Pathophysiology Of Primary Aldosteronism Research Articles

FRI167 Implication Of Serotonin In The Physiopathology Of Aldosterone-Producing Adenoma

Abstract Disclosure: C. Duparc: None. M. D'agostino: None. A. Lopez: None. S. Renouf: None. E. Louiset: None. H. Lefebvre: None. In the human adrenal gland, serotonin (5-HT), released by subcapsular mast cells strongly stimulates expression of CYP11B2, encoding aldosterone-synthase and aldosterone production. The effect of 5-HT on adrenocortical cells is mediated by activation of type 4 serotonin receptor (5-HT4R) positively coupled to cAMP/protein kinase A (PKA) signaling pathway and calcium influx. Consistently, administration of cisapride, a 5-HT4R agonist, to healthy volunteers induces a significant increase in plasma aldosterone levels. In aldosterone producing adenomas (APA), the density of mast cells is enhanced in comparison with normal adrenals. Moreover, molecular studies have shown overexpression of HTR4 gene, encoding 5-HT4R, in APA tissues. Administration of cisapride to patients with APA induced more robust plasma aldosterone responses than in healthy voluntaries. These results suggest that 5-HT could play a role in physiopathology of APA. The aim of our study was to examine expression of genes and proteins involved in aldosterone production and actors of the serotonergic pathway in a series of 31 adenomas removed from patients with primary aldosteronism. We have also investigated the in vitro effect of various 5-HT4R ligands on aldosterone production by explants or cultured cells derived from adenoma tissues collected at surgery. Firstly, aldosterone synthase (AS) immunostaining allowed identification of adenoma phenotypes accordingly to the new international histopathology consensus for unilateral Primary aldosteronism. Among the 31 tissues studied, 20 were classified as classical APAs, i.e. presenting with homogenous or heterogenous AS distribution, remaining being considered as 11 non-classical APA. Expression of the gene encoding the 5-HT-synthesizing enzyme tryptophan hydroxylase was similar in APA and normal adrenals. HTR4 overexpression was more robust in classical than non-classical APAs. HTR4 mRNA levels were positively correlated to those encoding CYP11B2. In addition, 5-HT4R immunostaining was widely distributed in most APA tissues, a pattern which was not exclusively noticed in AS-positive adenomas. BIMU-8, a potent 5-HT4R agonist, strongly increased aldosterone production by perifused APA explants. This effect was blocked by administration of GR-113808, a 5-HT4R antagonist. In cultured APA cells, BIMU-8 stimulated aldosterone synthesis in a dose-dependent manner with a higher efficiency than that observed in normal adrenocortical cells. Aldosterone secretion was less strongly stimulated by prucalopride, a partial 5-HT4R agonist used in the treatment of chronic constipation. These data reveal an enhancement of the 5-HT signaling pathway in APAs in comparison with normal adrenals, suggesting that 5-HT and the 5-HT4R may participate in the pathophysiology of primary aldosteronism. Presentation: Friday, June 16, 2023

FRI139 Identification Of Robust Aldosterone-Producing Adenomas-related Genes Using Adrenal Genome-wide Transcriptome Analysis

Abstract Disclosure: S. Lee: None. T. Lee: None. G. Yoo: None. J. Lim: None. Primary aldosteronism (PA), the most common cause of secondary hypertension, is caused by aldosterone overproduction in one or two adrenal glands. It carries a higher risk of cardiovascular disease and mortality compared to essential hypertension. In an effort to identify the underlying molecular mechanisms regarding aldosterone secretion and cell proliferation in aldosterone-producing adenomas (APA), genome-wide transcriptome analyses have been conducted; however, there are still some limitations that need to be addressed since a relatively small number of samples were analyzed at a single center in most studies. In this study, we performed integrative and systematic analysis using adrenal transcriptome datasets to verify candidate genes robustly associated with APA and obtain more generalized signatures involved in the pathophysiology of PA. Three mRNA datasets for adrenal tissues (GSE8514, GSE60042, and GSE64957) were obtained from the Gene Expression Omnibus Database. For the first two datasets, normal adrenal samples from patients with renal cell carcinoma and adrenal tissue samples adjacent to APA were included as controls, respectively. In GSE64957, zona glomerulosa (ZG) and zona fasciculata (ZF) samples were analyzed separately in the current study (GSE64957ZG and GSE64957ZF). Differentially expressed gene (DEG) investigation and comparative analysis were conducted using the limma method. The selection criteria for APA-related genes were as follows: those that are significantly dysregulated in more than three of the four datasets and show a consistent trend of up- or down-regulation in four datasets. 5,375 genes were present in all transcriptome datasets; for the GSE64957ZG, 57 DEGs were identified in the APA group, among which 14, 7, and 37 genes were also dysregulated in the APA group of GSE64957ZF, GSE8514, and GSE60042, respectively. All comparisons among four lists of DEGs exhibited significant enrichment results. The highest degree of overlap was shown in the DEG pair of GSE64957ZG-GSE60042. As a result, approximately 20 genes (12 upregulated and 12 downregulated DEGs), including CYP11B2, PCP4, and ATP2A3, were selected as the final APA-related genes. This study demonstrated several candidate genes that are strongly relevant to APA by examining whole genome disease-related signatures. Besides CYP11B2, it seems that alteration in PCP4 and ATP2A3 genes would be much more involved in the pathogenesis of PA, which warrants further investigation along with validation for the role of the remaining genes. Presentation: Friday, June 16, 2023

Modulation of calcium signaling “on demand” to decipher the molecular mechanisms responsible for primary aldosteronism

Primary aldosteronism (PA) is the most frequent form of secondary hypertension. Over the past two decades, major advances have been made in our understanding of the disease with the identification of germline or somatic mutations in ion channels and pumps. These mutations enhance calcium signaling, the main trigger of aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, thus mimicking some of the known mutations identified in PA. We have developed an adrenocortical H295R-S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the a7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3a named a7-5HT3. Its activation by a selective agonist named PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular sodium and calcium concentrations, cell proliferation, steroid production electrophysiological properties, and gene expression. Treatment of a7-5HT3 expressing cells with increasing concentration of PSEM-817 (from 10–9 to 10–5 M) induced a significant increase in intracellular calcium concentrations. Interestingly, whereas cells were hyperpolarized in absence of stimulation (around –60 mV), PSEM-817 induced a strong depolarization, with cells rising to a membrane potential of around –10 mV. The stimulation of calcium signaling by PSEM-817 leads to an increase of CYP11B2 (encoding for aldosterone synthase) mRNA expression and aldosterone biosynthesis but did not affect cell proliferation measured at different time points (8 h, 24 h, 48 h, 72 h). Interestingly, calcium kinetic analyses revealed significant differences in response to the modulation of potassium or sodium entry into cells. Gene expression analyses of gene expression by RNAseq highlighted the activation of specific signaling pathways in response to treatment with Angiotensin II, potassium, and PSEM-817. This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Adrenal Anion Channels: New Roles in Zona Glomerulosa Physiology and in the Pathophysiology of Primary Aldosteronism.

The mineralocorticoid aldosterone is produced in the zona glomerulosa of the adrenal cortex. Its synthesis is regulated by the serum concentrations of the peptide hormone angiotensin II and potassium. The primary role of aldosterone is to control blood volume and electrolytes. The autonomous production of aldosterone (primary aldosteronism, PA) is considered the most frequent cause of secondary hypertension. Aldosterone-producing adenomas and (micro-)nodules are frequent causes of PA and often carry somatic mutations in ion channels and transporters. Rare familial forms of PA are due to germline mutations. Both somatic and germline mutations in the chloride channel gene CLCN2, encoding ClC-2, have been identified in PA. Clinical findings and results from cell cultureand animal models have advanced our knowledge about the role of anions in PA. The zona glomerulosa of the adrenal gland has now been firmlyestablished as a tissue in which anions play a significant role for signaling. In this overview, we aim to summarize the current knowledge and highlight novel concepts as well as open questions.

S-55-1: PRIMARY ALDOSTERONISM – WHERE TO FROM HER E?

Over the past decade there have been remarkable advances in the pathophysiology of primary aldosteronism (PA); in contrast, there has been little if any change in the clinical management of PA for over 20 years. A patient suspected of PA is referred to an expert center, and their medications withdrawn for 4–6 weeks, with CCBs/alpha blockers used if needed to control blood pressure (BP).They undergo a single blood draw for plasma aldosterone concentration (PAC) and plasma renin activity or concentration (PRA/PRC), to establish the aldosterone to renin ratio (ARR). If the ARR 'suggests’ PA, the patient then undergoes confirmatory testing by one of at least five different procedures – to ensure no patient who does not have PA ever slips through the net. There are multiple reasons for change. First, in no country are more than 1% of hypertensives ever screened for PA. Secondly, a single blood draw for PAC is a very imperfect index of a patient’s actual aldosterone status; among those referred many are excluded on the basis of their PAC who in fact have PA. Third, the current work up – in addition to being exclusionary - is demanding and clunky. Fourth, the prevailing attitude among those treating hypertension is that if the BP is controlled all will be well, when in fact patients with PA have a three-fold higher risk profile than matched essential hypertensives with the same BP. What we are thus facing is a major public health crisis. There is finally increasing recognition that the current estimate of PA prevalence (5% - 10% of hypertensives) is far too low, and the actual prevalence in hypertensives is of the order of at least 30% (and of 10% in normotensives). The current protocols are useless facing figures such as these; what is needed are much simpler and inclusive measures to diagnose probable PA – rather than excluding all but the most obvious cases. This will require input not only from endocrinologists, but also from hypertension specialists, internists, primary care and public health physicians. It is important to distinguish newly presenting and established hypertension. When a patient is newly diagnosed with an elevated BP eschew immediate antihypertensive(s) and order a PRA/PRC assay. If renin is not suppressed, onto antihypertensives. If the renin is suppressed coach the patient to provide a 24 h urine collection for Na, K, and urinary excretion of aldosterone (UEA). If the UEA is < 6 mcg/24 h the patient does not have PA; if the UEA is 6–12, the patient may have PA; if the UEA is > 12 the patient has PA. For these two latter categories order 25 mg/d spironolactone and review at four weeks. If BP falls by < 10mmHg onto antihypertensives; if BP falls by > 10 mmHg continue spironolactone. Established hypertension is rather simpler. Add spironolactone 25 mg/d to current medication and review at 4 weeks. If BP falls < 10mmHg, discontinue; if BP falls > 10mmHg order a UEA. If UEA and BP are moderately elevated continue spironolactone, as such patients very probably have bilateral hyperaldosteonism; if UEA and BP are high, refer to an expert center. What this is calling for is a radical reassessment of how physicians should address hypertensive patients. The rationale is to save them from the double jeopardy of hypertension and PA, and the attendant increased morbidity and premature mortality. The time is now.

OR20-4 Expression of the Neuropeptide Substance P and the NK1 Receptor in Aldosterone-Producing Adenomas

Abstract Background Aldosterone-producing adenoma (APA) is a major cause of primary aldosteronism (PA) which is the most frequent form of secondary hypertension (1-2). The pathophysiology of PA is quite complex and still incompletely understood. Substance P (SP) encoded by the TAC1 gene belongs to a family of bioactive peptides named tachykinins. A recently published study indicated that SP, released by subcapsular nerve fibres, stimulates aldosterone production through activation of the neurokinin type 1 receptor (NK1R) in the human adrenal gland (3). The aim of our work was to investigate the presence of SP fibres and the NK1 receptor in a large series of APA in order to assess the potential role of this peptide in the pathophysiology of PA. Methods APA tissues were studied by molecular and histological approaches. Expression of SP and NK1 receptor was searched for in a series of 51 APA by RT-Q-PCR and immunohistochemistry. Results Quantitative RT-PCR data indicated that adenomas strongly express TAC1 mRNA. Immunohistochemistry showed the presence of SP-positive nerve fibres in APAs tissues. SP was also detected in a subpopulation of adenomatous cells. Adenomas strongly express mRNA encoding the NK1 receptor. The distribution of the NK1 receptor within APAs is similar to that of aldosterone synthase (CYP11B2), suggesting that SP may regulate aldosterone secretion by APAs. Conclusion These results suggest that SP and its NK1 receptor may be involved in the pathophysiology of aldosterone hypersecretion by APAs.

Primary aldosteronism: Pathophysiological mechanisms of cell death and proliferation.

Primary aldosteronism is the most common surgically curable form of hypertension. The sporadic forms of the disorder are usually caused by aldosterone overproduction from a unilateral adrenocortical aldosterone-producing adenoma or from bilateral adrenocortical hyperplasia. The main knowledge-advances in disease pathophysiology focus on pathogenic germline and somatic variants that drive the excess aldosterone production. Less clear are the molecular and cellular mechanisms that lead to an increased mass of the adrenal cortex. However, the combined application of transcriptomics, metabolomics, and epigenetics has achieved substantial insight into these processes and uncovered the evolving complexity of disrupted cell growth mechanisms in primary aldosteronism. In this review, we summarize and discuss recent progress in our understanding of mechanisms of cell death, and proliferation in the pathophysiology of primary aldosteronism.

DEVELOPMENT OF AN ADRENOCORTICAL CELL MODEL OF CALCIUM SIGNALING MODULATION TO DECIPHER THE MOLECULAR MECHANISMS RESPONSIBLE FOR PRIMARY ALDOSTERONISM

Objective: Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels (KCNJ5, CACNA1D, CACNA1H and CLCN2) and ATPases (ATP1A1 and ATP2B3) defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, mimicking some of known mutations identified in PA. Design and method: We have developed an adrenocortical H295R_S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the α7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3α and named α7–5HT3. Mutations have been introduced in the ligand binding domain to allow only synthetic drugs to activate this channel receptor. Activation of α7–5HT3 by a specific drug, PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production, steroidogenic expression and electrophysiological properties. Results: Treatment of α7–5HT3 expressing cells with increasing concentration of PSEM-817 (from 10–9 to 10–5 M) induced a significant increase in intracellular calcium concentrations, similarly to potassium (12 mM) or angiotensin II (10–8 M). This stimulation of calcium signaling did not affect cell proliferation, but was responsible for an increase in CYP11B2 expression and aldosterone production after 24 h of treatment. However, while increased intracellular calcium concentrations were observed starting from 10–8 M of PSEM-817, CYP11B2 expression and aldosterone production were only affected starting from 10–7 M, suggesting a dose dependent effect. Finally, whereas cells were hyperpolarized in absence of stimulation (around -60 mV), PSEM-817 induced a strong depolarization, cells rising to a membrane potential around -10 mV. Conclusions: This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Development of an adrenocortical cell model of calcium signaling modulation to decipher the molecular mechanisms responsible for primary aldosteronism

Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels and defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, mimicking some of known mutations identified in PA. We have developed an adrenocortical H295R-S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the α7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3α and named α7-5HT3. Mutations have been introduced in the ligand-binding domain to allow only synthetic drugs to activate this channel receptor. Activation of α7-5HT3 by a specific drug, PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production, steroidogenic expression and electrophysiological properties. Treatment of α7-5HT3 expressing cells with increasing concentration of PSEM-817 (from 10-9 to 10-5 M) induced a significant increase in intracellular calcium concentrations, similarly to potassium (12 mM) or angiotensin II (10-8 M). This stimulation of calcium signaling did not affect cell proliferation, but was responsible for an increase in CYP11B2 expression and aldosterone production after 24 h of treatment. However, while increased intracellular calcium concentrations were observed starting from 10-8 M of PSEM-817, CYP11B2 expression and aldosterone production were only affected starting from 10-7 M, suggesting a dose-dependent effect. Finally, whereas cells were hyperpolarized in absence of stimulation (around −60 mV), PSEM-817 induced a strong depolarization, cells rising to a membrane potential around −10 mV. This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Aldosterone and Primary Aldosteronism: Star Performers in Hypertension Research

Aldosterone and Primary Aldosteronism: Star Performers in Hypertension Research

Developments in Primary Aldosteronism Subtyping Using Steroid Profiling.

Adrenal venous sampling is the standard of care for identifying patients with unilateral primary aldosteronism, which is often caused by an aldosterone producing adenoma and can be cured with surgery. The numerous limitations of adrenal venous sampling, including its high cost, scarce availability, technical challenges, and lack of standardized protocols, have driven efforts to develop alternative, non-invasive tools for the diagnosis of aldosterone producing adenomas. Seminal discoveries regarding the pathogenesis of aldosterone producing adenomas made over the past decade have leveraged hypotheses-driven research of steroid phenotypes characteristic of various aldosterone producing adenomas. In parallel, the expanding availability of mass spectrometry has enabled the simultaneous quantitation of many steroids in single assays from small volume biosamples. Steroid profiling has contributed to our evolving understanding about the pathophysiology of primary aldosteronism and its subtypes. Herein, we review the current state of knowledge regarding the application of multi-steroid panels in assisting with primary aldosteronism subtyping.

Hypokalemia and the Prevalence of Primary Aldosteronism.

Hypokalemia is closely linked with the pathophysiology of primary aldosteronism (PA). Although hypokalemic PA is less common than the normokalemic course of the disease, hypokalemia is of particular importance for the manifestation and development of comorbidities. Specifically, a growing body of evidence demonstrates that hypokalemia in PA patients is associated with a more severe disease course regarding cardiovascular and metabolic morbidity and mortality. It is also well appreciated that low potassium levels per se can promote or exacerbate hypertension. The spectrum of hypokalemia-related symptoms ranges from asymptomatic courses to life-threatening conditions. Hypokalemia is found in 9-37% of all cases of PA with a predominance in patients with aldosterone producing adenoma. Conversely, hypokalemia resolves in almost 100% of cases after both, specific medical or surgical treatment of the disease. However, to date, high-level evidence about the prevalence of primary aldosteronism in a hypokalemic population is missing. Epidemiological data are expected from the recently launched IPAHK+study ("Incidence of Primary Aldosteronism in Patients with Hypokalemia").

Primary aldosteronism.

Primary aldosteronism (PA) is a common cause of secondary hypertension caused by excessive and inappropriate secretion of the hormone aldosterone from one or both adrenal glands. The prevalence of PA ranges from 10% in the general hypertensive population to 20% in resistant hypertension, yet only a small fraction of patients is diagnosed. Disease and symptom recognition, screening in indicated populations, multidisciplinary communication, and appropriate imaging and biochemical workup can identify patients who might benefit from effective and targeted treatment modalities. Effective treatments available include both surgical and medical approaches, usually dependent on the subtype of PA present. Our collective understanding of the pathophysiology of PA is expanded by recent developments in molecular biology and genetics, including understanding the specific somatic and germline mutations involved in pathogenesis. We review the pathophysiology, diagnostic workup, and treatment considerations for this disease process.

Mineralocorticoid Receptor-Dependent Impairment of Baroreflex Contributes to Hypertension in a Mouse Model of Primary Aldosteronism.

Primary aldosteronism (PA) is the most common cause of secondary hypertension. The paucity of good animal models hinders our understanding of the pathophysiology of PA and the hypertensive mechanism of PA remains incompletely known. It was recently reported that genetic deletion of TWIK-related acid-sensitive potassium-1 and potassium-3 channels from mice (TASK−/−) generates aldosterone excess and mild hypertension. We addressed the hypertensive mechanism by assessing autonomic regulation of cardiovascular activity in this TASK−/− mouse line that exhibits the hallmarks of PA. Here, we demonstrate that TASK−/− mice were hypertensive with 24-h ambulatory arterial pressure. Either systemic or central blockade of the mineralocorticoid receptor (MR) markedly reduced elevated arterial pressure to normal level in TASK−/− mice. The response of heart rate to the muscarinic cholinergic receptor blocker atropine was similar between TASK−/− and wild-type mice. However, the responses of heart rate to the β-adrenergic receptor blocker propranolol and of arterial pressure to the ganglion blocker hexamethonium were enhanced in TASK−/− mice relative to the counterparts. Moreover, the bradycardiac rather than tachycardiac gain of the arterial baroreflex was significantly attenuated and blockade of MRs to a large degree rescued the dysautonomia and baroreflex gain in TASK−/− mice. Overall, the present study suggests that the MR-dependent dysautonomia and reduced baroreflex gain contribute to the development of hyperaldosteronism-related hypertension.

Role of estrogen receptors in modulating aldosterone biosynthesis and blood pressure

Blood pressure is lower in premenopausal women than in age-matched men; after menopause blood pressure values and the prevalence of hypertension show opposite trends indicating that estrogens contribute to maintaining normal blood pressure values in women. In experimental studies menopause increases aldosterone levels, an effect alleviated by estrogen treatment. We have recently discovered a role of estrogen receptors (ER) in controlling aldosterone biosynthesis in the human adrenocortical zona glomerulosa, which expresses both the classical ERα and β receptors and G protein-coupled estrogen receptor (GPER). We have also identified that GPER mediates an aldosterone-induced aldosterone response. We found that 17 β-estradiol exerts a dual effect: it blunts aldosterone production via ERβ, but displays a potent aldosterone secretagogue effect via GPER activation after ERβ blockade. Thus, in premenopausal women high estrogen levels might tonically blunt aldosterone synthesis via ERβ, thereby maintaining normal blood pressure; after menopause loss of this estrogen-mediated inhibition can contribute to increasing blood pressure via GPER-mediated aldosterone release. The additional findings that GPER mediates an aldosterone-induced stimulation of aldosterone biosynthesis and that GPER predominates in aldosterone-producing adenomas strongly involves this receptor in the pathophysiology of primary aldosteronism. Our purpose here was to provide an update on estrogen receptor function in the normal adrenal cortex and its relevance for the sex differences in blood pressure in light of the newly discovered role of GPER in regulating aldosterone synthesis. The implications of the novel knowledge for the treatment of estrogen-dependent malignancies with ER modulators are also discussed.

SAT-002 Measurement of Visceral Fat Using Computed Tomography in Two Subtypes of Primary Aldosteronism

Context: A strong association between excess visceral fat and the presence of metabolic factors, hypertension and type 2 diabetes have been demonstrated. Patients with primary aldosteronism (PA) are complicated by metabolic syndrome more frequently than those without PA. Aldosterone-induced mineralocorticoid receptor activation has been reported to impair insulin sensitivity in adipocytes and skeletal muscle. An excess of visceral fat has been hypothesized to cause an elevation of aldosterone secretion, and to cause insulin resistance in patients with PA. Objectives: To clarify the role of visceral fat in the pathophysiology of PA, we investigated the correlation of visceral fat parameters with plasma aldosterone concentration (PAC), and the correlation of visceral fat parameters with homeostasis model assessment insulin resistance (HOMA-R) in patients with PA. Materials and methods: This retrospective observational study comprised 131 patients diagnosed with PA between 2007 and 2017 at Sapporo City General Hospital. We divided participants into two subtypes, aldosterone producing adenoma (APA, n = 47) and idiopathic hyperaldosteronism (IHA, n = 84), utilizing adrenal venous sampling. We excluded patients with suspected autonomous cortisol secretion, defined as serum cortisol levels ≧ 3 μg/dL after a 1-mg dexamethasone suppression test. We analyzed the correlations of visceral fat percentage (VF%), visceral fat area (VFA) evaluated by computed tomography studies and PAC, and the correlations of VF% and VFA with HOMA-R in each subtype group. Results: Age and sex distribution was not different between patients with APA and patients with IHA (p = 0.85, p = 0.18, respectively). PAC was significantly higher in patients with APA than patients with IHA (p < 0.001). Serum potassium levels were significantly lower in patients with APA than patients with IHA (p < 0.001). Body mass index was not different between these two subtypes (p = 0.87). VF% was significantly higher in patients with IHA than in those with APA (p = 0.02). The number of patients treated as type 2 diabetes mellitus with oral medicine, HbA1c, and HOMA-R were not different between these two subtypes (p =0.76, p =0.22, p = 0.12, respectively). Patients with IHA showed a positive correlation of VF% with PAC (r = 0.377, p < 0.001), and VFA with PAC (r = 0.443, p < 0.001). In contrast, patients with APA showed no significant correlation of VF% and VFA with PAC. Patients with APA and patients with IHA showed a positive correlation of VF% and VFA with HOMA-R. Conclusions: Between two subtypes of PA, the association of visceral fat on insulin resistance was not different. The association of visceral fat on PAC was different in two subtypes of PA. Only in patients with IHA, visceral fat may play a role in regulation of aldosterone secretion.

Paracrine Regulation of Aldosterone Secretion in Physiological and Pathophysiological Conditions.

Aldosterone secretion by the zona glomerulosa of the adrenal cortex is controlled by circulating factors including the renin angiotensin system (RAS) and potassium. Mineralocorticoid production is also regulated through an autocrine/paracrine mechanism by a wide variety of bioactive signals released in the vicinity of adrenocortical cells by chromaffin cells, nerve endings, cells of the immune system, endothelial cells and adipocytes. These regulatory factors include conventional neurotransmitters and neuropeptides. Their physiological role in the control of aldosterone secretion is not fully understood, but it is likely that they participate in the RAS-independent regulation of zona glomerulosa cells. Interestingly, recent observations indicate that autocrine/paracrine processes are involved in the pathophysiology of primary aldosteronism. The intraadrenal regulatory systems observed in aldosterone-producing adenomas (APA), although globally similar to those occurring in the normal adrenal gland, harbor alterations at different levels, which tend to strengthen the potency of paracrine signals to activate aldosterone secretion. Enhancement of paracrine stimulatory tone may participate to APA expansion and aldosterone hypersecretion together with somatic mutations of driver genes which activate the calcium signaling pathway and subsequently aldosterone synthase expression. Intraadrenal regulatory mechanisms represent thus promising pharmacological targets for the treatment of primary aldosteronism.

Relationship Between Visceral Fat and Plasma Aldosterone Concentration in Patients With Primary Aldosteronism.

ContextThe involvement of visceral fat in aldosterone secretion has not been reported in patients with primary aldosteronism (PA). Patients with PA are complicated by metabolic syndrome more frequently than those without PA. An excess of visceral fat has been hypothesized to cause an elevation of aldosterone secretion in patients with PA.ObjectivesTo clarify the role of visceral fat in the pathophysiology of PA, we investigated the correlation between plasma aldosterone concentration (PAC) and visceral fat parameters in patients with PA.DesignThis retrospective observational study comprised 131 patients diagnosed with PA between April 2007 and April 2017 at Sapporo City General Hospital. We divided participants into two PA subtypes, aldosterone-producing adenoma (APA; n = 47) and idiopathic hyperaldosteronism (IHA, n = 84), utilizing adrenal venous sampling. We analyzed the correlations of PAC with visceral fat percentage (VF%), visceral fat area (VFA), and subcutaneous fat area, by evaluating computed tomography studies in each subtype group.ResultsPatients with IHA showed a positive correlation of PAC with VF% (r = 0.377, P < 0.001) and VFA (r = 0.443, P < 0.001). The correlation was not evident in patients with APA.ConclusionsThis study revealed a relationship between visceral adipose tissue and aldosterone production only in patients with IHA.

Disordered CYP11B2 Expression in Primary Aldosteronism.

Primary aldosteronism is the most common type of secondary hypertension affecting 6-10% of patients with primary hypertension. PA is mainly caused by unilateral hyperaldosteronism due to an aldosterone-producing adenoma, unilateral hyperplasia with or without micronodules or bilateral zona glomerulosa hyperplasias with or without macro or micronodules. The development of antibodies against the terminal enzyme of aldosterone biosynthesis (CYP11B2) has permitted the further characterization of normal adrenals and resected adrenals from patients with primary aldosteronism. Normal adrenals exhibit two different patterns of cellular expression of CYP11B2: young individuals display a relatively uniform expression of the enzyme throughout the zona glomerulosa while the adrenals of older individuals have dispersed CYP11B2-expressing cells but have more groups of cells called aldosterone-producing cell clusters (APCC). APAs exhibit different patterns of CYP11B2 staining that vary from uniform to homogeneous. There are also a proportion of cells within the APA that co-express different enzymes that are not normally co-expressed in normal individuals. Approximately 30% of patients with unilateral hyperaldosteronism do not have an APA, but either have an increased number of CYP11B2 expressing micronodules or hyperplasia of the zona glomerulosa. In summary, the studies reported in this review are shedding new light on the pathophysiology of primary aldosteronism. The wide variation in histopathological features of the adenomas and concurrent presence of APCCs raises the possibility that most cases of unilateral production of aldosterone actually might represent bilateral asymmetric hyperplasia with nodules frequently due to the development of somatic aldosterone-driving mutations.

Genetic characterization of a mouse line with primary aldosteronism.

In an attempt to define novel genetic loci involved in the pathophysiology of primary aldosteronism, a mutagenesis screen after treatment with the alkylating agent N-ethyl-N-nitrosourea was established for the parameter aldosterone. One of the generated mouse lines with hyperaldosteronism was phenotypically and genetically characterized. This mouse line had high aldosterone levels but normal creatinine and urea values. The steroidogenic enzyme expression levels in the adrenal gland did not differ significantly among phenotypically affected and unaffected mice. Upon exome sequencing, point mutations were identified in seven candidate genes (Sspo, Dguok, Hoxaas2, Clstn3, Atm, Tipin and Mapk6). Subsequently, animals were stratified into wild-type and mutated groups according to their genotype for each of these candidate genes. A correlation of their genotypes with the respective aldosterone, aldosterone-to-renin ratio (ARR), urea and creatinine values as well as steroidogenic enzyme expression levels was performed. Aldosterone values were significantly higher in animals carrying mutations in four different genes (Sspo, Dguok, Hoxaas2 and Clstn3) and associated statistically significant adrenal Cyp11b2 overexpression as well as increased ARR was present only in mice with Sspo mutation. In contrast, mutations of the remaining candidate genes (Atm, Tipin and Mapk6) were associated with lower aldosterone values and lower Hsd3b6 expression levels. In summary, these data demonstrate association between the genes Sspo, Dguok, Hoxaas2 and Clstn3 and hyperaldosteronism. Final proofs for the causative nature of the mutations have to come from knock-out and knock-in experiments.