Effectiveness of resistant starch, compared to guar gum, in depressing plasma cholesterol and enhancing fecal steroid excretion.
Amylase-resistant starch (RS) represents a substrate that can be administered in substantial amounts in the diet, in contrast to gel-forming polysaccharides, such as guar gum (GG). The aim of this work was thus to compare the effects of GG and RS on cholesterol metabolism in rats adapted to 0.4% cholesterol diets, using dietary GG or RS levels (8 or 20%, respectively) that led to a similar development of fermentations, as assessed by the degree of enlargement of the cecum. The RS diet elicited a marked rise in the cecal pool of short-chain fatty acids, especially acetic and butyric acid, whereas the GG diet favored high-propionic acid fermentations. Both polysaccharides markedly altered the cholesterol excretion, from 50% of ingested cholesterol in controls, up to about 70% in rats adapted to the RS or GG diets. With these diets, the fecal excretion of bile acids was enhanced (67 and 144% with the RS and GG diets, respectively). RS and GG diets were effective in lowering plasma cholesterol (about -40%) and triglycerides (-36%). There was practically no effect of the diets on cholesterol in d > 1.040 lipoproteins (high density lipoproteins), whereas RS (and to a larger extent, GG) were very effective to depress cholesterol in d < 1.040 lipoproteins (especially in triglyceride-rich lipoproteins). Fermentable polysaccharides counteracted the accumulation of cholesterol in the liver, especially cholesterol esters. In parallel, liver acyl CoA:cholesterol acyltransferase was depressed in rats fed the RS or GG diets, whereas only the GG diet counteracted the downregulation of 3-hydroxy-3-methylglutaryl-CoA by cholesterol. These data suggest that RS may be practically as effective as a gel-forming gum, such as GG, on steroid excretion and on cholesterol metabolism.
Laboratoire des Maladies Métaboliques et Micronutriments, INRA de Clermont-Ferrand/Theix, St-Genés-Champanelle, France.
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Levrat
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Moundras
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Younes
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Morand
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Demigné
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Rémésy
D000818:Animals; D002784:Cholesterol / Q000097:blood*; D005243:Feces / Q000737:chemistry*; D005685:Galactans / Q000494:pharmacology*; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D008351:Mannans / Q000494:pharmacology*; D053149:Plant Gums; D051381:Rats; D017208:Rats, Wistar; D013256:Steroids / Q000378:metabolism*; D002785:Sterol O-Acyltransferase / Q000378:metabolism
D005685:Galactans; D008351:Mannans; D053149:Plant Gums; D013256:Steroids; D002784:Cholesterol; C007894:guar gum; D006903:Hydroxymethylglutaryl CoA Reductases; D002785:Sterol O-Acyltransferase