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Leptin (from Greek λεπτός ''leptos'', "thin"), the "satiety hormone," is a hormone made by adipose cells that helps to regulate energy balance by inhibiting hunger. Leptin is opposed by the actions of the hormone ghrelin, the "hunger hormone". Both hormones act on receptors in the arcuate nucleus of the hypothalamus to regulate appetite to achieve energy homeostasis. In obesity, a decreased sensitivity to leptin occurs, resulting in an inability to detect satiety despite high energy stores. Although regulation of fat stores is deemed to be the primary function of leptin, it also plays a role in other physiological processes, as evidenced by its multiple sites of synthesis other than fat cells, and the multiple cell types beside hypothalamic cells that have leptin receptors. Many of these additional functions are yet to be defined.〔〔〔〔 == Identification of the gene == In 1950, a non-obese mouse colony being studied at the Jackson Laboratory produced a strain of obese offspring, suggesting that a mutation had occurred in a hormone regulating hunger and energy expenditure. Mice homozygous for the so-called ob mutation (ob/ob) ate voraciously and were massively obese. In the 1960s, a second mutation causing obesity and a similar phenotype was identified by Douglas Coleman, also at the Jackson Laboratory, and was named diabetes (db), as both ob/ob and db/db were obese. In 1990 Rudolph Leibel and Jeffrey M. Friedman reported mapping of the ''ob'' gene. Consistent with Coleman’s and Leibel's hypothesis, several subsequent studies from Leibel's and Friedman’s labs and other groups confirmed that the ob gene encoded a novel hormone that circulated in blood and that could suppress food intake and body weight in ob and wild type mice, but not in db mice. In 1994, Friedman's laboratory reported the identification of the gene. In 1995, Jose F. Caro's laboratory provided evidence that the mutations in the mouse ob gene did not occur in humans. Furthermore since ob gene expression was increased, not decreased, in human obesity, it suggested resistance to leptin to be a possibility.〔 At the suggestion of Roger Guillemin, Friedman named this new hormone "leptin" from the Greek ''lepto'' meaning thin.〔 Leptin was the first fat cell-derived hormone (adipokine) to be discovered. Subsequent studies in 1995 confirmed that the db gene encodes the leptin receptor, and that it is expressed in the hypothalamus, a region of the brain known to regulate the sensation of hunger and body weight. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「leptin」の詳細全文を読む スポンサード リンク
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