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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.
LEPA 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.