Spatial insulin signalling in isolated skeletal muscle preparations |
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Authors: | Peter Sogaard Ferenc Szekeres Pablo M Garcia‐Roves Dennis Larsson Alexander V Chibalin Juleen R Zierath |
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Institution: | 1. Department of Molecular Medicine and Surgery, Section Integrative Physiology, Karolinska Institutet, S‐171 77 Stockholm, Sweden;2. Department of Biomedicine, School of Life Sciences, Systems Biology Research Centre, University of Sk?vde, Box 408, 541 28 Sk?vde, Sweden;3. Department of Physiology and Pharmacology, Section Integrative Physiology, Karolinska Institutet, S‐171 77 Stockholm, Sweden |
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Abstract: | During in vitro incubation in the absence or presence of insulin, glycogen depletion occurs in the inner core of the muscle specimen, concomitant with increased staining of hypoxia‐induced‐factor‐1‐alpha and caspase‐3, markers of hypoxia and apoptosis, respectively. The aim of this study was to determine whether insulin is able to diffuse across the entire muscle specimen in sufficient amounts to activate signalling cascades to promote glucose uptake and glycogenesis within isolated mouse skeletal muscle. Phosphoprotein multiplex assay on lysates from muscle preparation was performed to detect phosphorylation of insulin‐receptor on Tyr1146, Akt on Ser473 and glycogen‐synthases‐kinase‐3 on Ser21/Ser9. To address the spatial resolution of insulin signalling, immunohistochemistry studies on cryosections were performed. Our results provide evidence to suggest that during the in vitro incubation, insulin sufficiently diffuses into the centre of tubular mouse muscles to promote phosphorylation of these signalling events. Interestingly, increased insulin signalling was observed in the core of the incubated muscle specimens, correlating with the location of oxidative fibres. In conclusion, insulin action was not restricted due to insufficient diffusion of the hormone during in vitro incubation in either extensor digitorum longus or soleus muscles from mouse under the specific experimental settings employed in this study. Hence, we suggest that the glycogen depleted core as earlier observed is not due to insufficient insulin action. J. Cell. Biochem. 109: 943–949, 2010. © 2010 Wiley‐Liss, Inc. |
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Keywords: | in vitro incubation immunohistochemistry extensor digitorum longus soleus spatial |
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