lep·tin (lep'tin), [MIM*164160]
A helical protein secreted by adipose tissue and acting on a receptor site in the ventromedial nucleus of the hypothalamus to curb appetite and increase energy expenditure as body fat stores increase. Leptin levels are 40% higher in women, and show a further 50% rise just before menarche, later returning to baseline levels. Levels are lowered by fasting and increased by inflammation.
[G. leptos, thin, + -in]
Human genes encoding both leptin (locus 7q31.3) and the leptin receptor site (1p31) have been identified. Laboratory mice having mutations on the ob gene, which encodes leptin, become morbidly obese, diabetic, and infertile; administration of leptin to these mice improves glucose tolerance, increases physical activity, reduces body weight by 30%, and restores fertility. Mice with mutations of the db gene, which encodes the leptin receptor, also become obese and diabetic but do not improve with administration of leptin. Although mutations in both the leptin and leptin receptor genes have been found in a small number of morbidly obese human subjects with abnormal eating behavior, most obese people do not show such mutations, and have normal or elevated circulating levels of leptin. Leptin enhances insulin-mediated glucose transport into adipose cells in vitro. In controlled studies, both lean and overweight people following weight-reduction diets and receiving daily subcutaneous injections of recombinant methionyl human leptin experienced modest weight loss proportionate to leptin dosage. The immune deficiency seen in starvation may result from diminished leptin secretion. Mice lacking the gene for leptin or its receptor show impairment of T-cell function, and in laboratory studies leptin has induced a proliferative response in human CD4 lymphocytes. Elevation of leptin appears to be a risk factor for cardiovascular disease. Leptin has a stimulatory effect on platelet aggregation induced by adenosine phosphate. It has been suggested, with some support from limited animal studies, that elevation of the leptin level may play a role in the heightened risk of thrombosis noted in obesity.
Farlex Partner Medical Dictionary © Farlex 2012
A peptide hormone produced by fat cells and involved in the regulation of appetite and energy metabolism.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
LEP A gene on chromosome 7q31.3 that encodes leptin, a protein secreted by white adipocytes, which plays a key role in regulating body weight. By binding to its cognate receptor, leptin is part of a signalling pathway which inhibits food intake and regulates energy expenditure to maintain fat homeostasis. Leptin plays a role in the endocrine system, and is involved in regulating immune and inflammatory responses, haematopoiesis, angiogenesis, reproduction, glucose homeostasis, bone formation, and wound healing.
Mutations of LEP and/or its regulatory regions are linked to obesity, morbid obesity with hypogonadism, and type-2 diabetes.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
leptin Endocrinology An obese gene-encoded adipocyte-derived hormone with hypothalamic and CNS receptors, which induces a sensaton of fullness. See Obesity. Cf agouti yellow, diabetes, Ghrelin, obese, Orexin, tubby.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
A helical protein secreted by adipose tissue and acting on a receptor site in the ventromedial nucleus of the hypothalamus to curb appetite and increase energy expenditure as body fat stores increase. Leptin levels are 40% higher in women, and show a further 50% rise just before menarche, later returning to baseline levels; levels are lowered by fasting and increased by inflammation.
[G. leptos, thin, + -in]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
leptin A hormone produced by fat cells which signals the state of repletion. The substance was discovered at the end of 1994 and showed so much promise that more than 600 papers appeared on the topic within three years. Leptin is a protein of 167 amino acids coded for by the ob gene (for ‘obesity’). Its receptor is expressed in the hypothalamus in an area known to be concerned with satiety and hunger. Leptin was at first thought to be the complete answer to appetite control but its action in humans has been found to be more complex than its action in rats. Only about one fifth of people respond to a high concentration of leptin by reducing food intake. Leptin provides a feedback signal from fat to the nervous system, stimulates the neurons that express proopiomelanocortin. When this molecule is split by proteolytic enzymes the anorexogenic peptide alpha MELANOCYT STIMULATING HORMONE is produced.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
A protein hormone that affects feeding behavior and hunger in humans. At present it is thought that obesity in humans may result in part from insensitivity to leptin.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.