Interrelationships of α-tocopherol with plasma lipoproteins in African green monkeys: Effects of dietary fats

The distributions of plasma lipoprotein α-tocopherol and lipids were studied in African green monkeys consuming diets enriched in saturated, monounsaturated, or polyunsaturated fatty acids. Plasma total α-tocopherol concentrations were not different among the animals fed the three diets, whereas plasma total cholesterol concentrations were significantly different among the diet groups. The α-tocopherol: total lipid molar ratio in plasma high density lipoproteins (HDL) was significantly higher compared to low density lipoproteins (LDL) and very low plus intermediate-sized low density lipoprotein (VLDL + ILDL) of each diet group, suggesting that HDL may exhibit a greater affinity for α-tocopherol. The presence of a positive correlation between HDL α-tocopherol and plasma apoA-I concentration and the absence of a correlation between HDL α-tocopherol and total lipid in HDL suggested that α-tocopherol associates with the protein moiety of HDL on the surface of the particle. A direct relationship between the plasma apoA-I: apoB molar ratio and the percentage of α-tocopherol found in the HDL fraction indicated that a greater proportion of α-tocopherol associates with HDL as the number of HDL particles in plasma increases relative to LDL particles. LDL from monkeys fed diets high in saturated fat contained 40% and 33% fewer α-tocopherol molecules per particle than LDL from monkeys fed polyunsaturated and monounsaturated fats, respectively. The phase transition temperature of LDL cholesteryl esters, indicative of the physical state of the lipids in the particle core, was well above body temperature in LDL from saturated fat-fed monkeys and was significantly higher compared to the other diet groups. This difference in the physical state of the cholesteryl esters in LDL from the group of monkeys fed saturated fat may contribute to the ability of α- tocopherol to interact with lipoproteins. Our data indicate that α- tocopherol does not distribute uniformly with plasma lipid among lipoprotein particles; rather, physical and dietary factors influence the interaction of α-tocopherol with lipoproteins.