Yang Mingyu, Mandal Kousik, Södergren Moa, Dumral Özge, Winroth Lena, Tengholm Anders
Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
Acta Physiol (Oxf). 2025 Feb;241(2):e14268. doi: 10.1111/apha.14268.
Somatostatin from pancreatic δ-cells is a paracrine regulator of insulin and glucagon secretion, but the release kinetics and whether secretion is altered in diabetes is unclear. This study aimed to improve understanding of somatostatin secretion by developing a tool for real-time detection of somatostatin release from individual pancreatic islets.
Reporter cells responding to somatostatin with cytoplasmic Ca concentration ([Ca]) changes were generated by co-expressing somatostatin receptor SSTR2, the G-protein Gα15 and a fluorescent Ca sensor in HeLa cells.
Somatostatin induced dose-dependent [Ca] increases in reporter cells with half-maximal and maximal effects at 1.6 ± 0.4 and ~30 nM, respectively. Mouse and human islets induced reporter cell [Ca] elevations that were inhibited by the SSTR2 antagonist CYN154806. Depolarization of islets by high K, K channel blockade or increasing the glucose concentration from 3 to 11 mM evoked concomitant elevations of [Ca] in islets and reporter cells. Exposure of islets to glucagon, GLP-1 and ghrelin also triggered reporter cell [Ca] responses, whereas little effect was obtained by islet exposure to insulin, glutamate, GABA and urocortin-3. Islets from type 2 diabetic human donors induced higher reporter cell [Ca] responses at 11 mM and after K depolarization compared with non-diabetic islets, although fewer δ-cells were identified by immunostaining.
Type 2 diabetes is associated with hypersecretion of somatostatin, which has implications for paracrine regulation of insulin and glucagon secretion. The new reporter cell assay for real-time detection of single-islet somatostatin release holds promise for further studies of somatostatin secretion in islet physiology and pathophysiology.
胰腺δ细胞分泌的生长抑素是胰岛素和胰高血糖素分泌的旁分泌调节因子，但生长抑素的释放动力学以及其分泌在糖尿病中是否改变尚不清楚。本研究旨在通过开发一种实时检测单个胰岛中生长抑素释放的工具，增进对生长抑素分泌的理解。
通过在HeLa细胞中共表达生长抑素受体SSTR2、G蛋白Gα15和荧光钙传感器，构建出对生长抑素产生细胞质钙浓度（[Ca]）变化反应的报告细胞。
生长抑素在报告细胞中诱导剂量依赖性的[Ca]升高，半最大效应和最大效应分别出现在1.6±0.4 nM和~30 nM。小鼠和人类胰岛诱导报告细胞[Ca]升高，该升高被SSTR2拮抗剂CYN154806抑制。高钾使胰岛去极化、钾通道阻断或葡萄糖浓度从3 mM增加到11 mM，均引起胰岛和报告细胞中[Ca]的伴随升高。胰岛暴露于胰高血糖素、胰高血糖素样肽-1和胃饥饿素也触发报告细胞[Ca]反应，而胰岛暴露于胰岛素、谷氨酸、γ-氨基丁酸和尿皮质素-3几乎没有影响。与非糖尿病胰岛相比，来自2型糖尿病人类供体的胰岛在11 mM和钾去极化后诱导更高的报告细胞[Ca]反应，尽管通过免疫染色鉴定出的δ细胞较少。
2型糖尿病与生长抑素分泌过多有关，这对胰岛素和胰高血糖素分泌的旁分泌调节有影响。用于实时检测单个胰岛生长抑素释放的新型报告细胞测定法，有望用于进一步研究胰岛生理和病理生理学中的生长抑素分泌。
