维生素E饮食预防癌症

维生素E是否阻止或促进癌细胞生长已广泛在科学期刊上以及新闻媒体上进行了辩论，新泽西癌症研究所癌症预防研究中心欧内斯特·马里奥·罗格斯大学药学院的科学家，相信两种形式的维生素E-γ和油菜籽和玉米油以及坚果、大豆中的δ-生育酚能预防结肠癌、肺癌、乳腺癌和前列腺癌。

Chung S. Yang说：有研究表明维生素E会增加患癌症的风险，降低骨质密度。但γ-生育酚的维生素E形式，在美国饮食中，维生素E和δ-生育酚的含量是最丰富的，其在植物油中也发现，实有利于预防癌症的，而维生素E补充剂的使用并没有这样的好处。

Yang说，罗格斯大学的科学家进行结肠癌、肺癌、乳腺癌和前列腺癌的动物实验研究发现植物油，γ和δ-生育酚中发的维生素E，能防止动物模型中癌症的形成和生长。

Yang说：当动物暴露于致癌物质环境下，在他们的饮食中饲喂维生素E组肿瘤体积较少。当癌症细胞注射到小鼠体内后，再给予维生素E，也能减慢肿瘤的发展。
 
Yang和他的同事们、Nanjoo Suh和Ah-Ng Tony Kong总结他们的研究结果，并发表于美国癌症研究协会的Cancer Prevention Research杂志上。（生物谷：Bioon.com）

doi:10.1158/1940-6207.CAPR-11-0521
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δ- and γ-Tocopherols, but not α-Tocopherol, Inhibit Colon Carcinogenesis in Azoxymethane-Treated F344 Rats

Fei Guan1, Guangxun Li1, Anna B. Liu1, Mao-Jung Lee1, Zhihong Yang1, Yu-Kuo Chen1, Yong Lin2,3, Weichung Shih2,3, and Chung S. Yang1,3

The cancer preventive activity of vitamin E has been extensively discussed, but the activities of specific forms of tocopherols have not received sufficient attention. Herein, we compared the activities of δ-tocopherol (δ-T), γ-T, and α-T in a colon carcinogenesis model. Male F344 rats, seven weeks old, were given two weekly subcutaneous injections of azoxymethane (AOM) each at a dose of 15 mg/kg body weight. Starting 1 week before the AOM injection, the animals were maintained on a modified AIN76A diet, or the same diet containing 0.2% of δ-T, γ-T, α-T, or a γ-T-rich mixture of tocopherols (γ-TmT), until the termination of the experiment at 8 weeks after the second AOM injection. δ-T treatment showed the strongest inhibitory effect, decreasing the numbers of aberrant crypt foci by 62%. γ-T and γ-TmT were also effective, but α-T was not. Immunohistochemical analysis showed that δ-T and γ-T treatments reduced the levels of 4-hydroxynonenal and nitrotyrosine and the expression of cyclin D1 in the colon, preserved the expression of PPAR-γ, and decreased the serum levels of prostaglandin E2 and 8-isoprostane. Supplementation with 0.2% δ-T, γ-T, or α-T increased the respective levels of tocopherols and their side-chain degradation metabolites in the serum and colon tissues. Rather high concentrations of δ-T and γ-T and their metabolites were found in colon tissues. Our study provides the first evidence for the much higher cancer preventive activity of δ-T and γ-T than α-T in a chemically induced colon carcinogenesis model. It further suggests that δ-T is more effective than γ-T.