Endothelial nitric oxide synthase gene Glu298Asp polymorphism and blood pressure, left ventricular mass and carotid artery atherosclerosis in a population-based cohort

Genetic association between eNOS gene polymorphisms and risk of carotid atherosclerosis : A meta-analysis

BACKGROUND

Endothelial nitric oxide synthase (eNOS) has been reported to be involved in the atherosclerotic process. A number of studies have investigated the association between eNOS gene polymorphisms and the risk of carotid atherosclerosis (CAS). However, the results are conflicting and inconclusive. The aim of this study was to evaluate precisely the association between the eNOS T786C, G894T, and 4a/4b polymorphisms and CAS risk.

MATERIAL AND METHODS

A meta-analysis was carried out by retrieving relevant studies from PubMed, Embase, China National Knowledge Infrastructure (CNKI), and Cochrane databases without a restriction on publication year. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to describe the strength of the association with CAS.

RESULTS

Data were obtained from eight case-control studies comprising 2975 cases and 2624 controls. Significant associations were detected between the allelic and recessive models of the eNOS T786C polymorphism (allelic: p = 0.04; OR, 95% CI = 1.57 [1.01, 2.44]; recessive: p = 0.03; OR, 95% CI = 1.53 [1.04, 2.24]), as well as the allelic and dominant models of the eNOS 4a/4b polymorphism, and CAS risk in an Asian subgroup (allelic: p = 0.02; OR, 95% CI = 1.49 [1.07, 2.07]; dominant: p = 0.01; OR, 95% CI = 1.50 [1.09, 2.05]), but not in a Caucasian subgroup (p > 0.05). No association was observed between the eNOS G894T polymorphism and CAS risk (p > 0.05).

CONCLUSION

Our study provides evidence that the allelic and recessive models of the eNOS T786C polymorphism and the allelic and dominant models of the eNOS 4a/4b polymorphism may increase the risk of CAS in Asian populations.

Associations of the NOS3 rs1799983 polymorphism with circulating nitric oxide and lipid levels: a systematic review and meta-analysis

BACKGROUND

Circulating nitric oxide (NO) and lipid levels are closely associated with coronary artery disease (CAD). It is unclear whether the rs1799983 polymorphism in endothelial nitric oxide synthase (NOS3) gene is associated with plasma levels of NO and lipids. This systematic review and meta-analysis (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) aimed to clarify the relationships between the rs1799983 polymorphism and plasma levels of NO and lipids.

METHODS

Sixteen studies (2702 subjects) and 59 studies (14 148 subjects) were identified for the association analyses for NO and lipids, respectively. Mean difference (MD) and 95% CI were used to estimate the effects of the rs1799983 polymorphism on plasma NO and lipid levels. The primary outcome variable was NO, and the secondary outcomes included triglycerides, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C).

RESULTS

Carriers of the T allele had lower levels of NO (MD -0.27 μmol/L, 95% CI -0.42 to -0.12 μmol/L, p<0.001) and HDL-C (MD -0.07 mmol/L, 95% CI -0.14 to -0.00 mmol/L, p=0.04), and higher levels of TC (MD 0.13 mmol/L, 95% CI 0.06 to 0.20 mmol/L, p<0.001) and LDL-C (MD 0.14 mmol/L, 95% CI 0.05 to 0.22 mmol/L, p=0.002) than the non-carriers. Triglyceride levels were comparable between the genotypes.

CONCLUSION

The association between the NOS3 rs1799983 polymorphism and CAD may be partly mediated by abnormal NO and lipid levels caused by the T allele.

The Role of Genetic Polymorphism in the Formation of Arterial Hypertension, Type 2 Diabetes and their Comorbidity

BACKGROUND

Hereditary component plays a significant role in the formation of insulin resistance (IR) - one of the pathogenetic links of arterial hypertension (AH) and type 2 diabetes mellitus (DM2). However, the genetic predisposition to IR can not be realized and does not manifest itself clinically in the absence of appropriate factors of the environment (excessive nutrition, low physical activity, etc.).

OBJECTIVE

The review summarizes the results of studies which describe the contribution of genetic polymorphism to the formation and progression of AH, DM2 and their comorbidity in various populations.

RESULTS

In many studies, it has been established that genetic polymorphism of candidate genes is influenced by the formation, course and complication of AH and DM2. According to research data, the modulating effect of polymorphism of some genetic markers of AH and DM2 on metabolism and hemodynamics has been established. The results of numerous studies have shown a higher frequency of occurrence of AH and DM2, as well as their more severe course with adverse genetic polymorphisms. At the same time, the role of genetic polymorphism in the formation of AH and DM2 differs in different populations.

CONCLUSION

Contradictory data on the influence of gene polymorphisms on the formation of AH and DM2 in different populations, as well as a small number of studies on the combined effects of several polymorphisms on the formation of comorbidity, determine the continuation of research in this direction.

Genetic associations of bradykinin type 2 receptor, alpha-adrenoceptors and endothelial nitric oxide synthase with blood pressure and left ventricular mass in outpatients without overt heart disease

Background

Physiological pathways such as bradykinin, renin-angiotensin, neurohormones and nitric oxide have been shown to play an important role in the regulation of cardiovascular function. Genetic variants of these pathways may impact blood pressure and left ventricular (LV) mass in different populations. To evaluate associations of genetic polymorphisms of bradykinin B2 receptor (BDKRB2), alpha-adrenergic receptors (ADRA) and endothelial nitric oxide synthase (eNOS) on the modulation of the blood pressure and the left ventricular mass.

Methods

We enrolled 758 individuals without overt heart disease. Blood pressure was estimated by auscultatory method during the clinical examination. Left ventricular (LV) mass was assessed by echocardiography. Genotypes for ADRA1A rs1048101, ADRA2A rs553668, ADRA2B rs28365031, eNOS rs2070744, eNOS rs1799983, and BDKRB2 rs5810761 polymorphisms were assessed by high-resolution melting analysis.

Results

BDKRB2 polymorphism rs5810761 was associated with blood pressure. Carriers of DD genotype had higher levels of SBP and DBP than carrier of II genotype (p = 0.013 and p = 0.007, respectively). eNOS polymorphism rs1799983 was associated with DBP. Carriers of GT genotype had lower levels of DBP than carriers of GG genotype (p = 0.018). eNOS polymorphism rs2070744 was associated with LV mass. Carriers of TC genotype had higher LV mass than carriers of TT genotype (p = 0.028).

Conclusions

In a cohort of individuals without overt heart disease, the BDKRB2 rs5810761 polymorphism (DD genotype carriers) were associated higher systolic and diastolic blood pressures, and the eNOS rs1799983 polymorphism (T allele carriers) were associated with lower diastolic blood pressure. The eNOS rs2070744 polymorphism (C allele carriers) was associated with higher left ventricular mass. These data suggest that eNOS and bradykinin receptor genetic variants may be potential markers of common cardiovascular phenotypes.

Association of nitric oxide synthase 3 gene polymorphism with the risk of type 2 diabetes

Type-2 diabetes (T2D) is a multifactorial (environmental and genetic factors) and global epidemic disease with an estimated high prevalence worldwide. Studies have indicated that nitric oxide synthase 3 (NOS3) has several important roles in the pathogenesis of T2D. The present study aims to investigate the association between NOS3 rs1800779(A/G) and T2D in an Iranian sample population. A case-control study was conducted on 250 T2D patients and 250 healthy control subjects (HCs). Genotyping of the rs1800779(A/G) variant was conducted using a Tetra-Amplification Refractory Mutation System polymerase chain reaction. The frequencies of genotypes AA, AG and GG polymorphisms were 56.8, 39.2 and 4% in the T2D group, and 42.8, 56 and 1.2% in the HCs group, respectively. The frequency of the minor (G) allele was 23.6% in the T2D group and 29.2% in the HCs group. The genotype frequencies of the rs1800779(A/G) variant demonstrated statistically significant differences between T2D and controls in a codominant model (AG vs. AA, OR=0.527, 95% CI=0.368-0.756, P<0.001) and dominant model (AG+GG vs. AA, OR=0.569, 95% CI=0.399-0.811, P=0.002). There was no significant association between clinical and demographic characteristics and the NOS3 rs1800779(A/G) polymorphism in dominant status (P>0.05). The dominant model and AG genotype of NOS3 rs1800779(A/G) polymorphism may had a protective effect on T2D of Iranian population.

Roles of Vascular Oxidative Stress and Nitric Oxide in the Pathogenesis of Atherosclerosis

Major reactive oxygen species (ROS)–producing systems in vascular wall include NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase, xanthine oxidase, the mitochondrial electron transport chain, and uncoupled endothelial nitric oxide (NO) synthase. ROS at moderate concentrations have important signaling roles under physiological conditions. Excessive or sustained ROS production, however, when exceeding the available antioxidant defense systems, leads to oxidative stress. Animal studies have provided compelling evidence demonstrating the roles of vascular oxidative stress and NO in atherosclerosis. All established cardiovascular risk factors such as hypercholesterolemia, hypertension, diabetes mellitus, and smoking enhance ROS generation and decrease endothelial NO production. Key molecular events in atherogenesis such as oxidative modification of lipoproteins and phospholipids, endothelial cell activation, and macrophage infiltration/activation are facilitated by vascular oxidative stress and inhibited by endothelial NO. Atherosclerosis develops preferentially in vascular regions with disturbed blood flow (arches, branches, and bifurcations). The fact that these sites are associated with enhanced oxidative stress and reduced endothelial NO production is a further indication for the roles of ROS and NO in atherosclerosis. Therefore, prevention of vascular oxidative stress and improvement of endothelial NO production represent reasonable therapeutic strategies in addition to the treatment of established risk factors (hypercholesterolemia, hypertension, and diabetes mellitus).

Associations of the eNOS G894T gene polymorphism with target organ damage in children with newly diagnosed primary hypertension

BACKGROUND

The endothelial nitric oxide synthase (eNOS) G894T gene polymorphism is associated with the risk of primary hypertension (PH) and vascular complications in adults with PH.

METHODS

We explored the associations of the G894T polymorphism with 24-h ambulatory blood pressure, left ventricular mass (LVM), carotid intima media thickness (cIMT), urinary albumin excretion, oxidative stress and inflammatory parameters in 126 children with newly diagnosed PH and in 83 healthy children.

RESULTS

Among the 126 children with PH 92 (73%) had ambulatory hypertension and 34 (27%) had severe ambulatory hypertension. Left ventricular hypertrophy (LVH) was detected in 39 (31%) patients, cIMT of >2 standard deviation scores in 21 (16.6%) patients, albuminuria of >30 mg/24 h in 18 (14.3%) patients and metabolic syndrome (MS) in 22 (17.5%) patients. The frequency of the T allele was 52.4% in the PH group and 54.2% in the control group (not significant), and in both groups the frequency of the T allele was consistent with the Hardy-Weinberg equilibrium. Compared with G allele carriers, hypertensive T allele carriers had increased cIMT (p < 0.05) and more severe albuminuria (not significant, p = 0.1); there was no difference between the groups in hypertension severity and LVM. T and G allele distribution did not differ between patients with and without metabolic syndrome. No significant correlations between the assessed parameters and the eNOS G894T gene polymorphism were found in the controls, although T allele carriers tended to have an increased cIMT (p = 0.09).

CONCLUSION

The eNOS T allele is not more prevalent among hypertensive children than among healthy ones, but it is associated with early vascular damage in children with PH, independent of metabolic abnormalities. No associations between the eNOS G894T polymorphism and metabolic abnormalities were found.

Association of endothelial nitric oxide synthase gene polymorphisms with classical risk factors in development of premature coronary artery disease

Genetic polymorphism of the endothelial nitric oxide synthase (eNOS) affects the pathogenesis of atherosclerosis and associated with premature coronary artery disease (PCAD). We aimed to explore the association between Glu298Asp polymorphism of the eNOS gene and premature CAD in Egyptians, and the possible interaction between this polymorphism and other risk factors. The study population consisted of 116 patients with PCAD, and 119 controls. Glu298Asp polymorphism (rs1799983) of the eNOS gene was analyzed by polymerase chain reaction (PCR). We found that the TT genotype of the eNOS gene increased the risk of PCAD by 2.6. Hypertension, diabetes, smoking, total cholesterol, triglycerides, LDLc, HDLc and TT genotype of the eNOS gene were independent risk factors for the development of PCAD. We conclude that, the TT genotype of Glu298Asp polymorphism of eNOS gene is an independent risk factor of PCAD in Egyptians. The association of smoking, obesity, dyslipidemia and/or metabolic syndrome with the TT genotype increased the risk of the development of PCAD.

Endothelial nitric oxide synthase gene polymorphism and type 2 diabetic retinopathy among Asian Indians

Endothelial nitric oxide synthase (eNOS) has been shown to play an essential role in retinal vascular function, and disequilibrium in its production can lead to diabetic retinopathy (DR). Genetic polymorphisms of eNOS gene have been suggested to play a role in nitric oxide (NO) abnormalities which may contribute to the development and progression of DR. In view of the variable results that have been reported for the association between eNOS gene polymorphisms and DR, the present study was designed to study the association and interaction between eNOS gene polymorphisms and the development and progression of DR in Asian Indian type 2 diabetes mellitus patients (T2DM). We screened 1,720 T2DM patients, belonging to two independently ascertained cohorts out of which 1,446 were genotyped for three polymorphisms of eNOS (two SNPs: T-786C, G894T and one 27-bp repeat polymorphism in intron 4 (27VNTR)) using validated PCR-RFLP assays. In both the cohorts, consistently lower prevalence and decreased risk of DR was observed in patients with ba, aa and ba + aa genotype of 27VNTR (a/b), C-a-G and C-a-T haplotype (allele of T-786C, 27VNTR a/b and G894T) carrying "C" allele of T-786C and "a" allele of 27VNTR (a/b). Also, mean NO levels in T2DM subjects carrying ba + aa genotype were higher as compared to bb genotype. Our results suggest that eNOS genotypes 27VNTR carrying "aa" genotype is an independent protective factor for DR and is associated with low risk of DR.

Endothelial nitric oxide synthase gene polymorphisms and the risk of acute myocardial infarction in a South Indian population

Myocardial infarction (MI) is a complex multi-factorial, polygenic disorder which results from an interaction between a person's genetic makeup and various environmental factors. Nitric oxide (NO), a potent vasodilator produced by endothelial cells, plays an important role in the regulation of blood pressure, regional blood flow and also inhibits platelet aggregation, vascular smooth muscle cell proliferation and leukocyte adhesion to vascular endothelium. Our aim was to analyze the association of NOS3 (endothelial nitric oxide synthase 3) 894G>T and -786T>C gene polymorphisms and MI risk in the South Indian population. A total of 287 MI patients, 279 risk control patients and 321 healthy controls were recruited for the retrospective study. Genotyping was done using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). There was no significant association observed between NOS3 894G>T, -786T>C polymorphisms and MI. A significant difference was observed in the distribution of GT genotype of the NOS3 894G>T polymorphism between the cases and the risk controls (p = 0.05) but the odds ratio (0.6) did not show risk for MI. The present study showed lack of association between NOS3 gene polymorphisms and MI in South Indian population.

eNOS gene polymorphisms modify the association of PM(10) with oxidative stress

Previous studies have suggested that air pollution increases various health outcomes through oxidative stress and oxidative stress-related genes modify the relationship between air pollution and health outcomes. Therefore, we evaluated the effect of PM(10) on the levels of malondialdehyde (MDA), oxidative stress biomarker, and the effect modification by genetic polymorphisms of eNOS, oxidative stress-related gene, in the 560 Korean elderly. We obtained urine samples repeatedly from participants during five medical examinations between 2008 and 2010 and all ambient air pollutant concentration data from the Korea National Institute of Environmental Research air quality monitoring system. We measured urinary levels of MDA to assess oxidative stress and genotyped eNOS (rs1799983, rs2853796, and rs7830). Mixed-effect model was used to estimate the effect of PM(10) on the level of oxidative stress biomarker and their modification by genotypes. PM(10) showed apparent positive effect on MDA level after adjusting for age, sex, BMI, cotinine level, temperature, dew point, levels of SO(2), O(3), NO(2), and CO, and season (p=0.0133). Moreover, the association of PM(10) with MDA was found only in participants with eNOS GG genotype for rs1799983 (p=0.0107), TT genotype for rs2853796 (p=0.0289), or GT genotype for rs7830 (p=0.0158) and in participants with a set of risky haplotypes (GTT, GTG, GGT, and TGT) (p=0.0093). Our results suggest that PM(10) affect oxidative stress in the elderly and eNOS genotype affect the oxidative stress level in regard of exposure to PM(10).

Association of Endothelial Nitric Oxide Synthase Gene Variant (G894T) With Coronary Artery Disease in Western Iran

There are conflicting reports about the association of endothelial nitric oxide synthase (eNOS) gene polymorphism and the risk of coronary artery disease (CAD). To determine the frequency of eNOS G894T variant and to find the possible association between this polymorphism with CAD we studied 207 unrelated patients with total CAD (with and without diabetes) and 92 controls. The eNOS variants were detected by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP). The presence of GT + TT genotype was associated with 2.1-fold ( P = .006), 2.29-fold ( P = .006), and 1.93-fold ( P = .032) increased risk of CAD in total CAD, CAD with diabetes, and in CAD without diabetes patients, respectively. The presence of T allele of eNOS increased the risk of CAD 2.15-fold ( P = .001). The levels of low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG) tended to be higher in patients carrier for T allele compared to those with G allele. The results of present study revealed that eNOS G894T polymorphism is associated with increased risk of CAD in our population.

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.

Combination of polymorphisms in the beta2-adrenergic receptor and nitric oxide synthase 3 genes increases the risk for hypertension

OBJECTIVE

Hypertension is a major risk factor for cardiovascular disease. Polymorphism in the beta2-adrenergic receptor (ADRB2) and nitric oxide synthase 3 (NOS3) genes is associated with clinical cardiovascular phenotypes. The Arg16Gly and Glu298Asp polymorphisms of ADRB2 and NOS3 genes, respectively, have been reported to be associated with hypertension. We hypothesized that a combination of these two polymorphisms increases the risk for hypertension. Hence, we examined the effect of this combination of single-nucleotide polymorphisms on the risk for hypertension.

METHODS

Our cross-sectional study comprised 402 middle-aged and elderly human participants. We determined the genotypes of Arg16Gly and Glu298Asp single-nucleotide polymorphisms in ADRB2 and NOS3, respectively, by TaqMan PCR method; we also measured the resting blood pressure.

RESULTS

The odds ratio for the presence of hypertension in individuals having the Gly/Gly genotype of ADRB2 compared with those having the other genotypes (Arg/Arg and Arg/Gly) was 2.87. With regard to the Glu298Asp polymorphism in NOS3, the odds ratio for the presence of hypertension in individuals having the Glu/Glu genotype of NOS3 when compared with those having the other genotypes (Asp/Asp and Asp/Glu) was 2.79. Interestingly, the odds ratio was 7.64 for individuals having a combination of the Gly/Gly genotype of ADRB2 and Glu/Glu genotype of NOS3 when compared with those having a combination of Arg/Arg and Arg/Gly genotypes of ADRB2 and Asp/Asp and Asp/Glu genotypes of NOS3.

CONCLUSION

We revealed that a combination of the Arg16Gly and Glu298Asp polymorphisms in ADRB2 and NOS3, respectively, remarkably increased the risk for hypertension in middle-aged and elderly humans.

Lack of association between the Glu298Asp polymorphism of endothelial nitric oxide synthase and slow coronary flow in the Turkish population

BACKGROUND

Coronary endothelial dysfunction plays an important pathogenetic role in patients with slow coronary flow (SCF). No data exist regarding the possible contribution of the Glu298Asp polymorphism genotype of the endothelial nitric oxide synthase (eNOS) gene to human SCF in the literature.

OBJECTIVE

To investigate the association between SCF and the Glu298Asp polymorphism of the eNOS gene.

METHODS

The study population consisted of 85 consecutive patients. The patient group included 66 patients with angiographically proven normal coronary arteries with SCF, and 19 subjects with normal coronary arteries with no SCF. The thrombolysis in myocardial infarction frame count was used for the diagnosis of SCF. The Glu298Asp polymorphism was determined by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

The baseline characteristics were similar between the two groups, except for high-density lipoprotein cholesterol, which was higher in the SCF group than in the controls. The genotype distribution of Glu298Asp was as follows: GG 26%, GT 56% and TT 12%, where G is guanine and T is thymine. There was no difference in the frequency of the various genotypes or the alleles in patients with SCF versus normal controls.

CONCLUSIONS

The Glu298Asp polymorphism genotype of the eNOS gene is not a risk factor for SCF in the present study population.

Polymorphisms of the methylenetetrahydrofolate reductase, vascular endothelial growth factor, endothelial nitric oxide synthase, monocyte chemoattractant protein-1 and apolipoprotein E genes are not associated with carotid intima-media thickness

BACKGROUND

Single nucleotide polymorphisms in the 5,10-methylenetetrahydrofolate reductase (MTHFR), vascular endothelial growth factor (VEGF), endothelial nitric oxide synthase (eNOS), monocyte chemoattractant protein-1 (MCP-1) and apolipoprotein E (ApoE) genes appear to be a genetic risk factor for atherosclerosis. Common carotid intima-media thickness (cIMT) provides information on the severity of atherosclerosis.

OBJECTIVE

To investigate the relationship between cIMT and gene polymorphisms associated with atherosclerosis in Turkish patients with coronary artery disease (CAD).

METHODS

Sixty-two patients with angiographically diagnosed stable CAD were divided into two groups according to their cIMT values (group 1: n=35, cIMT of 1 mm or greater; group 2: n=27, cIMT of less than 1 mm). MTHFR 677 C/T, VEGF --460 C/T, eNOS 894 G/T, MCP-1 --2518 A/G and ApoE (E2, E3 and E4) gene polymorphisms (where A is adenine, C is cytosine, G is guanine and T is thymine) were analyzed by polymerase chain reaction and restriction fragment length polymorphism. Evaluations of cardiovascular risk factors and coronary atherosclerotic lesions were performed in all patients. Serum homocysteine and high-sensitivity C-reactive protein were measured and compared between the two groups.

RESULTS

Serum high-sensitivity C-reactive protein (P=0.04) and homocysteine (P=0.006) levels were higher in group 1 than in group 2. The ratio of multivessel CAD and previous myocardial infarction was significantly higher in group 1 than in group 2 (P=0.014). In the study population, no significant difference in cIMT was observed according to the polymorphisms studied. Only hyperhomocysteinemia (OR 1.17 [95% CI 1.01 to 1.35], P=0.033) and previous myocardial infarction (OR 3.76 [95% CI 1.10 to 12.81], P=0.034) maintained a significant correlation with cIMT on multiple logistic regression analysis.

CONCLUSION

cIMT is increased in patients with hyperhomocysteinemia, inflammation and extended CAD. MTHFR 677 C/T, VEGF --460 C/T, eNOS 894 G/T, MCP-1 --2518 A/G and ApoE single nucleotide polymorphisms were not associated with increased cIMT.

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.

Interaction of G-protein beta3 subunit and nitric oxide synthase gene polymorphisms on carotid artery intima-media thickness in young adults: the Bogalusa Heart Study

BACKGROUND

G-protein beta3 subunit (GNB3) gene C825T and endothelial nitric oxide (eNOS) gene G894T polymorphisms both influence arterial structure and function. However, information is scant regarding the interaction of these genes on arterial wall thickness.

METHODS

This aspect was examined in 654 white and black subjects, aged 25-43 years (72.9% white, 39.3% male). Arterial wall thickness was assessed in terms of the average intima-media thickness (IMT) of common carotid, internal carotid, and carotid bulb segments by B-mode ultrasonography.

RESULTS

Frequencies of T allele of the GNB3 C825T polymorphism (0.718 vs. 0.304, P < 0.0001) and G allele of the eNOS G894T polymorphism (0.868 vs. 0.661, P < 0.0001) were higher in blacks compared to whites. In a multivariate model including gender, age, mean arterial pressure, body mass index, triglycerides/HDL cholesterol ratio, insulin resistance index, smoking, and/or race, there was no significant genotypic effect on carotid IMT with respect to GNB3 C825T or eNOS G894T polymorphisms among whites, blacks, and total sample. However, the carriers of TT genotype of the GNB3 C825T and T allele of the eNOS G894T had a significantly lower carotid IMT among blacks (P = 0.003) and the total sample (P = 0.006).

CONCLUSION

These results indicate that the genetic variations of the eNOS gene in combination with the GNB3 gene jointly influence carotid artery wall thickening process in young adults, especially in blacks.

Endothelial nitric oxide synthase gene polymorphisms and cardiovascular damage in hypertensive subjects: an Italian case-control study

BACKGROUND

Nitric oxide (NO) synthesized by endothelial nitric oxide synthase (eNOS) plays an important role in regulation of endothelial function and in the control of blood pressure. However, the results from some studies on the association between three clinically relevant eNOS gene polymorphisms (G894T, T786C and intron 4b/a) and essential hypertension are unclear. We designed a case-control study to evaluate the influence of eNOS polymorphisms on target organ damage in 127 hypertensives and 67 normotensives. Clinical evaluation, biochemical parameters, Urinary Albumin Excretion (UAE) and echocardiogram were performed to characterize target organ damage. eNOS polymorphism were recognized by PCR method.

RESULTS

The distribution of eNOS genotypes was similar in hypertensives and normotensives but 4aa was present in the 2.5% of hypertensives and completely absent in normotensives. Subjects with 4bb, G894T, and T786C genotypes showed an increased prevalence of target organ damage. Moreover prevalence of G894T and introne 4 variants was significantly higher in hypertensives than in normotensives both with cardiovascular damage. Logistic regression analysis didn't show any association between eNOS polymorphisms, Body Mass Index (BMI), hypertension, gender and cardiovascular damage. Only the age (OR 1.11; IC 95% 1.06-1.18) was predictive of cardiovascular damage in our population.

CONCLUSION

Our results seem to indicate a lack of association with eNOS variants and cardiovascular damage onset.

Endothelial nitric oxide synthase gene haplotypes and diabetic nephropathy among Asian Indians

Endothelial dysfunction plays a key role in the pathogenesis of diabetic vascular disease, including diabetic nephropathy. Endothelial-derived nitric oxide synthase (eNOS) gene polymorphisms affect eNOS activity and are associated with endothelial dysfunction. We evaluated the association of the constitutive endothelial nitric oxide synthase gene (eNOS) polymorphisms with type 2 diabetic nephropathy. We genotyped three polymorphisms of eNOS (Two SNPs: -786T > C, 894G > T and one 27-bp repeat polymorphism in Intron 4 (27VNTR)) in type 2 diabetic nephropathy patients (cases: n = 195) and type 2 diabetic without nephropathy (controls: n = 255), using validated PCR-RFLP assays. We measured serum NO levels in these subjects and examined its correlation with diabetic nephropathy and eNOS genotypes. The frequency of CC (-786T > C), TT (894G > T) and aa genotypes (27VNTR) were significantly higher in diabetic nephropathy patients as compared to the diabetes without nephropathy group (CC: P = 0.003, TT: P = 0.03, aa: P < 0.0001). These mutant genotypes were found to be associated with higher risk of nephropathy (-786T > C: OR: 5.5, 95%CI: 1.53-19.79; 894G > T: OR: 1.8, 95%CI: 1.03-3.16; Intron 4: OR: 6.23, 95%CI: 2.23-16.31). Haplotype with all the wild alleles (T-b-G) was found to be associated with a decreased risk of nephropathy (OR: 0.68, P = 0.005) and haplotype with all mutant alleles (C-a-T) was associated with higher risk of diabetic nephropathy as compared to diabetes without nephropathy group (OR: 2.6, P = 0.14). No significant linkage disequilibria were observed among the variants in this case-control study. The serum NO levels were observed to be significantly (P < 0.05) lower in mutant allele carriers ('C' allele of T-786C SNP and/or 'T' allele of G894T SNP) as compared with the wild-type allele carriers (-786T and/or 894G) within each of the subject groups (with and without nephropathy). These results suggest that the eNOS gene locus is associated with diabetic nephropathy and the functional polymorphisms (-786T > C & 894G > T) might lead to a decreased expression of eNOS gene.

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.

Three endothelial nitric oxide (NOS3) gene polymorphisms in hypertensive and normotensive individuals: meta-analysis of 53 studies reveals evidence of publication bias

BACKGROUND

Studies on the relationship between endothelial nitric oxide (NOS3) gene variants and hypertension have been conflicting. To explore this hypothesis further, we performed a meta-analysis and re-evaluated the relationship between the three most widely studied NOS3 polymorphisms and hypertension status and blood pressure levels.

METHODS

Data on 40,413 subjects from 53 studies were combined in five distinct meta-analyses, and heterogeneity and publication bias were explored.

RESULTS

Heterogeneity was observed in all meta-analyses. By a random-effects model, carriers of the four 27-basepair repeat variable number of tandem repeats in intron 4 were associated with a 28% increase in the risk of hypertension compared with those homozygous for the 5 repeat: odds ratio (OR) 1.28, 95% confidence interval (CI) 1.11-1.47, P=0.001. In Asian individuals, Asp allele carriers displayed a similar association: OR 1.28, 95% CI 1.06-1.54, P=0.01, as well as a 2 mmHg increase in both systolic (P=0.04) and diastolic (P=0.009) blood pressure levels. Furthermore, meta-regression analysis indicated that the effect of the Glu298Asp genotype on the risk of hypertension might be dependent on total cholesterol status. No effect of the T-786C variant on hypertension was detected. There was evidence that such findings might be a result of selectively reporting/publishing positive reports.

CONCLUSION

Our results suggest that current data on the relationship between NOS3 variants and hypertension are subject not only to important heterogeneity but also to publication bias. Future research should preferentially focus on gene-environment interactions as well as haplotype analyses.

Endothelial nitric oxide synthase Glu298Asp gene polymorphism is associated with hypertensive response to exercise in well-controlled hypertensive patients

PURPOSE

Hypertensive response to exercise (HRE) is known to be an adverse prognostic factor for future cardiovascular events and may be associated to endothelial dysfunction. Previous studies regarding endothelial nitric oxide synthase (eNOS) Glu298Asp polymorphism focused upon its relation to hypertension. In this study, we hypothesize that the polymorphism may be associated with inherent difference in endothelial response to exercise.

PATIENTS AND METHODS

Two hundred sixty nine patients who underwent treadmill test were enrolled in this study; 77 patients (mean age 55.8 +/- 9.4 years) had hypertensive response (peak systolic BP of > or = 210 mmHg in men and > or = 190 mmHg in women). Pulse wave velocity (PWV) was measured on 153 patients of them. The Glu298Asp exchange in exon 7 was determined by the methods of single base extension with amplifying primers and probes for TaqMan.

RESULTS

The percentages of the GG, GT and TT genotypes were 81.0, 18.6 and 0.4 %, respectively. The presence of GT or TT genotype was independently associated with prevention of HRE when controlled for age, sex, baseline systolic BP and homeostatic model assessment (HOMA) index (OR=0.35, p=0.016). Subgroup analysis showed that preventive effect for HRE of T allele was significant in females (p < 0.001) and patients without insulin resistance (p=0.009).

CONCLUSION

In our study, eNOS Glu298Asp polymorphism was significantly associated with HRE. This result suggests that the presence of T allele of the Glu298Asp polymorphism may be a favorable factor to in preventing HRE, especially in female and patients without insulin resistance.

Association of eNOS Glu298Asp gene polymorphism with circadian blood pressure rhythm

Hypertensive patients with altered circadian blood pressure (BP) profile experience greater repercussion of hypertension on target organs and a higher risk of cardiovascular events, compared with those with physiological variations in BP. It has been demonstrated in animal models, that circadian variations in BP depend on several regulatory systems, in particular the nitric oxide-cGMP pathway. eNOS298 Glu/Asp polymorphism is a functional variant and may alter the amount of NO generated or eNOS activity. The objective of the present study was to find out whether eNOS298 gene polymorphism affects circadian BP regulation in 110 healthy subjects and 155 never-treated hypertensive patients recruited at Hypertension Units in Grenoble, Toulouse and Lille (France).

Vascular Stiffness and Genetic Variation at the Endothelial Nitric Oxide Synthase Locus

Arterial stiffness is a moderately heritable trait that is affected by alterations in the bioavailability of NO. Previous studies have found associations between variants in the gene for endothelial NO synthase ( NOS3 ) and arterial properties. We previously identified a linkage peak for forward pressure wave amplitude in the immediate vicinity of NOS3 . Therefore, we evaluated relations between arterial stiffness measures and common genetic variants at this locus. Eighteen single nucleotide polymorphisms capturing ≈90% of underlying common variation in NOS3 were genotyped in unrelated Framingham Heart Study participants (N=1157; 52.2% women; mean age: 62 years) with routinely ascertained tonometry data that provided 5 arterial phenotypes (forward and reflected pressure wave amplitude, central pulse pressure, carotid–femoral pulse wave velocity, and mean arterial pressure). In women but not men, the genotype for the common NOS3 missense mutation (Glu298Asp, rs1799983) was related to central pulse pressure (women: GG=53±0.9, GT=54±0.9, and TT=47±2.0 mm Hg, P =0.0047; men: GG=50±1.0, GT=49±0.9, and TT=47±1.8 mm Hg, P =0.30) and forward wave amplitude (women: GG=41±0.7, GT=42±0.7, and TT=38±1.6 mm Hg, P =0.029; men: GG=42±0.9, GT=41±0.8, and TT=39±1.5 mm Hg, P =0.47). The only other nominally significant sex-specific association in men but not women was between an intronic polymorphism (rs1800781) and reflected wave amplitude (women: AA=10.4±0.4, AG=11.1±0.6, and GG=8.9±2.2 mm Hg, P =0.50; men: AA=6.1±0.3, AG=7.3±0.5, and GG=11.3±2.3 mm Hg, P =0.014). After adjusting for multiple testing (18 polymorphisms and 5 phenotypes), these nominal associations were no longer significant. The present study was suggestive of modest relations between common genetic variants at the NOS3 locus and arterial stiffness.

Association of endothelial nitric oxide synthase gene G894T polymorphism with essential hypertension in an adult Pakistani Pathan population

This retrospective, case-control study was carried out to find putative correlations of eNOS G894T polymorphism with essential hypertension (EHT) amongst adult Pakistani Pathans. We investigated a sample population of 332 (154 men, 178 women) comprising groups of 146 hypertensives (HTs) and 186 normotensives (NTs) by assays based on polymerase chain reaction followed by restriction endonuclease analysis. The distribution of the genotypes or alleles was not statistically different in hypertensive and normotensive groups. In conclusion, the present study in a population of Pakistani adult Pathans does not support the association of the eNOS gene G894T polymorphism to essential hypertension.

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.

Both Nitric Oxide and Endothelin-1 Influence Cerebral Blood Flow Velocity at Rest and after Hyper- and Hypocapnic Stimuli in Hypertensive and Healthy Adolescents

BACKGROUND AND PURPOSE

Nitric oxide (NO)/endothelin imbalance may play a role in the regulation of cerebral blood flow. The aim of the present study was to assess whether these endothelial factors influence middle cerebral artery blood flow velocities (MCAV) and cerebrovascular reactivity (CVR) in healthy and hypertensive adolescents.

SUBJECTS AND METHODS

106 adolescents (61 hypertensive and 45 normotensive) underwent transcranial Doppler measurements of the middle cerebral artery at rest and after 30 s of breath-holding (BH) and 60 s of hyperventilation (HV). Additionally, NO and endothelin-1 (ET-1) concentrations of the serum were assessed. The correlation between NO and ET-1 levels as well as MCAV and CVR values was analyzed.

RESULTS

Resting MCAVs were higher among hypertensive teenagers (76.5 +/- 24 vs. 62.8 +/- 15.6 cm/s, respectively, p < 0.001). CVR values did not differ between hypertensive and healthy adolescents after the BH and HV procedure. A significant negative correlation was found between absolute MCAV values and NO concentrations. ET-1 was positively related to MCAV.

CONCLUSIONS

Cerebral blood flow velocities, but not CVR values, are associated with serum NO and ET-1 concentrations in adolescents.

Endothelial nitric oxide synthase G894T gene polymorphism in Chilean subjects with coronary artery disease and controls

BACKGROUND

Nitric oxide (NO) from the endothelium, produced by oxidation of l-arginine to L-citruline for the action at the endothelial nitric oxide synthase (eNOS), is considered an important atheroprotective factor. The Glu298Asp (G894T) polymorphic variant of the eNOS gene has been implicated in the development of coronary artery disease (CAD). We investigated the association between occurrence of CAD documented by angiography and the G894T polymorphism of the NOS3 gene in Chilean individuals.

METHODS

A total of 112 unrelated patients with diagnosis of CAD and 72 controls were included in this study. G894T gene polymorphism was analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

RESULTS

The frequency of TT homozygous genotype for G894T polymorphism was 7% in CAD patients and 1% in the control group. However, the genotype distribution and allele frequencies were not significantly different between CAD and control subjects (P>0.05). Moreover, the odds ratio for CAD associated with the T variant failed to reach statistical significance (OR=1.5; 95% CI: 0.87-2.59, P>0.05).

CONCLUSION

These findings suggest that the G894T polymorphism of the eNOS gene was not associated with CAD in Chilean individuals.

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.

Negative association of endothelial nitric oxide gene polymorphism with hypertension in Turkish patients: effect of ecNOS polymorphism on left ventricular hypertrophy

BACKGROUND

Endothelial nitric oxide synthase produces nitric oxide which is involved in many physiologic regulatory functions. Variable number of tandem repeats in intron 4 of endothelial nitric oxide synthase gene are reported to be associated with blood pressure regulation. Nitric oxide is involved in regulation of cardiomyocyte genes but it is not known If endothelial nitric oxide synthase 4 gene polymorphisms are related with left ventricular hypertrophy. We studied endothelial nitric oxide synthase 4a/b allele status in hypertensive and normotensive patients and echocardiographic parameters in a subgroup of hypertensive group.

METHODS

We performed a case-control study involving 110 Turkish hypertensive patients and 87 controls. All subjects were genotyped for endothelial nitric oxide synthase 4a/b polymorphism. Echocardiographic measurements were obtained in 94 of the hypertensive patients.

RESULTS

Endothelial nitric oxide synthase 4a/b genotype frequencies were 6.4%, 23.6%, 70% in hypertensives and 1.1%, 18.4%, 80.5% in controls for a/a, a/b, b/b, respectively. Left ventricular dimensions, mass and diastolic indices were not different across endothelial nitric oxide synthase 4 genotypes. Patients with 4a/a genotype had higher interventricular septal thickness than the other group; 14.83(1.6), 11.91(1.51), 12.21(1.56) for a/a, a/b, b/b, respectively and p = 0.0001.

CONCLUSION

Endothelial nitric oxide synthase 4a/b gene polymorphism is not associated with hypertension in Turkish patients. 4a/a genotype was associated with higher interventricular septal thickness in hypertensive patients.

Target-organ damage in adolescent hypertension. Analysis of potential influencing factors, especially nitric oxide and endothelin-1

BACKGROUND AND PURPOSE

To assess the role of the nitric oxide-endothelin imbalance in the development of target-organ damages (carotid intima-media thickness and left ventricular mass index) in adolescent hypertension.

METHODS

125 adolescents--67 hypertensive and 58 normotensive--underwent routine anthropology (height, weight) and blood pressure measurements, and laboratory (glucose, cholesterol and triglyceride levels) testing as well as sampling blood for determination of the plasma concentrations of nitric oxide (NOx) and endothelin-1 (ET-1), followed by measurement of the carotid intima-media thickness (IMT) and left ventricular mass index (LVMI).

RESULTS

Plasma concentration of NOx was significantly lower (27.7+/-13.7 vs. 35.8+/-7.0 micromol/l, respectively, p<0.001) and ET-1 was higher (3.11+/-3.9 vs. 1.09+/-1.07 fmol/ml, respectively, p<0.001) in hypertensive adolescents than that of controls. NOx negatively, endothelin positively correlated with blood pressure values, especially with systolic BP. An inverse relationship has been found between NOx and ET-1 concentrations (r=-0.29, p<0.003). In this adolescent population body weight, systolic blood pressure and plasma ET-1 were the most important factors influencing IMT, whereas LVMI correlated with height and weight and systolic BP of the teenagers.

CONCLUSIONS

NO/endothelin imbalance seems to play a role in the development of hypertension and target-organ damages in adolescence. Further studies are encouraged in order to clarify the pathophysiological role of NO/endothelin imbalance in adolescent 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.

Association analysis of genes in the renin-angiotensin system with subclinical cardiovascular disease in families with Type 2 diabetes mellitus: the Diabetes Heart Study

AIMS

Cardiovascular disease (CVD) is a major complication of Type 2 diabetes mellitus. The renin-angiotensin system (RAS) and nitric oxide production are both important regulators of vascular function and blood pressure. Genes encoding proteins involved in these pathways are candidates for a contribution to CVD in diabetic patients. We have investigated variants of the angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin type 1 receptor (AT1R) and endothelial nitric oxide synthase (NOS3) genes for association with subclinical measures of CVD in families with Type 2 diabetes mellitus (T2DM).

METHODS

Atherosclerosis was measured by carotid intima-media thickness and calcification of the carotid and coronary arteries in 620 European Americans and 117 African Americans in the Diabetes Heart Study. Because of the role of these systems in blood pressure regulation, blood pressure was also investigated.

RESULTS

Compelling evidence of association was not detected with any of the SNPs with any outcome measures after adjustments for covariates despite sufficient power to detect relatively small differences in traits for specific genotype combinations.

CONCLUSIONS

Genetic variation of the RAS and NOS3 genes do not appear to strongly influence subclinical cardiovascular disease or blood pressure in this diabetic population.

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.

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.

Interaction between -786TC polymorphism in the endothelial nitric oxide synthase gene and smoking for myocardial infarction in Korean population

BACKGROUND

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) mediates endothelium-dependent vasodilation and antithrombotic action. Controversial results regarding the association of eNOS gene polymorphisms with myocardial infarction (MI) have been reported.

METHODS

A total of 932 individuals living in Seoul and the suburb, Korea, were randomly selected. Genomic DNA was prepared from blood leukocytes. A GT missense mutation in exon 7 (894GT) was screened using PCR-RFLP analysis. The genotypes of 3 mutations (-786TC, -922AG, and -1468TA) in the 5'-flanking region were determined by a minisequencing protocol (SNaPshot), respectively.

RESULTS

Pair-wise linkage analysis revealed that 3 mutations of -786TC, -922AG, and -1468TA were completely linked with each other (mid R:D'mid R:=1, r(2)=0.96-1.0). Furthermore, each of these mutant alleles (-786C, -922G, or -1468A), but not 894T allele, was associated with the risk of MI. Multiple logistic regression analysis revealed that each of these mutant alleles was a predictive independent risk factor for the risk of MI (odds ratio, 1.69 for dominant effects, P<0.05) after age and sex adjustments. Smoking further increased the odds ratio by 2.04 for the risk of MI when it was combined with the mutant alleles.

CONCLUSION

Each of 3 mutations (-786TC, -922AG, or -1468TA) in the 5'-flanking region of eNOS gene may play a role in the pathogenesis of MI in Korean population, and also provides an evidence for a significant interaction between these mutations and smoking.

Influence of the eNOS gene on development of blood pressure and left ventricular mass: Longitudinal findings in multiethnic youth

OBJECTIVES

To evaluate the impact of the endothelial nitric oxide synthase (eNOS) gene on longitudinal development of blood pressure (BP) and left ventricular mass (LVM) from childhood into early adulthood.

METHODS

Three polymorphisms including -922A>G, intron 4VNTR, and Glu298Asp of the eNOS gene were investigated. Individual growth-curve modeling and haplotype trend regression analyses were conducted for 579 white and black American youths with 12 assessments over a 15-year period.

RESULTS

Significantly different allele and genotype frequencies were observed between blacks and whites for all three polymorphisms. Linkage disequilibrium (LD) patterns among these polymorphisms were also different between ethnic groups: strong LD between the -922A>G and intron 4 VNTR loci was observed in whites but not in blacks. Single locus analyses identified a significant interaction between the intron 4 VNTR and gender on diastolic BP (DBP) levels. The 4a allele carriers had significantly lower DBP levels in males (P=0.012), but higher DBP levels in females (P=0.045). Haplotype analyses confirmed the DBP lowering effect in males (P=0.049). DBP in males homozygous for haplotype G-4a-Glu was 2.58 mmHg lower than males homozygous for the most common haplotype (A-non4a-Glu). Additionally, individuals homozygous for haplotype G-non4a-Glu showed a 0.51 mmHg steeper increase in DBP per year with age as compared to the most common haplotype (P=0.007). No associations between single polymorphisms or haplotypes of the eNOS gene and systolic BP or LVM were found.

CONCLUSIONS

our results suggest that eNOS gene may have gender-specific and age-dependent effects on DBP and the development of hypertension risk.

Endothelial Nitric Oxide Synthase −786T>C, but Not 894G>T and 4a4b, Polymorphism Influences Plasma Homocysteine Concentrations in Persons with Normal Vitamin Status

Background: Nitric oxide (NO) plays a relevant role in various events during atherogenesis. In vitro data suggest that NO may modulate homocysteine (Hcy) concentrations. The aim of this study was to investigate the role of endothelial nitric oxide synthase (eNOS) −786T&gt;C, 894G&gt;T, and 4a4b polymorphisms in influencing Hcy concentrations.

Methods: Blood samples were obtained from 1287 unrelated persons. Plasma Hcy was measured by fluorescence polarization immunoassay, folate and vitamin B12 by RIA, vitamin B6 by HPLC, and eNOS and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms by PCR with restriction fragment length polymorphism analysis.

Results: MTHFR 677C&gt;T polymorphism significantly influenced Hcy concentrations after adjustment for all confounding variables (P &lt;0.0001 for trend). Univariate analysis showed that the eNOS −786T&gt;C polymorphism, but not 894G&gt;T and 4a4b, was significantly associated with the risk of having Hcy in the third tertile [&gt;13.4 μmol/L; odds ratio (OR) = 1.2; 95% confidence interval (CI), 1.02–1.5; P = 0.03]. After adjustment for all variables known to influence Hcy, the −786T&gt;C polymorphism still influenced Hcy concentrations (OR = 1.9; 95% CI, 1.1–3.2; P = 0.01). By analyzing the influence of eNOS polymorphisms on plasma Hcy concentrations according to vitamin concentrations (folate, vitamin B6, and vitamin B12), age, and smoking habits, we found a significant association between the eNOS −786T&gt;C polymorphism and Hcy in nonsmokers, in persons with normal vitamin status, and in persons &lt;60 years.

Conclusion: The eNOS −786T&gt;C polymorphism, but not 894G&gt;T and 4a4b, influences plasma Hcy concentrations mildly but significantly and independently.

Endothelial nitric oxide synthase polymorphism, nitric oxide production, salt sensitivity and cardiovascular risk factors in Hispanics

Mutations in the endothelial nitric oxide synthase (eNOS) gene may be associated with abnormal nitric oxide (NO) production and cardiovascular diseases. In this study, we investigated the prevalence of two eNOS polymorphisms, the Glu298Asp variant on exon 7, and the 4a/b variable number of tandem repeats (VNTR) on intron 4, and their association with blood pressure (BP), NO production, salt sensitivity and cardiovascular risk factors in healthy Venezuelans. The prevalence of both polymorphisms in Venezuelans was comparable to that described for Caucasians, but significantly different from that known for African-Americans and Japanese. The 4a/b genotype was associated with reduced levels of NO metabolites (25% decrease), larger BP lowering in response to salt restriction (9.0 vs 4.8 mmHg, P<0.05), greater prevalence of salt sensitivity (39% in 4a/b and 27% in 4b/b; P<0.05) and with higher LDL-cholesterol levels. The Glu298T polymorphism did not affect NO production, nor it was associated with salt sensitivity. Glu298Asp polymorphism was positively associated with higher weight, triglycerides and LDL-cholesterol. Neither polymorphism was associated with changes in fasting or postload serum glucose, BP, obesity and albuminuria. In conclusion, the prevalence of eNOS polymorphisms is strongly determined by ethnic factors. The 4a/b gene polymorphism could be a genetic susceptibility factor for the BP response to salt intake and for the genetic control of NO production. The reduced NO production in subjects with the 4a/b genotype may be responsible for the increased sensitivity of their BP to salt.

Relationship of eNOS gene variants to diseases that have in common an endothelial cell dysfunction

The endothelial cell (EC) dysfunction is a common characteristic of various pathologies that include atherosclerosis, hypertension, and Fabry's disease. Aware of the role of eNO and ACE in EC dysfunction, we questioned whether polymorphism of eNOS and/or ACE gene may be a common denominator in these pathologies. Patients with CHD (108), HT (109), Fabry's disease (37) and healthy subjects (control, 141) were genotyped for the eNOSG894T by RFLP-PCR technique and for eNOS4b/a, and ACEI/D polymorphisms by PCR amplification. The results of these studies were statistically evaluated. Compared to controls, the frequency of the eNOSG894T (T allele) was higher in CHD (P=0.03) and Fabry (P=0.01), while the eNOS4b/a (a allele) in CHD (P=0.01) and HT patients (P=0.01). The proportion of the ACEI/D was similar in all subjects. In CHD patients at "low risk" of atherogenic factors, the frequency of the T and a alleles of eNOS gene was high (P=0.03 and 0.02, respectively). Carriers of the T allele of eNOSG894T were over-represented (P=0.04) in Fabry subgroup with renal failure. Compared to women, the eNOS894T alleles were more frequent (P=0.03) in men with CHD and HT, whereas ACE I/D in men (P=0.03) with HT. These findings suggest: (i) the frequency of eNOSG894T and/or eNOS4b/a is significantly associated with coronary dysfunction; (ii) eNOS4b/a confers a relatively high risk of hypertension in subjects with atherogenic risk factors; (iii) the frequency of eNOSG894T is high in Fabry hemizygotes with renal complications. Therefore, eNOS gene polymorphism represent a frequent risk factor for vascular abnormalities in CHD, HT and Fabry's disease, afflictions which have in common, the endothelial dysfunction.