Abstract
Non-alcoholic fatty liver disease (NAFLD) is now the most common liver disease worldwide with its incidence closely linked to the rise in obesity. An estimated 20-30% of the UK population have fat accumulation in the liver (steatosis), which can progress to the more severe forms of NAFLO including steatohepatitis, fibrosis, cirrhosis and ultimately hepatocellular carcinoma. High dietary intakes of fructose have been associated with fibrosis severity in NAFLD, however the molecular mechanisms for this remain unknown. The objective of these experiments was to develop an in vitro model of fructose-induced steatosis. Initially, human hepatocytes (HepG2 liver cell line) were treated with fructose (0-60 mM), with and without glucose, and lipid accumulation was measured after 48,72 and 96h. There was no evidence of steatosis or altered cell viability in response to fructose or glucose treatment at any time point measured. Subsequently, primary mouse hepatocytes were isolated for culture with and without fructose. However, we observed that, regardless of glucose concentration in the isolation media (O versus 5 mM) or in the seeding media (5 versus 25 mM), the primary hepatocytes appeared steatotic at very early time points (4, 8 and 24h) after isolation and prior to fructose treatment. This is in contradiction to haematoxylin and eosin stained liver sections from matched littermates that exhibited no steatosis. Subsequent experiments aimed at manipulating both the primary hepatocyte isolation/seeding procedures to establish the cause of the steatosis observed immediately after seeding did not alter the extent of primary hepatocyte lipid content. Fatty acid treatments of the human liver cells under different culture conditions resulted in modest increase in hepatocyte lipid content. It was concluded that although fatty acid treatments could affect the HepG2 1ipid content, fructose treatments of HepG2 cells do not alter HepG2 cell lipid content. Future studies should determine the extent of fructose metabolism in HepG2 and the fate of secondary metabolites of fructose, and whether fructose alters expression of the enzymes of lipogenesis.