Polymorphisms in the apolipoprotein E gene regulatory region in relation to coronary heart disease and their effect on plasma apolipoprotein E.

In a previous study which examined the distribution of apolipoprotein E genotypes and plasma levels in a sample of male coronary heart disease (CHD) patients and controls, we found a significant excess of the genotypes carrying APOE*4 allele in CHD men (18.2%) vs. controls (9.6%) and an association between the APOE*4 allele and the lowest concentrations of apoE. In the present investigation, we re-examined in the same samples two recently identified polymorphisms in the promoter region of APOE, -491A/T and -427T/C, which may alter the level of apoE expression. No differences in the distributions of the -491A/T genotypes and alleles were observed between cases and controls (-491*A = 0.760 and 0.757 respectively). Polymorphism -427T/C showed in CHD patients an excess of -427*C allele (patients vs. controls = 0.123 vs. 0.074) and corresponding genotypes that was marginally significant. Stratification of the samples according to the presence/absence of APOE*4 showed that the excess of the -427*C allele concerned only CHD patients not carrying APOE*4 allele (patients vs. controls = 0.133 vs. 0.061; p=0.017). This result suggests that the presence of -427*C allele could represent a risk for developing CHD in subjects with E2/E2, E3/E2, and E3/E3 genotypes. Studies carried out on patients with Alzheimer's disease demonstrated that -491A/T and -427T/C polymorphisms affect the level of plasma apoE. In the present study, carried out on CHD patients and controls, the genetic variation at -427 and -491 sites of the APOE regulatory region had no apparent effect on apoE plasma concentration.