Genetic Polymorphisms of Angiotensinogen and Essential Hypertension in a Tibetan Population

Genetic Polymorphism in Angiotensinogen and Its Association with Cardiometabolic Diseases

Angiotensinogen (AGT) is one of the most significant enzymes of the renin-angiotensin-aldosterone system (RAAS) which is involved in the regulation and maintenance of blood pressure. AGT is involved in the production of angiotensin I which is then converted into angiotensin II that leads to renal homeostasis. However, various genetic polymorphisms in AGT have been discovered in recent times which have shown an association with various diseases. Genetic polymorphism increases the level of circulating AGT in blood which exaggerates the effects produced by AGT. The associated diseases occur due to various effects produced by increased AGT levels. Several cardiovascular diseases including myocardial infarction, coronary heart disease, heart failure, hypertrophy, etc. are associated with AGT polymorphism. Other diseases such as depression, obesity, diabetic nephropathy, pre-eclampsia, and liver injury are also associated with some variants of AGT gene. The most common variants of AGT polymorphism are M235T and T174M. The two variants are associated with many diseases. Some other variants such as G-217A, A-6G, A-20C and G-152A, are also present but they are not as significant as that of M235T and T174M variants. These variants increase the level of circulating AGT and are associated with prevalence of different diseases. These diseases occur through various pathological pathways, but the initial reason remains the same, i.e., increased level of AGT in the blood. In this article, we have majorly focused on how genetic polymorphism of different variants of AGT gene is associated with the prevalence of different diseases.

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

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

Polymorphism of Thyroid Hormones Receptor, Angiotensin-Converting Enzyme, and High Blood Pressure in Childbearing Age Women with Hyperthyroidism

AIM: This study aimed to investigate the association between two polymorphisms of thyroid hormone receptor and renin-angiotensin system (THRA C/T and angiotensin-converting enzyme (ACE) I/D) genes with hypertension in childbearing age women with hypertension. METHODS: This was a case–control study including 35 cases and 40 matched control subjects. The case group was hyperthyroid women with hypertension while the control group was hyperthyroid women with normotension. The polymorphisms were identified by a classical polymerase chain reaction. RESULTS: The THRA C/T gene and ACE I/D polymorphisms were not associated with the hypertension while the genotype frequencies in hyperthyroid women with hypertension were as follows: CC genotype was 25.71%, CT genotype was 54.29%, and TT genotype was 20.00%. The ACE I/D genotype frequencies in hyperthyroid women with hypertension were as follows: II genotype was 23.53%, whereas in hyperthyroid women without hypertension, the I/D genotype frequencies were CC: 7.50%, CT: 72.50%, and TT: 20.00%. There were no differences in age, thyroid-stimulating hormone, FT4, systolic blood pressure (SBP), diastolic BP between subgroups in ACE I/D, and at THRA rs-939348. There was a significant difference in the levels of FT4 concentrations in THRA rs-939348. Hypertension groups have higher SBP than controls. Genotype II had higher SBP but it was not statistically significant, while individuals with allele I had SBP higher than D allele. CONCLUSIONS: The I allele of the ACE gene is involved in susceptibility to hypertension and polymorphism in THRA increasing concentration of FT4. There was no statistically significant difference in blood pressure between hyperthyroid women with or without hypertension.

Association of with-no-lysine kinase 1 and Serine/Threonine kinase 39 gene polymorphisms and haplotypes with essential hypertension in Tibetans

Tibetans have a higher essential hypertension prevalence compared with other ethnics in China. The reason might be due to their unique environmental influence, as well as genetic factor. However, limited studies focus on Tibetan genetics and its association with hypertension. The aim of this study was to investigate the association between With-No-Lysine (K) Kinase 1 (WNK1), Serine/Threonine kinase 39(STK39) genes variants and hypertension in the Tibetan population. 204 Tibetan hypertensive patients and 305 normotensive controls were recruited in an epidemiological survey conducted at 2 sites in the Ganzi Tibetan autonomous region. Patients were genotyped for nineteen WNK1 candidate tag single nucleotide polymorphisms (SNPs) and three STK39 SNPs, and haplotype analysis was performed. Results showed that the allele A in rs1468326 was overrepresented in hypertensive patients versus control (53.4% vs 42.9%, P < 0.05). The multivariable-adjusted odds ratio (OR) for hypertension among CA + AA genotypes carriers was 1.60 (95% CI: 1.02-2.62, P < 0.05), and they also had a higher systolic blood pressure (136.5 ± 28.6 vs 131.7 ± 24.8 mmHg, P < 0.05). However, the TT genotype ratio in rs6749447 was lower in hypertensives (5.4% vs 10.8%, P < 0.05), and the hypertension risk for the TT genotype carriers in rs6749447 decreased after adjustment (OR 0.49, 95% CI 0.19-0.95, P < 0.05). Subjects with haplotype AGACAGGAATCGT showed 1.57 times higher risk of hypertension (95% CI 1.02-2.41, P < 0.05). In conclusion, SNP rs1468326 of WNK1, rs6749447 of STK39, and WNK1 haplotype AGACAGGAATCGT were associated with hypertension in Tibetan individuals. Environ. Mol. Mutagen. 59:151-160, 2018. © 2017 Wiley Periodicals, Inc.

Impact of interactions between risk alleles on clinical endpoints in hypertension

OBJECTIVE

Impairment of the renin-angiotensinogen-aldosterone system (RAAS), one of the characteristics of essential hypertension (EH), imbalances vascular homeostasis. Despite inconsistent reports on individual single nucleotide polymorphisms (SNPs) as a major predictor of EH, interactions among RAAS genetic variants are rarely investigated.

METHODS

Using SNP markers, we studied potential interactions between angiotensin 1 converting enzyme (ACE), angiotensinogen (AGT), angiotensin II-type 1 receptor (AGTR1), and α adducin (ADD1) variants and their correlation with clinical endpoints in 545 individuals with hypertension and 400 age- and ethnicity-matched unrelated controls. Generalised multifactor dimensionality reduction (GMDR) analysis identified the models for genotype interaction.

RESULTS

Although the results on single genes were significant, gene-gene interactions were more reliable and promising as markers in predisposing hypertension. The best models to represent association of multi-locus interactions with augmented hypertension susceptibility were: (a) within gene 4-locus model comprised of AGT SNPs -217G/A, -20A/C, -6G/A and 235M/T (p=0.022, OR 6.1); and (b) between genes 5-locus model comprised of AGT -217G/A, -20A/C, -6G/A, 235M/T and ACE I/D (p=0.05, OR 4.6). Stratification of 4- and 5-locus GMDR models on the basis of risk alleles from ≤1 to ≥7 increased the ORs from 2.8 to 36.1 and from 0.9 to 16.1, respectively. Moreover, compared to ≤1 risk alleles the ≥7 interacting risk alleles in both 4- and 5-locus models showed an increment of 14.2% and 11.1% in systolic blood pressure, 7.7% and 1.1% in diastolic blood pressure, and 10.5% and 5.1% in mean arterial pressure, respectively, in patients.

CONCLUSIONS

Interactions among the genetic loci of RAAS components may be used as a predictor for susceptibility to hypertension.

Synergistic effects of gene polymorphisms of the renin-angiotensin-aldosterone system on essential hypertension in Kazakhs in Xinjiang

OBJECTIVE

To assess the synergistic effects of gene polymorphisms of the renin-angiotensin-aldosterone system (RAAS) on essential hypertension (EH) in Kazakhs in Xinjiang.

METHODS

A cross-sectional case-control association study was conducted in 52 1 hypertensive and 623 normotensive subjects of Kazakh ethnicity on eight common single nucleotide polymorphisms (SNPs) interspersed over five genes of the RAAS. SNPs were genotyped by polymerase chain reaction-restriction fragment length polymorphism. Interactions among the SNPs were analyzed by the multifactor dimensionality reduction method (MDR).

RESULTS

In single-locus analysis, subjects with AGT -6G, ACE D, and CYP11B2 -344C had increased susceptibility to EH (OR: 1.249; 1.425; 1.201). When subgrouped by sex, males with the t allele of REN Taq I had decreased risk for EH (OR: 0.529), and those with AGT -6G and CYP11B2 -344 C had increased risk for EH (OR: 1.498; 1.449). In females, carrying ACE D increased the risk for EH. (OR: 1.327). In six AGT haplotypes, H1 was protective, while H3 increased susceptibility to EH (OR: 0.683; 2.025). Interaction analysis by MDR showed that there was a strong synergistic effect between ACE I/D and CY11B2 (T-344C) and a moderate interaction between both ACE I/D and CY11B2 T-344C and AGT A-6G.

CONCLUSIONS

There was a strong synergistic effect between ACE I/D and CY11B2 T-344C and a moderate effect between both ACE I/D and CY11B2 T-344C and AGT A-6G. AGT -6G, ACE D, and CY11B2 -344C increased susceptibility to EH. REN Taq I, AGT -6G, CY11B2 -344 C and ACE D were associated with male and female EH, respectively. H1 and H3 of AGT were protective and risk haplotypes, respectively.

Do genetic defects of DNA repair relevant proteins alter susceptibility to hypertension? A case-control study in northeastern Han Chinese

The aim of this study was to examine the individual and interactive associations of five non-synonymous variants of four DNA repair relevant genes (XRCC1, XRCC3, hOGG1, NQO1) with hypertension in a large northeastern Han Chinese population. This was a hospital-based study involving 1009 hypertensive patients and 756 normotensive controls. All five variants satisfied the Hardy-Weinberg equilibrium. With a Bonferroni corrected alpha of 0.05/5, significance was only attained in the genotype (P=0.007) and allele (P=0.006) distributions of rs25487 in XRCC1 gene between patients and controls, with its mutant allele conferring 29% (95% CI: 1.09-1.53; P=0.003), 31% (95% CI: 1.05-1.62; P=0.015) and 66% (95%CI: 1.10-2.52; P=0.016) increased risks of hypertension under the additive, dominant and recessive models, respectively after adjusting for confounders. The frequency of allele combination C-A-C-G-C (alleles in order of rs1799782, rs25487, rs861539, rs1052133 and rs1800566) was significantly higher in patients than in controls (P=0.003), while that of C-G-C-C-C was significantly lower (P=0.001). Interaction analysis failed to identify any suggestive evidence of synergism across five examined variants. Our findings provide evidence for a contributory role of XRCC1 gene rs25487 variant in the development of hypertension, and this variant possibly acted in a recessive pattern.

Positive Association of D Allele of ACE Gene With High Altitude Pulmonary Edema in Indian Population

OBJECTIVE

High altitude pulmonary edema (HAPE) is a potentially fatal high altitude illness occurring as a result of hypobaric hypoxia with an unknown underlying genetic mechanism. Recent studies have shown a possible association between HAPE and polymorphisms in genes of the renin-angiotensin-aldosterone system (RAAS), which play a key role in sensitivity of an individual toward HAPE.

METHODS

For the present investigation, study groups consisted of HAPE patients (HAPE) and acclimatized control subjects (rCON). Four single-nucleotide polymorphisms (SNPs) were genotyped using restriction fragment length polymorphism (RFLP) analysis in genes of the RAAS pathway, specifically, renin (REN) C(-4063)T (rs41317140) and RENi8-83 (rs2368564), angiotensin (AGT) M(235)T (rs699), and angiotensin-converting enzyme (ACE) insertion/deletion (I/D) (rs1799752).

RESULTS

Only the I/D polymorphism of the ACE gene showed a significant difference between the HAPE and rCON groups. The frequency of the D allele was found to be significantly higher in the HAPE group. Arterial oxygen saturation levels were significantly lower in the HAPE group compared with the rCON group and also decreased in the I/D and D/D genotypes compared with the I/I genotype in these groups. The other polymorphisms occurring in the REN and AGT genes were not significantly different between the 2 groups.

CONCLUSIONS

These findings demonstrate a possible association of the I/D polymorphism of the ACE gene with the development of HAPE, with D/D being the at-risk genotype.

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.

The contributory role of angiotensin receptor-like 1 gene multiple polymorphisms in hypertension among northeastern Han Chinese

Background and Objective

Via direct sequencing, we have recently identified six common polymorphisms in angiotensin receptor-like 1 (AGTRL1) gene, and found only two polymorphisms were significantly associated with hypertension in a family-based analysis on 1,015 southern Han Chinese. Extending our previous work and considering the ubiquity of epistasis in determining disease susceptibility, we, in this study, sought to explore the potential interaction of AGTRL1 gene six polymorphisms with hypertension in a large northeastern Han Chinese population.

Methods and Results

This was a case-control study involving 1,009 sporadic hypertensive patients and 756 normotensive controls. Data were analyzed by Haplo.Stats and multifactor dimensionality reduction (MDR) softwares. There were no deviations from Hardy-Weinberg equilibrium for all polymorphisms. The genotypes and alleles of rs7119675 and rs11544374 differed significantly between the two groups (P<0.0005), even after the Bonferroni correction. Under three genetic models, significant association was consistently observed for rs7119675 and rs11544374, and this association was independent of confounding factors. Taking rs7119375 as an example, the odds of having hypertension was 2.46 (95% confidence interval (95% CI): 2.06–2.94), 2.82 (95% CI: 2.29–3.46) and 3.97 (95% CI: 2.37–6.64) under additive, dominant and recessive models (P<0.001), respectively, whereas the adjusted risk estimates were slightly attenuated but still significant. The frequencies of most derived haplotypes differed significantly between patients and controls. Haplotype-phenotype analyses indicated marginal association for triglyceride (P_Sim = 0.011) and total cholesterol (P_Sim = 0.025) in patients and for triglyceride in controls (P_Sim = 0.023). The overall best MDR model included rs11544374, rs7119375 and rs948847 with the maximal testing accuracy of 0.737 and cross-validation consistency of 10 out of 10 (P<0.0001). Further interaction entropy graph suggested that the interaction of rs7119375 with rs11544374 and rs948847 was strongly antagonized.

Conclusions

Our findings demonstrate that AGTRL1 genetic polymorphisms might contribute to the development of hypertension independently and/or through complex interaction.

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

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

Exaggerated blood pressure response during the exercise treadmill test as a risk factor for hypertension

Exaggerated blood pressure response (EBPR) during the exercise treadmill test (ETT) has been considered to be a risk factor for hypertension. The relationship of polymorphisms of the renin-angiotensin system gene with hypertension has not been established. Our objective was to evaluate whether EBPR during exercise is a clinical marker for hypertension. The study concerned a historical cohort of normotensive individuals. The exposed individuals were those who presented EBPR. At the end of the observation period (41.7 months = 3.5 years), the development of hypertension was analyzed within the two groups. Genetic polymorphisms and blood pressure behavior were assessed as independent variables, together with the classical risk factors for hypertension. The I/D gene polymorphism of the angiotensin-converting enzyme and M235T of angiotensinogen were ruled out as risk factors for hypertension. EBPR during ETT is not an independent influence on the chances of developing hypertension. No differences were observed between the hypertensive and normotensive individuals regarding gender (P = 0.655), skin color (P = 0.636), family history of hypertension (P = 0.225), diabetes mellitus (P = 0.285), or hypertriglyceridemia (P = 0.734). The risk of developing hypertension increased with increasing body mass index (BMI) and advancing age. The risk factors, which independently influenced the development of hypertension, were age and BMI. EBPR did not constitute an independent risk factor for hypertension and is probably a preclinical phase in the spectrum of normotension and hypertension.

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.

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."

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.

Systems biology and heart failure: concepts, methods, and potential research applications

Dramatic advances in molecular biology dominated twentieth century biomedical science and delineated the function of individual genes and molecules in exquisite detail. However, biological processes cannot be fully understood based on the properties of individual genes and molecules alone, since these elements act in concert to enable the specific functions that make for living cells and organisms. The discipline of systems biology provides a novel conceptual framework for understanding biological phenomenon. Systems biology synthesizes information concerning the interactions of genes and molecules and allows characterization of the supramolecular networks and functional modules that represent the most essential aspects of cell organization and physiology.

Association of the renin gene polymorphism, three angiotensinogen gene polymorphisms and the haplotypes with essential hypertension in the Mongolian population

Renin is a rate-limiting enzyme of the renin-angiotensin system and plays a crucial role in the regulation of blood pressure (BP). Angiotensinogen (AGT) is the precursor of potent vasoactive hormone angiotensin II and the AGT gene has been incriminated as a marker for genetic predisposition to essential hypertension (EH) in some ethnic groups. The purpose of the study is to explore the association of a new genetic marker of renin gene, and AGT gene M235T, A-6G, and A-20C polymorphisms and their haplotypes with EH in the Mongolian population. On the basis of the prevalence survey, 243 hypertensives and 258 normotensives who had no blood relationship with each other were selected as subjects. All the subjects were interviewed with questionnaires and their blood specimens were collected. Renin gene insertion/ deletion (I/D) polymorphism was genotyped by PCR-polyacrylamide gel electrophoresis. AGT gene M235T, A-6G, and A-20C polymorphisms were genotyped by a PCR-restriction fragment length polymorphism and single-strand conformation polymorphism. The frequencies of renin genotype DD and allele D in hypertensives (36.21%, 63.79%, respectively) were significantly higher than those in normotensives (29.84%, 57.17%, respectively, P < 0.05). The odds ratios (OR) of renin genotype ID, DD to renin genotype II on hypertension were 1.98 (OR 95% CI 1.08-3.72) and 2.51 (OR 95% CI 1.33-4.88), respectively. There were no significant differences in the distributions of genotypes and alleles for AGT gene M235T, A-6G, and A-20C polymorphisms and all different haplotypes between the two groups. Renin gene I/D polymorphism is associated with EH, whereas AGT gene M235T, A-6G, and A-20C polymorphisms and the haplotypes are not associated with EH in the Mongolian population.

Association of renin BglI polymphism with essential hypertension: a meta-analysis involving 1811 cases and 1626 controls

In an effort to clarify association of an intronic polymorphism BglI in a renin gene with essential hypertension, we performed a meta-analysis of the case-control association studies. Publications in the English language and human subjects were searched in PubMed and EMBASE as of July 10, 2009. A fixed-effects model was applied to pool data in the absence of between-studies heterogeneity, and a random-effects model otherwise. Data and study quality were assessed in duplicate. Publication bias was evaluated using the fail-safe number. From three studies with four populations including 1811 patients with essential hypertension and 1626 controls, we found a significant association of renin BglI B with an increased risk for essential hypertension (OR = 1.25; 95% CI, 1.11 to 1.41; P = 0.0002). In addition, significance persisted after assuming the dominant (OR = 1.30; 95% CI, 1.13 to 1.51; P = 0.0004) mode of inheritance, while no significance was observed for the recessive mode (OR = 1.46; 95% CI, 0.82 to 2.60; P = 0.20). The fail-safe number at the level of 0.05 supported these significant associations. In sum, our meta-analysis expands previous findings by showing that the presence of renin BglI B allele is associated with an increased risk in developing essential hypertension, and this effect might act in a dominant mode of inheritance. Further studies are warranted to fully address questions about the etiologic mechanisms of this positive association.

Association of the angiotensin II type I receptor gene +1166 A>C polymorphism with hypertension risk: evidence from a meta-analysis of 16474 subjects

Mounting evidence suggests the potential susceptibility of individuals with a mutation in the angiotensin II type I receptor (AT1R) gene to hypertension. One polymorphism, +1166 A>C, has been extensively studied, but the results have often been irreproducible. We therefore aimed to meta-analyze all available case-control studies from the English language literature to explore the association of this polymorphism with hypertension. A total of 22 studies with 24 populations involving 8249 patients and 8225 controls were identified as of 25 February 2010. A random-effects model was performed regardless of the between-study heterogeneity. The study quality was assessed in duplicate. The data were analyzed using RevMan software (version 5.0.23). Overall, the presence of the +1166 C allele significantly conferred an increased risk of hypertension (odds ratio (OR)=1.14; 95% confidence interval, 1.00-1.30; P=0.05). Under the assumption of three genetic modes of inheritance, an elevated hypertension risk was observed for each comparison (codominant: AC vs. AA, OR=1.10 (P=0.20) and CC vs. AA, OR=1.21 (P=0.36); dominant: OR=1.13 (P=0.09); recessive: OR=1.21 (P=0.36)). Upon stratification by study design, more obvious associations were observed for the population-based design, whereas there were no changes in direction and only slight changes in magnitude upon stratification by sample size and geographical area. No publication biases were indicated by the fail-safe number. Our study pooled previous findings and showed that the AT1R +1166 C allele conferred an increased risk of hypertension. We suggest that confirmation in a large, well-designed study or from functional aspects of this polymorphism is critical.

Review: Association between angiotensin converting enzyme G2350A polymorphism and hypertension risk: a meta-analysis

Background and objective: An exonic polymorphism G2350A (rs4343) in angiotensin converting enzyme (protein: ACE; gene: ACE) was shown to exert the most significant influence on plasma ACE levels. We therefore performed a meta-analysis to investigate association of ACE G2350A polymorphism with hypertension.

Methods: Published case-control studies in English were identified. A total of four studies with 1699 cases and 1274 controls were identified. A random-effects model was performed irrespective of the between-study heterogeneity. Study quality was assessed in duplicate.

Results: Compared with 2350G, the ACE 2350A allele conferred a protective effect on hypertension (odds ratio (OR) = 0.81; 95% confidence interval (CI), 0.56—1.18; p = .28). Similarly, comparisons of 2350AA and 2350GA with 2350GG generated a nonsignificant reduced risk, respectively. Under the dominant model, the ACE 2350A allele conferred a reduced hypertension risk and such associations were divergent between Han Chinese and Muslims from the Arab Gulf and Pakistan. Under the recessive model, this protective effect was totally reversed (OR = 1.01; 95% CI, 0.77—1.33; p = .94). Subgroup analyses indicated a significant protective effect of ACE 2350A compared with 2350G among Muslims from the Arab Gulf and Pakistan (OR = 0.55; 95% CI, 0.42—0.71; p < .00001). No publication biases were observed.

Conclusions: Our results demonstrate that the ACE 2350A allele is associated with a significantly reduced hypertension risk among Muslims from the Arab Gulf and Pakistan, yet an elevated risk among Han Chinese.

Analysis of renin-angiotensin aldosterone system gene polymorphisms in Malaysian essential hypertensive and type 2 diabetic subjects

BACKGROUND

The renin-angiotensin aldosterone system (RAAS) plays an important role in regulating the blood pressure and the genetic polymorphisms of RAAS genes has been extensively studied in relation to the cardiovascular diseases in various populations with conflicting results. The aim of this study was to determine the association of five genetic polymorphisms (A6G and A20C of angiotensinogen (AGT), MboI of renin, Gly460Trp of aldosterone synthase and Lys173Arg of adducin) of RAAS genes in Malaysian essential hypertensive and type 2 diabetic subjects.

METHODS

RAAS gene polymorphisms were determined using mutagenically separated PCR and PCR-RFLP method in a total of 270 subjects consisting of 70 hypertensive subjects without type 2 diabetes mellitus (T2DM), 60 T2DM, 65 hypertensive subjects with T2DM and 75 control subjects.

RESULTS

There was significant difference found in age, body mass index, systolic/diastolic blood pressure, fasting plasma glucose and high density lipoprotein cholesterol levels between the hypertensive subjects with or without T2DM and control subjects. No statistically significant differences between groups were found in the allele frequency and genotype distribution for A20C variant of AGT gene, MboI of renin, Gly460Trp of aldosterone and Lys173Arg of adducin (p > 0.05). However, the results for A6G of AGT gene revealed significant differences in allele and genotype frequencies in essential hypertension with or without T2DM (p < 0.001).

CONCLUSION

Among the five polymorphisms of RAAS genes only A6G variant of AGT gene was significantly associated in Malaysian essential hypertensive and type 2 diabetic subjects. Therefore, A6G polymorphism of the AGT gene could be a potential genetic marker for increased susceptibility to essential hypertension with or without T2DMin Malaysian subjects.

Spectral analysis of heart rate variability (HRV) may predict the future development of essential hypertension

Presently, essential hypertension (EH) is among the most common morbid disorders of mankind. The fundamental pathophysiology of EH is sympathetic overactivity. It has been observed that the people having common risk factors for hypertension such as obesity, insulin resistance and stress generally have increased sympathetic activity. Therefore, it is presumed that patients suffering from EH develop some degree of increased sympathetic activity much before they clinically develop hypertension. Spectral analysis of heart rate variability (HRV) has been demonstrated to accurately assess change in sympathovagal balance (autonomic activity) even when the alteration is in its minimal form. Therefore, in the present paper we hypothesize that spectral analysis of HRV could be utilized for early prediction of EH. We also suggest that the predictive knowledge of sympathovagal imbalance in the development of EH should be employed in elucidating the mechanisms for prevention of this dysfunction.