Evidence that the apolipoprotein E-genotype effects on lipid levels can change with age in males: a longitudinal analysis
We previously reported that change, with age, in plasma levels of total cholesterol (TC) and LDL cholesterol (LDL-C) differed between apolipoprotein E (APOE) genotypes epsilon 3 epsilon 3 and epsilon 3 epsilon 4, in a sample of 77 older, unrelated males. By use of a larger sample from that cohort, followed longitudinally during 1969-87, the change in TC and in LDL-C, between the epsilon 3 epsilon 3 and epsilon 3 epsilon 4 APOE genotypes, over three exams, was reanalyzed. Additionally, the change in triglycerides (TG) and in HDL-cholesterol (HDL-C), between the epsilon 3 epsilon 3 and epsilon 3 epsilon 4 APOE genotypes-as well as the differences between the epsilon 3 epsilon 3 and epsilon 3 epsilon 2 genotypes, for TC, LDL-C, TG, and HDL-C-were contrasted over the three exams. At exam 1 TG was higher in the epsilon 3 epsilon 4 group than in the epsilon 3 epsilon 3 group (mean age 48 years), and at exams 2 and exam 3 (mean ages 58 and 63 years, respectively) it was similar (P = .009 for the exam-by-genotype-interaction effect in the repeated-measures analysis). A similar trend was seen for TC (P = .03), yet previously detected LDL-C effects were not apparent (P = .46). Those with the epsilon 3 epsilon 2 genotype had higher TG and lower LDL-C and TC at each exam than were seen in those with the epsilon 3 epsilon 3 genotype, although the differences in the values were not always statistically significant. Differences in TC, LDL-C, and TG, between the epsilon 3 epsilon 2-genotype and epsilon 3 epsilon 3-genotype groups, did not significantly change over the three exams. HDL-C levels were relatively stable over the exams; however, the exam-by-genotype interaction was significant for the epsilon 3 epsilon 2 genotype versus the epsilon 3 epsilon 3 genotype (P = .02). The epsilon 4 allele effects on TG and TC changed between longitudinal exams and may be age dependent. Changes, with age, in the effect of the epsilon 3 epsilon 4 genotype on lipids may impact the risk of developing atherosclerotic disease.