Apparent Mineralocorticoid Excess Research Articles

Review of the Pathophysiologic and Clinical Aspects of Hypokalemia in Children and Young Adults: an Update.

This article examines the regulatory function of the skeletal muscle, renal, and adrenergic systems in potassium homeostasis. The pathophysiologic bases of hypokalemia, systematic approach for an early diagnosis, and therapeutic strategy to avert life-threatening complications are highlighted. By promoting skeletal muscle uptake, intense physical exercise (post), severe trauma, and several toxins produce profound hypokalemia. Hypovolemia due to renal and extra-renal fluid losses and ineffective circulation activate secondary aldosteronism causing urinary potassium wasting. In addition to hypokalemic alkalosis, primary aldosteronism causes low-renin hypertension. Non-aldosterone mineralocorticoid activation leading to low-renin and low-aldosterone hypertension occurs in Liddle’s syndrome and apparent mineralocorticoid excess. Although there is enzymatic inhibition of cortisol synthesis in congenital adrenal hyperplasia, precursors of aldosterone produce low-renin hypokalemic hypertension. In addition to the glucocorticoid effect, hypercortisolism activates mineralocorticoid receptors in Cushing’s syndrome. Genetic mutations involving furosemide-sensitive Na+-K+-2Cl− co-transporters and thiazide-sensitive Na+-Cl− transporters result in (non-hypertensive) salt-wasting nephropathy. Proximal and distal renal tubular acidosis is associated with hypokalemia. Eating disorders causing hypokalemia include bulimia, laxative abuse, and diuretic misuse. Low urinary potassium (<15 mmol/day) and/or low urinary chloride (<20 mol/L) suggest a gastrointestinal pathology. Co-morbidity of hypokalemia with chronic pulmonary and cardiovascular diseases may increase the fatality rate.

Clinical and HSD11B2 gene analysis of a patient with apparent mineralocorticoid excess

患儿 女，12岁，因“发现血压高、血钾低11年，血压控制不佳1个月”就诊于北京儿童医院内分泌遗传代谢科。经过体格检查、血液电解质、血气分析、醛固酮检测、影像学检查、基因检测等手段，确诊为表观盐皮质增多综合征。表观盐皮质增多综合征是一种罕见的单基因原发性高血压，诊断相对困难。及早基因检测有助于早期诊断和规范治疗方可避免靶器官损伤。.

Interrogation of Novel Aldosterone‐induced Genes Associated With Acute Stimulation Of ENaC In Primary Collecting Duct Cells

Aldosterone (ALDO) is a key volume‐regulating hormone which promotes Na+ reabsorption in the distal nephron. ALDO sensitivity is conferred by the enzyme 11βHSD2 which breaks down the related more abundant steroid, cortisol. Mutations in Hsd11b2 give rise to the syndrome of apparent mineralocorticoid excess, where hypertension is associated with excessive renal Na+ reabsorption. In the distal nephron corticosteroid‐induced Na+ transport, via the epithelial Na+ channel ENaC, is due to transcriptional processes and previous studies have identified key genes including Sgk1. Our lab carried out transcriptomic analysis of mCCDcl1 cells following acute corticosteroid induced ENaC‐mediated Na+ transport, identifying several novel ALDO induced genes. The present study aimed to elucidate the effects of corticosteroids on these target genes in the collecting duct (CD), utilising an in vitro and in vivo approach.A CD‐specific reporter mouse was generated using Aqp2Cre to express eGFP. Primary cells were isolated by FACS and either grown in culture or RNA was extracted immediately. Cells were grown on filter membranes to allow development of polarised monolayers and electrometric properties were assessed using an epithelial volt‐ohm‐meter. Target gene expression was determined by qRT‐PCR.Assessment of nephron segment‐specific gene expression revealed an enrichment of genes encoding α‐ENaC, ROMK and 11βHSD2 but not NHE3 or NKCC2. NCC was detected but parvalbumin was absent, demonstrating isolation of cells from the late distal tubule onwards. In addition to genes associated with principal cells we also detected genes encoding pendrin and AE1, indicative of intercalated cells therefore this population reflects CD cells. When grown in culture for 9‐11 days, these cells exhibited Vt and Rt of ‑20.3±3.1 mV and 5.1 ±0.1 kΩ∙cm2, respectively. This gave rise to an Ieq of ‑3.9±0.6 μA·cm‑2 which was near abolished with 10 µM amiloride – indicating Na+ transport via ENaC.Acute application of steroid hormones to cells for 3h: ALDO (3 nM), DEX (100 nM) and CORT (10 nM) – the latter only when 11βHSD2 activity was inhibited using carbenoxolone (CBX, 10 µM) – stimulated amiloride‐sensitive currents by 2.0‐, 3.6‐ and 2.4‐fold, respectively. Analysis of ALDO‐induced genes revealed both ALDO and CORT upregulated Sgk1, Zbtb16 and Rasd1. ALDO also upregulated Sult1d1 whereas CORT also upregulated an unannotated gene Gm43305. DEX upregulated all of these as well as 2 additional genes previously detected: Defb1 and Gm16178.To determine the relevance of these findings in vivo reporter mice were administered ALDO, vehicle or CORT, by ip injection, the latter under control conditions or following CBX treatment for 8 days. Cells were isolated after 3h. The previously identified Zbtb16, Rasd1, Gm43305 and Sult1d1 were upregulated in both ALDO and CBX+CORT groups, though no change was detected in either Sgk1 or Defb1. Scnn1a was also upregulated in both groups and additionally Per1 and Sult1a1 were upregulated in mice treated with CBX‐CORT.Together these data confirm 4 novel corticosteroid‐induced genes in primary CD cells associated with acute stimulation of ENaC activity.

Syndromes of Pseudo-Hyperaldosteronism.

Syndromes of Pseudo-Hyperaldosteronism.

Альдостеронсинтаза, поліморфізм її гена CYP11B2 при артеріальній гіпертензії і асоційованих з нею кардіоваскулярних захворюваннях (огляд літератури)

В огляді надані дані зарубіжної та вітчизняної літератури щодо патогенетичної ролі альдостерону, рівнів альдостеронсинтази і поліморфізмів гена даного ферменту у хворих на різні форми артеріальної гіпертензії, при асоційованих з нею захворюваннях серця і судин, фібриляції передсердь, метаболічному синдромі, патології нирок, головного мозку. Розглядаються функції альдостерону, рівнів альдостеронсинтази і поліморфізмів гена даного ферменту в серцево-судинному ремоделюванні, можливості застосування даних маркерів для диференційно-діагностичних цілей, перспективи терапевтичного використання інгібіторів альдостеронсинтази серед різних категорій хворих з ознаками артеріальної гіпертензії.

Apparent mineralocorticoid excess - A rare cause of endocrine hypertension

Background: Endocrine causes of hypertension constitute a very small percentage of patients with secondary hypertension. Apparent mineralocorticoid excess (AME) is a rare genetic form of young-onset secondary hypertension. Clinical Description: We present a case of a 16-year-old boy who was diagnosed with hypertension at 5 years of age, had recurrent episodes of hypokalemic paralysis, and deranged renal function for 1 year. Hypertension was uncontrollable with multiple antihypertensive agents until an aldosterone antagonist (spironolactone) was added. Clinical history and evaluation could not identify any secondary causes of hypertension. There was no significant family history. Growth and puberty were age-appropriate. Management and Outcome: Endocrine workup was planned considering hypokalemia and metabolic alkalosis. This demonstrated hyporeninemic hypoaldosteronism and raised the possibility of AME and Liddle syndrome. Clinical exome sequencing revealed a probable diagnosis of AME due to a novel homozygous variant (c.911A>G) in HSD11B2 gene. Sanger sequencing confirmed heterozygosity of the same variant in both parents. Conclusion: A novel homozygous variant was found in HSD11B2 gene in a subject with early-onset hypertension associated with hypokalemic metabolic alkalosis, establishing the diagnosis of AME. The use of an algorithmic approach and individualized planning of genetic studies can help in early diagnosis. This helps clinicians to select the appropriate antihypertensive drug, attain good control, and prevent the development of end-organ damage. A high index of suspicion should be kept for AME and other hyporeninemic hypoaldosteronism conditions in the case of early-onset hypertension.

Antifungal Therapy with Azoles Induced the Syndrome of Acquired Apparent Mineralocorticoid Excess: a Literature and Database Analysis.

We aimed to estimate the risk of varied antifungal therapy with azoles causing the syndrome of acquired apparent mineralocorticoid excess (AME) in real-world practice. First, we conducted a disproportionality analysis based on data from the FDA Adverse Event Reporting System (FAERS) database to characterize the signal differences of triazoles-related AME. Second, a systematic review was conducted, and clinical features of AME cases reported in clinical practice were described. In the FAERS database, we identified 27 cases of triazoles-AME, posaconazole [ROR = 865.37; 95%CI (464.14; 1613.45)], and itraconazole [ROR = 556.21; 95% (303.05; 1020.85)] significantly increased the risk of AME events, while fluconazole, voriconazole, and isavuconazole did not affect any of the mineralocorticoid excess targets. Eighteen studies with 39 cases raised evidence of AME following posaconazole and itraconazole treatment, and another 27 cases were identified by analysis of the description of clinical features in the FAERS database. The average age of 66 patients was 55.5 years (6-87 years). AME mainly occurs in patients with posaconazole concentrations above 3 μg/mL (mean = 4.4 μg/mL, range 1.8∼9.5 μg/mL), and is less likely to occur when levels are below 2 μg/mL (6%). The median time to event onset was 11.5 weeks, and 50% of the adverse events occurred within 3 months for posaconazole. The presented study supports very recent findings that posaconazole and itraconazole, but not the other three azole antifungals investigated, are associated with AME and that the effects are dose-dependent, which allows for a dose de-escalation strategy and for substitution with fluconazole, isavuconazole, or voriconazole to resolve the adverse effects.

Novel metabolomic profile of subjects with non-classic apparent mineralocorticoid excess

Nonclassic apparent mineralocorticoid excess (NC-AME) is proposed as a novel clinical condition with a mild phenotypic spectrum that ranges from normotension to severe hypertension. This condition is mainly characterized by a high serum cortisol to cortisone ratio (F/E) and concomitant low cortisone (E), however further metabolic changes in NC-AME have not been studied. A cross-sectional study was performed in a primary-care cohort of 396 Chilean subjects, which were classified in two groups: NC-AME (n = 28) and healthy controls (n = 27). A discovery study based in untargeted metabolomics assay in serum samples from both groups was performed by UPLC-Q-TOF/MS. Global metabolomic variations were assayed by principal component analysis and further compared by orthogonal partial least-squares discriminant analysis (OPLS-DA). NC-AME subjects exhibited higher values of blood pressure, fractional excretion of potassium, and lower plasma renin activity and urinary sodium to potassium ratio. Metabolomic analyses showed 36 differentially regulated metabolites between NC-AME and control subjects. A ROC curve analyses identified eight metabolites with high discriminatory capacity between NC-AME and control subjects. Moreover, gamma-l-glutamyl-l-methionine sulfoxide and 5-sulfoxymethylfurfural, exhibited significant association with cortisone, which are potential biomarkers of NC-AME, however further assays should elucidate its biological role in setup and progression of this phenotype.

Monogenic forms of low-renin hypertension: clinical and molecular insights.

Monogenic disorders of hypertension are a distinct group of diseases causing dysregulation of the renin-angiotensin-aldosterone system and are characterized by low plasma renin activity. These can chiefly be classified as causing (i) excessive aldosterone synthesis (familial hyperaldosteronism), (ii) dysregulated adrenal steroid metabolism and action (apparent mineralocorticoid excess, congenital adrenal hyperplasia, activating mineralocorticoid receptor mutation, primary glucocorticoid resistance), and (iii) hyperactivity of sodium and chloride transporters in the distal tubule (Liddle syndrome and pseudohypoaldosteronism type 2). The final common pathway is plasma volume expansion and catecholamine/sympathetic excess that causes urinary potassium wasting; hypokalemia and early-onset refractory hypertension are characteristic. However, several single gene defects may show phenotypic heterogeneity, presenting with mild hypertension with normal electrolytes. Evaluation is based on careful attention to family history, physical examination, and measurement of blood levels of potassium, renin, and aldosterone. Genetic sequencing is essential for precise diagnosis and individualized therapy. Early recognition and specific management improves prognosis and prevents long-term sequelae of severe hypertension.

A life-threatening case of pseudo-aldosteronism secondary to excessive liquorice ingestion

BackgroundLiquorice is found in many food products, soft drinks, and herbal medicines. Liquorice ingestion is an uncommon cause of apparent mineralocorticoid excess or pseudo-aldosteronism. The mechanism involves the inhibition of 11-beta-hydroxysteroid dehydrogenase type-2 by the active ingredient called glycyrrhizin. This leads to the uninhibited activation of mineralocorticoid receptors by cortisol. Confectionary products that contain liquorice are readily available in many countries around the world.Case presentationWe report a case of severe refractory hypokalaemia with hypertensive crisis and acute pulmonary oedema due to excessive liquorice consumption. A 79-year-old female presented to the emergency department following a road traffic accident. She described feeling weak and dizzy while driving before the collision. She attended her general practitioner (GP) several weeks earlier for fatigue and was being managed for hypokalaemia on oral potassium supplements. Investigations revealed hypertension (BP 180/69 mmHg), severe hypokalaemia (K 2.2 mmol/l), normal renal function, normal serum magnesium with metabolic alkalosis. Spot urinary potassium was 22 mmol/l. The patient denied taking medications including over-the-counter or herbal medication that can cause hypokalaemia. Hypokalaemia persisted despite aggressive intravenous (i.v.) and oral potassium replacement. She later developed a hypertensive crisis (BP 239/114 mmHg) with pulmonary oedema. She required admission to the intensive care unit and was managed with intravenous furosemide infusion and isosorbide dinitrate infusion. On further discussion, our patient admitted to struggling with nicotine cravings since quitting smoking two months earlier. She began eating an excessive amount of liquorice sweets to manage her cravings. Suppression of plasma renin and aldosterone supported the diagnosis of apparent mineralocorticoid excess secondary to excessive liquorice consumption. Her symptoms and hypokalaemia resolved after stopping liquorice intake.ConclusionsThis case highlights the life-threatening and refractory nature of hypokalaemia secondary to excessive liquorice consumption. This case also emphasizes the importance of comprehensive history taking including dietary habits. Increased awareness among the public is required regarding the potential health hazards of excessive liquorice consumption.

An unusual cause of hypokalaemia: Itraconazole induced apparent mineralocorticoid excess syndrome

An unusual cause of hypokalaemia: Itraconazole induced apparent mineralocorticoid excess syndrome

Concurrent Pseudohyperaldosteronism and Primary Glucocorticoid Deficiency From Posaconazole

Abstract Background: Posaconazole can cause pseudohyperaldosteronism via inhibition of 11-beta hydroxylase and 11-beta-hydroxysteroid dehydrogenase type 2 (1). The accumulation of 11-deoxycorticosterone and increased cortisol-to-cortisone ratio in the kidney causes apparent mineralocorticoid excess. The effect of posaconazole on the glucocorticoid axis is less established. Clinical Case: A 56-year-old Hispanic man with a history of chronic septic arthritis of the left ankle from Coccidioides presented with 3 months of malaise, nausea, weight loss of 30 pounds, and recurrent hypokalemia. He was recently switched from long-term fluconazole therapy to posaconazole around the time his symptoms began. His initial labs at our hospital were notable for low potassium (2.9 mmol/L, nl 3.5–5.5 mmol/L) and a random cortisol of 5.8 mcg/dL (nl ≥2.0 mcg/dL). A Cosyntropin stimulation test revealed elevated ACTH (168 pg/mL, nl 7.2–63.3 pg/mL) with minimal rise of cortisol from 4.6 to 7.2 mcg/dL at 1 hour after Cosyntropin administration (nl ≥18 mcg/dL at 1-hour post-Cosyntropin). His plasma renin activity was below detection (&amp;lt;0.6 ng/ml/h, nl 0.6–3.0 ng/mL/h), consistent with renin suppression from apparent mineralocorticoid excess. Hydrocortisone for glucocorticoid deficiency was started. A posaconazole determination indicated elevation (5240 ng/mL, usual therapeutic range ≥1000 ng/mL). His posaconazole was stopped, and he was switched back to fluconazole. Three months later, his symptoms were improved with regain of lost weight. Repeat Cosyntropin stimulation test showed ongoing primary glucocorticoid deficiency (ACTH 123 pg/mL, cortisol 4.1 mcg/dL at 1-hour post-Cosyntropin) but normal levels of plasma renin activity (1.2 ng/mL/h), aldosterone (8.6 ng/dL, nl ≤21 ng/dL), and potassium. Quantiferon TB and 21-hydroxylase antibody tests were negative. Hydrocortisone has been continued with plans to repeat Cosyntropin testing in 3 months to reassess. Conclusion: Pseudohyperaldosteronism with glucocorticoid deficiency requiring hydrocortisone treatment has thus far not been reported with posaconazole. Our case shows that posaconazole may lead to true primary glucocorticoid deficiency that can persist after discontinuation of posaconazole and reversal of pseudohyperaldosteronism. Reference: (1) Sanchez-Niño MD, Ortiz A. Unravelling drug-induced hypertension: Molecular mechanisms of aldosterone-independent mineralocorticoid receptor activation by posaconazole. Clin Kidney J 2018;11(5):688–90.

Limited Efficacy of Mifepristone Due to Poor Tolerance: A Clinical Challenge in Managing Cortisol Excess

A 53-year male with incidental bilateral adrenal masses along with symptoms of proximal muscle weakness, anxiety, and depression. Past medical history of uric acid nephrolithiasis, hypertension, hyperlipidemia, type 2 diabetes mellitus, anxiety, and depression. A right adrenal mass of 2.8cm and a left adrenal mass of 1.5cm both of <10 HU on non-enhancing CT. Hormonal activity workup was ordered which showed cortisol levels of 4.7mcg/dL on 1mg ONDST suggestive of autonomous cortisol excess and workup for primary hyperaldosteronism was negative. On follow up CT adrenal masses remained stable, but the patient underwent the annual hormonal workup for incidentaloma with 1mg ONDST and found with cortisol 4.5mcg/dL, eventually repeated with 2-day LDDST which showed no suppression of cortisol with levels at 4.5 mcg/dL confirming the diagnosis of autonomous cortisol excess. ACTH found to be suppressed at 3.1pg/dL (7.2–63.3 pg/dL) which helped confirm the diagnosis of non-ACTH dependent autonomous cortisol excess. Referred to surgery evaluation due to complications associated with cortisol excess as osteoporosis and uncontrolled hyperglycemia however surgical intervention was deferred until the source of cortisol excess could be identified within the bilateral adrenal masses and it was recommended to continue with medical therapy.As the cortisol excess source cannot be identified by localizing procedures and despite adequate medical therapy and stable adrenal masses on imaging, patient persisted with uncontrolled DM/hypertension and worsening BMD in the spine and hip with surgery not being an option. The patient was started on glucocorticoid receptor antagonist mifepristone in which upon reevaluation weakness and fatigue were noticeable along with hypokalemia of 3.1mmol/L after 2 weeks of therapy that was eventually replaced but 2 weeks later the patient discontinued therapy as he could not tolerate side effects related to adrenal insufficiency associated with mifepristone, such as weakness, fatigue, and dependence of potassium supplementation due to hypokalemia.This effect is physiologically important, because cortisol binds as avidly as aldosterone to the mineralocorticoid receptor, and the plasma cortisol concentration is approximately 100-fold higher than the plasma aldosterone concentration and it can lead to hypokalemia by the mechanism of apparent mineralocorticoid excess. Also, as mifepristone blocks cortisol action, the levels of ACTH and cortisol increase so high that hormonal measurement cannot be used to judge either therapeutic efficacy or adrenal insufficiency, we must go based on signs and symptoms.

Investigating the Transitional Cell Type in the Kidney Collecting Duct

The kidney cortical collecting duct (CCD) has long been thought to contain two distinct cell types, principal cells (PC) and intercalated cells (IC), which facilitate 4-5% of sodium and 10% of water reabsorption in the kidney. Recent single cell RNA-Seq data has identified a distinct transitional cell expressing both PC and IC markers and a number of distinct markers. In this study, the presence of CCD cell types was investigated in mice and rats under the disease model of the syndrome of apparent mineralocorticoid excess (SAME, conferred by a mutation of the Hsd11b2gene, expressed by PCs) and also in two CCD derived cell lines. Inactivation of HSD11B2in humans results in a severe, and often fatal, phenotype in early neonatal life, whilst milder mutations, with residual enzyme activity cause hypertension, sodium retention and hypokalemia in adulthood. The Hsd11b2 gene knockout (KO) model of SAME in mice and rats was studied in the context of CCD cell plasticity and it was hypothesised to reduce the proportion of PCs within the CCD. Cells in the CCD were counted in WT and Hsd11b2 KO animals following immunofluorescent staining for PC- and IC-specific markers (Aqp2 and V-ATPase B1, respectively) in paraffin-embedded kidney sections. ImageJ and GraphPadPrism were used to analyse data, which are expressed as mean ± SEM. Significance was assessed using Tukey's multiple comparisons test, p<0.0001. PC proportion was significantly reduced in KO mice CCDs compared to controls at 4 weeks (52.1 ± 1.9 % vs. 73.0 ± 1.9 %) and 17 weeks (54.1 ± 1.8 % vs. 72.2 ± 1.3 %). A significant increase in the number of cells expressing both PC and IC markers was observed between WT and KO at 4 weeks (8.4 ± 1.2 % vs.25.9 ± 2.0 %) and at 17 weeks (6.5 ± 0.8 % vs. 22.1 ± 2.0 %). Similarly, in the rat KO a significant reduction in the proportion of PCs was noted compared to controls at 5 weeks (60.69 ± 2.51 % vs. 73.30 ± 1.84 %) and 24 weeks (38.40 ± 2.07 % vs. 66.80 ± 1.94 %). This study shows CCD cell plasticity in models of SAME, but also provides further evidence for a PC+/IC+cell in the kidney. The mCCDcl1­ and mpkCCDcl4­ cell lines are typically used as models of PC function. Immunofluorescent staining using antibodies against PC, IC and transitional cell markers (Aqp2, V-ATPase B1 and Parm1, respectively) was carried out on fixed, polarised cells and images analysed using ImageJ software. It was found that both cell line lines contained cells that co-expressed PC and IC markers, similar to the cell type seen in mouse and rat kidneys. Furthermore, a large proportion of cells in both cell lines expressed the transitional cell marker, Parm1. These results provide further support for the presence of a transitional cell type in the CCD, especially in pathophysiological states. The observation of similar cells in CCD cell lines also indicates their use as in vitro models for investigating the role and plasticity of CCD cell types.

A Teenager Presents With Hypokalemia and Metabolic Alkalosis

Hypokalemia is one of the most common electrolyte disorders in hospitalized patient. Causes of hypokalemia include impaired renal potassium (K+) excretion, gastrointestinal losses or transcelluar shifts. Assessments of urinary K+excretion, acid-base status, and blood pressure are three major components to the causes ofhypokalemia.A random urine K+-to-creatinine (K+/Cr) less than 13 mEq/g Cr ( 1.5 mEq/mmol indicates primary and secondary hyperaldosteronism, Liddle syndrome, or apparent mineralocorticoid excess. By contrast, in the absence of hypertension, a urine K+ /Cr>1.5, is usually suggestive of surreptitious use of diuretic, Bartter syndrome or Gitelman syndrome. Measurements of the plasma renin activity and plasma aldosterone concentration are necessary to differentiate these conditionsfrom one another.Severe or symptomatic hypokalemia, if not recognized early or treated appropriately can lead to significant mortality and morbidity. In this article the basic principles of normal K+homeostasis and the pathophysiology that can disturb this balance are discussed. A selected case report focusing on the essential aspect of patient’s presentation, signs and laboratory data followed by series of questions with particular attention to the diagnosis and management of hypokalemia needed to assist in the differential diagnosis and treatmentare also discussed.Each question is followed by detailed discussion and reviews the recent publications that are useful at thebedside. Keywords:Hypokalemia; Metaboloc alkalosis; Causes; Diagnoses; Treatment.

Abnormal neonatal sodium handling in skin precedes hypertension in the SAME rat

We discovered high Na+ and water content in the skin of newborn Sprague–Dawley rats, which reduced ~ 2.5-fold by 7 days of age, indicating rapid changes in extracellular volume (ECV). Equivalent changes in ECV post birth were also observed in C57Bl/6 J mice, with a fourfold reduction over 7 days, to approximately adult levels. This established the generality of increased ECV at birth. We investigated early sodium and water handling in neonates from a second rat strain, Fischer, and an Hsd11b2-knockout rat modelling the syndrome of apparent mineralocorticoid excess (SAME). Despite Hsd11b2−/− animals exhibiting lower skin Na+ and water levels than controls at birth, they retained ~ 30% higher Na+ content in their pelts at the expense of K+ thereafter. Hsd11b2−/− neonates exhibited incipient hypokalaemia from 15 days of age and became increasingly polydipsic and polyuric from weaning. As with adults, they excreted a high proportion of ingested Na+ through the kidney, (56.15 ± 8.21% versus control 34.15 ± 8.23%; n = 4; P < 0.0001), suggesting that changes in nephron electrolyte transporters identified in adults, by RNA-seq analysis, occur by 4 weeks of age. Our data reveal that Na+ imbalance in the Hsd11b2−/− neonate leads to excess Na+ storage in skin and incipient hypokalaemia, which, together with increased, glucocorticoid-induced Na+ uptake in the kidney, then contribute to progressive, volume contracted, salt-sensitive hypertension. Skin Na+ plays an important role in the development of SAME but, equally, may play a key physiological role at birth, supporting post-natal growth, as an innate barrier to infection or as a rudimentary kidney.

Species-specific differences in the inhibition of 11β-hydroxysteroid dehydrogenase 2 by itraconazole and posaconazole

11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) converts active 11β-hydroxyglucocorticoids to their inactive 11-keto forms, thereby preventing inappropriate mineralocorticoid receptor activation by glucocorticoids. Disruption of 11β-HSD2 activity by genetic defects or inhibitors causes the syndrome of apparent mineralocorticoid excess (AME), characterized by hypokalemia, hypernatremia and hypertension. Recently, the azole antifungals itraconazole and posaconazole were identified to potently inhibit human 11β-HSD2, and several case studies described patients with acquired AME. To begin to understand why this adverse drug effect was missed during preclinical investigations, the inhibitory potential of itraconazole, its main metabolite hydroxyitraconazole (OHI) and posaconazole against 11β-HSD2 from human and three commonly used experimental animals was assessed. Whilst human 11β-HSD2 was potently inhibited by all three compounds (IC50 values in the nanomolar range), the rat enzyme was moderately inhibited (1.5- to 6-fold higher IC50 values compared to human), and mouse and zebrafish 11β-HSD2 were very weakly inhibited (IC50 values above 7 μM). Sequence alignment and application of newly generated homology models for human and mouse 11β-HSD2 revealed significant differences in the C-terminal region and the substrate binding pocket. Exchange of the C-terminus and substitution of residues Leu170,Ile172 in mouse 11β-HSD2 by the corresponding residues His170,Glu172 of the human enzyme resulted in a gain of sensitivity to itraconazole and posaconazole, resembling human 11β-HSD2. The results provide an explanation for the observed species-specific 11β-HSD2 inhibition by the studied azole antifungals. The obtained structure-activity relationship information should facilitate future assessments of 11β-HSD2 inhibitors and aid choosing adequate animal models for efficacy and safety studies.

Impaired Distal Tubular Acidification, Renal Cysts and Nephrocalcinosis in Monogenic Hypertension.

Monogenic defects in tubular sodium handling contribute a small proportion to hypertension in childhood. Presentation varies from severe hypertension manifesting at birth to asymptomatic hypertension and hypokalemic metabolic alkalosis detected incidentally in adulthood. A 12-y-old girl presenting with polyuria, polydipsia, severe hypertension and seizures, was found to have hypokalemia, renal medullary cysts and nephrocalcinosis. Clinical exome revealed a homozygous variation of unknown significance in exon 5 of the HSD11B2 gene, indicating the diagnosis of apparent mineralocorticoid excess. Therapy with spironolactone was associated with resolution of hypokalemia and normal blood pressure during two-year follow up.

Apparent mineralocorticoid excess caused by novel compound heterozygous mutations in HSD11B2

Abstract Background Apparent mineralocorticoid excess (AME) is a rare autosomal recessive genetic disorder caused by a mutation in the 11β-hydroxysteroid dehydrogenase type 2 gene (HSD11B2). AME is characterized by early-onset and severe hypertension, hypokalemia, and metabolic alkalosis. Purpose This study aimed to study the molecular genetics, clinical presentation, biochemical parameters, and treatment in the proband with AME from a non-consanguineous Chinese family. Methods Genomic DNA was recovered from peripheral blood leukocytes from nine subjects in this family. Next-generation sequencing and Sanger sequencing were performed to identify the HSD11B2 variants. In silico and genotype-phenotype correlations analyses were used to predict pathogenicity of candidate variants. A tailored therapy was performed for identified mutations carriers. Results Genetic analysis identified novel compound heterozygous HSD11B2 mutations (c.343-348del/c.1099-1101del) in the proband. In silico analysis predicted these HSD11B2 mutations were deleterious. The structural change and predicted consequences owing to the compound mutations have been modeled. The same compound mutations were not found in any other family members, 100 hypertensives, or 100 healthy controls. The proband had typical manifestations of AME, including early-onset and severe hypertension, hypokalemia, low plasma aldosterone concentration, hypokalemic alkalosis and nephrolithiasis. The probands' blood pressure and serum potassium level had returned to normal after treatmennt with dexamethasone (1.5 mg/day) and spirolactone (40 mg/day) for three months. Conclusions We conclude that this novel compound mutations are responsible for AME in the proband. These genetic and clinical data expand the genetic spectrum of HSD11B2 and demonstrate the pathogenic effects of identified mutations and genotype-phenotype correlations. It is emphasized that genetic diagnosis and specific treatment play an important role in patients with AME. Figure 1 Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Key Research and Development Program of China; PUMC Youth Fund and the Fundamental Research Funds for the Central Universities

Apparent mineralocorticoid excess caused by novel compound heterozygous mutations in HSD11B2 and characterized by early-onset hypertension and hypokalemia

PurposeApparent mineralocorticoid excess (AME) is an ultrarare autosomal recessive disorder resulting from deficiency of 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) caused by mutations in HSD11B2. The purpose of this study was to identify novel compound heterozygous HSD11B2 mutations in a Chinese pedigree with AME and conduct a systematic review evaluating the AME clinical features associated with HSD11B2 mutations.MethodsNext-generation sequencing was performed in the proband, and Sanger sequencing was used to identify candidate variants in family members, 100 hypertensives, and 100 healthy controls. A predicted structure of 11βHSD2 was constructed by in silico modeling. A systematic review was used to identify cases of HSD11B2-related AME. Data for genotyping and clinical characterizations and complications were extracted.ResultsNext-generation sequencing showed novel compound heterozygous mutations (c.343_348del and c.1099_1101del) in the proband with early-onset hypertension and hypokalemia. Sanger sequencing verified the monoallelic form of the same mutations in five other relatives but not in 100 hypertensives or 100 healthy subjects. In silico structural modeling showed that compound mutations may simultaneously perturb the substrate and coenzyme binding pocket. A systematic review of 101 AME patients with 54 HSD11B2 mutations revealed early-onset hypertension, hypokalemia and homozygous mutations as common features. The homozygous HSD11B2 mutations correlated with low birth weight (r = 0.285, P = 0.02).ConclusionsWe report novel compound heterozygous HSD11B2 mutations in a Chinese teenager with early-onset hypertension, and enriched genotypic and phenotypic spectrums in AME. Genetic testing helps early diagnosis and treatment for AME patients, which may avoid target organ damage.