Garvan Institute of Medical Research, St Vincent's Clinical School, UNSW Sydney, 384 Victoria St, Darlinghurst, Sydney, NSW, 2010, Australia.
Diabetologia. 2019 Jun;62(6):993-999. doi: 10.1007/s00125-019-4844-y. Epub 2019 Mar 4.
AIMS/HYPOTHESIS: Mild islet inflammation has been suggested as a contributing factor to beta cell failure in type 2 diabetes. Macrophage levels are elevated in the islets of humans and mice with type 2 diabetes, but their effects on beta cells are not understood. Our goal was to examine the gene expression changes in islet-associated macrophages in obesity models with opposing disposition to diabetes development and to assess their potential contribution to beta cell (mal)adaptation.
Islets were isolated from lean control mice, obese diabetes-prone db/db mice and obese diabetes-resistant ob/ob mice. Macrophages were sorted using flow cytometry. Islets were treated ex vivo with clodronate-containing liposomes to deplete macrophages. Gene expression was assessed by real-time RT-PCR.
Macrophage levels were increased in islets from db/db mice but not in islets from ob/ob mice compared with lean control mice. Macrophages from db/db and ob/ob islets displayed distinct changes in gene expression compared with control islet macrophages, suggesting differential shifts in functional state. Macrophages from db/db islets displayed increased expression of interferon regulatory factor 5 (Irf5), IL-1 receptor antagonist (Il1rn) and mannose receptor C-type 1 (Mrc1), whereas macrophages from ob/ob islets showed elevated levels of transforming growth factor beta 1 (Tgfb1) and reduced IL-1β (Il1b). Clodronate-liposome treatment of islets depleted macrophages, as evidenced by reduced mRNA expression of Cd11b (also known as Itgam) and F4/80 (also known as Adgre1) compared with PBS-liposome-treated islets. The depletion of macrophages in db/db islets increased the expression of genes related to beta cell identity. The mRNA levels of islet-associated transcription factors (Mafa and Pdx1), glucose transporter (Glut2 [also known as Slc2a2]), ATP-sensitive K channel (Kcnj11), incretin receptor (Gipr) and adaptive unfolded protein response (UPR) genes (Xbp1, Hspa5, Pdia4 and Fkbp11) were increased in db/db islets after macrophage depletion, whereas the mRNA levels of the deleterious UPR effector, Ddit3, were reduced. In contrast, depletion of macrophages in islets of ob/ob mice did not affect beta cell identity gene expression.
CONCLUSIONS/INTERPRETATION: The findings of this study suggest that distinct alterations in islet macrophages of obese mice are critically important for the disruption of beta cell gene expression in diabetes.
目的/假设：轻度胰岛炎症被认为是 2 型糖尿病中β细胞衰竭的一个促成因素。在 2 型糖尿病患者的胰岛中，巨噬细胞水平升高，但它们对β细胞的影响尚不清楚。我们的目标是研究具有相反糖尿病发展倾向的肥胖模型中胰岛相关巨噬细胞的基因表达变化，并评估它们对β细胞（不良）适应的潜在贡献。
从瘦对照小鼠、肥胖糖尿病易感 db/db 小鼠和肥胖糖尿病抵抗 ob/ob 小鼠中分离胰岛。使用流式细胞术分选巨噬细胞。用载有氯膦酸盐的脂质体对胰岛进行离体处理以耗尽巨噬细胞。通过实时 RT-PCR 评估基因表达。
与瘦对照小鼠相比，db/db 小鼠的胰岛中巨噬细胞水平升高，但 ob/ob 小鼠的胰岛中没有升高。与对照胰岛巨噬细胞相比，db/db 和 ob/ob 胰岛巨噬细胞的基因表达发生了明显变化，表明功能状态的差异变化。db/db 胰岛巨噬细胞表现出干扰素调节因子 5（Irf5）、白细胞介素 1 受体拮抗剂（Il1rn）和甘露糖受体 C 型 1（Mrc1）的表达增加，而 ob/ob 胰岛巨噬细胞则表现出转化生长因子β 1（Tgfb1）水平升高和白细胞介素 1β（Il1b）减少。用载有氯膦酸盐的脂质体处理胰岛可耗尽巨噬细胞，与用 PBS 脂质体处理的胰岛相比，CD11b（也称为 Itgam）和 F4/80（也称为 Adgre1）的 mRNA 表达降低。db/db 胰岛中巨噬细胞的耗竭增加了与β细胞特征相关的基因的表达。db/db 胰岛中胰岛相关转录因子（Mafa 和 Pdx1）、葡萄糖转运体（Glut2[也称为 Slc2a2]）、ATP 敏感性 K 通道（Kcnj11）、肠促胰岛素受体（Gipr）和适应性未折叠蛋白反应（UPR）基因（Xbp1、Hspa5、Pdia4 和 Fkbp11）的 mRNA 水平增加，而有害 UPR 效应物 Ddit3 的 mRNA 水平降低。相反，ob/ob 小鼠胰岛中巨噬细胞的耗竭并不影响β细胞特征基因的表达。
结论/解释：这项研究的结果表明，肥胖小鼠胰岛中巨噬细胞的明显改变对于破坏糖尿病中β细胞的基因表达至关重要。
