title: Glucose-dependent insulinotropic polypeptide is a growth factor for beta (INS-1) cells by pleiotropic signaling.
abstract: Activation of the G-protein-coupled receptor for glucose-dependent insulinotropic polypeptide facilitates insulin-release from pancreatic beta-cells. In the present study, we examined whether glucose-dependent insulinotropic polypeptide also acts as a growth factor for the beta-cell line INS-1. Here, we show that glucose-dependent insulinotropic polypeptide induced cellular proliferation synergistically with glucose between 2.5 mM and 15 mM by pleiotropic activation of signaling pathways. Glucose-dependent insulinotropic polypeptide stimulated the signaling modules of PKA/cAMP regulatory element binder, MAPK, and PI3K/protein kinase B in a glucose- and dose-dependent manner. Janus kinase 2 and signal transducer and activators of transcription 5/6 pathways were not stimulated by glucose-dependent insulinotropic polypeptide. Activation of PI3K by glucose-dependent insulinotropic polypeptide and glucose was associated with insulin receptor substrate isoforms insulin receptor substrate-2 and growth factor bound-2 associated binder-1 and PI3K isoforms p85alpha, p110alpha, p110beta, and p110gamma. Downstream of PI3K, glucose-dependent insulinotropic polypeptide-stimulated protein kinase Balpha and protein kinase Bbeta isoforms and phosphorylated glycogen synthase kinase-3, forkhead transcription factor FKHR, and p70S6K. These data indicate that glucose-dependent insulinotropic polypeptide functions synergistically with glucose as a pleiotropic growth factor for insulin-producing beta-cells, which may play a role for metabolic adaptations of insulin-producing cells during type II diabetes.
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology and Metabolism, Philipps-University, Marburg, Germany D-35033.
authors.forename: A
authors.initials: A
authors.lastname: Trümper
authors.forename: K
authors.initials: K
authors.lastname: Trümper
authors.forename: H
authors.initials: H
authors.lastname: Trusheim
authors.forename: R
authors.initials: R
authors.lastname: Arnold
authors.forename: B
authors.initials: B
authors.lastname: Göke
authors.forename: D
authors.initials: D
authors.lastname: Hörsch
mesh_terms: D000818:Animals; D002455:Cell Division; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005749:Gastric Inhibitory Polypeptide / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D006133:Growth Substances / Q000378:metabolism*; D015151:Immunoblotting; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D005749:Gastric Inhibitory Polypeptide; D005947:Glucose; D006133:Growth Substances; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt