Cholesterol-lowering action of guar gum in the rat: Changes in bile acids and sterols excretion and in enterohepatic cycling of bile acids

Abstract

The mechanisms of the cholesterol-lowering effect of guar gum (5% in the 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 cholesterol esters in rats adapted to cholesterol-diets. The biliary bile acid flux into the small intestine was enhanced by dietary cholesterol (+25%) or GG (+60%) or both (+83%). The fecal excretion of steroids (sterols + bile acids) was markedly enhanced by GG, especially in rats fed the cholesterol-diet. The small intestine and the cecal content of bile acids were markedly higher in rats fed the GG and/or cholesterol diets than in controls. The portal vein flux of bile acids was enhanced by GG, whatever the dietary cholesterol level. There was also an increase in the cecal absorption of bile acids when cholesterol-fed rats also received GG in the diet. GG feeding induced liver HMG CoA reductase, even in cholesterol-fed rats, as well as cholesterol 7α-hydroxylase. The cholesterol-lowering effect of GG was not accompanied by a reduction of bile acid reabsorption in the small intestine, and their fecal excretion was moderatly increased by GG. Neutral sterol elimination in the feces was strongly increased by GG, whatever the dietary cholesterol level, suggesting a specific impact of this hydrocolloid on cholesterol absorption.