Cardioprotective Effects of Apelin in Myocardial Ischemia/Reperfusion Injury: A Systematic Review and Meta-Analysis

Myocardial ischemia/reperfusion (I/R) injury remains a major clinical challenge, because blood flow restoration can exacerbate tissue damage. Apelin, an endogenous peptide acting through the APJ receptor, has demonstrated cardioprotective effects in experimental models. The APJ receptor, a G-protein-coupled receptor widely expressed in cardiovascular tissues, mediates vasodilation, cardiac contractility, and angiogenesis. This systematic review and meta-analysis evaluates its efficacy in myocardial I/R injury. A systematic search in Medline (PubMed), Embase, Scopus, and Web of Science was conducted up to 2024, identifying rodent studies of cardiac I/R injury (Langendorff/in vivo) treated with apelin. Studies on pretreatment or chronic ischemia were excluded. A random-effects meta-analysis reported standardized mean differences with 95% confidence intervals, assessing heterogeneity using the I 2 statistic. From 1765 records, 26 preclinical studies met inclusion criteria. Apelin significantly improved +LVdp/dtmax, -LVdp/dtmax, left ventricular end-diastolic pressure, left ventricular end-systolic pressure, left ventricular ejection fraction, left ventricular developed pressure × heart rate, cardiac output, stroke volume, coronary flow, and left ventricular developed pressure, but did not affect heart rate, mean arterial pressure, left ventricular end-diastolic volume, or left ventricular end-systolic volume. It reduced infarct size, fibrosis, lactate dehydrogenase, malondialdehyde, and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling assay), while also reducing creatine kinase-MB and improving adenosine triphosphate, energy charge, and phosphocreatine. Meta-regression indicated most outcomes were dose independent, although a few (eg, mean arterial pressure, terminal deoxynucleotidyl transferase dUTP nick end labeling) showed dose-related responses. The risk of bias was high in most studies, and publication bias was observed for some outcomes. Apelin exerts cardioprotective effects in rodent I/R models, enhancing cardiac function and metabolism while reducing infarct size, oxidative stress, and apoptosis. Further standardized preclinical and clinical studies are warranted to optimize dosing protocols and define therapeutic applicability.