Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Borschkegasse 8a, 1090, Vienna, Austria.
Eur J Nutr. 2010 Jun;49(4):227-34. doi: 10.1007/s00394-009-0068-0. Epub 2009 Oct 23.
Consumption of green tea (GT) is associated with decreased incidences of specific forms of cancer in humans and it was postulated that its antioxidant (AO) properties may account for these effects. The evidence for AO effects of GT is mainly based on the results from in vitro experiments and on animal studies in which protection against chemically induced damage was monitored.
The goal of the study was the investigation of the prevention of strand breaks and DNA migration attributable to endogenous oxidation of bases by GT extract (GTE) in inner organs and lymphocytes of untreated rats. In addition, immunological parameters and biochemical markers were monitored.
DNA migration was measured in hepatocytes, colonocytes and lymphocytes after consumption of a low (1.3 mg/kg bw per day, 5 days) and a high dose (6.5 mg/kg bw per day, 5 days) of GTE in COMET assays (n = 5 animals per group). In addition, immunological parameters (TNF-alpha, IFN-gamma, IL-4 and IL-10), the total AO capacity and oxidized low-density lipoproteins were determined in plasma.
No evidence for reduction in DNA damage was found with a lower dose, whereas with the higher dose, reduction in DNA migration attributable to formamidopyrimidine-DNA-glycosylase sensitive lesions (oxidized purines) and endonuclease III-sensitive sites (oxidized pyrimidines) (58 and 73%) was observed in lymphocytes; also, in colonocytes (reduction in FPG-sensitive sites by 46%) and hepatocytes (decrease in Endo III-sensitive sites by 74%) protective effects were found, while none of the other parameters was altered.
Our results show that a dose of GTE, which is equivalent to consumption of 500 ml GT/p/day in humans protects lymphocytes and to a lesser extent inner organs against oxidative DNA damage, while no effect was seen with a lower dose corresponding to an uptake of 100 ml/p/day.
饮用绿茶（GT）与人类特定癌症发病率的降低有关，据推测其抗氧化（AO）特性可能是这些效果的原因。GT 的 AO 效应的证据主要基于体外实验和动物研究的结果，其中监测了对化学诱导损伤的保护作用。
本研究的目的是调查 GT 提取物（GTE）对内脏器官和未处理大鼠淋巴细胞内源性碱基氧化引起的链断裂和 DNA 迁移的预防作用。此外，还监测了免疫参数和生化标志物。
在 COMET 测定中（每组 5 只动物），在低剂量（1.3mg/kg bw/天，5 天）和高剂量（6.5mg/kg bw/天，5 天）的 GTE 消耗后，测量肝细胞、结肠细胞和淋巴细胞中的 DNA 迁移。此外，还测定了血浆中的免疫参数（TNF-α、IFN-γ、IL-4 和 IL-10）、总 AO 能力和氧化型低密度脂蛋白。
低剂量时未发现 DNA 损伤减少的证据，而高剂量时，淋巴细胞中与 formamidopyrimidine-DNA-糖苷酶敏感损伤（氧化嘌呤）和内切酶 III 敏感位点（氧化嘧啶）相关的 DNA 迁移减少（58%和 73%）；在结肠细胞（FPG 敏感位点减少 46%）和肝细胞（Endo III 敏感位点减少 74%）中也观察到保护作用，而其他参数均未改变。
我们的结果表明，相当于人类每天饮用 500ml GT 的 GTE 剂量可保护淋巴细胞和在一定程度上保护内脏器官免受氧化 DNA 损伤，而低剂量（相当于每天摄入 100ml GT）则没有效果。
