Pollard M, Wolter W, Sun L
Lobund Laboratory, University of Notre Dame, IN 46556, USA.
In Vivo. 2000 May-Jun;14(3):389-92.
Based on epidemiological surveys, the low incidence of clinical prostate cancer among aged men in Japan and China were attributed to high consumption of soybean-derived food in which phytoestrogens have numerous anticancer mechanisms. The prostate model in Lobund-Wistar (L-W) rats produce high levels of testosterone (T). They are inherently predisposed to develop induced and spontaneous metastasizing adenocarcinomas, which are (T)-dependent in early stages and T-independent in advanced stages. In the experiment reported here, 2 groups of L-W rats (age 2 months) were fed soy-containing diets: (a) commercial diet L-485 (TekLad) with soy meal; or (b) a soy-free diet (L-474) in which casein was replaced by soy protein isolate/isoflavones (SPII). At age 3 months, all rats were inoculated i.v. with MNU; and 14 months later, 17/58 (29.3%) of rats on diet L-485 developed cancer in avg 12 months, compared to 5/50 (10%) of rats on the SPII diet in avg 12.1 months (P = 0.001). In the latter rats, the serum levels of T, and weights of testes were significantly reduced; but in the former rats, serum levels of T remained elevated, suggesting that soy meal in L-4,85 blocked the estrogenic effects of phytoestrogens.
基于流行病学调查，日本和中国老年男性临床前列腺癌发病率较低归因于大豆类食物的高摄入量，其中植物雌激素具有多种抗癌机制。洛本德-威斯塔（L-W）大鼠的前列腺模型会产生高水平的睾酮（T）。它们天生易患诱导性和自发性转移性腺癌，早期依赖睾酮（T），晚期则不依赖。在本报告的实验中，两组2月龄的L-W大鼠喂食含大豆的饮食：（a）含豆粕的商业饮食L-485（TekLad）；或（b）不含大豆的饮食（L-474），用大豆分离蛋白/异黄酮（SPII）替代酪蛋白。3月龄时，所有大鼠静脉注射N-甲基-N-亚硝基脲（MNU）；14个月后，饮食L-485组的大鼠中有17/58（29.3%）在平均12个月时患癌，相比之下，SPII饮食组的大鼠中有5/50（10%）在平均12.1个月时患癌（P = 0.001）。在后一组大鼠中，血清睾酮（T）水平和睾丸重量显著降低；但在前一组大鼠中，血清睾酮（T）水平仍升高，这表明L-485中的豆粕阻断了植物雌激素的雌激素效应。
