Differential effects of smoking on myocardial infarction risk according to the Gln/Arg 192 variants of the human paraoxonase gene

Paraoxonase 1 gene variants concerning cardiovascular mortality in conventional cigarette smokers and non-smokers treated with hemodialysis

Cigarette smoking effects might correspond with paraoxonase 1 gene (PON1) single nucleotide variants (SNVs). We investigated the association of PON1 rs705379, rs854560, and rs662 with cardiovascular mortality in hemodialysis (HD) patients concerning conventional cigarette smoking. Cardiovascular, cardiac, coronary heart disease (CHD)- and non-CHD-related deaths were analyzed in 206 HD cigarette smokers and 659 HD non-smokers. P-values were adjusted for sex, age, and high-density lipoprotein cholesterol. Among all smokers, the rs705379 TT genotype was associated with cardiovascular (P = 0.028), cardiac (P = 0.046), and cardiac non-CHD-related (P = 0.001) mortality. Non-diabetic smokers showed similar qualitative significance to all smokers concerning mentioned death rates (P-values 0.011, 0.044, and 0.009, respectively). In diabetic non-smokers, the rs705379 T allele correlated with CHD-related deaths (P = 0.020). The rs854560 T allele was associated with lower cardiovascular mortality in non-diabetic smokers (P = 0.008). The rs854560 TT genotype showed a negative non-significant correlation with non-CHD-related cardiac death in all non-smokers (P = 0.079). In diabetic smokers, the rs662 G allele was associated with higher cardiac mortality (P = 0.005). In all non-smokers and non-diabetic non-smokers, the rs662 G correlated with cardiovascular deaths (P = 0.020 and P = 0.018, respectively). Genotyping PON1 SNVs may help argue HD smokers harboring the rs705379 TT genotype or T allele and non-smokers possessing the rs662 G allele for prevention against cardiovascular diseases. These groups are more burdened genetically for cardiovascular mortality.

Association between smoking status and outcomes in myocardial infarction patients undergoing percutaneous coronary intervention

Smoking is one of the leading risk factors for cardiovascular diseases, including ischemic heart disease and hypertension. However, in acute myocardial infarction (AMI) patients, smoking has been associated with better clinical outcomes, a phenomenon termed the “smoker’s paradox.” Given the known detrimental effects of smoking on the cardiovascular system, it has been proposed that the beneficial effect of smoking on outcomes is due to age differences between smokers and non-smokers and is therefore a smoker’s pseudoparadox. The aim of this study was to evaluate the association between smoking status and clinical outcomes in ST-segment elevation (STEMI) and non-STEMI (NSTEMI) patients treated by percutaneous coronary intervention (PCI), using a national multi-ethnic Asian registry. In unadjusted analyses, current smokers had better clinical outcomes following STEMI and NSTEMI. However, after adjusting for age, the protective effect of smoking was lost, confirming a smoker’s pseudoparadox. Interestingly, although current smokers had increased risk for recurrent MI within 1 year after PCI in both STEMI and NSTEMI patients, there was no increase in mortality. In summary, we confirm the existence of a smoker’s pseudoparadox in a multi-ethnic Asian cohort of STEMI and NSTEMI patients and report increased risk of recurrent MI, but not mortality, in smokers.

Antibodies to paraoxonase 1 are associated with oxidant status and endothelial activation in rheumatoid arthritis

Anti-paraoxonase 1 (PON1) antibodies could be a potential missing link between oxidative status, inflammation and cardiovascular disease (CVD) in rheumatoid arthritis (RA) patients. Therefore, they could represent an emerging clinical biomarker of CV risk in this condition.

Paraoxonase activity as a marker of exposure to xenobiotics in tobacco smoke

The paraoxonase (PON) family is composed of 3 proteins (PON1, PON2, and PON3), each of which plays a crucial role in the body, displaying antioxidant, anti-inflammatory, and antiatherosclerotic properties. The activities and properties of PON proteins can be modulated by a number of environmental factors, including cigarette smoke. In the present article, a review of existing literature is employed to analyze both the direct and the indirect impact of cigarette smoking on the activity of members of the PON family. Cigarette smoking leads to direct inhibition of the hydrolytic activity of PON enzymes by modification of thiol groups, by the reactions of free radicals, or by inhibiting enzyme-active regions with heavy metals. It has been shown that cigarette smoking correlates with a decrease in high-density lipoprotein (HDL) concentration as well as with an increase in other components of the lipid profile (low-density lipoprotein (LDL), triglycerides, and total cholesterol). By decreasing HDL levels, cigarette smoking likely acts indirectly to induce a decline in PON1 activity. Inhibition of PON1 activity by smoking is a reversible process after cessation of exposure to the xenobiotics in tobacco smoke.

Paraoxonase (PON)1 Q192R functional genotypes and PON1 Q192R genotype by smoking interactions are risk factors for the metabolic syndrome, but not overweight or obesity

Background The metabolic syndrome (MetS) is a complex of multiple risk factors that contribute to the onset of cardiovascular disorder, including lowered levels of high-density lipoprotein (HDL) and abdominal obesity. Smoking, mood disorders, and oxidative stress are associated with the MetS. Paraoxonase (PON)1 is an antioxidant bound to HDL, that is under genetic control by functional polymorphisms in the PON1 Q192R coding sequence. Aims and methods This study aimed to delineate the associations of the MetS with plasma PON1 activity, PON1 Q192R genotypes, smoking, and mood disorders (major depression and bipolar disorder), while adjusting for HDL cholesterol, body mass index, age, gender, and sociodemographic data. We measured plasma PON1 activity and serum HDL cholesterol and determined PON1 Q192R genotypes through functional analysis in 335 subjects, consisting of 97 with and 238 without MetS. The severity of nicotine dependence was measured using the Fagerström Nicotine Dependence Scale. Results PON1 Q192R functional genotypes and PON1 Q192R genotypes by smoking interactions were associated with the MetS. The QQ and QR genotypes were protective against MetS while smoking increased metabolic risk in QQ carriers only. There were no significant associations between PON1 Q192R genotypes and smoking by genotype interactions and obesity or overweight, while body mass index significantly increased MetS risk. Smoking and especially severe nicotine dependence are significantly associated with the MetS although these effects were no longer significant after considering the effects of the smoking by PON1 Q192R genotype interaction. The MetS was not associated with mood disorders, major depression or bipolar disorder. Discussion PON1 Q192R genotypes and genotypes by smoking interactions are risk factors for the MetS that together with lowered HDL and increased body mass and age contribute to the MetS.

The three-gene paraoxonase family: physiologic roles, actions and regulation

The paraoxonase (PON) gene family is composed of three members (PON1, PON2, PON3) that share considerable structural homology and are located adjacently on chromosome 7 in humans. By far the most-studied member is PON1, a high-density lipoprotein-associated esterase/lactonase, also endowed with the capacity to hydrolyze organophosphates, but all the three proteins prevent oxidative stress and fight inflammation. They therefore seem central to a wide variety of human illnesses, including atherosclerosis, diabetes mellitus, mental disorders and inflammatory bowel disease. The major goal of this review is to highlight the regulation of each of the paraoxonase components by diverse nutritional molecules and pharmacological agents as well as a number of pathophysiological events, such as oxidative stress and inflammation. Considerable and detailed cell-based studies and animal model experiments have been provided to allow a thorough scrutiny of PON modulation, which will increase our understanding and ability to target these genes in order to efficiently increase their transcriptional activity and decrease the risks of developing different disorders.

The genetics of cerebrovascular atherosclerosis

Ischemic stroke attributable to atherosclerosis remains a major public health problem. Genetic factors are increasingly recognized as influencing risk for atherosclerosis directly and indirectly. Genetic makeup may influence the development of major vascular risk factors or alter susceptibility of the cerebral vasculature to these risk factors. More recently, newly identified risk factors for atherosclerosis, such as plasma homocysteine and infection, have also been reported to be influenced by important genetic determinants. This article reviews the current nature on genetics of cerebral and precerebral atherosclerosis and seeks to identify areas of promise for future clinical application.

Synergistic Effects between Q192R Polymorphism of Paraoxonase 1 Gene and Some Conventional Risk Factors in Premature Coronary Artery Disease

BACKGROUND

Genetic susceptibility to coronary artery disease (CAD) may be determined by polymorphic variants of genes encoding isoforms involved in the processes important in the pathogenesis of atherosclerosis, including lipoprotein oxidation. Participation of single polymorphic variants is relatively small; however, its significance may increase in the presence of specific environmental background. The aim of the study was an evaluation of a possible association between R192Q polymorphism of PON1 gene and CAD as well as interactions between polymorphic variants and conventional risk factors of CAD in determining the risk of the disease.

METHODS

We studied 358 subjects: 178 patients with angiographically confirmed CAD and 180 blood donors without history of CAD. Polymorphisms were genotyped using PCR-RFLP method.

RESULTS

We observed statistically significant differences in the frequencies of Q allele and Q allele carriers of PON1 gene between CAD and controls. We also found a strong synergistic effect between Q allele carrier state and smoking, as well as Q allele carrier state and elevated level of total cholesterol.

CONCLUSIONS

The present study revealed an association between carrier state of Q allele of PON1 gene and coronary artery disease as well as synergistic effects between genotype and some conventional risk factors, mainly smoking and elevated level of total cholesterol.

Evaluation of the Paraoxonases as Candidate Genes for Stroke

Background and Purpose— The paraoxonases are involved in protecting low-density lipoprotein (LDL) from lipid oxidation. Paraoxonase 1 (PON1) was implicated in susceptibility to coronary artery disease and stroke in previous studies. We evaluated, in a comprehensive way, all 3 paraoxonase genes for association with stroke observed in the Cholesterol and Recurrent Events (CARE) trial.

Methods— Over 2500 subjects enrolled in the CARE trial were genotyped for 14 single nucleotide polymorphisms, including 7 newly identified in this study, in the 3 paraoxonase genes.

Results— A glutamine (Gln)/arginine (Arg) polymorphism at amino acid residue 192 in PON1 was significantly associated with stroke ( P =0.003 in multivariate analysis, including age, sex, LDL, hypertension, diabetes, smoking, and pravastatin treatment as covariates). The odds ratios were 2.28 (95% CI, 1.38 to 3.79) for Gln/Arg heterozygotes and 2.47 (95% CI, 1.18 to 5.19) for Arg/Arg homozygotes compared with Gln/Gln homozygotes. These results are consistent with 2 of 3 other published studies. In combined analysis of all 4 studies, the association between Gln192Arg SNP and stroke was highly significant (χ 2 8df =45.58, P <0.000001). Sequence analysis of the PON1 gene from seventy stroke cases revealed a novel nonsense mutation at codon 32 in one stroke case, which was not detected in over 2500 unaffected individuals. Polymorphisms in the PON2 and PON3 genes were not associated with stroke.

Conclusions— These results suggest that Gln192Arg genotype is an important risk factor for stroke.

Age-related decrease in high-density lipoproteins antioxidant activity is due to an alteration in the PON1's free sulfhydryl groups

The aim of this study was to evaluate the antioxidant activity of HDL with aging and to investigate the implication of PON1 in this process. The study involved 54 healthy subjects distributed in two age groups, young (20-25 years) and elderly (65-85 years). Lipid peroxidation was induced by *OH and O2*- oxygen free radicals produced by gamma-radiolysis of water. LDL oxidation was followed by the measurement of conjugated diene (CD), lipid peroxide (LP) and malondialdehyde (MDA) formation. PON1 was purified separately from young (Y-PON1) and elderly subjects (E-PON1). PON1 activity and structure was followed by measurement of PON1 paraoxonase (p.ase) activity, titration of the SH groups, and electrophoretic mobility by SDS-PAGE. Our results show a significant decrease in the HDL antioxidant activity: percentage of protection against CD formation=27.70% (p<0.01) for E-HDL versus 73.08% (p<0.001) for Y-HDL. Moreover, E-PON1 showed a lower antioxidant activity when compared to Y-PON1 47.08% versus 78.14%, respectively (p<0.0001). Exposition of PON1 to *OH and O2*- oxygen free radicals induced a significant decrease in PON1 p.ase activity as well as a reduction in the number of PON1's free sulfhydryl groups. Moreover, our results show a close association between PON1's free sulfhydryl groups and its capacity to protect LDL against lipid peroxidation. There was a significant decrease in the number of free sulfhydryls between Y-PON1 and E-PON1 with respect to cysteine-284 amino acid residues (p<0.0092).

Q192R polymorphism of the paraoxanase 1 gene and its association with serum lipoprotein variables and carotid artery intima-media thickness in young adults from a biracial community. The Bogalusa Heart Study

Paraoxanase (PON 1), a high-density lipoprotein-associated enzyme, exerts an antiatherogenic effect by protecting low-density lipoproteins (LDL) against oxidation. A common polymorphism at codon 192(Q/R) of the PON 1 gene has been shown to be associated with an adverse lipoprotein profile and increased coronary artery disease (CAD) risk. However, these observations are based mostly on case-control studies involving relatively older adults. This study examined the frequency and phenotypic (lipoprotein variables) effect of the Q192R variant in a community-based sample of 1786 black and white young adults (mean age: 32.5 years; 69% white, 44% males). In addition, the genotypic effect of this polymorphism on ultrasonographically measured carotid artery intima-media thickness (IMT), a surrogate measure of CAD risk, was examined in a subsample of 436 young adults (mean age: 32.6 years; 70% white, 42% male). The frequency of the variant allele (R192) was higher in blacks than in whites (0.668 versus 0.297, P <0.001). After adjusting for age, sex, body mass index, and smoking status, the R versus Q allele was associated with increased HDL cholesterol in whites (P=0.041), whereas the opposite was true in blacks (P=0.008). Neither the Q nor the R allele was associated with LDL cholesterol and triglycerides in both races. The genotypic effect on the carotid IMT adjusted for the covariates including lipoprotein variables was not apparent in whites or blacks. However, among whites, the carotid IMT was lower in carriers (QR + R) versus non-carriers (QQ) of the variant allele among females (P=0.008) and non-smokers (P=0.026). In addition, the variant allele negated the adverse positive relationship between the carotid IMT and triglycerides among whites (P=0.212 for carriers versus P <0.001 for non-carriers). These results indicate a differential effect of the Q192R variant on HDL cholesterol in whites versus blacks and a beneficial interaction effect of the variant allele with individual's sex, smoking status or triglyceride levels on the carotid IMT among whites.

New advances in identifying genetic anomalies in stroke-prone probands

The past several years have been marked by significant progress in identifying genetic anomalies in stroke-prone probands. These advances have occurred in both highly penetrant single-gene disorders and in common stroke, which is influenced by risk/susceptibility genes. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) can be challenging to diagnose because of the wide range of notch 3 mutations that can cause disease, but a new immunohistochemical technique using a skin biopsy sample appears to be highly sensitive and specific. In a landmark Icelandic study, linkage was established between stroke and a locus on chromosome 5q12 designated STRK1. Association studies continue to identify polymorphisms that predispose to stroke and to markers for cerebrovascular atherosclerosis, such as intima-media thickness. Intense interest now surrounds genes involved in inflammation, including genes that encode for the interleukin-1 receptor antagonist and paraoxonase-1. In the foreseeable future, prevention, diagnosis, and treatment will incorporate genetic data to refine and individualize management of cerebrovascular disease.

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.

Smoking is associated with reduced serum levels of the antioxidant enzyme, paraoxonase, in Type 2 diabetic patients

AIMS

To analyse the association of smoking with paraoxonase (PON1) in Type 2 diabetic patients.

METHODS

Type 2 diabetic patients were recruited independently in two centres (Ancona, Italy and Geneva, Switzerland) and serum PON1 mass and activities were assayed. Current smoking status was established and its association with serum PON1 analysed.

RESULTS

Type 2 diabetic patients who smoked had significantly lower serum PON1 mass and activity. This was evident in both groups of patients, even though Swiss patients were composed of coronary patients. Multivariate analyses established that smoking was an independent determinant of serum PON1 status.

CONCLUSIONS

Smoking is associated with reduced serum levels of the antioxidant enzyme, PON1, even against an already unfavourable background of diabetes and coronary disease. It suggests that a combination of smoking and diabetes may be particularly deleterious for PON1 and consequently for the anti-oxidant capacity of high-density lipoproteins.

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.

New advances in identifying genetic anomalies in stroke-prone probands

The past several years have been marked by significant progress in identifying genetic anomalies in stroke-prone probands. These advances have occurred in both highly penetrant single-gene disorders and in common stroke, which is influenced by risk/susceptibility genes. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) can be challenging to diagnose because of the wide range of notch 3 mutations that can cause disease, but a new immunohistochemical technique using a skin biopsy sample appears to be highly sensitive and specific. In a landmark Icelandic study, linkage was established between stroke and a locus on chromosome 5q12 designated STRK1. Association studies continue to identify polymorphisms that predispose to stroke and to markers for cerebrovascular atherosclerosis, such as intima-media thickness. Intense interest now surrounds genes involved in inflammation, including genes that encode for the interleukin-1 receptor antagonist and paraoxonase-1. In the foreseeable future, prevention, diagnosis, and treatment will incorporate genetic data to refine and individualize management of cerebrovascular disease.

Paraoxonase 192 Gln-->Arg polymorphism: an independent risk factor for nonfatal arterial ischemic stroke among young adults

BACKGROUND AND PURPOSE

The etiology of arterial ischemic stroke (AIS) in the young remains unknown in one third of patients. Serum paraoxonase (PON1) is an HDL-associated esterase that hydrolyzes products of lipid peroxidation and prevents the oxidation of LDL. Two common polymorphisms in the PON1 gene, the 192 Gln (Q) --> Arg (R) and 55 Leu (L) --> Met (M) substitutions, determine interindividual variation in PON1 activity. The association of these polymorphisms with the risk of AIS remains controversial.

METHODS

We analyzed 118 patients (64 women) with a first nonfatal AIS occurring <45 years of age and 118 1:1 age (+/-2 years)- and sex-matched controls. The PON1 polymorphisms were determined by polymerase chain reaction amplification and restriction digestion.

RESULTS

The prevalence of the PON1 192RR genotype (P=0.006) and the frequency of the R allele (P=0.010) were significantly increased among young AIS patients compared with controls. After adjustment for conventional vascular and prothrombotic risk factors, the 192RR genotype remained independently associated with a 4-fold increase in the risk of AIS (odds ratio=4.1; 95% CI, 1.14 to 14.73). Subanalyses stratified by the presence of vascular risk factors and ethnicity did not significantly modify the effect of the PON1 192 polymorphism on AIS risk. No significant differences were found between patients and controls regarding the PON1 55 polymorphism.

CONCLUSIONS

These findings suggest that the PON 192RR genotype is independently associated with an increased risk of nonfatal AIS among young adults. Further studies are necessary to understand better the mechanistic implications of these observations in the development of AIS in the young.

Genetic analysis of Paraoxonase (PON1) locus reveals an increased frequency of Arg192 allele in centenarians

Human Paraoxonase (PON1) is a High-Density Lipoprotein (HDL)-associated esterase that hydrolyses lipo-peroxides. PON1 has recently attracted attention as a protective factor against oxidative modification of LDL and may therefore play an important role in the prevention of the atherosclerotic process. Two polymorphisms have been extensively studied: a Leucine (L allele) to Methionine (M allele) substitution at codon 55, and a Glutamine (A allele) to Arginine (B allele) substitution at codon 192. We have examined these two aminoacidic changes in 579 people aged 20 to 65 years old, and 308 centenarians. We found that the percentage of carriers of the B allele at codon 192 (B+ individuals) is higher in centenarians than in controls (0.539 vs 0.447), moreover we found that among the B+ individuals, the phenomenon was due to an increase of people carrying M alleles at codon 55 locus. In conclusion, we propose that genetic variability at PON1 locus affects survival at extreme advanced age.

Gene:environment interaction in lipid metabolism and effect on coronary heart disease risk

Both genetic and environmental factors influence coronary heart disease, therefore studies of coronary heart disease risk are often confounded by gene:gene and gene:environment interactions. Such interactions imply that at the molecular level there is synergy between the gene products or with the by-products of the environmental insult, resulting in a greater than additive effect on risk. Genetic risk is thus modifiable in an environment-specific manner. This review focuses on recently reported effects of smoking (environmental factor) on the impact of variation in the genes for glutathione S-transferase, paraoxonase and apolipoprotein E on the risk of coronary heart disease and effects on intermediate lipid traits. We end on a cautionary note for the need for repeat studies to confirm these reported gene:environment effects.

The Paraoxonase-1 Codon192 Polymorphism Is Associated with Fasting Total Cholesterol and LDL-Cholesterol Concentrations only in Postmenopausal Women.The REGICOR Study

Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-linked enzyme which appears to protect low-density lipoproteins (LDL) from oxidation. PON1 activity is associated with variation at the PON1 gene locus, specifically the common amino acid polymorphism at codon 192, for which the Q192 allele specifies low activity and the R192 allele specifies high activity. We investigated the association between the PON1 codon 192 polymorphism and fasting concentrations of glucose, lipids, lipoproteins and PON1 activity in 1380 subjects (724 men and 656 women). Several anthropometric and environmental factors were assessed in the present study. The PON1 Q192 allele frequency was 0.70 and 0.68 in men and women, respectively. In women, but not in men, significant associations were found between the PON1 codon 192 genotype and both total and LDL-cholesterol (p=0.004 and p=0.008, respectively), and subgroup analysis indicated that this relationship was predominant in postmenopausal women. Specifically, the Q192 allele was associated with increased total and LDL-cholesterol concentrations. Furthermore, these lipoprotein variables were higher among postmenopausal women with Q192/Q192 and Q192/R192 genotypes than in premenopausal women with the same genotypes (p<0.001). The findings suggest a gender-specific lipoprotein-genotype association with PON1 codon 192 genotypes in this study sample.

Relationship of age-related myocardial infarction risk and Gln/Arg 192 variants of the human paraoxonase1 gene: the REGICOR study

Paraoxonase1 (PON1) seems to exert a major antioxidant effect by removing lipid-peroxidation products. A common polymorphism of the PON1 gene, the PON1-192 genetic polymorphism, modulates PON1 activity and has been related in some studies to coronary heart disease. Oxidized LDL is believed to play a crucial role in the pathogenesis of atherosclerosis and there are studies providing support for the oxidative stress theory of aging. We have conducted a case-control study to determine whether PON1 activity and PON1-192 genetic variants have a different impact on myocardial infarction (MI) risk among individuals stratified by tertiles of age distribution. PON1-192 genotypes and PON1 activity were determined in 280 consecutive MI patients and 396 control subjects. Serum PON1 activity levels were significantly higher in controls than in MI patients [226 U/l (159-351) vs. 216 U/l (146-298), median (interquartile range), P=0.005]. A decline of PON1 activity levels with advancing age in subjects carrying the low-activity QQ genotype was observed, particularly in MI patients. PON1 activity and age negatively correlated in MI patients but not in controls. In the entire population, middle-aged and older subjects showed MI risks of 1.89 (P=0.012) and 2.69 (P<0.001) respectively, compared with young subjects. These risks increased to 2.41 (P=0.016) and 4.39 (P<0.001), respectively, in QQ homozygotes in comparison with younger QQ homozygotes, decreased to 1.53 (P=0.314) and 2.08 (P=0.112), respectively, in QR heterozygotes, and also lowered to 1.95 (P=0.410) and 0.51 (P=0.508) in RR homozygotes who were middle-aged and older, respectively, compared with younger RR carriers. The effect of PON1-192 genotypes on the association of the older age-category and MI risk was gene-dosage related. PON1 activity decreases as a function of age in subjects homozygous for the Q allele. Age may also act on MI risk as a function of PON1-192 alleles. The risk of MI increases with advancing age, principally among subjects carrying the low-activity QQ genotype.

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.

Paraoxonase1-192 polymorphism modulates the nonfatal myocardial infarction risk associated with decreased HDLs

Serum paraoxonase1 (PON1), a high density lipoprotein (HDL)-linked enzyme, appears to have a role in the protection of low density lipoproteins from oxidative stress. PON1 enzyme activity for paraoxon as a substrate is modulated, along with others at the PON1 locus, by the PON1-192 polymorphism, which contains low paraoxon-activity and high paraoxon-activity alleles (Q and R, respectively). The association of PON1 with HDL suggests that impaired serum concentrations of the lipoprotein could have consequences for the susceptibility to oxidative stress. Because PON1-192 polymorphism strongly influences PON1 activity toward paraoxon, we tested the hypothesis that this polymorphism may modulate the myocardial infarction (MI) risk associated with low HDL cholesterol concentrations. Two hundred eighty consecutive MI patients and 396 control subjects were studied. When considered as a whole, PON1-192 genetic polymorphism was not associated with higher MI risk. In the entire population, decreased HDL cholesterol concentration (<0.90 mmol/L in men and <1.11 mmol/L in women) conferred an MI risk of 2.56 (P=0.0001) compared with normal HDL levels. The risk increased to 4.51 (P<0.0001) in QQ homozygous HDL-deficient subjects relative to QQ homozygotes with normal HDL levels, decreased to 1.83 (P=0.1046) in QR heterozygote HDL-deficient subjects, and also decreased (to 1.41, P=0.6243) in RR homozygote HDL-deficient individuals compared with RR carriers with normal HDL cholesterol concentration. The effect of PON1-192 genotypes on the association of low HDL cholesterol levels and MI was related to gene dosage. A significantly decreased enzyme activity was found in HDL-deficient MI patients compared with HDL-deficient control subjects (median 208 U/L [interquartile range 136 to 298 U/L] versus median 235 U/L [interquartile range 163 to 350 U/L], respectively; P=0.025]. QQ homozygous MI patients showed the greatest difference of PON1 activity levels between normal and HDL-deficiency state groups (14.9%, P=0.002). Our observations raise the question of whether the decrease in PON1 activity and the MI risk associated with HDL deficiency are more evident in the low paraoxon-activity QQ genotype. It can be argued that the low paraoxon-activity QQ genotype, which may be adequate to prevent lipid peroxidation in normolipidemic subjects, may be insufficient when an HDL-deficiency state and low PON1 activity reflecting oxidative stress coexist. The risk of nonfatal MI is increased in HDL-deficiency states, principally among subjects carrying the low paraoxon-activity QQ genotype.