The effects of dietary fat quality on cholesterol and lipoprotein metabolism in the guinea pig

The effects of dietary saturated versus polyunsaturated fat (7.5%; w/w) on sterol balance and lipoprotein metabolism were studied in guinea pigs. The polyunsaturated diet significantly reduced plasma cholesterol and triglyceride levels by 34% and 40%, respectively. Polyunsaturated dietary fat significantly reduced the percentage of cholesteryl ester in low density lipoprotein (LDL) while the relative proportion of LDL-phospholipids was increased. The ratio of LDL surface to core components in the polyunsaturated fed animals was significantly higher (P .02). Dietary fat quality had no effect on either sterol balance or hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Hepatic free and esterfield cholesterol levels were significantly higher in the polyunsaturated fat fed group (P .01). Feeding polyunsaturated fat caused a significant (1.9-fold) increase in hepatic membrane LDL (apo B/E) receptor binding. The data indicate that the hypocholesterolemic effect of polyunsaturated fat is not attributable to changes in cholesterol metabolism but rather to a redistribution of plasma cholesterol to tissues due to increased tissue LDL receptor binding