Department of Bioengineering, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.
Barbara Davis Center for Diabetes, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.
J Physiol. 2023 Sep;601(18):4053-4072. doi: 10.1113/JP282114. Epub 2023 Aug 14.
The secretion of insulin from β-cells in the islet of Langerhans is governed by a series of metabolic and electrical events, which can fail during the progression of type 2 diabetes (T2D). β-cells are electrically coupled via connexin-36 (Cx36) gap junction channels, which coordinates the pulsatile dynamics of [Ca ] and insulin release across the islet. Factors such as pro-inflammatory cytokines and free fatty acids disrupt gap junction coupling under in vitro conditions. Here we test whether gap junction coupling and coordinated [Ca ] dynamics are disrupted in T2D, and whether recovery of gap junction coupling can recover islet function. We examine islets from donors with T2D, from db/db mice, and islets treated with pro-inflammatory cytokines (TNF-α, IL-1β, IFN-ɣ) or free fatty acids (palmitate). We modulate gap junction coupling using Cx36 over-expression or pharmacological activation via modafinil. We also develop a peptide mimetic (S293) of the c-terminal regulatory site of Cx36 designed to compete against its phosphorylation. Cx36 gap junction permeability and [Ca ] dynamics were disrupted in islets from both human donors with T2D and db/db mice, and in islets treated with pro-inflammatory cytokines or palmitate. Cx36 over-expression, modafinil treatment and S293 peptide all enhanced Cx36 gap junction coupling and protected against declines in coordinated [Ca ] dynamics. Cx36 over-expression and S293 peptide also reduced apoptosis induced by pro-inflammatory cytokines. Critically, S293 peptide rescued gap junction coupling and [Ca ] dynamics in islets from both db/db mice and a sub-set of T2D donors. Thus, recovering or enhancing Cx36 gap junction coupling can improve islet function in diabetes. KEY POINTS: Connexin-36 (Cx36) gap junction permeability and associated coordination of [Ca ] dynamics is diminished in human type 2 diabetes (T2D) and mouse models of T2D. Enhancing Cx36 gap junction permeability protects against disruptions to the coordination of [Ca ] dynamics. A novel peptide mimetic of the Cx36 c-terminal regulatory region protects against declines in Cx36 gap junction permeability. Pharmacological elevation in Cx36 or Cx36 peptide mimetic recovers [Ca ] dynamics and glucose-stimulated insulin secretion in human T2D and mouse models of T2D.
胰岛中朗格汉斯岛β细胞的胰岛素分泌受一系列代谢和电事件的控制，这些事件在 2 型糖尿病（T2D）的进展过程中可能会失败。β细胞通过间隙连接蛋白 36（Cx36）间隙连接通道电偶联，协调胰岛中[Ca2+]的脉动动力学和胰岛素释放。在体外条件下，促炎细胞因子和游离脂肪酸等因素会破坏间隙连接偶联。在这里，我们测试 T2D 中是否存在间隙连接偶联和协调的[Ca2+]动力学的破坏，以及恢复间隙连接偶联是否可以恢复胰岛功能。我们检查了来自 T2D 供体、db/db 小鼠以及用促炎细胞因子（TNF-α、IL-1β、IFN-γ）或游离脂肪酸（棕榈酸）处理的胰岛的功能。我们使用 Cx36 过表达或通过莫达非尼的药理学激活来调节间隙连接偶联。我们还开发了一种 Cx36 羧基末端调节区的肽模拟物（S293），旨在与磷酸化竞争。来自 T2D 供体和 db/db 小鼠的胰岛以及用促炎细胞因子或棕榈酸处理的胰岛中，Cx36 间隙连接通透性和[Ca2+]动力学均受到破坏。Cx36 过表达、莫达非尼处理和 S293 肽都增强了 Cx36 间隙连接偶联，并防止了协调的[Ca2+]动力学的下降。Cx36 过表达和 S293 肽还减少了促炎细胞因子诱导的细胞凋亡。至关重要的是，S293 肽挽救了 db/db 小鼠和一部分 T2D 供体胰岛的间隙连接偶联和[Ca2+]动力学。因此，恢复或增强 Cx36 间隙连接偶联可以改善糖尿病中的胰岛功能。关键要点：在人类 2 型糖尿病（T2D）和 T2D 小鼠模型中，连接蛋白 36（Cx36）间隙连接通透性和相关[Ca2+]动力学的协调降低。增强 Cx36 间隙连接通透性可防止[Ca2+]动力学的协调中断。Cx36 羧基末端调节区的新型肽模拟物可防止 Cx36 间隙连接通透性下降。Cx36 或 Cx36 肽模拟物的药理学升高可恢复人类 T2D 和 T2D 小鼠模型中的[Ca2+]动力学和葡萄糖刺激的胰岛素分泌。
