Paraoxonase gene polymorphism in Japanese subjects with coronary heart disease

The Hydrolysis Rate of Paraoxonase-1 Q and R Isoenzymes: An In Silico Study Based on In Vitro Data

Human serum paraoxonase-1 (PON1) is an important hydrolase-type enzyme found in numerous tissues. Notably, it can exist in two isozyme-forms, Q and R, that exhibit different activities. This study presents an in silico (QSAR, Docking, MD and QM/MM) study of a set of compounds on the activity towards the PON1 isoenzymes (QPON1 and RPON1). Different rates of reaction for the Q and R isoenzymes were analyzed by modelling the effect of Q192R mutation on active sites. It was concluded that the Q192R mutation is not even close to the active site, while it is still changing the geometry of it. Using the combined genetic algorithm with multiple linear regression (GA-MLR) technique, several QSAR models were developed and relative activity rates of the isozymes of PON1 explained. From these, two QSAR models were selected, one each for the QPON1 and RPON1. Best selected models are four-variable MLR models for both Q and R isozymes with squared correlation coefficient R² values of 0.87 and 0.83, respectively. In addition, the applicability domain of the models was analyzed based on the Williams plot. The results were discussed in the light of the main factors that influence the hydrolysis activity of the PON1 isozymes.

Silent hyperlipidaemia modulated vascular endothelial markers

The aetiology of ischemic heart diseases is mainly based on atherosclerosis of coronary artery. Inflammation and oxidative reactions are initiating and aggravating the illness resulting in pathological remodelling of vasculaturze at site of injury. Endothelium lining of blood vessels participated in the reaction biochemically through releasing some proteins into circulatory system which further complicate the condition. The aim of this study was to determine early diagnosed hyperlipidaemia-associated changes of the plasma level of some of these endothelial biomolecules. Compared to healthy control, hyperlipidaemic patients have significantly increased arginase, metalloendopeptidase, peroxidase, myeloperoxidase, and peroxynitrite with concomitant reduction in arylesterase and nitric oxide. The present study concluded that hyperlipidaemia play a great role in modulation of certain plasma protein markers which might be directly related to patient pathological condition or could be used as a tool for diagnosis or patient follow up indicating the stage of vasculature remodelling, healing, inflammation or resolution.

Albuminuria, the High-Density Lipoprotein Proteome, and Coronary Artery Calcification in Type 1 Diabetes Mellitus

Objective- Albuminuria is an important risk factor for cardiovascular disease in diabetes mellitus. We determined whether albuminuria associates with alterations in the proteome of HDL (high-density lipoprotein) of subjects with type 1 diabetes mellitus and whether those alterations associated with coronary artery calcification. Approach and Results- In a cross-sectional study of 191 subjects enrolled in the DCCT (Diabetes Control and Complications Trial)/EDIC study (Epidemiology of Diabetes Interventions and Complications), we used isotope dilution tandem mass spectrometry to quantify 46 proteins in HDL. Stringent statistical analysis demonstrated that 8 proteins associated with albuminuria. Two of those proteins, AMBP (α1-microglobulin/bikunin precursor) and PTGDS (prostaglandin-H2 D-isomerase), strongly and positively associated with the albumin excretion rate ( P<10^-6). Furthermore, PON (paraoxonase) 1 and PON3 levels in HDL strongly and negatively associated with the presence of coronary artery calcium, with odds ratios per 1-SD difference of 0.63 (95% CI, 0.43-0.92; P=0.018) for PON1 and 0.59 (95% CI, 0.40-0.87; P=0.0079) for PON3. Only 1 protein, PON1, associated with both albumin excretion rate and coronary artery calcification. Conclusions- Our observations indicate that the HDL proteome is remodeled in type 1 diabetes mellitus subjects with albuminuria. Moreover, low concentrations of the antiatherosclerotic protein PON1 in HDL associated with both albuminuria and coronary artery calcification, raising the possibility that alterations in HDL protein cargo mediate, in part, the known association of albuminuria with cardiovascular risk in type 1 diabetes mellitus. Visual Overview- An online visual overview is available for this article.

Paraoxonase-1 Q192R polymorphism and its association with hs-CRP and fasting blood glucose levels and risk of coronary artery disease

AIMS

Paraoxonase-1 (PON1) has been shown to protect low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) against oxidative-modification and thereby might protect against coronary-artery-disease (CAD). Here we explored the relationship of a genetic variant (a substitution (R) Arg with (Q) Gln at position 192) of PON1 in 250 patients with/without CAD.

MATERIALS AND METHODS

Genotyping of PON1 Q192R was carried out using Real-Time-PCR TaqMan-based-probe. Demographic-characteristics and biochemical-analyses, including fasting blood sugar (FBS), HDL, LDL, triglycerides (TG) and C-reactive protein (CRP) were evaluated. Univariate/multivariate analyses were performed to determine the association of the genetic polymorphism and CAD as well as with clinical-characteristics of population.

RESULTS

Our findings showed that RR-genotype was more frequent in CAD-patients, compared to the wild-type genotype. Moreover, CAD patients with RR-genotype had an odd ratio of 5.0 (95% CI: 1.3-18.6; p = 0.017), versus wild-type genotype, in multivariate-analysis. Of note we also observed that CAD-patients with QQ-genotype had a significantly lower Hs-CRP level, compared to the RR-genotype.

CONCLUSION

we demonstrate that PON1-Q192R-polymorphism was associated with CRP and FBS levels; R-allele of PON1-Q192R may be an independent risk factor for CAD. Further studies are warranted to determine the value of this marker as a surrogate marker in CAD patients.

Effects of paraoxonase 1 gene polymorphisms on heart diseases: Systematic review and meta-analysis of 64 case-control studies

BACKGROUND

Associations between paraoxonase 1 (PON1) gene polymorphisms and heart diseases (HD) risk remain inconsistent. In order to obtain address this issue we performed a meta-analysis to assess the association between the L55M and Q192R polymorphisms of PON1 gene and heart diseases risk.

METHODS

Relevant studies were enrolled by searching databases systematically. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to calculate the strength of association. Subgroup analyses were conducted for diagnostic and ethnicity. The heterogeneity among each of the studies was calculated by using Cochran Qtest and the inconsistency index (I), and Begg's funnel plot and Egger's tests were performed to evaluate publication bias.

RESULT

Sixty four studies involving a total of 19,715 cases and 33,397 controls were included in this meta-analysis. We found that the L55M polymorphism showed a significant association with heart diseases in Europeans (OR 1.44, 95%CI 1.33-1.56) and Asians (OR 1.18, 95%CI 1.03-1.35). This meta-analysis also showed a protective association of Q192R polymorphism with HD in Asian (OR 0.49, 95%CI 0.37-0.66) and African populations (OR 0.67, 95%CI 0.53-0.84). The 192R allele significantly decreased the risk of myocardial infarction (OR 0.75, 95%CI 0.57-0.99) and coronary artery disease (OR 0.91, 95%CI 0.84-0.98); however, individuals with 192Q allele had a markedly increased risk of coronary artery disease development (OR 1.38, 95%CI 1.22-1.56).

CONCLUSION

This study demonstrated that the genetic risk for heart diseases is associated with the PON1 gene polymorphisms. L55M polymorphism is a risk factor and Q192R polymorphism is protective in certain populations. It is worth noting that the 192Q allele may be a risk factor to develop coronary artery disease.

Genetic variation at Q192R and L55M polymorphisms in PON1

Earlier we have reported Q192R allele frequencies among four Indian populations as a part of an investigation of the distribution of Paraoxonase 1 polymorphisms. Here we present the results obtained after screening eleven populations representing different regions of India for Q192R and L55M. Population genetic analysis examining the effect of micro-evolutionary forces at these loci confirmed genetic differentiation at Q192R earlier suggested. The study groups showed high frequencies of L55 and differential distribution of Q192 and R192. Tests for deviation from neutrality indicated heterozygote excess at rs662 which has Q192R polymorphism. Higher levels of heterozygosity at Q192R than L55M might be because of its role in wide substrate specificity of the enzyme. A small but highly significant correlation between genetic and geographic distances was observed in a spatial autocorrelation analysis indicating non-random distribution of Q192 allele. Our findings are pertinent to toxicogenetic studies evaluating risk assessment towards organophosphate compounds among different continental groups.

Exploring the role of paraoxonases in the pathogenesis of coronary artery disease: a systematic review

Paraoxonases (PON) are three enzymes (PON1, PON2 and PON3) that play a role in the organism’s antioxidant system; alterations in which are associated with diseases involving oxidative stress. In this review, we summarize the evidence of PON related to the pathogenesis of coronary artery disease (CAD) and atherosclerosis. We searched three electronic databases (PubMed, Scopus and Cochrane Database) with no date limit. All of the articles selected investigated PON enzymatic activity and/or PON gene polymorphisms. The selection focused on PON in relation to atherosclerosis, CAD and myocardial infarction. The exclusion criteria were a sample size <100 patients, non-human studies, editorials and systematic reviews without restrictions on the country of origin. With these criteria, we identified thirty-five prospective studies published between 1986 and 2014 with a total of 28,164 participants. The relationship between PON gene polymorphisms and CAD was not conclusive, but most studies support the concept that alterations in PON1 enzymatic activity levels do influence atheroma formation. Conversely, relationships between PON2 and PON3 vs. CAD have not been extensively investigated. Our review of the current data concludes that the bases of paraoxonases involvement in atherosclerosis are poorly understood and that this issue requires future comprehensive, multi-centered studies.

Effect of PON1 Q192R genetic polymorphism on clopidogrel efficacy and cardiovascular events in the Clopidogrel in the Unstable Angina to Prevent Recurrent Events trial and the Atrial Fibrillation Clopidogrel Trial with Irbesartan for Prevention of Vascular Events

BACKGROUND

A recent report suggested that carriers of the Q allele of the PON1 Q192R polymorphism had decreased biotransformation of clopidogrel into its active metabolite and decreased efficacy of clopidogrel in preventing cardiovascular events. Furthermore, PON1 has been reported to have a central role in the antioxidant function of high-density lipoprotein, and the Q192R polymorphism has been previously associated with cardiovascular risk in patients not treated with clopidogrel.

METHODS AND RESULTS

Patients (n=5059) from the Clopidogrel in Unstable Angina to Prevent Recurrent Events (CURE) randomized trial that demonstrated benefits of clopidogrel versus placebo in preventing cardiovascular events in acute coronary syndromes were genotyped for the PON1 Q192R polymorphism. Clopidogrel compared with placebo significantly reduced the first primary efficacy outcome, irrespective of PON1 Q192R genotype (P=0.07 for heterogeneity). No association was observed between the Q192R polymorphism and cardiovascular events in the overall sample (hazard ratio [HR], 1.09 per allele; 95% confidence interval [CI], 0.95-1.24; P=0.23). However, an association was observed between the Q allele and increased cardiovascular events in the placebo group (HR, 1.23 per allele; 95% CI, 1.03-1.47; P=0.03) but not in the clopidogrel group (HR, 0.93 per allele; 95% CI, 0.76-1.13; P=0.46). In 1156 atrial fibrillation patients from the Atrial Fibrillation Clopidogrel Trial With Irbesartan for Prevention of Vascular Events, there was no evidence of interaction between PON1 genotype and clopidogrel for any outcome or for an association between genotype and cardiovascular events.

CONCLUSIONS

In conclusion, our study shows that PON1 Q192R genotype does not modify the efficacy and safety of clopidogrel in patients with acute coronary syndromes. Further studies are needed to confirm or refute the association of the Q allele with adverse cardiovascular events independent of clopidogrel in secondary prevention patients.

Synergism between paraoxonase Arg 192 and the angiotensin converting enzyme D allele is associated with severity of coronary artery disease

We have previously shown that angiotensin-converting enzyme (ACE) gene D allele is an independent risk factor for early onset coronary artery disease (CAD). Little is known about the concomitant presence of the ACE gene D allele and paraoxonase (PON1) codon 192 arginine (Arg) on the severity of CAD. Regarding the high rate of CAD among Iranians the aim of present study was to examine the hypothesis of synergistic effects between ACE-D and PON1-Arg alleles on predisposition and the severity of CAD in our population. The PON1 192 and ACE insertion/deletion (I/D) genotypes were detected by PCR-RFLP and PCR, respectively in 414 individuals undergoing their first coronary angiography. Patients were placed into one of two groups: CAD and control without CAD or diabetes. We mentioned the synergistic effects of both genes and not ACE gene alone is a risk factor for CAD. We found that PON1 Arg 192 and ACE D allele act synergistically to increase the risk of CAD (OR 1.3, P = 0.044). Our results showed a significant correlation between the possession of both PON1 192 Arg and the ACE D allele and the extent of CAD in CAD patients and CAD subjects without diabetes, represented by the increased frequency of three-vessel disease with OR 2.7, P = 0.046; χ(2) = 4, P = 0.046 and OR 2.4, P = 0.051; χ(2) = 3.8, P = 0.051, respectively. We found that PON1 Arg 192 and ACE D alleles act synergistically to increase the risk of CAD in CAD patients and CAD subjects without diabetes from west of Iran, who have high frequency of three-vessel disease. Our data suggest that PON1 192 Arg and the ACE D allele in combination with each other can be important independent risk factor for severity of CAD in patients carrying both PON1 192 Arg and the ACE D allele in a west population of Iran.

Paraoxonase 1 (PON1) polymorphisms, haplotypes and activity in predicting cad risk in North-West Indian Punjabis

BACKGROUND

Human serum paraoxonase-1 (PON1) prevents oxidation of low density lipoprotein cholesterol (LDL-C) and hydrolyzes the oxidized form, therefore preventing the development of atherosclerosis. The polymorphisms of PON1 gene are known to affect the PON1 activity and thereby coronary artery disease (CAD) risk. As studies are lacking in North-West Indian Punjabi's, a distinct ethnic group with high incidence of CAD, we determined PON1 activity, genotypes and haplotypes in this population and correlated them with the risk of CAD.

METHODOLOGY/PRINCIPAL FINDINGS

350 angiographically proven (≥ 70% stenosis) CAD patients and 300 healthy controls were investigated. PON1 activity was determined towards paraoxon (Paraoxonase; PONase) and phenylacetate (Arylesterase; AREase) substrates. In addition, genotyping was carried out by using multiplex PCR, allele specific oligonucleotide -PCR and PCR-RFLP methods and haplotyping was determined by PHASE software. The serum PONase and AREase activities were significantly lower in CAD patients as compared to the controls. All studied polymorphisms except L55M had significant effect on PONase activity. However AREase activity was not affected by them. In a logistic regression model, after adjustment for the conventional risk factors for CAD, QR (OR: 2.73 (1.57-4.72)) and RR (OR, 16.24 (6.41-41.14)) genotypes of Q192R polymorphism and GG (OR: 2.07 (1.02-4.21)) genotype of -162A/G polymorphism had significantly higher CAD risk. Haplotypes L-T-G-Q-C (OR: 3.25 (1.72-6.16)) and L-T-G-R-G (OR: 2.82 (1.01-7.80)) were also significantly associated with CAD.

CONCLUSIONS

In conclusion this study shows that CAD patients had lower PONase and AREase activities as compared to the controls. The coding Q192R polymorphism, promoter -162A/G polymorphism and L-T-G-Q-C and L-T-G-R-G haplotypes are all independently associated with CAD.

Paraoxonase 1 polymorphism Q192R affects the pro-inflammatory cytokine TNF-alpha in healthy males

Background

Human paraoxonase 1 (PON1) is an HDL-associated enzyme with anti-oxidant/anti-inflammatory properties that has been suggested to play an important protective role against coronary heart diseases and underlying atherogenesis. The common PON1 Q192R polymorphism (rs662, A>G), a glutamine to arginine substitution at amino acid residue 192, has been analyzed in numerous association studies as a genetic marker for coronary heart diseases, however, with controversial results.

Findings

To get a better understanding about the pathophysiological function of PON1, we analyzed the relationships between the Q192R polymorphism, serum paraoxonase activity and serum biomarkers important for atherogenesis. Genotyping a cohort of 49 healthy German males for the Q192R polymorphism revealed an allele distribution of 0.74 and 0.26 for the Q and R allele, respectively, typical for Caucasian populations. Presence of the R192 allele was found to be associated with a significantly increased paraoxonase enzyme activity of 187.8 ± 11.4 U/l in comparison to the QQ192 genotype with 60.5 ± 4.9 U/l. No significant differences among the genotypes were found for blood pressure, asymmetric dimethylarginine, LDL, HDL, triglycerides, and cholesterol. As expected, MIP-2 alpha a cytokine rather not related to atherosclerosis is not affected by the PON1 polymorphism. In contrast to that, the pro-inflammatory cytokine TNF-alpha is enhanced in R192 carriers (163.8 ± 24.7 pg/ml vs 94.7 ± 3.2 pg/ml in QQ192 carriers).

Conclusions

Our findings support the hypothesis that the common PON1 R192 allele may be a genetic risk factor for atherogenesis by inducing chronic low-grade inflammation.

Paraoxonase Arg 192 allele is an independent risk factor for three-vessel stenosis of coronary artery disease

The role of the paraoxonase (PON1) codon 192 polymorphism [glutamine (Q)/arginine (R)] in coronary artery disease (CAD) is controversial. The aim of the present study was to evaluate whether the PON1 gene polymorphism is an independent risk factor for severity of coronary artery disease in patients from west of Iran. The PON1-Arg-192 genotypes were detected by PCR-RFLP in 414 individuals undergoing their first coronary angiography. Patients were placed into one of two groups: CAD and control without CAD or diabetes. The frequency of PON1-Arg-192 allele was significantly higher in the CAD (23.4 vs. 16%, P = 0.032) than in the control group and there was a higher risk of developing CAD (OR = 1.6, P = 0.02). In addition, this difference remained significant after adjustment for without history of diabetes (OR = 1.47, P = 0.048), presence of normolipidemia and absence of history of blood pressure (OR = 1.4, P = 0.05). This result indicated PON1-Arg-192 allele is a risk factor of CAD also when correcting for conventional risk factors. We found a significant association between the PON1-Arg-192 genotype (QR + RR) and the extent of CAD in CAD patients and CAD subjects without diabetes, represented by the increased frequency of three-vessel disease with OR = 1.49, P = 0.046; χ2 = 3.82, P = 0.048 and OR = 1.46, P = 0.05; χ2 = 3.48, P = 0.051, respectively. The CAD patients carrying PON1-Arg-192 genotype (QR + RR) had lower plasma HDL-C level (P = 0.019) and higher plasma LDL-C(P = 0.01) and TG(P = 0.05). Our results indicated that PON1-Arg-192 allele can be important independent risk factor of CAD in a west population of Iran, with carriers of PON1-Arg-192 having an increased frequency of three-vessel disease and also having a distinct plasma lipids profile. Larger collaborative studies are needed to confirm these results.

Four genetic polymorphisms of paraoxonase gene and risk of coronary heart disease: a meta-analysis based on 88 case-control studies

OBJECTIVE

The human paraoxonase (PON) is calcium dependent HDL associated ester hydrolase which has attracted considerable attention as a candidate gene for coronary heart disease based on its enzyme function as a key factor in lipoprotein catabolism pathways. Many studies have examined the association between polymorphisms in the PON gene and risk of coronary heart disease (CHD), but the results have been inconsistent.

METHODS

We conducted a meta-analysis of 88 studies on 4 PON polymorphisms [Q192R, L55M, and T(-107)C in the PON1 and the S311C in the PON2] published before August 2010, including a total of 24,702 CHD cases and 38,232 controls. We also systematically explored potential sources of heterogeneity.

RESULT

In a combined analysis, the summary per-allele odds ratio for CHD of the 192R was 1.11 (95% CI: 1.05-1.17). However, when the analyses were restricted to 10 larger studies (n>500 cases), the summary per-allele odds ratio was 0.96 (95% CI: 0.90-1.02). Our analyses detected a possibility of publication bias with an overestimate of the true association by smaller studies. A meta-analysis of studies on the 55M, (-107)T, and 311C variant showed no significant overall association with CHD, yielding a per-allele odds ratio of 0.94 (95% CI: 0.88-1.00), 1.02 (95% CI: 0.91-1.15) and 1.02 (95% CI: 0.90-1.16) respectively.

CONCLUSIONS

This meta-analysis suggested an overall weak association between the R192 polymorphism and CHD risk.

Relationship between Paraoxonase 1 (PON1) gene polymorphisms and susceptibility of stroke: a meta-analysis

Genetic variants of paraoxonase 1 (PON1) were implicated in stroke susceptibility in several case-control association studies. However, the studies have reported apparently conflicting results, rendering precise assessment of the disease risk associated with the variants difficult. A meta-analysis was therefore conducted by including the studies that examined the association between two common polymorphisms (L55M and Q192R) in the coding region of PON1 gene and the risk of stroke. Altogether 10 studies on L55M polymorphism and 11 studies on Q192R polymorphism were included in this meta-analysis. The results showed, although there was no significant association of the 55L allele with stroke [random effects OR = 1.09, 95% CI (0.93, 1.27), P = 0.29], the 192R allele conferred significant risk of stroke in the overall study population [random effects OR = 1.25, 95% CI (1.07, 1.46), P = 0.006]. Same pattern of results as both the allele contrasts was obtained for the homozygote contrasts and the dominant, recessive and additive models. Subgroup analyses for stroke type, age of patients and ethnicity revealed no association of the 55L allele with stroke, whereas the association of the 192R allele persisted significantly in the groups comprising ischemic stroke patients, stroke patients with mean age >60 years and Caucasian subjects. But no significant association of this allele with stroke susceptibility was detected in the East Asian population. Therefore, the results of this meta-analysis indicate, the Q192R polymorphism could be an important risk factor for stroke, especially in the Caucasian population.

The relationship between paraoxonase1-192 polymorphism and activity with coronary artery disease

OBJECTIVE

We tested the association between PON1 polymorphism, PON1 activity, oxidative susceptibility of LDL and coronary artery disease in Egyptians.

METHODS

PON1 polymorphism, serum PON1 activity, lipoprotein oxidation susceptibility and lipid profile were measured.

RESULTS

Levels of HDL and paraoxonase activity were significantly decreased in CAD patients compared to control group, and in patients with three vessels compared to those of single or two vessels disease. High-activity allele (R) has a more atherogenic lipid profile than for the low activity allele (Q). PON1 RR genotype has nine fold risks to develop CAD in Egyptians while those with PON1 QR genotype have four fold risks.

CONCLUSION

The PON1 activity is lower in subject with CAD and there is a significant relationship between activity of PON1 and the severity of coronary atherosclerosis. Also, we provide evidence of a significant association between R allele of the PON1 polymorphism and the development of coronary artery disease.

Role of angiotensin converting enzyme, paraoxonase 1 55, 192 gene polymorphisms in syndrome X and coronary heart disease

Aim of this study was to investigate the possible relationship between ACE and/or PON1 M55L, Q192R genetic polymorphisms and subjects with Coronary Heart Disease (CHD) and/or syndrome X (SX) when compared to the control group. ACE I/D, PON1 M55L and Q192R genetic polymorphisms, Body Mass Index (BMI) and biochemical parameters were investigated in subjects with CHD (n = 19), SX (n = 34) and healthy subjects (n = 26). All of the subjects were nonsmokers. According to the unrelated group t-test results; BMI, HDL-C and TG values were found to be slightly different in SX and control subjects but there was no significant difference in LDL-C and TC values. According to the Mann Whitney U-test results, BMI, TC, HDL-C and LDL-C values were found to be significantly different among CHD and control group subjects, but there was no difference in TG values. The results of this study indicates that ACE, PON1 192 and PON1 55 gene polymorphisms are not related to genetic susceptibility to SX and/or CHD in non-smokers. Obviously, the interpretation of these finding is difficult due to the small sample size and larger group studies are needed for more definitive conclusions.

Genetic polymorphism in paraoxonase 1 (PON1): Population distribution of PON1 activity

Paraoxonase-1 (PON1) is a serum esterase that hydrolyzes the activated oxon form of several organophosphates. The central role of PON1 in detoxification of organophosphate (OP) pesticides was demonstrated in knockout mouse studies, suggesting that human variability in PON1 needs to be considered in health risk assessments involving exposure to these pesticides. The current analysis focused on two genetic loci in which polymorphisms demonstrated to affect PON1 activity. Detailed kinetic studies and population studies found that the *192Q (wild type) allele is more active toward some substrates (such as sarin, soman, and diazoxon) and less active toward others (such as paraoxon or chlorpyrifos) relative to the variant *192R allele. Another allele that affects activity is *55M; PON1 enzyme quantity, rather than specific activity or substrate preference, is altered. The *192R variant occurs commonly with a frequency of 25-64% across the populations analyzed. The *55M allele is less common, occurring in 5-40% of individuals depending upon the ethnic group studied. These activity and allele frequency data were incorporated into Monte Carlo simulations in which the frequency of both variant alleles was simultaneously modeled in Caucasian, African American, and Japanese populations. The resulting Monte Carlo activity distributions were bimodal for the substrate paraoxon with approximately fourfold differences between low- and high-activity modal medians. Differences in activity between total population median and 1st percentile were five- to sixfold. When sarin metabolic variability was simulated, the population distributions were unimodal. However, there was an even greater degree of interindividual variability (median to 1st percentile difference >20-fold). These results show that the combined effects of two PON1 allelic variants yielded a population distribution that is associated with a considerable degree of interindividual variability in enzyme activity. This indicates that assessments involving PON1 substrates need to evaluate polymorphism-related variability in enzyme activity to display the distribution of internal doses and adverse responses. This may best be achieved via physiologically based pharmacokinetic (PBPK) models that input PON1 activity distributions, such as those generated in this analysis, to simulate the range of oxon internal doses possible across the population.

Polymorphisms in the paraoxonase and endothelial nitric oxide synthase genes and the risk of early-onset myocardial infarction

In young patients, the accumulative burden of traditional cardiovascular risk factors may not be as significant as in an older population. Genetic risk factors were suggested to have a role in the early development of myocardial infarction (MI). However, data about the association between polymorphisms in heart disease-related genes and the early onset of a first MI are limited. In the present study, age at onset of a first MI was related to individual single-nucleotide polymorphisms in each of 18 prespecified candidate genes in a cohort of 814 patients enrolled in the Thrombogenic Factors and Recurrent Coronary Events (THROMBO) Study. Multivariate regression analysis showed in patients who had the high-risk genotypes of paraoxonase 1 (PON1) Q192R and endothelial nitric oxide synthase (eNOS) E298D that ages at onset of a first MI were 1.8 (p = 0.02) and 3.5 years (p = 0.02) earlier than in noncarriers of the genotypes, respectively. Consistently, high-risk genotypes of the PON1 Q192R and eNOS E298D polymorphisms were significantly associated with onset of a first MI at age <50 years (adjusted odds ratio 1.70, p = 0.005, adjusted odds ratio 2.15, p = 0.01, respectively). In conclusion, our findings suggest that high-risk genotypes of the PON1 Q192R and eNOS E298D polymorphisms are independently associated with a significantly earlier occurrence of coronary events.

Accuracy and Biological Variation of Human Serum Paraoxonase 1 Activity and Polymorphism (Q192R) by Kinetic Enzyme Assay

Background: Paraoxonase 1 (PON1) phenotype is a better predictor of atherosclerosis risk than are PON1 genetic polymorphisms alone. Larger studies are required to determine the role of PON1 and there is a need for standardized PON1 assays between laboratories.

Methods: We have adapted 5 enzyme kinetic assays for high-throughput automated analysis of PON1 activity. Using different substrates and reaction conditions, we measured PON1 activity and used activity ratios to identify the PON1 Q192R genetic polymorphisms and assessed the accuracy of the genotype assignments in 79 adult study participants by comparing them with genotypes determined by AlwI restriction enzyme digestion of a 176-bp PCR amplification product from genomic DNA. Imprecision was determined using pooled serum and purified enzyme preparations. Biological variability was estimated by analysis of serial samples from 17 individuals. Variability parameters were compared with total cholesterol as a point of reference to a recognized biomarker of coronary heart disease risk.

Results: Salt stimulation and inhibition ratios were 97.4% and 94.7% correct in assigning Q192R genotype, respectively. Analytical imprecision (CV) was 1.0%–3.0% for phenylacetate and paraoxon substrate assays and 3.0%–8.0% for the para-nitrophenylacetate substrate assays. Combination of the 2 ratios into a double ratio resulted in 100% correct genotype classification.

Conclusion: The described methods for measurement of PON1 activity and accurate genotype assignment are rapid and have potential to facilitate the efficient investigation of PON1 status in clinical and epidemiological studies.

The 192R/Q polymorphs of serum paraoxonase PON1 differ in HDL binding, lipolactonase stimulation, and cholesterol efflux

Serum paraoxonase (PON1) is a HDL-associated enzyme exhibiting potentially antiatherogenic properties. Here, we examined the common PON1-192R/Q human polymorphism. Despite numerous studies, the effect of this polymorphism on the antiatherogenic potential of PON1 is yet unresolved. Our structural model suggests that amino acid 192 constitutes part of the HDL-anchoring surface and active site of PON1. Based on our findings that PON1 is an interfacially activated lipolactonase that selectively binds HDL carrying apolipoprotein A-I (apoA-I) and is thereby greatly stabilized and catalytically activated, we examined the interaction of the PON1-192 isozymes with reconstituted HDL-apoA-I particles. We found that PON1 position 192 is indeed involved in HDL binding. The PON1-192Q binds HDL with a 3-fold lower affinity than the R isozyme and consequently exhibits significantly reduced stability, lipolactonase activity, and macrophage cholesterol efflux. We also observed the lower affinity and stability of the 192Q versus the 192R isozyme in sera of individuals belonging to the corresponding genotypes. The observed differences in the properties of PON1-192R/Q isozymes provide a basis for further analysis of the contribution of the 192R/Q polymorphism to the susceptibility to atherosclerosis, although other factors, such as the overall levels of PON1, may play a more significant role.

Assessment of paraoxonase and arylesterase activities in patients with iron deficiency anemia

Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL) associated enzyme with three activities which are paraoxonase, arylesterase and dyazoxonase. We aimed to determine serum (a) paraoxonase and arylesterase activities and, lipid hydroperoxide (LOOH) levels in patients with iron deficiency anemia (IDA) (b) whether there is an association between the development of atherosclerosis and paraoxonase/arylesterase activities in patients with IDA. Twenty-five female with IDA and 22 healthy female as control were enrolled in the study. Serum basal/salt-stimulated paraoxonase and arylesterase activities were measured spectrophotometrically. LOOH levels were measured by ferrous oxidation with xylenol orange assay. Basal/salt-stimulated paraoxonase and arylesterase activities were significantly lower in patients with IDA than controls (p<0.001; for all), while LOOH levels were significantly higher (p<0.001). Our results show that paraoxonase and arylesterase activities, which have antiatherogenic capability, are decreased in patients with IDA. Reduced paraoxonase and arylesterase activities may play a role in pathogenesis of atherosclerosis through increased susceptibility to lipid peroxidation in patients with IDA.

TagSNP analyses of the PON gene cluster: effects on PON1 activity, LDL oxidative susceptibility, and vascular disease

Paraoxonase 1 (PON1) activity is consistently predictive of vascular disease, although the genotype at four functional PON1 polymorphisms is not. To address this inconsistency, we investigated the role of all common PON1 genetic variability, as measured by tagging single-nucleotide polymorphisms (tagSNPs), in predicting PON1 activity for phenylacetate hydrolysis, LDL susceptibility to oxidation ex vivo, plasma homocysteine (Hcy) levels, and carotid artery disease (CAAD) status. The biological goal was to establish whether additional common genetic variation beyond consideration of the four known functional SNPs improves prediction of these phenotypes. PON2 and PON3 tagSNPs were secondarily evaluated. Expanded analysis of an additional 26 tagSNPs found evidence of previously undescribed common PON1 polymorphisms that affect PON1 activity independently of the four known functional SNPs. PON1 activity was not significantly correlated with LDL oxidative susceptibility, but genotypes at the PON1(-108) promoter polymorphism and several other PON1 SNPs were. Neither PON1 activity nor PON1 genotype was significantly correlated with plasma Hcy levels. This study revealed previously undetected common functional PON1 polymorphisms that explain 4% of PON1 activity and a high rate of recombination in PON1, but the sum of the common PON1 locus variation does not explain the relationship between PON1 activity and CAAD.

Autopsy and postmortem examination case study on genetic risk factors for cardiac death: Polymorphisms of endothelial nitric oxide synthase gene Glu298asp variant and T-786c mutation, human paraoxonas

Background/Aim. The Glu298Asp variant in exon 7 and T-786C mutation in the 5'-flanking region of the endothelial nitric oxide synthase (eNOS) gene, paraoxonase I gene (PON1), and ?2?- adrenergic receptor gene (?2?-AR) have been reported to be genetic risk factors for coronary heart disease (CHD). The aim of this study was to investigate the effects of these four genetic polymorphisms on the probability of death due to CHD, using data obtained from medico-legal autopsies. Methods. Blood samples from three groups: healthy controls, dead cases with CHD and without CHD (the latter as a control for dead cases) were used. After DNA extraction, genotyping was performed by polymerase chain reaction ? restriction fragment length polymorphism (PCR-RFLP) test. Results. The frequency of the T allele in Glu298Asp variant in the dead cases with CHD was significantly higher than that in the healthy control (p < 0.001, OR = 4.47) and that in the dead cases without CHD (p < 0.001, OR = 7.62). The gene frequency of PON1 was significantly different (p = 0.007) between dead cases with and without CHD, and was also significantly different (p = 0.025) between the healthy control and dead cases without CHD. The gene frequency of PON1 was not significantly different (p = 0.401) between the healthy controls and dead cases with CHD. Hence this gene was not associated with death due to CHD. The other polymorphisms (T- 786C mutation, ?2?-AR) also showed no effect on death due to CHD. Conclusion. The polymorphism of Glu298Asp eNOS gene in dead cases may be useful for determining the cause of death in CHD cases in the Japanese population.

Investigation of the relationship between atherosclerosis and paraoxonase or homocysteine thiolactonase activity in patients with type 2 diabetes mellitus using a commercially available assay

BACKGROUND

It is known that serum paraoxonase activity decreases in patients with atherosclerotic diseases such as type 2 diabetes mellitus. Paraoxonase hydrolyzes homocysteine thiolactone, which is thought to be an endogenous substrate. The relationship between the status of atherosclerosis and homocysteine thiolactonase activity in patients with type 2 diabetes mellitus was investigated.

METHOD

Serum homocysteine thiolactonase activities in 207 patients with type 2 diabetes mellitus were measured with a recently developed commercially available assay.

RESULTS

The coefficient of variation for the assay was <0.7%. Serum paraoxonase and arylesterase activities were dependent on the PON1 192 polymorphism expressed by the subjects but homocysteine thiolactonase activity was not affected. A tendency for a negative association between homocysteine thiolactonase activity and the thickness of the carotid intima media was observed in patients with type 2 diabetes mellitus.

CONCLUSIONS

The serum homocysteine thiolactonase activity may represent the status of atherosclerosis in patients with type 2 diabetes mellitus. Since the assay can be used with a routine analyzer, the activities of thousands of samples can be measured with excellent precision in a few hours.

Measurement of homocysteine thiolactone hydrolase activity using high-performance liquid chromatography with fluorescence detection and polymorphisms of paraoxonase in normal human serum

We developed a non-radioactive and sensitive assay method for measurement of the HTL hydrolase (HTLase) activity in biological samples, using OPA as a fluorescent post-labeling agent, l-homocysteine thiolactone (L-HTL) as the substrate, and HPLC to achieve rapid and selective separation of the substrate and product. The method was applied to measure the activity of HTLase in human, rabbit, rat and mouse serum samples. In addition, the correlation between the serum HTLase activity and PON1 polymorphisms in Japanese subjects was also investigated. The serum HTLase activity in humans, as determined by measurement of the enzyme activity in 22 subjects, was found to be in the range of 0.89-2.06 nmol/min mg protein, with a mean activity of 1.44 nmol/min mg protein.

Paraoxonase 192 polymorphism and its relationship to serum lipids in Turkish renal transplant recipients

BACKGROUND

Cardiovascular disorders are the leading cause of death in patients with chronic renal insufficiency. Paraoxonase (PON1) gene variants have been identified as risk factors for cardiovascular disease (CVD).

METHODS

We investigated the effect of PON1 192 polymorphisms on serum lipid profiles in 29 renal transplant recipients and 26 control subjects. Distribution of the PON1 192-gene polymorphism was determined by polymerase chain reaction-based restriction fragment length polymorphism. Serum lipid levels were measured enzymatically.

RESULTS

Frequencies of PON1 192 AA, BB, and AB genotypes among the renal transplant recipients were 38.5%, 26.9%, and 34.6%, and among control subjects they were 35.75%, 17.9%, 46.4%, respectively. The genotype distribution for the PON1 192 polymorphism was not different between the two groups (P = NS, chi-square test). The PON1 192 polymorphisms failed to consistently influence the serum lipid profiles in renal transplant recipients.

CONCLUSION

We have shown that the 192 polymorphism of the PON1 gene is not associated with increased cardiovascular risk in renal transplant recipients.

Effect of pitavastatin on transactivation of human serum paraoxonase 1 gene

Hepatic hydroxymethyl glutary coenzyme A HMG-CoA reductase inhibitors (statins) have various anti atherosclerosis pleiotropic effects that are independent of cholesterol reduction. Human serum paraoxonase 1 (PON1) is associated with high-density lipoprotein (HDL) and inhibits the oxidative modification of low-density lipoprotein (LDL). We investigated the effects of statins on PON1 gene transcription using a reporter gene assay. Promoter activity of the PON1 gene was estimated by measuring luciferase activity of plasmids with a PON1 promoter region transfected into human hepatoma HepG2 cells and human embryonic kidney (HEK) 293 cells. Pitavastatin, simvastatin, and atorvastatin each significantly increased PON1 promoter activity, and the transactivation by pitavastatin was abrogated by mevalonic acid and farnesyl pyrophosphate (FPP), however, not by geranylgeranyl pyrophosphate. Further, PON1 promoter activity was enhanced by farnesyl transferase inhibitor (FTI), but not by geranylgeranyl transferase inhibitor (GGTI). PON1 gene transcription has been reported to be dependent on Sp1 and the transactivation by pitavastatin was completely abrogated by mithramycin, an inhibitor of Sp1. Our results suggest that pitavastatin activates transcription of the PON1 gene through the FPP pathway, which may play an important role in the anti atherosclerotic effects of statins.

Population differences in DNA sequence variation and linkage disequilibrium at the PON1 gene

Polymorphisms of the promoter region (-108C/T) and the coding region (192Q/R) of the paraoxonase 1 gene (PON1) showed differences in association with cardiovascular disease risk in various populations. To characterize the genetic variation underlying these important polymorphisms, we examined DNA sequence variation both in a 1.3-kb promoter region 16.5 kb from codon 192, and in a 1.7-kb region centered on the 192Q/R polymorphic site of the coding region of PON1, in 30 Africans, 30 Europeans and 64 Japanese. We found 10 polymorphic sites and 11 haplotypes in the 1.3-kb promoter region and 10 biallelic polymorphic sites and 10 haplotypes in the 1.7-kb region. From the PON1 sequences of chimpanzees and an orangutan, the ancestral type of codon 192 was found to be R. The number of pairs of polymorphic sites between the promoter and 1.7-kb regions that were in significant linkage disequilibrium was much higher in a Japanese population than in African and European populations. In addition, the pairs of polymorphic sites in linkage disequilibrium differed among the three populations. These results suggest that some of the population differences in association with risk for coronary heart disease can be explained by population differences in haplotype frequency of PON1 haplotypes.

The effects of lipid-lowering therapy on paraoxonase activities and their relationships with the oxidant???antioxidant system in patients with dyslipidemia

BACKGROUND

Atorvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, which is used for lipid-lowering therapy, is an effective statin modulating process involved in atherosclerosis. Paraoxonase (PON) associated with high-density lipoprotein (HDL) has been postulated to have a role in protecting low-density lipoprotein (LDL) against oxidative modification. Oxidation of serum LDL is an important early step in the development of atherosclerosis and auto-antibodies against oxidized LDL (AuAb-oxLDL) reflect in-vivo LDL oxidation.

DESIGN AND METHODS

To examine the effect of atorvastatin (10 mg/day) therapy on PON activity in serum and HDL, the study group included 40 patients with dyslipidemia (19 women and 21 men), 25 of whom had hypercholesterolemia and of 15 of whom had mixed-type hyperlipidemia. By taking blood samples from the patients, levels of serum lipids, lipid peroxidation product as malondialdehyde (MDA), total antioxidant status (TAS) and AuAb-oxLDL and the activities of PON in serum and isolated HDL were determined.

RESULTS

The mean levels of total cholesterol, triglyceride, LDL-cholesterol, MDA and AuAb-oxLDL were decreased while HDL-cholesterol and TAS were increased significantly after lipid-lowering therapy in patients with dyslipidemia. On the other hand, PON activities in serum and HDL were increased significantly. The percentage increase in serum PON activity was associated significantly with the percentage decrease in serum AuAb-oxLDL (r=-0.32, P=0.047) and that of HDL PON activity was associated with the percentage increase in HDL-cholesterol level after atorvastatin therapy (r=0.52, P=0.001). The therapy was more effective in increasing PON activity in patients with HDL levels above 35 mg/dl.

CONCLUSION

It was concluded that atorvastatin therapy in dyslipidemic patients decreases the level of oxidative stress and increases PON activity, especially in patients with HDL levels above 35mg/dl.

The association of the PON1 Q192R polymorphism with coronary heart disease: findings from the British Women's Heart and Health cohort study and a meta-analysis

BACKGROUND

There have been inconsistent results from case-control studies assessing the association of the PON1 Q192R polymorphism with coronary heart disease (CHD). Most studies have included predominantly men and the association in women is unclear. Since lipid levels vary between the sexes the antioxidant effect of PON1 and any genes associated with it may also vary by sex. We have examined the association of the PON1 Q192R polymorphism with CHD in a large cohort of British women and combined the results from our cohort study with those from all other published studies.

RESULTS

The distribution of genotypes was the same among women with CHD and those without disease. The odds ratio (95% confidence interval) of having CHD comparing those with either the QR or RR genotype to those with QQ genotype (dominant model of association) was 1.03 (0.89, 1.21) and the per allele odds ratio was 0.98 (0.95, 1.01). In a meta-analysis of this and 38 other published studies (10,738 cases and 17,068 controls) the pooled odds ratio for the dominant effect was 1.14 (1.08, 1.20) and for the per allele effect was 1.10 (1.06, 1.13). There was evidence of small study bias in the meta-analyses and the dominant effect among those studies with 500 or more cases was 1.05 (0.96, 1.15). Ethnicity and reporting of whether the genotyping was done blind to the participants clinical status also contributed to heterogeneity between studies, but there was no difference in effect between studies with 50% or more women compared to those with fewer women and no difference between studies of healthy populations compared to those at high risk (with diabetes, renal disease of familial hypercholesterolaemia).

CONCLUSION

There is no robust evidence that the PON1 Q192R polymorphism is associated with CHD risk in Caucasian women or men.

PON1 M/L55 mutation protects high-risk patients against coronary artery disease

The paraoxonase (PON) gene family contains at least three members: PON1, PON2, and PON3. The enzyme PON1 has been implicated in the pathogenesis of atherosclerosis. Recently, an association between PON2 and quantitative metabolic phenotypes, such as plasma lipoproteins, plasma glucose, and coronary artery disease (CAD), has been reported. We analyzed two common polymorphisms in PON1 (i.e., M/L55 and R/Q 192 mutations) and PON2 (i.e., G/A148 and C/S311 mutations) in 352 high-risk patients with angiographically defined CAD. These results were compared to those in 380 age- and sex-matched control subjects at high risk for CAD. Polymerase chain reaction with specific primers followed by Hsp92, Alw1, DdeI and Fnu4HI restriction digestion were employed to identify the PON1 M/L55 and R/Q192 and the PON2 G/A148 and C/S311 genotypes, respectively. Univariate analysis showed a higher prevalence of the MM genotype (12% vs. 5%; p=0.004) for the PON1 M/L55 polymorphism and the GG genotype (21% vs. 15%; p=0.047) PON2 G/A148 polymorphism in the control subjects. The PON1 M/L55 mutation (MM genotype) was associated with lower triglyceride levels and the PON2 G/A148 mutation (GG genotype), with higher total and low-density lipoprotein (LDL)-cholesterol levels. No mutation was associated with the number of major coronary artery vessels with a >50% reduction in lumen diameter. Multiple regression analysis disclosed smoking, a family history of CAD, high-density lipoprotein (HDL)-cholesterol and the PON1 M/L55 mutation [OR=0.59 (CI95%: 0.42-0.82); p=0.002] as independent markers for CAD. In contrast to traditional coronary risk factors, the PON1 M/L mutation can be considered predictive of protection against CAD.

Four paraoxonase gene polymorphisms in 11212 cases of coronary heart disease and 12786 controls: meta-analysis of 43 studies

BACKGROUND

Although there have been suggestions that serum paraoxonase is important in protecting against coronary heart disease (CHD), a large number of studies of genetic determinants of serum paraoxonase have reported apparently conflicting results about their association with CHD.

METHODS

We conducted a meta-analysis of 43 studies of the Q192R, L55M, and T(-107)C polymorphisms in the paraoxonase PON1 gene and the S311C polymorphism in the PON2 gene (all of which are in moderately strong linkage disequilibrium with one another), involving a total of 11212 CHD cases and 12786 controls. We explored potential sources of heterogeneity.

FINDINGS

In a combined analysis of all studies, the per-allele relative risk of R192 for CHD was 1.12 (95% CI 1.07-1.16), but in the five largest studies it was only 1.05 (0.98-1.13). Combined analyses of studies of the M55, (-107)T, and C311 variants showed no significant overall associations with CHD, yielding per-allele relative risks of 1.00 (0.95-1.06), 1.02 (0.92-1.14), and 1.04 (0.93-1.17), respectively.

INTERPRETATION

In contrast to previous suggestions, this meta-analysis shows no significant association of CHD with the L55M or T(-107)C polymorphism in PON1 or with the S311C polymorphism in PON2. The weak overall association between the Q192R polymorphism and CHD is of uncertain relevance, particularly since there was no significant association among the larger studies which should be less prone to selective publication. These findings reinforce the need for much larger and more rigorous investigations of the genetic determinants of complex diseases than is now customary, as well as for regularly updated systematic appraisals of such studies to help improve interpretation and prioritise hypotheses.

R/R genotype of human paraoxonase (PON1) is more protective against lipoprotein oxidation and coronary artery disease in Japanese subjects

Human paraoxonase (PON1) is an high-density lipoprotein (HDL) -associated enzyme that is proposed to protect against the oxidation of lipoproteins. Recently, the association of coronary artery disease (CAD) and PON1 activity was reported. Furthermore, the R/R genotype of PON1 has been related to the risk for CAD. In this study we investigated the PON1 genotype and susceptibility to lipoprotein oxidation to elucidate the contribution of PON1 to atherosclerosis in Japanese subjects. We studied 179 patients who underwent coronary angiography and their PON1 genotypes were determined. Lipoproteins were obtained from a patient's blood after at least 12 hours fasting and were separated with sequential ultracentrifugation. We analyzed the thiobarbituric acid reactive substances (TBARS) and continuously monitored the copper-induced oxidation three genotype groups. Genotype frequencies of Q/Q, Q/R, and R/R were 21.2%, 36.9%, and 41.9%, respectively. PON1 polymorphism clearly determined the lipid oxidation. The R/R genotype of PON1 had significantly lower levels of plasma and HDL TBARS and significantly retarded the initiation of oxidation in HDL and low-density lipoprotein (LDL). The R/R genotype was related to the lower prevalence of CAD. The PON1 genotype clearly determined the oxidative modification of lipoproteins and may play a role in the pathogenesis of atherosclerosis via its protective effect against lipoprotein oxidation in Japanese subjects.

Paraoxonase activity, but not haplotype utilizing the linkage disequilibrium structure, predicts vascular disease

OBJECTIVE

The effects of paraoxonase (PON1) activity and of genetic variation in the PON1 promoter and coding region on carotid artery disease (CAAD) were investigated.

METHODS AND RESULTS

We identified functional promoter polymorphisms and examined their effects in a cohort with and without CAAD. We used the full sequences in 23 white subjects to determine the linkage disequilibrium (LD) structure of the PON1 region and to direct the grouping of haplotypes for disease association testing. There are several discrete regions of the PON1 gene with strong local LD, but the useful levels of LD do not extend across the entire gene. Indeed, PON1-162/-108/55/192 haplotype did not predict additional variation in PON1 activities compared with the 4 genotypes separately. PON1 hydrolysis activity predicted CAAD status, but this was not attributable to the promoter or coding region polymorphisms or haplotype or to the effects of smoking or statin use on PON1 activity.

CONCLUSIONS

PON1 does not have LD across the gene, and use of haplotypes in association studies should consider the LD structure. PON1 activity predicts CAAD, yet 4 functional polymorphisms do not. Additional investigations of genetic and environmental factors that influence PON1 activity as a risk factor for vascular disease are warranted.

[From organophosphate compound toxicity to atherosclerosis: role of paraoxonase 1]

PURPOSE

Paraoxonase 1 is an ubiquitous human serum and tissue esterase known to hydrolyse organophosphorous compounds. It seems to be implicated in various vascular diseases.

CURRENT KNOWLEDGE AND KEY POINTS

Recently paraoxonase has been located on the surface of High Density Lipoproteins (HDL) which has directed studies towards its involvement in atherosclerosis. An antioxidant effect has been suggested from its structure rich in reducing amino acids (cysteine), which was confirmed on low density lipoproteins (LDL) first in vitro and then in vivo. Paraoxonase 1 hydrolyses an arachidonic acid derivative found on the surface of oxidised LDL known to participate in the essential initial step of atherogenesis. Clinically paraoxonase 1 activity is low when pathological vascular ageing occurs early (myocardial infarction) and when cardiovascular risk is high (diabetes mellitus, chronic renal failure, analphalipoproteinemia).

FUTURE PROSPECTS AND PROJECTS

The genetic polymorphism of this enzyme is one of the determinants of serum paraoxonase 1 activity variations. It could explain sensitivity differences in chronic organophosphate intoxications and has been suspected as a risk factor of vascular injury. A decrease of this enzyme activity with ageing could play a part in the high prevalence of cardiovascular diseases in the aged.

Functional genomic of the paraoxonase (PON1) polymorphisms: effects on pesticide sensitivity, cardiovascular disease, and drug metabolism

This review focuses on the functional genomics of the human paraoxonase (PON1) polymorphisms. Levels and genetic variability of the PON1 position 192 isoforms (Gln/Arg) influence sensitivity to specific insecticides or nerve agents and risk for cardiovascular disease. A more recent area of investigation, the role of PON1 in drug metabolism, is also discussed. We emphasize the importance of considering both PON1 isoforms and PON1 levels in disease/sensitivity association studies.

Serum paraoxonase activity decreases in rheumatoid arthritis

OBJECTIVE

To estimate the alterations of paraoxonase 1 (PON1) and high-density lipoprotein (HDL) in rheumatoid arthritis (RA).

DESIGN AND METHODS

We investigated the serum enzyme activity and concentration of PON1 and their relationship with serum lipids, high-density lipoprotein (HDL) parameters, and acute phase reactants of serum amyloid A (SAA) and C-reactive protein (CRP) in patients with RA.

RESULTS

Serum paraoxonase (PON) activity was significantly decreased in RA patients (n = 64, 131 +/- 53 micro mol/min/L) compared with healthy subjects (n = 155, 164 +/- 59) despite the absence of any difference in serum lipid levels between the two groups. This decrease of serum PON activity in RA patients was found in every genotype (Q/Q, Q/R, R/R) of PON1 at 192 Q/R. There was a different distribution in PON1 Q/R genotypes between RA patients and healthy subjects, and RA patients exhibited less (44%) positive PON1-Q than did the healthy subjects (66%). In a further investigation of age- and gender-matched subgroups of RA (n = 25) and healthy subjects (n = 25), not only serum PON activity, but also lecithin-cholesterol acyltransferase (LCAT) was found to be significantly decreased in RA patients (125 +/- 61 micro mol/min/L, 63.2 +/- 17.2 nmol/ml/hr/37 degrees C) than in healthy subjects (169 +/- 67, 74.7 +/- 19.5), respectively. PON1 and LCAT as well as HDL constituent apolipoprotein (apo) AI and apo AII, were altered significantly in RA patients.

CONCLUSIONS

Acute-phase HDL, which is remodeled structurally and functionally in RA, might be less anti-atherogenic due to the impairment of original HDL function. These alterations of HDL in RA patients may explain in part the reported increase in cardiovascular mortality in patients with RA.

Human paraoxonase 1 gene polymorphisms and the risk of coronary heart disease: a community-based study

Published data on the association between paraoxonase1 (PON1) polymorphisms and coronary heart disease (CHD) have yielded controversial results. The objective of this study was to determine the possible relationship between the two human PON1 amino acid variants, the Leu55Met and the Gln192Arg polymorphism, and the risk of CHD in a community-dwelling cohort of European ancestry. PON1 genotypes of 152 women and 151 men out of 1,998 randomly selected individuals aged 44-75 years were determined by polymerase chain reaction-based restriction enzyme digestion. Study participants underwent cardiological examination including a structured clinical interview, resting ECG, exercise testing and echocardiography. The diagnosis of CHD was based on history and/or appropriate findings during cardiac examination. Evidence for CHD was found in 43 (14.2%) study participants. The Leu/Leu (LL), Leu/Met (LM) and Met/Met (MM) genotypes at position 55 were noted in 131 (43.2%), 128 (42.2%) and 44 (14.5%) subjects; the Gln/Gln (QQ), Gln/Arg (QR) and Arg/Arg (RR) genotypes at codon 192 occurred in 167 (55.1%), 118 (38.9%) and 18 (5.9%) individuals, respectively. Homozygosity for the 55L-allele was significantly associated with CHD (p = 0.02), while the Gln192Arg polymorphism had no effect (p = 0.16). Logistic regression analysis demonstrated age (odds ratio 1.06/year), smoking (odds ratio 2.86), HDL cholesterol (odds ratio 0.94/mg/dl) and the paraoxonase LL genotype (odds ratio 2.25) to be significant predictors of CHD. These data suggest that the paraoxonase LL genotype at position 55 may present a risk factor for CHD.

PON1-192 phenotype and genotype assessments in 918 subjects of the Stanislas cohort study

This study describes the factors of variation of the enzymes related to the PON1-192 phenotype assessment, i.e., basal paraoxonase, salt-stimulated paraoxonase and arylesterase activities, and compares the PON1-192 phenotype to the PON1-192 genotype assessments in supposedly healthy subjects issued from the Stanislas cohort study. The studied population included 918 subjects, i.e., 221 families including 441 adults and 477 children aged 4 to 58 years. Potential determinants such as age, gender, body mass index, alcohol and tobacco consumption, and oral contraceptive intake have been studied. The PON ratio (salt-stimulated paraoxonase/arylesterase) was trimodally distributed and the cut-off values used to differentiate the two homozygous (AA and BB phenotypes) from the heterozygous (AB phenotype) subjects were 3.0 and 7.0 in this study. In males, basal paraoxonase and salt-stimulated paraoxonase activities were not affected by alcohol consumption and current smoking, but basal paraoxonase activity was decreased by 15% by current smoking and was increased by 15% by oral contraceptive intake in females as was the salt-stimulated paraoxonase activity. The level of discordance between phenotype and genotype assessments was 7.2% (66/918). Most of the discrepancies were observed between the BB and AB phenotypes (4.25%).