The effect of miR-471-3p on macrophage polarization in the development of diabetic cardiomyopathy

Aims: The imbalance of M1/M2 macrophage ratio promotes the occurrence of diabetic cardiomyopathy (DCM), but the precise mechanisms are not fully understood. The aim of this study was to investigate whether miR-471-3p/silent information regulator 1 (SIRT1) pathway is involved in the macrophage polarization during the development of DCM. Methods: Immunohistochemical staining was used to detect M1 and M2 macrophages infiltration in the heart tissue. Flow cytometry was used to detect the proportion of M1 and M2 macrophages. Expression of miR-471-3p was quantified by real time quantitative-PCR. Transfection of miRNA inhibitor into RAW264.7 cells was performed to investigate the underlying mechanisms. Bioinformatics methods and western blotting were used to explore the target gene of miR-471-3p and further confirmed by dual luciferase reporter assay. Key findings: We observed that M1 macrophages infiltration in the heart of tissue in DCM while M2 type was decreased. M1/M2 ratio was increased significantly in bone marrow-derived macrophages (BMDMs) from db/db mice and in RAW264.7 cells treated with advanced glycation end products (AGEs). Meanwhile, miR-471-3p was significantly upregulated in RAW264.7 cells induced by AGEs and inhibition of miR-471-3p could reduce the inflammatory polarization of macrophages. Bioinformatics analysis identified SIRT1 as a target of miR-471-3p. Both dual luciferase reporter assay and western blotting verified that miR-471-3p negatively regulated SIRT1 expression. SIRT1 agonist resveratrol could downregulate the increased proportion of M1 macrophages induced by AGEs. Conclusion: Our results indicated that the development of DCM was related to AGEs-induced macrophage polarized to M1 type through a mechanism involving the miR-471-3p/SIRT1 pathway.