Common and Rare Coding Genetic Variation Underlying the Electrocardiographic PR Interval.

BACKGROUND: Electrical conduction from the cardiac sinoatrial node to the ventricles is critical for normal heart function. Genome-wide association studies have identified more than a dozen common genetic loci that are associated with PR interval. However, it is unclear whether rare and low-frequency variants also contribute to PR interval heritability. METHODS: We performed large-scale meta-analyses of the PR interval that included 83 367 participants of European ancestry and 9436 of African ancestry. We examined both common and rare variants associated with the PR interval. RESULTS: We identified 31 genetic loci that were significantly associated with PR interval after Bonferroni correction (P<1.2×10-6), including 11 novel loci that have not been reported previously. Many of these loci are involved in heart morphogenesis. In gene-based analysis, we found that multiple rare variants at MYH6 (P=5.9×10-11) and SCN5A (P=1.1×10-7) were associated with PR interval. SCN5A locus also was implicated in the common variant analysis, whereas MYH6 was a novel locus. CONCLUSIONS: We identified common variants at 11 novel loci and rare variants within 2 gene regions that were significantly associated with PR interval. Our findings provide novel insights to the current understanding of atrioventricular conduction, which is critical for cardiac activity and an important determinant of health.

Exome-wide association study of plasma lipids in >300,000 individuals.

We screened variants on an exome-focused genotyping array in >300,000 participants (replication in >280,000 participants) and identified 444 independent variants in 250 loci significantly associated with total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), low-density-lipoprotein cholesterol (LDL-C), and/or triglycerides (TG). At two loci (JAK2 and A1CF), experimental analysis in mice showed lipid changes consistent with the human data. We also found that: (i) beta-thalassemia trait carriers displayed lower TC and were protected from coronary artery disease (CAD); (ii) excluding the CETP locus, there was not a predictable relationship between plasma HDL-C and risk for age-related macular degeneration; (iii) only some mechanisms of lowering LDL-C appeared to increase risk for type 2 diabetes (T2D); and (iv) TG-lowering alleles involved in hepatic production of TG-rich lipoproteins (TM6SF2 and PNPLA3) tracked with higher liver fat, higher risk for T2D, and lower risk for CAD, whereas TG-lowering alleles involved in peripheral lipolysis (LPL and ANGPTL4) had no effect on liver fat but decreased risks for both T2D and CAD.

Regulation of Corticosteroidogenic Genes by MicroRNAs.

The loss of normal regulation of corticosteroid secretion is important in the development of cardiovascular disease. We previously showed that microRNAs regulate the terminal stages of corticosteroid biosynthesis. Here, we assess microRNA regulation across the whole corticosteroid pathway. Knockdown of microRNA using Dicer1 siRNA in H295R adrenocortical cells increased levels of CYP11A1, CYP21A1, and CYP17A1 mRNA and the secretion of cortisol, corticosterone, 11-deoxycorticosterone, 18-hydroxycorticosterone, and aldosterone. Bioinformatic analysis of genes involved in corticosteroid biosynthesis or metabolism identified many putative microRNA-binding sites, and some were selected for further study. Manipulation of individual microRNA levels demonstrated a direct effect of miR-125a-5p and miR-125b-5p on CYP11B2 and of miR-320a-3p levels on CYP11A1 and CYP17A1 mRNA. Finally, comparison of microRNA expression profiles from human aldosterone-producing adenoma and normal adrenal tissue showed levels of various microRNAs, including miR-125a-5p to be significantly different. This study demonstrates that corticosteroidogenesis is regulated at multiple points by several microRNAs and that certain of these microRNAs are differentially expressed in tumorous adrenal tissue, which may contribute to dysregulation of corticosteroid secretion. These findings provide new insights into the regulation of corticosteroid production and have implications for understanding the pathology of disease states where abnormal hormone secretion is a feature.

ACTH and Polymorphisms at Steroidogenic Loci as Determinants of Aldosterone Secretion and Blood Pressure.

The majority of genes contributing to the heritable component of blood pressure remain unidentified, but there is substantial evidence to suggest that common polymorphisms at loci involved in the biosynthesis of the corticosteroids aldosterone and cortisol are important. This view is supported by data from genome-wide association studies that consistently link the CYP17A1 locus to blood pressure. In this review article, we describe common polymorphisms at three steroidogenic loci (CYP11B2, CYP11B1 and CYP17A1) that alter gene transcription efficiency and levels of key steroids, including aldosterone. However, the mechanism by which this occurs remains unclear. While the renin angiotensin system is rightly regarded as the major driver of aldosterone secretion, there is increasing evidence that the contribution of corticotropin (ACTH) is also significant. In light of this, we propose that the differential response of variant CYP11B2, CYP11B1 and CYP17A1 genes to ACTH is an important determinant of blood pressure, tending to predispose individuals with an unfavourable genotype to hypertension.

Analysis with the exome array identifies multiple new independent variants in lipid loci.

It has been hypothesized that low frequency (1-5% minor allele frequency (MAF)) and rare (<1% MAF) variants with large effect sizes may contribute to the missing heritability in complex traits. Here, we report an association analysis of lipid traits (total cholesterol, LDL-cholesterol, HDL-cholesterol triglycerides) in up to 27 312 individuals with a comprehensive set of low frequency coding variants (ExomeChip), combined with conditional analysis in the known lipid loci. No new locus reached genome-wide significance. However, we found a new lead variant in 26 known lipid association regions of which 16 were >1000-fold more significant than the previous sentinel variant and not in close LD (six had MAF <5%). Furthermore, conditional analysis revealed multiple independent signals (ranging from 1 to 5) in a third of the 98 lipid loci tested, including rare variants. Addition of our novel associations resulted in between 1.5- and 2.5-fold increase in the proportion of heritability explained for the different lipid traits. Our findings suggest that rare coding variants contribute to the genetic architecture of lipid traits.

Common Polymorphisms at the CYP17A1 Locus Associate With Steroid Phenotype: Support for Blood Pressure Genome-Wide Association Study Signals at This Locus.

Genome-wide association studies implicate the CYP17A1 gene in human blood pressure regulation although the causative polymorphisms are as yet unknown. We sought to identify common polymorphisms likely to explain this association. We sequenced the CYP17A1 locus in 60 normotensive individuals and observed 24 previously identified single-nucleotide polymorphisms with minor allele frequency >0.05. From these, we selected, for further studies, 7 polymorphisms located ≤ 2 kb upstream of the CYP17A1 transcription start site. In vitro reporter gene assays identified 3 of these (rs138009835, rs2150927, and rs2486758) as having significant functional effects. We then analyzed the association between the 7 polymorphisms and the urinary steroid metabolites in a hypertensive cohort (n=232). Significant associations included that of rs138009835 with aldosterone metabolite excretion; rs2150927 associated with the ratio of tetrahydrodeoxycorticosterone to tetrahydrodeoxycortisol, which we used as an index of 17α-hydroxylation. Linkage analysis showed rs138009835 to be the only 1 of the 7 polymorphisms in strong linkage disequilibrium with the blood pressure-associated polymorphisms identified in the previous studies. In conclusion, we have identified, characterized, and investigated common polymorphisms at the CYP17A1 locus that have functional effects on gene transcription in vitro and associate with corticosteroid phenotype in vivo. Of these, rs138009835--which we associate with changes in aldosterone level--is in strong linkage disequilibrium with polymorphisms linked by genome-wide association studies to blood pressure regulation. This finding clearly has implications for the development of high blood pressure in a large proportion of the population and justifies further investigation of rs138009835 and its effects.

Adaptor protein-2 sigma subunit mutations causing familial hypocalciuric hypercalcaemia type 3 (FHH3) demonstrate genotype-phenotype correlations, codon bias and dominant-negative effects.

The adaptor protein-2 sigma subunit (AP2σ2) is pivotal for clathrin-mediated endocytosis of plasma membrane constituents such as the calcium-sensing receptor (CaSR). Mutations of the AP2σ2 Arg15 residue result in familial hypocalciuric hypercalcaemia type 3 (FHH3), a disorder of extracellular calcium (Ca(2+) o) homeostasis. To elucidate the role of AP2σ2 in Ca(2+) o regulation, we investigated 65 FHH probands, without other FHH-associated mutations, for AP2σ2 mutations, characterized their functional consequences and investigated the genetic mechanisms leading to FHH3. AP2σ2 mutations were identified in 17 probands, comprising 5 Arg15Cys, 4 Arg15His and 8 Arg15Leu mutations. A genotype-phenotype correlation was observed with the Arg15Leu mutation leading to marked hypercalcaemia. FHH3 probands harboured additional phenotypes such as cognitive dysfunction. All three FHH3-causing AP2σ2 mutations impaired CaSR signal transduction in a dominant-negative manner. Mutational bias was observed at the AP2σ2 Arg15 residue as other predicted missense substitutions (Arg15Gly, Arg15Pro and Arg15Ser), which also caused CaSR loss-of-function, were not detected in FHH probands, and these mutations were found to reduce the numbers of CaSR-expressing cells. FHH3 probands had significantly greater serum calcium (sCa) and magnesium (sMg) concentrations with reduced urinary calcium to creatinine clearance ratios (CCCR) in comparison with FHH1 probands with CaSR mutations, and a calculated index of sCa × sMg/100 × CCCR, which was ≥ 5.0, had a diagnostic sensitivity and specificity of 83 and 86%, respectively, for FHH3. Thus, our studies demonstrate AP2σ2 mutations to result in a more severe FHH phenotype with genotype-phenotype correlations, and a dominant-negative mechanism of action with mutational bias at the Arg15 residue.

Characterization of the molecular genetic pathology in patients with 11ß-hydroxylase deficiency.

OBJECTIVE: Steroid 11ß-hydroxylase (CYP11B1) deficiency (11OHD) is the second most common form of congenital adrenal hyperplasia. Nonclassic or mild 11OHD appears to be a rare condition. Our study assessed the residual CYP11B1 function of detected mutations, adding to the spectrum of mild 11OHD, and illustrates the variability of the clinical presentation of 11OHD. PATIENTS AND METHODS: Five patients presented with mild to moderate 11OHD. Two women presented with mild hirsutism and in one case with secondary amenorrhoea. Two men presented with precocious pseudopuberty, gynaecomastia and elevated blood pressure. One 46,XX female patient was diagnosed with virilization of the external genitalia 2 years after birth. Direct DNA sequencing was carried out to perform CYP11B1 mutation analysis. The CYP11B1 mutations were functionally characterized using an in vitro expression system. RESULTS: CYP11B1-inactivating mutations were detected in all patients. Two novel missense mutations (p.P42L and p.A297V) and the previously characterized p.R143W mutation had residual CYP11B1 activities between 10% and 27%. A novel p.L382R and the previously uncharacterized p.G444D mutation both caused complete loss of CYP11B1 enzymatic activity. CONCLUSION: Mutations causing partial impairment of 11ß-hydroxylase activity (residual activity of 10% or above) are associated with a less severe clinical presentation of 11OHD, which can be classified as a nonclassic form. Our data demonstrate that patients with nonclassic 11OHD can present with androgen excess, precocious pseudopuberty and increased blood pressure. Timely diagnosis of nonclassic 11OHD and consequently initiation of personalized treatment is essential to prevent co-morbidities caused by androgen excess and hypertension.

Cardiac tissue engineering and regeneration using cell-based therapy.

Stem cell therapy and tissue engineering represent a forefront of current research in the treatment of heart disease. With these technologies, advancements are being made into therapies for acute ischemic myocardial injury and chronic, otherwise nonreversible, myocardial failure. The current clinical management of cardiac ischemia deals with reestablishing perfusion to the heart but not dealing with the irreversible damage caused by the occlusion or stenosis of the supplying vessels. The applications of these new technologies are not yet fully established as part of the management of cardiac diseases but will become so in the near future. The discussion presented here reviews some of the pioneering works at this new frontier. Key results of allogeneic and autologous stem cell trials are presented, including the use of embryonic, bone marrow-derived, adipose-derived, and resident cardiac stem cells.

Impact of month of birth on the development of autoimmune thyroid disease in the United Kingdom and Europe.

CONTEXT: Viral/bacterial infection is proposed as a trigger for the autoimmune thyroid diseases (AITD): Graves' disease (GD) and Hashimoto's thyroiditis (HT). Previous studies in European Caucasian AITD subjects found higher birth rates in the autumn/winter, suggesting those born in the autumn/winter experience increased viral/bacterial exposure after birth, impacting upon immune system development and predisposing to AITD later in life. OBJECTIVE: Month of birth effects were investigated in three independent European Caucasian AITD datasets. DESIGN: Variation in GD and HT onset was compared across months and seasons, with fluctuations across all 12 months analyzed using a Walter-Elwood test. SETTING: The study was conducted at a research laboratory. PATIENTS: National UK Caucasian AITD Case Control Collection (2746 GD and 502 HT compared with 1 423 716 UK births), National UK Caucasian GD Family Collection (239 GD and 227 unaffected siblings), and OXAGEN AITD Caucasian Family Collection (885 GD, 717 HT, and 794 unaffected siblings of European Caucasian decent). MAIN OUTCOME MEASURES: Case-control and family-based association studies were measured. RESULTS: No consistent month of birth effects were detected in GD females or males across all three collections. In HT females from the OXAGEN AITD Caucasian Family Collection, slightly higher birth rates were detected in autumn (Walter's test statistic = 7.47, P = .024) however, this was not seen in the HT females from the case-control cohort. CONCLUSION: Our results suggest in UK/Northern European Caucasian GD subjects, month of birth does not impact on AITD development. Although some month of birth effects for HT females in one collection cannot be excluded, only further work in larger European Caucasian AITD collections can confirm these effects.

Gene-centric meta-analysis in 87,736 individuals of European ancestry identifies multiple blood-pressure-related loci.

Blood pressure (BP) is a heritable risk factor for cardiovascular disease. To investigate genetic associations with systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP), we genotyped ~50,000 SNPs in up to 87,736 individuals of European ancestry and combined these in a meta-analysis. We replicated findings in an independent set of 68,368 individuals of European ancestry. Our analyses identified 11 previously undescribed associations in independent loci containing 31 genes including PDE1A, HLA-DQB1, CDK6, PRKAG2, VCL, H19, NUCB2, RELA, HOXC@ complex, FBN1, and NFAT5 at the Bonferroni-corrected array-wide significance threshold (p < 6 × 10(-7)) and confirmed 27 previously reported associations. Bioinformatic analysis of the 11 loci provided support for a putative role in hypertension of several genes, such as CDK6 and NUCB2. Analysis of potential pharmacological targets in databases of small molecules showed that ten of the genes are predicted to be a target for small molecules. In summary, we identified previously unknown loci associated with BP. Our findings extend our understanding of genes involved in BP regulation, which may provide new targets for therapeutic intervention or drug response stratification.

Progress in the identification of responsible genes and molecular mechanisms in primary aldosteronism.

Aldosterone, the mineralocorticoid hormone, plays an important role in blood regulation. Autonomous secretion of aldosterone is known as primary aldosteronism (PA), the most common cause of secondary hypertension. PA comprises a group of heterogenous disorders which makes their classification and management challenging. With the advent of the genomic era several germline and somatic mutations have been identified that are involved in the pathogenesis of primary aldosteronism. This article will review our current knowledge of the genetic mechanisms of familial hyperaldosterism, somatic mutations in genes encoding electrolyte channels and other potential genetic mechanisms implicated in the dysregulation of aldosterone production from in vitro and animal models. There is potential for novel targeted therapies and diagnosis for subsets of patient. The challenges to achieve them are highlighted in this review.

Quantitative variation in plasma angiotensin-I converting enzyme activity shows allelic heterogeneity in the ABO blood group locus.

Angiotensin-I converting enzyme (ACE) occupies a pivotal role in cardiovascular homeostasis. Major loci for plasma ACE have been identified at ACE on Chromosome 17 and at ABO on Chromosome 9. We sought to characterise the genetic architecture of plasma ACE at finer resolution in two populations. We carried out a GWAS in 1810 individuals of Japanese ethnicity; this identified signals at ACE and ABO that together accounted for nearly half of the population variability of the trait. We conducted measured haplotype analysis at the ABO locus in 1425 members of 248 British families using haplotypes of three SNPs, which together tagged the alleles responsible for the principal blood group antigens A1, A2, B and O. Type O alleles were associated with intermediate plasma ACE activity compared to Type A1 alleles (in whom plasma ACE activity was ∼36% lower) and Type B alleles (in whom plasma ACE activity was ∼36% higher). We demonstrated heterogeneity among A alleles: A2 alleles were associated with plasma ACE activity that was very similar to the O alleles. Variation at ACE accounted for 35% of the trait variance, and variation at ABO accounted for 15%. A further 10% could be ascribed to polygenic effects.

MicroRNA-24 is a novel regulator of aldosterone and cortisol production in the human adrenal cortex.

Dysregulation of aldosterone or cortisol production can predispose to hypertension, as seen in aldosterone-producing adenoma, a form of primary aldosteronism. We investigated the role of microRNA (miRNA) in their production, with particular emphasis on the CYP11B1 (11ß-hydroxylase) and CYP11B2 (aldosterone synthase) genes, which produce the enzymes responsible for the final stages of cortisol and aldosterone biosynthesis, respectively. Knockdown of Dicer1, a key enzyme in miRNA maturation, significantly altered CYP11B1 and CYP11B2 expression in a human adrenocortical cell line. Screening of nondiseased human adrenal and aldosterone-producing adenoma samples yielded reproducible but distinctive miRNA expression signatures for each tissue type, with levels of certain miRNA, including microRNA-24 (miR-24), differing significantly between the 2. Bioinformatic analysis identified putative binding sites for several miRNA, including miR-24, in the 3' untranslated region of CYP11B1 and CYP11B2 mRNAs. In vitro manipulation of miR-24 confirmed its ability to modulate CYP11B1 and CYP11B2 expression, as well as cortisol and aldosterone production. This study demonstrates that Dicer-dependent miRNA, including miR-24, can post-transcriptionally regulate expression of the CYP11B1 and CYP11B2 genes. Normal adrenal tissue and aldosterone-producing adenoma differ significantly and reproducibly in their miRNA expression profiles, with miR-24 significantly downregulated in the latter. Adrenal miRNA may, therefore, be a novel and valid target for the therapeutic manipulation of corticosteroid biosynthesis.

Ischemic mitral regurgitation: mechanisms, intraoperative echocardiographic evaluation, and surgical considerations.

Ischemic mitral regurgitation (IMR) is a subcategory of functional rather than organic, mitral valve (MV) disease. Whether reversible or permanent, left ventricular remodeling creates IMR that is complex and multifactorial. A comprehensive TEE examination in patients with IMR may have important implications for perioperative clinical decision making. Several TEE measures predictive of MV repair failure have been identified. Current practice among most surgeons is to typically repair the MV in patients with IMR. MV replacement is usually reserved for situations in which the valve cannot be reasonably repaired, or repair is unlikely to be tolerated clinically.

Assessment of the accuracy and reproducibility of adrenal volume measurements using MRI and its relationship with corticosteroid phenotype: a normal volunteer pilot study.

OBJECTIVE: The significant role of corticosteroids in hypertension and cardiovascular disease highlights the importance of the adrenal gland in these disorders. The ability to correlate corticosteroid production with adrenal volume offers a novel research tool and intermediate phenotype in cardiovascular disease. The aim of this study was to develop and validate the use of magnetic resonance imaging (MRI) in adrenal volume assessment and investigate whether this associates with corticosteroid production. DESIGN/METHODS: Twenty normotensive men underwent noncontrast 1·5T MRI scanning of adrenals, measurement of blood pressure and plasma corticosteroids. Left adrenal volume was calculated twice using standard segmentation software by four independent observers with differing levels of clinical expertise and segmentation experience. To optimize this process, adrenal 'phantoms' with known fixed volumes underwent MRI scanning and analysis by two observers. RESULTS: Intra-observer coefficients of repeatability (CoRs) in phantoms ranged from 0·23 to 0·43 ml (interobserver CoR 0·48 ml). In the subject group, mean adrenal volumes were 3·99-5·82 ml with intra-observer CoRs 0·27-1·94 ml. Interobserver variability was 2·73 ml. Segmentation expertise was the main factor affecting variability, with experienced observers having the lowest CoRs; clinical knowledge was a factor when combined with segmentation experience. Mean adrenal volume correlated with plasma glucocorticoids (r = 0·523, P < 0·05) and aldosterone (r = 0·515, P < 0·05) for the most experienced observer only. CONCLUSIONS: Measurement of adrenal volume using MRI is challenging; most accurate volumes are achieved using a single observer with both segmentation experience and anatomical knowledge. The data also provide novel preliminary evidence that adrenal gland volume may be associated with plasma corticosteroid concentrations supporting further study of adrenal volume and steroid production across a range of blood pressures.

Urinary sodium excretion is the main determinant of mineralocorticoid excretion rates in patients with chronic kidney disease.

BACKGROUND: Blockade of the mineralocorticoid receptor (MR) in patients with chronic kidney disease (CKD) improves surrogate cardiovascular outcomes, such as left ventricular mass. Animal models of renal disease support a pathological role of mineralocorticoids, in the context of a high sodium intake. We aimed to assess the regulation of mineralocorticoid biosynthesis in patients with CKD. METHODS: Seventy patients with CKD stages 3/4 and 30 patients with essential hypertension (EH) were recruited. Patients underwent detailed clinical phenotyping, drug history and biochemical assessment. Patients completed a 24-h urine collection for measurement of urinary tetrahydroaldosterone (THALDO) and tetrahydrocorticosterone (THDOC) excretion rates (measured using gas chromatography-mass spectrometry) and urinary electrolytes. The factors which correlated significantly with THALDO and THDOC excretion were entered into linear regression models. RESULTS: Patients with EH and CKD were well matched with no significant differences in gender, age or weight. The mean estimated glomerular filtration rate (eGFR) in CKD patients was 38.6/min/1.73 m(2). The mean urinary excretion rates of THALDO, THDOC and 24-h urinary sodium (24-h USod) were not significantly different between CKD and EH patients. The level of renal function did not correlate with THALDO or THDOC excretion. In patients with CKD, 24-h USodium (r = 0.614, P < 0.001) and 24-h UPotassium (r = 0.538, P < 0.001) were positively correlated with THALDO excretion. On multivariate linear regression analysis, 24-h USod was the strongest independent predictor (P = 0.004) of THALDO and THDOC excretion in CKD. In patients with EH, no relationship was seen between mineralocorticoid excretion and 24-h urinary sodium excretion. CONCLUSIONS: In patients with CKD, 24-h urinary sodium excretion is the strongest positive predictor of urinary mineralocorticoid excretion. The nature of this relationship is unexpected, novel, not seen in patients with EH and may explain the association seen between high urinary sodium excretion, mineralocorticoids and poor outcomes in patients with CKD.

Common polymorphisms in the CYP11B1 and CYP11B2 genes: evidence for a digenic influence on hypertension.

The locus encompassing the corticosteroidogenic genes CYP11B2 and CYP11B1 is of potential importance in essential hypertension. We analyzed the association of polymorphisms at this locus with risk of essential hypertension, using 2 white case-control collections for discovery (n=3340) and confirmation (n=2929). Single-marker and haplotype analyses were performed, with the CYP11B2 Intron 2 Conversion polymorphism showing strongest association with hypertension in both cohorts and in combined analysis (odds ratio=1.16, P=8.54×10(-5)). The CYP11B1 ACA haplotype associated with increased risk of hypertension relative to the alternative, GTC (odds ratio=1.11; P=7.4×10(-3)), whereas the CYP11B2 TWtC haplotype seemed protective relative to the contrasting CConvT (odds ratio=0.88, P=2.2×10(-3)). Analysis spanning the whole CYP11B1/CYP11B2 locus showed that haplotypes associated with raised risk of hypertension tend to coexist. Functional analysis of heterozygous human adrenal tissue demonstrated decreased CYP11B2 expression and increased CYP11B1 expression for those alleles associating with reduced risk of hypertension. These results confirm the hypertensive influence of this locus, with data suggesting a complex digenic mechanism whereby altered relative CYP11B1 and CYP11B2 gene expression could have a chronic effect on enzyme activity and corticosteroid synthesis.

Demonstration of blood pressure-independent noninfarct myocardial fibrosis in primary aldosteronism: a cardiac magnetic resonance imaging study.

BACKGROUND: Primary aldosteronism (PA) is common and associates with excess cardiovascular morbidity independent of blood pressure. Exposure to aldosterone and sodium leads to cardiac fibrosis and hypertrophy in humans and animals possibly mediated by inflammation and oxidative stress. We aimed to clarify the effects of aldosterone excess on myocardial structure and composition in human subjects with PA and essential hypertension using contrast-enhanced cardiac magnetic resonance imaging as well as explore the mechanistic basis for any observed differences. METHODS AND RESULTS: Twenty-seven subjects with recently diagnosed PA and 54 essential hypertension controls were recruited. Subjects underwent gadolinium-enhanced cardiac magnetic resonance; noninfarct related myocardial fibrosis was identified by a diffuse pattern of late gadolinium enhancement. Patients also underwent assessment of pulse wave velocity, measurement of circulating superoxide anion and C-reactive protein, as well as blood pressure and biochemical assessment. Subjects were well matched with no difference in severity or duration of hypertension. There was a significant increase in the frequency of noninfarct late gadolinium enhancement in PA (70%) when compared with essential hypertension subjects (13%; P<0.0001) with no difference in left ventricular mass. Pulse wave velocity, superoxide, and C-reactive protein were significantly higher in subjects with PA. CONCLUSIONS: These data illustrate that patients with PA exhibit frequent myocardial fibrosis as demonstrated by late gadolinium enhancement using cardiac magnetic resonance imaging; this finding is independent of blood pressure. This may be mediated partly through inflammation and oxidative stress. This study highlights the importance of specific targeting of aldosterone excess as well as blood pressure reduction to minimize cardiac morbidity in PA.

APEX1 regulation of aldosterone synthase gene transcription is disrupted by a common polymorphism in humans.

RATIONALE: The genetic mechanisms underlying hypertension are unclear, but relative aldosterone excess, present in ≈10% of hypertensive patients, is known to be a heritable trait. This phenotype associates with a T/C single nucleotide polymorphism (SNP) at position -344 of the aldosterone synthase gene (CYP11B2). However, deletion of this SNP has no effect on gene transcription. We have identified another T/C SNP at -1651, in tight linkage disequilibrium with the -344 SNP and here investigate its functional effect on CYP11B2 transcription. OBJECTIVE: We assessed the effect on transcriptional activity of the -1651 T/C SNP in vivo and in vitro and propose the mechanism by which transcriptional activity is altered. METHODS AND RESULTS: We demonstrated that the SNP at -1651 exerts significant allele-dependent effects on CYP11B2 transcription. We confirm binding of the transcriptional repressor APEX1 to -1651T, which is associated with reduced transcriptional activity in relation to the less strongly bound -1651C. We show that inhibiting APEX1 by small molecule inhibition or small interfering RNA (SiRNA) leads to increased CYP11B2 transcription. In addition, overexpression of APEX1 is associated with reduced transcriptional activity. Finally, we also show that -1651T associates with lower excretion rates of aldosterone metabolites in human subjects. CONCLUSIONS: We conclude that APEX1 is a novel transcriptional repressor of CYP11B2 and that differential APEX1 binding at -1651 of CYP11B2 results in altered gene expression. This mechanism may contribute to the observed relationship between CYP11B2 genotype and aldosterone phenotype in a subgroup of hypertensive patients.