Meta-analysis of the association of 4 angiotensinogen polymorphisms with essential hypertension: a role beyond M235T?

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.

Association study of M235T and A-6G polymorphisms in angiotensinogen gene with risk of developing preeclampsia in Iranian population

OBJECTIVE

Preeclampsia (PE) is a life-threatening complication of pregnancy that accounts for 12% of all maternal deaths worldwide. The aim of this study is to investigate the relationships between the polymorphisms of angiotensinogen (AGT) gene and preeclampsia.

MATERIAL AND METHODS

In this study, 240 unrelated preeclampsia patients and 178 normotensive women were examined. Genomic DNA was extracted then we assessed M235T(C/T) and A-6G polymorphisms of the AGT gene. Genotyping of M235T and A-6G polymorphisms were performed using SSP-PCR and MS-PCR, respectively.

RESULTS

A significant protective association was observed between A-6G G allele, A-6G A/G heterozygote genotype (OR = 0.6, p = 0.007 and OR = 0.6, p = 0.04) against PE. Furthermore, it was shown that two copies of A-6G A allele would increase PE risk (OR: 0.62, p = 0.04). Our results did not show a significant association for M235T polymorphism and PE. However, the combinations of A-6G A/A genotype and M235T T/C genotype (OR = 0.4, p = 0.02) and also A-6G A/G genotype and M235T T/C genotype (OR = 0.5, p = 0.04) in controls represented a significant protective association against PE.

CONCLUSION

According to the existence of significant correlation between two candidate polymorphisms, A-6G and M235T polymorphisms, with PE disease in our study, they may be considered as valuable factors in susceptibility to PE disease in Iranian women.

Influence of family history on the willingness of outpatients to undergo genetic testing for salt-sensitive hypertension: a cross-sectional study

OBJECTIVES

It is unclear whether family medical history influences the willingness to undergo genetic testing. This study aimed to determine how family history affected the willingness to undergo genetic testing for salt-sensitive hypertension in patients with and without hypertension.

DESIGN

Cross-sectional study using a self-administered questionnaire.

SETTING

Six primary care clinics and hospitals in Japan.

PARTICIPANTS

Consecutive 1705 outpatients aged >20 years, 578 of whom had hypertension.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome variable was the willingness to undergo genetic testing to determine the risk of salt-sensitive hypertension, and the secondary variables were age, sex, education level, family history and concerns about hypertension. Factors associated with a willingness to undergo genetic testing were evaluated in patients with and without hypertension using a logistic regression model.

RESULTS

In the hypertension and non-hypertension groups, 323 (55.9%) and 509 patients (45.2%), respectively, were willing to undergo genetic testing. This willingness was related with a high level of education (adjusted OR (ad-OR): 1.81, 95% CI 1.12 to 2.93), family history of stroke (1.55, 1.04 to 2.31) and concerns about hypertension (2.04, 1.27 to 3.28) in the hypertension group, whereas in the non-hypertension group, it was influenced by education level (ad-OR: 1.45, 95% CI 1.13 to 1.86), family history of hypertension (1.52, 1.17 to 1.98) and concerns about hypertension (2.03, 1.53 to 2.68).

CONCLUSIONS

The influence of family history on the willingness to undergo genetic testing for risk of salt-sensitivity hypertension differed between participants with and without hypertension. In particular, participants without hypertension wished to know their likelihood of developing hypertension, whereas those with hypertension were interested to know the risk of stroke (a complication of hypertension). Family history could help better counsel patients about genetic testing on the basis of their medical history.

Role of tagged SNPs of the AGT gene in causing susceptibility to essential hypertension

AIM

Angiotensinogen (AGT) is one of the candidate genes that has been extensively investigated for association of its variants with essential hypertension. Studies focusing on the contribution of tagged single nucleotide polymorphisms (SNPs) in the AGT gene are limited and lacking from Indian population. Hence, the present study was carried out to examine the role of five tagged SNPs viz., g.6147G>A (rs7539020), g.5978A>G (rs2493134); g.6241T>C (rs1078499), g.7781G>T (rs11122577), and g.5855G>A (rs3789678) in the development of hypertension.

MATERIALS AND METHODS

202 hypertensives and 222 normotensives were screened for five tagged SNPs using the method of polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The present study revealed significant association of g.5855G>A polymorphism with essential hypertension in different logistic regression models wherein protection was conferred by g.5855G>A against developing the condition. The polymorphism led to the creation of new exonic splicing enhancer and destruction of exonic splicing silencer site thereby enhancing the process of mRNA splicing. The haplotypes AGTG and GACG were found to have a significant protective effect. Other polymorphisms did not show any significant association with hypertension.

CONCLUSION

The present study is the first one to report the protective role of g.5855G>A polymorphism in the development of essential hypertension. The results reflect possibility of ethnic variation in the contribution of g.5855G>A polymorphism of the AGT gene to essential hypertension.

Differences in genotype frequencies of salt-sensitive genes between fishing and nonfishing communities in Japan

PURPOSE

To identify the differences in genotype frequencies of salt-sensitive genes between residents of fishing communities (FCs) and nonfishing communities (NFCs).

METHODS

The subjects included 18,156 individuals (8,043 males [44%] and 10,113 females [56%]; average age: 57.2±16.1 years) from the general population who were registered with large-scale genome banks and resided in 30 prefectures and 78 different regions in Japan. The measurement items were age, sex, blood pressure, presence or absence of hypertension, body mass index, alcohol consumption, and smoking habit. Furthermore, to analyze the genotype frequencies of salt-sensitive genes, α-adducin 1 (ADD1), angiotensinogen (AGT), angiotensin II receptor type 1 (AT1), and guanine nucleotide-binding protein β peptide 3 (GNB3) were measured. According to the 2004 government classification of municipalities (cities, towns, and villages), communities existing in areas bordering an ocean and with an ocean port were defined as FCs (28 areas). The others were defined as NFCs (50 areas). A logistic regression model was used for comparison of genotype frequencies between subjects residing in FCs and NFCs.

RESULTS

Of the included subjects, 4,916 (27.0%) and 13,240 (73.0%) resided in FCs and NFCs, respectively. In FCs, the mean age was 59.4±16.7 years and men accounted for 41.0% of the cohort (n=2,015). In NFCs, the mean age was 56.4±15.8 years and men accounted for 45.5% of the cohort (n=6,028). The adjusted odds ratios of the AA and AG genotypes compared with the GG genotype for AGT were 0.80 (95% confidence interval [CI]: 0.68-0.95) and 0.76 (95% CI: 0.64-0.91), respectively. The adjusted odds ratio of the CC genotype compared with AA for AT1 was 0.63 (95% CI: 0.40-0.93).

CONCLUSION

The incidence of the salt-sensitive genotypes AGT and AT1 in residents of FCs were significantly lower than in NFCs.

Angiotensinogen (AGT) M235T, AGT T174M and Angiotensin-1-Converting Enzyme (ACE) I/D Gene Polymorphisms in Essential Hypertension: Effects on Ramipril Efficacy

Background:

Hypertension, one of the most important risk factors for premature cardiovascular disease, is a major worldwide public health problem. Angiotensin-1-converting enzyme (ACE) and angiotensinogen (AGT) gene polymorphisms are thought to be associated with primary hypertension. In the present study, we examined the frequency of these gene polymorphisms in an adult population with and without essential hypertension. Furthermore, we evaluated the effect of ACE and AGT gene polymorphisms on ramipril treatment efficacy in the hypertensive patients.

Methods:

A total of 166 adults (83 hypertensives and 83 normotensives) were involved in the study and genotyped for AGTM235T (rs699), AGTT174M (rs4762) and ACEI/D (rs1799752) gene polymorphisms.

Results:

The genotype and allele distribution of the AGTM235T variant significantly differed between hypertensives and normotensives [odds ratio (OR) = 1.57% (T vs M allele), 95% confidence intervals (CIs): 1.01 - 2.44; p=0.045 for hypertensives]. However, none of the 3 studied Simple Nucleotide Polymorphisms were associated with the blood pressure-lowering response to ramipril.

Conclusion:

These results suggest that AGTM235T gene polymorphism is associated with essential hypertension. However, none of the AGTM235T, AGTT174M and ACEI/D gene polymorphisms influenced ramipril effectiveness.

Risk given by AGT polymorphisms in inducing susceptibility to essential hypertension among isolated populations from a remote region of China: A case-control study among the isolated populations

INTRODUCTION

Hypertension is a serious risk factor affecting up to 30% of the world's population with a heritability of more than 30-50%. The aim of this study was to investigate the contribution of the polymorphisms localized in the angiotensinogen (AGT) gene, a main component of the renin-angiotensin-aldosterone system, in inducing the susceptibility to essential hypertension (EH) among isolated populations (Yi and Hani minorities) with low prevalence rate from the remote region of Yunnan in China.

METHODS

A case-control association study was performed, and all subjects were genotyped for the seven single nucleotide polymorphisms localized in the AGT region by polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

Three polymorphisms, i.e. rs5046, rs5049, and rs2478544, were significantly associated with EH among the Hani minority. The associations, found in the Yi minority, did not reach a conclusive level of statistical significance. The polymorphisms of rs2478544 and rs5046 caused the transformations of exonic splicing enhancer sites and transcription factor binding sites, respectively, in the bioinformatic analyses. The haplotype-rs5046T, rs5049A, rs11568020G, rs3789679C, rs2478544C was susceptible for EH among the Hani minority.

CONCLUSION

Our findings suggested that the AGT polymorphisms have played a vital role in determining an individual's susceptibility to EH among the isolated population, which would be helpful for EH management in the remote mountainous region of Yunnan in China.

Association of T174M polymorphism of angiotensinogen gene with essential hypertension: a meta-analysis

The association between T174M polymorphism of angiotensinogen gene and essential hypertension risk remains controversial. We herein performed a meta-analysis to achieve a reliable estimation of their relationship. All the studies published up to May 2013 on the association between T174M polymorphism and essential hypertension risk were identified by searching the electronic repositories PubMed, MEDLINE and EMBASE, Springer, Elsevier Science Direct, Cochrane Library and Google Scholar. Data were extracted and pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated. Ultimately, nine eligible studies, including 2188 essential hypertension cases and 2459 controls, were enrolled in this meta-analysis. No significant associations were found under the overall ORs for M-allele comparison (M vs. T, pooled OR 0.92, 95% CI 0.62–1.37), MM vs. TT (pooled OR 0.86, 95% CI 0.29–2.51), TM vs. TT n (pooled OR 0.91, 95% CI 0.63–1.32), recessive model (MM vs. TT+TM, pooled OR 0.89, 95% CI 0.35–2.30), dominant model (MM+TM vs. TT, pooled OR 0.91, 95% CI 0.60–1.38) between T174M polymorphism and risk for essential hypertension. This meta-analysis suggested that the T174M polymorphism of the angiotensinogen gene might not be associated with the susceptibility of essential hypertension in Asian or European populations.

Renin-angiotensin-aldosterone system related gene polymorphisms and urinary total arsenic is related to chronic kidney disease

A recent study demonstrated that an increased risk of chronic kidney disease (CKD) was associated with high urinary total arsenic levels. However, whether genomic instability is related to CKD remains unclear. An association between CKD and genetic polymorphisms of regulation enzymes of the renin-angiotensin-aldosterone system (RAAS), such as angiotensin-converting enzyme (ACE), angiotensinogen (AGT), angiotensin II type I receptor (AT1R), and aldosterone synthase (CYP11B2) has not been shown. The aim of the present study was to investigate the relationship between arsenic, genetic polymorphisms of RAAS enzymes and CKD. A total of 233 patients and 449 age- and gender-matched controls were recruited from the Taipei Medical University Hospital, Taipei Municipal Wan Fang Hospital and the Shin Kong Wu Ho-Su Memorial Hospital. Concentrations of urinary arsenic were determined by a high-performance liquid chromatography-linked hydride generator, and atomic absorption spectrometry. Polymorphisms of ACE(I/D), AGT(A[-20]C), (T174M), (M235T), AT1R(A1166C) and CYP11B2(C[-344]T) were examined by polymerase chain reaction and restriction fragment length polymorphism. Subjects carrying the CYP11B2 TT genotype had a higher odds ratio (OR), 1.39 (0.96-2.01), of CKD; while those with the AGT(A[-20]C) CC genotype had an inverse OR of CKD (0.20 (0.05-0.81)), and a high-risk genotype was defined as A/A+A/C for AGT(A[-20C]) and T/T for CYP11B2(C[-344]T). The trend test showed a higher OR for CKD in patients who had either high urinary total arsenic levels or carried the high-risk genotype, or both, compared to patients with low urinary total arsenic levels, who carried the low-risk genotype, and could also be affected by the hypertension or diabetes status.

Variation in genes that regulate blood pressure are associated with glomerular filtration rate in Chinese

Chronic kidney disease (CKD) can be a consequence of diabetes, hypertension, immunologic disorders, and other exposures, as well as genetic factors that are still largely unknown. Glomerular filtration rate (GFR), which is widely used to measure kidney function, has a heritability ranging from 25% to 75%, but only 1.5% of this heritability is explained by genetic loci that have been identified to date. In this study we tested for associations between GFR and 234 SNPs in 26 genes from pathways of blood pressure regulation in 3,025 rural Chinese participants of the "Genetic Epidemiology Network of Salt Sensitivity" (GenSalt) study. We estimated GFR (eGFR) using baseline serum creatinine measurements obtained prior to dietary intervention. We identified significant associations between eGFR and 12 SNPs in 6 genes (ACE, ADD1, AGT, GRK4, HSD11B1, and SCNN1G). The cumulative effect of the protective alleles was an increase in mean eGFR of 4 mL/min per 1.73 m2, while the cumulative effect of the risk alleles was a decrease in mean eGFR of 3 mL/min per 1.73 m2. In addition, we identified a significant interaction between SNPs in CYP11B1 and ADRB2. We have identified common variants in genes from pathways that regulate blood pressure and influence kidney function as measured by eGFR, providing new insights into the genetic determinants of kidney function. Complex genetic effects on kidney function likely involve interactions among genes as we observed for CYP11B1 and ADRB2.

Risk conferred by tagged SNPs of AGT gene in causing susceptibility to essential hypertension

Abstract Introduction: AGT gene harbors several variants of which 21 are found to be in high linkage disequilibrium as per Hapmap database. Studies delineating the importance of these tagged SNPs are very limited and lacking from Indian population. In the present study, we evaluated the contribution of four tagged SNPs namely, g.6635G > A, g.6506G > A, g.12840G > A, and g.13828T > C at AGT locus along with the analyses of haplotype and epistatic interactions in causing susceptibility to essential hypertension (EHT).

METHODS

About 215 hypertensives and 230 normotensives were genotyped for selected tagged SNPs using PCR-RFLP method.

RESULTS

Significant association was obtained for g.6635G > A and g.6506G > A polymorphisms wherein GG homozygotes for both the markers were at risk for developing the condition. g.13828T > C polymorphism specially, female heterozygotes (TC) were found to be at increased risk for EHT. Haplotype GGGC was found to have a significant protective effect (p = 0.0059). Markers g.6506G > A and g.12840G > A resulted in the creation of new enhancer sites thereby affecting splicing process.

CONCLUSION

The present report is the first one in the literature showing general- and gender-specific association of g.6506G > A and g.13828T > C polymorphisms, respectively, with EHT. However, further studies for replication of present observations are warranted from other populations and other parts of India.

Multivariate meta-analysis of the association of G-protein beta 3 gene (GNB3) haplotypes with cardiovascular phenotypes

The objective of the present study was to review previous investigations on the association of haplotypes in the G-protein β3 subunit (GNB3) gene with representative cardiovascular risk factors/phenotypes: hypertension, overweight, and variation in the systolic and diastolic blood pressures (SBP and DBP, respectively) and as well as body mass index (BMI). A comprehensive literature search was undertaken in Pubmed, Web of Science, EMBASE, Biological Abstracts, LILACS and Google Scholar to identify potentially relevant articles published up to April 2011. Six genetic association studies encompassing 16,068 participants were identified. Individual participant data were obtained for all studies. The three most investigated GNB3 polymorphisms (G-350A, C825T and C1429T) were considered. Expectation-maximization and generalized linear models were employed to estimate haplotypic effects from data with uncertain phase while adjusting for covariates. Study-specific results were combined through a random-effects multivariate meta-analysis. After carefully adjustments for relevant confounding factors, our analysis failed to support a role for GNB3 haplotypes in any of the investigated phenotypes. Sensitivity analyses excluding studies violating Hardy-Weinberg expectations, considering gender-specific effects or more extreme phenotypes (e.g. obesity only) as well as a fixed-effects "pooled" analysis also did not disclose a significant influence of GNB3 haplotypes on cardiovascular phenotypes. We conclude that the previous cumulative evidence does not support the proposal that haplotypes formed by common GNB3 polymorphisms might contribute either to the development of hypertension and obesity, or to the variation in the SBP, DBP and BMI.

Novel variants detected in AGT gene among patients with essential hypertension

INTRODUCTION

AGT is the first gene to be linked to essential hypertension (EHT). It harbors several variants of which only few polymorphisms are found to exhibit positive and negative associations with hypertension. In the present study, the AGT gene was screened to detect already reported and novel variations contributing to the development of hypertension.

METHOD

In total, 215 hypertensives and 230 normotensives were screened for variations in all the five exons and a part of promoter of AGT gene using single strand conformation polymorphism analysis followed by sequencing of samples showing mobility shifts on polyacrylamide gels.

RESULTS

Five novel variants, namely c.-61G>A in promoter, c.-4+17C>T in intron1, c.24T>C and c.28A>T in Exon2, and c.*90 T>C in 3' untranslated region were detected in the AGT gene. c.-61G>A lies in the promoter region that plays a critical role in its expression. Variation c.-4+17C>T created a new enhancer site. c.24T>C (TCT-TCC) is a silent mutation while c.28A>T (p. M10L) has a possible damaging effect on the AGT protein. c.*90T>C, detected in the 3' untranslated region is thought to play an important role in the translation and stability of the mRNA.

CONCLUSION

Studies on the functional role of these novel variants are warranted to understand the mechanism underlying the development of EHT.

Primary care patient willingness for genetic testing for salt-sensitive hypertension: a cross sectional study

Background

The current research into single nucleotide polymorphisms has extended the role of genetic testing to the identification of increased risk for common medical conditions. Advances in genetic research may soon necessitate preparation for the role of genetic testing in primary care medicine. This study attempts to determine what proportion of patients would be willing to undergo genetic testing for salt-sensitive hypertension in a primary care setting, and what factors are related to this willingness.

Methods

A cross-sectional study using a self-report questionnaire was conducted among outpatients in primary care clinics and hospitals in Japan. The main characteristics measured were education level, family medical history, personal medical history, concern about hypertension, salt preference, reducing salt intake, and willingness to undergo genetic testing for salt-sensitive hypertension.

Results

Of 1,932 potential participants, 1,457 (75%) responded to the survey. Of the respondents, 726 (50%) indicated a willingness to undergo genetic testing. Factors related to this willingness were being over 50 years old (adjusted odds ratio [ad-OR] = 1.42, 95% Confidence interval = 1.09 – 1.85), having a high level of education (ad-OR: 1.83, 1.38 – 2.42), having a family history of hypertension (ad-OR: 1.36, 1.09 – 1.71), and worrying about hypertension (ad-OR: 2.06, 1.59 – 2.68).

Conclusions

Half of the primary care outpatients surveyed in this study wanted to know their genetic risk for salt-sensitive hypertension. Those who were worried about hypertension or had a family history of hypertension were more likely to be interested in getting tested. These findings suggest that primary care physicians should provide patients with advice on genetic testing, as well as address their anxieties and concerns related to developing hypertension.

Association between polymorphisms in the renin-angiotensin-aldosterone system genes and essential hypertension in the Han Chinese population

BACKGROUND

Renin-angiotensin-aldosterone system (RAAS) is the most important endocrine blood pressure control mechanism in our body, genes encoding components of this system have been strong candidates for the investigation of the genetic basis of hypertension. However, previous studies mainly focused on limited polymorphisms, thus we carried out a case-control study in the Han Chinese population to systemically investigate the association between polymorphisms in the RAAS genes and essential hypertension.

METHODS

905 essential hypertensive cases and 905 normotensive controls were recruited based on stringent inclusion and exclusion criteria. All 41 tagSNPs within RAAS genes were retrieved from HapMap, and the genotyping was performed using the GenomeLab SNPstream Genotyping System. Logistic regression analysis, Multifactor dimensionality reduction (MDR), stratified analysis and crossover analysis were used to identify and characterize interactions among the SNPs and the non-genetic factors.

RESULTS

Serum levels of total cholesterol (TC) and triglyceride (TG), and body mass index (BMI) were significantly higher in the hypertensive group than in the control group. Of 41 SNPs genotyped, rs3789678 and rs2493132 within AGT, rs4305 within ACE, rs275645 within AGTR1, rs3802230 and rs10086846 within CYP11B2 were shown to associate with hypertension. The MDR analysis demonstrated that the interaction between BMI and rs4305 increased the susceptibility to hypertension. Crossover analysis and stratified analysis further indicated that BMI has a major effect, and rs4305 has a minor effect.

CONCLUSION

These novel findings indicated that together with non-genetic factors, these genetic variants in the RAAS may play an important role in determining an individual's susceptibility to hypertension in the Han Chinese.

AGT M235T variant is not associated with risk of cancer

OBJECTIVE

The angiotensinogen (AGT) gene has been considered to be implicated in the development of cancer. However, the results have been inconsistent. In this study, we performed a meta-analysis to clarify the association of AGT M235T variant with cancer risk.

METHODS

Published literature from PubMed and Embase were retrieved. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using a fixed- or random-effects model.

RESULTS

A total of seven articles including eight studies (3639 cancer cases and 6684 controls) for AGT M235T variant were included. The present meta-analysis showed that AGT M235T variant was marginally associated with cancer risk under dominant model (OR=1.12, 95% CI=1.02-1.24). However, the positive association was not stable after sensitivity analysis. Further subgroup analysis by cancer type did not suggest any association of AGT M235T variant with various cancers (all p>0.05).

CONCLUSION

The present meta-analysis demonstrated that AGT M235T variant was not associated with risk of all cancer or various cancers. Further well-designed studies with large sample size should be conducted to confirm or refute the non-significant association.

Diagnostic tools for hypertension and salt sensitivity testing

PURPOSE OF REVIEW

One-third of the world's population has hypertension and it is responsible for almost 50% of deaths from stroke or coronary heart disease. These statistics do not distinguish salt-sensitive from salt-resistant hypertension or include normotensives who are salt-sensitive even though salt sensitivity, independent of blood pressure, is a risk factor for cardiovascular and other diseases, including cancer. This review describes new personalized diagnostic tools for salt sensitivity.

RECENT FINDINGS

The relationship between salt intake and cardiovascular risk is not linear, but rather fits a J-shaped curve relationship. Thus, a low-salt diet may not be beneficial to everyone and may paradoxically increase blood pressure in some individuals. Current surrogate markers of salt sensitivity are not adequately sensitive or specific. Tests in the urine that could be surrogate markers of salt sensitivity with a quick turn-around time include renal proximal tubule cells, exosomes, and microRNA shed in the urine.

SUMMARY

Accurate testing of salt sensitivity is not only laborious but also expensive, and with low patient compliance. Patients who have normal blood pressure but are salt-sensitive cannot be diagnosed in an office setting and there are no laboratory tests for salt sensitivity. Urinary surrogate markers for salt sensitivity are being developed.

Effects of disclosing hypothetical genetic test results for salt sensitivity on salt restriction behavior

BACKGROUND

A few studies have explored the effects of disclosure of genetic testing results on chronic disease predisposition. However, these effects remain unclear in cases of hypertension. Reducing salt intake is an important nonpharmacological intervention for hypertension. We investigated the effects of genetic testing for salt sensitivity on salt restriction behavior using hypothetical genetic testing results.

METHODS

We conducted a cross-sectional study using a self-completed questionnaire. We enrolled consecutive outpatients who visited primary care clinics and small hospitals between September and December 2009 in Japan. We recorded the patients' baseline characteristics and data regarding their salt restriction behavior, defined as reducing salt intake before and after disclosure of hypothetical salt sensitivity genetic test results. Behavioral stage was assessed according to the five-stage transtheoretical model. After dividing subjects into salt restriction and no salt restriction groups, we compared their behavioral changes following positive and negative test results and analyzed the association between the respondents' characteristics and their behavioral changes.

RESULTS

We analyzed 1562 participants with a mean age of 58 years. In the no salt restriction group, which included patients at the precontemplation, contemplation, and preparation stages, 58.7% stated that their behavioral stage progressed after a positive test result, although 29.8% reported progression after a negative result (P < 0.001). Conversely, in the salt restriction group, which included patients at the active and maintenance stages, 9.2% stated that they would quit restricting salt intake following a negative test result, and 2.2% reported they would quit following a positive result (P < 0.001). Age < 65 years (adjusted odds ratio [OR] 1.74; 95% confidence interval [CI] 1.12-2.71), female gender (adjusted OR 1.84; CI 1.29-2.62), graduation from college or university (adjusted OR 1.66; CI 1.11-2.49), and desire for genetic testing (adjusted OR 4.53; CI 3.13-6.57) were associated with progression of behavioral stage in the no salt restriction group. Conversely, salt preference (adjusted OR 2.13; CI 1.31-3.49) was associated with quitting salt restriction in the salt restriction group.

CONCLUSION

Patients in the no salt restriction group show the possibility of progression from the behavioral stage to the action stage after testing positive for salt sensitivity. Conversely, patients in the salt restriction group, particularly those with a salt preference, would quit salt restriction after testing negative.

Allele-specific expression of angiotensinogen in human subcutaneous adipose tissue

The angiotensinogen gene is genetically linked with hypertension, but the mechanistic basis for association of sequence variants in the promoter and coding region of the gene remains unclear. An E-box at position -20 has been hypothesized to control the level of angiotensinogen expression, but its mechanistic importance for angiotensinogen expression in human tissues is uncertain. We developed an allele-specific polymerase chain reaction-based assay to distinguish between angiotensinogen mRNA derived from variants at the -20 position (rs5050) in the angiotensinogen promoter in adipose tissues obtained during surgery. The assay takes advantage of linkage disequilibrium between the rs5050 (located in the promoter) and rs4762 (located in the coding region) single nucleotide polymorphisms. This strategy allowed us to assess the level of allele-specific expression in A-20C heterozygous subjects comparing the relative proportion of each allele with the total, thus eliminating the problem of variability in the level of total angiotensinogen mRNA among subjects. We show that angiotensinogen mRNA derived from the -20C allele is expressed significantly higher than that derived from the -20A allele in subcutaneous adipose tissue, and increased expression correlates with enriched chromatin binding of upstream stimulatory factor-2 to the -20C E-box compared with -20A. This may be depot selective because we were unable to detect these differences in omental adipose. This provides the first data directly comparing expression of angiotensinogen mRNA and differential transcription factor binding derived from 2 variant alleles in human tissue where the ratio of expression of one allele to another can be accurately determined.

Renin-angiotensin system, hypertension, and chronic kidney disease: pharmacogenetic implications

About 80% of CKD (chronic kidney disease) patients are hypertensive, and kidney function and blood pressure are clearly related to both physiologic and pathologic conditions in a "vicious cycle". In this pathologic scenario, there is a renin-angiotensin system (RAS) hyperactivity associated to progression of renal damage. Current guidelines indicate as the first choice of antihypertensive intervention, the pharmacologic blockade of the RAS. Nonetheless, both response to treatment and renal protection have considerable inter-individual variability. The main aims of this review are to describe the genetic characteristics of RAS components and to identify the possible pharmacogenetic implications for RAS-blocker drugs in the hypertension-CKD scenario. To date, RAS polymorphisms have not been consistently associated to antihypertensive response and studies focusing on CKD are scarce. Nonetheless, pharmacogenetic studies for the RAS-blocker drugs could still be further explored, especially with new generation tools and focusing not only on the antihypertensive response, but also on renal protection as well.

Hypertension-susceptibility gene prevalence in the Pacific Islands and associations with hypertension in Melanesia

Human essential hypertension is partly caused by genetic factors. Angiotensinogen (AGT), G-protein β3-subunit (GNB3) and cytochrome P450 3A5 (CYP3A5) are candidate hypertension susceptibility genes and risk alleles at these loci have been thought to arise owing to human adaptation to climatic changes following the migration out-of-Africa. This study aimed to reveal the frequencies of hypertension-susceptibility genotypes in Pacific Island populations and associations of these single-nucleotide polymorphisms (SNPs) to hypertension. Genotyping was conducted for 804 individuals from Melanesian, Micronesian and Polynesian populations at SNPs in the genes encoding AGT (rs699, rs5049 and rs5051), GNB3 (rs5443) and CYP3A5*1/*3 (rs776746). Associations between these SNPs and hypertension were tested for 383 Melanesian Solomon Islanders. We found that the A/A genotype at rs5049 was a risk factor for hypertension (P=0.025) in the Melanesian Solomon Islanders; three SNPs for AGT were in linkage disequilibrium. The ancestral alleles of rs699, rs5051 and rs776746, and the derived allele of rs5443 were as frequent in the populations surveyed here as in other equatorial populations. Although other polymorphisms associated with hypertension and additional populations remain to be studied, these findings suggest that the Pacific Islanders' susceptibility to hypertension arose because of human migration and adaptation.

Lack of association of A-6G polymorphism of AGT gene with essential hypertension in the Chinese population

BACKGROUND

The angiotensinogen (AGT) A-6G gene polymorphism has been indicated to be related to the susceptibility of essential hypertension. However, the results are still unclear.

OBJECTIVE AND METHODS

To survey the relationship between AGT A-6G gene polymorphism and essential hypertension, 18 separate studies with 9306 patients were analyzed through meta-analysis. The random-effect model was used to calculate the pooled odds ratio (OR) and its corresponding 95% confidence interval (CI).

RESULTS

In this AGT A-6G gene polymorphism and essential hypertension meta-analysis of the Chinese population, the distribution of the G-allele frequency was 0.23 for the essential hypertension group and 0.21 for the control group. The association between the AGT A-6G gene polymorphism and essential hypertension in the entire sample population was not significant. The pooled OR for the frequency of the G allele was 1.10 (95% CI 0.96 to 1.27, Pheterogeneity < 0.00001, P = 0.17). In the stratified analysis by ethnicity, a significant association in Li and Mongolian ethnicities (P ≤ 0.05) was achieved. However, no significant association was found in other ethnicities such as Han, Tibetan, Kazakh, Bai and Yi (P > 0.05).

CONCLUSIONS

The current meta-analysis suggested that AGT A-6G gene polymorphism might not be related to the increased risk of essential hypertension in the entire Chinese population. However, the G-allele of AGT A-6G might predispose to essential hypertension in the Li and Mongolian ethnicities.

Multilocus family-based association analysis of seven candidate polymorphisms with essential hypertension in an african-derived semi-isolated brazilian population

Background. It has been widely suggested that analyses considering multilocus effects would be crucial to characterize the relationship between gene variability and essential hypertension (EH). Objective. To test for the presence of multilocus effects between/among seven polymorphisms (six genes) on blood pressure-related traits in African-derived semi-isolated Brazilian populations (quilombos). Methods. Analyses were carried out using a family-based design in a sample of 652 participants (97 families). Seven variants were investigated: ACE (rs1799752), AGT (rs669), ADD2 (rs3755351), NOS3 (rs1799983), GNB3 (rs5441 and rs5443), and GRK4 (rs1801058). Sensitivity analyses were further performed under a case-control design with unrelated participants only. Results. None of the investigated variants were associated individually with both systolic and diastolic BP levels (SBP and DBP, respectively) or EH (as a binary outcome). Multifactor dimensionality reduction-based techniques revealed a marginal association of the combined effect of both GNB3 variants on DBP levels in a family-based design (P = 0.040), whereas a putative NOS3-GRK4 interaction also in relation to DBP levels was observed in the case-control design only (P = 0.004). Conclusion. Our results provide limited support for the hypothesis of multilocus effects between/among the studied variants on blood pressure in quilombos. Further larger studies are needed to validate our findings.

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

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

Hypercontrols in genotype-phenotype analysis reveal ancestral haplotypes associated with essential hypertension

The angiotensinogen gene locus has been associated with essential hypertension in most populations analyzed to date. Increased plasma angiotensinogen levels have been proposed as an underlying cause of essential hypertension in whites; however, differences in the genetic regulation of plasma angiotensinogen levels have also been reported for other populations. The aim of this study was to analyze the relationship between angiotensinogen gene polymorphisms and haplotypes with plasma angiotensinogen levels and the risk of essential hypertension in the Mexican population. We genotyped 9 angiotensinogen gene polymorphisms in 706 individuals. Four polymorphisms, A-6, C4072, C6309, and G12775, were associated with increased risk, and the strongest association was found for the C6309 allele (χ(2)=23.9; P=0.0000009), which resulted in an odds ratio of 3.0 (95% CI: 1.8-4.9; P=0.000006) in the recessive model. Two polymorphisms, A-20C (P=0.003) and C3389T (P=0.0001), were associated with increased plasma angiotensinogen levels but did not show association with essential hypertension. The haplotypes H1 (χ(2)=8.1; P=0.004) and H5 (χ(2)=5.1; P=0.02) were associated with essential hypertension. Using phylogenetic analysis, we found that haplotypes 1 and 5 are the human ancestral haplotypes. Our results suggest that the positive association between angiotensinogen gene polymorphisms and haplotypes with essential hypertension is not simply explained by an increase in plasma angiotensinogen concentration. Complex interactions between risk alleles suggest that these haplotypes act as "superalleles."

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A-6G and A-20C polymorphisms in the angiotensinogen promoter and hypertension risk in Chinese: a meta-analysis

Background

Numerous studies in Chinese populations have evaluated the association between the A-6G and A-20C polymorphisms in the promoter region of angiotensinogen gene and hypertension. However, the results remain conflicting. We carried out a meta-analysis for these associations.

Methods and Results

Case–control studies in Chinese and English publications were identified by searching the MEDLINE, EMBASE, CNKI, Wanfang, CBM, and VIP databases. The random-effects model was applied for dichotomous outcomes to combine the results of the individual studies. We finally selected 24 studies containing 5932 hypertensive patients and 5231 normotensive controls. Overall, we found significant association between the A-6G polymorphism and the decreased risk of hypertension in the dominant genetic model (AA+AG vs. GG: P = 0.001, OR = 0.71, 95%CI 0.57–0.87, P_{heterogeneity} = 0.96). The A-20C polymorphism was significantly associated with the increased risk for hypertension in the allele comparison (C vs. A: P = 0.03, OR = 1.14, 95%CI 1.02–1.27, P_{heterogeneity} = 0.92) and recessive genetic model (CC vs. CA+AA: P = 0.005, OR = 1.71, 95%CI 1.18–2.48, P_{heterogeneity} = 0.99). In the subgroup analysis by ethnicity, significant association was also found among Han Chinese for both A-6G and A-20C polymorphisms. A borderline significantly decreased risk of hypertension between A-6G and Chinese Mongolian was seen in the allele comparison (A vs. G: P = 0.05, OR = 0.79, 95%CI 0.62–1.00, P_{heterogeneity} = 0.84).

Conclusion

Our meta-analysis indicated significant association between angiotensinogen promoter polymorphisms and hypertension in the Chinese populations, especially in Han Chinese.

Association of polymorphisms in the AGT gene with essential hypertension in the Chinese population

OBJECTIVE

Although the angiotensinogen (AGT) gene has been implicated in the pathogenesis of essential hypertension, the results have been inconsistent. In this study, we performed a meta-analysis to assess the association of A-6G, A-20C and G-217A polymorphisms in the AGT gene with essential hypertension in the Chinese population.

METHODS

Published literature from PubMed, Embase, China National Knowledge Infrastructure, China Biological Medicine and Wanfang Data was retrieved. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects models.

RESULTS

Sixteen studies (4223 cases and 3743 controls) for A-6G polymorphism, ten studies (3116 cases and 2678 controls) for A-20C polymorphism and five studies (1268 cases and 1081 controls) for G-217A polymorphism were identified. The results from the meta-analyses indicated significant association of all three polymorphism with the risk of essential hypertension in the Chinese population (A-6G polymorphism: GG vs AA: OR = 1.45, 95% CI 1.17-1.81; A-20C polymorphism: CC vs AA: OR = 1.52, 95% CI 1.10-2.08; G-217A polymorphism: AA vs GG: OR = 2.36, 95% CI 1.44-3.89).

CONCLUSIONS

Our study indicated that three polymorphisms (A-6G, A-20C and G-217A) in the AGT gene are associated with essential hypertension in the Chinese population.

Variants and haplotypes in angiotensinogen gene are associated with plasmatic angiotensinogen level in Mexican population

INTRODUCTION

The plasmatic angiotensinogen (AGT) level has been associated with essential hypertension. Linkage analysis has found a relationship between the AGT gene locus and hypertension in the Mexican-American population, but studies have failed to identify genetic variants associated with hypertension or plasma AGT levels. This study analyzes the relationship between polymorphisms in the AGT gene and plasmatic AGT levels in Mexican population.

METHODS

Nine polymorphisms in AGT gene were genotyped, and plasma AGT level was determined by enzyme-linked immunosorbent assay.

RESULTS

Differences in AGT plasma levels were associated with 2 polymorphisms: T-20G, TT = 25.3 ± 8.3 versus TG + GG = 21.6 ± 8.8 μg/mL; P = 0.008 and C3389T (T174M), CC = 25.8 ± 9.9 versus TC + TT = 20.5 ± 5.4 μg/mL; P = 0.0002. Haplotype 2 was associated with low plasma AGT (-5.1 μg/mL [95% confidence interval: -8.6 to -1.6], P = 0.004) and Haplotype 8 was associated with high plasma AGT (6.5 μg/mL [95% confidence interval: 2.5 to 10.6], P = 0.001). This association remained after adjustment for covariates. A Likelihood Ratio Test for haplotype-phenotype association adjusted for covariates resulted in χ = 38.9, P = 0.0005. The total effect of the haplotypes on plasma AGT level variance was 19.5%. No association was identified between haplotypes and quantitative traits of blood pressure.

CONCLUSIONS

Two polymorphisms (T-20G and C3389T) and 2 haplotypes (H2 and H8) showed an association with plasma AGT levels in Mexican population.

Association between the angiotensinogen gene T174M polymorphism and hypertension risk in the Chinese population: a meta-analysis

No consensus has been reached on the association between the angiotensinogen gene polymorphism T174M and hypertension risk in the Chinese population. We conducted a meta-analysis to systematically pursue their possible association. Case-control studies in the Chinese and English publications were identified by searching the MEDLINE, EMBASE, CBM, CNKI, Wanfang and VIP databases. The fixed-effects model and the random-effects model were applied for dichotomous outcomes to combine the results of the individual studies. After this, we selected 16 studies that met the inclusion criteria. In total, the selected studies contributed a study population containing 3828 hypertensive patients and 3251 normotensive controls. We found no statistical association between the T174M polymorphism and hypertension risk in all subjects, in a Han Chinese subgroup or in non-Han Chinese minorities. However, a statistically significant association was observed between the T174M polymorphism and a hypertensive group (systolic blood pressure ≥160 mm Hg and/or diastolic blood pressure ≥95 mm Hg) in the dominant genetic model (MM+MT vs. TT: P=0.03, odds ratio=1.71, 95% confidence interval 1.07-2.74, P(heterogeneity)=0.27, I(2)=24%, fixed-effects model). No evidence of publication bias was observed. More studies, especially studies stratified for different stages of hypertension, should be performed in the future to fully examine this question. Studies investigating gene-gene interactions, gene-environment interactions, as well as their mutual interactions will also be important.

Evaluation of Transforming Growth Factor Beta-1 Gene 869T/C Polymorphism with Hypertension: A Meta-Analysis

Association between transforming growth factor beta-1 gene (TGFB1) 869T/C polymorphism and hypertension has been widely evaluated, yet with conflicting results. As meta-analysis is a reliable way to resolve discrepancies; I aimed to evaluate this association. Data were available from 9 study populations involving 6151 subjects. Overall, comparison of allele 869C with 869T generated a significant 30% increased hypertension risk (95% confidence interval [95% CI]: 1.11–1.51; P = 0.001), which was strengthened for homozygous comparison (869CC versus 869TT) with odds ratio (OR) doubled to 1.62 (95% CI: 1.23–2.14; P = 0.001). Stratified analysis by study design demonstrated stronger associations in population-based studies than in hospital-based studies with OR, except in the dominant model, being increased by 7.94–18.61%. Likewise, ethnicity-based analysis exhibited a contradictory association between Asians and Whites. Conclusively, these findings support the notion that TGFB1 gene 869T/C polymorphism may influence the risk of hypertension, especially in Asian populations.

ADRB2 and LEPR gene polymorphisms: synergistic effects on the risk of obesity in Japanese

The objective of the present study was to validate a recently reported synergistic effect between variants located in the leptin receptor (LEPR) gene and in the β-2 adrenergic receptor (ADRB2) gene on the risk of overweight/obesity. We studied a middle-aged/elderly sample of 4,193 nondiabetic Japanese subjects stratified according gender (1,911 women and 2,282 men). The LEPR Gln223Arg (rs1137101) variant as well as both ADRB2 Arg16Gly (rs1042713) and Gln27Glu (rs1042714) polymorphisms were analyzed. The primary outcome was the risk of overweight/obesity defined as BMI ≥25 kg/m(2), whereas secondary outcomes included the risk of a BMI ≥27 kg/m(2) and BMI as a continuous variable. None of the studied polymorphisms showed statistically significant individual effects, regardless of the group or phenotype studied. Haplotype analysis also did not disclose any associations of ADRB2 polymorphisms with BMI. However, dimensionality reduction-based models confirmed significant interactions among the investigated variants for BMI as a continuous variable as well as for the risk of obesity defined as BMI ≥27 kg/m(2). All disclosed interactions were found in men only. Our results provide external validation for a male specific ADRB2-LEPR interaction effect on the risk of overweight/obesity, but indicate that effect sizes associated with these interactions may be smaller in the population studied.

Multilocus analyses of seven candidate genes suggest interacting pathways for obesity-related traits in Brazilian populations

We investigated whether variants in major candidate genes for food intake and body weight regulation contribute to obesity-related traits under a multilocus perspective. We studied 375 Brazilian subjects from partially isolated African-derived populations (quilombos). Seven variants displaying conflicting results in previous reports and supposedly implicated in the susceptibility of obesity-related phenotypes were investigated: β2-adrenergic receptor (ADRB2) (Arg16Gly), insulin induced gene 2 (INSIG2) (rs7566605), leptin (LEP) (A19G), LEP receptor (LEPR) (Gln223Arg), perilipin (PLIN) (6209T > C), peroxisome proliferator-activated receptor-γ (PPARG) (Pro12Ala), and resistin (RETN) (-420 C > G). Regression models as well as generalized multifactor dimensionality reduction (GMDR) were employed to test the contribution of individual effects and higher-order interactions to BMI and waist-hip ratio (WHR) variation and risk of overweight/obesity. The best multilocus association signal identified in the quilombos was further examined in an independent sample of 334 Brazilian subjects of European ancestry. In quilombos, only the PPARG polymorphism displayed significant individual effects (WHR variation, P = 0.028). No association was observed either with the risk of overweight/obesity (BMI ≥ 25 kg/m2), risk of obesity alone (BMI ≥ 30 kg/m2) or BMI variation. However, GMDR analyses revealed an interaction between the LEPR and ADRB2 polymorphisms (P = 0.009) as well as a third-order effect involving the latter two variants plus INSIG2 (P = 0.034) with overweight/obesity. Assessment of the LEPR-ADRB2 interaction in the second sample indicated a marginally significant association (P = 0.0724), which was further verified to be limited to men (P = 0.0118). Together, our findings suggest evidence for a two-locus interaction between the LEPR Gln223Arg and ADRB2 Arg16Gly variants in the risk of overweight/obesity, and highlight further the importance of multilocus effects in the genetic component of obesity.

Association of hypertension drug target genes with blood pressure and hypertension in 86,588 individuals

We previously conducted genome-wide association meta-analysis of systolic blood pressure, diastolic blood pressure, and hypertension in 29,136 people from 6 cohort studies in the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium. Here we examine associations of these traits with 30 gene regions encoding known antihypertensive drug targets. We find nominal evidence of association of ADRB1, ADRB2, AGT, CACNA1A, CACNA1C, and SLC12A3 polymorphisms with 1 or more BP traits in the Cohorts for Heart and Aging Research in Genomic Epidemiology genome-wide association meta-analysis. We attempted replication of the top meta-analysis single nucleotide polymorphisms for these genes in the Global BPgen Consortium (n=34,433) and the Women's Genome Health Study (n=23,019) and found significant results for rs1801253 in ADRB1 (Arg389Gly), with the Gly allele associated with a lower mean systolic blood pressure (β: 0.57 mm Hg; SE: 0.09 mm Hg; meta-analysis: P=4.7×10(-10)), diastolic blood pressure (β: 0.36 mm Hg; SE: 0.06 mm Hg; meta-analysis: P=9.5×10(-10)), and prevalence of hypertension (β: 0.06 mm Hg; SE: 0.02 mm Hg; meta-analysis: P=3.3×10(-4)). Variation in AGT (rs2004776) was associated with systolic blood pressure (β: 0.42 mm Hg; SE: 0.09 mm Hg; meta-analysis: P=3.8×10(-6)), as well as diastolic blood pressure (P=5.0×10(-8)) and hypertension (P=3.7×10(-7)). A polymorphism in ACE (rs4305) showed modest replication of association with increased hypertension (β: 0.06 mm Hg; SE: 0.01 mm Hg; meta-analysis: P=3.0×10(-5)). Two loci, ADRB1 and AGT, contain single nucleotide polymorphisms that reached a genome-wide significance threshold in meta-analysis for the first time. Our findings suggest that these genes warrant further studies of their genetic effects on blood pressure, including pharmacogenetic interactions.

Polymorphisms of renin-angiotensin system genes as a risk factor for high-altitude pulmonary oedema

The genes of the renin—angiotensin system (RAS) play an important role in the regulation of pulmonary vascular tone. Although studies on individual genes polymorphisms have reported association with high-altitude pulmonary oedema (HAPE), studies on multiple genes or epistasis are lacking. We therefore investigated the association of the RAS polymorphisms with HAPE. In a case-control design, we screened 163 HAPE-resistant/controls (HAPE-r) and 160 HAPEpatients (HAPE-p) of Indian origin for eight polymorphisms of four RAS genes, ACE, AGT, AGTR1 and AGTR2. Significant difference in genotype and allele frequencies of the ACE I/D and AGT M235T polymorphisms was observed between HAPE-p and HAPE-r ( p < 0.05). In three-locus haplotype analysis of AGT the haplotype GTM was significantly higher in HAPE-p (29%) and haplotype GTT in HAPE-r (27%) after Bonferroni correction ( p < 0.006). The differences were insignificant for polymorphisms from AGTR1 and AGTR2. The MDR (multifactor dimensional reduction) approach for gene—gene interaction depicted individual polymorphism M235T as the best disease predicting model (cross validation consistency, CVC = 10/10). We found a significant association of D allele of ACE and M allele of AGT with HAPE. The findings are supported at the haplotypic level as well as through nested genetic interaction between the RAS gene polymorphisms using the MDR approach.

Contribution of a nuclear factor-kappaB binding site to human angiotensinogen promoter activity in renal proximal tubular cells

Intrarenal angiotensinogen (AGT) is expressed highly in renal proximal tubular cells (RPTCs) and contributes to the regulation of intrarenal angiotensin II levels. Inhibition of nuclear factor (NF)-κB suppressed human (h)AGT expression in human RPTCs. However, the presence and localization of an NF-κB binding site in the hAGT promoter region have not been determined. Therefore, this study was performed to demonstrate that an NF-κB binding site in the hAGT promoter region contributes to hAGT promoter activity in human RPTCs. The hAGT promoter region was cloned from -4358 to +122 and deletion analysis was performed. A possible NF-κB binding site was removed from the hAGT promoter region (M1) and mutated (M2). Human RPTCs were transfected, and hAGT promoter activity was determined by luciferase assay. The identity of DNA binding proteins from binding assays were determined by Western blot. Progressive 5'-end deletions demonstrated removal of a distal promoter element in hAGT_-2414/+122 reduced promoter activity (0.61 ± 0.12, ratio to hAGT_-4358/+122). Inhibition of NF-κB suppressed promoter activity in hAGT_-4358/+122 (0.51 ± 0.14, ratio to control) and hAGT_-3681/+122 (0.48 ± 0.06, ratio to control) but not in the construct without the NF-κB binding site. Promoter activity was reduced in the domain mutants M1 (0.57 ± 0.08, ratio to hAGT_-4358/+122) and M2 (0.61 ± 0.16, ratio to hAGT_-4358/+122). DNA binding levels of NF-κB protein were reduced in M1. These data demonstrate the functional importance of an NF-κB binding site in the hAGT promoter region, which contributes to hAGT promoter activity in human RPTCs.

The Relationship between Natriuretic Peptide Precursor a Gene T2238C Polymorphism and Hypertension: A Meta-Analysis

Single studies attempting to associate ANP gene T2238C (rs5065) polymorphism with hypertension have so far reported inconclusive results. We therefore aimed to evaluate this association via a meta-analysis. Data on 7 studies with a total of 4068 subjects were available and analyzed using the random-effects model with assessment of heterogeneity and publication bias. Overall comparison of 2238C with 2238T yielded a 23% reduced, albeit nonsignificant, risk for hypertension (95% CI: 0.38–1.59;P=.485), while accompanying significant heterogeneity (I2=88.3%) and publication bias (P=.051). Subgroup analysis by study design demonstrated opposite associations between population-based (OR=0.33; 95% CI: 0.13–0.80;P=.015) and hospital-based studies (OR=1.15; 95% CI: 0.79–1.68;P=.454). Further meta-regression analysis exclusively indicated the significant influence of study design (P=.042) on heterogeneity. Taken together, these findings support the notion that carriers of 2238C allele were at moderate decreased risk of developing hypertension, whereas study design was identified as a potentially significant source of between-study heterogeneity.

Association of angiotensinogen gene M235T and angiotensin-converting enzyme gene I/D polymorphisms with essential hypertension in Han Chinese population: a meta-analysis

BACKGROUND

The polymorphisms of angiotensinogen (AGT) and angiotensin-converting enzyme (ACE) genes have been linked to increased risk of essential hypertension in multiple populations, but the results were inconsistent.

OBJECTIVES AND METHODS

To evaluate the associations of these polymorphisms with essential hypertension, we carried out a meta-analysis of the association studies within Han Chinese population. In this study, we reviewed two most commonly investigated polymorphisms, AGT M235T and ACE I/D, and provided summary estimates regarding their associations with essential hypertension. PubMed and China Biological Medicine Database were searched, and a total of 71 studies (31 studies for AGT M235T and 40 studies for ACE I/D) comprising 10 547 essential hypertension patients and 9217 controls from 23 provinces and special districts in China were finally included in this study.

RESULTS

Statistically significant associations with essential hypertension were identified for TT genotype of AGT M235T polymorphism (odds ratio 1.54, 95% confidence interval 1.16-2.03, P = 0.002) and DD genotype of ACE I/D polymorphism (odds ratio 1.61, 95% confidence interval 1.32-1.98, P < 0.0001). Under dominant, recessive, and additive genetic models, positive associations were also found. The heterogeneity existed among the studies (P < 0.05), whereas the publication bias did not exist in both AGT analysis (P = 0.052) and ACE analysis (P = 0.103).

CONCLUSION

The present meta-analysis suggests that AGT M235T and ACE I/D modulate the risk of essential hypertension in Han Chinese population.

Genetics of hypertension: from experimental animals to humans

Essential hypertension affects 20 to 30% of the population worldwide and contributes significantly to cardiovascular mortality and morbidity. Heridability of blood pressure is around 15 to 40% but there are also substantial environmental factors affecting blood pressure variability. It is assumed that blood pressure is under the control of a large number of genes each of which has only relatively mild effects. It has therefore been difficult to discover the genes that contribute to blood pressure variation using traditional approaches including candidate gene studies and linkage studies. Animal models of hypertension, particularly in the rat, have led to the discovery of quantitative trait loci harbouring one or several hypertension related genes, but translation of these findings into human essential hypertension remains challenging. Recent development of genotyping technology made large scale genome-wide association studies possible. This approach and the study of monogenic forms of hypertension has led to the discovery of novel and robust candidate genes for human essential hypertension, many of which require functional analysis in experimental models.

Angiotensinogen promoter variants influence gene expression in human kidney and visceral adipose tissue

Human angiotensinogen (AGT) gene promoter polymorphisms (G-217A; A-20C; G-6A) influence AGT transcription in vitro and have been implicated in the genetics of essential hypertension. We analysed the association among AGT promoter variants and AGT mRNA levels in human kidney and visceral adipose tissue (VAT) in vivo. Samples of kidney and VAT were obtained from 35 consecutive patients undergoing renal surgery. The AGT gene promoter of each patient was sequenced to identify variants. AGT gene expression was studied by real-time PCR TaqMan assay. Clinical data obtained before surgery were also considered in the statistical analysis. Two new polymorphisms at -175 and at -163 were identified. Although AGT expression was significantly higher in VAT than in the kidney, when both variants were present together AGT expression in VAT was about fivefold lower (P=0.033) than in the wild haplotype. This lower AGT expression in VAT suggests that the proximity and linkage of -175A and -163A variants might destabilize the binding of specific transcription factors to an acute-phase responsive element 3. Among the known AGT promoter variants, only -20C SNP has an important effect on tissue-specific differential AGT expression in the human tissues studied, inducing a 3.8-fold increase in AGT mRNA localized only in the kidney medulla (P=0.038). The other known polymorphisms (G-6A; G-217A) were not associated with different levels of AGT expression. Our results support the hypothesis that some human AGT promoter variants influence transcriptional activity in a tissue-specific way in humans.

Genetic variation in angiotensin-converting enzyme-related pathways associated with sudden cardiac arrest risk

BACKGROUND

Angiotensin-converting enzyme (ACE)-related pathways influence arrhythmias and sudden cardiac arrest (SCA) risk.

OBJECTIVE

The purpose of this study was to investigate whether genetic variations in ACE-related pathways are associated with SCA risk. Because these pathways are sex dependent and are influenced by estrogen, we examined these genotype-SCA associations in the full study population and tested for interaction with gender.

METHODS

In a population-based case-control study set in King County, Washington, 211 SCA cases (80% male; mean age 59 years,) and 730 age- and gender-matched controls of European descent were genotyped for 47 single nucleotide polymorphisms (SNPs) in eight genes (ACE, AGT, REN, AGTR1, AGTR2, ACE2, KNG1, BDKRB2). The association of SNPs and haplotypes with SCA risk was examined using logistic regression.

RESULTS

AGTR1 SNP rs1492099 (allele frequency 15%) was associated with decreased SCA risk (odds ratio [OR] 0.62, 95% confidence interval [CI] 0.4-0.9). Haplotype variation in AGTR2 was associated with SCA risk (global haplotype test P = .001), with haplotype 2 (allele frequency 27%) associated with increased risk (OR 1.26, 95% CI 1.1-1.5). There was interaction with gender on SCA risk for variation in KNG1 (interaction P value range 0.0004-0.017 for 6/8 SNPs). KNG1 SNP rs710448 (allele frequency 42%) was associated with decreased risk (OR 0.44, 95% CI 0.3-0.8) among women but not men. Other SNPs and haplotypes in the eight genes examined were not associated with SCA risk after multiple testing correction.

CONCLUSION

Variations in AGTR1 and AGTR2 are associated with SCA risk in a population-based case-control study. There was evidence of interaction with gender on SCA risk for variation in KNG1. These study findings, if replicated, suggest that variation in genes in ACE-related pathways influence SCA risk.