Association between metabolic syndrome and periodontitis: The role of lipids, inflammatory cytokines, altered host response, and the microbiome

Abstract

Periodontitis has been associated with many systemic diseases and conditions, including metabolic syndrome. Metabolic syndrome is a cluster of conditions that occur concomitantly and together they increase the risk of cardiovascular disease and double the risk of type 2 diabetes. In this review, we focus on the association between metabolic syndrome and periodontitis; however, we also include information on diabetes mellitus and cardiovascular disease, since these two conditions are significantly intertwined with metabolic syndrome. With regard to periodontitis and metabolic syndrome, to date, the vast majority of studies point to an association between these two conditions and also demonstrate that periodontitis can contribute to the development of, or can worsen, metabolic syndrome. Evaluating the effect of metabolic syndrome on the salivary microbiome, data presented herein support the hypothesis that the salivary bacterial profile is altered in metabolic syndrome patients compared with healthy patients. Considering periodontitis and these three conditions, the vast majority of human and animal studies point to an association between periodontitis and metabolic syndrome, diabetes, and cardiovascular disease. Moreover, there is evidence to suggest that metabolic syndrome and diabetes can alter the oral microbiome. However, more studies are needed to fully understand the influence these conditions have on each other.

Keywords: cardiovascular disease; diabetes; metabolic syndrome; microbiome and inflammation; periodontitis.

FIGURE 1

Rarefaction plots show distinct levels of alpha diversity between healthy and metabolic syndrome subjects. The two‐group analysis rarefaction plot (A) represents the rarefaction curves of the healthy and metabolic syndrome subjects. Both curves show similar species richness and the curves plateau as the number of sequences rise per sample. The four‐group analysis rarefaction plot (B) shows similar alpha diversity in terms of species richness and both begin to plateau and the curves of all four groups begin to plateau as the number of sequences rises per sample. MetS, metabolic syndrome; MetS HP, metabolic syndrome with healthy periodontium; MetS PD, metabolic syndrome with periodontitis; OTUs, operational taxonomic units

FIGURE 2

Principal coordinate analysis (PCoA) for all groups show the relative relatedness within groups. A two‐dimensional view of the three‐dimensional PCoA plot, derived from UniFrac as a distance metric, is shown in A, representing beta diversity for the two‐group analysis. It can be appreciated that the two groups appear to be more related within group than between group as evidenced by clusters. A two‐dimensional view of the three‐dimensional PCoA plot, derived from UniFrac as a distance metric, is shown in B, representing beta diversity for the four‐group analysis. No conclusive result regarding beta diversity can be observed from these plots. MetS, metabolic syndrome; MetS HP, metabolic syndrome with healthy periodontium; MetS PD, metabolic syndrome with periodontitis

FIGURE 3

The cladograms show the phylogenetic relationship and taxonomic groupings of the taxa significantly associated with different subject groups.A, The phylogenetic relationship and taxonomic groupings of the taxa significantly associated with healthy and metabolic syndrome (MetSyndrome) subjects. Dots of red (health) and green (metabolic syndrome) represent significantly associated taxa to the labeled group and the size of the dot corresponds to relative abundance. At the outer edge of the cladogram, a letter is listed to represent this taxon and corresponds with the legend on the right. A strong association between taxa stemming from the phylum Proteobacteria and phylum SR1 and health is shown. Taxonomic relationships are shown in clusters of green for taxa significantly associated with the metabolic syndrome group. B, The phylogenetic relationship and taxonomic groupings of the taxa significantly associated with healthy (red), healthy* (green), metabolic syndrome with healthy periodontium (MetS_HP; blue), and metabolic syndrome with periodontitis (MetS_PD; purple). Colored dots represent significant taxa for the denoted group and the size of the dot corresponds to relative abundance. At the outer edge of the cladogram, letters are used to represent the significant taxa, listed in the legend on the right side of the figure. A strong association is shown between taxa stemming from the phyla Tenericutes and Spirochaetes and order Coriobacteriia for metabolic syndrome with periodontitis subjects; a strong association is shown between taxa stemming from the phylum SR1 and healthy* subjects, and taxa associated with the phylum Proteobacteria and healthy subjects