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Bailey CJ, Flatt PR. Duodenal enteroendocrine cells and GIP as treatment targets for obesity and type 2 diabetes. Peptides 2024; 174:171168. [PMID: 38320643 DOI: 10.1016/j.peptides.2024.171168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 02/02/2024] [Accepted: 02/02/2024] [Indexed: 02/08/2024]
Abstract
The duodenum is an important source of endocrine and paracrine signals controlling digestion and nutrient disposition, notably including the main incretin hormone glucose-dependent insulinotropic polypeptide (GIP). Bariatric procedures that prevent nutrients from contact with the duodenal mucosa are particularly effective interventions to reduce body weight and improve glycaemic control in obesity and type 2 diabetes. These procedures take advantage of increased nutrient delivery to more distal regions of the intestine which enhances secretion of the other incretin hormone glucagon-like peptide-1 (GLP-1). Preclinical experiments have shown that either an increase or a decrease in the secretion or action of GIP can decrease body weight and blood glucose in obesity and non-insulin dependent hyperglycaemia, but clinical studies involving administration of GIP have been inconclusive. However, a synthetic dual agonist peptide (tirzepatide) that exerts agonism at receptors for GIP and GLP-1 has produced marked weight-lowering and glucose-lowering effects in people with obesity and type 2 diabetes. This appears to result from chronic biased agonism in which the novel conformation of the peptide triggers enhanced signalling by the GLP-1 receptor through reduced internalisation while reducing signalling by the GIP receptor directly or via functional antagonism through increased internalisation and degradation.
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Affiliation(s)
| | - Peter R Flatt
- Diabetes Research Centre, School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA Northern Ireland, UK
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Ferguson SA, Panos JJ, Sloper D, Varma V, Sarkar S. Alzheimer's disease: a step closer to understanding type 3 diabetes in African Americans. Metab Brain Dis 2021; 36:1803-1816. [PMID: 34021875 DOI: 10.1007/s11011-021-00754-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 05/10/2021] [Indexed: 10/21/2022]
Abstract
Alzheimer's disease (AD) is the fourth leading cause of death in the United States and the most common cause of adult-onset dementia. Recent results suggest an increased prevalence and severity in African Americans compared to Caucasians. Our understanding of the potential mechanism(s) underlying this ethnicity difference is limited. We previously described ethnicity-related differences in levels of neurodegenerative proteins and cytokines/chemokines in the BA21 region of African Americans and Caucasians with AD. Here, similar multiplex assays were used to examine those endpoints in patient postmortem cerebrospinal fluid (CSF). Additionally, we measured levels of C-peptide, ghrelin, gastric inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1), glucagon, insulin, leptin, PAI-1, resistin, and visfatin using a human diabetes 10-plex assay. The cytokine and chemokine assays revealed that levels of 26 chemokines or cytokines differed significantly with ethnicity, and three of those were significantly associated with gender. The neurodegenerative disease panel indicated that levels of soluble RAGE were significantly elevated in African Americans compared to Caucasians. All measures in the diabetes disease panel assay were significantly elevated in African Americans: ghrelin, GIP, GLP-1, glucagon, insulin, and visfatin. Through peripheral sample analysis, these results provide further evidence that ethnicity is critically involved in the manifestation of AD.
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Affiliation(s)
- Sherry A Ferguson
- Division of Neurotoxicology, National Center for Toxicological Research/Food and Drug Administration, Jefferson, AR, 72079, USA
| | - John J Panos
- Division of Neurotoxicology, National Center for Toxicological Research/Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Daniel Sloper
- Division of Systems Biology, National Center for Toxicological Research/Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Vijayalakshmi Varma
- Division of Systems Biology, National Center for Toxicological Research/Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Sumit Sarkar
- Division of Neurotoxicology, National Center for Toxicological Research/Food and Drug Administration, Jefferson, AR, 72079, USA.
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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. Biochim Biophys Acta 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Abstract
OBJECTIVE The endopeptidase dipeptidyl peptidase-IV (DPP-IV) has been shown to NH2-terminally truncate incretin hormones, glucose-dependent insulinotropic polypeptide, and glucagon-like peptide-1, thus ablating their ability to potentiate glucose-stimulated insulin secretion. Increasing the circulating levels of incretins through administration of DPP-IV inhibitors has therefore been introduced as a therapeutic approach for the treatment of type 2 diabetes. DPP-IV inhibitor treatment has also been shown to preserve islet mass in rodent models of type 1 diabetes. The current study was initiated to define the effects of the DPP-IV inhibitor sitagliptin (MK0431) on transplanted islet survival in nonobese diabetic (NOD) mice, an autoimmune type 1 diabetes model. RESEARCH DESIGN AND METHODS Effects of MK0431 on islet graft survival in diabetic NOD mice were determined with metabolic studies and micropositron emission tomography imaging, and its underlying molecular mechanisms were assessed. RESULTS Treatment of NOD mice with MK0431 before and after islet transplantation resulted in prolongation of islet graft survival, whereas treatment after transplantation alone resulted in small beneficial effects compared with nontreated controls. Subsequent studies demonstrated that MK0431 pretreatment resulted in decreased insulitis in diabetic NOD mice and reduced in vitro migration of isolated splenic CD4+ T-cells. Furthermore, in vitro treatment of splenic CD4+ T-cells with DPP-IV resulted in increased migration and activation of protein kinase A (PKA) and Rac1. CONCLUSIONS Treatment with MK0431 therefore reduced the effect of autoimmunity on graft survival partially by decreasing the homing of CD4+ T-cells into pancreatic beta-cells through a pathway involving cAMP/PKA/Rac1 activation.
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Affiliation(s)
- Su-Jin Kim
- Department of Cellular and Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
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Mcintosh CH, Widenmaier S, Kim S. Chapter 15 Glucose‐Dependent Insulinotropic Polypeptide (Gastric Inhibitory Polypeptide; GIP). Insulin and IGFs. Elsevier; 2009. pp. 409-71. [DOI: 10.1016/s0083-6729(08)00615-8] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Parthier C, Kleinschmidt M, Neumann P, Rudolph R, Manhart S, Schlenzig D, Fanghänel J, Rahfeld JU, Demuth HU, Stubbs MT. Crystal structure of the incretin-bound extracellular domain of a G protein-coupled receptor. Proc Natl Acad Sci U S A 2007; 104:13942-7. [PMID: 17715056 PMCID: PMC1955799 DOI: 10.1073/pnas.0706404104] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Indexed: 11/18/2022] Open
Abstract
Incretins, endogenous polypeptide hormones released in response to food intake, potentiate insulin secretion from pancreatic beta cells after oral glucose ingestion (the incretin effect). This response is signaled by the two peptide hormones glucose-dependent insulinotropic polypeptide (GIP) (also known as gastric inhibitory polypeptide) and glucagon-like peptide 1 through binding and activation of their cognate class 2 G protein-coupled receptors (GPCRs). Because the incretin effect is lost or significantly reduced in patients with type 2 diabetes mellitus, glucagon-like peptide 1 and GIP have attracted considerable attention for their potential in antidiabetic therapy. A paucity of structural information precludes a detailed understanding of the processes of hormone binding and receptor activation, hampering efforts to develop novel pharmaceuticals. Here we report the crystal structure of the complex of human GIP receptor extracellular domain (ECD) with its agonist, the incretin GIP(1-42). The hormone binds in an alpha-helical conformation in a surface groove of the ECD largely through hydrophobic interactions. The N-terminal ligand residues would remain free to interact with other parts of the receptor. Thermodynamic data suggest that binding is concomitant with structural organization of the hormone, resulting in a complex mode of receptor-ligand recognition. The presentation of a well structured, alpha-helical ligand by the ECD is expected to be conserved among other hormone receptors of this class.
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Affiliation(s)
| | | | | | - Rainer Rudolph
- *Institut für Biochemie und Biotechnologie and
- *Mitteldeutsches Zentrum für Struktur und Dynamik der Proteine, Martin–Luther–Universität Halle–Wittenberg, D-06120 Halle (Saale), Germany; and
| | - Susanne Manhart
- Probiodrug AG, Biocenter Halle, D-06120 Halle (Saale), Germany
| | | | - Jörg Fanghänel
- *Mitteldeutsches Zentrum für Struktur und Dynamik der Proteine, Martin–Luther–Universität Halle–Wittenberg, D-06120 Halle (Saale), Germany; and
| | | | | | - Milton T. Stubbs
- *Institut für Biochemie und Biotechnologie and
- *Mitteldeutsches Zentrum für Struktur und Dynamik der Proteine, Martin–Luther–Universität Halle–Wittenberg, D-06120 Halle (Saale), Germany; and
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Gault VA, Hunter K, Irwin N, Green BD, Greer B, Harriott P, O'Harte FPM, Flatt PR. Characterisation and biological activity of Glu3 amino acid substituted GIP receptor antagonists. Arch Biochem Biophys 2007; 461:263-74. [PMID: 17428436 DOI: 10.1016/j.abb.2007.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 03/07/2007] [Accepted: 03/07/2007] [Indexed: 11/19/2022]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is an important gastrointestinal hormone, which regulates insulin release and glucose homeostasis, but is rapidly inactivated by enzymatic N-terminal truncation. Here we report the enzyme resistance and biological activity of several Glu(3)-substituted analogues of GIP namely; (Ala(3))GIP, (Lys(3))GIP, (Phe(3))GIP, (Trp(3))GIP and (Tyr(3))GIP. Only (Lys(3))GIP demonstrated moderately enhanced resistance to DPP-IV (p<0.05 to p<0.01) compared to native GIP. All analogues demonstrated a decreased potency in cAMP production (EC(50) 1.47 to 11.02 nM; p<0.01 to p<0.001) with (Lys(3))GIP and (Phe(3))GIP significantly inhibiting GIP-stimulated cAMP production (p<0.05). In BRIN-BD11 cells, (Lys(3))GIP, (Phe(3))GIP, (Trp(3))GIP and (Tyr(3))GIP did not stimulate insulin secretion with both (Lys(3))GIP and (Phe(3))GIP significantly inhibiting GIP-stimulated insulin secretion (p<0.05). Injection of each GIP analogue together with glucose in ob/ob mice significantly increased the glycaemic excursion compared to control (p<0.05 to p<0.001). This was associated with lack of significant insulin responses. (Ala(3))GIP, (Phe(3))GIP and (Tyr(3))GIP, when administered together with GIP, significantly reduced plasma insulin (p<0.05 to p<0.01) and impaired the glucose-lowering ability (p<0.05 to p<0.01) of the native peptide. The DPP-IV resistance and GIP antagonism observed were similar but less pronounced than (Pro(3))GIP. These data demonstrate that position 3 amino acid substitution of GIP with (Ala(3)), (Phe(3)), (Tyr(3)) or (Pro(3)) provides a new class of functional GIP receptor antagonists.
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Affiliation(s)
- Victor A Gault
- School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland, UK
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Hinke SA, Pederson RA, McIntosh CHS. Relative contribution of incretins to the glucose lowering effect of DP IV inhibitors in type 2 diabetes mellitus (T2DM). Adv Exp Med Biol 2006; 575:119-33. [PMID: 16700515 DOI: 10.1007/0-387-32824-6_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Affiliation(s)
- Simon A Hinke
- Department of Metabolism and Endocrinology, Diabetes Research Center, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
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Hinke SA, Manhart S, Speck M, Pederson RA, Demuth HU, McIntosh CHS. In depth analysis of the N-terminal bioactive domain of gastric inhibitory polypeptide. Life Sci 2004; 75:1857-70. [PMID: 15302229 DOI: 10.1016/j.lfs.2004.03.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 03/29/2004] [Indexed: 11/27/2022]
Abstract
Gastric inhibitory polypeptide/glucose-dependent insulinotropic polypeptide (GIP) is an important gastrointestinal regulator of insulin release and glucose homeostasis following a meal. Strategies have been undertaken to delineate the bioactive domains of GIP with the intention of developing small molecular weight GIP mimetics. The molecular cloning of receptors for GIP and the related hormone GLP-1 (glucagon-like peptide-1) has allowed examination of the characteristics of incretin analogs in transfected cell models. The current report examines the N-terminal bioactive domain of GIP residing in residues 1-14 by alanine scanning mutagenesis and N-terminal substitution/modification. Further studies examined peptide chimeras of GIP and GLP-1 designed to localize bioactive determinants of the two hormones. The alanine scan of the GIP(1-14) sequence established that the peptide was extremely sensitive to structural perturbations. Only replacement of amino acids 2 and 13 with those found in glucagon failed to dramatically reduce receptor binding and activation. Of four GIP(1-14) peptides modified by the introduction of DP IV-resistant groups, a peptide with a reduced bond between Ala2 and Glu3 demonstrated improved receptor potency compared to native GIP(1-14). The peptide chimera studies supported recent results on the importance of a mid-region helix for bioactivity of GIP, and confirmed existence of two separable regions with independent intrinsic receptor binding and activation properties. Furthermore, peptide chimeras showed that binding of GLP-1 also involves both N- and C-terminal domains, but that it apparently contains only a single bioactive domain in its N-terminus. Together, these results should facilitate development of incretin based therapies using rational drug design for potential treatment of diabetes.
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Affiliation(s)
- Simon A Hinke
- Department of Physiology, Faculty of Medicine, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3, Canada
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Irwin N, Gault VA, Green BD, Greer B, McCluskey JT, Harriott P, O'Harte FPM, Flatt PR. Effects of short-term chemical ablation of the GIP receptor on insulin secretion, islet morphology and glucose homeostasis in mice. Biol Chem 2004; 385:845-52. [PMID: 15493880 DOI: 10.1515/bc.2004.110] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone secreted by endocrine K-cells in response to nutrient absorption. In this study we have utilized a specific and enzymatically stable GIP receptor antagonist, (Pro3)GIP, to evaluate the contribution of endogenous GIP to insulin secretion and glucose homeostasis in mice. Daily injection of (Pro3)GIP (25 nmol/kg body weight) for 11 days had no effect on food intake or body weight. Non-fasting plasma glucose concentrations were significantly raised (p<0.05) by day 11, while plasma insulin concentrations were not significantly different from saline treated controls. After 11 days, intraperitoneal glucose tolerance was significantly impaired in the (Pro3)GIP treated mice compared to control (p<0.01). Glucose-mediated insulin secretion was not significantly different between the two groups. Insulin sensitivity of 11-day (Pro3)GIP treated mice was slightly impaired 60 min post injection compared with controls. Following a 15 min refeeding period in 18 h fasted mice, food intake was not significantly different in (Pro3)GIP treated mice and controls. However, (Pro3)GIP treated mice displayed significantly elevated plasma glucose levels 30 and 60 min post feeding (p<0.05, in both cases). Postprandial insulin secretion was not significantly different and no changes in pancreatic insulin content or islet morphology were observed in (Pro3)GIP treated mice. The observed biological effects of (Pro3)GIP were reversed following cessation of treatment for 9 days. These data indicate that ablation of GIP signaling causes a readily reversible glucose intolerance without appreciable change of insulin secretion.
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Affiliation(s)
- Nigel Irwin
- Diabetes Research Group, School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK.
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Hinke SA, Manhart S, Kühn-Wache K, Nian C, Demuth HU, Pederson RA, McIntosh CHS. [Ser2]- and [SerP2] incretin analogs: comparison of dipeptidyl peptidase IV resistance and biological activities in vitro and in vivo. J Biol Chem 2003; 279:3998-4006. [PMID: 14610075 DOI: 10.1074/jbc.m311304200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP; also known as gastric inhibitory polypeptide) are incretin hormones that reduce postprandial glycemic excursions via enhancing insulin release but are rapidly inactivated by enzymatic N-terminal truncation. As such, efforts have been made to improve their plasma stability by synthetic modification or by inhibition of the responsible protease, dipeptidyl peptidase (DP) IV. Here we report a parallel comparison of synthetic GIP and GLP-1 with their Ser2- and Ser(P)2-substituted analogs, examining receptor binding and activation, metabolic stability, and biological effects in vivo. Both incretins and their Ser2-substituted analogs showed similar EC50s (0.16-0.52 nm) and IC50s (4.3-8.1 nm) at their respective cloned receptors. Although both phosphoserine 2-modified (Ser(PO3H2); Ser(P)) peptides were able to stimulate maximal cAMP production and fully displace receptor-bound tracer, they showed significantly right-shifted concentration-response curves and binding affinities. Ser2-substituted analogs were moderately resistant to DP IV cleavage, whereas [Ser(P)2]GIP and [Ser(P)2] GLP-1 showed complete resistance to purified DP IV. It was shown that the Ser(P) forms were dephosphorylated in serum and thus in vivo act as precursor forms of Ser2-substituted analogs. When injected subcutaneously into conscious Wistar rats, all peptides reduced glycemic excursions (rank potency: [Ser(P)2]incretins > or = [Ser2] incretins > native hormones). Insulin determinations indicated that the reductions in postprandial glycemia were at least in part insulin-mediated. Thus it has been shown that despite having low in vitro bioactivity using receptor-transfected cells, in vivo potency of [Ser(P)2] incretins was comparable with or greater than that of native or [Ser2]peptides. Hence, Ser(P)2-modified incretins present as novel glucose-lowering agents.
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Affiliation(s)
- Simon A Hinke
- Department of Physiology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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