Effect of Dietary Cholesterol on Cholesterol and Bile Acid Metabolism in Rats

Abstract

Effect of dietary cholesterol on biliary and fecal excretion of cholesterol and bile acids was examined in rats. Cholesterol supplemented diet (2%) caused almost no change in plasma lipid levels, but produced an increase of pre β-lipoprotein and a decrease of α-lipoprotein. Dietary cholesterol increased bile secretion and biliary excretion of total bile acids but not of cholesterol. Biliary cholic and deoxycholic acids were not greatly changed but chenodeoxycholic acid was significantly increased. Dietary cholesterol also increased fecal excretion of sterols and bile acids. The excretion of coprostanol was increased about 10-fold and that of cholesterol was over 50-fold. Rat fecal bile acids consisted of lithocholic, deoxycholic, hyodeoxycholic or its 6β-isomer, α-muricholic, β-muricholic and some keto bile acids. Dietary cholesterol increased fecal excretion of mostly the secondary bile acids from chenodeoxycholic acid, and also deoxycholic acid. When a cholesterol supplemented fat-free diet was provided, no increase was found in either plasma or liver lipid levels, or in biliary excretion of bile acids, but a marked increase was produced in fecal excretion of sterols and bile acids. It is concluded that dietary cholesterol increases the formation and excretion of chenodeoxycholic acid, and also that of cholic acid but to a lesser extent. The increase of bile acids, particularly chenodeoxycholic acid, is responsible for the diminution of tissue and blood cholesterol, though only a minor amount of dietary cholesterol is absorbed in rats.