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, AMPKα 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 AMPKα2 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 AMPKα2‐ and PI3‐K‐independent.