Insulin sensitivity in skeletal muscle

项目摘要/摘要 糖尿病，一种以异常低的胰岛素刺激的葡萄糖转运进入骨骼为特征的疾病 肌肉，是对健康的一大威胁。AMPK的激活，如通过运动、肌肉收缩或血清 饥饿，提供了一种增加葡萄糖运输对胰岛素刺激的敏感性的方法。而当 AS160的增强磷酸化伴随着胰岛素敏感性的发展，完整的 胰岛素刺激的葡萄糖转运增加的分子机制尚不清楚。我们 目的通过检验mTOR和ULK1介导AMPK的假设来填补这一重要的知识空白。 诱导胰岛素敏感性。我们的初步数据表明，抑制mTOR复合体1(MTORC1)会导致 胰岛素刺激的葡萄糖转运增加。我们还发现，抑制ULK1可以阻止胰岛素- 血清饥饿的肌管刺激葡萄糖摄取，同时ULK1的药理激活剂增加 AS160磷酸化。最后，我们的数据显示，激活AMPK会导致mTORC2活性增加 在肌管中，如mTORC2底物Akt的磷酸化增加所证明的。测试我们的 在假设条件下，我们提出了三个具体目标。对于目标1，为了确定mTORC1在胰岛素敏感性中的作用， 我们将验证这样一种假设，即抑制mTORC1会导致胰岛素敏感性增加，并介导AMPK- 诱导胰岛素敏感性。实现这一目标的方法将包括确定通过以下方式抑制mTORC1 药物和遗传手段会增加胰岛素刺激的葡萄糖转运，是否激活 MTORC1通过生理和遗传手段阻止胰岛素敏感性的发展 AMPK、血清饥饿或运动/肌肉收缩。对于目标2，确定ULK1在胰岛素中的作用 敏感性，我们将检验ULK1激活足以增加胰岛素敏感性和 AMPK诱导胰岛素敏感性所必需的。实现这一目标的方法将包括确定 ULK1的药理激活增加胰岛素刺激的葡萄糖转运以及是否 药物抑制ULK1或表达失活或对AMPK不敏感的突变体可防止 胰岛素敏感性的发展。对于目标3，确定mTORC2在AS160磷酸化和 胰岛素敏感性，我们将检验mTORC2是AS160磷酸化的重要介质的假设 在胰岛素敏感性的发展过程中。方法将包括确定药理学或 MTORC2复合体的基因破坏将阻止AS160磷酸化在 血清饥饿、AMPK激活或运动/肌肉收缩，以及是否事先激活 MTORC2底物Akt导致胰岛素刺激的葡萄糖转运增加。已完成的 特异性靶点将阐明mTOR和ULK1在骨骼肌胰岛素敏感性控制中的新作用 并提出了克服胰岛素抵抗的未来策略。

Project Summary/Abstract Diabetes, a condition characterized by abnormally low insulin-stimulated glucose transport into skeletal muscle, is a major threat to health. Activation of AMPK, such as by exercise, muscle contractions, or serum starvation, provides a means to increase sensitivity of glucose transport to stimulation by insulin. While enhanced phosphorylation of AS160 occurs concomitant with development of insulin sensitivity, the complete molecular mechanisms underlying the increase in insulin-stimulated glucose transport remain unknown. We aim to fill this important knowledge gap by testing the hypothesis that mTOR and ULK1 mediate AMPK- induced insulin sensitivity. Our preliminary data show that inhibition of mTOR complex 1 (mTORC1) causes an increase in insulin-stimulated glucose transport. We have also found that inhibition of ULK1 prevents insulin- stimulated glucose uptake by serum-starved myotubes, while a pharmacological activator of ULK1 increases AS160 phosphorylation. Finally, our data show that activation of AMPK causes an increase in mTORC2 activity in myotubes, as demonstrated by increased phosphorylation of the mTORC2 substrate Akt. To test our hypotheses, we propose three specific aims. For Aim 1, to determine the role of mTORC1 in insulin sensitivity, we will test the hypothesis that inhibition of mTORC1 causes increased insulin sensitivity and mediates AMPK- induced insulin sensitivity. Approaches for this aim will include determining whether inhibition of mTORC1 by pharmacological and genetic means will increase insulin-stimulated glucose transport and whether activation of mTORC1 by physiological and genetic means will prevent development of insulin sensitivity after activation of AMPK, serum starvation, or exercise/muscle contractions. For Aim 2, to determine the role of ULK1 in insulin sensitivity, we will test the hypothesis that activation of ULK1 is sufficient to increase insulin sensitivity and necessary to induction of insulin sensitivity by AMPK. Approaches to this aim will include determining whether pharmacological activation of ULK1 increases insulin-stimulated glucose transport and whether pharmacological inhibition of ULK1 or expression of inactive or AMPK-insensitive mutants of ULK1 prevent development of insulin sensitivity. For Aim 3, to determine the role of mTORC2 in AS160 phosphorylation and insulin sensitivity, we will test the hypothesis that mTORC2 is an important mediator of AS160 phosphorylation during development of insulin sensitivity. Approaches will include determining whether pharmacological or genetic disruption of the mTORC2 complex will prevent the normal increase in AS160 phosphorylation after serum starvation, activation of AMPK, or exercise/muscle contractions and whether prior activation of the mTORC2 substrate Akt causes a later increase in insulin-stimulated glucose transport. Completion of the specific aims will elucidate novel roles of mTOR and ULK1 in control of insulin sensitivity in skeletal muscle and suggest future strategies to overcome insulin resistance.