Stretch-stimulated glucose uptake in skeletal muscle is mediated by reactive oxygen species and p38 MAP-kinase.
Alternatives to the canonical insulin-stimulated pathway for glucose uptake are exercise- and exogenous reactive oxygen species (ROS)-stimulated glucose uptake. We proposed a model wherein mechanical loading, i.e. stretch, stimulates production of ROS to activate AMP-activated kinase (AMPK) to increase glucose uptake. Immunoblotting was used to measure protein phosphorylation; the fluorochrome probe 2'7'-dichlorofluorescin diacetate was used to measure cytosolic oxidant activity and 2-deoxy-d[1,2-(3)H]glucose was used to measure glucose uptake. The current studies demonstrate that stretch increases ROS, AMPKalpha phosphorylation and glucose transport in murine extensor digitorum longus (EDL) muscle (+121%, +164% and +184%, respectively; P < 0.05). We also demonstrate that stretch-induced glucose uptake persists in transgenic mice expressing an inactive form of the AMPKalpha2 catalytic subunit in skeletal muscle (+173%; P < 0.05). MnTBAP, a superoxide dismutase (SOD) mimetic, N-acteyl cysteine (NAC), a non-specific antioxidant, ebselen, a glutathione mimetic, or combined SOD plus catalase (ROS-selective scavengers) all decrease stretch-stimulated glucose uptake (P < 0.05) without changing basal uptake (P > 0.16). We also demonstrate that stretch-stimulated glucose uptake persists in the presence of the phosphatidylinositol 3-kinase (PI3-K) inhibitors wortmannin and LY294001 (P < 0.05) but is diminished by the p38-MAPK inhibitors SB203580 and A304000 (P > 0.99). These data indicate that stretch-stimulated glucose uptake in skeletal muscle is mediated by a ROS- and p38 MAPK-dependent mechanism that appears to be AMPKalpha2- and PI3-K-independent.
Chambers
Melissa A
MA
Department of Physiology, University of Kentucky, Lexington, 40536-0298, USA. masmit8@uky.edu
Moylan
Jennifer S
JS
Smith
Jeffrey D
JD
Goodyear
Laurie J
LJ
Reid
Michael B
MB
D055372:AMP-Activated Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002478:Cells, Cultured; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013314:Stress, Mechanical; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D017382:Reactive Oxygen Species; D019869:Phosphatidylinositol 3-Kinases; C534978:Prkaa2 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases; D005947:Glucose