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-H-3]glucose was used to measure glucose uptake. The current studies demonstrate that stretch increases ROS, AMPK alpha 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 AMPK alpha 2 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 AMPK alpha 2- and PI3-K-independent.