Dietary Fat Dependence of Intestinal 3-Hydroxy-3-Methylglutaryl Coenzyme A (HMG-CoA) Reductase Activity in Rats

Abstract

The effects of dietary fats on intestinal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were studied in rats. Animals were fed experimental diets ad libitum for 7-13 d then killed in the morning for the determination of the reductase activity in an epithelial cell homogenate. When corn oil was the source of dietary fat, the specific activity of jejunal reductase depicted a biphasic pattern in response to dietary fat level with a peak activity when the diet contained 10% fat (by weight) whereas the specific activity of ileal reductase was independent of the fat level. Reductase activities were apparently independent of the degree of saturation of dietary fat (safflower oil, olive oil, lard and tallow) when each was fed as 10% of the diet. Both jejunal and ileal reductase activities were higher when trilaurin was fed than when other saturated fats (tricaprylin, trimyristin, tripalmitin and tristearin) were fed. The jejunum synthesized more cholesterol than the ileum. There was no significant correlation among the reductase activity, cholesterol content of the epithelial cells and the rate of fat absorption, suggesting a complex regulatory mechanism.

PPARalpha-mediated effects of dietary lipids on intestinal barrier gene expression

“…Functionally these results suggest that less cholesterol is absorbed from the lumen and more cholesterol is transferred to Apo-A1, resulting in reduced intracellular cholesterol levels in enterocytes. Enterocytes likely compensate for this by increasing the activity of HMG-CoA reductase, as has been reported before [ 59 - 61 ].…”

Site of Fat Absorption and Localization of 3-Hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) Reductase Activity along the Small Intestine of Rats

“…This study confirmed the previous observation 4 ) that the alteration by the type of dietary fat of the distribution of HMG-CoA reductase along the small intestine. In addition, results shown in Fig.…”

“…In addition, results shown in Fig. 1 showed that the jejunoileal gradient for reductase activity in rats fed a purified diet containing completely saturated fat 4 ) was not due to the deficiency of essential fatty acids.…”

“…3 ) We have shown in rats a dietary fatdependent modification of intestinal HMGCoA reductase, which is the rate-limiting enzyme in cholesterogenesis. 4 ) Dietary polyunsaturated fat preferentially stimulated the jejunal activity while saturated fat increased the ileal activity, and hence the gradient for the reductase activity was either ileojejunal or jejunoileal.…”