尿酸调控肝脏miR-149表达并诱导NAFLD发病的分子机制

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent and clinically significant chronic liver diseases worldwide, while its pathogenesis has not been fully understood. We previously found that hyperuricemia is closely associated with NAFLD. We also found that hyperuricemia significantly upregulated hepatic miR-149 expression, while lowering uric acid by allopurinol significantly downregulated hepatic miR-149 expression and ameliorated high fat diet induced hepatic steatosis. These results indicated that miR-149 is very likely to be a key mediator for the effect of uric acid on NAFLD. This study aims to explore the regulatory effect of uric acid on hepatic miR-149 expression and its downstream mechanisms in pathogenesis of NAFLD. The expression of miR-149 will be manipulated both in vitro and in vivo, and the functional consequences of these manipulations on hepatic steatosis, miR-149 target genes including FGF21, cyclin D1 and FoxM1, and their downstream molecules involved in hepatic lipid metabolism will be analyzed. The potential regulatory mechanisms of miR-149 in NAFLD will also be explored by microarray analysis, followed by qRT-PCR validation and functional investigations. This study will provide new evidence to expand our understanding of the mechanisms behind the relationship between hyperuricemia and NAFLD, and pave the way for the eventual development of hypouricemic therapy for the disease.

非酒精性脂肪性肝病（NAFLD）是临床常见且危害重大的慢性肝病，其发病机制尚未完全阐明。本项目组以往的研究发现，高尿酸是引发NAFLD的重要原因，并且高尿酸显著上调肝脏miR-149表达，降尿酸干预则下调miR-149并改善肝脏脂变，提示miR-149极可能是介导高尿酸引发NAFLD的关键分子。本项目拟在已有基础上，进一步确定高尿酸调节肝脏miR-149表达的时效及量效关系，同时建立miR-149表达干预技术并结合基因敲除小鼠，分析miR-149表达变化对高尿酸诱导NAFLD的影响，以及对靶基因FGF21、Cyclin D1和FoxM1及其下游的FAT、HADH、ChREBP、PPARγ、Cathepsin D等调控肝脏脂质代谢相关分子的调节作用，并用表达谱芯片筛选和验证miR-149新的靶基因及其调节机制。本项目实施将揭示高尿酸引发NAFLD的新机制，并为疾病防治提供新的理论依据。

非酒精性脂肪性肝病(NAFLD)是临床常见且危害重大的慢性肝病，其发病机制尚未完全阐明。本项目组以往的研究发现，高尿酸是引发NAFLD的重要原因，高尿酸显著上调肝脏miR-149-5p表达，降尿酸干预则下调miR-149-5p表达并改善肝脏脂变，提示miR-149-5p可能是介导高尿酸引发NAFLD的关键分子。本项目按计划探讨了miR-149-5p在高尿酸诱导NALFD过程中的作用及机制。细胞学实验证实，高尿酸刺激显著上调肝细胞miR-149-5p表达。过表达miR-149-5p可以显著加重高尿酸诱导的肝细胞脂变，而抑制miR-149-5p可以显著减轻高尿酸诱导的肝细胞脂变。进一步机制研究发现，成纤维细胞生长因子21（Fgf21）为miR-149-5p的靶基因，miR-149-5p对FGF21具有翻译抑制作用。沉默Fgf21可显著消除miR-149-5p抑制剂对尿酸诱导的肝细胞脂变的改善作用，而过表达Fgf21可显著缓解miR-149-5p模拟物对尿酸诱导的肝细胞脂变的加重作用，提示miR-149-5p通过FGF21介导尿酸对肝细胞的脂质贮积作用，从而影响NAFLD发生发展。.此外，本项目组在分析miRNA芯片数据时还发现，高脂饮食小鼠的肝脏miR-376b-3p表达显著下调，细胞学和小鼠实验验证了miR-376b-3p在NAFLD模型中的表达变化。在体外，过表达miR-376b-3p显著减轻游离脂肪酸（FFA）诱导的肝细胞脂变，而抑制miR-376b-3p显著加重FFA诱导的肝细胞脂变。小鼠实验发现，过表达miR-376b-3p可以缓解高脂饮食诱导的NAFLD，而抑制miR-376b-3p则加重高脂饮食诱导的NAFLD。进一步机制研究发现，miR-376b-3p对肝细胞脂质氧化通路具有调节作用。生物信息学分析及细胞学实验发现，成纤维细胞生长因子受体1（Fgfr1）为miR-376b-3p的靶基因。细胞学和小鼠实验发现，miR-376b-3p通过靶向作用于Fgfr1，调节脂质氧化通路，从而影响NAFLD发生发展。.本项目研究揭示了miR-149-5p和miR-376b-3p在NAFLD中的作用及机制，相关结果为进一步认识NAFLD发病机制并为疾病防治提供了新的线索。