Cancer promotive action of secondary bile acids and preventive effect owing to feeding of diets available for their capture

大豆抗性蛋白质包含约四分之一的不溶性“高分子量”级分（HMF），所述不溶性“高分子量”级分（HMF）产生自用微生物蛋白酶消化大豆蛋白分离物。给正在接受致癌物处理的生长中的F-344大鼠喂食添加或不添加脱氧胆酸（DCA）的基于HMF或酪蛋白的饮食，每隔4周切除几个结肠，但在12周内肉眼看不到肿瘤。在检查异常隐窝病灶（ACF）时，DCA喂养的酪蛋白组的ACF计数远低于其他饮食组。在39周时，喂食DCA的酪蛋白组的6只大鼠（n=10）和喂食DCA的HMF组的3只大鼠（n=9）证明分别具有18个长轴为4.0* 0.4mm的肿瘤和3个长轴为2.0* 0.1mm的肿瘤，而未喂食DCA的酪蛋白组仅具有单个肿瘤（未喂食DCA的HMF组为零）。也就是说，尽管ACF的频繁发生，HMF喂养延缓肿瘤的发展，这种效果可以解释在大豆抗性蛋白捕获次级胆汁酸的能力和结肠的执行方面。在第39周切除的结肠检查肿瘤病变。结果表明，回肠或空肠切除组在肿瘤发生率（Fisher概率检验）、荷瘤大鼠等级（Mann-Whitney U检验）和部位定向肿瘤分布（卡方独立性检验）方面存在显著差异。此外，在缺乏Na^+依赖性胆汁酸转运蛋白的回肠切除组中，近端结肠肿瘤的发生率出乎意料，这意味着大量的DCA一定流入了结肠，从而成为促进肿瘤发生的严重因素。

Soybean resistant protein comprises about a quarter of the insoluble "high- molecular-weight" fraction (HMF) arising from digestion of soy protein isolate with a microbial protease. Growing F-344 rats undergoing carcinogen treatment were fed HMF- or casein-based diets supplemented with or without deoxycholic acid (DCA), from which several individual colons were excised at 4 weeks' intervals but no tumors were invisible to the naked eye within 12 weeks. On inspection of aberrant crypt foci (ACF), their count in DCA-fed casein group was far less than in other dietary groups. At 39 weeks, 6 rats of the DCA-fed casein group (n=10) and 3 rats of the DCA-fed HMF group (n=9) proved to bear 18 tumors with major axis of 4.0*0.4 mm and 3 tumors with major axis of 2.0*0.1 mm, respectively, in contrast to only a single tumor for the the DCA-unfed casein group (nil for the DCA-unfed HMF group). That is to say, HMF feeding retarded tumor development despite the frequent occurrence of ACF.This effect can be interpreted in terms of the capacity of soybean resistant protein for catching secondary bile acids and carrying out of the colon.Meanwhile, young-adult rats under resectional operations on ileum and jejunum were treated woth azoxymethane and fed the same DCA-supplemented casein diet as above-mentioned. The colons excised at 39 weeks were inspected for neoplastic lesions. As a result, it turned out that there were significant differences between both groups with ileal or jejunal resection in tumor incidence (Fisher's probability test), ranks of tumor-bearing rats (Mann-Whitney U-test) and site-oriented tumor distribution (Chi-square test for independence). In addition, the unexpected frequency of tumors at proximal colon in the ileum-resected group devoid of Na^+-dependent bile acid transporter implies that lots of DCA must have flowed into the colon and thereby served as a severe rink factor of promoting tumorigenesis.