Pyr-apelin-13

Where it comes from

Made in

Heart and blood: the predominant apelin found in human heart tissue

Sent out by

With the other apelins

Acts on

• Heart muscle
• Vessels
• Kidney

What it does

• The pyroglutamate cap blocks the enzymes that chew peptides from the front, so it outlasts plain apelin-13 in blood ¹
• The form actually present in human heart tissue, which is why it, and not apelin-13, is what infusion studies use ¹
• At the receptor it behaves as apelin-13 does: vessel relaxation through the endothelium, and a stronger, faster heartbeat ²

In medicine

• Infused in healthy volunteers and in patients with heart failure as a research probe, where it raised cardiac output and lowered systemic resistance within minutes ²
• No approved medicine and no clinical assay. Commercial apelin kits do not report the isoforms separately, so a published apelin level is a mixture ¹

Beyond the body’s own use

• Its discovery changed what counts as the real human apelin: the peptide most earlier work had used is not the one the heart mainly holds ¹
• Analogues meant for the clinic start from this form because of its stability, and none has yet reached a registered trial
• Nothing is in human use beyond research infusions. How much of the apelin measured in blood is this form is still unknown ¹