AIM: To investigated the effects of urotensin Ⅱ(UII) on hepatic insulin resistance in Hep G2 cells and the potential mechanisms involved.METHODS: Human hepatoma Hep G2 cells were cultured with or without exogenous UII for 24 h, in the presence or absence of 100 nmol/L insulin for the last 30 min. Glucose levels were detected by the glucoseoxidase method and glycogen synthesis was analyzed by glycogen colorimetric/fluorometric assay. Reactive oxygen species(ROS) levels were detected with a multimode reader using a 2′,7′-dichlorofluorescein diacetate probe. The protein expression and phosphorylation levels of c-Jun N-terminal kinase(JNK), insulin signal essential molecules such as insulin receptor substrate-1(IRS-1), protein kinase B(Akt), glycogen synthase kinase-3β(GSK-3β), and glucose transporter-2(Glut 2), and NADPH oxidase subunits such as gp91 phox, p67 phox, p47 phox, p40 phox, and p22 phox were evaluated by Western blot.RESULTS: Exposure to 100 nmol/L UII reduced the insulin-induced glucose consumption(P < 0.05)and glycogen content(P < 0.01) in Hep G2 cells compared with cells without UII. UII also abolished insulin-stimulated protein expression(P < 0.01) and phosphorylation of IRS-1(P < 0.05), associated with down-regulation of Akt(P < 0.05) and GSK-3β(P < 0.05) phosphorylation levels, and the expression of Glut 2(P < 0.001), indicating an insulin-resistance state in Hep G2 cells. Furthermore, UII enhanced the phosphorylation of JNK(P < 0.05), while the activity of JNK, insulin signaling, such as total protein of IRS-1(P < 0.001), phosphorylation of IRS-1(P < 0.001) and GSK-3β(P < 0.05), and glycogen synthesis(P < 0.001) could be reversed by pretreatment with the JNK inhibitor SP600125. Besides, UII markedly improved ROS generation(P < 0.05) and NADPH oxidase subunit expression(P < 0.05). However, the antioxidant/NADPH oxidase inhibitor apocynin could decrease UII-induced ROS production(P < 0.05), JNK phosphorylation(P < 0.05), and insulin resistance(P < 0.05) in HepG 2 cells. CONCLUSION: UII induces insulin resistance, and this can be reversed by JNK inhibitor SP600125 and antioxidant/NADPH oxidase inhibitor apocynin targeting the insulin signaling pathway in HepG 2 cells. AIM: To investigate the effects of urotensin II (UII) on hepatic insulin resistance in Hep G2 cells and the potential mechanisms involved. METHODS: Human hepatoma Hep G2 cells were cultured with or without exogenous UII for 24 h, in the presence or absence of 100 nmol / L insulin for the last 30 min. Glucose levels were detected by the glucoseoxidase method and glycogen synthesis was analyzed by glycogen colorimetric / fluorometric assay. Reactive oxygen species (ROS) levels were detected with a multimode reader using a 2 ’, 7 The protein expression and phosphorylation levels of c-Jun N-terminal kinase (JNK), insulin signal essential molecules such as insulin receptor substrate-1 (IRS-1), protein kinase B (Akt), glycogen synthase kinase-3β (GSK-3β), and glucose transporter-2 (Glut 2), and NADPH oxidase subunits such as gp91 phox, p67 phox, p47 phox, p40 phox, and p22 phox were evaluated by Western blot .RESULTS: Exposure to 100 nmol / L UII reduced the insu (P <0.01) in Hep G2 cells compared with cells without UII. UII also abolished insulin-stimulated protein expression (P <0.01) and phosphorylation of IRS-1 (P < (P <0.05) and GSK-3β (P <0.05) phosphorylation levels, and the expression of Glut 2 (P <0.001), indicating an insulin-resistance state in Hep G2 cells. The activity of JNK, insulin signaling, such as total protein of IRS-1 (P <0.001), phosphorylation of IRS-1 (P < In addition, UII markedly improved ROS generation (P <0.05) and NADPH oxidase subunit expression (P <0.05). However, , the antioxidant / NADPH oxidase inhibitor apocynin could decrease UII-induced ROS production (P <0.05), JNK phosphorylation (P <0.05), and insulin resistanc e (P <0.05) in HepG 2 cells. CONCLUSION: UII induces insulin resistance, and this can be reversed by JNK inhibitor SP600125 and antioxidant / NADPH oxidase inhibitor apocynin targeting the insulin signaling pathway in HepG 2 cells.