Contribution of De Novo Lipogenesis in Severity of Nonalcoholic Fatty Liver Disease

The development of nonalcoholic fatty liver disease (NAFLD) progresses from a state of elevated intrahepatic triglycerides (IHTG) to liver inflammation, and ultimately, hepatic apoptosis and fibrosis. NAFLD is the most prevalent liver disease in the U.S., and there is a serious need to understand its progression to the advanced state, nonalcoholic steatohepatitis (NASH). Elevated de novo lipogenesis (DNL) is the unique, early event distinguishing patients with NAFLD from equally-obese participants with low IHTG. DNL is the process of liver synthesis of fatty acids (FAs) from carbohydrate. In humans, studies have shown that DNL significantly predicts the magnitude of IHTG, however, it is unknown whether the pathway plays a role in disease progression. Evidence supporting this concept includes the fact that the primary product of DNL is the saturated FA, palmitate, which in cell culture has been shown to significantly contribute to oxidative stress and inflammation. Recent rodent data show that upregulation of DNL through dietary supplementation of sucrose exacerbated the hepatotoxic effects of excess dietary FAs. A preliminary abstract presented by others at the 2017 Liver Meeting suggested that DNL may not be different between patients with low and high liver fibrosis, although these data were collected using an indirect measure of liver disease. Here, in the present study, the hypothesis will be tested directly by measuring DNL in human liver tissue and comparing it to liver histological scores (NAFLD Activity Score, NAS) from patient samples.