Variation at the paraoxonase gene locus contributes to carotid arterial wall thickness in subjects with familial hypercholesterolemia

Objectives: Paraoxonase (PON1) is a potent enzyme, physically associated with the high-density lipoprotein particle. PON1 may protect against cardiovascular disease (CVD), since it is capable of hydrolyzing oxidized LDL-cholesterol, thereby negating the detrimental effects of this lipoprotein on the arterial wall. Design and methods: In 187 patients with familial hypercholesterolemia, we studied the seven most common single nucleotide polymorphisms (SNPs) in both the coding and promoter sequences of PON1 (L55M, Q192R, T-107C, C-126G, G-162A, G-824A, and C-907G) in terms of PON1 activity and intima media thickness (IMT) of the carotid arterial wall, a validated surrogate marker for CVD. Results: In concordance with several previous studies, we observed that the L55M, T-107C, G-162A, G-824A, and C-907G SNPs conferred PON1 activity towards phenylacetate, while this was not the case for the Q192R and C-126G SNPs. Importantly, in a multivariate regression analysis, G-824A proved to be an independent predictor of carotid IMT. Additionally, the two fully discordant homozygous haplotypes, C-907/G-824/G-162/C-126/T-107/55M versus -907G/-824A/-162A/-126G/-107C/L55, differed by 22% in carotid IMT (P = 0.007). Conclusions: Genetic variation at the PON1 locus has a strong influence on PON1 activity as well as on carotid IMT. These data indicate that PON1 is indeed involved in the pathogenesis of atherosclerosis. Whether this also translates into a role for PON1 in the occurrence of CVD events needs to be confirmed by large prospective studies in the general population.