1
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Wilk B, Smailovic H, Sullivan R, Sistermans ER, Butler J, Jago H, Kovacs M, Wisenberg G, Thiessen JD, Prato FS. Myocardial glucose suppression may interfere with the detection of inflammatory cells with FDG-PET as suggested in a canine model of myocardial infarction. EJNMMI Res 2023; 13:90. [PMID: 37823919 PMCID: PMC10570261 DOI: 10.1186/s13550-023-01040-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 10/04/2023] [Indexed: 10/13/2023] Open
Abstract
BACKGROUND After myocardial infarction, fibrosis and an ongoing dysregulated inflammatory response have been shown to lead to adverse cardiac remodeling. FDG PET is an imaging modality sensitive to inflammation as long as suppression protocols are observed while gadolinium enhanced MRI can be used to determine extracellular volume (ECV), a measure of fibrosis. In patients, glucose suppression is achieved variously through a high fat diet, fasting and injection of heparin. To emulate this process in canines, a heparin injection and lipid infusion are used, leading to similar fatty acids in the blood. The aim of this study was to examine the effect of glucose suppression on the uptake of FDG in the infarcted myocardial tissue and also on the determination of ECV in both the infarcted tissue and in the myocardium remote to the zone of infarction during a long constant infusion of FDG and Gd-DTPA. RESULTS Extracellular volume was affected neither by suppression nor the length of the constant infusion in remote and infarcted tissue. Metabolic rate of glucose in infarcted tissue decreased during and after suppression of glucose uptake by lipid infusion and heparin injection. An increase in fibrosis and inflammatory cells was found in the center of the infarct as compared to remote tissue. CONCLUSION The decrease in the metabolic rate of glucose in the infarcted tissue suggests that inflammatory cells may be affected by glucose suppression through heparin injection and lipid infusion.
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Affiliation(s)
- Benjamin Wilk
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada.
- Medical Biophysics, Western University, London, ON, Canada.
| | - Haris Smailovic
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
- Medical Biophysics, Western University, London, ON, Canada
| | - Rebecca Sullivan
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
- Medical Biophysics, Western University, London, ON, Canada
| | - Erik R Sistermans
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
| | - John Butler
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
| | - Hannah Jago
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
| | - Michael Kovacs
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
- Medical Biophysics, Western University, London, ON, Canada
| | - Gerald Wisenberg
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
- Medical Biophysics, Western University, London, ON, Canada
- MyHealth Centre, Arva, ON, Canada
| | - Jonathan D Thiessen
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
- Medical Biophysics, Western University, London, ON, Canada
| | - Frank S Prato
- Department of Imaging, Lawson Health Research Institute, 268 Grosvenor St., London, ON, N6A 4V2, Canada
- Medical Biophysics, Western University, London, ON, Canada
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2
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Campaña M, Davis TR, Novak SX, Cleverdon ER, Bates M, Krishnan N, Curtis ER, Childs MD, Pierce MR, Morales-Rodriguez Y, Sieburg MA, Hehnly H, Luyt LG, Hougland JL. Cellular Uptake of a Fluorescent Ligand Reveals Ghrelin O-Acyltransferase Interacts with Extracellular Peptides and Exhibits Unexpected Localization for a Secretory Pathway Enzyme. ACS Chem Biol 2023; 18:1880-1890. [PMID: 37494676 PMCID: PMC10442857 DOI: 10.1021/acschembio.3c00334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 07/17/2023] [Indexed: 07/28/2023]
Abstract
Ghrelin O-acyltransferase (GOAT) plays a central role in the maturation and activation of the peptide hormone ghrelin, which performs a wide range of endocrinological signaling roles. Using a tight-binding fluorescent ghrelin-derived peptide designed for high selectivity for GOAT over the ghrelin receptor GHSR, we demonstrate that GOAT interacts with extracellular ghrelin and facilitates ligand cell internalization in both transfected cells and prostate cancer cells endogenously expressing GOAT. Coupled with enzyme mutagenesis, ligand uptake studies support the interaction of the putative histidine general base within GOAT with the ghrelin peptide acylation site. Our work provides a new understanding of GOAT's catalytic mechanism, establishes that GOAT can interact with ghrelin and other peptides located outside the cell, and raises the possibility that other peptide hormones may exhibit similar complexity in their intercellular and organismal-level signaling pathways.
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Affiliation(s)
- Maria
B. Campaña
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
| | - Tasha R. Davis
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
| | - Sadie X. Novak
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
| | | | - Michael Bates
- Department
of Biology, Syracuse University, Syracuse, New York 13244, United States
| | - Nikhila Krishnan
- Department
of Biology, Syracuse University, Syracuse, New York 13244, United States
| | - Erin R. Curtis
- Department
of Biology, Syracuse University, Syracuse, New York 13244, United States
| | - Marina D. Childs
- Department
of Chemistry, University of Western Ontario, London, Ontario N6A 2K7, Canada
| | - Mariah R. Pierce
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
| | | | - Michelle A. Sieburg
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
| | - Heidi Hehnly
- Department
of Biology, Syracuse University, Syracuse, New York 13244, United States
- BioInspired
Syracuse, Syracuse University, Syracuse, New York 13244, United States
| | - Leonard G. Luyt
- Department
of Chemistry, University of Western Ontario, London, Ontario N6A 2K7, Canada
- Department
of Oncology and Department of Medical Imaging, London Regional Cancer
Program, Lawson Health Research Institute, 800 Commissioners Road East, London, Ontario N6A 5W9, Canada
| | - James L. Hougland
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
- Department
of Biology, Syracuse University, Syracuse, New York 13244, United States
- BioInspired
Syracuse, Syracuse University, Syracuse, New York 13244, United States
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3
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Childs M, Chandrabalan A, Hodgson D, Ramachandran R, Luyt LG. Discovery of Ghrelin(1-8) Analogues with Improved Stability and Functional Activity for PET Imaging. ACS Pharmacol Transl Sci 2023; 6:1075-1086. [PMID: 37470019 PMCID: PMC10353549 DOI: 10.1021/acsptsci.3c00088] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Indexed: 07/21/2023]
Abstract
The highest affinity ghrelin-based analogue for fluorine-18 positron emission tomography, [Inp1,Dpr3(6-FN),1Nal4,Thr8]ghrelin(1-8) amide (1), has remarkable subnanomolar receptor affinity (IC50 = 0.11 nM) toward the growth hormone secretagogue receptor 1a (GHSR). However, initial in vivo PET imaging and biodistribution of [18F]1 in mice demonstrated an unfavorable pharmacokinetic profile with rapid clearance and accumulation in liver and intestinal tissue, prompting concerns about the metabolic stability of this probe. The aims of the present study were to examine the proteolytic stability of ghrelin analogue 1 in the presence of blood and liver enzymes, structurally modify the peptide to improve stability without impeding the strong binding affinity, and measure the presently unknown functional activity of ghrelin(1-8) analogues. The in vitro stability and metabolite formation of 1 in human serum and liver S9 fraction revealed a metabolic soft spot between amino acids Leu5 and Ser6 in the peptide sequence. A focused library of ghrelin(1-8) analogues was synthesized and evaluated in a structure-activity-stability relationship study to further understand the structural importance of the residues at these positions in the context of stability and receptor affinity. The critical nature of l-stereochemistry at position 5 was identified and substitution of Ser6 with l-2,3-diaminopropionic acid led to a novel ligand with substantially improved in vitro stability while maintaining subnanomolar GHSR affinity. Despite the highly modified nature of these analogues compared to human ghrelin, ghrelin(1-8) analogues were found to recruit all G protein subtypes (Gαq/11/13/i1/oB) known to associate with GHSR as well as β-arrestins with low micromolar to nanomolar potencies. The study of these analogues demonstrates the ability to balance desirable ligand properties, including affinity, stability, and potency to produce well-rounded candidate molecules for further in vivo evaluation.
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Affiliation(s)
- Marina
D. Childs
- Department
of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
| | - Arundhasa Chandrabalan
- Department
of Physiology and Pharmacology, University
of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5C1, Canada
| | - Derian Hodgson
- Department
of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
| | - Rithwik Ramachandran
- Department
of Physiology and Pharmacology, University
of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5C1, Canada
| | - Leonard G. Luyt
- Department
of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
- Departments
of Medical Imaging and Oncology, University
of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
- London
Regional Cancer Program, Lawson Health Research
Institute, 800 Commissioners
Road East, London, Ontario, N6A 4L6, Canada
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4
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Bergmann R, Chollet C, Els-Heindl S, Ullrich M, Berndt N, Pietzsch J, Máthé D, Bachmann M, Beck-Sickinger AG. Development of a ghrelin receptor inverse agonist for positron emission tomography. Oncotarget 2021; 12:450-474. [PMID: 33747360 PMCID: PMC7939532 DOI: 10.18632/oncotarget.27895] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 02/01/2021] [Indexed: 12/21/2022] Open
Abstract
Imaging of Ghrelin receptors in vivo provides unique potential to gain deeper understanding on Ghrelin and its receptors in health and disease, in particular, in cancer. Ghrelin, an octanoylated 28-mer peptide hormone activates the constitutively active growth hormone secretagogue receptor type 1a (GHS-R1a) with nanomolar activity. We developed novel compounds, derived from the potent inverse agonist K-(D-1-Nal)-FwLL-NH2 but structurally varied by lysine conjugation with 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), palmitic acid and/or diethylene glycol (PEG2) to allow radiolabeling and improve pharmacokinetics, respectively. All compounds were tested for receptor binding, potency and efficacy in vitro, for biodistribution and -kinetics in rats and in preclinical prostate cancer models on mice. Radiolabeling with Cu-64 and Ga-68 was successfully achieved. The Cu-64- or Ga-68-NODAGA-NH-K-K-(D-1-NaI)-F-w-L-L-NH2 radiotracer were specifically accumulated by the GHS-R1a in xenotransplanted human prostate tumor models (PC-3, DU-145) in mice. The tumors were clearly delineated by PET. The radiotracer uptake was also partially blocked by K-(D-1-Nal)-FwLL-NH2 in stomach and thyroid. The presence of the GHS-R1a was also confirmed by immunohistology. In the arterial rat blood plasma, only the original compounds were found. The Cu-64 or Ga-68-NODAGA-NH-K-K-(D-1-NaI)-F-w-L-L-NH2 radiolabeled inverse agonists turned out to be potent and safe. Due to their easy synthesis, high affinity, medium potency, metabolic stability, and the suitable pharmacokinetic profiles, they are excellent tools for imaging and quantitation of GHS-R1a expression in normal and cancer tissues by PET. These compounds can be used as novel biomarkers of the Ghrelin system in precision medicine.
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Affiliation(s)
- Ralf Bergmann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany.,Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.,These authors contributed equally to this work
| | - Constance Chollet
- Institute of Biochemistry, Faculty of Life Sciences, Universität Leipzig, Leipzig, Germany.,These authors contributed equally to this work
| | - Sylvia Els-Heindl
- Institute of Biochemistry, Faculty of Life Sciences, Universität Leipzig, Leipzig, Germany
| | - Martin Ullrich
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany
| | - Nicole Berndt
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany.,Faculty of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden, Dresden, Germany
| | - Domokos Máthé
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Michael Bachmann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany.,Tumor Immunology, University Cancer Center, Carl Gustav Carus Technische Universität Dresden, Dresden, Germany.,National Center for Tumor Diseases, Carl Gustav Carus Technische Universität Dresden, Dresden, Germany
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5
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Regional Differences in the Ghrelin-Growth Hormone Secretagogue Receptor Signalling System in Human Heart Disease. CJC Open 2020; 3:182-194. [PMID: 33644732 PMCID: PMC7893201 DOI: 10.1016/j.cjco.2020.10.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 10/27/2020] [Indexed: 12/20/2022] Open
Abstract
Background The hormone ghrelin and its receptor, the growth hormone secretagogue receptor (GHSR) are expressed in myocardium. GHSR binding activates signalling pathways coupled to cardiomyocyte survival and contractility. These properties have made the ghrelin-GHSR axis a candidate for a biomarker of cardiac function. The dynamics of ghrelin-GHSR are altered significantly in late stages of heart failure (HF) and cardiomyopathy, when left ventricular (LV) function is failing. We examined the relationship of GHSR with ghrelin in cardiac tissue from patients with valvular disease with no detectable changes in LV function. Methods Biopsy samples from the left ventricle and left atrium were obtained from 25 patients with valvular disease (of whom 13 also had coronary artery disease) and preserved LV ejection fraction, and compared to control samples obtained via autopsy. Using quantitative confocal fluorescence microscopy, levels of GHSR were determined using [Dpr3(n-octanoyl),Lys19(sulfo-Cy5)]ghrelin(1-19), and immunofluorescence determined ghrelin, the heart failure marker natriuretic peptide type-B (BNP), and contractility marker sarcoplasmic reticulum ATPase pump (SERCA2a). Results A positive correlation between GHSR and ghrelin was apparent in only diseased tissue. Ghrelin and BNP significantly correlated in the left ventricle and strongly colocalized to the same intracellular compartment in diseased and control tissue. GHSR, ghrelin, and BNP all strongly and significantly correlated with SERCA2a in the left ventricle of diseased tissue only. Conclusions Our results suggest that the dynamics of the myocardial ghrelin-GHSR axis is altered in cardiovascular disease in the absence of measurable changes in heart function, and might accompany a regional shift in endocrine programming.
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6
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Childs MD, Luyt LG. A Decade's Progress in the Development of Molecular Imaging Agents Targeting the Growth Hormone Secretagogue Receptor. Mol Imaging 2020; 19:1536012120952623. [PMID: 33104445 PMCID: PMC8865914 DOI: 10.1177/1536012120952623] [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] [Indexed: 01/23/2023] Open
Abstract
The growth hormone secretagogue receptor 1a (GHSR), also called the ghrelin receptor, is a G protein-coupled receptor known to play an important metabolic role in the regulation of various physiological processes, including energy expenditure, growth hormone secretion, and cell proliferation. This receptor has been implicated in numerous health issues including obesity, gastrointestinal disorders, type II diabetes, and regulation of body weight in patients with Prader-Willi syndrome, and there has been growing interest in studying its mechanism of behavior to unlock further applications of GHSR-targeted therapeutics. In addition, the GHSR is expressed in various types of cancer including prostate, breast, and testicular cancers, while aberrant expression has been reported in cardiac disease. Targeted molecular imaging of the GHSR could provide insights into its role in biological processes related to these disease states. Over the past decade, imaging probes targeting this receptor have been discovered for the imaging modalities PET, SPECT, and optical imaging. High-affinity analogues of ghrelin, the endogenous ligand for the GHSR, as well as small molecule inhibitors have been developed and evaluated both in vitro and in pre-clinical models. This review provides a comprehensive overview of the molecular imaging agents targeting the GHSR reported to the end of 2019.
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Affiliation(s)
- Marina D Childs
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada
| | - Leonard G Luyt
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada.,Lawson Health Research Institute, London, Ontario, Canada.,Department of Oncology, University of Western Ontario, London, Ontario, Canada.,Department of Medical Imaging, University of Western Ontario, London, Ontario, Canada
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7
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De Luca SN, Sominsky L, Soch A, Wang H, Ziko I, Rank MM, Spencer SJ. Conditional microglial depletion in rats leads to reversible anorexia and weight loss by disrupting gustatory circuitry. Brain Behav Immun 2019; 77:77-91. [PMID: 30578932 DOI: 10.1016/j.bbi.2018.12.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/04/2018] [Accepted: 12/12/2018] [Indexed: 01/12/2023] Open
Abstract
Microglia are highly sensitive to dietary influence, becoming activated acutely and long-term by high fat diet. However, their role in regulating satiety and feeding in healthy individuals remains unclear. Here we show that microglia are essential for the normal regulation of satiety and metabolism in rats. Short-term microglial depletion in a Cx3cr1-Dtr rat led to a dramatic weight loss that was largely accounted for by an acute reduction in food intake. This weight loss and anorexia were not likely due to a sickness response since the rats did not display peripheral or central inflammation, withdrawal, anxiety-like behavior, or nausea-associated pica. Hormonal and hypothalamic anatomical changes were largely compensatory to the suppressed food intake, which occurred in association with disruption of the gustatory circuitry at the paraventricular nucleus of the thalamus. Thus, microglia are important in supporting normal feeding behaviors and weight, and regulating preference for palatable food. Inhibiting this circuitry is able to over-ride strong compensatory drives to eat, providing a potential target for satiety control.
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Affiliation(s)
- Simone N De Luca
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia
| | - Luba Sominsky
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia
| | - Alita Soch
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia
| | - Hao Wang
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia
| | - Ilvana Ziko
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia
| | - Michelle M Rank
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia
| | - Sarah J Spencer
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Vic. 3138, Australia.
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8
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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.,Imaging Program, Lawson Health Research Institute, London, Ontario, Canada.,Metabolism and Diabetes, Lawson Health Research Institute, London, Ontario, Canada.,Medical Biophysics, Western University, London, Ontario, Canada
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9
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Franco Machado J, Silva RD, Melo R, G Correia JD. Less Exploited GPCRs in Precision Medicine: Targets for Molecular Imaging and Theranostics. Molecules 2018; 24:E49. [PMID: 30583594 PMCID: PMC6337414 DOI: 10.3390/molecules24010049] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 12/07/2018] [Accepted: 12/09/2018] [Indexed: 12/18/2022] Open
Abstract
Precision medicine relies on individually tailored therapeutic intervention taking into account individual variability. It is strongly dependent on the availability of target-specific drugs and/or imaging agents that recognize molecular targets and patient-specific disease mechanisms. The most sensitive molecular imaging modalities, Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), rely on the interaction between an imaging radioprobe and a target. Moreover, the use of target-specific molecular tools for both diagnostics and therapy, theranostic agents, represent an established methodology in nuclear medicine that is assuming an increasingly important role in precision medicine. The design of innovative imaging and/or theranostic agents is key for further accomplishments in the field. G-protein-coupled receptors (GPCRs), apart from being highly relevant drug targets, have also been largely exploited as molecular targets for non-invasive imaging and/or systemic radiotherapy of various diseases. Herein, we will discuss recent efforts towards the development of innovative imaging and/or theranostic agents targeting selected emergent GPCRs, namely the Frizzled receptor (FZD), Ghrelin receptor (GHSR-1a), G protein-coupled estrogen receptor (GPER), and Sphingosine-1-phosphate receptor (S1PR). The pharmacological and clinical relevance will be highlighted, giving particular attention to the studies on the synthesis and characterization of targeted molecular imaging agents, biological evaluation, and potential clinical applications in oncology and non-oncology diseases. Whenever relevant, supporting computational studies will be also discussed.
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Affiliation(s)
- João Franco Machado
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
- Centro de Química Estrutural, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Rúben D Silva
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
| | - Rita Melo
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
- Center for Neuroscience and Cell Biology; Rua Larga, Faculdade de Medicina, Polo I, 1ºandar, Universidade de Coimbra, 3004-504 Coimbra, Portugal.
| | - João D G Correia
- Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, CTN, Estrada Nacional 10 (km 139,7), 2695-066 Bobadela LRS, Portugal.
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10
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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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11
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Charron CL, McFarland MS, Dhanvantari S, Luyt LG. Development of a [ 68Ga]-ghrelin analogue for PET imaging of the ghrelin receptor (GHS-R1a). MEDCHEMCOMM 2018; 9:1761-1767. [PMID: 30429981 DOI: 10.1039/c8md00210j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 09/09/2018] [Indexed: 01/16/2023]
Abstract
The ghrelin receptor is a member of the growth hormone secretagogue receptor (GHS-R) family and is present at low concentrations in tissues such as the brain, kidney, cardiovascular system, and prostate. The ghrelin receptor plays an important role in cellular proliferation, apoptosis, invasion, and migration associated with the progression of many cancers, including prostate, breast, ovarian, testicular, and intestinal carcinomas. Ghrelin, the endogenous ligand, is a 28 amino acid peptide (IC50 = 3.1 nM) known to have poor in vivo stability. Herein, we report the synthesis and evaluation of [Dpr3(octanoyl),Lys19(Ga-DOTA)]ghrelin(1-19). This new ghrelin analogue has a binding affinity (IC50 = 5.9 nM) comparable to that of natural ghrelin. Preliminary in vivo evaluation shows higher uptake of [Dpr3(octanoyl),Lys19(68Ga-DOTA)]ghrelin(1-19) in HT1080/GHSR-1a xenografts than the non-transfected HT1080 xenografts in NOD-SCID mice, although considerable uptake is observed in the kidneys. This is the first example of ghrelin receptor PET imaging in a xenograft model using a peptide derived directly from the endogenous ligand and serves as motivation for developing more effective ghrelin-based radiopeptides.
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Affiliation(s)
- C L Charron
- Department of Chemistry , University of Western Ontario , 1151 Richmond Street , London , Ontario N6A 5B7 , Canada .
| | - M S McFarland
- Department of Chemistry , University of Western Ontario , 1151 Richmond Street , London , Ontario N6A 5B7 , Canada .
| | - S Dhanvantari
- Lawson Health Research Institute , 268 Grosvenor Street , London , Ontario N6A 4V2 , Canada.,Departments of Medical Biophysics , University of Western Ontario , 1151 Richmond Street , London , Ontario N6A 5B7 , Canada
| | - L G Luyt
- Department of Chemistry , University of Western Ontario , 1151 Richmond Street , London , Ontario N6A 5B7 , Canada . .,Department of Oncology , University of Western Ontario , 1151 Richmond Street , London , Ontario N6A 5B7 , Canada.,London Regional Cancer Program , Lawson Health Research Institute , 800 Commissioners Road East , London , Ontario N6A 5W9 , Canada
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12
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Fowkes MM, Lalonde T, Yu L, Dhanvantari S, Kovacs MS, Luyt LG. Peptidomimetic growth hormone secretagogue derivatives for positron emission tomography imaging of the ghrelin receptor. Eur J Med Chem 2018; 157:1500-1511. [PMID: 30282322 DOI: 10.1016/j.ejmech.2018.08.062] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 08/16/2018] [Accepted: 08/22/2018] [Indexed: 02/06/2023]
Abstract
The ghrelin receptor is a seven-transmembrane (7-TM) receptor known to have an increased level of expression in human carcinoma and heart failure. Recent work has focused on the synthesis of positron emission tomography (PET) probes designed to target and image this receptor for disease diagnosis and staging. However, these probes have been restricted to small-molecule quinalizonones and peptide derivatives of the endogenous ligand ghrelin. We describe the design, synthesis and biological evaluation of a series of 4-fluorobenzoylated growth hormone secretagogues (GHSs) derived from peptidic (GHRP-1, GHPR-2 and GHRP-6) and peptidomimetic (G-7039, [1-Nal4]G-7039 and ipamorelin) families in order to test locations for the insertion of fluorine-18 for PET imaging. The peptidomimetic G-7039 was found to be the most suitable for 18F-radiolabelling as its non-radioactive 4-fluorobenzoylated analogue ([1-Nal4,Lys5(4-FB)]G-7039), had both a high binding affinity (IC50 = 69 nM) and promising in vitro efficacy (EC50 = 1.1 nM). Prosthetic group radiolabelling of the precursor compound [1-Nal4]G-7039 using N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) delivered the PET probe [1-Nal4,Lys5(4-[18F]-FB)]G-7039 in an average decay-corrected radiochemical yield of 48%, a radio-purity ≥ 99% and an average molar activity of >34 GBq/μmol. This compound could be investigated as a PET probe for the detection of diseases that are characterised by overexpression of the ghrelin receptor.
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Affiliation(s)
- Milan M Fowkes
- Department of Chemistry, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada; London Regional Cancer Program, Lawson Health Research Institute, 790 Commissioners Road East, London, Ontario, N6A 4L6, Canada
| | - Tyler Lalonde
- Department of Chemistry, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada; London Regional Cancer Program, Lawson Health Research Institute, 790 Commissioners Road East, London, Ontario, N6A 4L6, Canada
| | - Lihai Yu
- Department of Chemistry, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada; London Regional Cancer Program, Lawson Health Research Institute, 790 Commissioners Road East, London, Ontario, N6A 4L6, Canada
| | - Savita Dhanvantari
- Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
| | - Michael S Kovacs
- Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada
| | - Leonard G Luyt
- Department of Chemistry, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada; London Regional Cancer Program, Lawson Health Research Institute, 790 Commissioners Road East, London, Ontario, N6A 4L6, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario, N6A 4V2, Canada.
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13
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Murrell E, Kovacs MS, Luyt LG. A Compact and Synthetically Accessible Fluorine-18 Labelled Cyclooctyne Prosthetic Group for Labelling of Biomolecules by Copper-Free Click Chemistry. ChemMedChem 2018; 13:1625-1628. [DOI: 10.1002/cmdc.201800334] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Indexed: 12/26/2022]
Affiliation(s)
- Emily Murrell
- Department of Chemistry; University of Western Ontario; 1151 Richmond Street London ON N6A 5B7 Canada
| | - Michael S. Kovacs
- Lawson Health Research Institute; 268 Grosvenor Street London ON N6A 4V2 Canada
- Departments of Medical Imaging and Medical Biophysics; University of Western Ontario; 1151 Richmond Street London ON N6A 5B7 Canada
| | - Leonard G. Luyt
- Department of Chemistry; University of Western Ontario; 1151 Richmond Street London ON N6A 5B7 Canada
- Department of Oncology; University of Western Ontario; 1151 Richmond Street London ON N6A 5B7 Canada
- London Regional Cancer Program; Lawson Health Research Institute; 790 Commissioners Road East London ON N6A 4L6 Canada
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14
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Lalonde T, Shepherd TG, Dhanvantari S, Luyt LG. Stapled ghrelin peptides as fluorescent imaging probes. Pept Sci (Hoboken) 2018. [DOI: 10.1002/pep2.24055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Tyler Lalonde
- Department of Chemistry; University of Western Ontario; London Ontario N6A 5B7 Canada
| | - Trevor G. Shepherd
- London Regional Cancer Program; London Ontario N6A 4L6 Canada
- Department of Obstetrics and Gynecology; University of Western Ontario; London Ontario N6A 5B7 Canada
| | - Savita Dhanvantari
- Imaging Program, Lawson Health Research Institute; London Ontario N6A 4V2 Canada
- Department of Medical Biophysics; University of Western Ontario; London Canada
- Department of Pathology; University of Western Ontario; London Canada
- Department of Laboratory Medicine; University of Western Ontario; London Canada
| | - Leonard G. Luyt
- Department of Chemistry; University of Western Ontario; London Ontario N6A 5B7 Canada
- London Regional Cancer Program; London Ontario N6A 4L6 Canada
- Department of Oncology; University of Western Ontario; London Ontario N6A 5B7 Canada
- Department of Medical Imaging; University of Western Ontario; London Ontario N6A 5B7 Canada
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15
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Hou J, Kovacs MS, Dhanvantari S, Luyt LG. Development of Candidates for Positron Emission Tomography (PET) Imaging of Ghrelin Receptor in Disease: Design, Synthesis, and Evaluation of Fluorine-Bearing Quinazolinone Derivatives. J Med Chem 2018; 61:1261-1275. [DOI: 10.1021/acs.jmedchem.7b01754] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jinqiang Hou
- London Regional Cancer Program, London N6A 4L6, Canada
- Lawson Health Research Institute, London N6C 2R5, Canada
| | | | | | - Leonard G. Luyt
- London Regional Cancer Program, London N6A 4L6, Canada
- Lawson Health Research Institute, London N6C 2R5, Canada
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16
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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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17
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Charron CL, Hou J, McFarland MS, Dhanvantari S, Kovacs MS, Luyt LG. Structure–Activity Study of Ghrelin(1–8) Resulting in High Affinity Fluorine-Bearing Ligands for the Ghrelin Receptor. J Med Chem 2017; 60:7256-7266. [DOI: 10.1021/acs.jmedchem.7b00164] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Carlie L. Charron
- Department
of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada
| | - Jinqiang Hou
- London
Regional Cancer Program, Lawson Health Research Institute, 790 Commissioners Road East, London, Ontario N6A 4L6, Canada
| | - Mark S. McFarland
- Department
of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada
| | - Savita Dhanvantari
- Imaging
Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
- Department
of Medical Biophysics, University of Western Ontario, 1151 Richmond
Street, London, Ontario N6A 5B7, Canada
| | - Michael S. Kovacs
- Imaging
Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
- Department
of Medical Biophysics, University of Western Ontario, 1151 Richmond
Street, London, Ontario N6A 5B7, Canada
| | - Leonard G. Luyt
- Department
of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada
- London
Regional Cancer Program, Lawson Health Research Institute, 790 Commissioners Road East, London, Ontario N6A 4L6, Canada
- Departments
of Oncology and Medical Imaging, University of Western Ontario, 1151
Richmond Street, London, Ontario N6A 5B7, Canada
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18
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Sominsky L, Ziko I, Nguyen TX, Andrews ZB, Spencer SJ. Early life disruption to the ghrelin system with over-eating is resolved in adulthood in male rats. Neuropharmacology 2017; 113:21-30. [DOI: 10.1016/j.neuropharm.2016.09.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 12/11/2022]
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19
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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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20
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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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