Metabolomic signatures in lipid-loaded HepaRGs reveal pathways involved in steatotic progression

OBJECTIVES: Non-alcoholic fatty liver disease (NAFLD) describes a spectrum of disorders including simple steatosis, non-alcoholic steatohepatitis, fibrosis, and cirrhosis. With the increased prevalence of obesity, and consequently NAFLD, there is a need for novel therapeutics in this area. To facilitate this effort, we developed a cellular model of hepatic steatosis using HepaRG cells and determined the resulting biochemical alterations. DESIGN AND METHODS: Using global metabolomic profiling, by means of a novel metabolite extraction procedure, we examined the metabolic profiles in response to the saturated fatty acid palmitate, and a mixture of saturated and unsaturated fatty acids, palmitate and oleate (1:2). RESULTS: We observed elevated levels of the branched chain amino acids, TCA cycle intermediates, sphingosine and acylcarnitines, and reduced levels of carnitine in the steatotic HepaRG model with both palmitate and palmitate:oleate treatments. In addition, palmitate-induced steatotic cells selectively displayed elevated levels of diacylglycerols and monoacylglycerols, as well as altered bile acid metabolism. CONCLUSION: This global metabolomics approach reveals biochemical changes in pathways important in the transition to hepatic steatosis including insulin resistance, altered mitochondrial metabolism, and oxidative stress. Moreover, our data demonstrate the utility of this in vitro model for investigating mechanisms of steatotic progression, insulin resistance and lipotoxicity in NAFLD.