Effects of Adenosine on Lipid Accumulation in a Human Hepatoma Cell Culture Model When Challenged with Excess Fatty Acid

Abstract

TITLE: EFFECTS OF ADENOSINE ON LIPID ACCUMULATION IN A HUMAN HEPATOMA CELL CULTURE MODEL WHEN CHALLENGED WITH EXCESS FATTY ACID Authors: Michael Brown B.S., School of Medicine, New York Medical College MS2 Dr. Robin DaSilva, PhD, Department of Food Science and Human Nutrition, University of Florida Background: Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disorder in western populations and is rapidly becoming one of the most common indications for orthotopic liver transplantation in the world. Fully understanding lipid metabolism in the liver is necessary for further understanding the progression of NAFLD to non-alcoholic steatohepatitis (NASH) and in finding an alternative treatment to weight loss for those diagnosed with NAFLD. Design/Methods: HepG2 cells treated with oleic acid (OA) were used as a model of liver cell lipid accumulation. Methionine, choline and purines are important metabolites and nutrients that are dysregulated in NAFLD, so we used methionine and choline deficiency (MCD) and excess purines in cultured HepG2 cells to assess the influence of these conditions. Cell Culture Quantitative real-time polymerase chain reaction Western Blot TG Assay Statistics: Analysis for statistics and all figures were made using the software Prism (GraphPad). A one way-ANOVA was used to test for statistical significance. A P-value less than 0.05 was taken as a significant difference. Results: MCD HepG2 cells had fewer total triglycerides and had higher expression of carnitine palmitoyltransferase 1 a (CPT-1a) and PPARa, genes involved in b-oxidation, as compared to control cells. MCD cells treated with extracellular adenosine or inosine with OA lowered phosphorylated-acetyl-CoA carboxylase (p-ACC). Adenosine was found to affect lipid metabolism through its role in activating AMP-activated protein kinase (AMPK) in the AMPK-ACC-CPT 1 pathway. Conclusions: HepG2 cells under a methionine and choline-deficient condition increased fatty acid oxidation and prevented cells from lipid-loading after treatment with exogenous fatty acids. The addition of excess purine molecules exacerbated lipid-loading in HepG2 cells in all conditions by decreasing fatty acid oxidation and potentially by increasing fatty acid synthesis. Impaired adenosine production in the MCD condition may reduce the inhibition of fatty acid synthesis and result in enhanced lipid oxidation.