Genetic variations related to hypertension: a review

Single nucleotide polymorphism-based biomarker in primary hypertension

Primary hypertension is a multiplex and multifactorial disease influenced by various strong components including genetics. Extensive research such as Genome-wide association studies and candidate gene studies have revealed various single nucleotide polymorphisms (SNPs) related to hypertension, providing insights into the genetic basis of the condition. This review summarizes the current status of SNP research in primary hypertension, including examples of hypertension-related SNPs, their location, function, and frequency in different populations. The potential clinical implications of SNP research for primary hypertension management are also discussed, including disease risk prediction, personalized medicine, mechanistic understanding, and lifestyle modifications. Furthermore, this review highlights emerging technologies and methodologies that have the potential to revolutionize the vast understanding of the basis of genetics in primary hypertension. Gene editing holds the potential to target and correct any kind of genetic mutations that contribute to the development of hypertension or modify genes involved in blood pressure regulation to prevent or treat the condition. Advances in computational biology and machine learning enable researchers to analyze large datasets and identify complex genetic interactions contributing to hypertension risk. In conclusion, SNP research in primary hypertension is rapidly evolving with emerging technologies and methodologies that have the potential to transform the knowledge about genetic basis related to the condition. These advances hold promise for personalized prevention and treatment strategies tailored to an individual's genetic profile ultimately improving patient outcomes and reducing healthcare costs.

Genome-wide association study meta-analysis of blood pressure traits and hypertension in sub-Saharan African populations: an AWI-Gen study

Most hypertension-related genome-wide association studies (GWASs) focus on non-African populations, despite hypertension (a major risk factor for cardiovascular disease) being highly prevalent in Africa. The AWI-Gen study GWAS meta-analysis for blood pressure (BP)-related traits (systolic and diastolic BP, pulse pressure, mean-arterial pressure and hypertension) from three sub-Saharan African geographic regions (N = 10,775), identifies two novel genome-wide significant signals (p < 5E-08): systolic BP near P2RY1 (rs77846204; intergenic variant, p = 4.95E-08) and pulse pressure near LINC01256 (rs80141533; intergenic variant, p = 1.76E-08). No genome-wide signals are detected for the AWI-Gen GWAS meta-analysis with previous African-ancestry GWASs (UK Biobank (African), Uganda Genome Resource). Suggestive signals (p < 5E-06) are observed for all traits, with 29 SNPs associating with more than one trait and several replicating known associations. Polygenic risk scores (PRSs) developed from studies on different ancestries have limited transferability, with multi-ancestry PRS providing better prediction. This study provides insights into the genetics of BP variation in African populations.

Does the quality of street greenspace matter? Examining the associations between multiple greenspace exposures and chronic health conditions of urban residents in a rapidly urbanising Chinese city

BACKGROUND

Numerous studies have demonstrated that greenspace(GS) exposure is associated with health improvements in individuals with hypertension and diabetes. However, studies examining the associations between multiple GS exposures and chronic health conditions in developing countries are limited.

METHODS

Geospatial data and spatial analysis were employed to objectively measure the total neighbourhood vegetative cover (mean value of normalised difference vegetation index [NDVI] within specific buffer zone) and proximity to park-based GS (network distance from home to the entrance of park-based GS). Street view imagery and machine learning techniques were used to measure the subjective perceptions of street GS quality. A multiple linear regression model was applied to examine the associations between multiple GS exposures and the prevalence of hypertension and diabetes in neighbourhoods located in Qingdao, China.

RESULTS

The model explained 29.8% and 28.2% of the prevalence of hypertension and diabetes, respectively. The results suggested that: 1) the total vegetative cover of the neighbourhood was inversely correlated with the prevalence of hypertension (β = -0.272, p = 0.013, 95% confidence interval (CI): [-1.332, -0.162]) and diabetes (β = -0.230, p = 0.037, 95% CI: [-0.720, -0.008]). 2) The street GS quality was negatively correlated with the prevalence of hypertension (β = -0.303, p = 0.007, 95% CI: [-2.981, -0.491]) and diabetes (β = -0.309, p = 0.006, 95% CI: [-1.839, -0.314]). 3) Proximity to park-based GS and the prevalence of hypertension and diabetes mellitus were not significantly correlated.

CONCLUSIONS

This study used subjective and objective methods to comprehensively assess the greenspace exposure from overhead to eye level, from quantity, proximity to quality. The results demonstrated the beneficial relationships between street GS quality, total vegetative cover, and chronic health in a rapidly urbanising Chinese city. Furthermore. the effect of street GS quality was more pronounced in potentially mitigating chronic health problems, and improving the quality of street GS might be an efficient and effective intervention pathway for addressing chronic health issues in densely populated cities.

Association of APP gene polymorphisms and promoter methylation with essential hypertension in Guizhou: a case-control study

BACKGROUND

Single-nucleotide polymorphisms (SNPs) and DNA methylation are crucial regulators of essential hypertension (EH). Amyloid precursor protein (APP) mutations are implicated in hypertension development. Nonetheless, studies on the association of APP gene polymorphism and promoter methylation with hypertension are limited. Therefore, this case-control aims to evaluate the genetic association of APP gene polymorphism and promoter methylation with EH in Guizhou populations.

OBJECTIVE AND METHODS

We conducted a case-control study on 343 EH patients and 335 healthy controls (including Miao, Buyi, and Han populations) in the Guizhou province of China to analyze 11 single-nucleotide polymorphisms (rs2040273, rs63750921, rs2211772, rs2830077, rs467021, rs368196, rs466433, rs364048, rs364051, rs438031, rs463946) in the APP gene via MassARRAY SNP. The MassARRAY EpiTYPER was employed to detect the methylation levels of the promoters.

RESULTS

In the Han population, the rs2211772 genotype distribution was significantly different between disease and control groups (χ² = 6.343, P = 0.039). The CC genotype reduced the risk of hypertension compared to the TT or TC genotype (OR 0.105, 95%CI 0.012-0.914, P = 0.041). For rs2040273 in the Miao population, AG or GG genotype reduced the hypertension risk compared with the AA genotype (OR 0.533, 95%CI 0.294-0.965, P = 0.038). Haplotype TCC (rs364051-rs438031-rs463946) increased the risk of EH in Guizhou (OR 1.427, 95%CI 1.020-1.996, P = 0.037). Each 1% increase in CpG_19 (- 613 bp) methylation level was associated with a 4.1% increase in hypertension risk (OR 1.041, 95%CI 1.002-1.081, P = 0.039). Each 1% increase in CpG_1 (- 296 bp) methylation level was associated with an 8% decrease in hypertension risk in women (OR 0.920, 95%CI 0.860-0.984, P = 0.015). CpG_19 significantly correlated with systolic blood pressure (r = 0.2, P = 0.03). The methylation levels of CpG_19 in hypertensive patients with rs466433, rs364048, and rs364051 minor alleles were lower than that with wild-type alleles (P < 0.05). Moreover, rs467021 and rs364051 showed strong synergistic interaction with EH (χ² = 7.633, P = 0.006). CpG_11, CpG_19, and rs364051 showed weak synergistic interaction with EH (χ² = 19.874, P < 0.001).

CONCLUSION

In summary, rs2211772 polymorphism and promoter methylation level of APP gene may be linked to EH in Guizhou populations. Our findings will provide novel insights for genetic research of hypertension and Alzheimer's disease.

Polymorphism of NOS3 gene and its association with essential hypertension in Guizhou populations of China

OBJECTIVE

A case-control study was conducted to evaluate the relationship between endothelial nitric oxide synthase (NOS3) gene polymorphism and essential hypertension in the Han, Miao, and Buyi populations in Guizhou China.

METHODS

DNA was collected from the blood samples of 353 essential hypertension patients and 342 healthy controls from Guizhou province of China. Eight polymorphisms of the NOS3 gene were genotyped using the Sequenom MassARRAY platform. For genetic analysis, SPSS 26.0, Haploview, SNPStats, SHEsis, and MDR were utilized.

RESULTS

All SNPs (rs11771443, rs1808593, rs753482, rs3918186, rs3918188, rs3918227, rs7830, and rs891512) satisfied the Hardy-Weinberg equilibrium test (P > 0.05). The allele and genotype frequencies of rs7830 and rs1808593 in case-control groups demonstrated significant differences (P < 0.05). Compared to the TT genotype of rs1808593, the TG or GG genotype reduced the risk of hypertension in the Miao population (OR = 0.410, 95% CI: 0.218-0.770, P = 0.006). Compared to the GG or GT genotype of rs7830, the TT genotype increased the risk of hypertension in the overall populations (OR = 1.716, 95%CI: 1.139-2.586, P = 0.010). The CATT (rs3918227-rs391818186-rs1808593-rs7830) haplotype was a risk factor for hypertension in the Miao and Han populations (OR = 1.471, 95%CI: 1.010-2.143, P = 0.044 and OR = 1.692, 95%CI: 1.124-2.545, P = 0.011). The CAGG haplotype in the Miao population was a protective factor against hypertension (OR = 0.555, 95%CI: 0.330-0.934, P = 0.025). The rs3918188, rs1808593, and rs7830 in the Miao population showed an interaction effect on hypertension (P < 0.001). The rs11771443, rs3918188, and rs7830 in the Buyi and Han populations showed an interaction effect on hypertension (P = 0.013 and P < 0.001).

CONCLUSION

The single nucleotide polymorphisms rs1808593 and rs7830 of NOS3 gene are associated with essential hypertension in Guizhou ethnic populations.

Summary of Known Genetic and Epigenetic Modification Contributed to Hypertension

Hypertension is a multifactorial disease due to a complex interaction among genetic, epigenetic, and environmental factors. Characterized by raised blood pressure (BP), it is responsible for more than 7 million deaths per annum by acting as a leading preventable risk factor for cardiovascular disease. Reports suggest that genetic factors are estimated to be involved in approximately 30 to 50% of BP variation, and epigenetic marks are known to contribute to the initiation of the disease by influencing gene expression. Consequently, elucidating the genetic and epigenetic mediators associated with hypertension is essential for better discernment of its pathophysiology. By deciphering the unprecedented molecular hypertension basis, it could help to unravel an individual's inclination towards hypertension which eventually could result in an arrangement of potential strategies for prevention and therapy. In the present review, we discuss known genetic and epigenetic drivers that contributed to the hypertension development and summarize the novel variants that have currently been identified. The effect of these molecular alterations on endothelial function was also presented.

Effects of hypotension and hypertension on source memory and working memory

OBJECTIVES

The effects of chronic low and high blood pressure on memory are unclear due to divergent results, originating in part due to participant misclassifications. The aim of this study was to compare source memory and working memory performance in individuals diagnosed with hypotension or hypertension with the performance of normotensive participants. Hypertensive and hypotensive individuals were receiving medical treatment.

METHOD

From a sample of 1656 participants, 219 were identified as hypertensive, and 37 were identified as hypotensive. Each of these two groups was compared with normotensive individuals matched by age, education and sex. Source memory performance and working memory performance were assessed through computerized tasks.

RESULTS

Source memory accuracy was poorer in hypotensive and hypertensive individuals than in normotensive individuals, and spatial working memory discrimination was inferior in hypertensive participants compared to normotensive individuals.

CONCLUSION

Blood pressure impairment should be considered a major concern because it has been linked to severe cardiovascular and cerebrovascular diseases. Furthermore, here we show that it has negative effects on the two types of memory that are most essential for preserving a self-sufficient lifestyle.

Methylenetetrahydrofolate Reductase Gene rs1801133 and rs1801131 Polymorphisms and Essential Hypertension Risk: A Comprehensive Analysis

Background

Essential hypertension (EH) is a common and multifactorial disorder that is likely to be influenced by multiple genes. The methylenetetrahydrofolate reductase (MTHFR) gene rs1801133 and rs1801131 polymorphisms influence MTHFR enzyme activity and plasma homocysteine concentration. In addition, variations in MTHFR functions likely play roles in the etiology of EH. Thus far, a large number of studies investigating the associations between the MTHFR polymorphisms and EH have provided controversial or inconclusive results. To better assess the purported relationship, we performed a comprehensive analysis of 52 published studies. Objective and Methods. Eligible studies were identified by searching the PubMed, Wanfang, and China National Knowledge Infrastructure (CNKI) databases. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated to assess the potential association between the MTHFR rs1801133 polymorphism and EH.

Results

Overall, 10712 patients and 11916 controls were involved; we observed significantly increased association between the MTHFR rs1801133 polymorphism and EH risk (such as T vs. C: OR = 1.38, 95% CI = 1.25 − 1.54, P ≤ 0.001), with similar results evident within race subgroups (such as Asian: T vs. C: OR = 1.47, 95% CI = 1.30 − 1.67, P ≤ 0.001; compared to Chinese: T vs. C: OR = 1.54, 95% CI = 1.33 − 1.79, P ≤ 0.001). Similar associations were also found in subgroups defined by the source of controls and genotype methods. To our regret, based on the limited studies, no association was detected for rs1801131 polymorphism.

Conclusions

Our study provides evidence that the MTHFR rs1801133 null genotype may increase EH risk. Future studies with larger sample sizes are warranted to evaluate this association in more detail.

The Association of Angiotensin-converting Enzyme I/D and Angiotensinogen M235T Polymorphism Genes with Essential Hypertension: A Meta-analysis

Objective:  Essential or primary hypertension in developing countries has become a major problem. Recent hypertension-related research has revealed susceptibility genes in genome-wide association studies. Several studies have associated angiotensin converting enzyme (ACE) I/D and angiotensinogen (AGT) M235T polymorphisms with essential hypertension, but results have been inconsistent. This meta-analysis aimed to clarify the association of AGT and ACE polymorphisms with the risk of primary hypertension. Methods: PubMed, Embase database, Medline, Goggle Scholar, Scopus.com, as well portal Garuda (www.garuda.ristekdikti.go.id) and Cochrane were used to retrieve all publications from 2006-2020 relating risk factors for hypertension with ACE I/D and AGT M235T polymorphisms. The meta-analysis was conducted from January –April 2020. All association studies were identified and data extracted from each study. Revman 5.3 software was used for meta-analysis to estimate odds ratios (OR) after extracting data and evaluating the quality of the enrolled studies. Results: A total of 27 studies (totaling 5,105 patients and 5196 controls) were identified. The overall effect suggested ACE I/D was significantly associated with primary hypertension (OR: 95%CI=1.51[1.29-1.77], p=0.004). There was no association between AGT M235T with risk of essential hypertension. Conclusion: This meta-analysis found significant association between ACE I/D gene polymorphisms with primary hypertension susceptibility. However, the AGT M235T gene had no association with the risk of primary hypertension. The Adrenoreceptor-beta/Renin Angiotensin System (ADRB/RAS) A allele should be considered a risk factor for essential hypertension.  

A Genome-Wide Association Study of a Korean Population Identifies Genetic Susceptibility to Hypertension Based on Sex-Specific Differences

Genome-wide association studies have expanded our understanding of the genetic variation of hypertension. Hypertension and blood pressure are influenced by sex-specific differences; therefore, genetic variants may have sex-specific effects on phenotype. To identify the genetic factors influencing the sex-specific differences concerning hypertension, we conducted a heterogeneity analysis of a genome-wide association study (GWAS) on 13,926 samples from a Korean population. Using the Illumina exome chip data of the population, we performed GWASs of the male and female population independently and applied a statistical test that identified heterogeneous effects of the variants between the two groups. To gain information about the biological implication of the genetic heterogeneity, we used gene set enrichment analysis with GWAS catalog and pathway gene sets. The heterogeneity analysis revealed that the rs11066015 of ACAD10 was a significant locus that had sex-specific genetic effects on the development of hypertension. The rs2074356 of HECTD4 also showed significant genetic heterogeneity in systolic blood pressure. The enrichment analysis showed significant results that are consistent with the pathophysiology of hypertension. These results indicate a sex-specific genetic susceptibility to hypertension that should be considered in future genetic studies of hypertension.

Low-dose Aspirin prevents hypertension and cardiac fibrosis when thromboxane A2 is unrestrained

Enhanced platelet activation has been reported in patients with essential hypertension and heart failure. The possible contribution of platelet-derived thromboxane (TX)A2 in their pathophysiology remains unclear. We investigated the systemic TXA2 biosynthesis in vivo and gene expression of its receptor TP in 22 essential hypertension patients and a mouse model of salt-sensitive hypertension. The contribution of platelet TXA2 biosynthesis on enhanced blood pressure (BP) and overload-induced cardiac fibrosis was explored in mice by treating with low-dose Aspirin, resulting in selective inhibition of platelet cyclooxygenase (COX)-1-dependent TXA2 generation. In essential hypertensive patients, systemic biosynthesis of TXA2 [assessed by measuring its urinary metabolites (TXM) reflecting predominant platelet source] was enhanced together with higher gene expression of circulating leukocyte TP and TGF-β, vs. normotensive controls. Similarly, in hypertensive mice with prostacyclin (PGI2) receptor (IP) deletion (IPKO) fed with a high-salt diet, enhanced urinary TXM, and left ventricular TP overexpression were detected vs. normotensive wildtype (WT) mice. Increased cardiac collagen deposition and profibrotic gene expression (including TGF-β) was found. Low-dose Aspirin administration caused a selective inhibition of platelet TXA2 biosynthesis and mitigated enhanced blood pressure, cardiac fibrosis, and left ventricular profibrotic gene expression in IPKO but not WT mice. Moreover, the number of myofibroblasts and extravasated platelets in the heart was reduced. In cocultures of human platelets and myofibroblasts, platelet TXA2 induced profibrotic gene expression, including TGF-β1. In conclusion, our results support tailoring low-dose Aspirin treatment in hypertensive patients with unconstrained TXA2/TP pathway to reduce blood pressure and prevent early cardiac fibrosis.

The genetic risk for hypertension is lower among the Hungarian Roma population compared to the general population

Estimating the prevalence of cardiovascular diseases (CVDs) and risk factors among the Roma population, the largest minority in Europe, and investigating the role of genetic or environmental/behavioral risk factors in CVD development are important issues in countries where they are significant minority. This study was designed to estimate the genetic susceptibility of the Hungarian Roma (HR) population to essential hypertension (EH) and compare it to that of the general (HG) population. Twenty EH associated SNPs (in AGT, FMO3, MTHFR-NPPB, NPPA, NPPA-AS1, AGTR1, ADD1, NPR3-C5orf23, NOS3, CACNB2, PLCE1, ATP2B1, GNB3, CYP1A1-ULK3, UMOD and GNAS-EDN3) were genotyped using DNA samples obtained from HR (N = 1176) and HG population (N = 1178) subjects assembled by cross-sectional studies. Allele frequencies and genetic risk scores (unweighted and weighted genetic risk scores (GRS and wGRS, respectively) were calculated for the study groups and compared to examine the joint effects of the SNPs. The susceptibility alleles were more frequent in the HG population, and both GRS and wGRS were found to be higher in the HG population than in the HR population (GRS: 18.98 ± 3.05 vs. 18.25 ± 2.97, p<0.001; wGRS: 1.52 [IQR: 0.99–2.00] vs. 1.4 [IQR: 0.93–1.89], p<0.01). Twenty-seven percent of subjects in the HR population were in the bottom fifth (GRS ≤ 16) of the risk allele count compared with 21% of those in the HG population. Thirteen percent of people in the HR group were in the top fifth (GRS ≥ 22) of the GRS compared with 21% of those in the HG population (p<0.001), i.e., the distribution of GRS was found to be left-shifted in the HR population compared to the HG population. The Roma population seems to be genetically less susceptible to EH than the general one. These results support preventive efforts to lower the risk of developing hypertension by encouraging a healthy lifestyle.

Methylenetetrahydrofolate Reductase C677T Gene Polymorphism as a Risk Factor for Hypertension in a Rural Population

Hypertension remains a public health burden despite advances in its management. Hence, the search for further risk stratification tools and prevention and new treatment approaches continues. Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with hypertension. Interestingly, riboflavin, as a cofactor of MTHFR, may control blood pressure in patients with mutant MTHFR variants. These double benefits of a risk stratification tool and treatment approach make it interesting. Because this polymorphism depends on ethnicity and geographic region, we aimed to determine the association between MTHFR C677T gene polymorphism and hypertension in a rural Indonesian-Sundanese population. This population-based case-control study included 213 hypertensive subjects and 202 nonhypertensive subjects as controls. The TaqMan assay was used to determine the MTHFR C677T genotypes. The odds ratio (OR) with 95% confidence interval (CI) was used to assess the risk of association. There was a significant difference in MTHFR C677T allele frequencies between the hypertensive and control groups (62.9% CC, 34.3% CT, 2.8% TT vs. 77.7% CC, 20.8% CT, 1.5% TT; p=0.004) and between mutant (TT and CT) and wild-type genotypes (CC) (p=0.001). The mutant genotype was associated with a risk of hypertension (OR 2.1; 95% CI 1.3-3.5) when adjusted for age, body mass index, waist circumference, and diabetes mellitus. The mutant of the MTHFR C677T gene increases the risk of hypertension in rural Indonesian-Sundanese population. These findings may be used in future studies to evaluate the effect of riboflavin supplementation in this population.

Neuroimmune crosstalk in the pathophysiology of hypertension

Hypertension is an important risk factor for cardiovascular morbidity and mortality and for events such as myocardial infarction, stroke, heart failure and chronic kidney disease and is a major determinant of disability-adjusted life-years. Despite the importance of hypertension, the pathogenesis of essential hypertension, which involves the complex interaction of several mechanisms, is still poorly understood. Evidence suggests that interplay between bone marrow, microglia and immune mediators underlies the development of arterial hypertension, in particular through mechanisms involving cytokines and peptides, such as neuropeptide Y, substance P, angiotensin II and angiotensin-(1-7). Chronic psychological stress also seems to have a role in increasing the risk of hypertension, probably through the activation of neuroimmune pathways. In this Review, we summarize the available data on the possible role of neuroimmune crosstalk in the origin and maintenance of arterial hypertension and discuss the implications of this crosstalk for recovery and rehabilitation after cardiac and cerebral injuries.

Circular RNAs in hypertension: challenges and clinical promise

Hypertension (HT), or high blood pressure (BP), is a chronic disease that is common among populations worldwide. The occurrence of HT is one of the leading causes of cardiovascular morbidity and mortality in adults. Although multiple studies have stressed the multifactorial and multigenic nature of HT, uncertainties about its etiology persist, and current diagnostic biomarkers can explain only a small part of the phenotypic variance of BP. Hence, the search for novel biomarkers that enable early disease prevention and guided therapy is warranted. Regulatory circRNAs have emerged as the newest player in HT-related gene networks and hold promise for improving the accuracy of diagnosis. These RNAs are genome products that are formed through back-splicing of specific regions of pre-mRNAs. Evidence suggests that these RNA species are involved in various metabolic diseases. Recent studies have revealed that aberrant expression of circRNAs is relevant to the occurrence and development of HT. Accordingly, circRNAs are proposed as a new generation of predictive biomarkers and potential therapeutic targets for different forms of HT, including pulmonary hypertension and preeclampsia. This paper presents an overview of the findings from current research focusing on the emerging role of circRNAs in the pathogenesis of hypertension. Furthermore, some of the challenges encountered by circRNA studies are highlighted, and perspectives are provided on the future of research in this area.

Haplotype-based association of renin gene polymorphisms with essential hypertension in Han population of northern china

INTRODUCTION

The renin gene has been suggested as a good candidate in the study of genetic mechanism of essential hypertension. However, studies on the contribution of renin gene polymorphisms to essential hypertension, have not had consistent outcomes. The purpose of the present study is to explore the association of renin gene polymorphisms with essential hypertension in the Han population of northern China.

METHODS

A case-control study was conducted among 3090 Han farmers (1533 essential hypertension patients and 1557 normotensives). Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism and polymerase chain reaction-sequencing.

RESULTS

The genotypic and allelic distributions of rs2368564 in essential hypertension and control was significant statistically ( p<0.001). The allelic distribution of rs10900557 showed marginal statistical significance ( p=0.048). There were no significant differences in other genotypic and allelic distributions ( p>0.05). In the haplotypes comprised by the six single-nucleotide polymorphisms, there were differences in the distribution of haplotypes A-T-C-G-C-A, A-T-C-G-C-G, G-C-T-G-T-A and G-C-T-G-T-G in both groups, and their differences reached to significant levels, respectively. After having corrected for false discovery rate, this association still remained significant.

CONCLUSIONS

The current study provides evidence for a possible association of renin gene polymorphisms with essential hypertension in a Han population of northern China.

Insulin-Like Growth Factor-1 and Receptor Contribute Genetic Susceptibility to Hypertension in a Han Chinese Population

BACKGROUND

Insulin-like growth factor 1 (IGF-1) and IGF-1 receptor (IGF-1R) have been suggested to mediate the pathophysiological response to elevated blood pressure. This study aims to evaluate the association of IGF-1 and IGF-1R with hypertension.

METHODS

Overall, 2,012 hypertensive cases and 2,210 controls were included in a case-control study, and 10 tagging single nucleotide polymorphisms (tagSNPs) were selected. The association of these SNPs with hypertension was further evaluated in a follow-up analysis and in an adolescent population.

RESULTS

A case-control study indicated that rs1815009 and rs2654981 in IGF-1R were significantly associated with hypertension, with odds ratios of 0.89 (P = 0.009) and 1.19 (P = 0.034), respectively, after adjusting for covariates. Stratification analyses revealed significant associations with hypertension (P < 0.05) for rs35767 in normal weight and obese populations; for rs2229765 in individuals <55 years of age and in overweight and nondrinking populations; and for rs2002880 in overweight and drinking populations. In a follow-up study, rs13379905 in IGF-1R was associated with hypertension incidence (hazard ratio, HR = 1.24, P = 0.042). This association was more significant in individuals with a hypertensive family history (HR = 2.10, P = 0.001). The association of rs13379905 with prehypertension and hypertension was further replicated in adolescent males (P = 0.005). Significant associations with hypertension incidence (P < 0.05) were observed for rs6219 in individuals <55 years of age and among those with obesity and a hypertensive family history as well as rs2002880 in obese individuals.

CONCLUSIONS

Our findings suggest that IGF-1R may contribute to the genetic susceptibility to hypertension, with BMI, age, and family history of hypertension all potentially modulating the genetic effects of IGF-1 on hypertension.

Brief Overview of a Decade of Genome-Wide Association Studies on Primary Hypertension

Primary hypertension is widely believed to be a complex polygenic disorder with the manifestation influenced by the interactions of genomic and environmental factors making identification of susceptibility genes a major challenge. With major advancement in high-throughput genotyping technology, genome-wide association study (GWAS) has become a powerful tool for researchers studying genetically complex diseases. GWASs work through revealing links between DNA sequence variation and a disease or trait with biomedical importance. The human genome is a very long DNA sequence which consists of billions of nucleotides arranged in a unique way. A single base-pair change in the DNA sequence is known as a single nucleotide polymorphism (SNP). With the help of modern genotyping techniques such as chip-based genotyping arrays, thousands of SNPs can be genotyped easily. Large-scale GWASs, in which more than half a million of common SNPs are genotyped and analyzed for disease association in hundreds of thousands of cases and controls, have been broadly successful in identifying SNPs associated with heart diseases, diabetes, autoimmune diseases, and psychiatric disorders. It is however still debatable whether GWAS is the best approach for hypertension. The following is a brief overview on the outcomes of a decade of GWASs on primary hypertension.

Association of the lipoprotein lipase gene Ser447Ter polymorphism with hypertension and blood pressure variation: evidence from an updated meta-analysis

The polymorphism of lipoprotein lipase (LPL) gene Ser447Ter (S447X) has long been linked to hypertension and blood pressure variation, but the established data remained controversial. To better elucidate this inconsistency, a meta-analysis was conducted. We comprehensively searched electronic databases, including Pubmed, EMBASE, China National Knowledge Infrastructure (CNKI), Web of Science, for all literatures with the last update on February 2016. The strength of association was calculated by using odds ratios (ORs) and weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs). Further stratified analyses, cumulative meta-analysis analysis, and sensitivity analyses were performed. A total of 14 studies (3592 cases and 4643 controls) for hypertension and 14 studies (n = 9254) for blood pressure were included. Overall, significant associations were revealed between S447X polymorphism and hypertension risk using allelic comparison (OR = 0.86, 95%CI 0.77 to 0.96), heterozygote comparison (OR = 0.85, 95%CI 0.75 to 0.96), and the dominant model (OR = 0.85, 95%CI 0.75 to 0.96), especially in Asians. Furthermore, in subgroup analyses restricted to the population-based controls studies, the high-quality studies, and the large sample size studies, these significant associations were still observed. As for blood pressure association, significant reductions of systolic blood pressure (WMD = -1.25 mmHg, 95%CI -2.25 to -0.25 mmHg) and diastolic blood pressure (WMD = -1.91 mmHg, 95%CI -3.25 to -0.56 mmHg) levels were found using dominant model. No publication bias was observed in any comparison model. Therefore, current meta-analysis suggested that the LPL S447X polymorphism is likely to be a protective factor in the development of hypertension.

A positive association between the human tissue kallikerin gene A2233C polymorphism and blood pressure response to benazepril

BACKGROUND

It is generally believed that essential hypertension is influenced by both genetic and environmental factors, as well as their interactions. Tissue kallikrein encoded by the tissue kallikrein gene (KLK1) is a key serine proteinase of kallikrein-kinin system, which is capable of generating potent vasactive peptides, kinins, by selective cleavage of the kininogen substrate. It was reported that the A2233 → C polymorphism in KLK1 gene is associated with essential hypertension. The aim of this study was to examine whether the molecular variations of KLK1 play role in determining the therapeutic response to benazepril, an ACE inhibitor.

METHODS

A total of 331 hypertensive individuals were recruited and treated with benazepril for 15 days. A variant impact of KLK1 A2233C was revealed. Chi-square analysis showed that the hypertensive subjects with the mutation genotype (AC + CC) had a higher proportion in systolic blood pressure (SBP, 88.1% vs. 79.0%, χ² = 4.141, p = 0.042) and diastolic blood pressure (DBP, 91.1% vs. 79.2%, χ² = 9.336, p = 0.002), respectively, to benazepril medication in good responders than in poor responders. Logistic regression analysis indicated that the hypertensive subjects with AC + CC genotype were more sensitive to the benazepril therapy in SBP (OR=1.97, 95% CI: 1.02-3.80, p = 0.044) and DBP (OR = 1.91, 95% CI: 2.69-5.16, p = 0.003), as compared with those hypertensive subjects with AA genotype.

CONCLUSION

Our findings suggest that the A2233C polymorphism of KLK1 may be a marker of evaluation of hypertensive subjects' responses to angiotensin I converting enzyme inhibitors benazepril.

Association of single nucleotide polymorphisms in the 5' upstream region of the C4BPA gene with essential hypertension in a northeastern Han Chinese population

A previous study of the authors using microarray analysis indicated that the expression of complement component 4 binding protein (C4BP)A is upregulated in essential hypertension (EH) patients, but the association between C4BPA variations and EH has not yet been clearly demonstrated. Since the 5′ upstream region is known to serve important roles in the gene expression regulation, the present study aimed to identify and analyze the association of single nucleotide polymorphisms (SNPs) in the 5′ upstream region between the C4BPA gene with EH in a case-control study among a northeastern Han Chinese population through direct sequencing as well as genotype detection. A total of 822 unrelated participants were included. The higher expression level of C4BPA in the peripheral blood of patients with EH was verified through reverse transcription-quantitative polymerase chain reaction and ELISA. A total of four SNPs, rs73079108, rs74148971, rs77660718 and rs11120211 were identified in the 5′ upstream region of C4BPA. Association analysis demonstrated that the genotypic frequencies of rs73079108 were significantly different between EH and the control groups (P=0.011), and A allelic frequency was lower in EH (P<0.001). Logistic regression analysis indicated that the rs73079108 polymorphism was closely associated with EH (AA:GA:GG genetic model: P=0.007, odds ratio (OR)=0.604, 95% confidence interval (CI) [0.418–0.873]; AA+GA:GG genetic model: P=0.005, OR=0.806, 95% CI[0.382–0.841]), and the A allele may be a protective factor. Subgroup analysis by sex and BMI presented concordant conclusions in female and non-obese samples. Further analysis indicated that rs73079108 was associated with systolic blood pressure (P<0.001), diastolic blood pressure (P=0.001) and fast blood glucose (FBG) (P=0.021). In addition, rs73079108 GA and GG carriers reported a significant increase in the level of the protein encoded by C4BPA than those of AA carriers. The rs73079108 polymorphism in the 5′ upstream region of C4BPA was associated with EH, and rs73079108-A may be an independent predictor.

Beyond the Cholesterol-Lowering Effect of Soy Protein: A Review of the Effects of Dietary Soy and Its Constituents on Risk Factors for Cardiovascular Disease

The hypocholesterolemic effect of soy is well-documented and this has led to the regulatory approval of a health claim relating soy protein to a reduced risk of cardiovascular disease (CVD). However, soybeans contain additional components, such as isoflavones, lecithins, saponins and fiber that may improve cardiovascular health through independent mechanisms. This review summarizes the evidence on the cardiovascular benefits of non-protein soy components in relation to known CVD risk factors such as hypertension, hyperglycemia, inflammation, and obesity beyond cholesterol lowering. Overall, the available evidence suggests non-protein soy constituents improve markers of cardiovascular health; however, additional carefully designed studies are required to independently elucidate these effects. Further, work is also needed to clarify the role of isoflavone-metabolizing phenotype and gut microbiota composition on biological effect.

CYP11B2 gene polymorphism and essential hypertension among Tibetan, Dongxiang and Han populations from northwest of China

Essential hypertension (EH) is a complex multifactorial condition influenced by both genetic and environmental factors; aldosterone synthase (CYP11B2) is a key enzyme which involves in the terminal steps of aldosterone synthesis. The result of relationship between C-344T of CYP11B2 polymorphism and EH was controversial. This study was undertaken to investigate the association of C-344T polymorphism with EH in the populations of Tibetan, Dongxiang and Han from northwest of China. A total of 2115 participants aged 18-70 years were enrolled in this study. In total, 1776 blood samples, including 545 Tibetan (305 hypertensive and 240 normotensive), 530 Dongxiang (254 hypertensive and 276 normotensive) and 701 Han (338 hypertensive and 363 normotensive), were analyzed successfully by using Snapshot minisequencing method, 30 samples were also performed by direct sequencing (5 hypertensive and 5 normotensive in each population, respectively). The frequencies of genotype and allele of CYP11B2 (C-344T) were not significantly different between EH group and control group in every ethnic population (p > 0.05). However, in female population of Tibetan, the frequencies of CC and CT genotype and C allele in EH group were higher than in control (p < 0.05) group. The frequencies of CC genotype and C allele in both the normotensive controls and EH patients in Tibetan population were higher than in Dongxiang and Han populations. Our study suggests that there is lack of association between C-344T polymorphism of CYP11B2 gene and EH in Dongxiang and Han populations, whereas the polymorphism was correlated with EH in female population of Tibetan.

Association of Polymorphisms in the Atrial Natriuretic Factor Gene with the Risk of Essential Hypertension: A Systematic Review and Meta-Analysis

BACKGROUND

Studies evaluating the association between the atrial natriuretic peptide (ANP) genetic polymorphism and the risk of essential hypertension (EH) have reported inconsistent results. The aim of this meta-analysis was to provide a more reliable estimation of the possible relationship between the atrial natriuretic peptide genetic polymorphism and the risk of essential hypertension (EH).

METHODS

Relevant articles were searched to identify all case-control or cohort design studies of the associations between ANP polymorphism and EH. The heterogeneity was checked using the Q test and the inconsistent index (I²). The odds ratio (OR) test and 95% confidence interval (CI) were calculated in a fixed or random effects model to evaluate the strength of association. Begg's test and Egger's test were applied to evaluate the publication bias.

RESULTS

A total of 25 case-control studies including 5520 cases and 5210 controls exploring the association between ANP polymorphism and EH were available for this meta-analysis. No significant association between the T2238C polymorphism and overall EH risk under the five genetic models was found (C vs. T: OR = 1.1, 95%CI = 0.94-1.2, p = 0.38; TC vs. TT: OR = 1.1, 95%CI = 0.88-1.5, p = 0.32; CC vs. TT: OR = 1.3, 95%CI = 0.90-1.9, p = 0.16; (CC + TC) vs. TT: OR = 1.1, 95%CI = 0.88-1.4, p = 0.35; CC vs. (TT + TC): OR = 1.1, 95%CI = 0.83-1.4, p = 0.55). We also found that the G1837A polymorphism had no significant association with overall EH risk (A vs. G: OR = 1.3, 95%CI = 0.96-1.9, p = 0.090; GA vs. GG: OR = 1.5, 95%CI = 0.83-2.6, p = 0.19; AA vs. GG: OR = 0.87, 95%CI = 0.34-2.3, p = 0.78; (AA + GA) vs. GG: OR = 1.5, 95%CI = 0.86-2.5, p = 0.17; AA vs. (GG + GA): OR = 1.3, 95%CI = 0.85-2.0, p = 0.22). In the analysis of the T1766C polymorphism, after removing the study of Nkeh, the 1766C allele suggested a protective effect in the model of TC vs. TT (OR = 0.64, 95%CI = 0.47-0.86, p = 0.003) and (CC + TC) vs. TT (OR = 0.64, 95%CI = 0.48-0.87, p = 0.004).

CONCLUSIONS

This meta-analysis suggested that no significant relationships between ANP T2238C, G1837A gene polymorphisms and the risk of essential hypertension exist. Conversely, the ANP T1766C gene polymorphism may be associated with the risk of essential hypertension, and the 1766C allele may be a protective factor against EH. However, due to the number of limited articles on the T1766C polymorphisms, further studies are still needed to accurately prove the association between the T1766C gene polymorphism and the risk of essential hypertension.

Genetic Variation in the Human SORBS1 Gene is Associated With Blood Pressure Regulation and Age at Onset of Hypertension: A SAPPHIRe Cohort Study

Essential hypertension is a complex disease involving multiple genetic and environmental factors. A human gene containing a sorbin homology domain and 3 SH3 domains in the C-terminal region, termed SORBS1, plays a significant role in insulin signaling. We previously found a significant association between the T228A polymorphism and insulin resistance, obesity, and type 2 diabetes. It has been hypothesized that a set of genes responsible for insulin resistance may be closely linked with genes susceptible to the development of hypertension. Identification of insulin resistance-related genetic factors may, therefore, enhance our understanding of essential hypertension. This study aimed to examine whether common SORBS1 genetic variations are associated with blood pressure and age at onset of hypertension in an ethnic Chinese cohort.We genotyped 9 common tagged single nucleotide polymorphisms of the SORBS1 gene in 1136 subjects of Chinese origin from the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance family study. Blood pressure was measured upon enrolment. The associations of the SORBS1 single nucleotide polymorphisms with blood pressure and the presence of hypertension were analyzed with a generalized estimating equation model. We used the false-discovery rate measure Q value with a cutoff <0.1 to adjust for multiple comparisons. In the Cox regression analysis for hypertension-free survival, a robust sandwich variance estimator was used to deal with the within-family correlations with age at onset of hypertension. Gender, body mass index, and antihypertension medication were adjustment covariates in the Cox regression analysis.In this study, genetic variants of rs2281939 and rs2274490 were significantly associated with both systolic and diastolic blood pressure. A genetic variant of rs2274490 was also significantly associated with the presence of hypertension. Furthermore, genetic variants of rs2281939 and rs2274490 were associated with age at onset of hypertension after adjustment for gender, body mass index, and antihypertension medication.In conclusion, we provide evidence for an association between common SORBS1 genetic variations and blood pressure, presence of hypertension, and age at onset of hypertension. The biological mechanism of genetic variation associated with blood pressure regulation needs further investigation.

Association Between Interleukin-6 -572 C>G and -174 G>C Polymorphisms and Hypertension: A Meta-analysis of Case-control Studies

Whether hypertension is associated with -572 C>G or -174 G>C polymorphism in interleukin (IL)-6 genes still remains hazy and ambiguous.We conducted a meta-analysis to offer a more reliable and clearer evaluation about the association.Electronic literature databases including PubMed, Web of Science, EMBASE, Google Scholar, Chinese National Knowledge Infrastructure and Wanfang database were searched.The study included the following: evaluating associations between -572 C>G or -174 G>C polymorphism in IL-6 gene and hypertension; case-control design; essential information must be offered; precise diagnostic criteria of hypertension; and no language restriction.Patients who met the diagnostic criteria and controls without a history of hypertension were included. Interventions were not available.A quality assessment was conducted using Newcastle-Ottawa scale. Combined odds ratios with 95% confidence intervals were calculated in 5 genetic models. Sources of heterogeneity were explored by subgroup analysis, meta-regression, and Galbraith plots. Finally, test for publication bias was performed to prove the stabilization.Fifteen studies were finally included. Eleven articles were judged high-quality reports. Overall, the -572 C>G polymorphism was proved to be significantly associated with hypertension in 4 genetic models. Subgroup analysis based on ethnicity revealed significant associations in Asian population in recessive model and homozygote comparison. The association in Europeans and Mid-East required further confirmation. No significant association was observed between the -174 G>C polymorphism and hypertension under all of the genetic models.The limitations of the study were the following: restrictive number of eligible studies limited the extrapolation range in subgroup analysis; gene-environment factors could not be described due to lack of data; some relevant studies could not be included because of various reasons.Current researches supported the association between the development of hypertension and the -572 C>G rather than -174 G>C polymorphism. Future well designed epidemiological studies may evaluate the possible gene-environment interactions.

Association between GRK4 and DRD1 gene polymorphisms and hypertension: a meta-analysis

The role of GRK4 and DRD1 genes in hypertension remains controversial. We performed a meta-analysis to determine whether GRK4 and DRD1 polymorphisms influence the risk of hypertension and examined the relationship between the genetic variances and the etiology of hypertension. Relevant case-control studies were retrieved by database searches and selected according to established inclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the associations. Meta-regression, subgroup analysis, and sensitivity analysis were performed. A total of 15 articles containing 29 studies were finally included. In the dominant model, rs4532 locus of DRD1 gene was related to hypertension with a pooled OR of 1.353 (95% CI =1.016-1.802, P=0.038). Subgroup analysis for ethnicity showed that rs1024323 locus of GRK4 gene was associated with hypertension in Caucasians (OR =1.826, 95% CI =1.215-2.745, P=0.004) but not in East Asians and Africans. Rs4532 locus was associated with hypertension in East Asians (OR =1.833, 95% CI =1.415-2.376, P,0.001) but not in Caucasians. These data provide possible references for future case-control studies in hypertension.

Generation of Hypertension-Associated STK39 Polymorphism Knockin Cell Lines With the Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 System

Previous genome-wide association studies identified serine threonine kinase 39 (STK39), encoding STE20/SPS1-related proline/alanine-rich kinase, as one of a limited number of hypertension susceptibility genes. A recent meta-analysis confirmed the association of STK39 intronic polymorphism rs3754777 with essential hypertension, among previously reported hypertension-associated STK39 polymorphisms. However, the biochemical function of this polymorphism in the mechanism responsible for hypertension is yet to be clarified. We generated rs3754777G>A knockin human cell lines with clustered regularly interspaced short palindromic repeats-mediated genome engineering. Homozygous (A/A) and heterozygous (G/A) knockin human embryonic kidney cell lines were generated using a double nickase, single-guide RNAs targeting STK39 intron 5 around single-nucleotide polymorphism, and a 100-bp donor single-stranded DNA oligonucleotide. Reverse transcription polymerase chain reaction with sequencing analyses revealed the identical STK39 transcripts among the wild-type and both knockin cell lines. Quantitative reverse transcription polymerase chain reaction showed increased STK39 mRNA expression, and immunoblot analysis revealed increases in total and phosphorylated STE20/SPS1-related proline/alanine-rich kinase with increased phosphorylated Na-K-Cl cotransporter isoform 1 in both knockin cell lines. The largest increases in these molecules were observed in the homozygous cell line. These findings indicated that this intronic polymorphism increases STK39 transcription, leading to activation of the STE20/SPS1-related proline/alanine-rich kinase-solute carrier family 12A signaling cascade. Increased interactions between STE20/SPS1-related proline/alanine-rich kinase and the target cation-chloride cotransporters may be responsible for hypertension susceptibility in individuals with this polymorphism.

Impaired nitric oxide production and increased blood pressure in systemic heterozygous ATP2B1 null mice

BACKGROUND

In the 'Millennium Genome Project', we identified ATP2B1 as a gene responsible for hypertension through single-nucleotide polymorphism analysis. The ATP2B1 gene encodes the plasma membrane calcium ATPase isoform 1, which contributes to the maintenance of intracellular calcium homeostasis by removing calcium ions.

METHOD

Since ATP2B1 knockout mice are reported to be embryo-lethal, we generated systemic heterozygous ATP2B1 null (ATP2B1(+/-)) mice, and evaluated the implication of ATP2B1 in blood pressure.

RESULTS

ATP2B1(+/-) mice revealed significantly higher SBP as measured by a radiotelemetric method. Phenylephrine-induced vasoconstriction was significantly increased in vascular rings from ATP2B1(+/-) mice, and the difference in this contraction disappeared in the presence of a nitric oxide synthase (NOS) inhibitor. Vasorelaxation to acetylcholine was significantly attenuated in vascular rings from ATP2B1(+/-) mice. In addition, cultured endothelial cells of ATP2B1(+/-) mice showed that the phosphorylation (Ser-1177) level of endothelial NOS protein was significantly lower, and nitric oxide production in endothelial cells and aorta was lower compared with those in control mice. In contrast, neural NOS expression in vascular smooth muscle cells from ATP2B1(+/-) mice and control mice were not significantly different.

CONCLUSION

These results suggest that decreased ATP2B1 gene expression is associated with impaired endothelial NOS activity and nitric oxide production, and the ATP2B1 gene plays a crucial role in the regulation of blood pressure.

Association of single nucleotide polymorphisms in the 3'UTR of ERAP1 gene with essential hypertension in the Northeastern Han Chinese

Endoplasmic reticulum aminopeptidase 1 (ERAP1) may be involved in blood pressure regulation by inactivation of angiotensin II and generation of bradykinin. Our previous study with cDNA microarray indicated that the expression of ERAP1 is down-regulated in essential hypertension (EH) patients. Since the 3'untranslated region (3'UTR) is known to play an important role in the post-transcriptional regulation by influencing the stability and translation process of mRNA, the present study aims to identify single nucleotide polymorphisms (SNPs) in the 3'UTR of ERAP1 gene in a case-control study among the Northeastern Han Chinese through PCR-sequencing, and analyze the association with EH. Our results further verified the lower expression level of ERAP1 in the peripheral blood cells in patients with EH (917.12±517.57 vs. 1506.59±1214.09pg/mL, P=0.011). Four SNPs, 3'UTR-761G>A, 3'UTR-787C>T, 3'UTR-1008A>C and 3'UTR-1055A>G, were identified in the 3'UTR of ERAP1. 3'UTR-1008A>C and 3'UTR-1055A>G were in almost complete linkage disequilibrium. Association analysis showed that the genotypic and allelic frequencies of 3'UTR-1008A>C and 3'UTR-1055A>G were significantly different between EH and the control groups. Logistic regression and haplotypic analysis indicated that alleles of E20-1037C and E20-1084G as well as haplotype of C-G were the risk factors of EH (P<0.05). Subgroup analysis performed by age suggested that the frequencies of genotype and allele of 3'UTR-1008A>C and 3'UTR-1055A>G as well as the haplotypes C-G and A-A were significantly different between EH and the control in the younger group (<50), but not in the older group (≥50). Younger population with the 3'UTR-1008CC and/or 3'UTR-1055GG genotypes also tended to have higher blood pressure, especially the diastolic blood pressure. In conclusion, the 3'UTR-1008A>C and 3'UTR-1055A>G polymorphisms of ERAP1 gene were associated with EH, especially in the younger population, and the haplotype C-G could be the independent marker of EH.

Systematic Analysis of Integrated Gene Functional Network of Four Chronic Stress-related Lifestyle Disorders

Background:

Stress is a term used to define factors involved in changes in the physiological balances resulting in disease conditions. Chronic exposure to stress conditions in modern lifestyles has resulted in a group of disorders called lifestyle disorders. Genetic background and environmental factors are interrelated to lifestyle in determining the health status of individuals. Hence, identification of disease-associated genes is the primary step toward explanations of pathogenesis of these diseases. In functional genomics, large-scale molecular and physiological data are used for the identification of causative genes associated with a disease.

Aim:

The objective of our study was to find a common set of genes involved in chronic stress-related lifestyle diseases such as cardiovascular diseases (CVDs), type 2 diabetes (T2D), hypertension (HTN), and obesity.

Materials and Methods:

In our study, we have performed a systematic analysis of the functional gene network of four chronic stress-related lifestyle diseases by retrieving genes from published databases. We have tried to systematically construct a functional protein-protein interaction (PPI) network. The goals of establishing this network were the functional enrichment study of interacting partners as well as functional disease ontology annotation (FunDO) of the enriched genes.

Results:

This study enabled the identification of key genes involved in these stress-related lifestyle diseases by prioritizing candidate genes based on their degree of involvement. In this systematic analysis, we have found key genes for these diseases based on their involvement and association at the gene network level and PPI.

Conclusion:

We have deciphered a group of genes that in combination play a crucial role and may impact the function of the whole genome in the four lifestyle disorders mentioned.

Association between methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms and essential hypertension: a systematic review and meta-analysis

OBJECTIVE

Many studies have investigated the role of 5,10-methylenetetrahydrofolate reductase gene (MTHFR) C677T/A1298C polymorphisms in essential hypertension (EH), but results are inconclusive. The purpose of this meta-analysis was to clarify the effects of MTHFR C677T/A1298C polymorphisms on the risk of EH.

METHODS

Electronic databases were searched to identify relevant studies published until January 2014. Data were extracted by two independent authors. Odds ratios (ORs) with 95%confidence intervals (CIs) were used to assess the association between MTHFR C677T/A1298C polymorphisms and the risk of EH using random effect models or fixed effect models. Finally,30 studies with 5207 cases and 5383 controls were included for C677T polymorphism and 6 studies with 1009 cases and 994 controls were included for A1298C polymorphism.

RESULTS

Meta-analysis results indicated that MTHFR C677T polymorphism contributed to an increased risk of EH (for T vs. C: OR=1.30, 95%CI=1.18–1.43; for TT+CT vs. CC: OR=1.34, 95%CI=1.24–1.46; for TT vs. CC: OR=1.62, 95%CI=1.32–1.99; for TT vs. CT+CC: OR=1.41, 95%CI=1.26–1.59). However, no significant association was detected between MTHFR A1298C polymorphism and the risk of EH.

CONCLUSION

This meta-analysis supports that MTHFR C677T polymorphism plays a role in developing EH. MTHFR A1298C polymorphism may not be associated with an increased risk of EH. Further large and well-designed studies are warranted to confirm these findings.

Comprehensive assessment of the association of WNK4 polymorphisms with hypertension: evidence from a meta-analysis

The relationship between with-no-lysine [K] kinase 4 (WNK4) gene polymorphisms and hypertension has been widely investigated, However, the studies yielded contradictory results. To evaluate these inconclusive findings comprehensively, we therefore performed a meta-analysis. Ten articles encompassing 16 independent case-control studies with 6089 hypertensive cases and 4881 normotensive controls were selected for this meta-analysis. Four WNK4 gene polymorphisms were identified (G1155942T, G1156666A, T1155547C, and C6749T). The results showed statistically significant associations of G1155942T polymorphism (allelic genetic model: odds ration or OR = 1.62, 95% confidence interval or CI: 1.11–2.38, P = 0.01; dominant model: OR = 1.85, 95% CI: 1.07–3.19, P = 0.03) and C6749T polymorphism (allele contrast: OR = 2.04, 95% CI: 1.60–2.59, P<0.01; dominant model: OR = 2.04, 95%CI: 1.59–2.62, P<0.01; and homozygous model: OR = 5.01, 95% CI: 1.29–19.54, P = 0.02) with hypertension risk. However, neither C1155547T nor G1156666A was associated significantly with hypertension susceptibility. In conclusion, this meta-analysis suggested that WNK4 G1155942T and C6749T gene polymorphisms may contribute to the susceptibility and development of hypertension. Further well-designed studies with larger sample size are required to elucidate the association of WNK4 gene multiple polymorphisms with hypertension risk.

Prehypertension: Underlying pathology and therapeutic options

Prehypertension (PHTN) is a global major health risk that subjects individuals to double the risk of cardiovascular disease (CVD) independent of progression to overt hypertension. Its prevalence rate varies considerably from country to country ranging between 21.9% and 52%. Many hypotheses are proposed to explain the underlying pathophysiology of PHTN. The most notable of these implicate the renin-angiotensin system (RAS) and vascular endothelium. However, other processes that involve reactive oxygen species, the inflammatory cytokines, prostglandins and C-reactive protein as well as the autonomic and central nervous systems are also suggested. Drugs affecting RAS have been shown to produce beneficial effects in prehypertensives though such was not unequivocal. On the other hand, drugs such as β-adrenoceptor blocking agents were not shown to be useful. Leading clinical guidelines suggest using dietary and lifestyle modifications as a first line interventional strategy to curb the progress of PHTN; however, other clinically respected views call for using drugs. This review provides an overview of the potential pathophysiological processes associated with PHTN, abridges current intervention strategies and suggests investigating the value of using the "Polypill" in prehypertensive subjects to ascertain its potential in delaying (or preventing) CVD associated with raised blood pressure in the presence of other risk factors.

Associations of MTHFR gene polymorphisms with hypertension and hypertension in pregnancy: a meta-analysis from 114 studies with 15411 cases and 21970 controls

BACKGROUND

Several epidemiological studies have investigated the associations of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms with hypertension (H) or hypertension in pregnancy (HIP). However, the results were controversial. We therefore performed a comprehensive meta-analysis to provide empirical evidences on the associations.

METHODOLOGIES

The English and Chinese databases were systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the associations. Meta-regression, subgroup analysis, sensitivity analysis, cumulative meta-analysis and assessment of publication bias were performed in our study.

PRINCIPAL FINDINGS

A total of 114 studies with 15411 cases and 21970 controls were included, 111 studies with 15094 cases and 21633 controls for the C677T polymorphism and 21 with 2533 cases and 2976 controls for the A1298C polymorphism. Overall, the C677T polymorphism was significantly associated with H and HIP (H & HIP: OR = 1.26, 95% CI = 1.17-1.34; H: OR = 1.36, 95% CI = 1.20-1.53; HIP: OR = 1.21, 95% CI = 1.08-1.32). Stratified analysis by ethnicity revealed a significant association among East Asians and Caucasians, but not among Latinos, Black Africans, and Indians and Sri Lankans. In the stratified analyses according to source of controls, genotyping method, sample size and study quality, significant associations were observed in all the subgroups, with the exception of population based subgroup in H studies and large sample size and "others" genotyping method subgroups in HIP studies. For the A1298C polymorphism, no significant association was observed either in overall or subgroup analysis under all genetic models.

CONCLUSIONS

This meta-analysis suggests that the MTHFR C677T rather than A1298C polymorphism may be associated with H & HIP, especially among East Asians and Caucasians.

Renin gene polymorphisms in bangladeshi hypertensive population

Objective: Linkages of renin gene polymorphisms with hypertension have been implicated in several populations with contrasting results. Present study aims to assess the pattern of renin gene polymorphisms in Bangladeshi hypertensive individuals.

Methodology: Introns 1, 9 of renin gene and 4063 bases upstream of promoter sequence of renin gene were amplified from the genomic DNA of the total 124 (hypertensive and normotensive) subjects using respective primers. Polymerase chain reaction-based restriction fragment length polymorphisms were performed using BglI, MboI and TaqI restriction enzymes.

Results: Homozygosity was common in renin gene regarding BglI (bb=48.4%, Bb=37.9%, BB=13.7%, χ² =1.91, P>0.05), TaqI (TT=81.5%, Tt=14.5%, tt=4.0%, χ² =7.50, P<0.01) and MboI (mm=63.7%, Mm=32.3%, MM=4.0%, χ²=0.00, P>0.05) polymorphisms among total study population. For BglI and TaqI genotype distribution, hypertensive subjects (BglI: χ² =6.66, P<0.05; TaqI: χ² = 10.28, P<0.005) significantly deviate from Hardy-Weinberg Equilibrium law compared to normotensive subjects (BglI: χ²=0.51, P>0.05; TaqI: χ²=0.20, P>0.05). On the other hand, with respect to MboI polymorphisms of renin gene, only normotensive subjects deviate from the law (patients: χ²=1.28, P>0.05; vs controls: χ²=6.81, P<0.01). In the context of allelic frequency, common T allele was clearly prevalent (T frequency=0.86, t frequency = 0.14) for TaqI, but rare alleles b and m were more frequent for both BglI (b frequency=0.69, B frequency=0.31) and MboI (m frequency=0.80 M frequency=0.20) polymorphisms, respectively.

Conclusion: Thus, we report that Bangladeshi hypertensive subjects did not show any distinct pattern of renin gene polymorphisms compared to their healthy control subjects with regard to their genotypic and allelic frequencies.

The A(1166)C polymorphism of the AT1R gene is associated with an early onset of hypertension and high waist circumference in Jordanian males attending the Jordan University Hospital

There is no agreement on the involvement of angiotensin II type 1 receptor (AT1R) gene A(1166)C variant and essential hypertension. The purpose of this study was to investigate the association between angiotensin II type 1 receptor (AT1R) gene A(1166)C variants with essential hypertension and some related parameters in a sample of Jordanian hypertensive patients. DNA samples from 108 hypertensive individuals and 102 age- and gender-matched non-hypertensive controls of the Jordanian population were analyzed by polymerase chain reaction followed by restriction fragment length polymorphism assay (PCR-RFLP) methods to determine the frequency of A(1166)C variants alleles. No statistically significant differences were found in the distribution of alleles and genotypes between hypertensive and non-hypertensive individuals, not even after gender segregation. The frequency of the variant allele (C(1166)) was significantly higher in the early-onset compared to the late-onset group of hypertensive males, in subjects with positive family history of hypertension, and in subjects with high waist circumference. In conclusion, the A(1166)C polymorphism is not associated with essential hypertension in Jordanian hypertensive individuals. However, it was associated with an early onset of hypertension in males, with positive family history of hypertension, and with high waist circumference irrespective of blood pressure status.

STK39 polymorphism is associated with essential hypertension: a systematic review and meta-analysis

BACKGROUND

A recent genome-wide association study identified STK39as a candidate gene for blood pressure (BP) in Europeans. Subsequently, several studies have attempted to replicate the association across different ethnic populations. However, the results have been inconsistent.

OBJECTIVE AND METHODS

We performed a meta-analysis to elucidate the association between the STK39 rs3754777 polymorphism (or proxy) and hypertension. Published literature from PubMed and Embase databases were retrieved and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects model.

RESULTS

Using appropriate inclusion/exclusion criteria, we identified 10 studies that included 21, 863 hypertensive cases and 24, 480 controls from different ethnicities. The meta-analysis showed a significant association of STK39 rs3754777 variant with hypertension (OR = 1.10, 95%CI = 1.06-1.15, p = 7.95 × 10(-6)). Further subgroup analysis by ethnicity suggested that the association was significant in Europeans (OR = 1.08, 95% CI = 1.03-1.14, p = 0.002) and in East Asians (OR = 1.16, 95%CI = 1.07-1.25, p = 4.34 × 10(-4)), but not in Africans (OR = 1.01, 95%CI 0.80-1.27, p = 0.932). We further confirmed the positive association by sensitivity analysis. No publication bias was detected (Begg's test, p = 0.721; Egger's test, p = 0.744).

CONCLUSIONS

The present meta-analysis confirms the significant association of STK39 polymorphism with susceptibility to hypertension in Europeans and East Asians. Future studies should include gene-gene and gene-environment interactions to investigate the identified association.

Association of CLCNKB haplotypes and hypertension in Mongolian and Han populations

We investigated a possible association between genetic variations in chloride channel Kb (CLCNKB) gene and essential hypertension (EH) in the Mongolian and Han populations in Inner Mongolia. Our study included 414 unrelated Mongolian herdsmen and 524 Han farmers. Two tagSNPs of CLCNKB (rs945393 and rs10803414) were identified from the Chinese HapMap database based on pairwise r(2) ≥ 0.5 and minor allele frequency ≥0.05. Genotyping was performed using the PCR/ligase detection reaction assay. There was significant difference in allele frequency of rs10803414 between the EH group (35%) and the control group (26%) in the Mongolian population (P < .05). Significant association was identified between rs10803414 and EH in the Mongolian population (P < .05) and rs945393 and EH in the Han population (P < .01). The frequency of haplotype CC in the EH group (9.4%) was significantly higher than in the control group (4.6%) in the Mongolian population; individuals who possessed the CC haplotype had a significantly higher risk of EH in the Mongolian population. There was no association between haplotype and EH in the Han population. After adjusting for age, sex, and other confounding risk factors, only rs10803414 was the risk factor of hypertension in Mongolians. Our results indicate that rs10803414 in CLCNKB confers a significant risk of EH in the Mongolian population and haplotype CC of CLCNKB is a genetic factor for EH in the Mongolian population. Our study expands the association between CLCNKB and EH to a non-European ancestry population and provides the first evidence of a cross-race susceptibility of EH locus.

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.

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.

Prevalence of H1299R polymorphism in the Factor V gene among the Taif-Saudi Arabia population using polymerase chain reaction-reverse hybridization technique

Cardiovascular disease (CVD) remains a major health hazard worldwide. Single nucleotide polymorphisms (SNPs) represent a part of risk factors that contributes to cardiovascular disease. SNP in the coagulation factor V genes have been shown to play a role in the development of cardiovascular disease. Coagulation Factor V is an enzyme cofactor of the coagulation system and contributes to a normal haemostatic balance. The His1299Arg polymorphism in the Factor V gene has been identified and linked to hereditary thrombophilia. The aim of the present study is to determine the prevalence of HR2 haplotype and allele frequency of His1299Arg polymorphism in the Factor V gene among randomly selected healthy individuals from Taif population which belonging to western region of Saudi Arabia. Genotyping of this SNP was carried out via CVD StripAssay, which based on a polymerase chain reaction-reverse hybridization technique. Two hundred healthy unrelated individuals were included in the study. Seventeen out of the studied population (8.5%) had the HR2 haplotype; 14 (7%) were heterozygous (R1/R2), and three (1.5%) were homozygous (R2/R2), with an allelic frequency of 0.05. This is the first report for a Saudi Arabian population that estimates the prevalence of HR2 haplotype and its allele frequencies. In conclusion, the His1299Arg mutant was noticeable within population of western Saudi Arabia. Further larger studies are needed to (1) estimate the prevalence of this mutant among individuals belonging to different KSA locations (2) assess the relative contribution of this mutational event separately and in combination with other thrombophilic polymorphisms in the etiology of cardiovascular disease in KSA.