Genetic Characteristics of Aldosterone-Producing Adenomas in Blacks

Comprehensive Analysis of Steroid Biomarkers for Guiding Primary Aldosteronism Subtyping

Adrenal vein sampling (AVS) is required to distinguish unilateral from bilateral aldosterone sources in primary aldosteronism (PA), and cortisol is used for AVS data interpretation, but cortisol has several pitfalls. In this study, we present the utility of several other steroids in PA subtyping, both during AVS, as well as in peripheral serum. We included patients with PA who underwent AVS at University of Michigan between 2012 and 2018. We used mass spectrometry to simultaneously quantify 17 steroids in adrenal veins (AV) and periphery, both at baseline and after cosyntropin administration. PA was classified as unilateral or bilateral based on a lateralization index ≥ or <4, respectively, separately for baseline and post-cosyntropin administration. Of 131 participants, AV catheterizations was deemed failed in 28 (21 %) patients (36 AVs) at baseline. Eight steroids demonstrated higher AV/periphery ratios than cortisol (P<0.01 for all); 11β-hydroxyandrostenedione, 11-deoxycortisol, and corticosterone rescued most failed baseline catheterizations. Lateralization was generally consistent when using these alternative steroids. Based on pre- and post-cosyntropin data, the remaining 103 patients were classified as: U/U, 37; B/B, 32; U/B, 20; B/U, 14. Discriminant analysis of multi-steroid panels from peripheral serum showed distinct profiles across the 4 groups, with highest aldosterone, 18-oxocortisol and 11-deoxycorticosterone in U/U patients. In conclusion, 11β-hydroxyandrostenedione and 11-deoxycortisol are superior to cortisol for AVS data interpretation. Single assay multi-steroid panels measured in peripheral serum are helpful in stratified PA subtyping and have the potential to circumvent AVS in a subset of patients with PA.

Resistant Hypertension: A Clinical Perspective

Resistant hypertension is a common clinical entity, defined as suboptimal blood pressure response to multiple therapies after excluding medication nonadherence and secondary forms of hypertension. Patients with resistant hypertension generally share several comorbidities. Resistant hypertension is more common in individuals of African descent. Blood pressure should be optimized using multiple strategies, including lifestyle changes and single-pill combination therapies, with the aim of reducing cardiovascular events while reducing side effects from using antihypertensive therapy. A renin/aldosterone-based diagnostic and treatment approach will help tailor therapy. The use of mineralocorticoid receptor antagonists or amiloride as appropriate is favored.

Molecular Mechanisms of Primary Aldosteronism

Primary aldosteronism (PA) results from excess production of mineralocorticoid hormone aldosterone by the adrenal cortex. It is normally caused either by unilateral aldosterone-producing adenoma (APA) or by bilateral aldosterone excess as a result of bilateral adrenal hyperplasia. PA is the most common cause of secondary hypertension and associated morbidity and mortality. While most cases of PA are sporadic, an important insight into this debilitating disease has been derived through investigating the familial forms of the disease that affect only a minor fraction of PA patients. The advent of gene expression profiling has shed light on the genes and intracellular signaling pathways that may play a role in the pathogenesis of these tumors. The genetic basis for several forms of familial PA has been uncovered in recent years although the list is likely to expand. Recently, the work from several laboratories provided evidence for the involvement of mammalian target of rapamycin pathway and inflammatory cytokines in APAs; however, their mechanism of action in tumor development and pathophysiology remains to be understood.

Three Discrete Patterns of Primary Aldosteronism Lateralization in Response to Cosyntropin During Adrenal Vein Sampling

CONTEXT

Cosyntropin [ACTH (1-24)] stimulation during adrenal vein (AV) sampling (AVS) enhances the confidence in the success of AV cannulation and circumvents intraprocedure hormonal fluctuations. Cosyntropin's effect on primary aldosteronism (PA) lateralization, however, is controversial.

OBJECTIVES

To define the major patterns of time-dependent lateralization, and their determinants, after cosyntropin stimulation during AVS.

METHODS

We retrospectively studied patients with PA who underwent AVS before, 10, and 20 minutes after cosyntropin stimulation between 2009 and 2018. Unilateral (U) or bilateral (B) PA was determined on the basis of a lateralization index (LI) value ≥4 or <4, respectively. Available adrenal tissue underwent aldosterone synthase-guided next-generation sequencing.

RESULTS

PA lateralization was concordant between basal and cosyntropin-stimulated AVS in 169 of 222 patients (76%; U/U, n = 110; B/B, n = 59) and discordant in 53 patients (24%; U/B, n = 32; B/U, n = 21). Peripheral and dominant AV aldosterone concentrations and LI were highest in U/U patients and progressively lower across intermediate and B/B groups. LI response to cosyntropin increased in 27% of patients, decreased in 33%, and remained stable in 40%. Baseline aldosterone concentrations predicted the LI pattern across time (P < 0.001). Mutation status was defined in 61 patients. Most patients with KCNJ5 mutations had descending LI, whereas those with ATP1A1 and ATP2B3 mutations had ascending LI after cosyntropin stimulation.

CONCLUSION

Patients with severe PA lateralized robustly regardless of cosyntropin use. Cosyntropin stimulation reveals intermediate PA subtypes; its impact on LI varies with baseline aldosterone concentrations and aldosterone-driver mutations.

Primary Aldosteronism Diagnosis and Management: A Clinical Approach

Primary aldosteronism used to be considered a rare cause of secondary hypertension. However, accruing evidence indicates that primary aldosteronism is more common than previously recognized. The implications of this increased prevalence are important to public health because autonomous aldosterone production contributes to cardiovascular disease and can be treated in a targeted manner. This article focuses on clinical approaches for diagnosing primary aldosteronism more frequently and earlier in its course, as well as practical treatment objectives to reduce the risk for incident cardiovascular disease.

[Primary aldosteronism : Genetics and pathology]

BACKGROUND

Primary aldosteronism, the excessive production of the steroid hormone aldosterone, is the most common cause of secondary hypertension. Common subforms include bilateral adrenal hyperplasia and aldosterone-producing adenoma.

OBJECTIVES

The goal of this review is to summarize important publications on the genetic basis of primary aldosteronism.

RESULTS

Somatic mutations in the KCNJ5, CACNA1D, ATP1A1, and ATP2B3 genes have been described as causes of aldosterone-producing adenomas. They eventually all lead to increased cellular calcium influx and aldosterone production. The mechanisms of rare CTNNB1 mutations are less defined. Correlations between mutations and different histologic characteristics as well as gender and ethnicity remain unexplained. Recent publications suggest that bilateral hyperplasia is at least partially due to so-called aldosterone-producing cell clusters, often with mutations in CACNA1D. Rare familial forms show mutations in the CYP11B2, CLCN2, KCNJ5, CACNA1H, or CACNA1D genes.

CONCLUSIONS

These results suggest that a significant fraction of primary aldosteronism is due to somatic mutations in single genes.

Genetic causes of primary aldosteronism

Primary aldosteronism is characterized by at least partially autonomous production of the adrenal steroid hormone aldosterone and is the most common cause of secondary hypertension. The most frequent subforms are idiopathic hyperaldosteronism and aldosterone-producing adenoma. Rare causes include unilateral hyperplasia, adrenocortical carcinoma and Mendelian forms (familial hyperaldosteronism). Studies conducted in the last eight years have identified somatic driver mutations in a substantial portion of aldosterone-producing adenomas, including the genes KCNJ5 (encoding inwardly rectifying potassium channel GIRK4), CACNA1D (encoding a subunit of L-type voltage-gated calcium channel Ca_V1.3), ATP1A1 (encoding a subunit of Na⁺/K⁺-ATPase), ATP2B3 (encoding a Ca²⁺-ATPase), and CTNNB1 (encoding ß-catenin). In addition, aldosterone-producing cells were recently reported to form small clusters (aldosterone-producing cell clusters) beneath the adrenal capsule. Such clusters accumulate with age and appear to be more frequent in individuals with idiopathic hyperaldosteronism. The fact that they are associated with somatic mutations implicated in aldosterone-producing adenomas also suggests a precursor function for adenomas. Rare germline variants of CYP11B2 (encoding aldosterone synthase), CLCN2 (encoding voltage-gated chloride channel ClC-2), KCNJ5, CACNA1H (encoding a subunit of T-type voltage-gated calcium channel Ca_V3.2), and CACNA1D have been reported in different subtypes of familial hyperaldosteronism. Collectively, these studies suggest that primary aldosteronism is largely due to genetic mutations in single genes, with potential implications for diagnosis and therapy.

KCNJ5 Somatic Mutation Is a Predictor of Hypertension Remission After Adrenalectomy for Unilateral Primary Aldosteronism

CONTEXT

Primary aldosteronism (PA) is the most common cause of endocrine hypertension (HT). HT remission (defined as blood pressure <140/90 mm Hg without antihypertensive drugs) has been reported in approximately 50% of patients with unilateral PA after adrenalectomy. HT duration and severity are predictors of blood pressure response, but the prognostic role of somatic KCNJ5 mutations is unclear.

OBJECTIVE

To determine clinical and molecular features associated with HT remission after adrenalectomy in patients with unilateral PA.

METHODS

We retrospectively evaluated 100 patients with PA (60 women; median age at diagnosis 48 years with a median follow-up of 26 months). Anatomopathological analysis revealed 90 aldosterone-producing adenomas, 1 carcinoma, and 9 unilateral adrenal hyperplasias. All patients had biochemical cure after unilateral adrenalectomy. KCNJ5 gene was sequenced in 76 cases.

RESULTS

KCNJ5 mutations were identified in 33 of 76 (43.4%) tumors: p.Gly151Arg (n = 17), p.Leu168Arg (n = 15), and p.Glu145Gln (n = 1). HT remission was reported in 37 of 100 (37%) patients. Among patients with HT remission, 73% were women (P = 0.04), 48.6% used more than three antihypertensive medications (P = 0.0001), and 64.9% had HT duration <10 years (P = 0.0015) compared with those without HT remission. Somatic KCNJ5 mutations were associated with female sex (P = 0.004), larger nodules (P = 0.001), and HT remission (P = 0.0001). In multivariate analysis, only a somatic KCNJ5 mutation was an independent predictor of HT remission after adrenalectomy (P = 0.004).

CONCLUSION

The presence of a KCNJ5 somatic mutation is an independent predictor of HT remission after unilateral adrenalectomy in patients with unilateral PA.

ARMC 5 Variants and Risk of Hypertension in Blacks: MH- GRID Study

Background We recently found that ARMC 5 variants may be associated with primary aldosteronism in blacks. We investigated a cohort from the MH - GRID (Minority Health Genomics and Translational Research Bio-Repository Database) and tested the association between ARMC 5 variants and blood pressure in black s. Methods and Results Whole exome sequencing data of 1377 black s were analyzed. Target single-variant and gene-based association analyses of hypertension were performed for ARMC 5, and replicated in a subset of 3015 individuals of African descent from the UK Biobank cohort. Sixteen rare variants were significantly associated with hypertension ( P=0.0402) in the gene-based (optimized sequenced kernel association test) analysis; the 16 and one other, rs116201073, together, showed a strong association ( P=0.0003) with blood pressure in this data set. The presence of the rs116201073 variant was associated with lower blood pressure. We then used human embryonic kidney 293 and adrenocortical H295R cells transfected with an ARMC 5 construct containing rs116201073 (c.*920T>C). The latter was common in both the discovery ( MH - GRID ) and replication ( UK Biobank) data and reached statistical significance ( P=0.044 [odds ratio, 0.7] and P=0.007 [odds ratio, 0.76], respectively). The allele carrying rs116201073 increased levels of ARMC5 mRNA , consistent with its protective effect in the epidemiological data. Conclusions ARMC 5 shows an association with hypertension in black s when rare variants within the gene are considered. We also identified a protective variant of the ARMC 5 gene with an effect on ARMC 5 expression confirmed in vitro. These results extend our previous report of ARMC 5's possible involvement in the determination of blood pressure in blacks.

Genetics of Hypertension in African Americans and Others of African Descent

Hypertension is the leading cause of cardiovascular disease in the United States, affecting up to one-third of adults. When compared to other ethnic or racial groups in the United States, African Americans and other people of African descent show a higher incidence of hypertension and its related comorbidities; however, the genetics of hypertension in these populations has not been studied adequately. Several genes have been identified to play a role in the genetics of hypertension. They include genes regulating the renin-aldosterone-angiotensin system (RAAS), such as Sodium Channel Epithelial 1 Beta Subunit (SCNN1B), Armadillo Repeat Containing 5 (ARMC5), G Protein-Coupled Receptor Kinase 4 (GRK4), and Calcium Voltage-Gated Channel Subunit Alpha1 D (CACNA1D). In this review, we focus on recent genetic findings available in the public domain for potential differences between African Americans and other populations. We also cover some recent and relevant discoveries in the field of low-renin hypertension from our laboratory at the National Institutes of Health. Understanding the different genetics of hypertension among various groups is essential for effective precision-guided medical therapy of high blood pressure.