Intracellular mediators in regulation of leptin secretion from adipocytes.

Leptin is a hormone primarily secreted by adipocytes and participating in the regulation of food intake and energy expenditure. Its blood levels usually correlate with adiposity. The secretion of this hormone is affected, among others, by food consumption, insulin, fasting and cold exposure. Regulation of leptin secretion depends on many intracellular events. It is known that the activation of mTOR (the mammalian target of rapamycin) as well as increase in ATP and malonyl-CoA content in adipocytes enhance secretion of leptin. The rise in intracellular cAMP and fatty acids is thought to evoke the opposite effect. Moreover, the undisturbed action of endogenous adenosine in adipocytes and the proper intracellular Ca(2+) concentration in these cells were also found to have an important function in leptin release. The role of mTOR, ATP, cAMP, fatty acids, malonyl-CoA, adenosine and Ca(2+) in the regulation of leptin secretion from adipocytes is discussed.