Impact of β-cyclodextrin and resistant starch on bile acid metabolism and fecal steroid excretion in regard to their hypolipidemic action in hamsters

Abstract

To examine the impact on bile acid metabolism and fecal steroid excretion as a mechanism involved in the lipid-lowering action of β-cyclodextrin and resistant starch in comparison to cholestyramine, male golden Syrian hamsters were fed 0% (control), 8% or 12% of β-cyclodextrin or resistant starch or 1% cholestyramine. Resistant starch, β-cyclodextrin and cholestyramine significantly lowered plasma total cholesterol and triacylglycerol concentrations compared to control. Distinct changes in the bile acid profile of gallbladder bile were caused by resistant starch, β-cyclodextrin and cholestyramine. While cholestyramine significantly reduced chenodeoxycholate independently of its taurine–glycine conjugation, β-cyclodextrin and resistant starch decreased especially the percentage of taurochenodeoxycholate by −75% and −44%, respectively. As a result, the cholate:chenodeoxycholate ratio was significantly increased by 100% with β-cyclodextrin and by 550% with cholestyramine while resistant starch revealed no effect on this ratio. β-Cyclodextrin and resistant starch, not cholestyramine, significantly increased the glycine:taurine conjugation ratio demonstrating the predominance of glycine conjugated bile acids. Daily fecal excretion of bile acids was 4-times higher with 8% β-cyclodextrin and 19-times with 1% cholestyramine compared to control. β-Cyclodextrin and cholestyramine also induced a 2-fold increase in fecal neutral sterol excretion, demonstrating the sterol binding capacity of these two compounds. Resistant starch had only a modest effect on fecal bile acid excretion (80% increase) and no effect on excretion of neutral sterols, suggesting a weak interaction with intestinal steroid absorption. These data demonstrate the lipid-lowering potential of β-cyclodextrin and resistant starch. An impaired reabsorption of circulating bile acids and intestinal cholesterol absorption leading to an increase in fecal bile acid and neutral sterol excretion is most likely the primary mechanism responsible for the lipid-lowering action of β-cyclodextrin. In contrast, other mechanisms involving the alterations in the biliary bile acid profile or repressed hepatic lipogenesis, e.g., VLDL production, appear to be involved in the hypolipidemic effect of resistant starch.