Apelin-17

Where it comes from

Made in

Brain, heart and kidney, cut from the same precursor

Sent out by

With the other apelins

Acts on

• Vessels
• Hypothalamus
• Kidney

What it does

• Lowers blood pressure more lastingly than apelin-13 in rats ¹
• Pulls the apelin receptor into the cell far more strongly than apelin-13 does, which is the clearest difference between the two ¹
• Stronger at water handling in animal studies, through the vasopressin neurons of the hypothalamus ¹

In medicine

• No medicine, no test and no human infusion study: it has stayed a laboratory peptide
• It reaches the clinic only through what it taught about the receptor. Removing its last phenylalanine separates the signalling from the internalisation, and that is the design idea behind biased apelin agonists ²

Beyond the body’s own use

• The work on it is about biased signalling rather than treatment: a ligand that drives the Gi pathway without dragging the receptor inside might lower blood pressure without the receptor going quiet ²
• Nothing is in trials. Whether the longer apelins are present in human blood in meaningful amounts, or are largely an artefact of how tissue is extracted, is still argued ¹
• The practical reading is that the apelins are one hormone cut to several lengths, and the length decides how long the signal lasts rather than what it says ¹