The Gln-Arg 191 polymorphism of the human paraoxonase gene is not associated with the risk of coronary artery disease among Chinese in Taiwan

Association of APOE (rs429358 and rs7412) and PON1 (Q192R and L55M) Variants with Myocardial Infarction in the Pashtun Ethnic Population of Khyber Pakhtunkhwa, Pakistan

Coronary Artery Diseases (CAD) remains the top among Non-communicable Diseases (NCDs). Variations in Apolipoprotein E (APOE) and Paroxonase 1 (PON1) have been associated with Myocardial Infarction (MI) in several populations. However, despite the high prevalence of CAD, no such study has been reported in the Pashtun ethnic population of Pakistan. We have conducted a two-stage (i.e., screening and validation) case-control study in which 200 cases and 100 control subjects have been recruited. In the first stage, Whole Exome Sequencing (WES) was used to screen forpathogenic variants of Myocardial Infarction (MI). In the second stage, selected variants of both APOE and PON1 genes (rs7412, rs429358, rs854560, and rs662) were analyzed through MassARRAY genotyping. Risk Allele Frequencies (RAFs) distribution and association of the selected SNPs with MI were determined using the Chi-square test and logistic regression analysis. WES identified a total of 12 sequence variants in APOE and 16 in PON1. Genotyping results revealed that APOE variant rs429358 (ɛ4 allele and ɛ3/ɛ4 genotype) showed significant association in MI patients (OR = 2.11, p value = 0.03; 95% CI = 1.25–2.43); whereas no significant difference (p˃ 0.05) was observed for rs7412. Similarly, the R allele of PON1 Q192R (rs662) was significantly associated with cases (OR = 1.353, p value = 0.048; 95% CI = 0.959–1.91), with particular mention of RR genotype (OR = 1.523, p value = 0.006; 95% CI = 1.087–2.132). Multiple logistic regression analysis showed that rs429358 (C allele) and rs662 (R allele) have a significantly higher risk of MI after adjustment for the conventional risk factors. Our study findings suggested that the rs429358 variant of APOE and PON1 Q192R are associated with MI susceptibility in the Pashtun ethnic population of Pakistan.

Role of Single Nucleotide Polymorphism L55M in the Paraoxonase 1 Gene as a Risk and Prognostic Factor in Acute Coronary Syndrome

The aim of the current study is to explore the possible role of L55M, (rs 854560, 163T > A) SNP as a predisposing factor for acute coronary syndrome (ACS) and to assess its potency as a prognostic biomarker for short (1 year) survival and for median (5 years) and 9-year long patients’ outcome. Methods: The current work is a prospective case-control study with 77 patients with acute coronary syndrome (53 with ST-elevation myocardial infarction, STEMI, 14 with non-ST-elevation myocardial infarction, NSTEMI and 10 with unstable angina, UA) and 122 control individuals. Patients were followed-up for 9 years. The genotyping for PON1 L55M SNP was carried on by PCR-RFLP method. Results: The results of the genotyping for PON1 L55M SNP showed a statistically significant difference (p = 0.023) between the controls and the whole group of patients with acute coronary syndrome, as the individuals with genotype with at least one variant M allele had about 2.5-fold higher risk for developing ACS than those which are homozygous of the wild-type L allele (LL genotype). In patients with variant M allele genotypes (LM + MM) which suffer from non-ST-segment elevation ACS (NSTEACS, i.e., UA or NSTEMI), the serum levels of total cholesterol (TC) and triacylglycerols (TAG) are significantly higher than in NSTEACS patients with LL genotype (p = 0.022 for TC and p = 0.015 for TAG). There was no significant difference in the survival rate at the 1st, 5th and 9th year of follow-up between ACS patients with different genotypes, although it is worth to note that in the subgroup of NSTEACS, all patients (n = 13) with variant M allele genotypes (LM + MM) were alive at the end of the first year, while 2 of the patients with LL genotype (18.2%) were dead. Conclusions: The results of our current study suggest that the variant M allele and the M allele genotypes (LM + MM) of the PON1 L55M polymorphism are risk factors for acute coronary syndrome, especially for patients with STEMI, but do not support the possible effect of this polymorphism on the clinical progression and outcome of the patients with ACS either in short or long follow-up periods.

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.

Associations of the PON1 rs662 polymorphism with circulating oxidized low-density lipoprotein and lipid levels: a systematic review and meta-analysis

BACKGROUND

Several meta-analyses have demonstrated that the rs662 polymorphism in Paraoxonase 1 gene (PON1) gene is associated with coronary heart disease (CHD). However, it is still uncertain whether this polymorphism is associated with the plasma levels of oxidized low-density lipoprotein (Ox-LDL) and lipids. This meta-analysis is aimed to clarify the relationships between the rs662 polymorphism and plasma levels of Ox-LDL and lipids.

METHODS

By searching in PubMed, Google Scholar, Web of Science, Cochrane Library, Wanfang, VIP and CNKI databases, 5 studies (1369 subjects) and 85 studies (46,740 subjects) were respectively identified for Ox-LDL association analysis and lipid association analysis. Standardized mean difference (SMD) was used to estimate the effects of the rs662 polymorphism on plasma Ox-LDL and lipid levels.

RESULTS

The carriers of the variant R allele had higher levels of Ox-LDL (SMD = 0.23, 95% CI = 0.10-0.36, P <  0.01), triglyceride (TG) (SMD = 0.06, 95% CI = 0.01-0.11, P = 0.02), total cholesterol (TC) (SMD = 0.04, 95% CI = 0.00-0.07, P = 0.05) and low-density lipoprotein cholesterol (LDL-C) (SMD = 0.04, 95% CI = 0.00-0.08, P = 0.04) than the non-carriers.

CONCLUSIONS

This meta-analysis suggests that the association between the PON1 rs662 polymorphism and CHD may partly be mediated by abnormal Ox-LDL and lipid levels caused by the R allele.

Association between the PON1 Q192R polymorphism and coronary heart disease in Chinese: A meta-analysis

BACKGROUND

The relation has not been reported consistently between the PON1 Q192R polymorphism and coronary heart disease (CHD). To clarify the discrepancy, we performed the present meta-analysis to evaluate the association between the PON1 gene Q192R polymorphism and CHD risk in Chinese population.

METHODS

We conducted a comprehensive search of the PubMed, EMBASE, and China National Knowledge Infrastructure databases for all available case-control studies. Two reviewers independently selected studies. Data were analyzed by STATA software package v 12.0.

RESULTS

Thirteen studies investigating the association between the PON1 Q192R polymorphism and risk of CHD were selected in this meta-analysis with 4353 cases and 4882 controls. The association between the PON1 Q192R polymorphism and CHD is statistically significant under the recessive genetic model (R/R vs Q/R + Q/Q, odds ratio [OR] = 1.111, 95% confidence interval [CI] = 1.017-1.214). We observed no statistical association between PON1 Q192R polymorphism and risk of CHD under allele model (R vs Q, OR = 1.087, 95% CI = 0.976-1.209), homozygous model (RR vs QQ, OR = 1.192, 95% CI = 0.949-1.496), and dominant genetic model (Q/R + R/R vs Q/Q, OR = 1.127, 95% CI = 0.938-1.354).

CONCLUSION

This meta-analysis suggests that the PON1 Q192R polymorphism has a weak association with CHD risk in Chinese.

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.

Serum paraoxonase level and paraoxonase polymorphism in patients with acromegaly

BACKGROUND

Acromegalic patients have increased cardiometabolic risk factors due to an elevation of growth hormone (GH) levels. Human serum paraoxonase (PON), a high-density lipoprotein (HDL)-related enzyme, is one of the major bioscavengers and decreases the oxidation of low-density lipoprotein (LDL), a key regulator in the pathogenesis of atherosclerosis. In this study, we investigated a potential relationship between serum PON levels or PON polymorphisms and acromegaly.

METHODS

A total of 48 acromegalic patients and 44 healthy controls were included in this study. Serum GH levels, insulin-like growth factor-1 levels and lipid profiles were measured. Serum PON levels, as well as PON 1 L55M and Q192R gene polymorphisms, were examined.

RESULTS

No significant differences were found in terms of age, gender, presence of diabetes, serum LDL cholesterol (LDL-C), HDL-C, or triglyceride levels between the case and control groups (P > 0.05). A statistically significant difference was found in serum PON levels between the cases and controls (P = 0.007). The median serum PON level was 101 ± 63.36 U/l in the case group and 63 ± 60.50 U/l in the control group. There was a significant correlation between serum PON levels and IGF-1 levels (P = 0.004, r = 0.319); however, no significant differences were found in PON1 L55M and PON Q192R polymorphisms between the patients and controls (P = 0.607 and P = 0.308, respectively). In addition, no significant differences were found in serum PON levels in acromegalic patients who were and were not in remission (P = 0.385), nor between those with PON1 L55M and Q192R polymorphisms (P = 0.161 and P = 0.336, respectively).

CONCLUSIONS

Elevated serum PON levels were detected in acromegalic patients, independently of their remission status. This suggests protective effects for cardiometabolic risk parameters.

Association between Paraoxonase 1 (PON1) Polymorphisms and the Risk of Acute Coronary Syndrome in a North African Population

The purpose of the present study was to investigate the distribution of PON1 Q192R and L55M polymorphisms and activities in a North African population and to determine their association with cardiovascular complications. The prevalence of the QQ, QR, RR, LL, LM, and MM genotypes in the study population was 55.4%, 34.09%, 9.83%, 41.97%, 48.20%, and 9.83% respectively. The Q, R, L, and M alleles had a gene frequency of 0.755, 0.245, 0.67, and 0.33, respectively. The PON1 192 RR genotype was significantly more prevalent among ACS patients than among healthy subjects. There was a 4.33-fold increase in the risk of ACS in subjects presenting the PON1 192 RR genotype compared to those with the QQ genotype (OR=4.33; 95% CI=1.27–17.7). There was a significantly different distribution of PON1 L55M in the ACS patient groups (UA, STEMI, NSTEMI). Moreover, individuals presenting the PON1 55MM genotype present a higher risk for ACS than those with LL genotype (OR=3.69; 95% CI=1.61–11.80). Paraoxonase activities were significantly lower in coronary patients than in healthy subjects. The decrease in PON1 activity was inversely correlated with the number of concomitant risk factors for CVD (r=0.57, p<0.0001). The results of the present study suggested that the PON1 R and M alleles may play a role in the pathogenesis of cardiac ischemia in our North African population and that a decrease in PON1 activity may be a valuable marker for monitoring the development of the atherosclerosis process and the associated cardiovascular complications.

The association of paraoxonase 1 gene L55M polymorphism with the extent and severity of coronary artery disease in the Turkish population and its dependence on gender

OBJECTIVE

Coronary artery disease (CAD) is a common, complex, and progressive disorder characterized by the accumulation of lipids and fibrous elements in the arteries. It is one of the leading causes of death in industrialized nations. Oxidative modification of low-density lipoprotein (LDL) in the arterial wall plays an important role in the initiation and progression of atherosclerosis. Paraoxonase1 (PON1) is involved in lipid metabolism and is believed to protect LDL oxidation. In our study, we aimed to clarify the relationship between PON1 gene L55M polymorphism and the extent and severity of CAD.

METHODS

In total, 114 patients (54 males, mean age: 56.7 ± 12.0 years; 60 females, mean age: 55.7 ± 13.2 years) with stable angina or angina equivalent symptoms were enrolled in this prospective study. Cardiological evaluation was performed with electrocardiogram and transthoracic echocardiogram. The presence of hypertension, dyslipidemia, diabetes, and smoking status were ascertained. The patients were grouped according to their Gensini scores and gender. Genetic analysis of the PON1 gene L55M polymorphism was performed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

We determined that the LL genotype was more prevalent in patients with Gensini score higher than or equal to 20 (p=0.026) and that this correlated with severe atherosclerotic coronary artery lesions in both gender groups, reaching a statistical significance in the female subjects (p=0.038).

CONCLUSION

It was thought that the PON1 gene L55M polymorphism plays a significant role in CAD progression, especially in females.

Interaction effects between Paraoxonase 1 variants and cigarette smoking on risk of coronary heart disease in a Singaporean Chinese population

OBJECTIVE

Paraoxonase 1 (PON1) plays an important role in reducing the risk of coronary heart disease (CHD). Smoking is known to reduce PON1 activity. We aimed to investigate the effects of interactions between PON1 variants and smoking on CHD in the Singaporean Chinese population.

METHODS

In a case-control study nested within Singapore Chinese Health Study (N=1914), subjects with and without CHD were classified into never-smokers and ever-smokers (ever smoked at least one cigarette a day for 1 year or longer). Associations at four independent SNPs at the PON1 locus (rs3735590, rs3917550, rs662, rs3917481) with CHD were evaluated using logistic regression, before/after stratification on smoking status. Interactions between smoking and PON1 variants were analyzed with likelihood ratio tests, by including the SNP*smoking interaction term in regression analyses.

RESULTS

The T allele at the coding SNP, rs662, was associated with higher risk of CHD in ever-smokers only (OR=1.35, 95% CI 1.08-1.68; adjusted P=0.036). At the miR-SNP, rs3735590, carrying at least one copy of minor allele T was associated with increased risk of CHD in a dominant manner in never-smokers only (OR=1.53, 95% CI 1.11-2.11; adjusted P=0.036). Significant interactions between two PON1 SNPs and smoking in relation to CHD risk were identified (adjusted P=0.012 for rs662; adjusted P=0.044 for rs3735590). These associations remained significant after adjustment for known CHD risk factors and upon correction for multiple tests.

CONCLUSIONS

Two PON1 SNPs, rs662 and rs3735590, were found to significantly interact with cigarette smoking to modulate the risk of CHD in the Singaporean Chinese population.

Effects of cytochrome P450 2C19 and paraoxonase 1 polymorphisms on antiplatelet response to clopidogrel therapy in patients with coronary artery disease

Clopidogrel is an antiplatelet prodrug that is recommended to reduce the risk of recurrent thrombosis in coronary artery disease (CAD) patients. Paraoxonase 1 (PON1) is suggested to be a rate-limiting enzyme in the conversion of 2-oxo-clopidogrel to active thiol metabolite with inconsistent results. Here, we sought to determine the associations of CYP2C19 and PON1 gene polymorphisms with clopidogrel response and their role in ADP-induced platelet aggregation. Clopidogrel response and platelet aggregation were determined using Multiplate aggregometer in 211 patients with established CAD who received 75 mg clopidogrel and 75–325 mg aspirin daily for at least 14 days. Polymorphisms in CYP2C19 and PON1 were genotyped and tested for association with clopidogrel resistance. Linkage disequilibrium (LD) and their epistatic interaction effects on ADP-induced platelet aggregation were analysed. The prevalence of clopidogrel resistance in this population was approximately 33.2% (n = 70). The frequencies of CYP2C19*2 and *3 were significantly higher in non-responder than those in responders. After adjusting for established risk factors, CYP2C19*2 and *3 alleles independently increased the risk of clopidogrel resistance with adjusted ORs 2.94 (95%CI, 1.65–5.26; p<0.001) and 11.26 (95%CI, 2.47–51.41; p = 0.002, respectively). Patients with *2 or *3 allele and combined with smoking, diabetes and increased platelet count had markedly increased risk of clopidogrel resistance. No association was observed between PON1 Q192R and clopidogrel resistance (adjusted OR = 1.13, 95%CI, 0.70–1.82; p = 0.622). Significantly higher platelet aggregation values were found in CYP2C19*2 and *3 patients when compared with *1/*1 allele carriers (p = 1.98×10⁻⁶). For PON1 Q192R genotypes, aggregation values were similar across all genotype groups (p = 0.359). There was no evidence of gene-gene interaction or LD between CYP2C19 and PON1 polymorphisms on ADP-induced platelet aggregation. Our findings indicated that only CYP2C19*2 and *3 alleles had an influence on clopidogrel resistance. The risk of clopidogrel resistance increased further with smoking, diabetes, and increased platelet count.

Human serum paraoxonase gene polymorphisms, Q192R and L55M, are not associated with the risk of cerebral infarction in Chinese Han population

OBJECTIVES

It has been reported that human serum paraoxonase (PON1) gene is associated with coronary heart disease (CHD) and diabetes mellitus (DM). However, little is known about the role of PON1 gene polymorphism in cerebral infarction (CI). For this, we have investigated the relationship between PON1 gene polymorphisms, Q192R and L55M, and CI in Chinese Han population.

METHODS

The PON1 genotypes, Q192R and L55M, from 153 CI patients and 153 healthy individuals, were determined by polymerase chain reaction (PCR) and restriction enzyme digestion. Their allele frequencies were then determined. The association of the PON1 gene polymorphism with the risk of CI was analysed by statistical analysis software.

RESULTS

The frequencies of PON1-Q192R genotypes in CI and control group are 13.7 and 9.8% (QQ), 51.6 and 53.6% (QR), 34.6 and 36.6% (RR) respectively. There is no significant difference in PON1-Q192R genotype (p=0.566) and allele frequencies (p=0.505) between CI patients and controls. The frequencies of PON1-55 genotypes in the CI and control group are 96.7 and 93.5% (LL), 3.3 and 6.5% (LM) respectively. No MM genotype was found in both CI and control group. No significant difference in genotype (p=0.289) and allele (p=0.296) distribution between CI patients and controls was observed.

DISCUSSION

Our results suggest that the human serum paraoxonase polymorphisms, Q192R and L55M, are not associated with the risk of cerebral infarction in Chinese Han population.

The Q192R polymorphism of the paraoxonase 1 gene is a risk factor for coronary artery disease in Saudi subjects

Paraoxonase-1 (PON1) is a HDL-bound antioxidant enzyme that protects LDL from oxidative modification. Discovery of the antioxidant properties of PON1 led to extensive research on its role in the initiation and progression of atherosclerosis. The Q192R (rs662; A/G) polymorphism, which results in the glutamine to arginine substitution at position 192, of the PON1 gene has been linked to increased atherosclerosis risk in several but not all population studies. Besides genetic factors, environmental variables and ethnicity have been implicated as factors responsible for the ambiguity in relating the PON1 gene with atherosclerotic risk. Here, we tested the association of the Q192R polymorphism with coronary artery disease (CAD) in Saudi ethnic subjects taking environmental factors into consideration. The genomic DNA samples from 121 angiographically confirmed CAD cases and 108 normal healthy control subjects were genotyped by PCR-RFLP analysis. The distribution of QQ, QR, and RR genotypes was significantly different between cases and controls (p < 0.005). The RR genotype was associated with CAD risk independently of several established risk factors including age, gender, smoking, obesity, and diabetes (OR 2.2, 1.4-7.4, p < 0.01). Genotype-based stratification of demographic and biochemical data revealed that the RR genotype has proatherogenic properties. This study, thus, identifies the Q192R polymorphism as an additional risk factor for CAD in the Saudi population and suggests that it may have prognostic value. The negative effect of this genetic variant is presumably due to the diminished ability of the RR variant genotype of PON1 to blunt LDL oxidation.

Association of the angiotensinogen gene polymorphism with atherosclerosis and its risk traits in the Saudi population

Background

Angiotensinogen (AGT) constitutes a central component of the renin-angiotensin system that controls the systemic blood pressure and several other cardiovascular functions and may play an important role in atherosclerosis pathways. In this study, we employed TaqMan genotyping assays to evaluate the role of 8 AGT variants in primary hypertension (HTN), type 2 diabetes mellitus (T2DM), and obesity as a possible trigger of coronary artery disease (CAD) in a population of 4615 angiographed native Saudi individuals.

Methods

Linkage analysis was done by using the Affymetrix Gene Chip array, sequencing by using the MegaBACE DNA analysis system and genotyping accomplished by TaqMan chemistry using the Applied Biosystem real-time Prism 7900HT Sequence Detection System.

Results

Six variants, rs2067853 GG [Odds ratio(95% Confidence Interval) = 1.44(1.17-1.78); p = 0.001], rs7079 [1.49(1.20-1.85); p < 0.0001], rs699 G [1.19(1.08-1.13); p < 0.0001], rs3789679 A [1.51(1.14-1.99); p = 0.004], rs2148582 GG [1.31(1.11-1.55); p = 0.002] and rs5051 TC + CC [1.32(1.13-1.60); p = 0.001] conferred risk for HTN (3521 cases versus 1094 controls). The rs2067853 (p = 0.042), rs699G (p = 0.007) and rs5051 (p = 0.051) also conferred risk for myocardial infarction (MI; 2982 vs 1633), while rs3789679 A (p < 0.0001) and GA + AA (p < 0.0001) as well as rs4762G (p = 0.019) were associated with obesity (1576 vs 2458). However, while these variants appeared to be also associated with CAD (2323 vs 2292), only the rs7079G (p = 0.035) retained its significant relationship. Interestingly, among the haplotypes constructed from these SNPs, the baseline 8-mer haplotype, GGTGGGGT (χ² = 7.02; p = 0.0081) and another GGCGGAGT (χ² = 5.10; p = 0.024), together with several of their derivatives were associated with HTN. T2DM was associated with two 8-mer haplotypes, GGTAGGAC (χ² = 5.66; p = 0.017) and ATTGAGAC (χ² = 5.93; p = 0.015), obesity with GGCGGAGT (χ² = 9.49; p = 0.0021) and MI was linked to ATTGGGAC (χ² = 6.68; p = 0.010) and GGTGGGAT (χ² = 4.25; p = 0.039). Furthermore, several causative haplotypes were also shared among the risk traits as well as with CAD.

Conclusion

These results point to AGT as independently conferring risk for various cardiovascular traits, and possibly interacting with these traits in events leading to atherosclerosis.

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.

Association between paraoxonase-1 gene polymorphisms and risk of metabolic syndrome

Paraoxonase-1 (PON1), a high-density lipoprotein (HDL) associated enzyme, is involved in the metabolism and detoxification of insecticides and pesticides. Three polymorphisms within the PON1 gene affect the enzyme activity. Two of these (L55M and Q192R) are located at the coding region and the third (-107C/T) is in promoter region. We performed a case-control study in order to elucidate the possible contribution of variability within PON1 at three mentioned positions to the risk of MS in a South-East Iranian population. DNA was isolated from peripheral blood of patients (N = 119) with MS and healthy controls (N = 201). Allelic polymorphisms at positions Q192R, L55M and -107C/T in the PON1 gene were studied by Amplification Refractory Mutation System (ARMS)-PCR. It was observed that genotypes RR and QR + RR of Q192R locus significantly increased the risk of MS (OR = 2; 95% CI: 1.17-3.40, P = 0.0001 and OR = 1.62; 95% CI: 1.0-2.63; P = 0.05, respectively). The risk in patients with MM and LM + MM genotypes at the L55M locus was marginal (OR = 1.33; 95% CI: 0.68-1.85; P = 0.34 and OR = 1.12; 95% CI: 0.68-1.85; P = 0.73 respectively). The CC genotype at -107C/T locus also increased the risk of metabolic syndrome, but was not significant. This association was somewhat stronger when combined genotypes at Q192R and L55M loci were analyzed (OR = 3.30; 95% CI: 1.34-8.24; P = 0.007). Our results, in this first study, provide evidence for association of PON1 gene polymorphisms with the risk for metabolic syndrome.

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.

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 PON1L55M and Q192R gene polymorphisms and high APO B/APO A-I ratios

Elevated Apolipoprotein B Apolipoprotein A-I ratio is a risk factor for predicting coronary artery disease (CAD). Paraoxonase 1 (PON1) is a high density lipoprotein (HDL) associated serum enzyme. PON1 protects lowdensity lipoproteins (LDLs) from oxidative modifications and thus has a protective effect against CAD progression. There are two common polymorphisms, Q192R and L55M, in PON1 gene. There may be a relationship between these polymorphisms and elevated ApoB/ApoA-I ratios. Therefore, we decided to evaluate effect of these polymorphisms on individuals with high and normal ApoB/ApoA-I ratios. To evaluate Q192R and L55M polymorphisms in Iranian case group (n=75) with high ApoB/ApoA-I ratio, and control group (n=75) with normal ApoB/ApoA-I ratio, we carried out PCR using specific primers. Then, we digested PCR products by RFLP. ApoB and ApoA-I levels were determined by immunoturbidimetry method. Genotype frequencies for Q192R were determined: 49.3%QQ, 44%QR, 6.7%RR in case group, and 53.3%QQ, 33.3%QR, 13.4%RR in controls (P= 0.236). Genotype frequencies for L55M were determined: 21.3%LL, 68%LM, 10.7%MM in case group and 42.7%LL, 52%LM, 5.3%MM in controls (P= 0.016). A significant relationship between L55M polymorphism and familial history of cardiovascular disease was found (P= 0.011). In our study PON1L55M polymorphism was associated with high ApoB/ApoA-I ratios in case group. Thus, L55M polymorphism may be an independent risk factor for cardiovascular disease. Since L55M polymorphism was associated with familial history of cardiovascular disease, it is better to evaluate L55M polymorphism in younger ages even in the absence of high ApoB/ApoA-I ratios.

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.

Paraoxonase Genotype, LDL-oxidation and Carotid Atherosclerosis in Male Life-long Smokers

Paraoxonase (PON-1) is a high-density lipoprotein (HDL) associated enzyme that hydrolyzes lipid peroxides in vitro, which may therefore protect against the onset of atherosclerosis. Heavy smokers are more exposed to oxidative stress and hence at high-risk for oxidative modification of LDL. Our hypothesis is that the anti-oxidative properties of PON-1 inhibit LDL oxidation, especially in populations exposed to high oxidative stress. We have studied the effects of PON-1 genotype and smoking to variation in oxidative status parameters and intima-media thickness (IMT), a surrogate marker of atherosclerosis. The contribution of two common polymorphisms in the PON-1 gene (Q192R and L55M) to LDL oxidizability, autoantibodies directed against oxLDL and IMT were studied in 207 male life-long smokers. Smokers were classified into average, heavy and excessive smokers based on pack years of cigarettes smoked. PON-1 genotype was not associated with autoantibodies to oxLDL, LDL oxidizability or IMT. Smoking was associated with IMT in subgroups with the high levels of LDL, but not in the population at large. The lack of association of PON-1 genotype with oxidative status parameters and IMT suggests that PON-1 is not a major inhibitor of LDL oxidation in a population of life-long smokers.

PON1Q192R polymorphism is associated with lipid profile in Mexican men with Mayan ascendancy

Paraoxonase (PON1) enzyme is associated with high-density lipoproteins (HDL) that prevents low-density lipoprotein (LDL) oxidation. PON1Q192R polymorphism is associated with a risk of coronary heart disease and low HDL levels in case-control studies, but the issue is yet unresolved. Mexico has shown an increase in cardiovascular diseases, and some genetic factors may play a role. Our purpose was to evaluate the association between PON1Q192R and L55M polymorphisms and serum lipid profile in a healthy Mexican population. Ninety unrelated male inhabitants from southeastern Mexico with Mayan ascendancy agreed to participate. Demographic characteristics, lifestyle and medical history were obtained by questionnaire. Lipid profile was determined by enzymatic methods, PON1 activity by using paraoxon and phenylacetate and PON1 genotype by real-time PCR. HDL-cholesterol (HDL-C) levels were associated with genotype: 192RR homozygote subjects had lower HDL-C levels than 192QQ homozygotes, and individuals with 192RR and 192QR genotypes had an odds ratio (OR)=7.05 (95% confidence interval (CI)=1.29-38.34) of having HDL-C <60 mg/dL. Individuals with higher paraoxonase activity (>600.18 U/L) had a slight risk (OR=4.9, 95% CI=0.83-22.02) of having HDL-C <60 mg/dL. PON155LM polymorphism was associated with higher LDL-cholesterol. PON1Q192R polymorphism showed a role in modulating lipid profile: 192RR homozygotes showed the least favorable lipoprotein levels.

Paraoxonase (PON)1 192R allele carriage is associated with reduced risk of inflammatory bowel disease

The paraoxonase (PON) genes family maps to chromosome 7q21-q22, within a loci that also showed evidence of susceptibility genes for both Crohn's disease (CD) and ulcerative colitis (UC). In this case-control study we investigated the possible relationship between PON1 and PON2 polymorphisms and the risk of inflammatory bowel disease (IBD). PON1 192Q/R, PON1 55L/M, and PON2 311S/C polymorphisms were investigated by RFLP analysis in DNA samples from 224 patients with CD, 58 patients with UC, and 311 healthy controls. The PON1 192R allele was significantly less common among IBD Ashkenazi patients (allelic OR = 0.61, P = 0.004, 95% CI = 0.44-0.85). In agreement with the individual SNP analysis, Ashkenazi IBD patients had a higher frequency of haplotype PON1 192Q/PON1 55L/PON2 311S (26.3% vs 17.3%; P=0.003) and a lower frequency of haplotype PON1 192R/PON1 55L/PON2 311S (18.9% vs 27.7%; P=0.008). Our results suggest that in this Ashkenazi Jewish population, carriage of PON1 R192 allele may confer protection against the development of IBD.

Paraoxonase gene polymorphism and vitamin levels during pregnancy: Relationship with maternal oxidative stress and neonatal birthweights

The aim of this study was to determine the association between maternal oxidative stress and adverse birth outcome, and serum vitamin levels and paraoxonase (PON) polymorphism during pregnancy. We investigated 276 pregnant women who visited a hospital for prenatal care during gestational weeks 24 and 28. We measured serum Vitamins C and E levels and urinary levels of 8-hydroxy-2-deoxyguanosine (8-OH-dG). We determined the presence of a maternal PON polymorphism (Q-to-R substitution at a nucleotide located on 7q21.3) using a polymerase chain reaction-restriction fragment length polymorphism assay. High levels (relative to the median) of Vitamins C and E were associated with a reduced concentration of urinary 8-OH-dG, but increased birthweight and gestational age in subjects with the Q/Q and Q/R types of PON polymorphism. Even with the high-risk PON polymorphism (R/R), the results show that birthweight increased with high levels of Vitamins C and E. Our data demonstrate that oxidative stress and neonatal birthweight are affected by maternal levels of Vitamins C and E in subjects with a PON polymorphism.

Paraoxonase 1 gene Q192R polymorphism affects stroke and myocardial infarction risk

OBJECTIVES

Paraoxonase (PON1), an enzyme associated with high-density lipoprotein (HDL) particles, inhibits oxidation and atherogenesis. We sought to investigate the association of the PON1 Q192R polymorphism with stroke and heart disease.

DESIGN AND METHODS

In a case control study, we genotyped 242 ischemic stroke, 231 myocardial infarction (MI), and 310 healthy control subjects, all Chinese.

RESULTS

R-containing genotypes (R+) were associated with vascular disease, OR = 1.5, P = 0.03. RR was increased in MI patients who were either smokers (OR = 3.1, P = 0.01), male, or younger than 60. R+ but not RR genotypes were increased in stroke patients, particularly large artery type (OR = 2.6 and P = 0.02 for R+, OR = 1.0 for RR) or among smokers. The relative dearth of RR in stroke might be due to earlier MI or death in at-risk people, such as smokers. R+ genotypes were increased with stroke in hypertensive (OR = 2.1, P = 0.02) but not normotensive (OR = 1.0) subjects.

CONCLUSIONS

PON1 192R+ genotypes were associated with stroke and MI, particularly in subsets of patients, in patterns suggesting a possible survivor effect.

PON1 polymorphism, diabetes mellitus, obesity, and risk of myocardial infarction: Modifying effect of diabetes mellitus and obesity on the association between PON1 polymorphism and myocardial infarction

PURPOSE

Previous studies on PON1 gene polymorphism and the risk of coronary atherosclerotic diseases have been inconsistent. This may be in part due to population difference in prevalence of high oxidative stress and its modifying effect on the association. Diabetes and obesity are two major risk factors of myocardial infarction (MI) and associated with high oxidative stress. We investigated the association between PON1 Q192R polymorphism and the risk of myocardial infarction (MI) and in particular, whether the association can be modified by diabetes mellitus (DM) and obesity.

METHODS

We conducted a case-control study, including 154 MI cases and 154 controls enrolled in Beijing, China. Epidemiological and clinical data and PON1 Q192R genotype were obtained from each subject.

RESULTS

Without considering the modifying effect of DM and obesity, PON1 Q192R polymorphism was not associated with MI. When simultaneously examining the joint association of this polymorphism, DM, and obesity with MI, as compared to subjects with QQ genotypes and without DM and obesity, subjects with QR/RR genotypes and with either DM or obesity had significantly higher risk of MI (OR = 3.6, 95% CI: 1.5-8.7).

CONCLUSION

Our data suggest that PON1 Q192R polymorphism was not independently associated with MI but further increased the risk of MI among the subjects with DM, obesity, or both, the conditions associated with high oxidative stress.

Genetic variations of apolipoprotein A5 gene is associated with the risk of coronary artery disease among Chinese in Taiwan

Recently, a T/C polymorphism of the promoter region of the APOA5 gene at position -1131 and a G/T polymorphism at position 553 were found to be associated with increased levels of plasma triglyceride. Triglyceride plays a role in coronary artery disease (CAD), so this case-control study tested for a possible link between these two APOA5 polymorphisms, their common haplotypes and the risk of CAD. The subjects included 211 CAD patients and 677 unrelated controls. A significantly higher level of triglycerides and a lower level of high-density lipoprotein cholesterol (HDL-C) were noted for carriers with -1131C than for non-carriers (P<0.001 and 0.013, respectively) among controls. Plasma triglyceride levels were significantly higher (P=0.014) in controls with genotypes that contained the c.553T allele than in homozygotes for the G allele. Subjects homozygous for the wild-type haplotype had significantly lower triglyceride levels and higher HDL-C levels than subjects with all other haplotype pairs. The -1131C homozygous carriers and c.553T heterozygous carriers were found more frequently in 211 patients with CAD than in the 317 age/sex-matched controls (P=0.008 and 0.023, respectively) in univariate analysis. The significant association between c.553T allele carriers with CAD remained in multivariate regression analysis (OR, 1.79; CI, 1.07-3.00; P=0.028), after adjustments were made for other risk factors. Notably, haplotype analysis further verified that the APOA5 -1131C and c.553T bi-loci haplotype was significantly overpresented in CAD, as compared to the controls. These results indicate that the variants of APOA5 gene modulate plasma triglyceride and may use them to predict CAD susceptibility in Taiwanese Chinese.

The ratio of serum paraoxonase/arylesterase activity using an improved assay for arylesterase activity to discriminate PON1(R192) from PON1(Q192)

Human serum paraoxonase (PON1) exists in 2 major polymorphic forms: Q (glutamine) or R (arginine) at codon 192. The PON1(192) activity polymorphism is substrate dependent. The PON1(Q192) isoform has a higher rate of in vitro hydrolysis of diazoxon, sarin, and soman, whereas the PON1(R192) isoform has higher activity for the hydrolysis of paraoxon and chlorpyrifos oxon. Both isoforms hydrolyze phenyl acetate at approximately the same rate. The present study described and evaluated a kinetic method of arylesterase activity determination with a modified fixed incubation method that used the oxidative coupling of phenol with 4-aminoantipyrine of phenyl acetate as the substrate. Our improved method shows that arylesterase activity is lower with the PON1(R192) isoform than with the PON1(Q192) isoform. The average activities of serum of individuals of a specific PON1(Q192) genotype showed higher arylesterase and lower paraoxonase activity than the PON1(R192) genotype. The ratio of paraoxonase/arylesterase activity showed a clear separation of all three PON1(192) genotypes with no overlap between the groups (QQ: < 5.0, QR: 5.0-11.0, RR: > 11.0). PCR has suggested that the PON1(192) phenotypes correspond to the PON1(192) genotypes. Therefore, when conducting epidemiological or mechanistic studies that examine the role of PON1 in organophosphorus or lipid metabolism, this ratio is more useful and informative than a PCR-based genotype alone.

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.

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.

Interaction between smoking and PON2 Ser311Cys polymorphism as a determinant of the risk of myocardial infarction

BACKGROUND

Increased oxidative stress is thought to play a role in the pathogenesis of the atherothrombotic process. Paraoxonases (PONs) are closely related antioxidant enzymes encoded by clustered genes on chromosome 7q. We evaluated three PON polymorphisms (PON1 Leu55Met and Gln192Arg; PON2 Ser311Cys) as possible risk factors for coronary atherosclerotic disease (CAD) and/or its main thrombotic complication, myocardial infarction (MI).

MATERIALS AND METHODS

We studied 890 subjects with angiographic documentation of coronary vessels (272=CAD-free; 618=CAD). In the CAD group, 341 subjects had a previous MI.

RESULTS

Frequencies of various genotypes were not significantly different between CAD-free subjects and the entire CAD population. In the latter group, there were more carriers of the PON2 311Cys variation among those who had suffered a MI than among those who had not (P<0.01 by chi2). The adjusted OR for MI among PON2 311Cys carriers was 1.5 (95%CI, 1.03-2.19). A gene-environmental interaction was found between PON2 Ser311Cys and smoking. Smoking by itself was associated with an increased MI risk. Among smokers, however, the MI risk was related to PON2 genotype: Cys/Cys homozygotes (OR=5.3; 95%CI, 1.7-16.4) and Ser/Cys heterozygotes (OR=2.1; 95%CI, 1.3-3.6) were at greater risk than Ser/Ser subjects (OR=1.2; 95%CI, 0.8-1.8). The PON2 polymorphism did not influence the MI risk among nonsmokers.

CONCLUSIONS

In CAD subjects, a proportion of the risk of MI may be influenced by the interaction between smoking and a polymorphism in the antioxidant enzyme PON2.

Paraoxonase gene polymorphisms, oxidative stress, and diseases

The paraoxonase (PON) gene cluster contains at least three members, including PON1, PON2, and PON3, located on chromosome 7q21.3-22.1. Until now there has been little insight into the role of the respective gene products in human physiology and pathology. However, emerging evidence from biochemical and genetic experiments is providing clues about the role(s) of the products of these genes, which indicates that PON(s) acts as important guardians against cellular damage from toxic agents, such as organophosphates, oxidized lipids in the plasma low-density lipoproteins. In parallel, substantial data have been published on the association between the polymorphisms of PON(s) and coronary heart disease. It has become clear that the polymorphisms significantly affect the prevalence of coronary heart disease. However, the associations between the PON(s) polymorphisms and most of these conditions were found to be inconsistent when additional populations were investigated. This contribution provides an overview of the status of research of each of the three genes and the available association studies and the potential problems in interpreting the data. We also review the current evidence on the association between PON(s) polymorphisms and diseases other than coronary heart disease and some metabolic quantitative phenotypes, such as plasma lipoproteins, plasma glucose, and birthweight. Finally, we suggest directions for the future that might elucidate the role of the PON genetic polymorphisms in this potentially important function of PON(s) and the role in coronary heart disease and other related diseases.

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.

[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.

Paraoxonase-1 promoter haplotypes and serum paraoxonase: a predominant role for polymorphic position - 107, implicating the Sp1 transcription factor

Accumulating data suggest that paraoxonase-1 (PON1) is a primary determinant of the antioxidant and anti-inflammatory capacities of high-density lipoproteins (HDLs). Variations in HDLs and PON1 have been shown to influence the functions of both. There is a wide spectrum of serum PON1 mass in humans, to which promoter polymorphisms make an important contribution. The present studies attempted to define: (i) the relevance in vivo of promoter polymorphisms by analysing haplotype structure; and (ii) molecular mechanisms implicated in promoter activity. Highly significant differences (P <0.0001) in serum mass and activity were observed as a function of haplotype sequence. Of three promoter polymorphisms (-107, -824 and -907), the -107 site was shown to be of predominant importance to serum PON1. Significant increases in serum PON1 mass and activities between haplotype subgroups could be explained by unit increases in the number of high-expresser variants of the -107 site (-107C) alone. No significant contribution was observed for the -824 and -907 sites. The coding-region Leu(55)-->Met (L55M) polymorphism made an independent contribution to serum PON1 mass, which may account for variations in serum PON1 mass and activity within haplotype subgroups defined by the -107 site. A molecular basis for the effect of the -107 polymorphism on serum PON1 was indicated by the greater affinity of the high-expresser variant (-107C) for hepatocyte nuclear extracts, indicating higher affinity for transcription factors. Competition studies with oligonucleotides representing the consensus (and mutated) sequence for Sp1, and the use of Sp1 antibodies, confirmed formation of complexes between the transcription factor and the PON1 promoter during incubation with nuclear extracts. The data underline the importance of the region containing the C(-107)T polymorphism for gene expression in vivo. Differences in the affinity of the -107C and -107T polymorphic fragments for nuclear extracts have been demonstrated, and coincide with their impact on gene expression. A potential role for the transcription factor Sp1 has been demonstrated, which is consistent with the disruption of an Sp1 recognition sequence by the -107 polymorphism.

Association between the severity of angiographic coronary artery disease and paraoxonase gene polymorphisms in the National Heart, Lung, and Blood Institute-sponsored Women's Ischemia Syndrome Evaluation (WISE) study

Paraoxonase (PON), a high-density lipoprotein-associated enzyme, is believed to protect against low-density lipoprotein oxidation and thus affects the risk of coronary artery disease (CAD). Three polymorphisms in the PON1 (Leu55Met and Gln192Arg) and PON2 (Ser311Cys) genes have been shown to be associated with the risk of CAD in several European or European-derived populations. In the present study, we examined the associations between these three markers and the severity of CAD as determined by the number of diseased coronary artery vessels in 711 subjects (589 whites and 122 blacks) from the Women's Ischemia Syndrome Evaluation (WISE) study. WISE is a National Heart, Lung, and Blood Institute-sponsored multicenter study designed to address issues related to ischemic-heart-disease recognition and diagnosis in women. Subjects were classified as having normal/minimal CAD (<20% stenosis), mild CAD (20%-49% stenosis), and significant CAD (>/=50% stenosis). The women who had >/=50% stenosis were further classified into groups with one-, two-, or three-vessel disease if any of the three coronary arteries had diameter stenosis >/=50%. No significant association was found between the PON polymorphisms and stenosis severity in either white or black women. However, among white women, when data were stratified by the number of diseased vessels, the frequency of the PON1 codon 192 Arg/Arg genotype was significantly higher in the group with three-vessel disease than in the other groups (those with one-vessel and two-vessel disease) combined (17.02% vs. 4.58%; P=.0066). Similarly, the frequency of the PON2 codon 311 Cys/Cys genotype was significantly higher in the group with three-vessel disease than in the other groups combined (15.22% vs. 4.61%; P=.018). The adjusted odds ratios for the development of three-vessel disease were 2.80 (95% confidence interval 1.06-7.37; P=.038) for PON1 codon 192 Arg/Arg and 3.68 (95% confidence interval 1.26-10.68; P=.017) for PON2 codon 311 Cys/Cys. Our data indicate that the severity of CAD, in terms of the number of diseased vessels, may be affected by common genetic variation in the PON gene cluster, on chromosome 7.

High expressor paraoxonase PON1 gene promoter polymorphisms are associated with reduced risk of vascular disease in younger coronary patients

Human paraoxonase-1 is hypothesised to protect serum lipoproteins from oxidative stress. Decreased serum activity of paraoxonase-1 in animal models is associated with an increased risk of vascular disease and has been linked to the anti-oxidant capacity of the enzyme. Promoter polymorphisms of the human paraoxonase-1 gene strongly influence serum concentrations of the enzyme. The present study examined the hypothesis that promoter polymorphisms may be genetic risk factors for vascular disease in man. Genotypes arising from the promoter C(-907)G polymorphism were analysed in the ECTIM2 population. The global odds ratio for myocardial infarction, comparing the high expressor GG genotype to other genotypes, was 0.77 (0.61-0.97) (P=0.024). The association with the promoter genotype was more pronounced in the youngest age group (odds ratio 0.52 (0.31-0.87), P=0.012) and was progressively lost with age (respectively 50 years to <60 years, P=0.26; >60 years, P=0.45). There was no association between the promoter genotypes and serum lipids. The data are consistent with the high expressor promoter genotype being linked to reduced risk of myocardial infarction. The influence of the genotype may be compromised in older patients.

Paraoxonase status in coronary heart disease: are activity and concentration more important than genotype?

Human serum paraoxonase (PON1) hydrolyzes oxidized lipids in low density lipoprotein (LDL) and could therefore retard the development of atherosclerosis. In keeping with this hypothesis, several case-control studies have shown a relationship between the presence of coronary heart disease (CHD) and polymorphisms at amino acid positions 55 and 192 of PON1, which we associated with a decreased capacity of PON1 to protect LDL against the accumulation of lipid peroxides, but some other studies have not. However, the PON1 polymorphisms are only 1 factor in determining the activity and concentration of the enzyme. Only 3 of the previous 18 studies directly determined PON1 activity and concentration. Therefore, we studied PON1 activity, concentration, and gene distribution in 417 subjects with angiographically proven CHD and in 282 control subjects. We found that PON1 activity and concentration were significantly lower in subjects with CHD than in control subjects (activity to paraoxon 122.8 [3.3 to 802.8] versus 214.6 [26.3 to 620.8] nmol. min(-1). mL(-1), P<0.001; concentration 71.6 [11.4 to 489.3] versus 89.1 [16.8 to 527.4] microg/mL, P<0.001). There were no differences in the PON1-55 and -192 polymorphisms or clusterin concentration between patients with CHD and control subjects. These results indicate that lower PON1 activity and concentration and, therefore, the reduced ability to prevent LDL lipid peroxidation may be more important in determining the presence of CHD than paraoxonase genetic polymorphisms.

Paraoxonase and atherosclerosis

There is considerable evidence that the antioxidant activity of high density lipoprotein (HDL) is largely due to the paraoxonase-1 (PON1) located on it. Experiments with transgenic PON1 knockout mice indicate the potential for PON1 to protect against atherogenesis. This protective effect of HDL against low density lipoprotein (LDL) lipid peroxidation is maintained longer than is the protective effect of antioxidant vitamins and could thus be more important. There is evidence that the genetic polymorphisms of PON1 least able to protect LDL against lipid peroxidation are overrepresented in coronary heart disease, particularly in association with diabetes. However, these polymorphisms explain only part of the variation in serum PON1 activity; thus, a more critical test of the hypothesis is likely to be whether low serum PON1 activity is associated with coronary heart disease. Preliminary case-control evidence suggests that this is indeed the case and, thus, that the quest for dietary and pharmacological means of modifying serum PON1 activity may allow the oxidant model of atherosclerosis to be tested in clinical trials.