Gardner Carla D, Eguchi Satoru, Reynolds Cherilynn M, Eguchi Kunie, Frank Gerald D, Motley Evangeline D
Department of Anatomy and Physiology, Meharry Medical College, Nashville, Tennessee 37208, USA.
Exp Biol Med (Maywood). 2003 Jul;228(7):836-42. doi: 10.1177/15353702-0322807-09.
Both insulin resistance and reactive oxygen species (ROS) have been reported to play essential pathophysiological roles in cardiovascular diseases, such as hypertension and atherosclerosis. However, the mechanistic link between ROS, such as H2O2 and insulin resistance in the vasculature, remains undetermined. Akt, a Ser/Thr kinase, mediates various biological responses induced by insulin. In this study, we examined the effects of H2O2 on Akt activation in the insulin-signaling pathway in vascular smooth muscle cells (VSMCs). In VSMCs, insulin stimulates Akt phosphorylation at Ser473. Pretreatment with H2O2 concentration- and time-dependently inhibited insulin-induced Akt phosphorylation with significant inhibition observed at 50 microM for 10 min. A ROS inducer, diamide, also inhibited insulin-induced Akt phosphorylation. In addition, H2O2 inhibited insulin receptor binding partially and inhibited insulin receptor autophosphorylation almost completely. However, pretreatment with a protein kinase C inhibitor, GF109203X (2 microM), for 30 min did not block the inhibitory effects of H2O2 on insulin-induced Akt phosphorylation, suggesting that protein kinase C is not involved in the inhibition by H2O2. We conclude that ROS inhibit a critical insulin signal transduction component required for Akt activation in VSMCs, suggesting potential cellular mechanisms of insulin resistance, which would require verification in vivo.
胰岛素抵抗和活性氧（ROS）均被报道在心血管疾病如高血压和动脉粥样硬化中发挥重要的病理生理作用。然而，诸如过氧化氢（H2O2）等ROS与血管系统中胰岛素抵抗之间的机制联系仍未明确。Akt是一种丝氨酸/苏氨酸激酶，介导胰岛素诱导的各种生物学反应。在本研究中，我们检测了H2O2对血管平滑肌细胞（VSMCs）胰岛素信号通路中Akt激活的影响。在VSMCs中，胰岛素刺激Akt在丝氨酸473位点的磷酸化。用H2O2预处理呈浓度和时间依赖性地抑制胰岛素诱导的Akt磷酸化，在50微摩尔浓度处理10分钟时观察到显著抑制。一种ROS诱导剂二酰胺也抑制胰岛素诱导的Akt磷酸化。此外，H2O2部分抑制胰岛素受体结合，并几乎完全抑制胰岛素受体自身磷酸化。然而，用蛋白激酶C抑制剂GF109203X（2微摩尔）预处理30分钟并未阻断H2O2对胰岛素诱导的Akt磷酸化的抑制作用，这表明蛋白激酶C不参与H2O2的抑制作用。我们得出结论，ROS抑制VSMCs中Akt激活所需的关键胰岛素信号转导成分，提示胰岛素抵抗的潜在细胞机制，这需要在体内进行验证。
