Department of General Surgery, The Third Xiangya Hospital, Central South University, 138 Tongzipo Road, Changsha 410013, China; Department of General Surgery, Xiangya Hospital, Central South University, No.87 Xiangya Road, Changsha 410008, China.
Department of General Surgery, The Third Xiangya Hospital, Central South University, 138 Tongzipo Road, Changsha 410013, China.
Metabolism. 2019 May;94:1-8. doi: 10.1016/j.metabol.2019.01.018. Epub 2019 Feb 1.
Hepatic lipogenesis dysregulation is essential for the development of non-alcoholic fatty liver disease (NAFLD). Emerging evidence indicates the importance of the involvement of long non-coding RNAs (LncRNAs) in lipogenesis. However, the specific mechanism underlying this process is not clear.
This study aimed to investigate the functional implication of LncRNA MEG3 (MEG3) in fatty degeneration of hepatocytes and in the pathogenesis of NAFLD.
The expression of MEG3 was analysed in in vitro and in vivo models of NAFLD, which were established by free fatty acid (FFA)-challenged HepG2 cells and high-fat diet-fed mice, respectively. Endogenous MEG3 was over-expressed by a specific pcDNA3.1-MEG3 to evaluate the regulatory function of MEG3 on triglyceride (TG)- and lipogenesis-related genes. Bioinformatic analysis was used to predict the target genes and binding sites, and the targeted regulatory relationship was verified with a dual luciferase assay. Finally, the possible pathway that regulates MEG3 was also evaluated.
We found that the downregulation of MEG3 in vitro and in vivo models of NAFLD was negatively correlated with lipogenesis-related genes and that overexpression of MEG3 reversed FFA-induced lipid accumulation in HepG2 cells. miR-21 was upregulated in the FFA-challenged HepG2 cells and was physically associated with MEG3 in the process of lipogenesis. Our mechanistic studies demonstrated that MEG3 competitively binds to miR-21 with LRP6, followed by the inhibition of the mTOR pathway, which induces intracellular lipid accumulation.
Our data are the first to document the working model of MEG3 functions as a potential hepatocyte lipid degeneration suppressor. MEG3 helps to alleviate lipid over-deposition, probably by binding to miR-21 to regulate the expression of LRP6. Our results suggest the potency of MEG3 as a biomarker for NAFLD and as a therapeutic target for treatment.
肝脂生成失调是非酒精性脂肪性肝病（NAFLD）发展的关键。新出现的证据表明长链非编码 RNA（LncRNA）在脂生成中的作用很重要。然而，这一过程的确切机制尚不清楚。
本研究旨在探讨 LncRNA MEG3（MEG3）在肝细胞脂肪变性和 NAFLD 发病机制中的功能意义。
采用游离脂肪酸（FFA）刺激的 HepG2 细胞和高脂肪饮食喂养的小鼠分别建立 NAFLD 的体外和体内模型，分析 MEG3 的表达。通过特异性 pcDNA3.1-MEG3 过表达内源性 MEG3，评估 MEG3 对甘油三酯（TG）和脂生成相关基因的调控作用。生物信息学分析用于预测靶基因和结合位点，并通过双荧光素酶测定验证靶向调控关系。最后，还评估了调节 MEG3 的可能途径。
我们发现，在 NAFLD 的体外和体内模型中，MEG3 的下调与脂生成相关基因呈负相关，而过表达 MEG3 可逆转 FFA 诱导的 HepG2 细胞脂质堆积。miR-21 在 FFA 刺激的 HepG2 细胞中上调，并在脂生成过程中与 MEG3 发生物理结合。我们的机制研究表明，MEG3 与 LRP6 竞争性结合 miR-21，随后抑制 mTOR 通路，导致细胞内脂质堆积。
我们的数据首次记录了 MEG3 作为潜在的肝细胞脂质变性抑制因子的工作模式。MEG3 有助于减轻脂质过度沉积，可能通过与 miR-21 结合来调节 LRP6 的表达。我们的研究结果表明，MEG3 作为 NAFLD 的生物标志物和治疗靶点具有潜力。
