Obesity is associated with increased risk for epithelial tumors such as hepatocellular carcinoma (HCC). It is not known, however, whether obesity increases the risk for HCC simply because it promotes cirrhosis, a general risk factor for HCC, or through other mechanisms that operate independently of cirrhosis. Among these, obesity is associated with a chronic inflammatory state, with the release of cytokines such as IL-6 and TNFalpha, well-known HCC mediators. Obesity is normally linked to diabetes and in consequence, to hyperinsulinemia. This increase in circulating insulin levels is suggested to be a factor that contributes to cancer. Moreover, the increase in free fatty acids (FFA) in blood among obese patients promotes a compensatory response from liver that activates the transcription of genes required for beta-oxidation, leading to a reduction in non-physiological stores of lipids in the liver. This increase in beta-oxidation could result in oxidative stress, inflammation and the production of lipid peroxidation bioproducts, which are known mutagens. The precise mechanisms whereby FFA and cytosolic triglycerides exert their effects, resulting in the diabetic phenotype, remain poorly understood. Emerging evidence nonetheless links microRNA (miRNA) with lipid metabolism, suggesting that these small RNAs mediate this increase in beta-oxidation.Our goal is to study how the components of the obesity state (inflammation, steatosis hyperinsulinemia and microRNA control of gene regulation) affect HCC development. We will use several mouse models in which one or more of these factors are reduced following induction of metabolic disease. We will also determine whether specific miRNAs that are down- or upregulated in the liver of mice on a high fat diet are implicated in HCC development.