Direct inhibition by angiotensin II of insulin-dependent glucose transport activity in mammalian skeletal muscle involves a ROS-dependent mechanism

No previous study has investigated how the vaso-constrictive peptide Ang II impacts insulin action in isolated mammalian skeletal muscle. We investigated the molecular actions of Ang II on insulin signalling and glucose transport in skeletal muscle from lean Zucker rats. Soleus strips were incubated with insulin (5 mU/ml) and/or Ang II (500nM) for 2 hours. Ang II caused significant (p<0.05) inhibition of insulin-stimulated glucose transport (39%) and decreased phosphorylation of Akt Ser⁴⁷³ (37%) and glycogen synthase kinase-3β Ser⁹ (42%) without affecting phosphorylation of IRS-1 Ser³⁰⁷ or p38 MAPK. We used the superoxide dismutase mimetic, tempol (1mM), to determine if reactive oxygen species (ROS) contribute to Ang II-mediated insulin resistance. Tempol partially reversed (42%) Ang II-induced inhibition of insulin-stimulated glucose transport. These results indicate that Ang II inhibits distal insulin signalling and insulin-stimulated glucose transport in isolated mammalian skeletal muscle, and that this effect is partially mediated by ROS.