脂滴蛋白Perilipin 5和Cideb在肝脏脂肪代谢调控中的作用及机制研究

The incidence of non-alcoholic fatty liver disease (NAFLD), which is mainly characterized as excessive lipid accumulation in hepatocytes, is increased year by year recently. The lipid droplet proteins (LDPs) are the key molecules in the regulation of lipid droplet (LD) metabolism. Perilipin5 (Plin5) and Cideb are the most abundant and specific LDPs in the liver. As their important roles in regulating LD metabolism, more and more attentions are paid to their roles in the development of NAFLD. However, their mechanisms in hepatic LD metabolism are yet unknown. Our previous studies have shown that Plin5 deficiency leads to hepatic lipotoxic injury and reduced hepatic lipid contents, and LDs in Cideb-deficient hepatocytes are significantly smaller compared to wild-type. Moreover, we found that Plin5 interacts with Cideb. Based on the previous results, using Knock-out mice and primary hepatocytes, this study is designed to further investigate the effects of Plin5 and Cideb on hepatic lipid contents and lipid metabolism, to definite the role of the interaction between Plin5 and Cideb in the enlargement of hepatic LDs, and its mechanism in regulating LD metabolism. This study could help us to understand the role of LDs in the development of NAFLD, and contribute to the basic foundation for studies on prevention and treatment of NAFLD.

近年来，非酒精性脂肪性肝病（NAFLD）的发生率逐年升高，肝细胞内脂质过度累积是其主要表现，脂滴蛋白是调控脂滴代谢的关键分子。Perilipin 5 (Plin5)和Cideb是肝脏中表达丰富且特异的脂滴蛋白，二者均能调控脂滴的代谢，在NAFLD发生和发展过程中的作用越来越受到重视，但二者在肝脏脂滴代谢调控中的作用机制尚不十分清楚。我们此前的研究显示，Plin5缺失导致小鼠肝脏脂毒性损伤，肝脏脂肪含量明显降低，肝细胞脂滴数量减少，Cideb缺失导致小鼠肝细胞脂滴明显变小；同时我们发现Plin5和Cideb能够相互作用。本课题拟利用敲除小鼠和原代肝细胞，探索Cideb和Plin5对小鼠肝脏脂肪代谢的影响，明确其在脂滴增大中的作用，确定Cideb和Plin5相互作用在肝细胞脂滴代谢调控中的作用及机制。本研究不仅有助于了解脂滴蛋白在NAFLD发生中的作用，也为NAFLD的病因和防治研究奠定基础。

近年来，非酒精性脂肪性肝病（NAFLD）的发生率逐年升高，已严重威胁到人们的健康。NAFLD的主要表现是肝细胞内脂质过度累积和脂肪代谢紊乱，而脂滴蛋白是调控脂滴代谢的关键分子。Perilipin 5 (Plin5)和Cideb是肝脏中表达丰富且特异的脂滴蛋白，二者均能调控脂滴的代谢，在NAFLD发生和发展过程中的作用越来越受到重视，本研究主要探讨二者在肝脏脂滴代谢调控中的作用及其作用机制。我们此前的研究显示，Plin5缺失导致小鼠肝脏脂毒性损伤，肝脏脂肪含量明显降低，肝细胞脂滴数量减少，Cideb缺失导致小鼠肝细胞脂滴明显变小。本研究利用人肝脏穿刺标本，确定了Plin5的表达水平与NAFLD的进展相关；利用双敲除小鼠和原代肝细胞，探索了Plin5和Cideb对小鼠肝脏脂滴形态和脂肪代谢的影响，确定二者在肝细胞脂滴代谢调控中的作用，并阐明其作用机制。结果显示，Plin5和Cideb缺失能够促进彼此的表达，并且饥饿促进Plin5的表达，但却抑制Cideb的表达；Plin5-/-Cideb-/-小鼠体重和肝脏组织学形态未见显著改变，但其肝脏中脂肪含量明显降低，肝细胞脂滴数量减少，体积变小；在Plin5-/-Cideb-/-小鼠肝细胞中过表达Plin5能够增加脂滴的数量，而脂滴的体积未见显著改变；在Plin5-/-Cideb-/-小鼠肝细胞中过表达Cideb后脂滴体积明显增大，数量有所增加；在Plin5-/-Cideb-/-小鼠肝细胞中同时过表达Plin5和Cideb后，小鼠肝细胞中脂滴的数量和体积均出现显著变化，表明Plin5和Cideb共同促进肝细胞脂滴的形成；Plin5和Cideb在细胞内存在共定位并且能够相互作用，Plin5与Cideb的这种相互作用在肝脏脂滴形成过程中的作用可能与他们的内质网定位有关，二者在内质网和脂滴的定位可能共同调控肝细胞中脂滴的代谢。