CHOLESTEROL-LOWERING AND GALLSTONE-PREVENTING ACTION OF CHITOSANS WITH DIFFERENT DEGREES OF DEACETYLATION IN HAMSTERS FED CHOLESTEROL-RICH DIETS

The lipid-lowering potential of chitin and chitosan (CHI) and their pr otective effect against cholesterol gallstone formation was investigat ed by feeding male Golden Syrian hamsters gallstone-inducing diets. Si nce the physicochemical properties like degree of deacetylation or vis cosity are thought to be involved in the hypocholesterolemic action of CHI, two varieties of CHI, a 92% and a 79% deacetylated CHI (CHI92 an d CHI79) were tested. Hamsters were fed semipurified, gallstone-induci ng diets containing 5% fat, 0.4% cholesterol and 10% cellulose with or without supplements of chitin (8%) or the two CHIs (8% and 4%). After 5 weeks, 8% CHI79 significantly reduced plasma lipids (total choleste rol (TC): 4.5 +/- 0.7 vs 10.1 +/- 3.9 mmol/L and triglycerides (TG): 2 .9 +/- 1.5 vs 7.3 +/- 3.6 mmol/L compared to the control diet), wherea s 8% CHI92 produced only a minor hypocholesterolemic effect (-10%). Fe eding 8% CHI92 or CHI79 caused a significant reduction in food intake, body weight gain and liver weight. The adverse effect on food intake and growth was lessened by feeding 4% CHI92 or CHI79, but the differen ces were still significant for CHI92. The supplementation with 4% of b oth CHIs resulted in a significant lowering of plasma cholesterol with a reduction in TC of 38% with CHI92 and 32% with CHI79 compared to th e control diet. Hepatic cholesterol was significantly decreased with 8 % CHI79, whereas 8% CHI92 caused only a negligible reduction. The 4% s upplement of CHI92 did not alter cholesterol accumulation in the Ever, but hepatic total cholesterol was significantly increased with 4% CHI 79. While the 8% supplements of both CHIs completely inhibited cholest erol gallstone formation, 4% CHI92 or CHI79 added to the diet had no p reventive effect and a 90% incidence of cholesterol gallstones was obs erved. 8% chitin produced no apparent effects on plasma, hepatic and b iliary lipids. Whereas 8% CHI79 significantly increased the cholate : chenodeoxycholate ratio of gallbladder bile by decreasing particularly taurochenodeoxycholate, 8% CHI92 had no distinct impact on bile acid composition. The 4% supplements of CHI92 or CHI79 did not alter biliar y lipids and bile acid distribution. The dried fecal weight was double d by feeding 8% and 4% of CHI92 or CHI79 compared to the control diet. Whereas the daily excretion of neutral sterols was significantly expa nded with the 8% supplements of CHI92 and CHI 79, only CHI79 caused al so a 1.9-fold increase in the daily bite acid excretion. The supplemen tation with 4% of CHI92 or CHI79 did not significantly change fecal ex cretion of bile acids or neutral sterols although daily excretion of n eutral sterols was increased by 20%. These data demonstrate that in ha msters feeding CHI is associated with a reduced food intake and that t he cholesterol-lowering effect seems mainly related to an increase in the fecal excretion of neutral sterols. (C) 1997 Elsevier Science Inc.