Establishment of an in vitro model in which HBV promotes hepatocellular steatosis and lipotoxicity

At least one quarter of individuals with chronic hepatitis B virus (HBV) infection have fatty livers, but little is known about the influence of HBV on hepatic steatosis. Furthermore, hepatic steatosis is a known risk factor for disease progression in HBV-infected individuals but the underlying mechanisms are widely unknown.

The aim of this study was to establish a model to study the effect of HBV on hepatic steatosis and lipotoxicity.

Methods and Results: The HBV producing cell lines HepG2.2.15 and HepG2.4A5 and the parental hepatoma cell line HepG2 were incubated with different concentrations of palmitic and oleic acid. In all 3 cell lines oleat did not affect cell viability up to a concentration of 5µM. In contrast, palmitate dose-dependently induced toxic effects in all 3 cell-lines, however, cytotoxic effects occurred at significantly lower palmitate concentration in HBV producing cells. Assessment of intracellular lipid accumulation upon stimulation with oleat revealed significantly higher levels of triglycerides and free fatty-acids in HBV producing cell lines. In line with this, the expression of diacylglycerol acyltransferase 2 (DGAT2), which catalyzes the final step in hepatocyte triglyceride biosynthesis, was significantly induced in HBV producing but not in the parental HepG2 cell line. In contrast, expression of fatty acid synthase (FASN) and stearoyl-CoA desaturase1 (SCD1) did not differ significantly between cell lines indicating that the observed difference in cellular lipid accumulation is not caused by de novo lipogenesis.

Conclusions: Our data indicate greater susceptibility to lipotoxicity as well as increased cellular lipid accumulation of HBV producing cell lines in vitro. This novel in vitro model allows studying the underlying mechanisms of this phenomenon, which may lead to new therapeutic strategies in chronically HBV infected patients.