胰岛素调节骨骼肌细胞葡萄糖转运子4内在活性的研究

The study of intrinsic activity of glucose transporter 4 (GluT4) regulated by insulin in skeletal muscle cells

目的探讨胰岛素刺激骨骼肌摄取葡萄糖的机制。方法观察GluT4转位和葡萄糖摄取对SB203580和Wortmannin的响应,以及胰岛素在分化前后的细胞中对两者的作用,研究胰岛素信号通路。结果胰岛素分别增加GluT4转位和葡萄糖摄取2.5±0.2倍和2.2±0.1倍;但t1/2不同,分别为3.3min和6.0min;且两者对Wortmannin的敏感性不同,IC50分别为43nmol/L和3nmol/L。SB203580分别抑制64%和62%胰岛素刺激的葡萄糖摄取和细胞膜上GluT4的标记,但不影响GluT4转位;胰岛素刺激前骨骼肌细胞葡萄糖摄取增加的倍数(1.7±0.1倍vs对照组)小于GluT4转位增加的倍数(2.3±0.1倍vs对照组)。结论成熟骨骼肌细胞中存在两个胰岛素信号转导途径,分别介导GluT4的转位和活化,胰岛素利用这两条信号通路达到最大的刺激细胞摄取葡萄糖的作用。

Obiective To study the mechanism of insulin-stimulated glueose uptake in skeletal muscle cells. Methods The responses of GluT4 transloeation and glucose uptake to the investigational drugs of SB203580 and Wortmannin as well as the effect of insulin on the drugs during differentiation were detected to study the insulin signal pathway. Results The GluT4 transloeation and glucose transport were increased under insulin stimulation by 2.5±0.2 and 2.2±0.1 folds, respectively while compared with control; but t1/2 were 3.3 rain and 6.0 rain, and IC50 to wortmannin were 43 nmol/L and 3 nmol/L respectively. SB203580 inhibited 64% and 62% of insulin-stimulated glucose uptake and photolabelling of cell surface GluT4, respectively, but had no effect on GluT4 transloea- tion. The fold increase of insulin-stimulated glucose uptake （1.7±0.1 fold vs control）was lower than that of GluT4 translocation （2.3±0.1 fold vs control） in myoblasts. Conclusions In skeletal muscle cells, two insulin signal pathways mediate GluT4 translocation and activation of GluT4, respectively. Insulin engages both of the pathways to stimulate the cells for maximum glucose uptake.