估计很多人都听说过“生物钟”，但知道“食物钟”的人可能很少。生物钟以24小时为周期，掌管着生物的“觉醒”与“睡眠”节奏。它受光线的控制，其感受器分布在大脑超交叉神经核的下丘脑中。生物钟有“基于光照的生物节律器”之称。
食物钟负责进食、消化和营养摄取，通常与生物钟同步，在白天和夜晚的运作程序几乎与生物钟相平行。大脑、胃和肝中都有感受器，可以接受食物传递的信号，被称为“食物相关的生物节律器”。
看起来生物钟似乎主导着食物钟，但实际上受食物的诱导，食物钟可以“反客为主”。人们早就知道生物钟蛋白BMAL1，现在，来自美国旧金山加州大学和德国马普研究所的科学家又发现食物钟蛋白PKCγ，并且弄清了食物钟可以“凌驾”于生物钟之上的原因。
这篇近日发表在美国《国家科学院院刊》上的论文指出，原来PKCγ可以结合BMAL1使其结构更稳定，然后共同结合在时钟蛋白上，促进周期基因和隐色素基因的节律性转录，由此产生食物钟特有的时钟效应。食物钟的这种奇妙特性可以让你快速倒时差！
北京与纽约之间横跨12个时区，倒时差通常需要一周左右。由于生物钟只能一天天地往前拨或向后拨，倒时差的速度如此之慢也就不足为奇了。假如你能耐得住饥饿，在旅行途中不吃不喝，然后在落地后大吃一顿，你只要16个小时就能把时差倒过来!(生物谷Bioon.com)
doi: 10.1073/pnas.1218699110
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PMID:
PKCγ participates in food entrainment by regulating BMAL1
Luoying Zhanga, Diya Abrahama,b, Shu-Ting Lina, Henrik Osterb, Gregor Eicheleb, Ying-Hui Fua,1, and Louis J. Ptáčeka,c,1
Temporally restricted feeding (RF) can phase reset the circadian clocks in numerous tissues in mammals, contributing to altered timing of behavioral and physiological rhythms. However, little is known regarding the underlying molecular mechanism. Here we demonstrate a role for the gamma isotype of protein kinase C (PKCγ) in food-mediated entrainment of behavior and the molecular clock. We found that daytime RF reduced late-night activity in wild-type mice but not mice homozygous for a null mutation of PKCγ (PKCγ−/−). Molecular analysis revealed that PKCγ exhibited RF-induced changes in activation patterns in the cerebral cortex and that RF failed to substantially phase shift the oscillation of clock gene transcripts in the absence of PKCγ. PKCγ exerts effects on the clock, at least in part, by stabilizing the core clock component brain and muscle aryl hydrocarbon receptor nuclear translocator like 1 (BMAL1) and reducing its ubiquitylation in a deubiquitination-dependent manner. Taken together, these results suggest that PKCγ plays a role in food entrainment by regulating BMAL1 stability.
