Background and purpose: Atherosclerosis is a complex disorder with hereditary and environmental causes. Carotid artery intima-media wall thickness (IMT) is a useful measure of atherosclerosis. The objective of this study was to determine the association between carotid IMT and functional promoter variants of stromelysin-1 (MMP3: -1612 5A>6A), interleukin-6 (IL6: -174G>C), and hepatic lipase (HL: -480C>T) genes.
Methods: B-mode carotid ultrasound was performed among 87 subjects (mean age, 70+/-12 years; 55% women; 60% Caribbean-Hispanic, 25% black, and 13% white) from the Northern Manhattan Prospective Cohort Study. Carotid IMT was calculated as a composite measure (mean of the maximum IMT in the bifurcation, the common carotid artery, and the internal carotid artery).
Results: For all polymorphisms, genotype distribution was not significantly different from Hardy-Weinberg equilibrium. The frequencies of the rare alleles were as follows: MMP3 -1612 5A>6A, 0.31 (95% CI, 0.25 to 0.39); IL6 -174 G>C, 0.20 (95% CI, 0.13 to 0.25); and HL -480 C>T, 0.45 (95% CI, 0.35 to 0.50). Carotid IMT in the sample was 0.78+/-0.18 mm. Subjects with the MMP3 genotype 6A6A had 8% greater mean carotid IMT than the other MMP3 genotypes combined (0.95+/-0.17 versus 0.87+/-0.15 mm; P=0.04). Subjects with the IL6 genotype GG had 11% greater IMT (0.85+/-0.17 versus 0.76+/-0.16 mm; P=0.03), and those with the HL genotype CC had 13% greater IMT (0.87+/-20 versus 0.76+/-0.18 mm; P=0.02) than the other genotypes combined. Adjustment for other risk factors did not change these associations.
Conclusions: Carotid IMT is higher among subjects homozygous for functional variants in genes related to matrix deposition (MMP3 -16126A), inflammation (IL6 -174G), and lipid metabolism (HL -480C). These associations were independent of race-ethnicity and some environmental exposures. Further studies are needed to confirm these genotype-phenotype associations.