Association of the Glu298Asp polymorphism in the endothelial nitric oxide synthase gene with essential hypertension resistant to conventional therapy

The deleterious impact of a non-synonymous SNP on protein structure and function is apparent in hypertension

Essential hypertension (EH) is a significant health issue around the globe. The indifferent therapy regimen suggests varied physiological functions due to the lifestyle and genetic presentations of an individual. The endothelial nitric oxide synthase (NOS3) gene is a crucial vascular system marker in EH that contributes significantly to the phenotype. Hence, the present study aimed to employ the candidate gene approach and investigate the association between NOS3 single nucleotide polymorphism (SNP) E298D (G894T/rs1799983) by applying several in silico tools and validation through human samples screening. We corroborated computational findings through a case-control study comprising 294 controls and 299 patients; the 894T allele emerged significantly as the risk allele (odds ratio=2.07; P=6.38E-05). The in silico analyses highlighted the significance of E298D on the native structure and function of NOS3. The dynamics simulation study revealed that the variant type 298D caused structural destabilization of the protein to alter its function. Plasma nitrite levels were reduced in patients (P=0.0002), and the same correlated with the 894T allele. Furthermore, correlations were apparent between clinical, genotype, and routine biochemical parameters. To conclude, the study demonstrated a perceptible association between the SNP E298D and NOS3 protein structure stability that appears to have a bearing on the enzyme's function with a deleterious role in EH.

A genome-wide association study identifies a novel candidate locus at the DLGAP1 gene with susceptibility to resistant hypertension in the Japanese population

Numerous genetic variants associated with hypertension and blood pressure are known, but there is a paucity of evidence from genetic studies of resistant hypertension, especially in Asian populations. To identify novel genetic loci associated with resistant hypertension in the Japanese population, we conducted a genome-wide association study with 2705 resistant hypertension cases and 21,296 mild hypertension controls, all from BioBank Japan. We identified one novel susceptibility candidate locus, rs1442386 on chromosome 18p11.3 (DLGAP1), achieving genome-wide significance (odds ratio (95% CI) = 0.85 (0.81–0.90), P = 3.75 × 10⁻⁸) and 18 loci showing suggestive association, including rs62525059 of 8q24.3 (CYP11B2) and rs3774427 of 3p21.1 (CACNA1D). We further detected biological processes associated with resistant hypertension, including chemical synaptic transmission, regulation of transmembrane transport, neuron development and neurological system processes, highlighting the importance of the nervous system. This study provides insights into the etiology of resistant hypertension in the Japanese population.

Endothelial nitric oxide synthase G894T, intron 4 VNTR, and T786C polymorphisms in retinopathy of prematurity

BACKGROUND

Our objective in this study was to assess the association between eNOS gene, that achieves synthesis of nitric oxide especially in the endothelial cells known to have an important role in angiogenesis and vasculogenesis, G894T, intron 4 VNTR (27-bp repeat) and T786C functional polymorphisms and retinopathy of prematurity (ROP), which is an important cause of morbidity in premature or low birth weight babies.

METHODS

A total of 139 babies who were followed up in our neonatal intensive care unit because of premature birth in our hospital or admitted to our unit. 69 of them had retinopathy of prematurity and comprised the patients group. The remaining 70 babies who did not have ROP comprised the control group. An additional of 1 ml of blood samples were drawn from babies who were in the study groups during routine laboratory analysis. eNOS gene polymorphisms were determined by using polymerase chain reaction method.

RESULTS

eNOS G894T, intron 4 VNTR and T786C gene polymorphisms did not differ between the patient and control groups (p >  0.05). Using logistic regression analysis; while gender did not differ between two groups; gestational age, birth weight, time on mechanical ventilation differ between two groups. After adjustment for variables other than eNOS gene polymorphisms, we found no significant difference in the genotype distribution of eNOS G894T, intron 4 VNTR and T786C polymorphisms (p >  0.05).

CONCLUSION

We observed no association between ROP and eNOS gene polymorphisms but needs more investigation.

Association between eNOS rs1799983 polymorphism and hypertension: a meta-analysis involving 14,185 cases and 13,407 controls

BACKGROUND

Essential hypertension is a complex disease determined by the interaction of genetic and environmental factors, eNOS is considered to be one of the susceptible genes for hypertension. Our study aimed to evaluate the association between eNOS rs1799983 polymorphism and hypertension, and to provide evidence for the etiology of hypertension.

METHODS

Case-control studies of eNOS rs1799983 polymorphism and hypertension were included by searching PubMed, Embase, Web of Science, Medline, Scopus, WanFang datebase, Vip datebase, and CNKI database according to PRISMA guideline. Eligible data were extracted and pooled, and were analyzed using R software based on five different genetic models.

RESULTS

A total of 60 eligible articles involving 14,185 cases and 13,407 controls were finally selected. We found significant association between eNOS rs1799983 polymorphism and hypertension under any genetic model (T vs G: OR = 1.44, 95% CI 1.26-1.63; GT vs GG: OR 1.34, 95% CI 1.18-1.52; TT vs GG: OR 1.80, 95% CI 1.41-2.31; GT + TT vs GG: OR 1.42, 95% CI 1.25-1.63; TT vs GG + GT: OR 1.68, 95% CI 1.35-2.08; GT vs GG + TT: OR 1.24, 95% CI 1.11-1.40).

CONCLUSIONS

We found that eNOS rs1799983 polymorphism is associated with the increased risk of hypertension under any genetic model. Moreover, investigations of gene-gene and gene-environment interactions are needed to give more insight into the association between eNOS rs1799983 polymorphism and hypertension.

Association Between Endothelial Nitric Oxide Synthase (eNOS) -786 T/C and 27-bp VNTR 4b/a Polymorphisms and Preeclampsia Development

The aim of the present study was to analyze the distribution of genotypes and haplotypes of functional eNOS gene polymorphisms in the promoter (-786 T/C), intron 4 (VNTR4b/a) and exon 7 (894 G/T), in Serbian population of pregnant women, and establish a possible association between these polymorphisms and preeclampsia development. DNA was isolated from venous blood samples of 50 heathy pregnant women and 50 preeclampsia patients. Polymerase Chain Reaction/Restriction Fragment Length Polymorphism (PCR/RFLP) technique, with appropriate sets of primers and specific restriction enzymes, was used to determine polymorphisms in eNOS gene. Statistical analysis was done using the SPSS and HAPLOVIEW software packages. eNOS -786 T/C polymorphism was significantly associated with preeclampsia (P = 0.006). Homozygotes for the VNTR polymorphism had also an elevated risk of developing preeclampsia (OR=7.68, 95%CI (0.89-65.98)), especially the mild (OR=9.33, 95%CI (0.98-88.57)) and late form (OR=8.52, 95%CI (0.90-80.58)). The 894 G/T polymorphism was not associated with preeclampsia. "G-C-b" and "T-4a-T" haplotypes were more frequent in preeclampsia, though without reaching statistical significance. -786 T/C and VNTR 4b/a eNOS gene polymorphisms were associated with preeclampsia risk in Serbian patients.

Bicuspid Aortic Valve: Role of Multiple Gene Variants in Influencing the Clinical Phenotype

Background. Bicuspid aortic valve (BAV) is a common congenital heart defect with increased prevalence of aortic dilatation and dissection. BAV has an autosomal dominant pattern of inheritance with reduced penetrance and variable expressivity. BAV has been described as an isolated trait or associated with other clinical manifestations in syndromic conditions. Identification of a syndromic condition in a BAV patient is clinically relevant in order to personalize indication to aortic surgery. We aimed to point out how genetic diagnosis by next-generation sequencing (NGS) can improve management of a patient with complex BAV clinical picture. Methods and Results. We describe a 45-year-old Caucasian male with BAV, thoracic aortic root and ascending aorta dilatation, and connective features evocative but inconclusive for clinical diagnosis of Marfan syndrome (MFS). Targeted (91 genes) NGS was used. Proband genetic variants were investigated in first-degree relatives. Proband carried 5 rare variants in 4 genes: FBN1(p.Asn542Ser and p.Lys2460Arg), NOTCH1(p.Val1739Met), LTBP1(p.Arg1330Gln), and TGFBR3(p.Arg423Trp). The two FBN1 variants were inherited in cis by the mother, showing systemic features evocative of MFS, but with a milder phenotype than that observed in the proband. Careful clinical observation along with the presence of the FBN1 variants allowed diagnosis of MFS in the proband and in his mother. NOTCH1 variant was found in mother and brother, not exhibiting BAV, thus not definitely supporting/excluding association with BAV. Interestingly, the proband, his brother and father, all showing root dilatation, and his sister, with upper range aortic root dimension, were carriers of a TGFBR3 variant. LTBP1 might also modulate the vascular phenotype. Conclusions. Our results underline the usefulness of NGS together with family evaluation in diagnosis of patients with monogenic traits and overlapping clinical manifestations due to contribution of the same genes and/or presence of comorbidities determined by different genes.

The polymorphism G894 T of endothelial nitric oxide synthase (eNOS) gene is associated with susceptibility to essential hypertension (EH) in Morocco

BACKGROUND

Hypertension is a multifactorial disease involving both environmental and genetic Factros. G894 T eNOS polymorphism has been suggested to be responsible for reduced NO synthesis, and EH development. The objective of our case-control study is to evaluate the potential association of G894 T eNOS polymorphism with Essential Hypertension (EH) susceptibility, among a sample of Moroccan patients.

METHODS

One hundred forty five hypertensive patients were recruited from the department of Cardiology, University Hospital Center Ibn Rochd, Casablanca, Morocco, and compared to 184 apparently healthy subjects. DNA samples were genotype by PCR-RFLP method using MboI restriction enzyme.

RESULTS

Our results showed a positive correlation between G894 T eNOS distribution and Alcohol and Obesity rik factors (P = 0.009 and 0.02 respectively). Patients with elevated Cardio Vascular Risk (CVR) carried out the higher frequency of homozygous mutant genotype TT (62.2%) and T mutant allele (77.8%), compared to median and low CVR groups. G894 T eNOS distribution was significantly associated to a high risk of EH occurrence under the GT and TT genotypes (OR [95% CI] = 20.2 [7.7-52.4], P <  0.0001; OR [95% CI] = 332.5 [98.2-1125.4], P <  0.0001 respectively), and the 3 genotypic transmission models (Dominant: OR [95% CI] = 43.2 [17.9-104.09], P <  0.0001; Recessive: OR [95% CI] = 47.7 [18.6-122.3]; P <  0.0001; Additive: OR [95% CI] = 14.02 [9.6-20.45], P <  0.0001).

CONCLUSION

Our study suggests a strong association of G894 T eNOS polymorphism with susceptibility to EH in Morocco. Studies trying to identify contributing genes may be very useful and allow recognizing the vulnerable individuals and classifying patients in subgroups with definite genetic and pathogenic mechanisms to achieve better prevention and therapeutics.

Association of NOS3 gene polymorphisms with essential hypertension in Sudanese patients: a case control study

BACKGROUND

Essential hypertension (EH) is influenced by various environmental and genetic factors. Nitric oxide is important for the functional integrity of the vascular endothelium and is produced in endothelial cells by the enzyme endothelial nitric oxide synthase (eNOS). EH has a strong genetic component, and the NOS3 gene, which encodes eNOS, represents an interesting candidate for contribution to the phenotype. The most clinically relevant polymorphisms in the NOS3 gene are rs1799983 in exon 7 (encoding Glu298Asp), a variable number tandem repeat (VNTR) in intron 4, and rs2070744 (T-786C) in the promoter region. This study aims to investigate the association between these three polymorphisms in the NOS3 gene and EH in Sudanese patients.

METHODS

Hypertensive patients (n = 157) > 18 years of age with established hypertension from various hospitals in Khartoum, and controls (n = 85) > 18 years of age and with blood pressure measurements <140/90, were included in this case control study. Genotypes at the NOS3 variants were determined using TaqMan and polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analyses. Genotype and allele frequencies were compared between the two groups by χ² analysis, and differences were expressed as odds ratios with 95% confidence intervals (CIs). P values <0.05 were considered statistically significant.

RESULTS

The rs2070744 polymorphism in NOS3 was found to be associated with EH in the Sudanese population as the patients group had higher frequency of CC genotype compared with the controls (6.6% vs 6.1%, p = 0.02). Considering a dominant inheritance model, the frequency of TC + CC genotypes in patients was significantly higher than that in the control subjects (52.6% vs 34.1%, respectively; p < 0.01), with an odds ratio (95% CI) of 2.14 (1.23-3.74). In addition, the C allele was more frequent in the patients than the control group (29.6% vs 20%, p = 0.03, OR = 1.84 (1.15-2.93)). The c allele of intron 4 VNTR was reported in >1% of the Sudanese population under study.

CONCLUSION

The results of this study indicated that the rs2070744 polymorphism in NOS3 may be a genetic susceptibility factor for EH in the Sudanese population. The c allele of intron 4 VNTR is not rare in the Sudanese population.

Association Between the Polymorphism of Glu298Asp in Exon 7 of the eNOS Gene With Foot Ulcer and Oxidative Stress in Adult Patients With Type 2 Diabetes

OBJECTIVES

Diabetic foot ulcer (DFU) is a common and major manifestation in patients with diabetes. Oxidative stress (OS) plays an important role in diabetic complications, such as DFU. Nitric oxide deficiency contributes to the impairment of diabetic wound healing. The aim of this study was to examine the association between the eNOS Glu298Asp polymorphism and DFU and oxidative stress in patients with type 2 diabetes mellitus in an Iranian population.

METHODS

In this case-control study, 123 patients with type 2 diabetes and DFU and 134 patients without DFU were recruited. The genotypes of eNOS Glu298Asp polymorphism in exon 7 were determined by the polymerase chain reaction-restriction fragment length polymorphism analysis. We measured the levels of thiobarbituric reactive substances and ferric-reducing ability of plasma as the potential markers of OS.

RESULTS

There were significant differences in genotype frequencies of eNOS Glu298Asp polymorphism between case and control groups (GG+TG vs. TT; p=0.002; OR=0.22, 95% CI 0.83 to 0.62). Also, the frequency of the T allele in cases was less common than in controls (p=0.004). There was no significant difference in levels of OS parameters and various genotypes (p>0.05).

CONCLUSIONS

These results imply that the T allele might be protective against DFU.

Genome-wide study of resistant hypertension identified from electronic health records

Resistant hypertension is defined as high blood pressure that remains above treatment goals in spite of the concurrent use of three antihypertensive agents from different classes. Despite the important health consequences of resistant hypertension, few studies of resistant hypertension have been conducted. To perform a genome-wide association study for resistant hypertension, we defined and identified cases of resistant hypertension and hypertensives with treated, controlled hypertension among >47,500 adults residing in the US linked to electronic health records (EHRs) and genotyped as part of the electronic MEdical Records & GEnomics (eMERGE) Network. Electronic selection logic using billing codes, laboratory values, text queries, and medication records was used to identify resistant hypertension cases and controls at each site, and a total of 3,006 cases of resistant hypertension and 876 controlled hypertensives were identified among eMERGE Phase I and II sites. After imputation and quality control, a total of 2,530,150 SNPs were tested for an association among 2,830 multi-ethnic cases of resistant hypertension and 876 controlled hypertensives. No test of association was genome-wide significant in the full dataset or in the dataset limited to European American cases (n = 1,719) and controls (n = 708). The most significant finding was CLNK rs13144136 at p = 1.00x10^-6 (odds ratio = 0.68; 95% CI = 0.58–0.80) in the full dataset with similar results in the European American only dataset. We also examined whether SNPs known to influence blood pressure or hypertension also influenced resistant hypertension. None was significant after correction for multiple testing. These data highlight both the difficulties and the potential utility of EHR-linked genomic data to study clinically-relevant traits such as resistant hypertension.

Endothelial Nitric Oxide Synthase G894T Polymorphism Associates with Disease Severity in Puumala Hantavirus Infection

Introduction

Hantavirus infections are characterized by both activation and dysfunction of the endothelial cells. The underlying mechanisms of the disease pathogenesis are not fully understood. Here we tested the hypothesis whether the polymorphisms of endothelial nitric oxide synthase, eNOS G894T, and inducible nitric oxide synthase, iNOS G2087A, are associated with the severity of acute Puumala hantavirus (PUUV) infection.

Patients and Methods

Hospitalized patients (n = 172) with serologically verified PUUV infection were examined. Clinical and laboratory variables reflecting disease severity were determined. The polymorphisms of eNOS G894T (Glu298Asp, rs1799983) and iNOS G2087A (Ser608Leu, rs2297518) were genotyped.

Results

The rare eNOS G894T genotype was associated with the severity of acute kidney injury (AKI). The non-carriers of G-allele (TT-homozygotes) had higher maximum level of serum creatinine than the carriers of G-allele (GT-heterozygotes and GG-homozygotes; median 326, range 102–1041 vs. median 175, range 51–1499 μmol/l; p = 0.018, respectively). The length of hospital stay was longer in the non-carriers of G-allele than in G-allele carriers (median 8, range 3–14 vs. median 6, range 2–15 days; p = 0.032). The rare A-allele carriers (i.e. AA-homozygotes and GA-heterozygotes) of iNOS G2087A had lower minimum systolic and diastolic blood pressure than the non-carriers of A-allele (median 110, range 74–170 vs.116, range 86–162 mmHg, p = 0.019, and median 68, range 40–90 vs. 72, range 48–100 mmHg; p = 0.003, respectively).

Conclusions

Patients with the TT-homozygous genotype of eNOS G894T had more severe PUUV-induced AKI than the other genotypes. The eNOS G894T polymorphism may play role in the endothelial dysfunction observed during acute PUUV infection.

Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms

Nitric oxide (NO) is an important vasodilator with a well-established role in cardiovascular homeostasis. While mediator is synthesized from L-arginine by neuronal, endothelial, and inducible nitric oxide synthases (NOS1,NOS3 and NOS2 respectively), NOS3 is the most important isoform for NO formation in the cardiovascular system. NOS3 is a dimeric enzyme whose expression and activity are regulated at transcriptional, posttranscriptional,and posttranslational levels. The NOS3 gene, which encodes NOS3, exhibits a number of polymorphic sites including single nucleotide polymorphisms (SNPs), variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions. Some NOS3 polymorphisms show functional effects on NOS3 expression or activity, thereby affecting NO formation. Interestingly, many studies have evaluated the effects of functional NOS3 polymorphisms on disease susceptibility and drug responses. Moreover, some studies have investigated how NOS3 haplotypes may impact endogenous NO formation and disease susceptibility. In this article,we carried out a comprehensive review to provide a basic understanding of biochemical mechanisms involved in NOS3 regulation and how genetic variations in NOS3 may translate into relevant clinical and pharmacogenetic implications.

eNOS polymorphisms as predictors of efficacy of bevacizumab-based chemotherapy in metastatic colorectal cancer: data from a randomized clinical trial

BACKGROUND

Bevacizumab plus chemotherapy is a widely used therapeutic option for first-line treatment of metastatic colorectal cancer (mCRC). However, molecular predictors of bevacizumab efficacy have not yet been identified. We analyzed vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) polymorphisms in relation to response to bevacizumab.

METHODS

Two hundred and thirty-seven patients with mCRC enrolled onto the phase III prospective multicentre randomized "Italian Trial in Advanced Colorectal Cancer (ITACa)" trial were evaluated. One hundred fourteen patients received chemotherapy plus bevacizumab (CT + B) and 123 received chemotherapy (CT) alone. Five single nucleotide polymorphisms (SNPs) (-2578, -1498, -1154, -634 and +936) for VEGF and 2 SNPs (-786, +894) and one variable number tandem repeat in intron 4 for eNOS were analyzed for each patient. The polymorphisms were assessed in relation to progression-free survival (PFS), objective response rate (ORR) and overall survival (OS).

RESULTS

VEGF 936C/T, eNOS +894 G/T and VNTR were significantly correlated with outcome in CT + B patients, but not in CT-only patients. In particular, patients with a specific haplotype combination of the 2 eNOS polymorphisms (defined eNOS Haplo1/Haplo1 and eNOS Haplo 2/Haplo2) showed significantly longer PFS (15.0 vs 9.1 months, P = 0.001) and OS (34.5 vs 20.5 months P = 0.002), and a higher ORR (71 vs 45.9%, P = 0.013) than those with the other genotypes, respectively.

CONCLUSIONS

Specific eNOS polymorphisms may be capable of identifying a subset of mCRC patients who are more responsive to bevacizumab-based chemotherapy. If confirmed, these results would permit individually tailored treatment with bevacizumab.

Nitric oxide synthase (NOS) single nucleotide polymorphisms are associated with coronary heart disease and hypertension in the INTERGENE study

OBJECTIVE

Nitric oxide synthase (NOS) exists in three distinct isoforms, each encoded by a specific gene: neuronal NOS (NOS1 gene), inducible NOS (NOS2 gene) and endothelial NOS (NOS3 gene). Single nucleotide polymorphisms (SNPs) in NOS genes have been associated with cardiovascular pathology. We aimed to comprehensively investigate which NOS gene variants are most strongly associated with coronary heart disease (CHD) and hypertension, using a set of tagging SNPs with good coverage across the 3 genes.

METHOD AND RESULTS

CHD cases (n=560) and randomly selected population controls (n=2791) were genotyped at 58 SNPs in the NOS genes. Control individuals with systolic blood pressure ≥140, diastolic blood pressure ≥90 or on antihypertensive medication were defined as hypertensive. A structured stepwise logistic regression approach was used to select the SNPs most strongly associated with CHD and hypertension. NOS1 SNP rs3782218 showed the most consistent association with both phenotypes, odds ratio 0.59 (95% confidence interval 0.44-0.80) and 0.81 (0.67-0.97) per T-allele for CHD and hypertension respectively. For CHD, another NOS1 SNP (rs2682826) and a NOS3 SNP (rs1549758) also showed effect. For hypertension associations were seen for additional SNPs including NOS3 SNP rs3918226, previously associated with hypertension in genome-wide association study (GWAS) data.

CONCLUSION

We found a previously unreported association between NOS1 SNP rs3782218 and both CHD and hypertension, and confirmed NOS1 as the most important NOS risk gene for CHD. In contrast, variants in all three NOS genes were seen to be associated with hypertension in the same source population.

Genetic association of rs1800780 (A→G) polymorphism of the eNOS gene with susceptibility to essential hypertension in a Chinese Han population

To investigate the association of eNOS gene polymorphism with essential hypertension in the Chinese Han population, we examined polymorphisms of the rs2070744 (T→C), rs1800780 (A→G), and rs3918181 (A→G) loci. The results demonstrated that the genotypic frequency at the rs1800780 (A→G) locus was significantly different between patients with essential hypertension and the control cohorts (P < 0.05); while genotypic frequencies and allelic frequencies at rs2070744 (T→C) and rs3918181 (A→G) loci had no statistical difference between the patient group and controls (P > 0.05). In addition, haplotype analysis found a statistically significant difference for haplotype TGA, with OR (95% CI) of 1.549 (1.116-2.150) (P < 0.05). These findings suggest that polymorphism of rs1800780 (A→G) in the eNOS gene may be one of the most important genetic factors associated with essential hypertension susceptibility, and those who have haplotype TGA may be at risk to develop essential hypertension.

Adrenoreceptors and nitric oxide in the cardiovascular system

Nitric Oxide (NO) is a small molecule that continues to attract much attention from the scientific community. Since its discovery, it has been evident that NO has a crucial role in the modulation of vascular tone. Moreover, NO is involved in multiple signal transduction pathways thus contributing to the regulation of many cellular functions. NO effects can be either dependent or independent on cGMP, and rely also upon several mechanisms such as the amount of NO, the compartmentalization of the enzymes responsible for its biosynthesis (NOS), and the local redox conditions. Several evidences highlighted the correlation among adrenoreceptors activity, vascular redox status and NO bioavailability. It was suggested a possible crosstalk between NO and oxidative stress hallmarks in the endothelium function and adaptation, and in sympathetic vasoconstriction control. Adrenergic vasoconstriction is a balance between a direct vasoconstrictive effect on smooth muscle and an indirect vasorelaxant action caused by α₂- and β-adrenergic endothelial receptor-triggered NO release. An increased oxidative stress and a reduction of NO bioavailability shifts this equilibrium causing the enhanced vascular adrenergic responsiveness observed in hypertension. The activity of NOS contributes to manage the adrenergic pathway, thus supporting the idea that the endothelium might control or facilitate β-adrenergic effects on the vessels and the polymorphic variants in β₂-receptors and NOS isoforms could influence aging, some pathological conditions and individual responses to drugs. This seems to be dependent, almost in part, on differences in the control of vascular tone exerted by NO. Given its involvement in such important mechanisms, the NO pathway is implicated in aging process and in both cardiovascular and non-cardiovascular conditions. Thus, it is essential to pinpoint NO involvement in the regulation of vascular tone for the effective clinical/therapeutic management of cardiovascular diseases (CVD).

Functional variants of eNOS and iNOS genes have no relationship to the portal hypertension in patients with liver cirrhosis

OBJECTIVE

Nitric oxide is an important vasoactive mediator. Changes in NO production, caused by functional variants of both endothelial and inducible NO synthase (eNOS, iNOS), might play a role in portal hypertension. The aim was to study the significance of functional eNOS and iNOS gene variants in cirrhotic patients and their interrelationship to both inflammatory and endothelial activation parameters.

MATERIAL AND METHODS

One hundred and thirty-two patients with liver cirrhosis (age 36-72 years) and 101 controls were examined for functional variants of eNOS (E298D, 27bpintr4, 786T/C) and iNOS (R221W, S608L) genes. Inflammatory (IL6, IL8, IL10) and vasoactive (sVCAM-1, E-selectin) cytokines were measured using ELISA kits.

RESULTS

The frequency of E298D (GG 12%, GT 41%, TT 47%), 28bpintr4 (AA 6%, AB 28%, BB 66%), 786T/C genotypes (CC 17%, CT 45%, TT 38%), as well as R221W (CC 93%, CT 7%, TT 0%), and S608L (CC 65%, CT 32%, TT 3%) genotypes in cirrhotic patients did not differ from the controls (p > 0.05 for all comparisons). No relationship was found between the frequency of these genotypes and the severity of portal hypertension, or either inflammatory or vasoactive cytokines. A positive correlation was found between hepatic venous pressure gradient and cytokine concentration: sVCAM-1, IL6, IL8, IL10.

CONCLUSIONS

Examined eNOS and iNOS variants have no relationship to pathogenesis of liver cirrhosis. Severity of portal hypertension was associated with the changes in endothelial activation.

Glu298Asp Endothelial Nitric Oxide Synthase Polymorphism Is a Risk Factor for Erectile Dysfunction in the Mexican Mestizo Population

Penile erection depends on the balanced action between antagonist vasoactive molecules such as nitric oxide (NO) and angiotensin. Endothelial nitric oxide synthase (eNOS) and angiotensin-converting enzyme (ACE) polymorphisms have been associated with endothelial dysfunction, which is described as a cause of erectile dysfunction (ED). Endothelial NOS and ACE are both regulators of vascular and corporal smooth muscle tone, which are connected by interaction between the NO-cyclic guanosine monophosphate pathway and the renin-angiotensin system. We analyzed the frequencies of 894 G/T (Glu298Asp) eNOS and ACE I/D polymorphisms in Mexican patients with ED (n=53) and in an age-matched control group (n=62). The populations analyzed were in Hardy Weinberg equilibrium. We found significant differences in allelic (chi2=4.42; P=.03) and genotypic frequencies (chi2=3.96; P=.04) between patients and controls for the 894 G/T eNOS polymorphism. Presence of the 894T allele in carriers increased the risk of ED (odds ratio [TT + GT versus GG] = 2.37; 95% confidence interval, 1.08 to 5.21; P=.02). Multiple logistic regression analysis showed that the Glu298Asp polymorphism was an independent factor for ED, as was diabetes mellitus, hypertension, cardiac disease, and cigarette smoking. No association was found between ACE I/D polymorphism and ED in the population studied. Therefore, our results suggest that Glu298Asp eNOS polymorphism plays a role as a genetic susceptibility factor for ED.

ACE I/D and eNOS E298D gene polymorphisms in Saudi subjects with hypertension

BACKGROUND

Hypertension has a multifactorial background based on genetic and environmental interactive factors.

OBJECTIVES

We aimed to test for the association of the angiotensin-converting enzyme (ACE) and endothelial nitric oxide synthase (eNOS) gene polymorphisms with hypertension.

SUBJECTS AND METHODS

Participants included 120 Saudi patients with hypertension and 250 normal healthy controls. For all participants, DNA was processed for characterization of ACE I/D and eNOS E298D gene polymorphisms.

RESULTS

Hypertensive cases showed a significantly higher frequency of the ACE mutant D allele carriage (98.3% vs. 92.4%, p = 0.028, OR = 4.8). Cases with hypertension associated with diabetes and obesity showed 100% mutant D allele carriage. Regarding the eNOS E298D polymorphism, the frequency of the mutant D allele carriage was only observed to be higher among cases with hypertension associated with diabetes and obesity, in comparison with controls, yet not reaching statistical significance (41.2% vs. 34%, p > 0.05).

CONCLUSIONS

There is increased frequency of ACE and eNOS mutant allele carriage among Saudi patients affected with hypertension, particularly if accompanied by obesity and diabetes.

The interaction of AGT and NOS3 gene polymorphisms with conventional risk factors increases predisposition to hypertension

Renin-angiotensin and kallikrein-kinin systems are interconnected, regulating blood pressure homeostasis. We have demonstrated the interactions among polymorphisms of the angiotensinogen (AGT) and endothelial nitric oxide synthase (NOS3) genes and conventional risk factors affecting the hypertension occurrence. Individuals were recruited (n=192) and classified into hypertensive (HG; n=140) and normotensive (NG; n=52) groups. The genotypic distribution of the Met235Thr (AGT) and Glu298Asp (NOS3) polymorphisms demonstrated that both are independent risk factors of hypertension (p=0.02 and p=0.008, respectively). The concomitant presence of these polymorphisms in the HG group was significantly different (p=0.001) from the NG. Both gene polymorphisms presented an additive effect for the unfavourable alleles T and A, respectively, and 95% of the double mutant homozygotes were classified into the HG. Specific interactions among certain conventional factors and the presence of at least one unfavourable allele presented significant odds towards hypertension. Blood pressure homeostasis was affected by genetic polymorphisms conditioned by the T and A alleles of the AGT and NOS3 genes, respectively, which acted independently. However, their interaction with smoking, sedentariness, age and total cholesterol may have increased the predisposition to hypertension, which may explain most of the hypertension cases.

Pharmacogenetic association of NOS3 variants with cardiovascular disease in patients with hypertension: the GenHAT study

Nitric oxide synthase 3 (NOS3) catalyzes production of NO in the endothelium and may play a role in cardiovascular disease (CVD). We assessed the pharmacogenetic associations of three NOS3 polymorphisms and three antihypertensive drugs with CVD outcomes. Hypertensive subjects (n = 30,280) from a multi-center, double-blind clinical trial were randomized to chlorthalidone, amlodipine, or lisinopril treatment (mean follow up, 4.9 years). Outcomes included coronary heart disease (CHD: fatal CHD and nonfatal myocardial infarction); stroke; heart failure (fatal, requiring hospitalization, or outpatient treatment); all-cause mortality; and end-stage renal disease (ESRD). Main effects of NOS3 variants on outcome and genotype-treatment interactions were tested. For NOS3 −690 C>T (rs3918226), a higher hazard ratio (HR) was found in minor allele carriers for CHD (CC = 1.00, CT+TT = 1.12 (95% confidence interval (CI) = 1.00–1.26), P = 0.048). For NOS3 −922 A>G (rs1800779), a higher HR was found in minor allele carriers for heart failure (AA = 1.00, AG+GG = 1.10 (CI = 1.00–1.21), P = 0.046). Significant pharmacogenetic findings were observed for stroke and all-cause mortality. For −690 C>T, a lower HR was observed for stroke in minor allele carriers when treated with amlodipine versus lisinopril (CC = 0.85 (CI = 0.73–0.99), CT+TT = 0.49 (CI = 0.31–0.80), P = 0.04). For glu298asp G>T (rs1799983), a lower HR was observed for all-cause mortality in minor allele carriers when treated with amlodipine versus lisinopril (GG = 1.01 (CI = 0.91–1.13), GT+TT = 0.85 (CI = 0.75–0.97), P = 0.04). We observed significant associations with NOS3 variants and CHD and heart failure and significant pharmacogenetic effects for stroke and all cause mortality. This suggests that NOS3 variants may potentially provide useful clinical information with respect to treatment decisions in the future.

A Hypertension Gene: Are We There Yet?

Cardiovascular diseases are the leading cause of death worldwide. Essential hypertension is a major risk factor for the development of other cardiovascular diseases and is caused by a combination of environmental and genetic factors, with up to 50% of blood pressure variance currently attributed to an individual's genetic makeup. By studying genes that cause monogenic forms of hypertension and pathways relevant to blood pressure control, a number of polymorphisms have been identified that increase an individual's risk of developing high blood pressure. We report on candidate gene association studies and genome-wide association studies that have been performed to date in the field of hypertension research. It is becoming clear that for the majority of people there is no single gene polymorphism that causes hypertension, but rather a number of common genetic variants, each having a small effect. Using pharmacogenomics to personalize the treatment of hypertension holds promise for achieving and sustaining normotensive pressures quickly, while minimizing the risk of adverse reactions and unwanted side-effects. This will decrease the risk of stroke and myocardial infarction in individuals and lead to a reduced burden of disease upon society as a whole.

Association of pregnancy-associated plasma protein A polymorphism with preeclampsia - a pilot study

OBJECTIVES

The aim of the study was to investigate genetic and biochemical background of PAPP-A (pregnancy-associated plasma protein A) in patients with risk pregnancies.

DESIGN AND METHODS

Five PAPP-A gene polymorphisms and PAPP-A maternal serum levels were studied together in 165 women in third trimester pregnancies complicated with threatening preterm labor (n=98), preeclampsia (n=35), intrauterine growth restriction (n=34) and ICP (intrahepatic cholestasis of pregnancy) (n=15). 114 healthy pregnant women served as controls.

RESULTS

Preeclamptic patients had significantly higher frequency of TT genotype of Cys327Cys polymorphism compared to controls (p<0.01). Patients with ICP had increased serum levels of PAPP-A compared to controls and correlation analysis showed significant relationship between PAPP-A and CRP (C-reactive protein) in the patients with intrauterine growth restriction (r=0.49, p=0.007).

CONCLUSION

Our study indicates the association of TT genotype of Cys327Cys polymorphism of the PAPP-A gene with preeclampsia. However, further study with larger groups of preeclamptic patients is needed to confirm our results.

An updated meta-analysis of endothelial nitric oxide synthase gene: three well-characterized polymorphisms with hypertension

Background

Numerous individually underpowered association studies have been conducted on endothelial nitric oxide synthase (eNOS) genetic variants across different ethnic populations, however, the results are often irreproducible. We therefore aimed to meta-analyze three eNOS widely-evaluated polymorphisms, G894T (rs1799983) in exon 7, 4b/a in intron 4, and T−786C (rs2070744) in promoter region, in association with hypertension from both English and Chinese publications, while addressing between-study heterogeneity and publication bias.

Methods

Data were analyzed using Stata software (version 11.0), and random-effects model was applied irrespective of between-study heterogeneity, which was evaluated by subgroup and meta-regression analyses. Publication bias was weighed using the Egger's test and funnel plot.

Results

There were total 19284/26003 cases/controls for G894T, and 6890/6858 for 4b/a, and 5346/6392 for T−786C polymorphism. Overall comparison of allele 894T with 894G in all study populations yielded a 16% increased risk for hypertension (odds ratio [OR] = 1.16; 95% confidence interval [95% CI]: 1.07–1.27; P = 0.001), and particularly a 32% increased risk (95% CI: 1.16–1.52; P<0.0005) in Asians and a 40% increased risk (95% CI: 1.19–1.65; P<0.0005) in Chinese. Further subgroup analyses suggested that published languages accounted for the heterogeneity for G894T polymorphism. The overall OR of allele 4a versus 4b was 1.29 (95% CI: 1.13–1.46; P<0.0005) in all study populations, and this estimate was potentiated in Asians (OR = 1.42; 95% CI: 1.16–1.72; P<0.0005). For T−786C, ethnicity-stratified analyses suggested a significantly increased risk for −786C allele (OR = 1.25; 95% CI: 1.06–1.47; P = 0.007) and −786CC genotype (OR = 1.69; 95% CI: 1.20–2.38; P = 0.003) in Whites. As an aside, the aforementioned risk estimates reached significance after Bonferroni correction. Finally, meta-regression analysis on other study-level covariates failed to provide any significance for all polymorphisms.

Conclusion

We, via a comprehensive meta-analysis, ascertained the role of eNOS G894T and 4b/a polymorphisms on hypertension in Asians, and T−786C polymorphism in Whites.

Gene variation in resistant hypertension: multilocus analysis of the angiotensin 1-converting enzyme, angiotensinogen, and endothelial nitric oxide synthase genes

Resistant hypertension, a complex multifactorial hypertensive disease, is triggered by genetic and environmental factors and involves multiple physiological pathways. Single genetic variants may not reveal significant associations with resistant hypertension because their effects may be dependent on gene-gene or gene-environment interactions. We examined the interaction of angiotensin I-converting enzyme (ACE), angiotensinogen (AGT), and endothelial nitric oxide synthase (NOS3) polymorphisms with environmental factors (gender, age, body mass index, glycemia, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, estimated glomerular filtration rate, and urinary sodium excretion) in 70 resistant, 80 well-controlled hypertensive patients, and 70 normotensive controls. All subjects were genotyped for ACE insertion/deletion (rs1799752); AGT M235T (rs699), and NOS3 Glu298Asp (rs 1799983). Multifactorial associations were tested using two statistical methods: the traditional parametric method (adjusted logistic regression analysis) and gene-gene and gene-environment interactions evaluated by multifactor dimensionality reduction analyses. While adjusted logistic regression found no significant association between the studied polymorphisms and controlled or resistant hypertension, the multifactor dimensionality reduction analyses showed that carriers of the AGT 235T allele were at increased risk for resistant hypertension, especially if they were older than 50 years. The AGT 235T allele constituted an independent risk factor for resistant hypertension.

An evaluation of inflammatory gene polymorphisms in sibships discordant for premature coronary artery disease: the GRACE-IMMUNE study

BACKGROUND

Inflammatory cytokines play a crucial role in coronary artery disease (CAD). We investigated the association between 48 coding and three non-coding single nucleotide polymorphisms (SNPs) from 35 inflammatory genes and the development of CAD, using a large discordant sibship collection (2699 individuals in 891 families).

METHODS

Family-based association tests (FBAT) and conditional logistic regression (CLR) were applied to single SNPs and haplotypes and, in CLR, traditional risk factors of CAD were adjusted for.

RESULTS

An association was observed between CAD and a common three-locus haplotype in the interleukin one (IL-1) cluster with P = 0.006 in all CAD cases, P = 0.01 in myocardial infarction (MI) cases and P = 0.0002 in young onset CAD cases (<50 years). The estimated odds ratio (OR) per copy of this haplotype is 1.21 (95% confidence interval [95CI] = 1.04 - 1.40) for CAD; 1.30 (95CI = 1.09 - 1.56) for MI and 1.50 (95CI = 1.22 - 1.86) for young onset CAD. When sex, smoking, hypertension and hypercholesterolaemia were adjusted for, the haplotype effect remained nominally significant (P = 0.05) in young onset CAD cases, more so (P = 0.002) when hypercholesterolaemia was excluded. As many as 82% of individuals affected by CAD had hypercholesterolaemia compared to only 29% of those unaffected, making the two phenotypes difficult to separate.

CONCLUSION

Despite the multiple hypotheses tested, the robustness of family design to population confoundings and the consistency with previous findings increase the likelihood of true association. Further investigation using larger data sets is needed in order for this to be confirmed. See the related commentary by Keavney: http://www.biomedcentral.com/1741-7015/8/6.

Association between -T786C NOS3 polymorphism and resistant hypertension: a prospective cohort study

Background

It is estimated that 5% of the hypertensive patients are resistant to conventional antihypertensive therapy. Polymorphisms in the endothelial nitric oxide synthase (NOS3) gene have been associated with high blood pressure levels, but not with resistant hypertension. The aim of the present study was to investigate if the -786T>C and G894T (Glu298Asp) polymorphisms of the NOS3 gene were associated with resistant hypertension.

Methods

A prospective case-control observational study was performed. From a series of 950 consecutive patients followed up during 42 months, 48 patients with resistant hypertension were detected. 232 patients with controlled high blood pressure were also included.

Results

No differences were observed in the distribution of G894T (Glu298Asp) NOS3 genotypes between the resistant hypertension group and the controlled hypertension patients. However, genotype -786CC was more frequent in the group of patients with resistant hypertension (33.3%) than in the group of patients with controlled high blood pressure (17.7%) (p 0.03). Furthermore carriers of allele T (-786TC and -786TT) were more frequent in patients with controlled hypertension (82.3%) than those with resistant hypertension (66.7%) (Multivariate analysis; RR 2.09; 95% CI 1.03–4.24; p 0.004).

Conclusion

Our results indicate that genotype -786CC of the NOS3 gene increase the susceptibility to suffer resistant hypertension, which suggest that resistance to conventional therapy could be determined at the endothelial level.

Endothelial nitric oxide synthase (NOS3) polymorphisms in African Americans with heart failure: results from the A-HeFT trial

BACKGROUND

Genetic heterogeneity at the endothelial nitric oxide synthase (NOS3) locus influences heart failure outcomes. The prevalence of NOS3 variants differs in black and white cohorts, but the impact of these differences is unknown.

METHODS AND RESULTS

Subjects (n = 352) in the Genetic Risk Assessment of Heart Failure (GRAHF) substudy of the African-American Heart Failure Trial were genotyped for NOS3 polymorphisms: -786 T/C promoter, intron 4a/4b, and Glu298Asp and allele frequencies and compared with a white heart failure cohort. The effect of treatment with fixed-dose combination of isosorbide dinitrates and hydralazine (FDC I/H) on event-free survival and composite score (CS) of survival, hospitalization, and quality of life (QoL) was analyzed within genotype subsets. In GRAHF, NOS3 genotype frequencies differed from the white cohort (P < .001). The -786 T allele was associated with lower left ventricular ejection fraction (LVEF) (P = .01), whereas the intron 4a allele was linked to lower diastolic blood pressure and higher LVEF (P = .03). Only the Glu298Asp polymorphism influenced treatment outcome; therapy with FDC I/H improved CS (P = .046) and QoL (P = .03) in the Glu298Glu subset only.

CONCLUSIONS

In black subjects with heart failure, NOS3 genotype influences blood pressure and left ventricular remodeling. The impact of genetic heterogeneity on treatment with FDC I/H requires further study.

Syndromes, disorders and maternal risk factors associated with neural tube defects (VI)

Neural tube defects (NTDs) may be associated with syndromes, disorders, and maternal and fetal risk factors. This article provides a comprehensive review of the syndromes, disorders, and maternal and fetal risk factors associated with NTDs, including maternal fumonisin consumption, periconceptional zinc deficiency, parental occupational exposure and residential proximity to pesticides, lower socioeconomic status, fetal alcohol syndrome, mutations in the VANGL1 gene, human athymic Nude/SCID fetus, and single nucleotide polymorphism in the NOS3 gene. NTDs associated with these syndromes, disorders, and maternal and fetal risk factors are a rare but important cause of NTDs. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders and maternal risk factors may be different from those of nonsyndromic multifactorial NTDs. Perinatal diagnosis of NTDs should alert doctors to the syndromes, disorders, and maternal and fetal risk factors associated with NTDs, and prompt thorough etiologic investigation and genetic counseling.

Association of a 27-bp repeat polymorphism in intron 4 of endothelial constitutive nitric oxide synthase gene with hypertension in a Tunisian population

OBJECTIVES

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) mediates endothelium-dependent vasodilatation and antithrombotic action. Controversial results regarding the association of eNOS gene (NOS3) polymorphisms with hypertension have been reported. In the present study, we examined a possible association between the 27-base pair (bp) repeat polymorphism in intron 4 of the NOS3 gene and hypertension in a sample of the Tunisian population.

DESIGN AND METHODS

A total of 295 Tunisian patients with hypertension and 395 healthy controls were included in the study. The NOS3 gene intron 4a4b variable number of tandem repeats polymorphism was analyzed by PCR.

RESULTS

A significant differences in genotype distribution and allele frequency was observed between patients and controls. Patients with hypertension had a frequency of 6.4% for the 4a4a genotype, 32.7% for the 4a4b genotype and 60.9% for the 4b4b genotype. The controls had a frequency of only 2.3% for the 4a4a genotype, 28.4% for the 4a4b genotype and 69.4% for the 4b4b genotype (chi(2)=11.81, p=0.003). The hypertension patient group showed a significant higher frequency of the 4a allele compared to the controls (0.23 vs. 0.16; chi(2)=8.61, p=0.003). The odds ratio of hypertension for 4a vs 4b allele frequencies was statistically significant 1.66 [1.09-2.53] at 95% CI, p=0.01 in males, whereas it was non-significant in females (1.23 [0.84-1.81], p=0.26).

CONCLUSION

The present study showed a significant and independent association between the NOS34a4b gene polymorphism (presence of 4a allele) and hypertension in the Tunisian population.

Severity of metabolic syndrome unfavorably influences oxidative stress and fatty acid metabolism in men

Metabolic syndrome (MS) is defined by the clustering of several components (MSC), which include abdominal fat accumulation, impaired glucose homeostasis, hypertriglyceridemia, lowered high-density lipoprotein cholesterol, increased blood pressure, and hyperuricemia. Metabolic syndrome is also accompanied by increased oxidative stress and inflammation as well as by altered composition of esterified fatty acids (FA). Therefore, we have investigated 210 men (categorized into six groups with increasing number of MSC) to find trends in the extent of oxidative stress, FA pattern and frequency of pathological alleles of the selected candidate genes for lipid metabolism. Increasing number of MSC was connected with the raised serum glucose and insulin, increased concentrations of conjugated dienes in low-density lipoprotein (all p < 0.0001), and high frequency of e2 and e4 alleles of the apolipoprotein E gene (p < 0.005). However, the last significance was lost after the adjustment for age. The incidence of 54Thr allele for intestinal isoform of the fatty acid-binding protein (FABP-2) gene was comparable in all groups. The most important findings were the raised content of saturated FA and the increased activities of Delta9 and Delta6 desaturases (all p < 0.0001), and the decreased content of polyunsaturated FA n-6 family and the decreased activity of Delta5 desaturase (both p < 0.001) in connection with increasing number of MSC. In conclusion, the severity of MS is connected with the progression of oxidative stress and the unfavorable changes in the FA composition. These changes are independent of the studied gene polymorphisms.

Pharmacogenomics and antihypertensive drugs: a path toward personalized medicine

Pharmacogenomics focuses on genes and the transcriptome and proteome. It has the potential to enhance healthcare management by improving disease diagnosis and implementing treatments adapted to each patient. Previously, pharmacogenetics of candidate genes focused on clinical research. It is now extended by using genome-wide approaches to elucidate the inherited basis of differences between individuals in their response to drugs. We summarize relevant polymorphisms of genes involved in the pharmacokinetics and pharmacodynamics of antihypertensive drugs and we give an overview of the state of pharmacogenomic research in hypertension medicine. Even if things are getting better, current pharmacogenetic studies still lack power, adequate selection of candidate genes and knowledge of their functions at the physiological level. Finally, some specific end point phenotypes (i.e., peptides or proteins related to the metabolic cycle targeted by the drug) should be integrated to propose data that are easily applicable to personalized medicine.

Endothelial nitric oxide synthase haplotypes are related to blood pressure elevation, but not to resistance to antihypertensive drug therapy

OBJECTIVES

Most hypertensive patients require two or more drugs to control arterial blood pressure effectively. Although endothelial nitric oxide synthase (eNOS) haplotypes have been associated with hypertension, it is unknown whether eNOS genotypes/haplotypes are associated with resistance to antihypertensive therapy.

METHODS

We studied the distribution of three eNOS genetic polymorphisms: single nucleotide polymorphisms in the promoter region (T(-786)C), and in exon 7 (Glu298Asp), and a variable number of tandem repeats in intron 4 (b/a). Genotypes were determined for 111 normotensive controls (NT), 116 hypertensive individuals who were well controlled (HT), and 100 hypertensive individuals who were resistant to conventional antihypertensive therapy (RHT). We also compared the distribution of eNOS haplotypes in the three groups of subjects.

RESULTS

No differences were found in genotype or allele distribution among the three groups (all P > 0.05). Conversely, the 'C Glu b' haplotype was more commonly found in the NT than in the HT or RHT groups (21 versus 8 and 7%, respectively; both P < 0.00625). In addition, the 'C Asp b' haplotype was more commonly found in the HT or RHT groups than in the NT group (22 and 20%, respectively, versus 8%; both P < 0.00625). The distribution of eNOS haplotypes was not significantly different in the HT and RHT groups (P > 0.05).

CONCLUSIONS

Whereas our findings suggest a protective effect for the 'C Glu b' haplotype against hypertension and that the 'C Asp b' haplotype increases the susceptibility to hypertension, our results suggest that eNOS haplotypes are not associated with resistance to antihypertensive therapy.

Endothelial nitric oxide synthase (Glu298Asp) polymorphism is an independent risk factor for migraine with aura

OBJECTIVE

The aim of the present study was to evaluate whether the functional endothelial nitric oxide synthase (eNOS) Glu298Asp polymorphism, which has been demonstrated to decrease the endothelial NOS activity, might be a risk factor for migraine.

BACKGROUND

It has widely demonstrated that nitric oxide (NO) is involved in migraine pathogenesis. Several genetic risk factors have been associated with migraine, but no study has unraveled a possible relationship between migraine and eNOS Glu298Asp. Methods.-One hundred fifty-six migraine patients and 125 healthy nonheadache volunteers entered the study. Demographic and clinical characteristics were carefully recorded, and a neurological workup was performed.

RESULTS

eNOS AspAsp homozygous patients had a 3-fold time risk for migraine with aura (MA) when compared to migraine without aura (MO) patients (OR-3.02, 95% CI-1.21 to 7.51), and more than 2-fold time increased risk when compared to control subjects (OR-2.21, 95% CI-1.00 to 5.04). In migraine patients, no difference in age at onset, mean attack's intensity, family history for any of the studied comorbidities, or the presence of comorbidities was found in eNOS AspAsp homozygous compared to eNOS GluGlu or eNOS GluAs carriers.

CONCLUSIONS

Homozygous Asp298, a common variant of the eNOS gene, is an independent risk factor for MA in this study population.

A direct assessment of genetic contribution to the incidence of coronary infarct in the general population Greek EPIC cohort

To estimate the fraction of the incidence of coronary infarct attributable to the combined action of common genetic polymorphisms likely to be related to this condition, we conducted a case-control study nested within the Greek component of the European Prospective Investigation into Cancer and Nutrition. A total of 202 cases with a new, medically confirmed coronary infarct and 197 controls who had not developed an infarct by the time the corresponding case was diagnosed, were identified. A simple a priori score, relying on a total of 11 genetic polymorphisms was developed. Each polymorphism contributed 1 unit if the subject was homozygous for the high-risk allele, 0.5 units if the subject was heterozygous and 0 units if the subject was homozygous for the low-risk allele. Cases were over-represented in the presumed high genetic risk score values (chi square for trend = 10.18; p = 0.0014). The odds ratio to develop coronary infarct was 1.55 (95% confidence interval: 1.02-2.37) for score > or = 3.0, and 2.02 (1.31-3.11) for score > or = 3.5. In both instances the population fraction of the disease attributable to genetic predisposition exceeded 22%. Assuming a prior probability of at least 0.10 for the score to be predictive of coronary infarct risk, our findings are more likely than not to be truly positive. Our results, based on a simple score integrating the additive impact of 11 genetic polymorphisms, indicate that genetic predisposition accounts for a considerable fraction of the incidence of coronary infarct in the community.

Endothelial nitric oxide synthase gene polymorphisms and cardiovascular disease: a HuGE review

This review examines the association of a subset of endothelial nitric oxide synthase gene (NOS3) polymorphisms (Glu298Asp, intron 4, and -786T>C) with cardiovascular disease. The Glu298Asp polymorphism within exon 7 is the only common nonsynonymous variant. The variants have been associated with low plasma nitric oxide concentrations and reduced vascular reactivity; difficulties in measuring those phenotypes means that their functional role remains unclear. A large meta-analysis of NOS3 polymorphisms in coronary heart disease revealed per-allele odds ratios of 1.17 (95% confidence interval: 1.07, 1.28) for Glu298Asp, 1.17 (95% confidence interval: 1.07, 1.28) for -786T>C, and 1.12 (95% confidence interval: 1.01, 1.24) for intron 4. However, there was evidence that small studies with more striking results could affect the associations of the Glu298Asp and -786T>C polymorphisms with coronary heart disease. Associations of NOS3 polymorphisms with hypertension, preeclampsia, stroke, and diabetes remain uncertain. To date, no reliable gene-gene or gene-environmental interactions have been described. Use of these variants in predictive testing is unlikely to be useful, although the population attributable fraction could be substantial if the modest associations are causal. The need for large-scale genetic association studies using tagging polymorphisms is warranted to confirm or refute a role of the NOS3 gene in coronary heart disease.

Endothelial NO synthase gene polymorphisms and hypertension: a meta-analysis

Studies investigated the association between endothelial NO synthase gene polymorphisms and hypertension-reported contradicted or nonconclusive results. A meta-analysis of 35 genetic association studies that examined the relation between hypertension and the G894T, 4a/b, T786C, and G23T polymorphisms of the endothelial nitric oxide synthase gene was carried out. Subgroup analysis by ethnicity and potential sources of heterogeneity and bias were explored. The meta-analysis included genotype data on 7779/10 498, 2216/3222, 2491/3913, and 833/587 cases/controls for G894T, 4b/a, T786C, and G23T, respectively. For the 4b/a polymorphism, overall, the heterogeneity between studies was not significant (P=0.82), and the allele b was associated with a 15% decreased risk of hypertension relative to allele a (odds ratio: 0.85; 95% CI: 0.74 to 0.98). Overall and in whites, the recessive model for allele b produced significant results (odds ratios: 0.78; 95% CI: 0.68 to 0.90 and OR: 0.76 95% CI: 0.62 to 0.92, respectively), whereas the dominant model produced nonsignificant results. In studies involved East Asians and blacks, an association was not demonstrated. Regarding the G894T, T768C, and G23T polymorphisms, in no case (ie, overall, in whites, or in East Asians) was a statistically significant association and heterogeneity found. There was no substantial source of bias in the selected studies. In conclusion, there is evidence of association only between 4b/a polymorphism and hypertension; however, studies exploring combinations of the polymorphisms may help us better understand the genetics of hypertension.

Susceptible and protective eNOS haplotypes in hypertensive black and white subjects

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been inconsistently associated with hypertension. This inconsistency may derive from population stratification secondary to ethnic diversity, and consideration limited to only one rather than combinations of polymorphisms. We studied three genetic variations in the eNOS gene: a single nucleotide polymorphism in the promoter region (T-786C), in exon 7 (Glu298Asp), and a variable number of tandem repeats in intron 4 (b/a) of the eNOS gene in hypertensives (112 whites and 91 blacks) and normotensives (113 whites and 87 blacks). In addition, we also examined the association of eNOS gene haplotypes with hypertension in white and black subjects. No differences were observed in the frequencies of genotypes and alleles of the three polymorphisms when white hypertensives and white normotensives were compared, or when black hypertensives and black normotensives were compared (all P>0.05). Conversely, the haplotypes "T Asp b" and "C Glu b" were more common among white (16 and 24%, respectively) and black (17 and 16%, respectively) normotensives than in white (7 and 8%, respectively) and black (4 and 6%, respectively) hypertensives, respectively (all P<0.0039). In addition, the haplotype "C Asp b" was more commonly found in white hypertensives than in white normotensives (P=0.0007). These results suggest a contribution of eNOS haplotypes to the development of hypertension that is obscured when specific eNOS genotypes alone are considered. In addition, our results suggest two eNOS haplotypes associated with a protective effect against hypertension in both ethnic groups, and one eNOS haplotype conferring susceptibility to hypertension in white subjects.

Recent advances in understanding endothelial dysfunction in atherosclerosis

Over the last two decades, it has become evident that decreased bioavailability of endothelial nitric oxide (NO) produced from endothelial NO synthase (eNOS), referred to as endothelial dysfunction, plays a crucial role in the development and progression of atherosclerosis. Much progress has been made in understanding the mechanisms of decreased endothelial NO bioavailability at the levels of regulation of eNOS gene expression, eNOS enzymatic activity and NO inactivation. Initial studies suggest that increasing eNOS gene expression would improve endothelial NO release in the hope of inhibiting the progression of atherosclerosis. Recent experimental studies, however, do not always support this therapeutic concept and show some evidence that overexpression of eNOS in atherosclerosis may be even harmful for the disease progression.Thus, recent research to improve endothelial function in atherosclerosis has focused on regulation of eNOS enzymatic activity and prevention of NO inactivation by oxidative stress. Since the role of oxidative stress in endothelial NO bioavailability has been reviewed in a large number of comprehensive articles, this article focuses on the relevant regulatory mechanisms of eNOS enzymatic activity that are emerging to play a role in endothelial dysfunction in atherosclerosis.

Endothelial nitric oxide synthase haplotypes affect the susceptibility to hypertension in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) and hypertension (HT) commonly coexist. While endothelial nitric oxide synthase (eNOS) haplotypes have been associated with HT, it is unknown whether eNOS genotypes/haplotypes are associated with altered susceptibility to HT in patients with T2DM. We studied the distribution of three eNOS genetic polymorphisms: a single nucleotide polymorphism in the promoter region (T(-786)C), in exon 7 (Glu298Asp), and a variable number of tandem repeats in intron 4(b/a). Genotypes were determined for 102 healthy controls, 119 patients with HT, 66 patients with T2DM, and 113 patients with T2DM+HT. In addition, we also compared the distribution of eNOS haplotypes in the four groups of subjects. No differences were found in genotype and allele distribution among the four groups. Conversely, the haplotypes "C Glu b" and "C Asp b" were, respectively, more and less common in healthy controls than in HT or in T2DM+HT groups (24% versus 6% and 5%, respectively; both P<0.00625; and 8% versus 18% and 18%, respectively; both P<0.00625). Moreover, DM patients presented an overall distribution of eNOS haplotypes that was not different from healthy controls (P>0.05). Additionally, the haplotypes "C Glu b" and "C Asp b" were, respectively, more and less common in T2DM group than in T2DM+HT group (19% versus 5%; and 7% versus 18%, respectively; both P<0.00625). Our findings suggest a protective effect for eNOS haplotype "C Glu b" against the development of hypertension, and that haplotype "C Asp b" increases the susceptibility to hypertension in patients without or with T2DM.

Genetic determinants of blood pressure regulation

Hypertension is a multifactorial disorder that probably results from the inheritance of a number of susceptibility genes and involves multiple environmental determinants. Existing evidence suggests that the genetic contribution to blood pressure variation is about 30-50%. Although a number of candidate genes have been studied in different ethnic populations, results from genetic analysis are still inconsistent and specific causes of hypertension remain unclear. Furthermore, the abundance of data in the literature makes it difficult to piece together the puzzle of hypertension and to define candidate genes involved in the dynamic of blood pressure regulation. In this review, we attempt to highlight the genetic basis of hypertension pathogenesis, focusing on the most important existing genetic variations of candidate genes and their potential role in the development of this disease. Our objective is to review current knowledge and discuss limitations to clinical applications of genotypic information in the diagnosis, evaluation and treatment of hypertension. Finally, some principles of pharmacogenomics are presented here along with future perspectives of hypertension.

Endothelial nitric oxide synthase Glu298Asp gene polymorphism, blood pressure and hypertension in a general population sample

OBJECTIVE

The Glu298Asp (E/D) polymorphism of the endothelial nitric oxide synthase (eNOS) gene has been related to hypertension. Since several studies have produced contradictory results, this issue is still subject to ongoing debate. We investigated the association of the eNOS E298D polymorphism with hypertension and with blood pressure (BP) in a large population-based sample of Caucasian ethnicity.

DESIGN

Cross-sectional study in a random sample of the general population.

METHODS

The eNOS E298D polymorphism was determined by 5'-exonuclease assay among 4219 participants aged 20-79 years of the Study of Health in Pomerania (SHIP).

RESULTS

The percentages of the EE298, ED298 and DD298 genotypes were 49.2, 42.0 and 8.8%, respectively. The D allele frequencies did not differ between the groups of normotensive and hypertensive subjects (29.7 versus 29.9%, P = 0.812). Similarly, no association could be established between E298D genotype and prevalent hypertension, neither for D allele carriership (multivariate odds ratio 0.97, 95% confidence interval 0.83-1.12) nor for DD homozygosity (multivariate odds ratio 1.10, 95% confidence interval 0.84-1.43). Likewise, genotype groups did not differ as to the distribution of systolic (ANCOVA P = 0.917) or diastolic BP values (ANCOVA P = 0.657). Nearly identical results were obtained if the analyses were repeated sex-specifically or if subjects on antihypertensive medication were excluded.

CONCLUSION

In a population-based cohort of Caucasians covering a broad age range, the eNOS E298D polymorphism is neither associated with prevalent hypertension nor with systolic or diastolic BP. These results do not support the hypothesis that the E298D polymorphism contributes to the genetic susceptibility to hypertension.