Abstract
BackgroundThe peripheral circadian clock in mice is entrained not only by light-dark cycles but also by daily restricted feeding schedules. Behavioral and cell culture experiments suggest an increase in glucose level as a factor in such feeding-induced entrainment. For application of feeding-induced entrainment in humans, nutrient content and dietary variations should be considered.Principal FindingTo elucidate the food composition necessary for dietary entrainment, we examined whether complete or partial substitution of dietary nutrients affected phase shifts in liver clocks of mice. Compared with fasting mice or ad libitum fed mice, the liver bioluminescence rhythm advanced by 3–4 h on the middle day in Per2::luciferase knock-in mice that were administered a standard mouse diet, i.e. AIN-93M formula [0.6–0.85 g/10 g mouse BW] (composition: 14% casein, 47% cornstarch, 15% gelatinized cornstarch, 10% sugar, 4% soybean oil, and 10% other [fiber, vitamins, minerals, etc.]), for 2 days. When each nutrient was tested alone (100% nutrient), an insignificant weak phase advance was found to be induced by cornstarch and soybean oil, but almost no phase advance was induced by gelatinized cornstarch, high-amylose cornstarch, glucose, sucrose, or casein. A combination of glucose and casein without oil, vitamin, or fiber caused a significant phase advance. When cornstarch in AIN-93M was substituted with glucose, sucrose, fructose, polydextrose, high-amylose cornstarch, or gelatinized cornstarch, the amplitude of phase advance paralleled the increase in blood glucose concentration.ConclusionsOur results strongly suggest the following: (1) balanced diets containing carbohydrates/sugars and proteins are good for restricted feeding-induced entrainment of the peripheral circadian clock and (2) a balanced diet that increases blood glucose, but not by sugar alone, is suitable for entrainment. These findings may assist in the development of dietary recommendations for on-board meals served to air travelers and shift workers to reduce jet lag-like symptoms.
Highlights
Various physiological phenomena such as body temperature, food intake, and the sleep-wake cycle are under the control of an endogenous circadian clock [1]
Our results strongly suggest the following: (1) balanced diets containing carbohydrates/sugars and proteins are good for restricted feeding-induced entrainment of the peripheral circadian clock and (2) a balanced diet that increases blood glucose, but not by sugar alone, is suitable for entrainment
Strong support for the existence of a foodentrainable timing system is provided by the circadian pattern of food anticipatory activity (FAA) rhythms that have been shown to develop in intact and suprachiasmatic nucleus (SCN)-ablated animals maintained on restricted feeding schedules [5,6,8,9,10]
Summary
Various physiological phenomena such as body temperature, food intake, and the sleep-wake cycle are under the control of an endogenous circadian clock [1]. Clock genes such as Per, Per, Clock, Bmal, Cry, and Cry are expressed in the central autonomic clock, i.e., the suprachiasmatic nucleus (SCN) of the hypothalamus, and in other brain regions [2] and various peripheral tissues [3,4], including the heart, liver, and kidney. The peripheral circadian clock in mice is entrained by light-dark cycles and by daily restricted feeding schedules. When cornstarch in AIN-93M was substituted with glucose, sucrose, fructose, polydextrose, highamylose cornstarch, or gelatinized cornstarch, the amplitude of phase advance paralleled the increase in blood glucose concentration
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