Comparative Genomics and Transcriptome Profiling in Primary Aldosteronism

Clinical Management of Primary Aldosteronism: An Update

Despite carrying an excess risk of cardiovascular events, primary aldosteronism (PA) is a commonly overlooked secondary form of arterial hypertension. An increased awareness of its high prevalence and broader screening strategies are urgently needed to improve its detection rate and allow early diagnosis and targeted treatment. For patients with unilateral PA, these measures can correct hyperaldosteronism and ensure cure of hypertension, even when resistant to drug treatment, thus preventing adverse cardiovascular events. Among these, atrial fibrillation is the most common, but left ventricular hypertrophy, stroke, chronic kidney disease, and myocardial infarction also occur more often than in patients with hypertension and no PA. Young patients, who have higher chances of being cured long term, and high-risk patients, such as those with stage III or resistant hypertension, are those who will benefit most from an early diagnosis of PA. Therefore, the implementation of strategies to detect PA by a simplified diagnostic algorithm is necessary. In the patients who seek for surgical cure, adrenal vein sampling is key for the identification of unilateral PA and the achievement of optimal outcomes. Unfortunately, being technically demanding and poorly available, adrenal vein sampling represents the bottleneck in the workup of PA. Considering the novel knowledge generated in the past 5 years in many studies, particularly in the AVIS-2 study (Adrenal Vein Sampling International Study-2), based on 4 decades of experience at our center and on the last guidelines, we herein provide an update on the management of PA with recommendations for drug treatment and strategies to avoid adrenal vein sampling wherever it is poorly, or not, available.

Saline suppression testing-induced hypocalcemia and implications for clinical interpretations

BACKGROUND

Extracellular calcium critically regulates physiologic aldosterone production. Moreover, abnormal calcium flux and signaling are involved in the pathogenesis of the majority of primary aldosteronism cases.

METHODS

We investigated the influence of the saline suppression test (SST) on calcium homeostasis in prospectively recruited participants (n = 86).

RESULTS

During SST, 100% of participants had decreases in serum calcium, with 48% developing frank hypocalcemia. Serum calcium declined from 2.30 ± 0.08 mmol/L to 2.13 ± 0.08 mmol/L (P < .001) with parallel increases in parathyroid hormone from 6.06 ± 2.39 pmol/L to 8.13 ± 2.42 pmol/L (P < .001). In contrast, serum potassium and bicarbonate did not change, whereas eGFR increased and serum glucose decreased (P < .001). Lower body surface area (translating to greater effective circulating volume expansion during SST) was associated with greater reductions in (β = .33, P = .001), and absolutely lower, serum calcium levels (β = .25, P = .001). When evaluating clinically-relevant diagnostic thresholds, participants with post-SST aldosterone levels <138 pmol/L had lower post-SST calcium and 25-hydroxyvitamin D levels (P < .05), and higher post-SST parathyroid hormone levels (P < .05) compared with those with post-SST aldosterone levels >277 pmol/L.

CONCLUSION

SST uniformly decreases serum calcium, which is likely to be due to the combination of variable dilution, increased renal clearance, and vitamin D status. These acute reductions in bioavailable calcium are associated with lower post-SST aldosterone. Given the critical role of extracellular calcium in regulating aldosterone production, these findings warrant renewed inquiry into the validity of SST interpretations for excluding primary aldosteronism.

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.

The Bioinformatics Analysis of Aldosterone-Producing Adenoma and Verification of Differentially Expressed Genes

PURPOSE

Previous studies have investigated the transcriptional modulations of aldosterone overproduction of aldosterone-producing adenomas (APAs). We aimed to systematically study the genes and pathways associated with molecular mechanism underlying APA by bioinformatics analysis and experimental validation for the expression profile.

METHODS

This study was performed based on three gene expression profiles (GSE64957, GSE8514, and GSE60042). Differentially expressed gene (DEG) investigation, function and pathway enrichment analysis, and protein-protein interaction (PPI) network analysis were performed by the bioinformatics analysis. For the validation with quantitative PCR, tissues from 11 patients with nonfunctioning adrenal adenoma (NFA) and 13 with APA were included in our cohort.

RESULTS

In this study, the bioinformatics analysis was performed and 182 upregulated and 88 downregulated DEGs were identified. As expected, the upregulated DEGs were primarily involved in calcium ion homeostasis (p = 2.00X10-4). In the KEGG pathway analysis, calcium signaling pathway (p = 4.38X10-6) and the aldosterone synthesis and secretion (p = 8.73X10-6) were enriched. Moreover, quantitative PCR was performed to detect the expression of 7 upregulated genes (PCP4, ATP2A3, CYP11B2, CLCN5, HTR4, VDR, and AQP2) among the intersection of DEGs. The mRNA levels of CYP11B2, HTR4, and AQP2 were significantly increased in APA samples compared to NFA (24.420 folds of NFA, p < 0.001; 3.753 folds of NFA, p = 0.002; and 11.487 folds of NFA, p = 0.018).

CONCLUSION

In summary, the present study showed several candidate genes with high expression from bioinformatics analysis and our cohort. Also, the DEGs were enriched in aldosterone synthesis and secretion and calcium signaling pathway as expected.

Primary Aldosteronism: JACC State-of-the-Art Review

Primary aldosteronism (PA) is a common, but frequently overlooked, cause of arterial hypertension and excess cardiovascular events, particularly atrial fibrillation. As timely diagnosis and treatment can provide a cure of hyperaldosteronism and hypertension, even when the latter is resistant to drug treatment, strategies to screen patients for PA early with a simplified diagnostic algorithm are justified. They can be particularly beneficial in some subgroups of hypertensive patients, as those who are at highest cardiovascular risk. However, identification of the surgically curable cases of PA and achievement of optimal results require subtyping with adrenal vein sampling, which, as it is technically challenging and currently performed only in tertiary referral centers, represents the bottleneck in the work-up of PA. Measures aimed at improving the clinical use of adrenal vein sampling and at developing alternative techniques for subtyping, alongside recommendations for drug treatment, including new development in the field, and for follow-up are discussed.

The 2020 Italian Society of Arterial Hypertension (SIIA) practical guidelines for the management of primary aldosteronism

Background and aim

Considering the amount of novel knowledge generated in the last five years, a team of experienced hypertensionlogists was assembled to furnish updated clinical practice guidelines for the management of primary aldosteronism.

Methods

To identify the most relevant studies, the authors utilized a systematic literature review in international databases by applying the PICO strategy, and then they were required to make use of only those meeting predefined quality criteria. For studies of diagnostic tests, only those that fulfilled the Standards for Reporting of Diagnostic Accuracy recommendations were considered.

Results

Each section was jointly prepared by at least two co-authors, who provided Class of Recommendation and Level of Evidence following the American Heart Association methodology. The guidelines were sponsored by the Italian Society of Arterial Hypertension and underwent two rounds of revision, eventually reexamined by an External Committee. They were presented and thoroughly discussed in two face-to-face meetings with all co-authors and then presented on occasion of the 36th Italian Society of Arterial Hypertension meeting in order to gather further feedbacks by all members. The text amended according to these feedbacks was subjected to a further peer review.

Conclusions

After this process, substantial updated information was generated, which could simplify the diagnosis of primary aldosteronism and assist practicing physicians in optimizing treatment and follow-up of patients with one of the most common curable causes of arterial hypertension.

Steroid Metabolome Analysis in Disorders of Adrenal Steroid Biosynthesis and Metabolism

Steroid biosynthesis and metabolism are reflected by the serum steroid metabolome and, in even more detail, by the 24-hour urine steroid metabolome, which can provide unique insights into alterations of steroid flow and output indicative of underlying conditions. Mass spectrometry-based steroid metabolome profiling has allowed for the identification of unique multisteroid signatures associated with disorders of steroid biosynthesis and metabolism that can be used for personalized approaches to diagnosis, differential diagnosis, and prognostic prediction. Additionally, steroid metabolome analysis has been used successfully as a discovery tool, for the identification of novel steroidogenic disorders and pathways as well as revealing insights into the pathophysiology of adrenal disease. Increased availability and technological advances in mass spectrometry-based methodologies have refocused attention on steroid metabolome profiling and facilitated the development of high-throughput steroid profiling methods soon to reach clinical practice. Furthermore, steroid metabolomics, the combination of mass spectrometry-based steroid analysis with machine learning-based approaches, has facilitated the development of powerful customized diagnostic approaches. In this review, we provide a comprehensive up-to-date overview of the utility of steroid metabolome analysis for the diagnosis and management of inborn disorders of steroidogenesis and autonomous adrenal steroid excess in the context of adrenal tumors.

Proteomic Landscape of Aldosterone-Producing Adenoma

Primary aldosteronism is a disease of excessive production of adrenal steroid hormones and the most common cause of endocrine hypertension. Primary aldosteronism results mainly from bilateral adrenal hyperplasia or unilateral aldosterone-producing adenoma (APA). Primary aldosteronism cause at the molecular level is incompletely understood and a targeted treatment preventing excessive adrenal steroid production is not available. Here, we perform deep quantitative proteomic and phosphoproteomic profiling of 6 pairs of APA and adjacent nontumoral adrenal cortex. We show that increased steroidogenesis in APA is accompanied by upregulation of steroidogenic enzymes (HSD3B2, CYP21A2, CYP11B2) and of proteins involved in cholesterol uptake (LSR). We demonstrate that HSD3B2 is phosphorylated at Ser95 or 96 and identify a novel phosphorylation site, Ser489, in CYP21A2, suggesting that steroidogenic enzymes are regulated by phosphorylation. Our analysis also reveals altered ECM (extracellular matrix) composition in APA that affects ECM-cell surface interactions and actin cytoskeleton rearrangements. We show that RHOC, a GTPase controlling actin organization in response to extracellular stimuli, is upregulated in APA and promotes expression of the aldosterone synthase gene CYP11B2. Our data also indicate deregulation of protein N-glycosylation and GABAergic signaling in APAs. Finally, we find that mTORC1 (mammalian target of rapamycin complex 1) signaling is the major pathway deregulated in APA. Our study provides a rich resource for future research on the molecular mechanisms of primary aldosteronism.

Genomics of benign adrenocortical tumors

Benign adrenocortical adenomas and hyperplasia are relatively common and include a spectrum of distinct entities, which diagnosis depends on the macroscopic aspect and the secretion profile. Recent advances in genomics have proposed high-throughput molecular characterization of adrenal tumors, thereby improving our knowledge on the pathophysiology and tumorigenesis of these tumors. Genomic (exome and chromosome alteration profiles), epigenomic (micro-RNAs expression and methylation profiles) and transcriptomic (gene expression profiles) studies highlighted the major roles of intracellular calcium signaling in aldosterone-producing adenomas (APA), of protein kinase A (PKA)/cAMP pathway in cortisol-producing tumors, and of Wnt/beta-catenin pathway in non-secreting tumors. Exome sequencing revealed new major drivers in all tumor types, including KCNJ5, ATP1A1, ATP2B3, CACNA1D and CACNA1H mutations in APA, PRKACA mutations in cortisol-producing adenomas (CPA) and ARMC5 mutations in primary macronodular adrenocortical hyperplasia (PMAH). The clinical impact of these findings is just starting to evolve. The identification of genetic syndromes, such as germline ARMC5 mutations in PMAH, has allowed genetic counseling. Key molecular alterations could serve as a basis for the development of targeted medical treatments for benign adrenal tumors. The recent developments in genomics, including single-cell technologies, and in proteomics and metabolomics will probably offer new perspectives for characterizing benign adrenal tumorigenesis.

CT and MRI of adrenal gland pathologies

Besides ultrasound and nuclear medicine techniques, computed tomography (CT) and magnetic resonance imaging (MRI) are commonly used to examine adrenal lesions in both symptomatic and asymptomatic patients. Some adrenal lesions have characteristic radiological features. If an adrenal nodule is discovered incidentally, determining whether the lesion is benign or malignant is of great importance. According to their biological behavior, lesions can be divided into benign (mainly: adenoma, hyperplasia, pheochromocytoma, cyst, hemorrhage, cystic lymphangioma, myelolipoma, hemangioma, ganglioneuroma, teratoma) and malignant (mainly: metastases, adrenal cortical carcinoma, neuroblastoma, lymphoma) conditions. In this paper, we review CT/MRI findings of common adrenal gland lesions.