3-hydroxy-3-methylglutaryl coenzyme A reductase activity in the small intestine of rats fed non-purified and semipurified diets.

The effects of diet types on microsomal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in the intestinal villus and crypt cells isolated by scraping were studied in rats. The jejunoileal gradient for the reductase specific activity, a phenomenon usually observable in rats fed a commercial non-purified diet, disappeared when sucrose- or glucose-enriched semipurified diets were ingested. Feeding these semipurified diets resulted in a significant increase in reductase activity in jejunal villi and crypts with a concomitant decrease in that of the ileal populations. Neutral detergent fiber prepared from the non-purified diet, but not cellulose powder, when included to semipurified diets at the levels equivalent to those in the non-purified diet, eliminated the ileojejunal gradient, reductase activity was virtually the same in the proximal and distal portions of the intestine or the distribution pattern resembled that shown in rats fed a non-purified diet. Potato and corn starches replaced for sucrose in a low-fiber semipurified diet were also effective for elimination of the gradient, but wheat starch was less effective in the respect. It is clear that intestinal sterogenesis via HMG-CoA reductase is specifically regulated by the complex interplay of dietary components, in particular carbohydrate sources.