Division of Metabolism, Endocrinology and Nutrition, Veteran Affairs Puget Sound Health Care System (151) and University of Washington, 1660 S. Columbian Way, Seattle, WA, 98108, USA.
Department of Chemistry, Stony Brook University, Stony Brook, NY, USA.
Diabetologia. 2020 Nov;63(11):2385-2395. doi: 10.1007/s00125-020-05232-2. Epub 2020 Jul 29.
AIMS/HYPOTHESIS: Aggregation of the beta cell secretory product human islet amyloid polypeptide (hIAPP) results in islet amyloid deposition, a pathological feature of type 2 diabetes. Amyloid formation is associated with increased levels of islet IL-1β as well as beta cell dysfunction and death, but the mechanisms that promote amyloid deposition in situ remain unclear. We hypothesised that physiologically relevant concentrations of IL-1β stimulate beta cell islet amyloid polypeptide (IAPP) release and promote amyloid formation.
We used a humanised mouse model of endogenous beta cell hIAPP expression to examine whether low (pg/ml) concentrations of IL-1β promote islet amyloid formation in vitro. Amyloid-forming islets were cultured for 48 h in the presence or absence of IL-1β with or without an IL-1β neutralising antibody. Islet morphology was assessed by immunohistochemistry and islet mRNA expression, hormone content and release were also quantified. Cell-free thioflavin T assays were used to monitor hIAPP aggregation kinetics in the presence and absence of IL-1β.
Treatment with a low concentration of IL-1β (4 pg/ml) for 48 h increased islet amyloid prevalence (93.52 ± 3.89% vs 43.83 ± 9.67% amyloid-containing islets) and amyloid severity (4.45 ± 0.82% vs 2.16 ± 0.50% amyloid area/islet area) in hIAPP-expressing mouse islets in vitro. This effect of IL-1β was reduced when hIAPP-expressing islets were co-treated with an IL-1β neutralising antibody. Cell-free hIAPP aggregation assays showed no effect of IL-1β on hIAPP aggregation in vitro. Low concentration IL-1β did not increase markers of the unfolded protein response (Atf4, Ddit3) or alter proIAPP processing enzyme gene expression (Pcsk1, Pcsk2, Cpe) in hIAPP-expressing islets. However, release of IAPP and insulin were increased over 48 h in IL-1β-treated vs control islets (IAPP 0.409 ± 0.082 vs 0.165 ± 0.051 pmol/5 islets; insulin 87.5 ± 8.81 vs 48.3 ± 17.3 pmol/5 islets), and this effect was blocked by co-treatment with IL-1β neutralising antibody.
CONCLUSIONS/INTERPRETATION: Under amyloidogenic conditions, physiologically relevant levels of IL-1β promote islet amyloid formation by increasing beta cell release of IAPP. Neutralisation of this effect of IL-1β may decrease the deleterious effects of islet amyloid formation on beta cell function and survival.
目的/假设：β细胞分泌产物人胰岛淀粉样多肽（hIAPP）的聚集导致胰岛淀粉样沉积，这是 2 型糖尿病的一个病理特征。淀粉样形成与胰岛 IL-1β 水平升高以及β细胞功能障碍和死亡有关，但促进原位淀粉样沉积的机制仍不清楚。我们假设生理相关浓度的 IL-1β 可刺激β细胞胰岛淀粉样多肽（IAPP）释放并促进淀粉样形成。
我们使用内源性β细胞 hIAPP 表达的人源化小鼠模型来研究低（pg/ml）浓度的 IL-1β 是否会促进体外胰岛淀粉样形成。用或不用 IL-1β 中和抗体，将形成淀粉样的胰岛在存在或不存在 IL-1β 的情况下培养 48 小时。通过免疫组织化学评估胰岛形态，还定量检测胰岛 mRNA 表达、激素含量和释放。使用无细胞硫黄素 T 测定法监测有无 IL-1β 存在时 hIAPP 聚集动力学。
用低浓度（4pg/ml）IL-1β 处理 48 小时可增加 hIAPP 表达小鼠胰岛中的胰岛淀粉样病变发生率（93.52±3.89%含淀粉样病变的胰岛比 43.83±9.67%）和淀粉样病变严重程度（4.45±0.82%比 2.16±0.50%淀粉样物质/胰岛面积）。在 hIAPP 表达的胰岛与 IL-1β 中和抗体共同处理时，IL-1β 的这种作用会降低。体外无细胞 hIAPP 聚集测定法显示 IL-1β 对 hIAPP 聚集无影响。低浓度 IL-1β 不会增加未折叠蛋白反应的标志物（Atf4、Ddit3）或改变 proIAPP 加工酶基因表达（Pcsk1、Pcsk2、Cpe）在 hIAPP 表达的胰岛中。然而，与对照胰岛相比，IL-1β 处理的胰岛在 48 小时内 IAPP 和胰岛素的释放增加（IAPP 0.409±0.082 比 0.165±0.051 pmol/5 胰岛；胰岛素 87.5±8.81 比 48.3±17.3 pmol/5 胰岛），这种作用可被 IL-1β 中和抗体共同处理所阻断。
结论/解释：在淀粉样形成条件下，生理相关水平的 IL-1β 通过增加β细胞 IAPP 的释放来促进胰岛淀粉样形成。中和这种 IL-1β 的作用可能会降低胰岛淀粉样形成对β细胞功能和存活的有害影响。
