创伤后大鼠胰岛素信号转导与葡萄糖转运关系的研究

Research of the relationship between insulin signal transduction and glucose transportation in rats after trauma

目的探讨创伤后大鼠骨骼肌组织中胰岛素受体后信号转导通路的变化及其与葡萄糖转运能力之间的关系。方法通过对大鼠实施小肠部分切除手术建立创伤模型，观察胰岛素受体后信号转导通路上关键蛋白——胰岛素受体底物-1（IRS-1）和蛋白激酶B（PKB又名Akt）的含量及磷酸化状态的改变。采用。H标记葡萄糖示踪法检测创伤后骨骼肌葡萄糖转运能力的变化，并分别测定大鼠骨骼肌组织中葡萄糖转运蛋白-4（GLT-4）的mRNA和蛋白表达水平。结果两组大鼠骨骼肌组织中IRS-1和PKB／Akt蛋白总量没有明显差异，但是创伤组骨骼肌中酪氨酸位点磷酸化的IRS-1蛋白含量较对照组下降了31％（P=0．018），而丝氨酸位点磷酸化的IRS-1蛋白含量较对照组增加了63％（P=0．000），相应的创伤组骨骼肌巾磷酸化的PKB／Akt蛋白含量较对照组下降了48％（P=0．000）。创伤组大鼠骨骼肌对葡萄糖的转运能力明显低于对照组（P〈0．01）。两组大鼠骨骼肌中GLUT-4mRNA和蛋白总量的表达没有明显差异（P=0．805和P=0．702），但是创伤组大鼠骨骼肌细胞膜上的GLUT-4蛋白含量明显少于对照纰（P=0．028）。结论创伤后大鼠骨骼肌组织中IRS-1蛋白酪氨酸位点磷酸化减弱而丝氨酸位点磷酸化增强，导致下游PKB／Akt蛋白活性降低，从而使得骨骼肌细胞膜上GLUT-4分布减少以及对葡萄糖的转运能力降低，这可能是导致大鼠创伤后胰岛素抵抗的机制之一。

Objective To investigate the relationship between insulin post-receptor signal transduction and the change of glucose transportation by skeleton muscle after surgical trauma in rats. Methods Small intestine bowel resection was performed to establish the surgical trauma model in rats. The content and the phosphorylation state of two key proteins in the insulin signaling pathway： insulin receptor substrate-1 （IRS-1） and protein kinase B （PKB/Akt） in skeletal muscle were measured respectively. The ^3H labeled glucose uptake experiment was carried out to evaluate the glucose transportation function in both groups. Finally, the expression and the distribution of glucose transporter-4 （ GLUT-4 ） in skeletal muscle were detected respectively. Results The total content of IRS-1 and PKB/Akt in skeletal muscle in both groups had no difference. The phosphorylation of tyrosine （Tyr） residue of IRS-1 in the operation group was attenuated by 31% （P = 0. 018 ）, whereas the phosphorylation of serine （Ser） residue of IRS-1 was significantly enhanced by 63% compared with the control group （P = 0. 000）. Accordingly, the phosphorylation state of PKB/Akt （activated） was attenuated by 48% in the operation group（P =0. 000）. The rate of 2-Deoxy-D-[ 1-^3H ] glucose transported by skeletal muscle in the operation group was significantly lower than that in the control group. Both the expressions of GLUT-4 mRNA and the total content of GLUT- 4 protein in two groups had no significant difference. But the expression of GLUT-4 in the plasma membrane was decreased in the operation group than that in the control group. Conclusions Insulin resistance was associated with enhanced Ser phosphorylation of IRS-1, which impaired its interaction with its downstream target PKB/Akt. Such impaired interactions abolished the ability of IRS-1 to undergo insulin-induced Tyr phosphorylation and further propagate the insulin receptor signal. Uncoupling of signal transduction led to decrease in glucose uptake which associated with a defect in insulin-stimulated glucose transport and GLUT- 4 translocation.