title: Characterization of the cellular and metabolic effects of a novel enzyme-resistant antagonist of glucose-dependent insulinotropic polypeptide.
abstract: A novel N-terminally substituted Pro(3) analogue of glucose-dependent insulinotropic polypeptide (GIP) was synthesized and tested for plasma stability and biological activity both in vitro and in vivo. Native GIP was rapidly degraded by human plasma with only 39 +/- 6% remaining intact after 8 h, whereas (Pro(3))GIP was completely stable even after 24 h. In CHL cells expressing the human GIP receptor, (Pro(3))GIP antagonized the cyclic adenosine monophosphate (cAMP) stimulatory ability of 10(-7) M native GIP, with an IC(50) value of 2.6 microM. In the clonal pancreatic beta cell line BRIN-BD11, (Pro(3))GIP over the concentration range 10(-13) to 10(-8) M dose dependently inhibited GIP-stimulated (10(-7) M) insulin release (1.2- to 1.7-fold; P < 0.05 to P < 0.001). In obese diabetic (ob/ob) mice, intraperitoneal administration of (Pro(3))GIP (25 nmol/kg body wt) countered the ability of native GIP to stimulate plasma insulin (2.4-fold decrease; P < 0.001) and lower the glycemic excursion (1.5-fold decrease; P < 0.001) induced by a glucose load (18 mmol/kg body wt). Collectively these data demonstrate that (Pro(3))GIP is a novel and potent enzyme-resistant GIP receptor antagonist capable of blocking the ability of native GIP to increase cAMP, stimulate insulin secretion, and improve glucose homeostasis in a commonly employed animal model of type 2 diabetes.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, United Kingdom.
authors.forename: Victor A
authors.initials: VA
authors.lastname: Gault
authors.forename: Finbarr P M
authors.initials: FP
authors.lastname: O'Harte
authors.forename: Patrick
authors.initials: P
authors.lastname: Harriott
authors.forename: Peter R
authors.initials: PR
authors.lastname: Flatt
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D000242:Cyclic AMP / Q000096:biosynthesis; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism* / Q000494:pharmacology; D005749:Gastric Inhibitory Polypeptide / Q000037:antagonists & inhibitors* / Q000378:metabolism* / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D051379:Mice; D008820:Mice, Obese; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D051381:Rats; D011964:Receptors, Gastrointestinal Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D010446:Peptide Fragments; D011964:Receptors, Gastrointestinal Hormone; C120067:glucose-dependent-insulinotropic-polypeptide (7-30)-amide; D018698:Glutamic Acid; D005749:Gastric Inhibitory Polypeptide; D011392:Proline; D000242:Cyclic AMP; D018819:Dipeptidyl Peptidase 4