4.7 Article

Green tea extract protects against nonalcoholic steatohepatitis in ob/ob mice by decreasing oxidative and nitrative stress responses induced by proinflammatory enzymes

Journal

JOURNAL OF NUTRITIONAL BIOCHEMISTRY
Volume 23, Issue 4, Pages 361-367

Publisher

ELSEVIER SCIENCE INC
DOI: 10.1016/j.jnutbio.2011.01.001

Keywords

Green tea; NADPH oxidase; Myeloperoxidase; Lipid peroxidation; Protein nitration; Nonalcoholic steatohepatitis

Funding

  1. National Research Initiative from the US Department of Agriculture Cooperative State Research, Education and Extension Service [2007-02303]
  2. US Department of Agriculture [CONS00802]

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Oxidative and nitrative stress responses resulting from inflammation exacerbate liver injury associated with nonalcoholic steatohepatitis (NASH) by inducing lipid peroxidation and protein nitration. The objective of this study was to investigate whether the anti-inflammatory properties of green tea extract (GTE) would protect against NASH by suppressing oxidative and nitrative damage mediated by proinflammatory enzymes. Obese mice (ob/ob) and their 5-week-old C57BL6 lean littermates were fed 0%, 0.5% or 1% GTE for 6 weeks (n=12-13 mice/group). In obese mice, hepatic lipid accumulation, inflammatory infiltrates and serum alanine aminotransferase activity were markedly increased, whereas these markers of hepatic steatosis, inflammation and injury were significantly reduced among obese mice fed GTE. GTE also normalized hepatic 4-hydroxynonenal and 3-nitro-tyrosine (N-Tyr) concentrations to those observed in lean controls. These oxidative and nitrative damage markers were correlated with alanine aminotransferase (P<.05; r=0.410-0.471). Improvements in oxidative and nitrative damage by GTE were also associated with lower hepatic nicotinamide adenine dinucleotide phosphate oxidase activity. Likewise, GTE reduced protein expression levels of hepatic myeloperoxidase and inducible nitric oxide synthase and decreased the concentrations of nitric oxide metabolites. Correlative relationships between nicotinamide adenine dinucleotide phosphate oxidase and hepatic 4-hydroxynonenal (r=0.364) as well as nitric oxide metabolites and N-Tyr (r=0.598) suggest that GTE mitigates lipid peroxidation and protein nitration by suppressing the generation of reactive oxygen and nitrogen species. Further study is warranted to determine whether GTE can be recommended as an effective dietary strategy to reduce the risk of obesity-triggered NASH. (C) 2012 Elsevier Inc. All rights reserved.

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