CHOLESTEROL-LOWERING ACTION OF GUAR GUM IN THE RAT - CHANGES IN BILE-ACIDS AND STEROLS EXCRETION AND IN ENTEROHEPATIC CYCLING OF BILE-ACIDS

The mechanisms of the cholesterol-lowering effect of guar gum (5% in t he diet) has been investigated in rats adapted to cholesterol-free or 0.3% cholesterol diets. GG showed a potent plasma cholesterol-lowering effect and counteracted the liver accumulation of triglyceride and ch olesterol esters in rats adapted to cholesterol-diets. The biliary bil e acid flux into the small intestine was enhanced by dietary cholester ol (+25%) or GG (+60%) or both (+83%). The fecal excretion of steroids (sterols + bile acids) was markedly enhanced by GG, especially in rat s fed the cholesterol-diet. The small intestine and the cecal content of bile acids were markedly higher in rats fed the GG and/or cholester ol diets than in controls. The portal vein flux of bile acids was enha nced by GG, whatever the dietary cholesterol level. There was also an increase in the cecal absorption of bile acids when cholesterol-fed ra ts also received GG in the diet. GG feeding induced liver HMG CoA redu ctase, even in cholesterol-fed rats, as well as cholesterol 7 alpha-hy droxylase. The cholesterol-lowering effect of GG was not accompanied b y a reduction of bile acid reabsorption in the small intestine, and th eir fecal excretion was moderatly increased by GG. Neutral sterol elim ination in the feces was strongly increased by GG, whatever the dietar y cholesterol level, suggesting a specific impact of this hydrocolloid on cholesterol absorption. (C) 1998 Elsevier Science Inc.