Attenuation of lipotoxicity by liver regeneration protein ALR

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic pathology, ranging from steatosis to cirrhosis with nonalcoholic steatohepatitis (NASH) on an intermediate level. The aim of our study was to investigate the potential role of liver regeneration factors such as ALR (augmenter of liver regeneration) in NASH. ALR, a protein known to have a beneficial impact on liver regeneration was analyzed for its potential protective role under conditions of NASH in vitro and in vivo. A mouse model for NASH was used to analyze ALR mRNA expression by quantitative RT-PCR revealing elevated ALR levels in mice fed with lard diet for 3 weeks. Furthermore in an in vitro model, primary human hepatocytes and hepatoma cells (HepG2, Huh-7) were treated with free fatty acids (oleat, palmitate 2: 1) and showed dose / time depended accumulation of triglycerides. Cell viability was determined by release of LDH and revealed that concentrations of 0,5mM FFA at 24h treatment showed significant lipotoxicity. To elucidate the role of ALR under conditions leading to NASH we generated stably ALR transfected HepG2 cells expressing human ALR. We cultured wt HepG2 and HepG2-ALR cells with increasing concentrations of FFAs and observed a significant lower toxicity in cells stably expressing ALR compared to wildtype was (0.5mM FFA after 24h). Further, lipotoxicity of wt HepG2 could be reduced to levels of HepG2-ALR by supplementing culture media with recombinant human ALR (250ng/ml). ALR overexpression or supplementary treatment with ALR had no influence on FFA uptake and subsequently cellular triglyceride levels. Besides its possible direct influence on FFA mediated lipotoxicity we analyzed the influence of ALR treatment on expression of profibrogenic genes, which is described as a prerequisite for NASH development. This data indicate, that ALR might have beside its hepatoprotective effect, additionally an anti-fibrogenic impact in NAFLD/ NASH as well as fibrosis related liver diseases.