The role of intestinal bacteria in gallstone formation in animal model. A study on biliary lipid composition and bile acid profiles in bile, small intestinal contents and feces of Clostridium butyricum MIYAIRI No. 588 monocontaminated mice

Summary

Contradictory results in the studies on experimental gallstone formation using conventional and germfree mice have been reported. To study the role of bacteria in gallstone formation in the animal model JCL:ICR male germfree mice were monocontaminated with Clostridium butyricumMIYAIRI No. 588. Gallstone formation, biliary lipid composition and bile acid profiles in the bile, small intestinal contents and feces were analyzed after feeding the diet containing cholesterol and cholic acid. The rate of gallstone formation in the monocontaminated mice (38%) was less than that in the germfree mice (100%). The relative concentrations of biliary lipids of the two groups were located out of the micellar zone on the triangular co-ordinates by Admirand and Small. The bile acid concentrations in the small intestine and fecal excretions in the monocontaminated mice were higher than in the germfree mice. The composition as well as the mode of conjugation of the bile acids did not differ significantly between the two groups. The infestation of bacteria in the intestine enhanced the excretion of bile acids and inhibited the gallstone formation in mice, in which direct metabolic activity by bacterial enzymes on bile acid did not seem necessary to exert such effect.