A brain-liver circuit in regulation of alcoholic liver disease

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DESCRIPTION (provided by applicant): Liver disease is one of the leading causes of illness and death in the United States. Excessive alcohol consumption is a major risk factor for liver damage, and more than 2 million Americans suffer from liver disease caused by alcohol. Although hepatic steatosis is a prevalent phenotype among heavy alcohol drinkers, the mechanisms underlying its development are not well understood. It is currently thought that alcohol acts directly on the liver to alter lipid metabolism leading to development of hepatic steatosis. Our lab has recently delineated a novel brain-liver circuit in regulation of non-alcoholc fatty liver under physiologic conditions such as starvation and obesity. We show that hypothalamic neuropeptide Agouti-related protein (AGRP) acts in the brain to suppress hepatic sympathetic activity and to stimulate lipid synthesis. AGRP is required for the development of hepatic steatosis that occurs in starvation and obesity. Intriguingly, ethanol administration stimulates Agrp expression in the mouse hypothalamus, and AGRP-deficient mice are resistant to development of ethanol-induced hepatic steatosis without alteration of feeding and body weight. The goal of this proposal is to test the hypothesis that ethanol induces hepatic steatosis, at least in part, by stimulation of hypothalamic Agrp expression, resulting in alteration of hepati sympathetic activity and development of hepatic steatosis. Signaling mechanisms underlying alcohol's effects on Agrp expression and hepatic steatosis will be determined. We will further investigate the importance of modulating hepatic sympathetic activity in ethanol-induced hepatic steatosis. Finally, we will evaluate the therapeutic potentials of RNA-interference against Agrp in alleviating liver injury induced by chronic plus binge alcohol consumption. Taken together, experiments outlined in this proposal will define a new mechanism that underlies the etiology of ethanol- induced hepatic steatosis and will explore a novel strategy to treat alcoholic liver diseases.