[Pyr1]-Apelin-13 acts as a ligand for the apelin receptor (APJ) G protein-coupled receptor and is a substrate for angiotensin-converting enzyme 2. Apelin is a member of the adipokine hormone family from adipose tissue. Adipokines are involved in processes such as vascular homeostasis and angiogenesis.

Apelin and the apelin receptor are widely distributed throughout the body. Apelin is associated with cardiovascular diseases, obesity, diabetes and cancer. Apelin is expressed in the spinal cord and the human brain. Immunohistochemistry shows that Apelin-17 is significantly expressed in the human heart, brain, lungs and endothelial cells. Studies show myocardial infarction apelin mRNA expression is greater during human heart failure than in healthy tissue. Apelin protects against heart failure due to the pyroglutamic form of apelin, [Pyr1]-Apelin-13, which decreases infarct size of myocardial infarctions. Furthermore, rats with hypertension have reduced levels of apelin and APJ. [Pyr1]-Apelin-13 exhibits higher APJ agonist potency than Apelin-13. We also have the alternative [Tyr0]-Apelin-13 available.