Apelin
Also known as: apelin-13, apelin-36, APLNR ligand
Apelin is a peptide hormone that binds to the apelin receptor (APLNR), also called APJ, found in various tissues such as blood vessels, the heart, and the brain. It starts as a precursor and is processed into several active isoforms, including apelin-36. Research explores the apelin system's roles in cardiovascular homeostasis, fluid balance, metabolism, muscle adaptation, and tumor biology.
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Overview
Mammalian protein found in Homo sapiens
Apelin is a peptide that in humans is encoded by the APLN gene. Apelin is one of two endogenous ligands for the G-protein-coupled APJ receptor that is expressed at the surface of some cell types. It is widely expressed in various organs such as the heart, lung, kidney, liver, adipose tissue, gastrointestinal tract, brain, adrenal glands, endothelium, and human plasma.
Mechanism of Action
Apelin interacts with the APJ receptor, a G protein-coupled receptor, as a balanced agonist. It activates Gi protein signaling, which reduces cAMP and initiates ERK pathways, and recruits beta-arrestin, desensitizing and internalizing the receptor. This balance dictates the duration and intensity of cellular responses and is a focal point of drug-discovery research targeting this receptor system.
Research History
The APJ receptor was initially discovered as an orphan receptor in the 1990s, lacking a known natural ligand. In 1998, apelin was isolated from bovine tissue and identified as this ligand. Research has since expanded into understanding its roles in the cardiovascular system and brain, discovering a second ligand named elabela, and investigating the significance of apelin in exercise physiology and cancer biology.
What Researchers Are Saying
Community Reports - Not Medical Advice
The following is aggregated from public forums, Reddit, and research communities. These are anecdotal reports from researchers only - not verified clinical data and not a recommendation of any kind.
Apelin (also known as apelin-13, apelin-36) is studied within the peptide research community. Endogenous APJ receptor ligand with cardioprotective and anti-hypertensive properties studied in heart failure and pulmonary hypertension.
Last updated October 28, 2026
Research status: emerging. Apelin appears across peptide research forums and academic literature. Researchers note this compound falls in the other category.
Last updated October 28, 2026
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