IRS1 and Insulin resistance: To further elucidate the molecular mechanisms of OA on insulin resistance and investigate the role of NF-κB in regulating IRS-1 signal by OA, the levels of TNF-α and IL-6 were analyzed and protein expression of nuclear factor kappa B (NF-κB), insulin receptor substrate 1 (IRS1), and glucose transporter 4 (GLUT4) in insulin-resistant HepG2 cells treated with OA was measured.