Collins A R, Olmedilla B, Southon S, Granado F, Duthie S J
Rowett Research Institute, Bucksburn, Aberdeen, UK.
Carcinogenesis. 1998 Dec;19(12):2159-62. doi: 10.1093/carcin/19.12.2159.
Carotenoids are thought to act as antioxidants in vivo, decreasing oxidative damage to biomolecules and thus protecting against coronary heart disease and cancer. However, human intervention studies with beta-carotene have given equivocal results in terms of cancer incidence. In an alternative molecular epidemiological approach, we have employed the 'comet assay' (single cell alkaline gel electrophoresis) to measure strand breaks, oxidized pyrimidines and altered purines in the DNA of lymphocytes from volunteers supplemented with alpha/beta-carotene, lutein, lycopene or placebo. In addition, we measured concentrations of the main serum carotenoids, and vitamins E and C, by HPLC. We report a significant negative correlation between basal concentrations of total serum carotenoids and oxidized pyrimidines. A similar correlation was seen between individual carotenoids (notably lutein and beta-carotene) and oxidized pyrimidines. However, carotenoid supplementation did not have a significant effect on endogenous oxidative damage. This suggests that there are some factors in the basal diet, probably found in fruit and vegetables, that decrease oxidative damage to DNA. In this case, basal serum carotenoids may simply be markers of consumption of fruit and vegetables, they themselves having little or no protective value.
类胡萝卜素被认为在体内起到抗氧化剂的作用，减少对生物分子的氧化损伤，从而预防冠心病和癌症。然而，关于β-胡萝卜素的人体干预研究在癌症发病率方面给出了模棱两可的结果。在另一种分子流行病学方法中，我们采用了“彗星试验”（单细胞碱性凝胶电泳）来测量补充了α/β-胡萝卜素、叶黄素、番茄红素或安慰剂的志愿者淋巴细胞DNA中的链断裂、氧化嘧啶和改变的嘌呤。此外，我们通过高效液相色谱法测量了主要血清类胡萝卜素以及维生素E和C的浓度。我们报告了总血清类胡萝卜素的基础浓度与氧化嘧啶之间存在显著的负相关。在单个类胡萝卜素（特别是叶黄素和β-胡萝卜素）与氧化嘧啶之间也观察到了类似的相关性。然而，补充类胡萝卜素对内源性氧化损伤没有显著影响。这表明基础饮食中存在一些因素，可能存在于水果和蔬菜中，这些因素可减少对DNA的氧化损伤。在这种情况下，基础血清类胡萝卜素可能仅仅是水果和蔬菜摄入量的标志物，它们本身几乎没有或没有保护价值。
