Effects of the ApoE polymorphism on plasma lipoproteins in Mexican Americans

PURPOSE: To evaluate the impact of apolipoprotein E (apoE) genotypes on lip oprotein measurements relative to that of other known cardiovascular risk f actors in participants of a large population-based family study. METHODS: We measured concentrations of apoE, the major constituents of HDL (cholesterol, apoAI), LDL-C (cholesterol and apoB), and fraction of apoE in lipoprotein size classes in 859 participants of the San Antonio Family Hea rt Study, and then tested the association between the three common apoE gen otypes (epsilon2 epsilon3, epsilon3 epsilon3, and epsilon3 epsilon4) and li poprotein traits using the measured genotype approach to account for residu al familial correlations. RESULTS: Allele frequencies in this population for epsilon2, epsilon3, and epsilon4 were 3.5%, 89.6%, and 6.9%, respectively. As expected, adjust-ed a poE concentrations were highest in those with epsilon2 epsilon3, intermedia te in those with epsilon3 epsilon3, and lowest in those with epsilon3 epsil on4. The concentrations of total cholesterol, LDL-C and apoB were lowest in those with epsilon2 epsilon3, intermediate in those with epsilon3 epsilon3 , and highest in those with epsilon3 epsilon4. There was no significant eff ect of apoE genotypes on triglycerides, HDLC, or apoAI levels. Compared to subjects with epsilon3 epsilon4, subjects With epsilon2 epsilon3 had relati vely less apoE in LDL and HDL1, and relatively more in HDL2 and HDL3 size f ractions. The effect of apoE genotypes was significantly greater on apoB in women than in men (sex x apoE interaction p-value = 0.02). ApoE genotypes accounted for 4.5%, 12.3%, and 4.7% of the total genetic variation in apoB, apoE, and LDL-C, respectively. CONCLUSION: ApoE genotypes account for a modest, albeit significant, propor tion of phenotypic variation in concentrations of LDL-C, apoB, and apoE, an d distributions of apoE among lipoproteins in this population; these genoty pes have a greater effect on apoB levels in women than in men. (C) 2000 Els evier Science Inc. All rights reserved.