Alcoholic liver disease (ALD) accounts for over fifty percent of all chronic liver diseases in industrialized countries and is responsible for > 25,000 deaths in 2005 in the United States alone. ALD comprises a spectrum of liver injury ranging from simple fatty liver to alcohol-induced liver scarring and, potentiall, cirrhosis. While literally all heavy drinkers have fatty liver, only a minority of 10-35% develop more severe let alone end-stage liver damage. Aggravation of ALD is modulated by environmental factors such as gender, obesity and chronic infection with hepatitis viruses. Twin studies suggest that up to 50% of the risk of cirrhosis in alcoholics is determined by inherited factors. The search for genetic factors that modulate the progression of ALD has resulted in abundant data from studies in humans of which the vast majority, however, remain unconfirmed. A highly topical finding constitutes the recent identification of a genetic variant in the gene coding for PNPLA3 as risk factors for severe ALD by several investigators including the principle applicant who found this to be true also in drinkers from central Europe.
In the present research project, the function and relevance of genetic variants found to associated with ALD shall be researched in mice in which the same genes have been inactivated artificially. Specifically, the function of two gene variants (patatin-like phospholipase domain-containing 3, PNPLA3 rs2073081; macrophage galactose-type C-type lectin 1, CLEC10A/MGL1; rs11654772) showing significant association with ALD in a recently performed genome-wide association study (GWAS) in 514 cases of alcoholic liver cirrhosis and 1,175 alcoholics without relevant liver injury is planned (pilot data leading to the project hypothesis). Emphasis will be put on the genes' effect on modulating the evolution of experimental liver scarring (fibrosis), fat accumulation and inflammation in these animals (AIM1). For this, mice with inactivated genes PNPLA3 and CLEC10A/MGL1 and normal control mice will be subjected to a recently developed animal model of alcoholic liver injury. To confirm the relevance of findings derived from animal experimentation, frozen human liver tissues shall be used to assess the tissue distribution and expression of the risk genes (AIM2). In addition, cultured cells (HuH-7) expressing normal or aberrant PNPLA3 will be treated with compunds that are known to mediate of ethanol totoxicity (acetaldehyde, hydrogen peroxide, hypoxia) to assess their impact on PNPLA3 expression and enzyme activity (AIM3). Finally, a possible association of the same genetic risk variants with progression of non-ALD chronic liver diseases (non-alcoholic fatty liver disease, NAFLD; chronic hepatitis C, CHC; hemochromatosis, HFE) will be tested by means of separate genetic case control studies (AIM4)The research is structured as a Swiss single centre research endeavour but exploits data from an established Swiss/German/Austrian collaboration with access to unique patient collections, expertise and infrastructure required for systematic genetic detection, and further functional and clinical confirmation.