Role of Aldosterone and Mineralocorticoid Receptor in Cardiovascular Aging

Esaxerenone, a novel nonsteroidal mineralocorticoid receptor blocker (MRB) in hypertension and chronic kidney disease

The steroidal mineralocorticoid receptor (MR) antagonists, spironolactone and eplerenone, decrease blood pressure, and attenuate the progression of chronic kidney disease (CKD). However, their use is limited by the fear of inducing hyperkalemia, gynecomastia, impotence, and amenorrhea. Esaxerenone is a novel nonsteroidal MR blocker (MRB) that has been recently developed. In vitro studies have revealed that esaxerenone has a high potency and selectivity for MR compared with spironolactone and eplerenone. Further studies have shown that esaxerenone elicits a strong blood pressure-lowering effect in hypertensive animals. Following the results from phase III clinical trials that esaxerenone is an effective and well-tolerated MRB in Japanese hypertensive patients, esaxerenone became clinically available in Japan from May 2019 for hypertensive patients. Thus, esaxerenone is a promising treatment option for patients with hypertension. In addition, both preclinical studies and phase II clinical trials have shown that esaxerenone elicits renoprotection independent of its antihypertensive effect. Recently, a phase III clinical trial (ESAX-DN study) has also demonstrated the safety and efficacy of esaxerenone in patients with type 2 diabetes and microalbuminuria. These data support future clinical development of esaxerenone for the treatment of renal disease.

mTORC1 Deficiency Modifies Volume Homeostatic Responses to Dietary Sodium in a Sex-Specific Manner

The mechanistic target of the rapamycin (mTOR) pathway plays a role in features common to both excess salt/aldosterone and cardiovascular/renal diseases. Dietary sodium can upregulate mTORC1 signaling in cardiac and renal tissue, and the inhibition of mTOR can prevent aldosterone-associated, salt-induced hypertension. The impact of sex and age on mTOR's role in volume homeostasis and the regulation of aldosterone secretion is largely unknown. We hypothesize that both age and sex modify mTOR's interaction with volume homeostatic mechanisms. The activity of 3 volume homeostatic mechanisms-cardiovascular, renal, and hormonal (aldosterone [sodium retaining] and brain natriuretic peptide [BNP; sodium losing])-were assessed in mTORC1 deficient (Raptor+/-) and wild-type male and female littermates at 2 different ages. The mice were volume stressed by being given a liberal salt (LibS) diet. Raptor+/-mice of both sexes when they aged: (1) reduced their blood pressure, (2) increased left ventricular internal diameter during diastole, (3) decreased renal blood flow, and (4) increased mineralocorticoid receptor expression. Aldosterone levels did not differ by sex in young Raptor+/- mice. However, as they aged, compared to their littermates, aldosterone decreased in males but increased in females. Finally, given the level of Na+ intake, BNP was inappropriately suppressed, but only in Raptor+/- males. These data indicate that Raptor+/- mice, when stressed with a LibS diet, display inappropriate volume homeostatic responses, particularly with aging, and the mechanisms altered, differing by sex.

A direct comparison of the transcriptional activities of progestins used in contraception and menopausal hormone therapy via the mineralocorticoid receptor

A variety of structurally and functionally distinct progestins is used in contraception and menopausal hormone therapy (MHT). Some progestins elicit off-target effects by binding to steroid receptors other than the progesterone receptor, which may impact their therapeutic and side-effect profiles. We directly compared the binding affinities, efficacies and potencies of selected progestins via the mineralocorticoid receptor (MR). We did not detect a significant difference in the affinities of medroxyprogesterone acetate (MPA), norethisterone acetate (NET-A), levonorgestrel (LNG), gestodene (GES), etonogestrel (ETG), nestorone (NES) and nomegestrel acetate (NoMAC) for the MR, while these were significantly lower compared to drospirenone (DRSP). While GES and NoMAC display affinities indistinguishable from progesterone (P₄), the binding affinity of DRSP is significantly greater and all other progestins significantly lower than that of P₄. Dose-response analyses showed that P₄, GES and ETG display indistinguishable MR antagonist potencies for transactivation to the well-known MR antagonist spironolactone, while LNG, NoMAC and DRSP are significantly more potent than spironolactone and MPA, NET-A and NES are significantly less potent. Similar to our previous findings for NET-A, we show that LNG, GES, ETG and NES dissociate between transactivation and transrepression via the MR. Together our results provide strong evidence for progestin- and promoter-specific transcriptional effects via the MR, which are poorly predicted by relative binding affinities. A comparison of the binding affinities and potencies with reported free serum concentrations of progestins relative to the endogenous mineralocorticoid aldosterone, suggest that all progestins except MPA, NET-A and NES will likely compete with aldosterone for binding to the MR in vivo at doses used in hormonal therapy to elicit physiologically significant off-target effects.