新型肝特异性脂滴蛋白17β-HSD13在NAFLD发生中的作用及机制

Hepatic lipid droplet accumulation and abnormal lipid metabolism correlate tightly with NAFLD progression. Previous studies by our laboratory have reported a newly identified liver lipid droplet (LD)-associated protein-17β-HSD13 as a pathogenic molecule in the development of NAFLD through the LXR/SREBP-1c axis. Overexpression of 17β-HSD13 caused markedly accumulation of lipid in mouse liver. The molecular mechanisms by which 17β-HSD13 participates in hepatic lipid homeostasis and promotes the pathogenesis of NAFLD remains largely unknown. In the present proposal, we hypothesize that 17β-HSD13 may play a critical role in the regulation of liver lipid metabolism and its dysfunction may disrupt hepatic lipid homeostasis. Three specific aims are proposed to test the hypothesis. Specific aim 1 will define the phenotypes of 17β-HSD13 liver-specific transgenic and knockout mice; Specific aim 2 will determine the pathophysiogical role of 17β-HSD13 in the pathogenesis of NAFLD by placing both liver-specific transgenic mouse and knockout animals under high-fat diet、MCD and STAM models；Specific aim 3 will characterize the biological function of 17β-HSD13 by using biochemical, lipidomic, and metabolomic approaches. The completion of the proposed studies will not only help clarify the role of 17β-HSD13 in the pathogenesis of NALFD, but also provide a potential therapeutic target for the treatment NAFLD.

肝脏脂滴异常蓄积和脂代谢紊乱与非酒精性脂肪肝（NAFLD）的发生密切相关。申请人在前期研究中发现一个新型肝脂滴蛋白17β-HSD13在NAFLD中显著上调，且受LXR/SREBP-1c调控；肝脏过表达17β-HSD13可显著促进小鼠肝脏脂质聚集。然而，17β-HSD13在NAFLD发生发展中的作用尚不明确。本课题拟使用转基因和基因敲除小鼠及组学等分子生物学手段，进一步阐明17β-HSD13在NAFLD中的作用和机制。我们将：1）明确17β-HSD13转基因和敲除小鼠的代谢表型；2）使用反映脂肪肝不同阶段特征的动物模型（高脂、MCD和STAM模型），探讨17β-HSD13在NAFLD发生、转归中的作用；3）用脂质组和代谢组学等技术探讨17β-HSD13的酶学功能及其在调节肝脏脂质稳态中的机制。本研究的完成不仅有助于揭示NAFLD发生和发展的机制，也将为脂肪肝的防治提供新的潜在靶点。

申请人在前期研究中发现一个新型肝脂滴蛋白17β-HSD13在NAFLD中显著上调，而17β-HSD13在NAFLD发生发展中的作用尚不明确。本课题使用转基因和基因敲除小鼠及组学等分子生物学手段，进一步阐明17β-HSD13在NAFLD中的作用和机制。通过本项目的开展，申请人获得如下重要结果：1）明确17β-HSD13转基因和敲除小鼠的代谢表型；2）使用反映脂肪肝不同阶段特征的动物模型（高脂、MCD和STAM模型），探讨17β-HSD13在NAFLD发生、转归中的作用；通过脂质组和代谢组学等技术探讨17β-HSD13的酶学功能及其在调节肝脏脂质稳态中的机制；3）发现HSD17B13的一个PKA保守磷酸化调控位点丝氨酸33位，并通过稳转细胞系到构建磷酸化位点失活小鼠代谢表型分析，完整的阐述了HSD17B13的丝氨酸33位受PKA磷酸化后动态调控ATGL的酶活性，调控脂滴的水解，参与脂肪肝发生的原创机制；4）基于该磷酸化位点进行计算机辅助药物设计，寻找到一个FDA批准的治疗哮喘的药物瑞普特罗（β2受体激动剂），在原代肝细胞实验和体内均确认该药物可以通过激活PKA信号通路磷酸化17β-HSD13 Ser33位点，调控脂滴代谢，保护脂肪肝的发生。发表包括Nature Communications在内的系列原创论文6篇。本课题在前期大量相关工作的基础上，进一步揭示HSD17B13翻译后修饰尤其是磷酸化与脂肪肝发生和发展的关系。本课题的开展将有助于理解HSD17B13的翻译后修饰尤其是磷酸化在肝脏脂代谢稳态调节中的重要作用，从而为精准评估HSD17B13作为人类脂肪肝治疗靶点的提供理论和实验依据。