Cell lines

H9c2 cells

Preparation Method

Cells were allowed to reach 80% confluence in complete DMEM and were incubated for an additional 24 h in serum-free medium prior to experimental treatments. Following this, H9c2 cells were treated with 0, 5, 25, 50, 100, 200, 400, 600, 800 or 1,000 nM Apelin-13 for 24 h

Reaction Conditions

0, 5, 25, 50, 100, 200, 400, 600, 800 or 1,000 nM for 24 hours

Applications

Apelin-13 treatment increased the percentage cell viability compared with the baseline constitutive release over a range of physiological extracellular concentrations from 50 to 600 nM, with a maximal effect at 200 nM.

Animal models

male Sprague-Dawley rats

Preparation Method

Rats were injected with a 0.9% equivolume saline control before peptide injection. Apelin-13 was dissolved as a stock solution of 40 µg/ml in 0.9% saline and administered intravenously at ∼3-6 µg/kg B.W., i.e., 1-2 µg per 300-g rat.

Dosage form

Intravenous injection, 1-2 µg per 300-g

Applications

An apelin-13 dose of 1 µg/300 g B.W. elicited an immediate change in blood pressure of -10.0 ± 1.9 mm Hg systolic and -13.0 ± 2.8 mm Hg diastolic. A 2 µg/300 g B.W. dose elicited immediate blood pressure changes of -9.8 ± 1.2 systolic and -13.2 ± 1.7 mm Hg diastolic.

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(C)\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.