miR-23b正向调控靶基因抑制非酒精性脂肪肝的机制研究

Recently, we first reported that overexpression of miR-23b could reverse diabetic nephropathy. However we also found increased miR-23b could decreased db/db mice body and white fat weight, which indicated miR-23b is related to lipid metabolism or non-alcoholic fatty liver disease(NAFLD). Interestingly our preliminary experiments showed excessive miR-23b could inhibit NAFLD. Traditionaly study consider miRNA is negative with target gene. Whereas the newly research found miRNA stabilize or promote mRNA expression by binding to 5'UTR and enhancer sequence, which is called positive regulation that is becomed central issue. Furthermore，if miRNA reverse NAFLD through postive regulation of target is not clear. Accordingly, we hypothesized that miR-23b may positively regulate target to inhibit NAFLD process and affect AMPK, P38MAPK or PPAR signal pathway, or these pathway cross-talk. In this project, we employed a series of molecular and cellular methods to confirm a axis of miR-23b and target gene in vivo and in vitro study. This may provide a new target for intervene NAFLD, and theoretically develop new concept of miRNA postive regulate target mRNA.

我们首先报告了过表达miR-23b逆转糖尿病db/db小鼠肾病,同时还降低了小鼠体重及白脂肪重量。这提示我们miR-23b可能与脂代谢或者非酒精性脂肪肝(NAFLD)相关，我们的预实验证明升高miR-23b可以抑制NAFLD。传统研究认为miRNA负向调控靶基因。而新近发现的miRNA通过结合靶基因的5’UTR或者增强子序列促进靶基因的稳定或表达，这一正向调控现象成为了miRNA研究的热点。但目前不清楚miRNA是否通过正向调控靶基因抑制NAFLD。因此，我们假设：miR-23b抑制NAFLD是通过正向调控靶基因，进而调控AMPK、P38MAPK、PPAR信号通路或者介导它们之间的交联。本项目将采用在体和离体实验相结合的病理模型，运用多种手段，证明体内存在一个“以miR-23b为起点，以其靶基因为节点”的信号轴，为干预NAFLD提供新靶点，并从理论上扩展“miRNA正向调控”的新概念。

非酒精性脂肪肝（NAFLD）是指除酒精和其他明确的肝损伤因素以外所致的以肝实质细胞脂肪变性和脂肪贮积为主要特征的临床病理综合征，但其发病机制不清。我们既往研究发现给予肥胖小鼠dbdb小鼠可以显著降低db/db小鼠体重，因此我们推测miR-23b可能参与脂代谢过程，尤其是NAFLD的发生。在本项目中，我们首先发现miR-23b在临床NAFLD患者血清中表达降低。同时正常C57小鼠降低miR-23b表达可以导致NAFLD，具体表现为：血清甘油三酯、低密度脂蛋白显著升高，肝脏病理检测发现大量脂肪空泡、油红染色强阳性。更重要的是，我们还证实miR-23b基因敲除小鼠也表现为同样症状。我们给予dbdb小鼠miR-23b类似物，即过表达miR-23b，db/db小鼠NAFLD症状显著减轻，主要包括：体重降低，血脂及肝功明显改善，肝脏病理表现为脂肪空泡减少，肝脏纤维化显著降低。我们进行肝脏RNA-seq发现miR-23b通过调节靶基因AMPK信号通路中的Acot4分子进而调控了NAFLD的发生。本项目另一重大发现为miR-23b基因敲除小鼠可以导致IgA肾病的发生。5月龄的miR-23b基因敲除小鼠检测发现：尿蛋白、血肌酐显著升高，肾脏病理检测发现IgA、C3免疫荧光强阳性，IgG/IgM无明显变化。同时血清中IgA也显著升高，IgG/IgM无明显变化。进一步研究发现调控IgA向IgM转换的关键酶AICDA是miR-23b的关键靶基因。综上所述，本项目进展顺利，围绕本课题，申请者共发表SCI文章6篇，其中2篇为领域内Top级期刊，获得授权专利1项。.