Chronobiology and circadian rhythms establish a connection to diagnosis

Abstract

Circadian rhythms are synchronized by the light/dark (L/D) cycle over the 24-h day. A suprachiasmatic nucleus in the hypothalamus governs time keeping based on melanopsin messages from the retina in the eyes and transduces regulatory signals to tissues through an array of hormonal, metabolic and neural outputs. Currently, vague impressions on circadian regulation in health and disease are replaced by scientific facts: in addition to L/D cyling, oscillation is maintained by genetic (Clock, Bmal1, Csnk1, CHRONO, Cry, Per) programs, autonomous feedback loops, including melatonin activities, aerobic glycolysis intensity and lipid signalling, among others. Such a multifaceted influential system on circadian rhythm is bound to be fragile and genomic clock acitvities can become disrupted by epigenetic modifications or such environmental factors as mistimed sleep and feeding schedules albeit leaving the centrally driven melatonin-dependent pacemakter more or less unaffected.