Department of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan.
Department of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan; Department of Earth and Life Science, University of Taipei, Taipei, Taiwan.
Cell Signal. 2021 May;81:109930. doi: 10.1016/j.cellsig.2021.109930. Epub 2021 Jan 28.
MicroRNA-27 is a critical non-coding metabolic gene that is often aberrantly overexpressed in non-alcoholic fatty livers (NAFLD). However, the pathogenic role of miR-27 in NAFLD remains unknown. In this study, we attempted to identify the mechanism by which miR-27 was regulated in the context of insulin resistance, a predisposed metabolic disorder in NAFLD. Our data from cell culture and animal studies showed that insulin, CREB, and Hippo signalings coordinately regulated miR-27. First, miR-27 was upregulated in palmitate-treated cells and high fat diet-fed mouse livers, which exhibited insulin resistance and CREB overexpression. Second, miR-27 peaked in the mouse liver at the post-absorptive phase when CREB activity was increased. Also, miR-27 was increased rapidly in cell lines when CREB was deactivated by insulin treatment. Third, miR-27 was decreased in cultured cells when CREB was downregulated by siRNA or metformin treatment. In contrast, Forskolin-mediated activation of CREB promoted miR-27 expression. Fourth, Hippo signaling repressed miR-27 in a CREB-independent manner: miR-27 was reduced in cells at full confluence but was inhibited in cells transfected with siRNA against Lats2 and Nf2, which were two positive regulators of Hippo signaling. Lastly, bioinformatics and luciferase assay showed that miR-27 inhibited Akt phosphorylation by targeting Pdpk1 and Pik3r1. Overexpression of miR-27 impaired Akt phosphorylation in cell lines and primary mouse hepatocytes upon insulin stimulation. In conclusion, our data suggest that insulin, CREB, and Hippo signalings contribute to aberrant miR-27 overexpression and eventually lead to insulin resistance in NAFLD.
miR-27 是一种关键的非编码代谢基因，在非酒精性脂肪性肝病（NAFLD）中经常异常过表达。然而，miR-27 在 NAFLD 中的致病作用尚不清楚。在这项研究中，我们试图确定胰岛素抵抗情况下 miR-27 调节的机制，胰岛素抵抗是 NAFLD 中一种易患的代谢紊乱。我们的细胞培养和动物研究数据表明，胰岛素、CREB 和 Hippo 信号协同调节 miR-27。首先，miR-27 在棕榈酸处理的细胞和高脂肪饮食喂养的小鼠肝脏中上调，这些细胞表现出胰岛素抵抗和 CREB 过表达。其次，当 CREB 活性增加时，miR-27 在小鼠肝脏中的吸收后阶段达到峰值。此外，当胰岛素处理使 CREB 失活时，miR-27 在细胞系中迅速增加。第三，当用 siRNA 或二甲双胍处理下调 CREB 时，培养细胞中的 miR-27 减少。相反， forskolin 介导的 CREB 激活促进了 miR-27 的表达。第四，Hippo 信号以 CREB 独立的方式抑制 miR-27：在细胞完全汇合时 miR-27 减少，但在用针对 Lats2 和 Nf2 的 siRNA 转染的细胞中被抑制，Lats2 和 Nf2 是 Hippo 信号的两个正调节剂。最后，生物信息学和荧光素酶测定表明，miR-27 通过靶向 Pdpk1 和 Pik3r1 抑制 Akt 磷酸化。在胰岛素刺激下，miR-27 的过表达会损害细胞系和原代小鼠肝细胞中的 Akt 磷酸化。总之，我们的数据表明，胰岛素、CREB 和 Hippo 信号有助于异常的 miR-27 过表达，并最终导致 NAFLD 中的胰岛素抵抗。
