PDF(Pubmed)
Abstract：
UNASSIGNED: Biphasic insulin secretion is an intrinsic characteristic of the pancreatic islet and has clinical relevance due to the loss of first-phase in patients with Type 2 diabetes. As it has long been shown that first-phase insulin secretion only occurs in response to rapid changes in glucose, we tested the hypothesis that islet response to an increase in glucose is a combination of metabolism plus an osmotic effect where hypertonicity is driving first-phase insulin secretion.
UNASSIGNED: Experiments were performed using perifusion analysis of rat, mouse, and human islets. Insulin secretion rate (ISR) and other parameters associated with its regulation were measured in response to combinations of D-glucose and membrane-impermeable carbohydrates (L-glucose or mannitol) designed to dissect the effect of hypertonicity from that of glucose metabolism.
UNASSIGNED: Remarkably, the appearance of first-phase responses was wholly dependent on changes in tonicity: no first-phase in NAD(P)H, cytosolic calcium, cAMP secretion rate (cAMP SR), or ISR was observed when increased D-glucose concentration was counterbalanced by decreases in membrane-impermeable carbohydrates. When D-glucose was greater than 8 mM, rapid increases in L-glucose without any change in D-glucose resulted in first-phase responses in all measured parameters that were kinetically similar to D-glucose. First-phase ISR was completely abolished by H89 (a non-specific inhibitor of protein kinases) without affecting first-phase calcium response. Defining first-phase ISR as the difference between glucose-stimulated ISR with and without a change in hypertonicity, the peak of first-phase ISR occurred after second-phase ISR had reached steady state, consistent with the well-established glucose-dependency of mechanisms that potentiate glucose-stimulated ISR.
UNASSIGNED: The data collected in this study suggests a new model of glucose-stimulated biphasic ISR where first-phase ISR derives from (and after) a transitory amplification of second-phase ISR and driven by hypertonicity-induced rise in H89-inhibitable kinases likely driven by first-phase responses in cAMP, calcium, or a combination of both.
UNASSIGNED: Experiments were performed using perifusion analysis of rat, mouse, and human islets. Insulin secretion rate (ISR) and other parameters associated with its regulation were measured in response to combinations of D-glucose and membrane-impermeable carbohydrates (L-glucose or mannitol) designed to dissect the effect of hypertonicity from that of glucose metabolism.
UNASSIGNED: Remarkably, the appearance of first-phase responses was wholly dependent on changes in tonicity: no first-phase in NAD(P)H, cytosolic calcium, cAMP secretion rate (cAMP SR), or ISR was observed when increased D-glucose concentration was counterbalanced by decreases in membrane-impermeable carbohydrates. When D-glucose was greater than 8 mM, rapid increases in L-glucose without any change in D-glucose resulted in first-phase responses in all measured parameters that were kinetically similar to D-glucose. First-phase ISR was completely abolished by H89 (a non-specific inhibitor of protein kinases) without affecting first-phase calcium response. Defining first-phase ISR as the difference between glucose-stimulated ISR with and without a change in hypertonicity, the peak of first-phase ISR occurred after second-phase ISR had reached steady state, consistent with the well-established glucose-dependency of mechanisms that potentiate glucose-stimulated ISR.
UNASSIGNED: The data collected in this study suggests a new model of glucose-stimulated biphasic ISR where first-phase ISR derives from (and after) a transitory amplification of second-phase ISR and driven by hypertonicity-induced rise in H89-inhibitable kinases likely driven by first-phase responses in cAMP, calcium, or a combination of both.
摘要：
■双相胰岛素分泌是胰岛的内在特征，并且由于2型糖尿病患者的第一阶段丧失而具有临床相关性。因为长期以来已经证明第一阶段胰岛素分泌仅在响应葡萄糖的快速变化时发生，我们检验了以下假设:胰岛对葡萄糖增加的反应是代谢加渗透效应的组合,其中高渗性驱动第一阶段胰岛素分泌.
■使用大鼠的灌注分析进行实验，鼠标,和人类胰岛。响应于D-葡萄糖和膜不可渗透的碳水化合物（L-葡萄糖或甘露醇）的组合，测量了胰岛素分泌率（ISR）和与其调节相关的其他参数，该组合旨在从葡萄糖代谢中剖析高渗性的影响。
■值得注意的是，第一阶段反应的出现完全取决于张力的变化：NAD（P）H中没有第一阶段，胞质钙，cAMP分泌率（cAMPSR），当增加的D-葡萄糖浓度被膜不透性碳水化合物的减少抵消时，观察到ISR。当D-葡萄糖大于8mM时，在D-葡萄糖没有任何变化的情况下,L-葡萄糖的快速增加导致所有测量参数的第一阶段反应在动力学上与D-葡萄糖相似.H89（蛋白激酶的非特异性抑制剂）完全消除了第一阶段ISR，而不会影响第一阶段钙反应。将第一阶段ISR定义为有和没有高渗性变化的葡萄糖刺激ISR之间的差异，第一阶段ISR的峰值出现在第二阶段ISR达到稳定状态之后，与已确立的增强葡萄糖刺激ISR的机制的葡萄糖依赖性一致。
■本研究中收集的数据表明了葡萄糖刺激的双相ISR的新模型，其中第一阶段ISR来自（和之后）第二阶段ISR的短暂放大，并由高渗性引起H89抑制激酶的升高可能由cAMP的第一阶段反应驱动，钙，或两者的组合。
■使用大鼠的灌注分析进行实验，鼠标,和人类胰岛。响应于D-葡萄糖和膜不可渗透的碳水化合物（L-葡萄糖或甘露醇）的组合，测量了胰岛素分泌率（ISR）和与其调节相关的其他参数，该组合旨在从葡萄糖代谢中剖析高渗性的影响。
■值得注意的是，第一阶段反应的出现完全取决于张力的变化：NAD（P）H中没有第一阶段，胞质钙，cAMP分泌率（cAMPSR），当增加的D-葡萄糖浓度被膜不透性碳水化合物的减少抵消时，观察到ISR。当D-葡萄糖大于8mM时，在D-葡萄糖没有任何变化的情况下,L-葡萄糖的快速增加导致所有测量参数的第一阶段反应在动力学上与D-葡萄糖相似.H89（蛋白激酶的非特异性抑制剂）完全消除了第一阶段ISR，而不会影响第一阶段钙反应。将第一阶段ISR定义为有和没有高渗性变化的葡萄糖刺激ISR之间的差异，第一阶段ISR的峰值出现在第二阶段ISR达到稳定状态之后，与已确立的增强葡萄糖刺激ISR的机制的葡萄糖依赖性一致。
■本研究中收集的数据表明了葡萄糖刺激的双相ISR的新模型，其中第一阶段ISR来自（和之后）第二阶段ISR的短暂放大，并由高渗性引起H89抑制激酶的升高可能由cAMP的第一阶段反应驱动，钙，或两者的组合。
