Objective:To investigate the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) in type 2 diabetic rats with periodontitis.Methods:46 male Wistar rats were randomly divided into the healthy group(n =10),the periodontitis group(n =12),the type 2 diabetes mellitus group(n =12) and the type 2 diabetic periodontitis group(n =12).Animal models were prepared respectively.The expression of OPG and RANKL protein in alveolar bone was detected by immunohistochemistry(IHC).Results:Compared with the healthy group,the expression of OPG in the type 2 diabetes mellitus group,the periodontitis group,the type 2 diabetes mellitus with periodontitis group decreased in turn,however the expression of RANKL increased in turn.The expression of OPG and RANKL had no significant difference between periodontitis group and type 2 diabetes periodontitis group,while there was statistically significant difference among the other groups (P ＜ 0.05).Conclusion:Inflammation may lcad to upregulation of RANKL in osteoclasts and immune cells,and downregulation of OPG in osteoblasts.