PRICKLY PEAR (OPUNTIA SP) PECTIN ALTERS HEPATIC CHOLESTEROL-METABOLISM WITHOUT AFFECTING CHOLESTEROL ABSORPTION IN GUINEA-PIGS FED A HYPERCHOLESTEROLEMIC DIET

Prickly pear pectin intake decreases plasma LDL concentrations by incr easing hepatic apolipoprotein B/E receptor expression in guinea pigs f ed a hypercholesterolemic diet. To investigate whether prickly pear pe ctin has an effect on cholesterol absorption and on enzymes responsibl e for hepatic cholesterol homeostasis, guinea pigs were fed one of thr ee semipurified diets, each containing 15 g lard/100 g diet: 1) the la rd-basal diet with no added cholesterol or prickly pear pectin (LB die t); 2) the LB diet with 0.25 g added cholesterol/100 g diet (LC diet); or 3) the LC diet containing 2.5 g prickly pear pectin/100 g diet, ad ded at the expense of cellulose (LC-P diet). Animals fed the LB diet h ad the lowest plasma LDL and hepatic cholesterol concentrations, follo wed by animals fed the LC-P diet (P < 0.001). Hepatic 3-hydroxy-3-meth ylglutaryl CoA (HMG-CoA) reductase activity was highest in the group f ed the LB diet, with similar values for animals in the other two group s. A positive correlation existed between plasma LDL cholesterol conce ntration and hepatic acyl CoA:cholesterol acyltransferase activity (r = 0.87, P < 0.001). Cholesterol absorption was not different among the three dietary groups. These results indicate that the decreased plasm a and hepatic cholesterol concentrations of animals fed prickly pear p ectin are not explained by differences in cholesterol absorption but r ather are due to mechanisms that alter hepatic cholesterol homeostasis , resulting in lower plasma LDL concentrations.