Plasma concentrations of the novel peptide apelin are decreased in patients with chronic heart failure

The Metabolically Resistant Apelin-17 Analogue LIT01-196 Reduces Cardiac Dysfunction and Remodelling in Heart Failure After Myocardial Infarction

BACKGROUND

To protect patients after myocardial infarction (MI) and preserve cardiac function, the development of new therapeutics remains an important issue. Apelin, a neuro-vasoactive peptide, increases aqueous diuresis and cardiac contractility while reducing vascular resistance. However, its in vivo half-life is very short. We therefore developed a metabolically resistant apelin-17 analogue, LIT01-196 and investigated its effects on cardiac function and remodelling in a murine MI model.

METHODS

The selectivity of LIT01-196 toward the apelin receptor was checked in vitro. Its in vivo half-life was assessed in male Swiss mice using radioimmunoassay. After permanent coronary artery ligation to induce MI, mice received subcutaneous administration of LIT01-196 (MI + LIT01-196, 9 mg/kg/d) or saline (MI + vehicle) for 4 weeks. Left ventricular (LV) function was assessed using echocardiography and Millar (Houston, TX) catheter, vascular density using immunofluorescence, and cardiac fibrosis using Sirius red staining. Real-time quantitative PCR was used to measure mRNA expression of heart failure (HF) fibrosis biomarkers and sarco/endoplasmic reticulum Ca2+-ATPase-2.

RESULTS

The in vivo half-life of LIT01-196, a specific and selective apelin receptor agonist, was 2.5 hours. MI + LIT01-196 showed significantly improved LV function, reduced HF biomarkers, and enhanced cardiac contractility and sarco/endoplasmic reticulum Ca2+-ATPase-2 expression compared with MI + vehicle. LIT01-196 treatment almost doubled cardiac vascular density and maintained LV wall thickness post MI. It also significantly reduced cardiac fibrosis and fibrosis biomarkers, without decreasing arterial blood pressure.

CONCLUSIONS

Chronic LIT01-196 treatment post MI improves LV function without decreasing blood pressure, increases cardiac vascular density, and reduces cardiac remodelling. This suggests that apelin receptor activation by LIT01-196 might constitute an original pharmacological approach for HF treatment after MI.

The vascular footprint in cardiac homeostasis and hypertensive heart disease-A link between apelin receptor, vascular endothelial growth factor, and neuronal nitric oxide synthase

Recent studies have suggested a connection between disturbances of the apelin system and various cardiac pathologies, including hypertension, heart failure, and atherosclerosis. Vascular endothelial growth factor is crucial for cardiac homeostasis as a critical molecule in cardiac angiogenesis. Neuronal nitric oxide synthase is an essential enzyme producing nitric oxide, a key regulator of vascular tone. The present study aims to shed light upon the complex interactions between these three vital signaling molecules and examine their changes with the progression of hypertensive heart disease. We used two groups of spontaneously hypertensive rats and age-matched Wistar rats as controls. The expression of the apelin receptor, vascular endothelial growth factor, and neuronal nitric oxide synthase were assessed immunohistochemically. We used capillary density and cross-sectional area of the cardiomyocytes as quantitative parameters of cardiac hypertrophy. Immunoreactivity of the molecules was more potent in both ventricles of spontaneously hypertensive rats compared with age-matched controls. However, capillary density was lower in both ventricles of the two age groups of spontaneously hypertensive rats compared with controls, and the difference was statistically significant. In addition, the cross-sectional area of the cardiomyocytes was higher in both ventricles of the two age groups of spontaneously hypertensive rats compared with controls, and the difference was statistically significant. Our study suggests a potential link between the apelin receptor, vascular endothelial growth factor, and neuronal nitric oxide synthase in cardiac homeostasis and the hypertensive myocardium. Nevertheless, further research is required to better comprehend these interactions and their potential therapeutic implications.

The significance of the apelinergic system in doxorubicin-induced cardiotoxicity

Cancer is the leading cause of death worldwide, and the number of cancer-related deaths is expected to increase. Common types of cancer include skin, breast, lung, prostate, and colorectal cancers. While clinical research has improved cancer therapies, these treatments often come with significant side effects such as chronic fatigue, hair loss, and nausea. In addition, cancer treatments can cause long-term cardiovascular complications. Doxorubicin (DOX) therapy is one example, which can lead to decreased left ventricle (LV) echocardiography (ECHO) parameters, increased oxidative stress in cellular level, and even cardiac fibrosis. The apelinergic system, specifically apelin and its receptor, together, has shown properties that could potentially protect the heart and mitigate the damages caused by DOX anti-cancer treatment. Studies have suggested that stimulating the apelinergic system may have therapeutic benefits for heart damage induced by DOX. Further research in chronic preclinical models is needed to confirm this hypothesis and understand the mechanism of action for the apelinergic system. This review aims to collect and present data on the effects of the apelinergic system on doxorubicin-induced cardiotoxicity.

Evaluating Biomarkers as Tools for Early Detection and Prognosis of Heart Failure: A Comprehensive Review

There is a high prevalence of heart failure (HF) worldwide, which has significant consequences for healthcare costs, patient death and quality of life. Therefore, there has been much focus on finding and using biomarkers for early diagnosis, prognostication and therapy of HF. This overview of the research presents a thorough examination of the current state of HF biomarkers and their many uses. Their function in diagnosing HF, gauging its severity and monitoring its response to therapy are all discussed. Particularly promising in HF diagnosis and risk stratification are the cardiac-specific biomarkers, B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide. Markers of oxidative stress, extracellular matrix, renal function, inflammation and cardiac peptides have shown promise in evaluating HF severity and prognosis. MicroRNAs and insulin-like growth factor are two emerging biomarkers that have shown potential in helping with HF diagnosis and prognosis.

Decreased plasma ELABELA level as a novel screening indicator for heart failure: a cohort and observational study

The predictive power of B-type natriuretic peptide (BNP) and left ventricular ejection fraction (LVEF) is limited by its low specificity in patients with heart failure (HF). Discovery of more novel biomarkers for HF better diagnosis is necessary and urgent. ELABELA, an early endogenous ligand for the G protein-coupled receptor APJ (Apelin peptide jejunum, Apelin receptor), exhibits cardioprotective actions. However, the relationship between plasma ELABELA and cardiac function in HF patients is unclear. To evaluate plasma ELABELA level and its diagnostic value in HF patients, a total of 335 patients with or without HF were recruited for our monocentric observational study. Plasma ELABELA and Apelin levels were detected by immunoassay in all patients. Spearman correlation analysis was used to analyze the correlation between plasma ELABELA or Apelin levels and study variables. The receiver operating characteristic curves were used to access the predictive power of plasma ELABELA or Apelin levels. Plasma ELABELA levels were lower, while plasma Apelin levels were higher in HF patients than in non-HF patients. Plasma ELABELA levels were gradually decreased with increasing New York Heart Association grade or decreasing LVEF. Plasma ELABELA levels were negatively correlated with BNP, left atrial diameter, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, and left ventricular posterior wall thickness and positively correlated with LVEF in HF patients. In contrast, the correlation between plasma Apelin levels and these parameters is utterly opposite to ELABELA. The diagnostic value of ELABELA, Apelin, and LVEF for all HF patients was 0.835, 0.673, and 0.612; the sensitivity was 62.52, 66.20, and 32.97%; and the specificity was 95.92, 67.23, and 87.49%, respectively. All these parameters in HF patients with preserved ejection fraction were comparable to those in total HF patients. Overall, plasma ELABELA levels were significantly reduced and negatively correlated with cardiac function in HF patients. Decreased plasma ELABELA levels may function as a novel screening biomarker for HF. A combined assessment of BNP and ELABELA may be a good choice to increase the accuracy of the diagnosis of HF.

Influence of Adipokines on Metabolic Dysfunction and Aging

Currently, 30% of the global population is overweight or obese, with projections from the World Obesity Federation suggesting that this figure will surpass 50% by 2035. Adipose tissue dysfunction, a primary characteristic of obesity, is closely associated with an increased risk of metabolic abnormalities, such as hypertension, hyperglycemia, and dyslipidemia, collectively termed metabolic syndrome. In particular, visceral fat accretion is considered as a hallmark of aging and is strongly linked to higher mortality rates in humans. Adipokines, bioactive peptides secreted by adipose tissue, play crucial roles in regulating appetite, satiety, adiposity, and metabolic balance, thereby rendering them key players in alleviating metabolic diseases and potentially extending health span. In this review, we elucidated the role of adipokines in the development of obesity and related metabolic disorders while also exploring the potential of certain adipokines as candidates for longevity interventions.

Apelin C-Terminal Fragments: Biological Properties and Therapeutic Potential

Creation of bioactive molecules for treatment of cardiovascular diseases based on natural peptides is the focus of intensive experimental research. In the recent years, it has been established that C-terminal fragments of apelin, an endogenous ligand of the APJ receptor, reduce metabolic and functional disorders in experimental heart damage. The review presents literature data and generalized results of our own experiments on the effect of apelin-13, [Pyr]apelin-13, apelin-12, and their chemically modified analogues on the heart under normal and pathophysiological conditions in vitro and in vivo. It has been shown that the spectrum of action of apelin peptides on the damaged myocardium includes decrease in the death of cardiomyocytes from necrosis, reduction of damage to cardiomyocyte membranes, improvement in myocardial metabolic state, and decrease in formation of reactive oxygen species and lipid peroxidation products. The mechanisms of protective action of these peptides associated with activation of the APJ receptor and manifestation of antioxidant properties are discussed. The data presented in the review show promise of the molecular design of APJ receptor peptide agonists, which can serve as the basis for the development of cardioprotectors that affect the processes of free radical oxidation and metabolic adaptation.

APJ as Promising Therapeutic Target of Peptide Analogues in Myocardial Infarction- and Hypertension-Induced Heart Failure

The widely expressed G protein-coupled apelin receptor (APJ) is activated by two bioactive endogenous peptides, apelin and ELABELA (ELA). The apelin/ELA-APJ-related pathway has been found involved in the regulation of many physiological and pathological cardiovascular processes. Increasing studies are deepening the role of the APJ pathway in limiting hypertension and myocardial ischaemia, thus reducing cardiac fibrosis and adverse tissue remodelling, outlining APJ regulation as a potential therapeutic target for heart failure prevention. However, the low plasma half-life of native apelin and ELABELA isoforms lowered their potential for pharmacological applications. In recent years, many research groups focused their attention on studying how APJ ligand modifications could affect receptor structure and dynamics as well as its downstream signalling. This review summarises the novel insights regarding the role of APJ-related pathways in myocardial infarction and hypertension. Furthermore, recent progress in designing synthetic compounds or analogues of APJ ligands able to fully activate the apelinergic pathway is reported. Determining how to exogenously regulate the APJ activation could help to outline a promising therapy for cardiac diseases.

Potential role of the apelin-APJ pathway in sex-related differential cardiotoxicity induced by doxorubicin in mice

Preclinical and clinical findings suggest sexual dimorphism in cardiotoxicity induced by a chemotherapeutic drug, doxorubicin (DOX). However, molecular alterations leading to sex-related differential vulnerability of heart to DOX toxicity are not fully explored. In the present study, RNA sequencing in hearts of B6C3F₁ mice indicated more differentially expressed genes in males than females (224 vs. 19; ≥1.5-fold, False Discovery Rate [FDR] < 0.05) at 1 week after receiving 24 mg/kg total cumulative DOX dose that induced cardiac lesions only in males. Pathway analysis further revealed probable inactivation of cardiac apelin fibroblast signaling pathway (p = 0.00004) only in DOX-treated male mice that showed ≥1.25-fold downregulation in the transcript and protein levels of the apelin receptor, APJ. In hearts of DOX-treated females, the transcript levels of apelin (1.24-fold) and APJ (1.47-fold) were significantly (p < 0.05) increased compared to saline-treated controls. Sex-related differential DOX effect was also observed on molecular targets downstream of the apelin-APJ pathway in cardiac fibroblasts and cardiomyocytes. In cardiac fibroblasts, upregulation of Tgf-β2, Ctgf, Sphk1, Serpine1, and Timp1 (fibrosis; FDR < 0.05) in DOX-treated males and upregulation of only Tgf-β2 and Timp1 (p < 0.05) in females suggested a greater DOX toxicity in hearts of males than females. Additionally, Ryr2 and Serca2 (calcium handling; FDR < 0.05) were downregulated in conjunction with 1.35-fold upregulation of Casp12 (sarcoplasmic reticulum-mediated apoptosis; FDR < 0.05) in DOX-treated male mice. Drug effect on the transcript level of these genes was less severe in female hearts. Collectively, these data suggest a likely role of the apelin-APJ axis in sex-related differential DOX-induced cardiotoxicity in our mouse model.

Adipokine profile in long-term juvenile dermatomyositis, and associations with adipose tissue distribution and cardiac function: a cross-sectional study

OBJECTIVES

In long-term juvenile dermatomyositis (JDM), altered adipose tissue distribution and subclinical cardiac dysfunction have been described. Our aims were to compare adipokine levels in patients with JDM after long-term disease with controls, and explore associations between adipokines and (1) adipose tissue distribution and (2) cardiac function.

METHODS

The study cohort included 59 patients with JDM (60% female, mean age 25.2 years, mean disease duration 16.9 years), and 59 age/sex-matched controls. Updated Pediatric Rheumatology International Trials Organization criteria for clinically inactive JDM were used to stratify patients into active (JDM-active) or inactive (JDM-inactive) disease groups. Lipodystrophy was clinically assessed in all patients. In all study participants, we measured adipose tissue distribution by dual-energy X-ray absorptiometry and cardiac function by echocardiography. Serum adipokines (adiponectin, apelin-12, lipocalin-2, leptin, visfatin and resistin) were analysed using ELISA.

RESULTS

Patients with JDM had higher leptin levels compared with controls (p≤0.01). In JDM-active, apelin-12 and visfatin were higher compared with JDM-inactive (p≤0.05). In JDM-total and JDM-active, lower adiponectin correlated with lipodystrophy and total fat mass. Also, systolic dysfunction correlated with: lower adiponectin in JDM-total, JDM-inactive and JDM-active, and with lower apelin-12 in JDM-total and JDM-active and resistin in JDM-active (all p≤0.05). Lower adiponectin correlated with diastolic dysfunction in JDM-total and JDM-active.

CONCLUSION

After long-term disease, leptin levels were unfavourably regulated in patients with JDM compared with controls, and apelin-12 and visfatin in JDM-active versus JDM-inactive. We found associations between adipokines and both adipose tissue distribution and cardiac systolic function in all patients with JDM, which was most prominent in patients with active disease.

Efficacy of serum apelin and galectin-3 as potential predictors of mortality in severe COVID-19 patients

Apelin is a cardioprotective biomarker while galectin-3 is a pro-inflammatory and profibrotic biomarker. Endothelial dysfunction, hyperinflammation, and pulmonary fibrosis are key mechanisms that contribute to the development of adverse outcomes in Coronavirus disease 2019 (COVID-19) infection. This study aims to analyze the prognostic value of serum apelin and galectin-3 levels to early predict patients at high risk of mortality in patients hospitalized for severe COVID-19 pneumonia. The study included 78 severe COVID-19 patients and 40 healthy controls. The COVID-19 patients were divided into two groups, survivors and nonsurvivors, according to their in-hospital mortality status. Basic demographic and clinical data of all patients were collected, and blood samples were taken before treatment. In our study, serum apelin levels were determined to be significantly lower in both nonsurvivor and survivor COVID-19 patients compared to the control subjects (for both groups, p < 0.001). However, serum apelin levels were similar in survivor and nonsurvivor COVID-19 patients (p > 0.05). Serum galectin-3 levels were determined to be higher in a statistically significant way in nonsurvivors compared to survivors and controls (for both groups; p < 0.001). Additionally, serum galectin-3 levels were significantly higher in the survivor patients compared to the control subjects (p < 0.001). Positive correlations were observed between galectin-3 and age, ferritin, CK-MB and NT-proBNP variables (r = 0.32, p = 0.004; r = 0.24, p = 0.04; r = 0.24, p = 0.03; and r = 0.33, p = 0.003, respectively) while a negative correlation was observed between galectin-3 and albumin (r = -0.31, p = 0.006). Multiple logistic regression analysis revealed that galectin-3 was an independent predictor of mortality in COVID-19 patients (odds ratio [OR] = 2.272, 95% confidence interval [CI] = 1.106-4.667; p = 0.025). When the threshold value for galectin-3 was regarded as 2.8 ng/ml, it was discovered to predict mortality with 80% sensitivity and 57% specificity (area under the curve = 0.738, 95% CI = 0.611-0.866, p = 0.002). Galectin-3 might be a simple, useful, and prognostic biomarker that can be utilized to predict patients who are at high risk of mortality in severe COVID-19 patients.

Apelin and its ratio to lipid factors are associated with cardiovascular diseases: A systematic review and meta-analysis

Background

The present systematic review and meta-analysis aimed to ascertain if the circulating levels of apelin, as an important regulator of the cardiovascular homeostasis, differ in patients with cardiovascular diseases (CVDs) and controls.

Methods

A comprehensive search was performed in electronic databases including PubMed, Scopus, EMBASE, and Web of Science to identify the studies addressing apelin in CVD up to April 5, 2021. Due to the presence of different units to measure the circulating levels of apelin across the included studies, they expressed the standardized mean difference (SMD) and their 95% confidence interval (CI) as summary effect size. A random-effects model comprising DerSimonian and Laird method was used to pool SMDs.

Results

Twenty-four articles (30 studies) comprised of 1793 cases and 1416 controls were included. Pooled results obtained through random-effects model indicated that apelin concentrations in the cases’ blood samples were significantly lower than those of the control groups (SMD = -0.72, 95% CI: -1.25, -0.18, P = 0.009; I2 = 97.3%, P<0.001). New combined biomarkers showed a significant decrease in SMD of apelin/high-density lipoprotein cholesterol (apelin/HDL-C) ratio [-5.17; 95% CI, -8.72, -1.63, P = 0.000; I2 = 99.0%], apelin/low-density lipoprotein cholesterol (apelin/LDL-C) ratio [-4.31; 95% CI, -6.08, -2.55, P = 0.000; I2 = 98.0%] and apelin/total cholesterol (apelin/TC) ratio [-17.30; 95% CI, -22.85, -11.76, P = 0.000; I2 = 99.1%]. However, no significant differences were found in the SMD of apelin/triacylglycerol (apelin/TG) ratio in cases with CVDs compared to the control group [-2.96; 95% CI, -7.41, 1.49, P = 0.000; I2 = 99.2%].

Conclusion

The association of apelin with CVDs is different based on the region and disease subtypes. These findings account for the possible usefulness of apelin as an additional biomarker in the diagnosis of CVD in diabetic patients and in the diagnosis of patients with CAD. Moreover, apelin/HDL-c, apelin/LDL-c, and apelin/TC ratios could be offered as diagnostic markers for CVD.

Biochemistry of the Endocrine Heart

Simple Summary

Besides being a muscle and an electrochemically active organ, the heart is a true endocrine organ. As endocrine cells, cardiac myocytes possess all the needed chemical necessities for translation, post-translational modifications, and complex peptide proteolysis. In addition, intracellular granules in the cells contain not only peptides destined for secretion but also important granin molecules involved in maintaining a regulated secretory pathway. In this review, we highlight the biochemical phenotype of the endocrine heart, recapitulating that the cardiac myocytes are truly and fully capable endocrine cells.

Abstract

Production and release of natriuretic peptides and other vasoactive peptides are tightly regulated in mammalian physiology and involved in cardiovascular homeostasis. As endocrine cells, the cardiac myocytes seem to possess almost all known chemical necessities for translation, post-translational modifications, and complex peptide proteolysis. In several ways, intracellular granules in the cells contain not only peptides destined for secretion but also important granin molecules involved in maintaining a regulated secretory pathway. In this review, we will highlight the biochemical phenotype of the endocrine heart recapitulating that the cardiac myocytes are capable endocrine cells. Understanding the basal biochemistry of the endocrine heart in producing and secreting peptides to circulation could lead to new discoveries concerning known peptide products as well as hitherto unidentified cardiac peptide products. In perspective, studies on natriuretic peptides in the heart have shown that the post-translational phase of gene expression is not only relevant for human physiology but may prove implicated also in the development and, perhaps one day, cure of human cardiovascular disease.

Significance and Determinants of Plasma Apelin in Patients With Obstructive Hypertrophic Cardiomyopathy

Background

Recent studies suggest apelin has multiple protective effects in some cardiovascular diseases. However, there are few data concerning apelin levels in patients with obstructive hypertrophic cardiomyopathy (OHCM) or the relationship between apelin levels and severity of OHCM.

Methods

We studied 88 patients with OHCM and 32 control subjects with matched age and sex distribution. Complete medical history was collected and related examinations were performed. Cardiac magnetic resonance (CMR) and echocardiography were employed to characterize cardiac morphology and function. Plasma apelin was measured by enzyme-linked immunosorbent assay (ELISA).

Results

Plasma apelin levels were significantly lower in patients with OHCM than those in control subjects (96.6 ± 34.3 vs. 169.4 ± 62.5 μg/L, p < 0.001). When patients with OHCM were divided into two groups according to the mean value of plasma apelin, patients with lower apelin levels (plasma apelin ≤ 96.6 μg/L) had greater septal wall thickness (SWT; 25.6 ± 5.5 vs. 23.2 ± 4.3 mm, p = 0.035) and less right ventricular end-diastolic diameter (RVEDD; 20.4 ± 3.3 vs. 23.0 ± 3.6 mm, p = 0.001). Consistently, plasma apelin levels were inversely correlated with SWT (r = −0.334, p = 0.002) and positively correlated with RVEDD (r = 0.368, p < 0.001). Besides, plasma apelin levels were inversely correlated with Ln (NT-proBNP) (r = −0.307, p = 0.008) and positively correlated with body mass index (BMI; r = 0.287, p = 0.008). On multivariate analysis, the SWT was independently associated with decreasing plasma apelin, while the RVEDD was independently associated with increasing plasma apelin.

Conclusion

Plasma apelin levels are reduced in patients with OHCM. The apelin levels are inversely related to SWT and positively related to RVEDD.

Towards harnessing the value of organokine crosstalk to predict the risk for cardiovascular disease in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Importantly, NAFLD increases the risk for cardiovascular disease (CVD). A causal relationship has been substantiated. Given the pandemic proportions of NAFLD, a reliable scoring system for predicting the risk of NAFLD-associated CVD is an urgent medical need. We here review cumulative evidence suggesting that systemically released organokines - especially certain adipokines, hepatokines, and cardiokines - may serve this purpose. The underlying rationale is that these signalers directly communicate between white adipose tissue, liver, and heart as key players in the pathogenesis of NAFLD and resultant CVD events. Moreover, evidence suggests that these organ-specific cytokines are secreted in a biologically predetermined, cascade-like pattern. Consequently, upon pinpointing organokines of relevance, we sketch requirements to establish an algorithm predictive of the CVD risk in patients with NAFLD. Such an algorithm, as to be consolidated in the form of an applicable equation, may be improved continuously by machine learning. To the best of our knowledge, such an option has not yet been considered. Establishing and implementing a reliable algorithm for determining the NAFLD-associated CVD risk has the potential to save many NAFLD patients from life-threatening CVD events.

The therapeutic potential of apelin in kidney disease

Chronic kidney disease (CKD) is a leading cause of global morbidity and mortality and is independently associated with cardiovascular disease. The mainstay of treatment for CKD is blockade of the renin-angiotensin-aldosterone system (RAAS), which reduces blood pressure and proteinuria and slows kidney function decline. Despite this treatment, many patients progress to kidney failure, which requires dialysis or kidney transplantation, and/or die as a result of cardiovascular disease. The apelin system is an endogenous physiological regulator that is emerging as a potential therapeutic target for many diseases. This system comprises the apelin receptor and its two families of endogenous ligands, apelin and elabela/toddler. Preclinical and clinical studies show that apelin receptor ligands are endothelium-dependent vasodilators and potent inotropes, and the apelin system has a reciprocal relationship with the RAAS. In preclinical studies, apelin regulates glomerular haemodynamics and acts on the tubule to promote aquaresis. In addition, apelin is protective in several kidney injury models. Although the apelin system has not yet been studied in patients with CKD, the available data suggest that apelin is a promising potential therapeutic target for kidney disease.

Association Between Apelin and Atrial Fibrillation in Patients With High Risk of Ischemic Stroke

Background: Atrial fibrillation (AF) is associated with high risk of stroke preventable by timely initiation of anticoagulation. Currently available screening tools based on ECG are not optimal due to inconvenience and high costs. Aim of this study was to study the diagnostic value of apelin for AF in patients with high risk of stroke.

Methods: We designed a multicenter, matched-cohort study. The population consisted of three study groups: a healthy control group (34 patients) and two matched groups of 60 patients with high risk of stroke (AF and non-AF group). Apelin levels were examined from peripheral blood.

Results: Apelin was significantly lower in AF group compared to non-AF group (0.694 ± 0.148 vs. 0.975 ± 0.458 ng/ml, p = 0.001) and control group (0.982 ± 0.060 ng/ml, p < 0.001), respectively. Receiver operating characteristic (ROC) analysis of apelin as a predictor of AF scored area under the curve (AUC) of 0.658. Apelin's concentration of 0.969 [ng/ml] had sensitivity = 0.966 and specificity = 0.467. Logistic regression based on manual feature selection showed that only apelin and NT-proBNP were independent predictors of AF. Logistic regression based on selection from bivariate analysis showed that only apelin was an independent predictor of AF. A logistic regression model using repeated stratified K-Fold cross-validation strategy scored an AUC of 0.725 ± 0.131.

Conclusions: Our results suggest that apelin might be used to rule out AF in patients with high risk of stroke.

ACE2 and Apelin-13: Biomarkers with a Prognostic Value in Congestive Heart Failure

The progression of heart failure is the result of the interaction of several pathogenetic processes that involve the activation of biomarkers belonging to the renin angiotensin aldosterone system (RAAS), to its counterregulatory mechanisms, to the sympathetic nervous system and inflammation, and to oxidative stress. This study is aimed at determining the prognostic role of biomarkers in the evolution of patients with heart failure. These biomarkers are representative of different pathogenetic pathways involved in the progression of heart failure and the possible interrelationships between them and heart remodelling. Method. This is a progressive observational study on 53 hospitalized patients with low ejection fraction heart failure, who were followed up for 12 months. The aetiology of heart failure was ischemic heart disease and dilated cardiomyopathy. The patients were clinically and biochemically evaluated by EKG (echocardiography) on admission and at 6 and 12 months. The biomarkers included in the present study were angiotensin-converting enzyme type 2 (ACE2), apelin-13, NT-proBNP (biomarkers involved in the counterregulation of RAAS), interleukin 17 (IL-17), hsCRP (inflammatory biomarkers), and urinary 8-iso-PGF2α (oxidative stress biomarker). The evolution was considered unfavourable if the patients presented complications during hospitalization, were readmitted for decompensated heart failure, or died. Results. From the study group, 14 patients (24.52%) presented an unfavourable clinical evolution. The biomarkers that were associated with the evolution of patients during hospitalization were ACE2, apelin-13, NT-proBNP, and hsCRP. Multivariate logistic regression analysis identified ACE2 and apelin-13 as independent, predictive biomarkers for the unfavourable evolution of patients over the study period. Values of ACE2 above 4000.75 pg/mL and of apelin-13 less than 402.5 pg/mL were associated with an unfavourable evolution (poor clinical outcomes). Conclusion. The serum values of ACE2 and apelin-13 correlate with the unfavourable evolution of patients with reduced ejection fraction heart failure.

The Impact of Transcatheter Aortic Valve Implantation (TAVI) on Serum Apelin Levels in Patients with Aortic Valvular Stenosis

INTRODUCTION

In this study, we aimed to investigate the impact of transcatheter aortic valve implantation (TAVI) on serum apelin levels in patients with severe symptomatic aortic valve stenosis (AS).

METHODS

Forty-six consecutive patients (76.9±7.4 years, n=27 women) who underwent TAVI and 45 age- and sex-matched control subjects were included in the study. Echocardiographic parameters, serum apelin, pro-brain natriuretic peptide (Pro-BNP), and troponin I levels were compared between the groups. In addition, the preprocedural and first-month follow-up echocardiographic parameters and serum apelin values of TAVI patients were compared.

RESULTS

Serum median troponin I and Pro-BNP levels were significantly higher and serum apelin levels were significantly lower in TAVI patients before TAVI procedure than in the control subjects (P<0.001, for all). Median troponin I and Pro-BNP levels were significantly decreased and apelin levels were significantly increased after TAVI procedure compared to the peri-procedural levels. There was a significant and moderate negative correlation between Pro-BNP and apelin levels measured before and after TAVI procedure. A statistically significant and strong negative correlation was found between aortic valve area and Pro-BNP level before TAVI procedure, while a statistically significant but weak positive correlation was found between valve area and apelin level.

CONCLUSION

In our study, apelin levels were significantly lower and Pro-BNP levels were higher in AS patients compared with the control group. Moreover, after TAVI procedure, a significant increase in apelin levels and a significant decrease in Pro-BNP levels were observed. There was also a negative and moderate correlation between apelin and Pro-BNP levels.

Association Between Serum Elabela Levels and Chronic Totally Occlusion in Patients with Stable Angina Pectoris

BACKGROUND

The beneficial effects of Elabela on the cardiovascular system have been shown in studies.

OBJECTIVE

To compare serum Elabela levels of chronic total occlusion (CTO) patients with control patients with normal coronary arteries, and to investigate whether there is a correlation with collateral development.

METHODS

The study was planned cross-sectionally and prospectively. Fifty patients (28.0% female, mean age 61.6±7.3years) with CTO in at least one coronary vessel and 50 patients (38% female, mean age 60,7±6.38 years) with normal coronary arteries were included in the study. Patients in the CTO group were divided into two groups as Rentrop 0-1, those with weak collateral development, and Rentrop 2-3 with good collateral development. In addition to the age, sex, demographic characteristics and routine laboratory tests of the patients, Elabela levels were measured.

RESULTS

Demographic characteristics and laboratory values were similar in both groups. While the mean NT-proBNP and troponin were higher in the CTO group, the Elabela mean was lower (p <0.05 for all). In the multivariate regression analysis, NT-proBNP and Elabela levels were found to be independent predictors for CTO. Also, Elabela level was found to be statistically higher in Rentrop class 2-3 patients compared to Rentrop class 0-1 patients (p<0.05).

CONCLUSION

In our study, we showed that the average Elabela level was low in CTO patients compared to normal patients. In addition, we found the level of Elabela to be lower in patients with weak collateral development compared to patients with good collateral development. (Arq Bras Cardiol. 2021; [online].ahead print, PP.0-0).

Heart Failure With Targeted Cancer Therapies: Mechanisms and Cardioprotection

Oncology has seen growing use of newly developed targeted therapies. Although this has resulted in dramatic improvements in progression-free and overall survival, challenges in the management of toxicities related to longer-term treatment of these therapies have also become evident. Although a targeted approach often exploits the differences between cancer cells and noncancer cells, overlap in signaling pathways necessary for the maintenance of function and survival in multiple cell types has resulted in systemic toxicities. In particular, cardiovascular toxicities are of important concern. In this review, we highlight several targeted therapies commonly used across a variety of cancer types, including HER2 (human epidermal growth factor receptor 2)+ targeted therapies, tyrosine kinase inhibitors, immune checkpoint inhibitors, proteasome inhibitors, androgen deprivation therapies, and MEK (mitogen-activated protein kinase kinase)/BRAF (v-raf murine sarcoma viral oncogene homolog B) inhibitors. We present the oncological indications, heart failure incidence, hypothesized mechanisms of cardiotoxicity, and potential mechanistic rationale for specific cardioprotective strategies.

Interaction between the apelinergic system and ACE2 in the cardiovascular system: therapeutic implications

The apelinergic system is widely expressed and acts through autocrine and paracrine signaling to exert protective effects, including vasodilatory, metabolic, and inotropic effects on the cardiovascular (CV) system. The apelin pathway's dominant physiological role has delineated therapeutic implications for coronary artery disease, heart failure (HF), aortic aneurysm, pulmonary arterial hypertension (PAH), and transplant vasculopathy. Apelin peptides interact with the renin-angiotensin system (RAS) by promoting angiotensin converting enzyme 2 (ACE2) transcription leading to increased ACE2 protein and activity while also antagonizing the effects of angiotensin II (Ang II). Apelin modulation of the RAS by increasing ACE2 action is limited due to its rapid degradation by proteases, including ACE2, neprilysin (NEP), and kallikrein. Apelin peptides are hence tightly regulated in a negative feedback manner by ACE2. Plasma apelin levels are suppressed in pathological conditions, but its diagnostic and prognostic utility requires further clinical exploration. Enhancing the beneficial actions of apelin peptides and ACE2 axes while complementing existing pharmacological blockade of detrimental pathways is an exciting pathway for developing new therapies. In this review, we highlight the interaction between the apelin and ACE2 systems, discuss their pathophysiological roles and potential for treating a wide array of CV diseases (CVDs).

Supplement therapy with apelin for improving the TSH level and lipid disorders in PTU-induced hypothyroid rats

Hyperlipidemia is a common metabolic disorder in the general population, which may arise in hypothyroidism. Apelin is an endogenous ligand that acts as an adiponectin, and is involved in energy storage and metabolism. This study evaluated the effects of apelin administration per se or in combination with T4 on the serum level of thyroid-stimulating hormone (TSH), body weight, and lipid profile, along with the serum level of apelin, and its mRNA expression in heart, in 6-propyl-2-thiouracil (PTU)-induced hypothyroid rats. Male Wistar rats were assigned to five different groups: control, H (hypothyroid), H+A, H+T, and H+A+T. All groups except the control one received PTU (0.05%) in the drinking water for 6 weeks. In addition to PTU, the H+A, H+T, and H+A+T groups received apelin (200 μg/kg/day, i.p.), l-thyroxin (T4) (20 μg/kg/day, via gavage tube), and apelin+T4 during the last 14 days of the trial, respectively. A combined application of T4 and apelin in the H+A+T group effectively diminished mean TSH level, low-density-lipoprotein cholesterol/high-density-lipoprotein cholesterol ratio, and atherogenic index in these animals when compared with these values for the H group. Coadministration of apelin with T4 may offer valuable therapeutic benefits, specifically lowering blood plasma TSH, lipid disorder, and atherosclerosis biomarkers in PTU-induced hypothyroid rats.

Lower Plasma Elabela Levels in Hypertensive Patients With Heart Failure Predict the Occurrence of Major Adverse Cardiac Events: A Preliminary Study

Background: Elabela, a novel cardiac developmental peptide, has been shown to improve heart dysfunction. However, the roles and correlation of Elabela in predicting adverse cardiac events in hypertensive patients with heart failure (HF) remain largely unclear.

Objective: To measure plasma levels of Elabela in hypertensive patients with HF and evaluate its prognostic value.

Methods: A single-site, cohort, prospective, observational study was investigated with all subjects, including control subjects and hypertensive patients with or without HF, whom were recruited in Beijing Chaoyang Hospital Affiliated to Capital Medical University form October 2018 to July 2019. The subjects among different groups were matched based on age and sex. The clinical characteristics were collected, and plasma Elabela levels were detected in all subjects. The hypertensive patients with HF were followed up for 180 days, and the major adverse cardiac events (MACE) were recorded. The Cox regression was used to explore the correlation between Elabela level and MACE in hypertensive patients with or without HF. The receiver operating characteristic curves were used to access the predictive power of plasma Elabela level.

Results: A total of 308 subjects, including 40 control subjects, 134 hypertensive patients without HF, and 134 hypertensive patients with HF were enrolled in this study. Plasma levels of Elabela were lower in hypertensive patients compared with control subjects [4.9 (2.8, 6.7) vs. 11.8 (9.8, 14.0) ng/ml, P < 0.001]. Furthermore, HF patients with preserved ejection fraction had a higher plasma Elabela level than those with impaired left ventricular systolic function (heart failure with mid-range ejection fraction and heart failure with reduced ejection fraction). The hypertensive patients with HF and higher plasma Elabela levels had a better readmission-free and MACE-free survival than those with lower plasma Elabela levels in survival analysis. The Cox regression analysis revealed that plasma Elabela levels were negatively associated with MACE (HR 0.75, 95% CI 0.61–0.99, P = 0.048) in hypertensive patients with HF.

Conclusion: Plasma Elabela levels were decreased in hypertensive patients with left ventricular systolic dysfunction. Thus, Elabela may be potentially used as a novel predictor for MACE in hypertensive patients with HF.

Maternal serum Apelin 13 and APLN gene promoter variant -1860T > C in preeclampsia

OBJECTIVE

To evaluate the apelin (APLN) -1860 T > C (rs56204867) polymorphism and maternal serum apelin 13 levels in preeclampsia and its association with blood pressure.

METHODS

This case-control study was conducted in department of Biochemistry, Sri Devaraj Urs Medical College, Karnataka, India. A total of 181 subjects were enrolled in the study from department of Department of Obstetrics and Gynecology. The recruited women were grouped as: Group-I (n = 91) cases with preeclampsia and Group-II (n = 90) normotensive healthy pregnant women as controls. Under aseptic conditions, the collected 5 mL blood was distributed for serum separation (3 mL) and genetic analysis (2 mL). Serum was stored at -80 °C after centrifugation at 3000 rpm for 10 min. The collected five mL urine sample was used for urinary protein analysis by dipstick method. The APLN gene -1860 T > C polymorphism and Apelin 13 levels were analyzed by molecular methods and ELISA technique respectively. Birth weight and demographic details were recorded.

RESULTS

In the present study, no significant difference was observed for mean gestational age and maternal age. Systolic (158.7 ± 14.0 mmHg) and diastolic (104.9 ± 10.7 mmHg) blood pressure, and mean arterial pressure (MAP) (123.0 ± 11.1 mmHg) (p-value .001) were significantly increased in preeclamptic women compared with healthy pregnant women. Birth weight (2.4 ± 0.5 kg) (p-value .001) was significantly decreased in babies born to preeclamptic mothers. Birth weights were also expressed in centiles, according to Fenton Chart. Number of small for gestational age (SGA) babies were more in preeclampsia (n = 55) than healthy pregnant women (n = 28). Mean maternal serum apelin 13 (239.4 ± 126.3 pg/mL) (p-value .001) concentrations were significantly lower in preeclampsia compared with healthy controls. Maternal serum apelin 13 concentration in preeclampsia was negatively correlated with systolic blood pressure (r = -0.235), diastolic blood pressure (r= -0.172) and mean arterial pressure (r = -0. 206). However, maternal serum apelin 13 levels showed insignificant positive correlation with age, gestational age and birth weight. The genotype and allele frequencies of APLN gene were found significant between study groups as in preeclampsia (χ² = 11.69; df = 2; p = .0028 and χ2 = 14.27; df = 1; p = .00013 respectively). CC genotype and C allele of APLN - 1860 T > C site was high in preeclampsia.

CONCLUSION

Study concludes that preeclamptic women have low level of serum apelin 13 and -1860 T > C polymorphism at APLN gene promoter site with increased allelic frequency of CC genotype and C allele compared to normotensive pregnant women. And this evidence may link to cardiac complications in preeclamptic women after delivery in later stage.

Adipokines: New Potential Therapeutic Target for Obesity and Metabolic, Rheumatic, and Cardiovascular Diseases

Besides its role as an energy storage organ, adipose tissue can be viewed as a dynamic and complex endocrine organ, which produces and secretes several adipokines, including hormones, cytokines, extracellular matrix (ECM) proteins, and growth and vasoactive factors. A wide body of evidence showed that adipokines play a critical role in various biological and physiological functions, among which feeding modulation, inflammatory and immune function, glucose and lipid metabolism, and blood pressure control. The aim of this review is to summarize the effects of several adipokines, including leptin, diponectin, resistin, chemerin, lipocalin-2 (LCN2), vaspin, omentin, follistatin-like 1 (FSTL1), secreted protein acidic and rich in cysteine (SPARC), secreted frizzled-related protein 5 (SFRP5), C1q/TNF-related proteins (CTRPs), family with sequence similarity to 19 member A5 (FAM19A5), wingless-type inducible signaling pathway protein-1 (WISP1), progranulin (PGRN), nesfatin-1 (nesfatin), visfatin/PBEF/NAMPT, apelin, retinol binding protein 4 (RPB4), and plasminogen activator inhibitor-1 (PAI-1) in the regulation of insulin resistance and vascular function, as well as many aspects of inflammation and immunity and their potential role in managing obesity-associated diseases, including metabolic, osteoarticular, and cardiovascular diseases.

Angiotensin-Converting Enzyme 2: SARS-CoV-2 Receptor and Regulator of the Renin-Angiotensin System: Celebrating the 20th Anniversary of the Discovery of ACE2

ACE2 (angiotensin-converting enzyme 2) has a multiplicity of physiological roles that revolve around its trivalent function: a negative regulator of the renin-angiotensin system, facilitator of amino acid transport, and the severe acute respiratory syndrome-coronavirus (SARS-CoV) and SARS-CoV-2 receptor. ACE2 is widely expressed, including, in the lungs, cardiovascular system, gut, kidneys, central nervous system, and adipose tissue. ACE2 has recently been identified as the SARS-CoV-2 receptor, the infective agent responsible for coronavirus disease 2019, providing a critical link between immunity, inflammation, ACE2, and cardiovascular disease. Although sharing a close evolutionary relationship with SARS-CoV, the receptor-binding domain of SARS-CoV-2 differs in several key amino acid residues, allowing for stronger binding affinity with the human ACE2 receptor, which may account for the greater pathogenicity of SARS-CoV-2. The loss of ACE2 function following binding by SARS-CoV-2 is driven by endocytosis and activation of proteolytic cleavage and processing. The ACE2 system is a critical protective pathway against heart failure with reduced and preserved ejection fraction including, myocardial infarction and hypertension, and against lung disease and diabetes mellitus. The control of gut dysbiosis and vascular permeability by ACE2 has emerged as an essential mechanism of pulmonary hypertension and diabetic cardiovascular complications. Recombinant ACE2, gene-delivery of Ace2, Ang 1-7 analogs, and Mas receptor agonists enhance ACE2 action and serve as potential therapies for disease conditions associated with an activated renin-angiotensin system. rhACE2 (recombinant human ACE2) has completed clinical trials and efficiently lowered or increased plasma angiotensin II and angiotensin 1-7 levels, respectively. Our review summarizes the progress over the past 20 years, highlighting the critical role of ACE2 as the novel SARS-CoV-2 receptor and as the negative regulator of the renin-angiotensin system, together with implications for the coronavirus disease 2019 pandemic and associated cardiovascular diseases.

The Association of Plasma Apelin Levels with Plaque Vulnerability

Objectives:

Apelin is a recently discovered peptide that is expressed in many tissues particularly in the cardiovascular system and exerts several actions, most of which are vasodilatory and positive inotropic effects. Based on this, an apelin deficiency is believed to play a significant role in the development of hypertension and heart failure. However, the association of apelin with the pathogenesis of atherosclerosis and especially plaque vulnerability remains unestablished. Thus, to contribute to the literature, in this study, we sought to determine the association of apelin concerning plaque vulnerability in the setting of the acute coronary syndrome.

Methods:

In this study, we prospectively enrolled a total of 80 patients; 40 with acute coronary syndrome and 40 patients with stable chronic ischemic heart disease. Plasma apelin levels were measured in all patients along with other routine biochemical parameters, and all patients underwent a transthoracic echocardiographic examination.

Results:

Plasma apelin levels were significantly lower in patients with the acute coronary syndrome (221.2±66.7 vs 254.3±77.9 p=0.04). However, there was no correlation between plasma apelin levels and serum inflammatory markers or coronary artery disease severity.

Conclusion:

Low plasma apelin levels may create a tendency towards vulnerable plaque and acute coronary syndrome.

Apelin/Elabela-APJ: a novel therapeutic target in the cardiovascular system

Apelin and Elabela (ELA) are endogenous ligands of angiotensin domain type 1 receptor-associated proteins (APJ). Apelin/ELA-APJ signal is widely distributed in the cardiovascular system of fetuse and adult. The signal is involved in the development of the fetal heart and blood vessels and regulating vascular tension in adults. This review described the effects of apelin/ELA-APJ on fetal (vasculogenesis and angiogenesis) and adult cardiovascular function [vascular smooth muscle cell (VSMC) proliferation, vasodilation, positive myodynamia], and relative diseases [eclampsia, hypertension, pulmonary hypertension, heart failure (HF), myocardial infarction (MI), atherosclerosis, etc.] in detail. The pathways of apelin/ELA-APJ regulating cardiovascular function and cardiovascular-related diseases are summarized. The drugs developed based on apelin and ELA suggests APJ is a prospective strategy for cardiovascular disease therapy.

Serum Levels of Chemerin, Apelin, and Adiponectin in Relation to Clinical Symptoms, Quality of Life, and Psychological Factors in Irritable Bowel Syndrome

BACKGROUND

Adipokines have endocrine roles in metabolism and immunity. Dysregulation of adipokine levels is associated with several diseases with chronic inflammation. We aimed to assess the serum concentrations of chemerin, apelin, and adiponectin in irritable bowel syndrome (IBS). Furthermore, we evaluated the possible association of these adipokines with clinical symptoms, quality of life (QoL), and psychological factors.

MATERIALS AND METHODS

In this case-control study, 114 male and female IBS patients were recruited from outpatient clinics. Along with the IBS patients, 114 sex and age-matched healthy volunteers were recruited. Patients filled in the questionnaires of the IBS severity scoring system (IBSSS), gastrointestinal (GI) and somatic symptoms, IBS specific QoL (IBS-QoL), and psychological disorders, and went to the lab for blood sampling.

RESULTS

Serum levels of both adiponectin and apelin were significantly (P=0.04, 0.03, respectively) lower, whereas chemerin was significantly (P=0.01) higher in IBS patients. Chemerin was higher in IBS-D compared with both IBS-C and IBS-A, while apelin and adiponectin were not different between subtypes. After adjustments for confounders only, chemerin had a positive association with IB severity scoring system and GI symptoms. Furthermore, chemerin had positive associations, whereas apelin and adiponectin had inverse associations with somatic symptoms and psychological factors. There were no significant associations between adipokines including chemerin, apelin, and adiponectin, and IBS-QoL.

CONCLUSIONS

Chemerin had significant associations with both the severity of clinical symptoms and psychological factors in IBS; thus, it could be considered as a potential therapeutic target in these patients; however, further studies are needed.

Development and validation of an LC-MS/MS method for detection and quantification of in vivo derived metabolites of [Pyr1]apelin-13 in humans

[Pyr1]apelin-13 is the predominant apelin peptide isoform in the human cardiovascular system and plasma. To date, few studies have investigated [Pyr1]apelin-13 metabolism in vivo in rats with no studies examining its stability in humans. We therefore aimed to develop an LC-MS/MS method for detection and quantification of intact [Pyr1]apelin-13 and have used this method to identify the metabolites generated in vivo in humans. [Pyr1]apelin-13 (135 nmol/min) was infused into six healthy human volunteers for 120 minutes and blood collected at time 0 and 120 minutes after infusion. Plasma was extracted in the presence of guanidine hydrochloride and analysed by LC-MS/MS. Here we report a highly sensitive, robust and reproducible method for quantification of intact [Pyr1]apelin-13 and its metabolites in human plasma. Using this method, we showed that the circulating concentration of intact peptide was 58.3 ± 10.5 ng/ml after 120 minutes infusion. We demonstrated for the first time that in humans, [Pyr1]apelin-13 was cleaved from both termini but the C-terminal was more susceptible to cleavage. Consequently, of the metabolites identified, [Pyr1]apelin-13(1-12), [Pyr1]apelin-13(1-10) and [Pyr1]apelin-13(1-6) were the most abundant. These data suggest that apelin peptides designed for use as cardiovascular therapeutics, should include modifications that minimise C-terminal cleavage.

Usefulness of Biomarkers for Predicting Response to Cardiac Resynchronization Therapy

Cardiac Resynchronization Therapy (CRT) is an effective treatment strategy for heart failure. It significantly improves clinical symptoms and decreases mortality and long-term morbidity. However, some patients do not respond properly to this treatment. In this review, the role of different biomarkers in predicting response to CRT is discussed. Some biomarkers, including natriuretic peptides and inflammatory markers have promising results but further trials are needed for more evaluation.

The influence of post-infarct heart failure and high fat diet on the expression of apelin APJ and vasopressin V1a and V1b receptors

Vasopressin and apelin are reciprocally regulated hormones which are implicated in the pathophysiology of heart failure and the regulation of metabolism; however, little is known about their interactions under pathological conditions. In this study, we determined how post-infarct heart failure (HF) and a high fat diet (HFD) affect expression of the apelin APJ receptor (APJR) and the V1a (V1aR) and V1b (V1bR) vasopressin receptors in the hypothalamus, the heart, and the retroperitoneal adipose tissue. We performed experiments in male 4-week-old Sprague Dawley rats. The animals received either a normal fat diet (NFD) or a HFD for 8 weeks, then they underwent left coronary artery ligation to induce HF or sham surgery (SO), followed by 4 weeks of NFD or HFD. The HF rats showed higher plasma concentration of NT-proBNP and copeptin. The HF reduced the APJR mRNA expression in the hypothalamus. The APJR and V1aR protein levels in the hypothalamus were regulated both by HF and HFD, while the V1bR protein level in the hypothalamus was mainly influenced by HF. APJR mRNA expression in the heart was significantly higher in rats on HFD, and HFD affected the reduction of the APJR protein level in the right ventricle. The regulation of APJR, V1aR and V1bR expression in the heart and the retroperitoneal adipose tissue were affected by both HF and HFD. Our study demonstrates that HF and HFD cause significant changes in the expression of APJR, V1aR and V1bR, which may have an important influence on the cardiovascular system and metabolism.

Roles of the Hepatic Endocannabinoid and Apelin Systems in the Pathogenesis of Liver Fibrosis

Hepatic fibrosis is the consequence of an unresolved wound healing process in response to chronic liver injury and involves multiple cell types and molecular mechanisms. The hepatic endocannabinoid and apelin systems are two signalling pathways with a substantial role in the liver fibrosis pathophysiology-both are upregulated in patients with advanced liver disease. Endogenous cannabinoids are lipid-signalling molecules derived from arachidonic acid involved in the pathogenesis of cardiovascular dysfunction, portal hypertension, liver fibrosis, and other processes associated with hepatic disease through their interactions with the CB₁ and CB₂ receptors. Apelin is a peptide that participates in cardiovascular and renal functions, inflammation, angiogenesis, and hepatic fibrosis through its interaction with the APJ receptor. The endocannabinoid and apelin systems are two of the multiple cell-signalling pathways involved in the transformation of quiescent hepatic stellate cells into myofibroblast like cells, the main matrix-producing cells in liver fibrosis. The mechanisms underlying the control of hepatic stellate cell activity are coincident despite the marked dissimilarities between the endocannabinoid and apelin signalling pathways. This review discusses the current understanding of the molecular and cellular mechanisms by which the hepatic endocannabinoid and apelin systems play a significant role in the pathophysiology of liver fibrosis.

International Union of Basic and Clinical Pharmacology. CVII. Structure and Pharmacology of the Apelin Receptor with a Recommendation that Elabela/Toddler Is a Second Endogenous Peptide Ligand

The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr1]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54-amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein.

Plasma concentration and expression of adipokines in epicardial and subcutaneous adipose tissue are associated with impaired left ventricular filling pattern

Background

Adipokines in serum derive mainly from subcutaneous and visceral adipose tissues. Epicardial adipose tissue (EAT), being a relatively small but unique fat depot, probably does not make an important contribution to systemic concentrations of adipokines. However, proximity of EAT to cardiac muscle and coronary arteries allows cells and proteins to penetrate between tissues. It is hypothesized that overexpression of proinflammatory cytokines in EAT plays an important role in pathophysiology of the heart. The aim of the study was to analyze the relationship between echocardiographic heart parameters and adipokines in plasma, epicardial, and subcutaneous fat in patients with obesity and type 2 diabetes mellitus (T2DM). Additionally, we evaluate proinflammatory properties of EAT by comparing that depot with subcutaneous adipose tissue.

Methods

The study included 55 male individuals diagnosed with coronary artery disease (CAD) who underwent planned coronary artery bypass graft. Plasma concentrations of leptin, adiponectin, resistin, visfatin, apelin, IL-6, and TNF-α, as well as their mRNA and protein expressions in EAT and subcutaneous adipose tissue (SAT) were determined.

Results

Obesity and diabetes were associated with increased leptin and decreased adiponectin plasma levels, higher protein expression of leptin and IL-6 in SAT, and higher visfatin protein expression in EAT. Impaired left ventricular (LV) diastolic function was associated with increased plasma concentrations of leptin, resistin, IL-6, and adiponectin, as well as with increased expressions of resistin, apelin, and adiponectin in SAT, and leptin in EAT.

Conclusions

Obesity and T2DM in individuals with CAD have a limited effect on adipokines. Expression of adipokines in EAT and SAT is linked to certain heart parameters, however diastolic dysfunction of the LV is strongly associated with circulating adipokines.

Catalpol pretreatment attenuates cardiac dysfunction following myocardial infarction in rats

Objective:

To investigate the effects and mechanisms of catalpol on cardiac function in rats with isoproterenol (ISO)-induced myocardial infarction (MI).

Methods:

Adult male Wistar rats were divided into four groups: control group, ISO group, catalpol (L, low dose) group, and catalpol (H, high dose) group. Isoproterenol (85 mg/kg) was injected subcutaneously for 2 consecutive days to induce experimental MI. At the end of experiment, the effects of catalpol on cardiac function; apelin levels; apoptosis index; apelin, APJ, Bcl-2, and Bax protein expression; and caspase-3/9 activities were investigated.

Results:

The rats in the ISO group showed lower left ventricular maximum rate of positive or negative pressure development (±LVdp/dt_max) and left ventricular end-systolic pressure (LVSP) and higher left ventricular end-diastolic pressure (LVEDP) than those in the control group, suggesting severe cardiac dysfunction. Interestingly, catalpol administration significantly ameliorated the ISO-induced cardiac dysfunction. The groups administered low and high dosages catalpol (5 and 10 mg/kg/day, respectively) showed higher ±LVdp/dt_max and LVSP and lower LVEDP than the group administered ISO alone. Catalpol markedly upregulated apelin levels in the plasma and myocardium. Further, catalpol increased the apelin and APJ expression levels in the myocardium of the ISO-treated rats. In addition, catalpol pretreatment inhibited cardiomyocyte apoptosis as indicated by a decrease in the TUNEL-positive cell percentage, alterations in the Bax and Bcl-2 expression levels, and a decline in caspase-3 and caspase-9 activities.

Conclusion:

Our results revealed that catalpol can improve cardiac function. Its protective effects may be linked to the enhancement of myocardium contractility, regulation of the apelin/APJ pathway, and inhibition of cardiomyocyte apoptosis.

(3R)‑5,6,7‑trihydroxy‑3‑isopropyl‑3‑methylisochroman‑1‑one attenuates cardiac dysfunction via the apelin/APJ signaling pathway

Myocardial infarction (MI) is associated with a high risk of mortality and is a major global health concern. The present study aimed to investigate the protective effects of (3R)‑5,6,7‑trihydroxy‑3‑isopropyl‑3‑methylisochroman‑1‑one (TIM) against MI induced by isoproterenol (ISO) in a rat model and the underlying mechanisms. Wistar rats were assigned to 4 groups (n=10): The control group received saline treatment; the ISO group received an intraperitoneal injection of ISO (100 mg/kg); and the TIM (low) and TIM (high) groups received an intraperitoneal injection of ISO, plus a 1 and 2 mg/kg dose of TIM orally, respectively. TIM rats were treated with TIM daily for 12 days and received ISO injections on the final 2 days to induce MI. Cardiac function, apoptosis index and protein expression were subsequently determined. The levels of oxidative stress markers were determined by ELISAs, whereas DNA damage was detected using a Cell Death Detection ELISA kit. Gene and protein expression were determined via reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. Following treatment with ISO, the maximum left ventricular contraction/relaxation velocity and left ventricular systolic pressure were significantly decreased, whereas the left ventricular end‑diastolic pressure was increased; however, treatment with TIM significantly ameliorated ISO‑induced cardiac dysfunction. Additionally, TIM treatment significantly decreased oxidative stress and inhibited the apoptosis of cardiomyocytes, as determined by a decrease in caspase activities, increased expression of B‑cell lymphoma 2 (Bcl‑2) and reduced expression of cleaved caspase‑3, cleaved caspase‑9 and Bcl‑2‑associated X. Furthermore, treatment with TIM upregulated the levels of apelin in the plasma and myocardium of ISO‑treated rats. The results indicated that TIM protected cardiomyocytes against ISO‑induced MI, potentially via the apelin/apelin receptor signaling pathway. The results of the present study suggested that TIM may be a potential novel therapy for the treatment of MI.

The Significance of the Effect of Visceral Adiposity on Left Ventricular Diastolic Function in the General Population

We evaluated the association between visceral adiposity and left ventricular (LV) diastolic function in association with plasma adiponectin levels in 213 subjects without overt cardiac diseases. Abdominal visceral fat area was quantified by computed tomography. Excessive visceral fat was significantly associated with impaired diastolic parameters including E/A, E′ and E/E′. Although serum adiponectin levels decreased with increased visceral adiposity, there was no independent association between serum adiponectin levels and diastolic parameters, which suggest that the role of adiponectin in this association might be indirect.

Cardioprotective apelin effects and the cardiac-renal axis: review of existing science and potential therapeutic applications of synthetic and native regulated apelin

First described in 1998, apelin is one of the endogenous ligands of the apelinergic receptor. Since its discovery, its possible role in human physiology and disease has been intensively studied. Apelin is a native cardioprotective agent that the body synthesizes to create atheroprotective, antihypertensive, and regenerative effects in the body. By antagonizing the RAA system, apelin could play an important role in heart failure and hypertension. It is also involved in myocardial protection against ischemia/reperfusion injury, post-ischemic remodeling, and myocardial fibrosis. A small number of studies even suggest that serum apelin levels may be involved the development of life-threatening arrhythmias. All this information generated excitement about potential therapeutic effects in patients with heart failure and myocardial infarction. The therapeutic index of apelin is unknown but is anticipated to be favorable based on the small number of studies. In this review, we summarize the mechanisms by which apelin exerts its cardioprotective effects and its connection with the cardiorenal axis. Also, we report the potential therapeutic applications of synthetic and native regulated apelin. If larger studies can be performed, it is possible that apelin-mediated drug treatment may play a major role for a large number of patients worldwide in the future.

Apelin and Elabela/Toddler; double ligands for APJ/Apelin receptor in heart development, physiology, and pathology

Apelin is an endogenous peptide ligand for the G protein-coupled receptor APJ/AGTRL1/APLNR and is widely expressed throughout human body. In adult hearts Apelin-APJ/Apelin receptor axis is potently inotropic, vasodilatory, and pro-angiogenic and thereby contributes to maintaining homeostasis in normal and pathological hearts. Apelin-APJ/Apelin receptor is also involved in heart development including endoderm differentiation, heart morphogenesis, and coronary vascular formation. APJ/Apelin receptor had been originally identified as an orphan receptor for its sequence similarity to Angiotensin II type 1 receptor, and it was later deorphanized by identification of Apelin in 1998. Both Apelin and Angiotensin II are substrates for Angiotensin converting enzyme 2 (ACE2), which degrades the peptides and thus negatively regulates their agonistic activities. Elabela/Toddler, which shares little sequence homology with Apelin, has been recently identified as a second endogenous APJ ligand. Elabela plays crucial roles in heart development and disease conditions presumably at time points or at areas of the heart different from Apelin. Apelin and Elabela seem to constitute a spatiotemporal double ligand system to control APJ/Apelin receptor signaling in the heart. These expanding knowledges of Apelin systems would further encourage therapeutic applications of Apelin, Elabela, or their synthetic derivatives for cardiovascular diseases.

[The functional role of endogenous APJ agonists; Apelin and Elabela/Toddler in cardiovascular diseases]

Apelin is an endogenous peptide ligand for APJ receptor, which is widely expressed in human body, and exerts various physiological effects such as vasodilation, inotropic effect, water balance, heart development, angiogenesis and energy metabolism. The beneficial effects of Apelin in cardiovascular diseases have been elucidated, and the roles of Apelin in aging-associated diseases are recently implicated. The mechanisms for therapeutic effects of Aplein include an antagonistic action to renin-angiotensin system (RAS) in addition to inotropic and vasodilatory actions. We have revealed that endogenous Apelin negatively regulates RAS via upregulation of Angiotensin converting enzyme 2 (ACE2). In addition, a second ligand for APJ receptor, Elabela/Toddler, was identified as an essential hormone for heart development, and it has been reported to have physiological effects similar to Apelin. We and others have shown that Elabela exerts inotropic and protective effects in the heart. Although the number of heart failure patients is rapidly increasing, the pathophysiology of heart failure remains elusive and further development of new therapeutic option is awaited. Apelin is a unique bifunctional molecule, which has both inotropic and cardioprotective effects in heart failure, and thus further elucidation of the mechanisms for Apelin/Elabela-APJ signaling would contribute to development of a novel therapeutics for heart failure patients.

Designer Approaches for G Protein-Coupled Receptor Modulation for Cardiovascular Disease

The new horizon for cardiac therapy may lie beneath the surface, with the downstream mediators of G protein–coupled receptor (GPCR) activity. Targeted approaches have shown that receptor activation may be biased toward signaling through G proteins or through GPCR kinases (GRKs) and β-arrestins, with divergent functional outcomes. In addition to these canonical roles, numerous noncanonical activities of GRKs and β-arrestins have been demonstrated to modulate GPCR signaling at all levels of receptor activation and regulation. Further, research continues to identify novel GRK/effector and β-arrestin/effector complexes with distinct impacts on cardiac function in the normal heart and the diseased heart. Coupled with the identification of once orphan receptors and endogenous ligands with beneficial cardiovascular effects, this expands the repertoire of GPCR targets. Together, this research highlights the potential for focused therapeutic activation of beneficial pathways, with simultaneous exclusion or inhibition of detrimental signaling, and represents a new wave of therapeutic development.

Prognostic Value of Serum Apelin Level in Children with Heart Failure Secondary to Congenital Heart Disease

Apelin is an endogenous inotrope that decreased in heart failure (HF). We aimed to evaluate the prognostic value of its level in children with HF due to congenital heart disease (CHD). Sixty children with HF due to CHD were included as a patient group. Sixty healthy children matched for age, sex, and weight served as a control group. Chest X-ray, electrocardiogram (ECG), echocardiography, and laboratory investigations such as complete blood count, c-reactive protein, and serum apelin levels were performed for all included children at admission. All children were followed up for 3 months. Serum apelin level was significantly decreased in patients with HF at admission than healthy control group and this decrease went with advanced stage of HF. Serum apelin levels were significantly decreased in patients with unfavorable prognosis than those with favorable prognosis. At a cutoff lower than 126 ng/l, the sensitivity of serum apelin to predict unfavorable prognosis in children with HF was 96% with a specificity of 82%. Serum apelin level had a significant positive correlation with left ventricular systolic function (P < 0.05). Moreover, it had a significant negative correlation with heart rate, respiratory rate, Ross classification, c-reactive protein, cardiothoracic ratio, and both left and right ventricular dimensions (P < 0.05). Serum apelin level has a good predictive value for adverse outcome in children with HF due to CHD.

Downregulation of the Apelinergic Axis Accelerates Aging, whereas Its Systemic Restoration Improves the Mammalian Healthspan

Aging drives the occurrence of numerous diseases, including cardiovascular disease (CVD). Recent studies indicate that blood from young mice reduces age-associated pathologies. However, the "anti-aging" factors in juvenile circulation remain poorly identified. Here, we characterize the role of the apelinergic axis in mammalian aging and identify apelin as an anti-aging factor. The expression of apelin (apln) and its receptor (aplnr) exhibits an age-dependent decline in multiple organs. Reduced apln signaling perturbs organismal homeostasis; mice harboring genetic deficiency of aplnr or apln exhibit enhanced cardiovascular, renal, and reproductive aging. Genetic or pharmacological abrogation of apln signaling also induces cellular senescence mediated, in part, by the activation of senescence-promoting transcription factors. Conversely, restoration of apln in 15-month-old wild-type mice reduces cardiac hypertrophy and exercise-induced hypertensive response. Additionally, apln-restored mice exhibit enhanced vigor and rejuvenated behavioral and circadian phenotypes. Hence, a declining apelinergic axis promotes aging, whereas its restoration extends the murine healthspan.

Apelin/APJ axis improves angiotensin II-induced endothelial cell senescence through AMPK/SIRT1 signaling pathway

INTRODUCTION

Previous studies have shown that endothelial cell senescence is involved in cardiovascular diseases such as cardiac fibrosis, atherosclerosis and heart failure. Accumulating evidence indicates that apelin exerts protective effects on ageing-related endothelial dysfunction. In this study, we aim to investigate the role of the apelin/APJ axis in angiotensin II (AngII)-induced endothelium senescence and its associated mechanisms.

MATERIAL AND METHODS

Senescence-related β-gal activity assay and western blot were used to evaluate human umbilical vein endothelial cell (HUVEC) senescence. In addition, DCFH-DA staining was carried out to detect the generation of reactive oxygen species (ROS). A validated, high-sensitivity real-time quantitative telomeric repeat amplification protocol (RQ-TRAP) was applied to determine telomerase activity in HUVECs, and a CCK-8 assay was employed to measure cellular viability.

RESULTS

AngII induced an increase in SA-β-Gal-positive cells and upregulation on expression of P21 and PAI-1 compared to the control group (p < 0.05), while apelin against this process (p < 0.05). The protective effects were attenuated when APJ, AMPK and SIRT1 expression was knocked down (p < 0.05). Furthermore, apelin reduced AngII-induced ROS generation and enhanced telomerase activity in HUVECs (p < 0.05), which contributed to increased HUVEC viability as assessed by the CCK-8 assay (p < 0.05).

CONCLUSIONS

The apelin/APJ axis improved AngII-induced HUVEC senescence via the AMPK/SIRT1 signaling pathway, and the underlying mechanisms might be associated with reduced ROS production and enhanced telomerase activity.