Insulin-stimulated Glut 4 translocation in human skeletal muscle: a quantitative confocal microscopical assessment |
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Authors: | Simon C Watkins Alan Frederickson Remy Theriault Mary Korytkowski David S Turner David E Kelley |
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Institution: | (1) Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA;(2) Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA |
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Abstract: | Summary Insulin stimulation of glucose transport in skeletal muscle is considered to involve translocation of the skeletal muscle_adipose
tissue glucose transporter isoform, Glut 4, from cytosolic vesicles to the cell surface. The current study was undertaken
to investigate Glut 4 translocation in skeletal muscle of healthy volunteers during euglycaemic insulin infusion. Previous
quantitative studies of glucose transport have depended on differential centrifugation methods, which demand large biopsy
samples. In this study we have developed and applied a quantitative method using confocal laser microscopy, well suited to
the small needle biopsies that are typically available clinically. Percutaneous biopsy of vastus lateralis skeletal muscle
was performed during basal and euglycaemic insulin-stimulated conditions, and Glut 4 translocation was assessed using immunohistochemical
labelling and confocal laser microscopy imaging in 14 healthy lean subjects. At physiological hyperinsulinaemia (536 _ 16
pm), mean systemic glucose utilization was 9.27 _ 0.78 mg_kg-min, indicative of normal insulin sensitivity. The presence of
Glut 4 at the sarcolemma increased significantly (p· 0.01), with a ratio of insulin-stimulated to basal sarcolemmal Glut 4 of 1.85 _ 0.33, indicative of insulin-stimulated Glut
4 translocation. The area of Glut 4-labelled sites also increased significantly (p· 0.01) in response to insulin infusion; this ratio was 1.56 _ 0.13. Thus, at physiological hyperinsulinaemia, the amount
of Glut 4 at the cell surface of skeletal muscle in healthy, lean individuals increases approximately twofold over basal conditions,
and this process can be measured using immunohistochemical labelling imaged by confocal laser scanning microscopy.
This revised version was published online in November 2006 with corrections to the Cover Date. |
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