A Novel Link Between Circadian Clocks and Adipose Tissue Energy Metabolism

Many behaviors and physiological processesare influenced by internal recurrent dailyrhythms, which likely represent an adaptationto the Earth’s rotation around the Sun and the recurrent 24-h light-dark cycles in the external environ-ment. These circadian rhythms are an important regulator of many key biological processes that influence cellular metabolic pathways and organ function (1,2). The results from a series of studies have demonstrated the importance of normal circadian action for maintaining health in people and the disruption of circadian rhythm, which can have adverse effects on metabolic function. For example, ex-perimentally induced sleep restriction and/or circadian misalignment, generated by inducing recurrent 28-h sleep-wake cycles, decrease insulin sensitivity and glucose tol-erance (3–6). Data from epidemiological studies suggest that long-term alteration in sleep pattern increases the risk of obesity and metabolic diseases. The prevalence o