Soybean Phosphatides and Blood Lipids of Primates ¹

Ten pigtail monkeys ( Macaca nemestrina ) were used to study the effects of soybean phosphatides on blood lipid levels. Two monkeys were maintained on a control low-fat diet and eight monkeys were made hypercholesterolemic by feeding a diet containing 16% butter oil and 1% cholesterol for a 12-week period. Soybean phosphatides were administered to the animals by infusion or incorporation into the diet. All animals were placed on low-fat diets after 12 weeks and maintained on this diet for 5 weeks. Incorporation of 3% soybean phosphatides into the butter oil-cholesterol diet before the animals became hypercholesterolemic or a twice weekly infusion of 5 ml of a 10% emulsion of soybean phosphatides after the animals were hypercholesterolemic partially prevented increases in plasma total cholesterol, cholesterol esters and lipid phosphate induced by the butter oil-cholesterol diets. Alterations in the blood plasma lipoprotein patterns resulting from the butter oil-cholesterol diet were also prevented by these methods of phosphatide administration. Switching the animals to a diet containing phosphatides after the animals were already hypercholesterolemic was not effective in preventing alterations in blood lipid levels or lipoprotein patterns. Blood triglyceride levels were not affected by any of the treatments. The phosphatide treatments had no significant effect on the rate of decrease of blood lipid levels after placing the hypercholesterolemic animals on a low fat-low cholesterol diet. Studies of the turnover of phosphatidyl choline indicate that this phospholipid or its component parts is/are rapidly absorbed and that 10% of the radioactivity of a single oral dose of the phospholipid is released from the tissues of monkeys with a half life of about 2 days. Prior treatment with phosphatides appears to delay excretion of phosphatidyl choline. Possible mechanisms of the action of phosphatides on blood lipids are discussed.