Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia.
Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia.
Front Endocrinol (Lausanne). 2023 Aug 28;14:1225486. doi: 10.3389/fendo.2023.1225486. eCollection 2023.
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.
β 细胞将葡萄糖刺激与胰岛素分泌偶联，这种偶联的损伤在糖尿病中起着核心作用。环腺苷酸（cAMP）通过蛋白激酶 A 和鸟苷酸交换蛋白 2（Epac2A）放大刺激-分泌偶联。本研究旨在阐明 cAMP 升高的二萜化合物福司可林对细胞质钙动力学和细胞间网络活动的影响，这是正常β细胞刺激-分泌偶联的两个关键要素，以及 Epac2A 在正常和刺激条件下的作用。为此，我们在野生型和 Epac2A 敲除小鼠的胰腺组织切片中进行了β细胞的功能型多细胞钙成像，以检测葡萄糖和福司可林刺激后的钙动力学。福司可林在亚刺激葡萄糖中诱发钙信号，而 Epac2A 敲除小鼠的β细胞表现出更快的激活。在平台期，与野生型同窝仔相比，Epac2A 敲除小鼠的β细胞对葡萄糖的反应活性时间稍长，而福司可林刺激通过增加振荡频率和缩短振荡持续时间来增加活性时间，这在 Epac2A 敲除和野生型小鼠中均如此。Epac2A 敲除小鼠在葡萄糖刺激期间的功能网络特性没有差异，但 Epac2A 的存在对于福司可林刺激在预防β细胞功能连接随时间下降方面的保护作用至关重要。最后，福司可林刺激延长了β细胞在去激活期间的活性，尤其是在 Epac2A 敲除小鼠中。
