Green Tea Extract Protects Leptin-deficient, Spontaneously Obese Mice from Hepatic Steatosis and Injury

The incidence of nonalcoholic fatty liver disease (NAFLD) has risen along with the ongoing obesity epidemic. Green tea extract (GTE) inhibits intestinal lipid absorption and may regulate hepatic lipid accumulation. The objective of this study was to determine whether GTE protects against hepatic lipid accumulation during the development of NAFLD in an obese mouse model. Five-wk-old ob/ob (obese) mice and their lean littermates (8 mice x genotype(-1) x dietary treatment(-1)) were fed GTE at 0, 1, or 2% (wt:wt) for 6 wk. The body weights of obese mice and lean littermates fed diets containing GTE were 23-25% and 11-20% lower (P < 0.05) than their respective controls fed no GTE. Histologic evaluation showed a significant reduction in hepatic steatosis in GTE-fed obese mice only and histologic scores were correlated with hepatic lipid concentration (r = 0.84; P < 0.05), which was reduced dose dependently by GTE. GTE protected against hepatic injury as suggested by 30-41% and 22-33% lower serum alanine aminotransferase and aspartate aminotransferase activities, respectively. Hepatic alpha-tocopherol was 36% higher in obese mice than lean mice. GTE tended (P = 0.06) to lower hepatic alpha-tocopherol, which was not fully explained by the GTE-mediated reduction in hepatic lipid. Hepatic ascorbic acid was lower in obese mice than in lean mice (P < 0.05) and was unaltered by GTE. Obese mice had lower serum adiponectin than lean mice and this was not affected by GTE. The results suggest that GTE protects against NAFLD by limiting hepatic lipid accumulation and injury without affecting hepatic antioxidant status and adiponectin-mediated lipid metabolism. Further study is underway to define the events by which GTE protects against obesity-triggered NAFLD.