Mendoza J
Institut des Neurosciences Cellulaires et Intégratives, Département de Neurobiologie des Rythmes UMR7168, CNRS et Université Louis Pasteur, Strasbourg, France.
J Neuroendocrinol. 2007 Feb;19(2):127-37. doi: 10.1111/j.1365-2826.2006.01510.x.
In mammals, daily rhythms in behaviour and physiology are driven by a circadian timing system comprised, in a hierarchical way, of a master pacemaker in the suprachiasmatic nuclei (SCN) of the hypothalamus and of peripheral oscillators in most body cells. At the molecular level, in both the SCN and peripheral oscillators, the circadian clock mechanism is built from interconnected feedback loops in gene expression that operate in a cell-autonomous and self-sustained fashion. The SCN clock is mainly entrained by light/dark cycles. By contrast, peripheral oscillators can be strongly affected by daily feeding cycles, which have little effect on the phase of the SCN. However, when feeding schedules are coupled with a caloric restriction, behavioural and physiological circadian rhythms and gene expression in the SCN are shifted and/or entrained to meal-time. Moreover, the reward and motivational value of food can also be a potent synchroniser for the SCN clock. This suggests that energy metabolism and motivational properties of food can influence the clock mechanism of the SCN. Food-related cues may entrain clock genes of the SCN with a direct effect, or be mediated indirectly by another neural or peripheral site. In addition, there may be one or more oscillator sites that would play an integral role as a food-entrained oscillator (FEO), responsible for anticipation of meal-time. The site housing, or the network underlying, this putative FEO is still unknown. The aim of this review is to summarise our current knowledge of the central and peripheral circadian clocks and how they can be entrained by feeding at the physiological and molecular levels.
在哺乳动物中，行为和生理的日常节律由昼夜节律计时系统驱动，该系统以分层方式由下丘脑视交叉上核（SCN）中的主起搏器和大多数身体细胞中的外周振荡器组成。在分子水平上，在SCN和外周振荡器中，昼夜节律时钟机制由基因表达中的相互连接的反馈环构建而成，这些反馈环以细胞自主和自我维持的方式运行。SCN时钟主要受光/暗周期的影响。相比之下，外周振荡器会受到每日进食周期的强烈影响，而进食周期对SCN的相位影响很小。然而，当进食时间表与热量限制相结合时，SCN中的行为和生理昼夜节律以及基因表达会发生改变和/或被调整到进餐时间。此外，食物的奖励和动机价值也可能是SCN时钟的有效同步器。这表明食物的能量代谢和动机特性可以影响SCN的时钟机制。与食物相关的线索可能直接影响SCN的时钟基因，或者由另一个神经或外周部位间接介导。此外，可能存在一个或多个振荡器位点，作为食物诱导振荡器（FEO）发挥不可或缺的作用，负责预测进餐时间。这个假定的FEO所在的位点或其潜在的网络仍然未知。本综述的目的是总结我们目前对中枢和外周昼夜节律时钟的了解，以及它们在生理和分子水平上如何通过进食被调整。
