The mechanisms responsible for the two-way relationship between diabetes and periodontal disease is still unclear; however, infection, such as that observed in periodontal disease may serve as a metabolic stressor, resulting in an increased demand for insulin, glucose and lipids [261,262,263], as well as the systemic challenge of pyrogenic cytokines such as IL-1β, TNF-α and IL-6 [264,265,266,267]. The gene discussed is TNF; the disease is periodontal disorder.