Department of Anesthesiology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
Int J Mol Sci. 2020 Sep 19;21(18):6884. doi: 10.3390/ijms21186884.
MicroRNA-29a (miR-29a) has been shown to ameliorate hepatocellular damage, such as in the context of non-alcoholic fatty liver disease (NAFLD), steatohepatitis (NASH), and cholestatic injury. However, the mechanism mediating the hepatoprotective effect of miR-29a in diet-induced NASH remains elusive. In the present study, C57BL/6 mice of wild-type (WT) or miR-29a overexpression were fed with methionine-choline sufficient (MCS) or methionine-choline-deficient (MCD) diet for four weeks. The C57BL/6 mice harboring miR-29a overexpression presented reduced plasma AST, hepatic CD36, steatosis, and fibrosis induced by MCD. The TargetScan Release7.2-based bioinformatic analysis, KEGG pathway analysis, and luciferase reporter assay confirmed that miR-29a targets 3'UTR of glycogen synthase kinase 3 beta () mRNA in the HepG2 hepatocyte cell line. Furthermore, miR-29a overexpression in the MCD-fed group resulted in inhibition of mRNA and GSK3β protein levels in the liver. GSK3β was notably expressed jointly with the extent of aggregated protein, which was then identified to be associated with mitochondrial unfolded protein response (UPR), but not with endoplasmic reticulum UPR (UPR). Additionally, in silico analysis of protein-protein interaction, in vivo, and in vitro correlation analyses of protein expression demonstrated that GSK3β closely associated with sirtuin 1(SIRT1). Finally, the implication of SIRT1-mediated mitochondrial biogenesis in the perturbation of proteostasis was observed. We herein provide novel insight into a hepatoprotective pathway, whereby miR-29a inhibits GSK3β to repress SIRT1-mediated mitochondrial biogenesis, leading to alleviation of mitochondrial proteostatic stress and UPR in the context of NASH. miR-29a, GSK3β, and SIRT1 could thus serve as possible therapeutic targets to improve the treatment of NAFLD/NASH.
微小 RNA-29a（miR-29a）已被证明可改善肝细胞损伤，例如在非酒精性脂肪性肝病（NAFLD）、脂肪性肝炎（NASH）和胆汁淤积性损伤的情况下。然而，miR-29a 在饮食诱导的 NASH 中发挥肝保护作用的机制仍不清楚。在本研究中，野生型（WT）或 miR-29a 过表达的 C57BL/6 小鼠分别用蛋氨酸-胆碱充足（MCS）或蛋氨酸-胆碱缺乏（MCD）饮食喂养 4 周。过表达 miR-29a 的 C57BL/6 小鼠表现出降低的血浆天冬氨酸转氨酶（AST）、肝 CD36、脂肪变性和纤维化，这是由 MCD 诱导的。TargetScan Release7.2 生物信息学分析、KEGG 通路分析和荧光素酶报告基因测定证实，miR-29a 在 HepG2 肝细胞系中靶向糖原合酶激酶 3β（GSK3β）mRNA 的 3'UTR。此外，在 MCD 喂养组中过表达 miR-29a 导致肝脏中 GSK3β mRNA 和 GSK3β 蛋白水平的抑制。GSK3β 与聚集蛋白的程度明显表达相关，然后发现与线粒体未折叠蛋白反应（UPR）相关，而与内质网 UPR（UPR）无关。此外，通过蛋白质-蛋白质相互作用的计算机分析、体内和体外蛋白质表达相关性分析表明，GSK3β 与 SIRT1 密切相关。最后，观察到 SIRT1 介导的线粒体生物发生在蛋白质稳态失调中的作用。我们在此提供了一个新的肝保护途径的见解，miR-29a 通过抑制 GSK3β 来抑制 SIRT1 介导的线粒体生物发生，从而减轻 NASH 中与线粒体蛋白质稳态应激和 UPR 相关的蛋白。miR-29a、GSK3β 和 SIRT1 因此可能成为改善 NAFLD/NASH 治疗的潜在治疗靶点。
