Kynurenine Pathway in Parkinson's Disease

Periodontal Inflammation and Tryptophan-Kynurenine Metabolism in Parkinson's Disease

Parkinson's disease is a slowly progressing disease that affects the motor and non-motor functions of an individual. Periodontitis is an inflammatory chronic disease resulting in the destruction of tooth supporting structures. Inflammation has been identified as an important factor in both diseases. Given this common mechanism, the question arises as to how they may affect each other when both diseases occur together. In this study, we compared the metabolism of tryptophan, a natural amino acid of the human body, and observed whether such a process provides a biological link between periodontitis and Parkinson's disease. We extracted the saliva and blood samples of patients of Parkinson's disease and periodontitis, patients of periodontitis and healthy human beings. Comparisons between the three were made, and it was found that levels of some metabolites of tryptophan were higher in the patients of both diseases. These findings raise the possibility of a close biological connection between periodontal and brain health. Through an increased understanding of this connection in the future, new approaches for diagnosis and treatment of Parkinson's disease and periodontitis may be developed.

Saliva and serum samples were collected from 20 Stage III, Grade B periodontitis patients with PAD (Parkinson+periodontitis group) and without PAD (periodontitis group), and 20 periodontally and systemically healthy (control group). Samples were analyzed for TRP, KYN, KYN/TRP ratio, KYNA, 3OHKYN, picolinic acid (PA), and quinolinic acid (QA) by liquid chromatography-mass spectrometry. Clinical periodontal parameters [plaque index (PI), probing pocket depth (PPD), clinical attachment loss (CAL), and bleeding on probing (BOP)] were recorded.

Inclusion Criteria:

• systemically healthy

  • clinical diagnosis of periodontitis
  • clinical diagnosis of periodontal health

Exclusion Criteria:

• history of regular use of systemic antibiotics anti-inflammatory, or antioxidant drugs (previous 3 months)

  • nonsurgical periodontal treatment (previous 6 months)
  • surgical periodontal treatment (previous 12 months)
  • presence of<10 teeth
  • current medications affecting gingival health (calcium channel blockers, phenytoin, cyclosporine, and hormone replacement therapy)
  • diabetes
  • diagnosis of rheumatoid arthritis
  • pregnancy
  • lactating
  • smoking
  • excessive alcohol consumption.