Elevated Levels of Apelin-36 in Heart Failure Due to Chronic Systemic Hypoxia

Early Administration of Apelin Could Prevent Heart Failure Following Myocardial Injury; A Systematic Review and Meta-Analysis

Introduction

Heart failure (HF) is a prevalent and advancing cardiovascular disorder that impacts 1-2% of the worldwide population, particularly the elderly. Studies indicate that the intravenous administration of apelin may yield advantageous effects in preventing heart failure subsequent to myocardial injury. This meta-analysis aimed to assess the effects of exogenous apelin administration on heart failure in animal models, in light of the lack of a definitive consensus on the matter.

Method

An extensive search was performed in the Medline (via PubMed), Web of Science, Embase, and Scopus databases till the end of January 2024. Two independent reviewers screened and summarized the relevant articles. Outcomes related to cardiac function, including ejection fraction (EF), maximum and minimum rate of left ventricle systolic pressure (+dp/dt and -dp/dt, respectively), heart rate, left ventricular end-diastolic pressure (LVEDP), and left ventricular systolic pressure (LVSP) were assessed. Findings were reported as a pooled standardized mean difference (SMD) with a 95% confidence interval (95% CI).

Results

12 studies were included. Pooled analysis demonstrated that early treatment with apelin following myocardial injury significantly increases +dp/dt (SMD = 2.36; 95% CI: 1.58 to 3.15; p < 0.001) and decreases -dp/dt (SMD = -3.31; 95% CI: -4.46 to -2.17; p < 0.001). Furthermore, the administration of apelin resulted in a significant increase in EF (SMD = 0.79; 95% CI: 0.15 to 1.44; p = 0.02) and LVSP (SMD = 2.09; 95% CI: 0.82 to 3.36; p < 0.001), while it led to a decrease in LVEDP in the animals (SMD = -1.85; 95% CI: -2.81 to -0.88; p < 0.001). Noteworthy, apelin treatment was shown to have no significant influence on the heart rate of the animals (SMD = -0.12; 95% CI: -0.82 to -0.58; p = 0.73).

Conclusion

The current study demonstrated that the early administration of apelin has the potential to improve cardiac function and mitigate the onset of heart failure subsequent to myocardial injury. Further, in vivo research is essential to lay the groundwork for the integration of apelin into clinical practice.

Proprotein convertase subtilisin/kexin type 9 and apelin in fibromyalgia syndrome

OBJECTIVES

This study aimed to investigate the potential roles of proprotein convertase subtilisin/ kexin type 9 (PCSK9) and apelin in the etiology of fibromyalgia syndrome (FS).

PATIENTS AND METHODS

The retrospective study was conducted between May 2022 and February 2023. Fifty-eight female FS patients (mean age: 45.2±9.9 years; range, 25 to 66 years) and 30 age- and body mass index-matched control subjects (mean age: 43.1±9.9 years; range, 26 to 67 years) were included in the study. Apelin and PCSK9 levels of all individuals were measured using appropriate methods.

RESULTS

The levels of PCSK9 (173.2±62.2 vs. 75.1±44.1, p<0.001) and apelin (354.6±195.5 vs. 229.0±83.2, p<0.001) were significantly higher in patients with FS compared to the control group. A positive correlation was found between PCSK9 and apelin levels and various measures, including the Fibromyalgia Impact Questionnaire (FIQ), Symptom Severity Scale (SSS), Pittsburgh Sleep Quality Index (PSQI), and Beck Depression Inventory (BDI). Additionally, there was a positive correlation between apelin levels and FIQ, SSS, PSQI, Beck Anxiety Inventory, and BDI scores. The optimal cutoff value for PCSK9 in predicting FS was 110.0 ng/mL, with a sensitivity of 84.5% and specificity of 83.9% (area under the curve [AUC]=0.920, 95% confidence interval [CI]: 0.852-0.987, p<0.001). For apelin, the optimal cutoff value for predicting FS was 258.8 ng/L, with a sensitivity of 63.8% and specificity of 64.5% (AUC=0.732, 95% CI: 0.623-0.840, p<0.001).

CONCLUSION

Our findings suggest that PCSK9 may play a role in FS etiology and potentially contribute to oxidative stress. Increased apelin levels may be a compensatory response to high oxidative stress, possibly leading to hyperalgesia. Both PCSK9 and apelin can be predictive markers for FS.

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.

The Role of Oxidative Stress and Inflammatory Parameters in Heart Failure

Heart failure (HF) remains a major medical and social problem. The NT-pro-brain natriuretic peptide (NT-proBNP) and its active form, brain-type natriuretic peptide (BNP), in a simple blood test are the gold-standard biomarkers for HF diagnosis. However, even good biomarkers such as natriuretic peptides fail to predict all the risks associated with HF due to the diversity of the mechanisms involved. The pathophysiology of HF is determined by numerous factors, including oxidative stress, inflammation, neuroendocrine activation, pathological angiogenesis, changes in apoptotic pathways, fibrosis and vascular remodeling. High readmission and mortality rates prompt a search for new markers for the diagnosis, prognosis and treatment of HF. Oxidative-stress-mediated inflammation plays a crucial role in the development of subsequent changes in the failing heart and provides a new insight into this complex mechanism. Oxidative stress and inflammatory biomarkers appear to be a promising diagnostic and prognostic tool in patients with HF. This systematic review provides an overview of the current knowledge about oxidative stress and inflammation parameters as markers of HF.

Circumventricular Organ Apelin Receptor Knockdown Decreases Blood Pressure and Sympathetic Drive Responses in the Spontaneously Hypertensive Rat

The central site(s) mediating the cardiovascular actions of the apelin-apelin receptor (APJ) system remains a major question. We hypothesized that the sensory circumventricular organs (CVOs), interfacing between the circulation and deeper brain structures, are sites where circulating apelin acts as a signal in the central nervous system to decrease blood pressure (BP). We show that APJ gene (aplnr) expression was elevated in the CVOs of spontaneously hypertensive rats (SHRs) compared to normotensive Wistar Kyoto (WKY) controls, and that there was a greater mean arterial BP (MABP) decrease following microinjection of [Pyr¹]apelin-13 to the CVOs of SHRs compared to WKY rats. Lentiviral APJ-specific-shRNA (LV-APJ-shRNA) was used to knockdown aplnr expression, both collectively in three CVOs and discretely in individual CVOs, of rats implanted with radiotelemeters to measure arterial pressure. LV-APJ-shRNA-injection decreased aplnr expression in the CVOs and abolished MABP responses to microinjection of [Pyr¹]apelin-13. Chronic knockdown of aplnr in any of the CVOs, collectively or individually, did not affect basal MABP in SHR or WKY rats. Moreover, knockdown of aplnr in any of the CVOs individually did not affect the depressor response to systemic [Pyr¹]apelin-13. By contrast, multiple knockdown of aplnr in the three CVOs reduced acute cardiovascular responses to peripheral [Pyr¹]apelin-13 administration in SHR but not WKY rats. These results suggest that endogenous APJ activity in the CVOs has no effect on basal BP but that functional APJ in the CVOs is required for an intact cardiovascular response to peripherally administered apelin in the SHR.

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.

Relationship between Apelin/APJ Signaling, Oxidative Stress, and Diseases

Apelin, a peptide hormone, is an endogenous ligand for G protein-coupled receptor and has been shown to be widely expressed in human and animal tissues, such as the central nervous system and adipose tissue. Recent studies indicate that the apelin/APJ system is involved in the regulation of multiple physiological and pathological processes, and it is associated with cardiovascular diseases, metabolic disorders, neurological diseases, ischemia-reperfusion injury, aging, eclampsia, deafness, and tumors. The occurrence and development of these diseases are closely related to the local inflammatory response. Oxidative stress is that the balance between oxidation and antioxidant is broken, and reactive oxygen species are produced in large quantities, causing cell or molecular damage, which leads to vascular damage and a series of inflammatory reactions. Hence, this article reviewed recent advances in the relationship between apelin/APJ and oxidative stress, and inflammation-related diseases, and highlights them as potential therapeutic targets for oxidative stress-related inflammatory diseases.