Gln-Arg192 polymorphism of paraoxonase and coronary heart disease in type 2 diabetes

The importance of paraoxonase 1 activity in chronic kidney disease

Paraoxonase 1 (PON1) is one of the most significant antioxidative enzymes associated with high-density lipoprotein (HDL). It has been proved that is involved in the pathogenesis of many diseases including chronic kidney disease (CKD). The association between PON1 and CKD seems to be mutual, such that the disease produces a significant decrease in PON1 activity levels, while the genetics of PON1 may affect the risk of susceptibility to CKD. Recent studies reveal that the decrease in serum PON1 activity observed in non-dialyzed and dialyzed CKD patients as well as in renal transplant (RT) patients is linked to an increased vulnerability to atherosclerosis. We intend to summarize current literature concerning PON1 activity in CKD, highlighting on the main determinants of PON1 activity, its association with oxidative stress, the impact of its genetic polymorphism on the disease development, the effect of drugs and nutritional state. Furthermore, evidence supporting the implication of reduced PON1 activity in the incident of cardiovascular disease in CKD patients, is also examined. It appears that despite the lack of standardization of PON1 activity measurement, PON1 remains a valuable biomarker for the researchers through the last decades, which contributes to the assessment of the antioxidant status having prognostic benefit on adverse clinical outcomes at various stages and etiologies of kidney disease.

Paraoxonase-1 as a Cardiovascular Biomarker in Caribbean Hispanic Patients Treated with Clopidogrel: Abundance and Functionality

Clopidogrel, a prescription drug to reduce ischemic events in cardiovascular patients, has been extensively studied in mostly European individuals but not among Caribbean Hispanics. This study evaluated the low abundance and reduced activity of paraoxonase-1 (PON1) in clopidogrel-resistant patients as a predictive risk biomarker of poor responders and disease severity in this population. Thirty-six patients on clopidogrel (cases divided into poor and normal responders) were enrolled, along with 11 cardiovascular patients with no clopidogrel indications (positive control) and 13 healthy volunteers (negative control). Residual on-treatment platelet reactivity unit (PRU), PON1 abundance by Western blotting, and PON1 activity by enzymatic assays were measured. PON1 genotyping and computational haplotype phasing were performed on 512 DNA specimens for two genetic loci (rs662 and rs854560). No statistical differences in mean relative PON1 abundance were found among the groups (p > 0.05). However, a significantly lower enzymatic activity was found in poor responders (10.57 ± 6.79 µU/mL) when compared to controls (22.66 ± 8.30 µU/mL and 22.21 ± 9.66 µU/mL; p = 0.004). PON1 activity among carriers of the most prevalent PON1 haplotype (AA|AA) was significantly lower than in wild types (7.90 µU/mL vs. 22.03 µU/mL; p = 0.005). Our findings suggested that PON1 is a potential biomarker of cardiovascular disease severity in Caribbean Hispanics.

Paraoxonase 1: evolution of the enzyme and of its role in protecting against atherosclerosis

PURPOSE OF REVIEW

To review the discoveries which led to the concept that serum paraoxonase 1 (PON1) is inversely related to atherosclerotic cardiovascular disease (ASCVD) incidence, how this association came to be regarded as causal and how such a role might have evolved.

RECENT FINDINGS

Animal models suggest a causal link between PON1 present on HDL and atherosclerosis. Serum PON1 activity predicts ASCVD with a similar reliability to HDL cholesterol, but at the extremes of high and low HDL cholesterol, there is discordance with PON1 being potentially more accurate. The paraoxonase gene family has its origins in the earliest life forms. Its greatest hydrolytic activity is towards lactones and organophosphates, both of which can be generated in the natural environment. It is active towards a wide range of substrates and thus its conservation may have resulted from improved survival of species facing a variety of evolutionary challenges.

SUMMARY

Protection against ASCVD is likely to be the consequence of some promiscuous activity of PON1, but nonetheless has the potential for exploitation to improve risk prediction and prevention of ASCVD.

Paraoxonase 1 and atherosclerosis

Paraoxonase 1 (PON1), residing almost exclusively on HDL, was discovered because of its hydrolytic activity towards organophosphates. Subsequently, it was also found to hydrolyse a wide range of substrates, including lactones and lipid hydroperoxides. PON1 is critical for the capacity of HDL to protect LDL and outer cell membranes against harmful oxidative modification, but this activity depends on its location within the hydrophobic lipid domains of HDL. It does not prevent conjugated diene formation, but directs lipid peroxidation products derived from these to become harmless carboxylic acids rather than aldehydes which might adduct to apolipoprotein B. Serum PON1 is inversely related to the incidence of new atherosclerotic cardiovascular disease (ASCVD) events, particularly in diabetes and established ASCVD. Its serum activity is frequently discordant with that of HDL cholesterol. PON1 activity is diminished in dyslipidaemia, diabetes, and inflammatory disease. Polymorphisms, most notably Q192R, can affect activity towards some substrates, but not towards phenyl acetate. Gene ablation or over-expression of human PON1 in rodent models is associated with increased and decreased atherosclerosis susceptibility respectively. PON1 antioxidant activity is enhanced by apolipoprotein AI and lecithin:cholesterol acyl transferase and diminished by apolipoprotein AII, serum amyloid A, and myeloperoxidase. PON1 loses this activity when separated from its lipid environment. Information about its structure has been obtained from water soluble mutants created by directed evolution. Such recombinant PON1 may, however, lose the capacity to hydrolyse non-polar substrates. Whilst nutrition and pre-existing lipid modifying drugs can influence PON1 activity there is a cogent need for more specific PON1-raising medication to be developed.

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

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

The Impact of Different rs3917538 Genotypes with the PON-1 Activity, Atherosclerosis Severity in Patients of Coronary Atherosclerosis

Background: Coronary atherosclerosis is one of the coronary artery diseases (CAD) responsible for a significant percentage of mortality and morbidity in Iraqi subjects. Atherosclerosis compresses about 17 million death cases; 45% are under the age of 70. The improvement in atherosclerosis disease management paly a critical role in preventing this disease; despite that, new risk factors have been studied, including genetic studies. Many polymorphisms have been associated with coronary atherosclerosis in different ethnic populations. Paraoxonase is an enzyme located on HDL in serum. PON acts as a protective factor or agent against oxidative modification of LDL, suggesting that it could play an essential and influential role in atherosclerotic processes prevention. Objective: To evaluate the rs3917538 genotypes in the PON-1 gene associated with the coronary atherosclerosis risk and the effect of this single nucleotide polymorphism on the serum activity of PON-1 and the severity of coronary atherosclerosis. Methods: A case-control study included sixty patients diagnosed with coronary atherosclerosis and sixty healthy volunteers diagnosed with angiography examination. The study was carried out during the period from February 2019 till June 2020. Serum PON-1 was measured by fluorometric technique, and the genetic assessment was by RT-PCR technique. Results: The activity for PON-1 in patients was significantly lower than controls; the median activity of PON-1 in controls was 197.32 mU/ml, which was higher than that of patients (median =163.46 mU/ml). There was an impact of rs3917538 genotypes on the severity of the disease, P=0.041. The rs3917538 genotypes have no association with the risk of coronary atherosclerosis and the activity of PON-1. Conclusion: The measurement of serum PON-1 activity may help in the diagnosis  of coronary atherosclerosis patients. The rs3917538 genotypes in the PON-1 gene among the patient’s group impact the severity of coronary atherosclerosis.

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.

Paraoxonase 1 concerning dyslipidaemia, cardiovascular diseases, and mortality in haemodialysis patients

Paraoxonase 1 (PON1) is known for preventing atherosclerosis through lipid-modifying features, antioxidant activity, anti-inflammatory, anti-apoptosis, anti-thrombosis, and anti-adhesion properties. Uremic patients requiring haemodialysis (HD) are especially prone to atherosclerosis and its complications. We analysed the PON1 gene (PON1) polymorphisms and serum PON1 (paraoxonase) activity concerning dyslipidaemia and related cardiovascular diseases and mortality to show how they associate under uremic conditions modified by maintenance HD treatment. The rs662 AA + AG (OR 1.76, 95%CI 1.10-2.80, P = 0.018), rs854560 TT (OR 1.48, 95%CI 1.04-2.11, P = 0.031), and rs854560 AT + TT (OR 1.28, 95%CI 1.01-1.63, P = 0.040) contributed to the prevalence of atherogenic dyslipidaemia diagnosed by the triglyceride (TG)/HDL-cholesterol ratio ≥ 3.8. The normalized serum PON1 activity positively correlated with atherogenic dyslipidaemia (ẞ 0.67 ± 0.25, P = 0.008). The PON1 rs854560 allele T was involved in the higher prevalence of ischemic cerebral stroke (OR 1.38, 1.02-1.85, P = 0.034). The PON1 rs705379 TT genotype contributed to cardiovascular (HR 1.27, 95% CI 1.03-1.57, P = 0.025) and cardiac (HR 1.34, 95% CI 1.05-1.71, P = 0.018) mortality. All P-values were obtained in multiple regression analyses, including clinical variables. Multifaceted associations of PON1 with dyslipidaemia, ischemic cerebral stroke, and cardiovascular mortality in HD patients provide arguments for the consideration of PON1 and its protein product as therapeutic targets in the prevention of atherosclerosis and its complications in uremic patients.

Diabetes and cardiovascular disease: inter-relation of risk factors and treatment

Background

The diabetes mellitus prevalence is still advancing and increasingly becoming one of the globally most severe and expensive chronic illnesses. The strong correlation between diabetes as well as the most prominent reason for diabetes and death in diabetic patients is cardiovascular disorders. Health conditions like dyslipidemia, hypertension, obesity, and other factors of risk like the risk of cardiovascular are frequent in diabetic persons and raise the likelihood of heart attacks.

Main text

In particular, several researchers have found diabetes mellitus-related biochemical pathways that raise the likelihood of cardiovascular disorder in people with diabetes individually. This review describes diabetes-cardiovascular disorder relationships, explores potential therapeutic mechanisms, addresses existing treatment, care, and describes the directions for the future for study.

Conclusion

Thus, in individuals with diabetes, it is important to concentrate on cardiovascular threat variables to reduce the illness’s lasting cardiovascular complications. Further work to enhance knowledge of the disease state and its impact on cardiovascular function is required to boost medical treatment and cardiovascular disorders result in people with diabetes.

Paraoxonase 1 gene polymorphisms concerning non-insulin-dependent diabetes mellitus nephropathy in hemodialysis patients

AIMS

Data on involvement of paraoxonase 1 gene (PON1) in non-insulin-dependent diabetes mellitus (NIDDM) nephropathy are scarce. We investigated PON1 polymorphisms concerning end-stage NIDDM nephropathy and atherosclerotic complications in NIDDM nephropathy patients treated with hemodialysis (HD).

METHODS

In NIDDM nephropathy (n = 402) and non-diabetic (n = 998) HD subjects, we obtained PON1 polymorphisms by HRM analysis (rs662) or predesigned TaqMan SNV Genotyping Assay (rs854560, rs705379).

RESULTS

Only PON1 rs705379 was associated with end-stage NIDDM nephropathy in the recessive (OR 1.451, 95% CI 1.104-1.906, P = 0.009) and additive (OR 1.398, 95%CI 1.009-1.936, P = 0.046) inheritance modes. NIDDM nephropathy patients bearing the rs854560 T allele were at higher risk for ischemic cerebral stroke (OR 2.087, 95%CI 1.145-3.801, P = 0.016). In non-diabetic patients but not NIDDM nephropathy subjects, atherogenic dyslipidemia corresponded with PON1 rs662 A allele and PON1 rs854560 TT homozygosity.

CONCLUSIONS

In HD patients, NIDDM nephropathy correlates with the TT genotype of PON1 rs705379. The rs854560 T allele indicates a higher risk for atherosclerotic diseases in NIDDM nephropathy subjects. The T alleles of both PON1 SNVs are known as low expression variants downregulated serum PON1 activity. An increase of diminished PON1 activity may be a target in the prevention of NIDDM nephropathy and NIDDM atherosclerotic complications.

The most effective polymorphisms of paraoxonase-1 gene on enzyme activity and concentration of paraoxonase-1 protein in type 2 diabetes mellitus patients and non-diabetic individuals: A systematic review and meta-analysis

INTRODUCTION

Many studies have evaluated the association of paraoxonase-1 (PON1) gene polymorphisms with enzyme activity and concentration in type 2 diabetes mellitus (T2DM). However, the exact impact of these polymorphisms is not still obvious. Hence, we conducted a systematic review and meta-analysis to clarify the association of PON1 polymorphisms with its enzyme characteristics in T2DM patients and non-diabetic individuals.

METHODS

We searched electronic databases including PubMed, Web of Science, Embase and Scopus for publications by April 2018. The pooled response ratio (rr) for the association and their corresponding 95% confidence intervals (CIs) were calculated using a fixed-effect model.

RESULTS

Fifteen relevant studies fulfilled our inclusion criteria. The results showed a 1.25-fold increase in total PON1 activity in non-diabetic group against T2DM patients (p-value = 0.024). Also, only Q192R and L55M polymorphisms had sufficient studies to be included in the meta-analysis. All three genotypes of Q192R polymorphism showed significantly different activities between the study groups with the highest pooled effect size for RR genotype (rr_QQ < rr_QR < rr_RR) while this difference was seen only in LL genotype of L55M polymorphism. Therefore, Q192R polymorphism was more correlated with type 2 diabetes mellitus. In case of concentration, there was no significant differences between two groups (p-value = 0.897).

CONCLUSION

Current meta-analysis suggested that the observed difference of total PON1 activity was due to the different activity of various genotypes of PON1 enzyme in case of L55M and Q192R polymorphisms so that LL and RR genotypes had the most important role in the establishment of mentioned difference.

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.

Type 2 Diabetes Mellitus and Cardiovascular Disease: Genetic and Epigenetic Links

Type 2 diabetes mellitus (DM) is a common metabolic disorder predisposing to diabetic cardiomyopathy and atherosclerotic cardiovascular disease (CVD), which could lead to heart failure through a variety of mechanisms, including myocardial infarction and chronic pressure overload. Pathogenetic mechanisms, mainly linked to hyperglycemia and chronic sustained hyperinsulinemia, include changes in metabolic profiles, intracellular signaling pathways, energy production, redox status, increased susceptibility to ischemia, and extracellular matrix remodeling. The close relationship between type 2 DM and CVD has led to the common soil hypothesis, postulating that both conditions share common genetic and environmental factors influencing this association. However, although the common risk factors of both CVD and type 2 DM, such as obesity, insulin resistance, dyslipidemia, inflammation, and thrombophilia, can be identified in the majority of affected patients, less is known about how these factors influence both conditions, so that efforts are still needed for a more comprehensive understanding of this relationship. The genetic, epigenetic, and environmental backgrounds of both type 2 DM and CVD have been more recently studied and updated. However, the underlying pathogenetic mechanisms have seldom been investigated within the broader shared background, but rather studied in the specific context of type 2 DM or CVD, separately. As the precise pathophysiological links between type 2 DM and CVD are not entirely understood and many aspects still require elucidation, an integrated description of the genetic, epigenetic, and environmental influences involved in the concomitant development of both diseases is of paramount importance to shed new light on the interlinks between type 2 DM and CVD. This review addresses the current knowledge of overlapping genetic and epigenetic aspects in type 2 DM and CVD, including microRNAs and long non-coding RNAs, whose abnormal regulation has been implicated in both disease conditions, either etiologically or as cause for their progression. Understanding the links between these disorders may help to drive future research toward an integrated pathophysiological approach and to provide future directions in the field.

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.

Review: The genetics of macrovascular disease in diabetes

Patients with diabetes mellitus show an increased risk of developing macrovascular disease. Although common cardiovascular risk factors are abnormally high in patients with type 2 diabetes compared to the general population, they cannot fully explain the high rate of vascular complications. Indeed the occurrence and the severity of such complications are highly heterogeneous even in patients with comparable levels of glycaemic control and similar prevalence of cardiovascular risk factors. Large-vessel atherosclerosis can precede the clinical manifestation of diabetes. This suggests that both atherosclerosis and type 2 diabetes may have common genetic and environmental antecedents. A large body of evidence supports the possible role of genetics in determining the expression of the ischaemic vascular phenotype in diabetic patients, mainly derived from studies in ethnic groups or in first-degree relatives of diabetic patients and from association studies with genetic polymorphisms. Unravelling the polygenic susceptibility factors for macrovascular complications of diabetes is difficult, since diabetes per se has multifactorial inheritance. Direct evidence is largely based on the candidate gene approach in case-control studies. Several systems provide candidate genes that could by themselves or by interacting with other factors, increase the risk of ischaemic vascular disease in diabetic patients mainly related to lipid metabolism, lipoprotein oxidation and haemostatic processes.

Molecular Dynamics Approach in the Comparison of Wild-Type and Mutant Paraoxonase-1 Apoenzyme Form

There is some evidence linking the mammalian paraoxonase-1 (PON1) loops (L1 and L2) to an increased flexibility and reactivity of its active site with potential substrates. The aim of this work is to study the structural, dynamical, and functional effects of the most flexible regions close to the active site and to determine the impact of mutations on the protein. For both models, wild-type (PON1wild) and PON1 mutant (PON1mut) models, the L1 loop and Q/R and L/M mutations were constructed using MODELLER software. Molecular dynamics simulations of 20 ns at 300 K on fully modeled PON1wild and PON1mut apoenzyme have been done. Detailed analyses of the root-mean-square deviation and fluctuations, H-bonding pattern, and torsion angles have been performed. The PON1wild results were then compared with those obtained for the PON1mut. Our results show that the active site in the wild-type structure is characterized by two distinct movements of opened and closed conformations of the L1 and L2 loops. The alternating and repetitive movement of loops at specific times is consistent with the presence of 11 defined hydrogen bonds. In the PON1mut, these open-closed movements are therefore totally influenced and repressed by the Q/R and L/M mutations. In fact, these mutations seem to impact the PON1mut active site by directly reducing the catalytic core flexibility, while maintaining a significant mobility of the switch regions delineated by the loops surrounding the active site. The impact of the studied mutations on structure and dynamics proprieties of the protein may subsequently contribute to the loss of both flexibility and activity of the PON1 enzyme.

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.

Paraoxonases and chemokine (C-C motif) ligand-2 in noncommunicable diseases

Oxidative stress and inflammation underpin most diseases; their mechanisms are inextricably linked. Chronic inflammation is associated with oxidation, anti-inflammatory cascades are linked to decreased oxidation, increased oxidative stress triggers inflammation, and redox balance inhibits the inflammatory cellular response. Whether or not oxidative stress and inflammation represent the cause or consequence of cellular pathology, they contribute significantly to the pathogenesis of noncommunicable diseases (NCD). The incidence of obesity and other related metabolic disturbances are increasing, as are age-related diseases due to a progressively aging population. Relationships between oxidative stress, inflammatory signaling, and metabolism are, in the broad sense of energy transformation, being increasingly recognized as part of the problem in NCD. In this chapter, we summarize the pathologic consequences of an imbalance between circulating and cellular paraoxonases, the system for scavenging excessive reactive oxygen species and circulating chemokines. They act as inducers of migration and infiltration of immune cells in target tissues as well as in the pathogenesis of disease that perturbs normal metabolic function. This disruption involves pathways controlling lipid and glucose homeostasis as well as metabolically driven chronic inflammatory states that encompass several response pathways. Dysfunction in the endoplasmic reticulum and/or mitochondria represents an important feature of chronic disease linked to oxidation and inflammation seen as self-reinforcing in NCD. Therefore, correct management requires a thorough understanding of these relationships and precise interpretation of laboratory test results.

HDL-cholesterol in coronary artery disease risk: function or structure?

High-density lipoproteins (HDL) are inversely related with coronary artery disease (CAD) and HDL-cholesterol is the only standardized and reproducible parameter available to estimate plasma concentration of these lipoproteins. However, pharmacological interventions intended to increase HDL-cholesterol have not been consistently associated to an effective CAD risk reduction. Among patients with a myocardial infarction, 43 and 44% of men and women, respectively, had normal plasma levels of HDL-cholesterol, whereas genetic studies have failed to show a causal association between HDL-cholesterol and CAD risk. Instead, HDL functionality seems to be the target to be evaluated, but the existing methods are still poorly reproducible and far to be adapted to the clinical laboratory. HDL subclasses rise as a potential alternative for the evaluation of CAD risk; HDL subclasses are a surrogate of intravascular metabolism of these lipoproteins and probably of their functionality. Low levels of large HDL and increased proportions of small particles are the most remarkable features associated to an increased risk of type 2 diabetes mellitus (T2DM) or CAD. However, inflammation and other environmental factors are related with abnormal HDL structure, and, as a consequence, more prospective studies are needed to better support the clinical usefulness of HDL subclasses. New insights from proteome and lipidome profiles of HDL will provide potential HDL-related biomarkers in the coming years.

The determination of Q192R polymorphism of paraoxonase 1 by using non-toxic substrate p-nitrophenylacetate

CONTEXT

The human serum paraoxonase 1 (PON1) is calcium-dependent esterase and associates with the high density serum lipoproteins. PON1 plays a major role in oxidation of high density lipoprotein and low density lipoprotein and prevention of atherogenesis in coronary heart disease. PON1Q and R allele hydrolyses number of substrates like paraoxon (PO) (diethyl p-nitrophenyl phosphate) and phenylacetate.

AIMS

The aim of the study is to the determination of Q192R polymorphism of PON1 by using non-toxic substrate p-nitrophenylacetate and compares it with the phenotype determined by using PO as substrate.

MATERIALS AND METHODS

The study group consists of 60 healthy normal patients. Paraoxonase activity was measured using the procedure described by Eckerson (Reference method) and for phenotyping; the ratio of hydrolysis of PO in the presence of 1 M NaCl (salt-stimulated PON1, SALT) to the hydrolysis of phenylacetate (PA) is calculated. In new method (Haagen et al.) arylesterase activity measured using p-nitrophenylacetate and for phenotyping arylesterase, the ratio of inhibition of enzymatic hydrolysis of p-nitrophenylacetate (substrate) by phenyl acetate to non-inhibited hydrolysis of p-nitrophenylacetate (inhibited arylesterase activity (IA-IA0)/non-inhibited arylesterase activity (NIA).

RESULTS

It was found that paraoxonase activity is trimodally distributed in both the methods. There is no significant difference in the distribution of PON1 phenotypes of both reference method and new method being frequencies 0.946 and 0.376 respectively and there was no significant difference for phenotypic polymorphism for an individual by both methods (χ(2)= 0.15 and P = 0.9262).

CONCLUSION

The Q192R polymorphism of PON1 by using non-toxic substrate p-nitrophenylacetate showed trimodal distribution of QQ (homozygous), QR (heterozygous), and RR (homozygous) phenotype and it is comparable with reference method. This method can be used for PON1 phenotype in different pathological and complex disease conditions.

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.

Paraoxonases: ancient substrate hunters and their evolving role in ischemic heart disease

Interest in the role of paraoxonases (PON) in cardiovascular research has increased substantially over the past two decades. These multifaceted and pleiotropic enzymes are encoded by three highly conserved genes (PON1, PON2, and PON3) located on chromosome 7q21.3-22.1. Phylogenetic analysis suggests that PON2 is the ancient gene from which PON1 and PON3 arose via gene duplication. Although PON are primarily lactonases with overlapping, but distinct specificities, their physiologic substrates remain poorly characterized. The most interesting characteristic of PON, however, is their multifunctional roles in various biochemical pathways. These include protection against oxidative damage and lipid peroxidation, contribution to innate immunity, detoxification of reactive molecules, bioactivation of drugs, modulation of endoplasmic reticulum stress, and regulation of cell proliferation/apoptosis. In general, PON appear as "hunters" of old and new substrates often involved in athero- and thrombogenesis. Although reduced PON activity appears associated with increased cardiovascular risk, the correlation between PON genotype and ischemic heart disease remains controversial. In this review, we examine the biochemical pathways impacted by these unique enzymes and investigate the potential use of PON as diagnostic tools and their impact on development of future therapeutic strategies.

Paraoxonase 1 Phenotype and Mass in South Asian versus Caucasian Renal Transplant Recipients

South Asian renal transplant recipients have a higher incidence of cardiovascular disease compared with Caucasian renal transplant recipients. We carried out a study to determine whether paraoxonase 1, a novel biomarker for cardiovascular risk, was decreased in South Asian compared with Caucasian renal transplant recipients. Subjects were matched two to one on the basis of age and sex for a total of 129 subjects. Paraoxonase 1 was measured by mass, arylesterase activity, and two-substrate phenotype assay. Comparisons were made by using a matched design. The frequency of PON1 QQ, QR and RR phenotype was 56%, 37%, and 7% for Caucasian subjects versus 35%, 44%, and 21% for South Asian subjects (χ(2) = 7.72, P = 0.02). PON1 mass and arylesterase activity were not significantly different between South Asian and Caucasian subjects. PON1 mass was significantly associated with PON1 phenotype (P = 0.0001), HDL cholesterol (P = 0.009), LDL cholesterol (P = 0.02), and diabetes status (P < 0.05). Arylesterase activity was only associated with HDL cholesterol (P = 0.003). Thus the frequency of the PON1 RR phenotype was higher and that of the QQ phenotype was lower in South Asian versus Caucasian renal transplant recipients. However, ethnicity was not a significant factor as a determinant of PON1 mass or arylesterase activity, with or without analysis including PON1 phenotype. The two-substrate method for determining PON1 phenotype may be of value for future studies of cardiovascular complications in renal transplant recipients.

Interaction of folate intake and the paraoxonase Q192R polymorphism with risk of incident coronary heart disease and ischemic stroke: the atherosclerosis risk in communities study

PURPOSE

To investigate the potential interaction between folate intake and the paraoxonase 1 (PON1) Q192R polymorphism with the risk of incident coronary heart disease (CHD) and ischemic stroke in the Atherosclerosis Risk in Communities study, a population-based prospective cohort of cardiovascular disease in 15,792 white and African-American subject.

METHODS

Race-stratified Cox proportional hazards models were performed to examine the interaction between folate intake and the PON1 Q192R polymorphism.

RESULTS

A significant inverse association between folate intake and risk of incident CHD among white subjects was found (hazard rate ratio, 1.30; 95% confidence interval, 1.09-1.56; P = .004; folate intake ≤155 μg vs ≥279 μg, reference group). An interaction effect was observed between the dominant genetic model and folate intake with regards to incident ischemic stroke in white subjects (hazard rate ratio, 0.68; 95% confidence interval, 0.91-0.99; and 1.24 from 1st-4th quartile, respectively; P-trend = .05).

CONCLUSIONS

There was an interaction between folate intake and PON1 Q192 polymorphism with regard to the risk of ischemic stroke in white subjects. Future studies should investigate the interaction between additional polymorphisms within the PON1 gene and genetic variants in other folate metabolizing genes with folate intake on the risk of incident CHD and stroke.

Effects of paraoxonase activity and gene polymorphism on coronary vasomotion

Background

Paraoxonase 1 [PON1] is recognized as a protective enzyme against LDL oxidation, and PON1 polymorphism has been described as a factor influencing coronary heart disease [CHD] free survival. As coronary vasoreactivity is a surrogate of future cardiovascular events, we aimed at assessing the respective effect of the PON1 genotype and activity on coronary vasoreactivity in a population of type 2 diabetic patients.

Methods

Nineteen patients with type 2 diabetes mellitus underwent ⁸²Rb cardiac PET/CT to quantify myocardial blood flow [MBF] at rest, during cold pressor testing [CPT], and during adenosine-induced hyperaemia to compute myocardial flow reserve [MFR]. They were allocated according to Q192R and L55M polymorphisms into three groups (wild-type and LM/QR heterozygotes, MM homozygotes, and RR homozygotes) and underwent a measurement of plasmatic PON1 activity. Relations between rest-MBF, stress-MBF, MFR, and MBF response to CPT and PON1 genotypes and PON1 activity were assessed using Spearman's correlation and multivariate linear regression analysis.

Results

Although PON1 activity was significantly associated with PON1 polymorphism (p < 0.0001), there was no significant relation between the PON1 genotypes and the rest-MBF, stress-MBF, or MBF response to CPT (p ≥ 0.33). The PON1 activity significantly correlated with the HDL plasma level (ρ = 0.63, p = 0.005), age (ρ = -0.52, p = 0.027), and MFR (ρ = 0.48, p = 0.044). Moreover, on multivariate analysis, PON1 activity was independently associated with MFR (p = 0.037).

Conclusion

Our study supports an independent association between PON1 activity and MFR. Whether PON1 contributes to promote coronary vasoreactivity through its antioxidant activity remains to be elucidated. This putative mechanism could be the basis of the increased risk of CHD in patients with low PON1 activity.

Serum paraoxonase-1 (PON1) activities (PONase/AREase) and polymorphisms in patients with type 2 diabetes mellitus in a North-West Indian population

OBJECTIVE

Paraoxonase-1 (PON1), an HDL-C associated enzyme, protects lipoproteins from oxidation. There is evidence that PON1 enzyme activity is reduced in the patients with type 2 diabetes mellitus (T2DM). North-West Indian Punjabis, a distinct ethnic group has high incidence of T2DM. However till date there is no information regarding PON1 enzyme activities and PON1 polymorphisms in T2DM patients of this ethnic group.

METHODS

We identified polymorphisms in the coding Q192R, L55M and promoter -909G/C, -162A/G, -108C/T of the PON1 gene by using PCR-RFLP, multiplex PCR and allele specific oligonucleotide PCR assays in 250 T2DM patients and 300 healthy controls. We also assessed paraoxonase (PONase) and arylesterase (AREase) activities of PON1 enzyme.

RESULTS

The serum PONase (114.2 vs. 178.0nmol/min/ml) and AREase (62.7 vs. 82.5μmol/min/ml) activities were significantly lower (p<0.0001) in patients as compared to controls. PONase activity was affected by all the studied PON1 polymorphisms. However, AREase activity was not affected by any of these polymorphisms. Coding Q192R and promoter -909G/C polymorphisms showed significant differences in genotypic distribution. QR, RR (Q192R) and GC, CC (-909G/C) genotypes and L-C-A-R-G, L-T-A-R-G, L-T-G-Q-C haplotypes showed significant association with type 2 diabetes. No significant linkage disequilibrium was observed among the five polymorphisms.

CONCLUSION

Both PONase and AREase activities are lower in patients and this could lead to increased lipid peroxidation and accelerated atherosclerosis in them. PONase activity, but not AREase activity is influenced by PON1 polymorphisms. QR, RR, GC, CC genotypes and L-C-A-R-G, L-T-A-R-G, L-T-G-Q-C haplotypes are commoner in diabetics as compared to controls and may be related to genetic susceptibility to type 2 diabetes.

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

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

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

BACKGROUND

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

METHODOLOGY/PRINCIPAL FINDINGS

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

CONCLUSIONS

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

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

Background

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

Findings

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

Conclusions

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

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

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

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

OBJECTIVE

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

METHODS

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

RESULT

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

CONCLUSIONS

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

Paraoxonase 1 192 and 55 polymorphisms in osteosarcoma

Paraoxonase is an HDL-associated enzyme that plays a preventive role against oxidative stres. Previous studies suggested that involved an amino acid substitution at position 192 gives rise to two alloenzymes with a low activity (Q allele) and a high activity (R allele) towards paraoxon. There also exists a second polymorphism of the human PON1 gene affecting amino acid 55, giving rise to a leucine (L-allele) substitution for methionine (M-allele). PON1 gene polymorphisms were studied in 50 patients with osteosarcoma and 50 healthy controls. Paraoxonase genotypes were determined by PCR-RFLP. We found a reduction in the frequency of PON1 192 R allele in patients (P=0.015). Besides, PON1 192 wild type QQ genotype (P=0.015) and PON1 55 wild type L allele (P=0.001) were higher in patients compared to healthy controls. PON1 192 QQ genotype was associated with osteosarcoma in multivariate logistic regression analysis. Our findings have suggested that PON1 192 wild type genotypes may be associated with a risk of developing osteosarcoma.

The genetics of vascular complications in diabetes mellitus

Prospective identification of which individuals with diabetes mellitus (DM) are at greatest risk for developing cardiovascular disease (CVD) complications would have considerable public health importance by allowing the allocation of limited resources to be focused on those individuals who would most benefit from aggressive intervention. Over the past 20 years genetic disease association studies have demonstrated that polymorphisms at specific genetic loci may identify those individuals at greatest risk for developing CVD in the setting of DM. This article reviews the evidence accumulated to date on four polymorphic loci with the aim of explaining how these polymorphisms modify the risk for CVD in DM by modifying the functional activity of a specific gene. Use of the knowledge of these genetic differences among individuals in targeting drug therapy (pharmacogenomics) is also discussed.

Serum paraoxonase 1 activity status in patients with liver disorders

BACKGROUND/AIM

Paraoxonase 1 (PON1) is an esterase, exclusively synthesized by liver. The present study has two objectives: to determine the PON1 activity status in various disorders associated with hepatocellular damage and to correlate the changes of PON1 activity with the standard liver function and fasting lipid profile tests in these disorders.

PATIENTS AND METHODS

The study groups consisted of 95 patients with liver diseases including acute viral hepatitis (14), cirrhosis with portal hypertension (33), leptospirosis (14), sepsis and multi organ failure (15), left ventricular failure (9), and falciparum malaria (10); and 53 healthy controls. Serum PON1 activity was measured manually using spectrophotometer. Liver function test parameters and fasting lipid profile were performed in clinical chemistry auto analyzer (Hitachi 912).

RESULTS

The serum PON1 activity in patients with acute viral hepatitis and sepsis decreased significantly ( P < 0.001) and moderately in falciparum malaria ( P < 0.05). However, in patients with cirrhosis, leptospirosis and left ventricular patients, its activity did not change significantly. On applying Pearson correlation, serum PON1 activity correlated positively with high-density lipoprotein-cholesterol (HDL-C) in patients with sepsis (r=0.633, P < 0.05), left ventricular failure patients (r=0.814, P < 0.05) and negatively with acute viral hepatitis patients (r=-0.528, P <0.05).

CONCLUSION

PON1 activity has decreased significantly in acute viral hepatitis, sepsis with multi organ failure and falciparum malaria patients. Determination of PON1 activity may serve as a useful additional test in assessing these conditions.

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.

The Role of Polymorphisms Within Paraoxonases (192 Gln/Arg in PON1 and 311Ser/Cys in PON2) in the Modulation of Cardiovascular Risk: A Pilot Study

Paraoxonases (PONs) may exert anti-atherogenic action by reducing lipid peroxidation. We evaluated the influence of 2 polymorphisms within PON1 (192 Gln/ Arg) and PON2 (311 Ser/Cys) genes in 407 young Poles: 273 patients who experienced a first myocardial infarction (MI) under the age of 45 (study group) and 134 healthy volunteers (control group) with a HEART Score ≤2 (low risk). Paraoxonase 1 polymorphism 192Gln/Arg influenced the risk of premature MI (P = .0054). A positive family history of coronary artery disease (CAD) was associated with the 192Arg allele (P = .0107). The association between PON1 genotype (192 Gln/Arg) and low-density lipoprotein cholesterol (LDL-C) (P = .036) levels was also observed. However, we did not find any relationship between polymorphism 311Ser/Cys and CAD risk (P = .418). PON1 polymorphism 192Gln/Arg influenced the risk of premature MI. The association between PON1 genotype (192 Gln/Arg) and serum LDL-C levels may be explained by PON participation in reverse cholesterol transport.