Inhibitory effect of microfibril wheat bran on azoxymethane-induced colon carcinogenesis in CF1 mice

Microfibril wheat bran (MFW), a processed dietary fiber prepared by milling of coarse wheat bran (WB), is softer and has a more pleasant taste than WE . In this study, we examined the inhibitory effect of MFW on azoxymethane ( AOM)-induced colon carcinogenesis in female CF1 mice and compared its effec t with that of WE and cellulose (CL). The mice were fed a modified AIN 76 A diet supplemented with either MFW, WE, or CL at a final concentration of 2 0% (w/w). Six weekly s.c. injections of AOM (10 mg/kg body weight) were adm inistered per mouse commencing I week after the start of the feeding period . Control mice were injected with saline only. Thirty-three weeks after the initial injection, the mice were sacrificed, examined for tumors, and the cecal contents were analyzed to determine the moisture content and the conc entrations of short-chain fatty acids (SCFA). The average number of total t umors per mouse in the MFW (2.9 +/- 0.6, P = 0.017) and WE (5.3 +/- 1.3, P = 0.373) diet groups was lower than that of the CL diet group (7.5 +/- 1.3) , though there was no significant difference in tumor incidence (94.7%, 90. 0% and 94.7%, respectively) between the groups. More than 90% of the tumors in each group were adenocarcinomas. The incidence of adenoma and that of c arcinoma in situ in the MFW diet group (5.3% and 0%, respectively) were als o lower than those in the CL diet group (26.3 and 26.3%, respectively; P = 0.180 and P = 0.046, respectively). Analysis of the cecal contents revealed a significantly higher moisture content and significantly higher concentra tions of SCFA, butyrate in particular, in the MFW and WE diet groups. The r esults of this study indicate that the source and texture of dietary fiber can influence tumor development in CF1 mice, and more specifically that MFW is a promising and useful dietary supplement with properties serving to pr otect against the development of colon cancer. (C) 1999 Elsevier Science Ir eland Ltd. All rights reserved.