Paraquat-induced Oxidative Stress Represses Phosphatidylinositol 3-Kinase Activities Leading to Impaired Glucose Uptake in 3T3-L1 Adipocytes
Paraquat-induced Oxidative Stress Represses Phosphatidylinositol 3-Kinase Activities Leading to Impaired Glucose Uptake in 3T3-L1 Adipocytes
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DOI：
10.1074/jbc.m110.126482
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发表时间：
2010-07-02
影响因子：
4.8
通讯作者：
Takahashi, Shin-Ichiro
中科院分区：
文献类型：
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作者：
Shibata, Michihiro;Hakuno, Fumihiko;Takahashi, Shin-Ichiro
累积的证据表明，氧化应激导致和/或促进胰岛素抵抗;然而，发生这种情况的机制尚未完全了解。本研究旨在阐明百草枯诱导的氧化应激损害3 T3-L1脂肪细胞胰岛素依赖性葡萄糖摄取的分子机制。我们证实，百草枯诱导的氧化应激减少葡萄糖转运蛋白4（GLUT 4）易位到细胞表面，导致抑制胰岛素依赖的2-脱氧葡萄糖摄取。在这些条件下，氧化应激不影响胰岛素受体、胰岛素受体底物（IRS）-1和-2的胰岛素依赖性酪氨酸磷酸化，或磷脂酰肌醇3 '-OH激酶（PI 3-激酶）p85调节亚基或p110 α催化亚基与每个IRS的结合。与此相反，我们发现，百草枯诱导的氧化应激抑制PI 3-激酶结合IRS的活动，也抑制Akt的磷酸化，下游丝氨酸/苏氨酸激酶，已被证明在胰岛素依赖的GLUT 4转运到质膜中发挥重要作用。活性形式Akt（myr-Akt）的过表达恢复了百草枯对胰岛素依赖性葡萄糖摄取的抑制，表明百草枯诱导的氧化应激抑制Akt上游的胰岛素信号。百草枯处理与胰岛素治疗和不治疗降低了Ia类PI 3-激酶p110 α和p110 β的活性，主要在3 T3-L1脂肪细胞中表达。然而，百草枯处理并没有抑制P85结合区Cys（90）突变的PI 3-激酶p110 α的活性。这些结果表明，PI 3-激酶p110可能是百草枯诱导的氧化应激的主要目标，以减少PI 3-激酶活性和受损的葡萄糖摄取在3 T3-L1脂肪细胞。
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 p110 alpha 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 p110 alpha and p110 beta that are mainly expressed in 3T3-L1 adipocytes. However, paraquat treatment did not repress the activity of the PI 3-kinase p110 alpha mutated at Cys(90) 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.