Genetic analysis of 22 candidate genes for hypertension in the Japanese population

Molecular mechanisms and potential therapeutic targets in the pathogenesis of hypertension in visceral adipose tissue induced by a high-fat diet

Background

Hypertension (HTN) presents a significant global public health challenge with diverse causative factors. The accumulation of visceral adipose tissue (VAT) due to a high-fat diet (HFD) is an independent risk factor for HTN. While various studies have explored pathogenic mechanisms, a comprehensive understanding of impact of VAT on blood pressure necessitates bioinformatics analysis.

Methods

Datasets GSE214618 and GSE188336 were acquired from the Gene Expression Omnibus and analyzed to identify shared differentially expressed genes between HFD-VAT and HTN-VAT. Gene Ontology enrichment and protein-protein interaction analyses were conducted, leading to the identification of hub genes. We performed molecular validation of hub genes using RT-qPCR, Western-blotting and immunofluorescence staining. Furthermore, immune infiltration analysis using CIBERSORTx was performed.

Results

This study indicated that the predominant characteristic of VAT in HTN was related to energy metabolism. The red functional module was enriched in pathways associated with mitochondrial oxidative respiration and ATP metabolism processes. Spp1, Postn, and Gpnmb in VAT were identified as hub genes on the pathogenic mechanism of HTN. Proteins encoded by these hub genes were closely associated with the target organs-specifically, the resistance artery, aorta, and heart tissue. After treatment with empagliflozin, there was a tendency for Spp1, Postn, and Gpnmb to decrease in VAT. Immune infiltration analysis confirmed that inflammation and immune response may not be the main mechanisms by which visceral adiposity contributes to HTN.

Conclusions

Our study pinpointed the crucial causative factor of HTN in VAT following HFD. Spp1, Postn, and Gpnmb in VAT acted as hub genes that promote elevated blood pressure and can be targets for HTN treatment. These findings contributed to therapeutic strategies and prognostic markers for HTN.

Role of collecting duct principal cell NOS1β in sodium and potassium homeostasis

The nitric oxide (NO)-generating enzyme, NO synthase-1β (NOS1β), is essential for sodium (Na+ ) homeostasis and blood pressure control. We previously showed that collecting duct principal cell NOS1β is critical for inhibition of the epithelial sodium channel (ENaC) during high Na+ intake. Previous studies on freshly isolated cortical collecting ducts (CCD) demonstrated that exogenous NO promotes basolateral potassium (K+ ) conductance through basolateral channels, presumably Kir 4.1 (Kcnj10) and Kir 5.1 (Kcnj16). We, therefore, investigated the effects of NOS1β knockout on Kir 4.1/Kir 5.1 channel activity. Indeed, in CHO cells overexpressing NOS1β and Kir 4.1/Kir 5.1, the inhibition of NO signaling decreased channel activity. Male littermate control and principal cell NOS1β knockout mice (CDNOS1KO) on a 7-day, 4% NaCl diet (HSD) were used to detect changes in basolateral K+ conductance. We previously demonstrated that CDNOS1KO mice have high circulating aldosterone despite a high-salt diet and appropriately suppressed renin. We observed greater Kir 4.1 cortical abundance and significantly greater Kir 4.1/Kir 5.1 single-channel activity in the principal cells from CDNOS1KO mice. Moreover, blocking aldosterone action with in vivo spironolactone treatment resulted in lower Kir 4.1 abundance and greater plasma K+ in the CDNOS1KO mice compared to controls. Lowering K+ content in the HSD prevented the high aldosterone and greater plasma Na+ of CDNOS1KO mice and normalized Kir 4.1 abundance. We conclude that during chronic HSD, lack of NOS1β leads to increased plasma K+ , enhanced circulating aldosterone, and activation of ENaC and Kir 4.1/Kir 5.1 channels. Thus, principal cell NOS1β is required for the regulation of both Na+ and K+ by the kidney.

Association Between ALDH-2 rs671 and Essential Hypertension Risk or Blood Pressure Levels: A Systematic Review and Meta-Analysis

Background: The association between Aldehyde dehydrogenase II (ALDH-2) rs671 polymorphism and essential hypertension (EH) risk or blood pressure (BP) levels remains unclear. Objective: To systematically review the influence of the aldehyde dehydrogenase II rs671 polymorphism on essential hypertension risk and blood pressure levels. Methods: The PubMed, EMbase, Web of Science, Cochrane Library, CNKI and CBM databases were electronically searched to identify case-control or cohort studies published prior to July 2019 that examined the association between the rs671 polymorphism and the risk of essential hypertension or blood pressure levels. A meta-analysis was conducted with Stata 15.1 software. Results: Twenty-two articles were included. Among these articles, 20 incorporated 30 individual studies evaluating the association between the rs671 polymorphism and EH (11,051 hypertensive patients and 15,926 normotensive controls), and 8 incorporated 12 individual studies evaluating the association between the rs671 polymorphism and BP (20,512 subjects). The results of the meta-analysis showed that the mutation of the rs671 polymorphism was associated with a significantly decreased risk of EH in all models: allelic model (OR = 0.80, 95% CI: 0.73-0.87), homozygous model (OR = 0.71, 95% CI: 0.63-0.80), heterozygous model (OR = 0.79, 95% CI: 0.72-0.87), dominant model (OR = 0.79, 95% CI: 0.71-0.87), and recessive model (OR = 0.76, 95% CI: 0.68-0.85). In the stratified analyses, significant associations were found for males, drinkers and population-based studies. Simultaneously, the A carriers had lower SBP (WMD = -1.78, 95% CI: -3.02 to -0.53) and DBP (WMD = -1.09, 95% CI: -1.58 to -0.61) levels than individuals with the GG homozygote. Conclusion: The collective findings of this meta-analysis suggested that the ALDH-2 rs671 polymorphism represented an important genetic marker in the development of hypertension. Considering the overall quality of evidence and the relatively small pooled sample size, more well-conducted high-quality studies are required to verify the above conclusion. Systematic Review Registration Number: PROSPERO (CRD42019129746).

Genetic polymorphisms associated with reactive oxygen species and blood pressure regulation

Hypertension is the most prevalent cause of cardiovascular disease and kidney failure, but only about 50% of patients achieve adequate blood pressure control, in part, due to inter-individual genetic variations in the response to antihypertensive medication. Significant strides have been made toward the understanding of the role of reactive oxygen species (ROS) in the regulation of the cardiovascular system. However, the role of ROS in human hypertension is still unclear. Polymorphisms of some genes involved in the regulation of ROS production are associated with hypertension, suggesting their potential influence on blood pressure control and response to antihypertensive medication. This review provides an update on the genes associated with the regulation of ROS production in hypertension and discusses the controversies on the use of antioxidants in the treatment of hypertension, including the antioxidant effects of antihypertensive drugs.

Acetaldehyde Dehydrogenase 2 rs671 Polymorphism Affects Hypertension Susceptibility and Lipid Profiles in a Chinese Population

Previous studies revealed that the rs671 polymorphism in the acetaldehyde dehydrogenase 2 (ALDH2) genes is correlated with alcohol consumption in Japanese population. The ALDH2 gene variants and drinking are associated with hypertension and dyslipidemia. However, it remains unclear whether there might be potent relationships among ALDH2 rs671 polymorphism, alcohol consumption, hypertension, and dyslipidemia in Shandong population. A total of 467 male volunteers from Shandong area were enrolled in this study. The ALDH2 rs671 polymorphism was genotyped using polymerase chain reaction-restriction fragment length polymorphism. The concentrations of total cholesterol (TC), triglycerides, low-density lipoprotein, and high-density lipoprotein (HDL) in serum were measured using commercial kits. SPSS 23.0 was used for statistical analysis. The significance of differences between subgroups was determined using chi-square test, and multiple comparisons were performed with the least-significant difference method. The ALDH2 variant frequencies were 80.5% with GG, 17.1% with GA, and 2.4% with AA. The ALDH2 genotypes had significant correlations with alcohol consumption (p = 0.001), whereas the GA genotype was associated with a decreased risk of alcohol consumption (odds ratio = 0.27; 95% confidence interval = 0.130-0.539; p = 0.001). The ALDH2 genotypes frequencies and drinking habits were significantly different between hypertension and healthy individuals (p = 0.034; p = 0.044). The ALDH2 GG genotype individuals have high average lipids levels, and the proportion of TC disorder among GG individuals was higher than that of GA individuals (p = 0.006). Individuals who had drinking habits have a high average lipids levels; especially average TC levels (p = 0.048), and had high proportions of dyslipidemia (TC and HDL; p = 0.016 and p = 0.033, respectively). The frequencies of ALDH2 variants were evaluated according to the Hardy-Weinberg equilibrium among enrolled population. Our study suggested that the individuals with ALDH2 rs671 GA genotype were less prone to developing a drinking habit in Shandong population. The ALDH2 genotypes and drinking habit were associated with hypertension and lipid profiles especially TC profile in Shandong province. The ALDH2 rs671 genotypes indicated that the gene-related drinking habit and gene variant altogether may affect hypertension and dyslipidemia.

Genetics of Human Primary Hypertension: Focus on Hormonal Mechanisms

Increasingly, primary hypertension is being considered a syndrome and not a disease, with the individual causes (diseases) having a common sign-an elevated blood pressure. To determine these causes, genetic tools are increasingly employed. This review identified 62 proposed genes. However, only 21 of them met our inclusion criteria: (i) primary hypertension, (ii) two or more supporting cohorts from different publications or within a single publication or one supporting cohort with a confirmatory genetically modified animal study, and (iii) 600 or more subjects in the primary cohort; when including our exclusion criteria: (i) meta-analyses or reviews, (ii) secondary and monogenic hypertension, (iii) only hypertensive complications, (iv) genes related to blood pressure but not hypertension per se, (v) nonsupporting studies more common than supporting ones, and (vi) studies that did not perform a Bonferroni or similar multiassessment correction. These 21 genes were organized in a four-tiered structure: distant phenotype (hypertension); intermediate phenotype [salt-sensitive (18) or salt-resistant (0)]; subintermediate phenotypes under salt-sensitive hypertension [normal renin (4), low renin (8), and unclassified renin (6)]; and proximate phenotypes (specific genetically driven hypertensive subgroup). Many proximate hypertensive phenotypes had a substantial endocrine component. In conclusion, primary hypertension is a syndrome; many proposed genes are likely to be false positives; and deep phenotyping will be required to determine the utility of genetics in the treatment of hypertension. However, to date, the positive genes are associated with nearly 50% of primary hypertensives, suggesting that in the near term precise, mechanistically driven treatment and prevention strategies for the specific primary hypertension subgroups are feasible.

Role of Alcohol Oxidative Metabolism in Its Cardiovascular and Autonomic Effects

Several review articles have been published on the neurobehavioral actions of acetaldehyde and other ethanol metabolites as well as in major alcohol-related disorders such as cancer and liver and lung disease. However, very few reviews dealt with the role of alcohol metabolism in the adverse cardiac and autonomic effects of alcohol and their potential underlying mechanisms, particularly in vulnerable populations. In this chapter, following a brief overview of the dose-related favorable and adverse cardiovascular effects of alcohol, we discuss the role of ethanol metabolism in its adverse effects in the brainstem and heart. Notably, current knowledge dismisses a major role for acetaldehyde in the adverse autonomic and cardiac effects of alcohol because of its low tissue level in vivo. Contrary to these findings in men and male rodents, women and hypertensive individuals are more sensitive to the adverse cardiac effects of similar amounts of alcohol. To understand this discrepancy, we discuss the autonomic and cardiac effects of alcohol and its metabolite acetaldehyde in a model of hypertension, the spontaneously hypertensive rat (SHR) and female rats. We present evidence that enhanced catalase activity, which contributes to cardioprotection in hypertension (compensatory) and in the presence of estrogen (inherent), becomes detrimental due to catalase catalysis of alcohol metabolism to acetaldehyde. Noteworthy, studies in SHRs and in estrogen deprived or replete normotensive rats implicate acetaldehyde in triggering oxidative stress in autonomic nuclei and the heart via (i) the Akt/extracellular signal-regulated kinases (ERK)/nitric oxide synthase (NOS) cascade and (ii) estrogen receptor-alpha (ERα) mediation of the higher catalase activity, which generates higher ethanol-derived acetaldehyde in female heart. The latter is supported by the ability of ERα blockade or catalase inhibition to attenuate alcohol-evoked myocardial oxidative stress and dysfunction. More mechanistic studies are needed to further understand the mechanisms of this public health problem.

Genetic polymorphisms in very important pharmacogenomic variants in the Zhuang ethnic group of Southwestern China: A cohort study in the Zhuang population

Pharmacogenomics, the study of the role of genetics in drug response, has recently become a focal point of research. Previous studies showed that genes associated with drug detoxification vary among different populations. However, pharmacogenomic information of the Zhuang ethnic group is scarce. The aim of the present study was to screen members of the Zhuang ethnicity in southwestern China for genotype frequencies of very important pharmacogenomic (VIP) variants and to determine the differences between the Zhuang ethnicity and other human populations.We genotyped 80 variants of VIP genes in 100 unrelated healthy Zhuang adults from the Yunnan province of China. Next, we analyzed the genotyping data with Structure and F-statistics (Fst).We compared our data with those of other populations using the HapMap data set, and observed that the frequency distribution of Zhuang population in Yunnan closely resembles that of JPT. Furthermore, population structure and Fst analysis showed that the Zhuang population is closely related to the Shaanxi Han population with respect to genetic background.Our study supplements existing information on Zhuang population pharmacogenomics and provides an extensive overview for developing personalized medicine.

Collecting Duct Nitric Oxide Synthase 1ß Activation Maintains Sodium Homeostasis During High Sodium Intake Through Suppression of Aldosterone and Renal Angiotensin II Pathways

BACKGROUND

During high sodium intake, the renin-angiotensin-aldosterone system is downregulated and nitric oxide signaling is upregulated in order to remain in sodium balance. Recently, we showed that collecting duct nitric oxide synthase 1β is critical for fluid-electrolyte balance and subsequently blood pressure regulation during high sodium feeding. The current study tested the hypothesis that high sodium activation of the collecting duct nitric oxide synthase 1β pathway is critical for maintaining sodium homeostasis and for the downregulation of the renin-angiotensin-aldosterone system-epithelial sodium channel axis.

METHODS AND RESULTS

Male control and collecting duct nitric oxide synthase 1β knockout (CDNOS1KO) mice were placed on low, normal, and high sodium diets for 1 week. In response to the high sodium diet, plasma sodium was significantly increased in control mice and to a significantly greater level in CDNOS1KO mice. CDNOS1KO mice did not suppress plasma aldosterone in response to the high sodium diet, which may be partially explained by increased adrenal AT1R expression. Plasma renin concentration was appropriately suppressed in both genotypes. Furthermore, CDNOS1KO mice had significantly higher intrarenal angiotensin II with high sodium diet, although intrarenal angiotensinogen levels and angiotensin-converting enzyme activity were similar between knockout mice and controls. In agreement with inappropriate renin-angiotensin-aldosterone system activation in the CDNOS1KO mice on a high sodium diet, epithelial sodium channel activity and sodium transporter abundance were significantly higher compared with controls.

CONCLUSIONS

These data demonstrate that high sodium activation of collecting duct nitric oxide synthase 1β signaling induces suppression of systemic and intrarenal renin-angiotensin-aldosterone system, thereby modulating epithelial sodium channel and other sodium transporter abundance and activity to maintain sodium homeostasis.

Associations between polymorphisms of the ADIPOQ gene and hypertension risk: a systematic and meta-analysis

ADIPOQ gene polymorphisms have been indicated to be associated with hypertension; however, published studies have reported inconsistent results. Eligible studies were retrieved by searching the PubMed, Embase and China National Knowledge Infrastructure databases. The case group consisted of patients with hypertension, and the control group consisted of subjects with normal blood pressure. Based on eleven published articles, involving 4837 cases and 5618 controls, the pooled results from rs2241766 polymorphism showed increased risk in the allelic model (G VS T: OR = 1.16, 95%CI = 1.06–1.27), recessive model (GG VS GT + TT: OR = 1.34, 95%CI = 1.10–1.63), dominant model (GG + GT VS TT: OR = 1.15, 95%CI = 1.02–1.30) and homozygote model (GG VS TT: OR = 1.38, 95%CI = 1.21–1.69). In addition, rs266729 polymorphism showed increased risk for hypertension in the recessive model (GG VS GC + CC: OR = 1.43, 95%CI = 1.02–2.01). In the Caucasian subgroup, rs1501299 polymorphism showed decreased risk of hypertension in the allelic model (T VS G: OR = 0.75, 95%CI = 0.58–0.97), dominant model (TT + TG VS GG: OR = 0.83, 95%CI = 0.71–0.98) and heterozygote model (TG VS GG: OR = 0.82, 95%CI = 0.68–0.99). The rs2241766 polymorphism was associated with a significant increase in hypertension risk based on our analysis. Moreover, an increased risk of rs266729 in hypertension patients was also detected. Our meta-analysis suggests that the rs1501299 polymorphism may play a protective role in hypertension in Caucasian subgroup; however, this finding requires further study.

Associations of the Serum/Glucocorticoid Regulated Kinase Genes With BP Changes and Hypertension Incidence: The Gensalt Study

BACKGROUND

Single-marker and novel gene-based methods were employed to examine the associations of the serum/glucocorticoid regulated kinases (SGK) gene family with longitudinal blood pressure (BP) changes and hypertension incidence in a family-based cohort study.

METHODS

Totally, 1,768 Chinese participants from the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) follow-up study were included in the current analyses. Nine BP measures were obtained at each of 3 visits during the GenSalt follow-up study. Mixed-model and Gene-based analyses were used to examine the associations of the SGK gene family with longitudinal BP phenotypes. Bonferroni correction was applied to account for multiple testing.

RESULTS

After an average 7.2-year follow-up, 32.2% (513) of participants free of hypertension at baseline developed hypertension. Four novel SNPs in the SGK1 gene were predictive of the longitudinal BP phenotypes. The major alleles of SGK1 rs1763498 and rs114414980 conferred 2.9- and 2.5-fold increased risks of hypertension development, respectively (P = 1.0×10^-4 and 6.0×10^-4, respectively). In addition, the major allele of SGK1 rs229133 was significantly associated with 0.4mm Hg larger annual increases in systolic BP (P = 4.2×10^-4), while the major allele of rs6924468 was significantly associated with 0.2mm Hg smaller annual increases in diastolic BP (P = 4.2×10^-4). Gene-based analyses revealed an association of the SGK1 gene with risk of hypertension development (P = 7.4×10^-3). No evidence for the SGK2 and SGK3 genes was found.

CONCLUSIONS

The findings of the current study suggest that the SGK1 gene may play a role in long-term BP regulation and hypertension incidence.

Impact of HSD11B1 polymorphisms on BMI and components of the metabolic syndrome in patients receiving psychotropic treatments

BACKGROUND

Metabolic syndrome (MetS) associated with psychiatric disorders and psychotropic treatments represents a major health issue. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) is an enzyme that catalyzes tissue regeneration of active cortisol from cortisone. Elevated enzymatic activity of 11β-HSD1 may lead to the development of MetS.

METHODS

We investigated the association between seven HSD11B1 gene (encoding 11β-HSD1) polymorphisms and BMI and MetS components in a psychiatric sample treated with potential weight gain-inducing psychotropic drugs (n=478). The polymorphisms that survived Bonferroni correction were analyzed in two independent psychiatric samples (nR1=168, nR2=188) and in several large population-based samples (n1=5338; n2=123 865; n3>100 000).

RESULTS

HSD11B1 rs846910-A, rs375319-A, and rs4844488-G allele carriers were found to be associated with lower BMI, waist circumference, and diastolic blood pressure compared with the reference genotype (Pcorrected<0.05). These associations were exclusively detected in women (n=257) with more than 3.1 kg/m, 7.5 cm, and 4.2 mmHg lower BMI, waist circumference, and diastolic blood pressure, respectively, in rs846910-A, rs375319-A, and rs4844488-G allele carriers compared with noncarriers (Pcorrected<0.05). Conversely, carriers of the rs846906-T allele had significantly higher waist circumference and triglycerides and lower high-density lipoprotein-cholesterol exclusively in men (Pcorrected=0.028). The rs846906-T allele was also associated with a higher risk of MetS at 3 months of follow-up (odds ratio: 3.31, 95% confidence interval: 1.53-7.17, Pcorrected=0.014). No association was observed between HSD11B1 polymorphisms and BMI and MetS components in the population-based samples.

CONCLUSIONS

Our results indicate that HSD11B1 polymorphisms may contribute toward the development of MetS in psychiatric patients treated with potential weight gain-inducing psychotropic drugs, but do not play a significant role in the general population.

Connexins: Intercellular Signal Transmitters in Lymphohematopoietic Tissues

Life-long hematopoietic demands are met by a pool of hematopoietic stem cells (HSC) with self-renewal and multipotential differentiation ability. Humoral and paracrine signals from the bone marrow (BM) hematopoietic microenvironment control HSC activity. Cell-to-cell communication through connexin (Cx) containing gap junctions (GJs) allows pluricellular coordination and synchronization through transfer of small molecules with messenger activity. Hematopoietic and surrounding nonhematopoietic cells communicate each other through GJs, which regulate fetal and postnatal HSC content and function in hematopoietic tissues. Traffic of HSC between peripheral blood and BM is also dependent on Cx proteins. Cx mutations are associated with human disease and hematopoietic dysfunction and Cx signaling may represent a target for therapeutic intervention. In this review, we illustrate and highlight the importance of Cxs in the regulation of hematopoietic homeostasis under normal and pathological conditions.

Extracellular water and blood pressure in adults with growth hormone (GH) deficiency: a genotype-phenotype association study

Objectives

Growth hormone deficiency (GHD) in adults is associated with decreased extracellular water volume (ECW). In response to GH replacement therapy (GHRT), ECW increases and blood pressure (BP) reduces or remains unchanged. Our primary aim was to study the association between polymorphisms in genes related to renal tubular function with ECW and BP before and 1 year after GHRT. The ECW measures using bioimpedance analysis (BIA) and bioimpedance spectroscopy (BIS) were validated against a reference method, the sodium bromide dilution method (Br⁻).

Design and Methods

Using a candidate gene approach, fifteen single-nucleotide polymorphisms (SNPs) in nine genes with known impact on renal tubular function (AGT, SCNN1A, SCNN1G, SLC12A1, SLC12A3, KCNJ1, STK39, WNK1 and CASR) were genotyped and analyzed for associations with ECW and BP at baseline and with their changes after 1 year of GHRT in 311 adult GHD patients. ECW was measured with the Br⁻, BIA, and BIS.

Results

Both BIA and BIS measurements demonstrated similar ECW results as the reference method. At baseline, after adjustment for sex and BMI, SNP rs2291340 in the SLC12A1 gene was associated with ECW volume in GHD patients (p = 0.039). None of the SNPs influenced the ECW response to GHRT. One SNP in the SLC12A3 gene (rs11643718; p = 0.024) and three SNPs in the SCNN1G gene [rs5723 (p = 0.02), rs5729 (p = 0.016) and rs13331086 (p = 0.035)] were associated with the inter-individual differences in BP levels at baseline. A polymorphism in the calcium-sensing receptor (CASR) gene (rs1965357) was associated with changes in systolic BP after GHRT (p = 0.036). None of these associations remained statistically significant when corrected for multiple testing.

Conclusion

The BIA and BIS are as accurate as Br⁻ to measure ECW in GHD adults before and during GHRT. Our study provides the first evidence that individual polymorphisms may have clinically relevant effects on ECW and BP in GHD adults.

Genetic risk score of NOS gene variants associated with myocardial infarction correlates with coronary incidence across Europe

Coronary artery disease (CAD) mortality and morbidity is present in the European continent in a four-fold gradient across populations, from the South (Spain and France) with the lowest CAD mortality, towards the North (Finland and UK). This observed gradient has not been fully explained by classical or single genetic risk factors, resulting in some cases in the so called Southern European or Mediterranean paradox. Here we approached population genetic risk estimates using genetic risk scores (GRS) constructed with single nucleotide polymorphisms (SNP) from nitric oxide synthases (NOS) genes. These SNPs appeared to be associated with myocardial infarction (MI) in 2165 cases and 2153 controls. The GRSs were computed in 34 general European populations. Although the contribution of these GRS was lower than 1% between cases and controls, the mean GRS per population was positively correlated with coronary incidence explaining 65–85% of the variation among populations (67% in women and 86% in men). This large contribution to CAD incidence variation among populations might be a result of colinearity with several other common genetic and environmental factors. These results are not consistent with the cardiovascular Mediterranean paradox for genetics and support a CAD genetic architecture mainly based on combinations of common genetic polymorphisms. Population genetic risk scores is a promising approach in public health interventions to develop lifestyle programs and prevent intermediate risk factors in certain subpopulations with specific genetic predisposition.

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

OBJECTIVE

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

METHOD AND RESULTS

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

CONCLUSION

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

Estrogen receptor α is not a candidate gene for metabolic syndrome in Caucasian elderly subjects

OBJECTIVE

Variants of estrogen receptor α (ERα) have been associated with obesity, dyslipidemia, diabetes and blood pressure. The Middle East registers some of the highest rate of metabolic syndrome worldwide. The aim of this study is to investigate the relationship between metabolic syndrome, a clustered combination of these metabolic factors, and polymorphisms PvuII and XbaI of ERα in Lebanese Caucasian elderly overweight subjects.

MATERIAL/METHODS

250 Caucasian Lebanese unrelated elderly men and women, median age 71 years, were studied. ERα intronic polymorphisms variants, PvuII and XbaI diplotypes and genotypes, were examined. Associations with metabolic syndrome, defined by the American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI), and its components, namely high density lipoprotein (HDL), fasting glucose levels, blood pressure, and waist circumference were evaluated in regression models.

RESULTS

ER α diplotypes and genotypes distributions were similar between participants with and without metabolic syndrome, in the overall group of subjects, and by gender. No consistent associations between the diplotypes and genotypes tested and metabolic syndrome, or its components, could be detected.

CONCLUSIONS

Genetic variants in ERα were not associated with metabolic syndrome or its components, in a group of 250 Lebanese Caucasian elderly participants, a group with a high prevalence of metabolic syndrome.

Renal collecting duct NOS1 maintains fluid-electrolyte homeostasis and blood pressure

Nitric oxide is a pronatriuretic and prodiuretic factor. The highest renal NO synthase (NOS) activity is found in the inner medullary collecting duct. The collecting duct (CD) is the site of daily fine-tune regulation of sodium balance, and led us to hypothesize that a CD-specific deletion of NOS1 would result in an impaired ability to excrete a sodium load leading to a salt-sensitive blood pressure phenotype. We bred AQP2-CRE mice with NOS1 floxed mice to produce flox control and CD-specific NOS1 knockout (CDNOS1KO) littermates. CDs from CDNOS1KO mice produced 75% less nitrite, and urinary nitrite+nitrate (NOx) excretion was significantly blunted in the knockout genotype. When challenged with high dietary sodium, CDNOS1KO mice showed significantly reduced urine output, sodium, chloride, and NOx excretion, and increased mean arterial pressure relative to flox control mice. In humans, urinary NOx is a newly identified biomarker for the progression of hypertension. These findings reveal that NOS1 in the CD is critical in the regulation of fluid-electrolyte balance, and this new genetic model of CD NOS1 gene deletion will be a valuable tool to study salt-dependent blood pressure mechanisms.

Dynamic genetic linkage of intermediate blood pressure phenotypes during postural adaptations in a founder population

Blood pressure (BP) is a dynamic phenotype that varies rapidly to adjust to changing environmental conditions. Standing upright is a recent evolutionary trait, and genetic factors that influence postural adaptations may contribute to BP variability. We studied the effect of posture on the genetics of BP and intermediate BP phenotypes. We included 384 sib-pairs in 64 sib-ships from families ascertained by early-onset hypertension and dyslipidemia. Blood pressure, three hemodynamic and seven neuroendocrine intermediate BP phenotypes were measured with subjects lying supine and standing upright. The effect of posture on estimates of heritability and genetic covariance was investigated in full pedigrees. Linkage was conducted on 196 candidate genes by sib-pair analyses, and empirical estimates of significance were obtained. A permutation algorithm was implemented to study the postural effect on linkage. ADRA1A, APO, CAST, CORIN, CRHR1, EDNRB, FGF2, GC, GJA1, KCNB2, MMP3, NPY, NR3C2, PLN, TGFBR2, TNFRSF6, and TRHR showed evidence of linkage with any phenotype in the supine position and not upon standing, whereas AKR1B1, CD36, EDNRA, F5, MMP9, PKD2, PON1, PPARG, PPARGC1A, PRKCA, and RET were specifically linked to standing phenotypes. Genetic profiling was undertaken to show genetic interactions among intermediate BP phenotypes and genes specific to each posture. When investigators perform genetic studies exclusively on a single posture, important genetic components of BP are missed. Supine and standing BPs have distinct genetic signatures. Standardized maneuvers influence the results of genetic investigations into BP, thus reflecting its dynamic regulation.

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.

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.

Common Variation at the 11-β Hydroxysteroid Dehydrogenase Type 1 Gene Is Associated With Left Ventricular Mass

Background—

Polymorphisms in 11-β hydroxysteroid dehydrogenase type 1 (11β-HSD1, encoded by HSD11B1 ) have been reported to be associated with obesity-related cardiovascular risk factors, such as type II diabetes and hypertension. Left ventricular hypertrophy (LVH) is an independent risk factor for cardiovascular death associated with these factors but has significant additional heritability, the cause of which is undetermined. The 11β-HSD1 is believed to maintain tonic inhibition of the mineralocorticoid receptor in cardiomyocytes, and mineralocorticoid receptor activation is involved in the pathophysiology of LVH. We assessed the association between polymorphisms in the HSD11B1 gene and left ventricular mass (LVM) in 248 families ascertained through a proband with hypertension.

Methods and Results—

LVM was measured by electrocardiography and echocardiography in 868 and 829 participants, respectively. Single-nucleotide polymorphisms (SNPs) tagging common variation in the HSD11B1 gene were genotyped by mass spectrometry. The rs846910 SNP, which lies in the flanking region 5′ to exon 1B of HSD11B1 , was associated with LVM both by electrocardiography (≈5% lower LVM per copy of the rare allele, P =0.02) and by echocardiography (≈10% lower LVM per copy of the rare allele, P =0.003). Genotype explained 1% to 2% of the population variability in LVM, or approximately 5% of the heritable fraction. There were no significant associations between any HSD11B1 SNP and blood pressure or body mass index that could have confounded the association with LVM.

Conclusions—

Genotype at HSD11B1 has a small, but significant effect on LVM, apparently independently of any effect on obesity-related traits. These findings suggest a novel action of 11β-HSD1 in the human cardiomyocyte, which may be of therapeutic importance.

Variants of gene for microsomal prostaglandin E2 synthase show association with disease and severe inflammation in rheumatoid arthritis

Microsomal PGE synthase 1 (mPGES-1) is the terminal enzyme in the induced state of prostaglandin E(2) (PGE(2)) synthesis and constitutes a therapeutic target for rheumatoid arthritis (RA) treatment. We examined the role of the prostaglandin E synthase (PTGES) gene polymorphism in susceptibility to and severity of RA and related variations in the gene to its function. The PTGES gene polymorphism was analyzed in 3081 RA patients and 1900 controls from two study populations: Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) and the Leiden Early Arthritis Clinic (Leiden EAC). Baseline disease activity score (DAS28) was employed as a disease severity measure. mPGES-1 expression was analyzed in synovial tissue from RA patients with known genotypes using immunohistochemistry. In the Swedish study population, among women a significant association with risk for RA was observed for PTGES single-nucleotide polymorphisms (SNPs) in univariate analysis and for the distinct haplotype. These results were substantiated by meta-analysis of data from EIRA and Leiden EAC studies with overall OR 1.31 (95% confidence interval 1.11-1.56). Several PTGES SNPs were associated with earlier onset of disease or with higher DAS28 in women with RA. Patients with the genotype associated with higher DAS28 exhibited significantly higher mPGES-1 expression in synovial tissue. Our data reveal a possible influence of PTGES polymorphism on the pathogenesis of RA and on disease severity through upregulation of mPGES-1 at the sites of inflammation. Genetically predisposed individuals may develop earlier and more active disease owing to this mechanism.

Effects of protein coding polymorphisms in the kallikrein 1 gene on baseline blood pressure and antihypertensive response to irbesartan in Chinese hypertensive patients

The aim of this study was to determine the association between coding variants in the human tissue kallikrein 1 (KLK1) gene and baseline blood pressure (BP) and antihypertensive response to irbesartan treatment in Chinese hypertensive patients. A total of 1061 hypertensives were recruited and received daily oral dosage of 150 mg irbesartan for 4 weeks. Predose BPs, BPs and blood irbesartan concentrations at postdose on the 28th day were all measured. Common functional single-nucleotide polymorphisms (SNPs) in the KLK1 gene were genotyped. On the basis of the HapMap data of Han Chinese in the Beijing population, two non-synonymous polymorphisms with minor allele frequency>0.1, SNP rs5517 (Glu162Lys) and rs5516 (Gln121Glu), were selected. Those with GG genotype in the rs5516 locus had higher average baseline systolic BP (SBP) than CC subjects (β±s.e.: 5.0±2.3, P=0.033); and no associations of rs5517 with baseline BP (diastolic BP (DBP) and SBP) and BP responses, or rs5516 with baseline DBP and BP response were observed. In a haplotype-based association test for the KLK1 gene, the Haplo-special score analyses identified that haplotype AG was marginally associated with SBP response (specific score: 1.75 for P=0.08), but not with DBP response. We did not find any associations between haplotypes (GC and AC) and BP responses. The Haplo-GLM analyses showed that, compared with haplotype GC subjects, the subjects with haplotype AG had a marginally greater SBP response (adjusted β±s.e.: 1.81±0.97, P=0.06), but DBP response did not differ. This study suggests that rs5516 in the KLK1 gene may be involved in the development of essential hypertension and in the regulation of SBP-lowering response to irbesartan in Chinese hypertensives.

The genetics of cardiovascular disease

Recent advances in genotyping technology and insights into disease mechanisms have increased interest in the genetics of cardiovascular disease. Several candidate genes involved in cardiovascular diseases were identified from studies using animal models, and the translation of these findings to human disease is an exciting challenge. There is a trend towards large-scale genome-wide association studies that are subject to strict quality criteria with regard to both genotyping and phenotyping. Here, we review some of the strategies that have been developed to translate findings from experimental models to human disease and outline the need for optimizing global approaches to analyze such results. Findings from ongoing studies are interpreted in the context of disease pathways instead of the more traditional focus on single genetic variants.

Glutathione S-transferase variants and hypertension

OBJECTIVES

Glutathione S-transferases are involved in defences against oxidative stress. We have recently demonstrated reduced expression of glutathione S-transferase mu type 1 (Gstm1) in a rat model of hypertension. Here, we examine the association between GSTM variants and hypertension in human.

METHODS

We screened 83 patients with hypertension and 46 controls for single nucleotide polymorphisms in GSTM genes by TaqMan single nucleotide polymorphism genotyping assays and DNA sequencing. We then genotyped 753 trios from the Medical Research Council British Genetics of Hypertension Study transmission disequilibrium test cohort for 10 single nucleotide polymorphisms and the GSTM1 deletion and examined renal GSTM expression in a cohort of 27 hypertensive and 18 normotensive subjects. Finally, we attempted to replicate our findings in 1675 cases and 1654 controls from the Medical Research Council British Genetics of Hypertension Study case-control cohort.

RESULTS

We identified two major linkage disequilibrium blocks including GSTM4/GSTM2 and GSTM5/GSTM3 separated by the GSTM1 gene. In the British Genetics of Hypertension transmission disequilibrium test resource, a single nucleotide polymorphism in the 3' region of GSTM5 (rs11807) was found to be associated with hypertension (P = 0.01) with the T-allele being over-transmitted to hypertensive offspring. GSTM5 mRNA expression was found to be reduced in kidney tissue of subjects homozygous for the T-allele of rs11807 as compared to C-allele homozygous and CT heterozygous subjects (P = 0.02). Nevertheless, rs11807 was not associated with hypertension in the British Genetics of Hypertension case-control cohort (P = 0.61).

CONCLUSION

Our studies do not provide an evidence of an association of GSTM gene variants with hypertension in humans. They, however, illustrate the essential role of replication of initial results in a second cohort.

Alcohol intake and blood pressure: a systematic review implementing a Mendelian randomization approach

BACKGROUND

Alcohol has been reported to be a common and modifiable risk factor for hypertension. However, observational studies are subject to confounding by other behavioural and sociodemographic factors, while clinical trials are difficult to implement and have limited follow-up time. Mendelian randomization can provide robust evidence on the nature of this association by use of a common polymorphism in aldehyde dehydrogenase 2 (ALDH2) as a surrogate for measuring alcohol consumption. ALDH2 encodes a major enzyme involved in alcohol metabolism. Individuals homozygous for the null variant (*2*2) experience adverse symptoms when drinking alcohol and consequently drink considerably less alcohol than wild-type homozygotes (*1*1) or heterozygotes. We hypothesise that this polymorphism may influence the risk of hypertension by affecting alcohol drinking behaviour.

METHODS AND FINDINGS

We carried out fixed effect meta-analyses of the ALDH2 genotype with blood pressure (five studies, n = 7,658) and hypertension (three studies, n = 4,219) using studies identified via systematic review. In males, we obtained an overall odds ratio of 2.42 (95% confidence interval [CI] 1.66-3.55, p = 4.8 x 10(-6)) for hypertension comparing *1*1 with *2*2 homozygotes and an odds ratio of 1.72 (95% CI 1.17-2.52, p = 0.006) comparing heterozygotes (surrogate for moderate drinkers) with *2*2 homozygotes. Systolic blood pressure was 7.44 mmHg (95% CI 5.39-9.49, p = 1.1 x 10(-12)) greater among *1*1 than among *2*2 homozygotes, and 4.24 mmHg (95% CI 2.18-6.31, p = 0.00005) greater among heterozygotes than among *2*2 homozygotes.

CONCLUSIONS

These findings support the hypothesis that alcohol intake has a marked effect on blood pressure and the risk of hypertension.

Pyrosequencing of polymorphisms in the COX-2 gene (PTGS2) with reported clinical relevance

INTRODUCTION

Genetic variants in the prostaglandin-endoperoxide synthase 2 (PTGS2) gene, which codes for COX-2, have been identified to modulate the response to COX-2-inhibiting drugs and to be possible risk factors for the incidence or prognosis of cardiovascular or neoplastic diseases, Alzheimer's disease, multiple sclerosis, asthma or osteoarthritis. Clinical evidence thus suggests a clinical importance of COX-2 genetics reaching from disease risk or prognostics up to a personalized therapy with COX-2 inhibitors. The aim of this study was to develop rapid and reliable screening assays for PTGS2 mutations with reported clinical consequences.

METHODS

SNPs (dbSNP-IDs rs689465, rs689466, rs3918304, rs20415, rs20417, rs5270, rs2745557, rs5277, rs2066826, rs4648276, rs5273, rs5275, rs4648298, rs689469) and a nucleotide-deletion variant (rs20431) were chosen according to reported functional associations. For this selection of variants spanning the whole PTGS2 gene range, Pyrosequencing assays were established in DNA from 350 healthy unrelated Caucasians.

RESULTS

In all 350 DNA samples, the 15 PTGS2 polymorphisms were identified correctly as verified by control samples obtained by conventional sequencing. In silico haplotype analysis based on ten SNPs of greater than 1% observed frequencies identified two haploblocks with a linkage disequilibrium of D' = 0.59. Approximately 50% of the reconstructed haplotypes consisted of non-mutated alleles.

CONCLUSION

The presently developed Pyrosequencing assays allow for quick and reliable detection of PTGS2 genotypes and may promote further research toward personalized approaches to pathophysiological conditions involving COX-2.

A coding polymorphism of the kallikrein 1 gene is associated with essential hypertension: a tagging SNP-based association study in a Chinese Han population

OBJECTIVE

The aim of this study was to investigate the association between common variants in the human tissue kallikrein 1 (KLK1) gene and susceptibility to essential hypertension in Chinese Han.

METHODS

A tagging single nucleotide polymorphism (tSNP) approach was used for a case-control study in 2411 patients with essential hypertension and 2348 controls. All DNA samples and clinical data were collected from the International Collaborative Study of Cardiovascular Disease in Asia (InterASIA).

RESULTS

Based on the HapMap data of Han Chinese in Beijing (CHB) population, two non-synonymous polymorphisms, namely rs5517 (Glu162Lys) and rs5516 (Gln121Glu), were selected as tSNPs which could efficiently tag eight SNPs of the KLK1 gene with R larger than 90% for both haplotypes and single locus. Significant differences were found between groups for frequencies of rs5517 A allele (42.48% in cases versus 39.32% in controls, P=0.0019) and AA genotype [adjusted odds ratio (OR)=1.25 for AA versus AG/GG, P=0.0067]. The haplotype composed of the rs5517 A and rs5516 G allele significantly increased the risk of hypertension, with adjusted OR of 1.12 [95% confidence interval (CI), 1.04-1.28, P=0.0377] when compared with the common haplotype G-C. Diplotype analysis also showed a significant association between the diplotype of AG-AC and essential hypertension (OR=1.34, 95% CI, 1.07-1.68, P=0.0096).

CONCLUSIONS

The present study suggested that rs5517 in the KLK1 gene was significantly associated with essential hypertension in a Chinese Han population.

Association of the estrogen receptor-alpha gene with the metabolic syndrome and its component traits in African-American families: the Insulin Resistance Atherosclerosis Family Study

OBJECTIVE

We previously detected an association between a region of the estrogen receptor-alpha (ESR1) gene and type 2 diabetes in an African-American case-control study; thus, we investigated this region for associations with the metabolic syndrome and its component traits in African-American families from the Insulin Resistance Atherosclerosis Family Study.

RESEARCH DESIGN AND METHODS

A total of 17 single nucleotide polymorphisms (SNPs) from a contiguous 41-kb intron 1-intron 2 region of the ESR1 gene were genotyped in 548 individuals from 42 African-American pedigrees. Generalized estimating equations were computed using a sandwich estimator of the variance and exchangeable correlation to account for familial correlation.

RESULTS

Significant associations were detected between ESR1 SNPs and the metabolic syndrome (P = 0.005 to P = 0.029), type 2 diabetes (P = 0.001), insulin sensitivity (P = 0.0005 to P = 0.023), fasting insulin (P = 0.022 to P = 0.033), triglycerides (P = 0.021), LDL (P = 0.016 to P = 0.034), cholesterol (P = 0.046), BMI (P = 0.016 to P = 0.035), waist circumference (P = 0.012 to P = 0.023), and subcutaneous adipose tissue area (P = 0.016).

CONCLUSIONS

It appears likely that ESR1 contributes to type 2 diabetes and CVD risk via pleiotropic effects, leading to insulin resistance, a poor lipid profile, and obesity.

A polymorphism of the aldehyde dehydrogenase 2 gene is a risk factor for multiple lacunar infarcts in Japanese men: the Takahata Study

The objective of the present study was to examine the association between a polymorphism of the aldehyde dehydrogenase 2 (ALDH2) gene and lacunar infarcts of the brain. We conducted a population-based, cross-sectional study on residents from two age groups (61- and 72-year olds). A total of 376 subjects participated in the study, which included brain magnetic resonance image and genetic analysis of the ALDH2 gene. Of the 61- and 72-year-old subjects, 46.4% and 64.3%, respectively, had one or more lacunar infarcts. The average number of infarcts also increased from 2.0 to 2.8 in men and from 2.3 to 3.5 in women. No significant association between the ALDH2 genotype and the presence of lacunar infarction (> or =1) was found. However, in subjects with lacunar infarction, the genotype of ALDH2 *1/*1 was associated with a larger number of the lesion ['single' versus 'multiple' odds ratio (OR) 3.73, 95%CI: 1.43-9.74] in men. The OR was comparable even after adjusting for alcohol consumption, tobacco habits, age, hypertension, hypercholesterolemia, and diabetes mellitus (DM) (OR 3.88; 95% CI: 1.10-13.66). In women, there was no significant association between the ALDH2 genotypes and lacunar infarcts. The present study revealed that the ALDH2 *1/*1 genotype was significantly associated with the prevalence of multiple lacunar infarcts in Japanese men.

Connexin37: a potential modifier gene of inflammatory disease

There is an increasing appreciation of the importance of gap junction proteins (connexins) in modulating the severity of inflammatory diseases. Multiple epidemiological gene association studies have detected a link between a single nucleotide polymorphism in the human connexin37 (Cx37) gene and coronary artery disease or myocardial infarction in various populations. This C1019T polymorphism causes a proline-to-serine substitution (P319S) in the regulatory C terminal tail of Cx37, a protein that is expressed in the vascular endothelium as well as in monocytes and macrophages. Indeed, these three cell types are key players in atherogenesis. In the early phases of atherosclerosis, blood monocytes are recruited to the sites of injury in response to chemotactic factors. Monocytes adhere to the dysfunctional endothelium and transmigrate across endothelial cells to penetrate the arterial intima. In the intima, monocytes proliferate, mature, and accumulate lipids to progress into macrophage foam cells. This review focuses on Cx37 and its impact on the cellular and molecular events underlying tissue function, with particular emphasis of the contribution of the C1019T polymorphism in atherosclerosis. We will also discuss evidence for a potential mechanism by which allelic variants of Cx37 are differentially predictive of increased risk for inflammatory diseases.

A comprehensive description of the transcriptome of the hypothalamoneurohypophyseal system in euhydrated and dehydrated rats

The hypothalamoneurohypophyseal system (HNS) consists of the large peptidergic magnocellular neurons of the supraoptic hypo thalamic nucleus (SON) and the paraventricular hypothalamic nucleus (PVN), the axons of which course through the internal zone of the median eminence and terminate at blood capillaries of the posterior lobe of the pituitary gland. The HNS is a specialized brain neurosecretory apparatus responsible for the production of the antidiuretic peptide hormone vasopressin (VP). VP maintains water balance by promoting water conservation at the level of the kidney. Dehydration evokes a massive increase in the regulated release of VP from magnocellular neuron axon terminals in the posterior pituitary, which is accompanied by a plethora of changes in the morphology, electrophysiological properties, and biosynthetic and secretory activity of the HNS. We wish to understand this functional plasticity in terms of the differential expression of genes. We have therefore used microarrays to comprehensively catalog the genes expressed in the PVN, the SON and the neurointermediate lobe of the pituitary gland of control and dehydrated rats. Comparison of these gene lists has enabled us to identify transcripts that are regulated as a consequence of dehydration as well as RNAs that are enriched in the PVN or the SON. We suggest that these differentially expressed genes represent candidate regulators and effectors of HNS activity and remodeling.

The search for the genetic basis of hypertension

PURPOSE OF REVIEW

This review surveys the literature on the search for the genetic basis of hypertension during the 10 months since November 2003. The goals set forth by this search are defined and the highlights of the work accomplished are provided.

RECENT FINDINGS

The search for the genetic basis of hypertension is ongoing, generating an abundance of new data. These data consist of a large number of candidate genes, association of previously known and novel candidate genes with various facets of hypertension, detection of new quantitative trait loci and identification of genes that mediate susceptibility to hypertension. The renin-zangiotensin-aldosterone system continues to dominate the interest of investigators. Other gene systems are also emerging but a single-gene system cannot be singled out beyond the renin-angiotensin-aldosterone system and the data are mostly sporadic and do not reflect a guided or coordinated effort to resolve unanswered issues. The notion that hypertension is polygenic is reinforced, yet few data are provided as to the actual number of genes involved, gene-gene interaction or gene-environment interaction. Advanced biotechnological tools involving transcriptomics and proteomics are underused.

SUMMARY

Research on the genetic basis of hypertension has generated over the past year a large number of candidate genes and tied them to various aspects of hypertension. How these genes fit into the complex pathophysiological network that induces hypertension remains unclear. The task of putting together these genes into a cohesive framework still lies ahead, but promises to enlighten us as to the true nature of hypertension, the pathogenic mechanisms involved and improved therapeutic and preventive measures.

Genetic variations of regulator of G-protein signaling 2 in hypertensive patients and in the general population

OBJECTIVES

Mice deficient in the regulator of G-protein signaling 2 (RGS2) exhibit a strong hypertensive phenotype. We studied whether genetic variations in RGS2 are implicated in hypertension or other phenotypes in Japanese hypertensive individuals and the general population.

METHODS

We sequenced all exons of RGS2 and the promoter region in 953 and 48 hypertensive individuals, respectively. Genotyping by the TaqMan polymerase chain reaction method was performed for six missense or frameshift mutations and common single nucleotide polymorphisms in the general population, with a sample size of 1872 individuals (862 men and 1011 women).

RESULTS

We identified five novel missense mutations (Q2L; n = 2, Q2R; n = 1, M5V; n = 1, R44H; n = 2, Q78H; n = 1) and one novel frameshift mutation (1925-1926insT; n = 2) in a heterozygous state, in addition to 33 variations including five common single nucleotide polymorphisms. Six missense/frameshift mutations and three common single nucleotide polymorphisms (-638A > G, 1026T > A, 1891-1892delTC) were successfully genotyped in the general population. Mutations Q2L (n = 2), M5V (n = 1), and 1925-1926insT (n = 2) were only identified in hypertensive subjects. Six out of seven individuals with the R44H mutation, which occurs in the amphipathic alpha-helical domain of RGS2, had hypertension. The results showed a significant association of two common single nucleotide polymorphisms, 1026T > A [TT versus TA + AA: odds ratio (OR) 1.33; 95% confidence interval (CI) 1.02-1.74; P = 0.035] and 1891-1892delTC (I: insertion allele, D: deletion allele, II versus ID + DD: OR 1.47; 95% CI 1.09-1.97; P = 0.012), with hypertension in women by multivariate logistic regression analysis.

CONCLUSION

Our results suggest that genetic variations in RGS2 contribute partly to the hypertensive phenotype.

Aldehyde dehydrogenase 2 plays a role in the bioactivation of nitroglycerin in humans

OBJECTIVE

Nitrates are used widely in clinical practice. However, the mechanism underlying the bioactivation of nitrates to release NO remains unclear. Recent animal data suggest that mitochondrial aldehyde dehydrogenase (ALDH2) plays a central role in nitrate bioactivation, but its role in humans is not known. We investigated the role of ALDH2 in the vascular effects of nitroglycerin (NTG) in humans in vivo.

METHODS AND RESULTS

Forearm blood flow (FBF) responses to intra-arterial infusions of NTG, sodium nitroprusside (SNP), and verapamil were measured in 12 healthy volunteers before and after ALDH2 inhibition by disulfiram. All drugs caused a dose-dependent vasodilatation. However, only the response to NTG was significantly reduced after disulfiram therapy (33% reduction in area under the curve [AUC]; P=0.002). Separately, 11 subjects of East Asian origin, with the loss-of-function glu504lys mutation in the ALDH2 gene, received intra-arterial NTG, SNP, and verapamil. Only the FBF response to NTG was lower in the volunteers with the glu504lys mutation compared with East Asian and non-Asian wild-type control subjects (40% reduction in AUC; P=0.02).

CONCLUSIONS

The findings suggest that ALDH2 is involved in the bioactivation of NTG in humans in vivo but accounts for less than half of the total bioactivation. This may be of clinical importance in patients with mutations in the ALDH2 gene and in those taking drugs that inhibit ALDH2.

Association Analysis Between Hypertension and CYBA, CLCNKB, and KCNMB1 Functional Polymorphisms in the Japanese Population-The Suita Study-

BACKGROUND

Reproducibility of results is important for the validity of genetic association studies. Recently, 3 functional polymorphisms, G(-930)A in CYBA, T481S in CLCNKB, and E65K in KCNMB1, were reported to be associated with blood pressure (BP) status and the aim of this study was to confirm those findings using a large cohort representing the general Japanese population.

METHODS AND RESULTS

The study population consisted of 3,652 subjects recruited from the Suita study as representative of the general population in Japan. The genotypes of the 3 polymorphisms were determined by the TaqMan method. Logistic analysis indicated that the CYBA/G(-930)A polymorphism was associated with hypertension in male subjects. In the male population, the odds ratio of the GG genotype over GA + AA was 1.27 (95% confidence interval 1.01-1.57, p=0.034). Moreover, residuals of systolic and diastolic BP values were significantly higher in subjects with the GG genotype than in those with the GA or AA genotype (p=0.0007). However, such significant effects of the genotype on BP status were not observed in the female population. The significance of the CLCNKB/T481S and KCNMB1/E65K polymorphisms were not replicated in the present study.

CONCLUSION

The significance of the G(-930)A polymorphism of CYBA was confirmed in the present study with adequate statistical power, which strengthens the hypothesis that this polymorphism is important in the pathogenesis of hypertension and confers susceptibility.