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Brom M, Woliner-van der Weg W, Joosten L, Frielink C, Bouckenooghe T, Rijken P, Andralojc K, Göke BJ, de Jong M, Eizirik DL, Béhé M, Lahoutte T, Oyen WJG, Tack CJ, Janssen M, Boerman OC, Gotthardt M. Non-invasive quantification of the beta cell mass by SPECT with ¹¹¹In-labelled exendin. Diabetologia 2014; 57:950-9. [PMID: 24488022 DOI: 10.1007/s00125-014-3166-3] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 12/23/2013] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS A reliable method for in vivo quantification of pancreatic beta cell mass (BCM) could lead to further insight into the pathophysiology of diabetes. The glucagon-like peptide 1 receptor, abundantly expressed on beta cells, may be a suitable target for imaging. We investigated the potential of radiotracer imaging with the GLP-1 analogue exendin labelled with indium-111 for determination of BCM in vivo in a rodent model of beta cell loss and in patients with type 1 diabetes and healthy individuals. METHODS The targeting of (111)In-labelled exendin was examined in a rat model of alloxan-induced beta cell loss. Rats were injected with 15 MBq (111)In-labelled exendin and single photon emission computed tomography (SPECT) acquisition was performed 1 h post injection, followed by dissection, biodistribution and ex vivo autoradiography studies of pancreatic sections. BCM was determined by morphometric analysis after staining with an anti-insulin antibody. For clinical evaluation SPECT was acquired 4, 24 and 48 h after injection of 150 MBq (111)In-labelled exendin in five patients with type 1 diabetes and five healthy individuals. The tracer uptake was determined by quantitative analysis of the SPECT images. RESULTS In rats, (111)In-labelled exendin specifically targets the beta cells and pancreatic uptake is highly correlated with BCM. In humans, the pancreas was visible in SPECT images and the pancreatic uptake showed high interindividual variation with a substantially lower uptake in patients with type 1 diabetes. CONCLUSIONS/INTERPRETATION These studies indicate that (111)In-labelled exendin may be suitable for non-invasive quantification of BCM. TRIAL REGISTRATION ClinicalTrials.gov NCT01825148, EudraCT: 2012-000619-10.
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Affiliation(s)
- Maarten Brom
- Department of Radiology and Nuclear Medicine, Radboud university medical center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands,
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Hong F, Liu L, Fan RF, Chen Y, Chen H, Zheng RP, Zhang Y, Gao Y, Zhu JX. New perspectives of vesicular monoamine transporter 2 chemical characteristics in mammals and its constant expression in type 1 diabetes rat models. Transl Res 2014; 163:171-82. [PMID: 24161354 DOI: 10.1016/j.trsl.2013.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 09/23/2013] [Accepted: 10/01/2013] [Indexed: 11/18/2022]
Abstract
Vesicular monoamine transporter 2 (VMAT2) has been exploited as a biomarker of β-cell mass in human islets. However, a current report suggested no immunoreactivity of VMAT2 in the β cells of rat islets. To investigate the cellular localization of VMAT2 in islets further, the pancreatic tissues from monkeys and humans were compared with those of rats and mice. The study was performed using among-species comparisons and a type 1 diabetes model (T1DM) for rats by Western blotting, double-label immunofluorescence, and confocal laser scanning microscopy. We found that VMAT2-immunoreactivity (IR) was distributed peripherally in the islets of rodents, but was widely scattered throughout the islets of primates. Consistent with rodent islets, VMAT2-IR did not exist in insulin (INS)-IR cells but was abundantly present in glucagon (GLU)-IR and pancreatic polypeptide (PP)-IR cells in monkey and human islets. VMAT2-IR had no colocalization with INS-IR in any part of the rat pancreas (head, body, and tail). INS-IR cells were reduced dramatically in T1DM rat islets, but no significant alteration in the proportion of VMAT2-IR cells and GLU-IR cells was observed. Furthermore, a strong colocalization of VMAT2-IR with GLU-IR was distributed in the peripheral regions of diabetic islets. For the first time, the current study demonstrates the presence of VMAT2 in α cells and PP cells but not in β cells in the islets of monkeys and humans. This study provides convinced morphologic evidence that VMAT2 is not present in β cells. There needs to be studies for new markers for β cell mass.
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Affiliation(s)
- Feng Hong
- Department of Physiology and Pathophysiology, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Li Liu
- Department of Human Anatomy, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Rui-Fang Fan
- Department of Physiology and Pathophysiology, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Ye Chen
- Department of Physiology and Pathophysiology, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Hui Chen
- Department of Physiology and Pathophysiology, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Rui-Pan Zheng
- Department of Human Anatomy, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Yue Zhang
- Department of Physiology and Pathophysiology, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Yan Gao
- Department of Human Anatomy, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China
| | - Jin-Xia Zhu
- Department of Physiology and Pathophysiology, School of Basic Medicinal Sciences, Capital Medical University, Beijing 100069, China.
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Araújo-Filho I, Rêgo ACM, Azevedo ÍM, Carvalho MDF, Medeiros AC. Ileal interposition and viability of pancreatic islets transplanted into intramuscular site of diabetic rats. J INVEST SURG 2014; 27:191-6. [PMID: 24377965 DOI: 10.3109/08941939.2013.870622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Assuming that ileal stimulation by food may increase incretin secretion, we aimed to investigate whether ileal interposition obtains adequate pancreatic islet viability and function after intramuscular islet transplantation in diabetic rats. METHODS We investigated four groups of eight Wistar rats: ileal interposition + islet transplantation, islet transplantation, ileal interposition, and diabetic control. All rats were subjected to streptozotocin-induced diabetes. We used the C-peptide/glucose ratio and islet image to investigate beta cell mass, and plasma glucagon like peptide-1 (GLP-1) measure. RESULTS Ileal interposition was effective in preserving function and increasing islet mass in animals with islets transplanted into alginate microcapsules. The plasma GLP-1 level in the diabetic control rats was a basal concentration (4.1 ± 1.2 pM). GLP-1 level after ileal interposition + islet transplantation (12.3 ± 3.3 pM) was significantly higher (p < .05) than in the islet transplantation group (8.2 ± 2.4 pM) and ileal interposition group rats (7.6 ± 1.8 pM). CONCLUSIONS Ileal interposition positively influenced beta cell viability after intramuscular transplantation of pancreatic islets in diabetic rats.
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Affiliation(s)
- Irami Araújo-Filho
- Department of Surgery, Federal University of Rio Grande do Norte, Natal , Brazil
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Blomberg BA, Codreanu I, Cheng G, Werner TJ, Alavi A. Beta-cell imaging: call for evidence-based and scientific approach. Mol Imaging Biol 2013; 15:123-30. [PMID: 23413090 DOI: 10.1007/s11307-013-0620-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Advances in positron emission tomography (PET) imaging have provided opportunities to develop radiotracers specific for imaging insulin-producing pancreatic β-cells. However, a host of lingering questions should be addressed before these radiotracers are advocated for noninvasive quantification of β-cell mass (BCM) in vivo in the native pancreas. METHOD We provide an overview of tetrabenazine-based PET tracers developed to image and quantify BCM and discuss several theoretical, technical, and biological limitations of applying these tracers in clinical practice. DISCUSSION VMAT2, a transporter protein expressed on pancreatic β-cells, has been advocated as a promising target for PET imaging tracers, such as dihydrotetrabenazine. However, the lack of radiotracer specificity for these proteins hampers their clinical application. Another important argument against their use is a striking discrepancy between radiotracer uptake and BCM in subjects with type I diabetes mellitus and healthy controls. Additionally, technical issues, such as the finite spatial resolution of PET, partial volume effects, and movement of the pancreas during respiration, impede PET imaging as a viable option for BCM quantification in the foreseeable future. CONCLUSION The assertion that BCM can be accurately quantified by tetrabenazine derived β-cell-specific radiotracers as density per unit volume of pancreatic tissue is not justifiable at this time. The fallacy of these claims can be explained by technical as well as biological facts that have been disregarded and ignored in the literature.
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Affiliation(s)
- Björn A Blomberg
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
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Positron emission tomography study on pancreatic somatostatin receptors in normal and diabetic rats with 68Ga-DOTA-octreotide: a potential PET tracer for beta cell mass measurement. Biochem Biophys Res Commun 2013; 442:79-84. [PMID: 24220338 DOI: 10.1016/j.bbrc.2013.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 11/02/2013] [Indexed: 12/14/2022]
Abstract
Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia, and the loss or dysfunction of pancreatic beta cells has been reported before the appearance of clinical symptoms and hyperglycemia. To evaluate beta cell mass (BCM) for improving the detection and treatment of DM at earlier stages, we focused on somatostatin receptors that are highly expressed in the pancreatic beta cells, and developed a positron emission tomography (PET) probe derived from octreotide, a metabolically stable somatostatin analog. Octreotide was conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), a chelating agent, and labeled with (68)Gallium ((68)Ga). After intravenous injection of (68)Ga-DOTA-octreotide, a 90-min emission scan of the abdomen was performed in normal and DM model rats. The PET studies showed that (68)Ga-DOTA-octreotide radioactivity was highly accumulated in the pancreas of normal rats and that the pancreatic accumulation was significantly reduced in the rats administered with an excess amount of unlabeled octreotide or after treatment with streptozotocin, which was used for the chemical induction of DM in rats. These results were in good agreement with the ex vivo biodistribution data. These results indicated that the pancreatic accumulation of (68)Ga-DOTA-octreotide represented specific binding to the somatostatin receptors and reflected BCM. Therefore, PET imaging with (68)Ga-DOTA-octreotide could be a potential tool for evaluating BCM.
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Nishimura W, Eto K, Miki A, Goto M, Kawaguchi M, Nammo T, Udagawa H, Hiramoto M, Shimizu Y, Okamura T, Fujiwara T, Yasuda Y, Yasuda K. Quantitative assessment of Pdx1 promoter activity in vivo using a secreted luciferase reporter system. Endocrinology 2013; 154:4388-95. [PMID: 24029239 DOI: 10.1210/en.2012-2248] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The luciferase reporter system is useful for the assessment of various biological processes in vivo. The transcription factor pancreatic and duodenal homeobox 1 (Pdx1) is critical for the formation and the function of pancreatic β-cells. A novel reporter system using secreted Gaussia princeps luciferase (GLuc) under the control of a Pdx1 promoter was generated and activated in rat and mouse β-cell lines. This Pdx1-GLuc construct was used as a transgene for the generation of reporter mice to monitor Pdx1 promoter activity in vivo via the measurement of secreted GLuc activity in a small aliquot of blood. Significantly increased plasma GLuc activity was observed in Pdx1-GLuc mice. Analysis of Pdx1-GLuc mice by bioluminescence imaging, GLuc reporter assays using homogenates of various organs, and immunohistochemistry revealed that GLuc expression and activity were exponentially higher in pancreatic β-cells than in pancreatic non-β-cells, the duodenum, and other organs. In addition, GLuc activity secreted into the culture medium from islets isolated from Pdx1-GLuc mice correlated with the number of islets. The transplantation of Pdx1-GLuc islets into severe combined immunodeficiency mice elevated their plasma GLuc activity. Conversely, a partial pancreatectomy in Pdx1-GLuc mice reduced plasma GLuc activity. These results suggest that a secreted luciferase reporter system in vivo enables not only the monitoring of promoter activity but also a quantitative and minimally invasive assessment of physiological and pathological changes in small cell masses, such as pancreatic β-cells.
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Affiliation(s)
- Wataru Nishimura
- Department of Metabolic Disorders, Diabetes Research Center, National Center for Global Health and Medicine, Tokyo 162-8655, Japan.
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Yang B, Cai H, Qin W, Zhang B, Zhai C, Jiang B, Wu Y. Bcl-2-functionalized ultrasmall superparamagnetic iron oxide nanoparticles coated with amphiphilic polymer enhance the labeling efficiency of islets for detection by magnetic resonance imaging. Int J Nanomedicine 2013; 8:3977-90. [PMID: 24204136 PMCID: PMC3804583 DOI: 10.2147/ijn.s52058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Based on their versatile, biocompatible properties, superparamagnetic iron oxide (SPIO) or ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are utilized for detecting and tracing cells or tumors in vivo. Here, we developed an innoxious and concise synthesis approach for a novel B-cell lymphoma (Bcl)-2 monoclonal antibody-functionalized USPIO nanoparticle coated with an amphiphilic polymer (carboxylated polyethylene glycol monooleyl ether [OE-PEG-COOH]). These nanoparticles can be effectively internalized by beta cells and label primary islet cells, at relatively low iron concentration. The biocompatibility and cytotoxicity of these products were investigated by comparison with the commercial USPIO product, FeraSpin™ S. We also assessed the safe dosage range of the product. Although some cases showed a hypointensity change at the site of transplant, a strong magnetic resonance imaging (MRI) was detectable by a clinical MRI scanner, at field strength of 3.0 Tesla, in vivo, and the iron deposition/attached in islets was confirmed by Prussian blue and immunohistochemistry staining. It is noteworthy that based on our synthesis approach, in future, we could exchange the Bcl-2 with other probes that would be more specific for the targeted cells and that would have better labeling specificity in vivo. The combined results point to the promising potential of the novel Bcl-2-functionalized PEG-USPIO as a molecular imaging agent for in vivo monitoring of islet cells or other cells.
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Affiliation(s)
- Bin Yang
- Department of Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China
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Yang L, Ji W, Xue Y, Chen L. Imaging beta-cell mass and function in situ and in vivo. J Mol Med (Berl) 2013; 91:929-38. [PMID: 23700217 DOI: 10.1007/s00109-013-1056-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 05/07/2013] [Accepted: 05/15/2013] [Indexed: 01/16/2023]
Abstract
Glucose-stimulated insulin secretion (GSIS) from pancreatic beta-cells is critical to the maintenance of blood glucose homeostasis in animals. Both decrease in pancreatic beta-cell mass and defects in beta-cell function contribute to the onset of diabetes, although the underlying mechanisms remain largely unknown. Molecular imaging techniques can help beta-cell study in a number of ways. High-resolution fluorescence imaging techniques provide novel insights into the fundamental mechanisms underlying GSIS in isolated beta-cells or in situ in pancreatic islets, and dynamic changes of beta-cell mass and function can be noninvasively monitored in vivo by imaging techniques such as positron emission tomography and single-photon emission computed tomography. All these techniques will contribute to the better understanding of the progression of diabetes and the search for the optimized therapeutic measures that reverse deficits in beta-cell mass and function.
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Affiliation(s)
- Lu Yang
- The State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking University and National Center for Nanoscience and Technology, Beijing, China.
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The role of exendin-4-conjugated superparamagnetic iron oxide nanoparticles in beta-cell-targeted MRI. Biomaterials 2013; 34:5843-52. [PMID: 23642536 DOI: 10.1016/j.biomaterials.2013.04.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 04/10/2013] [Indexed: 11/24/2022]
Abstract
Noninvasive targeted visualization of pancreatic beta cells or islets is becoming the focus of molecular imaging application in diabetes and islet transplantation studies, but it is currently unsuccessful due to the lack of specific beta cell biomarkers. Glucagon-like peptide 1 receptor (GLP-1R) is highly expressed in beta cells and considered as a promising target. We here developed a targeted superparamagnetic iron oxide (SPIO) nanoparticle using GLP-1 analog-exendin-4 which is conjugated to polyethylene glycol coated SPIO (PEG-SPIO). The results demonstrated that exendin-4 functionalized SPIO was able to specifically bind to and internalized by GLP-1R-expressing INS-1 cells, with the higher labeling efficiency than non-targeted nanoparticles. Notably, SPIO-exendin4 could differentially label islets in pancreatic slices or beta cell grafts in vitro. Systemic delivery of SPIO-exendin4 into nude mice bearing s.c. insulinomas (derived from INS-1 cells) leads to the accumulation of the nanoparticles in tumors, generating a strong magnetic resonance imaging contrast detectable by a clinical MRI scanner at field strength of 3.0 T, and the iron deposition in tumors was further confirmed by Prussian blue staining. Furthermore, preliminary biodistribution study indicated that SPIO-exendin4 had a tendency to accumulate in pancreas. Toxicity assessments demonstrated good biocompatibility in vivo. These results suggest that SPIO-exendin4 has potential as molecularly targeted imaging agents for in vivo imaging of insulinoma, and possibly for future beta cell imaging.
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Comley RA, Kallend D. Imaging in the cardiovascular and metabolic disease area. Drug Discov Today 2013; 18:185-92. [DOI: 10.1016/j.drudis.2012.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/14/2012] [Accepted: 09/24/2012] [Indexed: 01/09/2023]
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Weir GC, Bonner-Weir S. Islet β cell mass in diabetes and how it relates to function, birth, and death. Ann N Y Acad Sci 2013; 1281:92-105. [PMID: 23363033 PMCID: PMC3618572 DOI: 10.1111/nyas.12031] [Citation(s) in RCA: 237] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In type 1 diabetes (T1D) β cell mass is markedly reduced by autoimmunity. Type 2 diabetes (T2D) results from inadequate β cell mass and function that can no longer compensate for insulin resistance. The reduction of β cell mass in T2D may result from increased cell death and/or inadequate birth through replication and neogenesis. Reduction in mass allows glucose levels to rise, which places β cells in an unfamiliar hyperglycemic environment, leading to marked changes in their phenotype and a dramatic loss of glucose-stimulated insulin secretion (GSIS), which worsens as glucose levels climb. Toxic effects of glucose on β cells (glucotoxicity) appear to be the culprit. This dysfunctional insulin secretion can be reversed when glucose levels are lowered by treatment, a finding with therapeutic significance. Restoration of β cell mass in both types of diabetes could be accomplished by either β cell regeneration or transplantation. Learning more about the relationships between β cell mass, turnover, and function and finding ways to restore β cell mass are among the most urgent priorities for diabetes research.
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Affiliation(s)
- Gordon C Weir
- Section on Islet Cell Biology and Regenerative Medicine, Research Division, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, MA 02215, USA.
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Di Gialleonardo V, de Vries EFJ, Di Girolamo M, Quintero AM, Dierckx RAJO, Signore A. Imaging of β-cell mass and insulitis in insulin-dependent (Type 1) diabetes mellitus. Endocr Rev 2012; 33:892-919. [PMID: 22889646 DOI: 10.1210/er.2011-1041] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Insulin-dependent (type 1) diabetes mellitus is a metabolic disease with a complex multifactorial etiology and a poorly understood pathogenesis. Genetic and environmental factors cause an autoimmune reaction against pancreatic β-cells, called insulitis, confirmed in pancreatic samples obtained at autopsy. The possibility to noninvasively quantify β-cell mass in vivo would provide important biological insights and facilitate aspects of diagnosis and therapy, including follow-up of islet cell transplantation. Moreover, the availability of a noninvasive tool to quantify the extent and severity of pancreatic insulitis could be useful for understanding the natural history of human insulin-dependent (type 1) diabetes mellitus, to early diagnose children at risk to develop overt diabetes, and to select patients to be treated with immunotherapies aimed at blocking the insulitis and monitoring the efficacy of these therapies. In this review, we outline the imaging techniques currently available for in vivo, noninvasive detection of β-cell mass and insulitis. These imaging techniques include magnetic resonance imaging, ultrasound, computed tomography, bioluminescence and fluorescence imaging, and the nuclear medicine techniques positron emission tomography and single-photon emission computed tomography. Several approaches and radiopharmaceuticals for imaging β-cells and lymphocytic insulitis are reviewed in detail.
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Affiliation(s)
- Valentina Di Gialleonardo
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, 9700 AB, Groningen, The Netherlands
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Freeby M, Ichise M, Harris PE. Vesicular monoamine transporter, type 2 (VMAT2) expression as it compares to insulin and pancreatic polypeptide in the head, body and tail of the human pancreas. Islets 2012; 4:393-7. [PMID: 23221614 PMCID: PMC3605167 DOI: 10.4161/isl.22995] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The vesicular monoamine transporter, type 2 (VMAT2) is responsible for sequestering monoamine neurotransmitters into exocytic vesicles in neurons, enterochromaffin-like cells of the stomach and cells arising from the common myeloid progenitor. VMAT2 is also present in the pancreas and is expressed by insulin producing β cells, but not by glucagon or somatostatin expressing islet cells. Positron emission tomography (PET) targeting of VMAT2 is currently being evaluated as a non-invasive tool to measure β cell mass (BCM) in living humans. In recent trials, PET measurements of VMAT2 in the pancreas overestimated BCM in type 1 diabetes (T1D) patients predicted to have little to no BCM by metabolic measures. Recently, tissue immunohistochemistry studies suggested that VMAT2 staining may also co-localize with pancreatic polypeptide (PP) staining cells in pancreas tissue, but these studies were not quantitative. In this report, we evaluated VMAT2 specificity for β cells in sub-regions of the human pancreas using antibodies targeting VMAT2, insulin and PP by double-label immunofluorescence. Immunostaining for VMAT2 and insulin demonstrated 89 ± 8% overlap in the body and tail of the pancreas. However, 44 ± 12% and 53 ± 15% of VMAT2 cells co-stained with PP- and insulin-staining cells, respectively in the pancreatic head. Significant co-staining for VMAT2 and PP cells in the head of the pancreas may partly explain the apparent overestimation of BCM in T1D by PET. Specific targeting of the pancreatic body and tail using VMAT2 PET scanning may reflect BCM more accurately.
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Affiliation(s)
- Matthew Freeby
- Division of Endocrinology and the Naomi Berrie Diabetes Center; Columbia University; New York, NY USA
| | - Masanori Ichise
- Department of Radiology; Columbia University; New York, NY USA
| | - Paul E. Harris
- Division of Endocrinology and the Naomi Berrie Diabetes Center; Columbia University; New York, NY USA
- * Correspondence to: Paul Harris;
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Harris PE, Farwell MD, Ichise M. PET quantification of pancreatic VMAT 2 binding using (+) and (-) enantiomers of [¹⁸F]FP-DTBZ in baboons. Nucl Med Biol 2012; 40:60-4. [PMID: 23102539 DOI: 10.1016/j.nucmedbio.2012.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/06/2012] [Accepted: 09/18/2012] [Indexed: 10/27/2022]
Abstract
OBJECTIVES The exact cause(s) of apparent overestimation of β cell mass (BCM) with vesicular monoamine transporter type 2 (VMAT2) PET imaging in type 1 diabetes (T1D) is unknown. The objectives were to estimate in baboons non-displaceable binding of [¹⁸F]fluoropropyl (FP)-(+)-dihydrotetrabenazine (DTBZ) with its inactive enantiomer, [¹⁸F]FP-(-)-DTBZ, to validate the use of the reference tissue (renal cortex or spleen) in VMAT2 quantification; and also to compare specific pancreatic VMAT2 binding with that of the striatum in the same baboon brains because high specific binding signal for the pancreas would be desirable for its accurate quantification. METHODS Baboons (Papio ursinus) had multiple dynamic abdominal and brain PET scans each for 2 h with (+) and (-) enantiomers on separate occasions. Data were analyzed by compartmental models to estimate non-displaceable (V(ND)) and specific (V(S)) VMAT2 binding in respective organs. RESULTS [¹⁸F]FP-DTBZ PET showed excellent target tissue signal and specific VMAT2 binding in the pancreas (Vs =41±11 mL/cm³) at nearly 80% that of the striatum. Directly estimated non-displaceable binding in the pancreas (V(ND) =12±1 mL/cm³) was similar to that of the renal cortex, spleen or cerebellum. CONCLUSION ¹⁸FFP-DTBZ PET shows excellent specific VMAT2 binding in both the pancreas and striatum in baboons. The renal cortex or spleen as the reference tissue in VMAT2 quantification appears supported. However further studies appear warranted to directly estimate pancreatic non-displaceable binding in humans including T1D patients and also to clarify the cause of the apparent overestimation of BCM in T1D.
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Affiliation(s)
- Paul E Harris
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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Malaisse WJ, Maedler K. Imaging of the β-cells of the islets of Langerhans. Diabetes Res Clin Pract 2012; 98:11-8. [PMID: 22854107 DOI: 10.1016/j.diabres.2012.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 07/10/2012] [Indexed: 01/09/2023]
Abstract
The major aim of this paper is to review the present status of the techniques for the non-invasive imaging and quantification of insulin-producing pancreatic islet β-cells. Emphasis is placed on both the expansion of prior work already considered in a prior review and novel achievements. Thus, the use of d-mannoheptulose analogs, hypoglycemic sulfonylureas and glinides, neural imaging agents, neuro-hormonal receptor ligands and nanoparticles is first dealt with. Thereafter, consideration is given on optical imaging technologies, the identification of new β-cells specific binding and target proteins, the functional imaging of islets transplanted into the eye anterior chamber and in vivo manganese-enhanced magnetic resonance imaging.
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Affiliation(s)
- Willy J Malaisse
- Laboratory of Experimental Hormonology, Université Libre de Bruxelles, Brussels, Belgium.
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Abstract
Here, we outline how islet cells use autocrine and paracrine 'circuits' of classical neurotransmitters and their corresponding receptors and transporters to communicate with vicinal β-cells to regulate glucose-stimulated insulin secretion. Many of these same circuits operate in the central nervous system and can be visualized by molecular imaging. We discuss how these techniques might be applied to measuring the dynamics of β-cell function in real time.
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Affiliation(s)
- P E Harris
- Division of Endocrinology, Department of Medicine, The Naomi Berrie Diabetes Center and Columbia University College of Physicians and Surgeons, New York, NY, USA.
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Blomberg BA, Eriksson O, Saboury B, Alavi A. β-Cell mass imaging with DTBZ positron emission tomography: is it possible? Mol Imaging Biol 2012; 15:1-2. [PMID: 22983914 DOI: 10.1007/s11307-012-0593-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Watanabe A, Nishijima KI, Zhao S, Zhao Y, Tanaka Y, Takemoto H, Strauss HW, Blankenberg FG, Tamaki N, Kuge Y. Quantitative determination of apoptosis of pancreatic β-cells in a murine model of type 1 diabetes mellitus. J Nucl Med 2012; 53:1585-91. [PMID: 22930815 DOI: 10.2967/jnumed.111.102459] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
UNLABELLED Type 1 diabetes mellitus is characterized by a significant deficit in pancreatic β-cell mass, presumably caused by β-cell apoptosis. We investigated the incidence of β-cell apoptosis in streptozotocin-treated mice and nonobese diabetic (NOD) mice with (99m)Tc-annexin A5. METHODS Vehicle-treated mice, streptozotocin-treated mice, and NOD mice at the ages of 5, 9, 16, and 20 wk (5-8 mice per group) were injected with (99m)Tc-annexin A5 and sacrificed 6 h later for autoradiography, and the regional (99m)Tc-annexin A5 level in the pancreas was evaluated. Pancreatic islets were identified by insulin immunohistochemical staining, and apoptotic cells were determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. The (99m)Tc-annexin A5 level in pancreatic islets was expressed as the percentage injected dose per area of pancreatic islets and normalized by animal body weight (%ID × 10(6)/mm(2)/kg). The level of apoptotic cells in pancreatic islets was expressed as the number of TUNEL-positive cells per area of pancreatic islets (cells/mm(2)). RESULTS The (99m)Tc-annexin A5 accumulation level was significantly higher (2.5 ± 0.7 vs. 0.7 ± 0.1 %ID × 10(6)/mm(2)/kg, P < 0.05) and the number of TUNEL-positive cells was significantly higher (1,170 ± 535 vs. 5 ± 6 cells/mm(2), P < 0.05) in the pancreatic islets of the streptozotocin-treated mice than in those of the vehicle-treated mice. The (99m)Tc-annexin A5 accumulation level was significantly higher (1.1 ± 0.4 vs. 0.5 ± 0.1 %ID × 10(6)/mm(2)/kg, P < 0.05) and the number of TUNEL-positive cells was significantly higher (152 ± 82 vs. 4 ± 9 cells/mm(2), P < 0.05) in the pancreatic islets of 16-wk-old NOD mice than in those of 5-wk-old NOD mice. In addition, the level of (99m)Tc-annexin A5 correlated with the number of TUNEL-positive cells in the pancreatic islets of the streptozotocin-treated mice (r = 0.821, P < 0.001) and NOD mice (r = 0.721, P < 0.001). CONCLUSION There is significant islet cell apoptosis with (99m)Tc-annexin A5 accumulation in the pancreas of both streptozotocin and NOD mice.
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Affiliation(s)
- Ayahisa Watanabe
- Department of Radiobiology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
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Lebastchi J, Herold KC. Immunologic and metabolic biomarkers of β-cell destruction in the diagnosis of type 1 diabetes. Cold Spring Harb Perspect Med 2012; 2:a007708. [PMID: 22675665 PMCID: PMC3367537 DOI: 10.1101/cshperspect.a007708] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Type 1 diabetes (T1D), also known as insulin-dependent diabetes mellitus, is a chronic disorder that results from autoimmune destruction of insulin-producing β cells in the islets of Langerhans within the pancreas ( Atkinson and Maclaren 1994). This disease becomes clinically apparent only after significant destruction of the β-cell mass, which reduces the ability to maintain glycemic control and metabolic function. In addition, it continues for years after clinical onset until, generally, there is complete destruction of insulin secretory capacity. Because prevention and therapy strategies are targeted to this pathologic process, it becomes imperative to have methods with which it can be monitored. This work discusses current research-based approaches to monitor the autoimmunity and metabolic function in T1D patients and their potential for widespread clinical application.
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Affiliation(s)
- Jasmin Lebastchi
- Department of Immunobiology and Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
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72
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Normandin MD, Petersen KF, Ding YS, Lin SF, Naik S, Fowles K, Skovronsky DM, Herold KC, McCarthy TJ, Calle RA, Carson RE, Treadway JL, Cline GW. In vivo imaging of endogenous pancreatic β-cell mass in healthy and type 1 diabetic subjects using 18F-fluoropropyl-dihydrotetrabenazine and PET. J Nucl Med 2012; 53:908-16. [PMID: 22573821 DOI: 10.2967/jnumed.111.100545] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
UNLABELLED The ability to noninvasively measure endogenous pancreatic β-cell mass (BCM) would accelerate research on the pathophysiology of diabetes and revolutionize the preclinical development of new treatments, the clinical assessment of therapeutic efficacy, and the early diagnosis and subsequent monitoring of disease progression. The vesicular monoamine transporter type 2 (VMAT2) is coexpressed with insulin in β-cells and represents a promising target for BCM imaging. METHODS We evaluated the VMAT2 radiotracer (18)F-fluoropropyl-dihydrotetrabenazine ((18)F-FP-(+)-DTBZ, also known as (18)F-AV-133) for quantitative PET of BCM in healthy control subjects and patients with type 1 diabetes mellitus. Standardized uptake value was calculated as the net tracer uptake in the pancreas normalized by injected dose and body weight. Total volume of distribution, the equilibrium ratio of tracer concentration in tissue relative to plasma, was estimated by kinetic modeling with arterial input functions. Binding potential, the steady-state ratio of specific binding to nondisplaceable uptake, was calculated using the renal cortex as a reference tissue devoid of specific VMAT2 binding. RESULTS Mean pancreatic standardized uptake value, total volume of distribution, and binding potential were reduced by 38%, 20%, and 40%, respectively, in type 1 diabetes mellitus. The radiotracer binding parameters correlated with insulin secretion capacity as determined by arginine-stimulus tests. Group differences and correlations with β-cell function were enhanced for total pancreas binding parameters that accounted for tracer binding density and organ volume. CONCLUSION These findings demonstrate that quantitative evaluation of islet β-cell density and aggregate BCM can be performed clinically with (18)F-FP-(+)-DTBZ PET.
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Affiliation(s)
- Marc D Normandin
- Department of Diagnostic Radiology, Yale University, School of Medicine, New Haven, Connecticut 06520, USA
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Andralojc K, Srinivas M, Brom M, Joosten L, de Vries IJM, Eizirik DL, Boerman OC, Meda P, Gotthardt M. Obstacles on the way to the clinical visualisation of beta cells: looking for the Aeneas of molecular imaging to navigate between Scylla and Charybdis. Diabetologia 2012; 55:1247-57. [PMID: 22358499 PMCID: PMC3328679 DOI: 10.1007/s00125-012-2491-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 01/09/2012] [Indexed: 12/25/2022]
Abstract
For more than a decade, researchers have been trying to develop non-invasive imaging techniques for the in vivo measurement of viable pancreatic beta cells. However, in spite of intense research efforts, only one tracer for positron emission tomography (PET) imaging is currently under clinical evaluation. To many diabetologists it may remain unclear why the imaging world struggles to develop an effective method for non-invasive beta cell imaging (BCI), which could be useful for both research and clinical purposes. Here, we provide a concise overview of the obstacles and challenges encountered on the way to such BCI, in both native and transplanted islets. We discuss the major difficulties posed by the anatomical and cell biological features of pancreatic islets, as well as the chemical and physical limits of the main imaging modalities, with special focus on PET, SPECT and MRI. We conclude by indicating new avenues for future research in the field, based on several remarkable recent results.
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Affiliation(s)
- K. Andralojc
- Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands
| | - M. Srinivas
- Department of Tumour Immunology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - M. Brom
- Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands
| | - L. Joosten
- Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands
| | - I. J. M. de Vries
- Department of Tumour Immunology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - D. L. Eizirik
- Laboratory of Experimental Medicine, Université Libre de Bruxelles, Brussels, Belgium
| | - O. C. Boerman
- Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands
| | - P. Meda
- Deparment of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - M. Gotthardt
- Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands
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Novel pancreatic beta cell-specific proteins: antibody-based proteomics for identification of new biomarker candidates. J Proteomics 2012; 75:2611-20. [PMID: 22465717 DOI: 10.1016/j.jprot.2012.03.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 02/29/2012] [Accepted: 03/04/2012] [Indexed: 01/03/2023]
Abstract
Beta cell-specific surface targets are required for non-invasive monitoring of beta cell mass, which could be used for evaluation of new diabetes treatments as well as to help unravel pathogenic mechanisms underlying beta cell dysfunction. By antibody-based proteomics, we have identified and explored a set of islet cell-specific proteins. A search algorithm in the Human Protein Atlas was set up for identification of islet-specific proteins that yielded 27 hits, of which twelve showed a clear membranous expression pattern or had predicted transmembrane regions. The specificity of the identified proteins was investigated by immunohistochemical staining of pancreas sections from diabetic and non-diabetic subjects. No expression of these antigens could be detected in the exocrine pancreas. Colocalization with insulin and glucagon was further determined by confocal microscopy using isolated human islets. All antibodies specifically stained human islets and colocalization analysis revealed that four proteins were exclusively expressed in beta cells. Importantly, these antibodies were negative in sections from subjects with long-standing type 1 diabetes. In the present study, we present four proteins; DGCR2, GBF1, GPR44 and SerpinB10, the expression of which has not previously been described in beta cells.
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Liu G, Dou S, Akalin A, Rusckowski M, Streeter PR, Shultz LD, Greiner DL. Pretargeting vs. direct targeting of human betalox5 islet cells subcutaneously implanted in mice using an anti-human islet cell antibody. Nucl Med Biol 2012; 39:645-51. [PMID: 22316614 DOI: 10.1016/j.nucmedbio.2011.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 11/30/2011] [Accepted: 12/07/2011] [Indexed: 11/25/2022]
Abstract
INTRODUCTION We previously demonstrated MORF/cMORF pretargeting of human islets and betalox 5 cells (a human beta cell line) transplanted subcutaneously in mice with the anti-human islet antibody, HPi1. We now compare pretargeting with direct targeting in the beta cell transplant model to evaluate the degree to which target/non-target (T/NT) ratios may be improved by pretargeting. METHODS Specific binding of an anti-human islet antibody HPi1 to the beta cells transplanted subcutaneously in mice was examined against a negative control antibody. We then compared pretargeting by MORF-HPi1 plus 111In-labeled cMORF to direct targeting by 111In-labeled HPi1. RESULTS HPi1 binding to betalox5 human cells in the transplant was shown by immunofluorescence. Normal organ 111In backgrounds by pretargeting were always lower, although target accumulations were similar. More importantly, the transplant to pancreas and liver ratios was, respectively, 26 and 10 by pretargeting as compared to 9 and 0.6 by direct targeting. CONCLUSIONS Pretargeting greatly improves the T/NT ratios, and based on the estimated endocrine to exocrine ratio within a pancreas, pretargeting may be approaching the sensitivity required for successful imaging of human islets within this organ.
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Affiliation(s)
- Guozheng Liu
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
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Abstract
PURPOSE We have generated transgenic mouse lines expressing the positron emission tomography (PET) reporter gene, sr39tk, under the control of the mouse insulin I promoter (MIP-sr39tk) to image endogenous islets using PET. PROCEDURES The MIP-sr39tk transgene was constructed using the 8.3 kb fragment of the mouse insulin I promoter and the sr39tk coding sequence from the mrfp-hrl-ttk trifusion construct. Expression of sr39TK in beta cells was confirmed by fluorescence immunohistochemistry of pancreatic sections. Histological sections were used to determine beta cell mass, islet area and islet number. Beta cell function was determined using intraperitoneal glucose tolerance tests. For ex vivo biodistrubution, mice were injected i.v. with 9.25 MBq [(18)F]fluorohydroxymethyl-butyl-guanine (FHBG), euthanized 1 h later and pancreata and other organs were collected and counted. For PET scans, mice were injected i.v. with 9.25 MBq [(18)F]FHBG, and dynamic scans were conducted for 1 h, followed by a 30 min static acquisition. To induce type 1 diabetes-like symptoms, MIP-sr39tk mice were injected i.p. with 40 mg/kg streptozotocin (STZ) once per day for five consecutive days, and biodistribution and PET scans were conducted thereafter. RESULTS Ex vivo quantification of [(18)F]FHBG uptake in the pancreas showed a 4.5-fold difference in transgenic vs. non-transgenics, confirming that expression of sr39TK results in the retention of the PET tracer. In STZ-treated MIP-sr39tk mice, impairments in glucose tolerance and decreases in beta cell mass correlated significantly with a diminishment in [(18)F]FHBG uptake before fasting hyperglycemia became apparent. CONCLUSIONS The MIP-sr39tk mouse demonstrates that PET imaging can detect changes in beta cell mass that precede the onset of diabetes.
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Jahan M, Eriksson O, Johnström P, Korsgren O, Sundin A, Johansson L, Halldin C. Decreased defluorination using the novel beta-cell imaging agent [18F]FE-DTBZ-d4 in pigs examined by PET. EJNMMI Res 2011; 1:33. [PMID: 22214308 PMCID: PMC3284452 DOI: 10.1186/2191-219x-1-33] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 12/05/2011] [Indexed: 11/26/2022] Open
Abstract
Background Fluorine-18 dihydrotetrabenazine [DTBZ] analogues, which selectively target the vesicular monoamine transporter 2 [VMAT2], have been extensively studied for in vivo quantification of beta cell mass by positron-emission tomography [PET]. This study describes a novel deuterated radioligand [18F]fluoroethyl [FE]-DTBZ-d4, aimed to increase the stability against in vivo defluorination previously observed for [18F]FE-DTBZ. Methods [18F]FE-DTBZ-d4 was synthesized by alkylation of 9-O-desmethyl-(+)-DTBZ precursor with deuterated [18F]FE bromide ([18F]FCD2CD2Br). Radioligand binding potential [BP] was assessed by an in vitro saturation homogenate binding assay using human endocrine and exocrine pancreatic tissues. In vivo pharmacokinetics and pharmacodynamics [PK/PD] was studied in a porcine model by PET/computed tomography, and the rate of defluorination was quantified by compartmental modeling. Results [18F]FE-DTBZ-d4 was produced in reproducible good radiochemical yield in 100 ± 20 min. Radiochemical purity of the formulated product was > 98% for up to 5 h with specific radioactivities that ranged from 192 to 529 GBq/μmol at the end of the synthesis. The in vitro BP for VMAT2 in the islet tissue was 27.0 ± 8.8, and for the exocrine tissue, 1.7 ± 1.0. The rate of in vivo defluorination was decreased significantly (kdefluorination = 0.0016 ± 0.0007 min-1) compared to the non-deuterated analogue (kdefluorination = 0.012 ± 0.002 min-1), resulting in a six fold increase in half-life stability. Conclusions [18F]FE-DTBZ-d4 has similar PK and PD properties for VMAT2 imaging as its non-deuterated analogue [18F]FE-DTBZ in addition to gaining significantly increased stability against defluorination. [18F]FE-DTBZ-d4 is a prime candidate for future preclinical and clinical studies on focal clusters of beta cells, such as in intramuscular islet grafts.
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Affiliation(s)
- Mahabuba Jahan
- Karolinska Institutet, Department of Clinical Neuroscience, Centre for Psychiatry Research, Building R5:U1, Karolinska University Hospital, SE 171 76, Stockholm, Sweden.
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Multimodal image coregistration and inducible selective cell ablation to evaluate imaging ligands. Proc Natl Acad Sci U S A 2011; 108:20719-24. [PMID: 22143775 DOI: 10.1073/pnas.1109480108] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We combined multimodal imaging (bioluminescence, X-ray computed tomography, and PET), tomographic reconstruction of bioluminescent sources, and two unique, complementary models to evaluate three previously synthesized PET radiotracers thought to target pancreatic beta cells. The three radiotracers {[(18)F]fluoropropyl-(+)-dihydrotetrabenazine ([(18)F]FP-DTBZ), [(18)F](+)-2-oxiranyl-3-isobutyl-9-(3-fluoropropoxy)-10-methoxy-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinoline ((18)F-AV-266), and (2S,3R,11bR)-9-(3-fluoropropoxy)-2-(hydroxymethyl)-3-isobutyl-10-methoxy-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinolin-2-ol ((18)F-AV-300)} bind vesicular monoamine transporter 2. Tomographic reconstruction of the bioluminescent signal in mice expressing luciferase only in pancreatic beta cells was used to delineate the pancreas and was coregistered with PET and X-ray computed tomography images. This strategy enabled unambiguous identification of the pancreas on PET images, permitting accurate quantification of the pancreatic PET signal. We show here that, after conditional, specific, and rapid mouse beta-cell ablation, beta-cell loss was detected by bioluminescence imaging but not by PET imaging, given that the pancreatic signal provided by three PET radiotracers was not altered. To determine whether these ligands bound human beta cells in vivo, we imaged mice transplanted with luciferase-expressing human islets. The human islets were imaged by bioluminescence but not with the PET ligands, indicating that these vesicular monoamine transporter 2-directed ligands did not specifically bind beta cells. These data demonstrate the utility of coregistered multimodal imaging as a platform for evaluation and validation of candidate ligands for imaging islets.
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Eriksson O, Alavi A. Imaging the islet graft by positron emission tomography. Eur J Nucl Med Mol Imaging 2011; 39:533-42. [PMID: 21932118 DOI: 10.1007/s00259-011-1928-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 08/22/2011] [Indexed: 10/17/2022]
Abstract
Clinical islet transplantation is being investigated as a permanent cure for type 1 diabetes mellitus (T1DM). Currently, intraportal infusion of islets is the favoured procedure, but several novel implantation sites have been suggested. Noninvasive longitudinal methodologies are an increasingly important tool for assessing the fate of transplanted islets, their mass, function and early signs of rejection. This article reviews the approaches available for islet graft imaging by positron emission tomography and progress in the field, as well as future challenges and opportunities.
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Affiliation(s)
- Olof Eriksson
- Preclinical PET Platform, Department of Medicinal Chemistry, Uppsala University, Uppsala, Sweden.
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Vallabhajosula S, Solnes L, Vallabhajosula B. A Broad Overview of Positron Emission Tomography Radiopharmaceuticals and Clinical Applications: What Is New? Semin Nucl Med 2011; 41:246-64. [PMID: 21624560 DOI: 10.1053/j.semnuclmed.2011.02.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Tsao HH, Skovronsky DM, Lin KJ, Yen TC, Wey SP, Kung MP. Sigma receptor binding of tetrabenazine series tracers targeting VMAT2 in rat pancreas. Nucl Med Biol 2011; 38:1029-34. [PMID: 21982574 DOI: 10.1016/j.nucmedbio.2011.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Revised: 02/17/2011] [Accepted: 03/28/2011] [Indexed: 11/19/2022]
Abstract
UNLABELLED The vesicular monoamine transporter type II (VMAT2) is highly expressed in pancreatic β-cells and thus has been proposed to be a potential target for measuring β-cell mass (BCM) by molecular imaging. Several tracers based on the TBZ backbone, including 9-fluoropropyl-(+)-dihydrotetrabenazine ([(18)F]AV-133), have shown some promising results as potential biomarkers for BCM despite a relatively high background signal in the pancreas. In the present study, we explore the background binding characteristics of [(18)F]AV-133 in rat pancreas. METHODS Pancreatic exocrine cells and islet cells were isolated and purified from Sprague-Dawley rats. Membrane homogenates, prepared from both pancreatic exocrine and islet cells as well as from brain striatum regions, were used for in vitro binding studies of [(18)F]AV-133 under a selective masking condition. 1,3-Di-o-tolylguanidine (DTG), displaying high and roughly equal affinity for both sigma-1 and sigma-2 receptors, was chosen at 5 μM concentration for the masking/blocking studies. RESULTS [(18)F]AV-133 binding to rat striatum homogenates was not significantly altered by the presence of DTG. In contrast, [(18)F]AV-133 showed significant competition with DTG for binding sites in rat pancreatic exocrine homogenates as well as in rat islet cell homogenates. Importantly, in the presence of DTG, [(18)F]AV-133 showed a single high-affinity binding site on islet cell homogenates with a K(d) value of 3.8 nM which is consistent with the affinity reported previously for VMAT2 sites in rat pancreas. CONCLUSIONS [(18)F]AV-133, in addition to a high-affinity VMAT2 binding site, binds with low affinity (but high capacity) to sigma components that are present in the rat pancreas. Identification of the cause of background binding of [(18)F]AV-133 to rat pancreatic tissue may lead to improved methods for quantification.
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Affiliation(s)
- Hsin-Hsin Tsao
- Department of Nuclear Medicine, Molecular Imaging Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan
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Yong J, Rasooly J, Dang H, Lu Y, Middleton B, Zhang Z, Hon L, Namavari M, Stout DB, Atkinson MA, Tian J, Gambhir SS, Kaufman DL. Multimodality imaging of β-cells in mouse models of type 1 and 2 diabetes. Diabetes 2011; 60:1383-92. [PMID: 21441442 PMCID: PMC3292311 DOI: 10.2337/db10-0907] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE β-Cells that express an imaging reporter have provided powerful tools for studying β-cell development, islet transplantation, and β-cell autoimmunity. To further expedite diabetes research, we generated transgenic C57BL/6 "MIP-TF" mice that have a mouse insulin promoter (MIP) driving the expression of a trifusion (TF) protein of three imaging reporters (luciferase/enhanced green fluorescent protein/HSV1-sr39 thymidine kinase) in their β-cells. This should enable the noninvasive imaging of β-cells by charge-coupled device (CCD) and micro-positron emission tomography (PET), as well as the identification of β-cells at the cellular level by fluorescent microscopy. RESEARCH DESIGN AND METHODS MIP-TF mouse β-cells were multimodality imaged in models of type 1 and type 2 diabetes. RESULTS MIP-TF mouse β-cells were readily identified in pancreatic tissue sections using fluorescent microscopy. We show that MIP-TF β-cells can be noninvasively imaged using microPET. There was a correlation between CCD and microPET signals from the pancreas region of individual mice. After low-dose streptozotocin administration to induce type 1 diabetes, we observed a progressive reduction in bioluminescence from the pancreas region before the appearance of hyperglycemia. Although there have been reports of hyperglycemia inducing proinsulin expression in extrapancreatic tissues, we did not observe bioluminescent signals from extrapancreatic tissues of diabetic MIP-TF mice. Because MIP-TF mouse β-cells express a viral thymidine kinase, ganciclovir treatment induced hyperglycemia, providing a new experimental model of type 1 diabetes. Mice fed a high-fat diet to model early type 2 diabetes displayed a progressive increase in their pancreatic bioluminescent signals, which were positively correlated with area under the curve-intraperitoneal glucose tolerance test (AUC-IPGTT). CONCLUSIONS MIP-TF mice provide a new tool for monitoring β-cells from the single cell level to noninvasive assessments of β-cells in models of type 1 diabetes and type 2 diabetes.
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Affiliation(s)
- Jing Yong
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Julia Rasooly
- Departments of Radiology, Bioengineering, and Materials Science and Engineering, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, California
| | - Hoa Dang
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Yuxin Lu
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Blake Middleton
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Zesong Zhang
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Larry Hon
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Mohammad Namavari
- Departments of Radiology, Bioengineering, and Materials Science and Engineering, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, California
| | - David B. Stout
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Mark A. Atkinson
- Departments of Pathology and Pediatrics, University of Florida, Gainesville, Florida
| | - Jide Tian
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
| | - Sanjiv Sam Gambhir
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
- Departments of Radiology, Bioengineering, and Materials Science and Engineering, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, California
| | - Daniel L. Kaufman
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, California
- Corresponding author: Daniel L. Kaufman,
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Liu G, Dou S, Cheng D, Leif J, Rusckowski M, Streeter PR, Shultz LD, Hnatowich DJ, Greiner DL. Human islet cell MORF/cMORF pretargeting in a xenogeneic murine transplant model. Mol Pharm 2011; 8:767-73. [PMID: 21361360 DOI: 10.1021/mp100382m] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Noninvasive measurement of human islet cell mass in pancreas or following islet transplantation by nuclear imaging has yet to be achieved. It has been shown using mouse tumor models that pretargeting imaging strategies are sensitive and can greatly increase target to nontarget signal ratios. The objective now is to demonstrate the specific pretargeting of human islet cells in mice. Our pretargeting strategy uses an anti-human islet cell antibody HPi1, conjugated to a phosphorodiamidate morpholino oligomer (MORF) that binds specifically to a (99m)Tc labeled complementary MORF (cMORF). Sensitivity and specificity of the pretargeting were first validated in culture using a human beta cell line (betalox5) and a negative control human cell line (HEK293). Pretargeting was then used to target and visualize these two cell lines and human islets transplanted subcutaneously in NOD-scid IL2rγ(null) mice. In culture, (99m)Tc accumulation on the betalox5 cells pretargeted by MORF-HPi1 was 100-fold higher than on untreated betalox5 cells or following treatment with native HPi1 and much higher than on the MORF-HPi1 pretargeted control HEK293 cells. Small animal imaging readily localized the transplanted betalox5 cells and human islets, but not the HEK293 cells. Ex vivo counting demonstrated 3-fold higher (99m)Tc accumulation in the transplanted betalox5 cells and human islets than in the control HEK293 cells. The target accumulation was also shown to increase linearly with increased numbers of the implanted betalox5 cells. These results demonstrate specific binding of radioactivity and successful imaging of human betalox5 cells and human islets transplanted in mice. Thus MORF/cMORF pretargeting may be useful to measure noninvasively human islet cell mass within the pancreas or following islet transplantation.
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Affiliation(s)
- Guozheng Liu
- Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
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Pancreatic beta cell mass PET imaging and quantification with [11C]DTBZ and [18F]FP-(+)-DTBZ in rodent models of diabetes. Mol Imaging Biol 2010; 13:973-84. [PMID: 20824509 DOI: 10.1007/s11307-010-0406-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 07/06/2010] [Indexed: 12/15/2022]
Abstract
PURPOSE The aim of this study is to compare the utility of two positron emission tomography (PET) imaging ligands ((+)-[(11)C]dihydrotetrabenazine ([(11)C]DTBZ) and the fluoropropyl analog ([(18)F]FP-(+)-DTBZ)) that target islet β-cell vesicular monoamine transporter type II to measure pancreatic β-cell mass (BCM). PROCEDURES [(11)C]DTBZ or [(18)F]FP-(+)-DTBZ was injected, and serial PET images were acquired in rat models of diabetes (streptozotocin-treated and Zucker diabetic fatty) and β-cell compensation (Zucker fatty). Radiotracer standardized uptake values (SUV) were correlated to pancreas insulin content measured biochemically and histomorphometrically. RESULTS On a group level, a positive correlation of [(11)C]DTBZ pancreatic SUV with pancreas insulin content and BCM was observed. In the STZ diabetic model, both [(18)F]FP-(+)-DTBZ and [(11)C]DTBZ correlated positively with BCM, although only ∼25% of uptake could be attributed to β-cell uptake. [(18)F]FP-(+)-DTBZ displacement studies indicate that there is a substantial fraction of specific binding that is not to pancreatic islet β cells. CONCLUSIONS PET imaging with [(18)F]FP-(+)-DTBZ provides a noninvasive means to quantify insulin-positive BCM and may prove valuable as a diagnostic tool in assessing treatments to maintain or restore BCM.
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85
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Affiliation(s)
- Guy M Bormans
- Laboratory for Radiopharmaceutical, Sciences, KU Leuven, Leuven, Belgium.
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86
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Fagerholm V, Mikkola KK, Ishizu T, Arponen E, Kauhanen S, Någren K, Solin O, Nuutila P, Haaparanta M. Assessment of islet specificity of dihydrotetrabenazine radiotracer binding in rat pancreas and human pancreas. J Nucl Med 2010; 51:1439-46. [PMID: 20720057 DOI: 10.2967/jnumed.109.074492] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Vesicular monoamine transporter 2 (VMAT2) is a putative molecular target for the quantitative imaging of pancreatic beta-cell mass by PET. The VMAT2 PET tracer (11)C-dihydrotetrabenazine ((11)C-DTBZ) exhibits high pancreatic uptake that is reduced in type 1 diabetes. The aim of this study was to assess the islet and VMAT2 specificity of DTBZ binding in the pancreas. METHODS The biodistribution of (11)C-DTBZ in rats was determined 10 and 60 min after injection. The localization of DTBZ radioactivity in rat and human pancreatic tissue sections was investigated by autoradiography. Saturation and competition binding assays were performed with (3)H-DTBZ and sections of rat pancreatic and control tissues. The binding of (11)C-DTBZ in pancreatic sections from rats with streptozotocin-induced diabetes was compared with that in control rats. RESULTS The values for the pancreatic uptake of (11)C-DTBZ (percentage injected dose per gram of tissue) were 3.0 at 10 min and 2.7 at 60 min. At 10 min, pancreatic radioactivity was heterogeneously distributed, with higher levels toward the head of the pancreas (head-to-tail ratio, 1.7). No such gradient was observed in pancreatic sections incubated with (11)C-DTBZ and (3)H-DTBZ in vitro. In rats, (11)C-DTBZ and (3)H-DTBZ binding in pancreatic islets did not exceed binding in the exocrine pancreas. Saturable (3)H-DTBZ binding was observed in the rat brain striatum (dissociation constant [K(d)], 1.3 nM) and the bovine adrenal medulla (K(d), 3.3 nM), whereas in the rat pancreas, (3)H-DTBZ binding was nonsaturable. Competition binding with (3)H-DTBZ and VMAT2 antagonists also indicated that DTBZ binding in the rat pancreas was nonspecific and did not represent binding to VMAT2. Nonspecific pancreatic (11)C-DTBZ binding was lower in rats with streptozotocin-induced diabetes than in control rats. In sections of human pancreas, a subset of pancreatic islets were weakly but VMAT2-specifically labeled with (3)H-DTBZ. CONCLUSION The results showed that the pancreatic uptake of (11)C-DTBZ is mainly due to nonspecific binding in the exocrine pancreas and suggested that the reduction in pancreatic (11)C-DTBZ binding observed in type 1 diabetes is not specific for the loss of beta-cell mass.
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87
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Current world literature. Curr Opin Endocrinol Diabetes Obes 2010; 17:384-93. [PMID: 20588116 DOI: 10.1097/med.0b013e32833c4b2b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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88
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Abstract
In both type 1 and type 2 diabetes mellitus, beta-cell mass (BCM), which exclusively produces insulin, is lost. Various therapeutic strategies are being developed that target BCM to restore its function by promoting beta-cell neogenesis and regeneration or by preventing its apoptosis. To this end, it is essential to identify biomarkers of BCM. Of the various imaging platforms, radionuclide-based imaging methods using radioligands that directly target BCM appear promising. In particular, the vesicular monoamine transporter type 2 (VMAT2), which is expressed almost exclusively by beta-cells and found in close association with insulin, can be noninvasively imaged with PET and (11)C-dihydrotetrabenazine or its derivatives. Despite the major limitation that beta-cells are low in abundance (1%-2%) and dispersed throughout the pancreas, VMAT2 PET is sensitive enough to detect VMAT2 signal and to allow kinetic model-based quantification of VMAT2 binding within the pancreas. However, these techniques are still in early stages, and careful further evaluations and technical developments are needed before they can be clinically used as a valid biomarker of BCM.
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Affiliation(s)
- Masanori Ichise
- Department of Radiology, Columbia University Medical College, New York, New York 11032, USA.
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89
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Flamez D, Roland I, Berton A, Kutlu B, Dufrane D, Beckers MC, De Waele E, Rooman I, Bouwens L, Clark A, Lonneux M, Jamar JF, Goldman S, Maréchal D, Goodman N, Gianello P, Van Huffel C, Salmon I, Eizirik DL. A genomic-based approach identifies FXYD domain containing ion transport regulator 2 (FXYD2)gammaa as a pancreatic beta cell-specific biomarker. Diabetologia 2010; 53:1372-83. [PMID: 20379810 DOI: 10.1007/s00125-010-1714-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 01/13/2010] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Non-invasive imaging of the pancreatic beta cell mass (BCM) requires the identification of novel and specific beta cell biomarkers. We have developed a systems biology approach to the identification of promising beta cell markers. METHODS We followed a functional genomics strategy based on massive parallel signal sequencing (MPSS) and microarray data obtained in human islets, purified primary rat beta cells, non-beta cells and INS-1E cells to identify promising beta cell markers. Candidate biomarkers were validated and screened using established human and macaque (Macacus cynomolgus) tissue microarrays. RESULTS After a series of filtering steps, 12 beta cell-specific membrane proteins were identified. For four of the proteins we selected or produced antibodies targeting specifically the human proteins and their splice variants; all four candidates were confirmed as islet-specific in human pancreas. Two splice variants of FXYD domain containing ion transport regulator 2 (FXYD2), a regulating subunit of the Na(+)-K(+)-ATPase, were identified as preferentially present in human pancreatic islets. The presence of FXYD2gammaa was restricted to pancreatic islets and selectively detected in pancreatic beta cells. Analysis of human fetal pancreas samples showed the presence of FXYD2gammaa at an early stage (15 weeks). Histological examination of pancreatic sections from individuals with type 1 diabetes or sections from pancreases of streptozotocin-treated Macacus cynomolgus monkeys indicated a close correlation between loss of FXYD2gammaa and loss of insulin-positive cells. CONCLUSIONS/INTERPRETATION We propose human FXYD2gammaa as a novel beta cell-specific biomarker.
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Affiliation(s)
- D Flamez
- Laboratory of Experimental Medicine, Université Libre de Bruxelles, Route de Lennik 808, 1070, Brussels, Belgium.
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Hardy MA, Witkowski P, Sondermeijer H, Harris P. The long road to pancreatic islet transplantation. World J Surg 2010; 34:625-7. [PMID: 19830482 DOI: 10.1007/s00268-009-0246-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mark A Hardy
- Department of Surgery, Columbia University College of Physicians and Surgeons, 177 Fort Washington Ave., Milstein Pavilion, 7 SK, New York, NY, 10032, USA.
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Tsao HH, Lin KJ, Juang JH, Skovronsky DM, Yen TC, Wey SP, Kung MP. Binding characteristics of 9-fluoropropyl-(+)-dihydrotetrabenzazine (AV-133) to the vesicular monoamine transporter type 2 in rats. Nucl Med Biol 2010; 37:413-9. [DOI: 10.1016/j.nucmedbio.2010.01.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 12/22/2009] [Accepted: 01/07/2010] [Indexed: 10/19/2022]
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92
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Eriksson O, Jahan M, Johnström P, Korsgren O, Sundin A, Halldin C, Johansson L. In vivo and in vitro characterization of [18F]-FE-(+)-DTBZ as a tracer for beta-cell mass. Nucl Med Biol 2010; 37:357-63. [DOI: 10.1016/j.nucmedbio.2009.12.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 12/03/2009] [Accepted: 12/06/2009] [Indexed: 11/16/2022]
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Liu G, Dou S, Rusckowski M, Greiner D, Hnatowich D. Preparation of (111)In-DTPA morpholino oligomer for low abdominal accumulation. Appl Radiat Isot 2010; 68:1709-14. [PMID: 20359901 DOI: 10.1016/j.apradiso.2010.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 02/18/2010] [Accepted: 03/02/2010] [Indexed: 02/04/2023]
Abstract
An ability to quantitate the beta cell mass by noninvasive nuclear imaging will be very useful in the prevention, diagnosis, and treatment of diabetes. However, to be successful, radioactivity from the pancreas must not be obscured by the background radioactivity in the abdomen. Pretargeting offers the promise of achieving high target organ to normal tissue ratios. In preparation for pancreas imaging studies by pretargeting using morpholino oligomers (MORF/cMORF), it was necessary to develop a simple and efficient method to radiolabel the cMORF effector. Because we have shown that labeling the cMORF with (111)In via DTPA reduces excretion into the intestines compared to labeling with (99m)Tc via MAG(3), the conjugation of DTPA to cMORF was investigated for (111)In labeling. The amine-derivatized cMORF was conjugated with DTPA using 1-ethyl-3(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as an alternative to the conventional cyclic anhydride. The conjugation efficiency (represented by the number of DTPA groups attached per cMORF) was investigated by changing the EDC, DTPA, and cMORF molar ratios. Different open columns were considered for the purification of DTPA-cMORF. Before conjugation, each cMORF molecule was confirmed to have an amine by trinitrobenzene sulfonic acid (TNBS) assay using the omega-amino butyric acid as positive standard and the non-amine derivatized cMORF as negative standard. The average number of DTPA groups per cMORF was 0.15-0.20 following the conjugation over a cMORF/DTPA molar ratio of 0.5-5 and over a cMORF/EDC molar ratio of 20-60. The conjugation efficiency was lower than expected probably due to steric hindrance. A 1 x 50cm P-4 column using ammonium acetate as eluting buffer provided an adequate separation of DTPA-cMORF from free DTPA. The (111)In labeling efficiency by transchelation from acetate exceeded 95%, thus avoiding the need for postlabeling purification. Despite the lower than expected conjugation efficiency in which no more than one-fifth of the cMORF were DTPA-derivatized, a specific radioactivity of at least 300microCi/microg or 1.90Ci/micromol of cMORF was achieved. In conclusion, a protocol is described for (111)In-DTPA-cMORF that provides the high specific activity favorable to beta cell imaging because of the low mass fraction of beta cells in pancreas (1-2%) and obviates the need for postlabeling purification.
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Affiliation(s)
- Guozheng Liu
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA 01655-0243, USA.
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94
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Abstract
BACKGROUND Because the hepatic portal system may not be the optimal site for islet transplantation, several extrahepatic sites have been studied. Here, we examine an intramuscular transplantation site, bioengineered to better support islet neovascularization, engraftment, and survival, and we demonstrate that at this novel site, grafted beta cell mass may be quantitated in a real-time noninvasive manner by positron emission tomography (PET) imaging. METHODS Streptozotocin-induced rats were pretreated intramuscularly with a biocompatible angiogenic scaffold received syngeneic islet transplants 2 weeks later. The recipients were monitored serially by blood glucose and glucose tolerance measurements and by PET imaging of the transplant site with [11C] dihydrotetrabenazine. Parallel histopathologic evaluation of the grafts was performed using insulin staining and evaluation of microvasularity. RESULTS Reversal of hyperglycemia by islet transplantation was most successful in recipients pretreated with bioscaffolds containing angiogenic factors when compared with those who received no bioscaffolds or bioscaffolds not treated with angiogenic factors. PET imaging with [11C] dihydrotetrabenazine, insulin staining, and microvascular density patterns were consistent with islet survival, increased levels of angiogenesis, and with reversal of hyperglycemia. CONCLUSIONS Induction of increased neovascularization at an intramuscular site significantly improves islet transplant engraftment and survival compared with controls. The use of a nonhepatic transplant site may avoid intrahepatic complications and permit the use of PET imaging to measure and follow transplanted beta cell mass in real time. These findings have important implications for effective islet implantation outside of the liver and offer promising possibilities for improving islet survival, monitoring, and even prevention of islet loss.
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95
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Ueberberg S, Meier JJ, Waengler C, Schechinger W, Dietrich JW, Tannapfel A, Schmitz I, Schirrmacher R, Köller M, Klein HH, Schneider S. Generation of novel single-chain antibodies by phage-display technology to direct imaging agents highly selective to pancreatic beta- or alpha-cells in vivo. Diabetes 2009; 58:2324-34. [PMID: 19592622 PMCID: PMC2750237 DOI: 10.2337/db09-0658] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 07/03/2009] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Noninvasive determination of pancreatic beta-cell mass in vivo has been hampered by the lack of suitable beta-cell-specific imaging agents. This report outlines an approach for the development of novel ligands homing selectively to islet cells in vivo. RESEARCH DESIGN AND METHODS To generate agents specifically binding to pancreatic islets, a phage library was screened for single-chain antibodies (SCAs) on rat islets using two different approaches. 1) The library was injected into rats in vivo, and islets were isolated after a circulation time of 5 min. 2) Pancreatic islets were directly isolated, and the library was panned in the islets in vitro. Subsequently, the identified SCAs were extensively characterized in vitro and in vivo. RESULTS We report the generation of SCAs that bind highly selective to either beta- or alpha-cells. These SCAs are internalized by target cells, disappear rapidly from the vasculature, and exert no toxicity in vivo. Specific binding to beta- or alpha-cells was detected in cell lines in vitro, in rats in vivo, and in human tissue in situ. Electron microscopy demonstrated binding of SCAs to the endoplasmatic reticulum and the secretory granules. Finally, in a biodistribution study the labeling intensity derived from [(125)I]-labeled SCAs after intravenous administration in rats strongly predicted the beta-cell mass and was inversely related to the glucose excursions during an intraperitoneal glucose tolerance test. CONCLUSIONS Our data provide strong evidence that the presented SCAs are highly specific for pancreatic beta-cells and enable imaging and quantification in vivo.
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Affiliation(s)
- Sandra Ueberberg
- Department of Internal Medicine I, Division of Endocrinology and Metabolism, Berufsgenossenschaftliches University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany
| | - Juris J. Meier
- Department of Internal Medicine I, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Carmen Waengler
- Department of Nuclear Medicine, Hospital of the Ludwig-Maximilians-University, Munich, Germany
- Department of Neurology & Neurosurgery, Lady Davis Institute for Medical Research, McGill University, Montreal, Canada
| | - Wolfgang Schechinger
- Department of Internal Medicine I, Division of Endocrinology and Metabolism, Berufsgenossenschaftliches University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany
| | - Johannes W. Dietrich
- Department of Internal Medicine I, Division of Endocrinology and Metabolism, Berufsgenossenschaftliches University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany
| | - Andrea Tannapfel
- Institute for Pathology, Ruhr-University Bochum, Bochum, Germany
| | - Inge Schmitz
- Institute for Pathology, Ruhr-University Bochum, Bochum, Germany
| | - Ralf Schirrmacher
- Department of Neurology & Neurosurgery, Lady Davis Institute for Medical Research, McGill University, Montreal, Canada
| | - Manfred Köller
- Chirurgische Forschung, Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil, Ruhr-Universität Bochum, Bochum, Germany
| | - Harald H. Klein
- Department of Internal Medicine I, Division of Endocrinology and Metabolism, Berufsgenossenschaftliches University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany
| | - Stephan Schneider
- Department of Internal Medicine I, Division of Endocrinology and Metabolism, Berufsgenossenschaftliches University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany
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Bibliography. Current world literature. Curr Opin Endocrinol Diabetes Obes 2009; 16:328-37. [PMID: 19564733 DOI: 10.1097/med.0b013e32832eb365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Atkinson MA, Gianani R. The pancreas in human type 1 diabetes: providing new answers to age-old questions. Curr Opin Endocrinol Diabetes Obes 2009; 16:279-85. [PMID: 19502978 DOI: 10.1097/med.0b013e32832e06ba] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
PURPOSE OF REVIEW Although studies of pancreata from type 1 diabetes (T1D) patients largely fell dormant for a period of decades, research efforts have recently been 'rekindled' in this area to address, using modern techniques, many unanswered questions related to the pathogenesis of this disease. RECENT FINDINGS As historically noted, a pancreatic infiltrate commonly referred to as 'insulitis' is present at the symptomatic onset of T1D. Recent studies have further characterized this infiltrate both in terms of its cellular composition as well as the mechanisms that likely underlie beta cell death in T1D. In addition, the notion that the pancreas from T1D patients is completely devoid of insulin producing cells years after the onset of disease has been challenged, whereas the concepts of whether beta cell regeneration or replication are present have also been subject to much debate. Novel concepts regarding the rate and degree of beta cell loss throughout the natural history of the disease have also been put forward to aid in explaining the disorder's pathogenesis. SUMMARY Although answers to many long-standing questions in T1D have recently been addressed, perhaps the main finding has been one supporting a disease of remarkable heterogeneity. However, additional lessons remain to be learned from the pancreas in T1D. Hence, attempts aimed at organizing the scientific community to address these issues are ongoing, particularly those from collaborative efforts, including the Belgium Organ Donor Consortium and the Network for Pancreatic Organ Donors with Diabetes (nPOD).
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Affiliation(s)
- Mark A Atkinson
- Department of Pathology, University of Florida,1600 SW Archer Road, Gainesville, Florida 32610, USA.
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98
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Abstract
Noninvasive imaging and quantification of pancreatic, insulin-producing beta cells has been considered a high-priority field of investigation for the past decade. In the first review on this issue, attention was already paid to various agents for labeling beta cells, including 6-(125)I-D-glucose, (65)Zn, (3)H-glibenclamide, (3)H-mitiglinide, an (125)I-labeled mouse monoclonal antibody against beta-cell surface ganglioside(s), D-(U-(14)C)-glucose and 2-deoxy-2-(18)F-D-glucose to label glycogen accumulated in beta cells in response to sustained hyperglycemia, and, last but not least, an analog of D-mannoheptulose. This Review discusses these methods and further contributions. For instance, emphasis is placed on labeling beta cells with (11)C-dihydrotetrabenazine, which is the most advanced method at present. Attention is also drawn to the latest approaches for noninvasive imaging and functional characterization of pancreatic beta cells. None of these procedures is used in clinical practice yet.
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Fagan SP, Fischman AJ. Pancreatic Imaging with 11C-Dihydrotetrabenazine PET: A Perspective. J Nucl Med 2009; 50:335-7. [DOI: 10.2967/jnumed.108.059568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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