Buteau J, Roduit R, Susini S, Prentki M
Department of Nutrition, University of Montreal and the CR-CHUM, Institute of Cancer, Quebec, Canada.
Diabetologia. 1999 Jul;42(7):856-64. doi: 10.1007/s001250051238.
AIMS/HYPOTHESIS: Glucagon-like peptide-1 is a potent glucoincretin hormone and a potentially important drug in the treatment of Type II (non-insulin-dependent) diabetes mellitus. We have investigated whether it acts as a growth factor in beta (INS-1)-cells and have studied the signalling pathways and transcription factors implicated in this process.
Cell proliferation was assessed by tritiated thymidine incorporation measurements. We have examined the action of glucagon-like peptide-1 on the enzymatic activity of phosphatidylinositol 3-kinase. The DNA binding activity of transcription factors was investigated by electrophoretic mobility shift assay. Measurements of mRNA were done using the northern technique.
Glucagon-like peptide-1 caused an increase in tritiated thymidine incorporation in beta (INS-1)-cells and phosphatidylinositol 3-kinase activity in a dose-dependent manner non-additively with glucose. The phosphatidylinositol 3-kinase inhibitors wortmannin and LY294002 blocked the effects of glucagon-like peptide-1 on DNA synthesis. Transcription factor pancreatic and duodenal homebox gene 1 (PDX-1) DNA binding activity was increased by glucagon-like peptide-1 at 3 or 11 mmol/l glucose and the phosphatidylinositol 3-kinase inhibitor LY294002 suppressed the action of glucagon-like peptide-1 on PDX-1 DNA binding activity. Glucagon-like peptide-1 and glucose alone did not change activating protein-1 DNA binding activity. They synergised, however, to increase the activity of activating protein-1. Glucagon-like peptide-1 also increased the expression of PDX-1, glucose transporter 2, glucokinase and insulin mRNAs. Finally, glucagon-like peptide-1 increased the incorporation of tritiated thymidine in isolated rat islets.
CONCLUSION/INTERPRETATION: The results suggest that glucagon-like peptide-1 may act as a growth factor for the beta cell by a phosphatidylinositol 3-kinase mediated event. Glucagon-like peptide-1 could also regulate the expression of the insulin gene and genes encoding enzymes implicated in glucose transport and metabolism through the phosphatidylinositol 3-kinase/PDX-1 transduction signalling pathway.
目的/假设：胰高血糖素样肽-1是一种强效的肠促胰岛素激素，在治疗II型（非胰岛素依赖型）糖尿病方面可能是一种重要药物。我们研究了它在β（INS-1）细胞中是否作为生长因子起作用，并研究了参与这一过程的信号通路和转录因子。
通过氚标记胸腺嘧啶核苷掺入测量评估细胞增殖。我们检测了胰高血糖素样肽-1对磷脂酰肌醇3激酶酶活性的作用。通过电泳迁移率变动分析研究转录因子的DNA结合活性。使用Northern技术进行mRNA测量。
胰高血糖素样肽-1导致β（INS-1）细胞中氚标记胸腺嘧啶核苷掺入增加，以及磷脂酰肌醇3激酶活性呈剂量依赖性增加，且与葡萄糖无相加作用。磷脂酰肌醇3激酶抑制剂渥曼青霉素和LY294002阻断了胰高血糖素样肽-1对DNA合成的作用。在3或11 mmol/l葡萄糖条件下，胰高血糖素样肽-1增加了转录因子胰腺和十二指肠同源盒基因1（PDX-1）的DNA结合活性，磷脂酰肌醇3激酶抑制剂LY294002抑制了胰高血糖素样肽-1对PDX-1 DNA结合活性的作用。单独的胰高血糖素样肽-1和葡萄糖不会改变活化蛋白-1的DNA结合活性。然而，它们协同作用增加了活化蛋白-1的活性。胰高血糖素样肽-1还增加了PDX-1、葡萄糖转运蛋白2、葡萄糖激酶和胰岛素mRNA的表达。最后，胰高血糖素样肽-1增加了分离的大鼠胰岛中氚标记胸腺嘧啶核苷的掺入。
结论/解读：结果表明，胰高血糖素样肽-1可能通过磷脂酰肌醇3激酶介导的事件作为β细胞的生长因子。胰高血糖素样肽-1还可通过磷脂酰肌醇3激酶/PDX-1转导信号通路调节胰岛素基因以及编码参与葡萄糖转运和代谢的酶的基因的表达。
