Group 1: Control rats (n = 5). Group 2: Diabetic rats (n = 8). Group 3: Diabetic rats, treated with aldose reductase inhibitor (ARI) (n = 8). Rats used: Sprague-Dawley rats (male, diabetes induced by Streptozotocin injection, experimental periodontitis induced by injection of LPS from Escherichia coli). The gene discussed is AKR1B1; the disease is diabetes mellitus.