Might smoking assuage the pro-inflammatory effect of diabetes in periodontal sites?

Abstract

OBJECTIVES\nThis study evaluated the effects of type 2 diabetes mellitus (DM), smoking and these two factors combined on gingival crevicular fluid levels and ratios of pro-/anti-inflammatory cytokines. Associations between cytokines with each other and with key periodontal pathogens in periodontal sites under the challenge of one or both of these risk factors were also assessed.\n\n\nMETHODS\n102 subjects with periodontitis were included in this cross-sectional study and assigned to one of the following groups: non-diabetic non-smokers (control group/n=25), non-smokers with DM (DM group/n=30), non-diabetic smokers (S group/n=26), and smokers with DM (S+DM group/n=21). The levels of 13 pro-inflammatory (IFN-γ, TNF-α, MIP-1α, GM-CSF, IL-1β, IL-2, IL-6, IL-7, IL-8, IL-12, IL-17, IL-21, IL-23) and 5 anti-inflammatory cytokines (IL-4, IL-5, IL-10, IL-13, TGF-β) were assessed in healthy and diseased sites, using multiplex immunoassay. Ratios of pro/anti-inflammatory cytokines were obtained in all possible permutations. The levels of 7 key periodontal pathogens were evaluated by qPCR.\n\n\nRESULTS\nOverall, the ratios of pro-/anti-inflammatory cytokines were higher in healthy and diseased sites of the DM group and in healthy sites of the S+DM group, and lower in diseased sites of the S group, compared with the control (p<0.05). The proportion of the pro-inflammatory cytokines in relation to the 18 cytokines studied was higher in the DM group and lower in the S group whereas the proportion of the anti-inflammatory cytokines was lower in both diabetic groups and higher in the S group, compared to the control (p<0.05). A cluster of six common cytokines (IL-4, IL-5, IL-12, IL-13, IL-21, IL-23) was observed in the diseased sites of all groups studied. Eight common cytokines (IL-4, IL-5, IL-12, IL-13, IL-17, IL-21, IL-23, IFN-γ) grouped closely in the healthy sites of both diabetic groups. Significant associations between pathogens and cytokines occurred mainly in the diseased sites of the SDM group (p<0.05).\n\n\nCONCLUSION\nDM induced an overall pro-inflammatory state, while smoking mainly stimulated immunosuppression in periodontal sites. When the two risk factors overlapped, smoking seemed to partially assuage the hyperinflammatory effect of DM.