Structural analysis and evaluation of the aldosterone synthase gene in hypertension

Impact of Renin-Angiotensin-Aldosterone System (RAAS) Gene Polymorphism in Essential Hypertension and Antihypertensive Drug Therapy: A Review

Genetic, demographic and environmental factors all play a role in the frequency of an intricate multifactorial condition known as hypertension. Approximately 30% and 50% of BP fluctuation are influenced by genetic variability. Many genetic studies have confirmed the link between genetic variability and susceptibility to essential hypertension; hence, identifying genes associated with essential hypertension susceptibility will aid in understanding the pathophysiology and their influence on how an individual responds towards the antihypertensive therapy. There are also controversial results highlighted in some reports. This review summarises genetic variants of the renin-angiotensin-aldosterone system (RAAS), angiotensinogen (AGT) (M235T), angiotensin converting enzyme (ACE) (insertion/deletion), angiotensin II type 1 receptor (AT1R) (A1166C) and aldosterone synthase (C344T) that are known and might contribute towards the pathophysiology of essential hypertension. Furthermore, the review highlights the response of certain RAAS gene polymorphisms (renin, ACE and AT1R genes) to antihypertensive drugs.

Impact of Dietary Fructose and High Salt Diet: Are Preclinical Studies Relevant to Asian Societies?

Fructose consumption, especially in food additives and sugar-sweetened beverages, has gained increasing attention due to its potential association with obesity and metabolic syndrome. The relationship between fructose and a high-salt diet, leading to hypertension and other deleterious cardiovascular parameters, has also become more evident, especially in preclinical studies. However, these studies have been modeled primarily on Western diets. The purpose of this review is to evaluate the dietary habits of individuals from China, Japan, and Korea, in light of the existing preclinical studies, to assess the potential relevance of existing data to East Asian societies. This review is not intended to be exhaustive, but rather to highlight the similarities and differences that should be considered in future preclinical, clinical, and epidemiologic studies regarding the impact of dietary fructose and salt on blood pressure and cardiovascular health worldwide.

Effects of intron conversion in the human CYP11B2 gene on its transcription and blood pressure regulation in transgenic mice

The human cytochrome P450 family 11 subfamily B member 2 (hCYP11B2) gene encodes aldosterone synthase, the rate-limiting enzyme in the biosynthesis of aldosterone. In some humans, hCYP11B2 undergoes a unique intron conversion whose function is largely unclear. The intron conversion is formed by a replacement of the segment of DNA within intron 2 of hCYP11B2 with the corresponding region of the hCYP11B1 gene. We show here that the intron conversion is located in an open chromatin form and binds more strongly to the transcriptional regulators histone acetyltransferase P300 (p300), NFκB, and CCAAT enhancer-binding protein α (CEBPα). Reporter constructs containing the intron conversion had increased promoter activity on transient transfection in H295R cells compared with WT intron 2. We generated humanized transgenic (TG) mice containing all the introns, exons, and 5'- and 3'-flanking regions of the hCYP11B2 gene containing either the intron conversion or WT intron 2. We found that TG mice containing the intron conversion have (a) increased plasma aldosterone levels, (b) increased hCYP11B2 mRNA and protein levels, and (c) increased blood pressure compared with TG mice containing WT intron 2. Results of a ChIP assay showed that chromatin obtained from the adrenals of TG mice containing the intron conversion binds more strongly to p300, NFκB, and CEBPα than to WT intron 2. These results uncover a functional role of intron conversion in hCYP11B2 and suggest a new paradigm in blood pressure regulation.

Insights on the phenotypic heterogenity of 11β-hydroxylase deficiency: clinical and genetic studies in two novel families

PURPOSE

11β-hydroxylase deficiency accounts for 5% of congenital adrenal hyperplasia cases. Diagnosis suspiction is classically based on the association between abnormal virilization, precocious puberty, and hypertension in 46XX or 46XY subjects. We investigated two families with siblings presenting with opposed clinical features, and provided a review of the mechanisms involved in mineralocorticoid-dependent phenotypic heterogeneity.

METHODS

The coding region of the CYP11B1 gene of 4 patients was sequenced and familial segregation was confirmed. Clinical characterization and blood steroid profile were performed.

RESULTS

Family 1 comprised a female and a male siblings who presented in middle childhood with genital ambiguity (Prader II) and precocious puberty, respectively, associated with hypertension. In the second decade of life, the woman had three full-term pregnancies, and then evolved normotensive with no treatment over a 5-year follow up. On the other hand, her brother had hypertensive end-organ damage at age 24. In family 2, a 2.9 year-old boy presented with precocious puberty and hypertension, whereas his 21 days-old sister had genital ambiguity (Prader III) and salt wasting. A homozygous exon 4 splice site mutation was identified (IVS4ds-1G > A; c.799 G > A) in family 1, while a nonsense mutation in exon 6 (p. Q356X; c.1066 C > T) was found in family 2.

CONCLUSION

CYP11B1 mutations were associated with highly variable phenotypes, from mild to severe virilization, and early-onset hypertension or salt wasting. Further analysis of variants in other hypertension-related genes, steroid synthesis and metabolism compensatory pathways, and/or the investigation of chimeric CYP11B genes are needed to clarify the phenotypic heterogeneity in 11β-hydroxylase deficiency.

Interactions between CYP11B2 Promoter Methylation and Smoking Increase Risk of Essential Hypertension

Aldosterone synthase (CYP11B2) is closely linked to essential hypertension (EH). However, it remains unclear whether the methylation of the CYP11B2 promoter is involved in the development of EH in humans. Our study is aimed at evaluating the contribution of CYP11B2 promoter methylation to the risk of EH. Methylation levels were measured using pyrosequencing technology in 192 participants in a hospital-based case-control study. Logistic regression and multiple linear regression analyses were utilized to adjust for confounding factors and the GMDR method was applied to investigate high-order gene-environment interactions. Although no significant result was observed linking the four analyzed CpG sites to EH, GMDR detected significant interactions among CpG1, CpG3, CpG4, and smoking correlated with an increased risk of EH (OR = 4.62, adjusted P = 0.011). In addition, CpG2 (adjusted P = 0.013) and CpG3 (adjusted P = 0.039) methylation was significantly lower in healthy males than in healthy females. Likewise, after adjusting for confounding factors, CpG2 methylation (adjusted P = 0.007) still showed significant gender-specific differences among the participants of the study. CpG1 (P = 0.009) site was significantly positively correlated with age, and CpG3 (P = 0.007) and CpG4 (P = 0.006) were both inversely linked to smoking. Our findings suggest that gene-environment interactions are associated with the pathogenesis and progression of EH.

Haplotype association and synergistic effect of human aldosterone synthase (CYP11B2) gene polymorphisms causing susceptibility to essential hypertension in Indian patients

BACKGROUND

Aldosterone synthase (CYP11B2) is a key enzyme involved in the terminal steps of aldosterone biosynthesis. Genetic variability in CYP11B2 gene has been associated with heterogeneous aldosterone production, which can affect sodium homeostasis and thereby regulation of blood pressure. Hence, the present study was aimed to explore the single-locus variations, haplotype and epistasis patterns of CYP11B2 (C-344T, intron-2 gene conversion and Lys173Arg) gene polymorphisms, and the risk contributed by them to the development of essential hypertension (EHT).

METHODS

A total of 279 hypertensive patients and 200 normotensive controls were enrolled in this study. C-344T and Lys173Arg polymorphisms of CYP11B2 gene were genotyped by PCR-RFLP method and intron-2 gene conversion (IC) polymorphism by allele-specific PCR analysis.

RESULTS

Single-locus analysis revealed significant association of CYP11B2 C-344T and Lys173Arg polymorphisms with EHT (p < 0.05). Considering the sexes, Lys173 allele was found to be at risk for hypertension in males (OR 1.40; 95% CI = 1.01-1.96). Unphased haplotype analysis revealed H1 (T-Conv-Lys; p = 0.0017) to have significant risk for EHT, while haplotype H4 (T-Wt-Arg) had a significant protective effect. Multifactor dimensionality reduction (MDR) interaction analysis found the overall best model with C-344T and IC polymorphisms exhibiting strong synergistic effect.

CONCLUSION

The present study revealed a strong synergistic effect of CYP11B2 C-344T and IC polymorphisms causing susceptibility to EHT and haplotype H1 (-344T-Conv-Lys173) as the risk-conferring factor for hypertension predisposition.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

Aldosterone and cardiovascular remodelling: focus on myocardial failure

Heart failure is a clinical syndrome that may result from different disease states or conditions that injure the myocardium. The activation of circulating neurohormones, particularly aldosterone, may play a pivotal role in left ventricular (LV) remodelling. The Randomized Aldactone Evaluation Study and Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival trial have emphasised the clinical importance of aldosterone. This review addresses some of the proposed mechanisms of LV remodelling in heart failure.

Aldosterone Synthase Promoter Polymorphism and Cardiovascular Phenotypes in a Large, Multiethnic Population-Based Study

BACKGROUND

A single-nucleotide polymorphism in the aldosterone synthase gene (CYP11B2) promoter [-344C/T, rs1799998] has been reported to associate with cardiovascular phenotypes.

METHODS

The Dallas Heart Study is a large, multiethnic cohort with a high prevalence of hypertension. We genotyped 3452 Dallas Heart Study participants for -344C/T. Generalized linear models were used to assess whether variation at -344C/T associated with plasma aldosterone concentration (PAC), systolic and diastolic blood pressure (SBP and DBP), plasma glucose (in persons with no diabetes), HOMA IR (Homeostasis Model Assessment as an Index of Insulin Resistance), and left ventricular (LV) mass indexed to height. Systolic blood pressure and DBP were significantly higher in blacks compared with whites (P < 0.001 for SBP and for DBP) and Hispanics (P < 0.001 for SBP and for DBP). Log-transformed body mass index was also significantly higher in blacks compared with whites (P < 0.001), but not Hispanics (P = 0.10). Log-transformed PAC was higher in whites compared with blacks (P < 0.001), but did not differ significantly in whites compared with Hispanics (P = 0.73). In univariate and multivariable analysis, -344C/T was not significantly associated with PAC within any ethnicity. In univariate and multivariable analysis, -344C/T was not associated with SBP or DBP within any ethnicity. After adjustment for multiple testing, univariate and multivariable analyses revealed no association between -344C/T and plasma glucose in patients with no diabetes, HOMA IR, or LV mass indexed to height.

CONCLUSIONS

We were unable to reproduce previously reported associations between -344C/T and PAC, blood pressure, plasma glucose, or LV mass. Methodological differences might explain the differences between our findings and those previously reported.

Molecular genetics of essential hypertension

Hypertension is a major public health problem in the developing as well as in developed countries due to its high prevalence and its association with coronary heart disease, renal disease, stroke, peripheral vascular disease, and related disorders. Essential hypertension (EH) is the most common diagnosis in this disease, suggesting that a monocausal etiology has not been identified. However, a number of risk factors associated with EH have also been identified such as age, sex, demographic, environmental, genetic, and vascular factors. Recent advances in molecular biological research had achieved clarifying the molecular basis of Mendelian hypertensive disorders. Molecular genetic studies have now identified mutations in several genes that cause Mendelian forms of hypertension in humans. However, none of the single genetic variants has emerged from linkage or association analyses as consistently related to the blood pressure level in every sample and in all populations. Besides, a number of polymorphisms in candidate genes have been associated with differences in blood pressure. The most prominent candidate has been the polymorphisms in the renin-angiotensin-aldosterone system. In total, EH is likely to be a polygenic disorder that results from inheritance of a number of susceptibility genes and involves multiple environmental determinants. These determinants complicate the study of blood pressure variations in the general population. The complex nature of the hypertension phenotype makes large-scale studies indispensable, when screening of familial and genetic factors was intended. In this review, recent genetic studies exploring the molecular basis of EH, including different molecular pathways, are highlighted.

Relationship of Genetic Polymorphisms of Aldosterone Synthase Gene Cytochrome P450 11B2 and Mineralocorticoid Receptors with Coronary Artery Disease in Taiwan

The aldosterone synthase gene, cytochrome P450 11B2 (CYP11B2), and mineralocorticoid receptor (MR) genes have been reported to be associated with coronary artery disease (CAD). In this study, we investigated the association of single nucleotide polymorphisms (SNPs) of CYP11B2 (CYP11B2 T-344C) and MR (MR C3514G and MR C4582A) with CAD in Taiwanese. Six hundred and nine unrelated male and female subjects who received elective coronary angiography were recruited from Chung Shan Medical University Hospital. The enrolled subjects were those who had a positive noninvasive test. CYP11B2 T-344C, MR C3514G and MR C4582A were determined by polymerase chain reaction-restriction fragment length polymorphism. We found that women with CYP11B2 C/C had a higher risk of developing CAD. However, there were no significant differences in the genotype distributions of MR C3514G and MR C4582A between the women with and without CAD. In multivariate analysis, CYP11B2 T-344C was most significantly associated with CAD in Taiwanese women. In conclusions, CYP11B2 C/C was more significantly associated with the development of CAD than diabetes mellitus or hypertension. This implies that CYP11B2 C/C plays a more important role than some conventional risk factors in the development of CAD in Taiwanese women.

Analysis of the gene polymorphism of aldosterone synthase (CYP11B2) and atrial natriuretic peptide (ANP) in women with preeclampsia

OBJECTIVE

Preeclampsia (PE) is a major cause of mortality of mothers, fetuses and newborns around the world. The etiology of preeclampsia has not yet been clarified, but many studies indicate a multifactorial basis of PE. Aldosterone synthase (CYP11B2) is responsible for synthesis of aldosterone responsible for regulating blood pressure. Similarly, natriuretic peptide (ANP) regulates blood pressure through a variety of mechanisms affecting the sodium concentration and the amount of extracellular fluid. Currently, attention is paid to the role of the polymorphisms in the expression level of these genes. The aim of the study was to determine the frequencies of genotypes and alleles for polymorphisms of -344C>T CYP11B2 gene and 2238T>C ANP gene in women with preeclampsia and healthy pregnant women from the Caucasian population.

STUDY DESIGN

The study included a group of 165 pregnant women (59 women with preeclampsia and 109 healthy pregnant women). DNA was extracted from peripheral blood. Determination of the polymorphism of -344C>T CYP11B2 gene and 2238T>C ANP gene was performed by PCR-RFLP method.

RESULTS

The results showed that the frequencies of the TC and CC genotypes of 2238T>C polymorphism in ANP gene were significantly higher in patients with PE compared to control group. For -344C>T polymorphism of CYP11B2 gene, the frequency of TT genotype was significantly higher in patients with hypertension than in controls (32.2% vs. 23.58%).

CONCLUSIONS

Our findings showed that gene polymorphism of CYP11B2 (-344C>T) and ANP (2238T>C) may be associated with developing PE during pregnancy.

Polymorphisms of renin-angiotensin-aldosterone system gene in chinese han patients with nonfamilial atrial fibrillation

Background

Atrial fibrillation(AF) is the most common arrhythmia in the adult population. The activated renin-angiotensin-aldosterone system (RAS) has been reported to play an important role in the pathogenesis of atrial fibrillation. The aim of this study was to investigate the association between nonfamilial AF and polymorphisms in RAS gene.

Methods

A total of 931 patients with nonfamilial AF, 663 non-AF heart disease patients and 727 healthy subjects were selected. 10 tagSNPs (tSNPs) (ACE gene rs8066114, AGT gene rs7539020, rs3789678, rs2478544, rs11568023, rs2478523, rs4762, rs699 and CYP11B2 rs3802230, rs3097) were chosen and genotyped in our study. Single-locus analysis and haplotype analysis were used in this study.

Results

In single-locus analysis, we found rs11568023 and rs3789678 in AGT gene were associated with nonfamilial AF in Chinese Han population. AF risk was associated with rs3789678 between the AF group and control groups. Under dominant model, the significant AF risk was observed in rs3789678 between the AF group and non AF heart control group; And the protective effect was found in rs11568023, compared with the non-AF heart disease control group. In multilocus haplotype analysis, the association between frequencies of the haplotypes and AF risk was showed in AGT gene (rs7539020-rs3789678), compared ‘TT’ haplotype with the common ‘TC’ haplotype, adjusted for age, gender, LVEF, LVEDD, LAD and frequency of hypertension and diabetes. The diplotype with ‘TC’, carrying rs3789678-C-allele, was associated with reduced risk of AF between the AF group and the healthy control group. The diplotype with ‘TT’ haplotype in the same block, carrying rs3789678-T-allele, was associated with increased risk of AF.

Conclusions

Via a large-scale case-control study, we found that rs3789678 site was potential susceptible locus of AF whereas rs11568023 was protective factor.

Relationship between CYP11B2-344T>C polymorphsim and atrial fibrillation: A meta-analysis

INTRODUCTION

The aldosterone synthase (CYP11B2)-344T>C gene polymorphism has been reported to influence the risk of atrial fibrillation (AF) in many studies; however, the results remain controversial and ambiguous.

MATERIALS AND METHODS

We therefore carried out a meta-analysis of published case-control studies to investigate the association between CYP11B2-344T>C polymorphism and AF susceptibility. Electronic searches were conducted on links between this variant and AF in several databases. Odds ratios (ORs) and 95% confidence intervals (CIs) for homozygous, dominant model, recessive model and allele were calculated to estimate the strength of associations in fixed and random effect models. Heterogeneity and publication bias were also assessed.

RESULTS

A total of nine case-control studies were identified. The C allele was associated with an increased susceptibility risk of AF compared with the T allele among hypertension populations (OR=1.26; 95% CI=1.09-1.45). The contrast of homozygotes and the recessive model produced the same pattern of results as the allele contrast. In the hypertension population, a significant association was found for the genetic models that were examined.

CONCLUSIONS

Our pooled data suggest a significant association exists between CYP11B2-344T>C polymorphism and AF among hypertension populations.

Potential applications of pharmacogenomics to heart failure therapies

Pharmacogenomics explores one drug's varying effects on different patient genotypes. A better understanding of genomic variation's contribution to drug response can impact 4 arenas in heart failure (HF): (1) identification of patients most likely to receive benefit from therapy, (2) risk stratify patients for risk of adverse events, (3) optimize dosing of drugs, and (4) steer future clinical trial design and drug development. In this review, the authors explore the potential applications of pharmacogenomics in patients with HF in the context of these categories.

Computational analysis of functional single nucleotide polymorphisms associated with the CYP11B2 gene

Single nucleotide polymorphisms (SNPs) are the most common type of genetic variations in humans and play a major role in the genetics of human phenotype variation and the genetic basis of human complex diseases. Recently, there is considerable interest in understanding the possible role of the CYP11B2 gene with corticosterone methyl oxidase deficiency, primary aldosteronism, and cardio-cerebro-vascular diseases. Hence, the elucidation of the function and molecular dynamic behavior of CYP11B2 mutations is crucial in current genomics. In this study, we investigated the pathogenic effect of 51 nsSNPs and 26 UTR SNPs in the CYP11B2 gene through computational platforms. Using a combination of SIFT, PolyPhen, I-Mutant Suite, and ConSurf server, four nsSNPs (F487V, V129M, T498A, and V403E) were identified to potentially affect the structure, function, and activity of the CYP11B2 protein. Furthermore, molecular dynamics simulation and structure analyses also confirmed the impact of these nsSNPs on the stability and secondary properties of the CYP11B2 protein. Additionally, utilizing the UTRscan, MirSNP, PolymiRTS and miRNASNP, three SNPs in the 3'UTR region were predicted to exhibit a pattern change in the upstream open reading frames (uORF), and eight microRNA binding sites were found to be highly affected due to 3'UTR SNPs. This cataloguing of deleterious SNPs is essential for narrowing down the number of CYP11B2 mutations to be screened in genetic association studies and for a better understanding of the functional and structural aspects of the CYP11B2 protein.

Genetic variant of the renin-angiotensin system and prevalence of type 2 diabetes mellitus: a modest but significant effect of aldosterone synthase

Recent genome-wide association studies have identified multiple variants that confer risk of type 2 diabetes mellitus (DM). However, established associations explain only a part of the heritability. Thus, even at the genome-wide association studies era, candidate gene approach should be still useful. Recent interventional studies against the renin-angiotensin system (RAS) showed reduction in new onset of DM, implying the system is involved in the onset. We substantiated the hypothesis that genetic variants of RAS have significant association with prevalence of DM. We enrolled to the study consecutive 782 subjects who had consulted our hospitals for mainly lifestyle related diseases. They consisted of 282 (36.1 %) diabetes cases. Genotypes were assayed with genomic DNA for conventional four genes of the RAS, i.e., angiotensin converting enzyme (ACE) insertion/deletion variant, angiotensinogen (AGT) M235T variant, angiotensin II type I receptor (AT1) A1166C variant, and aldosterone synthase (CYP11B2) C-344T variant. Association between the genetic variants of the RAS and prevalence of type 2 DM was tested. A significant association of DM and CYP11B2 genotype was obtained. There was no significant association between DM and ACE, AGT and AT1 variants. A multivariate logistic regression showed that age, gender, and CYP11B2 genotype were independent factors for association to diabetes, the DM risk of CC/CT to TT being 1.40 (95 % CI 1.04-1.90, p = 0.029). Thus, it is concluded that a genetic variant of the RAS should have a modest but significant impact on the onset of type 2 diabetes mellitus.

Use of isosorbide dinitrate and hydralazine in African-Americans with heart failure 9 years after the African-American Heart Failure Trial

The 2013 American College of Cardiology Foundation/American Heart Association guidelines recommend combined isosorbide dinitrate (ISDN) and hydralazine to reduce mortality and morbidity for African-Americans with symptomatic heart failure (HF) and reduced ejection fraction, currently receiving optimal medical therapy (class I, level A). Nitrates can alleviate HF symptoms, but continuous use is limited by tolerance. Hydralazine may mitigate nitrate tolerance, and the ISDN-hydralazine combination in the Vasodilators in Heart Failure Trial (V-HeFT) I improved survival and exercise tolerance in men with dilated cardiomyopathy or HF with reduced ejection fraction, most notably in self-identified black participants. In the subsequent V-HeFT II, survival was greater with enalapril than with ISDN-hydralazine in the overall cohort, but mortality rate was similar in the enalapril and ISDN-hydralazine groups in the self-identified black patients. Consequently, in the African-American Heart Failure Trial (A-HeFT) in self-identified black patients with symptomatic HF, adding a fixed-dose combination ISDN-hydralazine to modern guideline-based care improved outcomes versus placebo, including all-cause mortality, and led to early trial termination. Hypertension underlies HF, especially in African-Americans; the A-HeFT and its substudies demonstrated not only improvements in echocardiographic parameters, morbidity, and mortality but also a decrease in hospitalizations, potentially affecting burgeoning HF health-care costs. Genetic characteristics may, therefore, determine response to ISDN-hydralazine, and the Genetic Risk Assessment in Heart Failure substudy demonstrated important hypothesis-generating pharmacogenetic data.

Role of the renin-angiotensin-aldosterone system and the glutathione S-transferase Mu, Pi and Theta gene polymorphisms in cardiotoxicity after anthracycline chemotherapy for breast carcinoma

BACKGROUND

Anthracyclines are among the most active drugs against breast cancer, but can exert cardiotoxic effects eventually resulting in congestive heart failure (CHF). Identifying breast cancer patients at high risk of developing cardiotoxicity after anthracycline therapy would be of value in guiding the use of these agents.

AIMS

We determined whether polymorphisms in the renin-angiotensin-aldosterone system (RAAS) and in the glutathione S-transferase (GST) family of phase II detoxification enzymes might be useful predictors of left ventricular ejection fraction (LVEF) kinetics and risk of developing CHF. We sought correlations between the development of cardiotoxicity and gene polymorphisms in 48 patients with early breast cancer treated with adjuvant anthracycline chemotherapy.

METHODS

We analyzed the following polymorphisms: p.Met235Thr and p.Thr174Met in angiotensinogen (AGT), Ins/Del in angiotensin-converting enzyme (ACE), A1166C in angiotensin II type-1 receptor (AGTR1A), c.-344T>C in aldosterone synthase (CYP11B2), p.Ile105Val in GSTP1. Additionally, we analyzed the presence or absence of the GSTT1 and GSTP1 genes. A LVEF <50% was detected at least once during the 3 years of follow-up period in 13 out of 48 patients (27.1%).

CONCLUSION

RAAS gene polymorphisms were not significantly associated with the development of cardiotoxicity. GSTM1may be useful as a biomarker of higher risk of cardiotoxicity, as demonstrated in our cohort of patients (p=0.147).

Genetics of mineralocorticoid excess: an update for clinicians

Aldosterone plays a major role in the regulation of sodium and potassium homeostasis and blood pressure. More recently, aldosterone has emerged as a key hormone mediating end organ damage. In extreme cases, dysregulated aldosterone production leads to primary aldosteronism (PA), the most common form of secondary hypertension. However, even within the physiological range, high levels of aldosterone are associated with an increased risk of developing hypertension over time. PA represents the most common and curable form of hypertension, with a prevalence that increases with the severity of hypertension. Although genetic causes underlying glucocorticoid-remediable aldosteronism, one of the three Mendelian forms of PA, were established some time ago, somatic and inherited mutations in the potassium channel GIRK4 have only recently been implicated in the formation of aldosterone-producing adenoma (APA) and in familial hyperaldosteronism type 3. Moreover, recent findings have shown somatic mutations in two additional genes, involved in maintaining intracellular ionic homeostasis and cell membrane potential, in a subset of APAs. This review summarizes our current knowledge on the genetic determinants that contribute to variations in plasma aldosterone and renin levels in the general population and the genetics of familial and sporadic PA. Various animal models that have significantly improved our understanding of the pathophysiology of excess aldosterone production are also discussed. Finally, we outline the cardiovascular, renal, and metabolic consequences of mineralocorticoid excess beyond blood pressure regulation.

Aldosterone synthase gene (CYP11B2) -344C/T polymorphism contributes to the risk of recurrent cerebral ischemia

BACKGROUND

Accumulating evidence suggests that CYP11B2 rs1799998 (-344C/T) polymorphism is independently associated with an increased risk of stroke. Our aim was to determine whether -344C/T also predisposes to recurrent cerebral ischemia following in patients with symptomatic intracranial atherosclerosis disease (ICAD).

METHODS

Genotypes of the CYP11B2 -344C/T polymorphism were determined by polymerase chain reaction-restriction fragment length polymorphism. A total of 208 ICAD patients were enrolled and underwent a long-term clinical follow-up to detect the recurrent cerebral ischemia.

RESULTS

During a median follow-up time of 35 months, 40 recurrent strokes (19.2%) were documented. Kaplan-Meier and multivariable Cox regression analyses adjusted for age, gender, and other cardiovascular risk factors identified that the presence of the TT genotype within the CYP11B2 -344C/T polymorphism was associated with an increased risk of 1.98-fold for recurrent cerebral ischemia (the hazard ratio 1.98, 95% confidence interval 1.16-3.41; p=0.01).

CONCLUSIONS

Our findings suggest that the -344C/T polymorphism of the CYP11B2 gene confers an increased risk of recurrent cerebral ischemia.

Association of angiotensin-converting enzyme gene I/D and CYP11B2 gene -344T/C polymorphisms with lone atrial fibrillation and its recurrence after catheter ablation

The renin-angiotensin-aldosterone system (RAAS) plays a key role in atrial structural and electrical remodeling. The aim of this study was to investigate the potential associations of angiotensin-converting enzyme (ACE) gene insertion/ deletion (I/D) and aldosterone synthase (CYP11B2) gene −344T/C polymorphisms with the risk and recurrence of lone atrial fibrillation (AF). One hundred and ninety-three patients who underwent successful catheter ablation for lone AF were recruited. Two hundred and ninety-seven sinus rhythm subjects without a history of arrhythmia served as controls. The subjects were genotyped for ACE gene I/D and CYP11B2 gene −344T/C polymorphisms. Results showed that the ACE gene DD genotype and D allele were associated with a greater prevalence of lone AF (both P<0.01). In addition, the ACE gene DD genotype had a significantly larger left atrial dimension (LAD; 41.6±5.7 mm vs. 39.6±5.2 mm; P=0.043) and higher risk of AF recurrence [44.7% vs. 23.2%; odds ratio (OR), 2.68; 95% confidence interval (CI), 1.28–5.61; P=0.008] compared with the II+ID genotype in lone AF patients. After adjustment for a variety of risk factors, the ACE gene DD genotype had a 1.97-fold increased risk for lone AF (OR, 1.97; 95% CI, 1.15–3.37; P= 0.013) and 2.35-fold increased risk for AF recurrence (RR, 2.35; 95% CI, 1.10–5.04; P=0.028) compared with the ACE gene II+ID genotype. However, no correlation between the CYP11B2 gene −344T/C polymorphism and lone AF or its recurrence was observed in this cohort. In conclusion, the ACE gene DD genotype was associated with an increased incidence of lone AF and its recurrence following ablation, which was partly mediated by LAD.

Treatment of primary aldosteronism: Where are we now?

Primary aldosteronism (PA) is an important cause of secondary hypertension, is being increasingly diagnosed and may account for more than 10% of hypertensive patients, both in primary care and in referral centers. Aldosterone excess is associated with adverse cardiovascular, renal and metabolic effects that are in part hypertension-independent. Laparoscopic adrenalectomy remains the mainstay of treatment for unilateral forms of PA, whereas medical treatment is recommended for bilateral forms of PA. However, a favourable surgical outcome depends on several factors and many patients are not suitable for this treatment. On the other hand, surgery in patients considered to have bilateral PA may contribute to better blood pressure control. In this review, established and novel strategies for the management of different types of PA are discussed.

Association between renin-angiotensin-aldosterone system-related genes and blood pressure in a Korean population

AIMS. Blood pressure control is influenced by various genetic and environmental factors, and genetic susceptibility is important in the development of essential hypertension. Because the renin-angiotensin-aldosterone system (RAAS) has a key role in vasoconstriction, vasodilation, and sodium and electrolyte balance, it is central in blood pressure control and so is an appropriate target in hypertension treatments. The present study assessed the association of RAAS-related genes with blood pressure and hypertension in a Korean population. Single nucleotide polymorphisms (SNPs, n = 114) in nine RAAS-related genes (AGT, REN, ACE, ACE2, AGTR1, CYP11B2, NR3C2, MAS1, and CMA1) were assessed for their correlation with blood pressure and hypertension using genotype data of 8842 individuals from the Korea Association Resource subject pool. MAJOR FINDINGS. Linear regression analysis revealed a statistically significant association with blood pressure of 10 SNPs in six genes (ACE, ACE2, CYP11B2, NR3C2, MAS1, and CMA1). An additional hypertension case-control study identified 10 SNPs in NR3C2 and ACE that were linked to hypertension. PRINCIPAL CONCLUSION. Three SNPs (rs11737660, rs6810951, and rs10519963) in NR3C2 correlate with both blood pressure and hypertension. Genetic polymorphisms in RAAS-related genes appear to be associated with hypertension in a Korean population.

RAAS and adrenergic genes in heart failure: Function, predisposition and survival implications

It is well appreciated that several neurohormones and signaling cascades are activated that promote long-term deterioration of cardiac function and structure. Activation of the renin-angiotensin-aldosterone system (RAAS) and the adrenergic system is closely related to heart failure. Common gene variants that encode neurohormonal, adrenergic and intracellular proteins have been demonstrated to modulate the course and consequences of heart failure. However, the literature is replete with conflicting results and it remains uncertain as to whether particular gene variants predispose heart failure. Therefore, the main purpose of this review was to discuss the effects of single nucleotide polymorphisms (SNPs) that are located in genes encoding elements of the RAAS and the adrenergic system on the predisposition to and survival from heart failure. Most studies indicate that common SNPs encoding elements of the RAAS and the adrenergic system do not predispose individuals to heart failure. Conversely, it has been demonstrated that ARB1 Arg389Gly, GRK5 Gln41Leu, ACE I/D, CYP11B2 C-344T and AGTR1 A+1166C modulate pharmacological responses and have a considerable impact on cardiac-related survival. It should not be expected, however, that a single polymorphism determines survival, given that multiple gene products and environmental factors contribute to the pathogenesis of heart failure. Therefore, future studies should consider the interaction effects of multiple genes in populations that are as homogeneous as possible with respect to environmental characteristics.

Association of the -344C/T aldosterone synthase (CYP11B2) gene variant with hypertension and stroke

Stroke is a complex disease caused by combination of multiple risk factors. Recent findings have suggested that stroke has a significant genetic component. Various types of genetic polymorphisms have been suggested to contribute to the risk of stroke. Gene polymorphisms of renin-angiontensin aldosterone system (RAAS) have been suggested to be risk factors for hypertension, cardiovascular diseases and stroke. In the present case-control study we investigated the association of -344C/T (rs1799998) [corrected] polymorphism in the promoter region of the human aldosterone (CYP11B2) gene with genetic predisposition to hypertension, ischemic stroke and stroke subtypes classified according to TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Four hundred and three stroke patients (hypertensives:normotensives=219:184) and three hundred and ninety four, sex and age matched healthy controls (hypertensives:normotensives=118:276) were involved in the study. The region of interest in the CYP11B2 gene was amplified by polymerase chain reaction and genotypes determined by subjecting the PCR products to restriction digestion by the enzyme HaeIII. Significant difference was observed in the genotypic distribution and allelic frequency between the stroke patients and healthy controls. TT genotype and T allele associated significantly with hypertension and stroke (p<0.000 in hypertension and p=0.000 in case of stroke). A stepwise logistic regression analysis confirmed these findings. To establish that this polymorphism is associated with stroke independent of hypertension, we compared stroke patients without hypertension with normotensive controls. Significant difference was observed in genotypic distribution and allelic frequency between the two groups (p=0.000). Further evaluating the association of this polymorphism with stroke subtypes we found significant associations with intracranial large artery atherosclerosis, lacunar stroke and cardioembolic stroke (p=0.000 in each case). In conclusion our study suggests that -344T allele of CYP11B2 gene is an important risk factor for hypertension and ischemic stroke. However, this is a preliminary study and the results need to be confirmed in a larger cohort.

Associations of the -344 T>C and the 3097 G>A polymorphisms of CYP11B2 gene with hypertension, type 2 diabetes, and metabolic syndrome in a French population

BACKGROUND

Aldosterone can affect both blood pressure (BP) and glucose metabolism. We assessed the association of two polymorphisms -344 T>C and the 3097 G>A in the aldosterone synthase gene (CYP11B2) with prevalent and incident hypertension (HT), type 2 diabetes (T2D), and the metabolic syndrome (MetS).

METHODS

We studied the 5,212 participants to D.E.S.I.R. (Data from Epidemiologic Study on the Insulin Resistance syndrome), a cohort from French general population. Genotyping was done by a TaqMan assay. Analysis of covariance, multivariate logistic regression (adjusted for age, MetS components) and haplotype analysis were performed.

RESULTS

The prevalences and 9-year incidences were 16.7 and 36.1% for HT, 2.6 and 6.2% for T2D, and 19.3 and 25.1% for the MetS. Risk for incident HT was reduced with the AA genotype of 3097 G>A, adjusted odds ratios (OR): 0.67; p = 0.04. The prevalence of HT was lower in women carrying the C allele of -344 T>C, OR 0.75; p = 0.03 for the TC genotype and 0.69; p = 0.03 for the CC genotype. In men, incident T2D was associated with both polymorphisms, adjusted OR for -344 T>C: 1.63; p = 0.04 for TC genotype and 2.12; p = 0.008 for CC genotype; for the 3097 G>A: the AA genotype was associated with a lower risk, OR 0.23; p = 0.02. In men, incident MetS was associated with 3097 G>A, OR: 0.57; p = 0.02 for AA genotype. Significant associations between haplotype combinations and the prevalence or incidence of the three diseases were also found.

CONCLUSION

The -344 T>C and 3097 G>A polymorphisms in the CYP11B2 are associated with T2D, hypertension and the MetS in European subjects with gender variations.

Aldosterone synthase (CYP11B2) C-344T polymorphism affects the association of age-related changes of the serum C-reactive protein

Aldosterone participates in vascular and myocardial inflammation either directly or indirectly through blood pressure (BP). Aldosterone synthase (CYP11B2) C-344T polymorphism may influence the severity of systemic inflammation. A total of 398 Japanese Americans (152 men and 246 women, age 19-92 years) from the Hawaii-Los Angeles-Hiroshima study were enrolled. BP and serum levels of C-reactive protein (CRP) were measured, and the CYP11B2 C-344T polymorphism, rs1799998, was determined. No influence of the polymorphism on baseline characteristics such as systolic, diastolic and mean BP, pulse pressure or serum CRP levels was observed. In all genotypes, systolic BP showed a significantly positive correlation with age (TT (n=178): r=0.283, P<0.001; TC (n=164): r=0.213, P=0.006; and CC (n=56): r=0.289, P=0.031). However, the regression coefficients of systolic BP with age were not different across genotypes. According to the results of univariate and multivariate analyses with adjustment for BP, the serum CRP level increased with age only in subjects with the CC genotype (P=0.027 and P=0.004, respectively), and elevation of serum CRP was mainly observed in the elderly population (aged >or=60 years). Moreover, the regression coefficient of CRP levels with age was significantly steeper in subjects with the CC genotype than in those with the TC or TT genotype (P=0.028). The CC genotype of the CYP11B2 C-344T polymorphism was associated with an age-dependent increase in the serum CRP level independent of BP, and may contribute to a cardiovascular phenotype by promoting vascular inflammation.

A systemic review of the relationship between aldosterone synthase - 344 C/T polymorphism and hypertension in Han

Many studies reported the association between aldosterone synthase gene CYP11B2 polymorphism and essential hypertension in Chinese. So far, no meta- analysis was conducted between the etiology of essential hypertension and CYP11B2 -344 C/T polymorphism in Han Chinese, the majority (93% of the total population) in China. Recruited literature was based on searching the Cochrane Library, MEDLINE, EMBASE, the Chinese Biomedicine Database (CBM), CNKI, VIP, and reference lists of articles without language restrictions. Nine studies with case-control involving 4259 unselected essential hypertension patients and 3213 controls were included in the analysis. From the nine homogeneous studies with gender, age, and ethnicity matched controls, we found no significant association between the etiology of essential hypertension and the -344 C/T variant in Han Chinese with random effect models (for homozygous CC: odds ratio (OR), 1.04, 95% confidence interval (CI), 0.791.37, P = 0.79; for allele C: OR, 1.04, 95% CI, 0.921.18, P = 0.56). No significant association was observed between CYP11B2 -344 C/T polymorphism and hypertension susceptibility in both sexes. Current large sample analysis did not support the association between the etiology of essential hypertension and CYP11B2 - 344 C/T polymorphism in Han Chinese.

Aldosterone Synthase Gene (CYP11B2) Polymorphism in Korean End-Stage Renal Disease Patients on Hemodialysis

Aldosterone synthase gene (CYP11B2) -344C/T polymorphism has been reported to be associated with serum aldosterone level, urinary aldosterone excretion, blood pressure, and left ventricular size and mass. The aim of this study was to evaluate the relation between CYP11B2 polymorphism and end-stage renal disease (ESRD) in the Korean population and the association with CYP11B2 polymorphism and cardiovascular morbidity in ESRD patients on hemodialysis. Genotyping was performed in 134 control subjects and 271 ESRD patients for CYP11B2 polymorphism using polymerase chain reaction through subsequent cleavage with restriction enzyme. Also current blood pressure, demographic, anthropometric and biochemical variables were investigated. The genotype distribution did not differ between ESRD patients and controls and there were no significant differences in blood pressure, use of antihypertensive medication, left ventricular hypertrophy and cardiovascular disease among the three genotypes in ESRD patients on hemodialysis. Our findings do not support the hypothesis that CYP11B2 polymorphism may be associated with prevalence of ESRD and suggest that CYP11B2 polymorphism may not be a genetic marker for cardiovascular morbidity in Korean ESRD patients.

CYP11B2 gene haplotypes independently and in concurrence with aldosterone and aldosterone to renin ratio increase the risk of hypertension

OBJECTIVES

Aldosterone synthase produces aldosterone, which regulates electrolytes and thereby blood pressure. Polymorphisms in aldosterone-synthase gene (CYP11B2) may associate with heterogeneous aldosterone production and hypertension. Hence, we investigated -344T/C, Iw/Ic polymorphisms of CYP11B2, plasma renin activity (PRA) and aldosterone concentration (PAC).

DESIGN AND METHODS

Consecutive ethnically-matched 450 hypertensive patients and 360 controls were screened by PCR-RFLP for genotypes and haplotypes; PRA and PAC were measured.

RESULTS

The Iw/Ic polymorphism distribution differed significantly between the two groups (LRT chi(2)=15.8, df=2, P=0.000). The mutant allele-Ic and genotype-Ic/Ic were overrepresented in patients (35% versus 27% and 13% versus 7%). Overrepresentation of T-Ic haplotype in patients was identified as risk haplotype (P=0.000). Patients had significantly higher PAC and aldosterone-to-renin ratio (ARR; P=0.000), which was Ic-allele dependent.

CONCLUSIONS

The haplotype T-Ic associated with hypertension susceptibility. Correlation between Ic-allele and raised ARR likely serve in hypertension management.

Aldosterone synthase (CYP11B2)­344T/C polymorphism and renoprotective response to losartan treatment in diabetic nephropathy

OBJECTIVE

It has been suggested that an aldosterone synthase gene polymorphism (CYP11B2 -344T/C) is predictive of the blood pressure lowering effect of angiotensin II receptor blockers in essential hypertension. We investigated whether this polymorphism is predictive of reductions in blood pressure and albuminuria and preservation of glomerular filtration rate (GFR) during short-term and long-term treatment with losartan in 57 hypertensive type-1 diabetic patients with diabetic nephropathy.

MATERIAL AND METHODS

After a 4-week washout period, patients received losartan (100 mg o.d.) and were followed for a mean follow-up of 36 months. At baseline, after 2 and 4 months, and every 6 months thereafter, GFR (51Cr-EDTA-clearance), albuminuria and 24-h blood pressure were determined. The CYP11B2 -344T/C polymorphism was determined by standard polymerase chain reaction (PCR).

RESULTS

The TT, CT and CC genotypes were found in 28 %, 58 % and 14 % of patients, respectively. At baseline albuminuria and blood pressure did not differ between genotype groups. Plasma aldosterone levels (geometric mean (95 % CI)) were similar at baseline: 87 (60-125), 77 (53-112), and 89 (49-161) pg mL(-1) and during follow-up (not significant). After initiation of losartan treatment, comparable mean (SE) reductions in blood pressure and albuminuria were seen in patients with TT, CT and CC genotypes (p >0.6 between groups). After long-term follow-up, there was a tendency towards a difference in systolic blood pressure reduction (p = 0.07, one-way ANOVA), suggesting a poorer response in patients with the CC genotype. No significant difference in rate of decline in GFR (median (range)) was seen between groups (TT, CT, CC): 4.2 (-1.0 to 16.0), 3.2 (-1.6 to 13.8) and 2.6 (-0.1 to 11.0) mL min(-1)year(-1), respectively (p = 0.5).

CONCLUSIONS

Compared to a previous smaller study of angiotensin II receptor blockade in essential hypertension, we could not confirm that CYP11B2 -344T/C genotypes contribute towards explaining the observed variability in response to treatment with angiotensin II receptor blockers, which could be due to lack of power.

Association of −344/T/C aldosterone synthase polymorphism (CYP11B2) with left ventricular structure and humoral parameters in young normotensive men

BACKGROUND

Aldosterone plays an important role in development of left ventricular (LV) hypertrophy and myocardial fibrosis. We assessed the influence of the T-344C polymorphism of aldosterone synthase - the rate-limiting enzyme in aldosterone biosynthesis - on the structure of the left ventricle in young normotensive men.

DESIGN AND METHODS

The population included 113 normotensive mid-European Caucasian men aged 18-40 years (mean 27 +/- 5 years). The genotype was assessed using polymerase chain reaction with subsequent cleavage with restriction enzyme HAEIII (restriction fragment length polymorphism method) and visualization with ethidium bromide. Plasma renin activity (PRA) and plasma aldosterone were measured. All subjects were examined by echocardiography and LV mass was assessed by using M-mode based ASE formula.

RESULTS

The distribution of the genotypes was TT 23%:TC 55%:CC 22%. There were no differences in blood pressure among the groups. Men with the TT genotype had significantly higher levels of PRA (2.7 +/- 1.7 vs 1.8 +/- 1.0 vs 1.8 +/- 1.1 ng/ml/h, p < 0.01) and slightly higher plasma levels of aldosterone (113 +/- 64 vs 93 +/- 43 vs 87 +/- 39 pg/ml, p = 0,12). In the whole population, LV mass index (LVMI) did not differ significantly among the genotypes (92 +/- 16 vs 86 +/- 18 vs 84 +/- 16 g/m, p=0.20). In the population divided according to PRA, subjects with high renin had significantly higher LVMI in presence of the TT genotype (95 +/- 17 vs 84 +/- 16 vs 81 +/- 15 g/m, p < 0.05).

CONCLUSIONS

In agreement with previous studies, we found that the TT genotype of T-344C polymorphism of aldosterone synthase gene was associated with significantly higher levels of PRA in normotensive men. In subjects with high PRA, the TT genotype was associated with higher values of the LVMI.

Functional polymorphisms in ACE and CYP11B2 genes and atrial fibrillation in patients with hypertensive heart disease

BACKGROUND

The activated renin-angiotensin-aldosterone system has been reported to play an important role in the pathogenesis of atrial fibrillation (AF). We hypothesized that functional genetic variations of angiotensin-converting enzyme (ACE) and CYP11B2 genes may influence the susceptibility to AF in patients with hypertensive heart disease.

METHODS

The I/D polymorphism of ACE was detected by polymerase chain reaction (PCR), and the -344C/T polymorphism of the CYP11B2 gene was detected using PCR and subsequent cleavage by HaeIII restriction endonuclease.

RESULTS

The overall distribution of ACE I/D genotypes in patients with and without AF was significantly different (p=0.001). The frequency of the DD genotype was significantly higher in patients with AF than in patients without AF (20.6% vs. 8.1%, OR 2.94, 95% CI 1.64-5.26, p<0.001). The frequency of the D allele was significantly higher in the AF group than in the non-AF group (p=0.001). After adjustment for age and left atrial dimension, multivariable analysis showed that the DD genotype of the ACE gene was an independent risk factor for AF in patients with hypertensive heart disease. No relationship between -344 C/T CYP11B2 polymorphism and AF was found in this cohort.

CONCLUSIONS

Our study suggests that ACE I/D polymorphism is associated with AF and the DD genotype may be an independent predictive factor for AF in patients with hypertensive heart disease.

Genetic polymorphisms and the risk of accelerated renal function decline in women

Background

Reduced glomerular filtration rate is an important predictor of cardiovascular disease and death. Genetic polymorphisms, particularly in genes involved in the renin-angiotensin system (RAS), may influence the rate of renal function decline.

Methodology/Principal Findings

We examined the relation between specific single nucleotide polymorphisms (SNPs), including those in the RAS, apolipoprotein E and alpha-adducin, and renal function decline assessed by estimated glomerular filtration rate (eGFR) over an 11-year period in 2578 Caucasian participants of the Nurses' Health Study. Logistic regression was used to examine the associations between genotype and risk of eGFR decline of ≥25%.

Results

After 11 years between creatinine measurements, the eGFR declined by ≥25% in 423 of 2578 (16%) women. The angiotensinogen (AGT) A-20C polymorphism was associated with a higher risk of renal function decline when two risk alleles were present than if one or no alleles were present (CC vs AA and AC) OR 1.83 (95% CI 1.02–3.26; p = 0.04). The angiotensin II type 1 receptor (AT₁R) A1166C polymorphism was marginally associated with a higher risk of renal function decline when two risk alleles were present (CC vs AA, OR = 1.41; 95% CI 0.98–2.01; p = 0.06). The alpha-adducin G460W polymorphism was associated with a lower risk of renal function decline when any number of risk alleles were present (WG vs GG, OR = 0.78, 95% CI 0.61–0.99, p = 0.04; WW vs GG, OR = 0.46; 95% CI 0.20–1.07, p = 0.07). Linear regression analysis with change in eGFR as the outcome showed a larger decline of 3.5 (95% CI 0.5 to 6.4, p = 0.02) ml/min/1.73 m² in AGT A-20C CC homozygotes. No other polymorphisms were significantly associated with renal function decline or absolute change in eGFR over the study period.

Conclusions

Genetic variants in the angiotensinogen, angiotensin II type 1 receptor and alpha-adducin genes may contribute to loss of renal function in the general female Caucasian population.

Altered corticosteroid biosynthesis in essential hypertension: A digenic phenomenon

Aldosterone plays an important role in electrolyte and blood pressure homeostasis. Our studies have focused on the role of aldosterone in essential hypertension. We have shown that plasma aldosterone and ARR are heritable characteristics and that aldosterone concentrations in older subjects are inversely correlated with birthweight and positively correlated with blood pressure. Aldosterone levels are also associated with polymorphic variation in the CYP11B2 gene, which encodes aldosterone synthase, the enzyme responsible for aldosterone production. Interestingly, CYP11B2 polymorphisms are also associated with less efficient activity of 11beta-hydroxylase, encoded by the neighbouring, highly homologous CYP11B1 gene. We propose that a digenic effect leads to increased aldosterone production, with inefficient 11beta-hydroxylation causing a long-term increase in ACTH drive to the adrenal gland and enhanced expression of CYP11B2, thereby resulting in chronically raised aldosterone secretion in response to factors such as angiotensin II and potassium. In susceptible subjects this is likely, over many years, to result in hypertension with relative aldosterone excess.

Hyperaldosteronism in pregnancy

Aldosterone is a key regulator of electrolyte and water homeostasis and plays a central role in blood pressure regulation. Hormonal changes during pregnancy, among them increased progesterone and aldosterone production, lead to the required plasma volume expansion of the maternal body as an accommodation mechanism for fetus growth. This review discusses the regulation of aldosterone production by aldosterone synthase (CYP11B2); the impact on aldosterone secretion due to the presence of a chimeric gene originating from a crossover between CYP11B1 and CYP11B2 in glucocorticoid remediable aldosteronism (GRA) — the inherited form of hypertension; enhanced aldosterone production in aldosterone-producing adenoma (APA); and idiopathic hyperaldosteronism (IHA). Features of hyperaldosteronism are also found in patients with apparent mineralocorticoid excess (AME), in which glucocorticoids exacerbate activation of the mineralocorticoid receptor (MR) because of a defect in the 11β-hydroxysteroid dehydrogenase type 2 enzyme. Regulation of aldosterone production and tissue-specific activation of the mineralocorticoid receptor are prerequisites for optimal control of body fluids and blood pressure during pregnancy and contribute largely to the wellbeing of the mother-to-be.

Comparison between essential hypertension and pregnancy-induced hypertension: a genetic perspective

Essential hypertension (EH) accounts for 80-90% of hypertension, and pregnancy-induced hypertension (PIH) is responsible for hypertension during pregnancy. Both considered multifactorial disorders. While both have many features in common, conditions and causes of these diseases have yet to be clarified. Since both diseases are associated with hypertension, the genetic backgrounds may contain common features. The present study reviewed similarities and differences between women with EH and PIH, with a particular focus on their genetic backgrounds.

The effect of polymorphisms in the renin-angiotensin-aldosterone system on diabetic nephropathy risk

OBJECTIVES

The risk of diabetic nephropathy (DN) can be increased by elevated intraglomerular pressure and glomerular filtration rate, leading to glomerular damage. This can be controlled by the renin-angiotensin-aldosterone (RAA) system, which has an important function regulating both systemic and intrarenal blood pressure. Smoking increases the risk of DN, but not all diabetic patients who smoke develop DN. There is a possibility that smoking has different effects depending on the different genotypes of the individual. We investigated the association of DN with seven polymorphisms in the RAA system and their possible interaction with smoking.

SUBJECTS AND METHODS

In the present case-control study, type 1 diabetic patients with diabetes duration > or =20 years, without albuminuria and without antihypertensive treatment (n=197), were included as controls. An albumin excretion rate (AER) of 20-200 microg/min (n=73) was considered as incipient DN, and an AER >200 microg/min was considered as overt DN (n=48). Smoking habits were obtained from questionnaires.

RESULTS

Homozygosity for the A allele, of the angiotensin II type 1 receptor (AGTR1) A1166C polymorphism, was associated with increased risk of overt DN (OR=3.04; 99% CI=1.02-9.06), independently of the other associated variables: age, duration of diabetes, ever smoking, HbA1c, and sex. The effect of the AA genotype was enhanced to a four times risk increase among ever-smoking patients. Two alleles of the microsatellite marker adjacent to the angiotensinogen gene were less common among nephropathy cases than among controls, but this was not significant when controlling for the same variables as above.

CONCLUSIONS

The risk of having overt DN was increased in patients homozygous for the A1166 allele, and smoking seemed to enhance the effect of the AGTR1 genotype.