Abstract

Elevated levels of fatty acids induce a number of cellular dysfunctions leading to a phenomenon known as “lipotoxicity”, which involves insulin resistance and beta pancreatic cell damage. Both these events favor the development of type 2 diabetes mellitus (T2DM), thus linking high fat diet to the genesis and progression of this disease. Although several studies have associated lipotoxicity in beta cells with cellular damage via oxidative stress, stress-activated MAP kinases and endoplasmic reticulum (ER) stress, to mention a few possibilities, many aspects of cellular pathways involved remain to be defined. We previously reported that the expression of the membrane protein caveolin-1 (CAV1) promotes lipotixicity-induced apoptosis in vitro in a mouse beta cell line (Wehinger et al, 2015). However, the signaling pathway implicated downstream of CAV1 and whether this finding is relevant to primary beta cells, remained to be clarified. Understanding the signaling pathways associated with fatty acid-induced beta cell demise can be expected to help identify promising targets for advanced therapies in T2DM. Strategy to address the problem: We will investigate the cellular signaling pathways involved in lipotoxicity downstream of CAV1 in the beta pancreatic cells MIN6 and in pancreatic islets from wild type (WT) and knockout mice for CAV1. Effects on apoptotic cell death in vitro in beta pancreatic cell lines and in murine islet preparations and the role of stress-induced MAP kinases downstream of CAV1 will be evaluated by determining phosphorylation of the respective proteins and by inhibiting JNK, p38 and ERK or by using specific dominant-negative forms in loss of function assays. Also we will evaluate the complex formation among CAV1-MAPK-BCL2-BCLxL that has been implicated in pro-apoptotic effects for CAV1 in other cells. Finally, we will characterize the metabolic and redox state of CAV1 wild type and null mice and their pancreatic islets, subjected to a normal or high fat diet, to analyze the islet´s response to these conditions.