Effect of fat and microflora on hepatic, small intestinal and colonic HMG CoA reductase, cytochrome P450 and cytochrome B5.

High levels of dietary fat caused a significant reduction in HMG CoA reductase activity in the liver of germ-free rats whereas significantly elevated small intestinal enzyme activity was observed. Dietary fat had no significant effect on HMG CoA reductase activity in any tissue studied in the conventional rat. No significant change in colonic HMG CoA reductase activity was observed between any of the experimental groups. Rats fed a high-fat diet tended to exhibit higher cytochrome P450 levels in all tissues studied, regardless of the presence of intestinal microflora.