Biliary,fecal and plasma deoxycholic acid in rabbit,hamster, guinea pig,and rat: comparative study and implication in colon cancer

Bile acids are believed to play a role in the etiology of colorectal cancer, and high fecal excretion of secondary bile acids was correlated with increased incidence of colon cancer. Recently, it was also reported that there is an increase in plasma of the secondary bile acid, deoxycholic acid in men with colorectal adenomas. Since deoxycholic acid is formed in the colon and absorbed into the portal systemic circulation, it was suggested that the blood concentration of this bile acid reflects the level of exposure of colonic cells to deoxycholic acid. The objective of this study was to investigate whether plasma deoxycholic acid level represents the fecal content of this bile acid in several animal species with different bile acid composition and deoxycholic acid contribution to the bile acid pool. Eight rabbits, hamsters, guinea pigs, and rats were used in this study. Blood samples and feces were collected on days 1, 3, 5 and 7. Bile samples were obtained only on day 7. The plasma, fecal and biliary bile acids were analyzed by gas chromatography-mass spectrometry. Bile acid composition and deoxycholic acid content varied greatly between the animal species studied. There was a variation in the concentration of total bile acids in the plasma and feces obtained at different times during the experiments, however, the bile acids profile remained constant throughout the study. The data obtained shows that although plasma bile acid profile was not similar to fecal bile acids profile, however, there was a significant correlation between the level of plasma and fecal deoxycholic acid. Plasma deoxycholic acid concentration might be a reliable biomarker for the degree of exposure of colon cells to this bile acid, and may be useful in further studies on the role of secondary bile acids in colon carcinogenesis.