THE IMPACT OF APELIN LIGAND BINDING ON APJ RECEPTOR ON THE VARIOUS PHYSIOLOGICAL AND PATHOPHYSIOLOGICAL ASPECTS OF METABOLISM and HOMEOSTASIS

Nihal Abdallah Ibrahim*

ABSTRACT

Apelin is identified as an endogenous ligand of the apelin receptor (APJ). APJ is a member of the G protein- coupled receptor family. The apelinergic system; apelin and its receptor APJ; are expressed in a wide variety of tissues including the heart, the kidneys and the lungs. Apelin is also synthesised and released by the adipocytes as an adipokine which has an important impact in obesity, glucose metabolism and energy homeostasis. Apelin and the APJ are also expressed in the hypothalamo- hypophysial system for regulation of fluid homeostasis and in the hypothalamo-hypophysial- adrenal axis for stress control. Their interaction may have relevant pathophysiologic effects in those tissues. In this review we have presented the structure, and regulation of apelin and its receptor. We have also explained the various roles played by apelin in human physiology, homeostasis and its probable involvement in the pathogenesis of high prevalent diseases such as hypertension, heart failure, Diabetes Mellitus Type 2, obesity, fluid imbalance, anxiety and depression. This involvement ranked it as a target for various therapeutic implications.

Keywords: Apelin, APJ receptor (APJR), G Protein Coupled Receptors (GPCRs), Inotropic effect, vasodilator effect.