Insulin resistance is a common metabolic complication in aged and obese skeletal muscle that is central to the pathophysiology of type 2 diabetes (T2D). In order to develop strategies to treat insulin resistance it is necessary to define the signaling transduction steps that lead to insulin-stimulated glucose uptake, particularly in skeletal muscle and adipocytes; remarkably, these steps have yet to be fully elucidated. Thus, the long-term objective of this research is to expand the knowledge of the molecular regulation of insulin-stimulated glucose transport. Currently, phosphorylation-based signaling from the insulin receptor through phosphoinositide 3- kinase (PI3K)-Akt, to Akt substrate of 160 kDa (AS160) and actin remodeling-related proteins, is considered the major mechanism regulating insulin-stimulated GLUT4 translocation to the plasma membrane and glucose uptake. In contrast to this `classical' model, herein this project proposes a new model in which lysine acetylation (in combination with phosphorylation-based signaling) of key insulin signaling and GLUT4 trafficking proteins is necessary for insulin-stimulated glucose uptake. Accordingly, the primary objective of this proposal is to elucidate the importance of the acetyltransferases (KATs), p300 (E1A binding protein p300) and CBP (cAMP response element-binding protein [CREB] binding protein), to insulin-stimulated glucose transport. The central hypothesis of this proposal is that acetylation, by p300 and/or CBP, of actin remodeling-related proteins are required for insulin-stimulated GLUT4 translocation and, therefore, the insulin-mediated increase in glucose uptake. To address this hypothesis, insulin-induced skeletal muscle glucose uptake, actin remodeling and GLUT4 translocation will be measured in murine and cell models in which p300 and CBP activity are manipulated. This proposal predicts that loss of both p300 and CBP activity will abolish insulin- stimulated actin reorganization, GLUT4 translocation and glucose transport. Specifically, in Aim #1 the necessity and redundancy of p300 and CBP for insulin-stimulated glucose uptake in skeletal muscle will be elucidated, whilst in Aim #2, the importance of p300/CBP to actin remodeling and polymerization, and GLUT4 translocation will be assessed. Overall, these studies will broaden the understanding of the contribution of p300, CBP and acetylation to skeletal muscle glucose uptake in response to insulin. Ultimately, knowledge gathered from this work is expected to manifest novel targets for the development of therapies to improve insulin sensitivity and treat type 2 diabetes, with enhancement of human health and quality of life being anticipated outcomes.
Skeletal muscle insulin resistance significantly increases morbidity and mortality risk, and is an underlying cause of type 2 diabetes. This project aims to define how glucose uptake by skeletal muscle is regulated by insulin, with particular focus on the contribution of the acetyltransferases, p300 and CBP. Knowledge gathered will contribute to the development of novel therapies for treating skeletal muscle insulin resistance and type 2 diabetes, which will unequivocally improve human health.
