The role of sphingolipids in the pancreatic beta cell

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Recent studies suggest that sphingolipids may have important regulatory roles in the survival and function of pancreatic beta-cells. Ceramides, which are produced in response to inflammatory cytokines (e.g. tumor necrosis factor-alpha (TNF-alpha), interleukin 1, etc.), have been shown to induce beta-cell apoptosis and inhibit insulin secretion. Gangliosides, which are glycosylated forms of ceramide, are putative autoantigens involved in the induction of insulitis and type 1 diabetes. And, sphingosine 1-phosphate, a derivative of ceramide produced by various growth factors, has been shown to promote beta-cell survival and growth, perhaps by opposing effects of its precursor, ceramide. Despite these isolated studies, the importance of sphingolipids as regulators of beta-cell growth, proliferation, and function has not been studied in detail, either in isolated cells or in intact animals. Herein we propose to initiate studies investigating the role of sphingolipids in beta-cell function. First, using pharmacological inhibitors and a novel knockout mouse that is incapable of making ceramides, we will determine the consequence of modulating sphingolipid levels on beta cell function in rodents. Second, we will investigate the molecular mechanisms through which ceramide and sphingosine 1-phosphate serve to divergently regulate cell survival, while evaluating the role of either as a modulator of cytokine or free fatty acid-induced cell death. Ultimately these studies will help reveal whether modulating beta-cell sphingolipid levels is beneficial for either blocking beta-cell death during transplantation or preventing the onset of type 1 or type 2 diabetes.