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

The Role of the CYP11B2 Promoter Polymorphism in the Diagnosis of Primary Aldosteronism

Background: nowadays, primary aldosteronism (PA) is suggested to be the most frequent cause of secondary hypertension and it reaches 10% of whole hypertensive population. The CYP11B2 promoter polymorphism might cause aldosterone overproduction. The aim of this study was to establish whether the polymorphism CYP11B2 promoter has a significant impact on diagnostic of PA. Material and Methods: study group consisted of 239 hypertensive patients previously diagnosed with adrenal incidentaloma. For diagnose of PA were performed: screening test–aldosterone-renin ratio (ARR) and saline suppression test (SIT) as a confirmatory test. Genotyping was carried out by the real time PCR method. The significance of differences between the groups was evaluated through Student’s t-test. Results: our study revealed that genotype TT had plasma aldosterone concentration (PAC), ARR and SIT significantly higher in comparison with CC patients. The mean PAC in CC was 12.71 ng/dL vs. 20.55 ng/dL in TT patients (p = 0.037), which consequently gave a higher ARR in TT patients (119 vs. 44, p = 0.034). Mean aldosterone concentration in SIT was 2.40 ng/dL in CC patients and 9.99 ng/dL in TT patients (p = 0.046). Patients with CC genotype required less hypotensive drugs in comparison with TT genotype (p = 0.044). PA was recognized in 16 patients. Nine patients had TC genotype, six TT, and one with CC genotype. Conclusion: our study revealed predisposing TT genotype to PA. Additionally, patients with TT genotype, regardless of the PA presence, had more severe hypertension. The determination of the CYP11B2 promoter polymorphism seems to be useful in the diagnosis of PA, especially in cases where it is difficult to properly prepare patients for hormonal tests or even results of the hormonal test are incoherent.

Genetics of Human Primary Hypertension: Focus on Hormonal Mechanisms

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

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.

Interactions between the genes of vasodilatation pathways influence blood pressure and nitric oxide level in hypertension

BACKGROUND

This study investigates the contribution of genetic interactions between the β-2 adrenergic receptor (ADRB2) and nitric oxide synthase (NOS3) genes to the complex etiology of hypertension.

METHODS

Using single nucleotide polymorphism (SNP) markers, we studied potential interactions between ADRB2 and NOS3 variants and their correlation with clinical, biochemical, and expression levels in 546 individuals with hypertension and 884 age-, sex-, and ethnicity-matched unrelated control subjects. Generalized multifactor dimensionality reduction (GMDR) analysis identified the models for genotype interaction.

RESULTS

The best models to represent association of genotypes with augmented hypertension susceptibility were the 4- and 5-locus interacting GMDR models of ADRB2 and NOS3 compared with within-gene 6-locus ADRB2 and 2-locus NOS3 (odds ratio (OR) = 4.8, P = 0.04; OR = 5.6, P = 0.02, respectively). Stratification of 4- and 5-locus GMDR models on the basis of risk alleles (in increasing order) increased the ORs from 1.26 to 14.17 and from 0.81 to 14.18, respectively, and correlated linearly with increased systolic blood pressure, diastolic blood pressure, and mean arterial pressure and decreased nitric oxide level (P ≤ 0.0004). We performed various analyses, such as single-locus, genetic interactions, sliding-window, and comparative analysis. Each analysis consistently revealed the 46A allele of ADRB2 46G/A SNP and 4a allele of NOS3 4b/4a SNP to be associated with risk of hypertension. These risk-conferring markers were associated with decreased ADRB2 and NOS3 expression and decreased nitric oxide level in the patients (P ≤ 0.04).

CONCLUSIONS

Evidence of interaction between the genetic loci of ADRB2 and NOS3 points to varied clinical, biochemical, and expression levels and a role in hypertension susceptibility.

Predictors of successful outcome after adrenalectomy for primary aldosteronism

The underlying cause of resistant hypertension after adrenalectomy for primary hyperaldosteronism remains controversial. The objective of this study was to identify preoperative factors predictive of resistant hypertension in patients after undergoing retroperitoneoscopic adrenalectomy. Between 2003 and 2009, 124 patients with unilateral aldosterone-producing adenoma or unilateral adrenal hyperplasia underwent retroperitoneoscopic adrenalectomy at our institution. Clinical and biochemical data were reviewed retrospectively at baseline and after a median follow-up time of 59.2 ± 37.2 months. Adrenalectomy cured hypertension in 68 patients (54.8%) and 43 (34.8%) had persistent hypertension that was much easier to control after surgery, whereas 13 patients (10.4%) had continued hypertension and poor blood pressure control. Multivariate regression analysis revealed that the main determinants of postoperative cure were duration of hypertension less than 5 years [odds ratio (OR): 6.515, 95% confidence interval (CI) 2.278-10.293), number of antihypertensive medications ≤2 (OR: 2.939, 95% CI 1.254-5.235), preoperative response to spironolactone (OR: 3.405, 95% CI 1.681-6.985), the TT genotype of the CYP11B2 gene (344 C/T) (OR: 2.765, 95% CI 1.221-4.986), and the presence of adenoma rather than hyperplasia (OR: 5.274, 95% CI 2.150-8.141). The main determinants of surgical cure or control of hypertension in patients with primary hyperaldosteronism were duration of hypertension, number of antihypertensive medications, preoperative response to spironolactone, the presence of adenoma, and CYP11B2 (344 C/T) genotype. Consideration of these factors may help in the evaluation of patients for surgery and for the identification of patients with continued postoperative hypertension that may require more long-term monitoring and treatment.

Aldosterone synthase gene polymorphism and renal histopathologic changes in kidney transplant patients receiving a calcineurin inhibitor

INTRODUCTION

Aldosterone participates in the pathogenesis of calcineurin inhibitor nephrotoxicity (CIN), producing renal vasoconstriction and transforming growth factor beta (TGFß) expression. The objective of this study was to assess aldosterone polymorphisms and relationships to plasma aldosterone levels and the development of renal histological lesions in kidney transplant patients.

MATERIAL AND METHODS

Patients with kidney graft biopsy were divided according to the presence or absence of CIN. We determined aldosterone synthase (AS) -344 T/C and int 2 W/C gene polymorphisms and plasma aldosterone levels. Histological, biochemical and clinical variables were measured.

RESULTS

Calcineurin inhibitor (CI) levels were significantly higher in patients with the int 2 WW genotype than in patients with WC or CC genotypes. There was a greater degree of interstitial fibrosis in patients with int 2 CC genotype. No relationship was found between the different polymorphisms and a higher degree and/or frequency of CIN. There was also no relationship with plasma aldosterone levels.

CONCLUSION

The frequency of the different polymorphisms studied was not related to plasma aldosterone levels or the development of CIN; however, the int 2 CC genotype was related to a greater degree of interstitial fibrosis, whereas the WW genotype was related to higher CI serum levels.

Polymorphic variation of CYP11B2 predicts postoperative resolution of hypertension in patients undergoing adrenalectomy for aldosterone-producing adenomas

OBJECTIVES

The surgical cure rate of patients with aldosterone-producing adenoma varies widely, and causes of persistent hypertension are not completely established. The objective of this study was to assess the blood pressure outcome in patients after retroperitoneoscopic adrenalectomy, and to analyze the CYP11B2 344 C/T polymorphism and any factors associated with the outcome.

METHODS

Between 2002 and 2009, 82 patients with unilateral aldosterone-producing adenoma underwent retroperitoneoscopic adrenalectomy. Clinical and biochemical data were reviewed retrospectively. Patients were investigated to assess the association of the CYP11B2 344 C/T polymorphism with resistant hypertension after surgery.

RESULTS

Adrenalectomy cured hypertension in 44 patients (53.7%), and 27 patients (32.9%) had persistent hypertension that was much easier to control after surgery, whereas 11 patients (13.4%) had continued hypertension and poor blood pressure control. Multivariate regression analysis showed that the main determinants of postoperative cure were duration of hypertension less than 5 years (OR 4.515, 95% CI 1.978-10.293), number of antihypertensive medications ≤2 (OR 2.639, 95% CI 1.154-6.035), preoperative response to spironolactone (OR 3.105, 95% CI 1.381-6.985) and the TT genotype of the CYP11B2 gene (344 C/T; OR 2.765, 95% CI 1.261-6.064).

CONCLUSIONS

The 344 C/T polymorphism of the CYP11B2 gene predicts resolution of hypertension in patients undergoing adrnelactomy for aldosterone-producing adenoma. Duration of hypertension, number of antihypertensive medications, and preoperative response to spironolactone also represents predictive factors that need to be considered for the identification of patients with continued postoperative hypertension requiring long-term monitoring and treatment.

Hypertension-Related Gene Polymorphisms of G-Protein-Coupled Receptor Kinase 4 Are Associated with NT-proBNP Concentration in Normotensive Healthy Adults

G protein-coupled receptor kinase 4 (GRK4) with activating polymorphisms desensitize the natriuric renal tubular D1 dopamine receptor, and these GRK4 polymorphisms are strongly associated with salt sensitivity and hypertension. Meanwhile, N-terminal pro-B-type natriuretic peptide (NT-proBNP) may be useful in detecting slight volume expansion. However, relations between hypertension-related gene polymorphisms including GRK4 and cardiovascular indices such as NT-proBNP are not clear, especially in healthy subjects. Therefore, various hypertension-related polymorphisms and cardiovascular indices were analyzed in 97 normotensive, healthy Japanese adults. NT-proBNP levels were significantly higher in subjects with two or more GRK4 polymorphic alleles. Other hypertension-related gene polymorphisms, such as those of renin-angiotensin-aldosterone system genes, did not correlate with NT-proBNP. There was no significant association between any of the hypertension-related gene polymorphisms and central systolic blood pressure, cardioankle vascular index, augmentation index, plasma aldosterone concentration, or an oxidative stress marker, urinary 8-OHdG. Normotensive individuals with GRK4 polymorphisms show increased serum NT-proBNP concentration and may be at a greater risk of developing hypertension and cardiovascular disease.

The epistasis between vascular homeostasis genes is apparent in essential hypertension

OBJECTIVE

The epistasis influence of vascular homeostasis genes is vital to multigenetic diseases. This study was designed to perceive the possible role of epistasis in the etiology of essential hypertension.

METHODS

We investigated seven polymorphisms of ACE, CYP11B2 and NOS3 epistatically, and SBP, DBP, MAP, ACE activity, plasma aldosterone concentration (PAC) and NOx level in 860 age- and ethnicity-matched unrelated north-Indian subjects.

RESULTS

The hypertension risk in individuals with interacted-genotypes (IwIw+IwIc)+(4aa), (IcIc)+(4bb+4ba) and IcIc+4aa of the CYP11B2 and NOS3 was significantly higher with odds ratio 5.5 (95% CI=2.9-10.6, P<0.0001), 2.4 (95% CI=1.4-4.1, P<0.0008) and 7.5 (95% CI=1.6-34.8, P=0.010), respectively. The odds ratio for hypertension with interacted-haplotypes (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) of CYP11B2 and NOS3 was 5.3 (95% CI=2.0-14.2, P=0.005) and 3.9 (95% CI=1.4-10.4, P=0.04), respectively; whereas for the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G), the odds ratio was 0.7 (95% CI=0.5-0.9, P=0.03). While the interacted-genotypes, IcIc+4aa correlated with higher SBP and MAP (P=0.006; P=0.04), the interacted-haplotypes, (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) correlated with higher MAP and lower NOx level (P=0.02 and P=0.03, respectively), and the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G) correlated with lower PAC and MAP (P=0.024 and P=0.018, respectively).

CONCLUSIONS

The epistasis between CYP11B2 and NOS3 and its correlation with varied clinical and biochemical parameters signify its possible contribution in the complex etiology of hypertension.

Aldosterone and arterial hypertension

In the setting of primary aldosteronism, elevated aldosterone levels are associated with increased blood pressure. Aldosterone concentrations within the normal range, however, can also alter blood pressure. Furthermore, the aldosterone-to-renin ratio, an indicator of aldosterone excess, is associated with hypertension, even in patients without excessive absolute aldosterone levels. In this Review we assess the data on the role of aldosterone in the development and maintenance of hypertension. We provide an overview of the complex crosstalk between genetic and environmental factors, and about aldosterone-mediated arterial hypertension and target organ damage. The discussion is organized according to major targets of aldosterone action: the collecting duct in the kidney, the vasculature and the central nervous system. The antihypertensive efficacy of mineralocorticoid-receptor blockers, even in patients with aldosterone values in the normal range, supports the evidence that aldosterone plays a part in blood pressure elevation in the absence of primary aldosteronism.