PPAR-alpha and -gamma agonist for the treatment of animal model of non-alcoholic fatty liver disease is effective in improving histological and biochemical changes

Abstract

Background: Although a variety of therapeutic trials has been carried out for the treatment of non-alcoholic fatty liver disease (NAFLD), the gold standard of treatment still remains to be defined. We have previously shown that reduced expression of PPAR-alpha may have an important role in the development of fatty liver disease in Otsuka Long-Evans Tokushima fatty rat model (OLETF). Aims of this study were to analyze the effect of PPAR-alpha and -gamma agonist in the treatment of NAFLD and verify the underlying mechanism of action using OLEFT rat model.

Materials and Methods: Liver tissue from control (Gr.I), NAFLD (Gr.II), PPAR-alpha agonist treatment (Gr. III, fenofibrate), PPAR-gamma agonist treatment (Gr.IV, rosiglitazone) were processed to histopatologic analysis. Sera from each group were frozen at -20°C mnil biochemical analysis was performed. The mRNA expression was determined by real time RT PCR. Primers for real time RT PCR were as follows: long-chain acyl-coA decarboxylase (LCAD), medium-chain acyl-coA decarboxylase (MCAD), carnitine-palmitoyltransferase (CPT), acetyl-coA oxidase (AOX), fatty acid binding protein (FABP), CD36 (FAT: fatty acid translocase) and TNF-alpha. Protein expression of TNF-alpha was determined by western blot analysis.

Results: Fasting glucose concentration was significantly reduced in Gr.III (mean 125 mg/dl) and IV (97 mg/dl) compared to Gr.II (182 mg/dl). Serum triglyceride concentration was also reduced in Gr.III (mean 36.6 mg/dl) and IV (39.4 mg/dl) compared to Gr.II (107.2 mg/dl). H&E and Oil red O' stain showed reduced steatosis in liver from Gr.III and Gr.IV compared to Gr.II. The mRNA expression of AOX, CPT, LCAD, MCAD, FABP, CD36/FAT was significantly devated after PPAR-alpha treatment. In NAFLD group (GR.II), TNF-alpha mRNA was elevated up to 8 times of normal. After treatment with PPAR-alpha, mRNA expression was reduced to 50% of Gr.II. Protein expression of TNF-alpha was also reduced after PPAR-alpha treatment although it did not reach statistical significance.

Conclusion: PPAR-alpha and -gamma agonist treatment were effective in reducing steatosis and hypertriglyceridemia in OLEFT rat model. The elevated expression of enzymes of mitochondrial and peroxisomal fatty acid oxidation accompanied by reduced expression of TNF-alpha is main mechanism of PPAR-alpha in the treatment of NAFLD.