Apelin-13

Apelin-13 is a peptide known as the ligand of the G-protein-coupled receptor APJ. ^[1]. Apelin-13 activated this G protein-coupled receptor with an EC50 value of 0.37 nM ^[2]. Apelin has been shown to be involved in the regulation of cardiovascular and fluid homeostasis, food intake, cell proliferation, and angiogenesis ^[1].

Apelin-13 was shown to inhibit insulin secretion stimulated by high glucose concentrations (10 mM) or potentiated by GLP-1 in INS-1 cells ^[3]. Apelin-13 at 200 nM can enhance H9c2 cell proliferation, which is mediated by the ERK1/2 and Akt signaling pathway ^[4].

Apelin-13 treatment significantly lowers blood glucose and protects HFD mice from hyperinsulinemia ^[5]. There are some contradictory reports about the effects of apelin-13/APJ on hypertension. Intraperitoneally administered Apelin-13 reduces blood pressure in hypertensive rats by inhibiting renin-angiotensin system ^[6]. Chronic infusion of apelin-13 into the paraventricular nucleus induces hypertension through increasing the levels of plasma norepinephrine and arginine vasopressin in normotensive rats ^[7].

References:
[1]. Castan-Laurell I, Dray C, AttanÉ C, et al. Apelin, diabetes, and obesity[J]. Endocrine, 2011, 40(1): 1-9.
[2]. Tatemoto K, Hosoya M, Habata Y, et al. Isolation and characterization of a novel endogenous peptide ligand for the human APJ receptor[J]. Biochemical and biophysical research communications, 1998, 251(2): 471-476.
[3]. Guo L, Li Q, Wang W, et al. Apelin inhibits insulin secretion in pancreatic β-cells by activation of PI3-kinase-phosphodiesterase 3B[J]. Endocrine research, 2009, 34(4): 142-154.
[4]. Yin L, Zhang P, Li C, et al. Apelin?13 promotes cell proliferation in the H9c2 cardiomyoblast cell line by triggering extracellular signal?regulated kinase 1/2 and protein kinase B phosphorylation[J]. Molecular Medicine Reports, 2018, 17(1): 447-451.
[5]. AttanÉ C, Foussal C, Le Gonidec S, et al. Apelin treatment increases complete Fatty Acid oxidation, mitochondrial oxidative capacity, and biogenesis in muscle of insulin-resistant mice[J]. Diabetes, 2012, 61(2): 310-320.
[6]. Akc?lar R, Turgut S, Caner V, et al. Apelin effects on blood pressure and RAS in DOCA-salt-induced hypertensive rats[J]. Clinical and Experimental Hypertension, 2013, 35(7): 550-557.
[7]. Zhang F, Sun H J, Xiong X Q, et al. Apelin©\13 and APJ in paraventricular nucleus contribute to hypertension via sympathetic activation and vasopressin release in spontaneously hypertensive rats[J]. Acta physiologica, 2014, 212(1): 17-27.