD - Institut fr Pharmakologie und ToxikologieAD - AachenAD - Germany.SO - J Mol Endocrinol 1998 Dec; 21(3):337-45DP - 1998 DecTA - J Mol EndocrinolPG - 337-45IP - 3VI - 21UI - 99061814; GENBANK/Y10296; GENBANK/Y10297143
AU - Lewandowski K
AU - Horn R
AU - O'Callaghan CJ
AU - Dunlop D
AU - Medley GF
AU - O'Hare P
AU - Brabant GTI - Free leptin, bound leptin, and soluble leptin receptor in normal and diabetic pregnancies.AB - We measured serum levels of free leptin, bound leptin, and soluble leptin receptor by specific RIA methods in 20 normal and 19 insulin-dependent diabetes mellitus subjects at 20 and 30 weeks gestation and postpartum, and analyzed the data using hierarchical statistical models. Total leptin levels rise from 20-30 weeks gestation (688 +/- 58 to 785 +/- 62 pmol/L, mean +/- SEM; P = 0.009). There is a significant postpartum fall to 445 +/- 47 pmol/L (P < 0.001). This rise is caused by the rise in the bound leptin levels, as there is no significant change in free leptin levels between 20 and 30 weeks (P = 0.17). There is a significant postpartum fall in free leptin levels (P < 0.001). Insulin requirements rise in the third trimester, but despite this there was no significant difference in free or bound leptin levels between the normal and diabetic subjects at any stage [free leptin, 223 +/- 35 and 266 +/- 24, 237 +/- 45 and 223 +/- 27, and 109 +/- 16 and 104 +/- 24 (P = 0.34); bound leptin, 410 +/- 73 and 428 +/- 54, 501 +/- 78 and 562 +/- 71, and 330 +/- 47 and 271 +/- 46 (P = 0.84); for normals and diabetics at 20 and 30 weeks gestation and postpartum, respectively]. Diabetic subjects, however,had significantly higher soluble leptin receptor levels at all stages (P << 0.001), which rose further in the third trimester from 3742 +/- 268 (mean +/- SEM) to 4134 +/- 239 pmol/L, whereas in the normal group there was a fall from 3149 +/- 169 to 2712 +/- 123 (P = 0.05). There is a linear relationship between the soluble leptin receptor levels and the body mass index in the diabetic group only.We conclude that there is no significant difference in free or bound leptin levels between the normal and insulin-dependent diabetic subjects either during pregnancy or postpartum, but female insulin-dependent diabetic subjects have significantly higher soluble leptin receptor levels.We speculate that high soluble leptin receptor levels might be implicated in the development of the leptin resistance in this group.MH - Carrier Proteins|*BLMH - Pregnancy|*BLMH - Pregnancy in Diabetes|*BLMH - Proteins|*ANAD - Department of Biological SciencesAD - University of WarwickAD - CoventryAD - United Kingdom.SO - J Clin Endocrinol Metab 1999 Jan; 84(1):300-6DP - 1999 JanTA - J Clin Endocrinol MetabPG - 300-6IP - 1VI - 84UI - 99116827144
AU - Koistinen HA
AU - Karonen SL
AU - Iivanainen M
AU - Koivisto VATI - Circulating leptin has saturable transport into intrathecal space in humans.AB - BACKGROUND: Leptin is an adipocyte-derived hormone that is thought to provide a negative feedback signal to control body fat mass by interacting with its hypothalamic receptor.The present study was undertaken to examine the uptake of leptin in cerebrospinal fluid (CSF) space in humans and whether the transport of leptin into CSF space is an active phenomenon or due to free access through the blood-CSF barrier. METHODS: We determined serum and CSF leptin concentrations by radioimmunoassay in 17 men [42 +/- 4 years, mean +/- SE; body mass index (BMI) 27.3 +/- 1.8 kg m-2] and 22 women (40 +/- 3 years, BMI 25.1 +/- 1.0 kg m-2). The function of the blood-CSF barrier was evaluated by determining the CSF/serum albumin ratio. RESULTS: Serum leptin concentration was lower in male (5.8 +/- 1.6 microgram L-1) than in female subjects (13.1 +/- 1.7 microgram L-1, P = 0. 001), whereas the concentrations of leptin in CSF were virtually identical in male (0.34 +/- 0.03 microgram L-1) and female (0.36 +/- 0. 03 microgram L-1) subjects.Serum leptin was correlated positively with BMI both in men (r = 0.89, P < 0.01, n = 10) and in women (r = 0.61,P < 0.05, n = 14), whereas no correlation between CSF leptin concentration and BMI was found in either group. The CSF/serum leptin ratio correlated negatively with serum leptin concentration both in men (r = -0.93, P < 0.001) and in women (r = -0.77, P < 0. 001) and with BMI both in men (r = -0.75, P = 0.02, n = 10) and in women (r = -0.64, P < 0.02, n = 14). The CSF/serum albumin ratio was not correlated with the CSF/serum leptin ratio in either group.CSF leptin concentrations and the CSF/serum leptin ratio were virtually identical in subjects with impaired and normal blood-CSF barrier function. CONCLUSION: Thus, our data support the presence of a saturable and active transporter of leptin from circulation into intrathecal space.MH - Blood-Brain Barrier|*PHMH - Proteins|*MEAD - Helsinki University Central HospitalAD - HelsinkiAD - Finland. heikki.koistinen@huch.fiSO - Eur J Clin Invest 1998 Nov; 28(11):894-7DP - 1998 NovTA - Eur J Clin InvestPG - 894-7IP - 11VI - 28UI - 99041770145
AU - Morton NM
AU - Emilsson V
AU - Liu YL
AU - Cawthorne MATI - Leptin action in intestinal cells.AB - The adipocyte hormone leptin activates signal transducer and activator of transcription 3 (STAT3) in the hypothalamus,mediating increased satiety and increased energy expenditure.To date, leptin-mediated activation of the STAT pathway in vivo has not been established in tissues other than hypothalamus. We now describe leptin receptor expression and in vivo signaling in discrete regions of the mouse gastrointestinal tract. Expression of the functional isoform leptin receptor (OB-Rb) is restricted to the jejunum and is readily detected by RT-PCR in isolated enterocytes from this site. Intravenous injection of leptin rapidly induced nuclear STAT5 DNA binding activity in jejunum of +/+ and obese (ob/ob) mice but had no effect in the diabetic (db/db) mouse that lacks the OB-Rb isoform. In addition, an induction of the immediate-early gene c-fos is observed in jejunum in vivo. Leptin-mediated induction of a number of immediate-early genes and activation of STAT3 and STAT5 in a human model of small intestine epithelium, CACO-2 cells, corroborate this effect. Furthermore, intravenous leptin administration caused a significant 2-fold reduction in the apolipoprotein AIV transcript levels in jejunum 90 min after a fat load. Our results suggest that the epithelium of jejunum is a direct target of leptin action, and this activity is dependent on the presence of OB-Rb. Lack of leptin or resistance to leptin action in this site may contribute to obesity and its related syndromes by directly affecting lipid handling.MH - Jejunum|*DEMH - Proteins|*PDSO - J Biol Chem 1998 Oct; 273(40):26194-201DP - 1998 OctTA - J Biol ChemPG - 26194-201IP - 40VI - 273UI - 98421549146
AU - Shimabukuro M
AU - Koyama K
AU - Chen G
AU - Wang MY
AU - Trieu F
AU - Lee Y
AU - Newgard CB
AU - Unger RHTI - Direct antidiabetic effect of leptin through triglyceride depletion of tissues [see comments]AB - Leptin is currently believed to control body composition largely, if not entirely, via hypothalamic receptors that regulate food intake and thermogenesis. Here we demonstrate direct extraneural effects of leptin to deplete fat content of both adipocytes and nonadipocytes to levels far below those of pairfed controls. In cultured pancreatic islets,leptin lowered triglyceride (TG) content by preventing TG formation from free fatty acids (FFA) and by increasing FFA oxidation. In vivo hyperleptinemia, induced in normal rats by adenovirus gene transfer, depleted TG content in liver, skeletal muscle, and pancreas without increasing plasma FFA or ketones, suggesting intracellular oxidation.In islets of obese Zucker Diabetic Fatty rats with leptin receptor mutations, leptin had no effect in vivo or in vitro. The TG content was approximately 20 times normal,and esterification capacity was increased 3- to 4-fold.Thus, in rats with normal leptin receptors but not in Zucker Diabetic Fatty rats, nonadipocytes and adipocytes esterify FFA, store them as TG, and later oxidize them intracellularly via an "indirect pathway" of intracellular fatty acid metabolism controlled by leptin. By maintaining insulin sensitivity and preventing islet lipotoxicity, this activity of leptin may prevent adipogenic diabetes.MH - Diabetes Mellitus, Experimental|GE/*MEMH - Hypoglycemic Agents|*PDMH - Islets of Langerhans|*DEMH - Proteins|GE/*PDMH - Triglycerides|*MESO - Proc Natl Acad Sci U S A 1997 Apr; 94(9):4637-41DP - 1997 AprTA - Proc Natl Acad Sci U S APG - 4637-41IP - 9VI - 94UI - 97272277147
AU - Satoh N
AU - Ogawa Y
AU - Katsuura G
AU - Numata Y
AU - Masuzaki H
AU - Yoshimasa Y
AU - Nakao KTI - Satiety effect and sympathetic activation of leptin are mediated by hypothalamic melanocortin system.AB - Leptin is an adipocyte-derived blood-borne satiety factor that decreases food intake and increases energy expenditure,thereby leading to a substantial decrease in body weight.To explore the possible roles of the hypothalamic melanocortin system in leptin action, we examined the effects of intracerebroventricular (i.c.v.) injection of leptin with or without SHU9119, a potent antagonist of alpha-melanocyte stimulating hormone,on food intake, body weight, and mitochondrial uncoupling protein-1 (UCP-1) mRNA expression in the brown adipose tissue (BAT) in rats. A single i.c.v. injection of leptin decreased cumulative food intake and body weight gain, and increased UCP-1 mRNA expression during 3 h at the onset of the dark phase. Inhibition of food intake and body weight change with leptin was reversed by co-injection of SHU9119 in a dose-dependent manner. Co-injection of SHU9119 also inhibited completely the leptin-induced increase in UCP-1 mRNA expression in the BAT. Treatment with SHU9119 alone did not affect food intake, body weight, and UCP-1 mRNA expression in rats. The present study provides evidence that the hypothalamic melanocortin system plays a central role in both satiety effect and sympathetic activation of leptin.MH - Eating|*DEMH - Hypothalamus|*PHMH - Proteins|AD/*PDMH - Satiety Response|*/DESO - Neurosci Lett 1998 Jun; 249(2-3):107-10DP - 1998 JunTA - Neurosci LettPG - 107-10IP - 2-3VI - 249UI - 98346358148
AU - Janssen JA
AU - Huizenga NA
AU - Stolk RP
AU - Grobbee DE
AU - Pols HA
AU - de Jong FH
AU - Attanasio AM
AU - Blum WF
AU - Lamberts SWTI - The acute effect of dexamethasone on plasma leptin concentrations and the relationships between fasting leptin, the IGF-I/IGFBP system, dehydroepiandrosterone, androstenedione and testosterone in an elderly population.AB - OBJECTIVE: To investigate the acute effect of dexamethasone administration on serum leptin levels and the relationships between dehydroepiandrosterone (DHEAS), androstenedione,testosterone and the IGF-I/IGFBP system and leptin levels in healthy elderly humans. METHODS: In 209 healthy elderly individuals (95 men, 114 women, aged 55-80 years) measurements were made in the fasting state (0800 h) and after an overnight dexamethasone suppression test (1 mg p.o. at 2300 h. RESULTS:Mean leptin levels increased from 6.2 +/- 0.4 (SE) micrograms/l to 7.3 +/- 0.5 (SE) micrograms/l in men and from 18.9 +/- 1.4 (SE) micrograms/l to 23.9 +/- 1.8 (SE) micrograms/l in women after 1 mg dexamethasone overnight ('post treatment')(P < 0.001 for both sexes). There was a significant relationship between post-treatment leptin and dexamethasone levels (men: P = 0.002; women: P < 0.001). The increase in leptin levels after dexamethasone administration was only partially related to the increase in plasma insulin concentrations.Cortisol levels were not related to leptin. In multivariate analyses the relationship between post-treatment leptin and dexamethasone levels remained after adjustment for post-treatment insulin levels, BMI, waist:hip ratio (WHR)and age (men: P < 0.001; women: P = 0.001). Plasma (free and total) IGF-I and IGFBP-3 levels were not related to leptin levels in men or women. IGFBP-1 levels were inversely related to leptin levels (P = 0.02), but this relationship was lost after adjustment for insulin, and/or BMI. In multivariate analyses the relationship between leptin and DHEAS was inverse in women (P = 0.04) (after adjustment for BMI, WHR, insulin and glucose), while there was no relationship between leptin and DHEAS in men. CONCLUSIONS: Administration of dexamethasone acutely increased leptin levels within 9 h in this elderly population. This increase was only partly related to changes in circulating insulin concentrations,but was independent of BMI and waist:hip ratio. No relation existed between leptin and (free or total) IGF-I and IGFBP-3 in men or women. Dehydroepiandrosterone was inversely related to leptin in women. These findings suggest a contributory regulatory role for corticosteroids in modulating circulating leptin concentrations in elderly healthy individuals of both sexes, which is at least in part independent of insulin,BMI and waist:hip ratio. Dehydroepiandrosterone might play a role in the gender-specific differences in serum leptin levels.MH - Dexamethasone|*PDMH - Fasting|*BLMH - Glucocorticoids, Synthetic|*PDMH - Insulin-Like Growth Factor I|*MEMH - Insulin-Like Growth-Factor-Binding Proteins|*MEMH - Proteins|*DE/MESO - Clin Endocrinol (Oxf) 1998 May; 48(5):621-6DP - 1998 MayTA - Clin Endocrinol (Oxf)PG - 621-6IP - 5VI - 48UI - 98331491149
AU - Kielar D
AU - Clark JS
AU - Ciechanowicz A
AU - Kurzawski G
AU - Sulikowski T
AU - Naruszewicz MTI - Leptin receptor isoforms expressed in human adipose tissue.AB - Leptin and its structural gene, Ob, are exclusively expressed in adipose tissue. Leptin is secreted into the blood and is responsible for fat mass regulation via leptin receptors in the hypothalamus. This has been considered the major role of leptin, but leptin receptor isoforms are expressed not only in the brain but also in most other tissues in humans and rodents: heart, placenta, lung, liver, muscle,kidney, pancreas, spleen, thymus, prostate, testes, ovary,small intestine, and colon. This implicates leptin regulation in other systems apart from fat mass regulation, and leptin action has been demonstrated in human fetal development and reproductive development, liver metabolism, hematopoiesis,and insulin secretion. Four splice variants of the leptin receptor have been identified in humans: the long isoform huOb-R and the shorter isoforms B219.1 to B219.3. It is known that the long isoform has full intracellular signaling capacity, and is responsible for anorectic action in the hypothalamus. The roles of the other isoforms are yet to be elucidated. Here, we report the identification by reverse transcriptase-polymerase chain reaction (RT-PCR) of three leptin receptor isoforms coexpressed in human visceral adipose tissue: the long isoform huOb-R and the short isoforms huB219.1 and huB219.3. The possible roles of these isoforms are discussed.MH - Adipose Tissue|*MEMH - Carrier Proteins|*BI/GEMH - Proteins|GE/*MESO - Metabolism 1998 Jul; 47(7):844-7DP - 1998 JulTA - MetabolismPG - 844-7IP - 7VI - 47UI - 98329807150
AU - Baskin DG
AU - Seeley RJ
AU - Kuijper JL
AU - Lok S
AU - Weigle DS
AU - Erickson JC
AU - Palmiter RD
AU - Schwartz MWTI - Increased expression of mRNA for the long form of the leptin receptor in the hypothalamus is associated with leptin hypersensitivity and fasting.AB - The responsiveness of the hypothalamus to the inhibitory effects of leptin on food intake and body weight is influenced by multiple factors, including deficiency of either leptin or leptin receptors (Ob-R). To investigate whether altered expression of Ob-R in the hypothalamus could potentially contribute to altered leptin sensitivity, we performed in situ hybridization with riboprobes that detected either mRNAs encoding both the long (Ob-Rb) and short (Ob-Ra) splice variants or mRNA encoding only Ob-Rb. In the arcuate nucleus, mRNA encoding Ob-Rb, the predominant signaling form of the receptor, was 2.3 times greater in obese db/db and ob/ob mice than in lean +/ob controls (P < 0.01). In ob/ob mice, systemic administration of leptin reduced Ob-Rb mRNA content of the arcuate nucleus by 30% compared with saline-treated, pair-fed controls (P < 0.05). A 48-h fast increased Ob-Rb mRNA levels in the arcuate nucleus of normal and neuropeptide Y (NPY)-knockout mice (P < 0.01), although the effect was greater in the NPY-knockout mice (400 vs. 247%, P < 0.05). In addition, Ob-Rb mRNA hybridization was elevated by 40% in the arcuate nucleus (P < 0.05) and by 75% in the ventromedial nucleus (P < 0.05) of rats fasted 48 h. The results suggest that expression of Ob-Rb mRNA in the hypothalamus is sensitive to genetic and physiological interventions that alter circulating leptin levels, and that overexpression of Ob-Rb in the hypothalamus may contribute to increased leptin sensitivity.MH - Arcuate Nucleus|DE/*MEMH - Carrier Proteins|*BI/GEMH - Fasting|*PHMH - Proteins|*ME/PDMH - RNA, Messenger|*BISO - Diabetes 1998 Apr; 47(4):538-43DP - 1998 AprTA - DiabetesPG - 538-43IP - 4VI - 47UI - 98227635151
AU - Fehmann HC
AU - Bode HP
AU - Ebert T
AU - Karl A
AU - G÷ke BTI - Interaction of GLP-I and leptin at rat pancreatic B-cells:effects on insulin secretion and signal transduction.AB - The incretin effect is reduced in NIDDM, although a corresponding attenuation of incretin hormone secretion does not occur.We characterized the direct interaction of GLP-I, an important incretin hormone, and leptin on insulin secretion and signal transduction in B-cells. Leptin inhibited GLP-I stimulated insulin release from the isolated perfused rat pancreas.Both phases of the biphasic insulin secretory response were inhibited. GLP-I receptor binding and GLP-I induced cAMP generation remained unchanged. Leptin reduced the GLP-I mediated increase of cytosolic Ca2+ concentration.It had similar effects on calcium elevations induced by forskolin. The effect was more pronounced during the plate
AU phase than during the initial peak. These effects could help to explain leptin's inhibitory effects on insulin secretion. The inhibition of GLP-I's insulinotropic effects by leptin may be an interesting aspect in the pathophysiology of NIDDM. The existence of an "adipo-insular axis" is suggested,in which leptin represents a negative feed-back signal from the adipose tissue to the endocrine pancreas.MH - Glucagon|AD/ME/*PDMH - Islets of Langerhans|*DEMH - Peptide Fragments|AD/ME/*PDMH - Protein Precursors|AD/ME/*PDMH - Proteins|AD/*PDSO - Horm Metab Res 1997 Nov; 29(11):572-6DP - 1997 NovTA - Horm Metab ResPG - 572-6IP - 11VI - 29UI - 98140185152
AU - Walder K
AU - Filippis A
AU - Clark S
AU - Zimmet P
AU - Collier GRTI - Leptin inhibits insulin binding in isolated rat adipocytes.AB - Leptin is secreted from adipose tissue, and is thought to act as a 'lipostat', signalling the body fat levels to the hypothalamus resulting in adjustments to food intake and energy expenditure to maintain body weight homeostasis.In addition, plasma leptin concentrations have been shown to be related to insulin sensitivity independent of body fat content, suggesting that the hyperleptinemia found in obesity could contribute to the insulin resistance. We investigated the effects of leptin on insulin binding by isolated adipocytes. Adipocytes isolated from Sprague-Dawley rats exhibited a dose-dependent reduction in the uptake of 125I-labelled insulin when incubated with various concentrations of exogenous leptin. For example, addition of 50 nM leptin reduced total insulin binding in isolated adipocytes by 19% (P < 0.05). Analysis of displacement curve binding data suggested that leptin reduced maximal insulin binding in a dose-dependent manner, but had no significant effect on the affinity of insulin for its binding site. We conclude that leptin directly inhibited insulin binding by adipocytes, and the role of leptin in the development of insulin resistance in obese individuals requires further investigation.MH - Adipocytes|DE/*MEMH - Insulin|*MEMH - Proteins|*PDSO - J Endocrinol 1997 Dec; 155(3):R5-7DP - 1997 DecTA - J EndocrinolPG - R5-7IP - 3VI - 155UI - 98148986153
AU - Zhang Y
AU - Olbort M
AU - Schwarzer K
AU - Nuesslein Hildesheim B
AU - Nicolson M
AU - Murphy E
AU - Kowalski TJ
AU - Schmidt I
AU - Leibel RLTI - The leptin receptor mediates apparent autocrine regulation of leptin gene expression.AB - The possibility that the leptin receptor (LEPR) mediates autocrine regulation of leptin expression in adipose tissue was examined in 10-day-old Zucker rat pups with different copy numbers of the leptin receptor mutation (Lepr(fa)). Plasma leptin concentrations and adipose tissue mRNA levels for leptin were related to copy number of the mutation (fa/fa > fa/+ > +/+). These relationships were independent of plasma insulin concentration. Reduced copy number for the functional leptin receptor apparently results in a diminished negative feedback signal to the leptin gene in adipose tissue. Thus, leptin appears to close a short regulatory loop controlling its own synthesis in adipose tissue.MH - Adipose Tissue|AH/*MEMH - Carrier Proteins|*GE/PHMH - Gene Expression Regulation|*MH - Proteins|*BI/MESO - Biochem Biophys Res Commun 1997 Nov; 240(2):492-5DP - 1997 NovTA - Biochem Biophys Res CommunPG - 492-5IP - 2VI - 240UI - 98049861154
AU - Li H
AU - Matheny M
AU - Nicolson M
AU - Tmer N
AU - Scarpace PJTI - Leptin gene expression increases with age independent of increasing adiposity in rats.AB - Humans and rats tend to gain weight as they age. Leptin is one regulator of food intake and energy expenditure.To determine if the increase in adiposity with age is related to altered leptin gene expression, we assessed adiposity levels, leptin mRNA levels in epididymal and inguinal white adipose tissue (EWAT and IWAT), and uncoupling protein (UCP1) mRNA levels in interscapular brown adipose tissue (IBAT) from F344 x BN rats ages 3, 12, 18, 24, and 30 months (n = 8/age). Levels of adiposity determined by the adiposity index and the Lee index increased between ages 3 and 24 months, with a decrease at age 30 months. There were parallel increases with age in body weight, EWAT, and IWAT depot size up to age 24 months, followed by a nonsignificant decrease at age 30 months. Daily food intake was unchanged with age. In EWAT, leptin mRNA per microgram of RNA was unchanged with age, whereas in IWAT, it increased up to 24 months, then declined at 30 months. Total leptin mRNA levels in both IWAT and EWAT depots increased with age,peaking at age 24 months, and were correlated with adiposity.Serum leptin levels increased with age, also peaking at age 24 months, and were correlated with total leptin mRNA in WAT pads and adiposity. The rate of increase in serum leptin was greater than the increase in adiposity with age, suggesting contributions from both the increase in leptin expression per unit of WAT and the increase in WAT depot size. In addition, UCP1 mRNA levels in IBAT did not change with age. These data suggest that adiposity increases with age and cannot be attributed to increased food intake,impaired leptin gene expression, or decreased UCP1 mRNA level in IBAT. Furthermore, leptin gene expression in IWAT increases with age independent of increasing adiposity.MH - Adipose Tissue|*/MEMH - Aging|*MH - Body Composition|*MH - Gene Expression|*MH - Proteins|*GE/MESO - Diabetes 1997 Dec; 46(12):2035-9DP - 1997 DecTA - DiabetesPG - 2035-9IP - 12VI - 46UI - 98052385155
AU - Islam MS
AU - Morton NM
AU - Hansson A
AU - Emilsson VTI - Rat insulinoma-derived pancreatic beta-cells express a functional leptin receptor that mediates a proliferative response.AB - In addition to its interaction at hypothalamic sites to affect feeding and energy expenditure, leptin has been shown to exhibit a proliferative response in erythropoietic cells. The functional leptin receptor is also present in pancreatic islets and we now demonstrate that a commonly used clonal insulin secreting beta-cell line, RINm5F, expresses high levels of the Ob-Rb mRNA. Leptin causes an increase in tyrosine phosphorylation of a number of intracellular proteins and a dose related (10 nM-200 nM) increase in expression of the immediate-early gene, c-fos. This precedes a leptin induced proliferative response in serum-deprived RINm5F cells, which suggests that leptin might be involved in the complex regulation of proliferation of the pancreatic beta-cell.MH - Carrier Proteins|*BI/PHMH - Islets of Langerhans|*MEMH - Receptors, Cytokine|*BI/PHSO - Biochem Biophys Res Commun 1997 Sep; 238(3):851-5DP - 1997 SepTA - Biochem Biophys Res CommunPG - 851-5IP - 3VI - 238UI - 97472300156
AU - Hoggard N
AU - Hunter L
AU - Duncan JS
AU - Williams LM
AU - Trayhurn P
AU - Mercer JGTI - Leptin and leptin receptor mRNA and protein expression in the murine fetus and placenta.AB - Leptin is a 167-aa protein that is secreted from adipose tissue and is important in the regulation of energy balance.It also functions in hematopoiesis and reproduction. To assess whether leptin is involved in fetal growth and development we have examined the distribution of mRNAs encoding leptin and the leptin receptor (which has at least six splice variants) in the 14.5-day postcoitus mouse fetus and in the placenta using reverse transcription-PCR and in situ hybridization. High levels of gene expression for leptin,the leptin receptor, and the long splice variant of the leptin receptor with an intracellular signaling domain were observed in the placenta, fetal cartilage/bone, and hair follicles. Receptor expression also was detected in the lung, as well as the leptomeninges and choroid plexus of the fetal brain. Western blotting and immunocytochemistry,using specific antibodies, demonstrated the presence of leptin and leptin receptor protein in these tissues. These results suggest that leptin may play a role in the growth and development of the fetus, both through placental and fetal expression of the leptin and leptin receptor genes.In the fetus, leptin may be multifunctional and have both paracrine and endocrine effects.MH - Carrier Proteins|*GE/MEMH - Fetus|*MEMH - Placenta|*MEMH - Proteins|*GE/MESO - Proc Natl Acad Sci U S A 1997 Sep; 94(20):11073-8DP - 1997 SepTA - Proc Natl Acad Sci U S APG - 11073-8IP - 20VI - 94UI - 98021495157
AU - Faggioni R
AU - Fuller J
AU - Moser A
AU - Feingold KR
AU - Grunfeld CTI - LPS-induced anorexia in leptin-deficient (ob/ob) and leptin receptor-deficient (db/db) mice.AB - Administration of endotoxin (lipopolysaccharide, LPS) induces profound anorexia. Injection of leptin decreases food intake in mice. Recently, we reported that LPS and cytokines increase leptin levels in hamsters. To further investigate the role of leptin in the LPS-induced anorexia, we administered LPS to leptin receptor-deficient (db/db) and leptin-deficient (ob/ob) mice. We found that LPS caused anorexia in both db/db and ob/ob mice. As might be predicted if leptin had a role in anorexia, the db/db mice were somewhat resistant to LPS-induced anorexia. However the ob/ob mice were more sensitive to LPS-induced anorexia. No differences between db/db and ob/ob mice and their respective littermate were observed in circulating tumor necrosis factor levels after LPS. These data suggest that leptin per se is not essential for LPS-induced anorexia.MH - Anorexia|*CI/GE/PPMH - Carrier Proteins|GE/*PHMH - Feeding Behavior|*DEMH - Lipopolysaccharides|*TOMH - Proteins|GE/*PHSO - Am J Physiol 1997 Jul; 273(1 Pt 2):R181-6DP - 1997 JulTA - Am J PhysiolPG - R181-6IP - 1 Pt 2VI - 273UI - 97393031158
AU - Luoh SM
AU - Di Marco F
AU - Levin N
AU - Armanini M
AU - Xie MH
AU - Nelson C
AU - Bennett GL
AU - Williams M
AU - Spencer SA
AU - Gurney A
AU - de Sauvage FJTI - Cloning and characterization of a human leptin receptor using a biologically active leptin immunoadhesin.AB - Leptin, the product of the ob gene, is a hormone secreted by fat cells which is primarily involved in the regulation of body weight. We have generated a leptin immunoadhesin (leptin-IgG) which was more potent than leptin alone at reducing body weight and food intake when injected into ob/ob mice. This molecule was used to identify high affinity binding sites on human embryonic 293 kidney cells and subsequently to isolate a cDNA encoding the leptin receptor from this cell line by expression cloning. This receptor corresponds to the short form of the recently isolated leptin receptor.Analysis of the expression pattern of the two forms of receptor by Northern blot, in situ hybridization and quantitative PCR showed that the receptor is expressed in most tissues but that the long form is prevalent in the hypothalamus.MH - Carrier Proteins|*GE/MEMH - Cell Adhesion Molecules|*MEMH - Chimeric Proteins|*MEMH - Proteins|*MESO - J Mol Endocrinol 1997 Feb; 18(1):77-85DP - 1997 FebTA - J Mol EndocrinolPG - 77-85IP - 1VI - 18UI - 97215244159
AU - Wang Q
AU - Bing C
AU - Al Barazanji K
AU - Mossakowaska DE
AU - Wang XM
AU - McBay DL
AU - Neville WA
AU - Taddayon M
AU - Pickavance L
AU - Dryden S
AU - Thomas ME
AU - McHale MT
AU - Gloyer IS
AU - Wilson S
AU - Buckingham R
AU - Arch JR
AU - Trayhurn P
AU - Williams GTI - Interactions between leptin and hypothalamic neuropeptide Y neurons in the control of food intake and energy homeostasis in the rat.AB - Leptin acts on the brain to inhibit feeding, increase thermogenesis,and decrease body weight. Neuropeptide Y (NPY)-ergic neurons of the hypothalamic arcuate nucleus (ARC) that project to the paraventricular nuclei (PVN) and dorsomedial nuclei (DMH) are postulated to control energy balance by stimulating feeding and inhibiting thermogenesis, especially under conditions of energy deficit. We investigated whether leptin's short-term effects on energy balance are mediated by inhibition of the NPY neurons. Recombinant murine leptin (11 microg) injected into the lateral ventricle of fasted adult Wistar rats inhibited food intake by 20-25% between 2 and 6 h after administration, compared with saline-treated controls (P < 0.05). Uncoupling protein mRNA levels in brown adipose tissue (BAT) rose by 70% (P < 0.01). Leptin treatment significantly reduced NPY concentrations by 20-50% (P < 0.05) in the ARC, PVN, and DMH and significantly decreased hypothalamic NPY mRNA levels (0.61 +/- 0.02 vs.0.78 +/- 0.03 arbitrary units; P < 0.01). A second study examined changes in leptin during 5 days' intracerebroventricular NPY administration (10 microg/day), which induced sustained hyperphagia and excessive weight gain. In NPY-treated rats,leptin mRNA levels in epididymal fat were comparable to those in saline-treated controls (0.94 +/- 0.17 vs. 1.0 +/- 0.28 arbitrary units; P > 0.1), but plasma leptin levels were significantly higher (4.88 +/- 0.66 vs. 2.85 +/- 0.20 ng/ml; P < 0.01). Leptin therefore acts centrally to decrease NPY synthesis and NPY levels in the ARC-PVN projection;reduced NPY release in the PVN may mediate leptin's hypophagic and thermogenic actions. Conversely, NPY-induced obesity results in raised circulating leptin concentrations. Leptin and the NPY-ergic ARC-PVN neurons may interact in a homeostatic loop to regulate body fat mass and energy balance.MH - Brown Fat|DE/*MEMH - Carrier Proteins|*BIMH - Cerebral Ventricles|DE/*PHMH - Feeding Behavior|*DEMH - Hypothalamus|DE/*PHMH - Membrane Proteins|*BIMH - Neurons|DE/*PHMH - Neuropeptide Y|AD/*ME/*PDMH - Proteins|AD/*BI/*PDSO - Diabetes 1997 Mar; 46(3):335-41DP - 1997 MarTA - DiabetesPG - 335-41IP - 3VI - 46UI - 97184284160
AU - Takekoshi K
AU - Motooka M
AU - Isobe K
AU - Nomura F
AU - Manmoku T
AU - Ishii K
AU - Nakai TTI - Leptin directly stimulates catecholamine secretion and synthesis in cultured porcine adrenal medullary chromaffin cells.AB - Leptin, a protein encoded by the ob gene, is an adipose tissue-derived signaling factor involved in body weight homeostasis. The hypothalamus is a major site of central action for leptin. However, mounting evidence indicates expression of leptin receptor mRNA in various peripheral organs including the adrenal medulla. Therefore, we investigated the effects of leptin on catecholamine secretion and synthesis in cultured porcine adrenal medullary chromaffin cells.We initially confirmed the expression of leptin receptor (Ob-Rb) mRNA in cultured porcine adrenal medullary cells.Murine recombinant leptin (>==50 nM) strongly induced the release of both epinephrine (E) and norepinephrine (NE)from chromaffin cells. Removal of external Ca(2+) significantly suppressed these effects. Also, leptin (>==1 nM) enhanced nicotine-induced increases in E- and NE. Leptin (1, 10,100 nM) significantly increased tyrosine hydroxylase (TH)(a rate-limiting enzyme in the biosynthesis of catecholamine)mRNA levels in a concentration-dependent manner. Furthermore,leptin (1, 10, 100 nM) significantly induced increases in cAMP levels, suggesting that the stimulatory effects on TH mRNA are mediated, at least in part, by the cAMP/protein kinase A pathway. These results indicate that leptin directly stimulates catecholamine release and synthesis,which in turn may potentiate the anti-obesity effects of leptin. Copyright 1999 Academic Press.MH - Chromaffin Cells|*DE/ME/*SEMH - Epinephrine|BI/*SEMH - Norepinephrine|BI/*SEMH - Proteins|*PDSO - Biochem Biophys Res Commun 1999 Aug; 261(2):426-31DP - 1999 AugTA - Biochem Biophys Res CommunPG - 426-31IP - 2VI - 261UI - 99355587161
AU - Mantzoros CSTI - Leptin in renal failure.AB - Leptin, an adipocyte-derived hormone, signals to the brain information on the amount of energy stored in adipose tissue and regulates energy homeostasis. In addition, leptin has been implicated in the regulation of neuroendocrine function,growth, hematopoiesis, and immune regulation. Plasma leptin is cleared by the kidney, and thus, leptin levels are elevated in hemodialysis patients. Whether the elevated leptin levels in hemodialysis patients contribute to the pathophysiology of the clinical manifestations of renal failure in humans remains to be conclusively shown in the future.MH - Kidney Failure, Chronic|*BL/THMH - Proteins|GE/ME/*PHSO - J Ren Nutr 1999 Jul; 9(3):122-5DP - 1999 JulTA - J Ren NutrPG - 122-5IP - 3VI - 9UI - 99362930162
AU - Brunner L
AU - Whitebread S
AU - Leconte I
AU - Stricker Krongrad A
AU - Cumin F
AU - Chiesi M
AU - Levens NTI - A peptide leptin antagonist reduces food intake in rodents.AB - OBJECTIVE: The purpose of the present study was to investigate the continuing validity of the hypothesis that leptin is a physiologically important regulator of food intake, using the human leptin mutant R128Q leptin. DESIGN: In a cellular proliferation assay, based on BAF-3 cells transfected with the murine ObRb receptor, R128Q leptin was shown to be devoid of agonistic activity and to competitively inhibit the proliferative effects of leptin. To determine whether R128Q leptin was also an antagonist of leptin in vivo, the leptin mutant was injected intracerebroventricularly (i.c.v.) into rats in the absence and presence of leptin.R128Q was also injected intraperitoneally (i.p.) into ob/ob and into db/db mice expressing, respectively, either normal or defective ObRb receptors. RESULTS: R128Q was shown to be a competitive antagonist of leptin induced cellular proliferation in vitro. Surprisingly, in vivo R128Q leptin produced a strong dose-dependent decrease in food intake, and was only slightly less potent than leptin itself. In fasted rats, the inhibitory effects of leptin and R128Q leptin (i.c.v.) on post-fast refeeding were additive. Finally, R128Q leptin produced the same inhibition of food intake as leptin when injected i.p. in ob/ob mice and, like leptin, was inactive after i.p.injection to db/db mice. CONCLUSION: R128Q leptin is a leptin agonist in vivo, but behaves as an antagonist against leptin induced proliferation in vitro. The data demonstrate that the human leptin mutant R128Q leptin is not a suitable tool for investigating the physiological actions of leptin.MH - Eating|*DEMH - Obesity|*MEMH - Proteins|AD/*AI/ME/*PDSO - Int J Obes Relat Metab Disord 1999 May; 23(5):463-9DP - 1999 MayTA - Int J Obes Relat Metab DisordPG - 463-9IP - 5VI - 23UI - 99301584163
AU - L÷nnqvist F
AU - Nordfors L
AU - Schalling MTI - Leptin and its potential role in human obesity.AB - Genetic studies in inbred obese mice have revealed the ob gene, its product leptin and the leptin receptor as important factors in the regulation of both appetite and energy expenditure. Treatment with recombinant leptin has resulted in a marked weight reduction in obese animals with ob gene mutations as well as in normal mice. Also mutations in the Ob receptor gene result in marked obesity in rodents. These data have given hope of new treatment options in obesity. Further support of leptin being involved in regulation of obesity in man comes from the observation that inactivating mutations in the human ob gene lead to profound early onset obesity. However, the role of leptin and its feedback system in man is still only partly revealed.This review focuses on our present knowledge and hypotheses about the leptin pathway in humans and its potential importance in the clinic of obesity.MH - Adipose Tissue|*MEMH - Carrier Proteins|*MEMH - Obesity|BL/DT/GE/*MEMH - Proteins|BI/GE/*ME/TUSO - J Intern Med 1999 Jun; 245(6):643-52DP - 1999 JunTA - J Intern MedPG - 643-52IP - 6VI - 245UI - 99321117164
AU - Kraeft S
AU - Schwarzer K
AU - Eiden S
AU - Nuesslein Hildesheim B
AU - Preibisch G
AU - Schmidt ITI - Leptin responsiveness and gene dosage for leptin receptor mutation (fa) in newborn rats.AB - To determine the degree to which the leptin receptor mutation (fa) influences the responsiveness to leptin during the first postnatal week, we injected recombinant leptin (600 pmol. g-1. day-1 sc from day 1 to day 7) into wild-type (+/+), heterozygous (+/fa), and fatty (fa/fa) rat pups.Growth and final body fat content of these leptin-treated pups were compared with those of saline-treated littermates of the same genotype. The body mass of the leptin-treated +/+ pups, but not that of the +/fa and fa/fa pups, increased more slowly than that of their respective controls, and fat content at day 7 was reduced by 37% in +/+ pups, by 22% in +/fa pups, but not at all in fa/fa pups. Plasma leptin remained excessively high throughout the day under this treatment, but a 30-fold lower leptin dose, causing only moderate changes of plasma leptin, still reduced the body fat of +/+ pups significantly. We conclude that leptin participates in the control of even the earliest stages of fat deposition and that the response to supraphysiological doses of leptin is markedly reduced in 1-wk-old pups with one fa allele and absent in pups with two fa alleles.MH - Carrier Proteins|*GEMH - Gene Dosage|*MH - Mutation|*MH - Obesity|*GE/PPMH - Proteins|ME/*PDSO - Am J Physiol 1999 May; 276(5 Pt 1):E836-42DP - 1999 MayTA - Am J PhysiolPG - E836-42IP - 5 Pt 1VI - 276UI - 99261862165
AU - Wilson BD
AU - Bagnol D
AU - Kaelin CB
AU - Ollmann MM
AU - Gantz I
AU - Watson SJ
AU - Barsh GSTI - Physiological and anatomical circuitry between Agouti-related protein and leptin signaling.AB - Agouti-related protein (AGRP) is an orexigenic neuropeptide that acts via central melanocortin receptors, and whose messenger RNA (mRNA) levels are elevated in leptin-deficient mice. Fasting associated with a decline in circulating leptin normally causes a 15-fold elevation of hypothalamic Agrp mRNA levels but has no effect in leptin-deficient mice. Chronic hyperleptinemia associated with the tubby and Cpe(fat) mutations has no effect on Agrp mRNA levels,but short term leptin administration causes a 17% reduction of Agrp mRNA levels in nonmutant mice and a 700% reduction in leptin-deficient mice. In young nonobese animals, melanocortin receptor blockade associated with the Ay mutation causes complete resistance to leptin-induced weight loss. Dual in situ hybridization reveals that Agrp-expressing neurons in the medial portion of the arcuate nucleus constitute a subpopulation different from Pomc-expressing neurons,and that a significant proportion of Agrp-expressing neurons (10-25%) coexpresses the leptin receptor, Lepr-b. Immunocytochemistry confirms distinct locations of AGRP- and POMC-expressing cell bodies, but reveals an overlapping distribution of their terminal fields in the arcuate nucleus, the paraventricular hypothalamus, and the dorsomedial hypothalamus. These results suggest that in the fed state, AGRP is normally suppressed by leptin, and that release of this suppression during fasting leads to increased ingestive behavior.MH - Proteins|GE/*ME/PDMH - Signal Transduction|*SO - Endocrinology 1999 May; 140(5):2387-97DP - 1999 MayTA - EndocrinologyPG - 2387-97IP - 5VI - 140UI - 99233377166
AU - Faggioni R
AU - Fantuzzi G
AU - Gabay C
AU - Moser A
AU - Dinarello CA
AU - Feingold KR
AU - Grunfeld CTI - Leptin deficiency enhances sensitivity to endotoxin-induced lethality.AB - Leptin is induced by lipopolysaccharide (LPS) and cytokines.We investigated the role of leptin in LPS-induced toxicity using leptin-deficient (ob/ob) and leptin receptor-deficient (db/db) mice. Sensitivity to LPS-induced mortality is significantly greater in ob/ob mice compared with their own lean littermates but not in db/db mice. LPS reduced serum glucose in both ob/ob and db/db mice but induced corticosterone only in db/db mice. Despite the very high basal levels of serum leptin in db/db mice, a twofold increase in serum leptin levels was observed after LPS in both db/db mice and their lean littermates. No differences were detected in LPS-induced serum levels of interleukin (IL)-1beta, tumor necrosis factor, macrophage inflammatory protein-1alpha, and interferon-gamma in ob/ob mice compared with their own littermates.In contrast, a blunted induction of IL-10 and IL-1 receptor antagonist (IL-1Ra) was observed in ob/ob mice compared with their littermates. In vitro, leptin induced IL-1Ra production and upregulated the IL-1Ra induction by LPS in macrophages. Moreover, treatment with leptin reversed the increased sensitivity to LPS-induced lethality found in ob/ob mice. These results suggest that leptin participates in the host response to inflammation by modulating the host immune and cytokine responses after LPS.MH - Endotoxins|*POMH - Proteins|ME/PD/*PHSO - Am J Physiol 1999 Jan; 276(1 Pt 2):R136-42DP - 1999 JanTA - Am J PhysiolPG - R136-42IP - 1 Pt 2VI - 276UI - 99104060167
AU - Hkansson ML
AU - Meister BTI - Transcription factor STAT3 in leptin target neurons of the rat hypothalamus.AB - Leptin is an adipose tissue-derived hormone that regulates body weight via interactions with hypothalamic neuronal circuitries expressing specific leptin receptors (Ob-R). The Ob-Rs act via the JAK-STAT (Janus kinase-signal transducers and activators of transcription) pathway of signal transduction.Recent evidence suggests that primarily the transcription factor STAT3 mediates leptin's action in the hypothalamus.We have investigated the presence and cellular localization of STAT3 protein in the rat hypothalamus by means of indirect immunofluorescence histochemistry using a rabbit polyclonal STAT3 antiserum. The antiserum identified a 92-kDa protein using Western blotting on rat hypothalamic homogenates,corresponding to the expected size of STAT3. STAT3 immunoreactivity was demonstrated in Ob-R-containing neurons of the paraventricular nucleus (parvocellular part), periventricular nucleus, arcuate nucleus and in the lateral hypothalamic area. Direct double-labeling showed presence of STAT3 immunoreactivity in neuropeptide Y (NPY)-containing neurons of the ventromedial part of the arcuate nucleus and in proopiomelanocortin (POMC)-containing neurons of the ventrolateral part of the arcuate nucleus. The results provide an anatomical basis for a leptin action mediated by STAT3 in Ob-R-containing NPY and POMC neurons of the arcuate nucleus, as well as by Ob-R-containing neurons of the parvocellular paraventricular nucleus and lateral hypothalamic area.MH - DNA-Binding Proteins|*MEMH - Hypothalamus|CY/*ME/ULMH - Neurons|*ME/ULMH - Proteins|*MEMH - Trans-Activators|*MEAD - Department of NeuroscienceAD - Karolinska InstituteAD - StockholmAD - Sweden.SO - Neuroendocrinology 1998 Dec; 68(6):420-7DP - 1998 DecTA - NeuroendocrinologyPG - 420-7IP - 6VI - 68UI - 99091767168
AU - Rizk NM
AU - Liu LS
AU - Eckel JTI - Hypothalamic expression of neuropeptide-Y in the New Zealand obese mouse.AB - OBJECTIVE: Increased levels of hypothalamic neuropeptide-Y (NPY) are thought to contribute to the manifestation of the obese phenotype. The aim of this study was to characterize the interactions between leptin, insulin and NPY in the pathogenesis of polygenic obesity. DESIGN AND METHODS: A polygenic obese animal model, the New Zealand obese mouse (NZO) and its age-matched control, was used to assess the hypothalamic mRNA expression of NPY, the insulin receptor (IR) and the leptin receptor (Ob-Rb), by semiquantitative polymerase chain reaction. Experiments were performed early (at eight weeks old) and late (at 40 weeks old) in the life of these animals. RESULTS: Serum glucose was significantly elevated in obese mice. Serum insulin levels were not different between obese and lean mice, whereas serum leptin levels were significantly elevated in obese mice and increased continuously during life [reaching extremely high values at 40 weeks (41.5+/-4.1 vs 3.4+/-0.25 ng/ml for obese and lean, respectively). The hypothalamic expression of NPY mRNA was significantly higher in NZO mice compared to controls at both eight weeks (2.3-fold) and 40 weeks (1.9-fold),respectively, whereas expression of IR and Ob-Rb remained unaffected. CONCLUSION: Increased hypothalamic expression of NPY due to leptin resistance, may be involved in the development of polygenic obesity. Unchanged Ob-Rb expression suggests that either a defective hypothalamic uptake or defects in Ob-Rb signalling underly this process.MH - Gene Expression|*MH - Hypothalamus|*MEMH - Neuropeptide Y|*GEMH - Obesity|*MEAD - Mansoura UniversityAD - Department of PhysiologyAD - Egypt.SO - Int J Obes Relat Metab Disord 1998 Dec; 22(12):1172-7DP - 1998 DecTA - Int J Obes Relat Metab DisordPG - 1172-7IP - 12VI - 22UI - 99093079169
AU - Boado RJ
AU - Golden PL
AU - Levin N
AU - Pardridge WMTI - Up-regulation of blood-brain barrier short-form leptin receptor gene products in rats fed a high fat diet.AB - Leptin is a 16-kDa protein synthesized in adipose tissue that produces a satiety effect in the CNS. Leptin may gain access to the brain via receptor-mediated transport through the blood-brain barrier (BBB), and the BBB leptin receptor (OBR) may regulate the availability of circulating leptin to brain cells. The aim of the present study was twofold:first, to identify the OBR isoform expressed at the BBB,i.e., short, or "a," and long, or "b," form; and second,to compare the abundance of the BBB OBR mRNA and protein between control and high fat-fed rats. RT-PCR with isoform-specific primers showed that OBRa is the most abundant isoform at the BBB. BBB OBRa transcript content was markedly increased in high fat-fed rats compared with controls (11-fold), and no changes were observed in the expression of the internal standard control actin. The high fat feeding induction of OBR mRNA was correlated with an increase in the immunoreactive BBB OBR determined by immunocytochemistry using an all-isoform reactive antibody in high fat-fed obese rats. This investigation demonstrates (a) the OBRa is the principal leptin receptor expressed at the BBB and (b) this BBB OBR isoform is up-regulated by a high fat diet.MH - Blood-Brain Barrier|*GEMH - Carrier Proteins|BI/*GE/*MEMH - Dietary Fats|*ADMH - Proteins|*MEMH - Up-Regulation (Physiology)|*GESO - J Neurochem 1998 Oct; 71(4):1761-4DP - 1998 OctTA - J NeurochemPG - 1761-4IP - 4VI - 71UI - 98421832170
AU - Mizuno A
AU - Murakami T
AU - Otani S
AU - Kuwajima M
AU - Shima KTI - Leptin affects pancreatic endocrine functions through the sympathetic nervous system.AB - The effects of leptin on the secretion of insulin and glucagon were examined. In an experiment involving insulin response to an i.v. glucose load in vagotomized rats, the plasma concentrations of insulin were significantly lower in the leptin (20 nmol/kg BW)-treated group than in a control group. However, in intact rats and rats that had undergone both vagotomy and chemical sympathectomy, this suppressive effect of leptin on insulin secretion was not detected.In an experiment involving a hypoglycemia-induced glucagon secretion test in intact rats, an i.v. injection of leptin (20 nmol/kg BW) augmented the plasma glucagon response to hypoglycemia. In the case of sympathectomized rats, however, this stimulative effect of leptin on glucagon secretion was not detected. In an experiment with perfused rat pancreas, the addition of leptin (20 nM) to the perfusate slightly suppressed insulin secretion, but had no effect on basal or glucopenia-induced glucagon secretion. In intact rats infused with leptin (0.31 micromol/day), the expression of uncoupling protein-1 messenger RNA in interscapular brown adipose tissue was increased, whereas no such effect of leptin on the uncoupling protein-1 messenger RNA expression was observed in brown adipose tissue in chemically sympathectomized rats. These findings suggest that leptin might indirectly affect pancreatic endocrine functions, probably through its stimulative effects on the sympathetic nervous system.MH - Islets of Langerhans|DE/*PH/SEMH - Proteins|*PDMH - Sympathetic Nervous System|*PHSO - Endocrinology 1998 Sep; 139(9):3863-70DP - 1998 SepTA - EndocrinologyPG - 3863-70IP - 9VI - 139UI - 98389434171
AU - Sharma K
AU - Considine RVTI - The Ob protein (leptin) and the kidney.AB - Mutation of the Ob gene, which encodes for leptin, or mutation of the leptin receptor leads to obesity in mice. Humans,for the most part, have a positive correlation of leptin with body fat mass suggesting possible defects in leptin effector mechanisms that may contribute to obesity. As patients on hemodialysis have difficulty with appetite,we investigated whether leptin is cleared by the kidney and is elevated in hemodialysis patients. In patients with intact renal function there was a net renal uptake of 12%of circulating leptin, whereas in patients with renal insufficiency there was no renal uptake of leptin. In a separate cohort of 36 patients with end-stage renal disease (ESRD), peripheral leptin levels factored for body mass index was increased by fourfold as compared to a group of healthy controls (N = 338). The leptin receptor exists in a long and short form, with the long form primarily expressed in the hypothalamus but also in the lungs and kidneys of the mouse. Further studies are necessary to clarify the role of leptin in regulating appetite in patients with ESRD and the role of leptin in directly affecting kidney function via its receptors.MH - Kidney|DE/ME/*PHMH - Proteins|ME/PD/*PHSO - Kidney Int 1998 Jun; 53(6):1483-7DP - 1998 JunTA - Kidney IntPG - 1483-7IP - 6VI - 53UI - 98270102172
AU - Hollopeter G
AU - Erickson JC
AU - Palmiter RDTI - Role of neuropeptide Y in diet-, chemical- and genetic-induced obesity of mice.AB - OBJECTIVE: The goal of this study was to ascertain whether neuropeptide Y (NPY) is required in mice for the development of obesity induced by a high-fat diet (HFD), chemical lesions of the hypothalamus caused by monosodium glutamate (MSG)or gold thioglucose (GTG), impaired brown adipose tissue (BAT) due to a diphtheria toxin transgene driven by the uncoupling protein 1 promoter (UCP-DTA) or the lethal yellow agouti mutation (Ay). BACKGROUND: The obesity syndrome of the leptin-deficient (ob/ob) mouse can be partially reversed by the genetic removal of NPY. In the murine models of obesity examined in this study, the animals become obese despite increased serum leptin levels, indicating that they are resistant to the weight-limiting actions of leptin.The role of NPY in these obesity models with elevated leptin levels is unknown. EXPERIMENTAL DESIGN: Mice lacking NPY due to genetic disruption of the gene and wildtype littermates were made obese by allowing them access to a highly palatable HFD, by treatment with MSG, or GTG, or by inheriting the dominant UCP-DTA or Ay alleles. Food consumption, body weight and dissectable fat pad weights were measured and compared to values obtained from non-obese littermates.RESULTS: In each model of obesity tested, NPY-deficient mice achieved the same food intake, body weight and fat content as wildtype littermates. CONCLUSION: NPY is not necessary for the progressive development of obesity exhibited by multiple murine models with leptin resistance.MH - Diet|*MH - Neuropeptide Y|*PHMH - Obesity|CI/*ET/GESO - Int J Obes Relat Metab Disord 1998 Jun; 22(6):506-12DP - 1998 JunTA - Int J Obes Relat Metab DisordPG - 506-12IP - 6VI - 22UI - 98328607173
AU - Houseknecht KL
AU - Baile CA
AU - Matteri RL
AU - Spurlock METI - The biology of leptin: a review.AB - Leptin, a 16-kDa protein secreted from white adipocytes,has been implicated in the regulation of food intake, energy expenditure, and whole-body energy balance in rodents and humans. The gene encoding leptin was identified by positional cloning and is the mutation leading to the profound obese phenotype of the ob/ob mouse. Exogenous administration of leptin to ob/ob mice leads to a significant improvement in reproductive and endocrine status as well as reduced food intake and weight loss. The expression and secretion of leptin is highly correlated with body fat mass and adipocyte size. Cortisol and insulin are potent stimulators of leptin expression, and expression is attenuated by beta-adrenergic agonists, cAMP, and thiazolidinediones. The role of other hormones and growth factors in the regulation of leptin expression and secretion is emerging. Leptin circulates specifically bound to proteins in serum, which may regulate its half-life and biological activity. Isoforms of the leptin receptor, members of the interleukin-6 cytokine family of receptors, are found in multiple tissues, including the brain. Many of leptin's effects on food intake and energy expenditure are thought to be mediated centrally via neurotransmitters such as neuropeptide Y. Multiple peripheral effects of leptin have also been recently described,including the regulation of insulin secretion by pancreatic beta cells and regulation of insulin action and energy metabolism in adipocytes and skeletal muscle. Leptin is thought to be a metabolic signal that regulates nutritional status effects on reproductive function. Leptin also plays a major role in hematopoeisis and in the anorexia accompanying an acute cytokine challenge. The profound effects of leptin on regulating body energy balance make it a prime candidate for drug therapies for humans and animals.MH - Obesity|GE/*MEMH - Proteins|GE/ME/*PHSO - J Anim Sci 1998 May; 76(5):1405-20DP - 1998 MayTA - J Anim SciPG - 1405-20IP - 5VI - 76UI - 98283266174
AU - Laughlin GA
AU - Dominguez CE
AU - Yen SSTI - Nutritional and endocrine-metabolic aberrations in women with functional hypothalamic amenorrhea.AB - The development of functional hypothalamic amenorrhea (FHA) in weight-stable, nonathletic women has long been thought to be psychogenic in origin. This study was designed to gain insight into the possibility that nutritional deficits and compensatory endocrine-metabolic adaptations contribute to the development and maintenance of FHA of the psychogenic type. Nutritional intake, insulin sensitivity, and 24-h dynamics of insulin/glucose, cortisol, leptin, somatotropic,and LH axes were simultaneously assessed in eight women with FHA not associated with exercise or weight loss and in eight age- and body mass index-matched regular cycling controls (NC). The percent fat body mass was lower and lean body mass was higher in FHA than in NC (P < 0.05).The FHA subjects scored higher (P < 0.05) on two Eating Disorder Inventory subscales and had a higher (P < 0.05)Beck depression rating than NC, although all were in the subclinical range. Although daily caloric intake did not differ, FHA consumed 50% less (P < 0.001) fat, twice (P < 0.05) as much fiber, and more carbohydrate (P < 0.05)compared to NC. During the feeding phase of the day, FHA exhibited lower glucose (P < 0.05) and insulin (P < 0.01)levels than NC, and the degree of hypoinsulinemia was directly related to relative dietary fat (r = 0.73). Although 24-h mean GH levels did not differ, the pattern of GH release in FHA was distinctly altered from that in NC. GH pulse amplitude was blunted, pulse frequency was accelerated 40% (P < 0.01), and interpulse GH concentrations were elevated 2-fold (P < 0.01) throughout the day for FHA compared to NC. This distorted pattern of GH pulses was associated with a 40% decrease (P < 0.01) in GH-binding protein levels.Levels of the insulin-dependent insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) were elevated (P < 0.001) during the feeding portion of the day in FHA and were inversely related to insulin (r = -0.50) and directly related to cortisol (r = 0.64) levels for FHA and NC groups together.Although levels of IGF-I and IGFBP-3 did not differ, the elevation of IGFBP-1 levels in FHA resulted in a reduced (P < 0.01) ratio of IGF-I/IGFBP-1, which may decrease the bioactivity and hypoglycemic effect of IGF-I. Twenty-four-hour mean leptin levels and the diurnal excursion of leptin in FHA did not differ from those in NC. LH pulse frequency was slowed 50% (P < 0.001) in FHA, with unaltered pulse amplitude, resulting in 45% lower (P < 0.01) 24-h mean LH levels for FHA compared to NC. LH pulse frequency for the two groups was related positively to insulin (r = 0.80) levels and the ratio of IGF-I/IGFBP-1 (r = 0.70) and negatively with cortisol (r = -0.61) and IGFBP-1 (r = -0.72) concentrations. In summary, we found evidence of subclinical eating disorders in weight-stable, nonathletic women with FHA accompanied by a severe restriction of dietary fat intake. Unbalanced nutrient intake in psychogenic FHA was associated with multiple endocrine-metabolic alterations.Among these, reduced levels of plasma glucose and serum GHBP, a decrease in the ratio of IGF-I/IGFBP-1, accelerated GH pulse frequency, and elevated interpulse GH levels are indicative of a hypometabolic state. In addition, the magnitude of glucoregulatory responses (increased cortisol secretion and decreased insulin/IGF-I action) were directly related to the degree of suppression of GnRH/LH pulse frequency.These results are remarkably similar to those seen in highly trained athletes with FHA(1). Thus, nutritional deficits may represent a common contributing factor to the development and maintenance of multiple neuroendocrine-metabolic aberrations underlying both psychogenic and exercise-related FHA.MH - Amenorrhea|BL/*PP/PXMH - Circadian Rhythm|*PHMH - Eating Disorders|*EPMH - Hormones|*BLMH - Hypothalamic Diseases|BL/*PP/PXMH - Nutrition Assessment|*SO - J Clin Endocrinol Metab 1998 Jan; 83(1):25-32DP - 1998 JanTA - J Clin Endocrinol MetabPG - 25-32IP - 1VI - 83UI - 98097538175
AU - L÷llmann B
AU - Grninger S
AU - Stricker Krongrad A
AU - Chiesi MTI - Detection and quantification of the leptin receptor splice variants Ob-Ra, b, and, e in different mouse tissues [published erratum appears in Biochem Biophys Res Commun 1997 Dec 29;241(3):803]AB - Ob-Ra, b, and e are the major splice forms of the leptin receptor. This study was performed to map the tissue distribution and to quantify the 3 receptor isoforms by heterologous competitive Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and RNase Protection Assay (RNase PA). The mRNA of the truncated, membrane bound isoform Ob-Ra was found to be represented ubiquitously. Messenger RNA for the putative functional isoform Ob-Rb could be detected in brain, hypothalamus and in some peripheral tissues (e.g. heart, lung, lymph nodes). The highest ratio between Ob-Rb and Ob-Ra mRNA was found in the hypothalamus, where leptin probably exerts its satiety action. The fact that Ob-Rb mRNA was found in peripheral tissues could indicate possible additional functions of leptin. Transcripts for the shortest splice variant, Ob-Re, which is expected to encode a soluble form of the receptor, were detected in relatively high amounts in many tissues. The levels were comparable to those of leptin mRNA in fat tissue. It is conceivable, therefore,that Ob-Re might be secreted in sufficient amounts to act as a buffering system for freely circulating leptin. Copyright 1997 Academic Press.MH - Carrier Proteins|*AN/GE/MEMH - RNA, Messenger|*ANSO - Biochem Biophys Res Commun 1997 Sep; 238(2):648-52DP - 1997 SepTA - Biochem Biophys Res CommunPG - 648-52IP - 2VI - 238UI - 97446041176
AU - Li H
AU - Matheny M
AU - Scarpace PJTI - beta 3-Adrenergic-mediated suppression of leptin gene expression in rats.AB - To investigate the role of beta 3-adrenergic receptors in the suppression of leptin gene expression, we fasted F-344 rats to decrease leptin mRNA levels, refed the rats to stimulate leptin mRNA production, and examined the ability of the beta 3-adrenergic agonist CGP-12177 to prevent the rise in leptin mRNA levels. In the initial 2 h after CGP-12177 (0.75 mg/kg), there were significant reductions in both food consumption and leptin mRNA levels in epididymal,perirenal, and interscapular white adipose tissue. We were unable to detect leptin mRNA in interscapular brown adipose tissue (IBAT), whereas there was a significant increase in uncoupling protein mRNA levels in IBAT after CGP-12177.The suppression of leptin mRNA and food intake by CGP-12177 was confirmed in a second experiment using another rat strain, the F-344 x BN. Furthermore, refeeding after a period of fasting increased leptin mRNA, which was prevented by CGP-12177. These data indicate a role for beta 3-adrenergic-mediated regulation of leptin gene expression in nonmutant rodents and are consistent with other reports suggesting that beta 3-adrenergic agonists suppress food intake.MH - Adipose Tissue|AH/DE/*MEMH - Adrenergic beta-Agonists|*PDMH - Propanolamines|*PDMH - Proteins|*BIMH - Receptors, Adrenergic, beta|*PHMH - Suppression, Genetic|*DEMH - Transcription, Genetic|*DESO - Am J Physiol 1997 Jun; 272(6 Pt 1):E1031-6DP - 1997 JunTA - Am J PhysiolPG - E1031-6IP - 6 Pt 1VI - 272UI - 97371223177
AU - Barthel A
AU - Kohn AD
AU - Luo Y
AU - Roth RATI - A constitutively active version of the Ser/Thr kinase Akt induces production of the ob gene product, leptin, in 3T3-L1 adipocytes.AB - The expression of the ob gene product leptin in adipose tissues has been previously described to be regulated by insulin in vivo and vitro. Akt, a ser/thr kinase with a pleckstrin homology domain, has recently been identified to function in the insulin receptor signaling cascade. The aim of this study was to investigate the role of Akt in the production of leptin by adipocytes. Therefore, we examined leptin production by 3T3-L1 adipocytes stably expressing a myristoylated version of Akt which is constitutively active. Leptin levels in the supernatants of serum starved,nonstimulated 3T3-L1 adipocytes were determined by radioimmunoassay (RIA). Expression of the constitutively active Akt was found to induce a more than 20-fold increase in leptin levels whereas a control non-myristoylated Akt had no effect.Leptin mRNA levels as determined by either RNase protection assay or reverse transcriptase (RT)-polymerase chain reaction (PCR) were not elevated by the constitutively active Akt.These results indicate that Akt can induce leptin production in 3T3-L1 adipocytes via a non-transcriptional mechanism.MH - Adipocytes|CY/*ME/PHMH - Fibroblasts|CY/*ME/PHMH - Obesity|*GE/PAMH - Protein-Serine-Threonine Kinases|*MEMH - Proteins|*BI/GESO - Endocrinology 1997 Aug; 138(8):3559-62DP - 1997 AugTA - EndocrinologyPG - 3559-62IP - 8VI - 138UI - 97375495178
AU - Emilsson V
AU - Liu YL
AU - Cawthorne MA
AU - Morton NM
AU - Davenport MTI - Expression of the functional leptin receptor mRNA in pancreatic islets and direct inhibitory action of leptin on insulin secretion.AB - Leptin, encoded for by the mouse ob gene, regulates feeding behavior and energy metabolism. Its receptor (Ob-R) is encoded by the mouse diabetic (db) gene and is mutated in the db/db mouse so that it lacks the cytoplasmic domain.We show that the full-length leptin receptor (Ob-Rb), which is believed to transmit the leptin signal, is expressed in pancreatic islets of ob/ob and wild-type mice, as well as in hypothalamus, liver, kidney, spleen, and heart. Recombinant leptin inhibited basal insulin release in the perfused pancreas preparation from ob/ob mice but not in that from Zucker fa/fa rats. Leptin (1-100 nmol/l) also produced a dose-dependent inhibition of glucose-stimulated insulin secretion by isolated islets from ob/ob mice. In contrast,leptin at maximum effective concentration (100 nmol/l) did not inhibit glucose-stimulated insulin secretion by islets from db/db mice. These results provide evidence that a functional leptin receptor is present in pancreatic islets and suggest that leptin overproduction, particularly from abdominal adipose tissue, may modify directly both basal and glucose-stimulated insulin secretion.MH - Carrier Proteins|*GEMH - Insulin|*SEMH - Islets of Langerhans|*MESO - Diabetes 1997 Feb; 46(2):313-6DP - 1997 FebTA - DiabetesPG - 313-6IP - 2VI - 46UI - 97153420179
AU - Mart A
AU - Berraondo B
AU - Martnez JATI - Leptin: physiological actions.AB - Leptin, a peptide hormone (167 aa) mainly expressed in adipocytes, and its hypothalamic receptors are integral components of a complex physiological system evolved to regulate fuel stores and energy expenditure. Thus, leptin discovery has constituted a great breakthrough in the understanding of body weight regulation and in the role of the fat tissue as an endocrine organ. Increasing scientific evidences suggest that, leptin has overall effects on metabolism.Leptin mRNA and/or protein are produced by placenta, fetal tissues, gastric mucosa and hepatic stellate cells and can participate in many physiological functions such as fetal growth, gut-derived satiety, immune or proinflammatory responses, reproduction, nutrient intestinal absorption,angiogenesis and lipolysis. The leptin participation in body weight homeostasis and obesity as well as other peripheral actions are revisited.MH - Proteins|ME/*PHSO - J Physiol Biochem 1999 Mar; 55(1):43-9DP - 1999 MarTA - J Physiol BiochemPG - 43-9IP - 1VI - 55UI - 99422850180
AU - Hkansson M
AU - de Lecea L
AU - Sutcliffe JG
AU - Yanagisawa M
AU - Meister BTI - Leptin receptor- and STAT3-immunoreactivities in hypocretin/orexin neurones of the lateral hypothalamus.AB - Hypocretins/orexins are recently characterized peptides that are synthesized in neurones of the lateral hypohalamus and stimulate food intake in rats. To clarify whether leptin may interact with hypocretin/orexin to reduce ingestive behaviour, the presence of leptin receptor-immunoreactivity in hypocretin/orexin-containing neurones was examined. Many leptin receptor-and hypocretin/orexin-immunoreactive neurones were demonstrated in the lateral hypothalamic area and perifornical region. Both direct double-labelling and elution-restaining methods showed that leptin receptor-immunoreactivity was present in the vast majority of hypocretin/orexin-containing neurones. Immunoreactivity for STAT3,a transcription factor activated by leptin, was also demonstrated in hypocretin/orexin-containing neurones. Isolated hypocretin/orexin cell bodies in the dorsal part of the lateral hypothalamic area and the ventral perifornical region were shown to contain immunoreactivity for galanin, another peptide known to affect feeding. Galanin neurones were also seen to contain leptin receptor-and STAT3-immunoreactivity. Melanin-concentrating hormone (MCH)-containing neurones constituted a cell population within the lateral hypothalamus distinct from the one containing hypocretin/orexin-immunoreactivity, as shown by elution-restaining methodology. The presence of leptin receptor-and STAT3-immunoreactivities in hypocretin/orexin-containing neurones of the lateral hypothalamus suggests that leptin may directly regulate these hypothalamic neurones, most likely via an inhibitory action on hypocretin/orexin expression and/or secretion resulting in reduced food intake.MH - Carrier Proteins|*AN/GEMH - DNA-Binding Proteins|*ANMH - Hypothalamus|*CHMH - Neurons|*CHMH - Neurotransmitters|*AN/GEMH - Trans-Activators|*ANSO - J Neuroendocrinol 1999 Aug; 11(8):653-63DP - 1999 AugTA - J NeuroendocrinolPG - 653-63IP - 8VI - 11UI - 99376734181
AU - Pankov YATI - Adipose tissue as an endocrine organ regulating growth,puberty, and other physiological functions.AB - There are reports on some patients with clearly manifested specific features of genotype and phenotype similar to those of ob/ob and db/db mice. Three patients from Turkey were described who had a homozygous mutation in the gene of leptin identical to the mutation in C57BL6J ob/ob mice.This mutation is a C --> T substitution in codon 105 of the amino acid sequence of leptin. In mice this mutation generates a stop-codon; in humans it substitutes Arg-105 with Trp. The mutant human leptin cannot be secreted by the cells and thus has no effect on the hypothalamus. Patients with a homozygous mutation of the leptin receptor resulting in the G --> T substitution in the splice donor site of exon 16 were studied in a family of Kabilian origin. Exon 16 was not included in the mature mRNA molecule, and a truncated leptin receptor was synthesized which lacked the transmembrane and intracellular domains; this receptor was unable to transduce the hormonal signal. Both groups of patients suffered from obesity, delayed linear growth,infertility, increased blood insulin level, and other disorders.Leptin influences lipid metabolism by stimulating the expression of the proopiomelanocortin (POMC) gene in melanocortinergic neurons of the hypothalamus. POMC is the precursor of alpha-melanocyte-stimulating hormone (alpha-MSH), which binds to the melanocortin receptor MC4-R in the brain, decreases appetite, and activates lipid metabolism. Patients with mutations in MC4-R suffered only from obesity, but their growth and puberty were not affected. Thus, leptin apparently stimulates growth and puberty not through its binding to the receptors on melanocortinergic neurons, but through its binding to receptors on other hypothalamic neurons;this effect of leptin is not affected by mutations in the MC4-R gene.MH - Adipose Tissue|*PHMH - Endocrine System|*PHMH - Growth|*PHMH - Puberty|*PHSO - Biochemistry (Mosc) 1999 Jun; 64(6):601-9DP - 1999 JunTA - Biochemistry (Mosc)PG - 601-9IP - 6VI - 64UI - 99327169182
AU - Kumar MV
AU - Sunvold GD
AU - Scarpace PJTI - Dietary vitamin A supplementation in rats: suppression of leptin and induction of UCP1 mRNA.AB - All-trans-retinoic acid (RA), an active metabolite of vitamin A, induces the gene expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) and suppresses leptin gene expression in white adipose tissue (WAT) when given as an acute dose. These contrasting effects of RA leave in doubt the overall effect of chronic RA or vitamin A supplementation on energy homeostasis. To investigate the effects of dietary vitamin A supplementation on leptin and UCP1 gene expression, rats were fed either a normal diet (2.6 retinol/kg diet) or a vitamin A-supplemented diet (129 mg retinol/kg diet) for 8 weeks, and adiposity,serum leptin levels, leptin mRNA levels in perirenal WAT,UCP1 and UCP2 mRNA levels in BAT, and beta3-adrenergic receptor mRNA levels in BAT and WAT were examined. Rats on both diets gained a similar amount of weight, but there was a small 9% decrease in the adiposity index in the vitamin A-supplemented rats. Dietary vitamin A supplementation increased UCP1 gene expression in BAT by 31%, but suppressed leptin gene expression by 44% and serum leptin levels by 65%. UCP2 and beta3-adrenergic receptor gene expression in BAT and perirenal WAT were unchanged by the vitamin A diet. These data suggest that dietary vitamin A has a role in regulating energy homeostasis by enhancing UCP1 gene expression and decreasing serum leptin levels.MH - Carrier Proteins|*GEMH - Membrane Proteins|*GEMH - Proteins|*GE/MEMH - RNA, Messenger|*BI/*GEMH - Vitamin A|*ADSO - J Lipid Res 1999 May; 40(5):824-9DP - 1999 MayTA - J Lipid ResPG - 824-9IP - 5VI - 40UI - 99240794183
AU - Glasow A
AU - Bornstein SR
AU - Chrousos GP
AU - Brown JW
AU - Scherbaum WATI - Detection of Ob-receptor in human adrenal neoplasms and effect of leptin on adrenal cell proliferation.AB - Leptin, a hormone mainly secreted from adipose tissue, communicates a metabolic signal to the adrenal gland. Ob-Receptor (Ob-R) expression was reported in rat, mice and human adrenal glands. This study intended to investigate possible differences in the Ob-R expression and distribution of Ob-R protein in human adrenal tumors as compared to normal adrenal tissue. Proliferative effects of leptin were analyzed in the human adrenocortical carcinoma cell line (NCI-H295). The full length Ob-R mRNA and the isoforms B219.1 and B219.3 could be demonstrated by RT-PCR in all adrenal tumors (n=8), the tumor cell line (NCI-H295) and normal tissue. In contrast the Ob-R isoform B219.2 was absent in the carcinoma cell line and in most of the adrenal tumors (n=5), whereas it was present in normal adrenals.The Ob-R protein could be demonstrated in benign and malignant adrenocortical tumors. Pheochromocytomas showed only a weak immunostaining with the human Ob-R antibody. Human leptin did not affect the proliferation or variability of adrenal tumor cells as demonstrated by [3H]-thymidine assay and WST-1 test. In conclusion, although functional leptin receptors are expressed in human adrenal tumors,leptin does not regulate tumor cell proliferation.MH - Adrenal Gland Neoplasms|*CH/PAMH - Carrier Proteins|*AN/GEMH - Cell Division|*DEMH - Proteins|*PDSO - Horm Metab Res 1999 Apr; 31(4):247-51DP - 1999 AprTA - Horm Metab ResPG - 247-51IP - 4VI - 31UI - 99263873184
AU - Xu B
AU - Kalra PS
AU - Farmerie WG
AU - Kalra SPTI - Daily changes in hypothalamic gene expression of neuropeptide Y, galanin, proopiomelanocortin, and adipocyte leptin gene expression and secretion: effects of food restriction.AB - The participation of hypothalamic neuropeptide Y (NPY)-, galanin (GAL)-, and opioid-producing neurons in the restraint on food intake exerted by adipocyte leptin has recently been recognized. To further understand the interplay between the central appetite-stimulating- and peripheral appetite-inhibiting signals in the management of daily food intake,we have examined the daily patterns in expression of the hypothalamic neuropeptides and leptin receptor (R) and adipocyte leptin gene expression and secretion in freely feeding (FF) rats. These analyses were extended to determine the impact of food restriction (FR) to 4 h daily for 4 weeks. Groups of FF and FR rats were killed at 4-h intervals during a 24-h period, and hypothalamic NPY, GAL, POMC, and leptin-R gene expression and leptin gene expression were evaluated by RNase protection assays and serum leptin and corticosterone (CORT) levels were estimated by RIA.The following new findings emerged: 1) In FF rats, hypothalamic NPY messenger RNA (mRNA) levels fluctuated during the course of 24 h with high levels at 0700 h and 1100 h followed by a decrease at 1500 h during the lights-on phase that was sustained throughout the dark phase (1900 h-0500 h)of the light-dark cycle. Hypothalamic GAL and POMC mRNA also displayed daily patterns but with a different time course; GAL and POMC gene expression were elevated 4 h later than NPY mRNA at 1100 h and 1500 h. 2) Although FR to 4 h between 1100 h and 1500 h resulted in maintenance of body weight compared with a steady weight gain in FF rats, the daily patterns of fluctuations in hypothalamic neuropeptide gene expression were abolished. 3) In FF rats,hypothalamic leptin-R and adipocyte leptin gene expression and serum leptin levels displayed a daily pattern temporally different from that of hypothalamic neuropeptide gene expression.Adipocyte leptin mRNA remained low during the lights-on phase but increased at the onset of the lights-off phase (1900 h) and remained elevated through the dark phase. 4) Hypothalamic leptin-R gene expression, like that of adipocyte leptin gene expression, rose abruptly at the onset of nocturnal feeding behavior but receded progressively to low range thereafter. 5) On the other hand, a dichotomy in the daily rise in adipocyte leptin gene expression and leptin secretion was observed in FF rats. Unlike adipocyte leptin mRNA, serum leptin increased at 2300 h, 4 h after initiation of ingestive behavior. 6) In FR rats, adipocyte leptin gene expression fluctuated little over the 24-h period but, as in FF rats, leptin hypersecretion peaked 4 h after initiation of food intake. 7) In both FF and FR rats, increased serum CORT levels preceded serum leptin rise. Overall, these results show that in FF rats, gene expression of hypothalamic appetite stimulating peptides first rise and then fall to nadir during the lights-on phase when leptin levels are in low range; adipocyte leptin mRNA rises before impending ingestive behavior and increased leptin secretion reaching peak manifests itself during nocturnal feeding. The FR regimen, which curtailed the normal body weight gain, abolished these daily fluctuations in gene expression of hypothalamic orexigenic peptides and adipocyte leptin but permitted feeding-associated increased leptin secretion. Thus, it may be important to consider the daily patterns of gene expression and availability of hypothalamic orexigenic peptides in investigations aimed at elucidating the central mechanisms underlying the feedback action of the normal and altered leptin secretion patterns.MH - Adipocytes|*MEMH - Eating|*MH - Galanin|*GEMH - Gene Expression|*MH - Hypothalamus|*MEMH - Neuropeptide Y|*GEMH - Pro-Opiomelanocortin|*GEMH - Proteins|*GE/SESO - Endocrinology 1999 Jun; 140(6):2868-75DP - 1999 JunTA - EndocrinologyPG - 2868-75IP - 6VI - 140UI - 99272307185
AU - Trayhurn P
AU - Hoggard N
AU - Mercer JG
AU - Rayner DVTI - Leptin: fundamental aspects.AB - The discovery of leptin, the product of the ob gene, has led to major developments in understanding the regulation of energy balance. It is now recognised that leptin is produced in several organs additional to white adipose tissue, including brown fat, the placenta and fetal tissues (such as heart and bone/cartilage). The hormone has multiple functions-in inhibiting food intake, in the stimulation/maintenance of energy expenditure, as a signal to the reproductive system and as a 'metabolic' hormone influencing a range of processes (for example, insulin secretion, lipolysis,sugar transport). The production of leptin by white fat is subject to a number of regulatory influences, including insulin and glucocorticoids (which are stimulatory), and fasting and beta-adrenoceptor agonists (which are inhibitory). A key role in the regulation of leptin production by white fat is envisaged for the sympathetic system, operating through beta3-adrenoceptors. The leptin receptor gene is widely expressed, with the several splice variants exhibiting different patterns of expression. The long form variant (Ob-Rb) is expressed particularly in the hypothalamus, although it is being increasingly identified in other tissues.Leptin exerts its central effects through several neuroendocrine systems, including neuropeptide Y, glucagon-like peptide-1, melanocortins, corticotrophin releasing hormone (CRH)and cocaine- and amphetamine-regulated transcript (CART). In essence, the leptin system now appears highly complex,the hormone being involved in a range of physiological processes in a manner far transcending the initial lipostatic concept. This complexity may reduce the potential of the leptin system as a target for anti-obesity therapy.MH - Proteins|GE/*PHSO - Int J Obes Relat Metab Disord 1999 Feb; 23 Suppl 1():22-8DP - 1999 FebTA - Int J Obes Relat Metab DisordPG - 22-8VI - 23 Suppl 1UI - 99208201186
AU - Baskin DG
AU - Schwartz MW
AU - Seeley RJ
AU - Woods SC
AU - Porte D Jr
AU - Breininger JF
AU - Jonak Z
AU - Schaefer J
AU - Krouse M
AU - Burghardt C
AU - Campfield LA
AU - Burn P
AU - Kochan JPTI - Leptin receptor long-form splice-variant protein expression in neuron cell bodies of the brain and co-localization with neuropeptide Y mRNA in the arcuate nucleus.AB - Reduced leptin (Ob protein) signaling is proposed to be a stimulus for the activation of neuropeptide Y (NPY) gene activity and increased expression of mRNA for the long form of the leptin receptor (Ob-Rb) in the hypothalamic arcuate nucleus. To determine if Ob-Rb protein is expressed in arcuate nucleus NPY neurons, we developed an affinity-purified polyclonal antibody against amino acids 956-1102 of human Ob-Rb. This antibody specifically recognizes the cytoplasmic tail of Ob-Rb and does not react with shorter leptin-receptor variants. Western immunoblots of Ob-Rb-transfected COS cells showed a single 150-kD band, and immunofluorescence revealed intense perinuclear staining in the cytoplasm. A 150-kD band was also present in Western immunoblots of hypothalamus. Immunocytochemical staining of brain slices revealed immunoreactive Ob-Rb protein concentrated in many neuronal cell bodies in the same regions of the forebrain that also express Ob-Rb mRNA. In the hypothalamus,Ob-Rb-positive cell bodies were abundant in the arcuate nucleus and ventromedial nucleus, with lesser numbers in the dorsomedial nucleus and paraventricular nucleus. Immunostaining was also detected in cell bodies of pyramidal cell neurons of the pyriform cortex and cerebral cortex, in neurons of the thalamus, and on the surface of ependymal cells lining the third ventricle. The choroid plexus, which expresses the short Ob-Ra form, was negative. Combined immunocytochemistry for Ob-Rb protein and fluorescence in situ hybridization for NPY mRNA identified arcuate nucleus neurons containing both NPY mRNA and Ob-Rb protein. The present finding of Ob-Rb protein in neurons that express NPY mRNA supports the hypothesis that arcuate nucleus NPY neurons are direct targets of leptin and play an important role in regulation of food intake and body weight.MH - Arcuate Nucleus|*MEMH - Carrier Proteins|*BI/GE/IMMH - Neurons|*MEMH - Neuropeptide Y|*GESO - J Histochem Cytochem 1999 Mar; 47(3):353-62DP - 1999 MarTA - J Histochem CytochemPG - 353-62IP - 3VI - 47UI - 99150405187
AU - Horvath TL
AU - Diano S
AU - van den Pol ANTI - Synaptic interaction between hypocretin (orexin) and neuropeptide Y cells in the rodent and primate hypothalamus: a novel circuit implicated in metabolic and endocrine regulations.AB - Hypocretin (orexin) has recently been shown to increase feeding when injected into the brain. Using both rat and primate brains, we tested the hypothesis that a mechanism of hypocretin action might be related to synaptic regulation of the neuropeptide Y (NPY) system. Hypocretin-immunoreactive terminals originating from the lateral hypothalamus make direct synaptic contact with neurons of the arcuate nucleus that not only express NPY but also contain leptin receptors.In addition, hypocretin-containing neurons also express leptin receptor immunoreactivity. This suggests a potential mechanism of action for hypocretin in the central regulation of metabolic and endocrine processes. The excitatory actions of hypocretin could increase NPY release, resulting in enhanced feeding behavior and altered endocrine regulation,whereas leptin, released from adipose tissue as an indicator of fat stores, would have the opposite effect on the same neurons, leading to a decrease in NPY and NPY-mediated hypothalamic functions. On the other hand, the innervation of hypocretin cells by NPY boutons raises the possibility that NPY may exert an effect on hypothalamic functions,at least in part, via mediation or feedback action on these lateral hypothalamic cells. Our data indicate that a direct interaction between leptin, hypocretin, and NPY exists in the hypothalamus that may contribute to the central regulation of metabolic and endocrine processes in both rodents and primates.MH - Carrier Proteins|ME/*PHMH - Hypothalamus|CY/ME/*PHMH - Neurons|*PHMH - Neuropeptide Y|*MEMH - Neuropeptides|*PHMH - Synapses|*PHAD - Department of Obstetrics and GynecologyAD - Yale University School of MedicineAD - New HavenAD - Connecticut 06520AD - USA.SO - J Neurosci 1999 Feb 1; 19(3):1072-87DP - 1999 Feb 1TA - J NeurosciPG - 1072-87IP - 3VI - 19UI - 99119451188
AU - Frhbeck G
AU - Jebb SA
AU - Prentice AMTI - Leptin: physiology and pathophysiology.AB - The identification and sequencing of the ob gene and its product, leptin, in late 1994 opened new insights in the study of the mechanisms controlling body weight and led to a surge of research activity. During this time, a considerable body of knowledge regarding leptin's actions has been accumulated and the field continues to expand rapidly. Currently there is particular interest in the interaction of leptin with other peripheral and neural mechanisms to regulate body weight, reproduction and immunological response. In this review, we attempt to place the current state of knowledge about leptin in the broader perspective of physiology, including its structural characteristics, receptors, binding proteins, signalling pathways, regulation of adipose tissue expression and production, secretion patterns, clearance mechanisms and functional effects. In addition, leptin's involvement in the pathophysiology of obesity, anorexia nervosa, diabetes mellitus, polycystic ovary syndrome, acquired immunodeficiency syndrome, cancer, nephropathy,thyroid disease, Cushing's syndrome and growth hormone deficiency will be reviewed.MH - Obesity|*MEMH - Proteins|ME/*PHSO - Clin Physiol 1998 Sep; 18(5):399-419DP - 1998 SepTA - Clin PhysiolPG - 399-419IP - 5VI - 18UI - 99001115189
AU - Bouloumi A
AU - Drexler HC
AU - Lafontan M
AU - Busse RTI - Leptin, the product of Ob gene, promotes angiogenesis.AB - The adipocyte-derived cytokine leptin is thought to play a key role in the control of satiety and energy expenditure.Because adipogenesis and angiogenesis are tightly correlated during the fat mass development, we tested the hypothesis that leptin is able to modulate the growth of the vasculature.Experiments were performed using cultured human umbilical venous endothelial cells (HUVECs) and porcine aortic endothelial cells. The presence of 170-kDa endothelial leptin receptor (Ob-R) was assessed in HUVECs by Western blot analysis.Reverse transcriptase-polymerase chain reaction analysis using specific oligonucleotides for the short and long Ob-R forms further revealed the expression of both Ob-R transcripts in endothelial cells. Moreover, leptin evoked a time-dependent tyrosine phosphorylation of a number of endothelial proteins, the most prominent of which were the mitogen-activated protein kinases Erk1/2. Treatment of HUVECs with leptin led to a concentration-dependent increase in cell number that was maximal at 10 ng/mL leptin and equivalent to that elicited by vascular endothelial growth factor. This effect was associated with an enhanced formation of capillary-like tubes in an in vitro angiogenesis assay and neovascularization in an in vivo model of angiogenesis.These results indicate that leptin, via activation of the endothelial Ob-R, generates a growth signal involving a tyrosine kinase-dependent intracellular pathway and promotes angiogenic processes. We speculate that this leptin-mediated stimulation of angiogenesis might represent not only a key event in the settlement of obesity but also may contribute to the modulation of growth under physiological and pathophysiological conditions in other tissues.MH - Neovascularization, Pathologic|DT/*PPMH - Neovascularization, Physiologic|DE/*PHMH - Obesity|*GEMH - Proteins|*GE/*ME/PDSO - Circ Res 1998 Nov; 83(10):1059-66DP - 1998 NovTA - Circ ResPG - 1059-66IP - 10VI - 83UI - 99032969190
AU - Arvaniti K
AU - Ricquier D
AU - Champigny O
AU - Richard DTI - Leptin and corticosterone have opposite effects on food intake and the expression of UCP1 mRNA in brown adipose tissue of lep(ob)/lep(ob) mice.AB - The present study was conducted to assess the interaction effect of leptin and corticosterone on food intake and the expression of uncoupling protein 1 (UCP1) mRNA in interscapular brown adipose tissue (IBAT). To this end, a 3 x 3 factorial experiment was designed in which adrenalectomized (ADX)lep(ob)/lep(ob) mice were subjected to three doses of corticosterone and three doses of leptin. The results confirm the anorectic and orexigenic effects of leptin and corticosterone, respectively.The results also emphasize the abilities of leptin and corticosterone to respectively increase and reduce the expression of UCP1 mRNA in IBAT. The effects of leptin and corticosterone on food intake and the expression of UCP1 mRNA translated into effects on body weight and body composition; leptin reduced body weight and corticosterone increased the weight of IBAT. The present results do not provide evidence for leptin-corticosterone interactions in the control of food intake and thermogenesis. Corticosterone increased food intake and reduced the expression of IBAT UCP1 regardless of the leptin status, and leptin reduced food intake and induced the expression of IBAT UCP1 independently of the corticosterone levels.MH - Brown Fat|*MEMH - Carrier Proteins|*GEMH - Corticosterone|*PDMH - Eating|*DEMH - Membrane Proteins|*GEMH - Obesity|*GE/*MEMH - Proteins|AN/*PDMH - RNA, Messenger|*MESO - Endocrinology 1998 Sep; 139(9):4000-3DP - 1998 SepTA - EndocrinologyPG - 4000-3IP - 9VI - 139UI - 98389449191
AU - Karonen SL
AU - Koistinen HA
AU - Nikkinen P
AU - Koivisto VATI - Is brain uptake of leptin in vivo saturable and reduced by fasting?AB - Leptin is a peptide hormone produced by adipocytes which provides a negative feedback signal to control the amount of body fat. The action of leptin on food intake and weight loss is thought to be mediated by interaction with its hypothalamic receptor. We examined the biodistribution and brain uptake of radioiodinated leptin (123I-leptin)by dynamic gamma imaging in six anaesthetized New Zealand white rabbits. Leptin uptake was seen in the brain, lungs,liver and kidneys. In the brain, increase in radioactivity as a function of time was seen in the choroid plexus area.The choroid plexus to brain radioactivity ratio (CP/BR)was used as the target to background ratio. The CP/BR ratio increased up to approximately 40-60 min, after which a steady state in CP/BR was achieved. The steady state uptake ratio was higher in the rabbits that had fasted for only 6-8 h before the experiment (CP/BR approximately 2.5) than in those that had fasted for 25-27 h before the experiment (CP/BR approximately 1.8). Thus, leptin uptake in vivo occurs in the choroid plexus region of the brain and in the lungs, kidney and the liver. The uptake of leptin in the choroid plexus appears to be saturable, as indicated by the achieved steady state in the CP/BR radioactivity curve 40-60 min following 123I-leptin injection. The lower steady state CP/BR after prolonged fasting may be the result of the downregulation of leptin receptors in the choroid plexus.MH - Brain|*ME/RIMH - Fasting|*MEMH - Proteins|DU/*PKSO - Eur J Nucl Med 1998 Jun; 25(6):607-12DP - 1998 JunTA - Eur J Nucl MedPG - 607-12IP - 6VI - 25UI - 98283899192
AU - Trayhurn P
AU - Hoggard N
AU - Mercer JG
AU - Rayner DVTI - Hormonal and neuroendocrine regulation of energy balance--the role of leptin.AB - A new dimension to the regulation of energy balance has come from the identification of the ob (obese) gene and its protein product, leptin. Leptin is produced primarily in white adipose tissue, but synthesis also occurs in brown fat and the placenta. Several physiological functions have been described for leptin the inhibition of food intake,the stimulation/maintenance of energy expenditure, as a signal of energy reserves to the reproductive system, and as a factor in haematopoiesis. The production of leptin by white fat is influenced by a number of factors, including insulin and glucocorticoids (which are stimulatory), and fasting, cold exposure and beta-adrenoceptor agonists (which are inhibitory). A key role in the regulation of leptin production is envisaged for the sympathetic nervous system, operating through beta 3-adrenoceptors. The leptin receptor gene is expressed in a wide range of tissues, and several splice variants are evident. A long form variant (Ob-Rb) with an intracellular signalling domain is found particularly in the hypothalamus. Leptin exerts its central effects through neuropeptide Y, and through the glucagon-like peptide-1 and melanocortin systems, but it may also interact with other neuroendocrine pathways. The role and function of the leptin system in agricultural animals has not been established, but it offers a potential new target for the manipulation of body fat.MH - Energy Metabolism|*MH - Hormones|*PHMH - Neurosecretory Systems|*PHMH - Proteins|BI/*PHSO - Arch Tierernahr 1998; 51(2-3):177-85DP - 1998TA - Arch TierernahrPG - 177-85IP - 2-3VI - 51UI - 98336586193
AU - Cusin I
AU - Zakrzewska KE
AU - Boss O
AU - Muzzin P
AU - Giacobino JP
AU - Ricquier D
AU - Jeanrenaud B
AU - Rohner Jeanrenaud FTI - Chronic central leptin infusion enhances insulin-stimulated glucose metabolism and favors the expression of uncoupling proteins.AB - Continuous (4 days) intracerebroventricular leptin infusion (12 microg/day) was performed in lean rats, and its hormonometabolic effects were determined. Intracerebroventricular leptin administration did not result in leakage of the hormone into the peripheral circulation. Thus, its effects were elicited by its presence within the central nervous system.Intracerebroventricular leptin infusion produced marked decreases in food intake and body weight gain relative to vehicle-infused fed ad libitum rats. Because decreases in food intake alter hormonometabolic homeostasis, additional control rats pair-fed to the amount of food consumed by leptin-infused ones were included in the study. Intracerebroventricular leptin-infused and vehicle-infused pair-fed rats were characterized,relative to vehicle-infused ad libitum-fed animals, by decreases in body weight and insulinemia and by increases in insulin-stimulated overall glucose utilization and muscle and brown adipose tissue glucose utilization index. Brown adipose tissue uncoupling protein (UCP)1, UCP2, and UCP3 mRNA levels were markedly decreased in pair-fed animals relative to those of fed ad libitum control animals, as were liver and white adipose tissue UCP2 and muscle UCP3 mRNA levels. In marked contrast, intracerebroventricular leptin administration was accompanied by the maintenance of high UCP1, UCP2, and UCP3 expression in all these tissues.Thus, despite analogies between leptin's effects and those of pair-feeding with regard to glucose handling, their respective underlying mechanisms differ. While leptin maintains or favors energy-dissipating mechanisms (UCP1, UCP2, and UCP3), the latter are markedly depressed in pair-fed rats.This effect of leptin may prevent subsequent excessive storage processes, thereby maintaining normal body homeostasis.MH - Carrier Proteins|*GEMH - Glucose|*MEMH - Insulin|BL/*PDMH - Membrane Proteins|*GEMH - Proteins|*AD/*GE/PDSO - Diabetes 1998 Jul; 47(7):1014-9DP - 1998 JulTA - DiabetesPG - 1014-9IP - 7VI - 47UI - 98311156194
AU - Lostao MP
AU - Urdaneta E
AU - Martnez Ans E
AU - Barber A
AU - Martnez JATI - Presence of leptin receptors in rat small intestine and leptin effect on sugar absorption.AB - Leptin is involved in food intake and thermogenesis regulation.Since leptin receptor expression has been found in several tissues including small intestine, a possible role of leptin in sugar absorption by the intestine was investigated. Leptin inhibited D-galactose uptake by rat small intestinal rings 33% after 5 min of incubation. The inhibition increased to 56% after 30 min. However, neither at 5 min nor at 30 min did leptin prevent intracellular galactose accumulation.This leptin effect was accompanied by a decrease of the active sugar transport apparent Vmax (20 vs. 4.8 micromol/g wet weight 5 min) and apparent Km (15.8 vs. 5.3 mM) without any change in the phlorizin-resistant component. On the other hand, immunohistochemical experiments using anti-leptin monoclonal antibodies recognized leptin receptors in the plasma membrane of immune cells located in the lamina propria. These results indicate for the first time that leptin has a rapid inhibitory effect on sugar absorption and demonstrate the presence of leptin receptors in the intestinal mucosa.MH - Carrier Proteins|*MEMH - Galactose|*PKMH - Intestinal Absorption|*DEMH - Proteins|*PDSO - FEBS Lett 1998 Feb; 423(3):302-6DP - 1998 FebTA - FEBS LettPG - 302-6IP - 3VI - 423UI - 98175479195
AU - Fong TM
AU - Huang RR
AU - Tota MR
AU - Mao C
AU - Smith T
AU - Varnerin J
AU - Karpitskiy VV
AU - Krause JE
AU - Van der Ploeg LHTI - Localization of leptin binding domain in the leptin receptor.AB - The leptin receptor is a member of the class I cytokine receptor family and is involved in the control of appetite and body weight. The predicted amino acid sequence of the extracellular region of the cloned leptin receptor differs from that of many other cytokine receptors in that it contains two homologous segments representing potential ligand binding sites. After the analysis of various deletion and substitution mutants of the leptin receptor, we found that the first potential binding motif is not required for leptin binding and receptor activation, whereas modification of the second potential binding motif can lead to inactive receptor mutants.Further deletion analysis generated a minimal binding domain that retains high affinity leptin binding. The leptin binding domain thus has been localized to residues 323-640, which contain the second segment of cytokine receptor domain/fibronectin type 3 domain (residues 428-635). Coexpression of the active isoform of leptin receptor (OB-Rb) with an inactive mutant lacking high affinity leptin binding site led to suppression of the activity mediated by OB-Rb, suggesting that the leptin receptor may exist as a multimeric complex in the absence of leptin.MH - Carrier Proteins|*CH/MEMH - Proteins|*MESO - Mol Pharmacol 1998 Feb; 53(2):234-40DP - 1998 FebTA - Mol PharmacolPG - 234-40IP - 2VI - 53UI - 98130694196
AU - Mason MM
AU - He Y
AU - Chen H
AU - Quon MJ
AU - Reitman MTI - Regulation of leptin promoter function by Sp1, C/EBP, and a novel factor.AB - Leptin is a hormone produced in adipose cells that regulates energy expenditure, food intake, and adiposity. To understand leptin's transcriptional regulation, we are studying its promoter. Four conserved and functional regions were identified.Mutations in the C/EBP and TATA motifs each caused an approximately 10-fold decrease in promoter activity. The C/EBP motif bound recombinant C/EBP alpha and mediated trans-activation by C/EBP alpha, -beta, and -delta. Mutation of a consensus Sp1 site reduced promoter activity 2.5-fold and abolished binding of Sp1. Mutation of a fourth factor-binding site,denoted LP1, abolished protein binding and reduced promoter activity 2-fold. Factor binding to the LP1 motif was observed with adipocyte, but not with nonadipocyte extracts. Adipocytes from fa/fa Zucker rats transcribed the reporter plasmids more efficiently than did control adipocytes. No effect on the transient expression of leptin was noted upon treatment with a thiazolidinedione, BRL49653, or upon cotransfection with peroxisome proliferator-activated receptor-gamma/retinoid X receptor-alpha or sterol response element-binding protein-1. Mutations of the Sp1, LP1, and C/EBP sites in pairwise combinations diminished promoter activity to the extent predicted assuming these motifs contribute independently to leptin promoter function. Our identification of motifs regulating leptin transcription is an important step in the elucidation of the mechanisms underlying hormonal and metabolic regulation of this gene.MH - DNA-Binding Proteins|*PHMH - Nuclear Proteins|*PHMH - Promoter Regions (Genetics)|*MH - Proteins|*GEMH - Transcription Factor, Sp1|*PHSO - Endocrinology 1998 Mar; 139(3):1013-22DP - 1998 MarTA - EndocrinologyPG - 1013-22IP - 3VI - 139UI - 98150997197
AU - Bi S
AU - Gavrilova O
AU - Gong DW
AU - Mason MM
AU - Reitman MTI - Identification of a placental enhancer for the human leptin gene.AB - Leptin is a hormone that regulates metabolic efficiency,energy expenditure, and food intake. Leptin is produced chiefly in adipose cells, but in humans, mRNA encoding leptin is also present in the placenta. Here we elucidate the basis for placental leptin production. The same promoter is used for adipose and placental transcription. An upstream enhancer functions in the JEG-3 and JAR choriocarcinoma cell lines but not in adipocytes or HeLa cells. The minimal positive acting region is 60 base pairs in length. This region is within a MER11 repetitive element, suggesting that human placental expression of leptin is the result of insertion of this element. Binding analyses demonstrated three protein binding sites, designated placental leptin enhancer elements (PLE)1, PLE2, and PLE3. PLE2 binds Sp1.Enhancer activity was reduced by mutation of the PLE1 or PLE3 sites but was unaffected by alteration of PLE2. Proteins binding to PLE3 were present in JEG-3 and human placental nuclear extracts but not in extracts from non-placental sources. Upon triplication, the PLE3 element was a strong enhancer in choriocarcinoma cells but not in HeLa cells.The protein binding to the PLE3 motif appears to be a novel,placenta-specific transcription factor.MH - Enhancer Elements (Genetics)|*MH - Placenta|*PHMH - Proteins|*GESO - J Biol Chem 1997 Nov; 272(48):30583-8DP - 1997 NovTA - J Biol ChemPG - 30583-8IP - 48VI - 272UI - 98043770198
AU - Pallett AL
AU - Morton NM
AU - Cawthorne MA
AU - Emilsson VTI - Leptin inhibits insulin secretion and reduces insulin mRNA levels in rat isolated pancreatic islets.AB - The ob gene product leptin over the concentration range 0.1-100 nM demonstrated a U-shaped dose-response inhibition of glucose-stimulated insulin secretion by rat pancreatic islets. Thus, leptin (1 and 10 nM) produced a significant inhibition whereas 100 nM was ineffective. The inhibitory effect of leptin was glucose dependent, had a rapid onset and was readily reversed upon removal of leptin. Sub-chronic exposure of islets to leptin (10 nM) reduced both insulin secretion and the level of insulin transcript. These findings support the hypothesis that excessive production of leptin by adipose tissue could play a role in the development of non-insulin dependent diabetes in obese subjects.MH - Insulin|*GE/*SEMH - Islets of Langerhans|DE/ME/*SEMH - Proteins|ME/*PDMH - RNA, Messenger|BI/*DESO - Biochem Biophys Res Commun 1997 Sep; 238(1):267-70DP - 1997 SepTA - Biochem Biophys Res CommunPG - 267-70IP - 1VI - 238UI - 97445164199
AU - Paolisso G
AU - Ammendola S
AU - Del Buono A
AU - Gambardella A
AU - Riondino M
AU - Tagliamonte MR
AU - Rizzo MR
AU - Carella C
AU - Varricchio MTI - Serum levels of insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in healthy centenarians: relationship with plasma leptin and lipid concentrations, insulin action,and cognitive function.AB - It has been demonstrated that healthy centenarians have more favorable anthropometric characteristics and insulin-mediated glucose uptake than aged subjects. The plasma insulin-like-growth factor I (IGF-I) concentration may account for such differences. Three groups of subjects were studied: 1) adults (< 50 yr; n = 30), 2) aged subjects (75-99 yr; n = 30), 3) centenarians (> 100 yr; n = 19).In all subjects, fasting plasma IGF-I, IGF-binding protein-3 (IGFBP-3), leptin, and lipid concentrations were determined;body composition was assessed by bioimpedance analysis;and insulin-mediated glucose up-take was evaluated by euglycemic hyperinsulinemic glucose clamp. IGF-I declined with advancing age, but no differences between aged subjects and centenarians were found. IGFBP-3 showed a trend similar to IGF-I, but lower values were present in centenarians than in aged subjects. Nevertheless, centenarians had a plasma IGF-I/IGFBP-3 molar ratio greater than that in aged subjects.Centenarians had also a whole body glucose disposal (WBGD)greater than that in aged subjects, but similar to that in adults. Mini Mental State Examination (27 +/- 2.1 vs.18.3 +/- 3.1; P < 0.02) and Instrumental Activities Daily Living (26 +/- 2.6 vs. 8.4 +/- 4.1; P < 0.001) scores were significantly different in aged subjects and centenarians,respectively. In centenarians, the plasma IGF-I/IGFBP-3 molar ratio correlated with the body mass index (r = -0.55; P < 0.009); the amount of body fat (r = -0.62; P < 0.003); fat-free mass (r = 0.56; P < 0.008); fasting plasma leptin (r = -0.63; P < 0.004), triglycerides (r = -0.58;P < 0.01), free fatty acid (r = -0.64; P < 0.005), and low density lipoprotein cholesterol (r = -0.59; P < 0.009)concentrations; Mini Mental State Examination (r = 0.53;P < 0.0.03); and WBGD (r = 0.64; P < 0.005). All correlations were independent of daily fat and carbohydrate intake and WBGD (P < 0.05 for all). No significant correlations between the plasma IGF-I/IGFBP-3 molar ratio and plasma total (r = 0.31; P = NS) and high density lipoprotein cholesterol (r = 0.34; P = NS) concentrations were present. The correlation between the plasma IGF-I/IGFBP-3 molar ratio and WBGD persisted after adjustment for body fat, fasting plasma insulin concentration,daily carbohydrate and fat intake, and daily physical activity (r = 0.55; P < 0.009), but not after further adjustment for plasma free fatty acid concentration (r = 0.30; P =0.17). In conclusion, healthy centenarians have plasma IGF-I/IGFBP-3 molar ratio greater than aged subjects. A more elevated plasma IGF-I/IGFBP-3 molar ratio might improve insulin action and plasma lipid concentration in centenarians.MH - Aged, 80 and over|*PHMH - Insulin|*MEMH - Insulin-Like Growth Factor Binding Protein 3|*BLMH - Insulin-Like Growth Factor I|*ANMH - Lipids|*BLMH - Proteins|*MESO - J Clin Endocrinol Metab 1997 Jul; 82(7):2204-9DP - 1997 JulTA - J Clin Endocrinol MetabPG - 2204-9IP - 7VI - 82UI - 97358175200
AU - Hollenberg AN
AU - Susulic VS
AU - Madura JP
AU - Zhang B
AU - Moller DE
AU - Tontonoz P
AU - Sarraf P
AU - Spiegelman BM
AU - Lowell BBTI - Functional antagonism between CCAAT/Enhancer binding protein-alpha and peroxisome proliferator-activated receptor-gamma on the leptin promoter.AB - The ob gene product, leptin, is a major hormonal regulator of appetite and fat cell mass. Recent work has suggested that the antidiabetic agents, the thiazolidinediones (TZ), which are also high affinity ligands of peroxisome proliferator-activated receptor-gamma (PPARgamma), inhibit leptin expression in rodents. To examine the effects of this class of drug on the leptin gene in adipocytes we performed Northern analysis on primary rat adipocytes cultured in the presence or absence of TZ. TZ reduced leptin mRNA levels by 75%.To determine whether this effect was mediated at the transcriptional level, we isolated 6510 base pairs of 5'-flanking sequence of the leptin promoter and studied reporter constructs in primary rat adipocytes and CV-1 cells. Sequence analysis demonstrated the presence of a consensus direct repeat with a 1-base-pair gap site between -3951 and -3939 as well as a consensus CCAAT/enhancer binding protein (C/EBP)site between -55 and -47. Our functional analysis in transfected primary rat adipocytes demonstrates that, despite the presence of a canonical direct repeat with a 1-base-pair gap site,TZ alone decreases reporter gene expression of leptin promoter constructs ranging from -6510 to +9 to -65 to +9. In CV-1 cells, which contain endogenous PPARgamma, TZ treatment alone had little effect on these constructs. However, TZ treatment did inhibit C/EBPalpha-mediated transactivation of the leptin promoter. This down-regulation of leptin reporter constructs mapped to a -65 to +9 promoter fragment which binds C/EBPalpha in gel-mobility shift assays but does not bind PPARgamma2 alone or as a heterodimer with 9-cis-retinoic acid receptor. Conversely, the promoter (-5400 to +24 base pairs) of the aP2 gene, another adipocyte-specific gene, was induced 7.3-fold by TZ. Co-transfection with C/EBPalpha minimally stimulated the aP2 promoter from basal levels but notably blocked activation by TZ. These data indicate that PPARgamma and C/EBPalpha can functionally antagonize each other on at least two separate promoters and that this mechanism may explain the down-regulation of leptin expression by thiazolidinediones.MH - Adipocytes|*MEMH - DNA-Binding Proteins|GE/*MEMH - Gene Expression Regulation|*MH - Nuclear Proteins|GE/*MEMH - Proteins|*GEMH - Receptors, Cytoplasmic and Nuclear|GE/*MEMH - Transcription Factors|GE/*MESO - J Biol Chem 1997 Feb; 272(8):5283-90DP - 1997 FebTA - J Biol ChemPG - 5283-90IP - 8VI - 272UI - 971841891
AU - White DW
AU - Kuropatwinski KK
AU - Devos R
AU - Baumann H
AU - Tartaglia LATI - Leptin receptor (OB-R) signaling. Cytoplasmic domain mutational analysis and evidence for receptor homo-oligomerization [published erratum appears in J Biol Chem 1997 May 2;272(18):12248]AB - The leptin receptor (OB-R) mediates the weight regulatory effects of the adipocyte secreted hormone leptin (OB). Previously we have shown that the long form of OB-R, expressed predominantly in the hypothalamus, can mediate ligand-induced activation of signal transducer and activator of transcription factors 1, 3, and 5 and stimulate transcription via interleukin-6 and hematopoietin receptor responsive gene elements. Here we report that deletion and tyrosine substitution mutagenesis of OB-R identifies two distinct regions of the intracellular domain important for signaling. In addition,granulocyte-colony stimulatory factor receptor/OB-R and OB-R/granulocyte-colony stimulatory factor receptor chimeras are signaling competent and provide evidence that aggregation of two OB-R intracellular domains is sufficient for ligand-induced receptor activation. However, signaling by full-length OB-R appears to be relatively resistant to dominant negative repression by signaling-incompetent OB-R, suggesting that mechanisms exist to permit signaling by the long form of OB-R even in the presence [corrected] of excess naturally occurring short form of OB-R.MH - Carrier Proteins|GE/*MEMH - Cytoplasm|*MEMH - Receptors, Granulocyte Colony-Stimulating Factor|GE/*MEMH - Signal Transduction|*SO - J Biol Chem 1997 Feb; 272(7):4065-71DP - 1997 FebTA - J Biol ChemPG - 4065-71IP - 7VI - 272UI - 971724712
AU - Mercer JG
AU - Moar KM
AU - Rayner DV
AU - Trayhurn P
AU - Hoggard NTI - Regulation of leptin receptor and NPY gene expression in hypothalamus of leptin-treated obese (ob/ob) and cold-exposed lean mice.AB - Leptin receptor gene expression has been measured in arcuate and ventromedial hypothalamic nuclei. Receptor mRNA in both hypothalamic areas was higher in obese mice than in lean littermates. Twice daily leptin administration for 7 days profoundly affected food intake, reduced leptin receptor mRNA in the arcuate nucleus, and had a similar effect on neuropeptide Y gene expression. A single leptin injection was ineffective. Exposure of lean mice to cold for 24 h caused an induction of leptin receptor and NPY mRNA which was normalized when animals were returned to the warm. Regulation of receptor gene expression may be an important component in the reading of the leptin signal.MH - Carrier Proteins|*BIMH - Feeding Behavior|*DEMH - Gene Expression Regulation|*DEMH - Hypothalamus|*MEMH - Obesity|GE/*MEMH - Proteins|*PDMH - Receptors, Neuropeptide Y|*BIMH - Transcription, Genetic|*DESO - FEBS Lett 1997 Feb; 402(2-3):185-8DP - 1997 FebTA - FEBS LettPG - 185-8IP - 2-3VI - 402UI - 971886073
AU - Yamaguchi M
AU - Murakami T
AU - Yasui Y
AU - Otani S
AU - Kawai M
AU - Kishi K
AU - Kurachi H
AU - Shima K
AU - Aono T
AU - Murata YTI - Mouse placental cells secrete soluble leptin receptor (sOB-R): cAMP inhibits sOB-R production.AB - The aims of this study were to identify whether mouse placenta secretes soluble OB-R (sOB-R) and to find the regulating factor of OB-R expression. Total RNAs were extracted from placenta and decidua, and OB-R expression was assessed by Northern blot analysis. Decidua did not express OB-R mRNA. However, OB-R mRNA expression was detectable in the placenta on day 13 of pregnancy, and then it increased and reached a peak on day 17 of pregnancy. Mouse placental cells from day 12 of pregnancy were cultured and OB-R gene expression was assessed by Northern blot analysis. OB-R mRNA expression was detectable from the second day of culture and reached a peak on the third day of culture. To determine whether placental cells release sOB-R, supernatant of cultured placental cells was subjected to Western blot analysis.sOB-R was detected in the medium by the second day of culture and sOB-R release increased up to the fourth day of culture.Addition of leptin to the medium did not affect expression of OB-R mRNA. However, 8-bromo cAMP inhibited both steady-state levels of OB-R mRNA and the amount of sOB-R protein in the medium in a dose- and time-dependent manner. These results suggest that trophoblast cells differentiate, express,and release sOB-R both in vivo and in vitro and that cAMP is one of several potent regulators of sOB-R secretion by the mouse placenta. Copyright 1998 Academic Press.MH - Carrier Proteins|BI/GE/*SEMH - Placenta|DE/ME/*SESO - Biochem Biophys Res Commun 1998 Nov; 252(2):363-7DP - 1998 NovTA - Biochem Biophys Res CommunPG - 363-7IP - 2VI - 252UI - 990454114
AU - Friedman JM
AU - Halaas JLTI - Leptin and the regulation of body weight in mammals.AB - The assimilation, storage and use of energy from nutrients constitute a homeostatic system that is essential for life.In vertebrates, the ability to store sufficient quantities of energy-dense triglyceride in adipose tissue allows survival during the frequent periods of food deprivation encountered during evolution. However, the presence of excess adipose tissue can be maladaptive. A complex physiological system has evolved to regulate fuel stores and energy balance at an optimum level. Leptin, a hormone secreted by adipose tissue, and its receptor are integral components of this system. Leptin also signals nutritional status to several other physiological systems and modulates their function.Here we review the role of leptin in the control of body weight and its relevance to the pathogenesis of obesity.MH - Body Weight|*PHMH - Proteins|BI/*PH/TUSO - Nature 1998 Oct; 395(6704):763-70DP - 1998 OctTA - NaturePG - 763-70IP - 6704VI - 395UI - 990108355
AU - Wang MY
AU - Koyama K
AU - Shimabukuro M
AU - Newgard CB
AU - Unger RHTI - OB-Rb gene transfer to leptin-resistant islets reverses diabetogenic phenotype.AB - In obese Zucker diabetic fatty (ZDF) rats with mutant leptin receptors, pancreatic islets have an approximately 50-fold increase in fat (TG), overproduce nitric oxide (NO), and lack a normal proinsulin mRNA response to fatty acids. We overexpressed the wild-type full-length "b" isoform of the leptin receptor (OB-Rb) in ZDF islets by perfusing ZDF pancreata with recombinant adenovirus containing the cDNA encoding OB-Rb. In cultured islets isolated from these animals, leptin lowered islet TG by 87% and completely blocked TG formation from free fatty acids. Overproduction of NO was reduced, and the preproinsulin mRNA response to free fatty acids was restored. This establishes defective leptin action as the proximate cause of lipotoxic diabetes in ZDF rats.MH - Carrier Proteins|*GE/MEMH - Diabetes Mellitus, Non-Insulin-Dependent|*GE/MEMH - Islets of Langerhans|*ME/PAMH - Proteins|*PDSO - Proc Natl Acad Sci U S A 1998 Jan; 95(2):714-8DP - 1998 JanTA - Proc Natl Acad Sci U S APG - 714-8IP - 2VI - 95UI - 981185786
AU - Kim JB
AU - Sarraf P
AU - Wright M
AU - Yao KM
AU - Mueller E
AU - Solanes G
AU - Lowell BB
AU - Spiegelman BMTI - Nutritional and insulin regulation of fatty acid synthetase and leptin gene expression through ADD1/SREBP1.AB - The ability to regulate specific genes of energy metabolism in response to fasting and feeding is an important adaptation allowing survival of intermittent food supplies. However,little is known about transcription factors involved in such responses in higher organisms. We show here that gene expression in adipose tissue for adipocyte determination differentiation dependent factor (ADD) 1/sterol regulatory element binding protein (SREBP) 1, a basic-helix-loop-helix protein that has a dual DNA-binding specificity, is reduced dramatically upon fasting and elevated upon refeeding; this parallels closely the regulation of two adipose cell genes that are crucial in energy homeostasis, fatty acid synthetase (FAS) and leptin. This elevation of ADD1/SREBP1,leptin, and FAS that is induced by feeding in vivo is mimicked by exposure of cultured adipocytes to insulin, the classic hormone of the fed state. We also show that the promoters for both leptin and FAS are transactivated by ADD1/SREBP1.A mutation in the basic domain of ADD1/SREBP1 that allows E-box binding but destroys sterol regulatory element-1 binding prevents leptin gene transactivation but has no effect on the increase in FAS promoter function. Molecular dissection of the FAS promoter shows that most if not all of this action of ADD1/SREBP1 is through an E-box motif at -64 to -59, contained with a sequence identified previously as the major insulin response element of this gene. These results indicate that ADD1/SREBP1 is a key transcription factor linking changes in nutritional status and insulin levels to the expression of certain genes that regulate systemic energy metabolism.MH - DNA-Binding Proteins|GE/*MEMH - Fatty Acid Synthetase Complex|*GE/MEMH - Helix-Loop-Helix Motifs|*MH - Nuclear Proteins|GE/*MEMH - Proteins|*GE/MESO - J Clin Invest 1998 Jan; 101(1):1-9DP - 1998 JanTA - J Clin InvestPG - 1-9IP - 1VI - 101UI - 980831187
AU - Chung WK
AU - Power Kehoe L
AU - Chua M
AU - Lee R
AU - Leibel RLTI - Genomic structure of the human OB receptor and identification of two novel intronic microsatellites [letter]AB - Identification of the OB (leptin) receptor (OBR) as the gene that is defective in diabetes (Leprdb) mice and fatty (Leprfa) rats provides an important candidate gene for the study of the genetics of human obesity. We defined the boundaries of the 18 coding exons for the long form of OBR, and sequenced the immediately adjacent intronic regions. These sequences can be used to generate reagents for genetic analysis (e.g., direct sequencing, single-stranded conformational polymorphism analysis, etc.) of the possible role of OBR in the regulation of adiposity in humans. In addition, we have identified two highly polymorphic intronic microsatellites that can be scored with the polymerase chain reaction.MH - Carrier Proteins|*GEMH - Dinucleotide Repeats|*MH - Introns|*SO - Genome Res 1996 Dec; 6(12):1192-9DP - 1996 DecTA - Genome ResPG - 1192-9IP - 12VI - 6UI - 971294068
AU - Adßn C
AU - Grasa MM
AU - Cabot C
AU - Esteve M
AU - Vil R
AU - Masan s R
AU - Estruch J
AU - Fernßndez L pez JA
AU - Remesar X
AU - Alemany MTI - Short-term treatment with estrone oleate in liposomes (Merlin-2) does not affect the expression of the ob gene in Zucker obese rats.AB - Young female Zucker fa/fa rats of 370-430 g were implanted with osmotic minipumps releasing 3.5 micromol/day-kg of estrone oleate in liposomes (Merlin-2) into the bloodstream for up to 14 days. Merlin-2 induced a sustained loss of appetite, and a decrease in body weight of 3.5%, which contrasts with the 8.2% increase in controls during the period studied. Plasma insulin, glucose and urea decreased,and liver glycogen increased with Merlin-2 treatment. Plasma ACTH and corticosterone increased to a maximum at the end of the experiment. The expression of the ob gene in adipose tissue was unchanged, and plasma leptin levels were also unchanged by treatment. Estrone levels increased more than 1500-fold, and estrone oleate rose 100-fold during treatment.The fact that estrone oleate had no effect on the leptin levels or expression in obese rats, in contrast with the marked inhibition observed in the lean suggests that the functionality of the leptin receptor is essential for estrone oleate inhibition of the ob gene. This also suggests that leptin may control ob gene expression in white adipose tissue and that estrone oleate may activate this process.The slimming effect of estrone oleate is, thus, not directly dependent on leptin, since both normoleptinemic and hyperleptinemic animals lose fat following treatment nor are the effects on appetite and energy expenditure mediated by leptin. However, leptin levels and the expression of the ob gene are directly linked with estrone oleate function. A possible involvement of leptin in estrone oleate action is postulated.The results support the participation of estrone oleate in the control of body weight and hint at the complexity of its regulation by leptin and glucocorticoids.MH - Estrone|AD/BL/*PDMH - Gene Expression Regulation|*DEMH - Obesity|*GEMH - Proteins|*GESO - Mol Cell Biochem 1999 Jul; 197(1-2):109-15DP - 1999 JulTA - Mol Cell BiochemPG - 109-15IP - 1-2VI - 197UI - 994133409
AU - G mez JM
AU - Molina A
AU - Fernßndez Casta±er M
AU - Casamitjana R
AU - Mart nez Matos JA
AU - Soler JTI - Insulin regulation of leptin synthesis and secretion in humans: the model of myotonic dystrophy.AB - OBJECTIVE: Myotonic dystrophy (MyD) is a systemic disorder in which insulin resistance is well recognized. In the present study we have characterized plasma leptin levels in patients with MyD and in age, sex and body mass index (BMI) matched controls and assessed the influence of leptin on the clinical manifestations of MyD. DESIGN AND PATIENTS:Body composition, plasma leptin, fasting and post-oral glucose tolerance test insulin, IGF-I and IGFBP3 were studied in 34 MyD patients and 33 controls. MEASUREMENTS: Body composition was measured using a bioelectrical impedance analyzer, and circulating levels of insulin, leptin, IGF-I, IGFBP3 were measured by IRMA or RIA. Insulin sensitivity was modelled according to a homeostasis model assessment (HOMA) computer-solved model. RESULTS: Percentage body fat was higher in patients than in controls (25.6 +/- 2.28% vs 18.8 +/- 1.53%, P = 0.013). Insulin levels, both fasting and after oral glucose were higher in patients than in controls, and insulin sensitivity was lower in patients than in controls. Serum leptin was higher in patients than in controls (20.98 +/- 3.11 micrograms/l vs 10.4 +/- 1.31 micrograms/l, P = 0.004), and higher in women than in men, both in patients and in controls. In patients, leptin levels were correlated with age, BMI, fasting insulin,insulin area under curve and lower insulin sensitivity,whereas leptin levels were not correlated with body fat or other parameters of body composition. In controls, leptin levels were correlated with BMI and body fat. The results were evaluated using logistic regression models for each of the 2 populations. In the model of MyD, insulin resistance and age correctly identified higher leptin levels in relation to controls out of 87.88% of patients, and in the model of controls male sex with a negative correlation and BMI correctly identified their leptin levels out of 84.33% cases. CONCLUSIONS: These findings show that MyD provides a different model of leptin regulation in humans, and suggest that in MyD patients there are correlations between leptin and insulin resistance and age, irrespective of body fat.In contrast, leptin levels in controls, correlate with sex and BMI. The data on leptin in this population of patients can not be related aetiologically to the muscle disease itself.MH - Insulin|BL/*PHMH - Myotonia Atrophica|*BL/PPMH - Proteins|BI/*ME/SESO - Clin Endocrinol (Oxf) 1999 May; 50(5):569-75DP - 1999 MayTA - Clin Endocrinol (Oxf)PG - 569-75IP - 5VI - 50UI - 9940510210
AU - Cai A
AU - Hyde JFTI - The human growth hormone-releasing hormone transgenic mouse as a model of modest obesity: differential changes in leptin receptor (OBR) gene expression in the anterior pituitary and hypothalamus after fasting and OBR localization in somatotrophs.AB - We reported previously an increase in leptin receptor (OBR) gene expression in the anterior pituitary of human GH-releasing hormone (hGHRH) transgenic mice. The primary goal of this study was to investigate the possible mechanisms regulating OBR expression in these mice. Compared with normal sibling controls, hGHRH transgenic mice had significantly greater amounts of abdominal fat, higher levels of leptin messenger RNA (mRNA), and a 2-fold increase in plasma leptin concentrations. Despite normal plasma glucose levels, hGHRH transgenic mice had 4.5-fold elevated levels of plasma insulin. Using a ribonuclease protection assay, we measured the mRNA levels of the OBR long form (OBR(L)) in the anterior pituitary and hypothalamus after 48 h of fasting. In the anterior pituitary, food deprivation induced dramatic increases in OBR(L) mRNA levels in both normal and transgenic mice.In contrast, in the hypothalamus, fasting resulted in a significant decrease in OBR(L) gene expression in normal mice, and no changes were detected in hGHRH transgenic mice. Using dual in situ hybridization, OBR(L) mRNA was detected in somatotrophs. Moreover, the number of OBR(L)-positive pituitary cells as well as the percentage of OBR(L)-positive cells that express GH mRNA were increased in transgenic mice. In conclusion, 1) the modest obesity in hGHRH transgenic mice is associated with increases in leptin synthesis and secretion as well as insulin secretion;2) GH and/or GHRH as well as leptin and insulin may differentially contribute to the changes in OBR(L) gene expression in the anterior pituitary and the hypothalamus; 3) the response of OBR(L) gene expression in the hypothalamus to fasting is absent in the modestly obese hGHRH transgenic mice; and 4) somatotrophs are target cells for leptin, and the increase in OBR(L) gene expression in the pituitary of hGHRH transgenic mice is due at least in part to the increase in the number of cells expressing OBR(L).MH - Carrier Proteins|AN/*GEMH - Gene Expression Regulation|*MH - Hypothalamus|CY/*ME/PAMH - Obesity|*GE/PPMH - Pituitary Gland, Anterior|CY/*ME/PAMH - Somatotropin-Releasing Hormone|GE/*PHSO - Endocrinology 1999 Aug; 140(8):3609-14DP - 1999 AugTA - EndocrinologyPG - 3609-14IP - 8VI - 140UI - 9936060011
AU - Baskin DG
AU - Breininger JF
AU - Bonigut S
AU - Miller MATI - Leptin binding in the arcuate nucleus is increased during fasting.AB - The arcuate nucleus (ARC) mediates the anorexic effects of leptin and expresses the long form (Ob-Rb) of the leptin receptor. To determine whether ARC leptin binding increases when plasma leptin levels are low during fasting, [125I]-leptin specific binding to rat brain slices was measured by quantitative autoradiography. [125I]-leptin specific binding was dense in the ARC and increased 2-fold after a 48-h fast (P<0.001). These findings suggest that leptin receptor binding in the ARC is upregulated during fasting and that fasting changes the sensitivity of the ARC to leptin. Copyright 1999 Elsevier Science B.V.MH - Arcuate Nucleus|*MEMH - Carrier Proteins|*MEMH - Fasting|*PHMH - Proteins|ME/*PDSO - Brain Res 1999 May; 828(1-2):154-8DP - 1999 MayTA - Brain ResPG - 154-8IP - 1-2VI - 828UI - 9925549412
AU - Magni P
AU - Vettor R
AU - Pagano C
AU - Calcagno A
AU - Beretta E
AU - Messi E
AU - Zanisi M
AU - Martini L
AU - Motta MTI - Expression of a leptin receptor in immortalized gonadotropin-releasing hormone-secreting neurons.AB - Leptin is secreted by adipocytes and regulates food intake and energy balance through the activation of specific receptors (OB-R). Recent evidence suggests that it is also involved in the control of reproductive processes, by possibly acting on central and peripheral targets. In particular, it has been shown that leptin may indirectly stimulate GnRH release from hypothalamic fragments by acting on interneurons impinging on GnRH-secreting neurons. The possibility that leptin might additionally modulate the activity of GnRH-secreting neurons in a direct way has been addressed in the present study, by using the immortalized GnRH-secreting cell line GT1-7. The presence of OB-R messenger RNA (mRNA) (long form) was detected by RT-PCR analysis of total RNA from GT1-7 cells. An OB-R protein is also expressed in these cells, as shown by immunocytochemistry and by Western blot analysis. The latter has revealed the presence of a single immunoreactive OB-R with an approximate size of 130 kDa.To study the functionality of these receptors, the effect of leptin treatment on GnRH secretion and gene expression in GT1-7 cells were evaluated. Under static conditions,GnRH release was stimulated by exposure to low concentrations of leptin (10(-12) M after 30 min; 10(-10) M after 60 min). The 10(-12) M dose was selected for studying the effect of leptin on GnRH secretion under dynamic conditions. To this purpose, GT1-7 cells were placed in a perifusion system;treatment with leptin (10(-12) M) for 60 min stimulated GnRH release with no changes of pulse frequency. On the contrary, exposure to leptin (10(-12)-10(-10) M) for 1,3, 6, and 24 h did not affect GnRH gene expression in GT1-7 cells. The present results indicate that GT1-7 cells possess OB-Rs and that leptin may directly affect their function. Taken together with the available reports, these findings suggest that leptin might participate in the regulation of reproductive processes by acting at multiple levels,both centrally and peripherally.MH - Carrier Proteins|*GEMH - Gene Expression|*MH - Gonadorelin|GE/*SEMH - Neurons|*MESO - Endocrinology 1999 Apr; 140(4):1581-5DP - 1999 AprTA - EndocrinologyPG - 1581-5IP - 4VI - 140UI - 9919612713
AU - Lee FY
AU - Li Y
AU - Yang EK
AU - Yang SQ
AU - Lin HZ
AU - Trush MA
AU - Dannenberg AJ
AU - Diehl AMTI - Phenotypic abnormalities in macrophages from leptin-deficient,obese mice.AB - Obesity is a complex syndrome that involves defective signaling by a number of different factors that regulate appetite and energy homeostasis. Treatment with exogenous leptin reverses hyperphagia and obesity in ob/ob mice, which have a mutation that causes leptin deficiency, proving the importance of this factor and its receptors in the obesity syndrome.Cells with leptin receptors have been identified outside of the appetite regulatory centers in the brain. Thus leptin has peripheral targets. Because macrophages express signaling-competent leptin receptors, these cells may be altered during chronic leptin deficiency. Consistent with this concept, the present study identifies several phenotypic abnormalities in macrophages from ob/ob mice, including decreased steady-state levels of uncoupling protein-2 mRNA,increased mitochondrial production of superoxide and hydrogen peroxide, constitutive activation of CCAAT enhancer binding protein (C/EBP)-beta, an oxidant-sensitive transcription factor, increased expression of interleukin-6 and cyclooxygenase (COX)-2, two C/EBP-beta target genes, and increased COX-2-dependent production of PGE2. Given the importance of macrophages in the general regulation of inflammation and immunity, these alterations in macrophage function may contribute to obesity-related pathophysiology.MH - Macrophages, Peritoneal|*PHMH - Obesity|*GE/*ME/PAMH - Proteins|GE/*MESO - Am J Physiol 1999 Feb; 276(2 Pt 1):C386-94DP - 1999 FebTA - Am J PhysiolPG - C386-94IP - 2 Pt 1VI - 276UI - 9913756714
AU - Konopleva M
AU - Mikhail A
AU - Estrov Z
AU - Zhao S
AU - Harris D
AU - Sanchez Williams G
AU - Kornbl
AU SM
AU - Dong J
AU - Kliche KO
AU - Jiang S
AU - Snodgrass HR
AU - Estey EH
AU - Andreeff MTI - Expression and function of leptin receptor isoforms in myeloid leukemia and myelodysplastic syndromes: proliferative and anti-apoptotic activities.AB - The receptor for the gene product of the obesity gene, leptin, was recently reported to be expressed on murine and human hematopoietic progenitor cells. Therefore, we studied the expression of the leptin receptor, OB-R, in normal myeloid precursors, human leukemia cell lines, and primary leukemic cells using reverse-transcriptase polymerase chain reaction. In normal hematopoiesis, OB-R was expressed in CD34(+) cells. Normal promyelocytes (CD34(-)33(+) and CD34(-)13(+)) expressed only very low levels of the short,presumably nonsignaling isoform. Both the long and short isoforms of OB-R were expressed in 10 of 22 samples from patients with newly diagnosed primary or secondary acute myeloid leukemia (AML), with a higher incidence of the long isoform in primary AML (87.6% v 28.6%; P =.01). The incidence of OB-R expression was higher in recurrent than in newly diagnosed AML (P <.001), and samples from four patients with refractory AML showed strong expression of both isoforms. Both OB-R isoforms were also expressed in newly diagnosed and recurrent acute promyelocytic leukemia cells but were essentially absent in samples of chronic or acute lymphocytic leukemia. In vitro growth of myeloid leukemic cell lines and of blasts from 14 primary AMLs demonstrated that recombinant human leptin alone induced low level proliferation, significantly (P <.05) increased proliferation induced by recombinant human granulocyte colony-stimulating factor, interleukin 3, and stem cell factor in a subset of AML and increased colony formation (P <.005). Also, leptin reduced apoptosis induced by cytokine withdrawal in MO7E and TF-1 cells. Serum leptin levels correlated only with body mass index (P <. 001) and gender (P =.03). Results confirm the reported expression of leptin receptor in normal CD34(+) cells and demonstrate the frequent expression of leptin receptors in AML blasts. While normal promyelocytes lack receptor expression, leukemic promyelocytes express both isoforms. We also demonstrate proliferative effects of leptin alone and in combination with other physiologic cytokines, and anti-apoptotic properties of leptin. These findings could have implications for the pathophysiology of AML.MH - Apoptosis|*/DEMH - Carrier Proteins|*BIMH - Leukemia, Myeloid|*ME/PAMH - Myelodysplastic Syndromes|*ME/PASO - Blood 1999 Mar; 93(5):1668-76DP - 1999 MarTA - BloodPG - 1668-76IP - 5VI - 93UI - 9915534615
AU - Maffei M
AU - Volpe L
AU - Di Cianni G
AU - Bertacca A
AU - Ferdeghini M
AU - Murru S
AU - Teti G
AU - Casadidio I
AU - Cecchetti P
AU - Navalesi R
AU - Benzi LTI - Plasma leptin levels in newborns from normal and diabetic mothers.AB - Leptin can be considered as a peripheral signal which informs the centers about the mass of energy stores. Studies done on the human adult population have demonstrated that degree of adiposity and insulin levels play a major role as determinants of leptin circulating levels. The aim of this study was to evaluate which factors may influence leptin levels at birth. We examined the role played by baby size and by the metabolic environment the fetus was exposed to during pregnancy. We considered 85 newborns from normal (n = 60), gestational (GDM, n = 17) and pregestational (IDDM = 8) diabetes mellitus mothers. At delivery, blood was taken from the umbilical cord vein. Babies from normal and GDM mothers were subdivided into AGA (appropriate for gestational age) and LGA (large for gestational age). There was no difference in leptin levels between babies from normal or GDM mothers belonging to the same weight category, but leptin levels were always higher in LGA than in AGA newborns,and highly correlated with birth weight (r = 0.34, P = 0.001). Moreover, IDDM mothers gave birth to newborns with significantly higher levels of leptin and insulin when compared with normal and GDM mothers. Diabetes of both GDM and IDDM mothers was clinically well controlled (HbA1c was 4.0 and 7.2, respectively). The correlation between leptin and insulin was significant only when newborns from IDDM mothers were included in the regression analysis (r = 0.39, P = 0.0002). Our results suggest that degree of adiposity is one of the main regulators of leptin concentration in the human newborn and that babies exposed to an altered,though clinically controlled, metabolic environment, as in IDDM mothers, have increased levels of leptin.MH - Diabetes Mellitus, Insulin-Dependent|*BLMH - Diabetes, Gestational|*BLMH - Proteins|*MESO - Horm Metab Res 1998 Sep; 30(9):575-80DP - 1998 SepTA - Horm Metab ResPG - 575-80IP - 9VI - 30UI - 9902351316
AU - Kiess W
AU - Siebler T
AU - Englaro P
AU - Kratzsch J
AU - Deutscher J
AU - Meyer K
AU - Gallaher B
AU - Blum WFTI - Leptin as a metabolic regulator during fetal and neonatal life and in childhood and adolescence.AB - Body weight is regulated by a feedback loop in which peripheral signals report nutritional information to an integratory center in the brain. The cloning of the ob gene is consistent with this concept and suggests that body fat content in adult rodents is regulated by a negative feedback loop centered in the hypothalamus/1-8/. In a recent report, two severely obese children with congenital leptin deficiency due to a homozygous frame-shift mutation involving the deletion of a single guanine nucleotide in codon 133 of the ob gene have been described. This discovery provides the first genetic evidence that leptin is an important regulator of energy balance in humans. However, it has become increasingly clear that apart from leptin's function in the central nervous system and in regulation of energy balance, leptin also acts in the periphery and might be important as a hormone modulating processes in regard to reproduction, glucose metabolism and insulin resistance,as well as growth and development of many tissues and organs either directly or indirectly. This report reviews some of the topics of leptin research that are of particular importance and relevance for pediatric and adolescent medicine and for pediatric endocrinology in particular.MH - Obesity|*BL/*GEMH - Proteins|*MESO - J Pediatr Endocrinol Metab 1998 Jul; 11(4):483-96DP - 1998 JulTA - J Pediatr Endocrinol MetabPG - 483-96IP - 4VI - 11UI - 9845074417
AU - Slieker LJ
AU - Sloop KW
AU - Surface PLTI - Differentiation method-dependent expression of leptin in adipocyte cell lines.AB - Leptin, the product of the ob gene, is expressed exclusively in adipose tissue. However, adipocyte cell lines, such as 3T3-L1 adipocytes, have generally been reported to express extremely low levels of leptin mRNA. We compared 3T3-L1's to the closely related line 3T3-F442A, and to another murine adipocyte line, TA1. TA1 cells, when differentiated by indomethacin/insulin treatment, express leptin at levels greater than those of 3T3-L1 adipocytes differentiated by the traditional methylisobutylxanthine/dexamethasone/insulin protocol. However, when 3T3-L1's are differentiated in the presence of indomethacin/insulin their expression levels of leptin increase dramatically. 3T3-F442A preadipocytes also express high levels of leptin when differentiated in the presence of T3 and insulin, but when differentiated in the presence of indomethacin/insulin, expression levels drop precipitously. These changes in leptin mRNA and protein expression are not reflected by changes in CCAAT/enhancer binding protein-alpha (c/EBPalpha), peroxizomal proliferator activated receptor-gamma (PPARgamma), lipoprotein lipase (LPL), fatty-acid binding protein aP2 or uncoupling protein-2 (UCP2) mRNA levels, and suggest a mechanism unique to the leptin gene. Copyright 1998 Academic Press.MH - Adipocytes|CY/DE/*MEMH - Proteins|*BI/DE/GESO - Biochem Biophys Res Commun 1998 Oct; 251(1):225-9DP - 1998 OctTA - Biochem Biophys Res CommunPG - 225-9IP - 1VI - 251UI - 9900925018
AU - Hotta K
AU - Gustafson TA
AU - Ortmeyer HK
AU - Bodkin NL
AU - Hansen BCTI - Monkey leptin receptor mRNA: sequence, tissue distribution,and mRNA expression in the adipose tissue of normal, hyperinsulinemic,and type 2 diabetic rhesus monkeys.AB - OBJECTIVE: We have cloned the rhesus monkey leptin receptor and examined its mRNA expression levels in the adipose tissue of monkeys to investigate the regulation of gene expression of the leptin receptor. RESEARCH METHODS AND PROCEDURES: Monkey leptin receptor cDNA was cloned by reverse transcriptase-polymerase chain reaction (RT-PCR). Tissue distribution of monkey leptin receptor was examined by Northern blot analysis and RT-PCR. The mRNA levels of monkey leptin receptor in adipose tissue of normal (n=10), hyperinsulinemic obese (n=8), and type 2 diabetic monkeys (n=8) were measured by quantitative RT-PCR. RESULTS: Monkey leptin receptor cDNA had at least two alternatively spliced isoforms (long and short forms). The long form of the leptin receptor mRNA was expressed relatively highly in liver, adipose tissue, hypothalamus, and choroid plexus, whereas the total leptin receptors were expressed in every tissue examined.The mRNA levels of the long form of the leptin receptor in adipose tissue were not correlated to body weight, fasting plasma insulin, plasma glucose, or plasma leptin levels.The mRNA levels of the long form of the leptin receptor were highly correlated to that of the total leptin receptor (long and short form). DISCUSSION: The long form of leptin receptor mRNA existed in adipose tissue as well as in liver and hypothalamus, suggesting that the leptin receptor in adipose tissue may be functional in adipose tissue. The expression of the leptin receptor mRNA in adipose tissue is not affected by obesity, hyperinsulinemia, or diabetes.MH - Adipose Tissue|*CHMH - Carrier Proteins|CH/*GEMH - Diabetes Mellitus, Non-Insulin-Dependent|GE/*VEMH - Hyperinsulinemia|GE/*VEMH - Macaca mulatta|*GEMH - Monkey Diseases|*GEMH - RNA, Messenger|AN/*CHSO - Obes Res 1998 Sep; 6(5):353-60DP - 1998 SepTA - Obes ResPG - 353-60IP - 5VI - 6UI - 9840893119
AU - Kristr÷m B
AU - Carlsson B
AU - Rosberg S
AU - Carlsson LM
AU - Albertsson Wikland KTI - Short-term changes in serum leptin levels provide a strong metabolic marker for the growth response to growth hormone treatment in children. Swedish Study Group for Growth Hormone Treatment.AB - The growth response to GH treatment varies between children.Besides regulating longitudinal growth, GH exerts important metabolic effects, including lipolysis. In this study we examined whether GH-induced changes in serum levels of the adipose tissue-derived hormone leptin can be used as a marker for the long term growth response to GH treatment in short prepubertal children. The study group consisted of 150 children (21 girls and 129 boys), who were 3-15 yr of age at the start of GH treatment and had a maximum GH secretory capacity ranging from very low to high. They were treated with GH (0.1 IU/kg x day) and followed for at least 1 yr. The first year mean increase in height SD score was 0.79 (SD, 0.34), with a broad range (0.08-2.27). Serum leptin concentrations were significantly reduced after 1, 3, and 12 months of GH treatment compared with levels at the start of treatment. The growth response correlated with the serum leptin concentration at the start of treatment (r = 0.49; P < 0.0001) and with the change in serum leptin concentration after both 1 month (r = -0.41; P < 0.01) and 3 months (r = -0.60; P < 0.0001) of treatment. When multiple stepwise regression analysis was applied to the auxological and biochemical variables that correlated (P < 0.10) with the first year growth response to GH treatment,the 3-month change in serum leptin concentration was the single most important variable for explaining the variance in individual growth responses. We conclude that leptin levels at the start of GH treatment as well as short term changes in leptin levels in response to GH treatment are valuable markers of the long term growth response.MH - Biological Markers|*BLMH - Growth|*MH - Proteins|*MEMH - Somatropin|*TUSO - J Clin Endocrinol Metab 1998 Aug; 83(8):2735-41DP - 1998 AugTA - J Clin Endocrinol MetabPG - 2735-41IP - 8VI - 83UI - 9837371420
AU - Oksanen L
AU - Kaprio J
AU - Mustajoki P
AU - Kontula KTI - A common pentanucleotide polymorphism of the 3'-untranslated part of the leptin receptor gene generates a putative stem-loop motif in the mRNA and is associated with serum insulin levels in obese individuals.AB - OBJECTIVE: To find out whether genetic alterations of the leptin receptor gene underlie human forms of obesity. DESIGN:Among 249 morbidly obese adults (body mass index, BMI >or = 40 kg/m2), we screened 30 patients with the highest serum leptin levels for alterations of their leptin receptor gene by single-strand conformation polymorphism (SSCP) technique. SUBJECTS: 249 severely obese subjects (present or past BMI > or = 40 kg/m2) and 138 lean controls (BMI < or = 25 kg/m2). MEASUREMENTS: DNA analysis was carried out using SSCP technique, sequencing and polymerase chain reaction (PCR) followed by digestion with the restriction enzyme Rsal. Serum leptin, glucose, insulin and lipid concentrations were determined in obese subjects. RESULTS: We were able to detect a pentanucleotide insertion (CTTTA) in the 3'-untranslated region of the leptin receptor gene. The presence of this pentanucleotide insert generates a putative stem-loop structure in the mRNA. Association studies were carried out on this variant. The frequency of the insertion allele did not differ between 249 obese (12.4%) and 138 lean (12.0%) subjects. There was no association of serum leptin,glucose or lipid levels with the pentanucleotide genotype in the obese individuals. However, when subjects without medication affecting insulin or glucose levels were considered,serum insulin levels were found to be lower in the heterozygous carriers of the insertion allele (15.1 +/- 9.2 mU/l) than in the subjects homozygous for the deletion allele (21.8 +/- 13.7 mU/l, P = 0.0035). CONCLUSIONS: We were able to confirm the presence of a frequent insertion/deletion polymorphism close to the 3'-end of the leptin receptor gene. We also showed that serum insulin levels in morbidly obese subjects are associated with 3'-UTR variant genotype.MH - Carrier Proteins|*GEMH - Insulin|*BLMH - Nucleic Acid Conformation|*MH - Obesity|*BL/*GEMH - Polymorphism, Single-Stranded Conformational|*MH - RNA, Messenger|*CHSO - Int J Obes Relat Metab Disord 1998 Jul; 22(7):634-40DP - 1998 JulTA - Int J Obes Relat Metab DisordPG - 634-40IP - 7VI - 22UI - 9836872021
AU - Kumar MV
AU - Scarpace PJTI - Differential effects of retinoic acid on uncoupling protein-1 and leptin gene expression.AB - All-trans-retinoic acid (RA), one of the active metabolites of vitamin A, can increase the expression of uncoupling protein-1 (UCP1) gene. To determine whether RA stimulates brown adipose tissue (BAT) thermogenesis and modulates leptin gene expression in vivo, 6-month-old, vitamin-A sufficient, F344 x BN rats were administered a single dose of RA (7.5 mg/kg, i.p.) or the beta 3-adrenergic receptor (beta 3AR) specific agonist, CGP 12177 (0.75 mg/kg). Levels of UCP1 mRNA in BAT and leptin mRNA in perirenal white adipose tissue (WAT) were examined 5 h after treatment.mRNA levels of lipoprotein lipase (LPL) were also examined in BAT and perirenal WAT. Administration of CGP 12177 caused the expected increase in UCP1 mRNA levels. RA treatment also significantly increased UCP1 mRNA levels but to a lesser extent than CGP 12177. In contrast, there was no acute effect of RA on whole body oxygen consumption, one measure of BAT thermogenesis. Both CGP 12177 and RA treatment decreased levels of leptin mRNA to a similar extent. RA treatment had no effect on mRNA levels of LPL in BAT or perirenal WAT. There were no changes in total DNA content,total protein content, or in the levels of beta-actin mRNA in either BAT or perirenal WAT upon administration of RA or CGP 12177. Thus, the acute effects of RA paralleled the effects of the beta 3AR specific agonist, CGP 12177,on UCP1 and leptin gene expression. This involvement of RA in positive regulation of UCP1 mRNA and negative regulation of leptin mRNA suggests a contrasting role for RA in energy homeostasis.MH - Adipose Tissue|*MEMH - Antineoplastic Agents|*PDMH - Carrier Proteins|*GEMH - Gene Expression Regulation|*DEMH - Membrane Proteins|*GEMH - Proteins|*GEMH - Tretinoin|*PDSO - J Endocrinol 1998 May; 157(2):237-43DP - 1998 MayTA - J EndocrinolPG - 237-43IP - 2VI - 157UI - 9832342222
AU - Mantzoros CS
AU - Frederich RC
AU - Qu D
AU - Lowell BB
AU - Maratos Flier E
AU - Flier JSTI - Severe leptin resistance in brown fat-deficient uncoupling protein promoter-driven diphtheria toxin A mice despite suppression of hypothalamic neuropeptide Y and circulating corticosterone concentrations [published erratum appears in Diabetes 1998 May;47(5):855]AB - Brown adipose tissue (BAT) has the capacity for uncoupled mitochondrial respiration and is proposed to be a key site for regulating energy expenditure in rodents. To better define the role of BAT in energy homeostasis, we previously created a line of transgenic mice with deficiency of BAT (UCP promoter-driven diphtheria toxin A transgenic mice [UCP-DTA]) mice. These mice develop obesity that initially is due to decreased energy expenditure and later accompanied by hyperphagia despite increased levels of circulating leptin. In addition, the obesity of these mice is accompanied by severe insulin-resistant diabetes and hyperlipidemia.To better define the basis for leptin resistance in this model, we treated UCP-DTA mice with leptin (300 microg i.p., b.i.d.) and compared their response with that of leptin-treated ob/ob and FVB control mice (30 microg i.p., b.i.d.). Leptin treatment of FVB and ob/ob mice decreased their body weight and food intake and improved their glucose homeostasis. In contrast, tenfold higher dosages of leptin had no effect on body weight, food intake, or circulating insulin or glucose concentrations of UCP-DTA mice. Hypothalamic neuropeptide Y (NPY) mRNA expression was lower in UCP-DTA mice than in littermate control FVB mice in the fed state,and increased progressively in response to food restriction as leptin levels fell. In parallel to the levels of hypothalamic NPY, corticosterone levels were initially suppressed and rose with food restriction. Thus food intake, body weight,and insulin and glucose homeostasis of UCP-DTA mice are all extraordinarily resistant to leptin, whereas hypothalamic NPY and the hypothalamopituitary adrenal (HPA) axis may remain under leptin control. Further elucidation of the mechanisms underlying leptin resistance in UCP-DTA mice may provide valuable insights into the basis for leptin resistance in human obesity.MH - Brown Fat|*PHMH - Carrier Proteins|*GEMH - Diphtheria Toxin|*GEMH - Hypothalamus|DE/*MEMH - Membrane Proteins|*GEMH - Neuropeptide Y|GE/*MEMH - Proteins|*PDSO - Diabetes 1998 Feb; 47(2):230-8DP - 1998 FebTA - DiabetesPG - 230-8IP - 2VI - 47UI - 9817853323
AU - Chung WK
AU - Belfi K
AU - Chua M
AU - Wiley J
AU - Mackintosh R
AU - Nicolson M
AU - Boozer CN
AU - Leibel RLTI - Heterozygosity for Lep(ob) or Lep(rdb) affects body composition and leptin homeostasis in adult mice.AB - In an effort to understand the genetics of human obesity,we have studied the physiology and molecular genetics of rodent models with monogenetic forms of obesity including the leptin gene-defective (Lep(ob)/Lep(ob)) and leptin receptor gene-defective (Lep(rdb)/Lep(rdb)) mouse. In the experiments reported here, we investigated the effects of heterozygosity at Lep(ob) and Lep(rdb) on body composition and circulating leptin concentration in +/+, Lep(rdb)/+, and Lep(ob)/+ adult mice to identify possible gene dosage effects of these mutations that might elucidate their physiology.Adult mice heterozygous for the Lep(ob) or Lep(rdb) allele had equivalent fat mass and percentage body fat, which was increased 27-47% and 23-35%, respectively, relative to +/+ littermates. Plasma leptin concentrations adjusted for fat mass were 6.5 ng/ml in the Lep(ob)/+, 9.6 ng/ml in the +/+, and 11.5 ng/ml in the Lep(rdb)/+ mice. Sex had no effect on plasma leptin after controlling for fat mass. These data, and data from a small number of mice heterozygous at both Lep(ob) and Lep(rdb) (compound heterozygotes), suggest that leptin protein produced per mass of body fat is reduced in Lep(ob)/+ mice and that body fat is increased in Lep(ob)/+ mice until plasma leptin concentrations reach that of a normal +/+ mouse. The elevated plasma leptin concentration in the Lep(rdb)/+ mice suggests that LEPR may mediate autocrine suppression of Lep expression. These results raise the possibility that human mutations that have even subtle effects on the leptin/leptin receptor system in either the homozygous or heterozygous state may have significant effects on adiposity.MH - Body Composition|*PHMH - Carrier Proteins|*GEMH - Heterozygote|*MH - Homeostasis|*PHMH - Obesity|BL/*GE/PAMH - Proteins|*GE/MESO - Am J Physiol 1998 Apr; 274(4 Pt 2):R985-90DP - 1998 AprTA - Am J PhysiolPG - R985-90IP - 4 Pt 2VI - 274UI - 9823687424
AU - Cl ment K
AU - Vaisse C
AU - Lahlou N
AU - Cabrol S
AU - Pelloux V
AU - Cassuto D
AU - Gourmelen M
AU - Dina C
AU - Chambaz J
AU - Lacorte JM
AU - Basdevant A
AU - Bougn res P
AU - Lebouc Y
AU - Froguel P
AU - Guy Grand BTI - A mutation in the human leptin receptor gene causes obesity and pituitary dysfunction [see comments]AB - The adipocyte-specific hormone leptin, the product of the obese (ob) gene, regulates adipose-tissue mass through hypothalamic effects on satiety and energy expenditure.Leptin acts through the leptin receptor, a single-transmembrane-domain receptor of the cytokine-receptor family. In rodents,homozygous mutations in genes encoding leptin or the leptin receptor cause early-onset morbid obesity, hyperphagia and reduced energy expenditure. These rodents also show hypercortisolaemia, alterations in glucose homeostasis,dyslipidaemia, and infertility due to hypogonadotropic hypogonadisms. In humans, leptin deficiency due to a mutation in the leptin gene is associated with early-onset obesity.Here we describe a homozygous mutation in the human leptin receptor gene that results in a truncated leptin receptor lacking both the transmembrane and the intracellular domains.In addition to their early-onset morbid obesity, patients homozygous for this mutation have no pubertal development and their secretion of growth hormone and thyrotropin is reduced. These results indicate that leptin is an important physiological regulator of several endocrine functions in humans.MH - Carrier Proteins|*GE/PHMH - Mutation|*MH - Obesity|*GEMH - Pituitary Diseases|*GE/PPSO - Nature 1998 Mar; 392(6674):398-401DP - 1998 MarTA - NaturePG - 398-401IP - 6674VI - 392UI - 9819667025
AU - Bennett PA
AU - Lindell K
AU - Karlsson C
AU - Robinson IC
AU - Carlsson LM
AU - Carlsson BTI - Differential expression and regulation of leptin receptor isoforms in the rat brain: effects of fasting and oestrogen.AB - Leptin affects body weight and reproduction mainly via receptors in the central nervous system. Different isoforms of the leptin receptor (leptin-R) exist, including a long isoform (leptin-RL) with signalling capacity and short isoforms (leptin-RS) with unknown function. The aim of this study was to examine leptin-R gene expression in different regions of the brain under conditions with altered body weight, in the female rat, including ovariectomy (OVX),oestradiol (E2) treatment, fasting and a genetic model of obesity (Zucker fa/fa). Leptin-R gene expression was analysed by in situ hybridization using probes recognizing all receptor isoforms (leptin-R) or specifically leptin-RL. Transcripts recognized by the leptin-R probe were abundant in the choroid plexus (CP), arcuate nucleus (ARC), ventromedial nucleus (VMN), thalamus (TH) and piriform cortex (PC). Leptin-RL transcripts were detected in the ARC, VMN, TH and PC but not in the CP. Although no sex difference was observed, leptin-R gene expression was reduced by E2 administration and increased by OVX. Administration of E2 reduced leptin-RL gene expression in the ARC and VMN but did not alter the expression in the TH or PC. OVX had no effect on the expression of leptin-RL mRNA. Fasting also caused a differential regulation of leptin-R mRNAs, with an increase in abundance of leptin-RL transcripts in the TH despite a decrease in leptin-R in this area. Obese Zucker rats had a similar pattern of expression with an increased expression of leptin-RL transcripts in all brain areas analysed and a decrease in leptin-R gene expression. These results demonstrate a differential regulation of leptin-RL and leptin-RS which could provide a mechanism for regulating access to, and sensitivity of, discrete regions of the brain for circulating leptin. We suggest that fasting and E2 alter the balance between leptin-RL and leptin-RS and that this could increase tissue sensitivity to leptin.MH - Brain Chemistry|DE/*PHMH - Carrier Proteins|*BI/DEMH - Estrogens|*PDMH - Fasting|*PHMH - Receptors, Cytokine|*BI/*DESO - Neuroendocrinology 1998 Jan; 67(1):29-36DP - 1998 JanTA - NeuroendocrinologyPG - 29-36IP - 1VI - 67UI - 9814370826
AU - Poitout V
AU - Rouault C
AU - Guerre Millo M
AU - Briaud I
AU - Reach GTI - Inhibition of insulin secretion by leptin in normal rodent islets of Langerhans.AB - The recently discovered adipose cell-specific hormone called leptin decreases food intake and increases energy expenditure in rodents through a pathway involving hypothalamic leptin receptors, OB-R. In addition, leptin decreases insulin circulating levels independent of the reduction in food intake. Whether or not the hormone has a direct effect on pancreatic beta-cells is not clear, because previous in vitro studies have led to controversial results depending on the animal model used. The present study was designed to investigate the effects of leptin in islets of Langerhans isolated from normal rodents. Three isoforms of the leptin receptor, OB-Ra, b, and f, were detected by RT-PCR analysis of total RNA from rat islets. In static incubations, leptin (10 ng/ml) did not alter basal insulin secretion nor insulin secretion stimulated by glucose alone, potassium chloride,or ketoisocaproic acid. In contrast, insulin secretion stimulated by glucose + 3-isobutyl 1-methylxanthine (IBMX)was inhibited by 34 +/- 15% (n = 4, P < 0.05). This was further substantiated in perifusion experiments, in which leptin decreased by 31 +/- 3% (n = 5, P < 0.01) glucose + IBMX-stimulated insulin release. Similarly, in mouse islets a significant inhibitory effect of leptin (-31 +/- 4%, n = 6, P < 0.05) was observed only on glucose + IBMX-stimulated insulin secretion, with no effect of the hormone on basal nor glucose-stimulated secretion. Finally,leptin was totally inefficient in islets isolated from obese fa/fa rats, which bear a mutation in OB-R. These results suggest that, in normal rodent islets, leptin specifically inhibits IBMX-potentiated glucose-induced insulin secretion,through a direct effect involving at least one of the three isoforms of OB-R expressed in islets.MH - Insulin|*SEMH - Islets of Langerhans|*DE/SEMH - Obesity|*MEMH - Proteins|*PDSO - Endocrinology 1998 Mar; 139(3):822-6DP - 1998 MarTA - EndocrinologyPG - 822-6IP - 3VI - 139UI - 9815097227
AU - Kellerer M
AU - Koch M
AU - Metzinger E
AU - Mushack J
AU - Capp E
AU - H ring HUTI - Leptin activates PI-3 kinase in C2C12 myotubes via janus kinase-2 (JAK-2) and insulin receptor substrate-2 (IRS-2) dependent pathways.AB - We have recently shown that leptin mimicks insulin effects on glucose transport and glycogen synthesis through a phosphatidylinositol-3 (PI) kinase dependent pathway in C2C12 myotubes. The aim of the present study was to identify the signalling path from the leptin receptor to the PI-3 kinase. We stimulated C2C12 myotubes with insulin (100 nmol/l, 5 min) or leptin (0.62 nmol/l, 10 min) and determined PI-3 kinase activity in immunoprecipitates with specific non-crossreacting antibodies against insulin-receptor substrate (IRS 1/IRS 2) and against janus kinase (JAK 1 and JAK 2). While insulin-stimulated PI-3 kinase activity is detected in IRS-1 and IRS-2 immunoprecipitates,leptin-stimulated PI-3 kinase activity is found only in IRS-2 immunoprecipitates, suggesting that the leptin signal to PI-3 kinase occurs via IRS-2 and not IRS-1. Leptin-,but not insulin-stimulated PI-3 kinase activity is also detected in immunoprecipitates with antibodies against JAK-2, but not JAK-1. The data suggest that JAK-2 and IRS-2 couple the leptin signalling pathway to the insulin signalling chain. Since we have also detected leptin-stimulated tyrosine phosphorylation of JAK-2 and IRS-2 in C2C12 myotubes it can be assumed that leptin activates JAK-2 which induces tyrosine phosphorylation of IRS-2 leading to activation of PI-3 kinase. As we could not detect the long leptin receptor isoform in C2C12 myotubes we conclude that this signalling pathway is activated by a short leptin receptor isoform.MH - Muscle Fibers|*MEMH - Phosphoproteins|IM/*MEMH - Protein-Tyrosine Kinase|*MEMH - Proteins|*PDMH - Signal Transduction|*MH - 1-Phosphatidylinositol 3-Kinase|DE/*MESO - Diabetologia 1997 Nov; 40(11):1358-62DP - 1997 NovTA - DiabetologiaPG - 1358-62IP - 11VI - 40UI - 9804929828
AU - H kansson ML
AU - Brown H
AU - Ghilardi N
AU - Skoda RC
AU - Meister BTI - Leptin receptor immunoreactivity in chemically defined target neurons of the hypothalamus.AB - The adipose tissue-derived hormone leptin regulates body weight homeostasis by decreasing food intake and increasing energy expenditure. The weight-reducing action of leptin is thought to be mediated primarily by signal transduction through the leptin receptor (LR) in the hypothalamus. We have used immunohistochemistry to localize LR-immunoreactive (LR-IR) cells in the rat brain using an antiserum against a portion of the intracellular domain of LR that is common to all LR isoforms. The antiserum recognized the short and long isoforms of LR in transfected hematopoietic BaF3 cells. To examine the chemical nature of target cells for leptin, direct double-labeling immunofluorescence histochemistry was applied. The results show extensive distribution of LR-like immunoreactivity (LR-LI) in the brain with positively stained cells present, e.g., in the choroid plexus, cerebral cortex, hippocampus, thalamus, and hypothalamus. In the hypothalamus, strongly LR-IR neurons were present in the supraoptic nucleus (SON) and paraventricular nucleus (PVN), periventricular nucleus, arcuate nucleus, and lateral hypothalamus. Weaker LR-IR neurons were also demonstrated in the lateral and medial preoptic nuclei, suprachiasmatic nucleus, ventromedial and dorsomedial nuclei, and tuberomammillary nucleus. Confocal laser scanning microscopy showed LR-LI in the periphery of individual cells. In magnocellular neurons of the SON and PVN, LR-LI was demonstrated in vasopressin-and oxytocin-containing neurons. In parvocellular neurons of the PVN, LR-LI was demonstrated in many corticotropin-releasing hormone-containing neurons. LR-IR neurons were mainly seen in the ventromedial aspect of the arcuate nucleus,where LR-LI co-localized with neuropeptide Y. In the ventrolateral part of the arcuate nucleus, LR-LI was present in many large adrenocorticotropic hormone-IR proopiomelanocortin-containing neurons and in a few galanin-, neurotensin-,and growth hormone-releasing hormone-containing neurons.In the dorsomedial arcuate nucleus, few tyrosine hydroxylase (dopamine)-containing neurons were seen to have LR-LI. Melanin-concentrating hormone-containing neurons in the lateral hypothalamus had LR-LI. Based on the immunohistochemical results, possible interactions of leptin with brain mechanisms are discussed.MH - Carrier Proteins|AN/*IMMH - Hypothalamus|*CH/*CYSO - J Neurosci 1998 Jan; 18(1):559-72DP - 1998 JanTA - J NeurosciPG - 559-72IP - 1VI - 18UI - 9807514929
AU - Karlsson C
AU - Lindell K
AU - Svensson E
AU - Bergh C
AU - Lind P
AU - Billig H
AU - Carlsson LM
AU - Carlsson BTI - Expression of functional leptin receptors in the human ovary.AB - The size of body fat stores is known to influence fertility,indicating a link between adipose tissue and the reproductive system. Studies in mice have identified the adipocyte-derived hormone, leptin (Ob protein), as a possible mediator of this effect. The aim of this study was to investigate the possibility that leptin may have direct effects on the human ovary. To probe this hypothesis we first analyzed the expression of leptin receptors in the human ovary. Transcripts encoding both the long and short isoforms of the leptin receptor were present in human granulosa cells and thecal cells; however, the short isoforms were expressed at much higher levels. Immunoreactive leptin was present in follicular fluid at levels similar to those found in serum. ob gene expression, however, was undetectable in the ovary, as determined by reverse transcription-PCR, whereas it was easily detected in adipose tissue. To determine whether leptin could induce a biological response in ovarian cells, we examined the effect of leptin on estradiol production in cultured granulosa cells. Leptin (100 ng/mL) inhibited LH (0.1 ng/mL)-stimulated estradiol production. In contrast,leptin had no effect on estradiol production in the absence of LH. In conclusion, this study has demonstrated that the leptin receptor is expressed in the human ovary, that leptin is present in follicular fluid, and that leptin can induce a biological response in ovarian cells. These results suggest that leptin may have a direct effect on the human ovary.MH - Carrier Proteins|*MEMH - Ovary|CY/*MESO - J Clin Endocrinol Metab 1997 Dec; 82(12):4144-8DP - 1997 DecTA - J Clin Endocrinol MetabPG - 4144-8IP - 12VI - 82UI - 9806097630
AU - Scarpace PJ
AU - Matheny M
AU - Pollock BH
AU - T mer NTI - Leptin increases uncoupling protein expression and energy expenditure.AB - In ob/ob mice, leptin increases energy expenditure and sympathetic outflow to brown adipose tissue (BAT). To test whether the mechanism of increased energy expenditure may involve increased thermogenesis in BAT, we acclimated normal rats to thermoneutrality for 2 wk followed by leptin administration for 1 wk. Some rats were food restricted for 1 wk to the level of food consumption in the leptin-treated ad libitum-fed rats, and the same rats were both food restricted and administered leptin for a second week. We examined oxygen consumption and uncoupling protein (UCP) expression in BAT. Leptin increased oxygen consumption after the 5th and 6th days in ad libitum-fed rats and after the 4th, 5th, and 6th days in food-restricted rats. Leptin increased BAT UCP mRNA levels greater than twofold in both ad libitum-fed and food-restricted rats. These data demonstrate a leptin-induced increase in energy expenditure in nonmutant rodents and suggest that one mechanism by which leptin increases energy expenditure is through increased thermogenesis in BAT, including increased expression of UCP.MH - Brown Fat|DE/IR/*PHMH - Carrier Proteins|*BIMH - Energy Metabolism|*DEMH - Membrane Proteins|*BIMH - Oxygen Consumption|*DEMH - Proteins|*PDMH - Transcription, Genetic|*DESO - Am J Physiol 1997 Jul; 273(1 Pt 1):E226-30DP - 1997 JulTA - Am J PhysiolPG - E226-30IP - 1 Pt 1VI - 273UI - 9739631031
AU - Casanueva FF
AU - Dieguez C
AU - Popovic V
AU - Peino R
AU - Considine RV
AU - Caro JFTI - Serum immunoreactive leptin concentrations in patients with anorexia nervosa before and after partial weight recovery.AB - Leptin, the product of the ob gene, is a recently discovered hormone secreted by adipocytes. Serum leptin concentrations increase in correlation with the percentage of body fat,but besides that little is known about the physiological actions of leptin in humans. In order to understand the role of leptin in severe malnutrition, in the present work 10 patients recently diagnosed with anorexia nervosa were studied both before and 2 months later, after partial weight recovery, and were compared with 18 normal-weight women as controls. Leptin was measured by a newly developed radioimmunoassay and both IGF-I and IGFBP-3 were measured by commercial radioimmunoassays. The mean (+/-SE) serum leptin concentrations (in microgram/liter) were 18.1 +/- 2.0 in control women with BMI of 21.1 +/- 0.3, significantly higher (P < 0.01)than that in the anorexia nervosa patients at diagnosis (2.2 +/- 0.1, BMI 15.3 +/- 0.6). These differences were also observed in IGF-I values (microgram/liter) that were 228.0 +/- 14.6 in controls and 157.4 +/- 28.7 in anorexia nervosa patients (P < 0.02). No differences were observed in IGF-BP3. After treatment, patients with anorexia nervosa experienced an increase in BMI (17.1 +/- 0.5, P < 0.0001 vs before) although they were still underweight. The partial recovery in weight led to a complete normalization of IGF-I levels (214.0 +/- 21.0 micrograms/liter) and to an enhancement in leptin levels (3.3 +/- 0.5 micrograms/liter; P < 0.03 vs before treatment), though still lower than those in normal-weight women (P < 0.05). Individually analyzed, a large dispersion was observed in control subjects, with leptin levels ranging from 5.5 to 38.7 micrograms/liter,while in all anorexia nervosa patients leptin levels were under 3 micrograms/liter. A treatment-induced increase in body weight led to an increase in leptin levels in 7 out of the 10 anorexia nervosa patients studied and the 3 patients with no increase in leptin were all initially under the 14.5 BMI. In conclusion, leptin levels are severely reduced in anorexia nervosa patients with severe malnutrition,and a significant rise occurred after partial weight recovery.There seems to be a level of BMI below which leptin levels do not drop further but also do not increase despite weight gain. While IGF-I reflects the energy intake of the previous few weeks, the serum leptin concentration reflects the true status of the adipose stores, a fact that has useful clinical implications.MH - Anorexia Nervosa|*BL/PA/THMH - Proteins|*MESO - Biochem Mol Med 1997 Apr; 60(2):116-20DP - 1997 AprTA - Biochem Mol MedPG - 116-20IP - 2VI - 60UI - 9731265032
AU - Zamorano PL
AU - Mahesh VB
AU - De Sevilla LM
AU - Chorich LP
AU - Bhat GK
AU - Brann DWTI - Expression and localization of the leptin receptor in endocrine and neuroendocrine tissues of the rat.AB - The obese gene (ob) product, leptin, has recently been shown to be produced by adipocytes and to circulate in the plasma acting as a hormone to modulate appetite and metabolism. Intriguingly, the ob/ob mutant female mouse,which does not produce an active form of leptin due to a mutation of the ob gene, has been shown to be acyclic and sterile. This sterility can be reversed by treatment with recombinant leptin, but not by diet restriction--suggesting that leptin is required for normal reproductive function.The mechanism(s) whereby leptin modulates reproductive function are unknown; however, it is possible that leptin could directly regulate reproductive tissues. To determine whether endocrine and neuroendocrine tissues could be targets for leptin action, we examined whether these tissues express the leptin receptor mRNA by utilizing reverse-transcription polymerase chain reaction (RT-PCR) analysis in selected tissues from the male and female rat. The results revealed that the leptin receptor mRNA transcript is highly expressed in the ovary, uterus and testis, moderately expressed in the hypothalamus and anterior pituitary, with low to no expression in the adrenal. The RT-PCR results were confirmed by Northern analysis. Furthermore, immortalized GnRH (GT1-7 and NLT) neurons and ovarian granulosa cells were also demonstrated by RT-PCR analysis to express the leptin receptor,suggesting that GnRH neurons and steroid-producing cells of the ovary could be targets for leptin action. Immunohistochemical studies revealed dense immunolocalization of the leptin receptor in the choroid plexus, and interestingly, in the arcuate nucleus/median eminence of the female rat--a key sit in the control of feeding and reproduction. Finally,treatment of the ob/ob mouse with recombinant leptin (0.15 mg/kg/day x 2 weeks) was found to markedly upregulate side chain cleavage and 17 alpha-hydroxylase mRNA levels in the ovary, demonstrating that leptin, acting either through a direct or indirect mechanism, can regulate gene expression in reproductive tissues.MH - Carrier Proteins|GE/*MEMH - Endocrine Glands|*MEMH - Neurosecretory Systems|*MESO - Neuroendocrinology 1997 Mar; 65(3):223-8DP - 1997 MarTA - NeuroendocrinologyPG - 223-8IP - 3VI - 65UI - 9724302433
AU - Dyer CJ
AU - Simmons JM
AU - Matteri RL
AU - Keisler DHTI - Leptin receptor mRNA is expressed in ewe anterior pituitary and adipose tissues and is differentially expressed in hypothalamic regions of well-fed and feed-restricted ewes.AB - Infertility associated with suboptimal nutrition is a major concern among livestock producers. Recently, much effort has been put into understanding the role of the protein leptin in regulating feed intake and reproduction. Leptin,produced by adipocytes, has receptors in the hypothalamus,but more precise locations of leptin receptor-expressing cell bodies have not been reported in a livestock species.The leptin receptor transcript has several splice variants in the mouse and human, but only the "long-form" product (OBRL) is capable of signal transduction. A partial ovine long-form leptin receptor cDNA was cloned and used to evaluate OBRL mRNA expression within hypothalamic, anterior pituitary,and adipose tissues of ovariectomized adult ewes. Expression was detected in reverse transcription-polymerase chain reaction products of all tissues examined. OBRL mRNA was detected by in situ hybridization in the ventromedial and arcuate nuclei of the hypothalamus. In ewes that had been feed restricted for 3 wk before tissue collection, the expression of OBRL mRNA in these areas was greater (P <0.05) than that found in well-fed ewes. These findings provide evidence that the full-length leptin receptor is expressed in hypothalamic, anterior pituitary, and adipose tissue (the latter proffering an autoregulatory mechanisms for leptin) and that within the hypothalamus, this receptor form is differentially expressed in well-fed vs. feed-restricted animals.MH - Adipose Tissue|*MEMH - Carrier Proteins|CH/*GEMH - Gene Expression|*MH - Hypothalamus|*MEMH - Pituitary Gland, Anterior|*MEMH - Sheep|*SO - Domest Anim Endocrinol 1997 Mar; 14(2):119-28DP - 1997 MarTA - Domest Anim EndocrinolPG - 119-28IP - 2VI - 14UI - 9721769334
AU - Cinti S
AU - Frederich RC
AU - Zingaretti MC
AU - De Matteis R
AU - Flier JS
AU - Lowell BBTI - Immunohistochemical localization of leptin and uncoupling protein in white and brown adipose tissue.AB - Leptin is synthesized exclusively by adipocytes and acts on the hypothalamus to regulate energy balance. Previous messenger RNA expression studies demonstrated that leptin is expressed in white adipocytes and also in brown adipose tissue, however expression in brown fat is markedly lower than in white fat. This suggests the possibility that leptin expression in brown adipose tissue is due to the presence of white adipocytes that reside within brown adipose tissue,and that brown adipocytes actually do not express leptin.To address this point, we performed immunohistochemistry on paraffin sections and studied leptin protein expression in different depots of white and brown fat of lean and obese (db/db) mice. To establish the cell type expressing leptin, we also assessed the size and organization of lipid droplets, the ultrastructural features of mitochondria,and the presence or absence of uncoupling protein, a brown fat-specific marker. In white adipose tissue of lean and obese (db/db) mice, leptin protein was expressed in adipocytes of various sizes (range examined: 19.67-200 microns), including adipocytes at the multilocular stage of differentiation.Leptin staining was more intense in some depots (retroperitoneal), and appeared to decrease with fasting. In brown adipose tissue of lean animals, multilocular uncoupling protein (UCP)-positive brown adipocytes had typical brown mitochondria and were leptin-negative, both in fed and fasted conditions.At the periphery of the interscapular brown adipose tissue depot, unilocular, UCP-negative adipocytes (mean diameter:41.55 microns) with white-type mitochondria were observed,and these cells were leptin-positive. In obese (db/db) animals, brown fat was composed mainly of small unilocular,UCP-positive. adipocytes (mean diameter: 40.08 microns), which were also leptin-positive. At the periphery of the organ, numerous large, unilocular, UCP-negative adipocytes (mean diameter: 73.65 microns) with white-like mitochondria were present. As expected, these cells were also leptin-positive. In summary, classical brown adipocytes differ from white adipocytes, not only by their morphology and UCP expression, but also by their apparent lack of detectable leptin expression. db/db brown adipocytes, however, were unilocular and leptin-positive. The molecular mechanisms mediating expression of leptin in white but not brown adipocytes of lean animals, and the significant expression of leptin in brown adipocytes of db/db mice will be the focus of future studies.MH - Adipose Tissue|*CHMH - Brown Fat|*CHMH - Carrier Proteins|*ANMH - Immunohistochemistry|*MH - Membrane Proteins|*ANMH - Proteins|*ANSO - Endocrinology 1997 Feb; 138(2):797-804DP - 1997 FebTA - EndocrinologyPG - 797-804IP - 2VI - 138UI - 9715662735
AU - Shimomura I
AU - Hammer RE
AU - Ikemoto S
AU - Brown MS
AU - Goldstein JLTI - Leptin reverses insulin resistance and diabetes mellitus in mice with congenital lipodystrophy.AB - Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by a paucity of adipose (fat) tissue which is evident at birth and is accompanied by a severe resistance to insulin, leading to hyperinsulinaemia,hyperglycaemia and enlarged fatty liver. We have developed a mouse model that mimics these features of CGL: the syndrome occurs in transgenic mice expressing a truncated version of a nuclear protein known as nSREBP-1c (for sterol-regulatory-element-binding protein-1c) under the control of the adipose-specific aP2 enhancer. Adipose tissue from these mice was markedly deficient in messenger RNAs encoding several fat-specific proteins, including leptin, a fat-derived hormone that regulates food intake and energy metabolism. Here we show that insulin resistance in our lipodystrophic mice can be overcome by a continuous systemic infusion of low doses of recombinant leptin, an effect that is not mimicked by chronic food restriction. Our results support the idea that leptin modulates insulin sensitivity and glucose disposal independently of its effect on food intake, and that leptin deficiency accounts for the insulin resistance found in CGL.MH - Diabetes Mellitus, Experimental|CO/DT/*ETMH - Insulin Resistance|*MH - Lipodystrophy|CN/CO/DT/*ETMH - Proteins|*PH/TUSO - Nature 1999 Sep; 401(6748):73-6DP - 1999 SepTA - NaturePG - 73-6IP - 6748VI - 401UI - 9941371736
AU - Baskin DG
AU - Breininger JF
AU - Schwartz MWTI - Leptin receptor mRNA identifies a subpopulation of neuropeptide Y neurons activated by fasting in rat hypothalamus.AB - The decline of leptin (Ob protein) concentrations during fasting is implicated as a signal for increasing the expression of the orexigenic peptide neuropeptide Y (NPY) in the hypothalamus.To test the hypothesis that the effects of food intake on arcuate nucleus NPY activation are mediated by leptin,we performed simultaneous triple in situ hybridization colocalization studies to determine whether the subset of NPY neurons that are activated by fasting preferentially expresses the long form of the leptin receptor (Ob-Rb).Thus, mRNAs encoding NPY and pro-opiomelanocortin (POMC)were colocalized in the arcuate nucleus of fed and fasted rats by fluorescence in situ hybridization in combination with isotopic in situ hybridization for Ob-Rb mRNA. In fed animals, 47% of arcuate nucleus neurons containing NPY mRNA also contained Ob-Rb mRNA, compared with 79% of POMC neurons (P < 0.01). After a 2-day fast, the number of arcuate nucleus neurons with NPY mRNA increased 50% (P < 0.05); the number of these that coexpressed Ob-Rb increased twofold (P = 0.013). Furthermore, Ob-Rb mRNA hybridization in individual NPY neurons increased by 64%(P < 0.02). In contrast, the number of POMC neurons that coexpressed Ob-Rb was unchanged. A significant interpretation of these findings is that the NPY neurons that do not express detectable levels of Ob-Rb mRNA are not activated by fasting,whereas the NPY neurons that are activated by fasting are the ones that express Ob-Rb. These data demonstrate a significant physiological difference between NPY neurons that express Ob-Rb and those that do not. The results support the conclusion that the effect of food intake on NPY neurons is mediated by the direct action of leptin via Ob-Rb receptors expressed by these NPY cells. The results also indicate that expression of Ob-Rb is a defining phenotypic characteristic of the subset of arcuate nucleus NPY neurons that are activated by fasting and play a central role in the adaptive response to negative energy balance.MH - Carrier Proteins|CH/*GEMH - Fasting|*PHMH - Hypothalamus|CY/*MEMH - Neurons|ME/*PHMH - Neuropeptide Y|*MEMH - RNA, Messenger|*MESO - Diabetes 1999 Apr; 48(4):828-33DP - 1999 AprTA - DiabetesPG - 828-33IP - 4VI - 48UI - 9920084537
AU - De Matteis R
AU - Cinti STI - Ultrastructural immunolocalization of leptin receptor in mouse brain.AB - Antibodies directed to amino acids 877-894 (M-18) and 32-51 (K-20) were used to localize leptin receptor by immunocytochemistry in mouse brain. Both antibodies stained several hypothalamic nuclei (paraventricular nucleus, supraoptic nucleus, supraoptic retrochiasmatic nucleus, suprachiasmatic nucleus, preoptic area, ventromedial nucleus, dorsomedial nucleus, lateral hypothalamus, arcuate nucleus, ventral and dorsal premammillary nuclei), the thalamic and amygdaloid nuclei, neurons of the neocortex and archicortex and the epithelial cells of the choroid plexus. While M-18 staining was concentrated in the Golgi area, with K-20 it was dispersed in the cytoplasm.Glial cells were stained only by K-20. These results suggest that the trans-membrane forms of the receptor are concentrated at the membrane level of the Golgi complex of neurons and in epithelial cells of the choroid plexus while the soluble form is dispersed in their cytoplasm. Glial cells express only the soluble form.MH - Brain|*ULMH - Brain Chemistry|*MH - Carrier Proteins|ME/*ULMH - Receptors, Cytokine|ME/*ULAD - Institute of Normal Human Morphology-AnatomyAD - University of AnconaAD - Italy.SO - Neuroendocrinology 1998 Dec; 68(6):412-9DP - 1998 DecTA - NeuroendocrinologyPG - 412-9IP - 6VI - 68UI - 9909176638
AU - Diano S
AU - Kalra SP
AU - Sakamoto H
AU - Horvath TLTI - Leptin receptors in estrogen receptor-containing neurons of the female rat hypothalamus.AB - This study was undertaken to reveal whether integration of the peripheral signals, leptin and estradiol, that convey information on the metabolic state and gonadal function,respectively, might occur in the same hypothalamic neuronal perikarya. Light and electron microscopic immunolabeling for leptin receptors (LRs) and estrogen receptors (ERs)was carried out on hypothalamic sections of female rats.In the medial preoptic area, periventricular regions, including the parvicellular paraventricular nucleus, the arcuate nucleus and the ventromedial hypothalamic nucleus, all of the cells that expressed immunoreactivity for ERs were also immunopositive for LR. On the other hand, only a subpopulation of LR-containing cells was found to express ERs. The extensive colocalization of receptors for leptin and estrogen in neuronal perikarya of all parts of the hypothalamus suggests a closely coupled interaction between these peripheral signals in the regulation of a variety of behavioral and neuroendocrine mechanisms. Copyright 1998 Elsevier Science B.V.MH - Carrier Proteins|*ANMH - Hypothalamus|*CH/CYMH - Neurons|*CHMH - Obesity|*MH - Receptors, Estrogen|*ANAD - Department of Obstetrics and GynecologyAD - Yale University School of MedicineAD - 333 Cedar St.AD - FMB 339AD - New HavenAD - CTAD - USA.SO - Brain Res 1998 Nov 23; 812(1-2):256-9DP - 1998 Nov 23TA - Brain ResPG - 256-9IP - 1-2VI - 812UI - 9903294939
AU - Niijima ATI - Afferent signals from leptin sensors in the white adipose tissue of the epididymis, and their reflex effect in the rat.AB - Afferent nerve signals were recorded from a peripheral cut end of the small nerve bundle innervating the white adipose tissue (WAT) of the epididymis in the anesthetized rat. An injection of leptin (2 ng, 0.2 ml) into the white adipose tissue facilitated the afferent activity. The response was dose dependent and the least effective dose was 100 pg (0.1 ml). An injection of 2 ng (0.2 ml) leptin into the one side of the WAT resulted in a reflex activation of efferent activity of the sympathetic nerve innervating the WAT of the bilateral epididymis. The observations suggest the existence of leptin sensors in WAT which send afferent signals from the WAT to the central nervous system and evoke a reflex activation of sympathetic outflow to the WAT which may accelerate lipolysis. This WAT to WAT reflex can explain a part of the effect of leptin on metabolic function of the fatty tissue such as the reduction of body weight and increase in energy expenditure as a negative feed-back reflex response.MH - Adipose Tissue|*CH/PHMH - Carrier Proteins|*PHMH - Epididymis|*CY/PHMH - Neurons, Afferent|DE/*PHMH - Reflex|*PHSO - J Auton Nerv Syst 1998 Aug; 73(1):19-25DP - 1998 AugTA - J Auton Nerv SystPG - 19-25IP - 1VI - 73UI - 9902355340
AU - Friedman JMTI - Leptin, leptin receptors, and the control of body weight.AB - The assimilation, storage, and disposition of nutrient energy constitute a complex homeostatic system central to the survival of both prokaryotic and eukaryotic organisms.In vertebrates, and especially among land dwelling mammalian species, the ability to store large quantities of energy-dense fuel in the form of adipose tissue triglyceride permits survival during prolonged periods of food deprivation. In order to maintain such fuel stores during times of dietary scarcity or surfeit, some balance between energy intake and expenditure must be achieved. Lesions of the hypothalamus alter body weight suggesting that this brain region regulates nutritional state. These and other studies led to the hypothesis that body weight was regulated by a feedback loop in which peripheral signals reported nutritional information to an integratory center in the brain. However, the identity of these nutrition signals proved elusive.MH - Carrier Proteins|GE/*PHMH - Obesity|*GE/PPMH - Proteins|GE/PD/*PHSO - Nutr Rev 1998 Feb; 56(2 Pt 2):s38-46; discussion s54-75DP - 1998 FebTA - Nutr RevPG - s38-46; discussion s54-75IP - 2 Pt 2VI - 56UI - 9822533641
AU - Bouloumie A
AU - Marumo T
AU - Lafontan M
AU - Busse RTI - Leptin induces oxidative stress in human endothelial cells.AB - Human umbilical vein endothelial cells (HUVEC) express functional receptors to leptin, the product of the ob gene.As human obesity is associated with atherosclerosis and hyperleptinemia, we investigated whether leptin, in addition to its angiogenic properties, exerts atherogenic effects through the generation of oxidative stress in endothelial cells. In HUVEC leptin increased the accumulation of reactive oxygen species (ROS), as assessed by the oxidation of 2', 7'- dichlorodihydrofluorescein, in a time- and concentration-dependent manner. In addition, leptin activated the NH2-terminal c-Jun kinase/stress-activated protein kinase pathway as demonstrated by enhanced JNK activity and AP-1 DNA binding.Both effects were sensitive to antioxidant treatment with N-acetylcysteine. NF-kappaB, another redox-sensitive transcription factor, was also activated by leptin stimulation in an oxidant-dependent manner. Finally, activation of both AP-1 and NF-kappaB was associated with an enhanced expression of the monocyte chemoattractant protein-1 in HUVEC. These findings demonstrate that ROS are second messengers involved in leptin-induced signaling in endothelial cells. Thus,chronic oxidative stress in endothelial cells under hyperleptinemia may activate atherogenic processes and contribute to the development of vascular pathology.MH - Endothelium, Vascular|CY/*DE/MEMH - Oxidative Stress|*DEMH - Proteins|*PDSO - FASEB J 1999 Jul; 13(10):1231-8DP - 1999 JulTA - FASEB JPG - 1231-8IP - 10VI - 13UI - 9931553842
AU - Bray MS
AU - Boerwinkle E
AU - Hanis CLTI - Linkage analysis of candidate obesity genes among the Mexican-American population of Starr County, Texas.AB - Recent advances in the molecular basis of body fat regulation have identified several genes in which genetic variation may influence obesity and related measures in human populations.Genes that have been shown to have a regulatory function in the control of body fat utilization, eating behavior,and/or metabolic rate in rodent models of obesity include leptin (LEP), leptin receptor (LEPR), neuropeptide Y (NPY), NPY Y1 receptor (NPYY1), glucagon-like peptide-1 (GLP-1), GLP-1 receptor (GLP1R), and uncoupling protein 1 (UCP1). We have typed microsatellite markers located within or near these seven candidate obesity genes in 302 non-diabetic individuals from 59 Mexican-American families from Starr County, Texas. Sib pair linkage analysis was used to examine linkage between these genes and obesity status (obese siblings only; n = 170 pairs) and several obesity-related quantitative variables (all siblings; n = 545 total sibling pairs). Significant linkage (P = 0.042) was found between obesity and NPY within the obese sibling pairs. No other candidate gene was linked to obesity status in this subsample. Consistent with the obese sib pair linkage results, NPY showed evidence of linkage to body weight (P = 0.020), abdominal circumference (P = 0.031), hip circumference (P = 0.012), diastolic blood pressure (P = 0.005), and a composite measure of body mass and size (P = 0.048) in the entire sibling sample. Other significant linkages observed were between LEP and waist/hip ratio (P = 0.010), total cholesterol (P = 0.030), and HDL cholesterol (P = 0.026) and between LEPR and fasting blood glucose (P = 0.018) and diastolic blood pressure (P = 0.003). These results support further investigation of NPY, LEP, and LEPR to identify genetic variation that may influence obesity status, glucose and lipid metabolism,and blood pressure in Mexican Americans.MH - Chromosome Mapping|*/MTMH - Mexican Americans|*GEMH - Obesity|DI/EH/*GE/MEMH - Variation (Genetics)|*GESO - Genet Epidemiol 1999; 16(4):397-411DP - 1999TA - Genet EpidemiolPG - 397-411IP - 4VI - 16UI - 9922412743
AU - Morton NM
AU - Emilsson V
AU - de Groot P
AU - Pallett AL
AU - Cawthorne MATI - Leptin signalling in pancreatic islets and clonal insulin-secreting cells.AB - Leptin is a cytokine secreted from adipose tissue at a rate commensurate with the size of the body's fat stores.In addition to its anorectic and thermogenic central actions,leptin is known to act on peripheral tissues, including the pancreatic beta-cell where it inhibits insulin secretion and reduces insulin transcript levels. However, the role of leptin signalling through its full-length receptor, OB-Rb, in the beta-cell remains unclear. In the present study, we show that leptin activates a signal transducer and activator of transcription (STAT)3 signalling mechanism in pancreatic islets and in a rat model of the pancreatic beta-cell, RINm5F. Leptin induced DNA binding to a STAT consensus oligonucleotide and resulted in transcriptional activation from STAT reporter constructs in a manner consistent with STAT3 activation. Western blot analysis confirmed activation of STAT3 in RINm5F and isolated rat islets. Conditions that mimic increased metabolic activity resulted in attenuation of leptin-mediated STAT DNA binding but had no significant effect on STAT3 tyrosine phosphorylation in RINm5F cells. In addition, leptin activated the mitogen activated protein (MAP) kinase pathway in RINm5F cells.The present study provides a framework for OB-Rb signalling mechanisms in the programming of the beta-cell by leptin and suggests that increased metabolic activity may modulate this function.MH - Insulin|*SEMH - Islets of Langerhans|CY/*ME/*SEMH - Proteins|*MESO - J Mol Endocrinol 1999 Apr; 22(2):173-84DP - 1999 AprTA - J Mol EndocrinolPG - 173-84IP - 2VI - 22UI - 9921196844
AU - Beck B
AU - Richy STI - Hypothalamic hypocretin/orexin and neuropeptide Y: divergent interaction with energy depletion and leptin.AB - The aim of this study was to measure the effects of chronic leptin treatment on two orexigenic peptides present in the hypothalamus namely hypocretin/orexin and neuropeptide Y (NPY). For this purpose, recombinant murine leptin (0.2 mg/rat/day) or saline were injected intraperitoneally in Long-Evans rats for 7 consecutive days. Food intake (-8%; p < 0.002) and body weight gain (23.7 +/- 1 vs 31.5 +/- 1.3 g; p < 0.003) were significantly lower in leptin-treated rats than the saline-treated rats. NPY concentrations did not change significantly in any of the microdissected brain areas including the arcuate and paraventricular nuclei.Orexin A concentration in the lateral hypothalamus was significantly decreased by the leptin treatment (-68%; p < 0.01). A smaller decrease (-46%; p < 0.04) was also noted in saline-treated rats pairfed to the level of the leptin-treated rats. We conclude that orexin/hypocretin could be considered as a new relay for leptin in the central nervous system. Its variation in case of lower energy supply observed in pairfed rats could constitute an alerting system for the brain and therefore considered as the first step in the establishment of defense mechanisms against energy depletion. Copyright 1999 Academic Press.MH - Carrier Proteins|*MEMH - Hypothalamus|*DE/MEMH - Neuropeptide Y|*MEMH - Neuropeptides|*MEMH - Neurotransmitters|*MEMH - Proteins|*PDSO - Biochem Biophys Res Commun 1999 Apr; 258(1):119-22DP - 1999 AprTA - Biochem Biophys Res CommunPG - 119-22IP - 1VI - 258UI - 9924051145
AU - Van den Berghe G
AU - Wouters P
AU - Weekers F
AU - Mohan S
AU - Baxter RC
AU - Veldhuis JD
AU - Bowers CY
AU - Bouillon RTI - Reactivation of pituitary hormone release and metabolic improvement by infusion of growth hormone-releasing peptide and thyrotropin-releasing hormone in patients with protracted critical illness.AB - Protracted critical illness is marked by protein wasting resistant to feeding, by accumulation of fat stores, and by suppressed pulsatile release of GH and TSH. We previously showed that the latter can be reactivated by brief infusion of GH-releasing peptide (GHRP-2) and TRH. Here, we studied combined GHRP-2 and TRH infusion for 5 days, which allowed a limited evaluation of the metabolic effectiveness of this novel trophic endocrine strategy. Fourteen patients (mean +/- SD age, 68 +/- 11 yr), critically ill for 40 +/- 28 days, were compared to a matched group of community-living control subjects at baseline and subsequently received 5 days of placebo and 5 days of GHRP-2 plus TRH (1 + 1 microg/kg x h) infusion in random order. At baseline, impaired anabolism, as indicated by biochemical markers (osteocalcin and leptin), was linked to hyposomatotropism [reduced pulsatile GH secretion, as determined by deconvolution analysis, and low GH-dependent insulin-like growth factor and binding protein (IGFBP) levels]. Biochemical markers of accelerated catabolism (increased protein degradation and bone resorption)were related to tertiary hypothyroidism and the serum concentration of IGFBP-1, but not to hyposomatotropism. Metabolic markers were independent of elevated serum cortisol. After 5 days of GHRP-2 plus TRH infusion, osteocalcin concentrations increased 19% vs. -6% with placebo, and leptin had rose 32% vs. -15% with placebo. These anabolic effects were linked to increased IGF-I and GH-dependent IGFBP, which reached near-normal levels from day 2 onward. In addition,protein degradation was reduced, as indicated by a drop in the urea/creatinine ratio, an effect that was related to the correction of tertiary hypothyroidism, with near-normal thyroid hormone levels reached and maintained from day 2 onward. Concomitantly, a spontaneous tendency of IGFBP-1 to rise and of insulin to decrease was reversed.Cortisol concentrations were not detectably altered. In conclusion, 5-day infusion of GHRP-2 plus TRH in protracted critical illness reactivates blunted GH and TSH secretion,with preserved pulsatility, peripheral responsiveness, and feedback inhibition and without affecting serum cortisol,and induces a shift toward anabolic metabolism. This provides the first evidence of the metabolic effectiveness of short term GHRP-2 plus TRH agonism in this particular wasting condition.MH - Critical Illness|*MH - Oligopeptides|*PDMH - Protirelin|*PDMH - Somatropin|*SEMH - Thyrotropin|*SESO - J Clin Endocrinol Metab 1999 Apr; 84(4):1311-23DP - 1999 AprTA - J Clin Endocrinol MetabPG - 1311-23IP - 4VI - 84UI - 9921386446
AU - Henson MC
AU - Swan KF
AU - ONeil JSTI - Expression of placental leptin and leptin receptor transcripts in early pregnancy and at term.AB - OBJECTIVE: To demonstrate the expression of messenger RNA (mRNA) transcripts for placental leptin and leptin receptor in early gestation and at term, to quantitate transcriptional changes relative to stage of gestation, to localize transcripts within specific placental cell types, and to determine if transcripts also are expressed in cultured cells. METHODS:Expression of leptin and leptin receptor was assessed by reverse transcriptase-polymerase chain reaction, and leptin quantitated against a leptin mRNA competitor (MIMIC), in human placental villous tissue collected at term cesarean deliveries and earlier during gestation (7-14 weeks) upon elective terminations. In situ hybridization was used to identify cell types exhibiting transcripts for genes of interest. Additionally, tissue was dispersed enzymatically,cytotrophoblast cells progressed to syncytiotrophoblastic maturity in culture, and transcripts were assessed. RESULTS:Placental leptin and leptin receptor transcripts were identified in early (n = 6) and late (n = 5) gestation. Although no changes (P > .05) were apparent for receptor, leptin mRNA declined (P < .005) from (mean+/-standard error) 1.815+/-.491 attomoles/microg total RNA early in gestation to .013+/-.003 attomoles/microg total RNA at term. Leptin and leptin receptor transcripts were localized in trophoblast by in situ hybridization and were expressed in culture.CONCLUSION: Results suggest an ontogenetic decline in leptin mRNA with advancing gestation. Localization of leptin and leptin receptor transcripts in syncytiotrophoblasts, cells also responsible for the production of hormones vital to pregnancy maintenance, suggest a potential for autocrine or paracrine interactions within this tissue. Finally, transcript expression in cultured cells suggests the suitability of in vitro paradigms for future studies of leptin in pregnancy.MH - Adipose Tissue|*MEMH - Carrier Proteins|*GEMH - Placenta|*MEMH - Proteins|*GEMH - Receptors, Cytokine|*GESO - Obstet Gynecol 1998 Dec; 92(6):1020-8DP - 1998 DecTA - Obstet GynecolPG - 1020-8IP - 6VI - 92UI - 9905430547
AU - McAbee DD
AU - Ling YY
AU - Stich CTI - Iron loading of isolated rat hepatocytes inhibits asialoglycoprotein receptor dynamics and induces formation of rat hepatic leptin-1 (RHL-1) oligomers.AB - The major subunit [rat hepatic lectin-1 (RHL-1)] of the asialoglycoprotein (ASGP) receptor mediates endocytosis of the iron-binding protein lactoferrin (Lf) by isolated rat hepatocytes, yet iron loading of cultured adult rat hepatocytes increases the binding and endocytosis of Lf while greatly inhibiting the uptake of desialylated ligand.In the present study, we determined whether the iron-induced Lf-binding site is RHL-1 and examined the nature of the iron-induced block in ASGP receptor endocytic function.Isolated rat hepatocytes increased their non-haem iron content from 70 to 470 p.p. b. following incubation with ferric ammonium citrate (<=100 microgram/ml). These conditions blocked internalization of 125I-asialo-orosomucoid (ASOR)by approximately 90% but increased 125I-Lf endocytosis by 40%. ASOR and anti-RHL-1 sera blocked the binding and endocytosis of 125I-Lf on control cells but not on iron-loaded cells, indicating that the iron-induced Lf-binding site on hepatocytes is not RHL-1. Iron-loading of hepatocytes in the presence or absence of excess ASOR did not significantly alter the number of active ASGP receptors on the cell surface.In contrast, iron-loading decreased the number of active intracellular receptors by 40% and blocked the uptake of 125I-ASOR prebound to the cells by approximately 80%. Under these conditions, we found an iron-dependent evolution of 88 and 140 kDa RHL-1-containing, beta-mercaptoethanol-sensitive multimers that constituted up to 34 and 23%, respectively, of total immunodetectable RHL-1. We propose that iron-induced formation of cystinyl-linked RHL-1-containing multimers inhibits ASGP receptor movement between cell surface and interior and disrupts acylation of intracellular receptors.MH - Iron|*MEMH - Lectins|*CH/IMMH - Liver|*MEMH - Receptors, Cell Surface|*MESO - Biochem J 1998 May; 331 ( Pt 3)():719-26DP - 1998 MayTA - Biochem JPG - 719-26VI - 331 ( Pt 3)UI - 9822820748
AU - Tonello C
AU - Dioni L
AU - Briscini L
AU - Nisoli E
AU - Carruba MOTI - SR59230A blocks beta3-adrenoceptor-linked modulation of upcoupling protein-1 and leptin in rat brown adipocytes.AB - Experimental evidence suggests that, by stimulating energy expenditure in brown fat, selective beta3-adrenoceptor agonists can reduce body weight in obese rodents. In order to investigate further the physiological role of beta3-adrenoceptors in brown adipocytes, we analysed the effects of selective beta3-adrenoceptor agonists and antagonists on uncoupling protein-1 and leptin gene expression in culture-differentiated brown fat cells. Our main findings were that: (i) the leptin gene is expressed in brown adipocytes;(ii) the selective beta3-adrenoceptor agonist, N[(2S)-7-carbethoxy-1,2,3,4-tetrahydronaphth-2-yl]-(2R)-2-hydroxy-2-(3-chlorophenil)ethanamine hydrochloride (SR58611A), inhibits leptin gene while inducing uncoupling protein-1 gene expression; (iii) these opposite effects of SR58611A are antagonized by the selective beta3-adrenoceptor antagonist,SS-enantiomer 3-(2-ethylphenoxy)-1-(1S),2,3,4-tetrahydronaphth-1-ylamin ol]-(2S)-2-propanol oxalate (SR59230A), but not by the selective beta1-adrenoceptor antagonist (+/-)-[2-(3-carbamoyl-4-hydroxyphenoxy)-ethylamino]-3-[4(1-methyl-4-trifluoromethyl-2-imidazolyl)-phenoxy]-2 propanol (CGP20712A); and (iv) these effects are due to increased cyclic AMP levels. These results confirm by means of a different experimental approach that beta3-adrenoceptors play a central role in controlling the expression of genes that are important for brown fat function.MH - Adrenergic beta-Agonists|*PDMH - Brown Fat|CY/*DE/MEMH - Carrier Proteins|*MEMH - Membrane Proteins|*MEMH - Propanolamines|*PDMH - Proteins|*MESO - Eur J Pharmacol 1998 Jul; 352(1):125-9DP - 1998 JulTA - Eur J PharmacolPG - 125-9IP - 1VI - 352UI - 9838240349
AU - Cioffi JA
AU - Van Blerkom J
AU - Antczak M
AU - Shafer A
AU - Wittmer S
AU - Snodgrass HRTI - The expression of leptin and its receptors in pre-ovulatory human follicles.AB - The expression of leptin and its receptors was examined by reverse transcriptase-polymerase chain reaction and immunofluorescence in granulosa and cumulus cells of pre-ovulatory follicles and in meiotically mature oocytes obtained from women undergoing in-vitro fertilization. Leptin concentrations were measured in newly aspirated follicular fluids and in maternal serum before and after the administration of an ovulatory dose of human chorionic gonadotrophin. The findings demonstrate leptin expression at the mRNA and protein levels by granulosa and cumulus cells, and the presence of leptin in mature human oocytes. While an association between follicular leptin concentration and embryo development was not observed, a post-ovulatory increase in serum leptin concentration was associated with implantation potential.The results are discussed with respect to possible roles of leptin in early human development.MH - Carrier Proteins|*GEMH - Follicular Phase|GE/*MEMH - Ovarian Follicle|CY/*MEMH - Proteins|*GE/*MESO - Mol Hum Reprod 1997 Jun; 3(6):467-72DP - 1997 JunTA - Mol Hum ReprodPG - 467-72IP - 6VI - 3UI - 9738375350
AU - Mehrabian M
AU - Wen PZ
AU - Fisler J
AU - Davis RC
AU - Lusis AJTI - Genetic loci controlling body fat, lipoprotein metabolism,and insulin levels in a multifactorial mouse model.AB - We analyzed the inheritance of body fat, leptin levels,plasma lipoprotein levels, insulin levels, and related traits in an intercross between inbred mouse strains CAST/Ei and C57BL/6J. CAST/Ei mice are unusually lean, with only approximately 8% of body weight as fat, whereas C57BL/6J mice have approximately 18% body fat. Quantitative trait locus analysis using > 200 F2 mice revealed highly significant loci (lod scores > 4.3) on chromosomes 2 (three separate loci) and 9 that contribute to mouse fat-pad mass for mice on a high-fat diet. Some loci also influenced plasma lipoprotein levels and insulin levels either on chow or high-fat diets.Two loci for body fat and lipoprotein levels (on central and distal chromosome 2) coincided with a locus having strong effects on hepatic lipase activity, an activity associated with visceral obesity and lipoprotein levels in humans. A locus contributing to plasma leptin levels (lod score 5.3) but not obesity was identified on chromosome 4, near the leptin receptor gene. These data identify candidate regions and candidate genes for studies of human obesity and diabetes, and suggest obesity is highly complex in terms of the number of genetic factors involved. Finally,they support the existence of specific genetic interactions between body fat, insulin metabolism, and lipoprotein metabolism.MH - Adipose Tissue|*MEMH - Chromosome Mapping|*MH - Insulin|*BLMH - Lipoproteins|*MEMH - Obesity|*GESO - J Clin Invest 1998 Jun; 101(11):2485-96DP - 1998 JunTA - J Clin InvestPG - 2485-96IP - 11VI - 101UI - 9828228451
AU - Sinha MK
AU - Caro JFTI - Clinical aspects of leptin.AB - Hyperleptinemia is an essential feature of human obesity.Total body fat mass > % body fat > BMI are the best predictors of circulating leptin levels. Although ob gene is differentially expressed in different fat compartments, apart from total body fat, upper or lower body adiposity or visceral fat does not influence basal leptin levels. Similarly, age,basal glucose levels, and ethnicity do not influence circulating leptin levels. Only in insulin-sensitive individuals do basal levels of insulin and leptin correlate positively even after factoring in body fat. Diabetes does not influence leptin secretion in both lean and obese subjects per se.Independent of adiposity, leptin levels are higher in women than in men. This sexual dimorphism is also present in adolescent children. In eating disorders anorexia nervosa and bulimea nervosa, leptin levels are not upregulated but simply reflect BMI and probably body fat. In spite of strong correlation between body fat and leptin levels,there is great heterogeneity in leptin levels at any given index of body fat. About 5% of obese populations can be regarded as "relatively" leptin deficient which could benefit from leptin therapy. Leptin has dual regulation in human physiology. During the periods of weight maintenance, when energy intake and energy output are equal, leptin levels reflect total bodyfat mass. However, in conditions of negative (weight-loss programs) and positive (weight-gain programs)energy balances, the changes in leptin levels function as a sensor of energy imbalance. This latter phenomenon is best illustrated by short-term fasting and overfeeding experiments. Within 24 h of fasting leptin levels decline to approximately 30% of initial basal values. Massive overfeeding over a 12-h period increases leptin levels by approximately 50% of initial basal values. Meal ingestion does not acutely regulate serum leptin levels. A few studies have shown a modest increase in leptin secretion at supraphysiological insulin concentrations 4-6 h following insulin infusion.Under in vitro conditions, insulin stimulates leptin production only after four days in primary cultures of human adipocytes,which is apparently due to its trophic effects and an increased fat-cell size. Similar to other hormones, leptin secretion shows circadian rhythm and oscillatory pattern. The nocturnal rise of leptin secretion is entrained to mealtime probably due to cumulative hyperinsulinemia of the entire day. Like other growth factors and cytokines, leptin binding proteins including soluble leptin receptor are present in human serum. In lean subjects, the majority of leptin circulates in the bound form whereas in obese subjects, the majority of leptin is present in the free form. When free-leptin levels are compared between lean and obese subjects, even more pronounced hyperleptinemia in obesity is observed than that reported by measuring total leptin levels. During short-term fasting, free-leptin levels in lean subjects decrease in much greater proportion than those in obese subjects. In lean subjects with a relatively small energy store and particularly during food deprivation, leptin circulating predominantly in the bound form could be the mechanism to restrict its availability to hypothalamic leptin receptors for inhibiting leptin's effect on food intake and/or energy metabolism. Unlike marked changes in serum leptin, CSF leptin is only modestly increased in obese subjects and the CSF leptin/serum leptin ratio decreases logarithmically with increasing BMI. If CSF leptin levels are any indication of brain interstitial fluid levels,then hypothalami of obese subjects are not exposed to abnormally elevated leptin concentrations. In the presence of normal leptin receptor (functional long form, i.e., OB-Rb) mRNA expression and in the absence of leptin receptor gene mutations,it is logical to assume defective leptin signaling and/or impaired affector system(s) are the likely causes of leptin resistance inMH - Obesity|CO/GE/*MEMH - Proteins|GE/*MESO - Vitam Horm 1998; 54():1-30DP - 1998TA - Vitam HormPG - 1-30VI - 54UI - 9819087652
AU - Zhou YT
AU - Shimabukuro M
AU - Lee Y
AU - Koyama K
AU - Trieu F
AU - Unger RHTI - Leptin normalizes the impaired response of proinsulin mRNA to long chain fatty acids in heterozygous Zucker diabetic fatty rats.AB - To determine if underleptinization of islets of Zucker diabetic fatty (ZDF) rats is the proximal cause of their inability to compensate for obesity, we compared the proinsulin/beta-actin mRNA ratio in heterozygous (fa/+) ZDF rats with that of wild-type (+/+) and homozygous (fa/fa) ZDF rats.In +/+ islets cultured with 2 mM free fatty acids (FFA)the proinsulin mRNA ratio rose 2.4-fold at 12 h. In fa/+ islets, the ratio rose only 65% above normal. There was no change in fa/fa islets. The presence of leptin (20 ng/ml) in the culture medium increased the FFA-induced response of proinsulin mRNA of fa/+ islets to that of +/+ islets while reducing FFA incorporation into triglycerides. The leptin-induced improvement in the proinsulin mRNA response was independent of any changes in glucose usage. These findings support a causal relationship between diminished leptin action on islets and the impaired beta-cell response to FFA in ZDF rats.MH - Adipose Tissue|DE/*MEMH - Obesity|*GEMH - Proinsulin|*GEMH - Proteins|*PDSO - J Biol Chem 1997 Oct; 272(41):25648-51DP - 1997 OctTA - J Biol ChemPG - 25648-51IP - 41VI - 272UI - 9746735753
AU - Chien EK
AU - Hara M
AU - Rouard M
AU - Yano H
AU - Phillippe M
AU - Polonsky KS
AU - Bell GITI - Increase in serum leptin and uterine leptin receptor messenger RNA levels during pregnancy in rats.AB - Pregnancy is a physiological state associated with significant changes in appetite, thermogenesis, and lipid metabolism,functions which are regulated in part by a hormone, leptin,secreted by adipocytes. Leptin has also been shown to have a role in reproduction, promoting centrally-regulated maturation of the reproductive system and signaling the presence of adequate maternal energy stores for fertility. Here we demonstrate that serum leptin levels are modulated during normal rat pregnancy with a 1.8-fold increase during pregnancy followed by a decrease just before parturition. Leptin receptor mRNA levels in the uterus are also regulated with an increase about 2.7-fold during this same period, whereas there is no change in other tissues examined. The results suggest that leptin may play a role during pregnancy, perhaps regulating energy utilization.MH - Carrier Proteins|*GEMH - Pregnancy, Animal|*MEMH - Proteins|*GEMH - RNA, Messenger|BL/*MEMH - Uterus|*MESO - Biochem Biophys Res Commun 1997 Aug; 237(2):476-80DP - 1997 AugTA - Biochem Biophys Res CommunPG - 476-80IP - 2VI - 237UI - 9741582554
AU - Wu Peng XS
AU - Chua SC Jr
AU - Okada N
AU - Liu SM
AU - Nicolson M
AU - Leibel RLTI - Phenotype of the obese Koletsky (f) rat due to Tyr763Stop mutation in the extracellular domain of the leptin receptor (Lepr): evidence for deficient plasma-to-CSF transport of leptin in both the Zucker and Koletsky obese rat.AB - The obese phenotypes of the diabetes (db) mouse and fatty fa) rat are due to functional null mutations of the leptin receptor (Lepr). The recessive mutation in the Koletsky (f) obese rat maps to the same genetic intervals as db and fa and fails to complement the fa mutation. Comparison of the sequence of brain Lepr cDNA from +/+ and f/f animals reveals a T2349A transversion resulting in a Tyr763Stop nonsense mutation in the gene just before the transmembrane domain. Virtual absence of Lepr mRNA in whole brain from f/f animals is consistent with the presence of a null mutation.The predicted reduced cerebrospinal fluid (CSF) transport of leptin in both f/f and fa/fa mutants is reflected in the approximately 10-fold lower ratio of CSF/plasma leptin concentration in the obese versus lean animals. However,equivalent CSF leptin concentration between lean and obese rats (fa/fa, f/f) indicates that leptin can enter the CSF through a non-Lepr-mediated mechanism, which may be saturated at normal physiological plasma leptin concentration.MH - Brain|*MEMH - Carrier Proteins|*GEMH - Mutation|*MH - Obesity|BL/CF/*GEMH - Proteins|*MEMH - Tyrosine|*SO - Diabetes 1997 Mar; 46(3):513-8DP - 1997 MarTA - DiabetesPG - 513-8IP - 3VI - 46UI - 9718430955
AU - Zakrzewska KE
AU - Cusin I
AU - Stricker Krongrad A
AU - Boss O
AU - Ricquier D
AU - Jeanrenaud B
AU - Rohner Jeanrenaud FTI - Induction of obesity and hyperleptinemia by central glucocorticoid infusion in the rat.AB - It has been claimed that factors favoring the development or maintenance of animal or human obesity may include increases in glucocorticoid production or hyperresponsiveness of the hypothalamic-pituitary-adrenal axis. In normal rats,glucocorticoids have been shown to be necessary for chronic intracerebroventricular infusion of neuropeptide Y to produce obesity and related abnormalities. Conversely, glucocorticoids inhibited the body weight-lowering effect of leptin. Such dual action of glucocorticoids may occur within the central nervous system, since both neuropeptide Y and leptin act within the hypothalamus. The aim of this study was to determine the effects of glucocorticoids (dexamethasone) given intracerebroventricularly to normal rats on body weight homeostasis and hypothalamic levels of neuropeptide Y and corticotropin-releasing hormone.Continuous central glucocorticoid infusion for 3 days resulted in marked sustained increases in food intake and body weight relative to saline-infused controls. The infusion abolished endogenous corticosterone output and produced hyperinsulinemia,hypertriglyceridemia, and hyperleptinemia, three salient abnormalities of obesity syndromes. Central glucocorticoid infusion also produced a marked decrease in the expression of uncoupling protein (UCP)-1 and UCP-3 in brown adipose tissue and UCP-3 in muscle. Finally, chronic central glucocorticoid administration increased the hypothalamic levels of neuropeptide Y and decreased those of corticotropin-releasing hormone.When the same dose of glucocorticoids was administered peripherally, it resulted in decreases in food intake and body weight, in keeping with the decrease in hypothalamic neuropeptide Y levels. These results suggest that glucocorticoids induce an obesity syndrome in rodents by acting centrally and not peripherally.MH - Brain|*PHMH - Dexamethasone|*ADMH - Glucocorticoids, Synthetic|*ADMH - Obesity|*CIMH - Proteins|*ANSO - Diabetes 1999 Feb; 48(2):365-70DP - 1999 FebTA - DiabetesPG - 365-70IP - 2VI - 48UI - 9926548456
AU - Barzilai N
AU - She L
AU - Liu BQ
AU - Vuguin P
AU - Cohen P
AU - Wang J
AU - Rossetti LTI - Surgical removal of visceral fat reverses hepatic insulin resistance.AB - We directly examined whether visceral fat (VF) modulates hepatic insulin action by randomizing moderately obese (body wt approximately 400 g) Sprague-Dawley rats to either surgical removal of epididymal and perinephric fat pads (VF-; n = 9) or a sham operation (VF+; n = 11). Three weeks later, total VF was fourfold increased (8.5 +/- 1.2 vs.2.1 +/- 0.3 g, P < 0.001) in the VF+ compared with the VF- group, but whole-body fat mass (determined using 3H2O)was not significantly different. The rates of insulin infusion required to maintain plasma glucose levels and basal hepatic glucose production in the presence of hepatic-pancreatic clamp were markedly decreased in VF- compared with VF+ rats (0.57 +/- 0.02 vs. 1.22 +/- 0.19 mU x kg(-1) x min(-1), P < 0.001). Similarly, plasma insulin levels were more than twofold higher in the VF+ group (P < 0.001). The heightened hepatic insulin sensitivity is supported by the decrease in gene expression of both glucose-6-phosphatase and PEPCK and by physiological hyperinsulinemia in VF- but not VF+ rats. The improvement in hepatic insulin sensitivity in VF- rats was also supported by a approximately 70% decrease in the plasma levels of insulin-like growth factor binding protein-1, a marker of insulin's transcription regulation in the liver. The removal of VF pads also resulted in marked decreases in the gene expression of tumor necrosis factor-alpha (by 72%) and leptin (by 60%) in subcutaneous fat.We conclude that visceral fat is a potent modulator of insulin action on hepatic glucose production and gene expression.MH - Adipose Tissue|AH/*PHMH - Insulin Resistance|*PHMH - Liver|DE/*PHMH - Viscera|*PHAD - Department of MedicineAD - and Diabetes Research and Training CenterAD - Albert Einstein College of MedicineAD - BronxAD - New York 10461AD - USA. barzilai@aecom.yu.eduSO - Diabetes 1999 Jan; 48(1):94-8DP - 1999 JanTA - DiabetesPG - 94-8IP - 1VI - 48UI - 9910724557
AU - McCowen KC
AU - Chow JC
AU - Smith RJTI - Leptin signaling in the hypothalamus of normal rats in vivo.AB - Leptin has been shown to activate multiple signaling molecules in cultured cells, including Janus kinase-2, STAT (signal transducer and activator of transcription) proteins, and mitogen-activated protein kinase, and to stimulate the DNA-binding activity of STAT3 in mouse hypothalamus. In this study, the activation of candidate leptin signaling molecules in the hypothalamus of normal rats in vivo was investigated. Fasted male Sprague-Dawley rats were injected iv with recombinant murine leptin or vehicle. Plasma leptin concentrations were determined at defined time points, and the phosphorylation of signaling proteins was assessed in hypothalamic lysates. There was a marked increase in plasma leptin concentration at 2 min and a gradual decline by 45 min after leptin injection. Immunoblotting analysis of hypothalamic lysates with a phosphospecific STAT3 antibody demonstrated a time-dependent stimulation of STAT3 tyrosine phosphorylation. STAT3 phosphorylation was first evident at 5 min and was maximal at 30 min after leptin injection.By contrast, leptin did not increase the phosphorylation of Janus kinase proteins, mitogen-activated protein kinase,or STAT1 and -5 despite abundant expression of these signaling molecules in the hypothalamus. These results differ from findings in cultured cells and in vitro systems. It remains unclear how signaling is propagated downstream from the leptin receptor to STAT3, but this may involve novel signaling intermediates.MH - Hypothalamus|DE/*PHMH - Proteins|ME/*PDMH - Signal Transduction|*DESO - Endocrinology 1998 Nov; 139(11):4442-7DP - 1998 NovTA - EndocrinologyPG - 4442-7IP - 11VI - 139UI - 9900858158
AU - Weigle DS
AU - Selfridge LE
AU - Schwartz MW
AU - Seeley RJ
AU - Cummings DE
AU - Havel PJ
AU - Kuijper JL
AU - BeltrandelRio HTI - Elevated free fatty acids induce uncoupling protein 3 expression in muscle: a potential explanation for the effect of fasting.AB - The newly described uncoupling protein 3 (UCP3) may make an important contribution to thermogenesis in humans because of its high level of expression in skeletal muscle. Contrary to expectations, fasting, a condition that reduces resting energy expenditure, has been reported to increase UCP3 expression in muscle. We have confirmed that a 10-fold increase in UCP3 mRNA levels occurs in rat quadriceps muscle between 12 and 24 h of food removal. A less consistent twofold increase in muscle UCP2 mRNA levels was observed in animals fasted for up to 72 h. Administration of recombinant leptin to prevent a fall in circulating leptin levels did not eliminate the fasting-induced increase in quadriceps UCP3 expression. Administration of a high dose of glucocorticoid to fed animals to mimic the increase in corticosterone induced by fasting did not reproduce the increase in UCP3 expression observed in fasted animals. In contrast, elevation of circulating free fatty acid levels in fed animals by Intralipid plus heparin infusion caused significant increases in the UCP3/actin mRNA ratio compared with saline-infused fed controls in both extensor digitorum longus (2.01 +/- 0.34 vs. 0.68 +/- 0.11, P = 0.002) and soleus muscles (0.31 +/- 0.07 vs. 0.09 +/- 0.02, P = 0.014). We conclude that free fatty acids are a potential mediator of the increase in muscle UCP3 expression that occurs during fasting. This seemingly paradoxical induction of UCP3 may be linked to the use of free fatty acid as a fuel rather than an increased need of the organism to dissipate energy.MH - Carrier Proteins|*GEMH - Fasting|*PHMH - Fatty Acids, Nonesterified|*MEMH - Gene Expression|*/DEMH - Muscle, Skeletal|DE/*MESO - Diabetes 1998 Feb; 47(2):298-302DP - 1998 FebTA - DiabetesPG - 298-302IP - 2VI - 47UI - 9817854759
AU - Considine RV
AU - Caro JFTI - Leptin and the regulation of body weight.AB - Leptin has received considerable attention as a newly recognized metabolic hormone and for its potential for therapeutic use in the treatment of human obesity. Furthermore, defects in the leptin signal pathway that result in obesity in animal models have raised the possibility of a similar etiology for obesity in humans. This review will summarize the current findings on leptin in both humans and rodents.These findings will be discussed with respect to our view of the physiology and potential for pathophysiology in leptin-mediated regulation of body weight and composition.MH - Body Weight|*PHMH - Carrier Proteins|*PHMH - Obesity|GE/*PPMH - Proteins|*PHMH - Receptors, Cytokine|*PHSO - Int J Biochem Cell Biol 1997 Nov; 29(11):1255-72DP - 1997 NovTA - Int J Biochem Cell BiolPG - 1255-72IP - 11VI - 29UI - 9811380460
AU - Verploegen SA
AU - Plaetinck G
AU - Devos R
AU - Van der Heyden J
AU - Guisez YTI - A human leptin mutant induces weight gain in normal mice.AB - Leptin, a fat secreted hormone, regulates ingestive behaviour and energy balance by binding to a specific receptor. Using site-directed mutagenesis, we screened for single amino acid residues in human leptin which are critical for receptor binding and biological activity. Here we report that one of these mutants has in vivo antagonistic properties. An Arg to Gln substitution at position 128 of human leptin does not affect receptor binding but knocks out biological activity. Repeated injection of R128Q in normal C57BL/6J mice results in a progressive increase in body weight. This demonstrates that R128Q is able to interfere with the negative feedback control of endogenous leptin. This mutant could be of therapeutic use for wasting disorders,such as anorexia and cachexia, where weight gain would be beneficial.MH - Carrier Proteins|*AIMH - Mutation|*MH - Obesity|*CIMH - Proteins|*GESO - FEBS Lett 1997 Mar; 405(2):237-40DP - 1997 MarTA - FEBS LettPG - 237-40IP - 2VI - 405UI - 9724445761
AU - Masaki T
AU - Yoshimatsu H
AU - Chiba S
AU - Kurokawa M
AU - Sakata TTI - Up-regulation of uterine UCP2 and UCP3 in pregnant rats.AB - Pregnancy produces profound changes in hormone dynamics,thermoregulation and energy metabolism. Uncoupling proteins (UCPs) have been identified in a variety of tissues and UCP1 is known to play important roles in energy homeostasis,while the regulation of UCP2 and UCP3 is still unclear.The present study aimed to investigate the effects of the changes during pregnancy on UCP gene expression in the uterus, as well as in brown adipose tissue (BAT), white adipose tissue (WAT), soleus muscle (Muscle), and liver,throughout the estrus and metestrus periods, at early, middle and late stages in pregnancy, and during post-gestational stages. The expression of uterine UCP2 and UCP3 were up-regulated by 3.2- and 1. 5-fold, respectively, during the late stage of pregnancy with an increase of WAT leptin mRNA expression and exogenous administration of leptin resulted in induction of the uterine UCP2 and UCP3 levels.Contrary to uterine UCPs, UCP1 mRNA expression in BAT was down-regulated by 0.5-fold and there were no remarkable changes in WAT or liver UCP2, or Muscle UCP3 expression throughout the periods. These results indicate that UCP gene expressions during pregnancy are regulated tissue-dependently, and up-regulation of uterine UCP2 and UCP3 mRNA may be due to increased leptin levels.MH - Carrier Proteins|*GEMH - Gene Expression Regulation|*MH - Proteins|*GE/PDMH - Up-Regulation (Physiology)|*MH - Uterus|DE/*MESO - Biochim Biophys Acta 1999 Aug; 1440(1):81-8DP - 1999 AugTA - Biochim Biophys ActaPG - 81-8IP - 1VI - 1440UI - 9940871662
AU - Plata Salamßn CR
AU - Ilyin SE
AU - Gayle D
AU - Flynn MCTI - Gram-negative and gram-positive bacterial products induce differential cytokine profiles in the brain: analysis using an integrative molecular-behavioral in vivo model.AB - Bacterial-derived products [e.g., lipopolysaccharide (LPS)from Gram-negative and muramyl dipeptide (MDP) from Gram-positive bacteria] are proposed to play a pivotal role in the generation of neurological and neuroinflammatory/immunological responses during bacterial infections of the nervous system. LPS and MDP may act through cytokines;cytokine-neuropeptide interactions may also be involved.Here, we investigated cytokine and neuropeptide mRNA profiles in specific brain regions in response to the intracerebroventricular administration of LPS and MDP. IL-beta1 system components (ligand, signalling receptor, receptor accessory proteins,receptor antagonist), TNF-alpha, TGF-beta1, glycoprotein 130 (IL-6 receptor signal transducer), OB protein (leptin)receptor, neuropeptide Y, Y5 receptor, and pro-opiomelanocortin (opioid peptide precursor) mRNAs were analyzed. The same brain region sample was assayed for all components. LPS and MDP administration induced significantly different behavioral and molecular profiles. LPS was significantly more potent than MDP in inducing anorexia and in up-regulating pro-inflammatory cytokines (IL- beta1 and TNF-alpha mRNAs in the cerebellum, hippocampus and hypothalamus; MDP was more potent in up-regulating anti-inflammatory cytokine (IL-1 receptor antagonist and TGF-beta1) mRNAs. LPS and MDP also modulated hypothalamic IL-1 receptor mRNA components,but did not affect any of the neuropeptide-related components examined. The results suggest that the magnitude of neurological manifestations induced by LPS and MDP may involve the ratio between stimulatory and inhibitory cytokines, and this ratio may have implications for the neuroinflammatory/neurotoxic events associated with bacterial infections of the central nervous system.MH - Acetylmuramyl-Alanyl-Isoglutamine|*IMMH - Brain|*IM/MIMH - Cytokines|*BI/GEMH - Lipopolysaccharides|*IMSO - 1998 Feb; 1(2):387-97DP - 1998 FebPG - 387-97IP - 2VI - 1UI - 9907443363
AU - Rosenblum CI
AU - Vongs A
AU - Tota MR
AU - Varnerin JP
AU - Frazier E
AU - Cully DF
AU - Morsy MA
AU - Van der Ploeg LHTI - A rapid, quantitative functional assay for measuring leptin.AB - At present, leptin is quantitated using immuno-assays that measure leptin mass. Leptin biological activity is determined using protocols that measure feed consumption and weight reduction. These in vivo protocols are semi-quantitative and require large quantities of leptin. We describe a rapid,sensitive and quantitative in vitro assay for leptin using HEK-293 cells stably co-transfected with the leptin receptor Ob-Rb isoform and a STAT-inducible promoter regulating the firefly luciferase cDNA. The assay, performed in a 96-well format, has an EC50 of 150 pM and is linear from 3 to 700 pM of leptin. We demonstrate that the assay is capable of measuring leptin in plasma samples. We demonstrate that bacterially-expressed, recombinant leptin and in vivo expressed leptin are equipotent. Furthermore, we demonstrate that a leptin-derived peptide, leptin fragment 22-56, previously shown to be capable of reducing feed intake following ICV injection does not act directly through the leptin receptor.MH - Biological Assay|*MH - Proteins|*ANSO - Mol Cell Endocrinol 1998 Aug; 143(1-2):117-23DP - 1998 AugTA - Mol Cell EndocrinolPG - 117-23IP - 1-2VI - 143UI - 9902119364
AU - Sloop KW
AU - Surface PL
AU - Heiman ML
AU - Slieker LJTI - Changes in leptin expression are not associated with corresponding changes in CCAAT/enhancer binding protein-alpha.AB - C/EBP-alpha binds a C/EBP consensus site in the leptin promoter and activates transcription in vitro. We assessed adipose tissue expression of C/EBP-alpha, leptin and beta-actin in Sprague Dawley rats under conditions that modulate leptin mRNA abundance in order to study the relationship between leptin and C/EBP-alpha expression patterns. During acute fasting, which decreased the level of leptin and beta-actin mRNA, C/EBP-alpha mRNA expression was unaltered.In leptin-treated and pair-fed animals, C/EBP-alpha mRNA was unaltered compared to ad libitum fed controls, while leptin and beta-actin mRNA expression was again decreased.These results indicate that changes in the level of leptin gene expression are not directly associated with changes in the level of C/EBP-alpha abundance. Copyright 1998 Academic Press.MH - DNA-Binding Proteins|*PHMH - Enhancer Elements (Genetics)|*MH - Nuclear Proteins|*PHMH - Proteins|*BI/GESO - Biochem Biophys Res Commun 1998 Oct; 251(1):142-7DP - 1998 OctTA - Biochem Biophys Res CommunPG - 142-7IP - 1VI - 251UI - 9900923665
AU - Takeda K
AU - Kaisho T
AU - Yoshida N
AU - Takeda J
AU - Kishimoto T
AU - Akira STI - Stat3 activation is responsible for IL-6-dependent T cell proliferation through preventing apoptosis: generation and characterization of T cell-specific Stat3-deficient mice.AB - Stat3, a member of STAT, is activated by a variety of cytokines such as IL-6 family of cytokines, granulocyte CSF, epidermal growth factor, and leptin. A recent study with mice genetically deficient in the Stat3 gene has revealed its important role in the early embryogenesis. To assess the function of Stat3 in adult tissues, we disrupted the Stat3 gene specifically in T cells by conditional gene targeting using Cre-loxP system. In Stat3-deficient T cells, IL-6-induced proliferation was severely impaired. IL-6 did not enhance cell cycle progression, but prevented apoptosis of normal T cells. In contrast, IL-6 did not prevent apoptosis of Stat3-deficient T cells. Antiapoptotic protein, Bcl-2, was normally up-regulated in response to IL-6 even in Stat3-deficient T cells. These results demonstrate that Stat3 activation is involved in IL-6-dependent T cell proliferation through prevention of apoptosis independently of Bcl-2.MH - Apoptosis|DE/*PHMH - DNA-Binding Proteins|GE/*PHMH - Interleukin-6|PD/*PHMH - T-Lymphocytes|*CY/DEMH - Trans-Activators|GE/*PHSO - J Immunol 1998 Nov; 161(9):4652-60DP - 1998 NovTA - J ImmunolPG - 4652-60IP - 9VI - 161UI - 9900852566
AU - Matsuda J
AU - Hosoda K
AU - Itoh H
AU - Son C
AU - Doi K
AU - Hanaoka I
AU - Inoue G
AU - Nishimura H
AU - Yoshimasa Y
AU - Yamori Y
AU - Odaka H
AU - Nakao KTI - Increased adipose expression of the uncoupling protein-3 gene by thiazolidinediones in Wistar fatty rats and in cultured adipocytes.AB - Uncoupling protein (UCP) 3 and UCP2, mitochondrial carrier proteins dissipating electrochemical gradient across the mitochondrial inner membrane, have been implicated in the regulation of energy metabolism. The UCP3 gene is expressed abundantly in the skeletal muscle, while the UCP2 gene is detected in the white adipose tissue (WAT) with diffuse localization throughout the body. Uncoupling of electron transport and ATP synthesis has been reported to increase glucose uptake, suggesting that UCP may be involved in glucose metabolism. Thiazolidinediones (TZDs), which are insulin-sensitizing agents for NIDDM, have been reported to increase energy expenditure. To elucidate the pathophysiologic significance of UCP3 and UCP2 in the effect of TZDs on glucose metabolism and energy expenditure, we examined their basal mRNA levels in the WAT, brown adipose tissue (BAT), and skeletal muscle from Wistar fatty rats, a rat model of NIDDM and obesity with leptin receptor defect,and investigated expression of the genes encoding UCP3 and UCP2 in Wistar fatty rats and in Wistar lean rats with 2-week oral administration of 3 mg x kg(-1) x day(-1) pioglitazone,a TZD derivative. Basal UCP3 mRNA levels were significantly lower (38 +/- 8, 45 +/- 13, and 76 +/- 6%) in the retroperitoneal WAT, BAT, and skeletal muscle from Wistar fatty rats than in those from Wistar lean rats, while basal UCP2 mRNA levels were significantly higher by 2.1-, 1.8-, and 2.5-fold in the subcutaneous WAT, retroperitoneal WAT, and BAT from Wistar fatty rats, respectively, than in those from Wistar lean rats. In pioglitazone-treated Wistar fatty rats, UCP3 mRNA levels were significantly increased by 2.1-, 2.0-,and 1.6-fold in the epididymal WAT, retroperitoneal WAT,and BAT, respectively, as compared with those in nontreated fatty rats. In pioglitazone-treated lean rats, UCP3 mRNA levels were significantly increased by 1.3-fold in the BAT as compared with those in nontreated lean rats. No significant change of UCP2 mRNA levels was observed in pioglitazone-treated fatty and lean rats. In addition, to examine the direct effect of TZDs on adipocytes, we examined the regulation of UCP3 and UCP2 gene expression using the primary culture of rat mature adipocytes from Sprague-Dawley rats. In rat cultured mature adipocytes,UCP3 mRNA levels were increased in a dose-responsive manner by 10(-5) to 10(-4) mol/l pioglitazone, while there was no significant change of UCP2 mRNA levels. These results clearly demonstrate that UCP3 gene expression is upregulated by TZDs in the WAT and BAT in Wistar fatty rats, an obese model with leptin receptor defect, and that adipose UCP3 gene expression is increased in response to TZDs in vitro.The present study suggests the involvement of UCP3 in the effects of TZDs on energy and glucose metabolism.MH - Adipose Tissue|*MEMH - Carrier Proteins|*GEMH - Gene Expression Regulation|*DEMH - Thiazoles|*PDSO - Diabetes 1998 Nov; 47(11):1809-14DP - 1998 NovTA - DiabetesPG - 1809-14IP - 11VI - 47UI - 9900704167
AU - Nowak KW
AU - Mackowiak P
AU - Nogowski L
AU - Szkudelski T
AU - Malendowicz LKTI - Acute leptin action on insulin blood level and liver insulin receptor in the rat.AB - Aim of the study was to investigate acute leptin effect on insulin blood level and liver insulin binding in the rat. The administration of leptin induced time and dose dependent decrease in the insulin level, which was statistically significant in comparison to the control animals 120 min after administration of higher dose of peptide (0.30 +/- 0.05 vs 0.14 +/- 0.01 nmol/l, respectively). Simultaneously,we have shown the attenuation of liver sensitivity to insulin 2 hours after higher leptin dose injection. This phenomenon was caused by the decrease of binding capacity of high affinity insulin receptor sites (HAIR), which was statistically significant after higher leptin dose administration at both time points (0.54 +/- 0.13 vs 0.26 +/- 0.03 and 0.71 +/- 0.12 vs 0.40 +/- 0.05 pmol/mg protein for 1 and 2 h, respectively). The present study provides evidence that leptin, in addition to its inhibitory effect on insulin secretion, acts as a modulator of insulin receptor, through the decrease of binding capacity. It seems legitimate to suggest that leptin-induced decrease of insulin receptor binding capacity may be one of several causes of insulin resistance.MH - Insulin|*BLMH - Liver|*DE/MEMH - Proteins|*PDMH - Receptors, Insulin|*MESO - Life Sci 1998; 63(15):1347-52DP - 1998TA - Life SciPG - 1347-52IP - 15VI - 63UI - 9843980868
AU - Krassas GE
AU - Kaltsas TT
AU - Pontikides N
AU - Jacobs H
AU - Blum W
AU - Messinis ITI - Leptin levels in women with polycystic ovary syndrome before and after treatment with diazoxide.AB - Leptin, a product of the ob gene, is a 16 kDa protein which is produced by adipocytes. In humans, obesity is a common finding in women with polycystic ovary syndrome (PCOS).The role, however, of leptin in PCOS is not clear. Some studies have reported increased levels of leptin in PCOS,while others report that they are normal. Also, insulin resistance is a common finding in PCOS. The aim of this study was to investigate further the role of insulin in leptin secretion in patients with PCOS by treating them for 10 days with diazoxide, an insulin-reducing compound.Eight women with PCOS, mean age 22.1 +/- 2.7 years, with mean body mass index (BMI) 28.4 +/- 5.7kg/m2, were studied.An oral glucose tolerance test (OGTT) was performed in all women and blood samples were taken before and at 30,60, 90, 120 and 150 min after the administration of glucose.Glucose, insulin, leptin, free testosterone, delta4 androstenedione,sex hormone binding globulin (SHBG), LH, FSH, IGF-I and insulin-like growth factor-binding protein-3 (IGFBP-3) were measured in the sera taken before the administration of glucose, while glucose and insulin levels were measured in all samples which were collected after the administration of glucose. Diazoxide 300 mg daily was given to all women starting after the end of the OGTT for 10 days. A second OGTT was performed the day after the discontinuation of the diazoxide treatment. The same hormonal and biochemical parameters were also measured in all patients during the second OGTT. After the administration of diazoxide a reduction in sum insulin (262 +/- 147 vs 679 +/- 341 microU/ml. P<().01), leptin (18.5 +/- 10.6 vs 24.2 +/- 10.2 ng/ml, P<0.01), free testosterone (3.0 +/- 1.9 vs 5.1 +/- 1.9 pg/ml, P<0.01), delta4 androstenedione (3.8 +/- 1.9 vs 5.7 +/- 2.0 ng/ml, P<0.01) and IGF-I (219.5 +/- 69.2 vs 314.5 +/- 82.3 ng/ml, P<0.01) levels was observed. Serum SHBG (38.8 +/- 16.8 vs 27.8 +/- 12.1 nmol/l, P<0.01) and sum glucose levels (994.1 +/- 252.7 vs 711.1 +/- 166.1 mg/dl,P<0.05) were increased while IGFBP-3 (3.96 +/- 2.49 vs 3.75 +/- 2.24mg/l), FSH (6.2 +/- 1.8 vs 6.0 +/- 2.5 mU/l) and LH (18.9 +/- 6.7 vs 21.4 +/- 6.7 mU/l) concentrations did not change significantly. A significant positive correlation was found between serum leptin and BMI values before and after administration of diazoxide as well as between leptin,insulin and IGFBP-3 values. Also, sum insulin values correlated significantly with BMI. However, when multiple regression analysis was used this correlation was eliminated except that between leptin and BMI. This was most probably due to the small number of cases. The mechanism of the reduction of leptin levels is unclear. However, it is suggested that the concomitant decrease of insulin levels may play a role.MH - Diazoxide|*TUMH - Polycystic Ovary Syndrome|*BL/*DTMH - Proteins|*MESO - Eur J Endocrinol 1998 Aug; 139(2):184-9DP - 1998 AugTA - Eur J EndocrinolPG - 184-9IP - 2VI - 139UI - 9838946769
AU - Liu Q
AU - Bai C
AU - Chen F
AU - Wang R
AU - MacDonald T
AU - Gu M
AU - Zhang Q
AU - Morsy MA
AU - Caskey CTTI - Uncoupling protein-3: a muscle-specific gene upregulated by leptin in ob/ob mice.AB - We identified and partially characterized another member of the uncoupling protein termed UCP3. Human and mouse UCP3 protein sequences are 86% identical to each other,and 73% and 59% identical to UCP2 and UCP1, respectively.Expression of human UCP3 in yeast resulted in a drastic decrease of mitochondria membrane potential. Northern analysis showed that UCP3 was highly expressed in skeletal muscle in human, rat, and mouse. Mapping of UCP3 placed it to the same chromosomal region of UCP2 in both human and mouse,a region that is linked to obesity and hyperinsulinemia.Furthermore, adenovirus-mediated leptin expression in obese ob/ob mice led to increased expression of UCP3 in skeletal muscle. The data indicate that UCP3 encodes a muscle-specific uncoupling protein that may play an important role in the regulation of energy expenditure and development of obesity.MH - Carrier Proteins|*GE/MEMH - Muscle, Skeletal|*MEMH - Proteins|*PDSO - Gene 1998 Jan; 207(1):1-7DP - 1998 JanTA - GenePG - 1-7IP - 1VI - 207UI - 9817272870
AU - Chua SC Jr
AU - Koutras IK
AU - Han L
AU - Liu SM
AU - Kay J
AU - Young SJ
AU - Chung WK
AU - Leibel RLTI - Fine structure of the murine leptin receptor gene: splice site suppression is required to form two alternatively spliced transcripts.AB - The fine structure of the murine leptin receptor gene (Lepr) is described. Duplicated ligand binding domains (conserved among cytokine receptors) are found in eight exons (coding exons 3 to 6 and 8 to 11). Thus, it is possible that a single leptin receptor molecule could have two functional ligand binding domains. The transmembrane region of Lepr is in coding exon 16 while the juxtamembrane JAK docking site is in coding exon 17. For all membrane-bound forms,the transcript must include 17 invariant exons and 1 alternatively spliced 3' terminal exon. The transcript encoding the soluble receptor (Re) includes 14 coding exons and an alternatively spliced 3' terminal exon. We have identified two splice variants (Rc and Re) for which there are no intervening sequences between the two final exons. This unusual juxtaposition of exons requires that splice donor sites at the 5' end of the respective terminal exons be ignored in the production of these splice variants. We suggest that splice site suppression is responsible for the formation of two of the alternatively spliced forms of the mouse Lepr gene. The juxtaposition of two coding exons separated by a consensus splice donor sequence is the structural substrate for this mode of alternative splicing. We present evidence that the Rc form is expressed in human tissues while the Re form, the soluble receptor,is not expressed. Copyright 1997 Academic Press.MH - Carrier Proteins|*GEMH - Receptors, Cytokine|*GESO - Genomics 1997 Oct; 45(2):264-70DP - 1997 OctTA - GenomicsPG - 264-70IP - 2VI - 45UI - 9800891371
AU - Gong DW
AU - He Y
AU - Karas M
AU - Reitman MTI - Uncoupling protein-3 is a mediator of thermogenesis regulated by thyroid hormone, beta3-adrenergic agonists, and leptin.AB - Mitochondrial uncoupling proteins (UCPs) are transporters that are important for thermogenesis. The net result of their activity is the exothermic movement of protons through the inner mitochondrial membrane, uncoupled from ATP synthesis.We have cloned a third member of the UCP family, UCP3. UCP3 is expressed at high levels in muscle and rodent brown adipose tissue. Overexpression in yeast reduced the mitochondrial membrane potential, showing that UCP3 is a functional uncoupling protein. UCP3 RNA levels are regulated by hormonal and dietary manipulations. In contrast, levels of UCP2, a widely expressed UCP family member, showed little hormonal regulation.In particular, muscle UCP3 levels were decreased 3-fold in hypothyroid rats and increased 6-fold in hyperthyroid rats. Thus UCP3 is a strong candidate to explain the effects of thyroid hormone on thermogenesis. White adipose UCP3 levels were greatly increased by treatment with the beta3-adrenergic agonist, CL214613, suggesting another pathway for increasing thermogenesis. UCP3 mRNA levels were also regulated by dexamethasone, leptin, and starvation, albeit differently in muscle and brown adipose tissue. Starvation caused increased muscle and decreased BAT UCP3, suggesting that muscle assumes a larger role in thermoregulation during starvation. The UCP3 gene is located close to that encoding UCP2, in a chromosomal region implicated in previous linkage studies as contributing to obesity.MH - Adrenergic alpha-Agonists|*PDMH - Body Temperature Regulation|*PHMH - Carrier Proteins|GE/*PHMH - Proteins|*PDMH - Receptors, Adrenergic, beta|*DEMH - Thyroid Hormones|*PDSO - J Biol Chem 1997 Sep; 272(39):24129-32DP - 1997 SepTA - J Biol ChemPG - 24129-32IP - 39VI - 272UI - 9745092572
AU - Fei H
AU - Okano HJ
AU - Li C
AU - Lee GH
AU - Zhao C
AU - Darnell R
AU - Friedman JMTI - Anatomic localization of alternatively spliced leptin receptors (Ob-R) in mouse brain and other tissues.AB - Leptin's effects are mediated by interactions with a receptor that is alternatively spliced, resulting in at least five different murine forms: Ob-Ra, Ob-Rb, Ob-Rc, Ob-Rd, and Ob-Re. A mutation in one splice form, Ob-Rb, results in obesity in mice. Northern blots, RNase protection assays,and PCR indicate that Ob-Rb is expressed at a relatively high level in hypothalamus and low level in several other tissues. Ob-Ra is expressed ubiquitously, whereas Ob-Rc,-Rd, and -Re RNAs are only detectable using PCR. In hypothalamus,Ob-Rb is present in the arcuate, ventromedial, dorsomedial,and lateral hypothalamic nuclei but is not detectable in other brain regions. These nuclei are known to regulate food intake and body weight. The level of Ob-Rb in hypothalamus is reduced in mice rendered obese by gold thioglucose (GTG), which causes hypothalamic lesions. The obesity in GTG-treated mice is likely to be caused by ablation of Ob-Rb-expressing neurons, which results in leptin resistance.MH - Brain|*MEMH - Carrier Proteins|GE/*MESO - Proc Natl Acad Sci U S A 1997 Jun; 94(13):7001-5DP - 1997 JunTA - Proc Natl Acad Sci U S APG - 7001-5IP - 13VI - 94UI - 9733813473
AU - Echwald SM
AU - Sçrensen TD
AU - Sçrensen TI
AU - Tybjaerg Hansen A
AU - Andersen T
AU - Chung WK
AU - Leibel RL
AU - Pedersen OTI - Amino acid variants in the human leptin receptor: lack of association to juvenile onset obesity.AB - The recently described putative lipostat system mediated in part by leptin and its hypothalamic receptor provides logical candidate genes for the molecular basis of inherited obesity in humans on the basis of the occurrence of profound obesity observed in obese and diabetic mice, in which the genes for leptin or its receptor, respectively, are mutated.In this study we tested the hypothesis that juvenile onset obesity in humans may be caused by leptin resistance mediated through genetic variations in isoforms of the hypothalamic leptin receptor. One hundred and fifty-six obese Danish men with a history of juvenile onset obesity were selected at the draft board examination with a body mass index (BMI) > or = 31 kg/m2. From the same study population a contr