关于肠内细菌在大肠癌发生过程中的作用的研究,根据疾病学调查和动物实验,已取得了某些进展。可是,因肠内细菌而生成的致癌物质和致癌的“启动子”在大肠癌发生过程中的具体作用等,迄今为止所知道的并不多。1.与胆盐代谢的关系: 肝脏内的胆固醇被合成胆酸和醌脱氧胆酸等一次胆汁酸与甘氨酸或牛磺酸结合,作为结合胆汁酸被分泌到胆汁中,这些结合胆汁酸在小肠的上部帮助脂肪的消化吸收。一部分被肠内细菌分解成游离胆汁酸,再从胆酸衍变成脱氧胆酸,醌脱氧胆酸则衍变成石胆酸,称为二次胆汁酸。被排泄到胆汁中的胆汁酸约有95%在小肠被重吸收回到肝脏,仍以结合胆汁酸的形式被排入肠内。不能重吸收的胆汁酸到达大肠,依靠 Regarding the role of intestinal bacteria in the development of colorectal cancer, some progress has been made on the basis of disease investigations and animal experiments. However, the specific role of carcinogens and oncogenic “promoters” produced by enterobacteria in colorectal carcinogenesis has not been known so far. 1. And the relationship between bile salt metabolism: cholesterol in the liver by synthetic bile acids and quinone deoxycholic acid and a bile acid with glycine or taurine, combined with bile acids are secreted into the bile, the combination of bile acids in the small intestine The upper part helps fat digestion and absorption. Part of the intestinal bacteria is decomposed into free bile acids, and then evolved from bile acid into deoxycholic acid, quinone deoxycholic acid is changed into lithocholic acid, called secondary bile acid. Approximately 95% of bile acids excreted into the bile are reabsorbed in the small intestine back into the liver and are still released into the intestine in the form of conjugated bile acids. Bile acids that can not be reabsorbed reach the large intestine and rely on it