microRNA-206 Regulates Pancreatic-β-Cell Function via Targeting Insulin-Like Growth Factor 1

Abstract

Background: Diabetes mellitus (DM), a common metabolic disease, is featured with chronic hyperglycemia and dysfunction of pancreatic β-cells. Various evidences suggested that microRNAs (miR-NAs) were tightly related to the occurrence of DM and can be regulated in pancreatic-β-cells. However, whether or not microRNA-206 (miR-206) affects the development of DM and the specific mechanisms remains elusive. We designed this study to clarify the function and associated potential mechanism of miR-206 in pancreatic β-cells via the insulin-like growth factor 1 reporter (IGF1R)/phosphatidylinositide 3-kinase (PI3 K)/protein kinase B (AKT) signaling pathway, which may provide novel diagnostic or therapies for DM. Methods: In this research, the levels of miR-206 and insulin-like growth factor 1 (IGF1) were assessed using quantitative reverse transcription PCR (qRT-PCR) and/or Western bolt assay. Bioinformatics and dual luciferase reporter assays were adopted to illustrate the relationship between miR-206 and IGF1. INS-1 cells were stimulated with stimulatory glucose (16.7 mM) or basal glucose (3.3 mM) for 1 h, and the insulin content was examined by enzyme linked immunosorbent assay (ELISA). Besides, 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay and flow cytometry (FCM) analysis were conducted to determine the INS1 cell viability and apoptosis. Furthermore, the related proteins in IGF1R/PI3 K/AKT pathway (IGF1R, p-AKT and AKT) were tested using Western blot assay, respectively. Results: Our data suggested that miR-206 level in the blood samples of DM patients was higher than that in healthy donors. IGF1 was identified as a direct target of miR-206. Moreover, we found that miR-206 negatively regulated IGF1 expression in INS-1 cells. It was also confirmed that miR-206 inhibitor led to an increase of total insulin content, an increase of INS-1 cell viability and a decrease of cell apoptosis. Accordingly, miR-206 inhibitor significantly enhanced IGF1R and p-AKT protein expression in INS-1 cells. All these findings were reversed by IGF1-siRNA co-transfection. Conclusion: Our observations clearly demonstrated that miR-206 could regulate the IGF1R/PI3K/AKT pathway by targeting IGF1, thereby regulating the cell viability of pancreatic β cells and the ability of pancreatic β cells to secrete insulin.