title: The cholesterol-lowering effect of guar gum is not the result of a simple diversion of bile acids toward fecal excretion.
abstract: The effects of partially hydrolyzed, nonviscous, guar gum (PHGG) on cholesterol metabolism and digestive balance have been compared with those of native guar gum (GUAR) in rats adapted to 0.4% cholesterol diets. Both types of guar gum elicited acidic fermentations in the large intestine, but only GUAR effectively lowered plasma cholesterol (P < 0.001), chiefly in the triglyceride-rich lipoprotein fraction. The biliary bile acid excretion was significantly enhanced in rats fed GUAR (P < 0.05), as well as the intestinal and cecal bile acid pool (P < 0.001). In rats fed GUAR and to a lesser extent in those fed PHGG, the fecal excretion of bile acids and neutral sterol was higher than in controls (P < 0.01). The digestive balance (cholesterol intake-steroid excretion) was positive in control rats (+47 mumol/d), whereas it was negative in rats fed GUAR (-20 mumol/d), which could involve a higher rate of endogenous cholesterol synthesis. In rats fed PHGG, the steroid balance remained slightly positive. Liver 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity was very low (22 pmol/min/mg protein), owing to cholesterol supplementation, in control rats or in rats fed PHGG, whereas it was markedly higher (+463%) in rats fed GUAR. In conclusion, even if PHGG does alter some parameters of the enterohepatic cycle of cholesterol and bile acids, its effects are not sufficient to elicit a significant cholesterol-lowering effect. The intestinal (ileal or cecal) reabsorption of bile acids was not reduced, but rather increased, by GUAR; nevertheless the intestinal capacities of reabsorption were overwhelmed by the enlargement of the digestive pool of bile acids. In the present model, induction of HMG-CoA reductase probably takes place in the presence of elevated portal bile acid concentrations.
authors.affiliation: Laboratoire des Maladies Métaboliques et Micronutriments, INRA de Clermont-Ferrand/Theix, Ceyrat, France.
authors.forename: M L
authors.initials: ML
authors.lastname: Favier
authors.forename: P E
authors.initials: PE
authors.lastname: Bost
authors.forename: C
authors.initials: C
authors.lastname: Guittard
authors.forename: C
authors.initials: C
authors.lastname: Demigné
authors.forename: C
authors.initials: C
authors.lastname: Rémésy
mesh_terms: D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D001646:Bile / Q000378:metabolism; D001647:Bile Acids and Salts / Q000378:metabolism*; D001835:Body Weight; D002432:Cecum / Q000254:growth & development / Q000378:metabolism; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D004041:Dietary Fats; D005243:Feces; D005685:Galactans / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007408:Intestinal Absorption; D008055:Lipids / Q000032:analysis / Q000097:blood; D008074:Lipoproteins / Q000032:analysis / Q000097:blood; D008099:Liver / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D008297:Male; D008351:Mannans / Q000494:pharmacology*; D009929:Organ Size; D053149:Plant Gums; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000924:Anticholesteremic Agents; D001647:Bile Acids and Salts; D004041:Dietary Fats; D005685:Galactans; D008055:Lipids; D008074:Lipoproteins; D008351:Mannans; D053149:Plant Gums; D002784:Cholesterol; C007894:guar gum; D006903:Hydroxymethylglutaryl CoA Reductases