Phase IIa chemoprevention trial of green tea polyphenols in high-risk individuals of liver cancer: Modulation of urinary excretion of green tea polyphenols and 8-hydroxydeoxyguanosine

The Institute of Environmental and Human Health and Department of Environmental Toxicology, Texas Tech University, PO Box 41163, Lubbock, TX 79409-1163, USA.
Carcinogenesis (Impact Factor: 5.33). 02/2006; 27(2):262-8. DOI: 10.1093/carcin/bgi147
Source: PubMed


Modulation of urinary excretion of green tea polyphenols (GTPs) and oxidative DNA damage biomarker, 8-hydroxydeoxyguanosine (8-OHdG), were assessed in urine samples collected from a randomized, double-blinded and placebo-controlled phase IIa chemoprevention trial with GTP in 124 individuals. These individuals were sero-positive for both HBsAg and aflatoxin-albumin adducts, and took GTP capsules daily at doses of 500 mg, 1000 mg or a placebo for 3 months. Twenty-four hour urine samples were collected before the intervention and at the first and third month of the study. Urinary excretion of 8-OHdG and GTP components was measured by HPLC-CoulArray electrochemical detection. The baseline levels of 8-OHdG and GTP components among the three groups showed homogeneity (P > 0.70), and a non-significant fluctuation was observed in the placebo group over the 3 months (P > 0.30). In GTP-treated groups, epigallocatechin (EGC) and epicatechin (EC) levels displayed significant and dose-dependent increases in both the 500 mg group and 1000 mg group (P < 0.05). The 8-OHdG levels did not differ between the three groups at the 1 month collection, with medians of 1.83, 2.08 and 1.86 ng/mg-creatinine for placebo, 500 and 1000 mg group, respectively (P = 0.999). At the end of the 3 months' intervention, 8-OHdG levels decreased significantly in both GTP-treated groups, with medians of 2.02, 1.03 and 1.15 ng/mg-creatinine for placebo, 500 mg and 1000 mg group, respectively (P = 0.007). These results suggest that urinary excretions of EGC and EC can serve as practical biomarkers for green tea consumption in human populations. The results also suggest that chemoprevention with GTP is effective in diminishing oxidative DNA damage.

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    • "It was shown that AFB1-induced 8-OHdG was prevented by prior treatment with polyethylene glycol-conjugated catalase (PEG-CAT) in isolated mouse lung cells following in vivo treatment with the toxin (Guindon et al., 2007), but PEG-CAT was not protective against AFB1 carcinogenicity in mouse lung despite preventing DNA oxidation (Guindon et al., 2008). Luo et al. (2006) have shown that chemoprevention with green tea poliphenols is effective in diminishing oxidative DNA damage, through the reduction of the urinary 8-OHdG levels. "
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    • "At the end of the 3- months intervention, the levels of 8-hydroxydeoxyguanosine, an oxidative DNA damage biomarker, were statistically significant 50% lower in both green tea treated groups than in the placebo group (P = 0.007). There was no difference in urinary levels of aflatoxin B 1 mecapturic acids and 8-hydroxydeoxyguanosine between the 500-mg and 1000-mg green tea polyphenol groups [61]. These results suggest that the oral administration of green tea polyphenols at 500-1000 mg/day is effective in enhancing the detoxification of aflatoxin and reducing oxidative DNA damage. "
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