A review of the genetics of essential hypertension

CYP17A1-ATP2B1 SNPs and Gene-Gene and Gene-Environment Interactions on Essential Hypertension

Background: The association between the CYP17A1 and ATP2B1 SNPs and essential hypertension (referred to as hypertension) is far from being consistent. In addition to the heterogeneity of hypertension resulting in inconsistent results, gene–gene and gene–environment interactions may play a major role in the pathogenesis of hypertension rather than a single gene or environmental factor.

Methods: A case–control study consisting of 1,652 individuals (hypertension, 816; control, 836) was conducted in Maonan ethnic minority of China. Genotyping of the four SNPs was performed by the next-generation sequencing technology.

Results: The frequencies of minor alleles and genotypes of four SNPs were different between the two groups (p < 0.001). According to genetic dominance model analysis, three (rs1004467, rs11191548, and rs17249754) SNPs and two haplotypes (CYP17A1 rs1004467G-rs11191548C and ATP2B1 rs1401982G-rs17249754A) were negatively correlated, whereas rs1401982 SNP and the other two haplotypes (CYP17A1 rs1004467A-rs11191548T and ATP2B1 rs1401982A-rs17249754G) were positively associated with hypertension risk (p ≤ 0.002 for all). Two best significant two-locus models were screened out by GMDR software involving SNP–environment (rs11191548 and BMI ≥ 24 kg/m²) and haplotype–environment (CYP17A1 rs1004467G-rs11191548C and BMI ≥ 24 kg/m²) interactions (p ≤ 0.01). The subjects carrying some genotypes increased the hypertension risk.

Conclusions: Our outcomes implied that the rs1004467, rs11191548, and rs17249754 SNPs and CYP17A1 rs1004467G-rs11191548C and ATP2B1 rs1401982G-rs17249754A haplotypes have protective effects, whereas the rs1401982 SNP and CYP17A1 rs1004467A-rs11191548T and ATP2B1 rs1401982A-rs17249754G haplotypes showed adverse effect on the prevalence of hypertension. Several SNP–environment interactions were also detected.

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

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

Birth weight, childhood obesity and risk of hypertension: a Mendelian randomization study

PURPOSES

Observational studies indicate that birth weight and childhood obesity are associated with essential hypertension, but their causal effect on essential hypertension remains unclear. The aim of our study is to elucidate the causal relationship between birth weight, childhood obesity, and essential hypertension by Mendelian randomization (MR) with genetic variants as instrumental variables (IVs).

METHODS

We identified IVs based on single nucleotide polymorphisms (SNPs) associated with birth weight (n = 160 295) and childhood obesity (n = 6889, 1509 cases and 5380 controls) from the meta-analysis of a genome-wide association study. Summary level data from the UK Biobank essential hypertension consortium (n = 463 010, 54 358 cases and 408 652 controls) was used to analyze the relationship between IVs and essential hypertension. Two MR analysis methods, two threshold values of selecting IVs, and leave-one-out analysis were used to ensure the robustness of the results.

RESULTS

Genetic predisposition to higher birth weight did not increase the risk of essential hypertension. In contrast, per one standard deviation increase in childhood body mass index was significantly associated with an increased risk of essential hypertension (odds ratio = 1.0075, 95% confidence interval: 1.0035-1.0116) when using seven SNPs that achieved genome-wide significance (P < 5 × 10-8). Sensitivity analysis and MR-Egger regression indicated that the results were robust and not influenced by pleiotropy.

CONCLUSIONS

No evidence of an association between birth weight and essential hypertension was found. Childhood obesity, however, showed a causal relationship with the risk of essential hypertension, which was helpful to understand the mechanisms of essential hypertension and develop strategies for its prevention.

Biological Pathways of Long-Term Visit-to-Visit Blood Pressure Variability in the American Population: Cardiovascular Health Study and Women’s Health Initiatives

Studies reported a positive relationship between visit-to-visit blood pressure variability (VVBPV) and cardiovascular morbidity and mortality independently of the mean arterial blood pressure across clinical visits. The literature is scarce on the genes and biological mechanisms that regulate long-term VVBPV. We sought to identify biological pathways that regulate visit-to-visit blood pressure variability. We used phenotypic and genotype data from the Women’s Health Initiatives and Cardiovascular Health Studies. We defined VVBPV of systolic and diastolic blood pressure phenotypes as the standard deviation about the participant’s regression line with systolic and diastolic blood pressure regressed separately across visits. We imputed missing genotypes and then conducted a genome-wide association analysis to identify genomic variants related to the VVBPV and detect biological pathways. For systolic VVBPV, we identified a neurological pathway, the GABAergic pathway (P values = 1.1E − 2), and a vascular pathway, the RAP1 signaling pathway (P values = 5.8E − 2). For diastolic VVBPV, the hippo signaling (P values = 4.1E − 2), CDO myogenesis (P values = 7.0E − 2), and O-glycosylation of TSR domain-containing protein pathways (P values = 9.0E − 2) were the significant pathways. Future studies are warranted to validate these results. Further understanding of the roles of the genes regulating the identified pathways will help researchers to improve future pharmacological interventions to treat VVBPV in clinical practice.

Positive association between ATP2B1 rs17249754 and essential hypertension: a case-control study in Burkina Faso, West Africa

Background

Genetic and environment play a significant role in the etiology of essential hypertension (EH). Recently STK39 rs3754777, ATP2B1 rs2681472 and rs17249754 have been associated with BP variation and hypertension. In this study we aimed to determine firstly whether index variants were associated with the risk of developing EH in Burkina Faso and secondly to characterize cardiovascular risk markers.

Methods

We conducted a case-control study with 380 participants including 180 case subjects with EH and 200 control subjects with normal BP. We used TaqMan genotyping assays with probes from Applied Biosystems to genotype polymorphisms using the 7500 Real-Time PCR System. Biochemical parameters were measured using chemistry analyzer COBAS C311.

Results

T-test showed that cardiovascular risk markers such as body mass index, waist circumference, blood sugar, total cholesterol and triglycerides were significantly higher in hypertensive compared to normotensive (all p <  0.05). Binary logistic regression analysis revealed in decreasing order that overweight, family history of hypertension, central obesity and alcohol intake increased the risk of developing EH (all OR > 3.8; all p <  0.001).

In genetic level we observed that individuals carrying the AA+AG genotype of ATP2B1 rs17249754 had a low risk of developing EH than those carrying the GG genotype (OR = 0.48 [95% CI: 0.31–0.75] p = 0.001) and the A allele frequency in the cases was significantly lower than that of the controls (OR = 0.56 [95% CI: 0.38–0.82] p = 0.003). We also observed that ATP2B1 rs17249754 was significantly associated with higher SBP and DPB in case and control groups (GG versus AG + AA; p <  0.05), ATP2B1 rs2681472 was significantly associated with higher SBP only in case and control group (AA versus AG + GG; p <  0.05), STK39 rs3754777 was not significantly associated with any of the BP traits (CC versus CT + TT; p > 0.05).

Conclusion

Our results confirmed the significant association of ATP2B1 rs17249754 with the risk of developing EH in Burkinabe and showed an increase of cardiovascular risk markers levels in subjects with EH.

Electronic supplementary material

The online version of this article (10.1186/s12872-019-1136-x) contains supplementary material, which is available to authorized users.

Interaction of heat shock protein 70 (HSP70) polymorphisms and occupational hazards increases the risk of hypertension in coke oven workers

OBJECTIVES

The interaction between genetic, epigenetic inheritance and environmental factors determines susceptibility to hypertension. Previous epidemiology studies have shown that coke oven workers who are frequently exposed to various occupational hazards have remarkable increase in the risk for hypertension. Among many genetic variants identified in hypertension, heat shock protein 70 (HSP70) was found to play important roles in the pathogenesis of hypertension and associated diseases. We therefore explore the possible role of HSP70 polymorphisms and their interaction with occupational environment in hypertension risk.

METHODS

We carried out a case-control study among 367 coke oven workers in northwest China, focused on three common HSP70 polymorphisms (HSP70-1 G190C, HSP70-2 A1267G and HSP70-hom T2437C), and evaluated the association of HSP70 gene polymorphisms with work sites for high risk of hypertension.

RESULTS

The results indicated that HSP70-1 GC and CC genotype had 2.73-fold and 4.26-fold increased relative risk (95% CI 1.33 to 5.55 and 1.17 to 15.53), respectively, comparing with HSP70-1 GG genotype. HSP70-2 AG and GG conferred a 47% and 36% reduced risk (95% CI 0.23 to 0.99 and 0.14 to 0.92) comparing with HSP70-2 AA genotype. Further analysis of the interaction of HSP70 polymorphisms with occupational environment indicated a strong positive interaction between HSP70 genotype (HSP70-1 GC+CC, HSP70-2 AA and HSP70-hom TC+CC) and oven top workplace.

CONCLUSIONS

Collectively, these data indicate that HSP70 polymorphisms interact with occupational hazards might increase the risk of hypertension in coke oven workers.

Association of ACE gene A2350G and I/D polymorphisms with essential hypertension in the northernmost province of China

Angiotensin converting enzyme (ACE) gene, as a strong candidate gene for essential hypertension(EH), has been extensively studied. In this study, we carried out a population-based case-control study to explore whether ACE gene I/D and A2350G polymorphisms could consider to be risk factors for EH. A total of 2040 subjeces were recruited from Chinese Han in this study, out of which 1010 were cases and 1030 were normotensive individuals. ACE gene A2350G and I/D polymorphisms were amplified by polymerase chain reaction (PCR) and A2350G polymorphism was detected after restriction enzyme digestion with BstuI. Besides, we choosed 10% samples randomly sequencing to verify the accuracy of results. Genotype and allele frequencies distribution of I/D and A2350G in EH and control groups were significantly different. After grouped by sex or age, there were still statistical significances for two polymorphisms. In dominant and recessive model of A2350G, we found significant differences between two groups, respectively. For ACE I/D polymorphism, we observed that the existence of dramatical difference in dominant model between two groups, while in recessive model, marginally significant difference was found. Among the four haplotypes composed by ACE gene A2350G and I/D, haplotype G-D reached the statistical significance in two groups, and exhibited to be a risk factor for the development of EH, whose P < 0.001 and OR 95%CI = 1.639(1.435-1.872), while the other haplotypes were the protective factors and decreased the susceptibility to EH(P < 0.05). ACE gene A2350G and I/D polymorphisms were associated with increasing the risk of suffering from EH in the northernmost province of China individuals, with D allele and G allele individuals had a higher risk of EH(OR = 1.443, 95%CI = 1.273-1.636 and OR = 1.481, 95%CI = 1.303-1.684).

Replication of a genome-wide association study on essential hypertension in Mongolians

Replication of genome-wide significant association SNPs in independent populations is an essential approach for identifying gene-disease relationships. Therefore, we sought to investigate the top 21 SNPs (rs10507454, rs11897156, rs11897991, rs12325203, rs12541835, rs13395322, rs1525035, rs16936892, rs17010027, rs17045859, rs17136827, rs1866525, rs2045590, rs4547758, rs4655688, rs7107438, rs761353, rs8127139, rs9312305, rs9407874 and rs9865108) from a genome-wide association study of essential hypertension in Mongolians. This was a community-based case-control study involving 428 hypertensives and 638 normotensives from Kerqinzuoyihou Banner,Tongliao, Inner Mongolian Autonomous Region, China. Genotyping was conducted with Sequenom MassArray (®) SNP detection technology. Overall, there were no significant differences in the genotype distributions and allele frequencies between the cases and controls. There was a significant difference between the allele frequencies at locus rs17010027 in cases (high systolic blood pressure) and controls in female (p = .036). There were significant differences in the distribution of genotypes and the allele frequencies at locus rs10507454 between cases (high diastolic blood pressure) and controls (p = .019 and p = .022, respectively) especially in male (p = .009 and p = .011, respectively). rs17010027 is associated with high systolic blood pressure in female, and rs10507454 is associated with high diastolic blood pressure especially in male of this Mongolian population.

Hypomethylation of the Angiotensin II Type I Receptor (AGTR1) Gene Along with Environmental Factors Increases the Risk for Essential Hypertension

OBJECTIVES

The present study aimed to evaluate the hypertension status of community residents, analyze environmental and epigenetic factors, and propose prevention measures for hypertension.

METHODS

In our study, different methylation levels were distinguished utilizing melting temperature (Tm) values in both the case and the control group. Multiple logistic regression analysis was used to estimate the risk of having essential hypertension (EH) between hypertensive and nonhypertensive participants. A receiver-operating characteristic curve was used to analyze Tm cutoff levels of methylation.

RESULTS

The average DNA Tm was 71.784 with a standard deviation of 0.210. The Tm value of community residents (Fujian, China) was inversely correlated with systolic and diastolic blood pressure. Student t test analysis showed a clear separation in Tm expression levels between the hypertensive and the control group (p < 0.05). The Tm value was lower in the hypertension group than in the normotensive group. Multivariate regression analysis showed that high levels of DNA methylation were a protective factor in hypertension with adjustment of demographic and environmental factors, whereas when the Tm value increased by 0.1 units, the risk of hypertension was reduced by 0.652 times. Patients that smoked and consumed an irregular diet demonstrated a lower degree of methylation in the presence of hypertension.

CONCLUSIONS

DNA methylation affects the risk for the development of hypertension; therefore, epigenetic markers could be used to measure hypertension levels to help elucidate the pathogenesis of EH.

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

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

Epigenetic regulation of L-type voltage-gated Ca2+ channels in mesenteric arteries of aging hypertensive rats

Accumulating evidence has shown that epigenetic regulation is involved in hypertension and aging. L-type voltage-gated Ca²⁺ channels (LTCCs), the dominant channels in vascular myocytes, greatly contribute to arteriole contraction and blood pressure (BP) control. We investigated the dynamic changes and epigenetic regulation of LTCC in the mesenteric arteries of aging hypertensive rats. LTCC function was evaluated by using microvascular rings and whole-cell patch-clamp in the mesenteric arteries of male Wistar-Kyoto rats and spontaneously hypertensive rats at established hypertension (3 month old) and an aging stage (16 month old), respectively. The expression of the LTCC α1C subunit was determined in the rat mesenteric microcirculation. The expression of miR-328, which targets α1C mRNA, and the DNA methylation status at the promoter region of the α1C gene (CACNA1C) were also determined. In vitro experiments were performed to assess α1C expression after transfection of the miR-328 mimic into cultured vascular smooth muscle cells (VSMCs). The results showed that hypertension superimposed with aging aggravated BP and vascular remodeling. Both LTCC function and expression were significantly increased in hypertensive arteries and downregulated with aging. miR-328 expression was inhibited in hypertension, but increased with aging. There was no significant difference in the mean DNA methylation of CACNA1C among groups, whereas methylation was enhanced in the hypertensive group at specific sites on a CpG island located upstream of the gene promoter. Overexpression of miR-328 inhibited the α1C level of cultured VSMCs within 48 h. The results of the present study indicate that the dysfunction of LTCCs may exert an epigenetic influence at both pre- and post-transcriptional levels during hypertension pathogenesis and aging progression. miR-328 negatively regulated LTCC expression in both aging and hypertension.

[Association of the -844G>A polymorphism in the catalase gene with the increased risk of essential hypertension in smokers]

AIM

To investigate whether the functionally relevant -844G>A promotor polymorphism in the catalase (CAT) gene is associated with the development of essential hypertension (EH).

SUBJECTS AND METHODS

The investigation enrolled 2,339 unrelated ethnic Russian people, including 1,269 EH patients and 770 apparently healthy individuals. Genotyping of CAT -844G>A (rs769214) polymorphism was performed using a TaqMan real-time polymerase chain reaction assay.

RESULTS

The -844A allele (odds ratio (OR)=1.31; 95% confidence interval (CI), 1.04 to 1.64; р=0.02) and the -844AA genotype (OR=1.41; 95% CI, 1.02 to 1.94; р=0.03) were found to be related to a higher risk of EH in the smokers. No association was found between this polymorphism and EH risk in the non-smokers.

CONCLUSION

Smoking is a predisposing factor for development of EH in CAT -844AA genotype carriers.

Review: Genetics of the cardiometabolic syndrome: new insights and therapeutic implications

Although the definition of the phenotype is imprecise, cardiometabolic syndrome (CMS) includes a constellation of complex diseases such as type 2 diabetes, dislipidemias, central obesity and hypertension, proinflammatory and prothrombotic states, ovarian polycystosis and fatty liver. The genetics of each disease is complex in itself and varies in spectrum from monogenic and syndromic models of inheritance, usually rare, to the most common polygenic and multifactorial forms. In addition, human studies using the candidate-gene approach indicate that common genetic variants of several genes are associated with the development of CMS. Genome-wide scans have also provided several chromosomal regions associated with some of the components of CMS. In addition, through comparative genomics animal models can generate a map for candidate loci in humans and a promising approach is offered by bioinformatic tools for gene prioritization. Lastly, the involvement of genes whose products are already the targets for approved drugs, such as SLC6A4, PPARα and PPARγ , in the development of CMS suggests new avenues for CMS pharmacological treatment.

Genetic predisposition in patients with hypertension and normal ejection fraction to oxidative stress

The role of oxidative stress (OXS) due to myocardial nitric oxide synthase (NOS) uncoupling related to oxidative depletion of its cofactor tetrahydrobiopterin (BH4) emerged in the pathogenesis of heart failure with preserved ejection fraction. We determined the prevalence of six single nucleotide polymorphisms (SNPs) of genes encoding enzymes related to OXS, BH4 metabolism, and NOS function in ≥60-year-old 94 patients with hypertension and 18 age-matched controls with normal ejection fraction. Using echocardiography, 56/94 (60%) patients with hypertension had left ventricular (LV) diastolic dysfunction (HTDD+ group) and 38/94 (40%) patients had normal LV diastolic function (HTDD- group). Four SNPs (rs841, rs3783641, rs10483639, and rs807267) of guanosine triphosphate cyclohydrolase-1, the rate-limiting enzyme in BH4 synthesis, one (rs4880) of manganese superoxide dismutase, and one (rs1799983) of endothelial NOS genes were genotyped using real-time polymerase chain reaction method and Taqman probes. Protein carbonylation, BH4, and total biopterin levels were measured from plasma samples. No between-groups difference in minor allele frequency of SNPs was found. We calculated a genetic score indicating risk for OXS based on the minor allele frequencies of the SNPs. A high genetic risk for OXS was significantly associated with HTDD+ even after adjustment for confounding variables (odds ratio [95% confidence interval]:4.79 [1.12-20.54]; P = .035). In both patient groups protein carbonylation (P < .05 for both), plasma BH4 (P < .01 for both) and in the HTDD+ group total biopterin (P < .05) increased versus controls. In conclusion, in patients with hypertension and normal ejection fraction, a potential precursor of heart failure with preserved ejection fraction, a partly genetically determined increased OXS, seems to be associated with the presence of LV diastolic dysfunction.

Polymorphisms and haplotype of ROCK2 associate with high altitude essential hypertension in native high altitude Ladakhi Indian population: a preliminary study

BACKGROUND AND OBJECTIVES

High-altitude essential hypertension (HAEH) is a disease occurring in permanent residents of high-altitude regions. The disease is characterized with SBP ≥140 mmHg and DBP ≥90 mmHg. HAEH is known to run in families, i.e. the disease has genetic component. Rho-associated coiled-coil containing protein kinase 2 (ROCK2) is a stress-activated serine-threonine kinase known to disturb vascular-homeostasis leading to an increase in systemic vascular resistance, hallmark of HAEH. ROCK2 is implicated in sea-level essential hypertension but its role in HAEH is yet to be elucidated.

METHODS

The present study deals with genotyping 13 polymorphisms of ROCK2 gene in demographicaly matched human cases (n = 65) and controls (n = 38) by Sequenom MS (TOF)-based MassARRAY platform using iPLEX Gold technology.

RESULTS

A significant association was observed for GG genotype (SNP, rs978906), AA genotype (SNP, rs6753921), GG genotype (SNP, rs10495582) and AA genotype (SNP, rs2230774) with HAEH (p < 0.05). The 4 SNPs were tagged to each other and formed a 35 kb LD block (r(2 )> 0.90). Haplotype AGCC, composed of wild-type alleles of the SNPs was over represented in controls. In contrast, haplotype GAGA, composed of variant-alleles was observed to be in higher proportion in cases. Moreover, SBP levels (mmHg) were higher in cases with risk genotype against the ones having protective genotype (p = 0.05). Bioinformatic analysis revealed binding of a critical transcription factor, SRF to variant-allele G of SNP rs10495582. SRF has been reported in previous studies to promote ROCK2 transcriptional expression.

INTERPRETATION AND CONCLUSIONS

The data clearly suggests association of ROCK2 polymorphisms and haplotypes with HAEH.

Leveraging Epidemiologic and Clinical Collections for Genomic Studies of Complex Traits

BACKGROUND/AIMS

Present-day limited resources demand DNA and phenotyping alternatives to the traditional prospective population-based epidemiologic collections.

METHODS

To accelerate genomic discovery with an emphasis on diverse populations, we--as part of the Epidemiologic Architecture for Genes Linked to Environment (EAGLE) study--accessed all non-European American samples (n = 15,863) available in BioVU, the Vanderbilt University biorepository linked to de-identified electronic medical records, for genomic studies as part of the larger Population Architecture using Genomics and Epidemiology (PAGE) I study. Given previous studies have cautioned against the secondary use of clinically collected data compared with epidemiologically collected data, we present here a characterization of EAGLE BioVU, including the billing and diagnostic (ICD-9) code distributions for adult and pediatric patients as well as comparisons made for select health metrics (body mass index, glucose, HbA1c, HDL-C, LDL-C, and triglycerides) with the population-based National Health and Nutrition Examination Surveys (NHANES) linked to DNA samples (NHANES III, n = 7,159; NHANES 1999-2002, n = 7,839).

RESULTS

Overall, the distributions of billing and diagnostic codes suggest this clinical sample is a mixture of healthy and sick patients like that expected for a contemporary American population.

CONCLUSION

Little bias is observed among health metrics, suggesting this clinical collection is suitable for genomic studies along with traditional epidemiologic cohorts.

Influence of ABO genotype and phenotype on angiotensin-converting enzyme plasma activity

INTRODUCTION

ABO rs495828 polymorphism has recently been associated with risk of hypertension and cough induced by angiotensin-converting enzyme (ACE) inhibitors, which could be due to low ACE plasma activity. To study whether ABO rs495828 is associated with ACE activity. The association between ABO genotype and phenotype, and differences in ACE activity between the ABO phenotype groups were also studied.

SUBJECTS AND METHODS

We genotyped 168 subjects for rs495828. ACE plasma activity and ABO histo-blood group were measured in all minor allele homozygous subjects (TT) that agreed to participate in the study (n=8) and in age- and gender-matched heterozygous subjects (GT; n=8) and major allele homozygous subjects (GG; n=8).

RESULTS

A non-significant trend was found in ACE activity among rs495828 genotype groups; however the polymorphism was significantly associated with ABO phenotype (p=0.007), which in turn was associated with ACE activity (p=0.029).

CONCLUSION

These results provide new evidence for the ABO-ACE relationship. Although the genetic marker studied here may be involved somehow, ABO phenotype is shown to be a better predictor of ACE plasma activity.

Genetics of hypertension: discoveries from the bench to human populations

Hypertension is a complex trait that is influenced by both heritable and environmental factors. The search for genes accounting for the susceptibility to hypertension has driven parallel efforts in human research and in research using experimental animals in controlled environmental settings. Evidence from rodent models of genetic hypertension and human Mendelian forms of hypertension and hypotension have yielded mechanistic insights into the pathways that are perturbed in blood pressure homeostasis, most of which converge at the level of renal sodium reabsorption. However, the bridging of evidence from these very diverse approaches to identify mechanisms underlying hypertension susceptibility and the translation of these findings to human populations and public health remain a challenge. Furthermore, findings from genome-wide association studies still require functional validation in experimental models. In this review, we highlight results and implications from key studies in experimental and clinical hypertension to date.

Chromogranin B: intra- and extra-cellular mechanisms to regulate catecholamine storage and release, in catecholaminergic cells and organisms

Chromogranin B (CHGB) is the major matrix protein in human catecholamine storage vesicles. CHGB genetic variation alters catecholamine secretion and blood pressure. Here, effective Chgb protein under-expression was achieved by siRNA in PC12 cells, resulting in ~ 48% fewer secretory granules on electron microscopy, diminished capacity for catecholamine uptake (by ~ 79%), and a ~ 73% decline in stores available for nicotinic cholinergic-stimulated secretion. In vivo, loss of Chgb in knockout mice resulted in a ~ 35% decline in chromaffin granule abundance and ~ 44% decline in granule diameter, accompanied by unregulated catecholamine release into plasma. Over-expression of CHGB was achieved by transduction of a CHGB-expressing lentivirus, resulting in ~ 127% elevation in CHGB protein, with ~ 122% greater abundance of secretory granules, but only ~ 14% increased uptake of catecholamines, and no effect on nicotinic-triggered secretion. Human CHGB protein and its proteolytic fragments inhibited nicotinic-stimulated catecholamine release by ~ 72%. One conserved-region CHGB peptide inhibited nicotinic-triggered secretion by up to ~ 41%, with partial blockade of cationic signal transduction. We conclude that bi-directional quantitative derangements in CHGB abundance result in profound changes in vesicular storage and release of catecholamines. When processed and released extra-cellularly, CHGB proteolytic fragments exert a feedback effect to inhibit catecholamine secretion, especially during nicotinic cholinergic stimulation.

A polymorphic 3'UTR element in ATP1B1 regulates alternative polyadenylation and is associated with blood pressure

Although variants in many genes have previously been shown to be associated with blood pressure (BP) levels, the molecular mechanism underlying these associations are mostly unknown. We identified a multi-allelic T-rich sequence (TRS) in the 3’UTR of ATP1B1 that varies in length and sequence composition (T_22-27 and T₁₂GT ₃GT₆). The 3’UTR of ATP1B1 contains 2 functional polyadenylation signals and the TRS is downstream of the proximal polyadenylation site (A2). Therefore, we hypothesized that alleles of this TRS might influence ATP1B1 expression by regulating alternative polyadenylation. In vitro, the T₁₂GT ₃GT₆ allele increases polyadenylation at the A2 polyadenylation site as compared to the T₂₃ allele. Consistent with our hypothesis, the relative abundance of the A2-polyadenylated ATP1B1 mRNA was higher in human kidneys with at least one copy of the T₁₂GT ₃GT₆ allele than in those lacking this allele. The T₁₂GT ₃GT₆ allele is also associated with higher systolic BP (beta = 3.3 mmHg, p = 0.014) and diastolic BP (beta = 2.4 mmHg, p = 0.003) in a European-American population. Therefore, we have identified a novel multi-allelic TRS in the 3’UTR of ATP1B1 that is associated with higher BP and may mediate its effect by regulating the polyadenylation of the ATP1B1 mRNA.

ET-1 actions in the kidney: evidence for sex differences

Hypertension and chronic kidney disease are more common in men than in premenopausal women at the same age. In animal models, females are relatively protected against genetic or pharmacological procedures that produce high blood pressure and renal injury. Overactivation or dysfunction of the endothelin (ET) system modulates the progression of hypertension or kidney diseases with the ET(A) receptor primarily mediating vasoconstriction, injury and anti-natriuresis, and ET(B) receptors having opposite effects. The purpose of this review is to examine the role of the ET system in the kidney with a focus on the inequality between the sexes associated with the susceptibility to and progression of hypertension and kidney diseases. In most animal models, males have higher renal ET-1 mRNA expression, greater ET(A) -mediated responses, including renal medullary vasoconstriction, and increased renal injury. These differences are reduced following gonadectomy suggesting a role for sex hormones, mainly testosterone. In contrast, females are relatively protected from high blood pressure and kidney damage via increased ET(B) versus ET(A) receptor function. Furthermore, ET(A) receptors may have a favourable effect on sodium excretion and reducing renal damage in females. In human studies, the genetic polymorphisms of the ET system are more associated with hypertension and renal injury in women. However, the knowledge of sex differences in the efficacy or adverse events of ET(A) antagonists in the treatment of hypertension and kidney disease is poorly described. Increased understanding how the ET system acts differently in the kidneys between sexes, especially with regard to receptor subtype function, could lead to better treatments for hypertension and renal disease. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.

The relationship between angiotensinogen gene polymorphisms and essential hypertension in a Northern Han Chinese population

Gene polymorphisms of the renin-angiotensin system are involved in the pathophysiology of hypertension. We genotyped 4 polymorphisms of angiotensinogen (AGT) gene A-20C (rs5050), A-6G (rs5051), C3889T (rs4762), and C4072T (rs699) by polymerase chain reaction-restriction fragment length polymorphism in 652 patients and 780 controls to examine the association of AGT and hypertension in a Northern Han Chinese population. There were significant differences in the distribution of genotypes and allele frequencies at C4072T between the patients and the controls (both P < .01); patients with CC genotype had a higher risk of hypertension (odds ratio = 1.7, 95% confidence interval 1.4-2.1). The distribution of genotypes at A-6G was significantly different between patients and controls (P < .05). No other significant differences in genotypes or frequencies were observed. No association was observed between the haplotypes of AGT and hypertension. The AGT-6A and 4072C alleles are associated with susceptibility to hypertension in this population.

Lower ADD1 gene promoter DNA methylation increases the risk of essential hypertension

The goal of our study is to investigate the contribution of promoter DNA methylation of α-adducin (ADD1) gene to the risk of essential hypertension (EH). Using the bisulphite pyrosequencing technology, DNA methylation levels of five CpG dinucleotides on ADD1 promoter were measured among 33 EH cases and 28 healthy controls. Significantly higher ADD1 DNA methylation levels were observed in the females than in the males (CpG1: P = 0.016; CpG2-5: P = 0.021). A breakdown analysis by gender showed that lower CpG1 methylation was associated with an increased risk of EH in females (adjusted P = 0.042). A much more significant association between lower CpG2-5 methylation levels and the increased risk of EH was found in males (adjusted P = 0.008). CpG1 methylation was inversely correlated with age in females (r = -0.407, P = 0.019) but not in males. ADD1 CpG1 and CpG2-5 methylation levels were significantly lower in post-menopausal (>50 years) women than pre-menopausal (≤50 years) women (CpG1: P = 0.006; CpG2-5: P = 0.034). A significant interaction between CpG1 methylation and age was found in females (CpG1*age: P = 0.029). CpG2-5 methylation was shown as a significant predictor of EH in males [area under curve (AUC) = 0.855, P = 0.001], in contrast that CpG1 methylation was a trend toward indicator in females (AUC = 0.699, P = 0.054). In addition, significant differences were observed between males and females for alanine aminotransferase (ALT, P = 0.001), aspartate aminotransferase (AST, P = 0.005) and uric acid (P<0.001). The concentration of AST was inversely correlated with ADD1 CpG2-5 methylation levels in female controls (r = -0.644, P = 0.024). These observations may bring new hints to elaborate the pathogenesis of EH.

A haplotype of the GOSR2 gene is associated with essential hypertension in Japanese men

OBJECTIVES

The Golgi SNAP receptor complex member 2 (GOSR2) gene is a Golgi-associated soluble factor attachment receptor (SNARE) protein involved in intra-Golgi protein trafficking on chromosome 17q21, which is the hypertension linkage peak on the human chromosome. The aim of the present study was to assess the association between the human GOSR2 gene and essential hypertension (EH) using a haplotype-based case-control study.

METHODS

A total of 320 EH patients and 205 age-matched controls were genotyped for the five single-nucleotide polymorphisms (SNPs) used as genetic markers for the human GOSR2 gene (rs197932, rs3785889, rs197922, rs17608766, and rs16941382). Data were analyzed for three separate groups: the total subjects, men, and women.

RESULTS

The overall distribution of the haplotypes in men was significantly different between the EH patients and the control subjects (P=0.002). Additionally, the frequency of the T-A-G haplotype (rs197932-rs3785889-rs197922) for men was significantly higher in the EH patients than in the control subjects (P=0.049). After adjustment for the major risk factors, multiple logistic regression analysis also revealed that the frequency of men with the T-A-G haplotype (homozygous and heterozygous diplotypes) was significantly higher than that in men without the haplotype (OR=1.756, P=0.039).

CONCLUSIONS

The results of this study indicate that the T-A-G haplotype may be a useful genetic marker for EH in Japanese men.

Novel findings and future directions on the genetics of hypertension

PURPOSE OF REVIEW

Modern molecular techniques are identifying pathways and genes involved in the pathogenesis of the complex disorder essential hypertension. This review provides an overview of genetic methodologies and recent results in the study of high blood pressure (BP), hypertension-attributed nephropathy, and related intermediate phenotypes.

RECENT FINDINGS

Candidate gene studies have implicated aberrations in ion channels, ion channel regulation, aldosterone signaling, vasoconstriction and inflammation in essential hypertension; genome-wide association studies (GWAS) have detected more than 50 BP loci, most previously unsuspected in essential hypertension. Mapping by admixture linkage disequilibrium (MALD; or admixture mapping) recently led to a major breakthrough in hypertension-attributed kidney disease in African Americans, demonstrating the role of the apolipoprotein L1 (APOL1) and nonmuscle myosin heavy chain 9 (MYH9) genes in this primary kidney disease residing in the spectrum of focal segmental glomerulosclerosis. GWAS have detected associations between kidney function and UMOD and SHROOM3.

SUMMARY

Genetic studies confirm that 'essential hypertension' consists of disparate mechanisms that ultimately lead to elevations in systemic BP. The cause of hypertension in the majority of cases remains unknown. It is anticipated that epigenetic phenomena, rare exonic mutations, and interactions with environmental factors make additional contributions.

Blood pressure and human genetic variation in the general population

PURPOSE OF REVIEW

Hypertension is a complex trait with multiple environmental and genetic contributors. Until recently, linkage studies of rare Mendelian disorders of hypertension and hypotension have produced the most notable progress toward understanding the heritable basis of blood pressure (BP). Association studies to identify common variants have been limited in the past by small sample sizes and most findings have lacked replication.

RECENT FINDINGS

Recently, well powered, targeted candidate gene and genome-wide association studies have reported reproducible associations between rare and common genetic variants and BP and hypertension at the population level.

SUMMARY

Identification of novel genes will lead to an improved understanding of BP regulation and the potential for novel therapies.

Genetic biomarkers of hypertension and future challenges integrating epigenomics

Essential hypertension is a multifactorial disease, considered to be one of the world's greatest public health problems. Despite recent, major, technical advances aiming to elucidate its genetic component, the discovered biomarkers up to now were reported to have only small effects, explaining consequently a tiny fraction of its phenotypic variance and resulting in a large proportion of missing heritability. Likewise, little evidence is available with regard to the epigenetic regulation of essential hypertension, since no robust biomarkers have yet been reported. In the current review, we discuss the main approaches used exclusively to study the genetics and epigenetics of essential hypertension, the biomarkers identified, their clinical utility and the difficulties to be overcome. Furthermore, we propose a new category of functional genetic-epigenetic biomarkers, eMethSNPs, and we provide their hypothetical gene expression profiles for a genetic functional regulation of hypertension via DNA methylation. Though believed to be infrequent, eMethSNPs could constitute a new category of mechanistically-based genetic biomarkers predisposing to essential hypertension.

Association of natriuretic peptide receptor-C gene with ischemic stroke and hypertension in Chinese Han population

To investigate whether natriuretic peptide receptor-C (NPR3) gene polymorphisms were associated with ischemic stroke (IS) and hypertension (a conventional risk factor for stroke), we conducted a case-control study in Chinese Han population. We found that rs696831, located in intron 2, was associated with IS. In addition, we found that rs16890208 and rs700925, in linkage disequilibrium (LD) with each other in intron 3, were associated with hypertension. The A allele of the rs16890208, T allele of the rs700925, and the AT haplotype, derived from rs16890208 and rs700925, increased the risk of hypertension with odds ratios (ORs) of 1.74 (95% CI = 1.23-2.47), 1.72 (95% CI = 1.21-2.42), and 1.54 (95% CI = 1.14-2.08), respectively. Further, we found that rs11745562 and rs2270915, in LD with each other in intron 5 and exon 8, were associated with hypertension. The A allele of the rs11745562 and the G allele of the rs2270915 increased the risk of hypertension with ORs of 1.53 (95% CI = 1.07-2.19) and 1.55 (95% CI = 1.08-2.22), respectively. Therefore, we provided novel evidences that polymorphisms or haplotype in NPR3 gene may influence the risk of IS or hypertension independently in Chinese population.

Between candidate genes and whole genomes: time for alternative approaches in blood pressure genetics

Blood pressure has a significant genetic component, but less than 3% of the observed variance has been attributed to genetic variants identified to date. Candidate gene studies of rare, monogenic hypertensive syndromes have conclusively implicated several genes altering renal sodium balance, and studies of essential hypertension have inconsistently implicated over 50 genes in pathways affecting renal sodium balance and other functions. Genome-wide linkage scans have replicated numerous quantitative trait loci throughout the genome, and over 50 single nucleotide polymorphisms (SNPs) have been replicated in multiple genome-wide association studies. These studies provide considerable evidence that epistasis and other interactions play a role in the genetic architecture of blood pressure regulation, but candidate gene studies have limited scope to test for epistasis, and genome-wide studies have low power for both main effects and interactions. This review summarizes the genetic findings to date for blood pressure, and it proposes focused, pathway-based approaches involving epistasis, gene-environment interactions, and next-generation sequencing to further the genetic dissection of blood pressure and hypertension.

Genetics and hypertension: is it time to change my practice?

Recent advances in genotyping technology and in particular a number of large-scale genome-wide association studies have helped to unravel the genetic basis of hypertension. Although our knowledge is still far from being complete it is important to ask how genetic findings could be translated to clinical practice. In a first step we summarize the strategies to dissect the genetics of hypertension from candidate gene studies to genome-wide association studies and recent sequencing experiments. The greatest hope in this context is the development of new drugs that are based on newly discovered pathophysiological principles. We describe examples where significant therapeutic effects are achieved with agents targeting pathways that contribute only small amounts to the genetic variability of a phenotype. There are good reasons to believe that new drugs will be developed based on genetic data in hypertension. We also highlight the potential for pharmacogenetics and risk stratification. The former is not currently supported by a larger body of evidence, but well designed studies are under way. The latter needs to follow the same principles for evaluation of other novel biomarkers of cardiovascular risk and is unlikely to influence clinical practice in the next few years.

The ACE I/D polymorphism in US adults: limited evidence of association with hypertension-related traits and sex-specific effects by race/ethnicity

BACKGROUND

The insertion/deletion (I/D) variant (rs4646994) of the angiotensin I-converting enzyme (ACE) gene is one of the most studied polymorphisms in relation to blood pressure and essential hypertension in humans. The evidence to date, however, on an association of this variant with blood pressure-related outcomes has been inconclusive.

METHODS

We examined 5,561 participants of the Third National Health and Nutrition Examination Survey (NHANES III), a population-based and nationally representative survey of the United States, who were ≥20 years of age and who self-identified as non-Hispanic white, non-Hispanic black, or Mexican American. Within each race/ethnicity, we assessed genetic associations of the I/D variant with systolic blood pressure (SBP), diastolic blood pressure (DBP), and hypertension, as well as genotype-sex interactions, in four genetic models (additive, dominant, recessive, and codominant).

RESULTS

The frequency of the I/D variant differed significantly by race/ethnicity (P = 0.001). Among non-Hispanic blacks, the D allele was significantly associated (P < 0.05) with increased SBP in additive and dominant covariate-adjusted models and was also associated with increased DBP in dominant models when participants taking ACE inhibitors were excluded from the analyses. No other significant associations were observed in any race/ethnic group. Significant genotype-sex interactions were detected among Mexican Americans, for whom positive associations with SBP and hypertension were seen among females, but not males.

CONCLUSIONS

This study gives limited support for association of the ACE I/D variant with blood pressure and for sex-specific effects among particular race/ethnic groups, though we cannot rule out the role of genetic or environmental interactions.

Genome-wide association studies of hypertension: Achievements, difficulties and strategies

Estimated from family studies, the heritability of hypertension ranges from 31% to 68%. Linkage studies and candidate gene association studies were once widely used to investigate the genetic mechanisms of hypertension. However, results from these studies could only explain 1%-2% heritability. With the technological advances and subsequently the accomplishment of the Human Genome Project, genome-wide association studies (GWA studies) have been applied to find genome-wide significant signals for many common diseases. Current GWA studies of hypertension have identified dozens of hypertension or blood pressure associated variants. However, different GWA study identified different variants and the results could hardly be replicated in other studies. Therefore, a debate took place on whether GWA studies will unlock the genetic basis of hypertension and whether we shall continue throwing millions of dollars on GWA studies. This review gives a short introduction to the history of genetic study on hypertension and summarizes the current findings for GWA studies of hypertension or blood pressure. Finally, we will discuss that debate and try to find alternative strategies and technologies that may hold a greater chance to make progress in understanding the genetic risk factors of hypertension and blood pressure regulation.

Genetic variants and blood pressure in a population-based cohort: the Cardiovascular Risk in Young Finns study

Clinical relevance of a genetic predisposition to elevated blood pressure was quantified during the transition from childhood to adulthood in a population-based Finnish cohort (N=2357). Blood pressure was measured at baseline in 1980 (age 3-18 years) and in follow-ups in 1983, 1986, 2001, and 2007. Thirteen single nucleotide polymorphisms associated with blood pressure were genotyped, and 3 genetic risk scores associated with systolic and diastolic blood pressures and their combination were derived for all of the participants. Effects of the genetic risk score were 0.47 mm Hg for systolic and 0.53 mm Hg for diastolic blood pressures (both P<0.01). The combination genetic risk score was associated with diastolic blood pressure from age 9 years onward (β=0.68 mm Hg; P=0.015). Replications in 1194 participants of the Bogalusa Heart Study showed essentially similar results. The participants in the highest quintile of the combination genetic risk score had a 1.82-fold risk of hypertension in adulthood (P<0.0001) compared with the lowest quintile, independent of a family history of premature hypertension. These findings show that genetic variants are associated with preclinical blood pressure traits in childhood; individuals with several susceptibility alleles have, on average, a 0.5-mm Hg higher blood pressure, and this trajectory continues from childhood to adulthood.

Age-dependent association of the polymorphisms in the mitochondria-shaping gene, OPA1, with blood pressure and hypertension in Korean population

BACKGROUND

Essential hypertension is associated with mitochondrial dysfunction. Because mitochondrial dynamics; mitochondrial morphological changes are closely linked with various mitochondrial functions, we aimed to examine whether the genetic variation of the mitochondria-shaping genes influenced the susceptibility to blood pressure (BP) and hypertension.

METHODS

The quantitative BP trait analysis and hypertension case-control analysis for the total 52 single-nucleotide polymorphisms (SNPs) in the five major mitochondria-shaping genes were performed in the Korean Association Resource (KARE) study cohort (8,512 subjects).

RESULTS

In the total subjects of the KARE study cohort, there were no statistically significant associations of the SNPs in the five mitochondria-shaping genes with BP or hypertension after adjusting for multiple tests. However, the age group analysis in the 40s, 50s, and 60s age subgroups revealed that 15 SNPs out of 26 SNPs genotyped in the OPA1 gene were significantly associated with BP and/or hypertension in the 60s age subgroup and their association P values satisfied the Bonferroni-corrected significance level (P < 0.00625). Noticeably, nine SNPs were consistently associated with all the three traits; systolic BP (SBP), diastolic BP (DBP), and hypertension. In silico lookup of the associated SNPs in the Southern German population did not reveal associations with BP traits.

CONCLUSIONS

Our results indicate that genetic variation of the mitochondrial fusion-regulating gene, OPA1, might be associated with BP and hypertension in an age-dependent and population-specific manner in the Korean study cohort, and suggest that altered mitochondrial dynamics, especially involved in the mitochondrial fusion event, may play an important role in the pathogenesis of hypertension.

Genetic variations in CYP17A1, CACNB2 and PLEKHA7 are associated with blood pressure and/or hypertension in She ethnic minority of China

OBJECTIVES

Two large-scale genome-wide association studies (GWAs) have identified multiple variants associated with blood pressure (BP) or hypertension. The present study was to investigate whether some variations were associated with BP traits and hypertension or even prehypertension in adult She ethnic minority of China.

METHODS

The population of the present study comprised 4460 (1979 males and 2481 females, respectively) unrelated she ethnic minority based on a cross-sectional study from Ningde City in Fujian province of China. There were 1692 hypertensives, 1600 prehypertensives and 1168 normotensive controls, respectively. We genotyped 7 variants in CYP17A1, PLEKHA7, CACNB2, ATP2B1, TBX3-TBX5, CSK-ULK3 and SH2B3 reported by the previous GWAs on Europeans. All analyses were performed in an additive genetic model.

RESULTS

As the minor allele of rs653178 in/near SH2B3 was very rare with the frequency of 0.018, we excluded this single nucleotide polymorphism (SNP) in the further analyses. Of the other 6 loci, linear regression analyses revealed that rs11191548 in CYP17A1 and rs11014166 in CACNB2 were significantly associated with systolic BP (β = -1.17, P = 0.002 and β = -0.50, P = 0.006, respectively), while only SNP rs11191548 was significantly associated with diastolic BP (β = -0.56, P=0.002) after adjusted by age, sex and BMI. Two variants in CACNB2 and PLEKHA7 were found to be significantly related to hypertension (odds ratios [OR] and (95% confidence interval [CI]): 0.79 (0.65-0.97) and 1.19 (1.01-1.41), respectively) in logistic regression analyses after adjusted by age, sex and BMI. In addition, we found that combined risk alleles of the 6 SNPs increased risk of hypertension in a stepwise fashion (P for trend < 0.001). However, none of the 6 SNPs was significantly associated with BMI or prehypertension status. While logistic analysis showed that subjects with cumulative risk alleles more than 9 had significantly higher risk for prehypertension (adjusted OR: 3.10, P < 0.001) compared with those with risk alleles less than 4.

CONCLUSIONS

We replicated that variations in CYP17A1, CACNB2 and PLEKHA7 were related to BP traits and/or hypertension in She population. In addition, although we failed to observe single gene associated with prehypertension, we first found that conjoint effect of multiple risk alleles on BP might increase the risk of progressing to prehypertension.

Interactions of genetic variants with physical activity are associated with blood pressure in Chinese: the GenSalt study

BACKGROUND

Blood pressure (BP) homeostasis involves complex interactions among genetic and nongenetic factors, providing major challenges to dissection of the genetic components that influence BP and hypertension. In this study, we examine the effects of interaction of genetic variants with physical activity on BP in a relatively genetically homogenous cohort of rural Chinese villagers.

METHODS

Generalized estimating equations analysis was used to test for associations of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with variants in 24 genes in BP pathways (196 single-nucleotide polymorphisms (SNPs)) among 3,142 Chinese participants divided according to physical activity (active vs. inactive groups).

RESULTS

In the physically active group, two SNPs in NR3C2 were significantly associated with lower SBP, and a SNP in SCNN1B was significantly associated with lower SBP and DBP. In the physically inactive group, a SNP in APLNR was associated with lower SBP, a SNP in GNB3 (guanine nucleotide binding protein, β polypeptide 3) was associated with higher SBP and DBP, and a SNP in BDKRB2 (bradykinin receptor B2) was associated with lower DBP. Cumulative effects in carriers of minor alleles of these SNPs showed reductions of SBP and DBP as large as 8 and 5 mm Hg, respectively, in the active individuals compared to inactive individuals carrying the same number of minor alleles.

CONCLUSIONS

We found that physical activity modifies the effects of genetic variants on BP. However, our results also show that active individuals with specific genotypes always have lower BP than inactive individuals with the same genotypes, demonstrating the overall beneficial effects of physical activity on BP.

Association of the CYP3A5 polymorphism (6986G>A) with blood pressure and hypertension

The cytochrome P450 family 3 subfamily A polypeptide 5 (CYP3A5) gene has been implicated in the regulation of blood pressure (BP) and thus, may serve as a potential risk factor for the development of hypertension. However, current results regarding the association between CYP3A5 single nucleotide polymorphisms and BP/hypertension have been inconsistent. In this study, we performed a meta-analysis to evaluate the association between the CYP3A5 rs776746 (6986G>A) polymorphism and BP/hypertension. Ten studies (representing 2799 cases and 6794 controls) were included to determine the association of this single nucleotide polymorphism with hypertension, and 12 studies (9076 subjects) were included to determine the association of this single nucleotide polymorphism with BP. Overall, no associations were observed between the rs776746 polymorphism and BP/hypertension. In subgroup analysis, CYP3A5*1 carriers had lower systolic BP, compared with non-carriers in white populations (mean difference=-1.322, 95% confidence interval -2.401 to -0.242 mm Hg, P=0.016). This meta-analysis suggested a modestly significant association between the CYP3A5 rs776746 polymorphism and systolic BP in white populations. Given the limited sample size, additional studies are necessary to investigate the role of CYP3A5 in the regulation of BP and the pathogenesis of hypertension.

Recent findings in the genetics of blood pressure and hypertension traits

We provide an overview of ongoing discovery efforts in the genetics of blood pressure (BP) and hypertension (HTN) traits. Two large genome-wide association meta-analyses of individuals of European descent were recently published, revealing ~13 new loci for BP traits. Only two of these loci harbor genes in a pathway known to affect BP (CYP17A1 and NPPA/NPPB). Functional variants in these loci are still unknown. Few genome-wide association studies (GWAS) of complex diseases have been published from non-European populations. The study of populations with different evolutionary history and linkage disequilibrium (LD) structure, such as individuals of African ancestry, may provide an opportunity to further narrow these regions to identify the causal gene(s). Several collaborative efforts toward discovery of low-frequency variants and copy number variation for BP traits are currently underway. As evidence for new loci for complex diseases accumulates the assessment of the epidemiologic architecture of these variants in populations assumes higher priority. The impact of public health-relevant contexts such as diet, physical activity, psychosocial factors, and aging has not been examined for most common variants associated with BP.