The abundances of periodontitis-associated gut microbiota taxa (e.g., Prevotella, Faecalibacterium, Haemophilus, Veillonella,Streptococcus, Aggregatibacter, Oxalobacter, and Eisenbergiella) also exhibited significant correlations with the blood levels of pro-inflammatory cytokines (e.g., PGE2, IFN-γ, IL-17, IL-6, and TNF-α) and plasma metabolic parameters (e.g., HbA1c, fasting blood glucose [FBG], total cholesterol [TCHO], high-density lipoprotein cholesterol [HDL-c], and low-density lipoprotein cholesterol [LDL-c]). The gene discussed is IL17A; the disease is periodontitis.