Isoform-specific defects of insulin stimulation of Akt/protein kinase B (PKB) in skeletal muscle cells from type 2 diabetic patients
Isoform-specific defects of insulin stimulation of Akt/protein kinase B (PKB) in skeletal muscle cells from type 2 diabetic patients
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DOI：
10.1007/s00125-007-0913-8
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发表时间：
2008-03-01
期刊：
影响因子：
8.2
通讯作者：
Vidal, H.
中科院分区：
文献类型：
--
作者：
Cozzone, D.;Froejdoe, S.;Vidal, H.
目的/假设丝氨酸/苏氨酸激酶Akt/蛋白激酶B（PKB）是胰岛素代谢作用所必需的。关于2型糖尿病患者肌肉中Akt缺陷激活的有争议的数据已被报道。由于三个Akt亚型存在，每一个有一个独特的生理作用，我们调查的贡献亚型特异性缺陷胰岛素信号在人体muscle.Methods的磷酸化模式和激酶活性的每个Akt亚型进行了比较，在初级肌管从健康对照组和2型糖尿病患者。磷酸化的丝氨酸（473）和苏氨酸（308）在每一个异构体后，在肌管治疗或不与insulin.Results的免疫沉淀显示糖尿病患者的肌细胞胰岛素的行动和胰岛素刺激的所有Akt异构体的活性急剧下降。这与其响应胰岛素的磷酸化模式的特定缺陷、受损的Akt 2-（和较低程度的Akt 3-）Ser（473）磷酸化以及改变的Akt 1-Thr（308）磷酸化有关。这些缺陷不是由于错误的磷酸肌醇依赖性蛋白激酶1（PDK 1）的生产或激活。相反，我们在糖尿病患者的肌肉中发现了更高水平的Akt 2-Ser（473）特异性蛋白磷酸酶PH结构域富含亮氨酸重复蛋白磷酸酶1（PHLPP 1），这可能有助于Akt 2-Ser（473）磷酸化的改变。可能是2型糖尿病骨骼肌胰岛素信号改变的基础。考虑到最近描述的Akt亚型特异性代谢功能，我们的研究结果提供了可能有助于糖尿病患者肌肉中葡萄糖和脂质代谢调节缺陷的机制见解。
Aims/hypothesis The serine/threonine kinase Akt/protein kinase B (PKB) is required for the metabolic actions of insulin. Controversial data have been reported regarding Akt defective activation in the muscle of type 2 diabetic patients. Because three Akt isoforms exist, each having a distinct physiological role, we investigated the contribution of isoform-specific defects to insulin signalling in human muscle.Methods The phosphorylation pattern and kinase activity of each Akt isoform were compared in primary myotubes from healthy control participants and type 2 diabetic patients. Phosphorylation of Ser(473) and of Thr(308) in each isoform was determined after immunoprecipitation in myotubes treated or not with insulin.Results Muscle cells from diabetic patients displayed defective insulin action and a drastic reduction of insulin-stimulated activity of all Akt isoforms. This was associated with specific defects of their phosphorylation pattern in response to insulin, with impaired Akt2- (and to a lower extent Akt3-) Ser(473) phosphorylation, and with altered Akt1-Thr(308) phosphorylation. These defects were not due to faulty phosphoinositide-dependent protein kinase 1 (PDK1) production or activation. Rather, we found higher levels of the Akt2-Ser(473)-specific protein phosphatase PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) in muscle from diabetic patients, which may contribute to the alteration of Akt2-Ser(473) phosphorylation.Conclusions/interpretations These suggest that several mechanisms affecting Akt isoforms, including deregulated production of PHLPP1, could underlie the alterations of skeletal muscle insulin signalling in type 2 diabetes. Taking into account the recently described isoform-specific metabolic functions of Akt, our results provide mechanistic insight that may contribute to the defective regulation of glucose and lipid metabolisms in the muscle of diabetic patients.