Evaluation of the protective effect of metformin on endoplasmic reticulum stress by modulating microRNAs in the pancreatic beta cell INS-1E

Abstract

The endoplasmic reticulum (ER) stress consists of mechanisms related to the progressive decline beta cell function and mass in type 2 diabetes mellitus (DM2). The loss of ER homeostasis activates stress responses, the UPR (unfolded protein response), which can be induced, among other factors, by free fatty acids or inflammatory cytokines. Metformin is an antihyperglycaemic drug widely used in the treatment of patients newly diagnosed with DM2, mainly by obese patients. Metformin regulates blood glucose levels primarily by lowering hepatic glucose production and improving insulin sensitivity, but its effects on pancreatic beta cells are not yet fully understood. There is evidence that metformin modulates plasma microRNAs (miRs) in diabetic patients, suggesting that the beneficial effects of this drug are mediated by miRs. In addition, it is known that miRs can modulate the expression of stress components of RE, and therefore, regulate UPR in the cell. In view of the relevance of the miRs in the regulation of ER stress proteins in the beta cell, this project aims to evaluate the protective role of metformin on stress of RE by modulating the expression pattern of specific miRs, in pancreatic beta cells INS-1E. Cells will be cultured and exposed to 12.4 ¼M CPA (an ER stress inducer) and treated with 0.5 mM metformin for 16 h. The following miRs will then be evaluated: miR-375, miR-15a, miR-16, miR-30d, miR-34a, miR-96, miR-124a, miR-200, miR-202, miR-222 and miR-211. Treatment with metformin will allow the identification of which miRs have been modulated in order to improve the stress of RE effects in response to the drug. After that, two miRs will be selected from those evaluated, and the cells will then be treated with their respective antagomiRs, whose effects will be evaluated through the analysis of the content of proteins involved in ER stress. In this way, it will be possible to obtain miRs relevant to the beneficial response with the treatment of metformin. This project will provide a better understanding of the use of an important drug and also point out possible new targets that may be relevant in the development of therapeutic strategies.