title: GIP(3-30)NH2is a potent competitive antagonist of the GIP receptor and effectively inhibits GIP-mediated insulin, glucagon, and somatostatin release.
abstract: Alternative processing of the precursor protein pro-GIP results in endogenously produced GIP(1-30)NH2, that by DPP-4 cleavage in vivo results in the metabolite GIP(3-30)NH2. We showed previously that GIP(3-30)NH2is a high affinity antagonist of the human GIPR in vitro. Here we determine whether it is suitable for studies of GIP physiology in rats since effects of GIP agonists and antagonists are strictly species-dependent. Transiently transfected COS-7 cells were assessed for cAMP accumulation upon ligand stimulation or assayed in competition binding using human125I-GIP(1-42) as radioligand. In isolated perfused rat pancreata, insulin, glucagon, and somatostatin-releasing properties were evaluated. Competition binding demonstrated that on the rat GIP receptor (GIPR), rat GIP(3-30)NH2bound with high affinity (Kiof 17nM), in contrast to human GIP(3-30)NH2(Kiof 250nM). In cAMP studies, rat GIP(3-30)NH2inhibited GIP(1-42)-induced rat GIPR activation and schild-plot analysis showed competitive antagonism with a pA2of 13nM and a slope of 0.9±0.09. Alone, rat GIP(3-30)NH2displayed weak, low-potent partial agonistic properties (EC50>1μM) with an efficacy of 9.4% at 0.32μM compared to GIP(1-42). In perfused rat pancreata, rat GIP(3-30)NH2efficiently antagonized rat GIP(1-42)-induced insulin, somatostatin, and glucagon secretion. In summary, rat GIP(3-30)NH2is a high affinity competitive GIPR antagonist and effectively antagonizes GIP-mediated G protein-signaling as well as pancreatic hormone release, while human GIP(3-30)NH2, despite a difference of only one amino acid between the two (arginine in position 18 in rat GIP(3-30)NH2; histidine in human), is unsuitable in the rat system. This underlines the importance of species differences in the GIP system, and the limitations of testing human peptides in rodent systems.
authors.affiliation: Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, The Panum Institute, University of Copenhagen, Denmark; NNF Center for Basic Metabolic Research, Denmark.
authors.forename: A H
authors.initials: AH
authors.lastname: Sparre-Ulrich
authors.affiliation: Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, The Panum Institute, University of Copenhagen, Denmark.
authors.forename: M N
authors.initials: MN
authors.lastname: Gabe
authors.affiliation: Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, The Panum Institute, University of Copenhagen, Denmark; NNF Center for Basic Metabolic Research, Denmark; Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Denmark.
authors.forename: L S
authors.initials: LS
authors.lastname: Gasbjerg
authors.affiliation: NNF Center for Basic Metabolic Research, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: C B
authors.initials: CB
authors.lastname: Christiansen
authors.affiliation: NNF Center for Basic Metabolic Research, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Svendsen
authors.affiliation: NNF Center for Basic Metabolic Research, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Hartmann
authors.affiliation: NNF Center for Basic Metabolic Research, Denmark; Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: J J
authors.initials: JJ
authors.lastname: Holst
authors.affiliation: Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, The Panum Institute, University of Copenhagen, Denmark. Electronic address: rosenkilde@sund.ku.dk.
authors.forename: M M
authors.initials: MM
authors.lastname: Rosenkilde
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D005749:Gastric Inhibitory Polypeptide / Q000737:chemistry / Q000494:pharmacology / Q000502:physiology*; D005934:Glucagon / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011964:Receptors, Gastrointestinal Hormone / Q000037:antagonists & inhibitors*; D017386:Sequence Homology, Amino Acid; D013004:Somatostatin / Q000378:metabolism*
chemical_list: D007328:Insulin; D010446:Peptide Fragments; D011964:Receptors, Gastrointestinal Hormone; C101760:gastric inhibitory polypeptide (1-42); C000619446:gastric inhibitory polypeptide (3-30)-amide; D013004:Somatostatin; D005749:Gastric Inhibitory Polypeptide; D005934:Glucagon; C041086:gastric inhibitory polypeptide receptor
keywords: Antagonist; Competition binding; Glucose-dependent insulinotropic polypeptide receptor; Pancreatic hormone secretion; cAMP