Transgenic model of aldosterone-driven cardiac hypertrophy and heart failure

Glucocorticoids with or without fludrocortisone in septic shock: a narrative review from a biochemical and molecular perspective

Two randomised controlled trials have reported a reduction in mortality when adjunctive hydrocortisone is administered in combination with fludrocortisone compared with placebo in septic shock. A third trial did not support this finding when hydrocortisone administered in combination with fludrocortisone was compared with hydrocortisone alone. The underlying mechanisms for this mortality benefit remain poorly understood. We review the clinical implications and potential mechanisms derived from laboratory and clinical data underlying the beneficial role of adjunctive fludrocortisone with hydrocortisone supplementation in septic shock. Factors including distinct biological effects of glucocorticoids and mineralocorticoids, tissue-specific and mineralocorticoid receptor-independent effects of mineralocorticoids, and differences in downstream signalling pathways between mineralocorticoid and glucocorticoid binding at the mineralocorticoid receptor could contribute to this interaction. Furthermore, pharmacokinetic and pharmacodynamic disparities exist between aldosterone and its synthetic counterpart fludrocortisone, potentially influencing their effects. Pending publication of well-designed, randomised controlled trials, a molecular perspective offers valuable insights and guidance to help inform clinical strategies.

Differential Role of Aldosterone and Transforming Growth Factor Beta-1 in Cardiac Remodeling

Angiotensin II, a major culprit in cardiovascular disease, activates mediators that are also involved in pathological cardiac remodeling. In this context, we aimed at investigating the effects of two of them: aldosterone (Ald) and transforming growth factor beta-1 (TGF-β1) in an in vivo model. Six-week-old male wild-type (WT) and TGF-β1-overexpressing transgenic (TGF-β1-TG) mice were infused with subhypertensive doses of Ald for 2 weeks and/or treated orally with eplerenone from postnatal day 21. Thehearts' ventricles were examined by morphometry, immunoblotting to assess the intracellular signaling pathways and RT qPCR to determine hypertrophy and fibrosis marker genes. The TGF-β1-TG mice spontaneously developed cardiac hypertrophy and interstitial fibrosis and exhibited a higher baseline phosphorylation of p44/42 and p38 kinases, fibronectin and ANP mRNA expression. Ald induced a comparable increase in the ventricular-heart-weight-to-body-weight ratio and cardiomyocyte diameter in both strains, but a less pronounced increase in interstitial fibrosis in the transgenic compared to the WT mice (23.6% vs. 80.9%, p < 0.005). Ald increased the phosphorylation of p44/42 and p38 in the WT but not the TGF-β1-TG mice. While the eplerenone-enriched chow partially prevented Ald-induced cardiac hypertrophy in both genotypes and interstitial fibrosis in the WT controls, it completely protected against additional fibrosis in transgenic mice. Ald appears to induce cardiac hypertrophy independently of TGF-β1, while in the case of fibrosis, the downstream signaling pathways of these two factors probably converge.

Primary hyperaldosteronism is associated with increased mortality and morbidity in patients with hypertension and diabetes

Aims

Primary hyperaldosteronism (PA) is a common cause of hypertension. It is more prevalent in patients with diabetes. We assessed the cardiovascular impact of PA in patients with established hypertension and diabetes.

Methods

Data from the National Inpatient Sample (2008-2016) was used to identify adults with PA with hypertension and diabetes comorbidities and then compared to non-PA patients. The primary outcome was in-hospital death. Secondary outcomes included ischemic stroke, hemorrhagic stroke, acute renal failure, atrial fibrillation, and acute heart failure.

Results

A total of 48,434,503 patients with hypertension and diabetes were included in the analysis, of whom 12,850 (0.03%) were diagnosed with primary hyperaldosteronism (PA). Compared to patients with hypertension and diabetes but no PA, those with PA were more likely to be younger [63(13) vs. 67 (14), male (57.1% vs. 48.3%), and African-Americans (32% vs. 18.5%) (p<0.001 for all). PA was associated with a higher risk of mortality (adjusted OR 1.076 [1.076-1.077]), ischemic stroke [adjusted OR 1.049 (1.049-1.05)], hemorrhagic stroke [adjusted OR 1.05 (1.05-1.051)], acute renal failure [adjusted OR 1.058 (1.058-1.058)], acute heart failure [OR 1.104 (1.104-1.104)], and atrial fibrillation [adjusted OR 1.034 (1.033-1.034)]. As expected, older age and underlying cardiovascular disease were the strongest predictors of mortality. However, the female gender conferred protection [OR 0.889 (0.886-0.892].

Conclusion

Primary hyperaldosteronism in patients with hypertension and diabetes is associated with increased mortality and morbidity.

Aldosterone and cardiovascular diseases

Aldosterone's role in the kidney and its pathophysiologic actions in hypertension are well known. However, its role or that of its receptor [minieralocorticoid receptor (MR)] in other cardiovascular (CV) disease are less well described. To identify their potential roles in six CV conditions (heart failure, myocardial infarction, atrial fibrillation, stroke, atherosclerosis, and thrombosis), we assessed these associations in the following four areas: (i) mechanistic studies in rodents and humans; (ii) pre-clinical studies of MR antagonists; (iii) clinical trials of MR antagonists; and (iv) genetics. The data were acquired from an online search of the National Library of Medicine using the PubMed search engine from January 2011 through June 2021. There were 3702 publications identified with 200 publications meeting our inclusion and exclusion criteria. Data strongly supported an association between heart failure and dysregulated aldosterone/MR. This association is not surprising given aldosterone/MR's prominent role in regulating sodium/volume homeostasis. Atrial fibrillation and myocardial infarction are also associated with dysregulated aldosterone/MR, but less strongly. For the most part, the data were insufficient to determine whether there was a relationship between atherosclerosis, stroke, or thrombosis and aldosterone/MR dysregulation. This review clearly documented an expanding role for aldosterone/MR's dysregulation in CV diseases beyond hypertension. How expansive it might be is limited by the currently available data. It is anticipated that with an increased focus on aldosterone/MR's potential roles in these diseases, additional clinical and pre-clinical data will clarify these relationships, thereby, opening approaches to use modulators of aldosterone/MR's action to more precisely treat these CV conditions.

Aldosterone suppresses cardiac mitochondria

Elevated serum aldosterone promotes arterial hypertension, cardiac hypertrophy, and diastolic dysfunction. However, the effect of elevated aldosterone levels on cardiac mitochondria remains unclear. We used primary cultures of mouse cardiomyocytes to determine whether aldosterone has direct effects on cardiomyocyte mitochondria, and aldosterone-infused mice as a preclinical model to evaluate the impact of aldosterone in vivo. We show that aldosterone suppressed mtDNA copy number and SOD2 expression via the mineralocorticoid receptor (MR)-dependent regulation of NADPH oxidase 2 (NOX2) and generation of reactive oxygen species (ROS) in primary mouse cardiomyocytes. Aldosterone suppressed cardiac mitochondria adenosine triphosphate production, which was rescued by N-acetylcysteine. Aldosterone infusion for 4 weeks in mice suppressed the number of cardiac mitochondria, mtDNA copy number, and SOD2 protein expression. MR blockade by eplerenone or the administration of N-acetylcysteine prevented aldosterone-induced cardiac mitochondrial damage in vivo. Similarly, patients with primary aldosteronism had a lower plasma leukocyte mtDNA copy number. Plasma leukocyte mtDNA copy number was positively correlated with 24-hour urinary aldosterone level and left ventricular mass index. In conclusion, aldosterone suppresses cardiac mitochondria in vivo and directly via MR activation of ROS pathways.

A Review of the Molecular Mechanisms Underlying Cardiac Fibrosis and Atrial Fibrillation

The cellular and molecular mechanism involved in the pathogenesis of atrial fibrosis are highly complex. We have reviewed the literature that covers the effectors, signal transduction and physiopathogenesis concerning extracellular matrix (ECM) dysregulation and atrial fibrosis in atrial fibrillation (AF). At the molecular level: angiotensin II, transforming growth factor-β1, inflammation, and oxidative stress are particularly important for ECM dysregulation and atrial fibrotic remodelling in AF. We conclude that the Ang-II-MAPK and TGF-β1-Smad signalling pathways play a major, central role in regulating atrial fibrotic remodelling in AF. The above signalling pathways induce the expression of genes encoding profibrotic molecules (MMP, CTGF, TGF-β1). An important mechanism is also the generation of reactive oxygen species. This pathway induced by the interaction of Ang II with the AT₂R receptor and the activation of NADPH oxidase. Additionally, the interplay between cardiac MMPs and their endogenous tissue inhibitors of MMPs, is thought to be critical in atrial ECM metabolism and fibrosis. We also review recent evidence about the role of changes in the miRNAs expression in AF pathophysiology and their potential as therapeutic targets. Furthermore, keeping the balance between miRNA molecules exerting anti-/profibrotic effects is of key importance for the control of atrial fibrosis in AF.

Burden of Hypertensive Heart Disease in Iran during 1990-2017: Findings from the Global Burden of Disease study 2017

Background

Hypertension and its consequent end-organ damage including Hypertensive Heart Disease (HHD) are a major concern that impact health, resulting into impairment and reduced quality of life (QOL). The purpose of this study was to describe the burden of HHD in Iran and comparing it with the World Bank upper middle-income countries (UMICs) in terms of disability-adjusted life years (DALY), mortality and prevalence.

Methods

Using data from the Global Burden of Disease study 2017, we compared the number of DALYs, deaths and prevalence trends for HHD from 1990 to 2017 in all age groups for both sex in Iran, and compared the epidemiology and trends with UMICs and globally.

Results

The age-standardized DALY rate for HHD increased by 51.6% for men (95% uncertainty interval [UI] 305.8 to 436.7 per 100,000) and 4.4% for women (95% UI 429.4 to 448.7 per 100,000) in Iran. The age-standardized prevalence of HHD in Iran was almost twice times higher than globally and 1.5-times more than the World Bank UMICs. The age-standardized death rate for HDD increased by 60.1% (95% UI 17.3 to 27.7% per 100,000) for men and by 21.7% (95% UI 25.85 to 31.48 per 100,000) for women from 1990 to 2017. Age-standardized death rate in Iran was 2.4 and 1.9 times higher than globally and UMICs, respectively.

Conclusions

The higher prevalence and death rate in Iran in comparison with UMICs and globally should encourage health care provider to perform intensive screening activities in at risk population to prevent HHD and mitigate its mortality.

New insights into the roles of glucocorticoid signaling dysregulation in pathological cardiac hypertrophy

Pathological cardiac hypertrophy is a process of abnormal remodeling of the myocardium in response to stress overload or ischemia that results in myocardial injury, which is an independent risk factor for the increased morbidity and mortality of heart failure. Elevated circulating glucocorticoids (GCs) levels are associated with an increased risk of pathological cardiac hypertrophy, but the exact role remains unclear. In the heart, GCs exerts physiological and pharmacological effects by binding the glucocorticoid receptor (GR, NR3C1). However, under the state of tissue damage or oxidative stress, GCs can also bind the closely related mineralocorticoid receptor (MR, NR3C2) to exert a detrimental effect on cardiac function. In addition, the bioavailability of GCs at the cellular level is mainly regulated by tissue-specific metabolic enzymes 11β-hydroxysteroid dehydrogenases (11β-HSDs), including 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and type 2 (11β-HSD2), which catalyze the interconversion of active GCs. In this paper, we provide an overview of GC signaling and its physiological roles in the heart and highlight the dynamic and diverse roles of GC signaling dysregulation, mediated by excessive ligand GCs levels, GR/MR deficiency or overexpression, and local GCs metabolic disorder by 11β-HSDs, in the pathology of cardiac hypertrophy. Our findings will provide new ideas and insights for the search for appropriate intervention targets for pathological cardiac hypertrophy.

Effect of long-term glucocorticoid therapy on cardiac functions in children with congenital adrenal hyperplasia

BACKGROUND

Glucocorticoids play an important role in cardiac physiology. Chronic exposure and higher doses may cause adverse effects on the myocardium, especially in young patients receiving long-term therapy.

OBJECTIVE

To assess cardiac function in children with congenital adrenal hyperplasia (CAH) and its relation to glucocorticoid dose and therapy duration.

METHODS

Forty-seven patients with CAH due to 21-hydroxylase deficiency were compared to 47 controls. Patients were subdivided according to treatment duration (Group A: less than 6 years, Group B: more than 6 years). Mean daily glucocorticoid and cumulative glucocorticoid doses were calculated. Echocardiography was performed for patients and controls to evaluate cardiac functions, chamber dimensions and tissue Doppler valvular status.

RESULTS

Compared to controls, patients had cardiac chamber hypertrophy reflected by higher M-mode dimensions. Patients had lower fractional shortening, defective ventricular relaxation, lower average mitral and tricuspid e´/a´ ratios (e´ early diastolic, a´ late diastolic) as well as s´ (systolic) velocities, higher average mitral E/e ratio and higher left ventricle TDI Tei index (P < .05). Group B had lower average mitral e´/a´ and tricuspid s´ velocities, and higher average mitral E/e ratio (P < .05). Cumulative glucocorticoid dose significantly correlated with different echocardiographic parameters.

CONCLUSION

Long-term glucocorticoid therapy even within the recommended therapeutic range adversely affects cardiac functions in children with 21-hydroxylase deficiency.

Long-term administration of prednisolone: Effects on the myocardial tissue of healthy beagle dogs

This study aimed to assess the structural and functional effects of long-term hyperglucocorticoidemia on canine myocardium and compare these parameters with histopathological changes. Twelve healthy male beagle dogs were enrolled and assigned to the high-dose prednisolone (P; n=6) and control (C; n=6) groups. The P group was treated with 2 mg/kg of prednisolone BID for 84 days. Clinical parameters were measured using echocardiography and non-invasive systolic blood pressure (SBP) measured before the initiation of synthetic corticosteroids and at 7, 28, 56, and 84 days after the start of medication. For histological evaluation, cardiovascular tissue was harvested from dogs in groups P (at the end of the medication period) and C (scheduled to be euthanized for unrelated reasons). In the P group, clinical changes including thickening of the left ventricular free wall (LVFW) and interventricular septum (IVS), decreased left ventricular (LV) diastolic function, and increased SBP were observed after the start of medication. During histological evaluation, fibrosis was observed in the LVFW and IVS in the P group. Furthermore, decreased glucocorticoid receptor (GCR) levels were observed in the LVFW, right ventricular free wall (RVFW), and IVS and increased mineralocorticoid receptor (MCR) levels were observed in the LVFW and RVFW in the P group compared with those in the C group. In conclusion, fibrosis may cause LV structural and functional abnormalities in dogs with hyperadrenocorticism. Furthermore, GCR downregulation and upregulated MCR might influence the myocardial fibrosis.

Pathology of Aldosterone Biosynthesis and its Action

Aldosterone plays pivotal roles in renin-angiotensin-aldosterone system in order to maintain the equilibrium of liquid volume and electrolyte metabolism. Aldosterone action is mediated by both mineralocorticoid receptor and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Its excessive actions directly induced tissue injuries in its target organs such as myocardial and vascular fibrosis in addition to chronic kidney diseases. Excessive aldosterone actions were also reported to be involved in unbalanced electrolyte metabolism in inflammatory bowel disease and development of pulmonary diseases. Hyperaldosteronism is tentatively classified into primary and secondary types. Primary aldosteronism is more frequent and has been well known to result in secondary hypertension with subsequent cardiovascular damages. Primary aldosteronism is also further classified into distinctive subtypes and among those, aldosterone-producing adenoma is the most frequent one accounting for the great majority of unilateral primary aldosteronism cases. In bilateral hyperaldosteronism, aldosterone-producing diffuse hyperplasia and aldosterone-producing micronodules or nodules are the major subtypes. All these aldosterone-producing lesions were reported to harbor somatic mutations including KCNJ5, CACNA1D, ATP1A1 and ATP2B3, which were all related to excessive aldosterone production. Among those mutations above, somatic mutation of KCNJ5 is the most frequent in aldosterone-producing adenoma and mostly composed of clear cells harboring abundant aldosterone synthase expression. In contrast, CACNA1D-mutated aldosterone-producing micronodules or aldosterone-producing nodules were frequently detected not only in primary aldosteronism patients but also in the zona glomerulosa of normal adrenal glands, which could eventually lead to an autonomous aldosterone production resulting in normotensive or overt primary aldosteronism, but their details have remained unknown.

The Cardiac Mineralocorticoid Receptor (MR): A Therapeutic Target Against Ventricular Arrhythmias

Mineralocorticoid antagonists have been shown to be useful in the treatment of severe heart failure and may even save lives in this context. However, the reason for the beneficial action of these drugs, as well as the physiological role played by the cardiac mineralocorticoid receptor (MR), are still poorly understood. While the proinflammatory action of aldosterone on the heart and the resulting fibrosis partly explain the improvement due to the anti-mineralocorticoid therapy, the reduction in sudden death is probably related to a lower occurrence of ventricular arrhythmias. In this review, the author explains the physiological mechanism linking the positive chronotropic response induced by aldosterone observed in vitro with isolated ventricular cardiomyocytes and the increased risk of ventricular arrhythmias reported in vivo in hyperaldosteronism. He describes the molecular steps involved between MR activation and acceleration of spontaneous myocyte contractions, including expression of a specific micro RNA (miR204), down-regulation of a silencing transcription factor (NRSF), and re-expression of a fetal gene encoding a low threshold voltage-gated calcium channel (CaV3.2). Finally, he provides evidence suggesting aldosterone-independent and redox-sensitive mechanisms of MR activation in cardiac myocytes. Taken together, this information suggests that the use of anti-mineralocorticoid therapy could benefit the heart by preventing ventricular arrhythmias, not only in established hyperaldosteronism, but also in various pathological situations such as Cushing's disease, oxidative stress, or even diabetes mellitus.

Pre- and Post-Conditioning of the Heart: An Overview of Cardioprotective Signaling Pathways

Since the discovery of ischemic pre- and post-conditioning, more than 30 years ago, the knowledge about the mechanisms and signaling pathways involved in these processes has significantly increased. In clinical practice, on the other hand, such advancement has yet to be seen. This article provides an overview of ischemic pre-, post-, remote, and pharmacological conditioning related to the heart. In addition, we reviewed the cardioprotective signaling pathways and therapeutic agents involved in the above-mentioned processes, aiming to provide a comprehensive evaluation of the advancements in the field. The advancements made over the last decades cannot be ignored and with the exponential growth in techniques and applications. The future of pre- and post-conditioning is promising.

TRIF/miR-34a mediates aldosterone-induced cardiac inflammation and remodeling

Aldosterone, as a major product of renin-angiotensin-aldosterone system (RAAS), determines multiple pathophysiological processes in cardiovascular diseases. The excess inflammatory response is one of the key profiles in aldosterone-mediated cardiac remodeling. However, the potential mechanisms of aldosterone/inflammatory signaling were still not fully disclosed. The present study aimed to investigate whether TIR-domain-containing adapter-inducing interferon-β (Trif) participated in the aldosterone-induced cardiac remodeling, and to explore potential molecular mechanisms. Trif knockout mice and their littermates were osmotically administrated with aldosterone (50 μg/kg per day) for 21 and 42 days. The cardiac structural analysis, functional parameters, and mitochondrial function were measured. Aldosterone dose- or time-dependently increased the levels of TRIF in primary mouse cardiomyocytes or mouse heart tissues. Trif deficiency protected against aldosterone-induced cardiac hypertrophy, fibrosis and dysfunction. Moreover, Trif deficiency also suppressed aldosterone-induced cardiac inflammatory response and mitochondrial injuries. Mechanistically, overexpression of cardiac microRNAs (miR)-34a reversed the cardiac benefits of Trif deficiency in aldosterone-treated mice. Taken together, Trif/miR-34a axis could provide a novel molecular mechanism for explaining aldosterone-induced cardiac hypertrophy, fibrosis and functional disorders.

Chemogenetic activation of adrenocortical Gq signaling causes hyperaldosteronism and disrupts functional zonation

The mineralocorticoid aldosterone is produced in the adrenal zona glomerulosa (ZG) under the control of the renin-angiotensin II (AngII) system. Primary aldosteronism (PA) results from renin-independent production of aldosterone and is a common cause of hypertension. PA is caused by dysregulated localization of the enzyme aldosterone synthase (Cyp11b2), which is normally restricted to the ZG. Cyp11b2 transcription and aldosterone production are predominantly regulated by AngII activation of the Gq signaling pathway. Here, we report the generation of transgenic mice with Gq-coupled designer receptors exclusively activated by designer drugs (DREADDs) specifically in the adrenal cortex. We show that adrenal-wide ligand activation of Gq DREADD receptors triggered disorganization of adrenal functional zonation, with induction of Cyp11b2 in glucocorticoid-producing zona fasciculata cells. This result was consistent with increased renin-independent aldosterone production and hypertension. All parameters were reversible following termination of DREADD-mediated Gq signaling. These findings demonstrate that Gq signaling is sufficient for adrenocortical aldosterone production and implicate this pathway in the determination of zone-specific steroid production within the adrenal cortex. This transgenic mouse also provides an inducible and reversible model of hyperaldosteronism to investigate PA therapeutics and the mechanisms leading to the damaging effects of aldosterone on the cardiovascular system.

The cardiovascular consequences of hyperaldosteronism

Primary aldosteronism (PA), the most common form of secondary hypertension, has been considered for decades as a "benign" form of hypertension, but evidences progressively built up to show that patients with PA had an excess rate of cardiovascular damage as compared to blood pressure-matched essential hypertensive patients. This review provides an updated view of structural and electrical cardiac remodeling and of vascular changes in hyperaldosteronism, and how they can favor development of cardiovascular events. The link between hyperaldosteronism and resistant hypertension is also examined, and the impact of targeted treatment of hyperaldosteronism on cardiovascular changes is finally discussed.

Effects of Eplerenone on Blood Pressure and Echocardiographic and Serum Biochemical Variables in Five Healthy Dogs: A Pilot Study

Eplerenone (EP), an aldosterone antagonist, is reported to produce renal and cardiac protective effects in noncanine species. However, there are no detailed reports available on cardiovascular effects of EP in dogs. This study aimed to determine effect of EP on echocardiographic parameters, blood pressures, and biochemical variables in healthy dogs. Five healthy Beagle dogs were randomly divided and repeatedly used in each of 3 dose groups, receiving 2.5, 5, or 10 mg/kg BW EP orally q24 h for 4 wks. Serum biochemical test, blood pressure, and Doppler echocardiography measurements were performed before EP administration and at 1, 2, and 4 weeks after EP administration. Treatment with EP reduced mean blood pressure in a dose-dependent manner and significantly (but in a dose-independent manner) decreased left atrium/aorta ratio, early diastolic transmitral flow, early diastolic transmitral flow/late diastolic transmitral flow, peak velocity of early diastolic transmitral flow/peak velocity of early diastolic mitral annular motion, left ventricle and right ventricle Tei indices, stroke volume, cardiac output, and mid systole myocardial velocity gradient 1 to 4 weeks after administration. Deceleration time of early diastolic transmitral flow significantly increased after EP administration. No significant changes were observed in serum biochemical variables. The results indicated that EP might reduce preload, thereby decreasing left atrial size. In addition, reduction of left ventricular stiffness may have theoretically taken place but this could not be tested using the present study design. It is suggested that EP administration within the dose range used in this study is safe for administration to healthy dogs. Further studies are needed to explore both safety and efficacy, as well as to seek a recommended dose range of EP treatment in client-owned dogs with heart disease.

Hypertension and Heart Failure

Hypertensive heart disease represents a spectrum of illnesses from uncontrolled hypertension to heart failure. The authors discuss the natural history and pathogenesis of heart failure owing to hypertensive heart disease, reviewing the important role of left ventricular hypertrophy as the inciting process leading to diastolic dysfunction and heart failure with preserved ejection fraction. They describe the various mechanisms by which a subset of patients ultimately develops systolic heart failure. They discuss management strategies for hypertensive heart disease at all stages of the disease process. Treatment in the initial stages before onset of heart failure may result in regression of disease.

The non-steroidal mineralocorticoid receptor antagonist finerenone prevents cardiac fibrotic remodeling

Mineralocorticoid receptor (MR) overactivation promotes cardiac fibrosis. We studied the ability of the non-steroidal MR antagonist finerenone to prevent fibrotic remodeling. In neonatal rat cardiac fibroblasts, finerenone prevented aldosterone-induced nuclear MR translocation. Treatment with finerenone decreased the expression of connective tissue growth factor (CTGF) (74 ± 15% of control, p = 0.005) and prevented aldosterone-induced upregulation of CTGF and lysyl oxidase (LOX) completely. Finerenone attenuated the upregulation of transforming growth factor ß (TGF-ß), which was induced by the Rac1 GTPase activator l-buthionine sulfoximine. Transgenic mice with cardiac-specific overexpression of Rac1 (RacET) showed increased left ventricular (LV) end-diastolic (63.7 ± 8.0 vs. 93.8 ± 25.6 µl, p = 0.027) and end-systolic (28.0 ± 4.0 vs. 49.5 ± 16.7 µl, p = 0.014) volumes compared to wild-type FVBN control mice. Treatment of RacET mice with 100 ppm finerenone over 5 months prevented LV dilatation. Systolic and diastolic LV function did not differ between the three groups. RacET mice exhibited overactivation of MR and 11ß hydroxysteroid dehydrogenase type 2. Both effects were reduced by finerenone (reduction about 36%, p = 0.030, and 40%, p = 0.032, respectively). RacET mice demonstrated overexpression of TGF-ß, CTGF, LOX, osteopontin as well as collagen and myocardial fibrosis in the left ventricle. In contrast, expression of these parameters did not differ between finerenone-treated RacET and control mice. Finerenone prevented left atrial dilatation (6.4 ± 1.5 vs. 4.7 ± 1.4 mg, p = 0.004) and left atrial fibrosis (17.8 ± 3.1 vs. 12.8 ± 3.1%, p = 0.046) compared to vehicle-treated RacET mice. In summary, finerenone prevented from MR-mediated structural remodeling in cardiac fibroblasts and in RacET mice. These data demonstrate anti-fibrotic myocardial effects of finerenone.

Aldosterone Research: 65 Years, and Counting

Aldosterone was characterized as the major mineralocorticoid hormone 65 years ago, and since then its physiologic role in epidural electrolyte homeostasis the province of nephrologists. In epithelia it acts via the mineralocorticoid receptor (MR) to retain Na⁺ and excrete K⁺; MRs, however, are widely expressed in organs not known to be aldosterone target tissues. MRs are not merely "aldosterone receptors," as they have equivalently high affinity for the physiologic glucocorticoids, and for progesterone. In epithelia (plus in the blood vessel wall and in the nucleus tractus solitarius of the brain) MRs are "protected" by coexpression of the enzyme 11β-hydroxysteroid dehydrogenase. This enzyme converts cortisol-which circulates at much higher concentrations than aldosterone-to receptor-inactive cortisone, thus allowing aldosterone selectively to activate "protected" MR. In tissues which do not express 11β-hydroxysteroid dehydrogenase, the default MR ligand is cortisol, which circulates at ≥100-fold higher plasma free concentrations than aldosterone. In such tissues there is as yet scant evidence for the physiologic role of cortisol-occupied MR: over the past decade, however, it has become clear that in damaged tissues cortisol can act as an MR-agonist, mimicking the effects seen with aldosterone under experimental conditions, in vitro and in vivo. Many pathophysiologic roles have been attributed to aldosterone: on the current evidence there are none outside its long established epithelial actions, those on the blood vessel wall and on the nucleus tractus solitarius.

The Aldosterone Receptor Antagonist Eplerenone Inhibits Isoproterenol-Induced Collagen-I and 11β-HSD1 Expression in Rat Cardiac Fibroblasts and the Left Ventricle

β-Adrenergic receptor (β-AR)-induction of collagen-I synthesis is partially mediated by the cardiac mineralocorticoid receptor (MR) system. However, it remains unclear whether the selective MR antagonist, eplerenone, inhibits collagen-I synthesis induced by β-AR stimulation. We investigated the effects of eplerenone on the responses to a non-selective β-AR agonist, isoproterenol, which induced collagen-I synthesis in primary cardiac fibroblasts (CFs) and the left ventricle. mRNAs encoding the MR and 11β-hydroxysteroid dehydrogenase type I (11β-HSD1) were evident in the left ventricle and primary CFs. mRNAs encoding the CYP family 11 subfamily B member 2 (CYP11-B2) were not detected, even after isoproterenol treatment. In vivo, isoproterenol induced collagenous fiber accumulation in the left ventricle. The phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), 11β-HSD1 levels, and mRNA/protein levels of collagen-I increased upon exposure to isoproterenol, but these increases were inhibited by eplerenone co-treatment. In primary CFs, isoproterenol increased the phosphorylation of ERK1/2 and the expression levels of both 11β-HSD1 and collagen-I; these isoproterenol-attributable effects were inhibited by co-treatment with eplerenone and PD98059, a specific inhibitor of mitogen-activated protein kinase/ERK kinase activity. The results suggest that 11β-HSD1 but not CYP11-B2 is expressed in primary CFs. Eplerenone inhibited isoproterenol-induced ERK1/2 phosphorylation and expression of 11β-HSD1 and collagen-I in primary CFs, as well as the progression of cardiac fibrosis in the left ventricle. Therefore, eplerenone inhibited the isoproterenol-induced increases in 11β-HSD1 and collagen-I expression in primary CFs, and progression of cardiac fibrosis in the left ventricle.

Similar efficacy from specific and non-specific mineralocorticoid receptor antagonist treatment of muscular dystrophy mice

BACKGROUND

Combined treatment with an angiotensin-converting enzyme inhibitor and a mineralocorticoid receptor (MR) antagonist improved cardiac and skeletal muscle function and pathology in a mouse model of Duchenne muscular dystrophy. MR is present in limb and respiratory skeletal muscles and functions as a steroid hormone receptor.

OBJECTIVE

The goals of the current study were to compare the efficacy of the specific MR antagonist eplerenone with the non-specific MR antagonist spironolactone, both in combination with the angiotensin-converting enzyme inhibitor lisinopril.

METHODS

Three groups of n=18 dystrophin-deficient, utrophin-haploinsufficient male mice were given chow containing: lisinopril plus spironolactone, lisinopril plus eplerenone, or no drug, from four to 20 weeks-of-age. Eighteen C57BL/10 male mice were used as wild-type controls. In vivo measurements included cardiac magnetic resonance imaging, conscious electrocardiography, and grip strength. From each mouse in the study, diaphragm, extensor digitorum longus, and cardiac papillary muscle force was measured ex vivo, followed by histological quantification of muscle damage in heart, diaphragm, quadriceps, and abdominal muscles. MR protein levels were also verified in treated muscles.

RESULTS

Treatment with specific and non-specific MR antagonists did not result in any adverse effects to dystrophic skeletal muscles or heart. Both treatments resulted in similar functional and pathological improvements across a wide array of parameters. MR protein levels were not reduced by treatment.

CONCLUSIONS

These data suggest that spironolactone and eplerenone show similar effects in dystrophic mice and support the clinical development of MR antagonists for treating skeletal muscles in Duchenne muscular dystrophy.

Genomic and rapid effects of aldosterone: what we know and do not know thus far

Aldosterone is the most known mineralocorticoid hormone synthesized by the adrenal cortex. The genomic pathway displayed by aldosterone is attributed to the mineralocorticoid receptor (MR) signaling. Even though the rapid effects displayed by aldosterone are long known, our knowledge regarding the receptor responsible for such event is still poor. It is intense that the debate whether the MR or another receptor-the "unknown receptor"-is the receptor responsible for the rapid effects of aldosterone. Recently, G protein-coupled estrogen receptor-1 (GPER-1) was elegantly shown to mediate some aldosterone-induced rapid effects in several tissues, a fact that strongly places GPER-1 as the unknown receptor. It has also been suggested that angiotensin receptor type 1 (AT1) also participates in the aldosterone-induced rapid effects. Despite this open question, the relevance of the beneficial effects of aldosterone is clear in the kidneys, colon, and CNS as aldosterone controls the important water reabsorption process; on the other hand, detrimental effects displayed by aldosterone have been reported in the cardiovascular system and in the kidneys. In this line, the MR antagonists are well-known drugs that display beneficial effects in patients with heart failure and hypertension; it has been proposed that MR antagonists could also play an important role in vascular disease, obesity, obesity-related hypertension, and metabolic syndrome. Taken altogether, our goal here was to (1) bring a historical perspective of both genomic and rapid effects of aldosterone in several tissues, and the receptors and signaling pathways involved in such processes; and (2) critically address the controversial points within the literature as regarding which receptor participates in the rapid pathway display by aldosterone.

Eplerenone Prevents Atrial Fibrosis via the TGF-β Signaling Pathway

OBJECTIVES

Eplerenone (EPL), an antagonist of the mineralocorticoid receptor, is beneficial for atrial fibrillation and atrial fibrosis. However, the underlying mechanism remains less well known. We aimed to investigate the effect of EPL on atrial fibrosis using a mouse with selective atrial fibrosis and to explore the underlying mechanisms.

METHODS

EPL-treated MHC-TGFcys33ser transgenic mice that have selective atrial fibrosis (Tx+EPL mice), as well as control mice, were used for in vivo studies including histological analyses, Western blotting, and qRT-PCR studies. TGF-β1-stimulated atrial fibroblasts were treated with EPL or vehicle for the in vitro studies including Western blotting and qRT-PCR studies. In addition, Smad7 siRNA was used to knock down Smad7.

RESULTS

EPL inhibited atrial fibrosis in the Tx mice. In addition, EPL suppressed the expression of fibrosis-related molecules induced by TGF-β1 in vivo and in vitro. This occurred in concert with a downregulation of Smad7 protein expression and an upregulation of p-Smad2/3 protein expression. In addition, knockdown of Smad7 by siRNA abolished the protective roles of EPL.

CONCLUSIONS

EPL inhibited atrial fibrosis in Tx mice. The underlying mechanism may involve increased protein expression of Smad7, which enhances the inhibitory feedback regulation of TGF-β1/Smad signaling.

Getting to the heart of intracellular glucocorticoid regeneration: 11β-HSD1 in the myocardium

Corticosteroids influence the development and function of the heart and its response to injury and pressure overload via actions on glucocorticoid (GR) and mineralocorticoid (MR) receptors. Systemic corticosteroid concentration depends largely on the activity of the hypothalamic-pituitary-adrenal (HPA) axis, but glucocorticoid can also be regenerated from intrinsically inert metabolites by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), selectively increasing glucocorticoid levels within cells and tissues. Extensive studies have revealed the roles for glucocorticoid regeneration by 11β-HSD1 in liver, adipose, brain and other tissues, but until recently, there has been little focus on the heart. This article reviews the evidence for glucocorticoid metabolism by 11β-HSD1 in the heart and for a role of 11β-HSD1 activity in determining the myocardial growth and physiological function. We also consider the potential of 11β-HSD1 as a therapeutic target to enhance repair after myocardial infarction and to prevent the development of cardiac remodelling and heart failure.

Mineralocorticoid regulation of cell function: the role of rapid signalling and gene transcription pathways

The mineralocorticoid receptor (MR) and mineralocorticoids regulate epithelial handling of electrolytes, and induces diverse effects on other tissues. Traditionally, the effects of MR were ascribed to ligand-receptor binding and activation of gene transcription. However, the MR also utilises a number of intracellular signalling cascades, often by transactivating unrelated receptors, to change cell function more rapidly. Although aldosterone is the physiological mineralocorticoid, it is not the sole ligand for MR. Tissue-selective and mineralocorticoid-specific effects are conferred through the enzyme 11β-hydroxysteroid dehydrogenase 2, cellular redox status and properties of the MR itself. Furthermore, not all aldosterone effects are mediated via MR, with implication of the involvement of other membrane-bound receptors such as GPER. This review will describe the ligands, receptors and intracellular mechanisms available for mineralocorticoid hormone and receptor signalling and illustrate their complex interactions in physiology and disease.

Aldosterone and cardiovascular remodelling: focus on myocardial failure

Heart failure is a clinical syndrome that may result from different disease states or conditions that injure the myocardium. The activation of circulating neurohormones, particularly aldosterone, may play a pivotal role in left ventricular (LV) remodelling. The Randomized Aldactone Evaluation Study and Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival trial have emphasised the clinical importance of aldosterone. This review addresses some of the proposed mechanisms of LV remodelling in heart failure.

Role of the Renin-Angiotensin-Aldosterone System beyond Blood Pressure Regulation: Molecular and Cellular Mechanisms Involved in End-Organ Damage during Arterial Hypertension

Arterial hypertension is a common condition worldwide and an important predictor of several complicated diseases. Arterial hypertension can be triggered by many factors, including physiological, genetic, and lifestyle causes. Specifically, molecules of the renin-angiotensin-aldosterone system not only play important roles in the control of blood pressure, but they are also associated with the genesis of arterial hypertension, thus constituting a need for pharmacological interventions. Chronic high pressure generates mechanical damage along the vascular system, heart, and kidneys, which are the principal organs affected in this condition. In addition to mechanical stress, hypertension-induced oxidative stress, chronic inflammation, and the activation of reparative mechanisms lead to end-organ damage, mainly due to fibrosis. Clinical trials have demonstrated that renin-angiotensin-aldosterone system intervention in hypertensive patients lowers morbidity/mortality and inflammatory marker levels as compared to placebo patients, evidencing that this system controls more than blood pressure. This review emphasizes the detrimental effects that a renin-angiotensin-aldosterone system (RAAS) imbalance has on health considerations above and beyond high blood pressure, such as fibrotic end-organ damage.

Mineralocorticoid receptor antagonist pretreatment to MINIMISE reperfusion injury after ST-elevation myocardial infarction (the MINIMISE STEMI Trial): rationale and study design

Novel therapies capable of reducing myocardial infarct (MI) size when administered prior to reperfusion are required to prevent the onset of heart failure in ST‐segment elevation myocardial infarction (STEMI) patients treated by primary percutaneous coronary intervention (PPCI). Experimental animal studies have demonstrated that mineralocorticoid receptor antagonist (MRA) therapy administered prior to reperfusion can reduce MI size, and MRA therapy prevents adverse left ventricular (LV) remodeling in post‐MI patients with LV impairment. With these 2 benefits in mind, we hypothesize that initiating MRA therapy prior to PPCI, followed by 3 months of oral MRA therapy, will reduce MI size and prevent adverse LV remodeling in STEMI patients. The MINIMISE‐STEMI trial is a prospective, randomized, double‐blind, placebo‐controlled trial that will recruit 150 STEMI patients from four centers in the United Kingdom. Patients will be randomized to receive either an intravenous bolus of MRA therapy (potassium canrenoate 200 mg) or matching placebo prior to PPCI, followed by oral spironolactone 50 mg once daily or matching placebo for 3 months. A cardiac magnetic resonance imaging scan will be performed within 1 week of PPCI and repeated at 3 months to assess MI size and LV remodeling. Enzymatic MI size will be estimated by the 48‐hour area‐under‐the‐curve serum cardiac enzymes. The primary endpoint of the study will be MI size on the 3‐month cardiac magnetic resonance imaging scan. The MINIMISE STEMI trial will investigate whether early MRA therapy, initiated prior to reperfusion, can reduce MI size and prevent adverse post‐MI LV remodeling.

Update on RAAS Modulation for the Treatment of Diabetic Cardiovascular Disease

Since the advent of insulin, the improvements in diabetes detection and the therapies to treat hyperglycemia have reduced the mortality of acute metabolic emergencies, such that today chronic complications are the major cause of morbidity and mortality among diabetic patients. More than half of the mortality that is seen in the diabetic population can be ascribed to cardiovascular disease (CVD), which includes not only myocardial infarction due to premature atherosclerosis but also diabetic cardiomyopathy. The importance of renin-angiotensin-aldosterone system (RAAS) antagonism in the prevention of diabetic CVD has demonstrated the key role that the RAAS plays in diabetic CVD onset and development. Today, ACE inhibitors and angiotensin II receptor blockers represent the first line therapy for primary and secondary CVD prevention in patients with diabetes. Recent research has uncovered new dimensions of the RAAS and, therefore, new potential therapeutic targets against diabetic CVD. Here we describe the timeline of paradigm shifts in RAAS understanding, how diabetes modifies the RAAS, and what new parts of the RAAS pathway could be targeted in order to achieve RAAS modulation against diabetic CVD.

Left ventricular hypertrophy in valvular aortic stenosis: mechanisms and clinical implications

Valvular aortic stenosis is the second most prevalent adult valve disease in the United States and causes progressive pressure overload, invariably leading to life-threatening complications. Surgical aortic valve replacement and, more recently, transcatheter aortic valve replacement effectively relieve the hemodynamic burden and improve the symptoms and survival of affected individuals. However, according to current American College of Cardiology/American Heart Association guidelines on the management of valvular heart disease, the indications for aortic valve replacement, including transcatheter aortic valve replacement, are based primarily on the development of clinical symptoms, because their presence indicates a dismal prognosis. Left ventricular hypertrophy develops in a sizeable proportion of patients before the onset of symptoms, and a growing body of literature demonstrates that regression of left ventricular hypertrophy resulting from aortic stenosis is incomplete after aortic valve replacement and associated with adverse early postoperative outcomes and worse long-term outcomes. Thus, reliance on the development of symptoms alone without consideration of structural abnormalities of the myocardium for optimal timing of aortic valve replacement potentially constitutes a missed opportunity to prevent postoperative morbidity and mortality from severe aortic stenosis, especially in the face of the quickly expanding indications of lower-risk transcatheter aortic valve replacement. The purpose of this review is to discuss the mechanisms and clinical implications of left ventricular hypertrophy in severe valvular aortic stenosis, which may eventually move to center stage as an indication for aortic valve replacement in the asymptomatic patient.

Lower aldosterone-renin ratio is a risk factor for total and cancer death in Japanese individuals: the Takahata study

OBJECTIVE

A higher plasma aldosterone-renin ratio (ARR) is an established marker for screening for primary aldosteronism (PA). The association between higher ARR and mortality in a general population has not been fully explored. We here examined whether higher ARR is a risk factor for total and cause-specific mortality in a Japanese population.

SUBJECTS AND METHODS

A population-based, longitudinal study of 1,310 Japanese individuals (age: 63·9 ± 9·8 years) enrolled in the Takahata study between 2004 and 2006 and followed for up to 8 years. The incidence and causes of death were monitored annually until 10 January 2012 (median follow-up: 2691 days).

RESULTS

During the follow-up period, 64 subjects died. Kaplan-Meier analysis showed a significantly increased risk for total and cancer mortality in subjects with lower ARR (log-rank P < 0·001). Cox's proportional hazard model analyses with adjustment for age and gender showed that lower ARR was associated with increased total and cancer mortality in subjects with low (≦72) vs high (>72) ARR (hazard ratios and 95% confidential intervals: 2·56, 1·44-4·56 and 2·78, 1·16-6·65, respectively).

CONCLUSIONS

Lower ARR was a significant and independent risk factor for increased total and cancer mortality in this Japanese population. Subjects with higher ARR were not-at-risk for total death in general. These findings increase the necessity for identifying people with PA from those with higher ARR. People with higher ARR without PA may be at very low risk for total and cancer death.

GEMIN4 functions as a coregulator of the mineralocorticoid receptor

The mineralocorticoid receptor (MR) is a member of the nuclear receptor superfamily. Pathological activation of the MR causes cardiac fibrosis and heart failure, but clinical use of MR antagonists is limited by the renal side effect of hyperkalemia. Coregulator proteins are known to be critical for nuclear receptor-mediated gene expression. Identification of coregulators, which mediate MR activity in a tissue-specific manner, may allow for the development of novel tissue-selective MR modulators that confer cardiac protection without adverse renal effects. Our earlier studies identified a consensus motif among MR-interacting peptides, MPxLxxLL. Gem (nuclear organelle)-associated protein 4 (GEMIN4) is one of the proteins that contain this motif. Transient transfection experiments in HEK293 and H9c2 cells demonstrated that GEMIN4 repressed agonist-induced MR transactivation in a cell-specific manner. Furthermore, overexpression of GEMIN4 significantly decreased, while knockdown of GEMIN4 increased, the mRNA expression of specific endogenous MR target genes. A physical interaction between GEMIN4 and MR is suggested by their nuclear co-localization upon agonist treatment. These findings indicate that GEMIN4 functions as a novel coregulator of the MR.

A reappraisal of loop diuretic choice in heart failure patients

The health and economic burden of heart failure is significant and continues to grow each year. Loop diuretics are an integral part of symptom management in heart failure. Furosemide is used disproportionately compared with other loop diuretics, and there is currently no guidance for physicians regarding which agent to choose. However, there exist pharmacologic differences as well as other mechanistic differences that appear to favor torsemide use over furosemide. Compared with furosemide, torsemide improves surrogate markers of heart failure severity such as left ventricular function, plasma brain natriuretic peptide levels, and New York Heart Association functional class and may also reduce hospitalizations, readmissions, and mortality. Data suggest that these benefits could be mediated through torsemide's ability to positively affect the renin-angiotensin-aldosterone system. Specifically, torsemide has been shown to inhibit aldosterone secretion, synthesis, and receptor binding in vitro, as well as decrease transcardiac extraction of aldosterone, myocardial collagen production, and cardiac fibrosis in patients with heart failure. We identified pertinent literature using keyword MEDLINE searches and cross-referencing prior bibliographies. We summarize the available data suggesting potential benefits with torsemide over furosemide, and call attention to the need for a reappraisal of diuretic use in heart failure patients and also for a well-powered, randomized control trial assessing torsemide versus furosemide use.

Eplerenone for early cardiomyopathy in Duchenne muscular dystrophy: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Cardiomyopathy is a leading cause of death in patients with Duchenne muscular dystrophy and myocardial damage precedes decline in left ventricular systolic function. We tested the efficacy of eplerenone on top of background therapy in patients with Duchenne muscular dystrophy with early myocardial disease.

METHODS

In this randomised, double-blind, placebo-controlled trial, boys from three centres in the USA aged 7 years or older with Duchenne muscular dystrophy, myocardial damage by late gadolinium enhancement cardiac MRI and preserved ejection fraction received either eplerenone 25 mg or placebo orally, every other day for the first month and once daily thereafter, in addition to background clinician-directed therapy with either angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB). Computer-generated randomisation was done centrally using block sizes of four and six, and only the study statistician and the investigational pharmacy had the preset randomisation assignments. The primary outcome was change in left ventricular circumferential strain (Ecc) at 12 months, a measure of contractile dysfunction. Safety was established through serial serum potassium levels and measurement of cystatin C, a non-creatinine measure of kidney function. This trial is registered with ClinicalTrials.gov, number NCT01521546.

FINDINGS

Between Jan 26, 2012, and July 3, 2013, 188 boys were screened and 42 were enrolled. 20 were randomly assigned to receive eplerenone and 22 to receive placebo, of whom 20 in the eplerenone group and 20 in the placebo group completed baseline, 6-month, and 12-month visits. After 12 months, decline in left ventricular circumferential strain was less in those who received eplerenone than in those who received placebo (median ΔEcc 1·0 [IQR 0·3-2·2] vs 2·2 [1·3-3·1]; p=0·020). Cystatin C concentrations remained normal in both groups, and all non-haemolysed blood samples showed normal potassium concentrations. One 23-year-old patient in the placebo group died of fat embolism, and another patient in the placebo group withdrew from the trial to address long-standing digestive issues. All other adverse events were mild: short-lived headaches coincident with seasonal allergies occurred in one patient given eplerenone, flushing occurred in one patient given placebo, and anxiety occurred in another patient given placebo.

INTERPRETATION

In boys with Duchenne muscular dystrophy and preserved ejection fraction, addition of eplerenone to background ACEI or ARB therapy attenuates the progressive decline in left ventricular systolic function. Early use of available drugs warrants consideration in this population at high risk of cardiac death, but further studies are needed to determine the effect of combination cardioprotective therapy on event-free survival in Duchenne muscular dystrophy.

FUNDING

BallouSkies, Parent Project for Muscular Dystrophy, US National Center for Advancing Translational Sciences, and US National Institutes of Health.

Mineralocorticoids in the heart and vasculature: new insights for old hormones

The mineralocorticoid aldosterone is a key regulator of water and electrolyte homeostasis. Numerous recent developments have advanced the field of mineralocorticoid pharmacology—namely, clinical trials have shown the beneficial effects of aldosterone antagonists in chronic heart failure and post-myocardial infarction treatment. Experimental studies using cell type-specific gene targeting of the mineralocorticoid receptor (MR) gene in mice have revealed the importance of extrarenal aldosterone signaling in cardiac myocytes, endothelial cells, vascular smooth cells, and macrophages. In addition, several molecular pathways involving signal transduction via the classical MR as well as the G protein-coupled receptor GPER mediate the diverse spectrum of effects of aldosterone on cells. This knowledge has initiated the development of new pharmacological ligands to specifically interfere with targets on different levels of aldosterone signaling. For example, aldosterone synthase inhibitors such as LCI699 and the novel nonsteroidal MR antagonist BAY 94-8862 have been tested in clinical trials. Interference with the interaction between MR and its coregulators seems to be a promising strategy toward the development of selective MR modulators.

Effects of adiponectin on calcium-handling proteins in heart failure with preserved ejection fraction

BACKGROUND

Despite the increasing prevalence of heart failure with preserved ejection fraction (HFpEF) in humans, there remains no therapeutic options for HFpEF. Adiponectin, an adipocyte-derived cytokine, exerts cardioprotective actions, and its deficiency is implicated in the development of hypertension and HF with reduced ejection fraction. Similarly, adiponectin deficiency in HFpEF exacerbates left ventricular hypertrophy, diastolic dysfunction, and HF. However, the therapeutic effects of adiponectin in HFpEF remain unknown. We sought to test the hypothesis that chronic adiponectin overexpression protects against the progression of HF in a murine model of HFpEF.

METHODS AND RESULTS

Adiponectin transgenic and wild-type mice underwent uninephrectomy, a continuous saline or d-aldosterone infusion and given 1.0% sodium chloride drinking water for 4 weeks. Aldosterone-infused wild-type mice developed HFpEF with hypertension, left ventricular hypertrophy, and diastolic dysfunction. Aldosterone infusion increased myocardial oxidative stress and decreased sarcoplasmic reticulum Ca(2+)-ATPase protein expression in HFpEF. Although total phospholamban protein expression was unchanged, there was a decreased expression of protein kinase A-dependent phospholamban phosphorylation at Ser16 and CaMKII (Ca(2+)/calmodulin-dependent protein kinase II)-dependent phospholamban phosphorylation at Thr17. Adiponectin overexpression in aldosterone-infused mice ameliorated left ventricular hypertrophy, diastolic dysfunction, lung congestion, and myocardial oxidative stress without affecting blood pressure and left ventricular EF. This improvement in diastolic dysfunction parameters in aldosterone-infused adiponectin transgenic mice was accompanied by the preserved protein expression of protein kinase A-dependent phosphorylation of phospholamban at Ser16. Adiponectin replacement prevented the progression of aldosterone-induced HFpEF, independent of blood pressure, by improving diastolic dysfunction and by modulating cardiac hypertrophy.

CONCLUSIONS

These findings suggest that adiponectin may have therapeutic effects in patients with HFpEF.

Eplerenone: a review of its use in patients with chronic systolic heart failure and mild symptoms

Eplerenone (Inspra®) is a selective mineralocorticoid receptor antagonist (MRA). In the EU, it is approved for use (in addition to standard optimal therapy) to reduce the risk of cardiovascular (CV) mortality and morbidity in adult patients with chronic systolic heart failure (HF) and mild symptoms. This article reviews the efficacy and tolerability of eplerenone in this indication and briefly summarizes its pharmacology. In the EMPHASIS-HF study, relative to placebo, the addition of eplerenone to optimal background therapy significantly reduced the risk of death from CV causes or hospitalization for HF in patients with chronic systolic HF and mild symptoms. Benefits of eplerenone therapy over placebo were also observed in several secondary outcomes, including: death from any cause or hospitalization for HF; death from any cause; hospitalization for any reason; or hospitalization for HF. Eplerenone was generally well tolerated in this study, with the most frequent adverse event being hyperkalaemia, which is a known adverse event of the drug class. Sexual adverse events (e.g. gynecomastia) occurred in <1 % of eplerenone recipients, reflecting the selectivity of eplerenone for mineralocorticoid receptors. Based on these results, European guidelines have been updated and recommend the use of an MRA to reduce the risk of HF hospitalization and premature death in all patients with persisting symptoms (New York Heart Association class II-IV) and a left-ventricular ejection fraction of ≤35 %, despite treatment with ACE inhibitor (or an angiotensin receptor blocker if an ACE inhibitor is not tolerated) and a β-blocker.

Significance of AT1 receptor independent activation of mineralocorticoid receptor in murine diabetic cardiomyopathy

Background

Diabetes mellitus (DM) has deleterious influence on cardiac performance independent of coronary artery disease and hypertension. The objective of the present study was to investigate the role of the renin-angiotensin-aldosterone system, especially angiotensin II type 1a receptor (AT_1aR) and mineralocorticoid receptor (MR) signaling, in left ventricular (LV) dysfunction induced by diabetes mellitus (DM).

Methods and Results

DM was induced by intraperitoneal injection of streptozotocin (200 mg/kg BW) in wild-type (WT) or AT_1aR knockout (KO) male mice, and they were bred during 6 or 12 weeks. Some KO mice were administered the MR antagonist eplerenone (100 mg/kg body weight). At 6 weeks, LV diastolic function was impaired in WT-DM, but preserved in KO-DM. At that time point MR mRNA expression was upregulated, NADPH oxidase subunit (p47phox) and glutathione peroxidase (GPx1) mRNA expression were upregulated, the staining intensities of LV tissue for 4-hydroxy-2-nonenal was stronger in immunohistochemistry, the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) positive cells was increased, Bcl-2 protein expression was significantly downregulated, and the expression of SERCA2a and phosphorylated phospholamban was depressed in WT-DM, while these changes were not seen in KO-DM. At 12 weeks, however, these changes were also noted in KO-DM. Eplerenone arrested those changes. The plasma aldosterone concentration was elevated in WT-DM but not in KO-DM at 6 weeks. It showed 3.7-fold elevation at 12 weeks even in KO-DM, which suggests “aldosterone breakthrough” phenomenon. However, the aldosterone content in LV tissue was unchanged in KO-DM.

Conclusions

DM induced diastolic dysfunction was observed even in KO at 12 weeks, which was ameliorated by minelarocorticoid receptor antagonist, eplerenone. AT₁-independent MR activation in the LV might be responsible for the pathogenesis of diabetic cardiomyopathy.

Rapid mineralocorticoid receptor trafficking

The mineralocorticoid receptor (MR) is a ligand-dependent transcription factor that physiologically regulates water-electrolyte homeostasis and controls blood pressure. The MR can also elicit inflammatory and remodeling processes in the cardiovascular system and the kidneys, which require the presence of additional pathological factors like for example nitrosative stress. However, the underlying molecular mechanism(s) for pathophysiological MR effects remain(s) elusive. The inactive MR is located in the cytosol associated with chaperone molecules including HSP90. After ligand binding, the MR monomer rapidly translocates into the nucleus while still being associated to HSP90 and after dissociation from HSP90 binds to hormone-response-elements called glucocorticoid response elements (GREs) as a dimer. There are indications that rapid MR trafficking is modulated in the presence of high salt, oxidative or nitrosative stress, hypothetically by induction or posttranslational modifications. Additionally, glucocorticoids and the enzyme 11beta hydroxysteroid dehydrogenase may also influence MR activation. Because MR trafficking and its modulation by micro-milieu factors influence MR cellular localization, it is not only relevant for genomic but also for nongenomic MR effects.

Modulation of the cardiac sodium/bicarbonate cotransporter by the renin angiotensin aldosterone system: pathophysiological consequences

The sodium/bicarbonate cotransporter (NBC) is one of the major alkalinizing mechanisms in the cardiomyocytes. It has been demonstrated the existence of at least two functional isoforms, one that promotes the co-influx of 1 molecule of Na⁺ per 1 molecule of HCO⁻₃ (electroneutral isoform; NBCn1) and the other one that generates the co-influx of 1 molecule of Na⁺ per 2 molecules of HCO⁻₃ (electrogenic isoform; NBCe1). Both isoforms are important to maintain intracellular pH (pH_i) and sodium concentration ([Na⁺]_i). In addition, NBCe1 generates an anionic repolarizing current that modulates the action potential duration (APD). The renin-angiotensin-aldosterone system (RAAS) is implicated in the modulation of almost all physiological cardiac functions and is also involved in the development and progression of cardiac diseases. It was reported that angiotensin II (Ang II) exhibits an opposite effect on NBC isoforms: it activates NBCn1 and inhibits NBCe1. The activation of NBCn1 leads to an increase in pH_i and [Na⁺]_i, which indirectly, due to the stimulation of reverse mode of the Na⁺/Ca²⁺ exchanger (NCX), conduces to an increase in the intracellular Ca²⁺ concentration. On the other hand, the inhibition of NBCe1 generates an APD prolongation, potentially representing a risk of arrhythmias. In the last years, the potentially altered NBC function in pathological scenarios, as cardiac hypertrophy and ischemia-reperfusion, has raised increasing interest among investigators. This review attempts to draw the attention on the relevant regulation of NBC activity by RAAS, since it modulates pH_i and [Na⁺]_i, which are involved in the development of cardiac hypertrophy, the damage produced by ischemia-reperfusion and the generation of arrhythmic events, suggesting a potential role of NBC in cardiac diseases.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

Mineralocorticoid receptor antagonists: emerging roles in cardiovascular medicine

Spironolactone was first developed over 50 years ago as a potent mineralocorticoid receptor (MR) antagonist with undesirable side effects; it was followed a decade ago by eplerenone, which is less potent but much more MR-specific. From a marginal role as a potassium-sparing diuretic, spironolactone was shown to be an extraordinarily effective adjunctive agent in the treatment of progressive heart failure, as was eplerenone in subsequent heart failure trials. Neither acts as an aldosterone antagonist in the heart as the cardiac MR are occupied by cortisol, which becomes an aldosterone mimic in conditions of tissue damage. The accepted term "MR antagonist", (as opposed to "aldosterone antagonist" or, worse, "aldosterone blocker"), should be retained, despite the demonstration that they act not to deny agonist access but as inverse agonists. The prevalence of primary aldosteronism is now recognized as accounting for about 10% of hypertension, with recent evidence suggesting that this figure may be considerably higher: in over two thirds of cases of primary aldosteronism therapy including MR antagonists is standard of care. MR antagonists are safe and vasoprotective in uncomplicated essential hypertension, even in diabetics, and at low doses they also specifically lower blood pressure in patients with so-called resistant hypertension. Nowhere are more than 1% of patients with primary aldosteronism ever diagnosed and specifically treated. Given the higher risk profile in patients with primary aldosteronism than that of age, sex, and blood pressure matched essential hypertension, on public health grounds alone the guidelines for first-line treatment of all hypertension should mandate inclusion of a low-dose MR antagonist.

Effects of salt status and blockade of mineralocorticoid receptors on aldosterone-induced cardiac injury

The mineralocorticoid aldosterone regulates sodium and water homeostasis in the human body. The combination of excess aldosterone and salt loading induces hypertension and cardiac damage. However, little is known of the effects of aldosterone on blood pressure and cardiac pathophysiology in the absence of salt loading. We have now investigated the effects of salt status and blockade of mineralocorticoid receptors (MRs) on cardiac pathophysiology in uninephrectomized Sprague-Dawley rats implanted with an osmotic minipump to maintain hyperaldosteronism. The rats were fed a low-salt (0.0466% NaCl in chow) or high-salt (0.36% NaCl in chow plus 1% NaCl in drinking water) diet in the absence or presence of treatment with a subdepressor dose of the MR antagonist spironolactone (SPL). Aldosterone excess in the setting of low salt intake induced substantial cardiac remodeling and diastolic dysfunction without increasing blood pressure. These effects were accompanied by increased levels of oxidative stress and inflammation as well as increased expression of genes related to the renin-angiotensin and endothelin systems in the heart. All of these cardiac changes were completely blocked by the administration of SPL. On the other hand, aldosterone excess in the setting of high salt intake induced hypertension and a greater extent of cardiac injury, with the cardiac changes being only partially attenuated by SPL in a manner independent of its antihypertensive effect. The combination of dietary salt restriction and MR antagonism is thus a promising therapeutic option for the management of hypertensive patients with hyperaldosteronism or relative aldosterone excess.

Mineralocorticoid receptors and the heart, multiple cell types and multiple mechanisms: a focus on the cardiomyocyte

MR (mineralocorticoid receptor) activation in the heart plays a central role in the development of cardiovascular disease, including heart failure. The MR is present in many cell types within the myocardium, including cardiomyocytes, macrophages and the coronary vasculature. The specific role of the MR in each of these cell types in the initiation and progression of cardiac pathophysiology is not fully understood. Cardiomyocyte MRs are increasingly recognized to play a role in regulating cardiac function, electrical conduction and fibrosis, through direct signal mediation and through paracrine MR-dependent activity. Although MR blockade in the heart is an attractive therapeutic option for the treatment of heart failure and other forms of heart disease, current antagonists are limited by side effects owing to MR inactivation in other tissues (including renal targets). This has led to increased efforts to develop therapeutics that are more selective for cardiac MRs and which may have reduced the occurrence of side effects in non-cardiac tissues. A major clinical consideration in the treatment of cardiovascular disease is of the differences between males and females in the incidence and outcomes of cardiac events. There is clinical evidence that female sensitivity to endogenous MRs is more pronounced, and experimentally that MR-targeted interventions may be more efficacious in females. Given that sex differences have been described in MR signalling in a range of experimental settings and that the MR and oestrogen receptor pathways share some common signalling intermediates, it is becoming increasingly apparent that the mechanisms of MRs need to be evaluated in a sex-selective manner. Further research targeted to identify sex differences in cardiomyocyte MR activation and signalling processes has the potential to provide the basis for the development of cardiac-specific MR therapies that may also be sex-specific.