Oxidative stress can contribute to the multifactorial etiology of whole body and skeletal muscle
insulin resistance. No investigation has directly assessed the effect of an in vitro
oxidant stress on
insulin action in intact mammalian skeletal muscle. Therefore, the purpose of the present study was to characterize the molecular actions of a low-grade
oxidant stress (H(2)O(2)) on
insulin signaling and
glucose transport in isolated skeletal muscle of lean Zucker rats. Soleus strips were incubated in 8 mM
glucose for 2 h in the absence or presence of 100 mU/ml
glucose oxidase, which produces H(2)O(2) at approximately 90 microM. By itself, H(2)O(2) significantly (P < 0.05) activated basal
glucose transport activity, net
glycogen synthesis, and
glycogen synthase activity and increased phosphorylation of
insulin receptor (Tyr), Akt (Ser(473)), and
GSK-3beta (Ser(9)). In contrast, this
oxidant stress significantly inhibited the expected
insulin-mediated enhancements in
glucose transport,
glycogen synthesis, and these signaling factors and allowed
GSK-3beta to retain a more active form. In the presence of CT-98014, a selective
GSK-3 inhibitor, the ability of
insulin to stimulate
glucose transport and
glycogen synthesis during exposure to this
oxidant stress was enhanced by 20% and 39% (P < 0.05), respectively, and
insulin stimulation of the phosphorylation of
insulin receptor, Akt, and
GSK-3 was significantly increased by 36-58% (P < 0.05). These results indicate that an
oxidant stress can directly and rapidly induce substantial
insulin resistance of skeletal muscle
insulin signaling,
glucose transport, and
glycogen synthesis. Moreover, a small, but significant, portion of this oxidative stress-induced
insulin resistance is associated with a reduced
insulin-mediated suppression of the active form of
GSK-3beta.