A Role of Hypothalamic Dysfunction in Alcoholic Liver Disease

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Insulin resistance is an important risk factor for alcoholic liver disease (ALD). Vice versa, heavy alcohol consumption induces insulin resistance that is associated with progression of hepatic fibrosis in non-alcoholic fatty liver disease (NAFLD). Insulin is the key hormone that regulates lipid and glucose metabolism; it is also an important regulator of inflammation. Thus, hepatic insulin action is likely a key player in the pathogenesis of ALD, yet the mechanisms through which impaired insulin action predisposes to ALD remain poorly understood. We and others have previously demonstrated that insulin signaling within the mediobasal hypothalamus (MBH) controls hepatic glucose production (hGP), very low density lipoprotein (VLDL) secretion, white adipose tissue (WAT) lipolysis and innate immunity through the autonomic nervous system. Based on our pilot data that demonstrate that in a rat model for binge drinking, i.e. short term alcohol consumption impairs glucose tolerance and induces insulin resistance that is due to impaired hepatic insulin action. Binge drinking markedly impairs hypothalamic insulin action, defined as the ability of hypothalamic insulin to suppress hGP and adipose tissue lipolysis. Thus, the major hypothesis proposed in this proposal is that some of the metabolic and innate immunity defects induced by alcohol are caused through brain effects disrupting autonomic control of both metabolism and innate immunity. In support ofthis novel paradigm we find that a central cause ofthe impaired hypothalamic insulin action is decreased insulin signaling in the hypothalamus likely due to increased inflammation, ER stress and expression of protein tyrosine phosphatase l b (PTPIb), a negative regulator of insulin signaling. Here we propose to delineate the mechanisms through which chronic alcohol consumption impairs insulin action, disrupts hepatic carbohydrate, amino acid and lipid metabolism and generates a pro-inflammatory environment within the liver that predisposes to ALD.