Scheduled food access during the daytime for nocturnal mice or rats entrains the food-entrainable oscillator (FEO) in the brain and the food-entrainable peripheral oscillator (FEPO) in the peripheral tissues. FEO and FEPO are not regulated by the central clock, which is in the suprachiasmatic nucleus. FEO produces food anticipatory activity (FAA) 2-3 h before the scheduled feeding time initiates. FEPO produces entrainment in the rhythm of peripheral clock gene expression and in the rhythm of food-metabolic functions in peripheral organs. At present, the mechanisms of the FEO and FEPO are not completely understood, despite many studies that have been performed in this field. In addition, circadian clocks affect metabolism of nutrition (absorption, distribution, metabolism, excretion). In this review, we describe and review the characteristics and biological implications of FEO and FEPO and the mechanism of metabolism of nutrition with day-night differences. We call this relationship between nutrition and chronobiology –Chrono-nutrition,— which is an important study field to understand how our body clocks contribute to our health throughout the day.
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