尿酸对肝细胞miR-92a的调节作用及其影响NAFLD的分子机制研究

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide, while its pathogenesis has not been fully elucidated. Our previous clinical and experimental studies found that hyperuricemia is closely associated with NAFLD. We also found that uric acid stimulation significantly upregulated miR-92a expression and induced fat accumulation in hepatocytes. The effect of uric acid on fat accumulation could be blocked by miR-92a mimics. These results suggested that miR-92a is very likely to be a key mediator for the effect of uric acid on NAFLD. Current study aims to investigate the regulatory effect of uric acid on miR-92a expression and the downstream mechanisms by which miR-92a mediates the effect of uric acid on NAFLD. The expression of miR-92a will be manipulated both in vivo and in vitro, and the functional consequences of these manipulations on the degree of hepatic steatosis, expressions of miR-92a targets, including KLF2, KLF4, FOXP1, PTEN and DUSP10, and their downstream molecules involved in hepatic glucose and lipid metabolism will be analyzed. The regulatory mechanisms of miR-92a in NAFLD will also be investigated by microarray analysis, followed by qRT-PCR validation and functional analysis. The results of this study will expand our understanding of the molecular mechanisms behind the association between hyperuricemia and NAFLD, and assist in the eventual development of hypouricemic therapy for the disease.

非酒精性脂肪性肝病（NAFLD）是临床常见的慢性肝病，其发病机制尚未完全明确。本项目组以往发表于J Hepatol等期刊的系列研究发现，高尿酸是引发NAFLD的重要原因；预实验还发现高尿酸刺激显著上调肝细胞miR-92a表达，抑制miR-92a能减轻高尿酸诱导的肝细胞脂变，提示miR-92a极可能是介导高尿酸引发NAFLD的关键分子，但具体下游机制尚不清楚。本项目拟在已有基础上，进一步确定高尿酸调节肝细胞miR-92a表达的时效及量效关系，同时建立miR-92a表达干预技术并结合基因敲除小鼠，分析miR-92a表达变化对高尿酸诱导NAFLD的影响，以及对靶基因KLF2/4、FOXP1、PTEN、DUSP10及其下游参与影响肝脏糖脂代谢相关分子的调节作用，并用表达谱芯片筛选和验证miR-92a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）是临床常见的慢性肝病，其发病机制尚未完全明确。本项目聚焦NAFLD的代谢机制。首先，我们探讨了miR-92a在高尿酸诱导NALFD过程中的作用及机制。细胞学实验发现，高尿酸刺激显著上调肝细胞miR-92a表达，抑制miR-92a可减轻高尿酸诱导的肝细胞脂变，但过表达miR-92a对肝细胞脂变程度并无影响；小鼠实验发现，尽管高尿酸饮食能上调小鼠肝脏miR-92a的表达，上调或下调肝细胞miR-92a的表达水平对小鼠肝脏脂变程度均无显著影响，提示小鼠肝脏中miR-92a表达上调很可能是高尿酸诱导肝细胞脂变的伴随改变，而不是介导高尿酸诱导肝细胞脂变的关键miRNA。本项目组转而关注miRNA芯片筛选出的另一个差异miRNA（miR-376b-3p）在NAFLD中的作用及机制，发现miR-376b-3p在NAFLD细胞及小鼠模型中显著下调。小鼠实验发现，敲低miR-376b-3p显著加重小鼠胰岛素抵抗和肝脏脂变程度，而过表达miR-376b-3p显著改善胰岛素抵抗和肝脏脂变程度，并且miR-376b-3p对肝细胞脂质氧化关键分子具有调节作用。进一步机制研究发现，miR-376b-3p通过成纤维细胞生长因子受体1（Fgfr1）调节脂质氧化并影响NAFLD。本项目组还依托NAFLD队列及标本库，分析了维生素D代谢与NAFLD的关系，结果发现维生素D缺乏与肥胖人群的NAFLD患病风险密切相关，并且NAFLD患者肝脏维生素D受体（VDR）表达显著上调，VDR通过肝细胞核因子4α（HNF4α）依赖途径调节NAFLD。我们也利用本项目建立的NAFLD细胞与小鼠模型，确认了GCSF、LECT2等分子在NAFLD中的作用及机制。我们还通过前瞻性研究，探讨了尿酸代谢紊乱等因素对NAFLD发病风险的影响，以及饮酒对NAFLD患者2型糖尿病发病风险的影响。项目实施过程中，项目组成员撰写了两篇NAFLD代谢机制相关综述。以上结果发表于Am J Gastroenterol、J Biol Chem、Metabolism等期刊，项目负责人作为主要完成人获得中华医学科技奖二等奖。本项目研究结果揭示了NAFLD发病新机制，并为疾病防治提供了潜在新方法。