Decreased adiponectin and antioxidant enzymes are associated with necroinflammatory changes and fibrosis in a rat model for non-alcoholic fatty liver disease (NAFLD)

Abstract

NAFLD is a chronic liver disease characterized by fatty liver, necroinflammation and fibrosis. We fed a diet containing 30% fish oil to female Sprague-Dawley rats (180-200g), consumed ad libitum for 8 weeks (NAFLD; n = 8). Control animals (CF; n = 8) were fed with isocaloric rat chow. At killing, blood and liver samples were collected for serum alanine aminotransferase (ALT), histology and molecular analysis. Histological sample was evaluated for fatty liver, necrosis and inflammation. Collagen was estimated based on the degree of Sirius Red staining. RT-PCR was carried out for adiponectin, glutathione peroxidase (GPx), superoxide dismutase (Cu/Zn SOD), catalase (CAT), TGF-ȕ1, procollagen (Pro-col), tissue inhibitors of metalloproteinases (TIMP-1; TIMP-2) matrix metalloproteinase (MMP-2). Zymography was performed to determine the enzyme activity of MMP-2. Electrophoretic mobility shift assay was done for nuclear factor-kappa B (NF-țB) activity. NAFLD rats had significantly higher serum ALT, fatty liver, necrosis, inflammation and amount of collagen formation. The mRNAs of GPx and CAT were reduced in NAFLD rats but the Cu/Zn SOD level was not altered. Liver adiponectin was also significantly diminished in NAFLD rats. mRNA levels of TGF-ȕ1, Pro-col, TIMP-1, TIMP-2 and MMP-2 were also significantly upregulated in the NAFLD group when compared to CF rats. MMP-2 enzyme and NF-țB activity were also markedly increased in the NAFLD rats. Our study shows that fatty liver and necroinflammation are accompanied by reduction in the antioxidant enzymes (GPx and CAT) and adiponectin. Liver fibrosis, another important feature of NAFLD was accompanied by upregulation of profibrogenic mediators.