Effect of bacterial metabolism in the intestine on colorectal tumors induced by 1,2-dimethylhydrazine in transgenic mice harboring human prototype c-Ha-ras genes

The number of colorectal tumors per mouse induced by 1,2-dimethylhydrazine in transgenic (Tg) mice carrying human c-Ha-ras genes was significantly reduced by ingestion of apple pectin (AP) or a culture condensate of Bifidobacterium longum(MB) compared with a control diet and non-Tg mice. However, there were no differences in the composition of fecal flora, water content, beta -glucuronidase and beta -glucosidase activities, and concentrations of organic acids and putrefactive products in the feces between the AP or MB diet and the control diet, or between the Tg mice and non-Tg mice. The concentration of secondary bile acids in the MB diet group was higher than that in the control group. These results suggested that there was no relationship between prevention of colorectal tumors in Tg mice and the AP or MB diet, or improvement of the intestinal environment due to these functional foods.