title: Des-acyl ghrelin has specific binding sites and different metabolic effects from ghrelin in cardiomyocytes.
abstract: The current study aimed to compare the effects of the peptide hormone ghrelin and des-G, its unacylated isoform, on glucose and fatty acid uptake and to identify des-G-specific binding sites in cardiomyocytes. In the murine HL-1 adult cardiomyocyte line, ghrelin and des-G had opposing metabolic effects: des-G increased medium-chain fatty acid uptake (BODIPY fluorescence intensity), whereas neither ghrelin alone nor in combination with des-G did so. Ghrelin inhibited the increase in glucose uptake normally induced by insulin (rate of 2-[(3)H]deoxy-d-glucose incorporation), but des-G did not; des-G was also able to partially reverse the inhibitory effect of ghrelin. In HL-1 cells and primary cultures of neonatal rat cardiomyocytes, des-G but not ghrelin increased insulin-induced translocation of glucose transporter-4 from nuclear to cytoplasmic compartments (immunohistochemistry and quantitative confocal analysis). AKT was phosphorylated by insulin but not affected by ghrelin or des-G, whereas neither AMP-activated protein kinase nor phosphatase and tensin homolog deleted from chromosome 10 was phosphorylated by any treatments. HL-1 and primary-cultured mouse and rat cardiomyocytes each possessed two independent specific binding sites for des-G not recognized by ghrelin (radioreceptor assays). Neither ghrelin nor des-G affected viability (dimethylthiazol diphenyltetrazolium bromide assays), whereas both isoforms were equally protective against apoptosis. Therefore, in cardiomyocytes, des-G binds to specific receptors and has effects on glucose and medium-chain fatty acid uptake that are distinct from those of ghrelin. Real-time PCR indicated that expression levels of ghrelin O-acyltransferase RNA were comparable between HL-1 cells, human myocardial tissue, and human and murine stomach tissue, indicating the possibility of des-G conversion to ghrelin within our model.
authors.affiliation: Molecular and Cellular Cardiology Unit, Institute of Biomedical Research, and Department of Cardiology, Travesia Choupana s/n, Santiago de Compostela 15706, Spain.
authors.forename: Pamela V
authors.initials: PV
authors.lastname: Lear
authors.forename: María J
authors.initials: MJ
authors.lastname: Iglesias
authors.forename: Sandra
authors.initials: S
authors.lastname: Feijóo-Bandín
authors.forename: Diego
authors.initials: D
authors.lastname: Rodríguez-Penas
authors.forename: Ana
authors.initials: A
authors.lastname: Mosquera-Leal
authors.forename: Vanessa
authors.initials: V
authors.lastname: García-Rúa
authors.forename: Oreste
authors.initials: O
authors.lastname: Gualillo
authors.forename: Corrado
authors.initials: C
authors.lastname: Ghè
authors.forename: Elisa
authors.initials: E
authors.lastname: Arnoletti
authors.forename: Giampiero
authors.initials: G
authors.lastname: Muccioli
authors.forename: Carlos
authors.initials: C
authors.lastname: Diéguez
authors.forename: José R
authors.initials: JR
authors.lastname: González-Juanatey
authors.forename: Francisca
authors.initials: F
authors.lastname: Lago
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D005753:Gastric Mucosa / Q000378:metabolism; D054439:Ghrelin / Q000378:metabolism* / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D007328:Insulin / Q000494:pharmacology; D007850:Lauric Acids / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats
chemical_list: D054439:Ghrelin; D051275:Glucose Transporter Type 4; D007328:Insulin; D007850:Lauric Acids; C422650:ghrelin, des-n-octanoyl; C030358:lauric acid; D051057:Proto-Oncogene Proteins c-akt; D055372:AMP-Activated Protein Kinases; D051059:PTEN Phosphohydrolase; D005947:Glucose