Clinical and Molecular Characteristics of Primary Aldosteronism in Blacks

Primary Aldosteronism (PA) is the most common cause of secondary hypertension, accounting for 6-8% of hypertension and 14-25% of resistant hypertension. This prevalence translates to approximately 1 in 30-50 adults or about 4,000,000 Americans with PA. Until recently, the deleterious effects of PA were thought to derive solely from aldosterone-mediated sodium retention and associated blood pressure rise. However, animal studies and clinical trials demonstrate that mineralocorticoid receptor (MR) blockade has cardio- and reno-protective effects that clearly exceed those expected from blood pressure reduction alone. Growing evidence supports the concept that excess aldosterone, in the presence of elevated blood pressure, initiates a cascade characterized by fibrosis, oxidative stress, and activation of pro-inflammatory and pro-fibrotic pathways, leading to morbidity via worsened insulin sensitivity, impaired bone formation, and accelerated cardiovascular remodeling. Recent studies have identified several new genetic underpinnings of PA, both germline and somatic, including mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D, and ARMC5. As the effects of chronic hyperaldosteronism differ between races, it is not surprising that the relative prevalence of these mutations differs among cohorts. African Americans (AA) in particular have increased susceptibility to end-organ damage from aldosterone excess-induced cardiovascular remodeling. They are more likely to have congestive heart failure, end-stage renal disease, and atherosclerotic events than age-matched Caucasians. However, to date no comprehensive analysis of mutations in PA has been performed in AA. (Note: for the purposes of this protocol, the terms Black or African American incorporate individuals who self-identify as Black, African American, or the Caribbean diaspora).

The aims of this study are to identify the germline and/or somatic mutations causing PA in AA, define the effects of these mutations on aldosterone production in AA, and to identify effective pharmacologic agents that will inhibit inappropriate aldosterone production in target cells. Aldosterone producing adenoma (APA) and other adrenocortical tumor (ACT) specimens will be gathered from archival (collected under protocol 00-CH-160 and other related NIH studies) and prospective research subjects with PA that will be evaluated at the NIH Clinical Research Center under the proposed protocol. Samples will be analyzed using state-of-the-art next-generation sequencing (NGS). Human adrenal cell lines (H295R and others, as appropriate) will be used to study the mutations effect on aldosterone production. Additionally, this will help identify possible effective pharmacologic therapeutics to treat PA. Animal models of novel genetic causes of PA may also be created to study the molecular mechanisms underpinning the disease.