MiR-149 Compromises the Reactions of Liver Cells to Fatty Acid via its Polymorphism and Increases Non-Alcoholic Fatty Liver Disease (NAFLD) Risk by Targeting Methylene Tetrahydrofolate Reductase (MTHFR)

BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is a worldwide health problem, and microRNA (miRNA) has been reported to be involved in NAFLD. The objective of our study was to explore the effect of polymorphism in miR-149 on the pathogenesis of NAFLD. MATERIAL AND METHODS Real-time PCR was performed to explore the effect of long-chain fatty acid (FFA) on the level of miR-149 and methylene tetrahydrofolate reductase (MTHFR). Then in-silicon analysis and luciferase assay were investigated to verify MTHFR was the target gene of miR-149. Finally, Western-blot analysis and real-time PCR were performed to confirm the control of MTHFR by miR-149. RESULTS In this study, we found that miR-149 was apparently upregulated in hepatocytes genotyped as TT treated with FFA; and MTHFR in hepatocytes genotyped as TT treated with FFA was evidently downregulated compared to control. Whereas, FFA had no obvious effect on MTHFR level in hepatocytes genotyped as CC. We searched an online miRNA database and found that miR-149 was a regulator of MTHFR expression, which was confirmed by luciferase assay. In hepatocytes genotyped as TT and treated with or without FFA, miR-149 mimic dose-dependently decreased the level of MTHFR, and miR-149 inhibitor dose-dependently increased the level of MTHFR. And in hepatocytes genotyped as CC treated with or without FFA exhibited a similar inhibition effect of miR-149 on expression of MTHFR. CONCLUSIONS The data suggested that the polymorphism in miR-149 played an important role in the development of NAFLD via altering the expression of miR-149 as well as its target, MTHFR.