In the present study, 67 cross-talk genes that were overlapping in periodontitis and T2DM were identified, including 10 hub genes (IL-6, IL-1B, MMP9, APOE, CXCL8, VCAM1, CCL5, CXCL12, PECAM1 and TIMP1). The gene discussed is APOE; the disease is type 2 diabetes mellitus.