Effect of Dietary Fiber on Spontaneous Liver Tumorigenesis in C3H/He Male Mice

Abstract

C3H/He male mice have a high incidence of spontaneous liver tumor. It is recognized that this tumorigenesis is modified by the intestinal microflora. The effects of dietary fiber (cellulose, apple pulp, guar gum) on spontaneous liver tumorigenesis in C3H/He male mice and on comutagenicity induced by Trp-P-1 in the cecal contents were studied. Eight-week-old mice were fed either a fiber-free diet or a semipurified diet containing 5% dietary fiber for 44 weeks. The results obtained were as follows: 1) No differences in body weight were found among the groups throughout the experimental period. 2) The incidence of spontaneous liver tumor was high, above 90% in the fiber-free, cellulose and apple pulp diet groups. However, the incidence of liver tumor in the guar gum diet group was 62%, which was significantly lower than in the other groups. 3) The number of liver tumor nodules per tumor-bearing mouse in the guar gum diet group was significantly lower than that in the other groups. 4) Because no mutagenicity in the Ames test was recognized in cecal contents from C3H male mice, comutagenicity in the cecal contents induced by Trp-P-1 was studied. Comutagenicity was found in the cellulose and apple pulp diet groups, but not in the fiber-free and guar gum diet groups. Thus, the present study demonstrated that dietary guar gum inhibited spontaneous liver tumorigenesis in C3H male mice and that at least the comutagenicity induced by Trp-P-1 was not related to this inhibitory effect.