Circadian aspects of adipokine regulation in rodents

Most hormones display daily fluctuations of secretion during the 24-h cycle. This is also the case for adipokines, in particular the anorexigenic hormone, leptin. The temporal organization of the endocrine system is principally controlled by a network of circadian clocks. The circadian network comprises a master circadian clock, located in the suprachiasmatic nucleus of the hypothalamus, synchronized to the ambient light, and secondary circadian clocks found in various peripheral organs, such as the adipose tissues. Besides circadian clocks, other factors such as meals and metabolic status impact daily profiles of hormonal levels. In turn, the precise daily pattern of hormonal release provides temporal signaling information. This review will describe the reciprocal links between the circadian clocks and rhythmic secretion of leptin, and discuss the metabolic impact of circadian desynchronization and altered rhythmic leptin.