生物钟紊乱促进非酒精性脂肪肝病发生发展的机理

Circadian rhythm (also known as Circadian clock) ubiquitously presents throughout the body that close to 24 hours. The molecular basis of cell-autonomous circadian clock relies on a network of core clock gene oscillation. It was found that almost 50% of gene expression is regulated by circadian clock pathway. Therefore, circadian clock plays important roles in various human diseases including liver diseases. Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease that may leads to liver fibrosis, and cirrhosis, which eventually turn into hepatocellular carcinoma (HCC). Recent researches have shown disruption of circadian rhythm play important roles in the pathogenesis of NAFLD. However, we still do not know the molecular mechanisms underlying which the circadian rhythm affect NAFLD. This project will investigate how disrupted circadian rhythm affects the pathogenesis and progression of NAFLD in vivo and in vitro and involved mechanisms. Firstly, we will evaluate the role of central clock and local liver clock in rat model of NAFLD and involved mechanisms. Secondly, we will elucidate molecular mechanisms underlying the effect of different microenvironment to the modulation of circadian rhythm, leading to the pathogenesis of NAFLD in different cell population. This study will help us better understand the molecular mechanisms that lead circadian rhythm affect the pathogenesis of NAFLD, which will provide basis to prevention and treatment for NAFLD.

生物钟以接近24小时的节律广泛存在于人体内各个部分。核心生物钟基因的是生物钟自我维持的分子基础。研究发现其通路可调节近半数基因的表达节律。因此生物钟在重大疾病，包括肝脏疾病方面有重要作用。非酒精性脂肪肝（NAFLD）已经成为中国第一大肝脏疾病, 可导致肝纤维化，肝硬化并最终发展成肝癌。近期研究表明生物钟紊乱在NAFLD的发生过程中有重要影响。但生物节律影响NAFLD的发生发展机制尚不明确。本项目将分别从体内外两方面来研究生物节律对NAFLD的发生发展的影响及其分子基础。首先在大鼠NAFLD模型中研究中央神经系统生物节律（简称中央生物钟）和肝脏周边生物节律（肝脏生物钟）对NAFLD的发生发展的作用及分子机制。其次通过不同细胞系实验来阐明细胞微环境的改变对生物节律的作用及其对NAFLD发生发展的分子机制。本项研究将加深人们对生物节律对NAFLD的致病机理的认识，为该病的预防和治疗提供理论依据。

非酒精性脂肪肝（NAFLD）已经成为全球最为关注的公共健康问题之一。NAFLD的持续发展可引起脂肪性肝炎（NASH）进而导致肝纤维化，肝硬化和肝癌。目前NAFLD的发生和发展的研究机理还并不清楚，导致缺乏对抗NAFLD的有效药物。已经有证据表明生物钟可以影响肝脏的新陈代谢。本课题主要的研究内容是通过对光照和饮食的调节研究核心生物钟基因的节律变化和 NAFLD 发生的相关性，及其对脂肪酸，糖代谢通路的调节作用。.我们成功建立了大鼠的NAFLD模型，并在此基础上通过改变光照条件和喂养时间来分析了大鼠肝功能，糖代谢和脂肪酸有关的信号通路。研究发现全黑天可以导致体重增长减缓而全白天刚好相反。甘油三脂和总胆固醇含量在全黑或者全光照作用下载4周左右的时候有上升但七周后趋于相近。血清中的leptin在高脂肪饮食组中升高。光照的变化导致肝细胞凋亡率上升。C/EBP homologous protein (CHOP)的mRNA和蛋白水平在全黑组下调在全光照组上调。这表明全光照可导致ER压力上升。同时我们发现下丘脑中的CLOCK和Per1对光照条件的变化最敏感。在通过对喂食时间的控制实验中，我们发现肝脏的损伤在黑夜喂食的情况下得到了明显的改善。生物钟CLOCK和Per1在喂食饮食时间限制后也降低了蛋白的表达。另外在体外实验中我们发现棕榈酸的处理可以导致肝脏细胞和星状细胞的凋亡增强。同时星状细胞的上清液和脂肪细胞的上清液也可以导致肝脏细胞的损伤。另外棕榈酸处理后的HepG2细胞和星状细胞都出现了Per1， CLOCK的生物节律的明显改变，但对BMAL1的变化不明显。另外棕榈酸的处理还导致星状细胞和HepG2的纤维化相关基因表达的增强。本研究证实了肝时钟在 NAFLD 中的发挥了重要作用, 并为生物钟疗法在NAFLD的临床应用提供理论依据。