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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hyperphagia and obesity can be experimentally induced in rodents by microinjection of 6-hydroxydopamine (6-OHDA) into the ventral noradrenergic bundle (VNAB) to interrupt efferent catecholaminergic pathways to the hypothalamus. Since hypothalamic neuropeptide Y (NPY) is implicated in the control of ingestive behavior, we evaluated hypothalamic NPY activity in this model of obesity. Adult male rats injected bilaterally with 12 microg of 6-OHDA in the VNAB displayed an enhanced rate of body weight gain and selective dark-phase hyperphagia that started at about 10 days postinjection and persisted for the entire duration of the experiment. NPY gene expression, assessed by ribonuclease protection assay, was significantly higher in the hypothalami of 6-OHDA-treated hyperphagic rats during the dark phase (p < 0.01 vs. levels during the light phase and in control, vehicle-injected rats). We also evaluated gene expression of NPY Y and Y5 receptors, receptor subtypes reported to mediate NPY-induced feeding. The dark-phase increase in NPY mRNA was accompanied by the concomitant upregulation of NPY Y5R gene expression, but not of Y1R mRNA levels. Leptin, the peripheral hormone secreted by adipocytes, is believed to maintain body weight and inhibit food intake, most likely by suppressing hypothalamic NPY activity. Evaluation of leptin gene expression in the epididymal fat revealed that the upregulation of leptin mRNA noted during the dark phase in control rats did not occur in 6-OHDA-treated rats. These observations implied that the normal restraint on NPY and feeding exercised by leptin in control rats may be abrogated in 6-OHDA-treated hyperphagic rats due to insufficient levels of leptin. If so, administration of leptin should inhibit food intake in these rats. Indeed, injection of leptin (2 mg/kg, intraperitoneally (i.p.)) on 2 consecutive days reduced 24-h food intake by 25% and significantly reduced body weight. These results suggest that the nocturnal hyperphagia and resultant obesity induced by 6-OHDA injected into the VNAB may be attributed to leptin deficiency concomitant with increased hypothalamic NPY.
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PMID:Evidence that dark-phase hyperphagia induced by neurotoxin 6-hydroxydopamine may be due to decreased leptin and increased neuropeptide Y signaling. 961 6

Leptin has been called a hormone of reproduction, and seems to link fat and fertility. It has been speculated that the neurotransmitter norepinephrine (NE) (noradrenaline), possibly via the sympathetic nervous system, may represent the afferent signal which modulates leptin release from adipocytes. The purpose of this study was to produce a state of decreased sympathetic output by using the catecholamine synthesis inhibitor alpha-methyl-para-tyrosine (AMPT), in order to study the effect of this compound on the secretion of leptin from fat cells. Ten subjects (five women and five men) received a total of 5 x 1 g doses of AMPT or 5 x 50 mg promethazine (active placebo) over a 26 h period, separated by 4-6 weeks using a randomized, double-blind, placebo-controlled, cross-over design. Blood samples for hormone measurements were obtained over 24 h (18 time points) on day 2 of each experiment. Urinary measurement of the NE metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) on study day 2 served as a marker of the effectiveness of AMPT as an inhibitor of NE synthesis. The daily excretion of this metabolite decreased from 1.56 +/- 0.22 mg in the placebo experiment to 0.53 +/- 0.1 mg in the active experiment (P < 0.05). Plasma leptin concentrations measured in the control group in women and men were similar to those reported previously in lean subjects with a body mass index < 27.5 kg/m2. Leptin concentrations in women were 3-fold higher than in men. Leptin is secreted in a circadian rhythm in both sexes with an increase of nocturnal concentrations by approximately 50%. Two-way analysis of variance reveals no significant difference in leptin secretion between the control and active groups in women and men. In summary, preliminary results do not support the hypothesis that NE represents the afferent signal from the central nervous system which modulates leptin release from adipocytes in the human. Further studies are needed to define the role of the sympathetic nervous system as well as NE in the regulation of leptin secretion and its involvement in obesity and reproduction.
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PMID:Prolonged inhibition of presynaptic catecholamine synthesis does not alter leptin secretion in normal-weight men and women. 961 31

Leptin is believed to play a role in regulating food intake and body weight. The aim of this study was to examine the influence of parental history of obesity on the association between baseline serum leptin concentrations and subsequent 4-y weight changes. Changes in food intake were also considered in the analysis. Middle-aged, obese women with no obese parent (n = 25) or at least one obese parent (n = 24) were included in the analysis. At baseline, women with no parental history of obesity and women with a parental history of obesity did not differ in body mass index (in kg/m2: 41.2 and 40.2, respectively) or median leptin concentrations (40.8 and 38.8 microg/L, respectively). Four-year weight changes varied widely in both groups combined (from -30 to 24 kg). Stratified regression analysis, adjusted for age, weight, and height, revealed that high leptin concentrations predicted less weight gain (or more weight loss) in women with no obese parent (beta = -21.2, P = 0.0006) but played no significant role in predicting weight gain in women with at least one obese parent (beta = -3.8, P = 0.41). Adding changes in energy and fat intakes to the model reduced the association between leptin and weight change to nonsignificance in the women with no obese parent, indicating that the effect of leptin could be explained largely by dietary changes. In conclusion, serum leptin concentrations predict long-term weight change in obese women with no history of parental obesity, an association largely mediated by changes in food intake.
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PMID:Familial predisposition for obesity may modify the predictive value of serum leptin concentrations for long-term weight change in obese women. 962 82

Leptin affects food intake and body weight by actions on the hypothalamus. Although leptin resistance is common in obesity, mechanisms have not been identified. We examined the effect of leptin on expression of the suppressors-of-cytokine-signaling (SOCS) family of proteins. Peripheral leptin administration to ob/ob, but not db/db mice, rapidly induced SOCS-3 mRNA in hypothalamus, but had no effect on CIS, SOCS-1, or SOCS-2. A leptin-dependent increase of SOCS-3 mRNA was seen in areas of hypothalamus expressing high levels of the leptin receptor long form. In mammalian cell lines, SOCS-3, but not CIS or SOCS-2, blocked leptin-induced signal transduction. Expression of SOCS-3 mRNA in the arcuate and dorsomedial hypothalamic nuclei is increased in Ay/a mice, a model of leptin-resistant murine obesity. In conclusion, SOCS-3 is a leptin-inducible inhibitor of leptin signaling, and a potential mediator of leptin resistance in obesity.
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PMID:Identification of SOCS-3 as a potential mediator of central leptin resistance. 966 Sep 46

What is the signal between the metabolic state and reproductive function--it is one of the scientific puzzles in gynecological endocrinology. Previously it was suggested that such substances as insulin, amino acids, IGFBP-I may play a role as a metabolic signal. Leptin a newly discovered hormonal product of obesity (ob) gene is expressed by adipocytes and thought to play a role in the regulation of food intake, metabolism and reproduction. In this article some informations about leptin secretion, its regulation and localization of leptin receptors have been presented. Particular attention to leptin influence on GnRH secretion have been paid. Probably on the base of this mechanism leptin acts as a link between metabolic state and reproductive system. Some data about leptin secretion in obesity, weight loss related amenorrhoea and anorexia nervosa have been discussed. The putative role of leptin in the pathophysiology of polycystic ovary syndrome and initiation of puberty also have been analyzed.
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PMID:[Leptin--missing link between the metabolic state and the reproductive system?]. 968 74

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.
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PMID:Protection against lipoapoptosis of beta cells through leptin-dependent maintenance of Bcl-2 expression. 968 19

Leptin is a fat cell-derived satiety factor that regulates food intake and energy expenditure. Its effects are mediated by interactions with the leptin receptor (Ob-R) that is alternatively spliced to encode at least five isoforms(a-e), which are distributed in a wide range of tissues including the hypothalamus. Ob-R is a member of cytokine receptors and involves the JAK-STAT signal transduction system. We found Ob-R mutations in Zucker fatty rats and obese Koletsky rats and demonstrated that Ob-R dysfunction brings around hyperphagia and obesity. However we and others have not found any Ob-R mutation in human obese subjects.
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PMID:[Leptin Receptor]. 970 77

Leptin is a hormone produced in the adipose tissue and its concentrations in peripheral blood are significantly correlated with the amount of body fat. Whether other factors, including the pattern of body fat distribution and several hormones (such as insulin, sex steroids, and glucocorticoids), may be involved in the regulation of circulating blood leptin levels is controversial. Women with the polycystic ovary syndrome (PCOS) are hyperandrogenic and most of them are characterized by hyperinsulinemia, insulin resistance, and obesity, particularly the visceral phenotype. To assess the potential contribution of anthropometric factors, androgens, and insulin in determining leptin levels, we examined their relationship with body-mass index (BMI), visceral (VAT) and subcutaneous (SAT) adipose tissue areas, basal androgen levels, and fasting and glucose-stimulated (AUC) insulin in different groups of obese women with PCOS (n = 23) and of age-matched obese (n = 16) and non-obese (n = 10) otherwise healthy controls. The VAT/SAT ratio was measured as a parameter of body fat distribution. Serum leptin levels were significantly higher in obese PCOS women than in obese and normal-weight healthy controls and, within the controls, in the obese than in the non-obese group. In all women considered together, and in each group separately, leptin concentrations were highly significantly correlated with BMI. In addition, after adjusting for BMI, both VAT and the VAT/SAT ratio were positively and significantly correlated with leptin. Partial correlations with the VAT/SAT ratio remained significant in both the obese PCOS group and in controls considered separately, whereas the correlation with the SAT value was significant only in the control group. After adjusting for BMI, no correlation between leptin, androgens and fasting or stimulated (like AUC) insulin was found. These findings indicate that leptin levels in obese women with PCOS are higher than those observed in obese and non-obese controls. Moreover, they suggest that, other than BMI, the pattern of body fat distribution may be an independent factor related to circulating leptin levels, which, on the contrary, do not appear to be related to either androgen or insulin concentrations.
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PMID:Serum leptin in obese women with polycystic ovary syndrome is correlated with body weight and fat distribution but not with androgen and insulin levels. 971 97

Obesity is at present one of the most important health risk factors in developed countries. Several studies show significant involvement of genetic factors. A gene called ob is active in the adipose tissue and its product leptin is secreted from adipocytes. Fully functional leptin receptors (encoded by the ob/R gene, also db) have been found in highest numbers in the hypothalamus and therefore it was suggested that it is the leptin plasma level which in forms the brain about total body fat mass and calories intake. Using this pathway it can directly influence a balance between food intake and energy expenditure. The phenotype of ob/ob mutant mice is characterized by severe obesity, NIDDM (non insulin dependent diabetes mellitus), diminished fertility and hypothermia. Db/db mutant mice show a similar phenotype, here the defect lies in the block of leptin receptor downstream signalling. After leptin administration, it was possible to correct the defect only in the ob/ob, but not db/db mice. There is a positive correlation between body mass index and leptin plasma level in humans and no obese patients have been found defective in leptin production or producing or producing ineffective leptin. Human obesity might be connected to a defect of leptin receptor or to its altered signal transduction. Leptin administration is therefore not important in human obesity treatment.
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PMID:[Leptin--the key to obesity?]. 972 70

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.
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PMID:Leptin levels in women with polycystic ovary syndrome before and after treatment with diazoxide. 972 74


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