reviewed april 2026|next review october 2026|88 physicians psi has verified|272652 published studies
Apelin-13
Apelin-13 is the shortest and most potent naturally occurring (the body's own) isoform of the apelin peptide family, a 13-amino-acid C-terminal fragment that activates the APJ/APLNR receptor with the strongest binding affinity among naturally occurring apelin forms, with the [Pyr1]apelin-13 variant showing improved resistance to enzymatic degradation.
Evidence landscape: 272652 published studies
Published studies indexed under this compound. Apelin-13 is the most commonly used isoform in both animal studies and clinical research on the apelin system.
- 5 Human
- 191 Animal
- 4 Reviews
- 272452 Other research
Not FDA-approved. No apelin-13-based drug has reached regulatory approval. Apelin receptor agonists are in early clinical development, using this isoform's pharmacology as a starting point.
Not commercially available as a therapeutic. Naturally occurring (the body's own) peptide fragment with a very short half-life. Available as a research compound from peptide suppliers.
The most potent naturally occurring (the body's own) APJ receptor agonist. Cross-reference with the apelin-peptide page for full apelin system biology. The [Pyr1] (pyroglutamyl) modification at position 1 is a naturally occurring variant that resists aminopeptidase degradation.
PSI Assessment
Among the three naturally occurring apelin isoforms (apelin-36, apelin-17, apelin-13), the 13-amino-acid fragment binds the APJ receptor most potently and is the isoform most pharmaceutical programs have used as a starting point for drug development. The naturally occurring [Pyr1]apelin-13 variant, which has a pyroglutamyl cap that protects against enzymatic degradation, has been particularly important for in vivo research because it survives longer in circulation than the unmodified form.
The most potent naturally occurring APJ receptor isoform. The [Pyr1] variant resists enzymatic degradation. Starting point for most apelin-based drug development programs.
The mechanism is APJ/APLNR receptor activation through the same pathway described on the apelin-peptide page, but apelin-13 has the highest receptor binding affinity among naturally occurring forms. It produces positive inotropy (stronger heart contractions) via PI3K/Akt and ERK (extracellular signal-regulated kinase) 1/2 signaling, vasodilation via nitric oxide release, and glucose uptake enhancement in peripheral tissues.
What the evidence supports
Apelin-13 is the most potent APJ receptor isoform with documented positive inotropic and vasodilatory effects. The [Pyr1]apelin-13 variant shows improved protease resistance compared to unmodified apelin fragments. Human vascular studies confirm nitric oxide-dependent vasodilation from apelin-13 infusion.
What is not yet established
Whether apelin-13-based therapeutics can achieve the sustained receptor activation needed for chronic cardiovascular disease. Optimal formulation and delivery for clinical use. Head-to-head comparison of apelin isoforms for therapeutic development.
Research Evidence
The findings below cover what human vascular studies and animal research have established for this specific apelin isoform.
Evidence by condition
Evidence dimensions across apelin-13 research areas. Cardiac contractility and vascular biology have the deepest characterization. Heart failure applications build on the broader apelin infusion data.
| Condition | Mechanism | Animal evidence | Human evidence | Replication |
|---|---|---|---|---|
| Cardiac Contractility | ||||
| Heart Failure Research | ||||
| Vascular Biology |
Apelin-13 infusion in healthy human volunteers produced forearm vasodilation through a nitric oxide-dependent mechanism, confirming direct vascular activity in living humans.
The vasodilation was blocked by nitric oxide synthase inhibition, establishing the mechanism in humans. These results are consistent with the hemodynamic findings from the broader apelin infusion studies in heart failure patients.
Apelin-13 maintained its beneficial hemodynamic effects even when the renin-angiotensin system was simultaneously activated by angiotensin II co-infusion. This is therapeutically relevant because heart failure patients have chronically elevated angiotensin II.
The ability to produce vasodilation in the presence of angiotensin II activation distinguishes apelin from some other vasodilatory peptides and supports its potential relevance in the heart failure setting where the renin-angiotensin system is overactive.
The [Pyr1]apelin-13 variant has a pyroglutamyl modification at position 1 that protects against aminopeptidase degradation, extending its functional half-life compared to unmodified apelin-13. This variant has become the standard research isoform for in vivo studies.
Despite the improved stability, [Pyr1]apelin-13 still has a half-life too short for therapeutic use without further modification. It serves as the pharmacological template for synthetic APJ agonists in drug development pipelines.
5 Human|191 Animal|4 Reviews
View all 272652 indexed studiesHow Apelin-13 Works
A shorter version of apelin that strengthens heart contractions and opens blood vessels. Apelin-13 is like a more concentrated version of the apelin signal. The same message delivered more potently through the same receptor.
A shorter version of apelin that strengthens heart contractions and opens blood vessels.
For a more detailed view of the biology, here is what researchers have observed at the molecular level.
Apelin-13 is the 13-amino-acid C-terminal fragment of the apelin precursor, representing the most potent naturally occurring APJ/APLNR agonist. It activates PI3K/Akt and ERK (extracellular signal-regulated kinase) 1/2 signaling cascades, producing positive inotropy without hypertrophic signaling, NO-dependent vasodilation, and enhanced glucose uptake. The [Pyr1]apelin-13 variant has a pyroglutamyl cap at position 1 that resists aminopeptidase degradation, extending functional half-life from seconds to minutes in circulation.
What is Apelin-13 being studied for?
Researchers are studying Apelin-13 across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for Apelin-13 overall. This means a compound can have human studies for one condition but only animal data for another.
Cardiac Contractility
·Animal StudiesApelin-13 is a positive inotrope that increases the force of heart contractions without increasing oxygen demand or promoting hypertrophy. This distinguishes it from conventional inotropic agents.
Limitations: Inotropic effects characterized primarily in isolated heart preparations and acute infusion studies. Chronic administration data is limited to animal models (animal research).
Heart Failure Research
·Animal StudiesApelin-13 produces vasodilation and improved cardiac output in the presence of angiotensin II activation, a condition that characterizes heart failure. Apelin levels are reduced in heart failure patients.
Limitations: Human heart failure data comes from the broader apelin infusion literature rather than apelin-13-specific trials. Therapeutic development requires stable analogs.
Vascular Biology
·Animal StudiesApelin-13 produces nitric oxide-dependent vasodilation in human forearm studies. The vasodilatory effect is maintained during concurrent renin-angiotensin system activation.
Limitations: Acute vascular study data. Whether sustained apelin-13 receptor activation produces long-term vascular benefit is not established.
Safety and Regulatory Status
FDA Status: Not FDA-approved. No apelin-13-based drug has reached regulatory approval. Apelin receptor agonists based on this isoform's pharmacology are in early clinical development.
Availability: Not commercially available as a therapeutic. Available as a research compound. The native peptide and [Pyr1] variant both have half-lives too short for therapeutic use.
Class context: Naturally occurring (the body's own) peptide fragment. Well tolerated in human vascular infusion studies with no significant adverse effects reported. The primary limitation is pharmacokinetic, not safety-related.
Apelin-13 is naturally occurring (the body's own) and well tolerated in human infusion studies. No safety concerns have been identified from acute administration. As with other apelin isoforms, the barrier to therapeutic use is the extremely short half-life rather than toxicity.
Peptide Structure
Technical molecular data for researchers and clinicians.
Questions and Comparisons
Questions the evidence raises for a Apelin-13 discussion.
Frequently Asked Questions
References
Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.
- 1.Investigated the vascular effects of apelin-13 infusion in healthy human volunteers. The study found that apelin-13 produced forearm vasodilation through a nitric oxide-dependent mechanism, establishing that this specific apelin fragment has direct vascular activity in living humans.Japp AG et al., 2010 in J Am Heart Assoc. View on PubMed
- 2.Examined sustained cardiovascular effects of apelin-13 infusion in the context of angiotensin II co-infusion and in heart failure patients. The results demonstrated that apelin-13 maintained its beneficial hemodynamic effects even when the renin-angiotensin system was activated, which is therapeutically relevant because heart failure patients have elevated angiotensin II levels.Barnes GD et al., 2013 in Heart. View on PubMed
- 3.Described the development of a modified apelin-13 analogue designed to resist enzymatic breakdown in the bloodstream. The analogue maintained receptor binding and functional activity while having a significantly longer half-life than native apelin-13, addressing one of the key barriers to using apelin peptides as therapeutics.Nyimanu D et al., 2020 in Front Pharmacol. View on PubMed
- 4.Authoritative pharmacological review of the apelin receptor (APJ). The paper characterized receptor binding properties of apelin-13 and other apelin fragments, described signal transduction pathways, and summarized the clinical potential of targeting this receptor system in cardiovascular disease, pulmonary hypertension, and metabolic disorders.Read C et al., 2021 in Br J Pharmacol. View on PubMed
- 5.Demonstrated that apelin-13 reduced pathological heart muscle thickening in an animal model of pressure overload. The protective effect was mediated through the PI3K/Akt/mTOR signaling pathway. This study provided mechanistic evidence for how apelin-13 may protect the heart from damage caused by chronically elevated blood pressure.Yang P et al., 2017 in J Cell Mol Med. View on PubMed
Medical Disclaimer
This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.