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

Novel SNPs of WNK1 and AKR1C3 are associated with preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy and is one of the most common causes of poor perinatal outcomes. Preeclampsia increases the risk of hypertension in the future. Variants of WNK1 (lysine deficient protein kinase 1), ADRB2 (β2 adrenergic receptor), NEDD4L (ubiquitin-protein ligase NEDD4-like), KLK1 (kallikrein 1) contribute to hypertension, and AKR1C3 (aldo-keto reductase family1 member C3), is associated with preeclampsia. The association of single nucleotide polymorphisms (SNPs) in these five candidate preeclampsia susceptibility genes and the related traits in Chinese individuals were investigated. In this study, 13 SNPs of the five genes were genotyped in 276 preeclampsia patients and 229 age- and area-matched normal pregnancies in women of Chinese Northern Han origin. The 95% confidence interval (CI) and odds ratio (OR) were estimated by binary logistic regression. No obvious linkage disequilibrium or haplotypes were observed among these SNPs. Those with GG genotype and allele G of AKR1C3 (rs10508293) had a decreased risk of preeclampsia (adjusted OR = 3.011, 95% CI = 1.758-5.159, and adjusted OR = 1.745, 95% CI = 1.349-2.257, respectively). The AA genotype and allele A of WNK1 (rs1468326) were significantly associated with an increased risk in preeclampsia (adjusted OR = 2.307, 95% CI = 1.206-3.443, and adjusted OR = 1.663, 95% CI = 1.283-2.157, respectively). The findings indicate that the GG genotype of AKR1C3 rs10508293 is associated with decreased risk for preeclampsia and the AA genotype of WNK1 rs1468326 are related with an increased risk for preeclampsia.

Interactions between the genes of vasodilatation pathways influence blood pressure and nitric oxide level in hypertension

BACKGROUND

This study investigates the contribution of genetic interactions between the β-2 adrenergic receptor (ADRB2) and nitric oxide synthase (NOS3) genes to the complex etiology of hypertension.

METHODS

Using single nucleotide polymorphism (SNP) markers, we studied potential interactions between ADRB2 and NOS3 variants and their correlation with clinical, biochemical, and expression levels in 546 individuals with hypertension and 884 age-, sex-, and ethnicity-matched unrelated control subjects. Generalized multifactor dimensionality reduction (GMDR) analysis identified the models for genotype interaction.

RESULTS

The best models to represent association of genotypes with augmented hypertension susceptibility were the 4- and 5-locus interacting GMDR models of ADRB2 and NOS3 compared with within-gene 6-locus ADRB2 and 2-locus NOS3 (odds ratio (OR) = 4.8, P = 0.04; OR = 5.6, P = 0.02, respectively). Stratification of 4- and 5-locus GMDR models on the basis of risk alleles (in increasing order) increased the ORs from 1.26 to 14.17 and from 0.81 to 14.18, respectively, and correlated linearly with increased systolic blood pressure, diastolic blood pressure, and mean arterial pressure and decreased nitric oxide level (P ≤ 0.0004). We performed various analyses, such as single-locus, genetic interactions, sliding-window, and comparative analysis. Each analysis consistently revealed the 46A allele of ADRB2 46G/A SNP and 4a allele of NOS3 4b/4a SNP to be associated with risk of hypertension. These risk-conferring markers were associated with decreased ADRB2 and NOS3 expression and decreased nitric oxide level in the patients (P ≤ 0.04).

CONCLUSIONS

Evidence of interaction between the genetic loci of ADRB2 and NOS3 points to varied clinical, biochemical, and expression levels and a role in hypertension susceptibility.

A common genetic variant of the chromogranin A-derived peptide catestatin is associated with atherogenesis and hypertension in a Japanese population

Chromogranin A (CHGA) is a major protein in the secretory granules of chromaffin cells. CHGA also gives rise to cardiovascular/metabolism regulatory peptides, such as catestatin (CST) and pancreastatin (PST). While CST is a potent inhibitor of catecholamine secretion, PST is a potent physiological inhibitor of glucose-induced insulin secretion. Recently, several SNPs were identified in the CST and PST domains of CHGA locus in different populations. Among the discovered SNPs, CST variant allele Ser-364 was associated with blood pressure alteration and PST variant allele Ser-297 was associated with significantly higher plasma glucose level. In this study, we examined whether these CST and PST variant alleles exist and influence cardiovascular and metabolic phenotypes in Japanese population. Our study comprised of 343 Japanese subjects aged 45-85 years (143 men and 200 women, mean age 66 ± 8 years). We determined the genotypes of CST and PST by PCR-direct sequencing method and carried out genotype-phenotype association analysis. In 343 participants, the minor allele frequency of CST variant Ser-364 was 6.10%. On the other hand, we did not detect the PST variant Ser-297 in this entire study population. The presence of Ser-364 allele was associated with increased in baPWV (an index of systemic arterial stiffness) that suggests an initiation and/or progression atherogenesis and hypertension. The Ser-364 allele was also associated with elevated systolic blood pressure and pulse pressure, consistent with increased baPWV. In conclusion, the CST Ser-364 allele may increase the risk for cardiovascular diseases in Japanese population.

NOS3 894G>T polymorphism is associated with progression of kidney disease and cardiovascular morbidity in type 2 diabetic patients: NOS3 as a modifier gene for diabetic nephropathy?

BACKGROUND/AIMS

We have previously associated SNP 894G>T in the NOS3 gene with diabetic nephropathy (DN) using multi-locus analysis. Variant 894G>T has been widely studied as a DN susceptibility factor with contradictory results. In the present study we genotyped 894G>T in the cohort of prospectively followed type 2 diabetics with the aim to investigate its possible role in the progression of DN and development of morbidity and mortality associated with diabetes.

METHODS

311 subjects with defined stage of DN were enrolled in the study and followed up for a median of 38 months. We considered three end-points: progression of DN, major cardiovascular event and all-cause mortality.

RESULTS

Considering baseline GFR, age at enrolment and diabetes duration as confounders, Cox regression analysis identified 894GT genotype as a risk factor for DN progression (HR = 1.843 [95% CI 1.088 - 3.119], P = 0.023) and 894TT genotype as a risk factor for major cardiovascular event (HR = 2.515 [95% CI 1.060 - 5.965], P = 0.036).

CONCLUSION

We ascertained the significant effect of the NOS3 894G>T variant on DN progression and occurrence of major cardiovascular event in T2DM subjects. Based on these results NOS3 can be considered a modifier gene for DN.

Interaction between the NOS3 gene and obesity as a determinant of risk of type 2 diabetes: the Atherosclerosis Risk in Communities study

Endothelial nitric oxide synthase 3 (NOS3) catalyzes the production of nitric oxide from L-arginine in endothelial cells. Obesity is a modifiable risk factor for diabetes, and obese individuals have been reported to have reduced nitric oxide availability compared to controls whose weight is in the normal range. Since homozygous carriers of the NOS3 G894T variant are predicted to have decreased enzyme activity, the association between NOS3 genotype and type 2 diabetes, and possible effect modification by body mass index (BMI) were evaluated. The prevalence of diabetes and BMI was determined at baseline in 14,374 participants 45-66 years of age from the prospective biracial population-based Atherosclerosis Risk in Communities (ARIC) Study of the development of atherosclerosis in four communities in the United States. Individuals with a BMI ≥30 kg/m(2) were considered obese. Those subjects not meeting the case definition were the comparison groups for the 728 African American and 980 white participants with diabetes. Multivariable logistic regression models adjusted for age, sex, and field center were used to test for main genetic effects and interaction with obesity. Although the NOS3 G894T variant was not independently associated with diabetes in either African Americans or whites, significant interaction between BMI and the NOS3 polymorphism indicated that obesity was an effect modifier of diabetes risk for white individuals with the TT genotype (odds ratio (OR) for interaction = 1.65, p = 0.04). In stratified analyses, homozygosity for the NOS3 T allele in obese white participants but not in those whose BMI <30 kg/m(2) was associated with an elevated risk of diabetes (OR = 1.47, p = 0.02) when compared to the common GG genotype. These results suggest that interaction between obesity and NOS3 genotype may be a determinant of diabetes case status in whites in the ARIC cohort. Replication in other populations will be required to confirm these observations.

Epistatic study reveals two genetic interactions in blood pressure regulation

Background

Although numerous candidate gene and genome-wide association studies have been performed on blood pressure, a small number of regulating genetic variants having a limited effect have been identified. This phenomenon can partially be explained by possible gene-gene/epistasis interactions that were little investigated so far.

Methods

We performed a pre-planned two-phase investigation: in phase 1, one hundred single nucleotide polymorphisms (SNPs) in 65 candidate genes were genotyped in 1,912 French unrelated adults in order to study their two-locus combined effects on blood pressure (BP) levels. In phase 2, the significant epistatic interactions observed in phase 1 were tested in an independent population gathering 1,755 unrelated European adults.

Results

Among the 9 genetic variants significantly associated with systolic and diastolic BP in phase 1, some may act through altering the corresponding protein levels: SNPs rs5742910 (P_adjusted≤0.03) and rs6046 (P_adjusted =0.044) in F7 and rs1800469 (P_adjusted ≤0.036) in TGFB1; whereas some may be functional through altering the corresponding protein structure: rs1800590 (P_adjusted =0.028, SE=0.088) in LPL and rs2228570 (P_adjusted ≤9.48×10^-4) in VDR. The two epistatic interactions found for systolic and diastolic BP in the discovery phase: VCAM1 (rs1041163) * APOB (rs1367117), and SCGB1A1 (rs3741240) * LPL (rs1800590), were tested in the replication population and we observed significant interactions on DBP. In silico analyses yielded putative functional properties of the SNPs involved in these epistatic interactions trough the alteration of corresponding protein structures.

Conclusions

These findings support the hypothesis that different pathways and then different genes may act synergistically in order to modify BP. This could highlight novel pathophysiologic mechanisms underlying hypertension.

Functional epistatic interaction between rs6046G>A in F7 and rs5355C>T in SELE modifies systolic blood pressure levels

Background

Although numerous genetic studies have been performed, only 0.9% of blood pressure phenotypic variance has been elucidated. This phenomenon could be partially due to epistatic interactions. Our aim was to identify epistatic interaction(s) associated with blood pressure levels in a pre-planned two-phase approach.

Methods and Results

In a discovery cohort composed of 3,600 French individuals, we found rs6046A allele in F7 associated with decreased blood pressure levels (P≤3.7×10⁻³) and rs5355T allele in SELE associated with decreased diastolic blood pressure levels (P = 5×10⁻³). Both variants interacted in order to influence blood pressure levels (P≤0.048). This interaction was replicated with systolic blood pressure in 4,620 additional European individuals (P = 0.03). Similarly, in this replication cohort, rs6046A was associated with decreased blood pressure levels (P≤8.5×10⁻⁴). Furthermore, in peripheral blood mononuclear cells of a subsample of 90 supposed healthy individuals, we found rs6046A positively associated with NAMPT mRNA levels (P≤9.1×10⁻⁵), suggesting an eventual involvement of NAMPT expression in blood pressure regulation. Confirming this hypothesis, further transcriptomic analyses showed that increased NAMPT mRNA levels were positively correlated with ICAM1, SELL, FPR1, DEFA1-3, and LL-37 genes expression (P≤5×10⁻³). The last two mRNA levels were positively associated with systolic blood pressure levels (P≤0.01) and explained 4% of its phenotypic variation.

Conclusion

These findings reveal the importance of epistatic interactions in blood pressure genetics and give new insights for the role of inflammation in its complex regulation.

The epistasis between vascular homeostasis genes is apparent in essential hypertension

OBJECTIVE

The epistasis influence of vascular homeostasis genes is vital to multigenetic diseases. This study was designed to perceive the possible role of epistasis in the etiology of essential hypertension.

METHODS

We investigated seven polymorphisms of ACE, CYP11B2 and NOS3 epistatically, and SBP, DBP, MAP, ACE activity, plasma aldosterone concentration (PAC) and NOx level in 860 age- and ethnicity-matched unrelated north-Indian subjects.

RESULTS

The hypertension risk in individuals with interacted-genotypes (IwIw+IwIc)+(4aa), (IcIc)+(4bb+4ba) and IcIc+4aa of the CYP11B2 and NOS3 was significantly higher with odds ratio 5.5 (95% CI=2.9-10.6, P<0.0001), 2.4 (95% CI=1.4-4.1, P<0.0008) and 7.5 (95% CI=1.6-34.8, P=0.010), respectively. The odds ratio for hypertension with interacted-haplotypes (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) of CYP11B2 and NOS3 was 5.3 (95% CI=2.0-14.2, P=0.005) and 3.9 (95% CI=1.4-10.4, P=0.04), respectively; whereas for the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G), the odds ratio was 0.7 (95% CI=0.5-0.9, P=0.03). While the interacted-genotypes, IcIc+4aa correlated with higher SBP and MAP (P=0.006; P=0.04), the interacted-haplotypes, (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) correlated with higher MAP and lower NOx level (P=0.02 and P=0.03, respectively), and the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G) correlated with lower PAC and MAP (P=0.024 and P=0.018, respectively).

CONCLUSIONS

The epistasis between CYP11B2 and NOS3 and its correlation with varied clinical and biochemical parameters signify its possible contribution in the complex etiology of hypertension.

Association study of the β2-adrenergic receptor gene polymorphisms and hypertension in the Northern Han Chinese

Background

The β2-adrenergic receptor (ADRB2) gene has been widely researched as a candidate gene for essential hypertension (EH), but no consensus has been reached in different ethnicities. The aim of the present study was to evaluate the possible association between the ADRB2 gene polymorphisms and the EH risk in the Northern Han Chinese population.

Methodology/Principal Findings

This study included 747 hypertensive subjects and 390 healthy volunteers as control subjects in the Northern Han Chinese. Genotyping was performed to identify the C-47T, A46G and C79G polymorphisms of the ADRB2 gene. G allelic frequency of A46G polymorphism was significantly higher in hypertensive subjects (P = 0.011, OR = 1.287, 95%CI [1.059–1.565]) than that in controls. Significant association could also be found in dominant genetic model (GG+AG vs. AA, P = 0.006, OR = 1.497, 95%CI [1.121–1.998]), in homozygote comparison (GG vs. AA, P = 0.025, OR = 1.568, 95%CI [1.059–2.322]), and in additive genetic model (GG vs. AG vs. AA, P = 0.012, OR = 1.282, 95%CI [1.056–1.555]). Subgroup analyses performed by gender suggested that this association could be found in male, but not in female. Stratification analyses by obesity showed that A46G polymorphism was related to the prevalence of hypertension in the obese population (GG vs. AG vs. AA, P<0.001, OR = 1.645, 95%CI [1.258–2.151]). Significant interaction was found between A46G genotypes and body mass index on EH risk. No significant association could be found between C-47T or C79G polymorphism and EH risk. Linkage disequilibrium was detected between the C-47T, A46G and C79G polymorphisms. Haplotype analyses observed that the T-47-A46-C79 haplotype was a protective haplotype for EH, while the T-47-G46-C79 haplotype increased the risk.

Conclusions/Significances

We revealed that the ADRB2 A46G polymorphism might increase the risk for EH in the Northern Han Chinese population.

Associations among objectively measured physical activity, fasting plasma homocysteine concentration, and MTHFR C677T genotype

Elevated fasting plasma homocysteine (Hcy) level is a vascular disease risk factor. Plasma Hcy is affected by 5,10-methylenetetrahydofolate reductase (MTHFR) genotype and dietary folate intake. This cross-sectional study in 434 Japanese adults examined the associations among objectively measured physical activity (PA), plasma Hcy adjusting for dietary folate intake, and MTHFR C677T genotype. Daily PA was measured by triaxial accelerometry and all subjects completed a questionnaire about their dietary habits. Plasma Hcy and MTHFR C677T genotype were determined. Plasma Hcy in subjects with the TT genotype was significantly higher than in those with CC or CT genotype (p < 0.001). Plasma Hcy was significantly different between ≥ 200 (7.6 ± 0.2 nmol/mL) and <200 µg/day (8.3 ± 0.3 nmol/mL) folate intake groups (p = 0.003). There were no differences in plasma Hcy adjusting for age, sex, and folate intake between groups according to PA category in all subjects. However, there were significant interactions between time spent in light PA (p = 0.003), vigorous PA (p = 0.001), or inactivity (p = 0.004), and MTHFR genotype. In only the TT genotype, shorter time spent in light PA was associated with higher plasma Hcy than a longer time spent in light PA (11.5 ± 3.3 nmol/mL vs. 8.5 ± 3.3 nmol/mL, p < 0.001), and longer time spent in vigorous PA and inactivity were associated with higher plasma Hcy (11.8 ± 3.3 nmol/mL vs. 8.4 ± 3.2 nmol/mL, 11.6 ± 3.3 nmol/mL vs. 8.4 ± 3.3 nmol/mL, respectively, p < 0.001). In conclusion, light and vigorous PA were associated with plasma Hcy only in the TT genotype, but there were no such associations in all genotypes.

Genetics and cardiovascular system: influence of human genetic variants on vascular function

Candidate gene association studies in cardiovascular diseases have provided evidence on the molecular basis of phenotypic differences between individuals. The comprehension of how inherited genetic variants are able to affect protein functions has increased the knowledge of how genes interact with environment in order to modulate a particular phenotype. Although it is known that the human genome contains more than 10 million SNPs, only a minor part of them are supposed to be functional. A causative SNP in a particular gene may confer a small to moderate effect in complex phenotypes, such as functions important to cardiovascular homeostasis. This paper is a selective review of the literature on the evidence for interactions between vascular function and naturally occurring genetic variants in endothelial nitric oxide synthase (eNOS) and beta-2 adrenergic receptor (ADRB2), two genes among those influencing vascular phenotype and examples for which there is a strong evidence base. eNOS and ADRB2 will be characterized, as well as the mechanisms by which the enzyme and the receptor work to control vascular responses will be described. Understanding the molecular mechanisms underlying gene-mediated vascular function and their modification by genetic variants is expected to result in a better comprehension about individual's phenotypic differences.

A46G and C79G polymorphisms in the β2-adrenergic receptor gene (ADRB2) and essential hypertension risk: a meta-analysis

No consensus has been reached on the association between the β2-adrenergic receptor polymorphisms A46G and C79G and essential hypertension risk. We performed a meta-analysis to confirm the possible association. After reviewing 303 reports in PubMed and 359 reports in Embase, we included in our meta-analysis 18 articles (20 studies) that met our inclusion criteria. The fixed-effects model and the random-effects model were applied for dichotomous outcomes to combine the results of the individual studies. There was no statistical association between A46G and hypertension risk in all subjects, Asians or Caucasians. However, an association was observed in the dominant genetic model (AA vs. (AG+GG)) (P=0.04, odds ratio (OR)=1.38, 95% confidence interval (CI) 1.01-1.87, P(heterogeneity)=0.98, fixed-effects model) in the subgroup of mixed Africans. No overall statistical association could be found between C79G and hypertension risk or any ethnic subgroup. In the research conducted on severe hypertension (systolic blood pressure ≥160 mm Hg and/or diastolic blood pressure ≥95 mm Hg hypertensive population), significant association was found in the dominant genetic model (CC vs. (CG+GG)) (P=0.04, OR=1.38, 95% CI 1.02-1.86, P(heterogeneity)=0.03, random-effects model), and there was also a borderline significance between the C79 allele and severe hypertension (P=0.05, OR=1.26, 95% CI 1.00-1.57, P(heterogeneity)=0.04, random-effects model). No association could be found in this study between the two polymorphisms and stage 2 hypertension. More studies stratified for different ethnicities and different stages of hypertension should be performed in the future.

Lack of carotid stiffening associated with MTHFR 677TT genotype in cardiorespiratory fit adults

The TT genotype of C677T polymorphism in 5,10-methylenetetrahydrofolate reductase (MTHFR) induces elevation of homocysteine level and leads to atherosclerosis and arterial stiffening. Furthermore, cardiorespiratory fitness level is also associated with arterial stiffness. In the present study, a cross-sectional investigation of 763 Japanese men and women (18-70 yr old) was performed to clarify the effects of cardiorespiratory fitness on the relationship between arterial stiffness and MTHFR C677T gene polymorphism. Arterial stiffness was assessed by carotid beta-stiffness with ultrasonography and tonometry. The study subjects were divided into high-cardiorespiratory fitness (High-Fit) and low-cardiorespiratory fitness (Low-Fit) groups based on the median value of peak oxygen uptake in each sex and decade. The plasma homocysteine level was higher in the TT genotype of MTHFR C677T polymorphism compared with CC and CT genotype individuals. MTHFR C677T polymorphism showed no effect on carotid beta-stiffness, but there was a significant interaction effect between fitness and MTHFR C677T polymorphism on carotid beta-stiffness (P = 0.0017). In the Low-Fit subjects, carotid beta-stiffness was significantly higher in individuals with the TT genotype than the CC and CT genotypes. However, there were no such differences in High-Fit subjects. In addition, beta-stiffness and plasma homocysteine levels were positively correlated in Low-Fit subjects with the TT genotype (r = 0.71, P < 0.0001), but no such correlations were observed in High-Fit subjects. In CC and CT genotype individuals, there were also no such correlations in either fitness level. These results suggest that the higher cardiorespiratory fitness may attenuate central artery stiffening associated with MTHFR C677T polymorphism.

Synopsis and data synthesis of genetic association studies in hypertension for the adrenergic receptor family genes: the CUMAGAS-HYPERT database

BACKGROUND

The adrenergic receptor (adrenoceptor) family genes have been extensively studied as candidate genes in hypertension but the results of individual genetic association studies (GAS) are controversial and inconclusive. To clarify these data, a systematic assessment of GAS for adrenoceptor family genes in hypertension was conducted.

METHODS

Data from 163 GAS involving 7 genes and 37 distinct genetic variants were analyzed and cataloged in CUMAGAS-HYPERT (Cumulative Meta-analysis of Genetic Association Studies-HYPERTension; a web-based information system, which allows the retrieval and synthesis of data from GAS in hypertension, available at http://biomath.med.uth.gr). Data from genome-wide association studies involving the adrenoceptor family genes were also systematically searched.

RESULTS

Individual GAS reported inconsistent associations and had limited power to detect modest genetic effects, with only 1.2% having power >80%. Thirteen variants were investigated by three or more studies and their results were subject to meta-analysis. In the main meta-analyses, significant results were shown for five variants (ADRB1 p.Arg389Gly, ADRB1 p.Ser49Gly, ADRB2 g.9368308A>G, ADRB3 p.Trp64Arg, and ADRA1A p.Cys347Arg) under the allelic contrast and/or the dominant model. Subgroup analyses by ethnicity and gender detected significant associations for three variants (ADRB1 p.Arg389Gly in east Asians, ADRB2 p.Gln27Glu in whites, and ADRB3 p.Trp64Arg in whites and in males). Heterogeneity ranged from none to high. No significant associations were recorded from genome-wide studies.

CONCLUSIONS

There is evidence to implicate adrenoceptor genes in hypertension, although future studies designed to investigate epistatic and gene-environment interactions would allow more solid conclusions to be drawn about the role of these genes in hypertension.

AnNOS3Haplotype Is Protective against Hypertension in a Caucasian Population

The endothelial nitric oxide synthase gene (NOS3) has been implicated in the development of hypertension, although the specific role of variants and haplotypes has not been clarified. In this study, the association of three polymorphisms (promoter T786C, intronic 4a/b, and nonsynonymous G894T) was tested in a case-control sample of 230 patients with essential hypertension and 306 healthy controls. Haplotype analysis was also performed. The mutant allele a^∗ of the 4a/b polymorphism showed a protective effect against hypertension under a dominant model (odds ratio = 0.64, 95% confidence interval (0.44–0.93)), although this effect was not significant after the adjustment for covariates (P = 0.06). The estimated frequency of the haplotype composed of the T786^∗, 4a^∗, and G894^∗ alleles was significantly higher in controls (5.5%) compared to cases (2%). These results indicate that although individual NOS3 polymorphisms are not associated with hypertension, a rare haplotype of the gene might be protective against the development of hypertension.