DIFFERENTIAL EFFECTS OF FATTY ACIDS ON AN IN VITRO MODEL OF HEPATOCYTE STEATOSIS

Thesis (Master's)--University of Washington, 2014Differential Effects of Fatty Acids on an In Vitro Model of Hepatocyte Steatosis Introduction: Non-alcoholic fatty liver disease (NAFLD) is characterized by excess hepatic fat accumulation in the setting of metabolic syndrome. It ranges from simple hepatic fat accumulation (steatosis), to steatosis with inflammation and fibrosis (steatohepatitis), to end-stage liver disease. Progression of NAFLD has been modeled by a 2 hit hypothesis. The first hit, characterized by triglyceride accumulation, sensitizes the hepatocyte to second hits such as inflammation. Dietary fats are an important contributor to the development of NAFLD. While saturated fatty acids (SFA) tend to promote NAFLD, poly-unsaturated fatty acids (PUFA) and ruminant trans-fatty acids (TFA), such as conjugated linoleic acid (CLA) may be protective. This study aims to investigate the effects of various fatty acids (FA) on hepatocyte triglyceride accumulation, inflammation and insulin sensitivity using an in vitro model. Methods: AML12 hepatocytes were chronically exposed to FAs including Palmitic acid (PA), Oleic acid (OA), Docosahexanoic Acid (DHA) and CLA t10, c12 (CLA 10,12). Hepatic triglyceride content, inflammatory, lipogenic, oxidative stress and ER stress gene expression and insulin signaling proteins were measured. Results: AML12 cells chronically exposed to FA visibly accumulated lipid droplets. Among the various FA treatments, CLA (10,12) induced the greatest triglyceride accumulation. DHA significantly decreased the expression of the lipogenic, inflammatory, oxidative and ER stress genes independent of effects on insulin sensitivity. Interestingly, CLA (10,12) had protective effects on gene expression similar to DHA. Conclusion: Chronic exposure of dietary FA promotes triglyceride accumulation in this in vitro hepatocyte model. DHA and CLA (10,12) have beneficial effects on lipogenesis and inflammatory, oxidative stress and ER stress gene expression despite increasing triglyceride accumulation, indicating that different FA have varying effects on steatotic hepatocyte