Hepatic and intestinal cytochrome P-450, glutathione-S-transferase and UDP-glucuronosyl transferase are affected by six types of dietary fiber in rats inoculated with human whole fecal flora.

The effects of six different sources of dietary fiber (inulin, wheat brain, carrot, cocoa, pea and oat fiber) on hepatic and intestinal cytochrome P-450 (EC 1.14.14.1), glutathione-S-transferase (GSH-T, EC 2.5.1.18) and UDP-glucuronosyl transferase (UDPG-T, EC 2.4.1.17) were studied using germ-free F344 rats subsequently inoculated with a human whole fecal flora. In the liver, the total concentration of P-450 was significantly lower in the wheat bran-fed group than in the carrot-fed group. The 2E1 form of P-450, involved in nitrosamine metabolism, was enhanced in the carrot-fed group compared with those fed most other types of fiber. Compared with the pea-fed group, rats fed cocoa had a lower constitutive 2C11 form and a higher 1A2 form. A very high concentration of small intestinal 1A1 form--involved in "toxication" reactions--was observed in rats fed cocoa. The specific activity of hepatic GSH-T was significantly higher in rats fed inulin than in all other groups, except the carrot-fed group. In the colon, GSH-T specific activity was twice as high in the oat-fed group as in the wheat bran-fed counterpart. Small intestinal GSH-T activity and hepatic and intestinal UDPG-T activities were unaffected by diet. Results are discussed in relation to potential health benefits.