Regulation Of Aldosterone Secretion Research Articles

The ex vivo perfused mouse adrenal gland—a new model to study aldosterone secretion

Aldosterone is a steroid hormone that is important for maintaining the volume and ionic composition of extracellular fluids and is produced in the zona glomerulosa of the adrenal cortex. The basic mechanisms controlling aldosterone secretion are known. However, more detailed studies on the regulation of aldosterone secretion often fail due to the lack of suitable models: although secretion can be studied in cultured adrenocortical cells under defined conditions, the differentiation status of the cells is difficult to control and the complex anatomy of the adrenal cortex is lost. In living animals, the physiological context is intact, but the influences are manifold and the examination conditions cannot be sufficiently controlled. One method that closes the gap between cell models and studies in living animals is the isolated perfused adrenal gland. In the past, this method has provided important data on the pathophysiology of adrenal glands from larger animals, but the technique was not used in mice. Here, we developed a method for isolation and perfusion of the mouse adrenal gland to study aldosterone secretion. This technique preserves the complex anatomical and functional context of the mouse adrenal cortex, to ensure defined experimental conditions and to minimize extra-adrenal influences. Initial series of experiments with the ex vivo perfused mouse adrenal gland show that this model offers the possibility for unique insights into pathophysiological regulatory principles and is suitable for the use of genetically modified mouse models.

FRI140 Impact Of Circadian Rhythm Of Aldosterone And Cortisol Levels Upon Adrenal Vein Sampling In Primary Aldosteronism

Abstract Disclosure: M. Kometani: None. M. Yoneda: None. K. Aiga: None. D. Aono: None. S. Karashima: None. Y. Takeda: None. T. Yoneda: None. Purpose: Adrenal venous sampling (AVS) is the gold standard technique for subtype differentiation of primary aldosteronism (PA). AVS is an invasive and challenging test; however, because of the high frequency of PA, it is currently performed at many institutions in Japan. Considering the effects of diurnal variations in the levels of aldosterone and cortisol, the guidelines recommends that AVS without ACTH loading should be performed in the morning. However, owing to staffing issues and general limitations, AVS is performed in the afternoon in many facilities. In this study, we examined the effects of AVS timing (AM/PM) on AVS results. Methods: This multicenter, retrospective, observational study included a total of 753 patients diagnosed with PA at four specialized institutions. The patients were divided into two groups according to the timing of the AVS procedure. The group classification of patients according to the time of the day when AVS was performed was not prospectively designed but rather determined based on feasible conditions at each facility. Among them, 504 and 249 patients underwent AVS in the morning (AM-AVS) and in the afternoon (PM-AVS), respectively. Results: The success rate of basal AVS in the AM-AVS group was 81% and that of ACTH-stimulated AVS was 92%. The success rate of basal AVS in the PM-AVS group was 74% and that of ACTH-stimulated AVS was 88%. There was no significant difference in the AVS success rate between the AM-AVS and PM-AVS groups. There was no significant difference between the AM-AVS and PM-AVS groups concerning the rate of unilateral diagnosis by AVS before ACTH stimulation, the rate of unilateral PA diagnosis by AVS after ACTH stimulation, and the percentage of cases with discrepancies between the two AVSs. Regarding patients with unilateral PA, aldosterone concentrations in adrenal venous blood did not differ between the two groups on the dominant or non-dominant side. Conversely, regarding patients with bilateral PA, aldosterone concentrations in adrenal venous blood were significantly higher in the AM-AVS than in the PM-AVS group. Conclusions: This study evaluated the effect of AVS timing. Although this was a multicenter study, there were no differences in the success rate of AVS, diagnostic rate of subtype, or frequency of deviation in the subtypes between the AM-AVS and PM-AVS groups. These results are relevant for facilities that can perform AVS only in the afternoon. Concerning aldosterone levels, no differences were observed between patients with unilateral lesions in the AM-AVS and PM-AVS groups, whereas its levels were different between patients with bilateral lesions in the AM-AVS and PM-AVS groups, suggesting the involvement of different mechanisms that regulate aldosterone secretion according to the circadian rhythm in patients with unilateral or bilateral lesions. Presentation: Friday, June 16, 2023

Phosphoproteomics Reveals the Wolframin-Calcium Axis as an Important Pathogenic Signaling Node in Primary Aldosteronism.

Aldosterone-producing adenoma (APA) is a benign adrenal tumor with autonomous aldosterone production which causes hypertension and excess cardiovascular risk. Protein phosphorylation regulates aldosterone secretion from adrenal cortical cells, but how signaling networks are remodeled in APA remains unknown. We performed an integrated proteomic and phosphoproteomic profiling of 15 APA and 10 matched nonfunctioning adrenocortical tumors (NFAT) based on the 4-dimensional label-free technique. We further validated our main findings in enlarged APA samples, mice, and adrenocortical cell line. The proteomic and phosphoproteomic profiling of APA and NFAT quantified 5989 proteins and 9011 phosphopeptides. We highlighted differentially expressed and phosphorylated proteins which modulated aldosterone synthesis and secretion from APA. As intracellular calcium is the central signal for aldosterone synthesis, our integrated calcium signaling network implicated wolframin in the control of calcium influx and CYP11B2 (aldosterone synthase) activation in APA (ratio of wolframin expression in APA to NFAT: 6.411, P<0.001). Among 97 APA cases for validation, a higher expression level of wolframin was associated with a higher plasma aldosterone concentration postcaptopril challenge test and a higher systolic blood pressure. In vitro, the secretion of aldosterone was enhanced by wolframin overexpression, while aldosterone secretion in response to potassium or angiotensin II was inhibited by the knockdown of wolframin. Further in vivo and in vitro data demonstrated the wolframin-calcium axis as an important regulator of CYP11B2 expression and aldosterone production. Wolframin is a regulatory protein in aldosterone hypersecretion. Remodeled calcium transportation and mitochondrial function are involved in wolframin-related aldosterone secretion.

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.

The neuropeptide substance P regulates aldosterone secretion in human adrenals

Aldosterone, produced by the adrenals and under the control of plasma angiotensin and potassium levels, regulates hydromineral homeostasis and blood pressure. Here we report that the neuropeptide substance P (SP) released by intraadrenal nerve fibres, stimulates aldosterone secretion via binding to neurokinin type 1 receptors (NK1R) expressed by aldosterone-producing adrenocortical cells. The action of SP is mediated by the extracellular signal-regulated kinase pathway and involves upregulation of steroidogenic enzymes. We also conducted a prospective proof-of-concept, double blind, placebo-controlled clinical trial aimed to investigate the impact of the NK1R antagonist aprepitant on aldosterone secretion in healthy male volunteers (EudraCT: 2008-003367-40, ClinicalTrial.gov: NCT00977223). Participants received during two 7-day treatment periods aprepitant (125 mg on the 1st day and 80 mg during the following days) or placebo in a random order at a 2-week interval. The primary endpoint was plasma aldosterone levels during posture test. Secondary endpoints included basal aldosterone alterations, plasma aldosterone variation during metoclopramide and hypoglycaemia tests, and basal and stimulated alterations of renin, cortisol and ACTH during the three different stimulatory tests. The safety of the treatment was assessed on the basis of serum transaminase measurements on days 4 and 7. All pre-specified endpoints were achieved. Aprepitant decreases aldosterone production by around 30% but does not influence the aldosterone response to upright posture. These results indicate that the autonomic nervous system exerts a direct stimulatory tone on mineralocorticoid synthesis through SP, and thus plays a role in the maintenance of hydromineral homeostasis. This regulatory mechanism may be involved in aldosterone excess syndromes.

This Month in Anesthesiology

This Month in Anesthesiology

The neuropeptide substance P regulates aldosterone secretion in human adrenals

Aldosterone, produced by the adrenals and under the control of plasma angiotensin and potassium levels, regulates hydromineral homeostasis and blood pressure. Here we report that the neuropeptide substance P (SP) released by intraadrenal nerve fibres, stimulates aldosterone secretion via binding to neurokinin type 1 receptors (NK1R) expressed by aldosterone-producing adrenocortical cells. The action of SP is mediated by the extracellular signal-regulated kinase pathway and involves upregulation of steroidogenic enzymes. We also conducted a prospective proof-of-concept, double blind, placebo-controlled clinical trial aimed to investigate the impact of the NK1R antagonist aprepitant on aldosterone secretion in healthy male volunteers (EudraCT: 2008-003367-40, ClinicalTrial.gov: NCT00977223). Participants received during two 7-day treatment periods aprepitant (125 mg on the 1st day and 80 mg during the following days) or placebo in a random order at a 2-week interval. The primary endpoint was plasma aldosterone levels during posture test. Secondary endpoints included basal aldosterone alterations, plasma aldosterone variation during metoclopramide and hypoglycaemia tests, and basal and stimulated alterations of renin, cortisol and ACTH during the three different stimulatory tests. The safety of the treatment was assessed on the basis of serum transaminase measurements on days 4 and 7. All pre-specified endpoints were achieved. Aprepitant decreases aldosterone production by around 30% but does not influence the aldosterone response to upright posture. These results indicate that the autonomic nervous system exerts a direct stimulatory tone on mineralocorticoid synthesis through SP, and thus plays a role in the maintenance of hydromineral homeostasis. This regulatory mechanism may be involved in aldosterone excess syndromes.

Neuropeptide Y (NPY) receptor 2 deletion in adipocytes blunts fat‐derived aldosterone production in female mice exposed to chronic stress

NPY is a 36‐amino acid peptide that plays a critical role in the regulation of energy homeostasis. In response to chronic environmental stress, NPY released by neurons innervating the fat promotes adipocyte proliferation and lipid storage via NPY receptor 2 (Y2). Y2 also stimulates aldosterone synthesis in the adrenal gland; however, little is known about its role in the regulation of aldosterone secretion in adipose tissue. We have previously shown that Maternal Separation and Early Weaning (MSEW), a mouse model of early life stress, exacerbates high fat diet (HF)‐induced adiposity and increases circulating aldosterone in female mice but not in males. Thus, the aim of this study was to investigate the effect of MSEW on chronic stress‐induced aldosterone release by adipose tissue with or without the deletion of Y2. In addition, we tested the capacity of adipose tissue conditioned media from these mice to modulate the endothelial function of aortic rings ex‐vivo. Y2‐WT and Y2‐KO pups were separated from the dam for 4 to 8 hours during postnatal days (PD) 2 to 16 and weaned on PD 17. Control mice remained undisturbed and were weaned on PD 21. At weaning, female mice were fed a HF (60% Kcal from fat) for 16 weeks. Following, a subset of mice were subjected to restraint stress (RS) for 6 more consecutive weeks and the other one was not disturbed (NORS). At the end of the experiment, mice were euthanized, and ~50 mg of fresh adipose tissue was incubated in DMEM + 2% fatty acid free BSA (1 hour, 37°C). Aldosterone concentration was measured in media explants by ELISA. Visceral adipose tissue‐derived aldosterone secretion was similar in WT MSEW and control explants from NORS mice (3.22±0.21 vs 3.50±0.76 pg/mg tissue). RS increased aldosterone levels in the media explant from MSEW mice compared to controls (5.34±0.85 vs. 2.96±0.35 pg/mg tissue). The deletion of Y2 from adipose tissue depots attenuated the increased aldosterone release in response to RS in MSEW mice only (5.34±0.85 to 3.46±0.21 pg/mg tissue; p &lt; 0.05). In additional studies, we used perivascular adipose tissue (PVAT) and mesenteric adipose tissue (MESAT) media explants from RS control and MSEW mice to test their effect on acetylcholine (Ach)‐dependent relaxation (pre‐constricted with ser 10−3 M, 3 ul). We performed relaxation dose‐response curves in thoracic aortic rings from healthy female mice (16‐week‐old fed a regular chow) before and after the incubation with fat explants. We found similar worsening of the baseline vascular relaxation when we incubated rings with PVAT media from MSEW and controls (14.38±4.58 vs. 19.95±3.80 Delta % relaxation). However, rings incubated with MESAT from MSEW mice showed significant worsening of the vascular relaxation compared to controls (26.71±4.44 vs. 12.43±2.63 Delta % relaxation, p&lt;0.05). Y2 deletion protected the vascular function in both groups. Taken together, female MSEW mice exposed to RS are prone to release aldosterone from adipose tissue, dependent upon Y2 signaling. Increased aldosterone release near vessels may explain impaired endothelial function, which could be prevented by targeting adipose tissue Y2.Support or Funding InformationR01 HL135158

MicroRNAs and Adrenocortical Tumors: Where do we Stand on Primary Aldosteronism?

MicroRNAs, the endogenous mediators of RNA interference, interact with the renin-angiotensin-aldosterone system, regulate aldosterone secretion and aldosterone effects. Some novel data show that the expression of some microRNAs is altered in primary aldosteronism, and some of these appear to have pathogenic relevance, as well. Differences in the circulating microRNA expression profiles between the two major forms of primary aldosteronism, unilateral aldosterone-producing adenoma and bilateral adrenal hyperplasia have also been shown. Here, we present a brief synopsis of these findings focusing on the potential relevance of microRNA in primary aldosteronism.

MTORC1 Deficiency Modifies Volume Homeostatic Responses to Dietary Sodium in a Sex-Specific Manner.

The mechanistic target of the rapamycin (mTOR) pathway plays a role in features common to both excess salt/aldosterone and cardiovascular/renal diseases. Dietary sodium can upregulate mTORC1 signaling in cardiac and renal tissue, and the inhibition of mTOR can prevent aldosterone-associated, salt-induced hypertension. The impact of sex and age on mTOR's role in volume homeostasis and the regulation of aldosterone secretion is largely unknown. We hypothesize that both age and sex modify mTOR's interaction with volume homeostatic mechanisms. The activity of 3 volume homeostatic mechanisms-cardiovascular, renal, and hormonal (aldosterone [sodium retaining] and brain natriuretic peptide [BNP; sodium losing])-were assessed in mTORC1 deficient (Raptor+/-) and wild-type male and female littermates at 2 different ages. The mice were volume stressed by being given a liberal salt (LibS) diet. Raptor+/-mice of both sexes when they aged: (1) reduced their blood pressure, (2) increased left ventricular internal diameter during diastole, (3) decreased renal blood flow, and (4) increased mineralocorticoid receptor expression. Aldosterone levels did not differ by sex in young Raptor+/- mice. However, as they aged, compared to their littermates, aldosterone decreased in males but increased in females. Finally, given the level of Na+ intake, BNP was inappropriately suppressed, but only in Raptor+/- males. These data indicate that Raptor+/- mice, when stressed with a LibS diet, display inappropriate volume homeostatic responses, particularly with aging, and the mechanisms altered, differing by sex.

L- and T-type calcium channels control aldosterone production from human adrenals.

Aldosterone, which plays a key role in the regulation of blood pressure, is produced by zona glomerulosa (ZG) cells of the adrenal cortex. Exaggerated overproduction of aldosterone from ZG cells causes primary hyperaldosteronism. In ZG cells, calcium entry through voltage-gated calcium channels plays a central role in the regulation of aldosterone secretion. Previous studies in animal adrenals and human adrenal adrenocortical cell lines suggest that the T-type but not the L-type calcium channel activity drives aldosterone production. However, recent clinical studies show that somatic mutations in L-type calcium channels are the second most prevalent cause of aldosterone-producing adenoma. Our objective was to define the roles of T and L-type calcium channels in regulating aldosterone secretion from human adrenals. We find that human adrenal ZG cells mainly express T-type CaV3.2/3.3 and L-type CaV1.2/1.3 calcium channels. TTA-P2, a specific inhibitor of T-type calcium channel subtypes, reduced basal aldosterone secretion from acutely prepared slices of human adrenals. Surprisingly, nifedipine, the prototypic inhibitor of L-type calcium channels, also decreased basal aldosterone secretion, suggesting that L-type calcium channels are active under basal conditions. In addition, TTA-P2 or nifedipine also inhibited aldosterone secretion stimulated by angiotensin II- or elevations in extracellular K+. Remarkably, blockade of either L- or T-type calcium channels inhibits basal and stimulated aldosterone production to a similar extent. Low concentrations of TTA-P2 and nifedipine showed additive inhibitory effect on aldosterone secretion. We conclude that T- and L-type calcium channels play equally important roles in controlling aldosterone production from human adrenals.

ROLE OF CRYPTOCHROME-1 AND CRYPTOCHROME-2 IN ALDOSTERONE SECRETION

Objective: Knock-out mice for the genes Cry1 and Cry2 lack the circadian clock components Cryptochrome-1 and Cryptochrome-2 and display a form of hyperaldosteronism sustained by the upregulation of type VI 3β-hydroxyl-steroid dehydrogenase (Hsd3b6). Type I 3β-hydroxyl-steroid dehydrogenase (HSD3B1) gene is the human counterpart of the murine Hsd3b6. The aim of this study was to evaluate the role of CRY1 and CRY2 and their potential interaction with HSD3B isoforms in human adrenocortical physiopathology. Design and method: The study included 46 sporadic aldosterone-producing adenomas (APA) and 20 paired samples of adjacent cortical tissue. Human adrenocortical cells HAC15 were used as in vitro model. Results: In our cohort of sporadic APAs, CRY1 resulted 1.7-fold [0.75–2.26] more expressed (p = 0.016) within the main node compared to adjacent cortical tissue, while CRY2 showed a 20% [0.80, 0.52–1.08] (p = 0.04) reduction in APA tissue. Type II HSD3B is the main isoform in APAs, being 317-fold [200–573] more expressed than HSD3B1. Both HSD3B isoforms are more expressed in APA compared with paired adjacent cortex, 5.7 (p < 0.001) and 3.5-fold (p = 0.001) respectively. Notably, HSD3B1 is significantly more expressed in APAs composed mainly of zona glomerulosa-like cells. In HAC15 cells, angiotensin II (AngII) stimulation causes the upregulation of CRY1 (1.7 ± 0.25-fold, p < 0.001) at 6 hours and the downregulation of CRY2 (1.6 ± 0.1-fold, p < 0.001) at 12 hours, through activation of type 1 AngII receptor. Independent silencing of CRY1 and CRY2 determines a mild upregulation of HSD3B2, whereas it does not influence HSD3B1 expression. Conclusions: We demonstrated the potential role of CRY1 and CRY2 in the adrenal cell physiology and in the regulation of aldosterone secretion, considering that these genes are AngII-regulated and show a differential expression in APAs when compared with the adjacent adrenal cortex.

An investigation into the role of parathyroid hormone in the regulation of aldosterone secretion in hypertensive cardiovascular patients

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

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.

Regulation of Aldosterone Secretion.

Secretion of the major mineralocorticoid aldosterone from the adrenal cortex is a tightly-regulated process enabling this hormone to regulate sodium homeostasis and thereby contribute to blood pressure control. The circulating level of aldosterone is the result of various regulatory mechanisms, the most significant being those controlled by the renin-angiotensin system and plasma potassium levels. The importance of maintaining tight control over aldosterone secretion is demonstrated by cases of dysregulation, which can result in severe hypertension and significantly increased cardiovascular risk. In this article we summarize current knowledge of the major regulatory mechanisms, focusing particularly on the systems operating within the adrenocortical zona glomerulosa cells; we also describe some of the other factors that influence aldosterone production to a lesser but still significant extent. Finally, we discuss the influence of common genetic polymorphisms on aldosterone secretion in large sections of the population and also the emerging role of microRNA as significant regulators of this system.

Genetic Characterization of GnRH/LH-Responsive Primary Aldosteronism.

Recently, somatic β-catenin mutations (CTNNB1) identified in aldosterone-producing adenomas (APAs) from three women were suggested to be responsible for the aberrant overexpression of luteinizing hormone/choriogonadotropin receptor and gonadotropin-releasing hormone receptor in the APA. To genetically characterize patients with primary aldosteronism (PA) evaluated in vivo for gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH)-responsive aldosterone secretion. Patients with PA were evaluated in vivo to determine the possible regulation of aldosterone secretion by GnRH or LH. Genetic analysis of the CTNNB1, KCNJ5, ATP1A1, ATP2B3, CACNA1D, and GNAS genes were performed in this cohort and a control cohort of PA not tested in vivo for GnRH response. We studied 50 patients with confirmed PA, including 36 APAs, 12 bilateral macronodular adrenal hyperplasias, 1 oncocytoma, and 1 bilateral hyperplasia with cosecretion of cortisol. Among 23 patients tested in vivo for GnRH response of aldosterone, 7 (30.4%) had a positive response, 4 (17.4%) a partial response, and 12 (52.2%) no response. No somatic CTNNB1 mutations were identified, but the disease-causing c.451G>C KCNJ5 mutation was found in two individuals with partial and no GnRH responses and an individual showing a positive response to LH. Two additional somatic pathogenic mutations, CACNA1D c.776T>A and ATP1A1 c.311T>G, were identified in two patients with no GnRH responses. In the 26 patients not tested for GnRH response, we identified 2 CTNNB1 (7.7%), 13 KCNJ5 (50%), and 1 CACNA1D (3.8%) mutations. Aberrant regulation of aldosterone by GnRH is frequent in PA, but is not often associated with somatic CTNNB1, although it may be found with somatic KCNJ5 mutations.

The regulation of aldosterone secretion by leptin: implications in obesity-related cardiovascular disease.

Although it has been known for some time that increases in body mass enhance aldosterone secretion, particularly in women, the origin of this elevation in aldosterone production is not well defined. Adipocyte-derived factors have emerged as potential candidates to increase aldosterone production in obesity. Emerging evidence suggests the presence of a mechanistic link in which the adipocyte-derived hormone leptin stimulates aldosterone production in obesity, thereby creating a positive feedback loop for obesity-associated cardiovascular disease. In addition, recent reports give credence to the concept that this leptin-aldosterone stimulation pathway in obesity is an underlying mechanism for sex-discrepancies in obesity-associated cardiovascular disease. Leptin appears as a new direct regulator of adrenal aldosterone production and leptin-mediated aldosterone production is a novel candidate mechanism underlying obesity-associated hypertension, particularly in females.

Regulation of aldosterone production by ion channels: From basal secretion to primary aldosteronism

Aldosterone is produced by zona glomerulosa (ZG) cells of the adrenal cortex and plays a key role in balancing water and electrolytes levels. Autonomous overproduction of aldosterone leads to primary aldosteronism (PA), which is the most common form of secondary endocrine hypertension. Recently, significant progress has been made towards understanding the genetic basis of PA, where increasing clinical evidence suggests that mutations in ion channels appear to be the major cause of aldosterone-producing adenomas. In this review, we focused on potassium and calcium channels that regulate aldosterone secretion, and their roles in the pathology of PA. Because potassium and calcium channels are differentially expressed in ZG cells in different species of mammals, the limitations of published studies are also discussed.

GSTA1 Expression Is Correlated With Aldosterone Level in KCNJ5-Mutated Adrenal Aldosterone-Producing Adenoma.

KCNJ5 mutation is a major cause of aldosterone-producing adenomas (APAs). The development of APA apart from KCNJ5 mutation is less investigated. To investigate other mechanisms affecting aldosterone secretion apart from KCNJ5. Six pairs of KCNJ5-mutated, high and low aldosterone-secreting APAs, five non-KCNJ5-mutated APAs, and four normal adrenal glands were assayed by Affymetrix GeneChip Human Transcriptome Array 2.0. A total of 113 APA samples were investigated to explore the expression of glutathione-S-transferase A1 (GSTA1). H295R cells were used to verify the function of GSTA1. GSTA1 was the top gene downregulated in high-aldosterone KCNJ5-mutated APAs. GSTA1 was also downregulated in KCNJ5-mutated APAs compared with wild-type KCNJ5 APAs. Accordingly, mutant KCNJ5 decreased GSTA1 messenger RNA and protein expression levels. GSTA1 overexpression suppressed aldosterone secretion whether in wild-type or mutant KCNJ5 H295R cells. Adding ethacrynic acid or silencing of GSTA1 increased aldosterone secretion by increasing reactive oxygen species (ROS), superoxide, H2O2 levels, and Ca2+ influx. The expression of the transcription factors NR4A1, NR4A2, and CAMK1 and intracellular Ca2+ were significantly upregulated by GSTA1 inhibition. The reduced form of NAD phosphate oxidase inhibitor or H2O2 scavenger or blocking calmodulin or calcium channels could significantly reduce aldosterone secretion in GSTA1-inhibited cells. (1) GSTA1 expression is reversely correlated with aldosterone level in KCNJ5-mutated APAs, (2) GSTA1 regulates aldosterone secretion by ROS and Ca2+ signaling, and (3) KCNJ5 mutation downregulates GSTA1 expression, and overexpression of GSTA1 reverses increased aldosterone in KCNJ5-mutated adrenal cells.

Of Mice and Man and the Regulation of Aldosterone Secretion

See related article, pp 347–356 Aldosterone is the most important mineralocorticoid for electrolyte and fluid homeostasis in mammals, birds, and some members of other orders. Although critical for life, even subtle inappropriate increases in aldosterone contribute to the development of hypertension and cardiovascular damage. Primary aldosteronism (PA), the autonomous and excessive secretion of aldosterone, is the most common form of secondary hypertension and is associated with more pathological cardiovascular remodeling than essential hypertension of a similar duration and severity. Aldosterone-producing adenomas and idiopathic hyperaldosteronism are responsible for most PA. Despite the importance of PA in cardiovascular and renal disease, its pathogenesis is only partially clarified in aldosterone-producing adenomas and remains unknown in idiopathic hyperaldosteronism. A report in this issue by Yao et al1 provides crucial new information on the normal control of aldosterone synthesis that could elucidate mechanisms for its dysregulation in PA. They used elegant technology to demonstrate that TASK-3 K+ channels (tandem pore domain acid-sensitive K+ channels) locate in the mitochondria and interact with proteins of the electron transport chain of the mitochondrial inner membrane and regulate mitochondrial membrane potential and morphology. They also showed that TASK-3 channels interact with the P450 side-chain cleavage enzyme that catalyzes the first step in the synthesis of all steroids from cholesterol, as well as with CYP11B2, or aldosterone synthase, the last and unique enzyme in a series of enzymatic reactions within the mitochondria. Synthesis of aldosterone is regulated primarily by angiotensin II (Ang-II) and plasma potassium (K+), with lesser influence by adrenocorticotropic hormone and several paracrine factors2 at 2 points in its synthetic pathway. Within minutes after stimulation by Ang-II or K+, …