No-flow ischemia inhibits insulin signaling in heart by decreasing intracellular pH
No-flow ischemia inhibits insulin signaling in heart by decreasing intracellular pH
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DOI：
10.1161/01.res.88.5.513
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发表时间：
2001-03-16
影响因子：
20.1
通讯作者：
Hue, L
中科院分区：
文献类型：
--
作者：
Beauloye, C;Bertrand, L;Hue, L
葡萄糖-胰岛素-钾液通过减少心肌梗死面积和死亡率，改善缺血后左心功能，对缺血心脏起到良好的治疗作用。胰岛素可能是这种混合物的关键保护成分，尽管对缺血和缺血后心肌的胰岛素反应尚未进行系统研究。这项工作的目的是通过分析胰岛素信号来研究缺血时的胰岛素反应。这是通过测量处于无血流缺血状态的离体灌流大鼠心脏中胰岛素信号元件的活性和/或磷酸化状态的变化来评估的。核磁共振法测定细胞内pH(pH(I))。无血流缺血可拮抗胰岛素信号转导通路，包括胰岛素受体、胰岛素受体底物-1、磷脂酰肌醇3-激酶、蛋白激酶B、p70核糖体S6激酶和糖原合成酶-3。这些变化伴随着细胞内酸中毒。在常氧条件下用哇巴因和阿米洛利灌流心脏可降低pH(I)和胰岛素信号，而在pH 8.2时灌流可抵消缺血引起的pH(I)下降和胰岛素信号的抑制。心肌细胞在常氧条件下孵育，但在pH值低于6.75的情况下，模拟了缺血的影响，也抑制了胰岛素刺激的葡萄糖摄取。最后，体外胰岛素受体酪氨酸激酶活性在低于生理pH(I)时逐渐受到抑制，在pH为6.0时被取消。因此，缺血性酸中毒降低了胰岛素受体的激酶活性和酪氨酸磷酸化，从而阻止了信号通路下游成分的激活。我们得出结论，严重的缺血通过降低pH(I)来抑制胰岛素信号传导。
Glucose-insulin-potassium solutions exert beneficial effects on the ischemic heart by reducing infarct size and mortality and improving postischemic left ventricular function. Insulin could be the critical protective component of this mixture, although the insulin response of the ischemic and postischemic myocardium has not been systematically investigated. The aim of this work was to study the insulin response during ischemia by analyzing insulin signaling. This was evaluated by measuring changes in activity and/or phosphorylation state of insulin signaling elements in isolated perfused rat hearts submitted to no-flow ischemia. Intracellular pH (pH(i)) was measured by NMR. No-flow ischemia antagonized insulin signaling including insulin receptor, insulin receptor substrate-1, phosphatidylinositol 3-kinase, protein kinase B, p70 ribosomal S6 kinase, and glycogen synthase kinase-3. These changes were concomitant with intracellular acidosis. Perfusing hearts with ouabain and amiloride in normoxic conditions decreased pH(i) and insulin signaling, whereas perfusing at pH 8.2 counteracted the drop in pH(i) and the inhibition of insulin signaling by ischemia. Incubation of cardiomyocytes in normoxic conditions, but at pH values below 6.75, mimicked the effect of ischemia and also inhibited insulin-stimulated glucose uptake. Finally, the in vitro insulin receptor tyrosine kinase activity was progressively inhibited at pH values below physiological pH(i), being abolished at pH 6.0. Therefore, ischemic acidosis decreases kinase activity and tyrosine phosphorylation of the insulin receptor thereby preventing activation of the downstream components of the signaling pathway. We conclude that severe ischemia inhibits insulin signaling by decreasing pH(i).