Cholesterol absorption during bile acid feeding: Effect of ursodeoxycholic acid (UDCA) administration

Abstract

We studied the effect of ursodeoxycholic acid (UDCA) administration (15 mg/kg/day) on cholesterol absorption in 11 volunteers. Cholesterol absorption was estimated by feeding a standard dose of cholesterol, dissolved in butter, containing 5 μCi of [14C]cholesterol and 10 μCi of [3H]sitosterol (as a nonabsorbable marker). Feces were then collected for 5–6 days. Cholesterol absorption with β-sitosterol, corrected for losses not due to absorption, was estimated from the recovered radioactivity. After 20 days of treatment with UDCA, the study was repeated with each patient acting as his own control. Cholesterol saturation of bile and biliary bile acid composition were also studied before and after treatment. UDCA was virtually undetectable in bile before treatment, but became the most abundant bile acid (42.0 ± 17.2% of the total) after treatment. Although the molar percentage of cholesterol in bile fell in each patient after treatment, bile saturation critically depended on the criteria adopted to calculate the saturation index. Mean cholesterol absorption was 36.7 ± 9.3% of the administered dose in basal conditions and fell to 17.5 ± 11.3% (48% decrement) after treatment (P < 0.01). In conclusion, given in doses effective to dissolve gallstones, UDCA causes a decrease of dietary cholesterol absorption. This effect could prevent the overaccumulation of cholesterol in the body during long-term bile acid feeding and could contribute to the desaturation of bile consequent to UDCA feeding.