Overexpression of bovine growth hormone in transgenic mice is associated with changes in hepatic insulin receptors and in their kinase activity
Overexpression of bovine growth hormone in transgenic mice is associated with changes in hepatic insulin receptors and in their kinase activity
复制标题
DOI：
10.1016/0024-3205(96)00462-6
复制
发表时间：
1996-09-13
期刊：
影响因子：
6.1
通讯作者：
Turyn, D
中科院分区：
文献类型：
--
作者：
Balbis, A;Bartke, A;Turyn, D
将磷酸烯醇式丙酮酸羧激酶（PEPCK）基因的启动子调控区与牛生长激素（bGH）基因连接，构建了一个杂交基因，用转基因小鼠研究了牛生长激素（bGH）对肝胰岛素受体的胰岛素结合和胰岛素依赖性酪氨酸激酶活性的影响。转基因小鼠的血糖水平正常，尽管高胰岛素血症，表明这些动物是胰岛素抵抗。转基因小鼠肝脏中胰岛素受体的数量在颗粒部分（25%）和溶解膜（40%）中均显著降低，表明表达（功能性）和非表达（隐蔽性）受体受到影响。对胰岛素竞争结合曲线的Scatchard分析表明，转基因小鼠和正常小鼠之间受体的亲和力没有差异。用小麦胚芽凝集素（WGA）琼脂糖层析法从溶解的肝膜中部分纯化胰岛素受体，测定其胰岛素依赖性酪氨酸激酶活性。与正常小鼠相比，使用相同的结合活性，转基因小鼠中胰岛素对合成底物（共聚物Glu-Tyr，4：1）磷酸化的刺激作用增加了100%。由于转基因小鼠是高胰岛素血症的，因此该组中胰岛素结合的降低可能反映了表达和非表达胰岛素受体的下调，而激酶活性的增加代表了一种代偿机制。我们的结论是胰岛素受体数量和酪氨酸激酶活性的改变，在响应胰岛素水平的变化。因此，在过度表达GH的转基因小鼠的肝脏中检测到的胰岛素抵抗可能是由于受体后缺陷。
Transgenic mice expressing a hybrid gene produced by linking the promoter regulatory region of phosphoenolpyruvate carboxykinase (PEPCK) gene to the bovine growth hormone (bGH) gene, were used to investigate the effects of GH on insulin binding and insulin dependent tyrosine kinase activity of hepatic insulin receptors. Transgenic mice had normal levels of blood glucose, despite hyperinsulinemia, indicating that these animals were insulin resistant. The number of insulin receptors in the liver of transgenic mice was significantly decreased in both the particulate fraction (25%) and the solubilized membranes (40%) indicating that expressed (functional) and non-expressed (cryptic) receptors were affected. Scatchard analysis of competitive binding curves for insulin indicated that the affinity of the receptor did not differ between transgenic and normal mice. Insulin dependent tyrosine kinase activity in insulin receptors partially purified by wheat germ agglutin (WGA) agarose chromatography from solubilized liver membranes, was measured. The stimulatory action of insulin on phosphorylation of the synthetic substrate (a copolymer Glu-Tyr, 4:1) was increased 100% in transgenic, as compared to normal mice, using the same binding activity. Since transgenic mice are hyperinsulinemic, it is likely that the decreased insulin binding in this group reflects down regulation of the expressed and non-expressed insulin receptors, and the increased kinase activity represents a compensatory mechanism. We conclude that alterations in the insulin receptor number and in the tyrosine kinase activity develop in response to changes in insulin levels. Thus, insulin resistance detected in the liver of transgenic mice overexpressing GH may be due to post receptor defects.