Free fatty acid-induced miR-22 inhibits gluconeogenesis via SIRT-1-mediated PGC-1α expression in nonalcoholic fatty liver disease

Free fatty acids (FFAs) are one of the important regulators of the progression of nonalcoholic fatty liver disease. The FFAs are shown to modulate the metabolic status of the liver by modulating several cellular pathways in hepatocytes. Here, we elucidated the role of miR-22 in modulating FFAs-mediated gluconeogenesis. Huh7 and WRL68 cells were transfected with nonspecific miRNA, miR-22 premiRs or anti-miR-22 oligos followed by incubation with palmitic acid, oleic acid, and linoleic acid (300 μM each) for 48 and 72 h after transfection. The expression of miR-22 was performed using real-time polymerase chain reaction and Western blots were performed for SIRT-1, PGC-1α, PEPCK, and glucose-6-phosphatase. Three groups of C57BL/6 mice (6 mice per group) were fed with standard diet, choline sufficient l-amino acid defined diet or choline-deficient l-amino acid defined (CDAA) diet for 6, 18, 32, or 54 weeks. Triglycerides content was measured in the serum. Expression of miR-22 and the protein expression of gluconeogenic enzymes were analyzed in the tissue samples. Incubation of miR-22-transfected cells with FFAs inhibited the expression of SIRT-1, PGC-1α, PEPCK, and glucose-6-phosphatase, while miR-22 expression was increased. These changes were reversed when the cells were transfected with anti-miR-22 oligos. CDAA-fed mice showed the significant increase in triglycerides content and miR-22 expression, while there was an inhibition of SIRT-1, PGC-1α, PEPCK, and glucose-6-phosphatase expression in CDAA-fed mice. These data confirm that FFAs inhibited gluconeogenesis via miR-22-mediated inhibition of SIRT-1, which in turn inhibited PGC-1α in hepatic cells.