Zirkadiane Uhren und Schlaf – nachgeschaltete Funktion oder Crosstalk?

Endogenous, so-called circadian clocks regulate numerous body functions—including our sleep–wake rhythm—with a period of 24 h. Although the role of the circadian system in regulating the timing of sleep (process C) has long been known, recent studies reveal a far closer connection of the clock system and sleep function on several levels. Genetic defects in the molecular clockwork have a marked impact on the sleep homeostat (process S). Conversely, changes in the natural sleep cycle affect the functioning of the circadian clock—and not only in the central nervous system (CNS), but also in peripheral organs in particular. This sleep-clock crosstalk could explain many of the negative effects of rhythm and sleep disorders on energy metabolism. At the same time, it offers new starting points for the prevention and treatment of sleep-associated pathological effects, e.g. in shift workers. This review describes the interaction of the clock system and sleep control circuits in the CNS and their effects on peripheral physiological processes with a focus on energy metabolism. It outlines a model of close coupling between sleep and clock function and its importance as a point of attack for the treatment of diseases associated with sleep disorders.