Del-1在牙龈卟啉单胞菌介导的牙周炎导致糖耐量异常中的作用及机制

Periodontitis, which is a chronic inflammatory disease caused by pathogenic oral microorganisms, is a pathogenic factor of diabetes, however, the mechanism by which periodontitis impacts the development of diabetes remain unclear. Porphyromonas gingivallis (Pg) promotes the homeostasis of the neutrophils and drives the development of periodontitis and diabetes. Del-1 is an endothelial cell secreted glycoprotein and play anti-inflammatory effect by outcompeting intercellular adhesion molecule–1 on the endothelium and then inhibits transendothelial migration of neutrophils. We found that salivary Del-1 expression level were lower in periodontitis and insulin resistance patients, based on our results and other previous studies, we hypothesize that Del-1 plays a crucial role in the development of diabetes driven by periodontitis induced by Pg. To determine whether Del-1 participates the progress of disease, our study is to investigate the Del-1exprssion level in the different organs and explore the relationship between Del-1 level and neurophils related inflammatory cytokines, glucose metabolism related genes in the liver during the progress of periodontitis and diabetes, and our study is also to seek the effect of exogenous Del-1 and IL-17 to the Del-1-deficient mouse during the progress of diabetes induced by Pg. And by the end of this study, we can confirm the effect of Del-1 to the development of Pg induced periodontitis and diabetes and address the mechanism of promotional effect of periodontitis on diabetes.

牙周病是糖尿病的危险因素，但在糖尿病发病过程中具体机制尚不明确。牙龈卟啉单胞菌促进中性粒细胞迁徙，延缓其凋亡，促进了牙周炎及糖耐量异常的形成。内皮细胞分泌的Del-1与血管内皮细胞表面受体结合后抑制中性粒细胞迁徙，抑制介导中性粒细胞聚集的IL-17的释放而发挥抗炎作用。前期结果显示牙周炎及胰岛素抵抗患者唾液中Del-1的表达水平显著下调，提示Del-1在牙周炎及糖耐量异常的发病过程中发挥作用，为明确其作用机制拟进行：1.Pg诱导小鼠牙周炎及糖耐量异常过程中，观察Del-1表达水平的变化及其与中性粒细胞相关炎症因子、糖代谢基因表达水平的关系；2. Pg诱导Del-1基因敲除小鼠糖耐量异常形成过程中，观察外源性Del-1/IL-17对糖代谢异常及中性粒细胞相关炎症因子的作用，了解Del-1在Pg诱导小鼠牙周炎及糖耐量异常的形成过程中作用机制，为明确牙周炎在糖尿病发病过程的作用机制提供依据。

牙周炎是由菌斑微生物引起的慢性炎症性疾病，是糖尿病的危险因素之一。既往研究显示牙龈卟啉单胞菌（Pg）在导致牙周炎形成的同时也促进了糖尿病的形成。内皮细胞分泌的Del-1与血管内皮细胞表面的受体结合后抑制中性粒细胞的迁徙，抑制介导中性粒细胞聚集的IL-17的释放，最终发挥抗炎作用。前期结果显示牙周炎及胰岛素抵抗患者唾液中Del-1的表达水平显著下调，提示Del-1在牙周炎及牙周炎导致糖尿病的发病过程中可能发挥作用。本研究中Pg感染小鼠22周后，牙槽骨吸收明显，糖耐量实验显示葡萄糖注射后30min及60min的血糖水平显著高于对照组，胰岛素敏感实验显示胰岛素注射15min及30min 后血糖水平也显著高于对照组，说明Pg感染后小鼠糖代谢水平（糖耐量水平及胰岛素抵抗水平）发生了一定异常。Pg感染组小鼠牙龈组织中Del-1表达水平较对照组明显下降，而IL-17、TNF-α与IL-6的表达水平较对照组明显升高，血清中IL-17、IL-23、TNF-α与IL-6的水平明显升高，MPO、CCR2与CXCL1的水平也均有明显升高,Pg感染组小鼠肝脏组织中糖代谢相关基因Ppara、Irs1、Saa与Pck1的表达水平均明显升高。Del-1基因敲除小鼠经Pg诱导感染22周后，与野生型小鼠相比其牙槽骨吸收更为明显，葡萄糖注射后30min的血糖及胰岛素注射15min后的血糖显著高于野生型小鼠组，基因敲除组小鼠其糖耐量异常及胰岛素抵抗更为明显。基因敲除小鼠牙龈组织中IL-17、IL-6与RANKL的表达水平较野生型小鼠明显升高，血清中IL17、IL-23、IL-6与RANKL的水平明显升高，MPO、CCL2、CCR2与CXCL1的水平有明显升高，肝脏组织中糖代谢相关基因（Ppara、Saa与Pck1 ）的表达水平均明显升高。上述结果说明Pg侵入机体后通过诱导中性粒细胞的稳态失调等引起牙周炎症及糖代谢异常，牙龈组织中Del-1的分泌减少促进了IL-17及IL-23的生成，促进了中性粒细胞的活性与功能，增加了中性粒细胞相关炎症因子的释放，从而促进了牙槽骨的吸收及糖代谢的异常，Del-1可能是Pg诱导牙周炎导致糖耐量异常及糖尿病的发生过程的重要调节介质。