Apelin, is the recently described endogenous ligand for the G-protein-coupled receptor, APJ, Biochem Biophys Res Commun. 1998 Oct 20;251(2):471-6. Apelin was hence named to signify APJ-Endogenous-LIgaNd. Long and short forms of the peptide have been described with different forms in various tissues as the heart, brain, Biochim Biophys Acta. 2000 Jun 21;1492(1):72-80. lung, testis, uterus and mammary gland. Biochim Biophys Acta. 2001 Apr 23;1538(2-3):162-71. Apelin exists in three forms, each form consisting of a variable number of amino acids, all originating from a common 77-amino-acid precursor.
Apelin is expressed in the GIT, predominantly in the stomach with lower levels in the intestine and none in the pancreas. Endocrinology.2004 Mar;145(3):1342-8. Apelin has been shown to stimulate gastric cell proliferations in vitro, with stimulation of CCK release. It has an angiogenic Biochem Biophys Res Commun. 2004 Dec 10;325(2):395-400 ; Dev Biol. 2006 Aug 1;296(1):177-89 and ionotropic role in the cardiovascular system , Med Sci Monit. 2006 Jun;12(6):RA112-9 with blood pressure reducing properties in the rat, J Neurochem. 2000 Jan;74(1):34-41. It may stimulate drinking behaviour, J Neurochem. 2001 May;77(4):1085-96. acting as a diuretic neuropeptide in the CNS, by inhibiting the release and activity of vasopressin. Proc Natl Acad Sci U S A. 2004 Jul 13;101(28):10464-9. Apelin has other endocrine actions including stimulation of the release of plasma ACTH and corticosterone while decreasing plasma prolactin, LH and FSH
Apelin has recently been identified to be secreted by rodent and human adipocytes, Endocrinology. 2005 Apr;146(4):1764-71 suggesting its potential role as an adipokine. Fasting decreases and re-feeding increases Apelin levels in fat cells, and initial data seem to suggest that insulin may control adipocyte Apelin gene expression. Endocrinology. 2005 Apr;146(4):1764-71 Apelin levels in fat and plasma seem to correlate with the hyperinsulinism of obesity with higher expression in adipocytes during the stage of differentiation. Obesity thus seems to up-regulate Apelin expression in adipose tissue. Data with regard to the correlation of Apelin and insulin sensitivity in the obese state is awaited. Initial studies do not suggest an appetite modifying action for Apelin with central administration, Biochem Biophys Res Commun. 2002 Mar 15;291(5):1208-12. The possibility of water intake modulation has been suggested although this effect is controversial. Physiol Behav. 2006 Jul 11; Apelin does not increase NPY levels on central injection.
Apelin is expressed in the GIT, predominantly in the stomach with lower levels in the intestine and none in the pancreas. Endocrinology.2004 Mar;145(3):1342-8. Apelin has been shown to stimulate gastric cell proliferations in vitro, with stimulation of CCK release. It has an angiogenic Biochem Biophys Res Commun. 2004 Dec 10;325(2):395-400 ; Dev Biol. 2006 Aug 1;296(1):177-89 and ionotropic role in the cardiovascular system , Med Sci Monit. 2006 Jun;12(6):RA112-9 with blood pressure reducing properties in the rat, J Neurochem. 2000 Jan;74(1):34-41. It may stimulate drinking behaviour, J Neurochem. 2001 May;77(4):1085-96. acting as a diuretic neuropeptide in the CNS, by inhibiting the release and activity of vasopressin. Proc Natl Acad Sci U S A. 2004 Jul 13;101(28):10464-9. Apelin has other endocrine actions including stimulation of the release of plasma ACTH and corticosterone while decreasing plasma prolactin, LH and FSH
Apelin has recently been identified to be secreted by rodent and human adipocytes, Endocrinology. 2005 Apr;146(4):1764-71 suggesting its potential role as an adipokine. Fasting decreases and re-feeding increases Apelin levels in fat cells, and initial data seem to suggest that insulin may control adipocyte Apelin gene expression. Endocrinology. 2005 Apr;146(4):1764-71 Apelin levels in fat and plasma seem to correlate with the hyperinsulinism of obesity with higher expression in adipocytes during the stage of differentiation. Obesity thus seems to up-regulate Apelin expression in adipose tissue. Data with regard to the correlation of Apelin and insulin sensitivity in the obese state is awaited. Initial studies do not suggest an appetite modifying action for Apelin with central administration, Biochem Biophys Res Commun. 2002 Mar 15;291(5):1208-12. The possibility of water intake modulation has been suggested although this effect is controversial. Physiol Behav. 2006 Jul 11; Apelin does not increase NPY levels on central injection.