title: Glucagon-like peptide (GLP)-1(9-36)amide-mediated cytoprotection is blocked by exendin(9-39) yet does not require the known GLP-1 receptor.
abstract: The widely expressed dipeptidyl peptidase-4 enzyme rapidly cleaves the gut hormone glucagon-like peptide-1 [GLP-1(7-36)amide] at the N terminus to generate GLP-1(9-36)amide. Both intact GLP-1(7-36)amide and GLP-1(9-36)amide exert cardioprotective actions in rodent hearts; however, the mechanisms underlying the actions of GLP-1(9-36)amide remain poorly understood. We used mass spectrometry of coronary effluents to demonstrate that isolated mouse hearts rapidly convert infused GLP-1(7-36)amide to GLP-1(9-36)amide. After ischemia-reperfusion (I/R) injury of isolated mouse hearts, administration of GLP-1(9-36)amide or exendin-4 improved functional recovery and reduced infarct size. The direct actions of these peptides were studied in cultured neonatal mouse cardiomyocytes. Both GLP-1(9-36)amide and exendin-4 increased levels of cAMP and phosphorylation of ERK1/2 and the phosphoinositide 3-kinase target protein kinase B/Akt. In I/R injury models in vitro, both peptides improved mouse cardiomyocyte viability and reduced lactate dehydrogenase release and caspase-3 activation. These effects were attenuated by inhibitors of ERK1/2 and phosphoinositide 3-kinase. Unexpectedly, the cardioprotective actions of GLP-1(9-36)amide were blocked by exendin(9-39) yet preserved in Glp1r(-/-) cardiomyocytes. Furthermore, GLP-1(9-36)amide, but not exendin-4, improved the survival of human aortic endothelial cells undergoing I/R injury, actions sensitive to the nitric oxide synthase inhibitor, N(G)-nitro-l-arginine methyl ester (L-NAME). In summary, our findings demonstrate separate actions for GLP-1(9-36)amide vs. the GLP-1R agonist exendin-4 and reveal the existence of a GLP-1(9-36)amide-responsive, exendin(9-39)-sensitive, cardioprotective signaling pathway distinct from that associated with the classical GLP-1 receptor.
authors.affiliation: TMDT 3-904, 200 Elizabeth Street, Toronto, Ontario, Canada M5G 2C4.
authors.forename: Kiwon
authors.initials: K
authors.lastname: Ban
authors.forename: Kyoung-Han
authors.initials: KH
authors.lastname: Kim
authors.forename: Chan-Kyung
authors.initials: CK
authors.lastname: Cho
authors.forename: Meghan
authors.initials: M
authors.lastname: Sauvé
authors.forename: Eleftherios P
authors.initials: EP
authors.lastname: Diamandis
authors.forename: Peter H
authors.initials: PH
authors.lastname: Backx
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Drucker
authors.forename: Mansoor
authors.initials: M
authors.lastname: Husain
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D019610:Cytoprotection / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D000077270:Exenatide; D052216:Glucagon-Like Peptide 1 / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism; D000067757:Glucagon-Like Peptide-1 Receptor; D006321:Heart / Q000187:drug effects; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D010446:Peptide Fragments / Q000008:administration & dosage / Q000378:metabolism*; D010455:Peptides / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D018027:Receptors, Glucagon / Q000235:genetics / Q000378:metabolism*; D020127:Recovery of Function; D015427:Reperfusion Injury / Q000188:drug therapy; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014688:Venoms / Q000494:pharmacology
chemical_list: C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D010446:Peptide Fragments; D010455:Peptides; D018027:Receptors, Glucagon; D014688:Venoms; C114437:glucagon-like peptide-1 (9-36)-amide; C083773:exendin (9-39); D052216:Glucagon-Like Peptide 1; D000077270:Exenatide