Amino acid profiles in relation to chronic periodontitis and rheumatoid arthritis

Chronic periodontitis (CP) and rheumatoid arthritis (RA) are chronic inflammatory conditions, and share many pathologic features. Plasma amino acid profiles have been shown to be associated with RA, but their relevance to CP remains unclear. The aim of the present study is to evaluate amino acid profiles in relation to CP and RA. The study participants consisted of 62 patients with RA (RA group), 30 patients with CP (CP group) and 29 healthy controls (H group) in age-, gender-, smoking status-balanced condition. Clinical periodontal and rheumatologic parameter values and plasma levels of 21 amino acids, C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) were determined. Multiple comparison analyses revealed that the RA group exhibited similar periodontal conditions but significantly higher levels of CRP, IL-6, and TNF-α than the CP group (P < 0.01). A total of four amino acids (glycine, histidine, ornithine, and alpha-aminobutyric acid) were significantly different in the concentrations among the three groups (P < 0.01). The RA group displayed significantly lower levels of glycine and histidine and significantly higher ornithine level than the CP and H groups (P < 0.01). The CP group showed significantly higher alpha-aminobutyric acid level than the RA and H groups (P < 0.01). Of these four amino acids, a significantly positive correlation was found between ornithine level and % of sites with bleeding on probing (P = 0.006) in the RA group. These results suggest a possibility that profiles of four amino acids may play a role in the pathogenesis of CP and RA.