miR-335-3p improves type II diabetes mellitus by IGF-1 regulating macrophage polarization

Previous studies have found that miR-335 is highly expressed in type II diabetes mellitus (T2DM) models and is related to insulin secretion, but there are few studies on the regulatory effects of miR-335-3p on insulin resistance and macrophage polarization in T2DM patients. This study aims to explore the effects of miR-335-3p on insulin resistance and macrophage polarization in T2DM patients. Blood glucose (insulin tolerance tests, glucose tolerance tests) and body weight of the T2DM model were measured; macrophages from adipose tissue were isolated and cultured, and the number of macrophages was detected by F4/80 immunofluorescence assay; the Real-time quantitative polymerase chain reaction (qPCR) assay and Western blot assay were used to detect the miR-335-3p expression levels, insulin-like growth factor 1 (IGF-1), M1-polarizing genes (inducible nitric oxide synthase [iNOS] and TNF-α) as well as M2-polarizing genes (IL-10 and ARG-1). The targeting link between miR-335-3p and IGF-1 was confirmed using bioinformatics and dual luciferase assay. The results showed that miR-335-3p expression level in adipose tissue of the T2DM model was significantly decreased, and the mice’s body weight and blood glucose levels dropped considerably, miR-335-3p inhibited the number of macrophages, inhibiting the iNOS and TNF-α relative mRNA expression levels, and up-regulated the IL-10 and ARG-1 relative mRNA expression levels, miR-335-3p negatively regulated target gene IGF-1, IGF-1 significantly increased the iNOS and TNF-α mRNA and protein expression levels, decreasing the IL-10 and ARG-1 mRNA and protein expression levels, indicating that miR-335-3p could affect the T2DM process by regulating macrophage polarization via IGF-1.