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Prickly Pear (Opuntia sp.) Pectin Alters Hepatic Cholesterol Metabolism without Affecting Cholesterol Absorption in Guinea Pigs Fed a Hypercholesterolemic Diet^{1, 2,}

Department of Nutritional Sciences and Interdisciplinary Nutritional Sciences Program, University of Arizona, Tucson, AZ 85721 ^* CIIDIR-IPN, Unidad Michoacan, Jiquilpan de Juarez, Michoacan, Mexico 59510

Prickly pear pectin intake decreases plasma LDL concentrations by increasing hepatic apolipoprotein B/E receptor expression in guinea pigs fed a hypercholesterolemic diet. To investigate whether prickly pear pectin has an effect on cholesterol absorption and on enzymes responsible for hepatic cholesterol homeostasis, guinea pigs were fed one of three semipurified diets, each containing 15 g lard/100 g diet: 1) the lard-basal diet with no added cholesterol or prickly pear pectin (LB diet); 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, added at the expense of cellulose (LC-P diet). Animals fed the LB diet had the lowest plasma LDL and hepatic cholesterol concentrations, followed by animals fed the LC-P diet (P < 0.001). Hepatic 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase activity was highest in the group fed the LB diet, with similar values for animals in the other two groups. A positive correlation existed between plasma LDL cholesterol concentration 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 plasma and hepatic cholesterol concentrations of animals fed prickly pear pectin are not explained by differences in cholesterol absorption but rather are due to mechanisms that alter hepatic cholesterol homeostasis, resulting in lower plasma LDL concentrations.

KEY WORDS: • acyl CoA:cholesterol acyltransferase • 3-hydroxy-3-methylglutaryl coenzyme A reductase • cholesterol • pectin • guinea pigs

¹ Supported by a grant-in-aid from the American Heart Association, Arizona Affiliate (IG-2-11-91).

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence and reprint requests should be addressed.

Manuscript received 30 September 1993. Revision accepted 31 January 1994.