Periodontitis and Diabetes Mellitus

Abstract

(Int Heart J 2018; 59: 680-682) I t has been known for a very long time that functional dentistry and oral health impact longevity. At New Year's feasts in Japan, we eat "hagatame-mochi (teeth-hardening rice cake)" to wish for longevity with healthy teeth. Indeed, multiple epidemiological studies have suggested there are associations between tooth loss and mortality, as well as cardiovascular and cancer risks. 1-3) Tooth loss is mainly caused by periodontitis. Local periodontal infections that affect the supporting structures of teeth can promote a systemic inflammatory state by spreading pathogenic oral microorganisms to other organs , and increase the risks of a variety of diseases such as preterm birth, cardiovascular diseases, stroke, pulmonary diseases, and diabetes mellitus (DM). 4) A particularly close and bidirectional relationship between periodontitis and DM has been reported (Figure), 5-7) although there is no unique feature that is characteristic of periodontitis in patients with DM. 8) It is established that DM is a major risk factor for periodontitis, and increases the prevalence, severity, and progression of periodontitis. 5,6,9) Conversely, periodontitis increases insulin resistance, and aggravates glycemic control and diabetic complications in patients with DM. 5,6,9) Article p. 802 In this issue of International Heart Journal, Aoyama and colleagues compared the periodontal conditions between well-controlled and poorly-controlled DM patients with cardiovascular complications such as hypertension and dyslipidemia. 10) Although the number of teeth and probing pocket depth were comparable, the clinical attachment level (CAL) and bleeding on probing (BOP) rate were significantly higher in poorly-controlled DM patients than in well-controlled DM patients. Tobacco smoking increases susceptibility to periodontal diseases, 4,11) but the percentage of smokers was comparable between the two groups in this study. In addition, the percentages of hyper-tension and dyslipidemia were also comparable. Therefore , the results in this study indicate an association between glycemic control and periodontal conditions, although there were positive, but not significant relationships between HbA1c levels and clinical periodontal parameters such as CAL and BOP. According to mechanistic studies, DM evokes a hyperinflammatory response to bacterial challenges in periodontium and impairs reparative processes, leading to exaggeration of periodontal destruction (Figure). 5-7) These processes are partly mediated by advanced glycation end products (AGEs) and the receptor for AGEs (RAGE). 5-7,12) In accordance with locally activated proinflammatory cytokines in periodontium, there is evidence that the levels of IL-1β, IL-6, and receptor acti-vator of nuclear factor-κB ligand (RANKL)/osteoprote-gerin (OPG) ratios are elevated in patients with periodon-titis who are complicated with DM, compared with patients with periodontitis alone. In the study by Aoyama and colleagues, 10) CRP levels were comparable between well-controlled and poorly-controlled DM patients, while clinical periodontal parameters were more severe in poorly-controlled DM patients. More sensitive and specific biomarkers for periodontal inflammation will be of clinical use to assess the impact of periodontitis on glyce-mic control and to predict the cardiovascular risks of DM patients complicated with periodontitis. Aoyama and colleagues also demonstrated that Por-phyromonas gingivalis (P. gingivalis) was more prevalent in poorly-controlled DM patients than in well-controlled DM patients. 10) There is a good evidence for the involvement of P. gingivalis in the promotion of systemic inflam-matory responses and pathogenesis in animal models of DM, 13-15) as well as vascular and left ventricular remodel-ing. 16,17) P. gingivalis counts showed a significant relationship with clinical periodontal parameters, but the relationship between P. gingivalis counts and HbA1c was not statistically significant. Further studies will be required to clarify the impact of periodontal microbiota including P. gingivalis on glycemic control.