Whole blood methylome-derived features to discriminate endocrine hypertension

Background

Arterial hypertension represents a worldwide health burden and a major risk factor for cardiovascular morbidity and mortality. Hypertension can be primary (primary hypertension, PHT), or secondary to endocrine disorders (endocrine hypertension, EHT), such as Cushing's syndrome (CS), primary aldosteronism (PA), and pheochromocytoma/paraganglioma (PPGL). Diagnosis of EHT is currently based on hormone assays. Efficient detection remains challenging, but is crucial to properly orientate patients for diagnostic confirmation and specific treatment. More accurate biomarkers would help in the diagnostic pathway. We hypothesized that each type of endocrine hypertension could be associated with a specific blood DNA methylation signature, which could be used for disease discrimination. To identify such markers, we aimed at exploring the methylome profiles in a cohort of 255 patients with hypertension, either PHT (n = 42) or EHT (n = 213), and at identifying specific discriminating signatures using machine learning approaches.

Results

Unsupervised classification of samples showed discrimination of PHT from EHT. CS patients clustered separately from all other patients, whereas PA and PPGL showed an overall overlap. Global methylation was decreased in the CS group compared to PHT. Supervised comparison with PHT identified differentially methylated CpG sites for each type of endocrine hypertension, showing a diffuse genomic location. Among the most differentially methylated genes, FKBP5 was identified in the CS group. Using four different machine learning methods—Lasso (Least Absolute Shrinkage and Selection Operator), Logistic Regression, Random Forest, and Support Vector Machine—predictive models for each type of endocrine hypertension were built on training cohorts (80% of samples for each hypertension type) and estimated on validation cohorts (20% of samples for each hypertension type). Balanced accuracies ranged from 0.55 to 0.74 for predicting EHT, 0.85 to 0.95 for predicting CS, 0.66 to 0.88 for predicting PA, and 0.70 to 0.83 for predicting PPGL.

Conclusions

The blood DNA methylome can discriminate endocrine hypertension, with methylation signatures for each type of endocrine disorder.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01347-y.

Preanalytical Pitfalls in Untargeted Plasma Nuclear Magnetic Resonance Metabolomics of Endocrine Hypertension

Despite considerable morbidity and mortality, numerous cases of endocrine hypertension (EHT) forms, including primary aldosteronism (PA), pheochromocytoma and functional paraganglioma (PPGL), and Cushing’s syndrome (CS), remain undetected. We aimed to establish signatures for the different forms of EHT, investigate potentially confounding effects and establish unbiased disease biomarkers. Plasma samples were obtained from 13 biobanks across seven countries and analyzed using untargeted NMR metabolomics. We compared unstratified samples of 106 PHT patients to 231 EHT patients, including 104 PA, 94 PPGL and 33 CS patients. Spectra were subjected to a multivariate statistical comparison of PHT to EHT forms and the associated signatures were obtained. Three approaches were applied to investigate and correct confounding effects. Though we found signatures that could separate PHT from EHT forms, there were also key similarities with the signatures of sample center of origin and sample age. The study design restricted the applicability of the corrections employed. With the samples that were available, no biomarkers for PHT vs. EHT could be identified. The complexity of the confounding effects, evidenced by their robustness to correction approaches, highlighted the need for a consensus on how to deal with variabilities probably attributed to preanalytical factors in retrospective, multicenter metabolomics studies.

Mitochondrial DNAs provide insight into trypanosome phylogeny and molecular evolution

Background

Trypanosomes are single-celled eukaryotic parasites characterised by the unique biology of their mitochondrial DNA. African livestock trypanosomes impose a major burden on agriculture across sub-Saharan Africa, but are poorly understood compared to those that cause sleeping sickness and Chagas disease in humans. Here we explore the potential of the maxicircle, a component of trypanosome mitochondrial DNA to study the evolutionary history of trypanosomes.

Results

We used long-read sequencing to completely assemble maxicircle mitochondrial DNA from four previously uncharacterized African trypanosomes, and leveraged these assemblies to scaffold and assemble a further 103 trypanosome maxicircle gene coding regions from published short-read data. While synteny was largely conserved, there were repeated, independent losses of Complex I genes. Comparison of pre-edited and non-edited genes revealed the impact of RNA editing on nucleotide composition, with non-edited genes approaching the limits of GC loss. African tsetse-transmitted trypanosomes showed high levels of RNA editing compared to other trypanosomes. The gene coding regions of maxicircle mitochondrial DNAs were used to construct time-resolved phylogenetic trees, revealing deep divergence events among isolates of the pathogens Trypanosoma brucei and T. congolense.

Conclusions

Our data represents a new resource for experimental and evolutionary analyses of trypanosome phylogeny, molecular evolution and function. Molecular clock analyses yielded a timescale for trypanosome evolution congruent with major biogeographical events in Africa and revealed the recent emergence of Trypanosoma brucei gambiense and T. equiperdum, major human and animal pathogens.

Prediction of hyperaldosteronism subtypes when adrenal vein sampling is unilaterally successful

OBJECTIVE

Adrenal venous sampling (AVS) is the gold standard to discriminate patients with unilateral primary aldosteronism (UPA) from bilateral disease (BPA). AVS is technically demanding and in cases of unsuccessful cannulation of adrenal veins, the results may not always be interpreted. The aim of our study was to develop diagnostic models to distinguish UPA from BPA, in cases of unilateral successful AVS and the presence of contralateral suppression of aldosterone secretion.

DESIGN

Retrospective evaluation of 158 patients referred to a tertiary hypertension unit who underwent AVS. We randomly assigned 110 patients to a training cohort and 48 patients to a validation cohort to develop and test the diagnostic models.

METHODS

Supervised machine learning algorithms and regression models were used to develop and validate two prediction models and a simple 19-point score system to stratify patients according to their subtype diagnosis.

RESULTS

Aldosterone levels at screening and after confirmatory testing, lowest potassium, ipsilateral and contralateral imaging findings at CT scanning, and contralateral ratio at AVS, were associated with a diagnosis of UPA and were included in the diagnostic models. Machine learning algorithms correctly classified the majority of patients both at training and validation (accuracy: 82.9-95.7%). The score system displayed a sensitivity/specificity of 95.2/96.9%, with an AUC of 0.971. A flow-chart integrating our score correctly managed all patients except 3 (98.1% accuracy), avoiding the potential repetition of 77.2% of AVS procedures.

CONCLUSIONS

Our score could be integrated in clinical practice and guide surgical decision-making in patients with unilateral successful AVS and contralateral suppression.

Patients With Primary Aldosteronism Respond to Unilateral Adrenalectomy With Long-Term Reduction in Salt Intake

CONTEXT

High dietary salt intake is known to aggravate arterial hypertension. This effect could be of particular relevance in the setting of primary aldosteronism (PA), which is associated with cardiovascular damage independent of blood pressure levels. The aim of this study was to determine the impact of therapy on salt intake in PA patients.

PATIENTS AND METHODS

A total of 148 consecutive PA patients (66 with unilateral and 82 with bilateral PA) from the database of the German Conn's Registry were included. Salt intake was quantified by 24-hour urinary sodium excretion before and after initiation of PA treatment.

STUDY DESIGN

Observational longitudinal cohort study.

SETTING

Tertiary care hospital.

RESULTS

At baseline, unilateral PA patients had a significantly higher urinary sodium excretion than patients with bilateral disease (205 vs 178 mmol/d, P = 0.047). Higher urinary sodium excretion correlated with an increased cardiovascular risk profile including proteinuria, impaired lipid, and glucose metabolism and was associated with higher daily doses of antihypertensive drugs to achieve blood pressure control. In unilateral disease, urinary sodium excretion dropped spontaneously to 176 mmol/d (P = 0.012) 1 year after unilateral adrenalectomy and remained low at 3 years of follow-up (174 mmol/d). In contrast, treatment with mineralocorticoid receptor antagonists (MRA) in bilateral PA patients was not associated with a significant change in urinary sodium excretion at follow-up (179 mmol/d vs 183 mmol/d).

CONCLUSION

PA patients consuming a high-salt diet, estimated based on urinary sodium excretion, respond to adrenalectomy with a significant reduction of salt intake, in contrast to MRA treatment.

Computed Tomography and Adrenal Venous Sampling in the Diagnosis of Unilateral Primary Aldosteronism

Unilateral primary aldosteronism is the most common surgically correctable form of endocrine hypertension and is usually differentiated from bilateral forms by adrenal venous sampling (AVS) or computed tomography (CT). Our objective was to compare clinical and biochemical postsurgical outcomes of patients with unilateral primary aldosteronism diagnosed by CT or AVS and identify predictors of surgical outcomes. Patient data were obtained from 18 internationally distributed centers and retrospectively analyzed for clinical and biochemical outcomes of adrenalectomy of patients with surgical management based on CT (n=235 patients, diagnosed from 1994-2016) or AVS (526 patients, diagnosed from 1994-2015) using the standardized PASO (Primary Aldosteronism Surgical Outcome) criteria. Biochemical outcomes were highly different according to surgical management approach with a smaller proportion in the CT group achieving complete biochemical success (188 of 235 [80%] patients versus 491 of 526 [93%], P<0.001) and a greater proportion with absent biochemical success (29 of 235 [12%] versus 10 of 526 [2%], P<0.001). A diagnosis by CT was associated with a decreased likelihood of complete biochemical success compared with AVS (odds ratio, 0.28; 0.16-0.50; P<0.001). Clinical outcomes were not significantly different, but the absence of a postsurgical elevated aldosterone-to-renin ratio was a strong marker of complete clinical success (odds ratio, 14.81; 1.76-124.53; P=0.013) in the CT but not in the AVS group. In conclusion, patients diagnosed by CT have a decreased likelihood of achieving complete biochemical success compared with a diagnosis by AVS.

Comparative Genomics and Transcriptome Profiling in Primary Aldosteronism

Primary aldosteronism is the most common form of endocrine hypertension with a prevalence of 6% in the general population with hypertension. The genetic basis of the four familial forms of primary aldosteronism (familial hyperaldosteronism FH types I–IV) and the majority of sporadic unilateral aldosterone-producing adenomas has now been resolved. Familial forms of hyperaldosteronism are, however, rare. The sporadic forms of the disease prevail and these are usually caused by either a unilateral aldosterone-producing adenoma or bilateral adrenal hyperplasia. Aldosterone-producing adenomas frequently carry a causative somatic mutation in either of a number of genes with the KCNJ5 gene, encoding an inwardly rectifying potassium channel, a recurrent target harboring mutations at a prevalence of more than 40% worldwide. Other than genetic variations, gene expression profiling of aldosterone-producing adenomas has shed light on the genes and intracellular signalling pathways that may play a role in the pathogenesis and pathophysiology of these tumors.

Abstract 054: Visinin Like Protein 1 Regulation of Aldosterone Biosynthesis

Visinin-Like Protein-1(Vsnl1) is a member of the EF-hand calcium sensor proteins. Its mRNA was found to be upregulated in aldosterone-producing adenomas and to be expressed in the zona glomerulosa (ZG) of the rat and human adrenal. We studied the expression pattern of Vsnl1 and its co-localization with the CYP11B2 enzyme and ZG marker Dlk1 (ZOG) using double and triple immunofluorescence in adrenal glands of rats on normal, high and low sodium diets and the effect of Vsnl1 on calcium mobilization and aldosterone biosynthesis in the human adrenocarcinoma cell line, the HAC15 cell. In rat adrenals, Vsnl1 was expressed only in ZG, in the same cells as Dlk1, in both functional and undifferentiated ZG cells. CYP11B2 co-localized with Vsnl1 in nearly all ZG cells of rats on a low sodium diet. Co-expression of CYP11B2 with Vsnl1 in adrenals of rats on normal and high sodium diets was significantly less. HAC15 were transduced with a lentivirus carrying Vsnl1 or an empty virus. Three days later cells were incubated with vehicle, A-II 10 nM, Forskolin 10μM, or potassium 16 mM. Aldosterone and cortisol were measured after 24 hr. Basal secretion of aldosterone was not increased; cortisol was. Aldosterone and cortisol secretion were greater after A-II, forskolin or potassium stimulation in cells overexpressing Vsnl1. Intracellular calcium measured by Fluo-4 AM dye and proliferation were increased by Vsnl1 overexpression. HAC15 cells were transduced with 2 different shRNA for Vsnl1. Aldosterone synthesis was reduced in HAC15 cells transduced with the shRNA for Vsnl1 stimulated with A-II. Vsnl1 has a myristoylation consensus sequence at the N-terminal domain. Site directed mutagenesis of Vsnl1 at the 2 position (G2A) resulted in a significant decrease in the aldosterone response to A-II. In summary, the calcium sensor protein Vsnl1 is ZG specific and detected in both steroidogenically active and inactive cells, as well as undifferentiated cells in the subcapsular area of the rat adrenal. Vsnl1 expression and activity in HAC15 cell correlate positively with calcium mobilization, proliferation and aldosterone synthesis.

Outcomes after adrenalectomy for unilateral primary aldosteronism: an international consensus on outcome measures and analysis of remission rates in an international cohort

BACKGROUND

Although unilateral primary aldosteronism is the most common surgically correctable cause of hypertension, no standard criteria exist to classify surgical outcomes. We aimed to create consensus criteria for clinical and biochemical outcomes and follow-up of adrenalectomy for unilateral primary aldosteronism and apply these criteria to an international cohort to analyse the frequency of remission and identify preoperative determinants of successful outcome.

METHODS

The Primary Aldosteronism Surgical Outcome (PASO) study was an international project to develop consensus criteria for outcomes and follow-up of adrenalectomy for unilateral primary aldosteronism. An international panel of 31 experts from 28 centres, including six endocrine surgeons, used the Delphi method to reach consensus. We then retrospectively analysed follow-up data from prospective cohorts for outcome assessment of patients diagnosed with unilateral primary aldosteronism by adrenal venous sampling who had undergone a total adrenalectomy, consecutively included from 12 referral centres in nine countries. On the basis of standardised criteria, we determined the proportions of patients achieving complete, partial, or absent clinical and biochemical success in accordance with the consensus. We then used logistic regression analyses to identify preoperative factors associated with clinical and biochemical outcomes.

FINDINGS

Consensus was reached for criteria for six outcomes (complete, partial, and absent success of clinical and biochemical outcomes) based on blood pressure, use of antihypertensive drugs, plasma potassium and aldosterone concentrations, and plasma renin concentrations or activities. Consensus was also reached for two recommendations for the timing of follow-up assessment. For the international cohort analysis, we analysed clinical data from 705 patients recruited between 1994 and 2015, of whom 699 also had biochemical data. Complete clinical success was achieved in 259 (37%) of 705 patients, with a wide variance (range 17-62), and partial clinical success in an additional 334 (47%, range 35-66); complete biochemical success was seen in 656 (94%, 83-100) of 699 patients. Female patients had a higher likelihood of complete clinical success (odds ratio [OR] 2·25, 95% CI 1·40-3·62; p=0·001) and clinical benefit (complete plus partial clinical success; OR 2·89, 1·49-5·59; p=0·002) than male patients. Younger patients had a higher likelihood of complete clinical success (OR 0·95 per extra year, 0·93-0·98; p<0·001) and clinical benefit (OR 0·95 per extra year, 0·92-0·98; p=0·004). Higher levels of preoperative medication were associated with lower levels of complete clinical success (OR 0·80 per unit increase, 0·70-0·90; p<0·001).

INTERPRETATION

These standardised outcome criteria are relevant for the assessment of the success of surgical treatment in individual patients and will allow the comparison of outcome data in future studies. The variable baseline clinical characteristics of our international cohort contributed to wide variation in clinical outcomes. Most patients derive clinical benefit from adrenalectomy, with younger patients and female patients more likely to have a favourable surgical outcome. Screening for primary aldosteronism should nonetheless be done in every individual fulfilling US Endocrine Society guideline criteria because biochemical success without clinical success is by itself clinically important and older women and men can also derive post-operative clinical benefit.

FUNDING

European Research Council; European Union's Horizon 2020; Else Kröner-Fresenius Stiftung; Netherlands Organisation for Health Research and Development-Medical Sciences; Japanese Ministry of Health, Labour and Welfare; Ministry of Health, Slovenia; US National Institutes of Health; and CONICYT-FONDECYT (Chile).

Is There a Role for Genomics in the Management of Hypertension?

Hypertension (HTN) affects about 1 billion people worldwide and the lack of a single identifiable cause complicates its treatment. Blood pressure (BP) levels are influenced by environmental factors, but there is a strong genetic component. Linkage analysis has identified several genes involved in Mendelian forms of HTN and the associated pathophysiological mechanisms have been unravelled, leading to targeted therapies. The majority of these syndromes are due to gain-of-function or loss-of-functions mutations, resulting in an alteration of mineralocorticoid, glucocorticoid, or sympathetic pathways. The diagnosis of monogenic forms of HTN has limited practical implications on the population and a systematic genetic screening is not justifiable. Genome-wide linkage and association studies (GWAS) have identified single nucleotide polymorphisms (SNPs), which influence BP. Forty-three variants have been described with each SNP affecting systolic and diastolic BP by 1.0 and 0.5 mmHg, respectively. Taken together Mendelian inheritance and all GWAS-identified HTN-associated variants explain 2–3% of BP variance. Epigenetic modifications, such as DNA methylation, histone modification and non-coding RNAs, have become increasingly recognized as important players in BP regulation and may justify a further part of missing heritability. In this review, we will discuss how genetics and genomics may assist clinicians in managing patients with HTN.

Recent Developments in Primary Aldosteronism

Primary aldosteronism (PA) is the most frequent endocrine cause of secondary arterial hypertension. Sporadic forms of PA caused mainly by an aldosterone producing adenoma (APA) or idiopathic adrenal hyperplasia (IAH) predominate; in contrast, familial forms (familial hyperaldosteronism types I, II and III) affect only a minor proportion of PA patients. Patient based registries and biobanks, international networks and next generation sequencing technologies have emerged over recent years. Somatic hot-spot mutations in the potassium channel GIRK4 (encoded by KCNJ5), in ATPases and a L-type voltage-gated calcium-channel correlate with the autonomous aldosterone production in approximately half of all APAs. The recently discovered form FH III is caused by different germline KCNJ5 mutations with variable clinical presentations and severity. Autoantibodies to the angiotensin II Type 1 receptor have been identified in patients with PA and possibly play a pathophysiological role in the development of PA. Adrenal vein sampling (AVS) represents the gold standard in differentiating unilateral and bilateral forms of PA. Recent consensus papers have tried to implement current guidelines in order to standardise the technique of AVS. New techniques like segmental AVS might allow a finer mapping of the aldosterone production within the adrenal gland. The measurement of the steroids 18-hydroxycortisol and 18-oxocortisol by liquid chromatography tandem mass spectrometry has been shown to be useful to distinguish between unilateral and bilateral forms of PA.

Mass Spectrometry-Based Adrenal and Peripheral Venous Steroid Profiling for Subtyping Primary Aldosteronism

BACKGROUND

Differentiating patients with primary aldosteronism caused by aldosterone-producing adenomas (APAs) from those with bilateral adrenal hyperplasia (BAH), which is essential for choice of therapeutic intervention, relies on adrenal venous sampling (AVS)-based measurements of aldosterone and cortisol. We assessed the utility of LC-MS/MS-based steroid profiling to stratify patients with primary aldosteronism.

METHODS

Fifteen adrenal steroids were measured by LC-MS/MS in peripheral and adrenal venous plasma from AVS studies for 216 patients with primary aldosteronism at 3 tertiary referral centers. Ninety patients were diagnosed with BAH and 126 with APAs on the basis of immunoassay-derived adrenal venous aldosterone lateralization ratios.

RESULTS

Among 119 patients confirmed to have APAs at follow-up, LC-MS/MS-derived lateralization ratios of aldosterone normalized to cortisol, dehydroepiandrosterone, and androstenedione were all higher (P < 0.0001) than immunoassay-derived ratios. The hybrid steroids, 18-oxocortisol and 18-hydroxycortisol, also showed lateralized secretion in 76% and 35% of patients with APAs. Adrenal venous concentrations of glucocorticoids and androgens were bilaterally higher in patients with BAH than in those with APAs. Consequently, peripheral plasma concentrations of 18-oxocortisol were 8.5-fold higher, whereas concentrations of cortisol, corticosterone, and dehydroepiandrosterone were lower in patients with APAs than in those with BAH. Correct classification of 80% of cases of APAs vs BAH was thereby possible by use of a combination of steroids in peripheral plasma.

CONCLUSIONS

LC-MS/MS-based steroid profiling during AVS achieves higher aldosterone lateralization ratios in patients with APAs than immunoassay. LC-MS/MS also enables multiple measures for discriminating unilateral from bilateral aldosterone excess, with potential use of peripheral plasma for subtype classification.

KCNJ5 Mutations: Sex, Salt and Selection

Somatic mutations have been identified in the KCNJ5 gene (encoding the potassium channel GIRK4) in aldosterone-producing adenomas (APA). Most of these mutations are located in or near the selectivity filter of the GIRK4 channel pore and several have been shown to lead to the constitutive overproduction of aldosterone. KCNJ5 mutations in APA are more frequent in women; however, this gender dimorphism is a reported phenomenon of Western but not East Asian populations. In this review we discuss some of the issues that could potentially underlie this observation.

Steroid Hormone Production in Patients with Aldosterone Producing Adenomas

Primary aldosteronism encompasses 2 major underlying causes: (1) aldosterone producing adenoma and (2) bilateral adrenal hyperplasia. In addition to the aldosterone excess, increased production of other compounds of the steroidogenic pathways may be involved. Until recently, most studies examined the production of steroids other than aldosterone in tumor tissue, urine, or peripheral plasma samples, but several new studies have also addressed steroid levels in adrenal venous blood samples using liquid chromatography tandem mass spectrometry. Plasma and tissue levels of several precursors of aldosterone with mineralocorticoid activity are higher in patients with aldosterone producing adenomas than in those with bilateral hyperplasia. These include corticosterone, deoxycorticosterone, and their 18-hydroxylated metabolites. Similarly, urinary, peripheral, and adrenal venous concentrations of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol are higher in patients with aldosterone producing adenomas than in bilateral hyperplasia. Differences in the pathophysiology and in clinical and biochemical phenotypes caused by aldosterone producing adenomas and bilateral adrenal hyperplasia may be related to the differential expression of steroidogenic enzymes, and associated to specific underlying somatic mutations. Correct appreciation of differences in steroid profiling between aldosterone producing adenomas and bilateral adrenal hyperplasia may not only contribute to a better understanding of the pathogenesis of primary aldosteronism but may also be helpful for future subtyping of primary aldosteronism.

Subtype Diagnosis of Primary Aldosteronism: Approach to Different Clinical Scenarios

Identification and management of patients with primary aldosteronism are of utmost importance because it is a frequent cause of endocrine hypertension, and affected patients display an increase of cardio- and cerebro-vascular events, compared to essential hypertensives. Distinction of primary aldosteronism subtypes is of particular relevance to allocate the patients to the appropriate treatment, represented by mineralocorticoid receptor antagonists for bilateral forms and unilateral adrenalectomy for patients with unilateral aldosterone secretion. Subtype differentiation of confirmed hyperaldosteronism comprises adrenal CT scanning and adrenal venous sampling. In this review, we will discuss different clinical scenarios where execution, interpretation of adrenal vein sampling and subsequent patient management might be challenging, providing the clinician with useful information to help the interpretation of controversial procedures.

ARMC5 mutation analysis in patients with primary aldosteronism and bilateral adrenal lesions

Idiopathic hyperaldosteronism (IHA) due to bilateral adrenal hyperplasia is the most common subtype of primary aldosteronism (PA). The pathogenesis of IHA is still unknown, but the bilateral disease suggests a potential predisposing genetic alteration. Heterozygous germline mutations of armadillo repeat containing 5 (ARMC5) have been shown to be associated with hypercortisolism due to sporadic primary bilateral macronodular adrenal hyperplasia and are also observed in African-American PA patients. We investigated the presence of germline ARMC5 mutations in a group of PA patients who had bilateral computed tomography-detectable adrenal alterations. We sequenced the entire coding region of ARMC5 and all intron/exon boundaries in 39 patients (37 Caucasians and 2 black Africans) with confirmed PA (8 unilateral, 27 bilateral and 4 undetermined subtype) and bilateral adrenal lesions. We identified 11 common variants, 5 rare variants with a minor allele frequency <1% and 2 new variants not previously reported in public databases. We did not detect by in silico analysis any ARMC5 sequence variations that were predicted to alter protein function. In conclusion, ARMC5 mutations are not present in a fairly large series of Caucasian patients with PA associated to bilateral adrenal disease. Further studies are required to definitively clarify the role of ARMC5 in the pathogenesis of adrenal nodules and aldosterone excess in patients with PA.

Immunohistochemical, genetic and clinical characterization of sporadic aldosterone-producing adenomas

Adrenal glands removed for unilateral primary aldosteronism (PA) display marked histological heterogeneity. Recently reported somatic mutations in KCNJ5, ATP1A1, ATP2B3 and CACNA1D can partially account for these differences. In this study we aimed at combining phenotypic and genotypic characteristics, integrating genetic and immunohistochemistry correlates in sporadic PA. Seventy-one adrenal glands have been included in the study and analyzed for mutations in KCNJ5, ATP1A1, ATP2B3 and CACNA1D. Histological examination and immunohistochemical staining for CYP11B1 (11β-hydroxylase) and CYP11B2 (aldosterone synthase) were performed on aldosterone-producing adenomas (APAs) and adjacent adrenal cortex. In our cohort, the final histopathological diagnosis was multinodular hyperplasia in 22.5% of the patients and single nodule in 77.5%. Forty-five percent of the removed adrenals displayed extra-APA CYP11B2-positive cell nests (B2-CN). Among adrenal vein sampling parameters the suppression of contralateral adrenal was more frequent and the lateralization index was higher in the subgroup of patients without extra-APA B2-CN compared to the subgroup with extra-APA B2-CN. KCNJ5-mutated APAs were composed mainly of zona fasciculata-like cells with high expression of CYP11B1, while ATP1A1, ATP2B3 and CACNA1D-mutated APAs presented more frequently a zona-glomerulosa-like phenotype with high expression of CYP11B2. We observed a significant inverse correlation between CYP11B2 expression and the size of the nodules and, if CYP11B2 expression was corrected for tumor volume, a significant correlation with plasma aldosterone and aldosterone to renin ratio. Our findings indicate that combination of genotyping and immunohistochemistry improves the final histopathological diagnosis between single nodule and multinodular hyperplasia of the assessed adrenals.

Renin and aldosterone measurements in the management of arterial hypertension

Renin-angiotensin-aldosterone system (RAAS) is recognized as the main regulatory system of hemodynamics in man, and its derangements have a key role in the development and maintenance of arterial hypertension. Classification of the hypertensive states according to different patterns of renin and aldosterone levels ("RAAS profiling") allows the diagnosis of specific forms of secondary hypertension and may identify distinct hemodynamic subsets in essential hypertension. In this review, we summarize the application of RAAS profiling for the diagnostic assessment of hypertensive patients and discuss how the pathophysiological framework provided by RAAS profiling may guide therapeutic decision-making, especially in the context of uncontrolled hypertension not responding to multi-therapy.

Understanding primary aldosteronism: impact of next generation sequencing and expression profiling

Primary aldosteronism (PA) encompasses a broad, heterogeneous group of disorders including both sporadic and familial forms (familial hyperaldosteronism type I, II and III). PA is the most common form of secondary hypertension and associated with a higher rate of cardiovascular complications, compared with essential hypertension. Despite significant progress in the diagnosis and management of PA, until recently the molecular mechanisms leading to inappropriate aldosterone production were largely unknown. The introduction of next-generation sequencing has had a profound impact on the field of human genetics and has given new insight in the molecular determinants that lead to both sporadic and familial forms of PA. Here we review the recent progress toward understanding of the genetic and molecular mechanisms leading to autonomous aldosterone production in PA.

A case of severe hyperaldosteronism caused by a de novo mutation affecting a critical salt bridge Kir3.4 residue

CONTEXT

Familial hyperaldosteronism type III (FH-III) is a rare and clinically heterogeneous condition, that can display mild as well as severe phenotypes. Point mutations in the KCNJ5 gene, affecting the ion selectivity of the inward rectifier K(+) channel 4 (Kir3.4), underlie the molecular basis of FH-III.

OBJECTIVE

The objective of the study was to investigate the effects of a de novo germline KCNJ5 mutation.

PATIENTS AND METHODS

We describe the case of a girl who came to medical attention at the age of 2 years because of polydipsia, polyuria, and failure to thrive. The patient, affected by hypertension and hypokalemia, was diagnosed with primary aldosteronism on the basis of extremely high aldosterone levels and suppressed plasma renin activity. Genomic DNA was isolated and KCNJ5 sequenced. Human adrenocortical cells were used as an in vitro model for the functional characterization of the mutant channel.

RESULTS

KCNJ5 sequencing in the index case and her parents revealed a de novo p.Glu145Gln germline mutation. The substitution resulted in Na(+)-dependent depolarization of adrenal cells and increased intracellular calcium concentration, which activated the transcription of NR4A2 and, in turn, CYP11B2. Pharmacological studies revealed that the mutant channel was insensitive to tertiapin-Q and calcium-channel blocker verapamil.

CONCLUSIONS

Herein we report the identification of a novel KCNJ5 germline mutation responsible for severe hyperaldosteronism that presented in infancy with symptoms of diabetes insipidus. The findings of this study further elucidate the etiology of FH-III and expand our knowledge of this rare condition.

Genome-wide association study identifies CAMKID variants involved in blood pressure response to losartan: the SOPHIA study

Background: Essential hypertension arises from the combined effect of genetic and environmental factors. A pharmacogenomics approach could help to identify additional molecular mechanisms involved in its pathogenesis. Aim: The aim of SOPHIA study was to identify genetic polymorphisms regulating blood pressure response to the angiotensin II receptor blocker, losartan, with a whole-genome approach. Materials & methods: We performed a genome-wide association study on blood pressure response in 372 hypertensives treated with losartan and we looked for replication in two independent samples. Results: We identified a peak of association in CAMK1D gene (rs10752271, effect size -5.5 ± 0.94 mmHg, p = 1.2 × 10-8). CAMK1D encodes a protein that belongs to the regulatory pathway involved in aldosterone synthesis. We tested the specificity of rs10752271 for losartan in hypertensives treated with hydrochlorothiazide and we validated it in silico in the GENRES cohort. Conclusion: Using a genome-wide approach, we identified the CAMK1D gene as a novel locus associated with blood pressure response to losartan. CAMK1D gene characterization may represent a useful tool to personalize the treatment of essential hypertension.

Original submitted 7 May 2014; Revision submitted 29 July 2014

1α,25-Dihydroxyvitamin D₃ inhibits the human H295R cell proliferation by cell cycle arrest: a model for a protective role of vitamin D receptor against adrenocortical cancer

Using the human H295R adrenocortical carcinoma cell line as a model, we analyzed the role of 1α,25-dihydroxyvitamin D₃ [1α,25(OH)₂D₃)]--vitamin D receptor (VDR) axis in the growth of adrenocortical cancer (ACC). The presence of VDR in various adrenocortical tissues, including ACC, was also investigated. DNA synthesis was evaluated by [³H]thymidine cell incorporation after treatment with 1α,25(OH)₂D₃ at increasing doses. The effect of 1α,25(OH)₂D₃ on cell cycle and apoptosis was analyzed with a flow cytometer. Cyclin-dependent kinase 4 (CDK4) expression, a molecular marker of G1-S cell cycle transition phase, was evaluated in cells treated with 1α,25(OH)₂D₃ before and after VDR gene silencing. 1α,25(OH)₂D₃ treatment inhibited cell proliferation by 20% at a dose of 1 nM, in parallel with steroid secretion decrease. A cell cycle arrest in G1, with no change in apoptotic cell proportion, was observed after 10 nM 1α,25(OH)₂D₃ cell exposure. CDK4 activation was reduced by 10 nM 1α,25(OH)₂D₃ but was not affected by 1α,25(OH)₂D₃ after VDR gene silencing. Expression of VDR mRNA was lower in ACC than in benign adrenocortical tumors. VDR immunostaining was evident in benign tumors but it was weak in ACC tissues.

CONCLUSIONS

Slightly supra-physiological concentrations of 1α,25(OH)₂D₃ have a moderate anti-proliferative effect on H295R cells. Anti-proliferative effect was due to cell cycle arrest in G1 phase, without inducing apoptosis. The low mRNA expression levels at qRT-PCR as well as the weak immunohistochemical expression of VDR in ACC, suggests a protective role of VDR against malignant adrenocortical growth.

a Novel Y152C KCNJ5 mutation responsible for familial hyperaldosteronism type III

CONTEXT

Primary aldosteronism is a heterogeneous group of disorders comprising both sporadic and familial forms. Mutations in the KCNJ5 gene, which encodes the inward rectifier K(+) channel 4 (G protein-activated inward rectifier K(+) channel 4, Kir3.4), cause familial hyperaldosteronism type III (FH-III) and are involved in the pathogenesis of sporadic aldosterone-producing adenomas.

OBJECTIVE

The objective of the study was to characterize the effects of a newly described KCNJ5 mutation in vitro.

PATIENTS AND METHODS

The index case is a 62-year-old woman affected by primary aldosteronism, who underwent left adrenalectomy after workup for adrenal adenoma. Exon 1 of KCNJ5 was PCR amplified from adrenal tissue and peripheral blood and sequenced. Electrophysiological and gene expression studies were performed to establish the functional effects of the new mutation on the membrane potential and adrenal cell CYP11B2 expression.

RESULTS

KCNJ5 sequencing in the index case revealed a new p.Y152C germline mutation; interestingly, the phenotype of the patient was milder than most of the previously described FH-III families. The tyrosine-to-cysteine substitution resulted in pathological Na(+) permeability, cell membrane depolarization, and disturbed intracellular Ca(2+) homeostasis, effects similar, albeit smaller, to the ones demonstrated for other KCNJ5 mutations. Gene expression studies revealed an increased expression of CYP11B2 and its transcriptional regulator NR4A2 in HAC15 adrenal cells overexpressing KCNJ5(Y152C) compared to the wild-type channel. The effect was clearly Ca(2+)-dependent, because it was abolished by the calcium channel blocker nifedipine.

CONCLUSIONS

Herein we describe a new germline mutation in KCNJ5 responsible for FH-III.

Effect of KCNJ5 mutations on gene expression in aldosterone-producing adenomas and adrenocortical cells

CONTEXT

Primary aldosteronism is a heterogeneous disease that includes both sporadic and familial forms. A point mutation in the KCNJ5 gene is responsible for familial hyperaldosteronism type III. Somatic mutations in KCNJ5 also occur in sporadic aldosterone producing adenomas (APA).

OBJECTIVE

The objective of the study was to define the effect of the KCNJ5 mutations on gene expression and aldosterone production using APA tissue and human adrenocortical cells.

METHODS

A microarray analysis was used to compare the transcriptome profiles of female-derived APA samples with and without KCNJ5 mutations and HAC15 adrenal cells overexpressing either mutated or wild-type KCNJ5. Real-time PCR validated a set of differentially expressed genes. Immunohistochemical staining localized the KCNJ5 expression in normal adrenals and APA.

RESULTS

We report a 38% (18 of 47) prevalence of KCNJ5 mutations in APA. KCNJ5 immunostaining was highest in the zona glomerulosa of NA and heterogeneous in APA tissue, and KCNJ5 mRNA was 4-fold higher in APA compared with normal adrenals (P < 0.05). APA with and without KCNJ5 mutations displayed slightly different gene expression patterns, notably the aldosterone synthase gene (CYP11B2) was more highly expressed in APA with KCNJ5 mutations. Overexpression of KCNJ5 mutations in HAC15 increased aldosterone production and altered expression of 36 genes by greater than 2.5-fold (P < 0.05). Real-time PCR confirmed increases in CYP11B2 and its transcriptional regulator, NR4A2.

CONCLUSIONS

KCNJ5 mutations are prevalent in APA, and our data suggest that these mutations increase expression of CYP11B2 and NR4A2, thus increasing aldosterone production.

Aldosterone does not modify gene expression in human endothelial cells

The toxic effects of aldosterone on the vasculature, and in particular on the endothelial layer, have been proposed as having an important role in the cardiovascular pathology observed in mineralocorticoid-excess states. In order to characterize the genomic molecular mechanisms driving the aldosterone-induced endothelial dysfunction, we performed an expression microarray on transcripts obtained from both human umbilical vein endothelial cells and human coronary artery endothelial cells stimulated with 10 - 7 M aldosterone for 18 h. The results were then subjected to qRT-PCR confirmation, also including a group of genes known to be involved in the control of the endothelial function or previously described as regulated by aldosterone. The state of activation of the mineralocorticoid receptor was investigated by means of a luciferase-reporter assay using a plasmid encoding a mineralocorticoid and glucocorticoid-sensitive promoter. Aldosterone did not determine any significant change in gene expression in either cell type both in the microarray and in the qRT-PCR analysis. The luciferase-reporter assay showed no activation of the mineralocorticoid receptor following aldosterone stimulation. The status of nonfunctionality of the mineralocorticoid receptor expressed in cultured human umbilical and coronary artery endothelial cells does not allow aldosterone to modify gene expression and provides evidence against either a beneficial or harmful genomic effect of aldosterone on healthy endothelial cells.

Outcome of ranibizumab treatment in neovascular age related macula degeneration in eyes with baseline visual acuity better than 6/12

BACKGROUND

The beneficial effect of intravitreal ranibizumab in the treatment of neovascular age-related macula degeneration (nAMD) is well known. Outcome data for eyes presenting with visual acuity better than 6/12 is limited.

AIMS

To assess the effect of baseline vision on outcome in ranibizumab-treated nAMD eyes, including a subgroup with baseline vision ≥6/12 (<0.30  logmar).

DESIGN

Prospective, consecutive and interventional case series.

METHODS

A consecutive cohort of patients treated with intravitreal ranibizumab for nAMD with 52-week follow-up were studied. Patients who had received previous treatment for nAMD were excluded. Eyes were stratified according to baseline logmar visual acuity into four groups: <0.30 (>6/12), 0.30-0.59 (6/12-6/24), 0.60-0.99 (6/24-6/60) and 1.00-1.20 (6/60-6/96). Intravitreal ranibizumab (0.5 mg in 0.05 ml) was administered in three loading monthly doses followed by PRN dosing according to optical coherence tomography (OCT) findings.

RESULTS

A total of 615 eyes were studied including 88 eyes with baseline vision <0.30. The mean change in logmar letters at 52 weeks was +5.5 (entire study group), -0.5 (<0.30 subgroup), +2.2 (0.30-0.59 subgroup), +6.5 (0.60-0.99 subgroup) and +15.3 (1.00-1.20 subgroup). In the <0.30 subgroup, 60 of 88 eyes (68%) had best-corrected visual acuity (BCVA) equal to or better than baseline and 82 of 88 eyes (93%) lost <15 letters at 52 weeks. Within this subgroup 56 of 67 eyes (84%) maintained UK driving standard BCVA visual acuity over the study period.

CONCLUSIONS

This study provides evidence that intravitreal ranibizumab treatment stabilises good vision in nAMD presenting with vision better than 6/12 over 52 weeks follow-up.

Effect of length of stay in intensive care unit on hospital and long-term mortality of critically ill adult patients

BACKGROUND

Critical illness leading to prolonged length of stay (LOS) in an intensive care unit (ICU) is associated with significant mortality and resource utilization. This study assessed the independent effect of ICU LOS on in-hospital and long-term mortality after hospital discharge.

METHODS

Clinical and mortality data of 22 298 patients, aged 16 yr and older, admitted to ICU between 1987 and 2002 were included in this linked-data cohort study. Cox's regression with restricted cubic spline function was used to model the effect of LOS on in-hospital and long-term mortality after adjusting for age, gender, acute physiology score (APS), maximum number of organ failures, era of admission, elective admission, Charlson's co-morbidity index, and diagnosis. The variability each predictor explained was calculated by the percentage of the chi(2) statistic contribution to the total chi(2) statistic.

RESULTS

Most hospital deaths occurred within the first few days of ICU admission. Increasing LOS in ICU was not associated with an increased risk of in-hospital mortality after adjusting for other covariates, but was associated with an increased risk of long-term mortality after hospital discharge. The variability on the long-term mortality effect associated with ICU LOS (2.3%) appeared to reach a plateau after the first 10 days in ICU and was not as important as age (35.8%), co-morbidities (18.6%), diagnosis (10.9%), and APS (3.6%).

CONCLUSIONS

LOS in ICU was not an independent risk factor for in-hospital mortality, but it had a small effect on long-term mortality after hospital discharge after adjustment for other risk factors.

Effect of an episode of critical illness on subsequent hospitalisation: a linked data study

Healthcare utilisation can affect quality of life and is important in assessing the cost-effectiveness of medical interventions. A clinical database was linked to two Australian state administrative databases to assess the difference in incidence of healthcare utilisation of 19,921 patients who survived their first episode of critical illness. The number of hospital admissions and days of hospitalisation per patient-year was respectively 150% and 220% greater after than before an episode of critical illness (assessed over the same time period). This was the case regardless of age or type of surgery (i.e. cardiac vs non-cardiac). After adjusting for the ageing effect of the cohort as a whole, there was still an unexplained two to four-fold increase in hospital admissions per patient-year after an episode of critical illness. We conclude that an episode of critical illness is a robust predictor of subsequent healthcare utilisation.

Conceptual basis and methodology of the SOPHIA study

To clarify the role of gene polymorphisms on the effect of losartan and losartan plus hydrochlorothiazide on blood pressure (primary end point) and on cardiac, vascular and metabolic phenotypes (secondary end point) after 4, 8, 12, 16 and 48 weeks treatment, an Italian collaborative study - The Study of the Pharmacogenomics in Italian hypertensive patients treated with the Angiotensin receptor blocker losartan (SOPHIA) - on never-treated essential hypertensives (n = 800) was planned. After an 8 week run-in, losartan 50 mg once daily will be given and doubled to 100 mg at week +4 if blood pressure is more than 140/90 mmHg. Hydroclorothiazide 25 mg once daily at week +8 and amlodipine 5 mg at week +16 will be added if blood pressure is more than 140/90 mmHg. Cardiac mass (echocardiography), carotid intima-media thickness, 24 h ambulatory blood pressure, homeostatic model assessment (HOMA) index, microalbuminuria, plasma renin activity and aldosterone, endogenous lithium clearance, brain natriuretic peptide and losartan metabolites will be evaluated. Genes of the renin-angiotensin-aldosterone system, salt sensitivity, the beta-adrenergic system and losartan metabolism will be studied (Illumina custom arrays). A whole-genome scan will also be performed in half of the study cohort (1M array, Illumina 500 GX beadstation).

Data linkage enables evaluation of long-term survival after intensive care

Outcomes of intensive care are important to the patient and for assessment of benefit. Short-term outcomes after critical illness are well described, but less is known about long-term outcomes. This study describes the use of data linkage, combining intensive care unit (ICU) clinical data with administrative morbidity and mortality data, to assess long-term outcomes after treatment in ICU. The hospital-based cohort study was conducted in a 22-bed general ICU in a metropolitan teaching hospital. All patient admissions admitted to ICU from 1 January 1987 to 31 December 2002 were included. The prospective ICU clinical database with patient demographics, ICU diagnoses, severity of illness, daily assessment of organ failures and common daily treatments used was linked using probabilistic methods to the state-wide hospital morbidity and mortality databases to describe long-term survival. There were 26,019 ICU admissions (22,980 patients) with 25,972 records (99.8%) linked to a hospitalization event that included the index ICU admission. Unadjusted survival was 84.7% at 1 year decreasing progressively to 50.7% at 15 years. Age, type of admission, severity of illness (measured by Acute Physiologic and Chronic Health Evaluation (APACHE) II and the presence of organ failure), ICU length of stay, comorbidity (Chronic Health Evaluation and Charlson comorbidity index) and ICU admission diagnosis, were all associated with survival at 1, 3, 5, 10, and 15 year follow-up (P<0.001 at all time points). Linkage of clinical and administrative data provides a feasible method for ascertaining long-term survival after critical illness. Age, admission severity of illness, diagnosis and comorbidity influenced long-term unadjusted survival.

Protective effect of spironolactone on endothelial cell apoptosis

Human umbilical vein endothelial cells (HUVECs) undergo apoptosis in response to serum deprivation. We show that the nonspecific mineralocorticoid receptor antagonist, spironolactone, protects from caspase-3 activation induced by serum deprivation in contrast to the selective mineralocorticoid receptor antagonist, eplerenone, that is nonprotective. We also demonstrate that progesterone, hydrocortisone, and dexamethasone all protect HUVECs from serum-deprivation-induced caspase-3 activation, whereas aldosterone and dihydrotestosterone have no effect. Spironolactone has been demonstrated to display agonist activity only to the progesterone receptor (PR), and we additionally show that spironolactone and progesterone, but not eplerenone, inhibit mitochondrial cytochrome c release and cleavage of nuclear poly (ADP-ribose) polymerase (PARP) and increase cell viability. Additionally, the PR antagonist mifepristone (RU486) partially blocked the inhibitory effect of both spironolactone and progesterone on caspase-3 activation, cytochrome c release, and nuclear PARP cleavage. Nitric oxide (NO) protects HUVECs from apoptosis in response to various stimuli including serum-deprivation; however, the NO synthase inhibitor N-monomethyl-l-arginine, did not abolish inhibition of caspase-3 activation or PARP cleavage by spironolactone. Thus, we demonstrate that spironolactone protects HUVECs from serum-deprivation-induced apoptosis by inhibition of caspase-3 activity, cytochrome c release and PARP cleavage by a NO-independent mechanism; further, this effect is likely mediated by the agonist properties of spironolactone toward the PR.

Role of HSD11B2 polymorphisms in essential hypertension and the diuretic response to thiazides

BACKGROUND

The renal 11beta-hydroxysteroid dehydrogenase type 2 (11beta HSD2) enzyme inactivates 11-hydroxy steroids in the kidney, thereby protecting the nonselective mineralocorticoid (MR) receptor from occupation by glucocorticoids. Loss-of-function mutations in the gene encoding 11beta HSD2 (HSD11B2) result in overstimulation of the MR and cause salt-sensitive hypertension.

METHODS

We have investigated the role of HSD11B2 in hypertension in 377 genetically homogeneous essential hypertensives from North Sardinia.

RESULTS

Thirty of these patients displayed increased urinary cortisol metabolite ratios (greater than or equal to 2) (tetrahydrocortisol [THF]+allotetrahydrocortisol [aTHF]/tetrahydrocortisone [THE]) reflecting a mild reduction in 11beta HSD2 activity. No mutations in HSD11B2 were detected in these patients. All 377 patients were genotyped for a CA repeat microsatellite in intron 1 of HSD11B2 and a G534A polymorphism in exon 3 of HSD11B2. CA repeat length was associated with the (THF+aTHF)/THE ratio, which in turn was significantly related to PRA levels. No associations were found between the G354A polymorphism and the other parameters. There were no differences in blood pressure (BP) levels between HSD11B2 genotypes, but in a subgroup of 91 patients that underwent diuretic therapy, CA repeat length was strongly associated with the BP response to hydrochlorothiazide.

CONCLUSION

This study highlights the role of this HSD11B2 polymorphism in sodium handling and is consistent with a role in the BP response to thiazide diuretics.

Bradykinin B2 receptor gene (???58T/C) polymorphism influences baroreflex sensitivity in never-treated hypertensive patients

BACKGROUND

Most evidence currently favours a fundamental role of the autonomic nervous system in the pathogenesis of essential hypertension. Recent studies suggest that about 40% of baroreflex variation, an index of cardiac autonomic control, is influenced by genetic factors.

METHODS AND RESULTS

The aim of this study was to investigate the effect of a common polymorphic variant of the bradykinin B2 receptor gene (B2R; -58T/C) on the autonomic regulation of baroreflex sensitivity (BRS) in 129 mild-moderate never-treated hypertensive patients. No significant differences were found for clinical and biochemical parameters among genotypes. BRS increased with the number of B2R T alleles. B2R genotype was a strong independent predictor of BRS, accounting for 12% of its variation. We suggest that a decrease in the transcription of the bradykinin B2R gene in the presence of the B2R -58C allele could reduce BRS via the diminished effect of bradykinin.

CONCLUSIONS

B2R genotype can explain part of the BRS variation that is unaccounted for by simple anthropometric variables and common risk factors.

Coexistence of different phenotypes in a family with glucocorticoid-remediable aldosteronism

In glucocorticoid-remediable aldosteronism (GRA), there is a large interfamily variation of phenotype. We report three subjects with GRA in a single family (parents, two brothers and two sisters), of whom only one (proband) displayed classical features of the mineralocorticoid excess. The proband was a man found to be hypertensive and hypokalaemic at the age of 24 years. Plasma renin activity was suppressed and plasma aldosterone was repeatedly elevated. Blood pressure and aldosterone levels normalized within 5 days of dexamethasone therapy. The presence of a chimaeric CYP11B1/CYP11B2 gene was demonstrated by long-PCR and Southern blotting (crossover site at the end of intron 3) in the proband, in the younger sister (sibling 1) and in the father. In these patients, sequencing of the chimaeric portion of CYP11B1 did not reveal any mutation, while sequencing of the chimaeric portion of CYP11B2 showed a V386A polymorphism in exon 7, known to cause only a minimal impairment of enzymatic activity. Sibling 1 was normotensive, normokalaemic and had normal PRA and aldosterone. The father had normal blood pressure and potassium, low-normal PRA and normal aldosterone. All three subjects had elevated levels of urinary 18-hydroxycortisol and 18-oxocortisol. Baseline 11-deoxycorticosterone (DOC), corticosterone (B) and aldosterone were high in the proband and normal in the father and sibling 1; 11-deoxycortisol (S) and cortisol (F) were normal. ACTH induced a normal increase of B, DOC, S and F, and an excessive aldosterone increase in all three patients. Abnormalities in the chimaeric portions of CYB11B1 or CYP11B2 genes did not account for the phenotypic disparity of the different members in a single GRA family. Altered regulation of the chimaeric gene may be responsible for differences in its activity.

A particular phenotype in a girl with aldosterone synthase deficiency

Aldosterone synthase deficiency (ASD) usually presents in infancy as a life-threatening electrolyte imbalance. A 4-wk-old child of unrelated parents was examined for failure to thrive and salt-wasting. Notable laboratory findings were hyperkalemia, high plasma renin, and low-normal aldosterone levels. Urinary metabolite ratios of corticosterone/18-hydroxycorticosterone and 18-hydroxycorticosterone/aldosterone were intermediate between ASD type I and type II. Sequence analysis of CYP11B2, the gene encoding aldosterone synthase (P450c11AS), revealed that the patient was a compound heterozygote carrying a previously described mutation located in exon 4 causing a premature stop codon (E255X) and a further, novel mutation in exon 5 that also causes a premature stop codon (Q272X). The patient's unaffected father was a heterozygous carrier of the E255X mutation, whereas the unaffected mother was a heterozygous carrier of the Q272X mutation. Therefore, the patient's CYP11B2 encodes two truncated forms of aldosterone synthase predicted to be inactive because they lack critical active site residues as well as the heme-binding site. This case of ASD is of particular interest because despite the apparent lack of aldosterone synthase activity, the patient displays low-normal aldosterone levels, thus raising the question of its source.

Bradykinin B2 receptor gene C-58T polymorphism and insulin resistance. A study on obese patients

The bradykinin B2 receptor (B2R) gene is a candidate in the pathogenesis of insulin resistance, which often clusters with other abnormalities in metabolic syndrome. We investigated the distribution of the C-58T B2R gene polymorphism within a population of overweight/obese patients (BMI > or = 25 kg/m2) potentially characterised by different levels of insulin resistance. Patients with type 2 diabetes, dyslipidemia and hypertension were excluded in order to distinguish the effect of obesity on insulin sensitivity from that of confounding factors. Ninety-two unrelated adults (41 men and 51 women, aged 33.7 +/- 11.6 years) were recruited by random sampling from a general population evaluated for cardiovascular risk stratification. Measurements included BMI, waist circumference, body composition, blood pressure, serum leptin, and lipid profile. Insulin sensitivity was calculated according to the homeostasis model assessment (HOMA) method. C-58T genotypes--CC (n = 20), CT (n = 47) and TT (n = 25)--were determined by restriction fragment-length polymorphism PCR. Patients subdivided on the basis of C-58T polymorphism, showed no difference in any of the parameters examined, including HOMA index values, after adjustment for age, sex, BMI and waist circumference. The results indicate that the C-58T B2R gene polymorphism is not associated with different levels of insulin resistance within a population of obese patients.

Earlier flowering between 1962 and 2002 in agricultural varieties of white clover

Date of first flowering was recorded for 40 years in the same agricultural varieties of white clover (Trifolium repens L.). Standard procedures, experimental conditions and germplasm allowed the unmediated effects of climatic trends to be observed. Flowering dates of the same varieties at the same site have become significantly earlier over this period, with an advance of first flowering of approximately 7.5 days per decade since 1978. Annual maximum, minimum and soil temperatures at the site increased during the 40-year period. First flowering dates (FFDs) were significantly negatively correlated with minimum and maximum temperatures during February and March and soil temperatures between January and April. Maximum, minimum and soil temperatures increased between 1962 and 2002 for these months. No significant correlation was seen between FFD and soil temperatures at other times of the year including the period of vernalisation during winter. The occurrence of ground frost in February was significantly correlated with later flowering. Total annual rainfall and the number of wet days in a year increased between 1962 and 2002. However, only rainfall in February had a significant impact on FFD.

Blood pressure in patients with primary aldosteronism is influenced by bradykinin B(2) receptor and alpha-adducin gene polymorphisms

Primary aldosteronism (PA) is the most common cause of endocrine hypertension. PA is most frequently presented as moderate to severe hypertension, but the clinical and biochemical features vary widely. The aim of our study was to identify genetic variants that influence the phenotype of patients with PA. We hypothesized that genetic variants potentially affecting aldosterone production (aldosterone synthase, CYP11B2), renal proximal tubule reabsorption (alpha-adducin), or the mechanisms of counterbalance leading to vasodilatation and sodium excretion (bradykinin B(2)-receptor, B(2)R) could influence the clinical and biochemical characteristics of patients with PA. We studied three polymorphisms of these genes (C-344T of CYP11B2, G460W of alpha-adducin, and C-58T of B(2)R) in 167 primary aldosteronism patients (56 with aldosterone-producing adenoma and 111 with idiopathic hyperaldosteronism). B(2)R and alpha-adducin genotypes were strong independent predictors of both systolic and diastolic blood pressure levels; plasma renin activity and aldosterone also play a marginal role on BP levels. Body mass index, age, sex, and CYP11B2 genotype displayed no significant effect on the clinical parameters of our population. In particular, alpha-adducin and B(2)R polymorphisms accounted for 13.2% and 11.0% of the systolic and diastolic blood pressure variance, respectively. These data suggest that genetic variants of alpha-adducin and the bradykinin B(2)-R influence the blood pressure levels in patients with primary aldosteronism.

Glucocorticoid remediable aldosteronism: low morbidity and mortality in a four-generation italian pedigree

Glucocorticoid remediable hyperaldosteronism (GRA) is a monogenic form of inherited hypertension caused by a chimeric gene originating from an unequal cross-over between the 11 beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes. GRA is characterized by high plasma levels of aldosterone (regulated by ACTH) with suppressed plasma renin activity and the production of two rare steroids, 18hydroxycortisol and 18oxocortisol. Affected patients usually show severe hypertension and an elevated frequency of stroke at a young age. Affected women have a high risk of developing preeclampsia during pregnancy. Here, we describe a 5-generation pedigree from Sardinia in which the presence of the chimeric gene is demonstrated in 4 generations. This family displays a mild phenotype with average blood pressure levels of 131/86 mm Hg for GRA+ patients. The occurrence of stroke is very low, and preeclampsia was not observed in 29 pregnancies from 8 GRA+ mothers. We investigated whether the cross-over site (between the CYP11B1 and CYP11B2 genes) or biochemical characteristics could explain this phenotype. The cross-over site was located at the end of intron 3, in the same region as described in other families. We found a significant correlation between blood pressure and 18hydroxycortisol, 18oxocortisol, and plasma aldosterone levels, but not with kallikrein. However, none of the biochemical or genetic parameters investigated could explain the mild phenotype of the family.

Developmental modularity and the evolutionary diversification of arthropod limbs

Segmentation is one of the most salient characteristics of arthropods, and differentiation of segments along the body axis is the basis of arthropod diversification. This article evaluates whether the evolution of segmentation involves the differentiation of already independent units, i.e., do segments evolve as modules? Because arthropod segmental differentiation is commonly equated with differential character of appendages, we analyze appendages by comparing similarities and differences in their development. The comparison of arthropod limbs, even between species, is a comparison of serially repeated structures. Arthropod limbs are not only reiterated along the body axis, but limbs themselves can be viewed as being composed of reiterated parts. The interpretation of such reiterated structures from an evolutionary viewpoint is far from obvious. One common view is that serial repetition is evidence of a modular organization, i.e., repeated structures with a common fundamental identity that develop semi-autonomously and are free to diversify independently. In this article, we evaluate arthropod limbs from a developmental perspective and ask: are all arthropod limbs patterned using a similar set of mechanisms which would reflect that they all share a generic coordinate patterning system? Using Drosophila as a basis for comparison, we find that appendage primordia, positioned along the body using segmental patterning coordinates, do indeed have elements of common identity. However, we do not find evidence of a single coordinate system shared either between limbs or among limb branches. Data concerning the other diagnostic of developmental modularity--semi-autonomy of development--are not currently available for sufficient taxa. Nonetheless, some data comparing patterns of morphogenesis provide evidence that limbs cannot always be temporally or spatially decoupled from the development of their neighbors, suggesting that segment modularity is a derived character.

Osteopontin is an autocrine mediator of hepatocyte growth factor-induced invasive growth

In epithelial cells, hepatocyte growth factor (HGF) activates a genetic program involving cell-cell dissociation ("scattering"), growth and invasiveness. The full program is not elicited by other growth factors like epidermal growth factor, and is aberrantly activated during cancer progression to the invasive-metastatic phenotype. To identify genes involved in the onset of invasive growth, we explored by cDNA microarrays the in vitro transcriptional response to HGF of mouse embryo liver cells. We identified osteopontin (OPN), a secreted matrix protein, as a major HGF transcriptional target. The wave of OPN induction is maximal at 6 h, in concomitance with the initiation of scattering, and is specific, because no other matrix protein among those explored by the microarray is affected. Interestingly, HGF, but not epidermal growth factor, promotes cell adhesion to OPN via the CD44 receptor. Scattering is significantly impaired by antibodies against OPN and CD44; conversely, constitutive OPN overexpression dramatically increases the motile and invasive responses to HGF, leading to disruption of the ordered morphogenetic program triggered by this ligand.