Long noncoding RNA Mirt2 upregulates USP10 expression to suppress hepatic steatosis by sponging miR-34a-5p

Non-alcoholic fatty liver disease (NAFLD) is always characterized by hepatic steatosis and insulin resistance. Dysregulated long noncoding RNAs regulate pathogenesis of NAFLD. However, the role of Mirt2 (long noncoding RNA myocardial infraction associated transcript 2) in NAFLD remains unclear. This original study aims to investigate the role of Mirt2 in hepatic steatosis and insulin resistance. Mirt2 was decreased in the livers of high-fat diet (HFD) mice, Ob/Ob, Db/Db, and fasting mice. Hepatic Mirt2 restoration attenuated hyperglycemia, insulin resistance and steatosis in the livers of obese mice, and Mirt2 inhibition promoted fasting hyperglycemia and lipid droplets accumulation in normal mouse livers. Furthermore, overexpression of Mirt2 resulted in suppression of miR-34a-5p, whereas knockdown of Mirt2 exerted opposite effects in the livers. Then, miR-34a-5p was a positive regulator of NAFLD by targeting USP10, which serves as a negative regulator of NAFLD. Overexpression of Mirt2 made miR-34a-5p mimic fail to reduce luciferase activity of USP10 3'-UTR, and this regulation was also demonstrated by Western blot. Similarly, overexpression of miR-34a-5p significantly let Mirt2 lost the ability to elevate USP10 protein level. Thus, Mirt2 can function as the sponge of miR-34a-5p. Moreover, Mirt2-mediated upregulation of USP10 protein expression can be reversed by silencing USP10. USP10 inhibition could abolish Mirt2 overexpression-induced suppression of glucose production and lipogenesis in hepatocytes. In conclusion, the decrease of Mirt2 expression contributed to hepatic insulin resistance and steatosis in obese mice, and Mirt2/miR-34a-5p/USP10 was involved in NAFLD development. Overexpression of Mirt2 might be a promising strategy for treatment of NAFLD.