Familial hyperaldosteronism type III

Single nucleotide polymorphism-based biomarker in primary hypertension

Primary hypertension is a multiplex and multifactorial disease influenced by various strong components including genetics. Extensive research such as Genome-wide association studies and candidate gene studies have revealed various single nucleotide polymorphisms (SNPs) related to hypertension, providing insights into the genetic basis of the condition. This review summarizes the current status of SNP research in primary hypertension, including examples of hypertension-related SNPs, their location, function, and frequency in different populations. The potential clinical implications of SNP research for primary hypertension management are also discussed, including disease risk prediction, personalized medicine, mechanistic understanding, and lifestyle modifications. Furthermore, this review highlights emerging technologies and methodologies that have the potential to revolutionize the vast understanding of the basis of genetics in primary hypertension. Gene editing holds the potential to target and correct any kind of genetic mutations that contribute to the development of hypertension or modify genes involved in blood pressure regulation to prevent or treat the condition. Advances in computational biology and machine learning enable researchers to analyze large datasets and identify complex genetic interactions contributing to hypertension risk. In conclusion, SNP research in primary hypertension is rapidly evolving with emerging technologies and methodologies that have the potential to transform the knowledge about genetic basis related to the condition. These advances hold promise for personalized prevention and treatment strategies tailored to an individual's genetic profile ultimately improving patient outcomes and reducing healthcare costs.

Familial hyperaldosteronism: an European Reference Network on Rare Endocrine Conditions clinical practice guideline

We describe herein the European Reference Network on Rare Endocrine Conditions clinical practice guideline on diagnosis and management of familial forms of hyperaldosteronism. The guideline panel consisted of 10 experts in primary aldosteronism, endocrine hypertension, paediatric endocrinology, and cardiology as well as a methodologist. A systematic literature search was conducted, and because of the rarity of the condition, most recommendations were based on expert opinion and small patient series. The guideline includes a brief description of the genetics and molecular pathophysiology associated with each condition, the patients to be screened, and how to screen. Diagnostic and treatment approaches for patients with genetically determined diagnosis are presented. The recommendations apply to patients with genetically proven familial hyperaldosteronism and not to families with more than one case of primary aldosteronism without demonstration of a responsible pathogenic variant.

Who needs to be screened for primary aldosteronism?

The prevalence of patients with primary aldosteronism (PA) is about 5%-15% in hypertensive patients, and it is common cause of secondary hypertension in clinical practice. Two major causes of PA are noted, namely bilateral adrenal hyperplasia and aldosterone-producing adenoma, and the general diagnosis is based on three steps: (1) screening, (2) confirmatory testing, and (3) subtype differentiation (Figure 1). The recommendation for screening patients is at an increased risk of PA, here we focus on which patients should be screened for PA, not only according to well-established guidelines but for potential patients with PA. We recommend screening for 1) patients with resistant or persistent hypertension, 2) hypertensive patients with hypokalemia (spontaneous or drug-induced), 3) young hypertensive patients (age <40 years), and 4) all hypertensive patients with a history of PA in first-degree relatives. Moreover, we suggest screening for 1) hypertensive patients themselves or first-degree relatives with early target organ damage, such as stroke and other diseases, 2) all hypertensive patients with a concurrent adrenal incidentaloma, 3) hypertensive patients with obstructive sleep apnea, 4) hypertensive patients with atrial fibrillation unexplained by structural heart defects and/or other conditions resulting in the arrhythmia, 5) hypertensive patients with anxiety and other psychosomatic symptoms, and 6) hypertensive patients without other comorbidities to maintain cost-effectiveness.

Nutrigenomics of inward rectifier potassium channels

Inwardly rectifying potassium (Kir) channels play a key role in maintaining the resting membrane potential and supporting potassium homeostasis. There are many variants of Kir channels, which are usually tetramers in which the main subunit has two trans-membrane helices attached to two N- and C-terminal cytoplasmic tails with a pore-forming loop in between that contains the selectivity filter. These channels have domains that are strongly modulated by molecules present in nutrients found in different diets, such as phosphoinositols, polyamines and Mg²⁺. These molecules can impact these channels directly or indirectly, either allosterically by modulation of enzymes or via the regulation of channel expression. A particular type of these channels is coupled to cell metabolism and inhibited by ATP (KATP channels, essential for insulin release and for the pathogenesis of metabolic diseases like diabetes mellitus). Genomic changes in Kir channels have a significant impact on metabolism, such as conditioning the nutrients and electrolytes that an individual can take. Thus, the nutrigenomics of ion channels is an important emerging field in which we are attempting to understand how nutrients and diets can affect the activity and expression of ion channels and how genomic changes in such channels may be the basis for pathological conditions that limit nutrition and electrolyte intake. In this contribution we briefly review Kir channels, discuss their nutrigenomics, characterize how different components in the diet affect their function and expression, and suggest how their genomic changes lead to pathological phenotypes that affect diet and electrolyte intake.

Relevance of KCNJ5 in Pathologies of Heart Disease

Abnormalities in G-protein-gated inwardly rectifying potassium (GIRK) channels have been implicated in diseased states of the cardiovascular system; however, the role of GIRK4 (Kir3.4) in cardiac physiology and pathophysiology has yet to be completely understood. Within the heart, the KACh channel, consisting of two GIRK1 and two GIRK4 subunits, plays a major role in modulating the parasympathetic nervous system's influence on cardiac physiology. Being that GIRK4 is necessary for the functional KACh channel, KCNJ5, which encodes GIRK4, it presents as a therapeutic target for cardiovascular pathology. Human variants in KCNJ5 have been identified in familial hyperaldosteronism type III, long QT syndrome, atrial fibrillation, and sinus node dysfunction. Here, we explore the relevance of KCNJ5 in each of these diseases. Further, we address the limitations and complexities of discerning the role of KCNJ5 in cardiovascular pathophysiology, as identical human variants of KCNJ5 have been identified in several diseases with overlapping pathophysiology.

Who should be screened for primary aldosteronism? A comprehensive review of current evidence

Arterial hypertension is a major risk factor for cardiovascular disease. The prevalence of primary aldosteronism (PA) ranges from 5% to 10% in the general hypertensive population and is regarded as one of the most common causes of secondary hypertension. There are two major causes of PA: bilateral adrenal hyperplasia and aldosterone-producing adenoma. The diagnosis of PA comprises screening, confirmatory testing, and subtype differentiation. The Endocrine Society Practice Guidelines for the diagnosis and treatment of PA recommends screening of patients at an increased risk of PA. These categories include patients with stage 2 and 3 hypertension, drug-resistant hypertension, hypertensive with spontaneous or diuretic-induced hypokalemia, hypertension with adrenal incidentaloma, hypertensive with a family history of early onset hypertension or cerebrovascular accident at a young age, and all hypertensive first-degree relatives of patients with PA. Recently, several studies have linked PA with obstructive sleep apnea and atrial fibrillation unexplained by structural heart defects and/or other conditions known to cause the arrhythmia, which may be partly responsible for the higher rates of cardiovascular and cerebrovascular accidents in patients with PA. The aim of this review is to discuss which patients should be screened for PA, focusing not only on well-established guidelines but also on additional groups of patients with a potentially higher prevalence of PA, as has been reported in recent research.

Pathophysiology of bilateral hyperaldosteronism

PURPOSE OF REVIEW

Renin-independent aldosterone production from one or both affected adrenal(s), a condition known as primary aldosteronism (PA), is a common cause of secondary hypertension. In this review, we aimed to summarize recent findings regarding pathophysiology of bilateral forms of PA, including sporadic bilateral hyperaldosteronism (BHA) and rare familial hyperaldosteronism.

RECENT FINDINGS

The presence of subcapsular aldosterone synthase (CYP11B2)-expressing aldosterone-producing micronodules, also called aldosterone-producing cell clusters, appears to be a common histologic feature of adrenals with sporadic BHA. Aldosterone-producing micronodules frequently harbor aldosterone-driver somatic mutations. Other potential factors leading to sporadic BHA include rare disease-predisposing germline variants, circulating angiotensin II type 1 receptor autoantibodies, and paracrine activation of aldosterone production by adrenal mast cells. The application of whole exome sequencing has also identified new genes that cause inherited familial forms of PA.

SUMMARY

Research over the past 10 years has significantly improved our understanding of the molecular pathogenesis of bilateral PA. Based on the improved understanding of BHA, future studies should have the ability to develop more personalized treatment options and advanced diagnostic tools for patients with PA.

A revised mechanism of action of hyperaldosteronism-linked mutations in cytosolic domains of GIRK4 (KCNJ5)

KEY POINTS

Mutations in GIRK4 (KCNJ5) G-protein gated channels cause primary aldosteronism, a major cause of secondary hypertension. The primary mechanism is believed to be loss of K⁺ selectivity. R52H and E246K, aldosteronism-causing mutations in cytosolic N- and C- termini of GIRK4, were reported to cause loss of K⁺ selectivity. We show that R52H, E246K and G247R mutations render homotetrameric GIRK channels non-functional. In heterotetrameric context with GIRK1, these mutations impair membrane expression, interaction with Gβγ and open probability, but do not alter K⁺ selectivity or inward rectification. In human aldosterone-secreting cell line, a GIRK4 opener and overexpression of heterotetrameric GIRK1/4_WT , but not over-expression of GIRK1/4 mutants, reduced aldosterone secretion. Aldosteronism-causing mutations in cytosolic domain of GIRK4 are loss-of-function mutations rather than gain-of-function, selectivity-loss mutations. Deciphering of exact biophysical mechanism that impairs the channel is crucial for setting the course of treatment.

ABSTRACT

G-protein gated, inwardly rectifying potassium channels (GIRK) mediate inhibitory transmission in brain and heart, and are present in adrenal cortex. GIRK4 (KCNJ5) subunits are abundant in the heart and adrenal cortex. Multiple mutations of KCNJ5 cause primary aldosteronism (PA). Mutations in the pore region of GIRK4 cause loss of K⁺ selectivity, Na⁺ influx, and depolarization of zona glomerulosa cells followed by hypersecretion of aldosterone. The concept of selectivity loss has been extended to mutations in cytosolic domains of GIRK4 channels, remote from the pore. We expressed aldosteronism-linked GIRK4_R52H , GIRK4_E246K , and GIRK4_G247R mutants in Xenopus oocytes. Whole-cell currents of heterotetrameric GIRK1/4_R52H and GIRK1/4_E246K channels were greatly reduced compared to GIRK1/4_WT . Nevertheless, all heterotetrameric mutants retained full K⁺ selectivity and inward rectification. When expressed as homotetramers, only GIRK4_WT , but none of the mutants, produced whole-cell currents. Confocal imaging, single channel and Förster Resonance Energy Transfer (FRET) analyses showed: 1) reduction of membrane abundance of all mutated channels, especially as homotetramers, 2) impaired interaction with Gβγ subunits, and 3) reduced open probability of GIRK1/4_R52H . VU0529331, a GIRK4 opener, activated homotetrameric GIRK4_G247R channels, but not GIRK4_R52H and GIRK4_E246K . In human adrenocortical carcinoma cell line (HAC15), VU0529331 and over-expression of heterotetrameric GIRK1/4_WT , but not over-expression of GIRK1/4 mutants, reduced aldosterone secretion. Our results suggest that, contrary to pore mutants of GIRK4, non-pore mutants R52H and E246K mutants are loss-of-function rather than gain-of-function/selectivity-loss mutants. Hence, GIRK4 openers may be a potential course of treatment for patients with cytosolic N- and C-terminal mutations. Abstract Figure: There are two mutations types in KCNJ5 (GIRK4) that can cause excessive secretion of aldosterone, leading to primary aldosteronism. Mutations of the first type render the channel non-selective to monovalent cations and often constitutively active, thus depolarizing the zona granulosa cells. This previously described mechanism underlies the disease-causing effects of mutations of amino acid residues located in the pore region (red color). Blockers of the channel may be useful as potential treatment to reduce aldosterone secretion. Here we show that mutations of the second type, located in the cytosolic domain remote from the pore, act by a different mechanism. They do not alter channel's ion selectivity or rectification but cause poor expression or poor activation by Gβγ, resulting in a reduction in cell's K⁺ conductance and depolarization. In this case, GIRK4 openers can potentially be useful to prevent the excessive aldosterone secretion. This article is protected by copyright. All rights reserved.

Progress on Genetic Basis of Primary Aldosteronism

Primary aldosteronism (PA) is a heterogeneous group of disorders caused by the autonomous overproduction of aldosterone with simultaneous suppression of plasma renin activity (PRA). It is considered to be the most common endocrine cause of secondary arterial hypertension (HT) and is associated with a high rate of cardiovascular complications. PA is most often caused by a bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenoma (APA); rarer causes of PA include genetic disorders of steroidogenesis (familial hyperaldosteronism (FA) type I, II, III and IV), aldosterone-producing adrenocortical carcinoma, and ectopic aldosterone-producing tumors. Over the last few years, significant progress has been made towards understanding the genetic basis of PA, classifying it as a channelopathy. Recently, a growing body of clinical evidence suggests that mutations in ion channels appear to be the major cause of aldosterone-producing adenomas, and several mutations within the ion channel encoding genes have been identified. Somatic mutations in four genes (KCNJ5, ATP1A1, ATP2B3 and CACNA1D) have been identified in nearly 60% of the sporadic APAs, while germline mutations in KCNJ5 and CACNA1H have been reported in different subtypes of familial hyperaldosteronism. These new insights into the molecular mechanisms underlying PA may be associated with potential implications for diagnosis and therapy.

Transcriptomics, Epigenetics, and Metabolomics of Primary Aldosteronism

INTRODUCTION

Primary aldosteronism (PA) is the most common cause of endocrine hypertension, mainly caused by aldosterone-producing adenomas or hyperplasia; understanding its pathophysiological background is important in order to provide ameliorative treatment strategies. Over the past several years, significant progress has been documented in this field, in particular in the clarification of the genetic and molecular mechanisms responsible for the pathogenesis of aldosterone-producing adenomas (APAs).

METHODS

Systematic searches of the PubMed and Cochrane databases were performed for all human studies applying transcriptomic, epigenetic or metabolomic analyses to PA subjects. Studies involving serial analysis of gene expression and microarray, epigenetic studies with methylome analyses and micro-RNA expression profiles, and metabolomic studies focused on improving understanding of the regulation of autonomous aldosterone production in PA were all included.

RESULTS

In this review we summarize the main findings in this area and analyze the interplay between primary aldosteronism and several signaling pathways with differential regulation of the RNA and protein expression of several factors involved in, among others, steroidogenesis, calcium signaling, and nuclear, membrane and G-coupled protein receptors. Distinct transcriptomic and metabolomic patterns are also presented herein, depending on the mutational status of APAs. In particular, two partially opposite transcriptional and steroidogenic profiles appear to distinguish APAs carrying a KCNJ5 mutation from all other APAs, which carry different mutations.

CONCLUSIONS

These findings can substantially contribute to the development of personalized treatment in patients with PA.

Diseases caused by mutations in the Na+/K+ pump α1 gene ATP1A1

Human cell survival requires function of the Na⁺/K⁺ pump; the heteromeric protein that hydrolyzes ATP to extrude Na⁺ and import K⁺ across the plasmalemma, thereby building and maintaining these ions' electrochemical gradients. Numerous dominant diseases caused by mutations in genes encoding for Na⁺/K⁺ pump catalytic (α) subunit isoforms highlight the importance of this protein. Here, we review literature describing disorders caused by missense mutations in ATP1A1, the gene encoding the ubiquitously expressed α1 isoform of the Na⁺/K⁺ pump. These various maladies include primary aldosteronism with secondary hypertension, an endocrine syndrome, Charcot-Marie-Tooth disease, a peripheral neuropathy, complex spastic paraplegia, another neuromuscular disorder, as well as hypomagnesemia accompanied by seizures and cognitive delay, a condition affecting the renal and central nervous systems. This article focuses on observed commonalities among these mutations' functional effects, as well as on the special characteristics that enable each particular mutation to exclusively affect a certain system, without affecting others. In this respect, it is clear how somatic mutations localized to adrenal adenomas increase aldosterone production without compromising other systems. However, it remains largely unknown how and why some but not all de novo germline or familial mutations (where the mutant must be expressed in numerous tissues) produce a specific disease and not the other diseases. We propose hypotheses to explain this observation and the approaches that we think will drive future research on these debilitating disorders to develop novel patient-specific treatments by combining the use of heterologous protein-expression systems, patient-derived pluripotent cells, and gene-edited cell and mouse models.

Advances in Genomics Research of Blood Pressure Responses to Dietary Sodium and Potassium Intakes

More than half of US adults have hypertension by 40 years of age and a subsequent increase in atherosclerotic cardiovascular disease risk. Dietary sodium and potassium are intricately linked to the pathophysiology of hypertension. However, blood pressure responses to dietary sodium and potassium, phenomena known as salt and potassium sensitivity of blood pressure, respectively, are heterogenous and normally distributed in the general population. Like blood pressure, salt and potassium sensitivity are complex phenotypes, and previous research has shown that up to 75% of individuals experience a blood pressure change in response to such dietary minerals. Previous research has also implicated both high salt sensitivity and low salt sensitivity (or salt resistance) of blood pressure to an increased risk of hypertension and potentially atherosclerotic cardiovascular disease risk. Given the clinical challenges required to accurately measure the sodium and potassium response phenotypes, genomic characterization of these traits has become of interest for hypertension prevention initiatives on both the individual and population levels. Here, we review advances in human genomics research of blood pressure responses to dietary sodium and potassium by focusing on 3 main areas, including the phenotypic characterization of salt sensitivity and resistance, clinical challenges in diagnosing such phenotypes, and the genomic mechanisms that may help to explain salt and potassium sensitivity and resistance. Through this process, we hope to further underline the value of leveraging genomics and broader multiomics for characterizing the blood pressure response to sodium and potassium to improve precision in lifestyle approaches for primordial and primary atherosclerotic cardiovascular disease prevention.

Diagnosis and Management of Endocrine Hypertension in Children and Adolescents

Hypertension in childhood and adolescence has increased in prevalence. Interest in the disease was raised after the 2017 clinical practice guidelines of the American Academy of Paediatrics on the definition and classification of paediatric hypertension. Among the secondary causes of paediatric hypertension, endocrine causes are relatively rare but important due to their unique treatment options. Excess of catecholamine, glucocorticoids and mineralocorticoids, congenital adrenal hyperplasia, hyperaldosteronism, hyperthyroidism and other rare syndromes with specific genetic defects are endocrine disorders leading to paediatric and adolescent hypertension. Adipose tissue is currently considered the major endocrine gland. Obesity-related hypertension constitutes a distinct clinical entity leading to an endocrine disorder. The dramatic increase in the rates of obesity during childhood has resulted in a rise in obesity-related hypertension among children, leading to increased cardiovascular risk and associated increased morbidity and mortality. This review presents an overview of pathophysiology and diagnosis of hypertension resulting from hormonal excess, as well as obesity-related hypertension during childhood and adolescence, with a special focus on management.

Genetics, prevalence, screening and confirmation of primary aldosteronism: a position statement and consensus of the Working Group on Endocrine Hypertension of The European Society of Hypertension

: Autonomous aldosterone overproduction represents the underlying condition of 5-10% of patients with arterial hypertension and carries a significant burden of mortality and morbidity. The diagnostic algorithm for primary aldosteronism is sequentially based on hormonal tests (screening and confirmation tests), followed by lateralization studies (adrenal CT scanning and adrenal venous sampling) to distinguish between unilateral and bilateral disease. Despite the recommendations of the Endocrine Society guideline, primary aldosteronism is largely underdiagnosed and undertreated with high between-centre heterogeneity. Experts from the European Society of Hypertension have critically reviewed the available literature and prepared a consensus document constituting two articles to summarize current knowledge on the epidemiology, diagnosis, treatment, and complications of primary aldosteronism.

The spectrum of low-renin hypertension

Low-renin hypertension (LRH) is a frequent condition in patients with arterial hypertension, accounting for 30% of patients. Monogenic forms can cause LRH in a minority of cases. However, in the large majority of patients, LRH is caused by the combined effects of congenital and acquired factors, comprising dietary habits. Several genetic variants have been proposed as co-factors in the pathogenesis of LRH with normal-low serum aldosterone. Emerging evidences support the hypothesis that a large proportion of LRH with normal-high serum aldosterone is associated with subclinical primary aldosteronism (PA). The recent identification of aldosterone-producing cell clusters (APCCs) as the possible cause of subclinical PA, further supported the concept of a continuous spectrum of autonomous aldosterone secretion, from subclinical forms towards overt PA. In this review we describe the main aspects of LRH, focusing on molecular basis, clinical risk profile and patients' management.

Old and new genes in primary aldosteronism

Primary aldosteronism (PA) is the most common form of secondary hypertension affecting 5%-10% of patients with arterial hypertension. In PA, high blood pressure is associated with high aldosterone and low renin levels, and often hypokalemia. In a majority of cases, autonomous aldosterone production by the adrenal gland is caused by an aldosterone producing adenoma (APA) or bilateral adrenal hyperplasia (BAH). During the last ten years, a better knowledge of the pathophysiology of PA came from the discovery of somatic and germline mutations in different genes in both sporadic and familial forms of the disease. Those genes code for ion channels and pumps, as well as proteins involved in adrenal cortex development and function. Targeted next generation sequencing following immunohistochemistry guided detection of aldosterone synthase expression allows detection of somatic mutations in up to 90% of APA, while whole exome sequencing has discovered the genetic causes of four different familial forms of PA. The identification, in BAH, of somatic mutations in aldosterone producing cell clusters open new perspectives in our understanding of the bilateral form of the disease and the development of new therapeutic approaches.

Mosaicism for KCNJ5 Causing Early-Onset Primary Aldosteronism due to Bilateral Adrenocortical Hyperplasia

BACKGROUND

Somatic variants in KCNJ5 are the most common cause of primary aldosteronism (PA). There are few patients with PA in whom the disease is caused by germline variants in the KCNJ5 potassium channel gene (familial hyperaldosteronism type III-FH-III).

METHODS

A 5-year-old patient who developed hypertension due to bilateral adrenocortical hyperplasia (BAH) causing PA had negative peripheral DNA testing for any known genetic causes of PA. He was treated medically with adequate control of his PA but by the third decade of his life, due to worsening renal function, he underwent bilateral adrenalectomy.

RESULTS

Focused exome sequencing in multiple nodules of his BAH uncovered a "hot-spot" pathogenic KCNJ5 variant, while repeated Sanger sequencing showed no detectable DNA defects in peripheral blood and other tissues. However, whole exome, "deep" sequencing revealed that 0.23% of copies of germline DNA did in fact carry the same KCNJ5 variant that was present in the adrenocortical nodules, suggesting low level germline mosaicism for this PA-causing KCNJ5 defect.

CONCLUSIONS

Thus, this patient represents a unique case of BAH due to a mosaic KCNJ5 defect. Undoubtedly, his milder PA compared with other known cases of FH-III, was due to his mosaicism. This case has a number of implications for the prognosis, treatment, and counseling of the many patients with PA due to BAH that are seen in hypertension clinics.

Overview of Monogenic Forms of Hypertension Combined With Hypokalemia

Hypertension is an important risk factor in many conditions and creates a heavy burden of disease and mortality globally. Polygenic hypertension is the most common form; however, it is increasingly recognized that monogenic hypertension is not rare, especially in patients with electrolyte disorders. Single genetic alterations are associated with plasma volume expansion and catecholamines/sympathetic excess with simultaneously increased potassium excretion in the urine and potassium intracellular shift. Early-onset refractory hypertension and profound hypokalemia are characteristics of monogenic hypertension. However, accumulated evidence shows the existence of phenotypic heterogeneity in monogenic hypertension meaning that, even for mild symptoms, clinicians cannot easily exclude the possibility of monogenic hypertension. Genetic, epigenetic and non-genetic factors are all possible mechanisms influencing phenotypic diversity. Genetic sequencing is a precise and efficient method that can broaden the mutant gene spectrum of the disease and is very helpful for understanding the pathophysiology of monogenic hypertension. Genetic sequencing, along with biochemical tests and imaging modalities, is essential for the early diagnosis and targeted management of monogenic hypertension to avoid long-term catastrophic complications.

Primary Aldosteronism: KCNJ5 Mutations and Adrenocortical Cell Growth

Aldosterone-producing adenomas with somatic mutations in the KCNJ5 G-protein-coupled inwardly rectifying potassium channel are a cause of primary aldosteronism. These mutations drive aldosterone excess, but their role in cell growth is undefined. Our objective was to determine the role of KCNJ5 mutations in adrenal cell proliferation and apoptosis. The Ki67 proliferative index was positively correlated with adenoma diameter in aldosterone-producing adenomas with a KCNJ5 mutation (r=0.435, P=0.007), a negative correlation was noted in adenomas with no mutation detected (r=-0.548, P=0.023). Human adrenocortical cell lines were established with stable expression of cumate-inducible wild-type or mutated KCNJ5. Increased cell proliferation was induced by low-level induction of KCNJ5-T158A expression compared with control cells (P=0.009), but increased induction ablated this difference. KCNJ5-G151R displayed no apparent proliferative effect, but KCNJ5-G151E and L168R mutations each resulted in decreased cell proliferation (difference P<0.0001 from control cells, both comparisons). Under conditions tested, T158A had no effect on apoptosis, but apoptosis increased with expression of G151R (P<0.0001), G151E (P=0.008), and L168R (P<0.0001). We generated a specific KCNJ5 monoclonal antibody which was used in immunohistochemistry to demonstrate strong KCNJ5 expression in adenomas without a KCNJ5 mutation and in the zona glomerulosa adjacent to adenomas irrespective of genotype as well as in aldosterone-producing cell clusters. Double immunofluorescence staining for KCNJ5 and CYP11B2 (aldosterone synthase) showed markedly decreased KCNJ5 immunostaining in CYP11B2-positive cells compared with CYP11B2-negative cells in aldosterone-producing adenomas with a KCNJ5 mutation. Together, these findings support the concept that cell growth effects of KCNJ5 mutations are determined by the expression level of the mutated channel.

Familial hyperaldosteronism type III a novel case and review of literature

Less than 15% of hypertension cases in children are secondary to a primary hyperaldosteronism. This is idiopathic in 60% of the cases, secondary to a unilateral adenoma in 30% and 10% remaining by primary adrenal hyperplasia, familial hyperaldosteronism, ectopic aldosterone production or adrenocortical carcinoma.To date, four types of familial hyperaldosteronism (FH I to FH IV) have been reported. FH III is caused by germline mutations in KCNJ5, encoding the potassium channel Kir3.4. The mutations cause the channel to lose its selectivity for potassium, allowing large quantities of sodium to enter the cell. As a consequence, the membrane depolarizes, voltage-gated calcium channels open, calcium enters the cell, initiating the cascade that leads to aldosterone synthesis. Somatic mutations in KCNJ5 has also been described in aldosterone-producing adenomas. The most frequent presentation of FH III is with severe hyperaldosteronism symptoms and resistance to pharmacological therapy which leads to bilateral adrenalectomy. We will review current literature and describe a child with FH III due to a novel de novo deletion in KCNJ5 with wild phenotype as a sign of clinical variability of this disease.

Diagnosis and treatment of primary aldosteronism: practical clinical perspectives

Primary aldosteronism (PA), the most common form of secondary hypertension, can be either surgically cured or treated with targeted pharmacotherapy. PA is frequently undiagnosed and untreated, leading to aldosterone-specific cardiovascular morbidity and nephrotoxicity. Thus, clinicians should perform case detection testing for PA at least once in all patients with hypertension. Confirmatory testing is indicated in most patients with positive case detection testing results. The next step is to determine whether patients with confirmed PA have a disease that can be cured with surgery or whether it should be treated medically; this step is guided by computed tomography scan of the adrenal glands and adrenal venous sampling. With appropriate surgical expertise, laparoscopic unilateral adrenalectomy is safe, efficient and curative in patients with unilateral adrenal disease. In patients who have bilateral aldosterone hypersecretion, the optimal management is a low-sodium diet and lifelong treatment with a mineralocorticoid receptor antagonist administered at a dosage to maintain a high-normal serum potassium concentration without the aid of oral potassium supplements.

Genetics and pathophysiology of low-renin arterial hypertension

The review is devoted to the consideration of genetic determination and pathophysiology of one of the forms of hypertensive disease known as low-renin hypertension. At frst glance, the development of low-renin hypertension is “unnatural”, as renin, as a key enzyme of the renin-angiotensin system, which plays an important role in the development of hypertensive disease, is suppressed in low-renin hypertension. At the same time, the most important drugs actual in the treatment of hypertensive disease belong to the renin-angiotensin system blockers. This contradiction was resolved by a study of genetic and pathophysiological mechanisms of hypertension in some groups of patients with characteristic symptoms bringing these people together. Genetic studies of some recent decades using both family analysis and modern molecular genetic technologies have revealed the main mechanisms underlying low-renin hypertension, which can be classifed as certain syndromes with well-defned genetic and clinical features. These syndromes include cases of sporadically occurring somatic mutations in the cells of the adrenal cortex, which begin to produce aldosterone in increased amounts. Also, several oligogenic forms of low-renin hypertension were studied, some of which are associated with the hyperproduction of aldosterone, but in the others the development of low-renin hypertension was associated with mutations of genes involved in regulation of the functioning of the kidney ion channels. The discovery of some types of arterial hypertension with known mechanisms of their development is of paramount importance for medicine, as it allows for targeted efective therapy and in some cases for achieving a complete cure. However, the main contingent of patients with low-renin hypertension belongs to cases with unexplained etiology, as their development is associated with polygenic systems and with a signifcant influence of numerous environmental factors. The study of genetic and physiological mechanisms of various forms of low-renin arterial hypertension provides a good example of how penetration into the intimate mechanisms of the blood pressure regulation in each personal case makes it possible to identify some specifc syndromes and establish its fnal causes. It seems that progress in understanding the causes and mechanisms of essential hypertension lies along this way.

Timeline of Advances in Genetics of Primary Aldosteronism

The overwhelming majority of cases of primary aldosteronism (PA) occur sporadically due to a unilateral aldosterone-producing adenoma (APA) or bilateral idiopathic adrenal hyperplasia. Familial forms of PA are rare with four subtypes defined to date (familial hyperaldosteronism types I-IV). The molecular basis of familial hyperaldosteronism type I (FH type I or glucocorticoid-remediable aldosteronism) was established in 1992; two decades later the genetic variant causing FH type III was identified and germline mutations causing FH type IV and FH type II were determined soon after. Effective diagnostic protocols and methods to detect the overactive gland in unilateral PA by adrenal venous sampling followed by laparoscopic adrenalectomy have made available APAs for scientific studies. In rapid succession, following the widespread use of next-generation sequencing, recurrent somatic driver mutations in APAs were identified in genes encoding ion channels and transporters. The development of highly specific monoclonal antibodies against key enzymes in adrenal steroidogenesis has unveiled the heterogeneous features of the diseased adrenal in PA and helped reveal the high proportion of APAs with driver mutations. We discuss what is known about the genetics of PA that has led to a clearer understanding of the disease pathophysiology.

Diagnostic approach to low-renin hypertension

Renin-angiotensin-aldosterone system (RAAS) plays a crucial role in maintaining water and electrolytes homoeostasis, and its deregulation contributes to the development of arterial hypertension. Since the historical description of the "classical" RAAS, a dramatic increase in our understanding of the molecular mechanisms underlying the development of both essential and secondary hypertension has occurred. Approximatively 25% of the patients affected by arterial hypertension display low-renin levels, a definition that is largely arbitrary and depends on the investigated population and the specific characteristics of the assay. Most often, low-renin levels are expression of a physiological response to sodium-volume overload, but also a significant number of secondary hereditary or acquired conditions falls within this category. In a context of suppressed renin status, the concomitant examination of plasma aldosterone levels (which can be inappropriately elevated, within the normal range or suppressed) and plasma potassium are essential to formulate a differential diagnosis. To distinguish between the different forms of low-renin hypertension is of fundamental importance to address the patient to the proper clinical management, as each subtype requires a specific and targeted therapy. The present review will discuss the differential diagnosis of the most common medical conditions manifesting with a clinical phenotype of low-renin hypertension, enlightening the novelties in genetics of the familial forms.

65 YEARS OF THE DOUBLE HELIX: Endocrine tumour syndromes in children and adolescents

As medicine is poised to be transformed by incorporating genetic data in its daily practice, it is essential that clinicians familiarise themselves with the information that is now available from more than 50 years of genetic discoveries that continue unabated and increase by the day. Endocrinology has always stood at the forefront of what is called today 'precision medicine': genetic disorders of the pituitary and the adrenal glands were among the first to be molecularly elucidated in the 1980s. The discovery of two endocrine-related genes, GNAS and RET, both identified in the late 1980s, contributed greatly in the understanding of cancer and its progression. The use of RET mutation testing for the management of medullary thyroid cancer was among the first and one of most successful applications of genetics in informing clinical decisions in an individualised manner, in this case by preventing cancer or guiding the choice of tyrosine kinase inhibitors in cancer treatment. New information emerges every day in the genetics or system biology of endocrine disorders. This review goes over most of these discoveries and the known endocrine tumour syndromes. We cover key genetic developments for each disease and provide information that can be used by the clinician in daily practice.

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.