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Williams IM, Valenzuela FA, Kahl SD, Ramkrishna D, Mezo AR, Young JD, Wells KS, Wasserman DH. Insulin exits skeletal muscle capillaries by fluid-phase transport. J Clin Invest 2018; 128:699-714. [PMID: 29309051 DOI: 10.1172/jci94053] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 11/14/2017] [Indexed: 12/12/2022] Open
Abstract
Before insulin can stimulate myocytes to take up glucose, it must first move from the circulation to the interstitial space. The continuous endothelium of skeletal muscle (SkM) capillaries restricts insulin's access to myocytes. The mechanism by which insulin crosses this continuous endothelium is critical to understand insulin action and insulin resistance; however, methodological obstacles have limited understanding of endothelial insulin transport in vivo. Here, we present an intravital microscopy technique to measure the rate of insulin efflux across the endothelium of SkM capillaries. This method involves development of a fully bioactive, fluorescent insulin probe, a gastrocnemius preparation for intravital microscopy, an automated vascular segmentation algorithm, and the use of mathematical models to estimate endothelial transport parameters. We combined direct visualization of insulin efflux from SkM capillaries with modeling of insulin efflux kinetics to identify fluid-phase transport as the major mode of transendothelial insulin efflux in mice. Model-independent experiments demonstrating that insulin movement is neither saturable nor affected by insulin receptor antagonism supported this result. Our finding that insulin enters the SkM interstitium by fluid-phase transport may have implications in the pathophysiology of SkM insulin resistance as well as in the treatment of diabetes with various insulin analogs.
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Affiliation(s)
- Ian M Williams
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | | | - Steven D Kahl
- Lilly Research Laboratories, Indianapolis, Indiana, USA
| | | | - Adam R Mezo
- Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - Jamey D Young
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.,Department of Chemical and Biomolecular Engineering, and.,Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
| | - K Sam Wells
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.,Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
| | - David H Wasserman
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.,Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
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Albu SA, Al-Karmi SA, Vito A, Dzandzi JPK, Zlitni A, Beckford-Vera D, Blacker M, Janzen N, Patel RM, Capretta A, Valliant JF. (125)I-Tetrazines and Inverse-Electron-Demand Diels-Alder Chemistry: A Convenient Radioiodination Strategy for Biomolecule Labeling, Screening, and Biodistribution Studies. Bioconjug Chem 2016; 27:207-16. [PMID: 26699913 DOI: 10.1021/acs.bioconjchem.5b00609] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A convenient method to prepare radioiodinated tetrazines was developed, such that a bioorthogonal inverse electron demand Diels-Alder reaction can be used to label biomolecules with iodine-125 for in vitro screening and in vivo biodistribution studies. The tetrazine was prepared by employing a high-yielding oxidative halo destannylation reaction that concomitantly oxidized the dihydrotetrazine precursor. The product reacts quickly and efficiently with trans-cyclooctene derivatives. Utility was demonstrated through antibody and hormone labeling experiments and by evaluating products using standard analytical methods, in vitro assays, and quantitative biodistribution studies where the latter was performed in direct comparison to Bolton-Hunter and direct iodination methods. The approach described provides a convenient and advantageous alternative to conventional protein iodination methods that can expedite preclinical development and evaluation of biotherapeutics.
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Affiliation(s)
- Silvia A Albu
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Salma A Al-Karmi
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Alyssa Vito
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - James P K Dzandzi
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Aimen Zlitni
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Denis Beckford-Vera
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Megan Blacker
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Nancy Janzen
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Ramesh M Patel
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - Alfredo Capretta
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
| | - John F Valliant
- Department of Chemistry and Chemical Biology and ‡Centre for Probe Development and Commercialization, McMaster University , 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1
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3
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Jacob D, Joan Taylor M, Tomlins P, Sahota TS. Synthesis and Identification of FITC-Insulin Conjugates Produced Using Human Insulin and Insulin Analogues for Biomedical Applications. J Fluoresc 2015; 26:617-29. [PMID: 26658795 DOI: 10.1007/s10895-015-1748-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/07/2015] [Indexed: 11/30/2022]
Abstract
Human insulin was fluorescently labelled with fluorescein isothiocyanate (FITC) and the conjugate species produced were identified using high performance liquid chromatography and electrospray mass spectroscopy. Mono-labelled FITC-insulin conjugate (A1 or B1) was successfully produced using human insulin at short reaction times (up to 5 h) however the product always contained some unlabelled native human insulin. As the reaction time was increased over 45 h, no unlabelled native human insulin was present and more di-labelled FITC-insulin conjugate (A1B1) was produced than mono-labelled conjugate with the appearance of tri-labelled conjugate (A1B1B29) after 20 h reaction time. The quantities switch from mono-labelled to di-labelled FITC-insulin conjugate between reaction times 9 and 20 h. In the presence of phenol or m-cresol, there appears to be a 10 % decrease in the amount of mono-labelled conjugate and an increase in di-labelled conjugate produced at lower reaction times. Clinically used insulin analogues present in commercially available preparations were successfully fluorescently labelled for future biomedical applications.
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Affiliation(s)
- Dolly Jacob
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester, LE1 9BH, UK
| | - M Joan Taylor
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester, LE1 9BH, UK
| | - Paul Tomlins
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester, LE1 9BH, UK
| | - Tarsem S Sahota
- Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, The Gateway, Leicester, LE1 9BH, UK.
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