A Food-entrainable, Circadian Rhythm in Humans : Ghrelin Secretion is Controlled by Regular Eating Habits

与同步食物预期活动相对应的生理昼夜节律尚未在人体研究中得到证实。血浆胃饥饿素水平的特点是每天有四个峰值，而其他激素的典型峰值是基于光可吸收的昼夜节律。我们研究了胃饥饿素的分泌是否主要受食物可携带的昼夜节律或代谢因素的控制。14名健康受试者接受固定时间三餐的常规饮食，为期14天。在第1和第14天的7:00 - 20:00期间，每隔60分钟通过静脉肱导管采血。在固定用餐时间的2周期间，BMI和体脂百分比没有显著差异。在平均7:00到20:00之间，胃饥饿素、血糖和皮质醇水平没有显著差异，但瘦素和胰岛素水平在第14天明显低于第1天。在2周的时间里，按照固定的喂养计划，胃饥饿素的昼夜节律有规律，反映了周期性的餐前升高，而不是个别的不规则模式（第1天与第14天的变异系数为0.64±0.10 vs 0.49±0.06,p<0.01）。血糖、胰岛素、瘦素和皮质醇的昼夜节律模式在第14天和第1天之间没有显著差异。目前的研究结果表明，在健康的成年人中，有规律的饮食习惯可以产生一种以胃饥饿素为基础的、食物可吸收的昼夜节律，这可能与瘦素和胰岛素抵抗的减少有关。

The physiological circadian rhythm corresponding to a synchronous food-anticipatory activity has not been demonstrated in human studies. The plasma ghrelin level characteristically shows four peaks per day, compared to the typical one peak of other hormones based on light-entrainable circadian rhythm. We examined whether ghrelin secretion is mainly controlled by food-entrainable circadian rhythm or metabolic factors. Fourteen healthy subjects received a regular diet with three meals at fixed times for 14 days. Blood was collected from an intravenous brachial catheter every 60 min between 7:00 and 20:00 on the 1st and 14th study day. There were no significant differences in BMI and % body fat during the 2-week period with fixed meal times. There were no meaningful differences between the average 7:00 to 20:00 ghrelin, blood glucose, and cortisol levels, but the leptin and insulin levels were significantly lower on Day 14 than on the Day 1. Following a fixed feeding schedule for the 2-week period resulted in a regular ghrelin circadian rhythm reflecting a periodic pre-meal elevation instead of an individually irregular pattern (coefficient of variation of Day 1 vs. Day 14, 0.64±0.10 vs. 0.49±0.06 ; p<0.01). The circadian patterns of blood glucose, insulin, leptin, and cortisol showed no significant differences between Day 14 and Day 1. The results of the present study show that, in healthy adults, a regular eating habit can create a ghrelin-based, food-entrainable circadian rhythm, which might be related to reductions in leptin and insulin resistance.