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Loh YP, Xiao L, Park JJ. Trafficking of hormones and trophic factors to secretory and extracellular vesicles: a historical perspective and new hypothesis. EXTRACELLULAR VESICLES AND CIRCULATING NUCLEIC ACIDS 2023; 4:568-587. [PMID: 38435713 PMCID: PMC10906782 DOI: 10.20517/evcna.2023.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
It is well known that peptide hormones and neurotrophic factors are intercellular messengers that are packaged into secretory vesicles in endocrine cells and neurons and released by exocytosis upon the stimulation of the cells in a calcium-dependent manner. These secreted molecules bind to membrane receptors, which then activate signal transduction pathways to mediate various endocrine/trophic functions. Recently, there is evidence that these molecules are also in extracellular vesicles, including small extracellular vesicles (sEVs), which appear to be taken up by recipient cells. This finding raised the hypothesis that they may have functions differentiated from their classical secretory hormone/neurotrophic factor actions. In this article, the historical perspective and updated mechanisms for the sorting and packaging of hormones and neurotrophic factors into secretory vesicles and their transport in these organelles for release at the plasma membrane are reviewed. In contrast, little is known about the packaging of hormones and neurotrophic factors into extracellular vesicles. One proposal is that these molecules could be sorted at the trans-Golgi network, which then buds to form Golgi-derived vesicles that can fuse to endosomes and subsequently form intraluminal vesicles. They are then taken up by multivesicular bodies to form extracellular vesicles, which are subsequently released. Other possible mechanisms for packaging RSP proteins into sEVs are discussed. We highlight some studies in the literature that suggest the dual vesicular pathways for the release of hormones and neurotrophic factors from the cell may have some physiological significance in intercellular communication.
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Affiliation(s)
- Y. Peng Loh
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lan Xiao
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Joshua J. Park
- Scientific Review Branch, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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2
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Štepihar D, Florke Gee RR, Hoyos Sanchez MC, Fon Tacer K. Cell-specific secretory granule sorting mechanisms: the role of MAGEL2 and retromer in hypothalamic regulated secretion. Front Cell Dev Biol 2023; 11:1243038. [PMID: 37799273 PMCID: PMC10548473 DOI: 10.3389/fcell.2023.1243038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/31/2023] [Indexed: 10/07/2023] Open
Abstract
Intracellular protein trafficking and sorting are extremely arduous in endocrine and neuroendocrine cells, which synthesize and secrete on-demand substantial quantities of proteins. To ensure that neuroendocrine secretion operates correctly, each step in the secretion pathways is tightly regulated and coordinated both spatially and temporally. At the trans-Golgi network (TGN), intrinsic structural features of proteins and several sorting mechanisms and distinct signals direct newly synthesized proteins into proper membrane vesicles that enter either constitutive or regulated secretion pathways. Furthermore, this anterograde transport is counterbalanced by retrograde transport, which not only maintains membrane homeostasis but also recycles various proteins that function in the sorting of secretory cargo, formation of transport intermediates, or retrieval of resident proteins of secretory organelles. The retromer complex recycles proteins from the endocytic pathway back to the plasma membrane or TGN and was recently identified as a critical player in regulated secretion in the hypothalamus. Furthermore, melanoma antigen protein L2 (MAGEL2) was discovered to act as a tissue-specific regulator of the retromer-dependent endosomal protein recycling pathway and, by doing so, ensures proper secretory granule formation and maturation. MAGEL2 is a mammalian-specific and maternally imprinted gene implicated in Prader-Willi and Schaaf-Yang neurodevelopmental syndromes. In this review, we will briefly discuss the current understanding of the regulated secretion pathway, encompassing anterograde and retrograde traffic. Although our understanding of the retrograde trafficking and sorting in regulated secretion is not yet complete, we will review recent insights into the molecular role of MAGEL2 in hypothalamic neuroendocrine secretion and how its dysregulation contributes to the symptoms of Prader-Willi and Schaaf-Yang patients. Given that the activation of many secreted proteins occurs after they enter secretory granules, modulation of the sorting efficiency in a tissue-specific manner may represent an evolutionary adaptation to environmental cues.
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Affiliation(s)
- Denis Štepihar
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
- Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Rebecca R. Florke Gee
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| | - Maria Camila Hoyos Sanchez
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
| | - Klementina Fon Tacer
- School of Veterinary Medicine, Texas Tech University, Amarillo, TX, United States
- Texas Center for Comparative Cancer Research (TC3R), Amarillo, TX, United States
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3
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Pettway YD, Saunders DC, Brissova M. The human α cell in health and disease. J Endocrinol 2023; 258:e220298. [PMID: 37114672 PMCID: PMC10428003 DOI: 10.1530/joe-22-0298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 04/27/2023] [Indexed: 04/29/2023]
Abstract
In commemoration of 100 years since the discovery of glucagon, we review current knowledge about the human α cell. Alpha cells make up 30-40% of human islet endocrine cells and play a major role in regulating whole-body glucose homeostasis, largely through the direct actions of their main secretory product - glucagon - on peripheral organs. Additionally, glucagon and other secretory products of α cells, namely acetylcholine, glutamate, and glucagon-like peptide-1, have been shown to play an indirect role in the modulation of glucose homeostasis through autocrine and paracrine interactions within the islet. Studies of glucagon's role as a counterregulatory hormone have revealed additional important functions of the α cell, including the regulation of multiple aspects of energy metabolism outside that of glucose. At the molecular level, human α cells are defined by the expression of conserved islet-enriched transcription factors and various enriched signature genes, many of which have currently unknown cellular functions. Despite these common threads, notable heterogeneity exists amongst human α cell gene expression and function. Even greater differences are noted at the inter-species level, underscoring the importance of further study of α cell physiology in the human context. Finally, studies on α cell morphology and function in type 1 and type 2 diabetes, as well as other forms of metabolic stress, reveal a key contribution of α cell dysfunction to dysregulated glucose homeostasis in disease pathogenesis, making targeting the α cell an important focus for improving treatment.
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Affiliation(s)
- Yasminye D. Pettway
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, 37232, USA
| | - Diane C. Saunders
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Marcela Brissova
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
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4
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Asadi F, Dhanvantari S. Misrouting of glucagon and stathmin-2 towards lysosomal system of α-cells in glucagon hypersecretion of diabetes. Islets 2022; 14:40-57. [PMID: 34923907 PMCID: PMC8726656 DOI: 10.1080/19382014.2021.2011550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Glucagon hypersecretion from the pancreatic α-cell is a characteristic sign of diabetes, which exacerbates fasting hyperglycemia. Thus, targeting glucagon secretion from α-cells may be a promising approach for combating hyperglucagonemia. We have recently identified stathmin-2 as an α-cell protein that regulates glucagon secretion by directing glucagon toward the endolysosomal system in αTC1-6 cells. We hypothesized that disruption of Stmn2-mediated trafficking of glucagon to the endolysosomes in diabetes contributes to hyperglucagonemia. In isolated islets from male mice treated with streptozotocin (STZ), glucagon secretion and cellular content were augmented, but cellular Stmn2 levels were reduced (p < .01), as measured by both ELISA and immunofluorescence intensity. Using confocal immunofluorescence microscopy, the colocalization of glucagon and Stmn2 in Lamp2A+ lysosomes was dramatically reduced (p < .001) in islets from diabetic mice, and the colocalization of Stmn2, but not glucagon, with the late endosome marker, Rab7, significantly (p < .01) increased. Further studies were conducted in αTC1-6 cells cultured in media containing high glucose (16.7 mM) for 2 weeks to mimic glucagon hypersecretion of diabetes. Surprisingly, treatment of αTC1-6 cells with the lysosomal inhibitor bafilomycin A1 reduced K+-induced glucagon secretion, suggesting that high glucose may induce glucagon secretion from another lysosomal compartment. Both glucagon and Stmn2 co-localized with Lamp1, which marks secretory lysosomes, in cells cultured in high glucose. We propose that, in addition to enhanced trafficking and secretion through the regulated secretory pathway, the hyperglucagonemia of diabetes may also be due to re-routing of glucagon from the degradative Lamp2A+ lysosome toward the secretory Lamp1+ lysosome.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Metabolism & Diabetes and Imaging Programs, Lawson Health Research Institute, London, ON, Canada
- CONTACT Savita Dhanvantari Lawson Health Research Institute, PO Box 5777, Stn B, London, ONN6A 4V2, Canada
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5
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Asadi F, Dhanvantari S. Pathways of Glucagon Secretion and Trafficking in the Pancreatic Alpha Cell: Novel Pathways, Proteins, and Targets for Hyperglucagonemia. Front Endocrinol (Lausanne) 2021; 12:726368. [PMID: 34659118 PMCID: PMC8511682 DOI: 10.3389/fendo.2021.726368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/13/2021] [Indexed: 12/15/2022] Open
Abstract
Patients with diabetes mellitus exhibit hyperglucagonemia, or excess glucagon secretion, which may be the underlying cause of the hyperglycemia of diabetes. Defective alpha cell secretory responses to glucose and paracrine effectors in both Type 1 and Type 2 diabetes may drive the development of hyperglucagonemia. Therefore, uncovering the mechanisms that regulate glucagon secretion from the pancreatic alpha cell is critical for developing improved treatments for diabetes. In this review, we focus on aspects of alpha cell biology for possible mechanisms for alpha cell dysfunction in diabetes: proglucagon processing, intrinsic and paracrine control of glucagon secretion, secretory granule dynamics, and alterations in intracellular trafficking. We explore possible clues gleaned from these studies in how inhibition of glucagon secretion can be targeted as a treatment for diabetes mellitus.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
- Imaging Research Program, Lawson Health Research Institute, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
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6
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Ma CIJ, Burgess J, Brill JA. Maturing secretory granules: Where secretory and endocytic pathways converge. Adv Biol Regul 2021; 80:100807. [PMID: 33866198 DOI: 10.1016/j.jbior.2021.100807] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 03/10/2021] [Accepted: 03/18/2021] [Indexed: 10/21/2022]
Abstract
Secretory granules (SGs) are specialized organelles responsible for the storage and regulated release of various biologically active molecules from the endocrine and exocrine systems. Thus, proper SG biogenesis is critical to normal animal physiology. Biogenesis of SGs starts at the trans-Golgi network (TGN), where immature SGs (iSGs) bud off and undergo maturation before fusing with the plasma membrane (PM). How iSGs mature is unclear, but emerging studies have suggested an important role for the endocytic pathway. The requirement for endocytic machinery in SG maturation blurs the line between SGs and another class of secretory organelles called lysosome-related organelles (LROs). Therefore, it is important to re-evaluate the differences and similarities between SGs and LROs.
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Affiliation(s)
- Cheng-I Jonathan Ma
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, Room 15.9716, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada; Institute of Medical Science, University of Toronto, Medical Sciences Building, Room 2374, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Jason Burgess
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, Room 15.9716, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada; Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Room 4396, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, Room 15.9716, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada; Institute of Medical Science, University of Toronto, Medical Sciences Building, Room 2374, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada; Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Room 4396, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
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7
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Saikia M, Holter MM, Donahue LR, Lee IS, Zheng QC, Wise JL, Todero JE, Phuong DJ, Garibay D, Coch R, Sloop KW, Garcia-Ocana A, Danko CG, Cummings BP. GLP-1 receptor signaling increases PCSK1 and β cell features in human α cells. JCI Insight 2021; 6:141851. [PMID: 33554958 PMCID: PMC7934853 DOI: 10.1172/jci.insight.141851] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 12/29/2020] [Indexed: 02/06/2023] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is an incretin hormone that potentiates glucose-stimulated insulin secretion. GLP-1 is classically produced by gut L cells; however, under certain circumstances α cells can express the prohormone convertase required for proglucagon processing to GLP-1, prohormone convertase 1/3 (PC1/3), and can produce GLP-1. However, the mechanisms through which this occurs are poorly defined. Understanding the mechanisms by which α cell PC1/3 expression can be activated may reveal new targets for diabetes treatment. Here, we demonstrate that the GLP-1 receptor (GLP-1R) agonist, liraglutide, increased α cell GLP-1 expression in a β cell GLP-1R-dependent manner. We demonstrate that this effect of liraglutide was translationally relevant in human islets through application of a new scRNA-seq technology, DART-Seq. We found that the effect of liraglutide to increase α cell PC1/3 mRNA expression occurred in a subcluster of α cells and was associated with increased expression of other β cell-like genes, which we confirmed by IHC. Finally, we found that the effect of liraglutide to increase bihormonal insulin+ glucagon+ cells was mediated by the β cell GLP-1R in mice. Together, our data validate a high-sensitivity method for scRNA-seq in human islets and identify a potentially novel GLP-1-mediated pathway regulating human α cell function.
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Affiliation(s)
- Mridusmita Saikia
- Department of Biomedical Sciences and
- Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York, USA
| | | | | | | | | | | | | | | | | | - Reilly Coch
- Cayuga Medical Center, Ithaca, New York, USA
| | - Kyle W Sloop
- Diabetes and Complications, Lilly Research Laboratories, Lilly, Indianapolis, Indiana, USA
| | | | - Charles G Danko
- Department of Biomedical Sciences and
- Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York, USA
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8
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Asadi F, Dhanvantari S. Stathmin-2 Mediates Glucagon Secretion From Pancreatic α-Cells. Front Endocrinol (Lausanne) 2020; 11:29. [PMID: 32117057 PMCID: PMC7011091 DOI: 10.3389/fendo.2020.00029] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/14/2020] [Indexed: 01/26/2023] Open
Abstract
Inhibition of glucagon hypersecretion from pancreatic α-cells is an appealing strategy for the treatment of diabetes. Our hypothesis is that proteins that associate with glucagon within alpha cell secretory granules will regulate glucagon secretion, and may provide druggable targets for controlling abnormal glucagon secretion in diabetes. Recently, we identified a dynamic glucagon interactome within the secretory granules of the α cell line, αTC1-6, and showed that select proteins within the interactome could modulate glucagon secretion. In the present study, we show that one of these interactome proteins, the neuronal protein stathmin-2, is expressed in αTC1-6 cells and in mouse pancreatic alpha cells, and is a novel regulator of glucagon secretion. The secretion of both glucagon and Stmn2 was significantly enhanced in response to 55 mM K+, and immunofluorescence confocal microscopy showed co-localization of stathmin-2 with glucagon and the secretory granule markers chromogranin A and VAMP-2 in αTC1-6 cells. In mouse pancreatic islets, Stathmin-2 co-localized with glucagon, but not with insulin, and co-localized with secretory pathway markers. To show a function for stathmin-2 in regulating glucagon secretion, we showed that siRNA-mediated depletion of stathmin-2 in αTC1-6 cells caused glucagon secretion to become constitutive without any effect on proglucagon mRNA levels, while overexpression of stathmin-2 completely abolished both basal and K+-stimulated glucagon secretion. Overexpression of stathmin-2 increased the localization of glucagon into the endosomal-lysosomal compartment, while depletion of stathmin-2 reduced the endosomal localization of glucagon. Therefore, we describe stathmin-2 as having a novel role as an alpha cell secretory granule protein that modulates glucagon secretion via trafficking through the endosomal-lysosomal system. These findings describe a potential new pathway for the regulation of glucagon secretion, and may have implications for controlling glucagon hypersecretion in diabetes.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
- *Correspondence: Savita Dhanvantari
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9
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Sullivan R, Randhawa VK, Stokes A, Wu D, Lalonde T, Kiaii B, Luyt L, Wisenberg G, Dhanvantari S. Dynamics of the Ghrelin/Growth Hormone Secretagogue Receptor System in the Human Heart Before and After Cardiac Transplantation. J Endocr Soc 2019; 3:748-762. [PMID: 30937420 PMCID: PMC6438351 DOI: 10.1210/js.2018-00393] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 02/11/2019] [Indexed: 12/14/2022] Open
Abstract
Currently, the early preclinical detection of left ventricular dysfunction is difficult because biomarkers are not specific for the cardiomyopathic process. The underlying molecular mechanisms leading to heart failure remain elusive, highlighting the need for identification of cardiac-specific markers. The growth hormone secretagogue receptor (GHSR) and its ligand ghrelin are present in cardiac tissue and are known to contribute to myocardial energetics. Here, we examined tissue ghrelin-GHSR levels as specific markers of cardiac dysfunction in patients who underwent cardiac transplantation. Samples of cardiac tissue were obtained from 10 patients undergoing cardiac transplant at the time of organ harvesting and during serial posttransplant biopsies. Quantitative fluorescence microscopy using a fluorescent ghrelin analog was used to measure levels of GHSR, and immunofluorescence was used to measure levels of ghrelin, B-type natriuretic peptide (BNP), and tissue markers of cardiomyocyte contractility and growth. GHSR and ghrelin expression levels were highly variable in the explanted heart, less in the grafted heart biopsies. GHSR and ghrelin were strongly positively correlated, and both markers were negatively correlated with left ventricular ejection fraction. Ghrelin had stronger positive correlations than BNP with the signaling markers for contractility and growth. These data suggest that GHSR-ghrelin have potential use as an integrated marker of cardiac dysfunction. Interestingly, tissue ghrelin appeared to be a more sensitive indicator than BNP to the biochemical processes that are characteristic of heart failure. This work allows for further use of ghrelin-GHSR to interrogate cardiac-specific biochemical mechanisms in preclinical stages of heart failure (HF).
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Affiliation(s)
- Rebecca Sullivan
- Pathology and Laboratory Medicine, Western University, London, Ontario, Canada
| | - Varinder K Randhawa
- Cardiac Imaging Research, Lawson Health Research Institute, London, Ontario, Canada
| | - Anne Stokes
- Metabolism and Diabetes, Lawson Health Research Institute, London, Ontario, Canada
| | - Derek Wu
- Pathology and Laboratory Medicine, Western University, London, Ontario, Canada
| | - Tyler Lalonde
- Chemistry, Western University, London, Ontario, Canada
| | - Bob Kiaii
- Cardiac Surgery, Western University, London, Ontario, Canada
| | - Leonard Luyt
- Chemistry, Western University, London, Ontario, Canada
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada
- Department of Oncology, London Regional Cancer Program, Western University, London, Ontario, Canada
| | - Gerald Wisenberg
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
| | - Savita Dhanvantari
- Pathology and Laboratory Medicine, Western University, London, Ontario, Canada
- Metabolism and Diabetes, Lawson Health Research Institute, London, Ontario, Canada
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
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10
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Asadi F, Dhanvantari S. Plasticity in the Glucagon Interactome Reveals Novel Proteins That Regulate Glucagon Secretion in α-TC1-6 Cells. Front Endocrinol (Lausanne) 2019; 9:792. [PMID: 30713523 PMCID: PMC6346685 DOI: 10.3389/fendo.2018.00792] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 12/17/2018] [Indexed: 12/27/2022] Open
Abstract
Glucagon is stored within the secretory granules of pancreatic alpha cells until stimuli trigger its release. The alpha cell secretory responses to the stimuli vary widely, possibly due to differences in experimental models or microenvironmental conditions. We hypothesized that the response of the alpha cell to various stimuli could be due to plasticity in the network of proteins that interact with glucagon within alpha cell secretory granules. We used tagged glucagon with Fc to pull out glucagon from the enriched preparation of secretory granules in α-TC1-6 cells. Isolation of secretory granules was validated by immunoisolation with Fc-glucagon and immunoblotting for organelle-specific proteins. Isolated enriched secretory granules were then used for affinity purification with Fc-glucagon followed by liquid chromatography/tandem mass spectrometry to identify secretory granule proteins that interact with glucagon. Proteomic analyses revealed a network of proteins containing glucose regulated protein 78 KDa (GRP78) and histone H4. The interaction between glucagon and the ER stress protein GRP78 and histone H4 was confirmed through co-immunoprecipitation of secretory granule lysates, and colocalization immunofluorescence confocal microscopy. Composition of the protein networks was altered at different glucose levels (25 vs. 5.5 mM) and in response to the paracrine inhibitors of glucagon secretion, GABA and insulin. siRNA-mediated silencing of a subset of these proteins revealed their involvement in glucagon secretion in α-TC1-6 cells. Therefore, our results show a novel and dynamic glucagon interactome within α-TC1-6 cell secretory granules. We suggest that variations in the alpha cell secretory response to stimuli may be governed by plasticity in the glucagon "interactome."
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
- Metabolism, Diabetes and Imaging Programs, Lawson Health Research Institute, London, ON, Canada
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11
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Abbas A, Yu L, Lalonde T, Wu D, Thiessen JD, Luyt LG, Dhanvantari S. Development and Characterization of an 18F-labeled Ghrelin Peptidomimetic for Imaging the Cardiac Growth Hormone Secretagogue Receptor. Mol Imaging 2018; 17:1536012118809587. [PMID: 30394854 PMCID: PMC6236854 DOI: 10.1177/1536012118809587] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
One-third of patients with heart disease develop heart failure, which is diagnosed
through imaging and detection of circulating biomarkers. Imaging strategies reveal
morphologic and functional changes but fall short of detecting molecular abnormalities
that can lead to heart failure, and circulating biomarkers are not cardiac specific. Thus,
there is critical need for biomarkers that are endogenous to myocardial tissues. The
cardiac growth hormone secretagogue receptor 1a (GHSR1a), which binds the hormone ghrelin,
is a potential biomarker for heart failure. We have synthesized and characterized a novel
ghrelin peptidomimetic tracer, an 18F-labeled analogue of G-7039, for positron
emission tomography (PET) imaging of cardiac GHSR1a. In vitro analysis showed enhanced
serum stability compared to natural ghrelin and significantly increased cellular uptake in
GHSR1a-expressing OVCAR cells. Biodistribution studies in mice showed that tissue uptake
of the tracer was independent of circulating ghrelin levels, and there was negligible
cardiac uptake and high uptake in the liver, intestines, and kidneys. Specificity of
tracer uptake was assessed using ghsr −/− mice; both static and dynamic PET imaging revealed no difference in cardiac
uptake, and there was no significant correlation between cardiac standardized uptake
values and GHSR1a expression. Our study lays the groundwork for further refinement of
peptidomimetic PET tracers targeting cardiac GHSR1a.
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Affiliation(s)
- Ahmed Abbas
- 1 Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - Lihai Yu
- 2 Department of Chemistry, Western University, London, Ontario, Canada
| | - Tyler Lalonde
- 2 Department of Chemistry, Western University, London, Ontario, Canada
| | - Derek Wu
- 3 Department of Pathology and Laboratory Medicine, Western University, London, Ontario, Canada
| | - Jonathan D Thiessen
- 1 Department of Medical Biophysics, Western University, London, Ontario, Canada.,4 Imaging Research, Lawson Health Research Institute, London, Ontario, Canada
| | - Leonard G Luyt
- 2 Department of Chemistry, Western University, London, Ontario, Canada.,4 Imaging Research, Lawson Health Research Institute, London, Ontario, Canada.,5 Department of oncology, Western University, London, Ontario, Canada
| | - Savita Dhanvantari
- 1 Department of Medical Biophysics, Western University, London, Ontario, Canada.,3 Department of Pathology and Laboratory Medicine, Western University, London, Ontario, Canada.,4 Imaging Research, Lawson Health Research Institute, London, Ontario, Canada.,6 Metabolism/Diabetes, Lawson Health Research Institute, London, Ontario, Canada
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12
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Sullivan R, McGirr R, Hu S, Tan A, Wu D, Charron C, Lalonde T, Arany E, Chakrabarti S, Luyt L, Dhanvantari S. Changes in the Cardiac GHSR1a-Ghrelin System Correlate With Myocardial Dysfunction in Diabetic Cardiomyopathy in Mice. J Endocr Soc 2017; 2:178-189. [PMID: 29450407 PMCID: PMC5799831 DOI: 10.1210/js.2017-00433] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 12/19/2017] [Indexed: 01/16/2023] Open
Abstract
Ghrelin and its receptor, the growth hormone secretagogue receptor 1a (GHSR1a), are present in cardiac tissue. Activation of GHSR1a by ghrelin promotes cardiomyocyte contractility and survival, and changes in myocardial GHSR1a and circulating ghrelin track with end-stage heart failure, leading to the hypothesis that GHSR1a is a biomarker for heart failure. We hypothesized that GHSR1a could also be a biomarker for diabetic cardiomyopathy (DCM). We used two models of streptozotocin (STZ)-induced DCM: group 1, adult mice treated with 35 mg/kg STZ for 3 days; and group 2, neonatal mice treated with 70 mg/kg STZ at days 2 and 5 after birth. In group 1, mild fasting hyperglycemia (11 mM) was first detected 8 weeks after the last injection, and in group 2, severe fasting hyperglycemia (20 mM) was first detected 1 to 3 weeks after the last injection. In group 1, left ventricular function was slightly impaired as measured by echocardiography, and Western blot analysis showed a significant decrease in myocardial GHSR1a. In group 2, GHSR1a levels were also decreased as assessed by Cy5-ghrelin(1–19) fluorescence microscopy, and there was a significant negative correlation between GHSR1a levels and glucose tolerance. There were significant positive correlations between GHSR1a and ghrelin and between GHSR1a and sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a), a marker for contractility, but not between GHSR1a and B-type natriuretic peptide, a marker for heart failure. We conclude that the subclinical stage of DCM is accompanied by alterations in the myocardial ghrelin-GHSR1a system, suggesting the possibility of a biomarker for DCM.
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Affiliation(s)
- Rebecca Sullivan
- Imaging Research, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada.,Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Rebecca McGirr
- Imaging Research, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Shirley Hu
- Department of Physiology and Pharmacology, Western University, London, Ontario N6A 3K7, Canada
| | - Alice Tan
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Derek Wu
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Carlie Charron
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
| | - Tyler Lalonde
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
| | - Edith Arany
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Subrata Chakrabarti
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Leonard Luyt
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada.,Departments of Oncology and Medical Imaging, Western University, London, Ontario N6A 4L6, Canada.,London Regional Cancer Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Savita Dhanvantari
- Imaging Research, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada.,Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada.,Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada
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13
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Cao T, Yang D, Zhang X, Wang Y, Qiao Z, Gao L, Liang Y, Yu B, Zhang P. FAM3D inhibits glucagon secretion via MKP1-dependent suppression of ERK1/2 signaling. Cell Biol Toxicol 2017; 33:457-466. [PMID: 28247283 DOI: 10.1007/s10565-017-9387-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 02/13/2017] [Indexed: 12/28/2022]
Abstract
Dysregulated glucagon secretion is a hallmark of type 2 diabetes (T2D). To date, few effective therapeutic agents target on deranged glucagon secretion. Family with sequence similarity 3 member D (FAM3D) is a novel gut-derived cytokine-like protein, and its secretion timing is contrary to that of glucagon. However, the roles of FAM3D in metabolic disorder and its biological functions are largely unknown. In the present study, we investigated whether FAM3D modulates glucagon production in mouse pancreatic alpha TC1 clone 6 (αTC1-6) cells. Glucagon secretion, prohormone convertase 2 (PC2) activity, and mitogen-activated protein kinase (MAPK) pathway were assessed. Exogenous FAM3D inhibited glucagon secretion, PC2 activity, as well as extracellular-regulated protein kinase 1/2 (ERK1/2) signaling and induced MAPK phosphatase 1 (MKP1) expression. Moreover, knockdown of MKP1 and inhibition of ERK1/2 abolished and potentiated the inhibitory effect of FAM3D on glucagon secretion, respectively. Taken together, FAM3D inhibits glucagon secretion via MKP1-dependent suppression of ERK1/2 signaling. These results provide rationale for developing the therapeutic potential of FAM3D for dysregulated glucagon secretion and T2D.
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Affiliation(s)
- Ting Cao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Dan Yang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Xiong Zhang
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Yueqian Wang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Zhengdong Qiao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Lili Gao
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Yongjun Liang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China
| | - Bo Yu
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
| | - Peng Zhang
- Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Pudong, Shanghai, 201399, China.
- Department of Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
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14
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Baldassano S, Amato A, Mulè F. Influence of glucagon-like peptide 2 on energy homeostasis. Peptides 2016; 86:1-5. [PMID: 27664588 DOI: 10.1016/j.peptides.2016.09.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 09/19/2016] [Accepted: 09/20/2016] [Indexed: 02/06/2023]
Abstract
Glucagon like peptide-2 (GLP-2) is a gastrointestinal hormone released from enteroendocrine L-type cells together with glucagon like peptide-1 in response to dietary nutrients. GLP-2 acts through a specific receptor, the GLP-2 receptor, mainly located in the gut and in the brain. Classically, GLP-2 is considered a trophic hormone involved in the maintenance of intestinal epithelial morphology and function. This role has been targeted for therapies promoting repair and adaptive growth of the intestinal mucosa. Recently, GLP-2 has been shown to exert beneficial effects on glucose metabolism specially in conditions related to increased uptake of energy, such as obesity. Several actions of GLP-2 are related to a positive energy balance: GLP-2 increases not only the absorptive surface, but also expression and activity of epithelial brush-border nutrient transporters and digestive enzymes, intestinal blood flow, postprandial chylomicron secretion and it inhibits gastrointestinal motility, providing the opportunity to increase absorption of nutrients. Other actions, including anorexigenic effects, appear in opposition to the energy intake. In this review, we discuss the GLP-2 functions related to energy homeostasis. GLP-2 could be considered an hormone causing positive energy balance, which, however has the role to mitigate the metabolic dysfunctions associated with hyper-adiposity.
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Affiliation(s)
- Sara Baldassano
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, 90128, Italy
| | - Antonella Amato
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, 90128, Italy
| | - Flavia Mulè
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, 90128, Italy.
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15
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Abbas A, Beamish C, McGirr R, Demarco J, Cockburn N, Krokowski D, Lee TY, Kovacs M, Hatzoglou M, Dhanvantari S. Characterization of 5-(2- 18F-fluoroethoxy)-L-tryptophan for PET imaging of the pancreas. F1000Res 2016; 5:1851. [PMID: 27909574 PMCID: PMC5112576 DOI: 10.12688/f1000research.9129.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/04/2016] [Indexed: 12/23/2022] Open
Abstract
Purpose: In diabetes, pancreatic beta cell mass declines significantly prior to onset of fasting hyperglycemia. This decline may be due to endoplasmic reticulum (ER) stress, and the system L amino acid transporter LAT1 may be a biomarker of this process. In this study, we used 5-(2-
18F-fluoroethoxy)-L-tryptophan (
18F-L-FEHTP) to target LAT1 as a potential biomarker of beta cell function in diabetes. Procedures: Uptake of
18F-L-FEHTP was determined in wild-type C57BL/6 mice by
ex vivo biodistribution. Both dynamic and static positron emission tomography (PET) images were acquired in wild-type and Akita mice, a model of ER stress-induced diabetes, as well as in mice treated with streptozotocin (STZ). LAT1 expression in both groups of mice was evaluated by immunofluorescence microscopy. Results: Uptake of
18F-L-FEHTP was highest in the pancreas, and static PET images showed highly specific pancreatic signal. Time-activity curves showed significantly reduced
18F-L-FEHTP uptake in Akita mice, and LAT1 expression was also reduced. However, mice treated with STZ, in which beta cell mass was reduced by 62%, showed no differences in
18F-L-FEHTP uptake in the pancreas, and there was no significant correlation of
18F-L-FEHTP uptake with beta cell mass. Conclusions: 18F-L-FEHTP is highly specific for the pancreas with little background uptake in kidney or liver. We were able to detect changes in LAT1 in a mouse model of diabetes, but these changes did not correlate with beta cell function or mass. Therefore,
18F-L-FEHTP PET is not a suitable method for the noninvasive imaging of changes in beta cell function during the progression of diabetes.
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Affiliation(s)
- Ahmed Abbas
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
| | - Christine Beamish
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Rebecca McGirr
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - John Demarco
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Neil Cockburn
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Dawid Krokowski
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ting-Yim Lee
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Michael Kovacs
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Maria Hatzoglou
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Savita Dhanvantari
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada; Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada; Department of Pathology and Laboratory Medicine, Western University, London, ON, N6A 5C1, Canada
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16
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Abbas A, Beamish C, McGirr R, Demarco J, Cockburn N, Krokowski D, Lee TY, Kovacs M, Hatzoglou M, Dhanvantari S. Characterization of 5-(2- 18F-fluoroethoxy)-L-tryptophan for PET imaging of the pancreas. F1000Res 2016; 5:1851. [PMID: 27909574 PMCID: PMC5112576 DOI: 10.12688/f1000research.9129.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/04/2016] [Indexed: 10/29/2023] Open
Abstract
Purpose: In diabetes, pancreatic beta cell mass declines significantly prior to onset of fasting hyperglycemia. This decline may be due to endoplasmic reticulum (ER) stress, and the system L amino acid transporter LAT1 may be a biomarker of this process. In this study, we used 5-(2- 18F-fluoroethoxy)-L-tryptophan ( 18F-L-FEHTP) to target LAT1 as a potential biomarker of beta cell function in diabetes. Procedures: Uptake of 18F-L-FEHTP was determined in wild-type C57BL/6 mice by ex vivo biodistribution. Both dynamic and static positron emission tomography (PET) images were acquired in wild-type and Akita mice, a model of ER stress-induced diabetes, as well as in mice treated with streptozotocin (STZ). LAT1 expression in both groups of mice was evaluated by immunofluorescence microscopy. Results: Uptake of 18F-L-FEHTP was highest in the pancreas, and static PET images showed highly specific pancreatic signal. Time-activity curves showed significantly reduced 18F-L-FEHTP uptake in Akita mice, and LAT1 expression was also reduced. However, mice treated with STZ, in which beta cell mass was reduced by 62%, showed no differences in 18F-L-FEHTP uptake in the pancreas, and there was no significant correlation of 18F-L-FEHTP uptake with beta cell mass. Conclusions:18F-L-FEHTP is highly specific for the pancreas with little background uptake in kidney or liver. We were able to detect changes in LAT1 in a mouse model of diabetes, but these changes did not correlate with beta cell function or mass. Therefore, 18F-L-FEHTP PET is not a suitable method for the noninvasive imaging of changes in beta cell function during the progression of diabetes.
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Affiliation(s)
- Ahmed Abbas
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
| | - Christine Beamish
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Rebecca McGirr
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - John Demarco
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Neil Cockburn
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Dawid Krokowski
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ting-Yim Lee
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Michael Kovacs
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Maria Hatzoglou
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Savita Dhanvantari
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
- Department of Pathology and Laboratory Medicine, Western University, London, ON, N6A 5C1, Canada
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