DNA修复酶家族成员TiPARP在非酒精性脂肪性肝病早期的作用及机制

The pathogenesis of nonalcoholic fatty liver disease (NAFLD) may be related to the imbalance of redox state and the activation of mammalian target of rapamycin (mTOR) signaling pathway during obesity and hyperlipidemia-induced hepatic lipid accumulation. 2,3,7,8 -Tetrachlorodibenzo-p-dioxin (TCDD)-inducible poly(ADP-ribose) polymerase (TiPARP) utilizes NAD+, the redox coenzyme, for ADP-ribosylation reactions. GWAS results and our preliminary studies showed that TiPARP was closely related with hyperlipidemia, and the expression of TiPARP significantly increased in liver of NAFLD. Therefore, we hypothesized that TiPARP promote the development of NAFLD by depletion of redox coenzyme NAD+ and activation of mTOR signaling pathway. In this project, combining animal models and cultured cells, through hepatic specific TiPARP gene inactivation or overexpression and intervention of NAD+ content and / or mTOR activity, we will observe the hepatic lipid accumulation, lipid metabolism related gene expression and cellular redox status, so as to clarify the key role of TiPARP in the pathogenesis of NAFLD and the possible molecular mechanism. The results of this project will reveal that blocking TiPARP may be a new intervention strategy for NAFLD, which will provide scientific evidence and new targets for the prevention and treatment of NAFLD.

非酒精性脂肪性肝病（NAFLD）发病与高脂血症时肝细胞内脂质沉积所致氧化还原状态失衡和mTOR信号通路过度激活密切相关。DNA修复酶家族成员TCDD诱导的聚（腺苷二磷酸-核糖）聚合酶（TiPARP）以氧化还原辅酶NAD+为底物调节细胞功能状态。前期GWAS研究与申请者预实验表明，TiPARP与高脂血症密切相关，且在NAFLD肝脏中表达明显升高，因此提出假说：TiPARP通过耗竭NAD+进而激活mTOR信号通路，促进NAFLD的发生发展。为此，本项目将采用TiPARP基因过表达或特异失活技术，结合整体动物模型和离体细胞研究，观察肝脂质蓄积、脂代谢相关基因表达和细胞内氧化还原状态，阐明TiPARP对NAFLD发生发展的作用；干预细胞内NAD+含量和/或mTOR信号通路活性，进而阐明其分子机制。本研究将揭示阻断TiPARP有可能成为NAFLD的新干预策略，为防治NAFLD提供科学依据和新靶点。

非酒精性脂肪性肝病（NAFLD）发病与高脂血症时肝细胞内脂质沉积所致氧化还原状态失衡和mTOR信号通路过度激活密切相关。DNA修复酶家族成员TCDD诱导的聚（腺苷二磷酸-核糖）聚合酶（TiPARP）以氧化还原辅酶NAD+为底物调节细胞功能状态。前期GWAS研究与申请者预实验表明， TiPARP与高脂血症密切相关，且在NAFLD肝脏中表达明显升高，因此提出假说：TiPARP通过耗竭NAD+进而激活mTOR信号通路，促进NAFLD的发生发展。为此，本项目采用TiPARP基因过表达或特异失活技术，结合整体动物模型和离体细胞研究，观察肝脂质蓄积、脂代谢相关基因表达和细胞内氧化还原状态，阐明TiPARP对NAFLD发生发展的作用；干预细胞内NAD+含量和/或mTOR信号通路活性，进而阐明其分子机制。我们发现，在高脂饮食诱导的NAFLD小鼠模型中，肝脏过表达TiPARP可加重肝脏脂质蓄积。人肝细胞系HepG2细胞，感染表达TiPARP的腺病毒可加重脂质蓄积。感染表达TiPARP 的腺病毒可上调小鼠肝细胞系AML12细胞和人肝细胞系HepG2细胞脂代谢相关基因表达。感染表达靶向TiPARP 的shRNA 腺病毒可下调小鼠肝细胞系AML12细胞脂代谢相关基因表达。感染表达TiPARP 的腺病毒可激活mTOR 信号途径下游分子S6 的磷酸化，以rapamycin 抑制mTOR 信号活性则可减轻细胞内脂质蓄积，下调脂代谢相关基因表达。激活mTOR信号活性则可以恢复被感染表达靶向TiPARP 的shRNA 腺病毒所下调的小鼠肝细胞系AML12细胞脂质蓄积。进一步的研究结果还表明，TiPARP在PM2.5所致NAFLD中起到重要的作用；TiPARP亦可调节脂肪细胞的分化。以上结果说明，在机体能量过剩或环境污染的状态下，肝脏TiPARP 表达上调，激活mTOR 信号途径，进而促进NAFLD的发生发展。我们进一步拓展了我们的研究，发现S100钙结合蛋白 A11 (S100A11) 可能与脂代谢密切相关；天然植物提取的黄酮木脂素类化合物水飞蓟宾可改善db/db小鼠糖脂代谢，缓解NAFLD。本研究将揭示NAFLD的新干预策略，为防治NAFLD提供科学依据和新靶点。