The role of the mineralocorticoid receptor in adipocyte biology and fat metabolism

Influence and implications of the renin-angiotensin-aldosterone system in obstructive sleep apnea: An updated systematic review and meta-analysis

Obstructive sleep apnea is a chronic, sleep-related breathing disorder, which is an independent risk factor for cardiovascular disease. The renin-angiotensin-aldosterone system regulates salt and water homeostasis, blood pressure, and cardiovascular remodelling. Elevated aldosterone levels are associated with excess morbidity and mortality. We aimed to analyse the influence and implications of renin-angiotensin-aldosterone system derangement in individuals with and without obstructive sleep apnea. We pooled data from 20 relevant studies involving 2828 participants (1554 with obstructive sleep apnea, 1274 without obstructive sleep apnea). The study outcomes were the levels of renin-angiotensin-aldosterone system hormones, blood pressure and heart rate. Patients with obstructive sleep apnea had higher levels of plasma renin activity (pooled wmd+ 0.25 [95% confidence interval 0.04-0.46], p = 0.0219), plasma aldosterone (pooled wmd+ 30.79 [95% confidence interval 1.05-60.53], p = 0.0424), angiotensin II (pooled wmd+ 5.19 [95% confidence interval 3.11-7.27], p < 0.001), systolic (pooled wmd+ 5.87 [95% confidence interval 1.42-10.32], p = 0.0098) and diastolic (pooled wmd+ 3.40 [95% confidence interval 0.86-5.94], p = 0.0086) blood pressure, and heart rate (pooled wmd+ 3.83 [95% confidence interval 1.57-6.01], p = 0.0009) compared with those without obstructive sleep apnea. The elevation remained significant (except for renin levels) when studies involving patients with resistant hypertension were removed. Sub-group analysis demonstrated that levels of angiotensin II were significantly higher only among the Asian population with obstructive sleep apnea compared with those without obstructive sleep apnea. Body mass index accounted for less than 10% of the between-study variance in elevation of the renin-angiotensin-aldosterone system parameters. Patients with obstructive sleep apnea have higher levels of renin-angiotensin-aldosterone system hormones, blood pressure and heart rate compared with those without obstructive sleep apnea, which remains significant even among patients without resistant hypertension.

Cardiovascular Disease in Obstructive Sleep Apnea: Putative Contributions of Mineralocorticoid Receptors

Obstructive sleep apnea (OSA) is a chronic and highly prevalent condition that is associated with oxidative stress, inflammation, and fibrosis, leading to endothelial dysfunction, arterial stiffness, and vascular insulin resistance, resulting in increased cardiovascular disease and overall mortality rates. To date, OSA remains vastly underdiagnosed and undertreated, with conventional treatments yielding relatively discouraging results for improving cardiovascular outcomes in OSA patients. As such, a better mechanistic understanding of OSA-associated cardiovascular disease (CVD) and the development of novel adjuvant therapeutic targets are critically needed. It is well-established that inappropriate mineralocorticoid receptor (MR) activation in cardiovascular tissues plays a causal role in a multitude of CVD states. Clinical studies and experimental models of OSA lead to increased secretion of the MR ligand aldosterone and excessive MR activation. Furthermore, MR activation has been associated with worsened OSA prognosis. Despite these documented relationships, there have been no studies exploring the causal involvement of MR signaling in OSA-associated CVD. Further, scarce clinical studies have exclusively assessed the beneficial role of MR antagonists for the treatment of systemic hypertension commonly associated with OSA. Here, we provide a comprehensive overview of overlapping mechanistic pathways recruited in the context of MR activation- and OSA-induced CVD and propose MR-targeted therapy as a potential avenue to abrogate the deleterious cardiovascular consequences of OSA.

Enantioselectivity in the toxicological effects of chiral pesticides: A review

As a special category of pesticides, chiral pesticides have increased the difficulty in investigating pesticide toxicity. Based on their usage, chiral pesticides can be divided into insecticides, herbicides, and fungicides. Over the past decades, great efforts have been made on elucidating their toxicological effects. However, no literature has reviewed the enantioselective toxicity of chiral pesticides since 2014. In recent years, more chiral pesticides have been registered for application. As such, huge research progresses have been achieved in enantioselective toxicity of chiral pesticides. Generally, more researches have remedied the knowledge gap in toxicological effects of old and new chiral pesticides. And the toxicological endpoints being evaluated have become more specific rather than centering on basic toxicity and target organisms. Besides, the underlying mechanisms accounting for the enantioselectivity in toxicological effects of chiral pesticides have been discussed as well. All in all, this review provides the critical knowledge for risk assessments, and help to drive the green-technology of single- or enriched-enantiomer pesticides and formulation of relevant laws and regulations.

The expression of glucocorticoid and mineralocorticoid receptors in pituitary tumors causing Cushing's disease and silent corticotroph tumors

OBJECTIVE

Pituitary neuroendocrine corticotroph tumors commonly cause Cushing's disease (CD) that results from increased adrenocorticotropic hormone (ACTH) secretion by the pituitary tumor and consequent increase of cortisol levels in blood. However, in some patients, corticotroph tumors remain clinically non-functioning. Cortisol secretion is regulated by the hypothalamic-pituitary-adrenal axis and includes a negative feedback between cortisol and ACTH secretion. Glucocorticoids reduce ACTH level both by hypothalamic regulation and acting on corticotrophs via glucocorticoid (GR) and mineralocorticoid (MR) receptors. The aim of the study was to determine the role of GR and MR expression at mRNA and protein levels in both functioning and silent corticotroph tumors.

METHODS

Ninety-five patients were enrolled, including 70 with CD and 25 with silent corticotroph tumors. Gene expression levels of NR3C1 and NR3C2 coding for GR and MR, respectively, were determined with qRT-PCR in the two tumor types. GR and MR protein abundance was assessed with immunohistochemistry.

RESULTS

Both GR and MR were expressed in corticotroph tumors. Correlation between NR3C1 and NR3C2 expression levels was observed. NR3C1 expression was higher in silent than in functioning tumors. In CD patients NR3C1 and NR3C2 levels were negatively correlated with morning plasma ACTH levels and tumor size. Higher NR3C2 was confirmed in patients with remission after surgery and in densely granulated tumors. Expression of both genes and GR protein was higher in USP8-mutated tumors. Similar relationship between USP8 mutations and expression levels were observed in analysis of silent tumors that also revealed a negative correlation between GR and tumor size and higher NR3C1 expression in densely granulated tumors.

CONCLUSIONS

Although the associations between gene/protein expression and patients clinical features are not strong, they consistently show an evident trend in which higher receptor expression corresponds to more favorable clinical characteristics.

Adipose Tissue Dysfunction in Obesity: Role of Mineralocorticoid Receptor

The mineralocorticoid receptor (MR) acts as an essential regulator of blood pressure, volume status, and electrolyte balance. However, in recent decades, a growing body of evidence has suggested that MR may also have a role in mediating pro-inflammatory, pro-oxidative, and pro-fibrotic changes in several target organs, including the adipose tissue. The finding that MR is overexpressed in the adipose tissue of patients with obesity has led to the hypothesis that this receptor can contribute to adipokine dysregulation and low-grade chronic inflammation, alterations that are linked to the development of obesity-related metabolic and cardiovascular complications. Moreover, several studies in animal models have investigated the role of MR antagonists (MRAs) in preventing the metabolic alterations observed in obesity. In the present review we will focus on the potential mechanisms by which MR activation can contribute to adipose tissue dysfunction in obesity and on the possible beneficial effects of MRAs in this setting.

The Mineralocorticoid Receptor Functions as a Key Glucose Regulator in the Skeletal Muscle of Zebrafish

Glucocorticoids (GCs) are essential for maintaining energy homeostasis as part of the adaptive stress response. Most work to date has characterized the metabolic role of GCs via the activation of the glucocorticoid receptor (nr3c1; GR), which is activated under high GC conditions. However, GCs also bind to the mineralocorticoid receptor (nr3c2; MR), a high-affinity corticosteroid receptor active under basal GC conditions. Despite the expression of MR in skeletal muscles, almost nothing is known about its physiological role. Here we tested the hypothesis that the MR promotes anabolic processes during resting cortisol levels and curtails the catabolic actions of the GR during high (stressed) levels of cortisol. To determine the effect of MR, a zebrafish line with a ubiquitous MR knockout (MRca402/ca402) was utilized. The GR was activated in the same group by chronically treating fish with exogenous cortisol. In the muscle, MR primarily promoted nutrient storage, and restricted energy substrate mobilization under resting conditions, whereas GR activation resulted in increased nutrient utilization. Interestingly, MR loss improved GR-driven metabolic flexibility, suggesting that the activation state of these receptors is a key determinant of skeletal muscle ability to switch fuel sources. To determine if the anabolism-promoting nature of MR was due to an interaction with insulin, fish were co-injected with insulin and the fluorescent glucose analogue 2-NBDG. A loss of MR abolished insulin-stimulated glucose uptake in the skeletal muscle. Taken together, we postulate that MR acts as a key modulator of glucose metabolism in the musculature during basal and stress conditions.

Efficacy and safety of finerenone for treatment of diabetic kidney disease: current knowledge and future perspective

INTRODUCTION

Diabetic kidney disease (DKD) represents a leading cause of morbidity and mortality in subjects with diabetes and develops in more than one third of diabetic patients. Steroidal mineralocorticoid receptor antagonists (MRAs - eplerenone and spironolactone) reduce mortality in patients with heart failure with reduced ejection fraction (HFrEF). However, in clinical practice the use of steroidal MRAs is limited by the significant risk of hyperkalaemia, especially in patients with impaired renal function. Finerenone, a novel nonsteroidal MRA, shows a higher selectivity and binding affinity for mineralocorticoid receptor (MR) compared to steroidal MRAs and has been shown to reduce chronic kidney disease (CKD) progression and cardiovascular mortality in patients with CKD and T2DM.

AREAS COVERED

This review summarizes the current evidence on efficacy and safety of finerenone in the treatment of patients with CKD and T2DM, and discusses its mechanisms of action investigated in preclinical studies.

EXPERT OPINION

Pharmacological properties of finerenone and its unique tissue distribution are responsible for a lower risk of hyperkalaemia. Therefore, finerenone represents a valuable therapeutic tool in patients with CKD/diabetic kidney disease (DKD). Recent studies have shown that finerenone delays the progression of CKD and reduce cardiovascular events in patients with DKD, highlighting its safety and efficacy in this high-risk population.

Low-dose spironolactone ameliorates adipose tissue inflammation and apoptosis in letrozole-induced PCOS rat model

BACKGROUND OF STUDY

Globally, many reproductive aged women are affected by polycystic ovarian syndrome (PCOS), which is a common endocrine and metabolic disorder that is linked with adipose dysfunction and chronic low-grade inflammation. Spironolactone (SPL), a mineralocorticoid receptor blocker has been documented as a metabolic modulator. However, its immunomodulatory effect in PCOS is unknown. Therefore, the present study hypothesized that SPL would ameliorate adipose dysfunction and inflammation in experimental PCOS animals.

MATERIALS AND METHODS

Female Wistar rats that were 8 weeks old were allocated into three groups. Group 1 received vehicle (distilled water; p.o.), group 2 received letrozole (1 mg/kg; p.o.) and group 3 received letrozole plus SPL (0.25 mg/kg, p.o.). The administration was performed once daily for 21 days.

RESULTS

The experimental PCOS animals showed insulin resistance, hyperinsulinemia and hyperandrogenism as well as oxidative stress and elevated inflammatory biomarkers (NF-kB/TNF-/IL-6) as well as a significant decrease in triglycerides, total cholesterol, free fatty acids, GSH and G6PD in the adipose tissue of PCOS animals. In addition, immunohistochemical assessment of adipose tissue showed significant expression of BAX and inflammasome, indicating apoptosis and inflammation compared to control animals. Nevertheless, administration of SPL attenuated these perturbations.

CONCLUSION

Altogether, the present study suggests that low-dose spironolactone confers protection against adipose dysfunction in experimental PCOS animals by attenuating inflammation, oxidative stress and cellular apoptosis.

Targeting mineralocorticoid receptors in diet-induced hepatic steatosis and insulin resistance

Mineralocorticoid receptor (MR) activation plays an important role in hepatic insulin resistance. However, the precise mechanisms by which MR activation promotes hepatic insulin resistance remains unclear. Therefore, we sought to investigate the roles and mechanisms by which MR activation promotes Western diet (WD)-induced hepatic steatosis and insulin resistance. Six-week-old C57BL6J mice were fed either mouse chow or a WD, high in saturated fat and refined carbohydrates, with or without the MR antagonist spironolactone (1 mg/kg/day) for 16 wk. WD feeding resulted in systemic insulin resistance at 8 and 16 wk. WD also induced impaired hepatic insulin metabolic signaling via phosphoinositide 3-kinases/protein kinase B pathways, which was associated with increased hepatic CD36, fatty acid transport proteins, fatty acid-binding protein-1, and hepatic steatosis. Meanwhile, consumption of a WD-induced hepatic mitochondria dysfunction, oxidative stress, and inflammatory responses. These abnormalities occurring in response to WD feeding were blunted with spironolactone treatment. Moreover, spironolactone promoted white adipose tissue browning and hepatic glucose transporter type 4 expression. These data suggest that enhanced hepatic MR signaling mediates diet-induced hepatic steatosis and dysregulation of adipose tissue browning, and subsequent hepatic mitochondria dysfunction, oxidative stress, inflammation, as well as hepatic insulin resistance.

Primary aldosteronism and obstructive sleep apnea: What do we know thus far?

Both primary aldosteronism and obstructive sleep apnea are well-known causes of hypertension and contribute to increased cardiovascular morbidity and mortality independently. However, the relationship between these two entities remains unclear, with studies demonstrating contradictory results. This review aims to collate and put into perspective current available research regarding the association between primary aldosteronism and obstructive sleep apnea. The relationship between these two entities, clinical characteristics, clinical implications, outcomes of treatment, potential causal links and mechanisms are hereby presented.

Nonsteroidal mineralcorticoid receptor antagonists: Novel therapeutic implication in the management of patients with type 2 diabetes

Growing evidencehas described a correlation between aldosterone, obesity, and insulin resistance, suggesting that adipocyte-related factors and mineralocorticoid receptor (MR) overactivation may alter aldosterone secretion, potentially leading to obesity and glucose intolerance. Preclinical studies showed that pharmacological antagonism of MR prevents white adipose tissue dysfunction(s) and expansion, activates brown adipose tissue, and improves glucose tolerance. The clinical use of nonsteroidal MR antagonists has been shown to reduce the risk of diabetic kidney disease progression and cardiovascular events in patients with diabetes. This review aims to summarize the effects of pharmacological MR blockade on obesity and its associated metabolic comorbidities, with a particular focus on the therapeutic implications of nonsteroidal MR antagonists in the management of patients with diabetes.

Generalized and tissue specific glucocorticoid resistance

Glucocorticoids (GCs) are steroid hormones that influence several physiologic functions and are among the most frequently prescribed drugs worldwide. Resistance to GCs has been observed in the context of the familial generalized GC resistance (Chrousos' syndrome) or tissue specific GC resistance in chronic inflammatory states. In this review, we have summarized the major factors that influence individual glucocorticoid sensitivity/resistance. The fine-tuning of GC action is determined in a tissue-specific fashion that includes the combination of different GC receptor promoters, translation initiation sites, splice isoforms, interacting proteins, post-translational modifications, and alternative mechanisms of signal transduction.

Mineralocorticoid receptors in the pathogenesis of insulin resistance and related disorders: from basic studies to clinical disease

Aldosterone is a steroid hormone that regulates blood pressure and cardiovascular function by acting on renal and vascular mineralocorticoid receptors (MRs) to promote sodium retention and modulate endothelial function. Indeed, MRs are expressed in endothelial cells, vascular smooth muscle cells, adipocytes, immune cells, skeletal muscle cells, and cardiomyocytes. Excessive aldosterone and associated MR activation impair insulin secretion, insulin metabolic signaling to promote development of diabetes, and the related cardiometabolic syndrome. These adverse effects of aldosterone are mediated, in part, via increased inflammation, oxidative stress, dyslipidemia, and ectopic fat deposition. Therefore, inhibition of MR activation may have a beneficial effect in prevention of impaired insulin metabolic signaling, type 2 diabetes, and cardiometabolic disorders. This review highlights findings from the recent surge in research regarding MR-related cardiometabolic disorders as well as our contemporary understanding of the detrimental effects of excess MR activation on insulin metabolic signaling.

A blubber gene expression index for evaluating stress in marine mammals

Evaluating the impacts of anthropogenic disturbance on free-ranging marine mammal populations, many of which are in decline, requires robust diagnostic markers of physiological stress and health. However, circulating levels of canonical 'stress hormones' such as glucocorticoids, which are commonly used to evaluate animal health, do not capture the complexity of species-specific responses and cannot be easily measured in large, fully aquatic marine mammals. Alternatively, expression of stress-responsive genes in hormone target tissues such as blubber, the specialized subcutaneous adipose tissue that can be manually or remotely sampled from many marine mammals, may be a more informative and sensitive indicator of recent (within 24 h) exposure to stressors. We previously identified genes that were upregulated in the inner blubber of juvenile northern elephant seals during experimental stimulation of the hypothalamic-pituitary-adrenal axis. In this study, we measured baseline expression levels of a subset of these genes in inner blubber of unmanipulated juvenile elephant seals of varying physiological states and correlated them with other stress markers (body condition index, corticosteroid and thyroid hormone levels). Expression of 10 genes, including those associated with lipid metabolism (ACSL1, HMGCS2, CDO1), redox homeostasis (GPX3), adipokine signaling (ADIPOQ), lipid droplet formation (PLIN1, CIDEA) and adipogenesis (DKK1, AZGP1, TGFBI), was described by three principal components and was associated with cortisol and thyroid hormone levels. Significantly, baseline gene expression levels were predictive of circulating hormone levels, suggesting that these markers may be potential indicators of exposure to stressors in marine mammal species that are inaccessible for blood sampling. A similar approach may be used to identify species-specific stress markers in other tissues that can be sampled by remote biopsy dart from free-ranging marine mammals, such as outer blubber and skin.

The role of aldosterone inhibitors in cardiac ischemia-reperfusion injury

Myocardial ischaemia-reperfusion (I/R) injury is a well-known term for exacerbation of cellular destruction and dysfunction after the restoration of blood flow to a previously ischaemic heart. A vast number of studies that have demonstrated that the role of mineralocorticoids in cardiovascular diseases is based on the use of pharmacological mineralocorticoid receptor (MR) antagonists. This review paper aimed to summarize current knowledge on the effects of MR antagonists on myocardial I/R injury as well as postinfarction remodeling. Animal models, predominantly the Langendorff technique and left anterior descending coronary artery occlusion, have confirmed the potency of MR antagonists as preconditioning and postconditioning agents in limiting infarct size and postinfarction remodeling. Several preclinical studies in rodents have established and proved possible mechanisms of cardioprotection by MR antagonists, such as reduction of oxidative stress, reduction of inflammation, and apoptosis, therefore limiting the infarct zone. However, the results of some clinical trials are inconsistent, since they reported no benefit of MR antagonists in acute myocardial infarction. Due to this, further studies and the results of ongoing clinical trials regarding MR antagonist administration in patients with acute myocardial infarction are being awaited with great interest.

Four cypermethrin isomers induced stereoselective metabolism in H295R cells

Cypermethrin (CP) is widely used for controlling agricultural and indoor vermin. Previous studies have reported the stereoselective difference of CP in biological activities. However, little is known about their potential mechanisms between metabolic phenotypes and endocrine-disrupting effects. Herein, nuclear magnetic resonance (NMR)-based metabolomics combining metabolite identification and pathway analysis were applied to evaluate the stereoselective metabolic cdisorders induced by CP isomers in human adrenocortical carcinoma cells (H295R) culture medium. Then, gene expression levels related to disturbed metabolic pathways were assessed to verify according to metabolic phenotypes. Metabolomics profiles showed that [(S)-cyano(3-phenoxyphenyl)methyl](1R,3R)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate [(1R,3R,αS)-CP] induced the most significant changes in metabolic phenotypes than did the other stereoisomers. There are 10 differential metabolites (isoleucine, valine, leucine, ethanol, alanine, acetate, aspartate, arginine, lactate, and glucose) as well as two significantly disturbed pathways, including "pyruvate metabolism" and "alanine, aspartate, and glutamate metabolism," that were confirmed in H295R cells culture medium of (1R,3R,αS)-CP compared with other stereoisomers. Polymerase chain reaction (PCR) array also confirmed the results of metabolomics. Our results can help to understand the potential mechanisms between the isomer selectivity in metabolic phenotypes and endocrine-disrupting effects. Data provided here not only lend authenticity to the cautions issued by the scientists and researchers but also offer a solution for the balance between environment and political regulations.

Beyond the heterodimer model for mineralocorticoid and glucocorticoid receptor interactions in nuclei and at DNA

Glucocorticoid (GR) and mineralocorticoid receptors (MR) are believed to classically bind DNA as homodimers or MR-GR heterodimers to influence gene regulation in response to pulsatile basal or stress-evoked glucocorticoid secretion. Pulsed corticosterone presentation reveals MR and GR co-occupy DNA only at the peaks of glucocorticoid oscillations, allowing interaction. GR DNA occupancy was pulsatile, while MR DNA occupancy was prolonged through the inter-pulse interval. In mouse mammary 3617 cells MR-GR interacted in the nucleus and at a chromatin-associated DNA binding site. Interactions occurred irrespective of ligand type and receptors formed complexes of higher order than heterodimers. We also detected MR-GR interactions ex-vivo in rat hippocampus. An expanded range of MR-GR interactions predicts structural allostery allowing a variety of transcriptional outcomes and is applicable to the multiple tissue types that co-express both receptors in the same cells whether activated by the same or different hormones.

Eplerenone Implantation Improved Adipose Dysfunction Averting RAAS Activation and Cell Division

Introduction: Mineralocorticoid receptor (MR) activation within adipose tissue, triggers inflammation and metabolic syndrome development. The pharmacological blockade of MR provides beneficial effects for adipose tissue. Our study evaluates the impact of eplerenone implantation upon obesity. Experimental approach: A group of mice with implanted placebo pellets were fed using two types of diet, a normal (ND) or a high fat (HFD) diet. Additionally, a group of mice fed HFD were implanted with an eplerenone pellet. Metabolic and biochemical parameters were assessed in each animal group. Adipocyte size and lipid accumulation were investigated in the liver and adipose tissue. We evaluated the components of renin-angiotensin-aldosterone system (RAAS) locally in adipose tissue. Key results: Eplerenone reduced HFD-induced body weight gain, fasting glucose levels, fat accumulation, HFD-induced adipocyte size and liver lipid accumulation and improved glucose tolerance. In the adipose tissue, HFD significantly increased the mRNA levels of the RAAS molecules relative to the ND group. Eplerenone lowered RAAS mRNA levels, components of lipid metabolism and markers of inflammation in HFD-fed animals. Conclusion: MR antagonism with eplerenone diminishes insulin resistance that is related to obesity partly via a reduction of RAAS activation, inflammatory progression and cytokines induction. This suggests that eplerenone should be further studied as a therapeutic option for obesity and overweight.

Focus on FKBP51: A molecular link between stress and metabolic disorders

BACKGROUND

Obesity, Type 2 diabetes (T2D) as well as stress-related disorders are rising public health threats and major burdens for modern society. Chronic stress and depression are highly associated with symptoms of the metabolic syndrome, but the molecular link is still not fully understood. Furthermore, therapies tackling these biological disorders are still lacking. The identification of shared molecular targets underlying both pathophysiologies may lead to the development of new treatments. The FK506 binding protein 51 (FKBP51) has recently been identified as a promising therapeutic target for stress-related psychiatric disorders and obesity-related metabolic outcomes.

SCOPE OF THE REVIEW

The aim of this review is to summarize current evidence of in vitro, preclinical, and human studies on the stress responsive protein FKBP51, focusing on its newly discovered role in metabolism. Also, we highlight the therapeutic potential of FKBP51 as a new treatment target for symptoms of the metabolic syndrome.

MAJOR CONCLUSIONS

We conclude the review by emphasizing missing knowledge gaps that remain and future research opportunities needed to implement FKBP51 as a drug target for stress-related obesity or T2D.

The renin-angiotensin-aldosterone system and its suppression

Chronic activation of the renin-angiotensin-aldosterone system (RAAS) promotes and perpetuates the syndromes of congestive heart failure, systemic hypertension, and chronic kidney disease. Excessive circulating and tissue angiotensin II (AngII) and aldosterone levels lead to a pro-fibrotic, -inflammatory, and -hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Understanding of the role of the RAAS in this abnormal pathologic remodeling has grown over the past few decades and numerous medical therapies aimed at suppressing the RAAS have been developed. Despite this, morbidity from these diseases remains high. Continued investigation into the complexities of the RAAS should help clinicians modulate (suppress or enhance) components of this system and improve quality of life and survival. This review focuses on updates in our understanding of the RAAS and the pathophysiology of AngII and aldosterone excess, reviewing what is known about its suppression in cardiovascular and renal diseases, especially in the cat and dog.

Minor role of mature adipocyte mineralocorticoid receptor in high-fat diet-induced obesity

Obesity is a major risk factor that contributes to the development of cardiovascular disease and type 2 diabetes. Mineralocorticoid receptor (MR) expression is increased in the adipose tissue of obese patients and several studies provide evidence that MR pharmacological antagonism improves glucose metabolism in genetic and diet-induced mouse models of obesity. In order to investigate whether the lack of adipocyte MR is sufficient to explain these beneficial metabolic effects, we generated a mouse model with inducible adipocyte-specific deletion of Nr3c2 gene encoding MR (adipo-MRKO). We observed a significant, yet not complete, reduction of Nr3c2 transcript and MR protein expression in subcutaneous and visceral adipose depots of adipo-MRKO mice. Notably, only mature adipocyte fraction lacks MR, whereas the stromal vascular fraction maintains normal MR expression in our mouse model. Adipo-MRKO mice fed a 45% high-fat diet for 14 weeks did not show any significant difference in body weight and fat mass compared to control littermates. Glucose and insulin tolerance tests revealed that mature adipocyte MR deficiency did not improve insulin sensitivity in response to a metabolic homeostatic challenge. Accordingly, no significant changes were observed in gene expression profile of adipogenic and inflammatory markers in adipose tissue of adipo-MRKO mice. Moreover, pharmacological MR antagonism in mature primary murine adipocytes, which differentiated ex vivo from WT mice, did not display any effect on adipokine expression. Taken together, these data demonstrate that the depletion of MR in mature adipocytes displays a minor role in diet-induced obesity and metabolic dysfunctions.

Antiviral activity of the mineralocorticoid receptor NR3C2 against Herpes simplex virus Type 1 (HSV-1) infection

Analysis of a genome-scale RNA interference screen of host factors affecting herpes simplex virus type 1 (HSV-1) revealed that the mineralocorticoid receptor (MR) inhibits HSV-1 replication. As a ligand-activated transcription factor the MR regulates sodium transport and blood pressure in the kidney in response to aldosterone, but roles have recently been elucidated for the MR in other cellular processes. Here, we show that the MR and other members of the mineralocorticoid signalling pathway including HSP90 and FKBP4, possess anti-viral activity against HSV-1 independent of their effect on sodium transport, as shown by sodium channel inhibitors. Expression of the MR is upregulated upon infection in an interferon (IFN) and viral transcriptional activator VP16-dependent fashion. Furthermore, the MR and VP16, together with the cellular co-activator Oct-1, transactivate the hormone response element (HRE) present in the MR promoter and those of its transcriptional targets. As the MR induces IFN expression, our data suggests the MR is involved in a positive feedback loop that controls HSV-1 infection.

Mineralocorticoid Receptor and Aldosterone-Related Biomarkers of End-Organ Damage in Cardiometabolic Disease

The mineralocorticoid receptor (MR) was first identified as a blood pressure regulator, modulating renal sodium handling in response to its principal ligand aldosterone. The mineralocorticoid receptor is also expressed in many tissues other than the kidney, such as adipose tissue, heart and vasculature. Recent studies have shown that MR plays a relevant role in the control of cardiovascular and metabolic function, as well as in adipogenesis. Dysregulation of aldosterone/MR signaling represents an important cause of disease as high plasma levels of aldosterone are associated with hypertension, obesity and increased cardiovascular risk. Aldosterone displays powerful vascular effects and acts as a potent pro-fibrotic agent in cardiovascular remodeling. Mineralocorticoid receptor activation regulates genes involved in vascular and cardiac fibrosis, calcification and inflammation. This review focuses on the role of novel potential biomarkers related to aldosterone/MR system that could help identify cardiovascular and metabolic detrimental conditions, as a result of altered MR activation. Specifically, we discuss: (1) how MR signaling regulates the number and function of different subpopulations of circulating and intra-tissue immune cells; (2) the role of aldosterone/MR system in mediating cardiometabolic diseases induced by obesity; and (3) the role of several MR downstream molecules as novel potential biomarkers of cardiometabolic diseases, end-organ damage and rehabilitation outcome.

Relationship Between Visceral Fat and Plasma Aldosterone Concentration in Patients With Primary Aldosteronism

Context

The involvement of visceral fat in aldosterone secretion has not been reported in patients with primary aldosteronism (PA). Patients with PA are complicated by metabolic syndrome more frequently than those without PA. An excess of visceral fat has been hypothesized to cause an elevation of aldosterone secretion in patients with PA.

Objectives

To clarify the role of visceral fat in the pathophysiology of PA, we investigated the correlation between plasma aldosterone concentration (PAC) and visceral fat parameters in patients with PA.

Design

This retrospective observational study comprised 131 patients diagnosed with PA between April 2007 and April 2017 at Sapporo City General Hospital. We divided participants into two PA subtypes, aldosterone-producing adenoma (APA; n = 47) and idiopathic hyperaldosteronism (IHA, n = 84), utilizing adrenal venous sampling. We analyzed the correlations of PAC with visceral fat percentage (VF%), visceral fat area (VFA), and subcutaneous fat area, by evaluating computed tomography studies in each subtype group.

Results

Patients with IHA showed a positive correlation of PAC with VF% (r = 0.377, P < 0.001) and VFA (r = 0.443, P < 0.001). The correlation was not evident in patients with APA.

Conclusions

This study revealed a relationship between visceral adipose tissue and aldosterone production only in patients with IHA.

Significant Association of Aldosterone and Liver Fat Among HIV-Infected Individuals With Metabolic Dysregulation

Objective

Fatty liver disease is increased among individuals with HIV. We sought to explore how aldosterone, a key hormone linked to insulin resistance and inflammation, relates to liver fat in the large population of individuals with HIV and metabolic abnormalities.

Methods

Forty-six individuals with HIV and increased waist circumference and dysglycemia were assessed for liver fat using proton magnetic resonance spectroscopy. Serum aldosterone level was obtained following strictly controlled posture conditions and a standardized sodium diet and was related to liver fat.

Results

Among the entire group [median (interquartile range) liver fat: 5% (3%, 12%) and homeostatic model assessment of insulin resistance: 1.74 (1.21, 2.83)], serum aldosterone significantly correlated with liver fat (r = 0.31; P = 0.049). Liver fat level was significantly higher in those with aldosterone above vs below the median [8% (3%, 20%) vs 4% (2%, 10%); P = 0.02]. In the presence of metabolic syndrome, individuals with aldosterone levels above vs below the median had markedly elevated liver fat values [14% (9%, 23%) vs 5% (3%, 12%); P = 0.005] and increased presence of fatty liver disease (FLD; 92% vs 50%; P = 0.02). Controlling for metabolic syndrome, hepatitis C virus, and alcohol use, aldosterone was a significant and independent predictor of liver fat (β estimate: 0.6038, P = 0.01; overall model r² = 0.41, P = 0.0005) and FLD (OR: 1.38, P = 0.02; overall model r² = 0.28, P = 0.002).

Conclusion

These data highlight a robust association between aldosterone and liver fat among individuals with HIV and metabolic dysregulation. Increased aldosterone may be a risk factor for liver fat accumulation among the population with HIV.

Enteric Microbiota⁻Gut⁻Brain Axis from the Perspective of Nuclear Receptors

Nuclear receptors (NRs) play a key role in regulating virtually all body functions, thus maintaining a healthy operating body with all its complex systems. Recently, gut microbiota emerged as major factor contributing to the health of the whole organism. Enteric bacteria have multiple ways to influence their host and several of them involve communication with the brain. Mounting evidence of cooperation between gut flora and NRs is already available. However, the full potential of the microbiota interconnection with NRs remains to be uncovered. Herewith, we present the current state of knowledge on the multifaceted roles of NRs in the enteric microbiota–gut–brain axis.

Aldosterone deficiency in mice burdens respiration and accentuates diet-induced hyperinsulinemia and obesity

Aldosterone synthase inhibitors (ASIs) should alleviate obesity-related cardiovascular and renal problems resulting partly from aldosterone excess, but their clinical use may have limitations. To improve knowledge for the use of ASIs, we investigated physiology in aldosterone synthase-knockout (ASKO) mice. On regular chow diet (CD), ASKO mice ate more and weighed less than WT mice, largely because they hyperventilated to eliminate acid as CO2. Replacing CD with high-fat diet (HFD) lessened the respiratory burden in ASKO mice, as did 12- to 15-hour fasting. The latter eliminated the genotype differences in respiratory workload and energy expenditure (EE). Thus, aldosterone deficiency burdened the organism more when the animals ate carbohydrate-rich chow than when they ate a HFD. Chronic HFD exposure further promoted hyperinsulinemia in ASKO mice that contributed to visceral fat accumulation accompanied by reduced lipolysis, thermogenic reprogramming, and the absence of weight-gain-related EE increases. Intracerebroventricular aldosterone supplementation in ASKO mice attenuated the HFD-induced hyperinsulinemia, but did not affect EE, suggesting that the presence of aldosterone increased the body's energetic efficiency, thus counteracting the EE-increasing effect of low insulin. ASIs may therefore cause acid-overload-induced respiratory burden and promote obesity. Their use in patients with preexisting renal and cardiopulmonary diseases might be contraindicated.

A model of neglect during postnatal life heightens obesity-induced hypertension and is linked to a greater metabolic compromise in female mice

.: Exposure to early life stress (ELS) is associated with behavioral-related alterations, increases in body mass index and higher systolic blood pressure in humans. Postnatal maternal separation and early weaning (MSEW) is a mouse model of neglect characterized by a long-term dysregulation of the neuroendocrine system.

OBJECTIVES

Given the contribution of adrenal-derived hormones to the development of obesity, we hypothesized that exposure to MSEW could contribute to  the worsening of cardiometabolic function in response to chronic high-fat diet (HF) feeding by promoting adipose tissue expansion and insulin resistance.

SUBJECTS

MSEW was performed in C57BL/6 mice from postnatal days 2-16 and weaned at postnatal day 17. Undisturbed litters weaned at postnatal day 21 served as the control (C) group. At the weaning day, mice were placed on a low-fat diet (LF) or HF for 16 weeks.

RESULTS

When fed a LF, male and female mice exposed to MSEW display similar body weight but increased fat mass compared to controls. However, when fed a HF, only female MSEW mice display increased body weight, fat mass, and adipocyte hypertrophy compared with controls. Also, female MSEW mice display evidence of an early onset of cardiometabolic risk factors, including hyperinsulinemia, glucose intolerance, and hypercholesterolemia. Yet, both male and female MSEW mice fed a HF show increased blood pressure compared with controls.

CONCLUSIONS

This study shows that MSEW promotes a sex-specific dysregulation of the adipose tissue expansion and glucose homeostasis that precedes the development of obesity-induced hypertension.

New roles of aldosterone and mineralocorticoid receptors in cardiovascular disease: translational and sex-specific effects

Recent advances in the field of mineralocorticoid receptor (MR) and its ligand aldosterone expanded the role of this hormone and its receptor far beyond their initial function as a regulator of Na⁺ and K⁺ homeostasis in epithelial cells. The symposium "New Roles of Aldosterone and Mineralocorticoid Receptors in Cardiovascular Disease: Translational and Sex-Specific Effects" presented at the 38th World Congress of the International Union of Physiological Sciences (Rio de Janeiro, Brazil) highlighted the contribution of extrarenal MRs to cardiovascular disease. This symposium showcased how MRs expressed in endothelial, vascular smooth muscle, and immune cells plays a critical role in the development of vascular disease associated with aging, obesity, and chronic aldosterone stimulation and demonstrated that MR antagonism prevents the acute renal dysfunction and tubular injury induced by ischemia-reperfusion injury. It was also shown that the adipocyte-derived hormone leptin is a new direct regulator of aldosterone secretion and that leptin-mediated aldosterone production is a major contributor to obesity-associated hypertension in women. Sex differences in the role of aldosterone and of endothelial MR in the cardiovascular outcomes of obesity were highlighted. This review summarizes these important emerging concepts regarding the contribution of aldosterone and cell-specific MR to cardiovascular disease in male and female subjects and further supports sex-specific benefits of MR antagonist drugs to be tested in additional populations.

The role of mineralocorticoid receptor signaling in the cross-talk between adipose tissue and the vascular wall

Vascular dysfunction and impaired endothelial mediated relaxation are powerful underlying abnormalities in the pathogenesis of hypertension, coronary heart disease, and stroke. Obesity, type 2 diabetes mellitus, and other metabolic abnormalities are associated with activation of mineralocorticoid receptor (MRs) in the vasculature and adipose tissue. While MR signaling is involved in the normal physiological differentiation and maturation of adipocyte, enhanced activation of MRs also contributes to increase oxidative stress, release of pro-inflammatory adipokines, and dysregulation of adipocyte autophagy. This, in turn, increases the maladaptive expansion of subcutaneous, visceral and perivascular adipose tissue, resulting in systemic and cardiovascular (CV) insulin resistance and increased CV stiffness and impaired vascular and cardiac relaxation. This review summarizes the normal role of MR activation in adipose tissues and explores the mechanisms by which excessive MR activation mediates adipose tissue inflammation and vascular dysfunction. Potential preventative and therapeutic strategies directed in the prevention of MR activation and CV disease are also discussed.

Derangements in adrenergic-adipokine signalling establish a neurohormonal basis for obesity-related heart failure with a preserved ejection fraction

Among patients with heart failure and a preserved ejection (HFpEF), obesity is associated with a distinct phenotype that is characterized by adiposity-driven plasma volume expansion and cardiac overfilling, which is coupled with an impairment of ventricular distensibility. These pathophysiological abnormalities may be related to the increased actions of specific adipocyte-derived signalling molecules (aldosterone, neprilysin and leptin) that work in concert with increased renal sympathetic nerve traffic and activated beta₂ -adrenergic receptors to promote sodium retention, microvascular rarefaction, cardiac fibrosis and systemic inflammation. This interplay leads to striking activation of the mineralocorticoid receptor, possibly explaining why obese patients with heart failure are most likely to benefit from spironolactone and eplerenone in large-scale clinical trials. Additionally, adipocytes express and release neprilysin, which (by degrading endogenous natriuretic peptides) can further promote plasma volume expansion and cardiac fibrosis. Heightened neprilysin activity may explain the low circulating levels of natriuretic peptides in obesity, the accelerated breakdown of natriuretic peptides in HFpEF, and the cardiac decompression following neprilysin inhibition in HFpEF patients who are obese. Furthermore, as adipose tissue accumulates and becomes dysfunctional, its secretion of leptin promotes renal sodium retention, microvascular changes and fibrotic processes in the heart, and systemic inflammation; these effects may be mediated or potentiated by the activation of beta₂ -adrenergic receptors. These adrenergic-adipokine interactions provide a mechanistic framework for novel therapeutic strategies to alleviate the pathophysiological abnormalities of obesity-related HFpEF. Ongoing trials are well-positioned to test this hypothesis.

Fat-brain connections: Adipocyte glucocorticoid control of stress and metabolism

Glucocorticoids act via multiple mechanisms to mobilize energy for maintenance and restoration of homeostasis. In adipose tissue, glucocorticoids can promote lipolysis and facilitate adipocyte differentiation/growth, serving both energy-mobilizing and restorative processes during negative energy balance. Recent data suggest that adipose-dependent feedback may also be involved in regulation of stress responses. Adipocyte glucocorticoid receptor (GR) deletion causes increased HPA axis stress reactivity, due to a loss of negative feedback signals into the CNS. The fat-to-brain signal may be mediated by neuronal mechanisms, release of adipokines or increased lipolysis. The ability of adipose GRs to inhibit psychogenic as well as metabolic stress responses suggests that (1) feedback regulation of the HPA axis occurs across multiple bodily compartments, and (2) fat tissue integrates psychogenic stress signals. These studies support a link between stress biology and energy metabolism, a connection that has clear relevance for numerous disease states and their comorbidities.

Eplerenone prevented obesity-induced inflammasome activation and glucose intolerance

Obesity-associated activation of the renin-angiotensin-aldosterone system is implicated in the pathogenesis of insulin resistance; however, influences of mineralocorticoid receptor (MR) inhibition remain unclear. Therefore, we aimed to clarify the anti-inflammatory mechanisms of MR inhibition using eplerenone, a selective MR antagonist, in C57BL/6 mice fed a high-fat diet (HFD) for 12 weeks. Eplerenone prevented excessive body weight gain and fat accumulation, ameliorated glucose intolerance and insulin resistance and enhanced energy metabolism. In the epididymal white adipose tissue (eWAT), eplerenone prevented obesity-induced accumulation of F4/80⁺CD11c⁺CD206^--M1-adipose tissue macrophage (ATM) and reduction of F4/80⁺CD11c^-CD206⁺-M2-ATM. Interestingly, M1-macrophage exhibited lower expression levels of MR, compared with M2-macrophage, in the ATM of eWAT and in vitro-polarized bone marrow-derived macrophages (BMDM). Importantly, eplerenone and MR knockdown attenuated the increase in the expression levels of proIl1b, Il6 and Tnfa, in the eWAT and liver of HFD-fed mice and LPS-stimulated BMDM. Moreover, eplerenone suppressed IL1b secretion from eWAT of HFD-fed mice. To reveal the anti-inflammatory mechanism, we investigated the involvement of NLRP3-inflammasome activation, a key process of IL1b overproduction. Eplerenone suppressed the expression of the inflammasome components, Nlrp3 and Caspase1, in the eWAT and liver. Concerning the second triggering factors, ROS production and ATP- and nigericin-induced IL1b secretion were suppressed by eplerenone in the LPS-primed BMDM. These results indicate that eplerenone inhibited both the priming and triggering signals that promote NLRP3-inflammasome activation. Therefore, we consider MR to be a crucial target to prevent metabolic disorders by suppressing inflammasome-mediated chronic inflammation in the adipose tissue and liver under obese conditions.

The effect of treatment for sleep apnoea on determinants of blood pressure control

Our aim was to assess the effect of continuous positive airway pressure (CPAP) on the nocturnal evolution of peripheral chemosensitivity, renin–angiotensin–aldosterone system activity, sympathetic tone and endothelial biomarkers in obstructive sleep apnoea (OSA) patients with isolated nocturnal hypertension (INH) or day–night sustained hypertension (D-NSH).

In a crossover randomised trial, 32 OSA patients newly diagnosed with hypertension and without antihypertensive treatment were randomly assigned to 12 weeks of CPAP or sham CPAP. Peripheral chemosensitivity was evaluated before and after sleep using the hypoxic withdrawal test (%ΔVI).

At baseline, D-NSH patients showed higher %ΔVI before sleep and higher levels of aldosterone and diurnal catecholamines. CPAP only reduced the nocturnal increase of %ΔVI in INH patients (6.9%, 95% CI 1.0–12.8%; p=0.026). CPAP-induced change from baseline in %ΔVI after sleep was 7.5% (95% CI 2.6–12.2%, p=0.005) in the INH group and 5.7% (95% CI 2.2–9.3%, p=0.004) in the D-NSH group. In contrast, %ΔVI before sleep only decreased with CPAP in the D-NSH patients (3.0%, 95% CI 0.5–5.6%; p=0.023).

In conclusion, CPAP reduces the nocturnal increase of peripheral chemosensitivity experienced by INH patients and corrects the high daytime sensitivity of patients with D-NSH. Differences in response to CPAP between these patients can help better understand the mechanisms of perpetuation of hypertension in sleep apnoea.

Nuclear receptors in neural stem/progenitor cell homeostasis

In the central nervous system, embryonic and adult neural stem/progenitor cells (NSCs) generate the enormous variety and huge numbers of neuronal and glial cells that provide structural and functional support in the brain and spinal cord. Over the last decades, nuclear receptors and their natural ligands have emerged as critical regulators of NSC homeostasis during embryonic development and adult life. Furthermore, substantial progress has been achieved towards elucidating the molecular mechanisms of nuclear receptors action in proliferative and differentiation capacities of NSCs. Aberrant expression or function of nuclear receptors in NSCs also contributes to the pathogenesis of various nervous system diseases. Here, we review recent advances in our understanding of the regulatory roles of steroid, non-steroid, and orphan nuclear receptors in NSC fate decisions. These studies establish nuclear receptors as key therapeutic targets in brain diseases.

Crosstalk between KCNK3-Mediated Ion Current and Adrenergic Signaling Regulates Adipose Thermogenesis and Obesity

Adrenergic stimulation promotes lipid mobilization and oxidation in brown and beige adipocytes, where the harnessed energy is dissipated as heat in a process known as adaptive thermogenesis. The signaling cascades and energy-dissipating pathways that facilitate thermogenesis have been extensively described, yet little is known about the counterbalancing negative regulatory mechanisms. Here, we identify a two-pore-domain potassium channel, KCNK3, as a built-in rheostat negatively regulating thermogenesis. Kcnk3 is transcriptionally wired into the thermogenic program by PRDM16, a master regulator of thermogenesis. KCNK3 antagonizes norepinephrine-induced membrane depolarization by promoting potassium efflux in brown adipocytes. This limits calcium influx through voltage-dependent calcium channels and dampens adrenergic signaling, thereby attenuating lipolysis and thermogenic respiration. Adipose-specific Kcnk3 knockout mice display increased energy expenditure and are resistant to hypothermia and obesity. These findings uncover a critical K⁺-Ca²⁺-adrenergic signaling axis that acts to dampen thermogenesis, maintain tissue homeostasis, and reveal an electrophysiological regulatory mechanism of adipocyte function.

Impact of Adrenal Steroids on Regulation of Adipose Tissue

Corticosteroids are secreted by the adrenal glands and control the functions of adipose tissue via the activation of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR). In turn, adipocytes release a large variety of adipokines into the bloodstream, regulating the function of several organs and tissues, including the adrenal glands, hereby controlling corticosteroid production. In adipose tissue, the activation of the MR by glucocorticoids (GC) and aldosterone affects important processes such as adipocyte differentiation, oxidative stress, autophagic flux, adipokine expression as well as local production of GC through upregulation of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Notably, the proinflammatory responses induced by the MR are counteracted by activation of the GR, whose activity inhibits the expression of inflammatory adipokines. Both GR and MR are deeply involved in adipogenesis and adipose expansion; hence pharmacological blockade of these two receptors has proven effective against adipose tissue dysfunction in experimental models of obesity and metabolic syndrome (MetS), suggesting a potential use for MR and GR antagonists in these clinical settings. Importantly, obesity and Cushing's syndrome (CS) share metabolic similarities and are characterized by high levels of circulating corticosteroids, which in turn are able to deeply affect adipose tissue. In addition, pharmacological approaches aimed at reducing aldosterone and GC levels, by means of the inhibition of CYP11B2 (aldosterone synthase) or 11β-HSD1, represent alternative strategies to counter the detrimental effects of excessive levels of corticosteroids, which are often observed in obesity and, more general, in MetS. © 2017 American Physiological Society. Compr Physiol 7:1425-1447, 2017.

Effect of eplerenone in patients with heart failure and reduced ejection fraction: potential effect modification by abdominal obesity. Insight from the EMPHASIS-HF trial

AIMS

An excessive production of aldosterone influences outcome in patients with heart failure (HF) and in obese patients. Findings from laboratory studies suggest that chronic aldosterone blockade maybe more beneficial in abdominally obese HF-prone rats. In the current study, we investigated if the clinical response to a mineralocorticoid receptor antagonist in mildly symptomatic HF patients varied by abdominal obesity.

METHODS AND RESULTS

A total of 2587 NYHA class II, reduced ejection fraction HF (HFrEF) patients enrolled in the EMPHASIS-HF trial were randomly assigned to eplerenone and placebo. In this post hoc analysis, patients were categorized according to waist circumference (WC) (normal if WC < 102 cm in men and < 88 cm in women; abdominal obesity if WC ≥ 102 cm in men and ≥ 88 cm women). The potential statistical interaction between the treatment and WC was assessed on the primary endpoint of death from cardiovascular causes or hospitalization for HF and other secondary endpoints. Over a median follow-up of 21 months, a significant benefit of eplerenone for the primary outcome was noted in both normal [hazard ratio (HR) 0.77, 95% confidence interval (CI) 0.61-0.98, P = 0.03] and increased (HR 0.48, 95% CI 0.37-0.63, P < 0.0001) WC subgroups, but the latter patients appeared to receive greater benefit than patients with normal WC (P for interaction = 0.01). This suggests a significant quantitative (treatment effect varies in magnitude by subgroup, but is always in same direction) rather than a qualitative interaction (direction of the treatment effect varies by subgroup) between eplerenone and WC in the adjusted analysis. Mean doses of eplerenone, blood pressure and serum potassium changes and adverse events were similar between WC subgroups.

CONCLUSION

In EMPHASIS-HF, eplerenone improved outcomes in HFrEF patients with and without abdominal obesity, although the benefit appeared to be more pronounced among those with abdominal obesity. The findings are potentially hypothesis generating and need to be replicated in other HFrEF populations.

Steroidal and Novel Non-steroidal Mineralocorticoid Receptor Antagonists in Heart Failure and Cardiorenal Diseases: Comparison at Bench and Bedside

Characterization of mice with cell-specific deletion or overexpression of the mineralocorticoid receptor (MR) shed a new light on its role in health and disease. Pathophysiological MR activation contributes to a plethora of deleterious molecular mechanisms in the development of cardiorenal diseases like chronic kidney disease (CKD) and heart failure (HF). Accordingly, the available steroidal MR antagonists (MRAs) spironolactone (first generation MRA) and eplerenone (second generation MRA) have been shown to be effective in reducing cardiovascular (CV) mortality and morbidity in patients with chronic HF and a reduced left ventricular ejection fraction (HFrEF). However, they remain underutilized, in large part owing to the risk inducing severe adverse events including hyperkalemia and worsening of kidney function, particularly when given on top of inhibitors of the renin angiotensin system (RAS) to patients with concomitant kidney dysfunction. Novel, potent, and selective non-steroidal MRAs (third generation) were identified in drug discovery campaigns and a few entered clinical development recently. One of these is finerenone with different physicochemical, pharmacokinetics, and pharmacological properties in comparison with the steroidal MRAs. Available data from five clinical phase II trials with finerenone in more than 2,000 patients with HF and additional CKD and/or diabetes as well as in patients with diabetic kidney disease demonstrated that neither hyperkalemia nor reductions in kidney function were limiting factors to its use. Moreover, finerenone demonstrated a nominally improved outcome compared to eplerenone in a phase IIb trial with 1,066 patients with HFrEF and concomitant type 2 diabetes mellitus (T2DM) and/or CKD.

The adipose tissue and the involvement of the renin-angiotensin-aldosterone system in cardiometabolic syndrome

Cardiometabolic diseases are linked to a cluster of modifiable factors, including risk factors closely related to central adiposity. Chronic renin-angiotensin-aldosterone system (RAAS) activation has far-reaching effects on cardiometabolic risk and is a substantial contributor to this clinical condition. RAAS components are locally expressed in the vessels and adipose tissue. This review appoints RAAS, through the classical and the alternative view, as the main mediator of the cross-talk in cardiometabolic syndrome.

Body Mass Index Predicts 24-Hour Urinary Aldosterone Levels in Patients With Resistant Hypertension

Prospective studies indicate that hyperaldosteronism is found in 20% of patients with resistant hypertension. A small number of observational studies in normotensive and hypertensive patients suggest a correlation between aldosterone levels and obesity while others could not confirm these findings. The correlation between aldosterone levels and body mass index (BMI) in patients with resistant hypertension has not been previously investigated. Our objective was to determine whether BMI is positively correlated with plasma aldosterone concentration, plasma renin activity, aldosterone:renin ratio, and 24-hour urinary aldosterone in black and white patients. We performed a cross-sectional analysis of a large diverse cohort (n=2170) with resistant hypertension. The relationship between plasma aldosterone concentration, plasma renin activity, aldosterone:renin ratio, 24-hour urinary aldosterone, and BMI was investigated for the entire cohort, by sex and race (65.3% white, 40.3% men). We demonstrate that plasma aldosterone concentration and aldosterone:renin ratio were significantly correlated to BMI (P<0.0001) across the first 3 quartiles, but not from the 3rd to 4th quartile of BMI. Plasma renin activity was not correlated with BMI. Twenty-four-hour urinary aldosterone was positively correlated across all quartiles of BMI for the cohort (P<0.0001) and when analyzed by sex (men P<0.0001; women P=0.0013) and race (P<0.05), and stronger for men compared with women (r=0.19, P<0.001 versus r=0.05, P=0.431, P=0.028) regardless of race. In both black and white patients, aldosterone levels were positively correlated to increasing BMI, with the correlation being more pronounced in black and white men. These findings suggest that obesity, particularly the abdominal obesity typical of men, contributes to excess aldosterone in patients with resistant hypertension.

Adipocyte-Specific Mineralocorticoid Receptor Overexpression in Mice Is Associated With Metabolic Syndrome and Vascular Dysfunction: Role of Redox-Sensitive PKG-1 and Rho Kinase

Mineralocorticoid receptor (MR) expression is increased in adipose tissue from obese individuals and animals. We previously demonstrated that adipocyte-MR overexpression (Adipo-MROE) in mice is associated with metabolic changes. Whether adipocyte MR directly influences vascular function in these mice is unknown. We tested this hypothesis in resistant mesenteric arteries from Adipo-MROE mice using myography and in cultured adipocytes. Molecular mechanisms were probed in vessels/vascular smooth muscle cells and adipose tissue/adipocytes and focused on redox-sensitive pathways, Rho kinase activity, and protein kinase G type-1 (PKG-1) signaling. Adipo-MROE versus control-MR mice exhibited reduced vascular contractility, associated with increased generation of adipocyte-derived hydrogen peroxide, activation of vascular redox-sensitive PKG-1, and downregulation of Rho kinase activity. Associated with these vascular changes was increased elastin content in Adipo-MROE. Inhibition of PKG-1 with Rp-8-Br-PET-cGMPS normalized vascular contractility in Adipo-MROE. In the presence of adipocyte-conditioned culture medium, anticontractile effects of the adipose tissue were lost in Adipo-MROE mice but not in control-MR mice. In conclusion, adipocyte-MR upregulation leads to impaired contractility with preserved endothelial function and normal blood pressure. Increased elasticity may contribute to hypocontractility. We also identify functional cross talk between adipocyte MR and arteries and describe novel mechanisms involving redox-sensitive PKG-1 and Rho kinase. Our results suggest that adipose tissue from Adipo-MROE secrete vasoactive factors that preferentially influence vascular smooth muscle cells rather than endothelial cells. Our findings may be important in obesity/adiposity where adipocyte-MR expression/signaling is amplified and vascular risk increased.

Adipocytes, aldosterone and obesity-related hypertension

Understanding the mechanisms linking obesity with hypertension is important in the current obesity epidemic as it may improve therapeutic interventions. Plasma aldosterone levels are positively correlated with body mass index and weight loss in obese patients is reported to be accompanied by decreased aldosterone levels. This suggests a relationship between adipose tissue and the production/secretion of aldosterone. Aldosterone is synthesized principally by the adrenal glands, but its production may be regulated by many factors, including factors secreted by adipocytes. In addition, studies have reported local synthesis of aldosterone in extra-adrenal tissues, including adipose tissue. Experimental studies have highlighted a role for adipocyte-secreted aldosterone in the pathogenesis of obesity-related cardiovascular complications via the mineralocorticoid receptor. This review focuses on how aldosterone secretion may be influenced by adipose tissue and the importance of these mechanisms in the context of obesity-related hypertension.

Preventive and chronic mineralocorticoid receptor antagonism is highly beneficial in obese SHHF rats

BACKGROUND AND PURPOSE

Mineralocorticoid receptor (MR) activation contributes to heart failure (HF) progression. Its overactivity in obesity is thought to accelerate cardiac remodelling and HF development. Given that MR antagonists (MRA) are beneficial in chronic HF patients, we hypothesized that early MRA treatment may target obesity-related disorders and consequently delay the development of HF.

EXPERIMENTAL APPROACH

Twenty spontaneously hypertensive HF dyslipidaemic obese SHHF(cp/cp) rats and 18 non-dyslipidaemic lean SHHF(+/+) controls underwent regular monitoring for their metabolic and cardiovascular phenotypes with or without MRA treatment [eplerenone (eple), 100 mg∙kg(-1) ∙day(-1) ] from 1.5 to 12.5 months of age.

KEY RESULTS

Eleven months of eple treatment in obese rats (SHHF(cp/cp) eple) reduced the obesity-related metabolic disorders observed in untreated SHHF(cp/cp) rats by reducing weight gain, triglycerides and total cholesterol levels and by preserving adiponectinaemia. The MRA treatment predominantly preserved diastolic and systolic functions in obese rats by alleviating the eccentric cardiac hypertrophy observed in untreated SHHF(cp/cp) animals and preserving ejection fraction (70 ± 1 vs. 59 ± 1%). The MRA also improved survival independently of these pressure effects.

CONCLUSION AND IMPLICATIONS

Early chronic eple treatment resulted in a delay in cardiac remodelling and HF onset in both SHHF(+/+) and SHHF(cp/cp) rats, whereas SHHF(cp/cp) rats further benefited from the MRA treatment through a reduction in their obesity and dyslipidaemia. These findings suggest that preventive MRA therapy may provide greater benefits in obese patients with additional risk factors of developing cardiovascular complications.

The Role of Aldosterone in Obesity-Related Hypertension

Obese subjects often have hypertension and related cardiovascular and renal diseases, and this has become a serious worldwide health problem. In obese subjects, impaired renal-pressure natriuresis causes sodium retention, leading to the development of salt-sensitive hypertension. Physical compression of the kidneys by visceral fat and activation of the sympathetic nervous system, renin-angiotensin systems (RAS), and aldosterone/mineralocorticoid receptor (MR) system are involved in this mechanism. Obese subjects often exhibit hyperaldosteronism, with increased salt sensitivity of blood pressure (BP). Adipose tissue excretes aldosterone-releasing factors, thereby stimulating aldosterone secretion independently of the systemic RAS, and aldosterone/MR activation plays a key role in the development of hypertension and organ damage in obesity. In obese subjects, both salt sensitivity of BP, enhanced by obesity-related metabolic disorders including aldosterone excess, and increased dietary sodium intake are closely related to the incidence of hypertension. Some salt sensitivity-related gene variants affect the risk of obesity, and together with salt intake, its combination is possibly associated with the development of hypertension in obese subjects. With high salt levels common in modern diets, salt restriction and weight control are undoubtedly important. However, not only MR blockade but also new diagnostic modalities and therapies targeting and modifying genes that are related to salt sensitivity, obesity, or RAS regulation are expected to prevent obesity and obesity-related hypertension.

The K+ channel TASK1 modulates β-adrenergic response in brown adipose tissue through the mineralocorticoid receptor pathway

Brown adipose tissue (BAT) is essential for adaptive thermogenesis and dissipation of caloric excess through the activity of uncoupling protein (UCP)-1. BAT in humans is of great interest for the treatment of obesity and related diseases. In this study, the expression of Twik-related acid-sensitive K(+) channel (TASK)-1 [a pH-sensitive potassium channel encoded by the potassium channel, 2-pore domain, subfamily K, member 3 (Kcnk3) gene] correlated highly with Ucp1 expression in obese and cold-exposed mice. In addition, Task1-null mice, compared with their controls, became overweight, mainly because of an increase in white adipose tissue mass and BAT whitening. Task1(-/-)-mouse-derived brown adipocytes, compared with wild-type mouse-derived brown adipocytes, displayed an impaired β3-adrenergic receptor response that was characterized by a decrease in oxygen consumption, Ucp1 expression, and lipolysis. This phenotype was thought to be caused by an exacerbation of mineralocorticoid receptor (MR) signaling, given that it was mimicked by corticoids and reversed by an MR inhibitor. We concluded that the K(+) channel TASK1 controls the thermogenic activity in brown adipocytes through modulation of β-adrenergic receptor signaling.