m6A甲基化修饰调控Th17 细胞分化在NAFLD中的作用

Nonalcoholic fatty liver disease (NAFLD) encompasses a broad spectrum of liver conditions ranging from non-alcoholic fatty liver to the more severe and progressive disease, non-alcoholic steatohepatitis (NASH). NAFL was the early stage of NAFLD, however, the mechanism of NAFL progression to NASH remains unclear. We have recently shown that Th17 cells were significantly fewer in hepatic issues with NAFL; IL17A has been associated with anti-adipogenesis, and we found Il17a-/- mice were inclined to adipogenesis in hepatic, furthermore, we also found that free fatty acids(FFAs) can inhibit the differentiate of Th17 cells and result in decrease of mettl3 expression, and mettl3-mediated m6A methylation control the naïve T cells differentiate to Th17 cells. So, we suppose that NAFLD can inhibit the differentiate of Th17 cells by decline the expression of mettl3, eventually promote the liver adipogenesis. This study intends to undertake the following projects:1, To confirm how Th17 cells change observed in various stage using a series of different mouse NAFLD;2, The role of IL17A in regulating adipogenesis; 3, To clarify the mechanism of FFAs inhibit the differentiate of Th17 cells by mettl3 control m6A mRNA methylation. The significantly of this study is further clarify the mechanism of Th17 cells in the progression of NAFLD, provide novel approaches for prevention and treatment of NASH.

非酒精性脂肪性肝病（NAFLD）包含单纯脂肪肝(NAFL)和非酒精性脂肪性肝炎（NASH），NAFL是NAFLD的早期阶段，但是NAFL进展至NASH的机制仍不明了。我们的结果显示Th17细胞在NAFL下降；在NAFL阶段，重组蛋白IL17A抑制肝脏脂滴形成，Il17a-/-小鼠脂滴沉积增加；游离脂肪酸（FFAs）抑制Th17细胞分化并伴随mettl3下降；有研究发现mettl3控制naïve T细胞分化为Th17细胞，因此我们推测在NAFL阶段，FFAs通过抑制mettl3表达水平，进而降低m6A甲基化水平，最终抑制Th17细胞分化促进NAFLD进展。我们拟进行：1、证实Th17细胞在NAFL中的变化；2、IL17A对脂滴形成的影响；3、FFAs通过mettl3影响m6A水平，从而影响Th17细胞分化。通过本研究我们将阐述Th17细胞在NAFL中的作用机制，为NASH早期干预提供新靶点。

非酒精性脂肪性肝病（Nonalcoholic fatty liver disease, NAFLD）是指除外酒 精、肝炎以及其他明确的损伤因素所导致的以肝细胞脂肪过度沉积为主要特征 的临床病理综合征，胰岛素抵抗和遗传易感性与其相关。流行病学数据提示 NAFLD 在世界范围内的患病率呈逐年升高趋势，我国的患病率也达到了15%，其中大约 15%的 NAFLD 患者可进展至 NASH（Non-alcoholic steatohepatitis），这些均为有限的医疗资源增添了沉重的负担。尽管NAFLD的发生与胰岛素抵抗、脂质代谢紊乱、遗传等多种因素相关，但其确切的发病机理至今尚未被人们完全认识从而限制了对其发生的有效预防和社区干预。既往研究显示CD4+T细胞在NAFLD进展至肝细胞癌（hepatocellular carcinoma，HCC）过程中呈动态变化，提示CD4+T细胞在NAFLD发生发展中可能具有重要意义。我们的前期研究发现游离脂肪酸FFA可抑制TH17细胞的分化，进一步体内研究发现小肠固有层中的TH17细胞在小鼠NASH模型中下降最为明显（ 论文已发表于 mBio. 2022 Jan，影响因子 7.786，附件1），并获得广东省自然科学基金面上的支持（附件2），我们推测FFA可通过抑制TH17细胞分化进而影响NAFLD进展。通过流式分析、m6A-RIP等手段，我们进一步通过体内外实验研究发现发现游离脂肪酸不仅降低TH17细胞m6A甲基化水平，而且通过影响SOCS3基因的m6A甲基化水平，影响SOCS3蛋白表达，进而抑制JAK-STAT通路，其最终结果是影响TH17细胞分化。本项目的提出m6A甲基化参与了FFA对TH17细胞的调控，认为FFA抑制TH17细胞的分化通过降低CD4+T的m6A甲基化水平，将对NAFLD的发生发展及其机制进行重要的补充，项目的实施过程将是通过不同学科、不同角度探讨NAFLD机制的有益尝试。