Plasma metabolic profiling reveals age-dependency of systemic effects of green tea polyphenols in mice with and without prostate cancer

Abstract

Green tea polyphenols (GTP) have been widely investigated for their potential to prevent prostate cancer. However, results from epidemiological and clinical studies are equivocal. Studies in the TRAMP (TRansgenic Adenocarcinoma of the Mouse Prostate) mouse suggest that the chemopreventive efficacy of GTP is higher in young animals with early stages of carcinogenesis than in old ones. Here, effects of GTP on prostate carcinogenesis in TRAMP mice were assessed by comparing pathological changes with ¹H-NMR metabolic profiling of plasma and extracts of prostate tissue. Mice received 0.05% GTP in their drinking water for 4 or 25 weeks after weaning. Age-matched wild-type mice were included in the study in order to establish differences in GTP effects between normal and TRAMP mice. Dietary GTP did not markedly alter prostate carcinogenesis as reflected by pathology and prostate tissue metabolic profile. However, a systemic effect of GTP consumption was observed in young mice, regardless of genotype. Plasma lipid signals were decreased in 8 week old mice which received GTP compared to age-matched controls by 19, 61, 27, 34 and 15% (p ≤ 0.05) in the CH₂CH₂CC (m 2.00 ppm), CH₂CH₂CO (m 1.58 ppm), CH₂ (m 1.26 ppm), CH₃ (m 0.88 ppm) and CH₃ fatty acid resonances (m 0.84 ppm), respectively. GTP consumption did not affect the plasma metabolic profile in 29 week old mice. These results suggest that age rather than disease state determines systemic effects of GTP. More studies are required to investigate factors, such as age or metabolic make-up, inherent to a population or an individual, which may modulate the chemopreventive efficacy of GTP.