Based on the recent evidence of IL-1 inhibition in patients with rheumatoid arthritis (RA) and concomitant type 2 diabetes (T2D), we evaluated the synovial tissue expression of IL-1 related genes in relationship to the ubiquitin–proteasome system and the effects of insulin on ubiquitinated proteins in fibroblast-like synoviocytes (FLSs). The synovial expression of IL-1 pathway genes was compared in early (< 1 year) treatment-naïve RA patients with T2D (RA/T2D n = 16) and age- and sex-matched RA patients without T2D (n = 16), enrolled in the Pathobiology of Early Arthritis Cohort (PEAC). The synovial expression of ubiquitin in macrophages and synovial lining fibroblasts was also assessed by Immunohistochemistry/immunofluorescence and correlated with synovial pathotypes. Finally, FLSs from RA patients (n = 5) were isolated and treated with human insulin (200 and 500 nM) and ubiquitinated proteins were assessed by western blot. Synovial tissues of RA/T2D patients were characterised by a consistent reduced expression of ubiquitin–proteasome genes. More specifically, ubiquitin genes (UBB, UBC, and UBA52) and genes codifying proteasome subunits (PSMA2, PSMA6, PSMA7, PSMB1, PSMB3, PSMB4, PSMB6, PSMB8, PSMB9, PSMB10, PSMC1, PSMD9, PSME1, and PSME2) were significantly lower in RA/T2D patients. On the contrary, genes regulating fibroblast functions (FGF7, FGF10, FRS2, FGFR3, and SOS1), and genes linked to IL-1 pathway hyper-activity (APP, IRAK2, and OSMR) were upregulated in RA/T2D. Immunohistochemistry showed a significant reduction of the percentage of ubiquitin-positive cells in synovial tissues of RA/T2D patients. Ubiquitin-positive cells were also increased in patients with a lympho-myeloid pathotype compared to diffuse myeloid or pauci-immune-fibroid. Finally, in vitro experiments showed a reduction of ubiquitinated proteins in RA-FLSs treated with a high concentration of insulin (500 nM). A different IL-1 pathway gene expression was observed in the synovial tissues of early treatment-naïve RA/T2D patients, linked to decreased expression of the ubiquitin–proteasome system. These findings may provide a mechanistic explanation of the observed clinical benefits of IL-1 inhibition in patients with RA and concomitant T2D.

中文翻译：

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早期未接受治疗的类风湿性关节炎并伴有 2 型糖尿病的患者中泛素蛋白酶体系统的表达减少可能与 IL-1 通路过度活跃有关； PEAC 队列的结果


基于类风湿关节炎（RA）合并2型糖尿病（T2D）患者IL-1抑制的最新证据，我们评估了IL-1相关基因与泛素-蛋白酶体系统关系的滑膜组织表达及其影响胰岛素对成纤维样滑膜细胞（FLS）中泛素化蛋白的影响。比较早期 (< 1 年) 未接受治疗的患有 T2D 的 RA 患者 (RA/T2D n = 16) 和年龄和性别匹配的无 T2D 的 RA 患者 (n = 16) 的滑膜表达，参加了早期关节炎病理学队列 (PEAC)。还通过免疫组织化学/免疫荧光评估了巨噬细胞和滑膜衬里成纤维细胞中泛素的滑膜表达，并与滑膜病理型相关。最后，分离 RA 患者 (n = 5) 的 FLS，并用人胰岛素（200 和 500 nM）处理，并通过蛋白质印迹评估泛素化蛋白。 RA/T2D 患者滑膜组织的特点是泛素蛋白酶体基因表达持续降低。更具体地说，泛素基因（UBB、UBC 和 UBA52）和编码蛋白酶体亚基（PSMA2、PSMA6、PSMA7、PSMB1、PSMB3、PSMB4、PSMB6、PSMB8、PSMB9、PSMB10、PSMC1、PSMD9、PSME1 和 PSME2）的基因显着RA/T2D 患者中较低。相反，调节成纤维细胞功能的基因（FGF7、FGF10、FRS2、FGFR3 和 SOS1）以及与 IL-1 通路过度活跃相关的基因（APP、IRAK2 和 OSMR）在 RA/T2D 中表达上调。免疫组织化学显示 RA/T2D 患者滑膜组织中泛素阳性细胞的百分比显着降低。与弥漫性骨髓细胞或寡免疫肌瘤患者相比，淋巴骨髓细胞病理型患者的泛素阳性细胞也有所增加。 最后，体外实验表明，用高浓度胰岛素（500 nM）处理的 RA-FLS 中泛素化蛋白减少。在早期未接受治疗的 RA/T2D 患者的滑膜组织中观察到不同的 IL-1 通路基因表达，这与泛素-蛋白酶体系统表达的降低有关。这些发现可能为 RA 合并 T2D 患者观察到的 IL-1 抑制临床益处提供机制解释。