The Apelin-APJ System in the Evolution of Heart Failure

Comprehensive Quality Analysis of Conventional and Novel Biomarkers in Diagnosing and Predicting Prognosis of Coronary Artery Disease, Acute Coronary Syndrome, and Heart Failure, a Comprehensive Literature Review

Coronary artery disease (CAD), acute coronary syndrome (ACS), and heart failure (HF) are major global health issues with high morbidity and mortality rates. Biomarkers like cardiac troponins (cTn) and natriuretic peptides (NPs) are crucial tools in cardiology, but numerous new biomarkers have emerged, proving increasingly valuable in CAD/ACS. These biomarkers are classified based on their mechanisms, such as fibrosis, metabolism, inflammation, and congestion. The integration of established and emerging biomarkers into clinical practice is an ongoing process, and recognizing their strengths and limitations is crucial for their accurate interpretation, incorporation into clinical settings, and improved management of CVD patients. We explored established biomarkers like cTn, NPs, and CRP, alongside newer biomarkers such as Apo-A1, IL-17E, IgA, Gal-3, sST2, GDF-15, MPO, H-FABP, Lp-PLA2, and ncRNAs; provided evidence of their utility in CAD/ACS diagnosis and prognosis; and empowered clinicians to confidently integrate these biomarkers into clinical practice based on solid evidence.

Clinical Significance of Apela in Acute Cardiorenal Insuffiency of Chronic Heart Failure

INTRODUCTION

Apela has a wide range of biological effects on the cardiovascular system, but the changes and significance of endogenous Apela in patients with chronic heart failure (CHF) and acute deterioration of cardiac and renal function are unclear.

METHODS

A total of 69 patients with stable CHF combined with well-preserved renal function were enrolled and followed for 12 months. The effects of Apela on human renal glomerular endothelial cells (hRGEC), human glomerular mesangial cells (hMC), and human renal tubular epithelial cells (HK-2) were observed.

RESULTS

Serum Apela concentration was positively correlated with NYHA class (r = 0.711) and N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration (r = 0.303) but negatively correlated with left ventricular ejection fraction (LVEF) (r = -0.374) and 6-min walk distance (r = -0.860) in patients with stable CHF. Twenty-one patients experiencing deterioration of renal and cardiac function were diagnosed with cardiorenal syndrome (CRS) during the follow-up period. In addition, the serum Apela, as well as the difference in Apela between stable and worsening phases (ΔApela), was correlated with the estimated glomerular filtration rate (eGFR) and ΔeGFR in patients with CRS. Apela significantly inhibited the upregulated expression of MCP-1 and TNF-α induced by angiotensin II (AngII) in hRGEC, hMC, and HK-2 cells. Apela inhibited the adhesion of THP-1 cells to hRGEC and promoted the tubular formation of hRGEC. Moreover, Apela enhanced the expression of MMP-9 in hMC but inhibited the upregulated expression of α-SMA and vimentin in HK-2 cells by AngII.

CONCLUSION

This study suggests that the level of Apela can be used to diagnose heart failure and assess the severity of cardiac dysfunction in patients with stable CHF, and its dynamic changes can be used to evaluate the damage to renal function in patients with CRS. Apela plays multiple protective effects on renal cells, highlighting its clinical application prospect in the prevention and treatment of CRS.

Predictors of Kidney Function Outcomes and Their Relation to SGLT2 Inhibitor Dapagliflozin in Patients with Type 2 Diabetes Mellitus Who Had Chronic Heart Failure

INTRODUCTION

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have a favorable impact on the kidney function in patients with heart failure (HF), while there is no clear evidence of what factors predict this effect. The aim of the study was to identify plausible predictors for kidney function outcome among patients with HF and investigate their association with SGLT2i.

METHODS

We prospectively enrolled 480 patients with type 2 diabetes mellitus (T2DM) treated with diet and metformin and concomitant chronic HF and followed them for 52 weeks. In the study, we determined kidney outcome as a composite of ≥ 40% reduced estimated glomerular filtration rate from baseline, newly diagnosed end-stage kidney disease or kidney replacement therapy. The relevant medical information and measurement of the biomarkers (N-terminal natriuretic pro-peptide, irisin, apelin, adropin, C-reactive protein, tumor necrosis factor-alpha) were collected at baseline and at the end of the study.

RESULTS

The composite kidney outcome was detected in 88 (18.3%) patients of the entire population. All patients received guideline-recommended optimal therapy, which was adjusted to phenotype/severity of HF, cardiovascular risk and comorbidity profiles, and fasting glycemia. Levels of irisin, adropin and apelin significantly increased in patients without clinical endpoint, whereas in those with composite endpoint the biomarker levels exhibited a decrease with borderline statistical significance (p = 0.05). We noticed that irisin ≤ 4.50 ng/ml at baseline and a ≤ 15% increase in irisin serum levels added more valuable predictive information than the reference variable. However, the combination of irisin ≤ 4.50 ng/ml at baseline and ≤ 15% increase in irisin serum levels (area under curve = 0.91; 95% confidence interval = 0.87-0.95) improved the discriminative value of each biomarker alone.

CONCLUSION

We suggest that low levels of irisin and its inadequate increase during administration of SGLT2i are promising predictors for unfavorable kidney outcome among patients with T2DM and concomitant HF.

Adipokines and Their Role in Heart Failure: A Literature Review

Obesity is a major risk factor for heart failure (HF). The relationship between adipokines and HF has been implicated in many previous studies and reviews. However, this review article summarizes the basic role of major adipokines, such as apelin, adiponectin, chemerin, resistin, retinol-binding protein 4 (RBP4), vaspin, visfatin, plasminogen activator inhibitor-1, monocyte chemotactic protein-1, nesfatin-1, progranulin, leptin, omentin-1, lipocalin-2, and follistatin-like 1 (FSTL1), in the pathogenesis of HF. Apelin is reduced in patients with HF and upregulated following favorable left ventricular (LV) remodeling. Higher levels of adiponectin have been found in patients with HF compared to in control patients. Also, high plasma chemerin levels are linked to a higher risk of HF. Serum resistin is related to the severity of HF and associated with a high risk for adverse cardiac events. Evidence indicates that RBP4 can contribute to inflammation and damage heart muscle cells, potentially leading to HF. Vaspin might stop the progression of cardiac degeneration, fibrosis, and HF according to experiments on rats with experimental isoproterenol-induced chronic HF. The serum concentrations of visfatin are significantly lower in patients with systolic HF. Leptin levels were found to be correlated with low LV mass and myocardial stiffness, both of which are significant risk factors for the development of HF with preserved ejection fraction (HFpEF). Measuring serum omentin-1 levels appears to be a novel prognostic indicator for risk stratification in HF patients. Increased expression of neutrophil gelatinase-associated lipocalin in both systemic circulation and myocardium in clinical and experimental HF suggests that innate immune responses may contribute to the development of HF. FSTL1 was elevated in patients with HF with reduced ejection fraction and associated with an increase in the size of the left ventricle of the heart. However, other adipokines, such as plasminogen activator inhibitor-1, monocyte chemotactic protein-1, nesfatin-1, and progranulin, have not yet been studied for HF.

Structure-function relationship and physiological role of apelin and its G protein coupled receptor

Apelin receptor (APJR) is a class A peptide (apelin) binding G protein-coupled receptor (GPCR) that plays a significant role in regulating blood pressure, cardiac output, and maintenance of fluid homeostasis. It is activated by a wide range of endogenous peptide isoforms of apelin and elabela. The apelin peptide isoforms contain distinct structural features that aid in ligand recognition and activation of the receptor. Site-directed mutagenesis and structure-based studies have revealed the involvement of extracellular and transmembrane regions of the receptor in binding to the peptide isoforms. The structural features of APJR activation of the receptor as well as mediating G-protein and β-arrestin-mediated signaling are delineated by multiple mutagenesis studies. There is increasing evidence that the structural requirements of APJR to activate G-proteins and β-arrestins are different, leading to biased signaling. APJR also responds to mechanical stimuli in a ligand-independent manner. A multitude of studies has focused on developing both peptide and non-peptide agonists and antagonists specific to APJR. Apelin/elabela-activated APJR orchestrates major signaling pathways such as extracellular signal-regulated kinase (ERKs), protein kinase B (PKB/Akt), and p70S. This review focuses on the structural and functional characteristics of apelin, elabela, APJR, and their interactions involved in the binding and activation of the downstream signaling cascade. We also focus on the diverse signaling profile of APJR and its ligands and their involvement in various physiological systems.

The Effect of SGLT2 Inhibitor Dapagliflozin on Serum Levels of Apelin in T2DM Patients with Heart Failure

Apelin is a multifunctional peptide that plays a pivotal role in cardiac remodeling and HF manifestation because of counteracting angiotensin-II. We hypothesized that positive influence of sodium-glucose co-transporter-2 (SGLT2) inhibitor on cardiac function in T2DM patients with HF might be mediated by apelin and that its levels seem to be a target of management. A total of 153 type 2 diabetes mellitus (T2DM) patients with II/III HF NYHA class and average left ventricular (LV) ejection fraction (EF) of 46% have been enrolled and treated with dapagliflosin. The serum levels of apelin and N-terminal brain natriuretic pro-peptide (NT-proBNP) were measured at baseline and over a 6-month period of dapagliflosin administration. We noticed that administration of dapagliflozin was associated with a significant increase in apelin levels of up to 18.3% and a decrease in NT-proBNP of up to 41.0%. Multivariate logistic regression showed that relative changes of LVEF, LA volume index, and early diastolic blood filling to longitudinal strain ratio were strongly associated with the levels of apelin, whereas NT-proBNP exhibited a borderline significance in this matter. In conclusion, dapagiflosin exerted a positive impact on echocardiographic parameters in close association with an increase in serum apelin levels, which could be a surrogate target for HF management.

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.

Biomarkers of Volume Overload and Edema in Heart Failure With Reduced Ejection Fraction

From a pathogenetic point of view, heart failure (HF) is characterized by the activation of several neurohumoral pathways with a role in maintaining the cardiac output and the adequate perfusion pressure in target organs and tissues. Decreased cardiac output in HF with reduced ejection fraction causes activation of the sympathetic nervous system, the renin angiotensin aldosterone system, arginine-vasopressin system, natriuretic peptides, and endothelin, all of which cause water and salt retention in the body. As a result, patients will present clinically as the main symptoms: dyspnea and peripheral edema caused by fluid redistribution to the lungs and/or by fluid overload. By studying these pathophysiological mechanisms, biomarkers with a prognostic and therapeutic role in the management of edema were identified in patients with HF with low ejection fraction. This review aims to summarize the current data from the specialty literature of such biomarkers with a role in the pathogenesis of edema in HF with low ejection fraction. These biomarkers may be the basis for risk stratification and the development of new therapeutic means in the treatment of edema in these patients.

Discriminative Utility of Apelin-to-NT-Pro-Brain Natriuretic Peptide Ratio for Heart Failure with Preserved Ejection Fraction among Type 2 Diabetes Mellitus Patients

Background: Apelin is a regulatory vasoactive peptide, which plays a pivotal role in adverse cardiac remodeling and heart failure (HF) with reduced ejection fraction. The purpose of the study was to investigate whether serum levels of apelin is associated with HF with preserved election fraction (HFpEF) in patients with T2DM. Methods: The study retrospectively involved 101 T2DM patients aged 41 to 62 years (48 patients with HFpEF and 28 non-HFpEF patients). The healthy control group consisted of 25 individuals with matched age and sex. Data collection included demographic and anthropometric information, hemodynamic performances and biomarkers of the disease. Transthoracic B-mode echocardiography, Doppler and TDI were performed at baseline. Serum levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and apelin were measured by ELISA in all patients at the study entry. Results: Unadjusted multivariate logistic model yielded the only apelin to NT-proBNP ratio (OR = 1.44; p = 0.001), BMI > 34 кг/м2 (OR = 1.07; p = 0.036), NT-proBNP > 458 pmol/mL (OR = 1.17; p = 0.042), LAVI > 34 mL/m2 (OR = 1.06; p = 0.042) and E/e’ > 11 (OR = 1.04; p = 0.044) remained to be strong predictors for HFpEF. After obesity adjustment, multivariate logistic regression showed that the apelin to NT-proBNP ratio < 0.82 × 10−2 units remained sole independent predictor for HFpEF (OR = 1.44; 95% CI: 1.18–2.77; p = 0.001) HFpEF in T2DM patients. In conclusion, we found that apelin to NT-proBNP ratio < 0.82 × 10−2 units better predicted HFpEF in T2DM patients than apelin and NT-proBNP alone. This finding could open new approach for CV risk stratification of T2DM at higher risk of HF.

APELIN IN HEART FAILURE

Apelin is a biologically active protein encoded by the APLN gene. It was first isolated in 1998 as a ligand for the APJ receptor. It exists in several isoforms differing in polypeptide chain length and biological activity. It is secreted by white adipose tissue, and its expression has been identified in many body tissues, including the cardiovascular system, kidneys, lungs, CNS (especially the hypothalamus, suprachiasmatic and ventricular nuclei), skeletal muscle, mammary glands, adrenal glands, ovaries, stomach, liver cells, placenta, and breast milk. However, the highest concentrations were observed in the endocardium and endothelium of vascular smooth muscle cells. In myocardial tissue, apelin has a positive inotropic effect and exerts an opposing effect to the RAA (renin-angiotensin-aldosterone) system, lowering blood pressure. Therefore, its positive role in early stages of heart failure, in patients with hypertension and ischemic heart disease is emphasized. The synthesis and secretion of apelin by adipocytes makes it possible to classify this peptide as an adipokine. Therefore, its production in adipose tissue is enhanced in obesity. Furthermore, apelin has been shown to increase cellular sensitivity to insulin and improve glucose tolerance in the onset of type 2 diabetes, and therefore appears to play a significant role in the pathogenesis of metabolic disease. An accurate assessment of the importance of apelin in cardiovascular disease requires further studies, which may contribute to the use of apelin in the treatment of heart failure.

Analysis of lncRNA-miRNA-mRNA expression pattern in heart tissue after total body radiation in a mouse model

Background

Radiation therapy is integral to effective thoracic cancer treatments, but its application is limited by sensitivity of critical organs such as the heart. The impacts of acute radiation-induced damage and its chronic effects on normal heart cells are highly relevant in radiotherapy with increasing lifespans of patients. Biomarkers for normal tissue damage after radiation exposure, whether accidental or therapeutic, are being studied as indicators of both acute and delayed effects. Recent research has highlighted the potential importance of RNAs, including messenger RNAs (mRNAs), microRNAs (miRNAs), and long non-coding RNAs (lncRNAs) as biomarkers to assess radiation damage. Understanding changes in mRNA and non-coding RNA expression will elucidate biological pathway changes after radiation.

Methods

To identify significant expression changes in mRNAs, lncRNAs, and miRNAs, we performed whole transcriptome microarray analysis of mouse heart tissue at 48 h after whole-body irradiation with 1, 2, 4, 8, and 12 Gray (Gy). We also validated changes in specific lncRNAs through RT-qPCR. Ingenuity Pathway Analysis (IPA) was used to identify pathways associated with gene expression changes.

Results

We observed sustained increases in lncRNAs and mRNAs, across all doses of radiation. Alas2, Aplnr, and Cxc3r1 were the most significantly downregulated mRNAs across all doses. Among the significantly upregulated mRNAs were cell-cycle arrest biomarkers Gdf15, Cdkn1a, and Ckap2. Additionally, IPA identified significant changes in gene expression relevant to senescence, apoptosis, hemoglobin synthesis, inflammation, and metabolism. LncRNAs Abhd11os, Pvt1, Trp53cor1, and Dino showed increased expression with increasing doses of radiation. We did not observe any miRNAs with sustained up- or downregulation across all doses, but miR-149-3p, miR-6538, miR-8101, miR-7118-5p, miR-211-3p, and miR-3960 were significantly upregulated after 12 Gy.

Conclusions

Radiation-induced RNA expression changes may be predictive of normal tissue toxicities and may indicate targetable pathways for radiation countermeasure development and improved radiotherapy treatment plans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02998-w.

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 role of Elabela in kidney disease

Elabela, also known as Toddler or Apela, is a recently discovered hormonal peptide containing 32 amino acids. Elabela is a ligand of the apelin receptor (APJ). APJ is a G protein-coupled receptor widely expressed throughout body, and together with its cognate ligand, apelin, it plays an important role in various physiological processes including cardiovascular functions, angiogenesis and fluid homeostasis. Elabela also participates in embryonic development and pathophysiological processes in adulthood. Elabela is highly expressed in undifferentiated embryonic stem cells and regulates endoderm differentiation and cardiovascular system development. During differentiation, Elabela is highly expressed in pluripotent stem cells and in adult renal collecting ducts and loops, where it functions to maintain water and sodium homeostasis. Other studies have also shown that Elabela plays a crucial role in the pathogenesis of kidney diseases. This review addresses the role of Elabela in kidney diseases including renal ischemia/reperfusion injury, hypertensive nephropathy, diabetic nephropathy, and cardiorenal syndrome.

Adipokines, Myokines, and Cardiokines: The Role of Nutritional Interventions

It is now established that adipose tissue, skeletal muscle, and heart are endocrine organs and secrete in normal and in pathological conditions several molecules, called, respectively, adipokines, myokines, and cardiokines. These secretory proteins constitute a closed network that plays a crucial role in obesity and above all in cardiac diseases associated with obesity. In particular, the interaction between adipokines, myokines, and cardiokines is mainly involved in inflammatory and oxidative damage characterized obesity condition. Identifying new therapeutic agents or treatment having a positive action on the expression of these molecules could have a key positive effect on the management of obesity and its cardiac complications. Results from recent studies indicate that several nutritional interventions, including nutraceutical supplements, could represent new therapeutic agents on the adipo-myo-cardiokines network. This review focuses the biological action on the main adipokines, myokines and cardiokines involved in obesity and cardiovascular diseases and describe the principal nutraceutical approaches able to regulate leptin, adiponectin, apelin, irisin, natriuretic peptides, and follistatin-like 1 expression.

Recently Approved and Under Investigation Drugs for Treating Patients with Heart Failure

Heart Failure (HF) represents a leading cause of morbidity and mortality worldwide. Despite the recent advances in the treatment of this condition, patients´ prognosis remains unfavorable in most cases. Sacubitril/valsartan and ivabradine have been recently approved to improve clinical outcomes in patients with HF with reduced ejection fraction. Drugs under investigation for treating patients with HF encompass many novel mechanisms including vasoactive peptides, blocking inflammatory- mediators, natriuretic peptides, selective non-steroidal mineralocorticoid-receptor antagonists, myocardial β3 adrenoreceptor agonists, inhibiting the cytochrome C/cardiolipin peroxidase complex, neuregulin-1/ErbB signaling and inhibiting late inward sodium current. The aim of this manuscript is to review the main drugs under investigation for the treatment of patients with HF and give perspectives for their implementation into clinical practice.

Apelin Improves Prognostic Value of HFSS (Heart Failure Survival Score) and MAGGIC (Meta-Analysis Global Group in Chronic Heart Failure) Scales in Ambulatory Patients with End-Stage Heart Failure

This prospective study aimed to determine the effect of adding apelin to the MAGGIC (Meta-Analysis Global Group In Chronic Heart Failure) and HFSS (Heart Failure Survival Score) scales for predicting one-year mortality in 240 ambulatory patients accepted for heart transplantation (HT) between 2015-2017. The study also investigated whether the combination of N-terminal pro-brain natriuretic peptide (NT-proBNP) with MAGGIC or HFSS improves the ability of these scales to effectively separate one-year survivors from non-survivors on the HT waiting list. The median age of the patients was 58.0 (51.50.0-64.0) years and 212 (88.3%) of them were male. Within a one year follow-up, 75 (31.2%) patients died. The area under the curves (AUC) for baseline parameters was as follows-0.7350 for HFSS, 0.7230 for MAGGIC, 0.7992 for apelin and 0.7028 for NT-proBNP. The HFSS-apelin score generated excellent power to predict the one-year survival, with the AUC of 0.8633 and a high sensitivity and specificity (80% and 78%, respectively). The predictive accuracy of MAGGIC-apelin score was also excellent (AUC: 0.8523, sensitivity of 75%, specificity of 79%). The addition of NT-proBNP to the HFSS model slightly improved the predictive power of this scale (AUC_{HFFSS-NT-proBNP}: 0.7665, sensitivity 83%, specificity 60%), while it did not affect the prognostic strength of MAGGIC (AUC_{MAGGIC-NT-proBNP}: 0.738, sensitivity 71%, specificity 69%). In conclusion, the addition of apelin to the HFSS and MAGGIC models significantly improved their ability to predict the one-year survival in patients with advanced HF. The MAGGIC-apelin and HFSS-apelin scores provide simple and powerful methods for risk stratification in end-stage HF patients. NT-proBNP slightly improved the prognostic power of HFSS, while it did not affect the predictive power of MAGGIC.

Apela improves cardiac and renal function in mice with acute myocardial infarction

Apela was recently identified as a new ligand of the apelin peptide jejunum (APJ) receptor. The purpose of this study was to investigate the role of apela in post-myocardial infarction (post-MI) recovery from cardiorenal damage. A murine MI model was established, and apela was then infused subcutaneously for two weeks. Echocardiographs were performed before and after infarction at the indicated times. Renal function was evaluated by serum and urine biochemistry. Immunohistochemistry of heart and kidney tissue was performed by in situ terminal deoxynucleotidyl transferase-mediated dUPT nick end-labelling reaction. Compared to the control group (MI/vehicle), the average value of the left ventricular ejection fraction in apela-treated mice increased by 32% and 39% at 2- and 4-week post-MI, respectively. The mean levels of serum blood urea nitrogen，creatinine, N-terminal pro-brain natriuretic peptide and 24-hour urine protein were significantly decreased at 4-week post-MI in apela-treated mice relative to that of control animals. At the cellular level, we found that apela treatment significantly reduced myocardial fibrosis and cellular apoptosis in heart and kidney tissue. These data suggest that apela improves cardiac and renal function in mice with acute MI. The peptide may be potential therapeutic agent for heart failure.

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.

Usefulness of the Adipokines as Biomarkers of Ischemic Cardiac Dysfunction

Cardiovascular disease is the leading cause of death among both women and men, but there is still a great percentage of misdiagnosis and lack of clearly defined criteria. Advances in biomolecular science have proven the crucial role of inflammation and, more importantly, the role of adipokines in mediating all stages of coronary artery disease. It has also been suggested that regional fat deposits, more precisely from thoracic region, have a major influence on the development of coronary artery disease by creating a local proatherogenic environment. The immune system closely interacts with metabolic risk factors to initiate, promote, and further aggravate the atherosclerotic lesions on the arterial wall all with the "help" of adipokines. So nowadays, research extensively focuses on uncovering biomarkers that would provide an increased chance of detecting subclinical cardiac distress and also add a consistent value to current guideline-imposed risk criteria.

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.

Hepatic and cardiac beneficial effects of a long-acting Fc-apelin fusion protein in diet-induced obese mice

BACKGROUND

Apelin is a peptide ligand of the G-protein-coupled receptor APJ and exhibits anti-diabetes and anti-heart failure activities. However, short serum half-life of the apelin peptide limits its potential clinical applications. This study aimed to develop a long-acting apelin analog.

METHODS

To extend apelin's in vivo half-life, we made a recombinant protein by fusing the IgG Fc fragment to apelin-13 (Fc-apelin-13), conducted pharmacokinetics studies in mice, and determined in vitro biological activities in suppressing cyclic adenosine monophosphate and activating extracellular signal-regulated kinase signalling by reporter assays. We investigated the effects of Fc-apelin-13 on food intake, body weight, fasting blood glucose and insulin levels, glucose tolerance test, hepatic steatosis, and cardiac function and fibrosis by subcutaneous administration of Fc-apelin-13 in diet-induced obese mice for 4 weeks.

RESULTS

The estimated half-life of Fc-apelin-13 in blood was approximately 33 hours. Reporter assays showed that Fc-apelin-13 was active in suppressing cyclic adenosine monophosphate response element and activating serum response element activities. Four weeks of Fc-apelin-13 treatment in obese mice did not affect food intake and body weight, but resulted in a significant improvement of glucose tolerance, and a decrease in hepatic steatosis and fibrosis, as well as in serum alanine transaminase levels. Moreover, cardiac stroke volume and output were increased and cardiac fibrosis was decreased in the treated mice.

CONCLUSIONS

Fc-apelin-13 fusion protein has an extended in vivo half-life and exerts multiple benefits on obese mice with respect to the improvement of glucose disposal, amelioration of liver steatosis and heart fibrosis, and increase of cardiac output. Hence, Fc-apelin-13 is potentially a therapeutic for obesity-associated disease conditions.

ROS-Autophagy pathway mediates monocytes-human umbilical vein endothelial cells adhesion induced by apelin-13

Apelin is the endogenous ligand of APJ receptor. Both monocytes (MCs) and human umbilical vein endothelial cells (HUVECs) express apelin and APJ, which play important roles in the physiological processes of atherosclerosis. Our previous research indicated that apelin-13 promoted MCs-HUVECs adhesion. Here, we further explore the mechanism responsible for MCs-HUVECs adhesion induced by apelin-13. Apelin-13 promoted reactive oxygen species (ROS) generation and NOX4 expression in HUVECs. Apelin-13 inducedautophagy, increased proteins beclin1 and LC3-II/I expression and induced autophagy flux in HUVECs, which was blocked by NAC, catalase and DPI. Autophagy flux induced by apelin-13 was inhibited by NAC and catalase but not hydroxychloroquine (HCQ). NAC, catalase, and DPI prevented apelin-13 induced ICAM-1 expression in HUVECs. Rapamycin enhanced MCs-HUVECs adhesion that was reversed by NAC, catalase, and DPI. Down-regulation of beclin1 and LC3 by siRNA blocked MCs-HUVECs adhesion. Apelin-13 induced atherosclerotic plaque and increased NOX4, LC3-II/I expression in ApoE-/-(HFD) mouse model. Our results demonstrated that apelin-13 induced MCs-HUVECs adhesion via a ROS-autophagy pathway.

Structural Basis for Apelin Control of the Human Apelin Receptor

Apelin receptor (APJR) is a key regulator of human cardiovascular function and is activated by two different endogenous peptide ligands, apelin and Elabela, each with different isoforms diversified by length and amino acid sequence. Here we report the 2.6-Å resolution crystal structure of human APJR in complex with a designed 17-amino-acid apelin mimetic peptide agonist. The structure reveals that the peptide agonist adopts a lactam constrained curved two-site ligand binding mode. Combined with mutation analysis and molecular dynamics simulations with apelin-13 binding to the wild-type APJR, this structure provides a mechanistic understanding of apelin recognition and binding specificity. Comparison of this structure with that of other peptide receptors suggests that endogenous peptide ligands with a high degree of conformational flexibility may bind and modulate the receptors via a similar two-site binding mechanism.

Targeting vasoactive peptides for managing calcific aortic valve disease

Calcific aortic valve disease (CAVD) represents a spectrum of disease spanning from milder degrees of calcification of valve leaflets, i.e., aortic sclerosis, to severe calcification i.e., aortic stenosis (AS) with hemodynamic instability. The prevalence of CAVD is increasing rapidly due to the aging of the population, being up to 2.8% among patients over 75 years of age. Even without significant aortic valve stenosis, aortic sclerosis is associated with a 50% increased risk of myocardial infarction and death from cardiovascular causes. To date, there is no pharmacological treatment available to reverse or hinder the progression of CAVD. So far, the cholesterol-lowering therapies (statins) and renin-angiotensin system (RAS) blocking drugs have been the major pharmacological agents investigated for treatment of CAVD. Especially angiotensin receptor blockers (ARB)s and angiotensin convertase enzyme inhibitors (ACEI)s, have been under active investigation in clinical trials, but have proven to be unsuccessful in slowing the progression of CAVD. Several studies have suggested that other vasoactive hormones, including endothelin and apelin systems are also associated with development of AS. In the present review, we discuss the role of vasoactive factors in the pathogenesis of CAVD as novel pharmacological targets for the treatment of aortic valve calcification. Key messages Vasoactive factors are involved in the progression of calcific aortic valve disease. Endothelin and renin-angiotensin systems seem to be most prominent targets for therapeutic interventions in the view of valvular pathogenesis. Circulating vasoactive factors may provide targets for diagnostic tools of calcified aortic valve disease.

Serum level of apelin-13 negatively correlated with NT-proBNP in heart failure patients

Background: Apelin is a potent endogenous inotropic peptide with a major role in counteracting the aldosterone and angiotensin II and their negative effects on the cardiovascular system. The exact role of apelin in the patho-physiology of this disease is not well understood. We aimed to investigate the possible associations of apelin-13 with clinical and paraclinical characteristics in HF patients as well as studying its dynamics during the course of the heart failure.

Method: We performed a prospective observational cohort single-center study. We compared the baseline serum levels of apelin-13 and NT-proBNP level in 53 heart failure patients (acute heart failure, chronic compensated heart failure and chronic decompensated heart failure). We divided the patients according to the apelin-13 level: above and below the median, and we analyzed the relationship between serum apelin-13 and the clinical, echocardiographic, electrocardiographic and biological parameters. Twenty patients were followed-up (after an average time interval of 9 months), investigating the same parameters.

Results: The median of apelin-13 was 495pg/mL (IQR 276-845pg/mL). We found strong, negative correlation between the serum levels of apelin-13 and NT-proBNP (Spearman rho= −0.83, p<0.001). For the reassessed patients the median apelin level was significantly higher at follow-up (460 pg/mL, IQR 342-871 pg/mL) as compared with the baseline level (395 pg/mL, IQR 270-603 pg/mL), p=0.019, and maintained the negative correlation with NT-proBNP level (Spearman’s rho −0.7, p<0.001. The Low Apelin-13 group have higher NT-proBNP levels and also contains all the patients in NYHA IV class heart failure, 71% of the acute HF patients, and 7 of 8 patients who died before follow-up.

Conclusion: Apelin-13 was negatively correlated with NT-proBNP. The Low Apelin-13 group contained the majority of the patients with a negative outcome (death before follow-up), most of the patients who presented with acute HF and all the patients in NYHA IV class.

Chronic Heart Failure Clinical Practice Guidelines' Class 1-A Pharmacologic Recommendations: Start-to-End Synergistic Drug Therapy?

BACKGROUND

Chronic heart failure (HF) disease as an emerging epidemic has a high economic-psycho-social burden, hospitalization, readmission, morbidity and mortality rates despite many clinical practice guidelines' evidenced-based and consensus driven recommendations that include trials' initial-baseline data.

OBJECTIVE

To show that the survival and hospitalization-free event rates in the reviewed chronic HF clinical practice guidelines' class I-A recommendations as initial HF drug therapy (IDT) is possibly a combination and 'start-to-end' synergistic effect of the add-on ('end') HF drug therapy (ADT) to the baseline ('start') HF drug therapy (BDT).

METHODOLOGY

The references cited in the chronic HF clinical practice guidelines of the 2005, 2009, and 2013 American Heart Association/American College of Cardiology (AHA/ACC), the 2006 Heart Failure Society of America (HFSA), and the 2005, 2008, and 2012 European Society of Cardiology (ESC) were reviewed and compared with the respective guidelines' and other countries' recommendations.

RESULTS

The BDT using glycosides and diuretics is 79%-100% in the cited HF trials. The survival rates attributed to the BDT ('start') is 46%-89% and IDT ('end') 61%-92.8%, respectively. The hospitalization-free event rate of the BDT group: 47.1% to 85.3% and IDT group 61.8%-90%, respectively. Thus, the survival and hospitalization-free event rates of the ADT is 0.4%-15% and 4.6% to 14.7%, respectively. The extrapolated BDT survival is 8%-51% based on a 38% estimated natural HF survival rate for the time period109.

CONCLUSION

The contribution of baseline HF drug therapy (BDT) is relevant in terms of survival and hospitalization-free event rates compared to the HF class 1-A guidelines initial drug therapy recommendations (IDT). Further, the proposed initial HF drug ('end') therapy (IDT) has possible synergistic effects with the baseline HF drug ('start') therapy (BDT) and is essentially the add on HF drug therapy (ADT) in our analysis. The polypharmacy HF treatment is a synergistic effect due to BDT and ADT.