内质网蛋白TM6SF2在脂质代谢及非酒精性脂肪性肝病中的作用及机制研究

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. The development and progression of NAFLD is closely associated with genetic susceptibility and endoplasmic reticulum stress. Recent international epidemiological and genetic studies have shown that TM6SF2, an endoplasmic reticulum transmembrane protein, is an important risk factor for NAFLD. TM6SF2 E167K polymorphism is significantly associated with NAFLD. TM6SF2 is highly expressed in the liver and small intestine, and is located in the endoplasmic reticulum. The physiological function of TM6SF2 protein in different organs, such as the liver and small intestine, and the role of the TM6SF2 E167K variant on lipid metabolism and the development of NAFLD, as well as the underlying molecular mechanism remain unclear. This proposed project will investigate the association between this variant and NAFLD at individual level. Conditional knockout mice models of TM6SF2 will be established to elucidate the physiological function of TM6SF2 protein in liver and small intestine. Meanwhile, knock in mouse model of TM6SF2 E167K will also be established to explore the effect of the variant on lipid metabolism, liver steatosis and the development of NAFLD at animal and cellular levels. Thus, the project will provide new scientific basis for revealing the pathogenesis of NAFLD.

非酒精性脂肪性肝病（NAFLD）是最常见的慢性肝脏疾病，其发生发展与遗传易感性及内质网应激等密切相关。国际最新基于流行病学与遗传学的研究发现内质网蛋白TM6SF2是一个重要的NAFLD致病风险因子，其E167K多态性与NAFLD进程显著相关。TM6SF2在肝脏和小肠等器官高表达，在细胞内跨内质网定位，但它在肝脏和小肠等不同器官的生理功能以及E167K突变在脂质代谢及NAFLD发生发展中的作用与机制尚不明确。本项目拟在人群水平深入分析该位点多态性与NAFLD的相关性；在动物水平，构建其在肝脏、小肠条件性敲除（knockout）小鼠模型，阐明TM6SF2蛋白在这些组织器官的生理功能；构建E167K敲入（knockin）小鼠模型，在动物和细胞水平探讨该位点突变通过内质网应激引发脂质代谢异常、肝脏脂肪变性及NAFLD的作用与机制。本项目的开展将为揭示NAFLD的发病机制提供新的科学依据。

非酒精性脂肪性肝病（NAFLD）是世界范围内最常见的慢性肝脏疾病。遗传因素在NAFLD发病中起重要作用。国内外研究发现人跨膜蛋白超家族 6 成员 2 基因(TM6SF2) 167K多态性与NAFLD显著相关，但其是否能独立导致NAFLD，以及影响肝脏脂肪代谢的作用机理不明。本项目从“人群-细胞-分子-动物”水平对TM6SF2 167K多态性与NAFLD的相关性及分子机制进行了深入研究 。人群水平，我们建立了中国汉族人群的NAFLD生物样本库。通过扩大样本量，证实了TM6SF2 167K多态性与中国汉族人群NAFLD的发生有显著相关性，并检测分析ABCA1，APOA5等基因多态性与NAFLD的相关性，推动了NAFLD诊断的完善和大规模NAFLD筛查的可行性；细胞分子水平，构建了TM6SF2稳定低表达细胞系及NAFLD细胞模型。揭示了DRAM介导的脂质诱导的外泌体分泌机制，同时提示血浆外泌体水平可能作为NAFLD患者的一种新的生物标志物。采用生物信息学进行TM6SF2在肝细胞癌组织中的表达及其功能分析。验证了肝细胞中miR-30b-5p通过靶向PPARGC1A调控脂质代谢；动物水平，构建了TM6SF2 E167K敲入型小鼠模型和TM6SF2 肝脏和小肠条件性敲除小鼠模型，揭示肝脏以及小肠等组织器官中 TM6SF2 蛋白的功能，阐明 TM6SF2 在不同组织器官的生理功能与 NAFLD 发生发展的关系。本研究为揭示 NAFLD 的发生机理提供新的科学认识，有助于建立NAFLD早期遗传分子学预警预测模型，应用于中国汉族人群NAFLD易感性人群的相关基因的筛查，筛查阳性人群进行早期干预，有望降低NAFLD发生率，有助于实现NAFLD早诊断早治疗，进一步降低NAFLD相关肝硬化、肝癌的发病率。