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Komatsu T, Abe S, Nakashima S, Sasaki K, Higaki Y, Saku K, Miura SI, Uehara Y. Dipeptidyl Peptidase-4 Inhibitor Sitagliptin Phosphate Accelerates Cellular Cholesterol Efflux in THP-1 Cells. Biomolecules 2023; 13:biom13020228. [PMID: 36830597 PMCID: PMC9953524 DOI: 10.3390/biom13020228] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 01/11/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023] Open
Abstract
Cholesterol efflux is a major atheroprotective function of high-density lipoproteins (HDLs) which removes cholesterol from the foam cells of lipid-rich plaques in Type 2 diabetes. The dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin phosphate increases plasma glucagon-like peptide-1 (GLP-1) concentrations and is used to treat Type 2 diabetes. GLP-1 plays an important role in regulating insulin secretion and expression via the GLP-1 receptor (GLP-1R), which is expressed in pancreatic islets as well as freshly isolated human monocytes and THP-1 cells. Here, we identified a direct role of GLP-1 and DPP-4 inhibition in HDL function. Cholesterol efflux was measured in cultivated phorbol 12-myristate 13-acetate-treated THP-1 cells radiolabeled with 3H-cholesterol and stimulated with liver X receptor/retinoid X receptor agonists. Contrary to vildagliptin, sitagliptin phosphate together with GLP-1 significantly (p < 0.01) elevated apolipoprotein (apo)A1-mediated cholesterol efflux in a dose-dependent manner. The sitagliptin-induced increase in cholesterol efflux did not occur in the absence of GLP-1. In contrast, adenosine triphosphate-binding cassette transporter A1 (ABCA1) mRNA and protein expressions in the whole cell fraction were not changed by sitagliptin in the presence of GLP-1, although sitagliptin treatment significantly increased ABCA1 protein expression in the membrane fraction. Furthermore, the sitagliptin-induced, elevated efflux in the presence of GLP-1 was significantly decreased by a GLP-1R antagonist, an effect that was not observed with a protein kinase A inhibitor. To our knowledge, the present study reports for the first time that sitagliptin elevates cholesterol efflux in cultivated macrophages and may exert anti-atherosclerotic actions that are independent of improvements in glucose metabolism. Our results suggest that sitagliptin enhances HDL function by inducing a de novo HDL synthesis via cholesterol efflux.
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Affiliation(s)
- Tomohiro Komatsu
- Research Institute for Physical Activity, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
- Center for Preventive, Anti-Aging and Regenerative Medicine, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Satomi Abe
- Research Institute for Physical Activity, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Shihoko Nakashima
- Faculty of Sports and Health Science, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Kei Sasaki
- Center for Preventive, Anti-Aging and Regenerative Medicine, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Yasuki Higaki
- Research Institute for Physical Activity, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
- Faculty of Sports and Health Science, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Keijiro Saku
- Department of Cardiology, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Shin-ichiro Miura
- Department of Cardiology, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
| | - Yoshinari Uehara
- Research Institute for Physical Activity, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
- Center for Preventive, Anti-Aging and Regenerative Medicine, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
- Faculty of Sports and Health Science, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
- Department of Cardiology, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan
- Correspondence: ; Tel.: +81-92-871-6631
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Boss M, Bos D, Frielink C, Sandker G, Bronkhorst P, van Lith SAM, Brom M, Buitinga M, Gotthardt M. Receptor-Targeted Photodynamic Therapy of Glucagon-Like Peptide 1 Receptor-Positive Lesions. J Nucl Med 2020; 61:1588-1593. [PMID: 32385165 PMCID: PMC8679620 DOI: 10.2967/jnumed.119.238998] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/25/2020] [Indexed: 01/04/2023] Open
Abstract
Treatment of hyperinsulinemic hypoglycemia is challenging. Surgical treatment of insulinomas and focal lesions in congenital hyperinsulinism is invasive and carries major risks of morbidity. Medication to treat nesidioblastosis and diffuse congenital hyperinsulinism has varying efficacy and causes significant side effects. Here, we describe a novel method for therapy of hyperinsulinemic hyperglycemia, highly selectively killing β-cells by receptor-targeted photodynamic therapy (rtPDT) with exendin-4-IRDye700DX, targeting the glucagon-like peptide 1 receptor (GLP-1R). Methods: A competitive binding assay was performed using Chinese hamster lung (CHL) cells transfected with the GLP-1R. The efficacy and specificity of rtPDT with exendin-4-IRDye700DX were examined in vitro in cells with different levels of GLP-1R expression. Tracer biodistribution was determined in BALB/c nude mice bearing subcutaneous CHL-GLP-1R xenografts. Induction of cellular damage and the effect on tumor growth were analyzed to determine treatment efficacy. Results: Exendin-4-IRDye700DX has a high affinity for the GLP-1R, with a half-maximal inhibitory concentration of 6.3 nM. rtPDT caused significant specific phototoxicity in GLP-1R–positive cells (2.3% ± 0.8% and 2.7% ± 0.3% remaining cell viability in CHL-GLP-1R and INS-1 cells, respectively). The tracer accumulates dose-dependently in GLP-1R–positive tumors. In vivo, rtPDT induces cellular damage in tumors, shown by strong expression of cleaved caspase-3, and leads to a prolonged median survival of the mice (36.5 vs. 22.5 d, respectively; P < 0.05). Conclusion: These data show in vitro as well as in vivo evidence of the potency of rtPDT using exendin-4-IRDye700DX. This approach might in the future provide a new, minimally invasive, highly specific treatment method for hyperinsulinemic hypoglycemia.
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Affiliation(s)
- Marti Boss
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Desiree Bos
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Cathelijne Frielink
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Gerwin Sandker
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Patricia Bronkhorst
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Sanne A M van Lith
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Maarten Brom
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mijke Buitinga
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Martin Gotthardt
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
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Boss M, Bos D, Frielink C, Sandker G, Ekim S, Marciniak C, Pattou F, van Dam G, van Lith S, Brom M, Gotthardt M, Buitinga M. Targeted Optical Imaging of the Glucagonlike Peptide 1 Receptor Using Exendin-4-IRDye 800CW. J Nucl Med 2020; 61:1066-1071. [PMID: 31924726 PMCID: PMC7383075 DOI: 10.2967/jnumed.119.234542] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/13/2019] [Indexed: 01/10/2023] Open
Abstract
The treatment of choice for insulinomas and focal lesions in congenital hyperinsulinism (CHI) is surgery. However, intraoperative detection can be challenging. This challenge could be overcome with intraoperative fluorescence imaging, which provides real-time lesion detection with a high spatial resolution. Here, a novel method for targeted near-infrared (NIR) fluorescence imaging of glucagonlike peptide 1 receptor (GLP-1R)–positive lesions, using the GLP-1 agonist exendin-4 labeled with IRDye 800CW, was examined in vitro and in vivo. Methods: A competitive binding assay was performed using Chinese hamster lung (CHL) cells transfected with GLP-1R. Tracer biodistribution was determined in BALB/c nude mice bearing subcutaneous CHL-GLP-1R xenografts. In vivo NIR fluorescence imaging of CHL-GLP-1R xenografts was performed. Localization of the tracer in the pancreatic islets of BALB/c nude mice was examined using fluorescence microscopy. Laparoscopic imaging was performed to detect the fluorescent signal of the tracer in the pancreas of mini pigs. Results: Exendin-4-IRDye 800CW binds GLP-1R with a half-maximal inhibitory concentration of 3.96 nM. The tracer accumulates in CHL-GLP-1R xenografts. Subcutaneous CHL-GLP-1R xenografts were visualized using in vivo NIR fluorescence imaging. The tracer accumulates specifically in the pancreatic islets of mice, and a clear fluorescent signal was detected in the pancreas of mini pigs. Conclusion: These data provide the first in vivo evidence of the feasibility of targeted fluorescence imaging of GLP-1R–positive lesions. Intraoperative lesion delineation using exendin-4-IRDye 800CW could benefit open as well as laparoscopic surgical procedures for removal of insulinomas and focal lesions in CHI.
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Affiliation(s)
- Marti Boss
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Desiree Bos
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Cathelijne Frielink
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Gerwin Sandker
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Selen Ekim
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Camille Marciniak
- Department of General and Endocrine Surgery, University Hospital 2 Lille, Lille, France
| | - Francois Pattou
- Department of General and Endocrine Surgery, University Hospital 2 Lille, Lille, France
| | - Go van Dam
- Department of Surgery, University Medical Center Groningen, Groningen, The Netherlands; and
| | - Sanne van Lith
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Maarten Brom
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Martin Gotthardt
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mijke Buitinga
- Department of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium
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Müller TD, Finan B, Bloom SR, D'Alessio D, Drucker DJ, Flatt PR, Fritsche A, Gribble F, Grill HJ, Habener JF, Holst JJ, Langhans W, Meier JJ, Nauck MA, Perez-Tilve D, Pocai A, Reimann F, Sandoval DA, Schwartz TW, Seeley RJ, Stemmer K, Tang-Christensen M, Woods SC, DiMarchi RD, Tschöp MH. Glucagon-like peptide 1 (GLP-1). Mol Metab 2019; 30:72-130. [PMID: 31767182 PMCID: PMC6812410 DOI: 10.1016/j.molmet.2019.09.010] [Citation(s) in RCA: 843] [Impact Index Per Article: 168.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 09/10/2019] [Accepted: 09/22/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity. SCOPE OF REVIEW In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases. MAJOR CONCLUSIONS Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.
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Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany; German Center for Diabetes Research (DZD), Neuherberg, Germany; Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany.
| | - B Finan
- Novo Nordisk Research Center Indianapolis, Indianapolis, IN, USA
| | - S R Bloom
- Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK
| | - D D'Alessio
- Division of Endocrinology, Duke University Medical Center, Durham, NC, USA
| | - D J Drucker
- The Department of Medicine, Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Ontario, M5G1X5, Canada
| | - P R Flatt
- SAAD Centre for Pharmacy & Diabetes, Ulster University, Coleraine, Northern Ireland, UK
| | - A Fritsche
- German Center for Diabetes Research (DZD), Neuherberg, Germany; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany; Division of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical Chemistry, Department of Internal Medicine, University of Tübingen, Tübingen, Germany
| | - F Gribble
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - H J Grill
- Institute of Diabetes, Obesity and Metabolism, Department of Psychology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - J F Habener
- Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Harvard University, Boston, MA, USA
| | - J J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - W Langhans
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - J J Meier
- Diabetes Division, St Josef Hospital, Ruhr-University Bochum, Bochum, Germany
| | - M A Nauck
- Diabetes Center Bochum-Hattingen, St Josef Hospital (Ruhr-Universität Bochum), Bochum, Germany
| | - D Perez-Tilve
- Department of Internal Medicine, University of Cincinnati-College of Medicine, Cincinnati, OH, USA
| | - A Pocai
- Cardiovascular & ImmunoMetabolism, Janssen Research & Development, Welsh and McKean Roads, Spring House, PA, 19477, USA
| | - F Reimann
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - D A Sandoval
- Department of Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - T W Schwartz
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, DL-2200, Copenhagen, Denmark; Department of Biomedical Sciences, University of Copenhagen, DK-2200, Copenhagen, Denmark
| | - R J Seeley
- Department of Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - K Stemmer
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - M Tang-Christensen
- Obesity Research, Global Drug Discovery, Novo Nordisk A/S, Måløv, Denmark
| | - S C Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, USA
| | - R D DiMarchi
- Novo Nordisk Research Center Indianapolis, Indianapolis, IN, USA; Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - M H Tschöp
- German Center for Diabetes Research (DZD), Neuherberg, Germany; Division of Metabolic Diseases, Department of Medicine, Technische Universität München, Munich, Germany; Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
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Smith NK, Hackett TA, Galli A, Flynn CR. GLP-1: Molecular mechanisms and outcomes of a complex signaling system. Neurochem Int 2019; 128:94-105. [PMID: 31002893 PMCID: PMC7081944 DOI: 10.1016/j.neuint.2019.04.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/26/2019] [Accepted: 04/15/2019] [Indexed: 12/15/2022]
Abstract
Meal ingestion provokes the release of hormones and transmitters, which in turn regulate energy homeostasis and feeding behavior. One such hormone, glucagon-like peptide-1 (GLP-1), has received significant attention in the treatment of obesity and diabetes due to its potent incretin effect. In addition to the peripheral actions of GLP-1, this hormone is able to alter behavior through the modulation of multiple neural circuits. Recent work that focused on elucidating the mechanisms and outcomes of GLP-1 neuromodulation led to the discovery of an impressive array of GLP-1 actions. Here, we summarize the many levels at which the GLP-1 signal adapts to different systems, with the goal being to provide a background against which to guide future research.
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Affiliation(s)
- Nicholas K Smith
- Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Troy A Hackett
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Aurelio Galli
- Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Charles R Flynn
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, USA.
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Babič A, Vinet L, Chellakudam V, Janikowska K, Allémann E, Lange N. Squalene-PEG-Exendin as High-Affinity Constructs for Pancreatic Beta-Cells. Bioconjug Chem 2018; 29:2531-2540. [PMID: 29869878 DOI: 10.1021/acs.bioconjchem.8b00186] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Novel drug delivery systems targeting native, transplanted, or cancerous beta-cells are of utmost importance. Herein, we present new exendin-4 derivatives with modified unnatural amino acids at strategic positions within the polypeptide sequence. The modified peptides allowed modular orthogonal chemical modifications to attach imaging agents and amphiphilic squalene-PEG groups. The resulting conjugates, SQ-PEG-ExC1-Cy5 and SQ-PEG-ExC40-Cy5 fluorescence probes, display low nanomolar affinity to GLP-1R in fluorescence-based binding assays with EC50 at 1.1 ± 0.2 and 0.8 ± 0.2 nM, respectively. Naturally expressing GLP-1R MIN6 cells and recombinantly transfected CHL-GLP-1R positive cells were specifically targeted by all of the new beta-cell probes in vitro. Specific islet targeting was observed after i.v. injection of SQ-PEG-ExC1-Cy5 with SQ-PEG in normoglycemic mice ex vivo. Semiquantitative biodistribution analysis by epifluorescence indicated prolonged blood half-life (3.8 h) for the amphiphilic Ex conjugate. Liver and pancreas were identified as main biodistribution organs for SQ-PEG-ExC1-Cy5.
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Affiliation(s)
- Andrej Babič
- School of Pharmaceutical Sciences Geneva-Lausanne , University of Geneva, University of Lausanne , 1211 , Geneva , Switzerland
| | - Laurent Vinet
- Institute for Molecular and Translational Imaging , University of Geneva , 1211 , Geneva , Switzerland
| | - Vineetha Chellakudam
- School of Pharmaceutical Sciences Geneva-Lausanne , University of Geneva, University of Lausanne , 1211 , Geneva , Switzerland
| | - Karolina Janikowska
- School of Pharmaceutical Sciences Geneva-Lausanne , University of Geneva, University of Lausanne , 1211 , Geneva , Switzerland
| | - Eric Allémann
- School of Pharmaceutical Sciences Geneva-Lausanne , University of Geneva, University of Lausanne , 1211 , Geneva , Switzerland
| | - Norbert Lange
- School of Pharmaceutical Sciences Geneva-Lausanne , University of Geneva, University of Lausanne , 1211 , Geneva , Switzerland
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Reed J, Kanamarlapudi V, Bain S. Mechanism of cardiovascular disease benefit of glucagon-like peptide 1 agonists. Cardiovasc Endocrinol Metab 2018; 7:18-23. [PMID: 31646274 DOI: 10.1097/xce.0000000000000147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 12/02/2017] [Indexed: 01/10/2023]
Abstract
Glucagon-like peptide 1 (GLP-1)-based therapies reduce hyperglycaemia in type 2 diabetes. Diabetes cardiovascular comorbidity remains prevalent, although current treatments are effective at reducing hyperglycaemia. GLP-1 exerts specific actions on the cardiovascular system in both healthy individuals and patients with cardiovascular pathology, and GLP-1 therapies have improved the cardiovascular profile of diabetic patients. GLP-1 exerts its action by binding to its receptor (GLP-1 receptor) at the cell surface. Mechanistically, it is not clear how GLP-1 therapies exert beneficial effects on the cardiovascular system. It is difficult to arrive at any conclusions on the ability of GLP-1 receptor agonism to reduce cardiovascular disease from animal/human studies because of varying experimental designs. This review highlights recent findings from long-term human GLP-1 therapy studies, and summarizes postulated mechanisms as to how GLP-1 receptor agonism may alleviate cardiovascular disease.
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Affiliation(s)
- Josh Reed
- School of Medicine, Institute of Life Science, Swansea University, Swansea, UK
| | | | - Stephen Bain
- School of Medicine, Institute of Life Science, Swansea University, Swansea, UK
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8
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Dialer LO, Jodal A, Schibli R, Ametamey SM, Béhé M. Radiosynthesis and evaluation of an 18F-labeled silicon containing exendin-4 peptide as a PET probe for imaging insulinoma. EJNMMI Radiopharm Chem 2018; 3:1. [PMID: 29503858 PMCID: PMC5824708 DOI: 10.1186/s41181-017-0036-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 12/14/2017] [Indexed: 12/05/2022] Open
Abstract
Background Analogues of exendin-4 have been radiolabeled for imaging the glucagon-like peptide type 1 receptors (GLP-1R) which are overexpressed in insulinoma. The aim of this research was to synthesize an 18F–labeled silicon containing exendin-4 peptide (18F-2) and to evaluate its in vitro and in vivo behavior in CHL-GLP-1 receptor positive tumor-bearing mice. 18F–labeled silicon containing exendin-4 peptide (18F-2) was prepared via one-step nucleophilic substitution of a silane precursor with 18F–fluoride in the presence of acetic acid and K222. 18F-2 was then administered to tumor-bearing mice for PET imaging and ex vivo biodistribution experiments. Results 18F-2 was produced in a radiochemical yield (decay corrected) of 1.5% and a molar activity of max. 16 GBq/μmol. The GLP-1R positive tumors were clearly visualized by PET imaging. Biodistribution studies showed reduced uptake of 18F-2 in the kidneys compared to radiometal labeled exendin-4 derivatives. The radiotracer showed specific tumour uptake which remained steady over 2 h. Conclusions This exendin-4 analogue, 18F-2, is a potential probe for imaging GLP-1R positive tumors.
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Affiliation(s)
- Lukas O Dialer
- 1Center for Radiopharmaceutical Sciences (CRS) of ETH, PSI and USZ, Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Hönggerberg, ETH Zurich, Zurich, Switzerland
| | - Andreas Jodal
- 2Center for Radiopharmaceutical Sciences (CRS), Research Department Biology and Chemistry, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - Roger Schibli
- 1Center for Radiopharmaceutical Sciences (CRS) of ETH, PSI and USZ, Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Hönggerberg, ETH Zurich, Zurich, Switzerland.,2Center for Radiopharmaceutical Sciences (CRS), Research Department Biology and Chemistry, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - Simon M Ametamey
- 1Center for Radiopharmaceutical Sciences (CRS) of ETH, PSI and USZ, Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Hönggerberg, ETH Zurich, Zurich, Switzerland
| | - Martin Béhé
- 2Center for Radiopharmaceutical Sciences (CRS), Research Department Biology and Chemistry, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
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9
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Shigeto M, Cha CY, Rorsman P, Kaku K. A role of PLC/PKC-dependent pathway in GLP-1-stimulated insulin secretion. J Mol Med (Berl) 2017; 95:361-368. [PMID: 28097390 DOI: 10.1007/s00109-017-1508-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Revised: 11/19/2016] [Accepted: 11/30/2016] [Indexed: 01/11/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) is an endogenous glucose-lowering hormone and GLP-1 receptor agonists are currently being used as antidiabetic drugs clinically. The canonical signalling pathway (including cAMP, Epac2, protein kinase A (PKA) and KATP channels) is almost universally accepted as the main mechanism of GLP-1-stimulated insulin secretion. This belief is based on in vitro studies that used nanomolar (1-100 nM) concentrations of GLP-1. Recently, it was found that the physiological concentrations (1-10 pM) of GLP-1 also stimulate insulin secretion from isolated islets, induce membrane depolarization and increase of intracellular [Ca2+] in isolated β cells/pancreatic islets. These responses were unaffected by PKA inhibitors and occurred without detectable increases in intracellular cAMP and PKA activity. These PKA-independent actions of GLP-1 depend on protein kinase C (PKC), involve activation of the standard GLP-1 receptor (GLP1R) and culminate in activation of phospholipase C (PLC), leading to an elevation of diacylglycerol (DAG), increased L-type Ca2+ and TRPM4/TRPM5 channel activities. Here, we review these recent data and contrast them against the effects of nanomolar concentrations of GLP-1. The differential intracellular signalling activated by low and high concentrations of GLP-1 could provide a clue to explain how GLP-1 exerts different function in the central nervous system and peripheral organs.
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Affiliation(s)
- Makoto Shigeto
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Old Road, Oxford, OX3 7LE, UK. .,Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama, 701-0192, Japan.
| | - Chae Young Cha
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Old Road, Oxford, OX3 7LE, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Old Road, Oxford, OX3 7LE, UK
| | - Kohei Kaku
- Department of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama, 701-0192, Japan
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10
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Berclaz C, Pache C, Bouwens A, Szlag D, Lopez A, Joosten L, Ekim S, Brom M, Gotthardt M, Grapin-Botton A, Lasser T. Combined Optical Coherence and Fluorescence Microscopy to assess dynamics and specificity of pancreatic beta-cell tracers. Sci Rep 2015; 5:10385. [PMID: 25988507 PMCID: PMC4437378 DOI: 10.1038/srep10385] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 04/10/2015] [Indexed: 12/22/2022] Open
Abstract
The identification of a beta-cell tracer is a major quest in diabetes research. However, since MRI, PET and SPECT cannot resolve individual islets, optical techniques are required to assess the specificity of these tracers. We propose to combine Optical Coherence Microscopy (OCM) with fluorescence detection in a single optical platform to facilitate these initial screening steps from cell culture up to living rodents. OCM can image islets and vascularization without any labeling. Thereby, it alleviates the need of both genetically modified mice to detect islets and injection of external dye to reveal vascularization. We characterized Cy5.5-exendin-3, an agonist of glucagon-like peptide 1 receptor (GLP1R), for which other imaging modalities have been used and can serve as a reference. Cultured cells transfected with GLP1R and incubated with Cy5.5-exendin-3 show full tracer internalization. We determined that a dose of 1 μg of Cy5.5-exendin-3 is sufficient to optically detect in vivo the tracer in islets with a high specificity. In a next step, time-lapse OCM imaging was used to monitor the rapid and specific tracer accumulation in murine islets and its persistence over hours. This optical platform represents a versatile toolbox for selecting beta-cell specific markers for diabetes research and future clinical diagnosis.
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Affiliation(s)
- Corinne Berclaz
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | | | - Arno Bouwens
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Daniel Szlag
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, PL-87-100 Torun, Poland
| | - Antonio Lopez
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Lieke Joosten
- Radboud University Medical Center, Nijmegen, The Netherlands
| | - Selen Ekim
- Radboud University Medical Center, Nijmegen, The Netherlands
| | - Maarten Brom
- Radboud University Medical Center, Nijmegen, The Netherlands
| | | | | | - Theo Lasser
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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11
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Jodal A, Pape F, Becker-Pauly C, Maas O, Schibli R, Béhé M. Evaluation of ¹¹¹in-labelled exendin-4 derivatives containing different meprin β-specific cleavable linkers. PLoS One 2015; 10:e0123443. [PMID: 25855967 PMCID: PMC4391719 DOI: 10.1371/journal.pone.0123443] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 03/04/2015] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Cleavable linkers, which are specifically cleaved by defined conditions or enzymes, are powerful tools that can be used for various purposes. Amongst other things, they have been successfully used to deliver toxic payloads as prodrugs into target tissues. In this work novel linker sequences targeting meprin β, a metalloprotease expressed in the kidney brush-border membrane, were designed and included in the sequence of three radiolabelled exendin-4 derivatives. As radiolabelled exendin-4 derivatives strongly accumulate in the kidneys, we hypothesised that specific cleavage of the radiolabelled moiety at the kidney brush-border membrane would allow easier excretion of the activity into the urine and therefore improve the pharmacological properties of the peptide. RESULTS The insertion of a cleavable linker did not negatively influence the in vitro properties of the peptides. They showed a good affinity to the GLP-1 receptor expressed in CHL cells, a high internalisation and sufficiently high stability in fresh human blood plasma. In vitro digestion with recombinant meprin β rapidly metabolised the corresponding linker sequences. After 60 min the majority of the corresponding peptides were digested and at the same time the anticipated fragments were formed. The peptides were also quickly metabolised in CD1 nu/nu mouse kidney homogenates. Immunofluorescence staining of meprin β in kidney sections confirmed the expression of the protease in the kidney brush-border membrane. Biodistribution in GLP-1 receptor positive tumour-xenograft bearing mice revealed high specific uptake of the 111In-labelled tracers in receptor positive tissue. Accumulation in the kidneys, however, was still high and comparable to the lead compound 111In-Ex4NOD40. CONCLUSION In conclusion, we show that the concept of cleavable linkers specific for meprin β is feasible, as the peptides are rapidly cleaved by the enzyme while retaining their biological properties.
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Affiliation(s)
- Andreas Jodal
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland
| | - Fabienne Pape
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | | | - Ole Maas
- Department of Radiology and Nuclear Medicine, Division of Nuclear Medicine, University Hospital Basel, Basel, Switzerland
| | - Roger Schibli
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - Martin Béhé
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland
- * E-mail:
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12
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Cho YM, Merchant CE, Kieffer TJ. Targeting the glucagon receptor family for diabetes and obesity therapy. Pharmacol Ther 2012; 135:247-78. [DOI: 10.1016/j.pharmthera.2012.05.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/15/2012] [Indexed: 12/11/2022]
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13
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Christensen M, Knop FK, Vilsbøll T, Holst JJ. Lixisenatide for type 2 diabetes mellitus. Expert Opin Investig Drugs 2011; 20:549-57. [PMID: 21391833 DOI: 10.1517/13543784.2011.562191] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
INTRODUCTION Type 2 diabetes mellitus (T2DM) is an increasing health problem worldwide. Glucagon-like peptide-1 (GLP-1) receptor agonists are an expanding drug class that target several of the pathophysiological traits of T2DM. Lixisenatide is a GLP-1 receptor agonist in development for once-daily treatment of T2DM. AREAS COVERED Pharmacological, preclinical and clinical evidence demonstrating the applicability of lixisenatide for the treatment of T2DM are reviewed. Available data and pending clinical development are summarized, critically appraised and compared to competitor drugs. The most relevant papers and meeting abstracts published up to November 2010 are used as sources for this review. EXPERT OPINION Efficacy and safety in T2DM are demonstrated with lixisenatide in monotherapy and in combination with metformin. However, limited data with the intended once-daily 20 μg subcutaneous dosing necessitate further evaluation of lixisenatide as add-on to various antidiabetic treatments. It remains to be established whether the slightly differing chemical properties compared to other GLP-1 receptor agonists including a rather short duration of action will be a disadvantage or maybe even an advantage, for example, when combined with long-acting insulin.
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Affiliation(s)
- Mikkel Christensen
- University of Copenhagen, Gentofte Hospital, Diabetes Research Division, Department of Internal Medicine F, Hellerup, Denmark.
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14
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Sebokova E, Christ AD, Wang H, Sewing S, Dong JZ, Taylor J, Cawthorne MA, Culler MD. Taspoglutide, an analog of human glucagon-like Peptide-1 with enhanced stability and in vivo potency. Endocrinology 2010; 151:2474-82. [PMID: 20382695 DOI: 10.1210/en.2009-1459] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Taspoglutide is a novel analog of human glucagon-like peptide-1 [hGLP-1(7-36)NH2] in clinical development for the treatment of type 2 diabetes. Taspoglutide contains alpha-aminoisobutyric acid substitutions replacing Ala(8) and Gly(35) of hGLP-1(7-36)NH2. The binding affinity [radioligand binding assay using [(125)I]hGLP-1(7-36)NH2], potency (cAMP production in CHO cells stably overexpressing hGLP-1 receptor), and in vitro plasma stability of taspoglutide compared with hGLP-1(7-36)NH2 have been evaluated. Effects on basal and glucose-stimulated insulin secretion were determined in vitro in INS-1E cells and in vivo in normal rats. Taspoglutide has comparable affinity (affinity constant 1.1 +/- 0.2 nm) to the natural ligand (affinity constant 1.5 +/- 0.3 nm) for the hGLP-1 receptor and exhibits comparable potency in stimulating cAMP production (EC(50) Taspo 0.06 nm and EC(50) hGLP-1(7-36)NH2 0.08 nm). Taspoglutide exerts insulinotropic action in vitro and in vivo and retains the glucoincretin property of hGLP-1(7-36)NH2. Stimulation of insulin secretion is concentration dependent and evident in the presence of high-glucose concentrations (16.7 mm) with a taspoglutide concentration as low as 0.001 nm. Taspoglutide is fully resistant to dipeptidyl peptidase-4 cleavage (during 1 h incubation at room temperature with purified enzyme) and has an extended in vitro plasma half-life relative to hGLP-1(7-36)NH2 (9.8 h vs. 50 min). In vitro, taspoglutide does not inhibit dipeptidyl peptidase-4 activity. This study provides the biochemical and pharmacological basis for the sustained plasma drug levels and prolonged therapeutic activity seen in early clinical trials of taspoglutide. Excellent stability and potency with substantial glucoincretin effects position taspoglutide as a promising new agent for treatment of type 2 diabetes.
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Affiliation(s)
- Elena Sebokova
- F. Hoffmann-La Roche AG, PRDM, Building 68/310 Grenzacherstrasse 124, CH-4070 Basel, Switzerland.
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15
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Abstract
The glucoincretins, glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide (GIP), are intestinal peptides secreted in response to glucose or lipid intake. Data on isolated intestinal tissues, dietary treatments and knockout mice strongly suggest that GIP and GLP-1 secretion requires glucose and lipid metabolism by intestinal cells. However, incretin secretion can also be induced by non-digestible carbohydrates and involves the autonomic nervous system and endocrine factors such as GIP itself and cholecystokinin. The classical pharmacological approach and the recent use of knockout mice for the incretin receptors have shown that a remarkable feature of incretins is the ability to stimulate insulin secretion in the presence of hyperglycaemia only, hence avoiding any hypoglycaemic episode. This important role is the basis of ongoing clinical trials using GLP-1 analogues. Since most of the data concern GLP-1, we will focus on this incretin. In addition, GLP-1 is involved in glucose sensing by the autonomic nervous system of the hepato-portal vein controlling muscle glucose utilization and indirectly insulin secretion. GLP-1 has been shown to decrease glucagon secretion, food intake and gastric emptying, preventing excessive hyperglycaemia and overfeeding. Another remarkable feature of GLP-1 is its secretion by the brain. Recently, elegant data showed that cerebral GLP-1 is involved in cognition and memory. Experiments using knockout mice suggest that the lack of the GIP receptor prevents diet-induced obesity. Consequently, macronutrients controlling intestinal glucose and lipid metabolism would control incretin secretion and would consequently be beneficial for health. The control of incretin secretion represents a major goal for new therapeutic as well as nutrition strategies for treating and/or reducing the risk of hyperglycaemic syndromes, excessive body weight and thus improvement of well-being.
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Affiliation(s)
- Rémy Burcelin
- UMR 5018 CNRS-UPS and IFR 31, Rangueil Hospital, Toulouse, France.
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16
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Hashiguchi H, Nakazaki M, Koriyama N, Fukudome M, Aso K, Tei C. Cyclic AMP/cAMP-GEF pathway amplifies insulin exocytosis induced by Ca2+ and ATP in rat islet beta-cells. Diabetes Metab Res Rev 2006; 22:64-71. [PMID: 16028217 DOI: 10.1002/dmrr.580] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Cyclic AMP (cAMP) plays a pivotal role in insulin secretion induced by incretins. The effects of the second messenger extend to many sites and there has been much controversy on the mechanisms. The aim of this study was to examine how cAMP amplified insulin exocytosis. METHODS Rat islets were permeabilized with alpha-toxin to measure insulin exocytosis in the fixed conditions of Ca(2+) and ATP. The effects of several agents on insulin exocytosis were observed in perifusion experiments. RESULTS Cyclic AMP enhanced the Ca(2+)-induced insulin release by around 30%, independent of Ca(2+) concentrations between 10 and 3000 nmol/L. A cAMP-GEF selective cAMP analogue, 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate, also amplified insulin release. The effect disappeared in the absence of ATP. Conversely, cAMP-independent gradual increase in insulin release was observed with ATP. These results suggested that the site of action of cAMP-GEF existed proximal to that of ATP. An analogue selective to PKA, N(6)-Benzoyladenosine-3',5'-cyclic monophosphate, had little effect. Also, a PKA-selective inhibitor, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide, reduced insulin releases induced by 1000 nmol/L Ca(2+), but did not influence the relative increase produced by Ca(2+) and cAMP. CONCLUSION Cyclic AMP potentiated Ca(2+) and ATP-induced exocytosis to a similar relative extent independent of Ca(2+) concentrations. The process appeared to be mainly mediated by cAMP-GEF. In addition, the cAMP/cAMP-GEF pathway may enhance insulin release by replenishing the readily releasable pool.
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Affiliation(s)
- Hiroshi Hashiguchi
- Department of Cardiovascular, Respiratory and Metabolic Medicine, Kagoshima University, Kagoshima, Japan
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17
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Abstract
Glucagon-like peptide-1 (GLP-1) is a gastrointestinal hormone, mainly secreted after meals, which enhances glucose-induced insulin secretion and induces satiety. It has been reported that GLP-1 levels after a mixed meal and after an oral glucose load are reduced in patients with Type 2 diabetes. The reduction of oral glucose-stimulated active GLP-1 levels in patients with Type 2 diabetes has also been observed during euglycemic iperinsulinemic clamp. The reduction of post-prandial circulating active GLP-1 in Type 2 diabetic subjects, as a consequence of chronic hyperglycemia, could contribute to the reduction of early post-prandial insulin secretion; in fact, the administration of GLP-1 receptor antagonists to healthy volunteers elicits both an impairment of meal-induced insulin secretion and an increase of post-prandial glycemia similar to that observed in Type 2 diabetes. GLP-1 is rapidly inactivated by dipeptidyl peptidase IV (DPP-IV), an enzyme produced by endothelial cells in different districts and that circulates in plasma. It is still not clear whether the reduction of mealor oral-glucose stimulated GLP-1 levels in Type 2 diabetic patients is due to impairment of secretion, increase of degradation, or both. The major limitation of using GLP-1 to treat diabetic patients is the short half-life of the native compound. There are now several compounds in various stages of pre-clinical or clinical development for the treatment of Type 2 diabetes that utilize the GLP-1 signaling pathway; these include GLP-1 receptor agonists with extended half-lives, and inhibitors of DPP-IV that increase circulating levels of endogenous, intact and bioactive GLP-1.
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Affiliation(s)
- C M Rotella
- Section of Endocrinology, Department of Clinical Pathophysiology, University of Florence, Firenze, Italy.
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18
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Ozyazgan S, Kutluata N, Afşar S, Ozdaş SB, Akkan AG. Effect of Glucagon-Like Peptide-1(7–36) and Exendin-4 on the Vascular Reactivity in Streptozotocin/Nicotinamide-Induced Diabetic Rats. Pharmacology 2005; 74:119-26. [PMID: 15746570 DOI: 10.1159/000084277] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Accepted: 01/10/2005] [Indexed: 01/18/2023]
Abstract
We investigated the vascular effects of glucagon-like peptide-1 (GLP-1) and Exendin-4 in type 2 diabetic rat aortae. Studies were performed in a normal control group (NC) (0.2 ml i.p. saline, n = 10), streptozotocin (STZ)/nicotinamide diabetic control group (DC) (a single dose of 80 mg/kg STZ i.p. injection 15 min after administration of 230 mg/kg nicotinamide i.p.), GLP-1 (GLPC) control group (1 microg/kg twice daily i.p. for 1 month, n = 10), Exendin-4 control group (EXC) (0.1 microg/kg twice daily i.p. for 1 month, n = 10), GLP-1-treated diabetic group (GLPT) (1 microg/kg twice daily i.p. for 1 month, n = 10), and Exendin-4-treated diabetic group (EXT) (0.1 microg/kg twice daily i.p. for 1 month, n = 10). One month of GLP-1 and Exendin-4 treatment significantly decreased the blood glucose levels of diabetic rats (113 +/- 2 mg/dl, p < 0.001, and 117 +/- 1 mg/dl, p < 0.001, respectively versus 181 +/- 9 mg/dl in the DC group). Sensitivity (pD2) and maximum response (% Max. Relax) of acetylcholine-stimulated relaxations in the DC group (pD2: 6.73 +/- 0.12 and 55 +/- 6, respectively) were decreased compared with the non-diabetic NC group (pD2: 7.41 +/- 0.25, p < 0.05, and 87 +/- 4, p < 0.01). Treating diabetic rats with GLP-1, pD2 values and with Exendin-4, Max. Relax %values of aortic strips to acetylcholine returned to near non-diabetic NC values (pD2: 7.47 +/- 0.15, p < 0.05, and 87 +/- 3, p < 0.01, respectively). Maximal contractile responses (Emax) to noradrenaline in aortic strips from the diabetic DC group (341 +/- 27 mg tension/mg wet weight) were significantly decreased compared with the non-diabetic NC (540 +/- 66 mg tension/mg wet weight, p < 0.001) and the GLPT group (490 +/- 25 mg tension/mg wet weight, p < 0.05). There were no significant differences in pD2 values of aortic strips to noradrenaline from all groups. Emax to KCl in aortic strips from the DC group (247 +/- 10 mg tension/mg wet weight, p < 0.01) was significantly decreased compared with non-diabetic NC group (327 +/- 26 mg tension/mg wet weight). Treating diabetic rats with GLP-1 (GLPT), Emax values of aortic strips to KCl returned to near non-diabetic NC values (271 +/- 12 mg tension/mg wet weight). GLP-1 and (partially) Exendin-4 treatment could improve the increased blood glucose level and normalize the altered vascular tone in type 2 diabetic rats.
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MESH Headings
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/physiology
- Blood Glucose/drug effects
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/physiopathology
- Dose-Response Relationship, Drug
- Exenatide
- Female
- Glucagon
- Glucagon-Like Peptide 1
- Glucagon-Like Peptides
- In Vitro Techniques
- Male
- Muscle Relaxation/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Niacinamide
- Oxidative Stress/drug effects
- Peptide Fragments/pharmacology
- Peptides/pharmacology
- Rats
- Rats, Wistar
- Streptozocin
- Vasodilator Agents/pharmacology
- Venoms/pharmacology
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Affiliation(s)
- Sibel Ozyazgan
- Department of Pharmacology and Clinical Pharmacology, Istanbul University, Cerrahpasa Faculty of Medicine, Istanbul, Turkey
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19
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Abstract
It has been known for at least one century that agents secreted from the intestine during meal absorption regulates glucose assimilation. Extensive research during the past three decades has identified two gut hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP, also known as gastric inhibitory polypeptide) that are important in postprandial glucose metabolism. Both peptides are incretins; they are secreted during carbohydrate absorption and increase insulin secretion. Since they are potent insulin secretagogues, GIP and GLP-1 have received considerable attention as potential diabetes therapeutics. However, only GLP-1 exerts insulinotropic properties when administered to patients with Type 2 diabetes. Both GLP-1 and GIP are rapidly inactivated in the circulation by the enzyme dipeptidyl peptidase IV (DPP-IV). The application of GLP-1 into clinical practice has been delayed due to the need to develop compounds that overcome this rapid inactivation. Two approaches have been taken to utilise the insulinotropic and glucose-lowering actions of GLP-1 as an antidiabetic agent: the development of DPP-IV-resistant analogues and the inhibition of DPP-IV. This review focuses on the physiology of GLP-1 and GIP and the advances that have been made thus far in developing treatments based on these physiological incretins for Type 2 diabetes.
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Affiliation(s)
- Torsten P Vahl
- University of Cincinnati, Department of Internal Medicine, OH 45220-0547, USA.
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20
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Mayo KE, Miller LJ, Bataille D, Dalle S, Göke B, Thorens B, Drucker DJ. International Union of Pharmacology. XXXV. The glucagon receptor family. Pharmacol Rev 2003; 55:167-94. [PMID: 12615957 DOI: 10.1124/pr.55.1.6] [Citation(s) in RCA: 330] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Peptide hormones within the secretin-glucagon family are expressed in endocrine cells of the pancreas and gastrointestinal epithelium and in specialized neurons in the brain, and subserve multiple biological functions, including regulation of growth, nutrient intake, and transit within the gut, and digestion, energy absorption, and energy assimilation. Glucagon, glucagon-like peptide-1, glucagon-like peptide-2, glucose-dependent insulinotropic peptide, growth hormone-releasing hormone and secretin are structurally related peptides that exert their actions through unique members of a structurally related G protein-coupled receptor class 2 family. This review discusses advances in our understanding of how these peptides exert their biological activities, with a focus on the biological actions and structural features of the cognate receptors. The receptors have been named after their parent and only physiologically relevant ligand, in line with the recommendations of the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR).
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Affiliation(s)
- Kelly E Mayo
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois, USA
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21
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Göke B, Hoppe B, Konrad A, Schirra J. [A therapeutic option for type-2 diabetes. The incretion hormone GLP-1]. PHARMAZIE IN UNSERER ZEIT 2002; 31:294-9. [PMID: 12071126 DOI: 10.1002/1615-1003(200205)31:3<294::aid-pauz294>3.0.co;2-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Burkhard Göke
- Medizinische Klinik II, Klinikum Grosshadern Ludwig-Maximilians-Universität Marchioninistr. 15, 81377 München.
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22
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Bazarsuren A, Grauschopf U, Wozny M, Reusch D, Hoffmann E, Schaefer W, Panzner S, Rudolph R. In vitro folding, functional characterization, and disulfide pattern of the extracellular domain of human GLP-1 receptor. Biophys Chem 2002; 96:305-18. [PMID: 12034449 DOI: 10.1016/s0301-4622(02)00023-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The N-terminal, extracellular domain of the receptor for glucagon-like peptide 1 (GLP-1 receptor) was expressed at a high level in E. coli and isolated as inclusion bodies. Renaturation with concomitant disulfide bond formation was achieved from guanidinium-solubilized material. A soluble and active fraction of the protein was isolated by ion exchange chromatography and gel filtration. Complex formation with GLP-1 was shown by cross-linking experiments, surface plasmon resonance measurements, and isothermal titration calorimetry. The existence of disulfide bridges in the N-terminal receptor fragment was proven after digestion of the protein with pepsin. Further analysis revealed a disulfide-binding pattern with links between cysteines 46 and 71, 62 and 104, and between 85 and 126.
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Affiliation(s)
- Ariuna Bazarsuren
- Institut für Biotechnologie der Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
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23
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Galehshahi FS, Göke B, Lankat-Buttgereit B. A novel silencer element repressing expression of the GLP-1 receptor gene in fibroblasts and pancreatic A-cells, but not in pancreatic B- and D-cells. Peptides 2000; 21:1169-76. [PMID: 11035202 DOI: 10.1016/s0196-9781(00)00256-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effects of the incretin hormone glucagon-like peptide 1 (7-36)amide (GLP-1) are mediated by the GLP-1 receptor (GLP-1R). This is expressed in a cell- and tissue-specific manner. Recently, we have cloned the 5'-flanking region of the human GLP-1R gene. The basal promoter activity is driven by the ubiquitous transcription factor Sp1. The tissue- and cell-specific expression of the gene requires several negatively acting cis-regulatory elements. We have now characterized one so far unknown distal cell-specific silencer element (DCS), repressing gene transcription of the human GLP-1R gene in fibroblasts and pancreatic A-cells, but not in pancreatic B- and D-cells. Our data suggests that the basal activity of the GLP-1R promoter is repressed in a tissue- and cell-specific manner by this novel silencer element.
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Affiliation(s)
- F S Galehshahi
- Clinical Research Unit for Gastrointestinal Endocrinology, Philipps-University of Marburg, Baldingerstr., D-35033 Marburg, Germany
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24
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Satoh F, Beak SA, Small CJ, Falzon M, Ghatei MA, Bloom SR, Smith DM. Characterization of human and rat glucagon-like peptide-1 receptors in the neurointermediate lobe: lack of coupling to either stimulation or inhibition of adenylyl cyclase. Endocrinology 2000; 141:1301-9. [PMID: 10746632 DOI: 10.1210/endo.141.4.7420] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) has been shown to bind to the posterior pituitary in the rat. We examined GLP-1 binding sites in human postmortem and rat pituitaries. Dense [125I]GLP-1 binding was seen in both human and rat posterior pituitary. In rat neurointermediate lobe membranes the binding site showed a Kd of 0.2 +/- 0.01 nM and a binding capacity of 600 +/- 33 fmol/mg protein (n = 3). In human pituitary membranes the binding site showed a Kd of 0.82 +/-0.05 nM and a binding capacity of 680 +/- 93 fmol/mg protein (n = 3). Chemical cross-linking showed a relative mol wt for the receptor-ligand complex of 73,100 +/- 1,400 (n = 3) in man and 59,300 +/- 900 (n = 3) in rat. GLP-1 (1 microM) failed to increase cAMP levels measured in rat neurointermediate lobes, whereas pituitary adenylate cyclase-activating polypeptide (100 nM) increased cAMP from a basal level of 14 +/-1 to 80 +/- 4 pmol/neurointermediate lobe 15 min (n = 5; P < 0.01). GLP-1 (up to 1 microM) did not affect the pituitary adenylate cyclase-activating polypeptide-stimulated cAMP levels. GLP-1 (up to 1 microM) also did not stimulate release of vasopressin or oxytocin from isolated rat neurointermediate lobes. The posterior pituitary shows the highest density of GLP-1-binding sites yet seen, but their function and signal transduction mechanism remain unknown.
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Affiliation(s)
- F Satoh
- Department of Metabolic Medicine, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom
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Galehshahi FS, Göke B, Lankat-Buttgereit B. Contribution of a PS1-like element to the tissue- and cell-specific expression of the human GLP-1 receptor gene. FEBS Lett 1998; 436:163-8. [PMID: 9781671 DOI: 10.1016/s0014-5793(98)01116-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The GLP-1 receptor (GLP-1R) mediates the insulinotropic effects of the incretion hormone glucagon-like peptide 1 (7-36) amide (GLP-1). Recently, we cloned the 5'-flanking region of the human GLP-1R gene. To characterize tissue- and cell-specific cis-regulatory elements, we constructed a series of 5'-deletions of the promoter. The activity of these constructs was tested in different cell lines. An element with high homology to PS1 was found to repress GLP-1R promoter activity in fibroblasts and pancreatic D-cells, but was not active in pancreatic A- and B-cells. PS1 was described to inhibit activation of a D-cell-specific enhancer. Cloning the PS1-like element upstream a heterologous promoter (SV40) revealed that it is functionally active independently from this enhancer. Our data suggest that basal activity of the GLP-1R promoter is silenced in a tissue- and cell-specific manner by negatively acting cis-regulatory elements, including a PS1-like element.
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Affiliation(s)
- F S Galehshahi
- Clinical Research Unit for Gastrointestinal Endocrinology, Philipps-University of Marburg, Germany
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Beak SA, Heath MM, Small CJ, Morgan DG, Ghatei MA, Taylor AD, Buckingham JC, Bloom SR, Smith DM. Glucagon-like peptide-1 stimulates luteinizing hormone-releasing hormone secretion in a rodent hypothalamic neuronal cell line. J Clin Invest 1998; 101:1334-41. [PMID: 9502775 PMCID: PMC508688 DOI: 10.1172/jci610] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To examine the influence of the putative satiety factor (GLP-1) on the hypothalamo-pituitary-gonadal axis, we used GT1-7 cells as a model of neuronal luteinizing hormone- releasing hormone (LHRH) release. GLP-1 caused a concentration-dependent increase in LHRH release from GT1-7 cells. Specific, saturable GLP-1 binding sites were demonstrated on these cells. The binding of [125I]GLP-1 was time-dependent and consistent with a single binding site (Kd = 0.07+/-0.016 nM; binding capacity = 160+/-11 fmol/mg protein). The specific GLP-1 receptor agonists, exendin-3 and exendin-4, also showed high affinity (Ki = 0.3+/-0.05 and 0.32+/-0.06 nM, respectively) as did the antagonist exendin-(9-39) (Ki = 0.98+/-0.24 nM). At concentrations that increased LHRH release, GLP-1 (0.5-10 nM) also caused an increase in intracellular cAMP in GT1-7 cells (10 nM GLP-1: 7.66+/-0.4 vs. control: 0.23+/-0.02 nmol/mg protein; P < 0.001). Intracerebroventricular injection of GLP-1 at a single concentration (10 microg) produced a prompt increase in the plasma luteinizing hormone concentration in male rats (GLP-1: 1.09+/-0.11 vs. saline: 0.69+/-0.06 ng/ml; P < 0.005). GLP-1 levels in the hypothalami of 48-h-fasted male rats showed a decrease, indicating a possible association of the satiety factor with the low luteinizing hormone levels in animals with a negative energy balance.
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Affiliation(s)
- S A Beak
- Division of Endocrinology and Metabolic Medicine, Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 ONN, United Kingdom
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27
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Lankat-Buttgereit B, Göke B. Cloning and characterization of the 5' flanking sequences (promoter region) of the human GLP-1 receptor gene. Peptides 1997; 18:617-24. [PMID: 9213353 DOI: 10.1016/s0196-9781(97)00001-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The glucagon-like peptide 1 (7-36) amide (GLP-1) receptor mediates the insulinotropic effects of the incretin hormone GLP-1. To elucidate the tissue-specific regulation of the GLP-1 receptor we screened a human genomic library with a human GLP-1 receptor cDNA. The gene spans 40 kb and consists of at least seven exons. The promoter contained no TATA- or CAAT-boxes, but several other putative cis-regulatory recognition sequences including three Sp1 binding sites. Transient transfections of GLP-1 receptor producing and non-producing cells with promoter/ reporter gene constructs revealed that the putative Sp1 binding sites and several other silencer and tissue specific elements are important for the activity. Therefore, 3000 bp upstream the GLP-1 receptor coding sequences comprise regulatory elements essential for the tissue- and cell-specific transcription of the gene.
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Wilmen A, Van Eyll B, Göke B, Göke R. Five out of six tryptophan residues in the N-terminal extracellular domain of the rat GLP-1 receptor are essential for its ability to bind GLP-1. Peptides 1997; 18:301-5. [PMID: 9149304 DOI: 10.1016/s0196-9781(96)00321-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oligonucleotide-directed mutagenesis was utilized to investigate the requirement of tryptophan residues located in the N-terminal domain of the glucagon-like peptide-1 (GLP-1) receptor for the ability to bind its ligand and to induce cAMP generation. W39, W72, W87, W91, W110, and W120 were mutated into alanine. Two of the six tryptophan residues, W72 and W110, are highly conserved within the receptor subfamily. After transfection of mutated cDNAs in COS-7 or CHL cells, it appeared that mutant W87 A bound [125I] GLP-1 with the same affinity as wild-type receptor and induced signal transduction to a comparable extent. In contrast, mutant receptors W39A, W72A, W91A, W110A, and W120A lost the ability to bind [125I] GLP-1. Because all mutated receptor cDNAs were transcribed on RNA level (Northern blot) and the receptor proteins were expressed at the plasma membrane level (Western blot), it is concluded that with the exception of W87 all trytophan residues are essential for receptor ligand interaction. This indicates the significance of hydrophobic interactions within the N-terminal domain of the GLP-1 receptor.
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Affiliation(s)
- A Wilmen
- Clinical Research Group for Gastrointestinal Endocrinology, Philipps-University of Marburg, Germany
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Fehmann HC, Schweinfurth J, Jiang J, Göke B. Regulation of glucagon-like peptide-I receptor expression and transcription by the protein kinase C pathway. RESEARCH IN EXPERIMENTAL MEDICINE. ZEITSCHRIFT FUR DIE GESAMTE EXPERIMENTELLE MEDIZIN EINSCHLIESSLICH EXPERIMENTELLER CHIRURGIE 1996; 196:219-25. [PMID: 8903097 DOI: 10.1007/bf02576844] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Glucagon-like peptide-I (GLP-I) is an important insulinotropic incretin hormone. The GLP-I receptor belongs to the family of seven transmembrane domain receptors. We studied the regulation of its expression by the protein kinase C (PKC)-dependent pathway in rat insulinoma RINm5F cells. Cells were incubated for 3, 6 and 24 h with an optimal concentration of tissue plasminogen activator (TPA), an activator of PKC. TPA induced significantly lower GLP-I receptor mRNA levels under steady-state conditions after 6 and 24 h. The stability of the GLP-I receptor mRNA was unchanged. The number of GLP-I receptors present on RINm5F cells was reduced after 6 and 24 h. TPA did not influence the affinity of remaining receptors to its specific ligand. These data indicate that PKC activation downregulates the expression of the GLP-I receptor gene, mainly at the transcriptional level.
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Affiliation(s)
- H C Fehmann
- Department of Medicine, Philipps University of Marburg, Germany
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30
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Linn T, Schneider K, Göke B, Federlin K. Glucagon-like-peptide-1 (7-36) amide improves glucose sensitivity in beta-cells of NOD mice. Acta Diabetol 1996; 33:19-24. [PMID: 8777280 DOI: 10.1007/bf00571935] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effect of the insulinotropic gut hormone glucagon-like-peptide-1 (GLP-1) was studied on the residual insulin capacity of prediabetic nonobese diabetic (NOD) mice, a model of insulin-dependent diabetes mellitus (type 1). This was done using isolated pancreas perfusion and dynamic islet perifusion. Prediabetes was defined by insulitis and fasting normoglycemia. Insulitis occurred in 100% of NOD mice beyond the age of 12 weeks. K values in the intravenous glucose tolerance test were reduced in 20-week-old NOD mice compared with age matched non-diabetes-prone NOR (nonobese resistant) mice (2.4 +/- 1.1 vs 3.8 +/- 1.5% min-1, P < 0.05). Prediabetic NOD pancreases were characterized by a complete loss of the glucose-induced first-phase insulin release. In perifused NOD islets GLP-1, at concentrations already effective in normal islets, left the insulin release unaltered. However, a significant rise of glucose-dependent insulin secretion occurred for GLP-1 concentrations > 0.1 nM. This was obtained with both techniques, dynamic islet perifusion and isolated pancreas perfusion, indicating a direct effect of GLP-1 on the beta-cell. Analysis of glucose-insulin dose-response curves revealed a marked improvement of glucose sensitivity of the NOD endocrine pancreas in the presence of GLP-1 (half-maximal insulin output without GLP-1 15.2 mM and with GLP-1 9.4 mM, P < 0.002). We conclude that GLP-1 can successfully reverse the glucose sensing defect of islets affected by insulitis.
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Affiliation(s)
- T Linn
- Medical Clinic III and Polyclinic, Justus Liebig University, Giessen, Germany
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Affiliation(s)
- J P Raufman
- Department of Medicine, State University of New York-Health Science Center at Brooklyn, NY 11203-2098, USA
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Van Eyll B, Göke B, Wilmen A, Göke R. Exchange of W39 by A within the N-terminal extracellular domain of the GLP-1 receptor results in a loss of receptor function. Peptides 1996; 17:565-70. [PMID: 8804062 DOI: 10.1016/0196-9781(96)00019-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The proglucagon-derived glucagon-like peptide-1 (GLP-1) secreted by the L-cells exerts an insulinotropic effect at pancreatic beta-cells. The GLP-1 receptor belongs to a new subfamily of the superfamily of seven transmembrane, G-protein-coupled receptors (7 TM receptors). We show that a single point mutation within a nonconserved motif of the N-terminal, extracellular domain of the GLP-1 receptor results in a dramatic impairment of receptor function. Thus, substitution of W39 by A or F is followed by a loss of GLP-1 binding. Exchange of K38 with A (mutant K) slightly decreased GLP-1 binding affinity. Replacement of the negatively charged Q37 by K and K38 by A, which is identical with a shift of the positively charged K one position upstream, resulted in a receptor mutant able to bind GLP-1 with higher affinity as the wild-type receptor and mutant K. Therefore, the presence of an imidazol ring structure in the investigated receptor region is necessary for an intact receptor function Furthermore, a positive charge at this location is important for the receptor-ligand interaction.
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Affiliation(s)
- B Van Eyll
- Clinical Research Group for Gastrointestinal Endocrinology, Philipps-University of Marburg, Germany
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Plisetskaya EM, Mommsen TP. Glucagon and glucagon-like peptides in fishes. INTERNATIONAL REVIEW OF CYTOLOGY 1996; 168:187-257. [PMID: 8843650 DOI: 10.1016/s0074-7696(08)60885-2] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Glucagon and glucagon-like peptides (GLPs) are coencoded in the vertebrate proglucagon gene. Large differences exist between fishes and other vertebrates in gene structure, peptide expression, peptide chemistry, and function of the hormones produced. Here we review selected aspects of glucagon and glucagon-like peptides in vertebrates with special focus on the contributions made by analysis of piscine systems. Our topics range from the history of discovery to gene structure and expression, through primary structures and regulation of plasma concentrations to physiological effects and message transduction. In fishes, the pancreas synthesizes glucagon and GLP-1, while the intestine may contribute oxyntomodulin, glucagon, GLP-1, and GLP-2. The pancreatic gene is short and lacks the sequence for GLP-2. GLP-1, which is produced exclusively in its biologically active form, is a potent metabolic hormone involved in regulation of liver glycogenolysis and gluconeogenesis. The responsiveness of isolated hepatocytes to glucagon is limited to high concentrations, while physiological concentrations of GLP-1 effectively regulate hepatic metabolism. Plasma concentrations of GLP-1 are higher than those of glucagon, and liver is identified as the major site of removal of both hormones from fish plasma. Ultimately, GLP-1 and glucagon exert effects on glucose metabolism that directly and indirectly oppose several key actions of insulin. Both glucagon and GLP-1 show very weak insulinotropic activity, if any, when tested on fish pancreas. Intracellular message transduction for glucagon, especially at slightly supraphysiological concentrations, involves cAMP and protein kinase A, while pathways for GLP are largely unknown and may involve a multitude of messengers, including cAMP. In spite of fundamental differences in GLP-1 function between fishes and mammals, fish GLP-1 is as powerful an insulinotropin for mammalian B-cells as mammalian GLP-1 is a metabolic hormone if tested on piscine liver.
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Affiliation(s)
- E M Plisetskaya
- School of Fisheries, University of Washington, Seattle 98195, USA
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Gronau KA, Brubaker PL. Mechanism of action of glucagon-like peptide-1(7-36NH2) in isolated rat pancreatic islets and abrogation of its effects in long-term incubations. Endocrine 1995; 3:795-9. [PMID: 21153123 DOI: 10.1007/bf02935683] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/1995] [Accepted: 08/18/1995] [Indexed: 01/17/2023]
Abstract
Glucagon-like peptide-1(7-37/36NH2) (GLP-1) potently stimulates acute glucose-dependent insulin secretionin vitro andin vivo. Islet cell lines have been used extensively to examine the effects of GLP-1(7-37/36NH2) on adenylyl cyclase as well as the phenomenon of homologous receptor desensitization. However, neither the effects of GLP-1(7-37/36NH2) on the protein kinase A pathway nor its chronic effects on insulin secretion have been examined in normal B cells. The isolated rat pancreatic islet was therefore employed to study these phenomena in a more physiologic model. GLP-1(7-36NH2) (10(-8)M) increased islet cAMP content to 391±196% of control after 30 min of incubation (P<0.05), and stimulated glucose-dependent insulin secretion by 2.0±0.1-fold in acutely perifused islets (P<0.001). In chronic 24 h incubations, insulin secretion was stimulated two to fourfold by 10 as compared to 5 mM glucose (P<0.001), and three to fourfold by 10 μM forskolin plus 10μM isobutylmethylxanthine (P<0.01-0.001). However, 10(-8) M GLP-1(7-36NH2) did not stimulate insulin secretion at either 5 or 10 mM glucose, or in the presence of forskolin and IBMX. This specific lack of GLP-1(7-36NH2) effectiveness was not due to peptide degradation or accumulation of somatostatin in the medium. The results of the present study establish for the first time that GLP-1(7-36NH2) induces insulin secretion in normal B cells through a protein kinase A-dependent mechanism. The loss of insulinotropic effect of GLP-1(7-36NH2) in long-term incubations, despite the ability of glucose and cAMP to increase insulin secretion, suggests that the GLP-1(7-37/36NH2) receptor in normal islets may undergo homologous desensitization during chronic exposure to GLP-1(7-36NH2).
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Affiliation(s)
- K A Gronau
- Department of Physiology, University of Toronto, M5S 1A8, Toronto, Ontario, Canada
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Volz A, Göke R, Lankat-Buttgereit B, Fehmann HC, Bode HP, Göke B. Molecular cloning, functional expression, and signal transduction of the GIP-receptor cloned from a human insulinoma. FEBS Lett 1995; 373:23-9. [PMID: 7589426 DOI: 10.1016/0014-5793(95)01006-z] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) plays an important role in the regulation of postprandial insulin secretion and proinsulin gene expression of pancreatic beta-cells. This study demonstrates the molecular cloning of a cDNA for the GIP-receptor from a human insulinoma lambda gt11 cDNA library. The cloned cDNA encoded a seven transmembrane domain protein of 466 amino acids which showed high homology (41%) to the human glucagon-like peptide 1 (GLP-1) receptor. Homology to the GIP receptor from rat or hamster was 79% and 81%, respectively. When transfected stably into fibroblast CHL-cells a high affinity receptor was expressed which coupled to the adenylate cyclase with normal basal cAMP and increasing intracellular cAMP levels under stimulation with human GIP-1-42 (EC50 = 1.29 x 10(-13) M). The receptor accepted only human GIP 1-42 (Kd = 1.93 +/- 0.2 x 10(-8) M) and porcine truncated GIP 1-30 (Kd = 1.13 +/- 0.1 x 10(-8) M) as high affinity ligands. At 1 microM, exendin-4 and (9-39)amide weakly reduced GIP-binding (25%) whereas secretin, glucagon, glucagon-like peptide-1, vasoactive intestinal polypeptide, peptide histidine-isoleucine, and pituitary adenylyl cyclase activating peptide were without effect. In transfected CHL cells, GIP-1-42 did not increase intracellular calcium. Northern analysis revealed one transcript of human GIP receptor mRNA with an apparent size of 5.5 kb. The exact understanding of GIP receptor regulation and signal transduction will aid in the understanding of the incretin hormone's failure to exert its biological action at the pancreatic B-cell in type II diabetes mellitus.
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Affiliation(s)
- A Volz
- Department of Internal Medicine, Philipps University of Marburg, Germany
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