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.

Study Overview

• Status: Completed
• Conditions: Inflammation; Periodontal Diseases
• Intervention / Treatment: Other: Saliva and serum sampling; Other: Saliva, serum and GCF sampling

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Actual): 60
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Fatih
    • Istanbul, Fatih, Turkey (Türkiye)
      • Istanbul Medipol University, School of Dentistry

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Active Comparator; Saliva and serum collection of patients and samples molecules analysis	Other: Saliva and serum sampling; 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.
Experimental: Experimental; 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.	Other: Saliva, serum and GCF sampling; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pocket probing depth	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.	6 months
Clinical attachment level	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)	6 months
Bleeding on probing	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.	6 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Saliva and serum samples processing and analyses	Samples were analyzed for TRP, KYN, KYN/TRP ratio, KYNA, 3OHKYN, picolinic acid (PA), and quinolinic acid (QA) by liquid chromatography-mass spectrometry.	1 month

Collaborators and Investigators

• Sponsor: Medipol University

Study record dates

Study Major Dates

• Study Start (Actual): May 15, 2022
• Primary Completion (Actual): January 10, 2023
• Study Completion (Actual): June 18, 2023

Study Registration Dates

• First Submitted: November 26, 2025
• First Submitted That Met QC Criteria: November 26, 2025
• First Posted (Estimated): December 9, 2025

Study Record Updates

• Last Update Posted (Estimated): December 9, 2025
• Last Update Submitted That Met QC Criteria: November 26, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: periodontal disease; Tryptophan; Kynurenine
• Additional Relevant MeSH Terms: Mouth Diseases; Stomatognathic Diseases; Pathologic Processes; Pathological Conditions, Signs and Symptoms; Inflammation; Periodontal Diseases
• Other Study ID Numbers: 1082

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No