Non-Alcoholic and Alcoholic Fatty Liver disease: two sides of the same coin.

Background and aims: The booming prevalence of obesity and diabetes in young age and the increased consumption of alcohol in adolescents lead to the development of Non-Alcoholic Fatty Liver Disease (NAFLD) and Alcoholic Liver Disease (ALD). Task 1 of this work is focused on the development of an in vivo model of pediatric NAFLD and in the study of the therapeutic properties of Silymarin. The task 2 investigated the source of MIF, a cytokine involved in the pathogenesis of ALD. Materials and Methods: NAFLD in vivo study: C57BL/6 male and female mice were exposed to HFHCD or chow diet (CTRL diet) for 16 weeks. Biochemical and biomolecular analysis were performed to follow the progression of the damage. In the second phase Silymarin properties were evaluated (33mg/animal/day). ALD in vitro study: MIF expression was measured in HuH7 and macrophages cells in response to 50mM ethanol. The ethanol-induced liver injury was assessed in C57BL/6 (WT) and Mif-/- bone marrow chimeras. MIF was measured in serum, as well as visualized by immunohistochemistry in liver biopsies, from patients with alcoholic hepatitis (AH). Results: NAFLD in vivo study: HFHCD induced immediately a significant body weight gain in both genders. Males presented an early epididymal fat-pads hyperplasia and after week 12, a significant hepatomegaly, with alteration of glycemia, insulinemia, lipid profile, and ALT. Comparable body/blood changes were observed in females after week 16. Liver histology showed in both genders a mixed macro-microvesicular steatosis. Inflammatory foci were observed only in males, confirmed also by an increase in MCP-1 and TNF-α mRNA. Conversely, females had no signs of inflammation but rather presented enhanced lipid peroxidation (MDA) and a reduced GSH/GSSG ratio, signs of oxidative stress. By week 8 both genders developed progressive fibrosis. HFHCD+Silymarin decreased liver and visceral fat weight and improved ALT and lipid profile. HFHCD→CTRL diet reverted all altered parameters under study. Histologically, Silymarin slightly reduced inflammatory foci and fibrosis. ALD in vitro study: HuH7, but not THP-1 macrophages, released MIF in response to ethanol challenge in cell culture. In chimeric mice expressing MIF in non-myeloid cells (Mif-/- →WT), chronic ethanol feeding increased ALT/AST, hepatic steatosis, and cytokine/chemokine mRNA expression. In contrast, chimeric mice not expressing MIF in non-myeloid cells (WT→ Mif-/-) were protected from ethanol-induced liver injury. Immunohistochemical staining of liver biopsies from patients with AH revealed a predominant localization of MIF to hepatocytes. Interestingly, the concentration of MIF in suprahepatic serum, but not peripheral serum, was positively correlated with clinical indicators of disease severity and with an increased risk of mortality in patients with AH. Conclusions: Data collected suggested that our juvenile NAFLD model had a faster and more aggressive liver injury progression compared with published adult models, with different molecular mechanisms between males and females. Silymarin exerted some beneficial effects without requiring lifestyle improvements, relevant aspect considering the general low compliance of obese subjects in modifying their nutritional behavior. ALD project provided evidence that hepatocyte-derived MIF was critical to the pathogenesis of ALD in mice and likely contributes to liver injury in patients with AH. Altogether these new findings can lead to new therapeutic perspective.