MiR-495 regulates macrophage M1/M2 polarization and insulin resistance in high-fat diet-fed mice via targeting FTO.

MicroRNA 495 (miR-495) has been discovered to be involved in the metabolism and immune response in human body. The purpose of this study was to investigate the effect of miR-495 on macrophage M1/M2 polarization and insulin resistance in type 2 diabetes (T2D). A T2D mouse model was established by feeding C57BL/6 mice with a high-fat diet (HFD). The expressions of M1/M2 polarization markers and miR-495 in peritoneal macrophages were determined by qRT-PCR or Western blot. Mouse insulin tolerance test (ITT) and glucose tolerance test (GTT) were performed, and the targeted binding effect between miR-495, fat mass, and obesity-associated gene (FTO) was verified by double luciferase gene reporter assay. The body weight, blood glucose content, and miR-495 expression in macrophages of the HFD group were remarkably higher than those of the normal diet (ND) group. Besides, miR-495 induced the transformation of macrophages into M1-type pro-inflammatory macrophages and enhanced the insulin resistance of T2D mice. More importantly, FTO was proved to be a direct target gene of miR-495 and silencing FTO could induce the transformation of macrophages into M1-type pro-inflammatory macrophages. These results demonstrated that miR-495 could promote the transformation of macrophages into M1-type pro-inflammatory macrophages by inhibiting the expression of its target gene FTO, and aggravate the insulin resistance and adipose tissue inflammation in T2D mice, which provided a certain theoretical basis for the targeted treatment of T2D.