Some studies have shown that periodontitis-derived virulence factors can upregulate the expression of cyclin E and downregulate the expression of the cell cycle inhibitor cyclin-dependent kinase inhibitor 1 (p21),63 while cyclin E and p21 are the key factors that regulate the G1/S stage of the cell cycle that promote β-cell proliferation.64 It is suggested that exposure to periodontitis-derived virulence factors has the potential to regulate the proliferation of β-cells, which can be explored in future research. The gene discussed is CCNE1; the disease is periodontitis.