Effect of bran and citrus pulp on hepatic, small intestinal and colonic HMG CoA reductase, cytochrome P450 and cytochrome b5 levels in rats.

The effect of dietary wheat bran and citrus pulp on hepatic, small intestinal and colonic HMG-CoA reductase activity, cytochrome P450 and cytochrome b5 levels was studied in F344 rats. Colonic and small intestinal HMG-CoA reductase activity was significantly lower in the wheat bran group than the control group. No differences in hepatic HMG-CoA reductase activity occurred between the wheat bran, citrus pulp and control groups. A direct relationship between hepatic cholesterol levels and hepatic Cytochrome P450 levels was demonstrated. A similar trend was exhibited between fecal cholesterol and colonic cytochrome P450 levels in the colon. These results suggest that the effect of certain types of dietary fiber in small intestinal and colonic cholesterogenesis is mediated through alterations in small intestinal and colonic mixed function oxidase activity.