Kulkarni N, Reddy B S
Division of Nutritional Carcinogenesis, American Health Foundation, Valhalla, New York 10595.
Proc Soc Exp Biol Med. 1994 Dec;207(3):278-83. doi: 10.3181/00379727-207-43817.
Epidemiologic and experimental studies suggest that consumption of fermented milk products and lactic bacterial cultures that are used to ferment the dairy products, decrease the incidence of certain types of cancer. The present study was designed to determine the effect of lyophilized cultures of Bifidobacterium longum (B. longum), a lactic bacteria, on the azoxymethane (AOM)-induced preneoplastic lesions such as aberrant crypt foci (ACF) formation in the colon and on fecal bacterial beta-glucuronidase activity in male F344 rats. At 5 weeks of age, groups of animals were fed the AIN-76A (control) and the experimental diets containing 1.5% and 3% lyophilized cultures of B. longum. At 10 weeks of age, all animals received sc injection of AOM dissolved in normal saline at a dose rate of 20 mg/kg body wt, once weekly for 2 weeks. The animals were necropsied 6 weeks after the last AOM injection, and the ACF were visualized under light microscopy in the formalin-fixed, unsectioned methylene blue-stained colons where they were distinguished by their increased size, more prominent epithelial cells, and pericryptal space. The cecal contents were analyzed for bacterial beta-glucuronidase activity. The feeding of lyophilized cultures of B. longum significantly inhibited the ACF formation (53%) and the crypt multiplicity in the colon. A significant decrease in the fecal bacterial beta-glucuronidase was also observed in the animals fed the diets containing Bifidobacterium supplements as compared with control diet. These results demonstrate that B. longum in diet influences the metabolic activity of certain types of intestinal microflora that are involved in the production of beta-glucuronidase. Furthermore, the findings also suggest that B. longum supplements inhibit ACF formation, an early preneoplastic marker of malignant potential in the process of colon carcinogenesis.
流行病学和实验研究表明，食用发酵乳制品以及用于发酵乳制品的乳酸菌培养物，可降低某些类型癌症的发病率。本研究旨在确定长双歧杆菌（一种乳酸菌）的冻干培养物对雄性F344大鼠结肠中由氧化偶氮甲烷（AOM）诱导的癌前病变（如异常隐窝灶（ACF）形成）以及粪便细菌β-葡萄糖醛酸酶活性的影响。5周龄时，将动物分组，分别喂食AIN-76A（对照）以及含有1.5%和3%长双歧杆菌冻干培养物的实验性饮食。10周龄时，所有动物均接受皮下注射溶解于生理盐水中的AOM，剂量为20 mg/kg体重，每周一次，共2周。在最后一次注射AOM 6周后对动物进行尸检，并在光镜下观察福尔马林固定、未切片的亚甲蓝染色结肠中的ACF，通过其增大的尺寸、更突出的上皮细胞和隐窝周围间隙来区分。分析盲肠内容物中的细菌β-葡萄糖醛酸酶活性。喂食长双歧杆菌冻干培养物可显著抑制结肠中ACF的形成（53%）和隐窝多重性。与对照饮食相比，喂食含有双歧杆菌补充剂饮食的动物粪便细菌β-葡萄糖醛酸酶也显著降低。这些结果表明，饮食中的长双歧杆菌会影响某些参与β-葡萄糖醛酸酶产生的肠道微生物群的代谢活性。此外，研究结果还表明，补充长双歧杆菌可抑制ACF的形成，ACF是结肠癌发生过程中恶性潜能的早期癌前标志物。
