Anderson Marianne S, Thamotharan M, Kao Doris, Devaskar Sherin U, Qiao Liping, Friedman Jacob E, Hay William W
Pediatrics/Neonatology, University of Colorado Health Sciences Center, Denver, Colorado, USA.
Am J Physiol Regul Integr Comp Physiol. 2005 Feb;288(2):R473-81. doi: 10.1152/ajpregu.00405.2004. Epub 2004 Nov 11.
To test the effects of acute fetal hyperinsulinemia on the pattern and time course of insulin signaling in ovine fetal skeletal muscle, we measured selected signal transduction proteins in the mitogenic, protein synthetic, and metabolic pathways in the skeletal muscle of normally growing fetal sheep in utero. In experiment 1, 4-h hyperinsulinemic-euglycemic clamps were conducted in anesthetized twin fetuses to produce selective fetal hyperinsulinemia-euglycemia in one twin and euinsulinemia-euglycemia in the other. Serial skeletal muscle biopsies were taken from each fetus during the clamp and assayed by Western blot for selected insulin signal transduction proteins. Tyrosine phosphorylation of the insulin receptor, insulin receptor substrate-1, and the p85 subunit of phosphatidylinositol 3-kinase doubled at 30 min and gradually returned to control values by 240 min. Phosphorylation of extracellular signal-regulated kinase 1,2 was increased fivefold through 120 min of insulin infusion and decreased to control concentration by 240 min. Protein kinase B phosphorylation doubled at 30 min and remained elevated throughout the study. Phosphorylation of p70 S6K increased fourfold at 30, 60, and 120 min. In the second experiment, a separate group of nonanesthetized singleton fetuses was clamped to intermediate and high hyperinsulinemic-euglycemic conditions for 1 h. GLUT4 increased fourfold in the plasma membrane at 1 h, and hindlimb glucose uptake increased significantly at the higher insulin concentration. These data demonstrate that an acute increase in fetal plasma insulin concentration stimulates a unique pattern of insulin signal transduction proteins in intact skeletal muscle, thereby increasing pathways for mRNA translation, glucose transport, and cell growth.
为了测试急性胎儿高胰岛素血症对绵羊胎儿骨骼肌胰岛素信号传导模式和时间进程的影响，我们测量了子宫内正常生长的胎儿绵羊骨骼肌中促有丝分裂、蛋白质合成和代谢途径中的特定信号转导蛋白。在实验1中，对麻醉的双胎胎儿进行4小时的高胰岛素-正常血糖钳夹，以使一个双胎胎儿出现选择性胎儿高胰岛素血症-正常血糖，另一个双胎胎儿出现正常胰岛素血症-正常血糖。在钳夹过程中从每个胎儿获取连续的骨骼肌活检样本，并通过蛋白质印迹法检测特定的胰岛素信号转导蛋白。胰岛素受体、胰岛素受体底物-1和磷脂酰肌醇3激酶的p85亚基的酪氨酸磷酸化在30分钟时增加了一倍，并在240分钟时逐渐恢复到对照值。细胞外信号调节激酶1、2的磷酸化在胰岛素输注120分钟内增加了五倍，并在240分钟时降至对照浓度。蛋白激酶B磷酸化在30分钟时增加了一倍，并在整个研究过程中保持升高。p70 S6K的磷酸化在30、60和120分钟时增加了四倍。在第二个实验中，将另一组未麻醉的单胎胎儿钳夹至中等和高胰岛素-正常血糖状态1小时。1小时时质膜中的葡萄糖转运蛋白4增加了四倍，在较高胰岛素浓度下后肢葡萄糖摄取显著增加。这些数据表明，胎儿血浆胰岛素浓度的急性增加会刺激完整骨骼肌中独特的胰岛素信号转导蛋白模式，从而增加mRNA翻译、葡萄糖转运和细胞生长的途径。
