The use of plasma aldosterone and urinary sodium to potassium ratio as translatable quantitative biomarkers of mineralocorticoid receptor antagonism

Isolated hypoaldosteronism is a cause of hypovolemic but not euvolemic hyponatremia

Introduction

Hypoaldosteronism is characterized by hyperkalemia, and/or hypovolemic hyponatremia (HH), often accompanied by metabolic acidosis. HH is typical of hypoaldosteronism, whereas euvolemic hyponatremia (EH) is not. The purpose of the current study is to describe the characteristics of hyponatremia in hypoaldosteronism and elucidate whether EH can be considered part of the disease's spectrum.

Methods

In a hypoaldosteronism cohort, we analyzed the factors associated with hyponatremia, comparing the characteristics of EH and HH and their associated factors. Correlation analyses of mineralocorticoid biomarkers, such as the transtubular potassium gradient (TTKG), the urinary Na+/K+ ratio (UNa+/UK+) with serum, and urinary electrolytes were performed in both types of hyponatremia.

Results

Of 112 hypoaldosteronism episodes, 77.7% were ≥65 years old, 44.6% were women, and 80 (71.4%) had hyponatremia. Hyponatremia was negatively associated with the presence of chronic kidney disease, and positively with a hypovolemic state, malnutrition, a prior history of hyponatremia, and glucocorticoid therapy. HH: 61/80 and EH: 19/80 episodes. HH was associated with an age ≥65 years and the use of diuretics, as well as factors related to an aldosterone deficit and/or mineralocorticoid resistance. In HH but not in EH, urinary potassium was correlated with the TTKG, and urinary sodium with both the TTKG and the UNa+/UK+.

Conclusion

Both HH and EH can be observed in hypoaldosteronism. However, only the former would be related to insufficient mineralocorticoid activity.

Significance statement

Isolated hypoaldosteronism is a poorly understood and underdiagnosed endocrinological disorder, classically recognized only when hyperkalemia is present. The development of hypovolemic hyponatremia, however, is also easily explained by the physiopathology of the disorder. The current study addresses the features of hyponatremia when found in the context of mineralocorticoid insufficiency, and confirms an association between hypovolemic hyponatremia and isolated hypoaldosteronism. Thus, the clinical spectrum of hypoaldosteronism is extended to include hypovolemic hyponatremia as a frequent manifestation of the disorder.

Relationship between the urinary Na/K ratio, diet and hypertension among community-dwelling older adults

The association between the urinary sodium (Na)/potassium (K) ratio and hypertension is well recognized. We investigated whether the urinary Na/K ratio might be associated with hypertension in community-dwelling older adults and whether the association was influenced by habitual dietary patterns. We enrolled a total of 684 older adults (mean age, 76.8 years) and conducted health examinations at Kusatsu, Japan, in 2021. The urinary Na/K ratio was found to be independently associated with systolic blood pressure (SBP) (p < 0.0001), years of education (p = 0.0027), number of cohabitants (p = 0.0175), estimated glomerular filtrate rate (eGFR) (p = 0.0244), and Geriatric Depression Scale short-version (GDS15) score (p = 0.0366). In addition, an unsupervised hierarchical clustering analysis revealed a spectrum of habitual dietary patterns for higher and lower values of the urinary Na/K ratio. The decision tree indicated that the urinary Na/K ratio was associated with the history of milk consumption. A positive history of daily milk consumption predicted a mean urinary Na/K ratio of 2.8, and a negative history of daily milk consumption predicted a mean urinary Na/K ratio of 3.3. Furthermore, the frequency of fruit and vegetable consumption also predicted the urinary Na/K ratio. The relationship between the urinary Na/K ratio and hypertension was influenced by the frequency of consumption of milk, fruits, and vegetables in the subjects. This finding might be due to the influence of education and/or depression. The results suggested the importance of nutritional education in the development of hypertension.

Pharmacokinetic and pharmacodynamic properties of orally administered torasemide in healthy cats

BACKGROUND

In people and dogs, torasemide has higher bioavailability, longer half-life, and longer duration of action than equivalent doses of furosemide but data regarding pharmacological properties of torasemide in cats are limited.

OBJECTIVE

To assess pharmacokinetic and pharmacodynamic parameters of torasemide in healthy cats, and to investigate the effects of a single administration of torasemide on indicators of diuresis, plasma creatinine concentration, blood pressure, electrolyte concentrations and markers of the renin-angiotensin-aldosterone system (RAAS).

ANIMALS

Six clinically healthy adult European shorthair cats.

METHODS

Randomized 4-period crossover design with 3 groups and 4 treatments. Pharmacokinetic parameters were obtained using a noncompartmental analysis, and the clinically effective dose was assessed using a Hill model.

RESULTS

Mean absolute bioavailability was estimated at 88.1%. Mean total body clearance was 3.64 mL/h/kg and mean terminal half-life was 12.9 hours. Urine output significantly increased after torasemide administration (P < .001). The urine sodium : potassium ratio (uNa : uK) paralleled and was statistically correlated to urine output (P < .001). Administration of a single torasemide dose led to a significant dose-dependent increase in urine aldosterone : creatinine ratio (uAldo : C; P < .001) and a transient decrease in plasma potassium concentration (P < .001) but did not affect blood pressure or plasma creatinine concentration.

CONCLUSIONS AND CLINICAL IMPORTANCE

A single torasemide dose leads to a significant increase in diuresis and renin-angiotensin-aldosterone system (RAAS) activation in healthy cats, with high absolute bioavailability, and without clinically relevant adverse effects. Pharmacokinetic parameters indicate that once daily dosing of 0.27 mg/kg may be appropriate in a clinical setting.

The Role of the Mineralocorticoid Receptor and Mineralocorticoid Receptor-Directed Therapies in Heart Failure

Mineralocorticoid receptor (MR) antagonists (MRA), also referred to as aldosterone blockers, are now well-recognized for their clinical benefit in patients who have heart failure (HF) with reduced ejection fraction (HFrEF). Recent studies have also shown MRA can improve outcomes in patients with HFpEF, where the ejection fraction is preserved but left ventricular filling is reduced. While the MR is a steroid hormone receptor best known for antinatriuretic actions on electrolyte homeostasis in the distal nephron, it is now established that the MR has many physiological and pathophysiological roles in the heart, vasculature, and other nonepithelial tissue types. It is the impact of MR activation on these tissues that underpins the use of MRA in cardiovascular disease, in particular HF. This mini-review will discuss the origins and the development of MRA and highlight how their use has evolved from the "potassium-sparing diuretics" spironolactone and canrenone over 60 years ago, to the more receptor-selective eplerenone and most recently the emergence of new nonsteroidal receptor antagonists esaxerenone and finerenone.

Mineralocorticoid Receptor Antagonists Eplerenone and Spironolactone Modify Adrenal Cortex Morphology and Physiology

Mineralocorticoid receptor antagonists (MRAs) are a class of anti-hypertensive drugs that act by blocking aldosterone action. The aim of this study was to evaluate whether the MRAs spironolactone and eplerenone influence adrenal cortical physiology and morphology. Spontaneous hypertensive rats (SHR, n = 18) and normotensive rats (WKY, n = 18) were randomly exposed to a daily dose of spironolactone (n = 6), eplerenone (n = 6), or no drug (n = 6) over 28 days. After that, aldosterone, corticosterone, and 11-deoxycorticosterone plasma concentrations were quantified. Adrenal glands were subjected to morphological analysis to assess lipid droplets content, capsular width, cell proliferation, and steroidogenic proteins expression. The adrenal cortex in untreated SHR showed higher lipid droplet content as than in WKY. In SHR, MRA treatment was associated with higher circulating aldosterone levels and Ki-67 expression in aldosterone-secreting cells. In WKY, the only difference observed after MRA spironolactone treatment was a narrower capsule. There was no difference in abundance of steroidogenic enzyme between groups. In conclusion, MRAs modify adrenal gland function and morphology in SHR. The effects observed within the adrenal glomerulosa with aldosterone-secreting cell proliferation and higher circulating aldosterone levels suggests that MRA treatment provokes activation of the renin angiotensin system. The prognostic value of hyperaldosteronism secondary to MRAs blockade requires further investigation.

Phase 1 Studies to Define the Safety, Tolerability, and Pharmacokinetic and Pharmacodynamic Profiles of the Nonsteroidal Mineralocorticoid Receptor Antagonist Apararenone in Healthy Volunteers

Apararenone is a long-acting, nonsteroidal mineralocorticoid receptor antagonist (MRA). The safety, tolerability, and pharmacokinetic (PK) and pharmacodynamic (PD) profiles of single- and multiple-dose apararenone were assessed in 3 phase 1 randomized, double-blind studies in 223 healthy adults. Study 1 assessed the PK, safety/tolerability, and PD of single-dose apararenone (3.75-640 mg) and multiple-dose apararenone (10-40 mg/day on days 1-14, 320 mg loading dose on day 1 + 10 mg/day on days 2-14, or 40-320 mg loading dose on day 1 + 2.5-20 mg/day on days 2-14) in Caucasian and Black men and women. Study 2 assessed the PK and safety of single-dose apararenone (5-320 mg) in healthy Japanese men. Study 3 assessed the PK, PD, and safety/tolerability of single-dose apararenone (160 or 640 mg) or eplerenone (200 mg; only for 160 mg of apararenone), each after fludrocortisone challenge in Caucasian men. In studies 1 and 2, an approximately dose-proportional increase was observed in PK parameters over the apararenone dose range of 3.75-40 mg; at higher doses, a less than dose-proportional increase was observed. Food, sex, age, and race had no apparent effect on apararenone PK. A long half-life was seen for apararenone and its principal metabolite; in addition, the exposure of the metabolite was lower than that of apararenone. Apararenone suppressed the decrease in urinary sodium and potassium ion ratio that occurs after loading with fludrocortisone. These studies support the mechanism of action of apararenone as an MRA, and further clinical development is warranted.

Effect of spironolactone and benazepril on furosemide-induced diuresis and renin-angiotensin-aldosterone system activation in normal dogs

Background

Diuretic braking during furosemide continuous rate infusion (FCRI) curtails urine production.

Hypothesis

Renin‐angiotensin‐aldosterone system (RAAS) activation mediates braking, and RAAS inhibition will increase urine production.

Animals

Ten healthy purpose‐bred male dogs.

Methods

Dogs received placebo, benazepril, or benazepril and spironolactone PO for 3 days before a 5‐hour FCRI (0.66 mg/kg/h) in a 3‐way, randomized, blinded, cross‐over design. Body weight (BW), serum creatinine concentration (sCr), serum electrolyte concentrations, PCV, and total protein concentration were measured before PO medications, at hours 0 and 5 of FCRI, and at hour 24. During the FCRI, water intake, urine output, urine creatinine concentration, and urine electrolyte concentrations were measured hourly. Selected RAAS components were measured before and after FCRI. Variables were compared among time points and treatments.

Results

Diuretic braking and urine production were not different among treatments. Loss of BW, hemoconcentration, and decreased serum chloride concentration occurred during FCRI with incomplete recovery at hour 24 for all treatments. Although unchanged during FCRI, sCr increased and serum sodium concentration decreased at hour 24 for all treatments. Plasma aldosterone and angiotensin‐II concentrations increased significantly at hour 5 for all treatments, despite suppressed angiotensin‐converting enzyme activity during benazepril background treatment.

Conclusions

The neurohormonal profile during FCRI supports RAAS mediation of diuretic braking in this model. Background treatment with benazepril with or without spironolactone did not mitigate braking, but was well tolerated. Delayed changes in sCr and serum sodium concentration and incomplete recovery of hydration indicators caused by furosemide hold implications for clinical patients.

Evaluation of the Diuretic Activity of the Aqueous and 80% Methanol Extracts of Ficus sur Forssk (Moraceae) Leaves in Saline-loaded Rats

Background

Although investigations on different pharmacological activities of the experimental plant, Ficus sur have been conducted, its folklore use for diuresis has not yet been validated. The current study, therefore, focused on the diuretic activity of aqueous and 80% methanol extracts of F. sur Forssk. leaves in rats.

Methods

Rats were randomly assigned into eight groups each consisting of six rats. Test groups received either 100 mg/kg, 200 mg/kg, or 400 mg/kg of aqueous or 80% methanol leaves extract. The negative control group and positive control were treated with 2 mL/100 g of distilled water and furosemide (10 mg/kg), respectively. Thereafter urine volume was recorded every hour until the end of the fifth hour, and cumulative urine volume of each rat was measured. Then, diuretic activity, diuretic index, saliuretic index, natriuretic index and carbonic anhydrase inhibition index in each group were calculated, and results were compared among the groups.

Results

The middle (200 mg/kg) and the highest (400 mg/kg) doses of both extracts significantly increased diuresis at the fifth hour (p<0.001) compared to the negative control, although the diuretic activity was less than that of the positive control. Regarding electrolyte excretion, all dose levels of both extracts showed significant natriuresis (p<0.001) and chloriuresis (p<0.01) compared to the negative control. Aqueous extract displayed more significant diuretic effect than 80% methanol extract. The aqueous and 80% methanol extracts produced alkaline urine.

Conclusion

The crude leaves extracts of F. sur increased urinary excretion and concentration of urinary electrolytes in a dose-dependent manner. These findings are in agreement with the traditional claim for use of F. sur as diuretic agent.

Preclinical study of simultaneous pharmacokinetic and pharmacodynamic herb-drug interactions between Yin-Chen-Hao-Tang and spironolactone

BACKGROUND

The prevalence and therapeutic effects of the use of herbal remedies for chronic liver diseases make the combined administration of herbal products with conventional treatment unable to be ignored. This study investigated the pharmacokinetic and pharmacodynamic herb-drug interactions between the herbal formula Yin-Chen-Hao-Tang (YCHT) and spironolactone.

METHODS

A selective high-performance liquid chromatography (HPLC) method was developed and validated for the detection of spironolactone and its metabolite canrenone in rat urine. The interaction study was conducted by collecting urine samples after oral administration of spironolactone alone or in combination with YCHT for 5 days. Urine pharmacokinetic parameters and urinary sodium, potassium, volume, and weight were analyzed.

RESULTS

The results revealed significant increases in the cumulative amount and the area under the rate curve (AURC) of the metabolite canrenone after pretreatment with the high dose of YCHT. The urine weight and volume were significantly reduced dose-dependently as a result of pretreatment with YCHT. The urinary sodium-to-potassium ratio, which indicates diuretic effects, was also reduced in the high-dose YCHT condition.

CONCLUSIONS

Herb-drug pharmacokinetic and pharmacodynamic interactions between YCHT and spironolactone were observed in the study. The herb-drug interaction that appeared with a single dose of spironolactone should be considered when patients are being treated with a continuous administration of this drug.

Blockade of mineralocorticoid receptor ameliorates oral contraceptive-induced insulin resistance by suppressing elevated uric acid and glycogen synthase kinase-3 instead of circulating mineralocorticoid

Context: Estrogen-progestin combined oral contraceptive (COC) has been connected to mineralocorticoid receptor (MR) activation and adverse cardiometabolic events. We consequently hypothesised that insulin resistance (IR), hyperuricemia, and elevated circulating GSK-3 induced by COC is through activation of MR via mineralocorticoid and glucocorticoid pathways.Methods: Female Wistar rats aged 12 weeks received (po) vehicle and COC (1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel) with or without MR blocker (0.25 mg/kg spironolactone; Spl), daily for eight weeks.Results: Data showed that COC treatment led to increased IR, 1-hour postload glucose level, insulinemia, triglyceride/HDL-cholesterol ratio, total cholesterol/HDL-cholesterol ratio, uric acid, GSK-3, aldosterone, corticosterone values, impaired glucose tolerance and pancreatic β-cell function. However, MR blockade by Spl ameliorated all these alterations except that of aldosterone.Conclusion: The results demonstrate that COC induces IR, hyperuricemia and high GSK-3 levels through activation of MR via glucocorticoid dependent pathway.

Apocynin and catalase prevent hypertension and kidney injury in Cyclosporine A-induced nephrotoxicity in rats

Oxidative stress is involved in the pathogenesis of a number of diseases including hypertension and renal failure. There is enhanced expression of nicotinamide adenine dinucleotide (NADPH oxidase) and therefore production of hydrogen peroxide (H2O2) during renal disease progression. This study investigated the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on Cyclosporine A (CsA) nephrotoxicity in Wistar-Kyoto rats. Rats received CsA (25mg/kg/day via gavage) and were assigned to vehicle, apocynin (2.5mmol/L p.o.), catalase (10,000U/kg/day i.p.) or apocynin plus catalase for 14 days. Renal functional and hemodynamic parameters were measured every week, and kidneys were harvested at the end of the study for histological and NADPH oxidase 4 (NOX4) assessment. Oxidative stress markers and blood urea nitrogen (BUN) were measured. CsA rats had higher plasma malondialdehyde (by 340%) and BUN (by 125%), but lower superoxide dismutase and total antioxidant capacity (by 40%, all P<0.05) compared to control. CsA increased blood pressure (by 46mmHg) and decreased creatinine clearance (by 49%, all P<0.05). Treatment of CsA rats with apocynin, catalase, and their combination decreased blood pressure to near control values (all P<0.05). NOX4 mRNA activity was higher in the renal tissue of CsA rats by approximately 63% (P<0.05) compared to controls but was reduced in apocynin (by 64%), catalase (by 33%) and combined treatment with apocynin and catalase (by 84%) compared to untreated CsA rats. Treatment of CsA rats with apocynin, catalase, and their combination prevented hypertension and restored renal functional parameters and tissue Nox4 expression in this model. NADPH inhibition and H2O2 scavenging is an important therapeutic strategy during CsA nephrotoxicity and hypertension.

Clinical determinants and prognostic implications of renin and aldosterone in patients with symptomatic heart failure

Aims

Activation of the renin–angiotensin–aldosterone system plays an important role in the pathophysiology of heart failure (HF) and has been associated with poor prognosis. There are limited data on the associations of renin and aldosterone levels with clinical profiles, treatment response, and study outcomes in patients with HF.

Methods and results

We analysed 2,039 patients with available baseline renin and aldosterone levels in BIOSTAT‐CHF (a systems BIOlogy study to Tailored Treatment in Chronic Heart Failure). The primary outcome was the composite of all‐cause mortality or HF hospitalization. We also investigated changes in renin and aldosterone levels after administration of mineralocorticoid receptor antagonists (MRAs) in a subset of the EPHESUS trial and in an acute HF cohort (PORTO). In BIOSTAT‐CHF study, median renin and aldosterone levels were 85.3 (percentile_25–75 = 28–247) μIU/mL and 9.4 (percentile_25–75 = 4.4–19.8) ng/dL, respectively. Prior HF admission, lower blood pressure, sodium, poorer renal function, and MRA treatment were associated with higher renin and aldosterone. Higher renin was associated with an increased rate of the primary outcome [highest vs. lowest renin tertile: adjusted‐HR (95% CI) = 1.47 (1.16–1.86), P = 0.002], whereas higher aldosterone was not [highest vs. lowest aldosterone tertile: adjusted‐HR (95% CI) = 1.16 (0.93–1.44), P = 0.19]. Renin and/or aldosterone did not improve the BIOSTAT‐CHF prognostic models. The rise in aldosterone with the use of MRAs was observed in EPHESUS and PORTO studies.

Conclusions

Circulating levels of renin and aldosterone were associated with both the disease severity and use of MRAs. By reflecting both the disease and its treatments, the prognostic discrimination of these biomarkers was poor. Our data suggest that the “point” measurement of renin and aldosterone in HF is of limited clinical utility.

Role of electrolyte concentrations and renin-angiotensin-aldosterone activation in the staging of canine heart disease

Background

Refractory congestive heart failure (CHF) and associated diuretic resistance are not well defined.

Objectives

To characterize renal function, electrolyte concentrations, indices of diuretic efficacy, and renin‐angiotensin‐aldosterone system (RAAS) activation in dogs with naturally occurring heart disease (HD) in American College of Veterinary Internal Medicine stages B1, B2, C, and D and to determine their usefulness in defining HD stages.

Animals

Group 1:149 dogs with HD stages B1, B2, C, and D. Group 2:22 dogs with HD stages C and D.

Methods

Group 1: Renal parameters, serum and urine electrolyte and diuretic concentrations, and urine aldosterone concentrations were measured. Medication dosages and measured variables were compared among stages. Correlation of furosemide dosages to serum concentrations was explored. Group 2: Angiotensin‐converting enzyme activity and RAAS components were measured and compared among CHF stages.

Results

Serum chloride concentration was the best differentiator of HD stage. Furosemide PO dosages (≤6 mg/kg/day) were weakly correlated with serum furosemide concentrations, whereas higher dosages were not significantly correlated. Angiotensin‐converting enzyme inhibitor dosage and RAAS inhibition were greater in stage D, compared to stage C dogs.

Conclusions and Clinical Importance

Hypochloremia is a useful marker for stage D HD in dogs. Poor furosemide dosage correlation to serum concentration may indicate variable and poor absorption, especially at higher dosages, advanced disease, or both. A small number of stage D dogs met proposed criteria for diuretic resistance. Greater RAAS inhibition in stage D versus stage C indicates effectiveness of RAAS‐suppressive treatments in this group of dogs with refractory CHF.

Comparison between the effects of torsemide and furosemide on the renin-angiotensin-aldosterone system of normal dogs

INTRODUCTION/OBJECTIVES

We hypothesized that torsemide and furosemide, at approximately equipotent dosages (similar diuresis), would have comparable effects on the circulating renin-angiotensin-aldosterone system.

ANIMALS, MATERIALS AND METHODS

Six, healthy, middle-aged, male Beagles were randomized to receive torsemide (0.1 mg/kg PO q 12 h), furosemide (2.0 mg/kg PO q 12 h), or placebo for 10 days during three separate periods, separated by a 10-day washout period, in a crossover design. Blood was collected on days 1, 5, and 9 and 24-h urine collection ended on days 2, 6, and 10. After repeated measures analysis and Bonferonni correction, variables with an adjusted p<0.05 were investigated further, using Tukey's method.

RESULTS

Twenty-four-hour urine production differed significantly between the diuretics only on day 10, with torsemide causing a 38% greater diuresis than furosemide. There was, however, no significant difference in average 3-day diuresis. There were no significant differences between diuretics in the 24-h urinary excretion of sodium, chloride, or potassium, though furosemide caused less kaliuresis than torsemide. Serum renin, angiotensin II, and aldosterone and the urine aldosterone-to-creatinine ratio were significantly increased in the diuretic groups, as compared to placebo on days 5/6 and 9/10. There were no significant differences in these values between diuretics. Creatinine and blood urea nitrogen concentrations rose comparably in the diuretic groups, remaining within reference intervals in all dogs.

CONCLUSIONS

At approximately equipotent dosages (20:1), torsemide and furosemide produced comparable renin-angiotensin-aldosterone system activation. Torsemide's similar potassium excretion profile to furosemide decreases support for a hypothesized mineralocorticoid-receptor blocking capability.

Safety, Tolerability, and Pharmacokinetics of the Mineralocorticoid Receptor Modulator AZD9977 in Healthy Men: A Phase I Multiple Ascending Dose Study

Excessive activation of the mineralocorticoid receptor (MR) underlies the pathophysiology of heart failure and chronic kidney disease. Hyperkalemia risk limits the therapeutic use of conventional MR antagonists. AZD9977 is a nonsteroidal, selective MR modulator that may protect nonepithelial tissues without disturbing electrolyte balance. This phase I study investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple oral doses of AZD9977 in healthy volunteers. Twenty‐seven male participants aged 23–45 years were randomized 3:1 to receive oral AZD9977 or placebo for 8 days (with twice‐daily dosing on days 2–7), in dose cohorts of 50, 150, and 300 mg (AZD9977, n = 6 per cohort; placebo, n = 3 per cohort). Adverse events occurred in 4 of 18 participants receiving AZD9977 (22.2%) and 6 of 9 receiving placebo (66.7%), all of mild or moderate severity; none were serious or led to withdrawal. AZD9977 was rapidly absorbed, with median time of maximum concentration of 0.50–0.84 hours across dose groups. Area under the curve and maximum concentration were approximately dose proportional but elimination and accumulation terminal half‐life increased with dose. Steady‐state was reached after 3–4 days, with dose‐dependent accumulation of 1.2–1.7‐fold. Renal clearance was 5.9–6.5 L/hour and 24–37% of AZD9977 was excreted in the urine. Serum aldosterone levels increased dose dependently from days −1 to 7 in participants receiving AZD9977, but serum potassium levels and urinary electrolyte excretion were unchanged. AZD9977 was generally well‐tolerated with no safety concerns. Exploratory outcomes suggested reduced hyperkalemia risk compared with MR antagonists. These findings support further clinical development of AZD9977.

The selective mineralocorticoid receptor modulator AZD9977 reveals differences in mineralocorticoid effects of aldosterone and fludrocortisone

Introduction:

AZD9977 is a novel mineralocorticoid receptor (MR) modulator, which in preclinical studies demonstrated organ protection without affecting aldosterone-regulated urinary electrolyte excretion. However, when tested in humans, using fludrocortisone as an MR agonist, AZD9977 exhibited similar effects on urinary Na⁺/K⁺ ratio as eplerenone. The aim of this study is to understand whether the contradictory results seen in rats and humans are due to the mineralocorticoid used.

Materials and methods:

Rats were treated with single doses of AZD9977 or eplerenone in combination with either aldosterone or fludrocortisone. Urine was collected for five to six hours and total amounts excreted Na⁺ and K⁺ were assessed.

Results:

AZD9977 dose-dependently increased urinary Na⁺/K⁺ ratio in rats when tested against fludrocortisone, but not when tested against aldosterone. Eplerenone dose-dependently increased urinary Na⁺/K⁺ ratio when tested against fludrocortisone as well as aldosterone.

Conclusions:

The data suggest that the contrasting effects of AZD9977 on urinary electrolyte excretion observed in rats and humans are due to the use of the synthetic mineralocorticoid fludrocortisone. Future clinical studies are required to confirm the reduced electrolyte effects of AZD9977 and the subsequent lower predicted hyperkalemia risk.

Diverging effects of enalapril or eplerenone in primary prevention against doxorubicin-induced cardiotoxicity

Aims

Clinical studies suggest beneficial effects of renin-angiotensin system blockade for prevention of left ventricular (LV) dysfunction after chemotherapy. However, the efficacy of this strategy as primary prevention has been poorly studied. This study aimed at identifying the pathophysiological mechanisms by which mineralocorticoid receptor antagonism (MRA) or angiotensin converting enzyme inhibition (ACEi) provide protection against doxorubicin-induced cardiotoxicity (DIC) in mouse models of acute and chronic toxicity.

Methods and results

Acute DIC was induced by a single injection of Dox at 15 mg/kg and chronic DIC applied 5 injections of Dox at 4 mg/kg/week. MRA was achieved using eplerenone or cardiomyocyte-specific ablation of the MR gene in transgenic mice and ACEi using enalapril. Drugs were provided with the first dose of Dox and applied until the end of the study. In both model of DIC, Dox induced cardiac atrophy with decreased LV volume, reduced cardiomyocyte cell size, and cardiac dysfunction. In the acute model, neither MRA nor ACEi protected against these manifestations of DIC. In the chronic model, concomitant treatment with eplerenone did not protect against DIC and drastically increased plasma aldosterone levels and cardiac levels of angiotensin II type 1 receptor and of connective tissue growth factor (CTGF), as observed in acute DIC. Enalapril treatment in the chronic model, however, protected against cardiac dysfunction and cardiomyocyte atrophy and was associated with increased activation of the PI3K/AKT/mTOR pathway along with normal levels of CTGF.

Conclusion

Enalapril and eplerenone disparately impact on cellular signalling in DIC. Eplerenone, on top of Dox treatment was not protective and associated with increased levels of plasma aldosterone and of cardiac CTGF. In contrast, we show that primary prevention with enalapril preserves LV morphology and function in a clinically relevant model of chronic DIC, with increased stimulation of the PI3K/AKT/mTOR axis and normal CTGF levels suggesting potential therapeutic implications.

Clinical safety, tolerability, pharmacokinetics and effects on urinary electrolyte excretion of AZD9977, a novel, selective mineralocorticoid receptor modulator

AIMS

AZD9977 is the first mineralocorticoid receptor modulator in clinical development exerting similar organ protection as eplerenone with minimal urinary electrolyte effects in preclinical studies. The aim was to perform the initial clinical assessment of AZD9977.

METHODS

A first-in-human trial explored doses from 5 to 1200 mg. To study effects on urinary electrolyte excretion an additional randomized placebo controlled cross-over four-period clinical trial was performed. Twenty-three healthy volunteers were administered fludrocortisone alone or in combination with AZD9977, eplerenone or both. AZD9977/eplerenone combination was given to assess if AZD9977 can attenuate eplerenone induced natriuresis.

RESULTS

AZD9977 at doses from 5 to 1200 mg was safe and well tolerated and pharmacokinetics were compatible with further development. AZD9977 exhibited similar effects on urinary ln [Na+ ]/[K+ ] as eplerenone when using fludrocortisone as mineralocorticoid receptor agonist, and the combination had an additive effect on ln [Na+ K+ ].

CONCLUSIONS

The results in man contradict the results in rodent models driven by aldosterone, in which AZD9977 has minimal electrolyte effects. Future clinical studies with AZD9977 should be performed in presence of endogenous or exogenous aldosterone to assess potential benefit of AZD9977 in patients.

Single- and multiple-dose escalation study to assess pharmacokinetics, pharmacodynamics and safety of oral esaxerenone in healthy Japanese subjects

AIMS

To characterize the pharmacokinetics, pharmacodynamics and safety of esaxerenone, a mineralocorticoid receptor antagonist, in healthy adult Japanese men.

METHODS

Double-blind, placebo-controlled, sequential, dose-escalation studies were conducted in subjects randomized to receive oral once-daily esaxerenone (ranges: 5-200 mg [single-dose]; 10-100 mg over 10 days [multiple-dose]) or placebo under fasting conditions. Plasma concentrations were analysed by liquid chromatograph-tandem mass spectrometry. Pharmacokinetic parameters were determined by noncompartment analysis. Plasma/urine levels of pharmacodynamic biomarkers for mineralocorticoid receptor activity were evaluated.

RESULTS

In total, 48/48 and 39/40 subjects completed the single- and multiple-dose studies, respectively. Exposures were generally dose-proportional. The t_max , t_1/2 and CL/F remained unchanged, independent of dose; the respective ranges were 1.5-4.0 h, 22.3-25.1 h, and 4.0-5.2 l h^-1 (multiple-dose study). V_z /F ranged from 136.5 to 283.7 l in the multiple-dose study, and exposure reached steady state by day 4. The mean observed accumulation ratio, by dose, ranged from 1.36-1.98. The urinary Na⁺ /K⁺ ratio increased after single-dose administration; however, its relationship to the doses tested remains unclear. Plasma renin activity, active renin concentration and aldosterone concentration increased dose-dependently. Although blood potassium levels increased dose-dependently in the multiple-dose study (reaching a maximum mean ± standard deviation of 4.63 ± 0.354 mmol l^-1 in the 100-mg group), no safety/tolerability-related problems were detected in either study.

CONCLUSIONS

Exposure levels in healthy adults receiving esaxerenone were generally dose-proportional. Dose-dependent changes in plasma pharmacodynamic biomarkers for the mineralocorticoid receptor were identified during multiple-dose treatment and support the pharmacological activity of esaxerenone. No important safety concerns were identified.

Pharmacodynamic assessment of diuretic efficacy and braking in a furosemide continuous infusion model

INTRODUCTION

Diuretic failure is a potential life-ending event but is unpredictable and poorly understood. The objectives of this study were to evaluate pharmacodynamic markers of furosemide-induced diuresis and to investigate mechanisms of diuretic braking in dogs receiving constant rate infusion (CRI) of furosemide.

ANIMALS

Six healthy male dogs.

METHODS

Raw data and stored samples from one arm of a previously published study were further analyzed to mechanistically investigate causes of diuretic braking in these dogs. Urine volume was recorded hourly during a 5-h furosemide CRI. Urine and blood samples were collected hourly to measure serum and urine electrolytes, urine aldosterone, and plasma and urine furosemide. Serum electrolyte fractional excretion was calculated. Urine sodium concentration was indexed to urine potassium (uNa:uK) and urine furosemide (uNa:uFur) concentrations, plasma furosemide concentration was indexed to urine furosemide concentration (pFur:uFur), and urine aldosterone was indexed to urine creatinine (UAldo:C). Temporal change and the relationship to urine volume were evaluated for these measured and calculated variables.

RESULTS

Urine volume was significantly correlated with urine electrolyte amounts and with uNa:uK. The ratio of pFur:uFur decreased during the infusion, whereas furosemide excretion was unchanged.

CONCLUSIONS

There was a strong relationship between urine volume and absolute urine electrolyte excretion. Urine volume was strongly correlated to uNa:uK, giving it potential as a spot indicator of urine production during diuresis. The decrease in uNa:uK over time during the infusion is consistent with mineralocorticoid modification of urinary electrolyte excretion, supporting renin-angiotensin-aldosterone activation as a cause of diuretic braking in this model.

Preclinical pharmacology of AZD9977: A novel mineralocorticoid receptor modulator separating organ protection from effects on electrolyte excretion

Excess mineralocorticoid receptor (MR) activation promotes target organ dysfunction, vascular injury and fibrosis. MR antagonists like eplerenone are used for treating heart failure, but their use is limited due to the compound class-inherent hyperkalemia risk. Here we present evidence that AZD9977, a first-in-class MR modulator shows cardio-renal protection despite a mechanism-based reduced liability to cause hyperkalemia. AZD9977 in vitro potency and binding mode to MR were characterized using reporter gene, binding, cofactor recruitment assays and X-ray crystallopgraphy. Organ protection was studied in uni-nephrectomised db/db mice and uni-nephrectomised rats administered aldosterone and high salt. Acute effects of single compound doses on urinary electrolyte excretion were tested in rats on a low salt diet. AZD9977 and eplerenone showed similar human MR in vitro potencies. Unlike eplerenone, AZD9977 is a partial MR antagonist due to its unique interaction pattern with MR, which results in a distinct recruitment of co-factor peptides when compared to eplerenone. AZD9977 dose dependently reduced albuminuria and improved kidney histopathology similar to eplerenone in db/db uni-nephrectomised mice and uni-nephrectomised rats. In acute testing, AZD9977 did not affect urinary Na+/K+ ratio, while eplerenone increased the Na+/K+ ratio dose dependently. AZD9977 is a selective MR modulator, retaining organ protection without acute effect on urinary electrolyte excretion. This predicts a reduced hyperkalemia risk and AZD9977 therefore has the potential to deliver a safe, efficacious treatment to patients prone to hyperkalemia.

Diuretic activity of the aqueous crude extract and hot tea infusion of Moringa stenopetala (Baker f.) Cufod. leaves in rats

Moringa stenopetala (Baker f.) Cufod. is a medicinal plant that has been used for the treatment of different ailments such as hypertension and diabetes in Ethiopia. This study aims to assess the diuretic activity of the aqueous crude extract and hot tea infusion of M. stenopetala leaves in saline-loaded rats. Male Wistar rats were divided into ten groups (n = 5). The control group received distilled water (5 mL/kg), whereas the reference group received Furosemide (10 mg/kg). Groups III–X orally received different doses of aqueous crude extract (62.5, 125, 250, and 500 mg/kg) and hot tea infusion (1, 2, 4, and 6 teaspoons [Tsp]) based on community use. Urine volume was recorded every hour until the end of the 5th hour, and total urine volume of each animal was calculated. The diuretic activity and diuretic action were determined based on the urine output. Additionally, concentration of urinary sodium, chloride, and potassium ions was determined. The urinary Na⁺/K⁺ ratio and carbonyl anhydrase activity (Cl⁻/(Na⁺/K⁺)) were also assessed. The findings verified that the aqueous crude extract as well as the hot tea infusion of the leaves of M. stenopetala possesses significant (P < 0.01) diuretic, natriuretic, and kaliuretic effects. The aqueous crude extract (125 mg/kg) and hot tea infusion (2 Tsp) displayed the highest diuretic activity (101% and 96%, respectively) comparable to the reference drug, Furosemide (10 mg/kg). They also displayed a good natriuretic activity. The aqueous crude extract and hot tea infusion revealed a significant Na⁺ urinary excretion (P < 0.001) and Na⁺/K⁺ ratio (P < 0.05) at all test doses. There was also a significant (P < 0.01) Cl⁻ urinary excretion at all test doses of aqueous crude extract except 62.5 mg/kg and all test doses of hot tea infusion except higher doses (4 and 6 Tsp). Thus, the aqueous crude extract as well as the hot tea infusion of the leaves of M. stenopetala causes a plausible increase in the urine volume and concentration of urinary electrolytes in rats.

Evidence of the role of the vagal nerves as a monitor in the gastrointestinal-renal axis of natriuresis in human: Effects of vagotomy

This study aimed to investigate the mechanism of gastrointestinal regulation of natriuresis. Sixteen subjects without (group I) and sixteen subjects with a truncal vagotomy (group II), were given a daily diet of 18mmol of sodium for 5days (D1-D5). The sodium deficit for this period was calculated for each subject and on the morning of day-6 (D6), their cumulative deficit (E) was given as 3% NaCl. In both groups the subjects were divided to receive the hypertonic saline either orally (Ior, IIor) or intravenously (Iiv, IIiv). During the period of low sodium diet when compared to group II subjects of group I (1) had a greater weight loss (p<0.005), (2) demonstrated a larger drop in pulse pressure (p<0.005), (3) achieved a positive sodium equilibrium later (D5 vs D4) and (4) developed a greater sodium deficit (p<0.005). During the two 12h periods of D6, both Ior and Iiv exhibited greater natriuresis during the first 12h period (p<0.0001) whereas both IIor and IIiv did so during the second 12h period (p<0.0001). On D6 Ior excreted the greatest percentage of E (E%; 35.63%±3.12%, p<0.0001) compared to Iiv (17.06%±1.78%), IIor (16.03%±3.54%) and IIiv (15.39%±2.77%) whereas E% was not different between the other subgroups. These results indicate that the differential natriuresis between oral and intravenous sodium loading in previously sodium deprived subjects, is due to a mechanism in which the vagal nerves play a significant role as part of neural reflex or via a natriuretic hormone.

Continuum of Renin-Independent Aldosteronism in Normotension

Primary aldosteronism is a severe form of autonomous aldosteronism. Milder forms of autonomous and renin-independent aldosteronism may be common, even in normotension. We characterized aldosterone secretion in 210 normotensives who had suppressed plasma renin activity (<1.0 ng/mL per hour), completed an oral sodium suppression test, received an infusion of angiotensin II, and had measurements of blood pressure and renal plasma flow. Continuous associations between urinary aldosterone excretion rate, renin, and potassium handling were investigated. Severe autonomous aldosterone secretion that was consistent with confirmed primary aldosteronism was defined based on accepted criteria of an aldosterone excretion rate >12 μg/24 hours with urinary sodium excretion >200 mmol/24 hours. Across the population, there were strong and significant associations between higher aldosterone excretion rate and higher urinary potassium excretion, higher angiotensin II-stimulated aldosterone, and lower plasma renin activity, suggesting a continuum of renin-independent aldosteronism and mineralocorticoid receptor activity. Autonomous aldosterone secretion that fulfilled confirmatory criteria for primary aldosteronism was detected in 29 participants (14%). Normotensives with evidence suggestive of confirmed primary aldosteronism had higher 24-hour urinary aldosterone excretion rate (20.2±12.2 versus 6.2±2.9 μg/24 hours; P<0.001) as expected, but also higher angiotensin II-stimulated aldosterone (12.4±8.6 versus 6.6±4.3 ng/dL; P<0.001) and lower 24-hour urinary sodium-to-potassium excretion (2.69±0.65 versus 3.69±1.50 mmol/mmol; P=0.001); however, there were no differences in age, aldosterone-to-renin ratio, blood pressure, or renal plasma flow between the 2 groups. These findings indicate a continuum of renin-independent aldosteronism and mineralocorticoid receptor activity in normotension that ranges from subtle to overtly dysregulated and autonomous. Longitudinal studies are needed to determine whether this spectrum of autonomous aldosterone secretion contributes to hypertension and cardiovascular disease.

A novel aldosterone synthase inhibitor ameliorates mortality in pressure-overload mice with heart failure

It has been elucidated that mineralocorticoid receptor antagonists reduce mortality in patients with congestive heart failure and post-acute myocardial infarction. A direct inhibition of aldosterone synthase (CYP11B2) is also expected to have therapeutic benefits equal in quality to mineralocorticoid receptor antagonists in terms of reducing mineralocorticoid receptor signaling. Therefore, we have screened our chemical libraries and identified a novel and potent aldosterone synthase inhibitor, 2,2,2-trifluoro-1-{4-[(4-fluorophenyl)amino]pyrimidin-5-y}-1-[1-(methylsulfonyl)piperidin-4-yl]ethanol (compound 1), by lead optimization. Pharmacological properties of compound 1 were examined in in vitro cell-based assays and an in vivo mouse model of pressure-overload hypertrophy by transverse aortic constriction (TAC). Compound 1 showed potent CYP11B2 inhibition against human and mouse enzymes (IC₅₀; 0.003μM and 0.096μM, respectively) in a cell-based assay. The oral administration of 0.06% compound 1 in the food mixture of a mouse TAC model significantly reduced the plasma aldosterone level and ameliorated mortality rate. This study is the first to demonstrate that a CYP11B2 inhibitor improved survival rates of heart failure induced by pressure-overload in mice. The treatment of 0.06% compound 1 did not elevate plasma potassium level in this model, although further evaluation of hyperkalemia is needed. These results suggest that compound 1 can be developed as a promising oral CYP11B2 inhibitor for pharmaceutical applications. Compound 1 could also be a useful compound for clarifying the role of aldosterone in cardiac hypertrophy.

Preclinical and Early Clinical Profile of a Highly Selective and Potent Oral Inhibitor of Aldosterone Synthase (CYP11B2)

Supplemental Digital Content is available in the text.

Primary hyperaldosteronism is a common cause of resistant hypertension. Aldosterone is produced in the adrenal by aldosterone synthase (AS, encoded by the gene CYP11B2). AS shares 93% homology to 11β-hydroxylase (encoded by the gene CYP11B1), responsible for cortisol production. This homology has hitherto impeded the development of a drug, which selectively suppresses aldosterone but not cortisol production, as a new treatment for primary hyperaldosteronism. We now report the development of RO6836191 as a potent (Ki 13 nmol/L) competitive inhibitor of AS, with in vitro selectivity >100-fold over 11β-hydroxylase. In cynomolgus monkeys challenged with synthetic adrenocorticotropic hormone, single doses of RO6836191 inhibited aldosterone synthesis without affecting the adrenocorticotropic hormone–induced rise in cortisol. In repeat-dose toxicity studies in monkeys, RO6836191 reproduced the adrenal changes of the AS^−/− mouse: expansion of the zona glomerulosa; increased expression of AS (or disrupted green fluorescent protein gene in the AS^−/− mouse); hypertrophy, proliferation, and apoptosis of zona glomerulosa cells. These changes in the monkey were partially reversible and partially preventable by electrolyte supplementation and treatment with an angiotensin-converting enzyme inhibitor. In healthy subjects, single doses of RO6836191, across a 360-fold dose range, reduced plasma and urine aldosterone levels with maximum suppression at a dose of 10 mg, but unchanged cortisol, on adrenocorticotropic hormone challenge, up to 360 mg, and increase in the precursors 11-deoxycorticosterone and 11-deoxycortisol only at or >90 mg. In conclusion, RO6836191 demonstrates that it is possible to suppress aldosterone production completely in humans without affecting cortisol production.

Spot urine sodium excretion as prognostic marker in acutely decompensated heart failure: the spironolactone effect

INTRODUCTION

Loop diuretic resistance characterized by inefficient sodium excretion complicates many patients with acutely decompensated heart failure (ADHF). Mineralocorticoid receptor antagonists (MRAs) in natriuretic doses may improve spot urine sodium excretion and outcomes.

OBJECTIVE

Our primary aim was to assess the association of high-dose spironolactone with short-term spot urine sodium excretion, and our secondary aim was to determine if this higher short-term spot urine sodium excretion is associated with reduction in the composite clinical outcome (of cardiovascular mortality and/or ADHF hospitalization) event rate at 180 days.

METHODS

Single-centre, non-randomized, open-label study enrolling 100 patients with ADHF. Patients were treated with standard ADHF therapy alone (n = 50) or oral spironolactone 100 mg/day plus standard ADHF therapy (n = 50). Spot urine samples were collected at day 1 and day 3 of hospitalization.

RESULTS

Spironolactone group had significantly higher spot urine sodium levels compared to standard care group at day 3 (84.13 ± 28.71 mmol/L vs 70.74 ± 34.43 mmol/L, p = 0.04). The proportion of patients with spot urinary sodium <60 mmol/L was lower in spironolactone group at day 3 (18.8 vs 45.7, p = 0.01). In multivariate analysis, spironolactone was independently associated with increased spot urinary sodium and urinary sodium/potassium ratio of >2 at day 3 (both, p < 0.05). Higher spot urine sodium levels were associated with a lower event rate [HR for urinary sodium >100 mmol/L = 0.16 (0.06-0.42), p < 0.01, compared to <60], and provided a significant prognostic gain measured by net reclassification indexes.

CONCLUSION

Spot urinary sodium levels >60 mmol/L and urinary sodium/potassium ratio >2 measured at day 3 of hospitalization for ADHF are associated with improved mid-term outcomes. Spironolactone is associated with increased spot urinary sodium and sodium/potassium ratio >2.

Renal denervation attenuates NADPH oxidase-mediated oxidative stress and hypertension in rats with hydronephrosis

Hydronephrosis is associated with the development of salt-sensitive hypertension. Studies have suggested that increased sympathetic nerve activity and oxidative stress play important roles in hypertension and the modulation of salt sensitivity. The present study primarily aimed to examine the role of renal sympathetic nerve activity in the development of hypertension in rats with hydronephrosis. In addition, we aimed to investigate if NADPH oxidase (NOX) function could be affected by renal denervation. Partial unilateral ureteral obstruction (PUUO) was created in 3-wk-old rats to induce hydronephrosis. Sham surgery or renal denervation was performed at the same time. Blood pressure was measured during normal, high-, and low-salt diets. The renal excretion pattern, NOX activity, and expression as well as components of the renin-angiotensin-aldosterone system were characterized after treatment with the normal salt diet. On the normal salt diet, rats in the PUUO group had elevated blood pressure compared with control rats (115 ± 3 vs. 87 ± 1 mmHg, P < 0.05) and displayed increased urine production and lower urine osmolality. The blood pressure change in response to salt loading (salt sensitivity) was more pronounced in the PUUO group compared with the control group (15 ± 2 vs. 5 ± 1 mmHg, P < 0.05). Renal denervation in PUUO rats attenuated both hypertension (97 ± 3 mmHg) and salt sensitivity (5 ± 1 mmHg, P < 0.05) and normalized the renal excretion pattern, whereas the degree of renal fibrosis and inflammation was not changed. NOX activity and expression as well as renin and ANG II type 1A receptor expression were increased in the renal cortex from PUUO rats and normalized by denervation. Plasma Na(+) and K(+) levels were elevated in PUUO rats and normalized after renal denervation. Finally, denervation in PUUO rats was also associated with reduced NOX expression, superoxide production, and fibrosis in the heart. In conclusion, renal denervation attenuates hypertension and restores the renal excretion pattern, which is associated with reduced renal NOX and components of the renin-angiotensin-aldosterone system. This study emphasizes a link between renal nerves, the development of hypertension, and modulation of NOX function.

Geographic differences in heart failure trials

Randomized controlled trials (RCTs) are essential to develop advances in heart failure (HF). The need for increasing numbers of patients (without substantial cost increase) and generalization of results led to the disappearance of international boundaries in large RCTs. The significant geographic differences in patients' characteristics, outcomes, and, most importantly, treatment effect observed in HF trials have recently been highlighted. Whether the observed regional discrepancies in HF trials are due to trial-specific issues, patient heterogeneity, structural differences in countries, or a complex interaction between factors are the questions we propose to debate in this review. To do so, we will analyse and review data from HF trials conducted in different world regions, from heart failure with preserved ejection fraction (HF-PEF), heart failure with reduced ejection fraction (HF-REF), and acute heart failure (AHF). Finally, we will suggest objective and actionable measures in order to mitigate regional discrepancies in future trials, particularly in HF-PEF where prognostic modifying treatments are urgently needed and in which trials are more prone to selection bias, due to a larger patient heterogeneity.

Myeloid mineralocorticoid receptor activation contributes to progressive kidney disease

Clinical and experimental studies have shown that mineralocorticoid receptor (MR) antagonists substantially reduce kidney injury. However, the specific cellular targets and mechanisms by which MR antagonists protect against kidney injury must be identified. We used conditional gene deletion of MR signaling in myeloid cells (MR(flox/flox) LysM(Cre) mice; MyMRKO) or podocytes (MR(flox/flox) Pod(Cre) mice; PodMRKO) to establish the role of MR in these cell types in the development of mouse GN. Accelerated anti-glomerular basement membrane GN was examined in groups of mice: MyMRKO, PodMRKO, wild-type (WT) littermates, and WT mice receiving eplerenone (100 mg/kg twice a day; EPL-treated). At day 15 of disease, WT mice had glomerular crescents (37%±5%), severe proteinuria, and a 6-fold increase in serum cystatin-C. MyMRKO, PodMRKO, and EPL-treated mice with GN displayed proteinuria similar to that in these disease controls. However, MyMRKO and EPL-treated groups had a 35% reduction in serum cystatin-C levels and reduced crescent numbers compared with WT mice, whereas PodMRKO mice were not protected. The protection observed in MyMRKO mice appeared to result predominantly from reduced recruitment of macrophages and neutrophils into the inflamed kidney. Suppression of kidney leukocyte accumulation in MyMRKO mice correlated with reductions in gene expression of proinflammatory molecules (TNF-α, inducible nitric oxide synthase, chemokine (C-C motif) ligand 2, matrix metalloproteinase-12), tubular damage, and renal fibrosis and was similar in EPL-treated mice. In conclusion, MR signaling in myeloid cells, but not podocytes, contributes to the progression of renal injury in mouse GN, and myeloid deficiency of MR provides protection similar to eplerenone in this disease.

Mineralocorticoid receptor antagonism in acutely decompensated chronic heart failure

BACKGROUND/OBJECTIVES

Mineralocorticoid receptor antagonist (MRA) use in acutely decompensated chronic heart failure (ADCHF) may improve congestion through diuretic effect and prevent neurohormonal activation. We aimed to evaluate the clinical effect and safety of spironolactone in ADCHF.

METHODS

Prospective, experimental, single-center, and single-blinded trial. Patients were treated with: standard ADCHF therapy or oral spironolactone 50-100mg/d plus standard ADCHF therapy.

RESULTS

During a 1year period, 100 patients were enrolled, 50 included in the treatment group. Mean (SD) spironolactone dose (mg) at day 1 was 94.5±23.3 and at day 3 was 62.7±24.3. Worsening renal function (increase in pCr≥0.3mg/dL from day 1 to day 3) was more likely to occur in control group (20% vs. 4%; p=0.038), serum potassium did not differ between groups, and plasma NTproBNP had a significant decrease in spironolactone group at day 3 (median [IQR], 2488 [4579] vs. 1555 [1832]; p=0.05). Furthermore, a greater proportion of patients in the treatment group were free of congestion at day 3: less edema, rales, jugular venous pressure (JVP) and orthopnea (all, p<0.05). In addition, a significantly higher proportion of patients were on oral furosemide at day 3 (44% vs. 82%; p<0.001).

CONCLUSIONS

Our study supports the safety of high dose spironolactone in ADCHF and suggests a positive impact in the resolution of congestion. The important findings of our pilot study need to be confirmed in larger trials.

PF-03882845, a non-steroidal mineralocorticoid receptor antagonist, prevents renal injury with reduced risk of hyperkalemia in an animal model of nephropathy

The mineralocorticoid receptor (MR) antagonists PF-03882845 and eplerenone were evaluated for renal protection against aldosterone-mediated renal disease in uninephrectomized Sprague-Dawley (SD) rats maintained on a high salt diet and receiving aldosterone by osmotic mini-pump for 27 days. Serum K(+) and the urinary albumin to creatinine ratio (UACR) were assessed following 14 and 27 days of treatment. Aldosterone induced renal fibrosis as evidenced by increases in UACR, collagen IV staining in kidney cortex, and expression of pro-fibrotic genes relative to sham-operated controls not receiving aldosterone. While both PF-03882845 and eplerenone elevated serum K(+) levels with similar potencies, PF-03882845 was more potent than eplerenone in suppressing the rise in UACR. PF-03882845 prevented the increase in collagen IV staining at 5, 15 and 50 mg/kg BID while eplerenone was effective only at the highest dose tested (450 mg/kg BID). All doses of PF-03882845 suppressed aldosterone-induced increases in collagen IV, transforming growth factor-β 1 (Tgf-β 1), interleukin-6 (Il-6), intermolecular adhesion molecule-1 (Icam-1) and osteopontin gene expression in kidney while eplerenone was only effective at the highest dose. The therapeutic index (TI), calculated as the ratio of the EC50 for increasing serum K(+) to the EC50 for UACR lowering, was 83.8 for PF-03882845 and 1.47 for eplerenone. Thus, the TI of PF-03882845 against hyperkalemia was 57-fold superior to that of eplerenone indicating that PF-03882845 may present significantly less risk for hyperkalemia compared to eplerenone.

Mineralocorticoid receptor blockade-a novel approach to fight hyperkalaemia in chronic kidney disease

Hyperkalaemia continues to be a major hazard of mineralocorticoid receptor blockade in an effort to retard the progression of chronic kidney disease (CKD). In cardiac patients on mineralocorticoid receptor blockade, RLY-5016 which captures K⁺ in the colon has been effective in reducing the risk of hyperkalaemia. This compound might be useful in CKD as well.