The effect of Porphyromonas gingivalis on the gut microbiome of mice in relation to aging.

Abstract

The translocation of oral bacteria, including Porphyromonas gingivalis, to the gut has been shown to alter gut microbiome. However, the effect of P.gingivalis on gut microbiome in relation to aging has not been demonstrated. We hypothesize that P.gingivalis has more detrimental effect on gut environment with increased age. The objective of this study is to investigate the effect of P.gingivalis on gut environment using aged mice. C57BL/6J mice aged 4 weeks (young) or 76 weeks (old) were divided into four groups: control-young, control-old, P.gingivalis-administered young, and P.gingivalis-administered old. P. gingivalis was orally administered thrice weekly for 5 weeks. At 30 days after the last P.gingivalis administration, 16S rRNA sequencing was performed to study the gut microbiome. The mRNA and protein expression of intestinal junctional barrier molecules and the levels of the inflammatory cytokines IL-1β and TNF-α in the serum were evaluated. Significant differences in the gut microbiomes between the groups, in terms of taxonomic abundance, bacterial diversity, and predicted metagenome function, were observed. A significant reduction in the alpha diversity and in the abundance of beneficial bacteria, such as Akkermansia and Clostridiaceae, in the P.gingivalis-administered old mice was observed. The mRNA and protein levels of Claudin-1 and Claudin-2 in the intestine were significantly elevated, while E-cadherin was significantly downregulated in the P.gingivalis-administered old mice, as were the serum levels of IL-1β and TNF-α. The effect of P.gingivalis on the gut environment is more pronounced in old mice than in young mice.