Paraquat-induced Oxidative Stress Represses Phosphatidylinositol 3-Kinase Activities Leading to Impaired Glucose Uptake in 3T3-L1 Adipocytes

• Published in: The Journal of biological chemistry 2010-07, Vol.285 (27), p.20915-20925
• Main Authors: Shibata, Michihiro, Hakuno, Fumihiko, Yamanaka, Daisuke, Okajima, Hiroshi, Fukushima, Toshiaki, Hasegawa, Takashi, Ogata, Tomomi, Toyoshima, Yuka, Chida, Kazuhiro, Kimura, Kumi, Sakoda, Hideyuki, Takenaka, Asako, Asano, Tomoichiro, Takahashi, Shin-Ichiro
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Adenoviridae - genetics; Adipocyte; Adipocytes - cytology; Adipocytes - drug effects; Adipocytes - enzymology; Adipocytes - metabolism; Animals; Biological Transport - drug effects; Cell Biology; Cell Line; Cell Membrane - metabolism; DNA Primers; Enzyme Repression; Glucose - metabolism; Glucose Transport; Glucose Transporter Type 4 - metabolism; Humans; Insulin Resistance; Kidney; Mice; Oxidative Stress; Oxidative Stress - drug effects; Paraquat - pharmacology; Phosphatidylinositol 3-Kinases - biosynthesis; Phosphatidylinositol 3-Kinases - drug effects; Phosphatidylinositol 3-Kinases - genetics; PI 3-Kinase; Plasmids; Signal Transduction; T-Lymphocytes - immunology; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.126482

Accumulated evidence indicates that oxidative stress causes and/or promotes insulin resistance; however, the mechanism by which this occurs is not fully understood. This study was undertaken to elucidate the molecular mechanism by which oxidative stress induced by paraquat impairs insulin-dependent glucose uptake in 3T3-L1 adipocytes. We confirmed that paraquat-induced oxidative stress decreased glucose transporter 4 (GLUT4) translocation to the cell surface, resulting in repression of insulin-dependent 2-deoxyglucose uptake. Under these conditions, oxidative stress did not affect insulin-dependent tyrosine phosphorylation of insulin receptor, insulin receptor substrate (IRS)-1 and -2, or binding of the phosphatidylinositol 3′-OH kinase (PI 3-kinase) p85 regulatory subunit or p110α catalytic subunit to each IRS. In contrast, we found that oxidative stress induced by paraquat inhibited activities of PI 3-kinase bound to IRSs and also inhibited phosphorylation of Akt, the downstream serine/threonine kinase that has been shown to play an essential role in insulin-dependent translocation of GLUT4 to the plasma membrane. Overexpression of active form Akt (myr-Akt) restored inhibition of insulin-dependent glucose uptake by paraquat, indicating that paraquat-induced oxidative stress inhibits insulin signals upstream of Akt. Paraquat treatment with and without insulin treatment decreased the activity of class Ia PI 3-kinases p110α and p110β that are mainly expressed in 3T3-L1 adipocytes. However, paraquat treatment did not repress the activity of the PI 3-kinase p110α mutated at Cys90 in the p85 binding region. These results indicate that the PI 3-kinase p110 is a possible primary target of paraquat-induced oxidative stress to reduce the PI 3-kinase activity and impaired glucose uptake in 3T3-L1 adipocytes.