Suppression of Rho-kinase 1 is responsible for insulin regulation of the AMPK/SREBP-1c pathway in skeletal muscle cells exposed to palmitate
Suppression of Rho-kinase 1 is responsible for insulin regulation of the AMPK/SREBP-1c pathway in skeletal muscle cells exposed to palmitate
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暴露于棕榈酸酯的骨骼肌细胞中，Rho 激酶 1 的抑制负责 AMPK/SREBP-1c 通路的胰岛素调节
DOI：
10.1007/s00592-017-0976-z
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发表时间：
2017-07-01
影响因子：
3.8
通讯作者：
Bi, Yan
中科院分区：
文献类型：
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作者：
Tang, Sunyinyan;Wu, Wenjun;Bi, Yan
临床和实验数据表明，早期胰岛素治疗可减轻2型糖尿病患者及动物模型的脂毒性。然而，其潜在机制仍有待阐明。固醇调节元件结合蛋白1c（SREBP - 1c）受5' - 腺苷酸活化蛋白激酶（AMPK）负调控，在骨骼肌细胞的脂毒性和胰岛素抵抗中发挥关键作用。在此，我们研究了胰岛素干预对长期暴露于棕榈酸（PA）的骨骼肌细胞中AMPK / SREBP - 1c通路的影响及其分子机制。
将雄性C57BL / 6小鼠喂食高脂饮食12周，随后分别用胰岛素、AMPK抑制剂或二甲双胍进行处理。用棕榈酸（PA）孵育L6肌管，再分别用胰岛素或二甲双胍处理。将显性负性AMPKα2（DN - AMPKα2）慢病毒、AMPKα2小干扰RNA（siRNA）或 Rho激酶1（ROCK1）siRNA转染至经PA处理的L6肌管中。
我们发现，在L6细胞中，胰岛素可逆转PA刺激SREBP - 1c及抑制AMPK的作用。此外，将DN - AMPKα2慢病毒和AMPKα2 siRNA转染至经PA处理的L6肌管中，胰岛素引起的SREBP - 1c表达降低可被AMPK抑制所阻断，且该过程不依赖于磷脂酰肌醇 - 4,5 - 二磷酸 - 3 - 激酶（PI3K）/蛋白激酶B（AKT）通路。丝氨酸/苏氨酸激酶Rho激酶（ROCK）1作为小G蛋白RhoA的下游效应分子，可被PA激活。有趣的是，通过siRNA敲低ROCK1可阻断PA处理的L6肌管中AMPK磷酸化的下调，这表明ROCK1介导了胰岛素对AMPK的作用。
我们的研究表明，在PA诱导的胰岛素抵抗状态下，胰岛素通过ROCK1减轻脂毒性，进而改善骨骼肌中的AMPK / SREBP - 1c信号通路。
AimsClinical and experimental data suggest that early insulin therapy could reduce lipotoxicity in subjects and animal models with type 2 diabetes mellitus. However, the underlying mechanisms need to be clarified. Sterol regulatory element-binding protein 1c (SREBP-1c), which is negatively regulated by AMP-activated protein kinase (AMPK), plays a critical role in lipotoxicity and insulin resistance in skeletal muscle cells. Here, we investigated the effect and molecular mechanism of insulin intervention on the AMPK/SREBP-1c pathway in skeletal muscle cells with chronic exposure to palmitic acid (PA).MethodsMale C57BL/6 mice were fed with a high-fat diet for 12 weeks and were then treated with insulin, AMPK inhibitor, or metformin. L6 myotubes incubated with palmitic acid (PA) were treated with insulin or metformin. Dominant-negative AMPKα2 (DN-AMPKα2) lentivirus, AMPKα2 siRNA, or Rho-kinase 1 (ROCK1) siRNA were transfected into PA-treated L6 myotubes.ResultsWe found that the ability of PA to stimulate SREBP-1c and inhibit AMPK was reversed by insulin in L6 cells. Moreover, DN-AMPKα2 lentivirus and AMPKα2 siRNA were transfected into PA-treated L6 myotubes, and the decrease in SREBP-1c expression caused by insulin was blocked by AMPK inhibition independent of the phosphatidylinositol-4,5-biphosphate-3-kinase (PI3K)/AKT pathway. The serine/threonine kinase Rho-kinase (ROCK) 1, a downstream effector of the small G protein RhoA, was activated by PA. Interestingly, knockdown of ROCK1 by siRNA blocked the downregulation of AMPK phosphorylation under PA-treated L6 myotubes, which indicated that ROCK1 mediated the effect of insulin action on AMPK.ConclusionsOur study indicated that insulin reduced lipotoxicity via ROCK1 and then improved AMPK/SREBP-1c signaling in skeletal muscle under PA-induced insulin resistance.