Leptin: physiological actions.

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.