Claudio Vinegoni, Ph.D. | Accurate measurement of pancreatic islet beta-cell mass using a second-generation fluorescent exendin-4 analog

P.N.A.S.
Accurate measurement of pancreatic islet beta-cell mass using a second-generation fluorescent exendin-4 analog

Reiner, T., Thurber, G., Gaglia, J., Vinegoni, C., Liew, C. W., Upadhyay, R., Kohler, R. H., Li, L., Kulkarni, R. N., Benoist, C., Mathis, D., and Weissleder^#, R.

Proceedings of the National Academy of Sciences of the United States of America 2011

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The hallmark of type 1 diabetes is autoimmune destruction of the insulin-producing beta-cells of the pancreatic islets. Autoimmune diabetes has been difficult to study or treat because it is not usually diagnosed until substantial beta-cell loss has already occurred. Imaging agents that permit noninvasive visualization of changes in beta-cell mass remain a high-priority goal. We report on the development and testing of a near-infrared fluorescent beta-cell imaging agent. Based on the amino acid sequence of exendin-4, we created a neopeptide via introduction of an unnatural amino acid at the K(12) position, which could subsequently be conjugated to fluorophores via bioorthogonal copper-catalyzed click-chemistry. Cell assays confirmed that the resulting fluorescent probe (E4(x12)-VT750) had a high binding affinity (similar to 3 nM). Its in vivo properties were evaluated using high-resolution intravital imaging, histology, whole-pancreas visualization, and endoscopic imaging. According to intravital microscopy, the probe rapidly bound to beta-cells and, as demonstrated by confocal microscopy, it was internalized. Histology of the whole pancreas showed a close correspondence between fluorescence and insulin staining, and there was an excellent correlation between imaging signals and beta-cell mass in mice treated with streptozotocin, a beta-cell toxin. Individual islets could also be visualized by endoscopic imaging. In short, E4(x12)-VT750 showed strong and selective binding to glucose-like peptide-1 receptors and permitted accurate measurement of beta-cell mass in both diabetic and nondiabetic mice. This near-infrared imaging probe, as well as future radioisotope-labeled versions of it, should prove to be important tools for monitoring diabetes, progression, and treatment in both experimental and clinical contexts.
@article{2011-PNAS, author= {Reiner, T. and Thurber, G. and Gaglia, J. and Vinegoni, C. and Liew, C. W. and Upadhyay, R. and Kohler, R. H. and Li, L. and Kulkarni, R. N. and Benoist, C. and Mathis, D. and Weissleder<sup>#</sup>, R.}, title= {Accurate measurement of pancreatic islet beta-cell mass using a second-generation fluorescent exendin-4 analog}, journal= {Proceedings of the National Academy of Sciences of the United States of America}, alternatejournal = {P.N.A.S.}, year = {2011}, volume = {108}, number = {31}, pages = {12815-12820}, issn = {0027-8424}, doi = {10.1073/pnas.1109859108}, pmcid = {PMC3150928}, pmid= {21768367} }
21768367

PMC3150928

10.1073/pnas.1109859108

Abstract

"The hallmark of type 1 diabetes is autoimmune destruction of the insulin-producing beta-cells of the pancreatic islets. Autoimmune diabetes has been difficult to study or treat because it is not usually diagnosed until substantial beta-cell loss has already occurred. Imaging agents that permit noninvasive visualization of changes in beta-cell mass remain a high-priority goal. We report on the development and testing of a near-infrared fluorescent beta-cell imaging agent. Based on the amino acid sequence of exendin-4, we created a neopeptide via introduction of an unnatural amino acid at the K(12) position, which could subsequently be conjugated to fluorophores via bioorthogonal copper-catalyzed click-chemistry. Cell assays confirmed that the resulting fluorescent probe (E4(x12)-VT750) had a high binding affinity (similar to 3 nM). Its in vivo properties were evaluated using high-resolution intravital imaging, histology, whole-pancreas visualization, and endoscopic imaging. According to intravital microscopy, the probe rapidly bound to beta-cells and, as demonstrated by confocal microscopy, it was internalized. Histology of the whole pancreas showed a close correspondence between fluorescence and insulin staining, and there was an excellent correlation between imaging signals and beta-cell mass in mice treated with streptozotocin, a beta-cell toxin. Individual islets could also be visualized by endoscopic imaging. In short, E4(x12)-VT750 showed strong and selective binding to glucose-like peptide-1 receptors and permitted accurate measurement of beta-cell mass in both diabetic and nondiabetic mice. This near-infrared imaging probe, as well as future radioisotope-labeled versions of it, should prove to be important tools for monitoring diabetes, progression, and treatment in both experimental and clinical contexts."

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For attribution in academic contexts, please cite this work as:

Reiner, T., Thurber, G., Gaglia, J., Vinegoni, C., Liew, C. W., Upadhyay, R., Kohler, R. H., Li, L., Kulkarni, R. N., Benoist, C., Mathis, D., & Weissleder^#, R. (2011). Accurate measurement of pancreatic islet beta-cell mass using a second-generation fluorescent exendin-4 analog. Proceedings of the National Academy of Sciences of the United States of America, 108(31), 12815–12820. https://doi.org/10.1073/pnas.1109859108