Effect of saturated and polyunsaturated fat diets on the composition and structure of human low density lipoproteins

Abstract

We have studied the effect of diets of saturated and polyunsaturated fat on the composition, structure and thermal behavior of human plasma low density lipoproteins (LDL). We find that relative to a saturated fat diet one of polyunsaturated fat produces: 1. (1) An increase. in the unsaturated acyl content of all lipid classes of LDL. 2. (2) An increase in the triglyceride content of LDL. 3. (3) A decrease in the temperature of the thermotropic liquid crystal to isotropic liquid phase transition of LDL. 4. (4) No effect on the temperature of LDL denaturation. In spite of major changes in the fatty acid composition of the major lipid of LDL, cholesteryl esters, the thermal properties of LDL are dominated by their triglyceride content. Since a polyunsaturated fat diet raised LDL triglyceride levels, our calorimetric and spectroscopic results suggest that the thermal properties and the structure of LDL at 37°C are sensitive to the composition of dietary fat.