THE EFFECT OF DIETARY FATS ON THE HEPATIC AND INTESTINAL 3-HYDROXY-3-METHYLGLUTARYL COENZYME A REDUCTASE ACTIVITIES IN CHICKS

This experiment was designed to evaluate the effect of degree of unsaturation (Experiment 1) and the chain length of constituent fatty acids of dietary fats (Experiment 2) on-3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activities in the liver and small intestine of chicks. Chicks were fed experimental diets for 10 days and then killed for the determination of the HMG-CoA reductase activities in the intestinal epithelial cell and hepatic microsomes. The hepatic HMG-CoA reductase activity showed the highest value in chicks fed the tallow-containing diet. Chicks fed diets containing safflower or coconut oil resulted in a significantly lower intestinal HMG-CoA reductase activity in comparison with those fed the olive oil-containing diet. The hepatic HMG-CoA reductase activity was significantly higher when fat-free and trilaurin were fed than when any other triglycerides were fed. This activity showed the lowest value in the chicks fed the diet containing tristearin. The HMG-CoA reductase activities in the jejunum and ileum were significantly or tended to be higher when trilaurin was fed than when any other triglycerides were fed. Except when trilaurin was fed, the presence of saturated fat in the diet did not have a significant effect on the intestinal HMG-CoA reductase activity, unlike the effect shown when a highly unsaturated fat was added to the diet. There was no significant correlation between the HMG-CoA reductase activities of the liver and intestinal, and the HMG-CoA reductase activity and cholesterol content of the intestinal epithelial cells.