State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
J Periodontol. 2019 Sep;90(9):1032-1042. doi: 10.1002/JPER.18-0528. Epub 2019 Jul 1.
Metformin, a classical treatment for diabetes mellitus, has shown sound anti-inflammatory effects. Emerging studies have focused on the mechanism underlying inflammation-related diabetic complications, such as diabetic periodontitis. Herein, we investigated the anti-inflammatory effects of metformin on the NIMA-related kinase 7 (Nek7)/nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) pathway both in vivo and in vitro in experimental diabetic periodontitis.
All procedures were conducted in Porphyromonas gingivalis (Pg)-infected streptozotocin (STZ)-induced diabetic mice and in lipopolysaccharide (LPS)-treated RAW 264.7 cells under high-glucose conditions. A range of techniques were performed in this study: microcomputed tomography, western blotting, and immunofluorescence were used to analyze periodontal tissues. Enzyme-linked immunosorbent assay (ELISA) was for serum interleukin-1β (IL-1β) detection. Specific pharmacological inhibition was used to stimulate cells. Flow cytometry was implemented to analyze cell cycle.
We found that metformin treatment can robustly ameliorate periodontal infection and tissue destruction and reduce blood glucose and serum IL-1β levels in mice with diabetic periodontitis. Moreover, gingival tissue exhibited less macrophage infiltration and decreased expression of Nek7, NLRP3, caspase-1, and mammalian target of rapamycin (mTOR), which were simultaneously observed in RAW 264.7 cell models stimulated with metformin. Metformin also affected the cell cycle in a dose-dependent way. Furthermore, after stimulation with the mTOR inhibitor rapamycin, additional metformin treatment could still downregulate Nek7/NLRP3.
Our research indicated that metformin significantly attenuated experimental diabetic periodontitis both in vivo and in vitro. Metformin suppressed the inflammatory state by inhibiting Nek7 expression to decrease NLRP3 inflammasome activity. Interestingly, mTOR inhibition was not involved in metformin-induced Nek7 downregulation. The observed Nek7 reduction could be related to metformin-mediated cell cycle arrest.
二甲双胍是治疗糖尿病的经典药物，具有良好的抗炎作用。新兴研究集中在与炎症相关的糖尿病并发症（如糖尿病性牙周炎）的发病机制上。在此，我们研究了二甲双胍在体内和体外实验性糖尿病性牙周炎中对 NIMA 相关激酶 7（Nek7）/核苷酸结合寡聚化结构域（NOD）样受体家族富含亮氨酸重复序列 3（NLRP3）途径的抗炎作用。
本研究采用牙龈卟啉单胞菌（Pg）感染链脲佐菌素（STZ）诱导的糖尿病小鼠和脂多糖（LPS）处理的 RAW 264.7 细胞在高糖条件下进行。采用多种技术进行研究：采用微计算机断层扫描、western blot 和免疫荧光分析牙周组织；采用酶联免疫吸附试验（ELISA）检测血清白细胞介素-1β（IL-1β）；采用特异性药理抑制剂刺激细胞；采用流式细胞术分析细胞周期。
我们发现，二甲双胍治疗可显著改善糖尿病牙周炎小鼠的牙周感染和组织破坏，降低血糖和血清 IL-1β水平。此外，在二甲双胍刺激的 RAW 264.7 细胞模型中，牙龈组织的巨噬细胞浸润减少，Nek7、NLRP3、半胱天冬酶-1 和哺乳动物雷帕霉素靶蛋白（mTOR）的表达降低。二甲双胍还以剂量依赖的方式影响细胞周期。此外，在用 mTOR 抑制剂雷帕霉素刺激后，额外的二甲双胍治疗仍可下调 Nek7/NLRP3。
本研究表明，二甲双胍在体内和体外均显著减轻实验性糖尿病性牙周炎。二甲双胍通过抑制 Nek7 表达抑制 NLRP3 炎性小体活性，从而抑制炎症状态。有趣的是，mTOR 抑制不参与二甲双胍诱导的 Nek7 下调。观察到的 Nek7 减少可能与二甲双胍介导的细胞周期停滞有关。
