Table_1_Human Islet Response to Selected Type 1 Diabetes-Associated Bacteria: A Transcriptome-Based Study.DOCX

Type 1 diabetes (T1D) is a chronic autoimmune disease that results from destruction of pancreatic β-cells. T1D subjects were recently shown to harbor distinct intestinal microbiome profiles. Based on these findings, the role of gut bacteria in T1D is being intensively investigated. The mechanism connecting intestinal microbial homeostasis with the development of T1D is unknown. Specific gut bacteria such as Bacteroides dorei (BD) and Ruminococcus gnavus (RG) show markedly increased abundance prior to the development of autoimmunity. One hypothesis is that these bacteria might traverse the damaged gut barrier, and their constituents elicit a response from human islets that causes metabolic abnormalities and inflammation. We have tested this hypothesis by exposing human islets to BD and RG in vitro, after which RNA-Seq analysis was performed. The bacteria altered expression of many islet genes. The commonly upregulated genes by these bacteria were cytokines, chemokines and enzymes, suggesting a significant effect of gut bacteria on islet antimicrobial and biosynthetic pathways. Additionally, each bacteria displayed a unique set of differentially expressed genes (DEGs). Ingenuity pathway analysis of DEGs revealed that top activated pathways and diseases included TREM1 signaling and inflammatory response, illustrating the ability of bacteria to induce islet inflammation. The increased levels of selected factors were confirmed using immunoblotting and ELISA methods. Our data demonstrate that islets produce a complex anti-bacterial response. The response includes both symbiotic and pathogenic aspects. Both oxidative damage and leukocyte recruitment factors were prominent, which could induce beta cell damage and subsequent autoimmunity.1型糖尿病（Type 1 diabetes, T1D）是一种由胰腺β细胞破坏引发的慢性自身免疫性疾病。近期研究表明，T1D患者存在独特的肠道微生物组特征。基于上述发现，肠道菌群在T1D中的作用正被深入研究。连接肠道微生物稳态与T1D发病的具体机制仍不明晰。特定肠道菌群，如多形拟杆菌（Bacteroides dorei, BD）与格氏瘤胃球菌（Ruminococcus gnavus, RG），在自身免疫症状出现前的丰度会显著升高。有假说提出，此类细菌可穿透受损的肠道屏障，其组分能够触发人胰岛产生反应，进而引发代谢异常与炎症反应。本研究通过体外将人胰岛暴露于BD与RG环境中验证了该假说，随后开展了RNA测序（RNA-Seq）分析。结果显示，两种细菌均改变了大量胰岛基因的表达水平。二者共同上调的基因涵盖细胞因子、趋化因子与酶类，提示肠道菌群对胰岛的抗菌及生物合成通路具有显著调控作用。此外，每种细菌各自诱导产生了一套独特的差异表达基因（differentially expressed genes, DEGs）。对差异表达基因进行的Ingenuity通路分析（Ingenuity Pathway Analysis）显示，排名最靠前的激活通路与疾病类型包括TREM1信号通路与炎症反应，证实了细菌可诱导胰岛产生炎症反应。本研究通过免疫印迹（immunoblotting）与酶联免疫吸附实验（ELISA）验证了部分靶因子的表达上调。数据表明，胰岛可产生复杂的抗菌应答反应，该应答兼具共生与致病双重特性；其中氧化损伤相关因子与白细胞募集因子均较为突出，这可能诱发β细胞损伤并引发后续的自身免疫反应。