DDX3-mediated miR-141 expression promotes NAFLD by targeting SIRT1/autophagy axis

Background and Aim: Non-alcoholic fatty liver disease (NAFLD), a metabolic disorder, is now one of the leading causes of chronic liver disease. Recent reports suggest that DEAD-box RNA helicase (DDX3) acts as sensor of free fat accumulation which belongs to family of RNA-binding proteins. DDX3 plays a crucial role in biogenesis of miRNAs and promotes pre-miRNAs conversion into mature miRNAs. Hence, we hypothesized that DDX3 might affect the NAFLD progression via involvement of miRNAs. Methods: C57BL/6 mice (6 mice per group) were fed with control diet, choline sufficient L-amino acid (CSAA) diet, or choline-deficient L-amino acid (CDAA) diet. After 6, 18, 32, and 54 weeks, the mice were euthanized, and the protein was isolated from the homogenized liver tissues, and DDX3 expression was determined. Huh7 cells were treated with free fatty acids (FFAs) and DDX3 expression was analysed. The expression of miR-141 was determined in Huh7 cells with DDX3 over-expression and knock-down using plasmid and siRNA, respectively. Huh7 cells were transfected with miR-141 mimics, and its effect on SIRT1 expression was analysed. Huh7 cells were transfected with DDX3 siRNA, and its effect on expression of SIRT1, beclin-1, ATG7 and LC3B were studied. Results: The DDX3 expression was increased in CDAA diet-fed mice, and in FFA-treated Huh7 cells. Downregulation or upregulation of DDX3 resulted in intracellular upregulation or downregulation of miR-141 in Huh7 cells, respectively. Transfection of Huh7 cells with miR-141 mimics downregulated SIRT1 expression, and DDX3 knock-down upregulated SIRT1 expression. ATG7, beclin1 and LC3B expression was upregulated in DDX3 knocked down Huh7 cells. Conclusion: This result suggested that in NAFLD, the DDX3 expression is upregulated, resulting in enhanced expression of miR-141, which in result targeted SIRT1 expression causing decreased autophagy.