PDF(Pubmed)
Abstract：
Beta cells couple stimulation by glucose with insulin secretion and impairments in this coupling play a central role in diabetes mellitus. Cyclic adenosine monophosphate (cAMP) amplifies stimulus-secretion coupling via protein kinase A and guanine nucleotide exchange protein 2 (Epac2A). With the present research, we aimed to clarify the influence of cAMP-elevating diterpene forskolin on cytoplasmic calcium dynamics and intercellular network activity, which are two of the crucial elements of normal beta cell stimulus-secretion coupling, and the role of Epac2A under normal and stimulated conditions. To this end, we performed functional multicellular calcium imaging of beta cells in mouse pancreas tissue slices after stimulation with glucose and forskolin in wild-type and Epac2A knock-out mice. Forskolin evoked calcium signals in otherwise substimulatory glucose and beta cells from Epac2A knock-out mice displayed a faster activation. During the plateau phase, beta cells from Epac2A knock-out mice displayed a slightly higher active time in response to glucose compared with wild-type littermates, and stimulation with forskolin increased the active time via an increase in oscillation frequency and a decrease in oscillation duration in both Epac2A knock-out and wild-type mice. Functional network properties during stimulation with glucose did not differ in Epac2A knock-out mice, but the presence of Epac2A was crucial for the protective effect of stimulation with forskolin in preventing a decline in beta cell functional connectivity with time. Finally, stimulation with forskolin prolonged beta cell activity during deactivation, especially in Epac2A knock-out mice.
摘要：
β细胞通过葡萄糖刺激与胰岛素分泌偶联，这种偶联中的损伤在糖尿病中起着重要作用。环磷酸腺苷（cAMP）通过蛋白激酶A和鸟嘌呤核苷酸交换蛋白2（Epac2A）放大刺激分泌偶联。根据目前的研究,我们旨在阐明cAMP升高的毛喉素二萜对细胞质钙动力学和细胞间网络活性的影响，这是正常β细胞刺激-分泌偶联的两个关键因素，以及Epac2A在正常和刺激条件下的作用。为此,我们对野生型和Epac2A基因敲除小鼠用葡萄糖和毛喉素刺激后的小鼠胰腺组织切片的β细胞进行了功能性多细胞钙成像.Forskolin在来自Epac2A敲除小鼠的其他弱刺激性葡萄糖和β细胞中引起的钙信号显示出更快的激活。在高原阶段,来自Epac2A敲除小鼠的β细胞对葡萄糖的反应时间比野生型同窝的稍高。在Epac2A敲除小鼠和野生型小鼠中，用毛喉素刺激通过增加振荡频率和减少振荡持续时间来增加活动时间。在用葡萄糖刺激期间的功能网络特性在Epac2A敲除小鼠中没有差异，但Epac2A的存在对于毛喉素刺激防止β细胞功能连接随时间下降的保护作用至关重要.最后,用毛喉素刺激在失活期间延长β细胞活性，尤其是在Epac2A敲除小鼠中。
