Apelin/ELABELA-APJ system in cardiac hypertrophy: Regulatory mechanisms and therapeutic potential

Apelin-13 Protects Against Myocardial Hypoxia/Reoxygenation (H/R) Injury by Inhibiting Ferroptosis Via Nrf2 Activation

Ischemia-reperfusion (IR)-induced myocardial damage represents a major pathological event in coronary artery disease (CAD). Effective therapeutic strategies are urgently needed to improve clinical outcomes for CAD patients. Apelin-13, primarily produced by magnocellular neurons, exhibits diverse biological functions across various cell types and tissues. However, its role in myocardial IR injury remains unexplored. In this study, we utilized an in vitro model of myocardial IR injury using H9c2 cardiomyocytes to investigate the potential protective effects of Apelin-13. Our findings reveal that Apelin-13 protects against hypoxia/reoxygenation (H/R)-induced oxidative stress in H9c2 cells by reducing mitochondrial reactive oxygen species (ROS) and malondialdehyde (MDA) levels, while enhancing superoxide dismutase (SOD) activity. Additionally, Apelin-13 alleviates H/R-induced mitochondrial dysfunction, as evidenced by increased mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP) production. Crucially, Apelin-13 mitigates H/R-induced cardiomyocyte injury, as shown by reduced levels of creatine kinase-myocardial band (CK-MB), cardiac troponin I (cTnI), and lactate dehydrogenase (LDH). Remarkably, Apelin-13 also counteracts ferroptosis during H/R by decreasing ferrous iron (Fe²⁺) concentrations, increasing glutathione (GSH) levels, and suppressing glutathione peroxidase 4 (GPX4) and ferritin heavy chain 1 (FTH1) expression. These protective actions were negated by the ferroptosis inducer Erastin. Further investigation revealed that Apelin-13 activates the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) through enhanced nuclear translocation and upregulation of heme oxygenase-1 (HO-1). Conversely, Nrf2 knockdown nullified the protective effects of Apelin-13 against ferroptosis and cardiomyocyte injury, underscoring the critical involvement of Nrf2 in mediating these benefits. Collectively, our results highlight the promising therapeutic potential of Apelin-13 in managing CAD.

Advances in the therapeutic potentials of ligands of the apelin receptor APJ

Angiotensin II protein J receptor, APJ, is a type A G protein coupled receptor. Endogenous apelin and elabela peptides stimulate APJ via distinct signalling profiles. A complex signalling map of elabela-stimulated APJ was published in 2022. Dimerization or oligomerization of APJ with itself or other receptor(s) can affect APJ signalling. Apelin has been shown to tolerate mutations and/or modifications at multiple sites without abolishing activity. This offers a great opportunity to design and engineer variants with desired signalling profiles and enhanced resistance to breakdown by peptidases. Several biased agonists with enhanced therapeutic potential have been generated. APJ agonists have therapeutic potential in multiple diseases including cardiovascular, renal, pulmonary and metabolic diseases, and viral infections. APJ antagonists may have therapeutic potential in cancer and retinopathy, and in related diseases in which unwanted angiogenesis is to be halted. A growing understanding of APJ signalling pathways and the robust therapeutic potential of associated ligands for many serious diseases will stimulate the clinical development of APJ ligands.

Apelin deficiency exacerbates cardiac injury following infarction by accelerating cardiomyocyte ferroptosis

Apelin is an endogenous ligand for the Apelin receptor and is a critical protective effector in myocardial infarction (MI). Nevertheless, these protective mechanisms are not fully understood. Ferroptosis is the major driving factor of MI. This study aimed to investigate the effects and underlying regulatory mechanisms of Apelin on cardiomyocyte ferroptosis in MI. A model of MI was induced in adult C57BL/6J wild type (WT) and Apelin knockout (Apelin-/-) mice. Cardiac function was examined by echocardiography 4 weeks post-MI. RNA-seq, histochemical analyses, and Western blotting were applied to examine the effects of Apelin knockout on the transcriptome and pathological remodeling following infarction and the molecular mechanisms. Mice neonatal cardiomyocytes (NCMs) were used to establish the serum deprivation/hypoxia (SD/H) model in vitro. Compared with WT mice, Apelin-/- mice exhibited more severe impairment of cardiac function and increased fibrosis following infarction. Transcriptome and biochemical analyses revealed the involvement of ferroptosis in mediating Apelin function in MI. Ferroptosis-related proteins were significantly increased post-MI in Apelin-/- mice whereas p-AMPK was greatly decreased. Apelin treatment activated the AMPK pathway and thereby inhibited ferroptosis of NCMs induced by SD/H in vitro. These protective effects were partially reversed by AMPK inhibitor. Apelin deficiency aggravated cardiac dysfunction following infarction by activating cardiomyocyte ferroptosis via inhibition of the AMPK pathway. This offers a novel potential therapeutic target for MI treatment.

Methods to predict heart failure in diabetes patients

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is one of the leading causes of cardiovascular disease and powerful predictor for new-onset heart failure (HF).

AREAS COVERED

We focus on the relevant literature covering evidence of risk stratification based on imaging predictors and circulating biomarkers to optimize approaches to preventing HF in DM patients.

EXPERT OPINION

Multiple diagnostic algorithms based on echocardiographic parameters of cardiac remodeling including global longitudinal strain/strain rate are likely to be promising approach to justify individuals at higher risk of incident HF. Signature of cardiometabolic status may justify HF risk among T2DM individuals with low levels of natriuretic peptides, which preserve their significance in HF with clinical presentation. However, diagnostic and predictive values of conventional guideline-directed biomarker HF strategy may be non-optimal in patients with obesity and T2DM. Alternative biomarkers affecting cardiac fibrosis, inflammation, myopathy, and adipose tissue dysfunction are plausible tools for improving accuracy natriuretic peptides among T2DM patients at higher HF risk. In summary, risk identification and management of the patients with T2DM with established HF require conventional biomarkers monitoring, while the role of alternative biomarker approach among patients with multiple CV and metabolic risk factors appears to be plausible tool for improving clinical outcomes.