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Krogh LSL, Henriksen K, Stensen S, Skov-Jeppesen K, Bergmann NC, Størling J, Rosenkilde MM, Hartmann B, Holst JJ, Gasbjerg LS, Knop FK. The naturally occurring GIP(1-30)NH2 is a GIP receptor agonist in humans. Eur J Endocrinol 2023; 188:6979719. [PMID: 36651162 DOI: 10.1093/ejendo/lvac015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 11/30/2022] [Accepted: 12/14/2022] [Indexed: 01/11/2023]
Abstract
OBJECTIVE The gut hormone glucose-dependent insulinotropic polypeptide (GIP) is an important regulator of glucose and bone metabolism. In rodents, the naturally occurring GIP variant, GIP(1-30)NH2, has shown similar effects as full-length GIP (GIP(1-42)), but its effects in humans are unsettled. Here, we investigated the actions of GIP(1-30)NH2 compared to GIP(1-42) on glucose and bone metabolism in healthy men and in isolated human pancreatic islets. METHODS Nine healthy men completed three separate three-step glucose clamps (0-60 minutes at fasting plasma glucose (FPG) level, 60-120 minutes at 1.5× FPG, and 120-180 minutes at 2× FPG) with infusion of GIP(1-42) (4 pmol/kg/min), GIP(1-30)NH2 (4 pmol/kg/min), and saline (9 mg/mL) in randomised order. Blood was sampled for measurement of relevant hormones and bone turnover markers. Human islets were incubated with low (2 mmol/L) or high (20 mmol/L) d-glucose with or without GIP(1-42) or GIP(1-30)NH2 in three different concentrations for 30 minutes, and secreted insulin and glucagon were measured. RESULTS Plasma glucose (PG) levels at FPG, 1.5× FPG, and 2× FPG were obtained by infusion of 1.45 g/kg, 0.97 g/kg, and 0.6 g/kg of glucose during GIP(1-42), GIP(1-30)NH2, and saline, respectively (P = .18), and were similar on the three experimental days. Compared to placebo, GIP(1-30)NH2 resulted in similar glucagonotropic, insulinotropic, and carboxy-terminal type 1 collagen crosslinks-suppressing effects as GIP(1-42). In vitro experiments on human islets showed similar insulinotropic and glucagonotropic effects of the two GIP variants. CONCLUSIONS GIP(1-30)NH2 has similar effects on glucose and bone metabolism in healthy individuals and in human islets in vitro as GIP(1-42).
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Affiliation(s)
- Liva S L Krogh
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Kristine Henriksen
- Department of Clinical Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
| | - Signe Stensen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Kirsa Skov-Jeppesen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Natasha C Bergmann
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Joachim Størling
- Department of Clinical Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mette M Rosenkilde
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bolette Hartmann
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Jens J Holst
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Lærke S Gasbjerg
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Filip K Knop
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Department of Clinical Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Ko J, Jang S, Kwon W, Kim SY, Jang S, Kim E, Ji YR, Park S, Kim MO, Choi SK, Cho DH, Lee HS, Lim SG, Ryoo ZY. Protective Effect of GIP against Monosodium Glutamate-Induced Ferroptosis in Mouse Hippocampal HT-22 Cells through the MAPK Signaling Pathway. Antioxidants (Basel) 2022; 11:antiox11020189. [PMID: 35204073 PMCID: PMC8868324 DOI: 10.3390/antiox11020189] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/10/2022] [Accepted: 01/17/2022] [Indexed: 02/08/2023] Open
Abstract
The effect of glucose-dependent insulinotropic polypeptide (GIP) on cells under oxidative stress induced by glutamate, a neurotransmitter, and the underlying molecular mechanisms were assessed in the present study. We found that in the pre-treatment of HT-22 cells with glutamate in a dose-dependent manner, intracellular ROS were excessively generated, and additional cell damage occurred in the form of lipid peroxidation. The neurotoxicity caused by excessive glutamate was found to be ferroptosis and not apoptosis. Other factors (GPx-4, Nrf2, Nox1 and Hspb1) involved in ferroptosis were also identified. In other words, it was confirmed that GIP increased the activity of sub-signalling molecules in the process of suppressing ferroptosis as an antioxidant and maintained a stable cell cycle even under glutamate-induced neurotoxicity. At the same time, in HT-22 cells exposed to ferroptosis as a result of excessive glutamate accumulation, GIP sustained cell viability by activating the mitogen-activated protein kinase (MAPK) signalling pathway. These results suggest that the overexpression of the GIP gene increases cell viability by regulating mechanisms related to cytotoxicity and reactive oxygen species production in hippocampal neuronal cell lines.
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Affiliation(s)
- Jiwon Ko
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Soyoung Jang
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Wookbong Kwon
- Core Protein Resources Center, DGIST, Daegu 42988, Korea; (W.K.); (S.-K.C.)
- Division of Biotechnology, DGIST, Daegu 42988, Korea
| | - Si-Yong Kim
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Soyeon Jang
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Eungyung Kim
- Department of Animal Science and Biotechnology, Kyungpook National University, Sangju-si 37224, Korea; (E.K.); (M.-O.K.)
| | - Young-Rae Ji
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
- Section on Sensory Cell Regeneration and Development, Laboratory of Molecular Biology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sijun Park
- School of Life Science, Kyungpook National University, Daegu 42988, Korea;
| | - Myoung-Ok Kim
- Department of Animal Science and Biotechnology, Kyungpook National University, Sangju-si 37224, Korea; (E.K.); (M.-O.K.)
| | - Seong-Kyoon Choi
- Core Protein Resources Center, DGIST, Daegu 42988, Korea; (W.K.); (S.-K.C.)
- Division of Biotechnology, DGIST, Daegu 42988, Korea
| | - Dong-Hyung Cho
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
- Brain Science and Engineering Institute, Kyungpook National University, Daegu 42988, Korea
| | - Hyun-Shik Lee
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
| | - Su-Geun Lim
- School of Life Science, Kyungpook National University, Daegu 42988, Korea;
- Correspondence: (S.-G.L.); (Z.-Y.R.)
| | - Zae-Young Ryoo
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea; (J.K.); (S.J.); (S.-Y.K.); (S.J.); (Y.-R.J.); (D.-H.C.); (H.-S.L.)
- Correspondence: (S.-G.L.); (Z.-Y.R.)
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3
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Abstract
This paper describes the early history of Gastric Inhibitory Polypeptide, better referred to simply as GIP, from its isolation by purification from a crude preparation of CCK-PZ (cholecystokinin/pancreozymin) to its recognition as a key play in the pathogenesis of obesity and other metabolic disorders far removed from the enterogastrone properties by which it was originally identified. Augmentation of glucose mediated insulin release, the incretin effect, was discovered soon after GIP was first isolated and only much later was its important role in the pathogenesis of obesity, through mechanism other than its insulin secretion, appreciated. Immunoassay - the method by which the concentration of GIP was measured in plasma until quite recently - was found to be flawed and to depend upon which specific epitope of the hormone an assay detected. This was especially true if it was an amino-acid sequence specific to porcine rather than human GIP. A further confounder was the discovery that much of the GIP measured by immunoassay was its biological antagonist produced by cleavage of its two N-terminal amino-acids in the circulation by the same dipeptidyl-peptidase as de-activates GLP-1. Potential use of synthetic agonistic and antagonistic GIP analogues in therapeutics was barely alluded to before year 2000.
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Marks V. The early history of GIP 1969-2000: From enterogastrone to major metabolic hormone. Peptides 2019; 122:170155. [PMID: 31539554 DOI: 10.1016/j.peptides.2019.170155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/07/2019] [Accepted: 09/15/2019] [Indexed: 10/26/2022]
Abstract
This paper describes the early history of Gastric Inhibitory Polypeptide, better referred to simply as GIP, from its isolation by purification from a crude preparation of CCK-PZ (cholecystokinin/pancreozymin) to its recognition as a key player in the pathogenesis of obesity and other metabolic disorders far removed from the enterogastrone properties by which it was originally identified. Augmentation of glucose mediated insulin release, the incretin effect, was discovered soon after GIP was first isolated and only much later was its important role in the pathogenesis of obesity, through mechanism other than insulin secretion, appreciated. Immunoassay - the only method by which the concentration of GIP was measured in plasma until quite recently - was found to be flawed and to depend upon which specific epitope of the hormone an assay detected. This was especially true if it was an amino-acid sequence specific to porcine rather than human GIP. A further confounder was the discovery that much of the GIP measured by immunoassay was its biological antagonist produced by cleavage of its two N-terminal amino-acids in the circulation by the same dipeptidyl-peptidase as de-activates GLP-1. Potential use of synthetic agonistic and antagonistic GIP analogues in therapeutics was barely alluded to before year 2000.
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Affiliation(s)
- Vincent Marks
- University of Surrey, 68, Walpole House, 126 Westminster Bridge Road, London, SE1 7UN, Guildford, UK.
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5
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Sparre-Ulrich A, Gabe M, Gasbjerg L, Christiansen C, Svendsen B, Hartmann B, Holst J, Rosenkilde M. GIP(3–30)NH2 is a potent competitive antagonist of the GIP receptor and effectively inhibits GIP-mediated insulin, glucagon, and somatostatin release. Biochem Pharmacol 2017; 131:78-88. [DOI: 10.1016/j.bcp.2017.02.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 02/14/2017] [Indexed: 12/31/2022]
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6
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Finan B, Müller TD, Clemmensen C, Perez-Tilve D, DiMarchi RD, Tschöp MH. Reappraisal of GIP Pharmacology for Metabolic Diseases. Trends Mol Med 2016; 22:359-376. [DOI: 10.1016/j.molmed.2016.03.005] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/15/2016] [Accepted: 03/17/2016] [Indexed: 12/31/2022]
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Hansen LS, Sparre-Ulrich AH, Christensen M, Knop FK, Hartmann B, Holst JJ, Rosenkilde MM. N-terminally and C-terminally truncated forms of glucose-dependent insulinotropic polypeptide are high-affinity competitive antagonists of the human GIP receptor. Br J Pharmacol 2016; 173:826-38. [PMID: 26572091 PMCID: PMC4761099 DOI: 10.1111/bph.13384] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 10/13/2015] [Accepted: 10/16/2015] [Indexed: 12/25/2022] Open
Abstract
Background and Purpose Glucose‐dependent insulinotropic polypeptide (GIP) affects lipid, bone and glucose homeostasis. High‐affinity ligands for the GIP receptor are needed to elucidate the physiological functions and pharmacological potential of GIP in vivo. GIP(1–30)NH2 is a naturally occurring truncation of GIP(1–42). Here, we have characterized eight N‐terminal truncations of human GIP(1–30)NH2. Experimental Approach COS‐7 cells were transiently transfected with human GIP receptors and assessed for cAMP accumulation upon ligand stimulation or competition binding with 125I‐labelled GIP(1–42), GIP(1–30)NH2, GIP(2–30)NH2 or GIP(3–30)NH2. Key Results GIP(1–30)NH2 displaced 125I‐GIP(1–42) as effectively as GIP(1–42) (Ki 0.75 nM), whereas the eight truncations displayed lower affinities (Ki 2.3–347 nM) with highest affinities for GIP(3–30)NH2 and GIP(5–30)NH2 (5–30)NH2. Only GIP(1–30)NH2 (Emax 100% of GIP(1–42)) and GIP(2–30)NH2 (Emax 20%) were agonists. GIP(2‐ to 9–30)NH2 displayed antagonism (IC50 12–450 nM) and Schild plot analyses identified GIP(3–30)NH2 and GIP(5–30)NH2 as competitive antagonists (Ki 15 nM). GIP(3–30) NH2 was a 26‐fold more potent antagonist than GIP(3–42). Binding studies with agonist (125I‐GIP(1–30)NH2), partial agonist (125I‐GIP(2–30)NH2) and competitive antagonist (125I‐GIP(3–30)NH2) revealed distinct receptor conformations for these three ligand classes. Conclusions and Implications The N‐terminus is crucial for GIP agonist activity. Removal of the C‐terminus of the endogenous GIP(3–42) creates another naturally occurring, more potent, antagonist GIP(3–30)NH2, which like GIP(5–30)NH2, was a high‐affinity competitive antagonist. These peptides may be suitable tools for basic GIP research and future pharmacological interventions.
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Affiliation(s)
- L S Hansen
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark
| | - A H Sparre-Ulrich
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - M Christensen
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark
| | - F K Knop
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark
| | - B Hartmann
- NNF Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - J J Holst
- NNF Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - M M Rosenkilde
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Venneti KC, Malthouse JPG, O'Harte FPM, Hewage CM. Conformational, receptor interaction and alanine scan studies of glucose-dependent insulinotropic polypeptide. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:882-8. [PMID: 21539943 DOI: 10.1016/j.bbapap.2011.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 03/28/2011] [Accepted: 04/04/2011] [Indexed: 10/18/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is an insulinotropic incretin hormone that stimulates insulin secretion during a meal. GIP has glucose lowering abilities and hence is considered as a potential target molecule for type 2 diabetes therapy. In this article, we present the solution structure of GIP in membrane-mimicking environments by proton NMR spectroscopy and molecular modelling. GIP adopts an α-helical conformation between residues Phe(6)-Gly(31) and Ala(13)-Gln(29) for micellar and bicellar media, respectively. Previously we examined the effect of N-terminal Ala substitution in GIP, but here eight GIP analogues were synthesised by replacing individual residues within the central 8-18 region with alanine. These studies showed relatively minor changes in biological activity as assessed by insulin releasing potency. However, at higher concentration, GIP(Ala(16)), and GIP(Ala(18)) showed insulin secreting activity higher than the native GIP (P<0.01 to P<0.001) in cultured pancreatic BRIN-BD11 cells. Receptor interaction studies of the native GIP with the extracellular domain of its receptor were performed by using two different docking algorithms. At the optimised docking conformation, the complex was stabilised by the presence of hydrophobic interactions and intermolecular hydrogen bonding. Further, we have identified some potentially important additional C-terminal interactions of GIP with its N-terminal extracellular receptor domain.
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Affiliation(s)
- Kalyana C Venneti
- School of Biomolecular and Biomedical Science, Centre for Synthesis and Chemical Biology, SEC Strategic Research Cluster, UCD Conway Institute, University College Dublin, Dublin 4, Ireland
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Fujita Y, Asadi A, Yang GK, Kwok YN, Kieffer TJ. Differential processing of pro-glucose-dependent insulinotropic polypeptide in gut. Am J Physiol Gastrointest Liver Physiol 2010; 298:G608-14. [PMID: 20185691 DOI: 10.1152/ajpgi.00024.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a hormone released from enteroendocrine K cells in response to meals. Posttranslational processing of the precursor protein pro-GIP at residue 65 by proprotein convertase subtilisin/kexin type 1 (PC1/3) in gut K cells gives rise to the established 42-amino-acid form of GIP (GIP(1-42)). However, the pro-GIP peptide sequence contains a consensus cleavage site for PC2 at residues 52-55 and we identified PC2 immunoreactivity in a subset of K cells, suggesting the potential existence of a COOH-terminal truncated GIP isoform, GIP(1-30). Indeed a subset of mouse and human K cells display GIP immunoreactivity with GIP antibodies directed to the mid portion of the peptide, but not with a COOH-terminal-directed GIP antibody, indicative of the presence of a truncated form of GIP. This population of cells represents approximately 5-15% of the total GIP-immunoreactive cells in mice, depending on the region of intestine, and is virtually absent in mice lacking PC2. Amidated GIP(1-30) and GIP(1-42) have comparable potency at stimulating somatostatin release in the perfused mouse stomach. Therefore, GIP(1-30) represents a naturally occurring, biologically active form of GIP.
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Affiliation(s)
- Yukihiro Fujita
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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A GIP receptor agonist exhibits beta-cell anti-apoptotic actions in rat models of diabetes resulting in improved beta-cell function and glycemic control. PLoS One 2010; 5:e9590. [PMID: 20231880 PMCID: PMC2834736 DOI: 10.1371/journal.pone.0009590] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 02/15/2010] [Indexed: 01/09/2023] Open
Abstract
AIMS The gastrointestinal hormone GIP promotes pancreatic islet function and exerts pro-survival actions on cultured beta-cells. However, GIP also promotes lipogenesis, thus potentially restricting its therapeutic use. The current studies evaluated the effects of a truncated GIP analog, D-Ala(2)-GIP(1-30) (D-GIP(1-30)), on glucose homeostasis and beta-cell mass in rat models of diabetes. MATERIALS AND METHODS The insulinotropic and pro-survival potency of D-GIP(1-30) was evaluated in perfused pancreas preparations and cultured INS-1 beta-cells, respectively, and receptor selectivity evaluated using wild type and GIP receptor knockout mice. Effects of D-GIP(1-30) on beta-cell function and glucose homeostasis, in vivo, were determined using Lean Zucker rats, obese Vancouver diabetic fatty rats, streptozotocin treated rats, and obese Zucker diabetic fatty rats, with effects on beta-cell mass determined in histological studies of pancreatic tissue. Lipogenic effects of D-GIP(1-30) were evaluated on cultured 3T3-L1 adipocytes. RESULTS Acutely, D-GIP(1-30) improved glucose tolerance and insulin secretion. Chronic treatment with D-GIP(1-30) reduced levels of islet pro-apoptotic proteins in Vancouver diabetic fatty rats and preserved beta-cell mass in streptozotocin treated rats and Zucker diabetic fatty rats, resulting in improved insulin responses and glycemic control in each animal model, with no change in body weight. In in vitro studies, D-GIP(1-30) exhibited equivalent potency to GIP(1-42) on beta-cell function and survival, but greatly reduced action on lipoprotein lipase activity in 3T3-L1 adipocytes. CONCLUSIONS These findings demonstrate that truncated forms of GIP exhibit potent anti-diabetic actions, without pro-obesity effects, and that the C-terminus contributes to the lipogenic actions of GIP.
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Chapter 15 Glucose‐Dependent Insulinotropic Polypeptide (Gastric Inhibitory Polypeptide; GIP). VITAMINS AND HORMONES 2009; 80:409-71. [DOI: 10.1016/s0083-6729(08)00615-8] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Alaña I, Malthouse JPG, O'Harte FPM, Hewage CM. The bioactive conformation of glucose-dependent insulinotropic polypeptide by NMR and CD spectroscopy. Proteins 2007; 68:92-9. [PMID: 17393464 DOI: 10.1002/prot.21372] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal incretin hormone, which modulates physiological insulin secretion. Because of its glucose-sensitive insulinotropic activity, there has been a considerable interest in utilizing the hormone as a potential treatment for type 2 diabetes. Structural parameters obtained from NMR spectroscopy combined with molecular modeling techniques play a vital role in the design of new therapeutic drugs. Therefore, to understand the structural requirements for the biological activity of GIP, the solution structure of GIP was investigated by circular dichroism (CD) followed by proton nuclear magnetic resonance (NMR) spectroscopy. CD studies showed an increase in the helical character of the peptide with increasing concentration of trifluoroethanol (TFE) up to 50%. Therefore, the solution structure of GIP in 50% TFE was determined. It was found that there was an alpha-helix between residues 6 and 29, which tends to extend further up to residue 36. The implications of the C-terminal extended helical segment in the inhibitory properties of GIP on gastric acid secretion are discussed. It is shown that the adoption by GIP of an alpha-helical secondary structure is a requirement for its biological activity. Knowledge of the solution structure of GIP will help in the understanding of how the peptide interacts with its receptor and aids in the design of new therapeutic agents useful for the treatment of diabetes.
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Affiliation(s)
- Iñigo Alaña
- UCD School of Biomolecular and Biomedical Science, Centre for Synthesis and Chemical Biology, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
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Hinke SA, Manhart S, Pamir N, Demuth H, W Gelling R, Pederson RA, McIntosh CH. Identification of a bioactive domain in the amino-terminus of glucose-dependent insulinotropic polypeptide (GIP). BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1547:143-55. [PMID: 11343800 DOI: 10.1016/s0167-4838(01)00181-9] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The incretins are a class of hormones released from the small bowel that act on the endocrine pancreas to potentiate insulin secretion in a glucose-dependent manner. Due to the requirement for an elevated glucose concentration for activity, the incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1, have potential in the treatment of non-insulin-dependent diabetes mellitus. A series of synthetic peptide GIP fragments was generated for the purpose of elucidating the bioactive domain of the molecule. Peptides were screened for stimulation of cyclic AMP (cAMP) accumulation in Chinese hamster ovary cells transfected with the rat islet GIP receptor. Of the GIP fragments tested, GIP(1-14) and GIP(19-30) demonstrated the greatest cAMP-stimulating ability over the range of concentrations tested (up to 20 microM). In contrast, GIP fragments corresponding to amino acids 15-42, 15-30, 16-30 and 17-30 all demonstrated weak antagonism of GIP(1-42) activity. Competitive-binding displacement studies indicated that these peptides were low-affinity ligands for the GIP receptor. To examine biological activity in vivo, a bioassay was developed in the anesthetized rat. Intravenous infusion of GIP(1-42) (1 pmol/min/100 g) with a concurrent intraperitoneal glucose load (1 g/kg) significantly reduced circulating blood glucose excursions through stimulation of insulin release. Higher doses of GIP(1-14) and GIP(19-30) (100 pmol/min/100 g) also reduced blood glucose excursions.
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Affiliation(s)
- S A Hinke
- Department of Physiology, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
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14
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Gelling RW, Coy DH, Pederson RA, Wheeler MB, Hinke S, Kwan T, McIntosh CH. GIP(6-30amide) contains the high affinity binding region of GIP and is a potent inhibitor of GIP1-42 action in vitro. REGULATORY PEPTIDES 1997; 69:151-4. [PMID: 9226399 DOI: 10.1016/s0167-0115(97)00009-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
GIP (Glucose-dependent Insulinotropic Polypeptide) is an important regulator of insulin secretion. The effects of truncated forms of the peptide, GIP(10-30), GIP(6-30amide) and GIP(7-30), on binding of 125I-GIP(1-42) to GIP receptors in transfected CHO-KI cells, and on cyclic AMP responses to GIP(1-42), have been studied with a view to defining further the receptor binding region of GIP, and to establish whether such truncated peptides exhibit agonist or antagonist activity. All three peptides were found to be receptor antagonists, however GIP(6-30amide) exhibited receptor binding affinity equivalent to that of GIP(1-42) in competitive binding studies (IC50 = 3.08+/-0.57 nM). GIP(6-30amide) inhibited GIP(1-42)-induced cAMP production by 58% at a concentration of 100 nM, whereas GIP(10-30) and GIP(7-30), inhibited only in the microM range. GIP(6-30amide) therefore contains the high affinity binding region of GIP and is a potent inhibitor of GIP(1-42) action in vitro.
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Affiliation(s)
- R W Gelling
- Department of Physiology, Faculty of Medicine, University of British Columbia, Vancouver, Canada
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Tseng CC, Kieffer TJ, Jarboe LA, Usdin TB, Wolfe MM. Postprandial stimulation of insulin release by glucose-dependent insulinotropic polypeptide (GIP). Effect of a specific glucose-dependent insulinotropic polypeptide receptor antagonist in the rat. J Clin Invest 1996; 98:2440-5. [PMID: 8958204 PMCID: PMC507699 DOI: 10.1172/jci119060] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is a 42-amino acid peptide produced by K cells of the mammalian proximal small intestine and is a potent stimulant of insulin release in the presence of hyperglycemia. However, its relative physiological importance as a postprandial insulinotropic agent is unknown. Using LGIPR2 cells stably transfected with rat GIP receptor cDNA, GIP (1-42) stimulation of cyclic adenosine monophosphate (cAMP) production was inhibited in a concentration-dependent manner by GIP (7-30)-NH2. Competition binding assays using stably transfected L293 cells demonstrated an IC50 for GIP receptor binding of 7 nmol/liter for GIP (1-42) and 200 nmol/liter for GIP (7-30)-NH2, whereas glucagonlike peptide-1 (GLP-1) binding to its receptor on ++betaTC3 cells was minimally displaced by GIP (7-30)-NH2. In fasted anesthetized rats, GIP (1-42) stimulated insulin release in a concentration-dependent manner, an effect abolished by the concomitant intraperitoneal administration of GIP (7-30)-NH2 (100 nmol/ kg). In contrast, glucose-, GLP-1-, and arginine-stimulated insulin release were not affected by GIP (7-30)-NH2. In separate experiments, GIP (7-30)-NH2 (100 nmol/kg) reduced postprandial insulin release in conscious rats by 72%. It is concluded that GIP (7-30)-NH2 is a GIP-specific receptor antagonist and that GIP plays a dominant role in mediating postprandial insulin release.
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Affiliation(s)
- C C Tseng
- Gastroenterology Division, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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16
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Orskov C, Wettergren A, Holst JJ. Secretion of the incretin hormones glucagon-like peptide-1 and gastric inhibitory polypeptide correlates with insulin secretion in normal man throughout the day. Scand J Gastroenterol 1996; 31:665-70. [PMID: 8819215 DOI: 10.3109/00365529609009147] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The insulinotropic hormones gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), secreted from the K-cells of the upper small intestine and from the L-cells of the lower small intestine, respectively, are thought to be responsible for intestinal stimulation of insulin secretion. If true, their plasma concentrations should parallel the meal-related diurnal changes in plasma insulin concentrations. METHODS Using COOH-terminal assays, thought to reflect accurately their rates of secretion, we measured circulating levels of GIP and GLP-1 in six normal subjects for 15 h of a day, during which they ate three mixed meals. RESULTS Both GIP and GLP-1 concentrations increased significantly and in parallel with insulin in response to all three meals. The plasma insulin concentrations correlated significantly with both GIP and GLP-1 values throughout the study period (correlation coefficients, 0.49 +/- 0.07 and 0.56 +/- 0.05; p < 0.001). CONCLUSIONS These results support the notion that GLP-1 and GIP are important incretin hormones.
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Affiliation(s)
- C Orskov
- Dept. of Medical Anatomy, Panum Institute, University of Copenhagen, Denmark
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Morrow GW, Kieffer TJ, McIntosh CHS, MacGillivray RTA, Brown JC, St-Pierre S, Pederson RA. The insulinotropic region of gastric inhibitory polypeptide; fragment analysis suggests the bioactive site lies between residues 19 and 30. Can J Physiol Pharmacol 1996. [DOI: 10.1139/y95-229] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
Originally characterized in terms of its gastric acid inhibitory properties, GIP (gastric inhibitory polypeptide) expressed in the upper small intestine, was subsequently shown to exert strong glucose-dependent insulin-releasing properties. This action is generally attributed to GIP(1-42) and, so far, no evidence for the contribution of other relevant GIP forms exists. In this study, we compared the effects of GIP(1-42) and C-terminally truncated GIP(1-30) on cAMP production and proinsulin gene transcription at clonal insulin-secreting cell lines (RIN 1046-38, beta TC-3). Both peptides were equally potent stimulators of cAMP generation in both cell lines. Insulin release from RIN 1046-38 cells stimulated by both GIP forms was identical. In both B-cell lines GIP(1-42) and GIP(1-30) stimulated proinsulin gene expression equipotently. GIP not only enhances insulin secretion but also insulin gene expression and, therefore, it is a true insulinotropic hormone.
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Affiliation(s)
- H C Fehmann
- Department of Medicine, Philipps-University of Marburg, Germany
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