IRS1 and Hyperglycemia: Thiazolidinediones can prevent or reverse the toxic effect of hyperglycemia on tyrosine kinase, promote the phosphorylation of IRS‐1 (Shen et al., 2004), increase the level of GLUT‐4 mRNA and protein in the skeletal muscle of insulin‐resistant mice, and promote the translocation of GLUT‐4 in the skeletal muscle (Yonemitsu et al., 2001).