Effects of lipotropic substances on the cholesterol content of the serum of rats

Abstract

Free and total cholesterol were determined in the blood sera of young adult rats maintained on natural and on purified diets. In rats of our colony fed the stock ration, the mean total cholesterol is 70 mg/100 ml (S. C. - 11) of which 12 mg/100 ml are in the free form. The values found in males and in females did not differ significantly. The time, with respect to the last meal, at which the blood sample is taken is important when the diet contains lipotropic agents and excessive amounts of cholesterol. The postprandial elevation in bound serum cholesterol was related to the concentration of cholesterol in the ration. Increasing the lipotropic agents (choline) above an undetermined minimal amount produced no further effect. The elevated serum cholesterol values returned slowly to normal after about 18-24 hours. In the absence of choline the postprandial increase (if any) was very slight even in the presence of large amounts of cholesterol in the diet. In rats fed purified hypolipotropic diets, the bound serum cholesterol fell progressively as the experiment continued. In preventive studies choline and betaine maintained the serum cholesterol within the normal range but inositol failed to prevent the characteristic fall. In curative studies replacement of choline in the diet promptly restored (within 24 hours) the concentration of serum cholesterol to normal; betaine also was able to restore and maintain the serum cholesterol; vitamin B12 exerted a similar effect; inositol did not alter the values observed in the rats continued on the basal ration. Our experimental findings do not support claims that lipotropic substances reduce the concentration of bound cholesterol in the serum. They do indicate that the same substances which prevent or cure fatty livers are also involved in the control of the cholesterol level in the serum.