Angiotensinogen T174M and M235T variants, sodium intake and hypertension among non-drinking, lean Japanese men and women

Structural effect of the H992D/H418D mutation of angiotensin-converting enzyme in the Indian population: implications for health and disease

The Non synonymous SNPs (nsSNPs) of the renin-angiotensin-system (RAS) pathway, unique to the Indian population were investigated in view of its importance as an endocrine system. nsSNPs of the RAS pathway genes were mined from the IndiGenome database. Damaging nsSNPs were predicted using SIFT, PredictSNP, SNP and GO, Snap2 and Protein Variation Effect Analyzer. Loss of function was predicted based on protein stability change using I mutant, PremPS and CONSURF. The structural impact of the nsSNPs was predicted using HOPE and Missense3d followed by modeling, refinement, and energy minimization. Molecular Dynamics studies were carried out using Gromacsv2021.1. 23 Indian nsSNPs of the RAS pathway genes were selected for structural analysis and 8 were predicted to be damaging. Further sequence analysis showed that HEMGH zinc binding motif changes to HEMGD in somatic ACE-C domain (sACE-C) H992D and Testis ACE (tACE) H418D resulted in loss of zinc coordination, which is essential for enzymatic activity in this metalloprotease. There was a loss of internal interactions around the zinc coordination residues in the protein structural network. This was also confirmed by Principal Component Analysis, Free Energy Landscape and residue contact maps. Both mutations lead to broadening of the AngI binding cavity. The H992D mutation in sACE-C is likely to be favorable for cardiovascular health, but may lead to renal abnormalities with secondary impact on the heart. H418D in tACE is potentially associated with male infertility.Communicated by Ramaswamy H. Sarma.

AGT rs4762 is associated with diastolic blood pressure in Mexicans with diabetic nephropathy

AIMS

Since angiotensinogen has a pivotal role in the renin-angiotensin-aldosterone system, the analysis of polymorphisms of the angiotensinogen (AGT) gene could help explain its potential involvement in hypertension and diabetic nephropathy (DN) pathogenesis. For that reason, we investigated 1) the association of AGT rs4762 with blood pressure (BP) and kidney function-related traits and 2) the interaction effect of AGT rs4762 with DN on BP and kidney function-related traits in 546 Mexican adults with type 2 diabetes (T2D).

METHODS

We enrolled 546 unrelated Mexican patients with T2D (350 cases with DN and 196 controls without DN). AGT rs4762 was genotyped in all participants using TaqMan technology (effect allele: A). BP and kidney function-related traits, including serum urea and creatinine, urinary albumin, urine albumin to urine creatinine ratio (ACR), and glomerular filtration rate, were studied. DN was defined as having a previous diagnosis of T2D and an ACR ≥ 30 mg/g. The association between these parameters was investigated using logistic regression with adjustment for covariates.

RESULTS

AGT rs4762 A allele was significantly associated with diastolic blood pressure (N = 546, β = 1.243 ± 0.918, p = 0.029). A significant interaction between DN and AGT rs4762 was also observed in relation to diastolic blood pressure (DBP) (N = 546, β = 0.930 ± 0.433, p=0.032). A follow-up analysis of simple effects particularly revealed a positive association between AGT rs4762 A allele and DBP only in patients with diabetic nephropathy (N = 350, β = 2.837 ± 1.267, p = 0.026).

CONCLUSION

Our results evidence that, although AGT rs4762 is not associated with DN, the AGT rs4762 A allele is positively associated with DBP in the Mexican population with DN.

Gene and environmental interactions according to the components of lifestyle modifications in hypertension guidelines

Risk factors for hypertension consist of lifestyle and genetic factors. Family history and twin studies have yielded heritability estimates of BP in the range of 34–67%. The most recent paper of BP GWAS has explained about 20% of the population variation of BP. An overestimation of heritability may have occurred in twin studies due to violations of shared environment assumptions, poor phenotyping practices in control cohorts, failure to account for epistasis, gene-gene and gene-environment interactions, and other non-genetic sources of phenotype modulation that are suspected to lead to underestimations of heritability in GWAS. The recommendations of hypertension guidelines in major countries consist of the following elements: weight reduction, a healthy diet, dietary sodium reduction, increasing physical activity, quitting smoking, and moderate alcohol consumption. The hypertension guidelines are mostly the same for each country or region, beyond race and culture. In this review, we summarize gene-environmental interactions associated with hypertension by describing lifestyle modifications according to the hypertension guidelines. In the era of precision medicine, clinicians who are responsible for hypertension management should consider the gene-environment interactions along with the appropriate lifestyle components toward the prevention and treatment of hypertension. We briefly reviewed the interaction of genetic and environmental factors along the constituent elements of hypertension guidelines, but a sufficient amount of evidence has not yet accumulated, and the results of genetic factors often differed in each study.

A new model of the mechanism underlying lead poisoning: SNP in miRNA target region influence the AGT expression level

Background

To determine if the rs7079 polymorphism located in the 3′ UTR of the angiotensinogen gene (AGT) altered AGT gene expression and the risk of lead poisoning. A case-control study and luciferase reporter gene assay identified a significant association between rs7079 variants and the risk of lead poisoning.

Results

Serum AGT levels were significantly higher in individuals carrying the rs7079 CA genotype, as compared to those carrying the rs7079 CC genotype. The binding of the miRNA mimics miR-31-5p and miR-584-5p to the 3′ UTR of AGT differed based on which rs7079 variant was present, implying that AGT gene expression depends on the rs7079 variant carried.

Conclusions

The rs7079 C to A substitution reduced the binding of miR-31-5p/miR-584-5p to the 3′ UTR of AGT, possibly altering the risk of lead poisoning.

Structure and functions of angiotensinogen

Angiotensinogen (AGT) is the sole precursor of all angiotensin peptides. Although AGT is generally considered as a passive substrate of the renin-angiotensin system, there is accumulating evidence that the regulation and functions of AGT are intricate. Understanding the diversity of AGT properties has been enhanced by protein structural analysis and animal studies. In addition to whole-body genetic deletion, AGT can be regulated in vivo by cell-specific procedures, adeno-associated viral approaches and antisense oligonucleotides. Indeed, the availability of these multiple manipulations of AGT in vivo has provided new insights into the multifaceted roles of AGT. In this review, the combination of structural and functional studies is highlighted to focus on the increasing recognition that AGT exerts effects beyond being a sole provider of angiotensin peptides.

Lead exposure increases blood pressure by increasing angiotensinogen expression

Lead exposure can induce increased blood pressure. Several mechanisms have been proposed to explain lead-induced hypertension. Changes in angiotensinogen (AGT) expression levels or gene variants may also influence blood pressure. In this study, we hypothesized that AGT expression levels or gene variants contribute to lead-induced hypertension. A preliminary HEK293 cell model experiment was performed to analyze the association between AGT expression and lead exposure. In a population-based study, serum AGT level was measured in both lead-exposed and control populations. To further detect the influence of AGT gene single nucleotide polymorphisms (SNPs) in lead-induced hypertension, two SNPs (rs699 and rs4762) were genotyped in a case-control study including 219 lead-exposed subjects and 393 controls. Lead exposure caused an increase in AGT expression level in HEK 293 cell models (P < 0.001) compared to lead-free cells, and individuals exposed to lead had higher systolic and diastolic blood pressure (P < 0.001). Lead-exposed individuals had higher serum AGT levels compared to controls (P < 0.001). However, no association was found between AGT gene SNPs (rs699 and rs4762) and lead exposure. Nevertheless, the change in AGT expression level may play an important role in the development of lead-induced hypertension.

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.

Association between dietary behavior and risk of hypertension among Japanese male workers

Dietary behavior can worsen or prevent hypertension. However, data on the association between dietary behavior and the risk of hypertension in Asians are limited. The aim of this study was to determine these associations in Japanese male workers. We conducted a prospective study of 30-71-year-old Japanese male workers in Osaka, Japan, between 2001 and 2011. The study subjects were 3486 normotensive males who were assessed for an average of 4.6 years using an annual survey. We defined hypertension by a systolic blood pressure of ≥140 mm Hg, a diastolic blood pressure of ≥90 mm Hg and/or the use of antihypertensive medications. Dietary behavior questionnaires were included in the annual surveys. For each question on dietary behavior, we calculated the odds ratios (ORs) for the risk of hypertension using logistic regression models. We used subjects who consistently gave affirmative answers in the baseline and end-point surveys as a reference. The number of new cases of hypertension was 846 among 3486 subjects. Compared with subjects who eat meat frequently, subjects who did not eat meat frequently showed a higher risk of hypertension (OR=1.26, 95% confidence interval (CI): 1.00-1.59). Subjects who did not consume dairy products every day showed a higher risk of hypertension (OR=1.39, 95% CI: 1.13-1.71) compared with those who did. Meat and dairy product intake was associated with the prevention of hypertension among Japanese male workers.

Angiotensinogen gene haplotype is associated with the prevalence of Japanese non-alcoholic steatohepatitis

AIM

  Non-alcoholic steatohepatitis (NASH) patients frequently have hypertension, which is considered to be an important predictive factor for the subsequent development of hepatic fibrosis. The renin-angiotensin system is also known to contribute to the progression of NASH. Various types of functional single-nucleotide polymorphisms (SNPs) involved in the development of NASH have been proposed. Angiotensinogen (AGT) gene SNPs related to cardiovascular diseases have been reported. We aimed to evaluate the involvement of the AGT gene haplotype in Japanese NASH patients.

METHODS

  Previously described genotypes of SNPs of the AGT gene, rs4762 C/T polymorphism (T207M), rs699 C/T polymorphism (T268M), and rs7079 C/A polymorphism (C11537A), were determined in 124 Japanese biopsy-proven NASH patients and 150 healthy volunteers (controls).

RESULTS

  The allele and genotype frequencies in rs4762 and rs699 SNPs in NASH patients were similar to those in controls, while the frequency of the A allele and A/- genotype in rs7079 SNPs were much higher in NASH patients than in controls. In addition, the 3-SNP haplotype CTA was significantly over-represented in NASH patients compared with controls. Regarding clinical features of NASH patients, diastolic blood pressures in patients with the CTA/- genotype were much higher than in patients with other genotypes.

CONCLUSIONS

  We found a 3-SNP haplotype of the AGT gene that is involved in the development of NASH and influences hypertension in NASH patients. These results provide new insight into the therapy of NASH patients with the CTA haplotype using ACE inhibitors or angiotensin II type 1 receptor blockers.

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.

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

Angiotensinogen (AGT) gene polymorphisms have been linked to increased risk of hypertension, but the data remain controversial. In this study we review the most commonly investigated polymorphisms at the AGT locus (other than M235T) and provide summary estimates regarding their association with essential hypertension, while addressing heterogeneity, as well as publication biases. Data on 26 818 subjects from 46 studies for the 4 most-studied AGT variants (T174M in exon 2 and 3 promoter variants: A-6G, A-20C, and G-217A) were meta-analyzed. Statistically significant associations with hypertension were identified for the T174M (odds ratio [OR]: 1.19; 95% CI: 1.07 to 1.33; P=0.002) and G-217A (OR: 1.37; 95% CI: 1.17 to 1.59; P=0.00006) polymorphisms. A dual but consistent effect was observed for the -20C allele, which was associated with a decreased risk of hypertension in populations of mixed and European ancestries (OR: 0.64; 95% CI: 0.44 to 0.92; P=0.02 and OR: 0.77; 95% CI: 0.65 to 0.91; P=0.003, respectively), but with a 24% increase in the odds of hypertension in Asian subjects (OR: 1.24; 95% CI: 1.04 to 1.48; P=0.02). No association of the A-6G variant with hypertension was detected. Current studies support the notion that single variants at the AGT might modulate the risk of hypertension but indicate caution in interpreting these results because of the putative presence of publication bias and gene-environment interactions.

Correlation between angiotensinogen gene and primary hypertension with cerebral infarction in the Li nationality of China

OBJECTIVE

To investigate the relationship of four single nucleotide polymorphism (SNP) haplotypes in the angiotensinogen (AGT) gene to the primary hypertension with or without cerebral infarction in the Li nationality of Hainan, China.

METHODS

Total 300 subjects were allocated into three different groups: Group 1, 100 patients who have primary hypertension; Group 2, 100 patients who have primary hypertension with cerebral infarction; and control group, 100 healthy individuals. The genotypes of all subjects were determined by PCR-sequencing to analyze the four polymorphisms at position -152 (G-A), -20 (A-C), -18 (C-T), and -6 (A-G) in the promoter region of AGT.

RESULTS

The frequencies of CT genotype of AGT-18 and T allele in Group 1 (P = 0.003, P = 0.004) and Group 2 (P = 0.002, P = 0.002) were both significantly higher than in healthy controls. The frequency of G allele of AGT-6 was significantly higher in Group 2 than in the control group (P = 0.016), while there is no significant difference between Group 1 and the control. Haplotype analysis revealed that H6 haplotype frequency which included -20C and -6G was significantly increased in Group 2 (P = 0.003) compared with the control group, while H5 haplotype frequency which included -20C and -18T was significantly increased in Group 1 (P = 0.006) versus the control.

CONCLUSION

The -20 (A-C) and -18 (C-T) of the AGT may play an important role in pathogenesis of primary hypertension; and -20 (A-C), -18 (C-T), and -6 (A-G) may be the genetic risk factors for the onset of primary hypertension with cerebral infarction in the Li nationality of Hainan, China.

Association between angiotensinogen, angiotensin II receptor genes, and blood pressure response to an angiotensin-converting enzyme inhibitor

BACKGROUND

To identify the genetic contribution to the variation in blood pressure (BP) response to angiotensin-converting enzyme inhibitors (ACEIs), single-nucleotide polymorphisms (SNPs) in the angiotensinogen (AGT), angiotensin receptor 1 (AGTR1), and angiotensin receptor 2 (AGTR2) genes were evaluated for their association with BP response to ACEI in Chinese patients with hypertension in a 2-stage design.

METHODS AND RESULTS

We selected 1447 hypertensive patients from a 3-year benazepril postmarket surveillance trial and genotyped them for 14 SNPs in the AGT, AGTR1, and AGTR2 genes. The AGT rs7079 (C/T) SNP (3'-untranslated region) was significantly associated with the response of diastolic BP to benazepril (diastolic BP response: -7.4 mm Hg for subjects with the CC genotype, -8.9 mm Hg for CA, and -10.1 mm Hg for AA; P=0.001). Although there was no association of individual SNPs in the AGTR1 gene, there was a graded response between common haplotypes and systolic BP reduction in the order of haplotype 2 (H2)/lack of haplotype 3 (non-H3) (-13.6 mm Hg) > non-H2/non-H3 (-10.9 mm Hg) > H3/non-H2 (-6.6 mm Hg) (P=0.004). The total variations in response to ACEI therapy that were explained by the AGT SNP and AGTR1 haplotype groups were 13% for systolic and 9% to 9.6% for diastolic BP, respectively.

CONCLUSIONS

AGT SNP rs7079 and AGTR1 haplotypes were associated with BP reduction in response to ACEI therapy in hypertensive Chinese patients. This will be useful in future studies, providing genetic markers to predict the hypertensive response to ACEI therapy.

G-protein beta-3 subunit C825T polymorphism, sodium and arterial blood pressure: a community-based study of Japanese men and women

Epidemiological evidence on gene-environment effects of the G-protein beta-3 subunit C825T polymorphisms and sodium on blood pressure in the free-living general population is limited. We examined the associations between the C825T polymorphism and blood pressure levels, stratified by the sodium variables estimated by 24-h urinary sodium excretion and a dietary questionnaire, among 1,471 men and women aged 30-74 from a community in Japan. Our a priori hypothesis was that individuals with the 825T allele have elevated blood pressure among subjects with a high sodium intake. Among the whole group, the systolic blood pressure level was +2.2 mmHg (p = 0.10) higher in TT than CC genotype individuals after adjustment for sex, age, antihypertensive medication use, body mass index, and alcohol consumption. This difference was more evident among individuals with low sodium excretion (+4.5 mmHg, p = 0.01), low present sodium intake (+3.2 mmHg, p = 0.11), and low past sodium intake (+4.8 mmHg, p = 0.02). No associations were observed among those with high sodium variables. Our results indicate that the G-protein beta-3 subunit C825T polymorphism is associated with higher systolic blood pressure levels in a large free-living Japanese population, and more specifically in women with a low sodium intake. This finding helps to explain part of the discrepancy between the previously reported genetic association among different ethnic groups.

The effect of genetic variation in angiotensinogen on serum levels and blood pressure: a comparison of Nigerians and US blacks

Molecular variants of angiotensinogen (AGT) have been associated with AGT level and hypertension (HT). However, results from reported studies vary considerably between- and within-studied populations. We performed association analysis of AGT gene variants with AGT levels and HT in samples of African descent families, including 595 Nigerians and 901 African Americans. We evaluated association using haplotypes defined by a set of single-nucleotide polymorphisms selected from a previous detailed study of the gene haplotype structure. In the sample of Nigerian families, AGT haplotype H1 was associated with high plasma level. Results were not significant for blood pressure (BP) or HT. For the African-American population, we found significant association between low plasma AGT level and haplotype H7. Furthermore, we found weak associations of H1 with hypertensive status and H7 with low systolic BP. However, no significant association between H1 and high plasma level was found. We conclude that the two distantly related haplotypes, H1 and H7, are associated, but have opposite effects on the phenotypes in two populations of African origin.

Association of angiotensinogen gene polymorphisms with essential hypertension in African-Americans and Caucasians

OBJECTIVE

Molecular variants of angiotensinogen (AGT) have been linked to essential hypertension, and promoter variants have been shown to alter the transcription rate of AGT in vitro. We employed a case-control study to determine whether single nucleotide polymorphisms (SNPs) in the promoter region of AGT were associated with hypertension in African-Americans and Caucasians.

METHODS

The frequencies of the variants at base positions -6, -20, -217, -793, and -776, both alone and in combination (haplotypes), were compared between cases and controls in samples stratified based on race and sex. A logistic regression model was applied to test whether AGT genotypes were significant predictors of the disease while adjusting for race, sex, and age.

RESULTS

Subjects with the AA or AG genotype at locus -793 were significantly more likely to have the disease (OR = 1.88, 95% CI = 1.12-3.15). Additionally, the differences in haplotype frequency distributions between cases and controls were significant at the 7% level for all four subgroups (stratified by race and sex) after adjusting for multiple testing. Based on the odds ratios for each individual haplotype, the haplotype AAAAT (nucleotide sequences at base positions -6, -20, -217, -793, -776) in African-American males, African-American females, and Caucasian females may confer susceptibility to the disease in these population subsets.

CONCLUSION

Overall, the present report provides statistical evidence for the association of AGT with essential hypertension.

Genetic variations related to hypertension: a review

Hypertension is a complex multifactorial disorder with genetic, environmental and demographic factors contributing to its prevalence. The genetic element contribution to blood pressure variation ranges from 30 to 50%. Therefore, identifying hypertension susceptibility genes will help understanding the pathophysiology of the disease. In addition to the potential impact of genomic information in selecting antihypertensive drug therapy, it may also help in recognizing those at risk of developing the disease, which may lead to new preventive approaches. Several strategies and methods have been used to identify hypertension susceptibility genes. Currently, genetic analysis of such data produced complex results, which makes it difficult to draw final conclusion on the use of genomic data in management of hypertension. This review attempts to summarize present known genetic variations that may be implicated in the pathogenesis of hypertension and to discuss various research strategies used to identify them. It also highlights some of the opportunities and challenges, which may be encountered in interpreting the value of these genetic variations to improve management of hypertension.

High Sodium Intake Strengthens the Association between Angiotensinogen T174M Polymorphism and Blood Pressure Levels among Lean Men and Women: a Community-Based Study

Evidence on the effect of salt intake on the interaction between angiotensinogen (AGT) T174M polymorphism and high blood pressure is sparse. We therefore conducted a large population-based cross-sectional study of 2,823 men and women aged 30-74 in a Japanese farming community to examine associations between AGT polymorphism and blood pressure levels stratified by age (30-64 and 65-74), body mass index (BMI; median), and salt intake (median) estimated by 24-h urine collection and dietary questionnaire. Our a priori hypothesis is that individuals, particularly younger and non-overweight individuals, with the 174M allele have elevated blood pressure levels in response to higher sodium intake, and thus the association between T174M polymorphism and blood pressure is more evident among individuals with higher sodium intake than those with lower sodium intake. There were no differences in systolic or diastolic blood pressure levels (SBP or DBP) between the TT and TM+MM genotype groups overall. However, the mean difference in DBP between the TM+MM and TT groups was +1.0 mmHg in subjects of younger age (p=0.06), +1.7 mmHg in non-overweight subjects (BMI<23.5 kg/m2, p=0.01), and +2.3 mmHg in younger and non-overweight subjects (p = 0.002). Furthermore, among younger and non-overweight subjects, blood pressure differences were larger for those with higher urinary sodium excretion (+3.1 mmHg, p = 0.03), those with a higher sodium/potassium excretion ratio (+4.1 mmHg, p=0.007), those with higher present sodium intake score (+3.0 mmHg, p=0.003), and those with higher past sodium intake score (+3.4 mmHg, p<0.001). In conclusion, AGT T174M polymorphism was associated with higher DBP levels in younger and non-overweight Japanese. This association was more evident among subjects with higher sodium intake.

The G???217A variant of the angiotensinogen gene affects basal transcription and is associated with hypertension in a Taiwanese population

OBJECTIVE

Polymorphisms of the angiotensinogen (AGT) gene, especially in the promoter region, are in linkage concordance and are associated with hypertension. In this study, we examined the role of AGT promoter polymorphisms, including G-217A, A-6G and M235T variants, and their promoter function in essential hypertension in Taiwanese populations.

DESIGN

An association study was conducted to assess the genotype distribution between hypertensive patients and normotensive subjects. We also used a transient transfection assay to examine basal transcriptional activity of G-217A and A-6G variants in a mammalian cell system.

METHODS

Hypertensive subjects (390) and normotensive controls (388) of Taiwanese ethnicity were genotyped for the AGT G-217A, A-6G and M235T variants. Promoter activity was studied by cloning the promoter region (-614 to +41 bp) of AGT into the pSEAP2-Basic reporter vector and performing a transient transfection assay in HuH7 and HepG2 cells.

RESULTS

The G-217A variant of the AGT gene was significantly associated with hypertension (P = 0.0047), but the A-6G and M235T polymorphisms were not (P = 0.17 and P = 0.33, respectively). Furthermore, the recessive model of homozygous genotype (-217AA) conferred a high risk for hypertension (odds ratio 3.64) in this population. The -217A variant expressed higher transcriptional activity than -217G in vitro.

CONCLUSIONS

Our study showed a significant association between the -217A variant of the AGT gene and hypertension. This variant plays a functional role in basal transcription of AGT, and may confer a risk for hypertension in Taiwanese populations.

An association study of angiotensinogen polymorphisms with serum level and hypertension in an African-American population

OBJECTIVE

To evaluate the association of angiotensinogen (AGT) gene with AGT level and hypertension based on the overall genetic variation of the AGT gene in among African-Americans.

METHODS

All non-rare single nucleotide polymorphisms (SNPs) in AGT were identified by resequencing 24 individuals. Five tagging SNPs were selected based on the pairwised linkage disequilibrium (LD) pattern and were genotyped in 284 individuals. Association studies of AGT level and hypertension were performed using these five tagging SNPs.

RESULTS

No significant association with AGT level or hypertension was found in analyses of each of the five single SNPs. However, one of the haplotypes defined by these five SNPs was significantly associated with AGT level (P = 0.046), although this haplotype was not associated with hypertension.

CONCLUSIONS

Identification of genetic polymorphisms associated with risk of hypertension has been frustratingly difficult. Two strategies adopted to improve precision are the use of intermediate phenotypes and summarization of genetic information using haplotypes. These strategies appeared to yield a modest increase in precision at the AGT locus with respect to the physiological intermediate, but did not lead to significant association of the molecular markers with hypertension. Additional research is required to increase confidence in haplotype mapping as an epidemiological analysis tool.

Angiotensinogen gene polymorphism, plasma angiotensinogen, and risk of hypertension and ischemic heart disease: a meta-analysis

OBJECTIVE

The aim of this study was to investigate whether the M235T polymorphism in the angiotensinogen gene was associated with angiotensinogen levels, systolic and diastolic blood pressure, hypertension, and risk of ischemic cardiovascular disease in different ethnic populations.

METHODS AND RESULTS

One hundred twenty-seven studies published between January 1992 and March 2002 examining the association of angiotensinogen gene polymorphisms with the above-mentioned end points were selected. Pooled effect sizes and Mantel-Haenszel odds ratios were calculated using Review Manager. In white subjects, genotype was associated with a stepwise increase in plasma angiotensinogen levels of 5% (95% CI, 2% to 8%; P=0.0004) in MT heterozygotes and 11% (7% to 15%; P<0.00001) in TT homozygotes compared with MM individuals. Correspondingly, genotype was associated with a stepwise increase in aggregated odds ratio for hypertension of 1.08 (95% CI, 1.01 to 1.15) in MT individuals and 1.19 (1.10 to 1.30) in TT individuals in white subjects and of 1.29 (95% CI, 0.96 to 1.74) and 1.60 (1.19 to 2.15) in Asian subjects. M235T genotype did not predict systolic or diastolic blood pressure or risk of ischemic heart disease or myocardial infarction in either ethnic group.

CONCLUSIONS

Angiotensinogen M235T genotype was associated with a stepwise increase in angiotensinogen levels in white subjects and a corresponding increase in risk of hypertension in both white and Asian subjects.

Relations of blood pressure to angiotensinogen gene T174M polymorphism and alcohol intake

To clarify the interactive effects of alcohol intake and angiotensinogen gene codon 174 (T174M) polymorphisms on blood pressure in Japanese male workers. On the basis of data from health examinations, nutrition survey and T174M genotype analysis conducted for 185 Japanese male workers at 2000, the prevalence of high-normal blood pressure (HNBP) and hypertension were compared between the four subgroups crossed by two T174M genotype categories ('TT' type, and 'TM or MM' type) and two alcohol intake categories (less than 13.7 g per day, and 13.7 g or more per day). Furthermore, for 95 subjects who had been normotensive at 1998 among them, risk of development into HNBP or hypertension at 2000 were compared across the four subgroups. The findings showed that the HNBP prevalence adjusted for age, body mass index, smoking habits and sodium intake in 2000 was significantly (p=0.03) greater in 'TM or MM' type (57.9%) than in 'TT' type (24.9%) in subjects with 13.7 g or more of daily alcohol intake, whereas no difference in this parameter was found between the two genotypes in those with less than 13.7 g of daily alcohol intake (18.2% and 18.3%, respectively). The risk for development into HNBP at 2000 was also greatest in 'TM or MM' type with 13.7 g or more of daily alcohol intake among the four subgroups, although there were not significant differences between the four subgroups. The prevalence of hypertension or development risk for hypertension did not significantly differ between the four subgroups. Therefore, it can be seen that alcohol drinking might be specifically associated with the HNBP in M allele carriers of angiotensinogen gene T174M polymorphism.

Linkage disequilibrium analysis of the renin-angiotensin system genes

The genes of the renin-angiotensin system (RAS) are important candidates to confer susceptibility to cardiovascular diseases. A large number of association studies between cardiovascular traits and the polymorphisms in RAS have been conducted, although inconsistent results are often reported. The patterns of linkage disequilibrium in RAS genes have also been reported in different populations. However, our understanding of the genetic architecture underlying the RAS is still limited despite rapid progress in empiric studies regarding the patterns of the human genome as a whole. In this review, the linkage disequilibrium among the polymorphisms within the four RAS genes and current association analyses involving the RAS are discussed, as well as some of the gaps of knowledge and possible solutions.

The relation of anger expression with blood pressure levels and hypertension in rural and urban Japanese communities

OBJECTIVE

To examine the relation of anger expression with blood pressure and hypertension among Japanese.

DESIGN

A cross-sectional study.

METHODS

Subjects were 4374 men and women aged 30-74 years from rural and urban communities. Anger expression was estimated using the anger-out and anger-in scores of the Spielberger Anger Expression Scale. Multiple linear regression analyses were performed to estimate the associations of anger expression scores with blood pressure. Proportions of hypertensives among the tertiles of anger expression scores and the relative odds of hypertension for low versus high tertiles of anger expression scales were calculated using logistic regression models.

RESULTS

The anger-out score was inversely associated with systolic and diastolic blood pressure levels for men; a four-point (one standard deviation) lower anger-out score was associated with 1.6 mmHg [95% confidence interval (CI), 0.6-2.6] greater systolic blood pressure and 0.6 mmHg (95% CI, -0.03 to 1.2) greater diastolic pressure after adjustment for age, body mass index, alcohol intake, smoking category, and parental history of hypertension. The adjusted relative odds of hypertension for low versus high tertiles of anger-out was 1.60 (95% CI, 1.19-2.15). These inverse associations were more evident among men with low coping behavior than among those with high coping behavior. For women, the anger-out score was not associated with blood pressure. There was no relation between the anger-in score and either blood pressure or hypertension in either men or women.

CONCLUSIONS

This study suggests that Japanese men who do not express their anger, especially when they have low coping behavior, may have an increased risk of high blood pressure.

Nucleotide diversity and haplotype structure of the human angiotensinogen gene in two populations

Variation in the angiotensinogen gene, AGT, has been associated with variation in plasma angiotensinogen levels. In addition, the T235M polymorphism in the AGT product is associated with an increased risk of essential hypertension in multiple populations, making AGT a good example of a quantitative-trait locus underlying susceptibility to a common disease. To better understand genetic variation in AGT, we sequenced a 14.4-kb genomic region spanning the entire AGT and identified 44 single-nucleotide polymorphisms (SNPs). Forty-two SNPs were observed both in 88 white and in 77 Japanese unselected subjects. Six major haplotypes accounted for most of the variation in this region, indicating less allelic complexity than in many other genomic regions. Although the two populations were found to share all of the major AGT haplotypes, there were substantial differences in haplotype frequencies. Pairwise linkage disequilibrium (LD), measured by the D', r(2), and d(2) statistics, demonstrated a general pattern of decline with increasing distance, but, as expected in a small genomic region, individual LD values were highly variable. LD between T235M and each of the other 39 SNPs was assessed in order to model the usefulness of LD to detect a disease-associated mutation. Among the Japanese subjects, 13 (33%) of the SNPs had r(2) values >0.1, whereas this statistic was substantially higher for the white subjects (occurring in 35/39 [90%]). LD between a hypertension-associated promoter mutation, A-6G, and 39 SNPs was also measured. Similar results were obtained, with 33% of the SNPs showing r(2)>0.1 in the Japanese subjects and 92% of the SNPs showing r(2)>0.1 in the white subjects. This difference, which occurs despite an overall similarity in LD patterns in the two populations, reflects a much higher frequency of the M235-associated haplotype in the white sample. These results have important implications for the usefulness of LD approaches in the mapping of genes underlying susceptibility to complex diseases.

Salt, kidney and hypertension: why and what to learn from genetic analyses?

The relation between salt intake and high blood pressure has been widely recognized, but its exact mechanisms and the reason of such a relation are not clearly understood. In this review, I discuss the sequence of factors relevant to our understanding of the pathophysiology of 'essential' hypertension. I will first consider the relation between two major determinants of systemic blood pressure, i.e. extracellular fluid volume (ECFV) and the renin-angiotensin-aldosterone system, and then the renal sensing mechanism of changes in ECFV, the historical background of salt intake in our culture, and finally suggest explanations of results of genetic analyses of hypertension. The discussion is aimed at furthering our understanding of how and why hypertension develops in response to present day high salt intakes. In addition, data are presented for the implementation of a practical health care policy to effectively reduce the incidence of hypertension.