Hyperglycemia inhibits insulin activation of Akt protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle
Hyperglycemia inhibits insulin activation of Akt protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle
复制标题
DOI：
10.2337/diabetes.48.3.658
复制
发表时间：
1999-03-01
期刊：
影响因子：
7.7
通讯作者：
Ruderman, NB
中科院分区：
文献类型：
--
作者：
Kurowski, TG;Lin, YS;Ruderman, NB
持续的高血糖会损害人和实验动物骨骼肌中胰岛素刺激的葡萄糖利用，这种现象在临床上称为葡萄糖毒性。为了研究这是如何发生的，开发了一种模型，其中高血糖症在体外产生胰岛素抵抗。将大鼠趾长伸肌在含有不同浓度葡萄糖或葡萄糖+胰岛素的Krebs-Henseleit溶液中预孵育4 h，然后研究胰岛素的作用。与0 mmol/l葡萄糖孵育的肌肉相比，25 mmol/l葡萄糖+胰岛素（10 mU/ml）预孵育导致胰岛素（10 mU/ml）刺激葡萄糖掺入糖原的能力降低70%，2-脱氧葡萄糖（2-DG）摄取降低30%。葡萄糖掺入脂质及其氧化为CO的作用略微减少（如果有的话）。糖原合成和2-DG摄取的改变在预孵育1 h后首次出现，在2 h后达到最大值;在用25 mmol/l葡萄糖+胰岛素预孵育5 min的肌肉中未观察到这些改变。在无胰岛素的情况下，用25 mmol/l葡萄糖预孵育4 h，胰岛素刺激的糖原合成产生类似但较小的减少;然而，它不改变2-DG摄取、葡萄糖氧化为CO或掺入脂质。对后者肌肉中胰岛素信号传导的研究表明：Akt/蛋白激酶B（PKB）的激活与无葡萄糖培养基中预孵育的肌肉相比减少了60%;而磷脂酰肌醇（PI）3-激酶（胰岛素信号级联中Akt/PKB的上游调节物）和丝裂原活化蛋白（MAP）激酶（平行信号）的激活不受影响。免疫印迹表明，这可能不是由于Akt/PKB丰度的变化。结果表明，高血糖诱导的胰岛素抵抗可以在离体大鼠骨骼肌中进行研究。他们认为，这些肌肉中胰岛素作用的损害与不影响PI 3-激酶的事件对Akt/PKB的抑制有关。
Sustained hyperglycemia impairs insulin-stimulated glucose utilization in the skeletal muscle of both humans and experimental animals-a phenomenon referred to clinically as glucose toxicity. To study how this occurs, a model was developed in which hyperglycemia produces insulin resistance in vitro. Rat extensor digitorum longus muscles were preincubated for 4 h in Krebs-Henseleit solution containing glucose or glucose + insulin at various concentrations, after which insulin action was studied. Preincubation with 25 mmol/l glucose + insulin (10 mU/ml) led to a 70% decrease in the ability of insulin (10 mU/ml) to stimulate glucose incorporation into glycogen and a 30% decrease in 2-deoxyglucose (2-DG) uptake, compared with muscles incubated with 0 mmol/l glucose. Glucose incorporation into lipid and its oxidation to CO, were marginally diminished, if at all. The alterations of glycogen synthesis and 2-DG uptake were first evident after 1 h and were maximal after 2 h of preincubation; they were not observed in muscles preincubated with 25 mmol/l glucose + insulin for 5 min. Preincubation for 4 h with 25 mmol/l glucose in the absence of insulin produced a similar although somewhat smaller decrease in insulin-stimulated glycogen synthesis; however, it did not alter 2-DG uptake, glucose oxidation to CO,, or incorporation into Lipids. Studies of insulin signaling in the latter muscles revealed that: activation of Akt/ protein kinase B (PKB) was diminished by 60%, compared with that of muscles preincubated in a glucose-free medium; whereas activation of phosphatidylinositol (PI) 3-kinase, an upstream regulator of Akt/PKB in the insulin-signaling cascade, and of mitogen-activated protein (MAP) kinase, a parallel signal, was unaffected. Immunoblots demonstrated that this mas not due to a change in Akt/PKB abundance. The results indicate that hyperglycemia-induced insulin resistance can be studied in rat skeletal muscle in vitro. They suggest that impairment of insulin action in these muscles is related to inhibition of Akt/PKB by events that do not affect PI 3-kinase.