Resistant starch is more effective than cholestyramine as a lipid-lowering agent in the rat.
Amylase-resistant starch (RS) represents a substrate for the bacterial flora of the colon, and the question arises as whether RS shares with soluble fibers common mechanisms for their lipid-lowering effects. It is uncertain whether a cholesterol-lowering effect depends basically on an enhanced rate of steroid excretion or whether colonic fermentations also play a role in this effect. In the present study, the effect of RS (25% raw potato starch), of a steroid sequestrant (0.8% cholestyramine), or both were compared on bile acid excretion and lipid metabolism in rats fed semipurified diets. RS diets led to a marked rise in cecal size and the cecal pool of short-chain fatty acids (SCFA), as well as SCFA absorption; cholestyramine did not noticeably affect cecal fermentation. Whereas cholestyramine was particularly effective at enhancing bile acid excretion, RS was more effective in lowering plasma cholesterol (-32%) and triglycerides (-29%). The activity of 3-hydroxy-3-methylglutaryl-CoA reductase was increased fivefold by cholestyramine and twofold by RS. This induction in rats fed RS diets was concomittant to a depressed fatty acid synthase activity. In rats fed the RS diet, there was a lower concentration of cholesterol in all lipoprotein fractions, especially the (d = 1.040-1.080) fraction high-density lipoprotein (HDL1), while those fed cholestyramine had only a significant reduction of HDL1 cholesterol. In contrast to cholestyramine, RS also depressed the concentration of triglycerides in the triglyceride-rich lipoprotein fraction.(ABSTRACT TRUNCATED AT 250 WORDS)
Younes
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Laboratoire des Maladies Métaboliques, INRA de Clermont-Ferrand/Theix, St-Genès-Champanelle, France.
Levrat
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Demigné
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Rémésy
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D000681:Amylases / Q000378:metabolism; D000818:Animals; D000924:Anticholesteremic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001647:Bile Acids and Salts / Q000378:metabolism*; D001835:Body Weight / Q000187:drug effects; D002432:Cecum / Q000187:drug effects; D002784:Cholesterol / Q000097:blood*; D002792:Cholestyramine Resin / Q000008:administration & dosage / Q000494:pharmacology*; D004435:Eating / Q000187:drug effects; D005243:Feces / Q000737:chemistry; D005285:Fermentation / Q000187:drug effects; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects; D008075:Lipoproteins, HDL / Q000097:blood; D008099:Liver / Q000187:drug effects; D008297:Male; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013213:Starch / Q000008:administration & dosage / Q000494:pharmacology*; D014280:Triglycerides / Q000097:blood*
D000924:Anticholesteremic Agents; D001647:Bile Acids and Salts; D008075:Lipoproteins, HDL; D014280:Triglycerides; D002792:Cholestyramine Resin; D013213:Starch; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D000681:Amylases