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Completed

NCT Number: NCT07272564

Kynurenine Pathway 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.

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Key information

Conditions

Periodontal Diseases Inflammation Mouth Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms Stomatognathic Diseases

Age range

18 year–75 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Istanbul Medipol University, School of Dentistry

Istanbul, Fatih, Turkey (Türkiye)

About this study

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.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

Saliva and serum sampling

Other

Saliva were collected to analyze the selected markers as unstimulated samples during the early hours of the day. The saliva was centrifuged and then transferred into Eppendorf tubes. Venous puncture was performed after saliva collection and 10 mL of blood samples were collected by qualified staff from each participant. Saliva and serum were then stored at -80 °C until analysis.

Saliva, serum and GCF sampling

Other

Saliva were collected to analyze the selected markers as unstimulated samples during the early hours of the day. The saliva was centrifuged and then transferred into Eppendorf tubes. Venous puncture was performed after saliva collection and 10 mL of blood samples were collected by qualified staff from each participant. Saliva and serum were then stored at -80 °C until analysis.

Primary outcomes

  1. Pocket probing depth

    Time frame: 6 months

    Measurement of the depth of a sulcus or periodontal pocket determined by measuring distance from a gingival margin to the base of the sulcus or pocket with a calibrated periodontal probe.

  2. Clinical attachment level

    Time frame: 6 months

    Clinical attachment level (or loss, CAL) is a more accurate indicator of the periodontal support around a tooth than probing depth alone. CAL is measured from a fixed point on the tooth that does not change, the CEJ.

    To calculate CAL, two measurements are needed: distance from the gingival margin to the CEJ and probing depth.

    In recession: probing depth (+) gingival margin to the CEJ (add). In tissue overgrowth: probing depth (-) gingival margin to the CEJ (subtract)

  3. Bleeding on probing

    Time frame: 6 months

    referring to bleeding that is induced by gentle manipulation of the tissue at the depth of the gingival sulcus, or interface between the gingiva and a tooth.

Secondary outcomes

  1. Saliva and serum samples processing and analyses

    Time frame: 1 month

    Samples were analyzed for TRP, KYN, KYN/TRP ratio, KYNA, 3OHKYN, picolinic acid (PA), and quinolinic acid (QA) by liquid chromatography-mass spectrometry.

Sponsors and collaborators

Lead sponsor

Medipol University

Other

Registry information

Official study title

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

Important dates

Study start
2022
Primary completion
2023
Study completion
2023
First posted
Dec 9, 2025
Registry last updated
Dec 9, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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