Study of the Mechanism of Hyperlipemia

Abstract

The fatty acid patterns of the serum chylomicrons of 10 normal and 10 hyperlipemic subjects were determined by gas-liquid chromatography, before and after feedings of cream, corn oil, and coconut oil. Their depot fat composition was analyzed. Changes in the composition of the fasting serum chylomicrons of these hyperlipemic patients after they were stabilized on low fat, and rice and fruit diets were also studied. Upon a full American diet, after 12 hours of fasting, the fatty acid pattern of the very light serum chylomicrons of the hyperlipemic patients was found to reflect that of the ingested fats, consisting chiefly of a mixture of saturated animal fats. The effect of food fats was less evident in the heavier serum chylomicrons and very low density lipoprotein fraction of these patients, where the pattern of endogenously synthesized fat predominated. A low-fat diet in eight of these patients caused a significant lowering of the serum chylomicron (triglyceride) concentration and a shift of chromatographic pattern of the very light serum chylomicrons toward that of the non-hyperlipemic subjects. It is apparent that the clearing of the exogenous fats from the serum permits the endogenous lipids to dominate the picture. A low caloric rice and fruit diet appeared to arouse a temporary acceleration in the mobilization of fat from the body depot in two patients. In these patients, the fatty acid composition of serum chylomicrons, the very low density lipoproteins, and the depot fat were found to be similar to one another. Dietary fat contributed directly to alimentary lipemia of the normal and diseased subjects. At or near the peak of alimentary lipemia, the composition of the very light serum chylomicrons of all subjects was found to be practically identical with the ingested fat. Alimentary lipemia of hyperlipemic patients was intensified and prolonged. A relative increase in oleic acid, together with an elevated oleic/stearic ratio has been reported in the serum chylomicrons of patients with coronary artery disease. The same findings occurred in our patients, when there was an increase (relative or absolute) in the very light serum chylomicrons, due either to excessive dietary fat intake or to increased mobilization of fat from the depot.