Effect of ursodeoxycholic acid treatment on ileal absorption of bile acids in man as determined by the SeHCAT test

Bile acids are produced by the liver and released into the small intestine in response to a meal; they aid in the efficient absorption of dietary fat and cholesterol. The bile acids are reabsorbed at a more distal point in the intestine, after they have accomplished their function, and return to the liver via the bloodstream where they await reentry into the cycle. The release and reabsorption of bile acids are part of a tightly controlled feedback cycle in which the rate of bile acid biosynthesis is regulated by both the demand for these compounds by the digestive tract and the rate at which they return to the liver. Ursodeoxycholic acid, a derivative of the major bile acids (and itself a minor constituent of bile) has been used in the treatment of a variety of disorders, including gall stones, primary biliary cirrhosis, and sclerosing cholangitis. The extent to which beneficial effects of ursodeoxycholic acid treatment may be related to its influence on intestinal absorption of bile acids is not known. To further investigate this issue, a newly available tracer technique involving monitoring the absorption of radioactively labelled selenium homocholic acid taurine (an easily measurable analog of naturally occurring bile acids) was used to quantify the effects of ursodeoxycholic acid on bile acid absorption. The radiolabelled acid was given orally, and bile acid absorption inferred from the rate of disappearance of radioactivity over a seven-day period. This was done before and after three weeks of treatment with ursodeoxycholic acid. Following treatment, there was a significant decrease in intestinal absorption of bile acids and blood cholesterol levels; blood levels of ursodeoxycholic acid increased. These results suggest that the beneficial effects of ursodeoxycholic acid treatment result, at least in part, from its suppressive actions on the absorption of bile acids. (Consumer Summary produced by Reliance Medical Information, Inc.)