鉱質コルチコイドが引き起こす加齢性高血圧のメカニズム：鉱質コルチコイド受容体拮抗薬およびアルドステロン合成酵素阻害薬の潜在的な治療的役割

Hypertension prevalence rises dramatically with advancing age, is not well controlled with current therapy, and contributes substantially to cardiovascular, renal, and neurological disorders that are common in the elderly. The renin-angiotensin-aldosterone system is a hormonal pathway with multiorgan involvement critical to controlling blood pressure. The production of the steroid hormone aldosterone and the activation state of its MR (mineralocorticoid receptor) are important clinical targets for hypertension treatment and cardiorenal disease prevention. This review summarizes studies demonstrating that aging is associated with (1) dysregulation of adrenal aldosterone production by autonomous aldosterone-producing adrenal cells and, when comorbid with obesity, by factors released from adipose tissue that promote adrenal aldosterone production; (2) increased expression of the MR due to oxidative stress-activated and inflammation-activated transcription factors; and (3) aldosterone-independent MR activation by oxidative stress-activated Rac1 (Ras-related C3 botulinum toxin substrate 1), angiotensin II signaling, and declining expression of the cortisol-inactivating enzyme 11β-HSD2 (11-beta-hydroxysteroid dehydrogenase type 2). Together, these data support the concept that elderly individuals are at high risk for mineralocorticoid-driven hypertension and associated cardiovascular, renal, and neurological disease. The review further describes the different classes of agents that inhibit this pathway, including traditional steroidal MR antagonists, newer nonsteroidal MR antagonists, and aldosterone synthase inhibitors, comparing their modes of action. The steroidal MR antagonists and nonsteroidal MR antagonists have different degrees of MR selectivity and potency, yet they all block MR activation by aldosterone, cortisol, and ligand-independent mechanisms. The aldosterone synthase inhibitors block aldosterone production in the adrenal gland and attenuate aldosterone-mediated MR effects. All 3 drug classes raise potassium proportional to the degree of renal MR inhibition. Trials are summarized showing efficacy of the new agents in reducing MR activation, aldosterone production, blood pressure, and adverse cardiorenal outcomes. Head-to-head studies in older individuals are needed to determine the relative efficacy of aldosterone synthase versus MR inhibition for blood pressure control to improve outcomes in the elderly and very old.