Green Tea Extract Suppresses NF kappa B Activation and Inflammatory Responses in Diet-Induced Obese Rats with Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is characterized by oxidative stress and inflammatory responses that exacerbate liver injury. The objective of this study was to determine whether the antioxidant and antiinflammatory activities of green tea extract (GTE) would protect against NASH in a model of diet-induced obesity. Adult Wistar rats were fed a low-fat (LF) diet or high-fat (HF) diet containing no GTE or GTE at 1% or 2% (HF+2GTE) for 8 wk. The HF group had greater (P <= 0.05) serum alanine (ALT) and aspartate aminotransferases and hepatic lipids than the LF group. Both GTE groups had lower ALT and hepatic lipid than the HF group. In liver and epididymal adipose, the HF group had lower glutathione as well as greater mRNA and protein expression of TNF alpha and monocyte chemoattractant protein-1 (MCP-1) and NF kappa B binding activity than the LF group. Compared to the HF group, the HF+2GTE group had greater glutathione and lower protein and mRNA levels of inflammatory cytokines in both tissues. NF kappa B binding activities at liver and adipose were also lower, likely by inhibiting the phosphorylation of inhibitor of NF kappa B. NF kappa B binding activities in liver and adipose (P <= 0.05; r = 0.62 and 0.46, respectively) were correlated with ALT, and hepatic NF kappa B binding activity was inversely related to liver glutathione (r = -0.35). These results suggest that GTE-mediated improvements in glutathione status are associated with the inhibition of hepatic and adipose inflammatory responses mediated by NF kappa B, thereby protecting against NASH. J. Nutr. 142: 57-63, 2012.