PECTIN ISOLATED FROM PRICKLY PEAR (OPUNTIA SP) MODIFIES LOW-DENSITY-LIPOPROTEIN METABOLISM IN CHOLESTEROL-FED GUINEA-PIGS

The effect of prickly pear soluble fiber on low density lipoprotein (LDL) metabolism was investigated by feeding male guinea pigs either a nonpurified diet containing 0.25% cholesterol (HC diet) or the HC diet + 1% prickly pear pectin (HC-P diet). Plasma cholesterol levels were significantly decreased by the HC-P diet, with a 33% decrease in LDL levels (p < 0.02) and an increase in LDL density. Hepatic free and esterified cholesterol levels were reduced 40 and 85%, respectively (p < 0.002), by the HC-P diet. Hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase levels were not different. 125I-LDL binding to hepatic membranes was increased 1.7-fold by the HC-P diet (p < 0.001), with receptor affinity (K(d)) being unaltered and receptor number (B(max)) being significantly increased (p < 0.001). These data suggest that prickly pear pectin may act by a mechanism similar to that of bile acid-binding resins in lowering plasma cholesterol levels. The observed reduction in LDL and hepatic cholesterol levels and increase in LDL density and hepatic apolipoprotein B/E receptors are responses suggesting an increased demand on hepatic cholesterol from increased excretion of bile acids and interruption of the enterohepatic circulation.