MicroRNA‐126 Regulates Inflammatory Cytokine Secretion in Human Gingival Fibroblasts Under High Glucose via Targeting Tumor Necrosis Factor Receptor Associated Factor 6

Background: MicroRNAs (miRs) play a crucial role in inflammatory diseases, including periodontitis. Meanwhile, miRs act as biomarkers for predicting diabetes mellitus (DM). However, the regulatory mechanism of miR‐126 on development of periodontitis in patients with DM still remains unclear. Methods: Human gingival fibroblasts were cultured with low (5.5 mmol/L), medium (15 mmol/L), and high (25 mmol/L) glucose, respectively. Expressions of miR‐126, tumor necrosis factor (TNF) receptor associated factor (TRAF) 6, and related cytokines were analyzed by real‐time polymerase chain reaction (PCR). After transfection with miR‐126 mimic, PCR and western blot were performed to detect level of TRAF6, and luciferase reporter assay confirmed if TRAF6 is the direct target of miR‐126. Production of cytokines was measured using enzyme‐linked immunosorbent assay. Results: Increased glucose significantly suppressed miR‐126 expression in human gingival fibroblasts ( P <0.05). Also, high glucose increased TRAF6, interleukin (IL)‐6, TNF‐α, and chemical chemokine ligand (CCL) 2 levels, whereas it decreased IL‐10 level. MiR‐126 mimic significantly decreased TRAF6 mRNA and protein levels under high glucose ( P <0.05). Also, miR‐126 directly targeted TRAF6 through binding to its 3′ untranslated region in human gingival fibroblasts. Overexpression of miR‐126 significantly abrogated high glucose–induced secretion of proinflammatory cytokines such as IL‐6, TNF‐α, and CCL2 and promoted production of IL‐10. Conclusion: These data suggest that miR‐126 inhibits inflammation of human gingival fibroblasts under high glucose through targeting TRAF6, which may be a potential therapeutic target for periodontitis concomitant with DM.