Identification of the molecules mediating the effects of resistance exercise training on pancreatic beta cell function and survival

Abstract

Resistance exercise improves glucose tolerance, reduces glycemia, and increases insulinemia in healthy and type 1 diabetic (T1D) mice. INS-1E cells (immortal rat pancreatic beta cells) treated with the serum from resistance-trained mice secrete more insulin in response to glucose, in addition, these cells are more resistant to injury and apoptosis induced by endoplasmic reticulum (ER) stress and pro-inflammatory cytokines. Thus, we believe that these alterations are mediated by exercise-induced molecules released in the bloodstream. In this context, this project aims to identify possible molecules that can mediate the effects of resistance exercise training on beta cells. For this, in the first phase of the project, we will use C57Bl/6 mice submitted to resistance training for blood collection and serum extraction. Next, we will analyze the serum (proteomics and/or metabolomics) in an attempt to identify and select one or more molecules for the study. Once the molecules are chosen, we will measure their concentration in the serum from control and trained mice, as well as the expression of their receptors in the pancreatic islets from trained mice. In the second phase of the project, we will investigate the role of the chosen molecules in insulin secretion, cell death, and the expression (gene and protein) of ER stress markers and apoptosis pathways, as well as the receptors of the molecules on beta cells, through three distinguished approaches: 1) INS-1E cells treated with the serum from trained mice in the presence or absence of inhibitors of the chosen molecules; 2) INS-1E cells treated with the molecules in different times of incubation and different concentrations; 3) INS-1E cells treated with the molecules and exposed to an ER stress inducer or pro-inflammatory cytokines. With these experiments, we will be able to confirm if the molecules chosen for the study can mediate resistance exercise-induced benefits on beta cell function and survival. In the third phase of the project, we will choose the molecule that displays the best results in the experiments in vitro, to evaluate its effects in a mice model of T1D. For this, we will use C57Bl/6 mice turned diabetic by multiple low doses of streptozotocin, which will be submitted to two types of interventions: a) treatment with the molecule or b) resistance training. Glucose homeostasis and pancreatic islet morphology will be evaluated, comparing both interventions in an attempt of verifying if the molecule itself will be able to mimic the benefits of resistance training. We believe that the characterization of the molecules identified in the serum from resistance-trained mice could be of great therapeutic interest, especially for T1D individuals, contributing to maintain their glycemic control, as well as their remaining beta cells.