Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
Mol Metab. 2017 May 31;6(8):833-844. doi: 10.1016/j.molmet.2017.05.016. eCollection 2017 Aug.
β-cell dysfunction and apoptosis associated with islet inflammation play a key role in the pathogenesis of type 2 diabetes (T2D). Growing evidence suggests that islet amyloid, formed by aggregation of human islet amyloid polypeptide (hIAPP), contributes to islet inflammation and β-cell death in T2D. We recently showed the role of interleukin-1β (IL-1β)/Fas/caspase-8 apoptotic pathway in amyloid-induced β-cell death. In this study, we used human islets in culture as an model of amyloid formation to: (1) investigate the effects of amyloid on islet levels of the natural IL-1 receptor antagonist (IL-1Ra); (2) examine if modulating the IL-1β/IL-1Ra balance can prevent amyloid-induced β-cell Fas upregulation and apoptosis.
Isolated human islets (n = 10 donors) were cultured in elevated glucose (to form amyloid) with or without a neutralizing human IL-1β antibody for up to 7 days. Parallel studies were performed with human islets in which amyloid formation was prevented by adeno-siRNA-mediated suppression of hIAPP expression (as control). β-cell levels of IL-1Ra, Fas, apoptosis as well as islet function, insulin- and amyloid-positive areas, and IL-1Ra release were assessed.
Progressive amyloid formation in human islets during culture was associated with alterations in IL-1Ra. Islet IL-1Ra levels were higher at early stages but were markedly reduced at later stages of amyloid formation. Furthermore, IL-1Ra release from human islets was reduced during 7-day culture in a time-dependent manner. These changes in IL-1Ra production and release from human islets during amyloid formation adversely correlated with islet IL-1β levels, β-cell Fas expression and apoptosis. Treatment with IL-1β neutralizing antibody markedly reduced amyloid-induced β-cell Fas expression and apoptosis, thereby improving islet β-cell survival and function during culture.
These data suggest that amyloid formation impairs the balance between IL-1β and IL-1Ra in islets by increasing IL-1β production and reducing IL-1Ra levels thereby promoting β-cell dysfunction and death. Restoring the IL-1β/IL-1Ra ratio may provide an effective strategy to protect islet β-cells from amyloid toxicity in T2D.
β细胞功能障碍和与胰岛炎症相关的细胞凋亡在 2 型糖尿病（T2D）的发病机制中起着关键作用。越来越多的证据表明，由人胰岛淀粉样多肽（hIAPP）聚集形成的胰岛淀粉样蛋白导致 T2D 中的胰岛炎症和β细胞死亡。我们最近研究了白细胞介素-1β（IL-1β）/Fas/半胱天冬酶-8 凋亡途径在淀粉样蛋白诱导的β细胞死亡中的作用。在这项研究中，我们使用体外培养的人胰岛作为淀粉样蛋白形成的模型：（1）研究淀粉样蛋白对胰岛中天然白细胞介素-1 受体拮抗剂（IL-1Ra）水平的影响；（2）研究调节 IL-1β/IL-1Ra 平衡是否可以防止淀粉样蛋白诱导的β细胞 Fas 上调和凋亡。
将分离的人胰岛（n=10 个供体）在高葡萄糖（形成淀粉样蛋白）中培养，同时或不使用中和人白细胞介素-1β的抗体培养长达 7 天。平行研究了通过腺病毒-siRNA 抑制 hIAPP 表达（作为对照）来预防淀粉样蛋白形成的人胰岛。评估β细胞中 IL-1Ra、Fas、凋亡以及胰岛功能、胰岛素和淀粉样蛋白阳性区和 IL-1Ra 释放。
在培养过程中人胰岛中淀粉样蛋白的逐渐形成与 IL-1Ra 的改变有关。在淀粉样蛋白形成的早期阶段，胰岛 IL-1Ra 水平较高，但在淀粉样蛋白形成的后期阶段显著降低。此外，人胰岛中 IL-1Ra 的释放随时间呈时间依赖性降低。在淀粉样蛋白形成过程中，人胰岛中 IL-1Ra 的产生和释放的这些变化与胰岛中 IL-1β 水平、β细胞 Fas 表达和凋亡呈负相关。用白细胞介素-1β中和抗体治疗可显著降低淀粉样蛋白诱导的β细胞 Fas 表达和凋亡，从而改善培养过程中人胰岛β细胞的存活和功能。
这些数据表明，淀粉样蛋白的形成通过增加 IL-1β 的产生和降低 IL-1Ra 水平，损害了胰岛中 IL-1β 和 IL-1Ra 之间的平衡，从而促进了β细胞功能障碍和死亡。恢复 IL-1β/IL-1Ra 比值可能是保护 T2D 中胰岛β细胞免受淀粉样蛋白毒性的有效策略。
