The complex mechanisms of peroxisome proliferator-activated receptor-γ agonist-mediated insulin sensitization. ACRP30, adipocyte complement related protein of 30 kDa; FATP, FA transport protein; FFA, free fatty acid; GLUT4, insulin-regulated glucose transporter isoform; PDK4, pyruvate dehydrogenase kinase 4; PEPCK, phosphoenolpyruvate carboxykinase; TNF, tumor necrosis factor; TZD, thiazolidinedione; UCP, uncoupling protein 2 and 3.