ABSTRACT
Nonalcoholic fatty liver disease (NAFLD) is one of the major causes of hepatocellular carcinoma (HCC). Although the intracellular cholesterol accumulation has been demonstrated to regulate the gene expression responsible for steatohepatitis, the role played by cholesterol in the development of NAFLD-associated HCC has not been fully elucidated. In this study, using microarray analysis, we investigated the molecular mechanisms governing cholesterol-mediated progression of NAFLD. To ensure hepatic cholesterol accumulation, either a high-fat and high-cholesterol (HFHC) diet or a high-fat and high-cholesterol with cholic acid (HFHCCA) diet was fed to diethylnitrosamine (DEN)-injected C57BL/6J mice for 10 weeks. While an HFHC diet increased hepatic triglyceride levels, an HFHCCA diet induced hepatic cholesterol accumulation by reducing bile acid biosynthesis in DEN-injected mice. Livers from both HFHC and HFHCCA groups exhibited increases in steatosis and necrosis; however, histological features of HCC were not observed in any of the experimental groups. Hepatic gene expression profile of the HFHCCA group was different from those of other groups. Functional analysis showed that cholic acid supplementation upregulated differentially expressed genes (DEGs) associated with inflammation, proliferation, apoptosis, chemical drug response, and cancer signaling pathway. Downregulated DEGs were associated with steroid metabolism, mitochondrial function, and oxidative phosphorylation pathway. Furthermore, hepatic cholesterol accumulation lowered the expression of DEGs associated with energy and macronutrient metabolism, especially amino acid metabolism. In this study, the results of a global gene expression profile demonstrated that feeding the HFHCCA diet to DEN-injected mice accelerated the carcinogenic progression of NAFLD, implicating the critical role played by hepatic accumulation of cholesterol.
