Comparison of aldosterone synthesis in adrenal cells, effect of various AT1 receptor blockers with or without atrial natriuretic peptide

Obesity: the perfect storm for heart failure

Obesity condition causes morphological and functional alterations involving the cardiovascular system. These can represent the substrates for different cardiovascular diseases, such as atrial fibrillation, coronary artery disease, sudden cardiac death, and heart failure (HF) with both preserved ejection fraction (EF) and reduced EF. Different pathogenetic mechanisms may help to explain the association between obesity and HF including left ventricular remodelling and epicardial fat accumulation, endothelial dysfunction, and coronary microvascular dysfunction. Multi-imaging modalities are required for appropriate recognition of subclinical systolic dysfunction typically associated with obesity, with echocardiography being the most cost-effective technique. Therapeutic approach in patients with obesity and HF is challenging, particularly regarding patients with preserved EF in which few strategies with high level of evidence are available. Weight loss is of extreme importance in patients with obesity and HF, being a primary therapeutic intervention. Sodium-glucose co-transporter-2 inhibitors have been recently introduced as a novel tool in the management of HF patients. The present review aims at analysing the most recent studies supporting pathogenesis, diagnosis, and management in patients with obesity and HF.

Natriuretic Peptide-Based Novel Therapeutics: Long Journeys of Drug Developments Optimized for Disease States

Simple Summary

Natriuretic peptides are endogenous hormones produced in the heart and vascular endothelium, and they enable cardiorenal protective actions or bone growth via cGMP stimulation through their receptor guanylyl cyclase receptor A or B. To optimize the drug for each disease state, we must consider drug metabolism, delivery systems, and target receptor(s). This review summarizes attempts to develop novel natriuretic peptide-based therapeutics, including novel designer natriuretic peptides and oral drugs to enhance endogenous natriuretic peptides. We introduce some therapeutics that have been successful in clinical practice, as well as the prospective drug developments in the natriuretic peptide system for disease states.

Abstract

The field of natriuretic peptides (NPs) as an endocrine hormone has been developing since 1979. There are three peptides in humans: atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), which bind to the guanylyl cyclase-A (GC-A) receptor (also called natriuretic peptide receptor-A (NPR-A)), and C-type natriuretic peptide (CNP), which binds to the GC-B receptor (also called the NPR-B) and then synthesizes intracellular cGMP. GC-A receptor stimulation has natriuretic, vasodilatory, cardiorenal protective and anti-renin–angiotensin–aldosterone system actions, and GC-B receptor stimulation can suppress myocardial fibrosis and can activate bone growth before epiphyseal plate closure. These physiological effects are useful as therapeutics for some disease states, such as heart failure, hypertension, and dwarfism. To optimize the therapeutics for each disease state, we must consider drug metabolism, delivery systems, and target receptor(s). We review the cardiac NP system; new designer NPs, such as modified/combined NPs and modified peptides that can bind to not only NP receptors but receptors for other systems; and oral drugs that enhance endogenous NP activity. Finally, we discuss prospective drug discoveries and the development of novel NP therapeutics.

Aldosterone breakthrough from a pharmacological perspective

Aldosterone (Aldo) breakthrough is a well-known phenomenon that occurs in patients with long-term renin-angiotensin aldosterone system (RAAS) blockade using inhibitors of renin or angiotensin converting enzyme or angiotensin II type 1 receptor blockers. The blockade of the mineralocorticoid receptor (MR), an Aldo binding receptor, is effective in managing patients with resistant hypertension, defined as uncontrollable blood pressure despite the concurrent use of three antihypertensive drugs. In other words, MR inhibitors are not used as first-line antihypertensive drugs in most guidelines for hypertension management. Aldo breakthrough puts hypertensive patients at higher risk of cardiovascular disease and worsens future outcomes. This review discusses Aldo secretion and the mechanism of Aldo breakthrough, dependent or independent of the RAAS, with consideration of the pharmacological aspects of this phenomenon, as well as hypothetical views.

Characterization of the inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction: a hypothesis to explain influence of sex on the evolution and potential treatment of the disease

Accumulating evidence points to the existence of an inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction (HFpEF), which is characterized by biomarkers of inflammation, an expanded epicardial adipose tissue mass, microvascular endothelial dysfunction, normal-to-mildly increased left ventricular volumes and systolic blood pressures, and possibly, altered activity of adipocyte-associated inflammatory mediators. A broad range of adipogenic metabolic and systemic inflammatory disorders - e.g. obesity, diabetes and metabolic syndrome as well as rheumatoid arthritis and psoriasis - can cause this phenotype, independent of the presence of large vessel coronary artery disease. Interestingly, when compared with men, women are both at greater risk of and may suffer greater cardiac consequences from these systemic inflammatory and metabolic disorders. Women show disproportionate increases in left ventricular filling pressures following increases in central blood volume and have greater arterial stiffness than men. Additionally, they are particularly predisposed to epicardial and intramyocardial fat expansion and imbalances in adipocyte-associated proinflammatory mediators. The hormonal interrelationships seen in inflammatory-metabolic phenotype may explain why mineralocorticoid receptor antagonists and neprilysin inhibitors may be more effective in women than in men with HFpEF. Recognition of the inflammatory-metabolic phenotype may improve an understanding of the pathogenesis of HFpEF and enhance the ability to design clinical trials of interventions in this heterogeneous syndrome.

The Role of Natriuretic Peptides in the Regulation of Cardiac Tolerance to Ischemia/Reperfusion and Postinfarction Heart Remodeling

In the past 10 years, mortality from acute myocardial infarction has not decreased despite the widespread introduction of percutaneous coronary intervention. The reason for this situation is the absence in clinical practice of drugs capable of preventing reperfusion injury of the heart with high efficiency. In this regard, noteworthy natriuretic peptides (NPs) which have the infarct-limiting effect, prevent reperfusion cardiac injury, prevent adverse post-infarction remodeling of the heart. Atrial natriuretic peptide does not have the infarct-reducing effect in rats with alloxan-induced diabetes mellitus. NPs have the anti-apoptotic and anti-inflammatory effects. There is indirect evidence that NPs inhibit pyroptosis and autophagy. Published data indicate that NPs inhibit reactive oxygen species production in cardiomyocytes, aorta, heart, kidney and the endothelial cells. NPs can suppress aldosterone, angiotensin II, endothelin-1 synthesize and secretion. NPs inhibit the effects aldosterone, angiotensin II on the post-receptor level through intracellular signaling events. NPs activate guanylyl cyclase, protein kinase G and protein kinase A, and reduce phosphodiesterase 3 activity. NO-synthase and soluble guanylyl cyclase are involved in the cardioprotective effect of NPs. The cardioprotective effect of natriuretic peptides is mediated via activation of kinases (AMPK, PKC, PI3 K, ERK1/2, p70s6 k, Akt) and inhibition of glycogen synthase kinase 3β. The cardioprotective effect of NPs is mediated via sarcolemmal K_ATP channel and mitochondrial K_ATP channel opening. The cardioprotective effect of brain natriuretic peptide is mediated via MPT pore closing. The anti-fibrotic effect of NPs may be mediated through inhibition TGF-β1 expression. Natriuretic peptides can inhibit NF-κB activity and activate GATA. Hemeoxygenase-1 and peroxisome proliferator-activated receptor γ may be involved in the infarct-reducing effect of NPs. NPs exhibit the infarct-limiting effect in patients with acute myocardial infarction. NPs prevent post-infarction remodeling of the heart. To finally resolve the question of the feasibility of using NPs in AMI, a multicenter, randomized, blind, placebo-controlled study is needed to assess the effect of NPs on the mortality of patients after AMI.

Soluble neprilysin: A versatile biomarker for heart failure, cardiovascular diseases and diabetic complications-A systematic review

The potential role of soluble neprilysin (sNEP) as a biomarker has been poorly documented. Hence, the present systematic review emphasizes to explore sNEP as an emerging biomarker for heart failure (HF), cardiovascular diseases, diabetic kidney diseases, and so on. A systematic review was performed using an online database search in PubMed, Science Direct, Scopus, and Cochrane Library. Articles reporting biomarker's performance to diagnose various diseases in human participants were included. The results of the search outcome were 4723 articles. Based on the inclusion criteria of the systematic review, finally, 12 articles fulfilled the selection criteria. In these studies, 8 cohort study, 2 cross-sectional study, 1 case-control, and 1 prospective cohort study were identified. All these studies clearly suggested sNEP as a potential biomarker for diagnosis of various diseases (HF, cardiovascular diseases, diabetic kidney diseases, metabolic syndrome). sNEP may be a potential biomarker for HF, cardiovascular diseases, diabetic kidney disease, and so on.

Obesity-Associated Heart Failure as a Theoretical Target for Treatment With Mineralocorticoid Receptor Antagonists

Importance

Despite their clinical benefits, mineralocorticoid receptor antagonists are greatly underprescribed by most practitioners who treat patients with chronic heart failure. A novel approach to encouraging the use of these drugs is to enhance awareness about the intimate link between aldosterone and obesity.

Observations

There is a strong association between abdominal obesity and circulating levels of aldosterone, and markers of abdominal obesity identify patients most likely to benefit from mineralocorticoid receptor antagonism. In a trial of patients with heart failure and a reduced ejection fraction, patients with an increased waist circumference exhibited an approximately 50% reduction in the risk of a primary end point. The magnitude of benefit was more than twice as great in patients with abdominal obesity than in those with a normal waist circumference, and patients with abdominal obesity tolerated treatment better than nonobese patients. Similarly, in a trial of patients with heart failure and a preserved ejection fraction, those who were most likely to have abdominal obesity (identified by their level of natriuretic peptides) were most likely to demonstrate a benefit of treatment with spironolactone, exhibiting an approximately 80% reduction in the risk of a primary end point (based on a small number of events).

Conclusions and Relevance

Although these analyses are post hoc, their concordance and strong biological foundation suggests that abdominal obesity may identify patients who respond most favorably to mineralocorticoid receptor antagonism. Given the easy availability of its measurement, targeting patients with an increased waist circumference could enhance the adoption of these important drugs for the treatment of chronic heart failure in clinical practice.

Impact of Obesity on Volume Status in Patients With Ambulatory Chronic Heart Failure

BACKGROUND

Fluid overload is common in heart failure (HF) and obesity; however, the relationship between the extent of intravascular volume expansion and indices such as body mass index (BMI) in obese and non-obese patients with HF has not been defined to address the issue of a HF obesity phenotype.

METHODS

Total blood volume (TBV) was measured clinically using a radiolabeled albumin indicator-dilution technique in patients with predominately class III ambulatory chronic HF (N=66). Obesity was defined by BMI ≥30 kg/m².

RESULTS

Markedly increased intravascular volume expansion (defined by TBV expansion >+25% above normal) was highly prevalent in the obese (53%) compared to non-obese patients with HF (29%, P = .04) driven by plasma volume expansion. TBV was correlated with excess body weight and BMI (both P < .01). Also, cardiac index was higher, systemic vascular resistance lower, and left ventricular filling pressures comparable in obese compared with non-obese patients.

CONCLUSIONS

Quantitative assessment of intravascular volume demonstrates for the first time that severe (not mild or moderate) volume expansion is highly common in obese patients with ambulatory chronic HF. This supports an evolving concept of an obesity-specific HF phenotype. Further study is needed to understand the mechanisms controlling volume regulation and the potential compensatory or detrimental impact on outcomes in obesity and HF.

The place of ARBs in heart failure therapy: is aldosterone suppression the key?

Since the launch of the first orally available angiotensin II (AngII) type 1 receptor (AT₁R) blocker (ARB) losartan (Cozaar) in the late 1990s, the class of ARBs (or ‘sartans’, short for Angiotensin-RecepTor-ANtagonistS) quickly expanded to include candesartan, eprosartan, irbesartan, valsartan, telmisartan, and olmesartan. All ARBs have high affinity for the AT₁ receptor, expressed in various tissues, including smooth muscle cells, heart, kidney, and brain. Since activation of AT₁R, the target of these drugs, leads, among other effects, to vascular smooth muscle cell growth, proliferation and contraction, activation of fibroblasts, cardiac hypertrophy, aldosterone secretion from the adrenal cortex, thirst-fluid intake (hypervolemia), etc., the ARBs are nowadays one of the most useful cardiovascular drug classes used in clinical practice. However, significant differences in their pharmacological and clinical properties exist that may favor use of particular agents over others within the class, and, in fact, two of these drugs, candesartan and valsartan, continuously appear to distinguish themselves from the rest of the ‘pack’ in recent clinical trials. The reason(s) for the potential superiority of these two agents within the ARB class are currently unclear but under intense investigation. The present short review gives an overview of the clinical properties of the ARBs currently approved by the United States Food and Drug Administration, with a particular focus on candesartan and valsartan and the areas where these two drugs seem to have a therapeutic edge. In the second part of our review, we outline recent data from our laboratory (mainly) on the molecular effects of the ARB drugs on aldosterone production and on circulating aldosterone levels, which may underlie (at least in part) the apparent clinical superiority of candesartan (and valsartan) over most other ARBs currently in clinical use.

Obesity-Related Heart Failure With a Preserved Ejection Fraction: The Mechanistic Rationale for Combining Inhibitors of Aldosterone, Neprilysin, and Sodium-Glucose Cotransporter-2

Obesity-related heart failure with a preserved ejection fraction (HFpEF) is an important phenotype prevalent in the community, especially in people with metabolic disorders (e.g., dyslipidemia, diabetes). These individuals exhibit a marked expansion of plasma volume, but ventricular distensibility is limited, most likely as a result of cardiac microvascular rarefaction acting in concert with myocardial and pericardial fibrosis. Consequently, the increase in plasma volume causes a disproportionate increase in cardiac filling pressures, leading to heart failure, even though systolic ejection is not impaired. The features of this syndrome appear to be related (in part) to the overproduction of adipocyte-derived cell-signaling molecules, including aldosterone and neprilysin. The resulting sodium retention and plasma volume expansion is exacerbated by their mutual actions to promote cardiac and systemic inflammation and fibrosis. Inhibitors of aldosterone, neprilysin, and the sodium-glucose transporter-2 (SGLT2) can ameliorate the plasma volume expansion and pro-inflammatory and profibrotic pathways, potentially opposing the action of diverse adipocytokines. All 3 classes of drugs can reduce the quantity of visceral adipose tissue and ameliorate its abnormal biological properties. This mechanistic framework is supported by the results of large-scale randomized trials with mineralocorticoid receptor antagonists and SGLT2 inhibitors and is being further tested in an ongoing large-scale trial of neprilysin inhibition. The promise of using mineralocorticoid receptor antagonists, neprilysin inhibitors, and SGLT2 inhibitors (alone or in combination) in the management of obesity-related HFpEF suggests that physicians might finally have a phenotype of HFpEF that they can understand and treat.

Olmesartan attenuates pressure-overload- or post-infarction-induced cardiac remodeling in mice

Either angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor 1 blocker (ARB) attenuates cardiac remodeling. However, the overall molecular modulation of the reversing remodeling process in response to the ACEI or ARB treatment is not yet well determined. In this study, we examined whether gene expressions are modulated by ACEI (temocapril), ARB (olmesartan) or both in a murine model with transverse aortic constriction (TAC) and confirm whether periostin is a target gene of olmesartan in mice with myocardial infarction (MI). We detected 109 genes that were significantly up-regulated in TAC mice and a majority of these were down-regulated in response to temocapril, olmesartan or their combination which significantly attenuated cardiac remodeling at one or four weeks. Real-time RT-PCR demonstrated that olmesartan, temocapril or their combination down-regulated the expression of periostin. In MI mice treated with olmesartan for 4 weeks, the left ventricular end-diastolic and systolic dimensions measured with echocardiography were lower, whereas maximum rate of rise and fall rate of LV pressure (±dp/dt max) were greater, and Azan-staining cardiac fibrotic area was smaller. Furthermore, periostin was upregulated in response to MI, whereas olmesartan blocked this upregulation. Post-MI fibrosis was smaller in periostin knockout adult mice than in wildtype mice, while glycogen synthase kinase 3β was increased and cyclin D1 was decreased in periostin knockout mice. These findings indicate that periostin is a target gene of ARB and olmesartan reverses cardiac remodeling at least partially through the downregulation of periostin.

The angiotensin II type 1 receptor-neprilysin inhibitor LCZ696 blocked aldosterone synthesis in a human adrenocortical cell line

A recent clinical study indicated that an angiotensin II (Ang II) type 1 (AT₁) receptor-neprilysin inhibitor (ARNi) designated LCZ696 (sacubitril/valsartan, as combined sodium complex) was superior to enalapril at reducing the risks of death and hospitalization due to heart failure. Therefore, we investigated the possible mechanisms of the beneficial effect of LCZ696, in which the inhibition of neprilysin enhances atrial natriuretic peptide (NP) or brain NP (ANP or BNP)-evoked signals that can block Ang II/AT₁ receptor-induced aldosterone (Ald) synthesis in human adrenocortical cells. The binding affinity of valsartan+LBQ657 (active moiety of sacubitril) to the AT₁ receptor was greater than that of valsartan alone in an AT₁ receptor-expressing human embryonic kidney cell-based assay. There was no difference in the dissociation from the AT₁ receptor between valsartan+LBQ657 and valsartan alone. In Ang II-sensitized human adrenocortical cells, ANP or BNP alone, but not LBQ657 or valsartan alone, significantly decreased Ald synthesis. The level of suppression of Ald synthesis by ANP or BNP with LBQ657 was greater than that by ANP or BNP without LBQ657. The suppression of ANP was blocked by inhibitors of regulator of G-protein signaling proteins and cyclic GMP-dependent protein kinase. The inhibition of neprilysin did not change the mRNA levels of the AT₁ receptor, ANP receptor A, regulator of G-protein signaling protein, renin or 3β-hydroxysteroid dehydrogenases. In conclusion, the inhibition of neprilysin by LBQ657 enhances the NP-evoked signals that can block Ang II/AT₁ receptor-induced Ald synthesis in human adrenocortical cells.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

The potential role of atrial natriuretic peptide in the effects of Angiotensin-(1-7) in a chronic atrial tachycardia canine model

Objective:

The objective of this article is to investigate the possible role of atrial natriuretic peptide (ANP) in Angiotensin-(1–7) (Ang-(1–7)) signaling pathway on atrial electrical and structural remodeling in a chronic rapid atrial pacing canine model.

Methods:

Twenty-four dogs were randomly assigned to four groups: a sham group, paced control group, a paced + Ang-(1–7) group and a paced + Ang-(1–7) + A-71915 group. Atrial rapid pacing (ARP) at 600 bpm was maintained for 14 days except in the animals from the sham group. During the pacing, Ang-(1–7) (6 μg•kg-1•h-1) or Ang-(1–7) (6 μg•kg-1•h-1) + A-71915 (ANP receptor antagonist, 0.30 μg•kg-1•h-1) were given intravenously, respectively. After pacing, it was measured that electrophysiological parameters including atrial effective refractory periods (ERPs), inducibility and duration of atrial fibrillation (AF), I_CaL and I_Na changed, where I_CaL refers to voltage-dependent L-type Ca²⁺ current and I_Na refers to cardiac sodium current. Then, the fibrosis and the expression of Cav1.2, I_Nav1.5α subunit, TGF-β₁ and ANP in atria were assessed.

Results:

After ARP, compared with the sham group, the atrial ERPs at six sites in each dog were shortened with the increasing in inducibility and duration of AF in the paced control group. The density of I_CaL, I_Na and the expression of Cav1.2, I_Nav1.5α subunit mRNA were decreased. Atrial tissue from the paced dogs showed significant interstitial fibrosis. The expression of TGF-β₁ and ANP in mRNA and protein levels were increased. Compared with the paced control group, the shortening of atrial ERPs, and the increasing of inducibility and duration of AF induced by ARP were alleviated by Ang-(1–7) treatment (p < 0.05). The density of I_CaL and I_Na and the expression of Cav1.2 and I_Nav1.5α subunit mRNA were slightly decreased. Atrial tissue showed less interstitial fibrosis after Ang-(1–7) treatment. The increasing of ANP expression was improved by Ang-(1–7), while the increasing of TGF-β₁ expression was alleviated by Ang-(1–7) (p < 0.05). A-71915 treatment blocked the beneficial effects of Ang-(1–7) on the aforementioned electrophysiological parameters and atrial fibrosis. And A-71915 treatment blocked Ang-(1–7), improving the expression of TGF-β₁.

Conclusion:

Ang-(1–7) prevented atrial structural and electrical remodeling induced by ARP. Furthermore, Ang-(1–7) promoted ANP secretion, and ANP played a crucial role in the cardiac protection of the former.