Objectives: The polymorphism of the apolipoprotein E gene (epsilon2, epsilon3, epsilon4) affects plasma cholesterol but the relationship with artery wall thickness has indicated contradictory results. This study investigated the relationship between apolipoprotein E polymorphism and vascular phenotypes of the carotid and radial arteries, two arterial sites differently affected by atherosclerosis.
Methods: We studied a cohort of 320 Caucasian subjects (age 49 +/- 12 years) without evidence of cardiovascular disease. Structural (internal diameter and wall thickness) and functional phenotypes (compliance, distensibility) were evaluated for the common carotid and the radial arteries using high resolution echo-tracking devices. Genotypes of apolipoprotein E were determined by allele-specific oligonucleotides hybridization. Because of the relative low frequency of some apolipoprotein E genotypes, they were designated as E2 (epsilon2/epsilon2, epsilon2/epsilon3), E3 (epsilon3/epsilon3), and E4 (epsilon4/epsilon4, epsilon3/epsilon4).
Results: Apolipoprotein E allele frequencies were epsilon2 = 0.08, epsilon3 = 0.79, epsilon4 = 0.13. Subjects with epsilon4 allele had the highest levels of total serum cholesterol and low density lipoprotein cholesterol; subjects with epsilon2 allele had the lowest levels (P < 0.001). Considering carotid hypertrophy as intima-media thickness > 660 microm, and radial hypertrophy as intima-media thickness > 260 microm, a logistic regression model testing determinants of arterial hypertrophy (age, gender, weight, systolic blood pressure, smoking habits, and total serum cholesterol) observed a significant and positive association between carotid hypertrophy and epsilon2 allele carriers (P= 0.03). In contrast, no association was found between hypertrophy and apolipoprotein E genotypes for the radial artery. No association was observed between the apolipoprotein E genotypes and functional artery parameters.
Conclusions: In subjects without any evidence of cardiovascular disease, the presence of the epsilon2 allele is related to wall hypertrophy in carotid artery despite favourable effect on the lipid profile.