Aldosterone-producing nodules and CYP11B1 signaling correlate in primary aldosteronism.

Autonomous cortisol secretion (ACS) could be found in some patients with unilateral primary aldosteronism (uPA). However, the histopathological patterns of uPA with concurrent ACS have not been well elucidated. The adrenal gland with the adenoma from 61 uPA patients who underwent unilateral adrenalectomy were assessed by immunohistochemistry. Bioinformatics analysis, including the Cancer Genome Atlas (TCGA) and Kyoto Encyclopedia of Genes and Genomes, was applied. The prevalence of multiple aldosterone-producing nodules or micronodules (mAPN/mAPM) was 65.6% (40/61) among our uPA patients. Concurrent ACS was identified in 32% of this uPA cohort; they were associated with the interaction of larger tumor size (>1.98 cm) and mAPN/mAPM (odds ratio = 3.08, P = 0.004). Transcriptome analysis uncovered a dominant enrichment of HSD3B7 overexpression (P = 0.004) in the adenomas of the histopathologically classical adrenal uPA lesions with concomitant mAPN/mAPM, compared with those uPA adenomas without concurrent surrounding mAPN/mAPM. We identified a novel linkage of enhanced steroidogenic genes of HSD3B7 expression concurrent with the downstream higher CYP11B1 expression; further relationship was confirmed by immunohistochemical staining and validated by TCGA bioinformatics. The presence of mAPN/mAPM in uPA patients had lower rate for biochemical success after adrenalectomy (P = 0.047). In summary, two-thirds of uPA patients had concomitant mAPN/mAPM; 1/3 of uPA patients had concurrent ACS. Steroidogenic HSD3B7/CYP11B1 signaling was associated with uPA adenomas with surrounding mAPN/mAPM. Interaction of larger adenoma size with the presence of mAPN/mAPM was linked to co-existing ACS. Such uPA patients with concomitant mAPN/mAPM had lower rate of biochemical success.

Phosphodiesterase 2A and 3B variants are associated with primary aldosteronism.

Familial primary aldosteronism (PA) is rare and mostly diagnosed in early-onset hypertension (HT). However, 'sporadic' bilateral adrenal hyperplasia (BAH) is the most frequent cause of PA and remains without genetic etiology in most cases. Our aim was to investigate new genetic defects associated with BAH and PA. We performed whole-exome sequencing (paired blood and adrenal tissue) in six patients with PA caused by BAH that underwent unilateral adrenalectomy. Additionally, we conducted functional studies in adrenal hyperplastic tissue and transfected cells to confirm the pathogenicity of the identified genetic variants. Rare germline variants in phosphodiesterase 2A (PDE2A) and 3B (PDE3B) genes were identified in three patients. The PDE2A heterozygous variant (p.Ile629Val) was identified in a patient with BAH and early-onset HT at 13 years of age. Two PDE3B heterozygous variants (p.Arg217Gln and p.Gly392Val) were identified in patients with BAH and HT diagnosed at 18 and 33 years of age, respectively. A strong PDE2A staining was found in all cases of BAH in zona glomerulosa and/or micronodules (that were also positive for CYP11B2). PKA activity in frozen tissue was significantly higher in BAH from patients harboring PDE2A and PDE3B variants. PDE2A and PDE3B variants significantly reduced protein expression in mutant transfected cells compared to WT. Interestingly, PDE2A and PDE3B variants increased SGK1 and SCNN1G/ENaCg at mRNA or protein levels. In conclusion, PDE2A and PDE3B variants were associated with PA caused by BAH. These novel genetic findings expand the spectrum of genetic etiologies of PA.

Immunohistochemistry of aldosterone synthase leads the way to the pathogenesis of primary aldosteronism.

Our group previously purified human and rat aldosterone synthase (CYP11B2 and Cyp11b2, respectively) from their adrenals and verified that it is distinct from steroid 11ß-hydroxylase (CYP11B1 or Cyp11b1), the cortisol- or corticosterone-synthesizing enzyme. We now describe their distributions immunohistochemically with specific antibodies. In rats, there is layered functional zonation with the Cyp11b2-positive zona glomerulosa (ZG), Cyp11b1-positive zona fasciculata (ZF), and Cyp11b2/Cyp11b1-negative undifferentiated zone between the ZG and ZF. In human infants and children (<12 years old), the functional zonation is similar to that in rats. In adults, the adrenal cortex remodels and subcapsular aldosterone-producing cell clusters (APCCs) replace the continuous ZG layer. We recently reported possible APCC-to-APA transitional lesions (pAATLs) in 2 cases of unilateral multiple adrenocortical micro-nodules. In this review, we present 4 additional cases of primary aldosteronism, from which the extracted adrenals contain pAATLs, with results of next generation sequencing for these lesions. Immunohistochemistry for CYP11B2 and CYP11B1 has become an important tool for the diagnosis of and research on adrenocortical pathological conditions and suggests that APCCs may be the origin of aldosterone-producing adenoma.

Disordered zonal and cellular CYP11B2 enzyme expression in familial hyperaldosteronism type 3.

Three forms of familial primary aldosteronism have been recognized. Familial Hyperaldosteronism type 1 (FH1) or dexamethasone suppressible hyperaldosteronism, FH2, the most common form of as yet unknown cause(s), and FH3. FH3 is due to activating mutations of the potassium channel gene KCNJ5 that increase constitutive and angiotensin II-induced aldosterone synthesis. In this study we examined the cellular distribution of CYP11B2, CYP11B1, CYP17A1 and KCNJ5 in adrenals from two FH3 siblings using immunohistochemistry and immunofluorescence and obtained unexpected results. The adrenals were markedly enlarged with loss of zonation. CYP11B2 was expressed sporadically throughout the adrenal cortex. CYP11B2 was most often expressed by itself, relatively frequently with CYP17A1, and less frequently with CYP11B1. KCNJ5 was co-expressed with CYP11B2 and in some cells with CYP11B1. This aberrant co-expression of enzymes likely explains the abnormally high secretion rate of the hybrid steroid, 18-oxocortisol.

Immunohistochemistry of the adrenal in primary aldosteronism.

PURPOSE OF REVIEW: Primary aldosteronism is a major cause of hypertension; aldosterone-producing adenomas (APA) cause about half of primary aldosteronism; idiopathic hyperplasia of adrenal glomerulosa cells are responsible for the rest. A surprising variety of mutations have recently been identified in ion channels and pumps in a significant number of APA. The present review addresses histological and molecular aspects of APA and the surrounding adrenal. RECENT FINDINGS: Specific antibodies against the CYP11B2 and CYP11B1 enzymes, the last enzyme in aldosterone and cortisol synthesis, respectively, allow for the first time study of the steroidogenic capabilities of cells within the APA and adjacent adrenal. Cells expressing CYP11B2 may be scattered and/or in clusters throughout the normal adrenal zona glomerulosa. APA differ widely in the number of cells expressing CYP11B2; some did not express it at all, but were surrounded by cells, some in clusters or micronodules, that expressed CYP11B2. Some APAs also comprised cells expressing both CYP11B1 and CYP17A1. In some samples, analysis of the tissue adjacent to APA detected ion channel and pump mutations heretofore associated only with APA. SUMMARY: APAs have a complex structure and expression of steroidogenic enzymes.

A Novel CYP11B2-Specific Imaging Agent for Detection of Unilateral Subtypes of Primary Aldosteronism.

CONTEXT: Although adrenal vein sampling is the standard method to distinguish unilateral from bilateral forms of primary aldosteronism, it is an invasive and technically difficult procedure. (11)C-metomidate (MTO)-positron emission tomography was reported as a potential replacement for adrenal vein sampling. However, MTO has low selectivity for CYP11B2 over CYP11B1. OBJECTIVE: This study aimed to determine the selectivity of (18)F-CDP2230, a new imaging agent, for CYP11B2 over CYP11B1 and determine whether the biodistribution profile of (18)F-CDP2230 is favorable for imaging CYP11B2. METHODS: The IC50 of CDP2230 for the enzymatic activities of CYP11B2 and CYP11B1 was determined using cells with stable expression of either enzyme. In vitro autoradiography of human adrenal sections with aldosterone-producing adenomas was performed to confirm the specific binding ability of (18)F-CDP2230 to CYP11B2-expressing regions. Furthermore, positron emission tomography and magnetic resonance imaging were performed to evaluate the biodistribution of (18)F-CDP2230 in rats. RESULTS: Although CDP2230 showed a significantly lower affinity for CYP11B2 and CYP11B1 than did MTO analogues, its selectivity for CYP11B2 over CYP11B1 was higher than that of MTO analogues. In vitro autoradiography revealed that the binding of (18)F-CDP2230 to CYP11B2-expressing regions in the adrenal gland was more specific than that of (123)I-IMTO. Moreover, the biodistribution study showed that (18)F-CDP2230 accumulated in adrenal glands with low background uptake. CONCLUSIONS: Our study showed a high selectivity of (18)F-CDP2230 for CYP11B2 over CYP11B1 with a favorable biodistribution for imaging CYP11B2. (18)F-CDP2230 is a promising imaging agent for detecting unilateral subtypes of primary aldosteronism.

Adrenal CYP11B1/2 expression in primary aldosteronism: immunohistochemical analysis using novel monoclonal antibodies.

CYP11B1 and CYP11B2 play pivotal roles in adrenocorticosteroids synthesis. We performed semi-quantitative immunohistochemical analysis of these proteins in adrenals from patients with primary aldosteronism using novel monoclonal antibodies. Clusters of cortical cells positive for CYP11B2 were detected in the zona glomerulosa (ZG) of normal adrenal gland (NA), idiopathic hyperaldosteronism (IHA) and the adjacent adrenal of aldosterone-producing adenoma (APA). In APA, heterogenous immunolocalization of CYP11B2 and diffuse immunoreactivity of CYP11B1 were detected in tumor cells, respectively. The relative immunoreactivity of CYP11B2 in the ZG of adjacent adrenal of APA was significantly lower than that of NA, IHA and APA tumor cells, suggestive of suppressed aldosterone biosynthesis in these cells. These findings did indicate the regulatory mechanisms of aldosterone biosynthesis were different between normal/hyperplastic and neoplastic aldosterone-producing cells in human adrenals. CYP11B2 immunoreactivity in the ZG could also serve as a potential immunohistochemical marker differentiating morphologically hyperplastic ZG of IHA and APA adjacent adrenal.

Association of the variations in the HSD3ß gene with primary aldosteronism.

OBJECTIVE: In mice, a lack of cryptochrome results in up-regulation of aldosterone production due to high expression of the 3ß-hydroxysteroid dehydrogenases (HSD3ß) gene. The HSD3ß pathway might play a pivotal role in aldosterone synthesis. This study aimed to determine the association of HSD3ß and HSD3ß2 gene variations with primary aldosteronism in a Taiwanese population. METHOD: In this case-control cohort, 688 consecutive ethnically matched unrelated individuals including 362 primary aldosteronism and 326 essential hypertension cases were recruited. Nineteen tag single-nucleotide polymorphisms (SNPs) across HSD3ß1, HSD3ß2, and CYP11ß2 were genotyped. Expression of HSD3ß mRNA and immunohistochemical stain of HSD3ß in the specimens of aldosterone-producing adenoma (APA) was compared with that in nonfunctional incidentaloma. RESULTS: The SNPs of rs12410453 A allele in HSD3ß2 gene [odds ratio (OR) 1.92, 95% confidence interval (CI) 1.13-3.32, P=0.018] and rs6203 C allele in the HSD3ß1 gene (OR 2.21, 95% CI 1.28-3.95, P=0.006) showed significant association with primary aldosteronism, with corresponding population attributable risk of 6.7 and 30.7%, respectively. Primary aldosteronism patients of non-CC in rs6203 and non-GA in rs12401453 had lower plasma aldosterone-to-renin ratio. A haplotype in a linkage disequilibrium block containing rs6203 associated significantly with serum potassium level (OR 1.24, 95% CI 1.02-1.24, P=0.026). The expressions of HSD3ß1 mRNA, HSD3ß2 mRNA and HSD3ß protein were increased in APA, as compared to incidentaloma. CONCLUSION: Risk-conferring genetic variations in the HSD3ß gene influenced susceptibility of primary aldosteronism. Concomitant presence of rs6203 CC and rs12410453 GA genotypes synergistically increased aldosterone-to-renin ratio.

Immunohistochemistry improves histopathologic diagnosis in primary aldosteronism.

BACKGROUND: In primary aldosteronism (PA) the main source of aldosterone hypersecretion is an aldosterone-producing adenoma (APA) or a bilateral hyperplasia. Histopathology of the adrenal gland from patients with PA has been difficult, as there are no morphological criteria to ascertain which are the cells that produce aldosterone. We therefore applied new specific antibodies to explore which cells in the adrenal contain the enzymes for aldosterone and cortisol production, respectively. METHODS: Adrenals from 24 patients with PA were studied. After routine preparation, consecutive sections were stained with antibodies for CYP11B1 (cortisol) and CYP11B2 (aldosterone) enzymes. RESULTS: APA had a strong immunoreactivity for CYB11B2. In adrenals from seven patients, we found no APA, but several nodules with strong CYB11B2 immunoreactivity, indicating aldosterone-producing nodular hyperplasia. CONCLUSIONS: Immunohistochemistry of adrenal steroidogenic enzymes provides novel diagnostic information. This may become an important part of routine histopathology, and contribute to improved clinical management in PA.

Characterization of NCI-H295R cells as an in vitro model of hyperaldosteronism.

In depth analysis of key molecular mechanisms involved in functional autonomy of aldosterone secretion is hampered by the lack of tumor cell lines that reflect functional characteristics of aldosterone producing adenomas. Herein, we describe the characteristics of the adrenocortical carcinoma cell line NCI-H295R and its suitability as a model of hyperaldosteronism in relation to different culture conditions. Steroid profiling revealed that NCI-H295R cells predominantly secrete cortisol, while aldosterone and other steroids are released at much lower concentrations. However, aldosterone output specifically increased in response to different stimuli such as ACTH and angiotensin II, and in particular to potassium in a dose dependent manner. NCI-H295R cells readily formed spheroids under specific culture conditions, a method widely used for the enrichment of progenitor cells. Unexpectedly, spheroid cells excelled with higher aldosterone concentration and higher expression levels of the steroidogenic enzymes StAR, 3ßHSD, CYP17, SF-1, and the MC2-receptor. Further investigations revealed that this phenomenon is mainly attributed to epithelial growth factor (EGF) and particularly fibroblast growth factor (FGF), which are both essential ingredients in the spheroid culture medium. Aldosterone release under the combinatory influence of EGF and FGF was not higher than the effect of FGF alone. Spheroid growth per se, therefore, does not ensure an enrichment of less differentiated cell types in this cell line.

Expression of aldosterone synthase and adrenocorticotropic hormone receptor in adrenal incidentalomas from normotensive and hypertensive patients: Distinguishing subclinical or atypical primary aldosteronism from adrenal incidentaloma.

The present study aimed to investigate the expression of aldosterone synthase (CYP11B2), adrenocorticotropic hormone receptor (ACTH-R) and their regulating transcription factors in adrenal incidentalomas (AIs) from normotensive and hypertensive patients to distinguish subclinical or atypical primary aldosteronism (PA) from AIs. Total RNA was extracted from 8 normal adrenal cortices (NAs), 46 AIs, 15 aldosterone-producing adenomas (APAs) and 6 idiopathic hyperaldosteronisms (IHAs). Real-time quantitative polymerase chain reaction (PCR) and immunohistochemistry were performed to determine the mRNA and protein expression of CYP11B2, ACTH-R, steroidogenic factor-1 (SF1) and dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1 (DAX-1) in the different tissues. The AI hypertensive subgroup displayed increased plasma aldosterone concentration (PAC) and PAC/PRA ratio (ARR) and decreased plasma renin activity (PRA) compared to the normotensive group. CYP11B2, ACTH-R and SF1 mRNAs were significantly higher in the APA group compared to the other groups, and gradually increased in AI hypertensive samples. DAX-1 mRNA was expressed faintly in PA compared with NA. In normotensive-AI samples, DAX-1 mRNA was higher compared to PA and AI hypertensive samples. Significant differences in gene expression levels in AIs were observed between probable and improbable PA patients. Immunohistochemical results were consistent with those of real-time PCR. Plasma aldosterone levels were positively correlated with CYP11B2, ACTH-R and SF1 mRNA and inversely correlated with DAX-1 mRNA. In conclusion, a significant number of hypertensive-AI patients may have subclinical forms of PA. CYP11B2, ACTH-R and their regulating transcription factors may be noteworthy in distinguishing subclinical PA from AIs.

Treatment with heme arginate alleviates adipose tissue inflammation and improves insulin sensitivity and glucose metabolism in a rat model of Human primary aldosteronism.

Visceral adiposity and insulin resistance are common pathophysiological denominators in patients with primary aldosteronism. Although we recently reported the antidiabetic effects of heme oxygenase (HO), no study has examined the effects of upregulating HO on visceral adiposity in uninephrectomized (UnX) deoxycorticosterone acetate (DOCA-salt) hypertensive rats, a model of human primary aldosteronism characterized by elevated endothelin (ET-1) and oxidative/inflammatory events. Here, we report the effects of the HO inducer heme arginate and the HO blocker chromium mesoporphyrin (CrMP) on visceral adipose tissue obtained from retroperitoneal fat pads of UnX DOCA-salt rats. UnX DOCA-salt rats were hypertensive but normoglycemic. Heme arginate reduced visceral adiposity and enhanced HO activity and cGMP in the adipose tissue, but suppressed ET-1, nuclear-factor κB (NF-κB), activating-protein (AP-1), c-Jun-NH2-terminal kinase (JNK), macrophage chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and 8-isoprostane. These were associated with reduced glycemia, increased insulin, and the insulin-sensitizing protein adiponectin, with corresponding reduction in insulin resistance. In contrast, the HO inhibitor, CrMP, abolished the effects of heme arginate, aggravating insulin resistance, suggesting a role for the HO system in insulin signaling. Importantly, the effects of the HO system on ET-1, NF-κB, AP-1, JNK, MCP-1, and ICAM-1 in visceral or retroperitoneal adiposity in UnX-DOCA-salt rats have not been reported. Because 8-isoprostane stimulates ET-1 to enhance oxidative insults, and increased oxidative events deplete adiponectin and insulin levels, the suppression of oxidative/inflammatory mediators such as 8-isoprostane, NF-κB, AP-1, MCP-1, ICAM-1, and JNK, an inhibitor of insulin biosynthesis, may account for the potentiation of insulin signaling/glucose metabolism by heme arginate. These data indicate that although UnX DOCA-salt rats were normoglycemic, insulin signaling was impaired, suggesting that dysfunctional insulin signaling may be a forerunner to overt diabetes in primary aldosteronism.

Diabetic lipoproteins and adrenal aldosterone synthesis--a possible pathophysiological link?

An increased prevalence of diabetes mellitus (DM) has been reported in patients with primary aldosteronism (PA). DM is associated with abnormal structure and metabolism of circulating lipoproteins, which normally serve as a major source of cholesterol for adrenocortical steroidogenesis. The present study has been designed to investigate the effect of diabetically modified lipoproteins on adrenocortical aldosterone synthesis. Lipoproteins (VLDL, LDL, HDL) isolated from healthy volunteers, were subjected to oxidation or glycoxidation in the presence of sodium hypochlorite (3 mmol/l) or glucose (200 mmol/l), and aldosterone synthesis in human adrenocortical cells (H295R) was examined. Native and glycoxidized VLDL had greatest stimulatory effect on aldosterone production by 15-fold and 14-fold, respectively. At the molecular level, these VLDL produced maximum increases in Cyp11B2 mRNA level up to 17-fold. Experiments with the highly selective scavenger receptor class B type I (SR-BI) inhibitor BLT-1 revealed that cholesterol uptake from native and glycoxidized HDL and VLDL for hormone production is considerably mediated by SR-BI. Western blot analysis of extracellular signal-regulated kinase (ERK 1/2) phosphorylation and experiments with the MEK inhibitor U0126 indicated a specific mechanistic role of the ERK cascade in lipoprotein-mediated steroid hormone release. In summary, diabetic dyslipidemia and modification of circulating lipoproteins may promote adrenocortical aldosterone synthesis.

Prevalence of primary aldosteronism in patient's cohorts and in population-based studies--a review of the current literature.

There is an ongoing controversy on the prevalence of primary aldosteronism (PA). We aimed to update a meta-analysis published in 2008, that compiled studies reporting the prevalence of positive ARR screening tests and PA. We therefore reviewed original studies published in 2008 or later to examine whether current reports provide similar, higher or lower prevalences of elevated ARRs or PA than reports included in the original meta-analysis. A systematic review of English articles using PubMed was conducted. Search and extraction of articles were performed by one review author; the second review author checked all extracted data. We identified 11 eligible studies. The updated, weighted mean prevalences of elevated ARRs and PA in primary care (prevalence of high ARRs 16.5%; prevalence of PA 4.3%) and referred patients (prevalence of high ARRs 19.6%; prevalence of PA 9.5%) were only marginally different from the mean values obtained in the original meta-analysis. Among the current studies the maximum values for the prevalence of elevated ARRs and PA were substantially lower than among the older studies. Our results confirm the main conclusions from the original meta-analysis. The prevalence of PA increases with the severity of hypertension and the inclusion of current study results did not alter the mean prevalences of elevated ARRs and PA in primary care and referred patients. Additionally, we found that current studies focus increasingly on patients in referral centers or special subgroups, while the prevalence of PA in the general hypertensive population is yet unknown.

Acute and chronic regulation of aldosterone production.

Aldosterone is the major mineralocorticoid synthesized by the adrenal and plays an important role in the regulation of systemic blood pressure through the absorption of sodium and water. Aldosterone production is regulated tightly by selective expression of aldosterone synthase (CYP11B2) in the adrenal outermost zone, the zona glomerulosa. Angiotensin II (Ang II), potassium (K(+)) and adrenocorticotropin (ACTH) are the main physiological agonists which regulate aldosterone secretion. Aldosterone production is regulated within minutes of stimulation (acutely) through increased expression and phosphorylation of the steroidogenic acute regulatory (StAR) protein and over hours to days (chronically) by increased expression of the enzymes involved in the synthesis of aldosterone, particularly CYP11B2. Imbalance in any of these processes may lead to several disorders of aldosterone excess. In this review we attempt to summarize the key molecular events involved in the acute and chronic phases of aldosterone secretion.

Clinical characteristics of primary hyperaldosteronism due to adrenal microadenoma.

An increasing number of patients are being diagnosed with primary aldosteronism (PA) due to aldosterone-producing macroadenoma (APA). However, there are only limited data available on the clinical characteristics of PA that are associated with adrenal microadenoma. Of the 55 patients that were diagnosed with PA in our study, 22 patients showed a unilateral adrenal over-production of aldosterone. The histopathology of the surgically removed adrenal tissues led to six patients being diagnosed with microadenoma, and the clinical features of microadenoma, macroadenoma and idiopathic hyperaldosteronism (IHA) were studied. The expression levels of CYP11B2, CYP17, CYP21 and 3ß-hydroxysteroid dehydrogenase 2 (HSD3B2) mRNA in the adrenal cortices (n=5 and 6, respectively) that remained attached to the adrenal microadenomas or macroadenomas were examined by real time-PCR and then compared to the expression levels in the adrenal cortices (n=5) of non-functioning adrenal adenomas (NF). The patients with microadenoma (n=6) had significantly higher diastolic blood pressure than the patients with macroadenoma (n=16) or IHA (n=33) (p<0.05). The systolic blood pressure, plasma aldosterone concentration, serum potassium level and renal function did not differ between the PA sub-groups. The levels of CYP11B2 and CYP17 mRNA were significantly increased in the adjacent tissues of microadenomas, as compared with macroadenomas or NF (p<0.05), whereas no significant differences in the CYP21 and HSD3B2 mRNA levels were found between the PA sub-groups. The tumor size did not influence the clinical characteristics of APA. The non-tumor portions of the microadenomas showed marked and sustained CYP11B2 mRNA expression under the suppressed renin-angiotensin system. We suggest that an increased number of microadenomas should be sampled, and the immunohistochemistry for steoridogenic enzymes should be investigated to clarify the etiology of microadenoma.

A de novo unequal cross-over mutation between CYP11B1 and CYP11B2 genes causes familial hyperaldosteronism type I.

UNLABELLED: Familial hyperaldosteronism type I (FH-I) is an autosomal dominant disorder caused by an unequal cross-over of the gene encoding steroid 11ß-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2), giving rise to a chimeric CYP11B1/CYP11B2 gene that displays aldosterone synthase activity regulated by ACTH instead of angiotensin II. AIM: To report an unprecedented case of a de novo unequal crossover mutation between CYP11B1 and CYP11B2 genes causing FH-I. PATIENTS AND METHODS: The index case is a 45-yr-old Chilean male diagnosed with primary aldosteronism (PA). All family members were also studied: his biological parents, 1 brother, 6 sisters, 2 daughters, and 1 son. Plasma renin activity, serum aldosterone, and its ratio were measured in all patients. Genetic analyses were performed using long-extension PCR (XL-PCR), DNA sequencing and Southern blot methods. RESULTS: PA was diagnosed for the index case, 1 of his daughters, his son but not for his parents or siblings. XLPCR and Southern blotting demonstrated the presence of the chimeric CYP11B1/CYP11B2 gene solely in PA-affected subjects, suggesting a case of a de novo mutation. Sequence analysis showed the unequal cross-over CYP11B1/CYP11B2 at intron 2 (c.2600-273 CYP11B2). We also identified a polymorphism at the same intron (c.2600-145C>A CYP11B2) in the genome of the index case's father. CONCLUSION: We describe an unprecedented case of unequal cross-over mutation for the chimeric CYP11B1/CYP11B2 gene causing FH-I, which may be linked to a polymorphism in the index case's father germ line.

Aldosterone increases Na+ -K+ -ATPase activity in skeletal muscle of patients with Conn's syndrome.

OBJECTIVE: In Conn's syndrome, hypokalaemia normally results from renal potassium loss because of the effect of excess aldosterone on Na(+) -K(+) -ATPase in principal cells. Little is known about the effect of aldosterone on cellular potassium redistribution in skeletal muscle. Our study determined the effect of aldosterone on muscle Na(+) -K(+) -ATPase. DESIGN: Muscle biopsies were taken from six patients immediately before and 1 month after adrenalectomy. Ten age-matched subjects with normal levels of circulating aldosterone served as controls. RESULTS: Average plasma aldosterone was significantly higher in presurgery (235·0 ± 51·1 pg/ml) than postsurgery (64·5 ± 25·1 pg/ml) patients. Similarly, Na(+) -K(+) -ATPase activity, relative mRNA expression of α(2) (not α(1) or α(3) ) and ß(1) (not ß(2) or ß(3) ), and protein abundance of α(2) and ß(1) subunits were greater in pre- than postsurgery samples (128·7 ± 12·3 vs 79·4 ± 13·3 nmol·mg/protein/h, 2·45 ± 0·31 vs 1·04 ± 0·17, 1·92 ± 0·22 vs1·02 ± 0·14, 2·17 ± 0·33 vs 0·98 ± 0·09 and 1·70 ± 0·17 vs 0·90 ± 0·17, respectively, all P<0·05). The activity and mRNA expression of the α(2) and ß(1) subunits correlated well with plasma aldosterone levels (r = 0·71, r = 0·75 and r = 0·78, respectively, all P < 0·01). CONCLUSIONS: Our study provides the first evidence in human skeletal muscle that increased plasma aldosterone leads to increased Na(+) -K(+) -ATPase activity via increases in α(2) and ß(1) subunit mRNAs and their protein expressions. The increased activity may contribute in part to the induction of hypokalaemia in patients with Conn's syndrome.

Pharmacodynamic and pharmacokinetic characterization of the aldosterone synthase inhibitor FAD286 in two rodent models of hyperaldosteronism: comparison with the 11beta-hydroxylase inhibitor metyrapone.

Aldosterone synthase (CYP11B2) inhibitors (ASIs) represent an attractive therapeutic approach for mitigating the untoward effects of aldosterone. We characterized the pharmacokinetic/pharmacodynamic relationships of a prototypical ASI, (+)-(5R)-4-(5,6,7,8-tetrahydroimidazo[1,5-a]pyridin-5-yl]benzonitrile hydrochloride (CGS020286A, FAD286, FAD) and compared these profiles to those of the 11beta-hydroxylase inhibitor metyrapone (MET) in two rodent models of secondary hyperaldosteronism and corticosteronism. In chronically cannulated Sprague-Dawley rats, angiotensin II (ANG II) (300 ng/kg bolus + 100 ng/kg/min infusion) or adrenocorticotropin (100 ng/kg + 30 ng/kg/min) acutely elevated plasma aldosterone concentration (PAC) from approximately 0.26 nM to a sustained level of approximately 2.5 nM for 9 h. Adrenocorticotropin but not ANG II elicited a sustained increase in plasma corticosterone concentration (PCC) from approximately 300 to approximately 1340 nM. After 1 h of Ang II or adrenocorticotropin infusion, FAD (0.01-100 mg/kg p.o.) or MET (0.1-300 mg/kg p.o.) dose- and drug plasma concentration-dependently reduced the elevated PACs over the ensuing 8 h. FAD was approximately 12 times more dose-potent than MET in reducing PAC but of similar or slightly greater potency on a plasma drug concentration basis. Both agents also decreased PCC in the adrenocorticotropin model at relatively higher doses and with similar dose potencies, whereas FAD was 6-fold weaker based on drug exposures. FAD was approximately 50-fold selective for reducing PAC versus PCC, whereas MET was only approximately 3-fold selective. We conclude that FAD is a potent, orally active, and relatively selective ASI in two rat models of hyperaldosteronism. MET is an order of magnitude less selective than FAD but is, nevertheless, more potent as an ASI than as an 11beta-hydroxylase inhibitor.