Effect of guar gum and cholestyramine on plasma lipoprotein cholesterol in rats

The effects of guar gum and cholestyramine on cholesterol metabolism were studied in meal-fed male Wistar adult rats maintained on a cholesterol-enriched or cholesterol-free purified diet for 2 weeks. At 3.5h after the last meal, blood was withdrawn by cardiac puncture, and then plasma and plasma lipoprotein-lipids, and liver cholesterol were determined. The results obtained were as follows: 1) In the cholesterol-fed rats, guar gum and cholestyramine suppressed the increase of plasma and liver cholesterol, and the decrease of HDL-cholesterol due to cholesterol intake. 2) In the rats fed the cholesterol-free diet, cholestyramine decreased chylomicron+VLDL-cholesterol, but did not alter the level of plasma cholesterol. 3) Guar gum decreased chylomicron+VLDL-, HDL- and plasma cholesterol in rats fed the cholesterol-free diet. These results demonstrate that the mechanism whereby guar gum lowers the plasma cholesterol level cannot be fully explained by interference with absorption of bile acid and cholesterol, which is the mode of action of cholestyramine.