Clin Chem Lab Med 2006;44(10):1206–1213  2006 by Walter de Gruyter • Berlin • New York. DOI 10.1515/CCLM.2006.216 2006/113 Article in press - uncorrected proof Paraoxonase-1 (PON1) activity, but not PON1 Q192R phenotype, is a predictor of coronary artery disease in a middle-aged Serbian population Jelena Kotur-Stevuljevic 1, * , Slavica Spasic 1 , Aleksandra Stefanovic 1 , Aleksandra Zeljkovic 1 , Natasa Bogavac-Stanojevic 1 , Dimitra Kalimanovska-Ostric 2 , Vesna Spasojevic- Kalimanovska 1 and Zorana Jelic-Ivanovic 1 1 Institute for Medical Biochemistry, Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia 2 Institute for Cardiology, Clinical Centre of Serbia, Belgrade, Serbia Abstract Background: Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme that pro- tects lipoproteins from oxidative modifications. Poly- morphisms in the gene, including PON1 Q192R , have been studied. However, inconsistencies regarding the above-mentioned polymorphism obscure its associa- tion with vascular disease. Methods: Using a two-substrate (paraoxon/diazoxon) activity method, we investigated the frequencies of PON1 Q192R phenotypes in 261 middle-aged subjects: 156 patients with angiographically assessed coronary heart disease (CHD) and 105 CHD-free subjects as the control group. The PON1 192 phenotype was predicted from examination of the two-dimensional plot of hydrolysis rates of diazoxon vs. paraoxon and by using the antimode of the histogram of the ratio of diazoxonase/paraoxonase activity. Results: The PON1 Q192R phenotype frequencies in 113 patients with occlusion )50% (coronary artery dis- ease-positive, CADq group) vs. control population were as follows: QQ (0.552 vs. 0.510), QR (0.382 vs. 0.408) and RR (0.066 vs. 0.082); x 2 s0.414, ps0.813. We found lower paraoxonase (POase) and diazoxo- nase (DZOase) activities in the CADq patients when compared to the control population. According to logistic regression analysis, POase activity was a bet- ter predictor of coronary disease onset compared with DZOase activity measurements and PON1 Q192R phenotyping. Conclusions: We conclude that enzyme activity (with- in a particular phenotypic group) is more important than phenotype alone in predicting susceptibility to coronary artery disease. Clin Chem Lab Med 2006;44:1206–13. *Corresponding author: Jelena Kotur-Stevuljevic, Institute for Medical Biochemistry, Faculty of Pharmacy, Vojvode Stepe 450, P. Box 146, 11000 Belgrade, Serbia Phone: q381-11-3970-379, Fax: q381-11-3972-840, E-mail: jkotur@pharmacy.bg.ac.yu Keywords: coronary artery disease; paraoxonase-1 (PON1) activity; PON1 Q192R phenotype. Introduction High-density lipoprotein (HDL) is known to play a sig- nificant anti-atherogenic role, in part due to its con- tribution to the reverse cholesterol transport process. HDL is also believed to protect against atherosclerosis by inhibiting the oxidative modification of low-density lipoproteins (LDL), thereby attenuating the biological activities of oxidised LDL (1). Such anti-oxidant and anti-atherogenic properties of HDL have been attrib- uted to various proteins associated with HDL, partic- ularly the enzyme paraoxonase (PON). Paraoxonase-1 (EC 3.1.8.1, aryldialkylphosphatase, PON1) is a HDL-associated serum enzyme (2). Accord- ing to Aviram et al. (3), the anti-atherogenic properties of PON1 are characterised by its ability to hydrolyse lipid peroxides in human atherosclerotic lesions. Recent evidence has confirmed that PON enzymes are primarily lactonases acting upon certain lactones/ hydroxyl acids as their endogenous substrates. Therefore, one of the physiological roles of PON1 is the metabolism of lipid mediators arising from oxi- dation of polyunsaturated fatty acids (4). PON1 has two common coding polymorphisms, a methionine (M) to leucine (L) substitution at position 55 and a glutamine (Q) to arginine (R) substitution at position 192. Both polymorphisms are associated with a number of pathophysiological conditions such as coronary artery disease (CAD), stroke, familial hypercholesterolemia, type 2 diabetes mellitus and Parkinson’s disease (1, 5–7). In addition to those two polymorphisms, at least five other polymorphisms have been detected in the PON1 promoter region (1, 8, 9). There are substrate-dependent differences among PON1 Q192R isoforms; the Q variant has a high- er diazoxonase activity (DZOase), whereas paraoxo- nase activity (POase) predominates in the R variant (10). By measuring the DZOase/POase activity ratios, it is possible to discriminate between the PON1 Q192 , PON1 QR192 , and PON1 R192 phenotypes. Reports that seek to show an association between the PON1 192R allele (or PON1 192RR genotype) and car- diovascular diseases are controversial. Some studies have reported a positive association (11–14), whereas others failed to show any association (15–18). There is also evidence that low PON1 activity is associated with atherosclerosis, irrespective of the PON1 phe- notype (19–21). Jarvik et al. have recently shown that PON1 activity was a better predictor of the disease than the PON1 genotype (21). Brought to you by | Karolinska Institute Authenticated Download Date | 5/24/15 4:58 AM