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Kynurenine pathway activation is associated with possible bruxism, with elevated cortisol, TNF-α, and KYN/Trp ratio in affected individuals

Q: What is the kynurenine pathway and how is it related to bruxism?

The kynurenine pathway is a metabolic route for tryptophan degradation, activated by stress and inflammation. This study found elevated kynurenine and KYN/Trp ratio in bruxism patients, suggesting stress-related activation of this pathway.

Q: What biomarkers were different between sleep bruxism and combined bruxism?

Sleep bruxism had significantly higher cortisol, KYN, KTR, and TNF-α, and lower melatonin compared to combined bruxism, indicating a stronger stress and inflammatory link.

Q: How were bruxism and its subtypes diagnosed in this study?

Bruxism was assessed using a five-item questionnaire evaluating sleep- and awake-related grinding and clenching behaviors, classifying participants as possible sleep bruxism or possible combined bruxism.

Q: What was the sample size and study design?

The study included 84 individuals with possible bruxism and 84 age-matched healthy controls, using a cross-sectional observational design with morning saliva collection and ELISA analysis.

Saliva cortisol, TNF-α, KYN, and KYN/Trp ratio were significantly higher, while Trp and IFN-γ were lower in individuals with possible bruxism compared to healthy controls (p<0.001 for all). Within bruxism subtypes, possible sleep bruxism showed higher cortisol, KYN, KTR, and TNF-α and lower melatonin than possible combined bruxism (p<0.01 to p<0.001).

Last updated: Jul 30, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score32/100

Human RCT☆☆☆☆☆

Meta-analysis☆☆☆☆☆

Mechanism★★★★★

Safety★★★★☆

Confidencelow

Study Evidence

Study 1. Activation of the kynurenine pathway in possible bruxism: associations with cortisol, TNF-α, and possible bruxism subtypes.

observational

Afşar E, Ayran Ş, Oral N, BahadırKuzzu K, Şanlı E, Avcı MA, Göz MS · Oral and maxillofacial surgery (2026)

Participants: N/A

Duration: N/A

Intervention: None (observational study comparing possible bruxism group vs. healthy controls, and sleep bruxism vs. combined bruxism subtypes)

Outcome: Saliva levels of cortisol, melatonin, tryptophan, serotonin, kynurenine, TNF-α, IFN-γ, and KYN/Trp ratio

Effect Size: N/A

Population: 84 individuals with possible bruxism and 84 age-matched healthy controls

Result:

PubMed: 42490003 DOI: 10.1007/s10006-026-01606-9

Mechanism Graph

Psychological stress activates HPA axis, increasing cortisol release

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Cortisol modulates immune responses and tryptophan metabolism via kynurenine pathway

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Kynurenine pathway activation leads to elevated KYN and KYN/Trp ratio, reduced tryptophan

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Result: Biochemical profile of elevated cortisol, TNF-α, KYN, and KTR in bruxism, with subtype differences

Limitations

⚠Possible bruxism diagnosis based on self-report questionnaire, not polysomnography or electromyography
⚠Cross-sectional design cannot establish causality between kynurenine pathway activation and bruxism
⚠Saliva samples collected only in the morning, limiting diurnal assessment of biomarkers

Frequently Asked Questions

What is the kynurenine pathway and how is it related to bruxism?▼

The kynurenine pathway is a metabolic route for tryptophan degradation, activated by stress and inflammation. This study found elevated kynurenine and KYN/Trp ratio in bruxism patients, suggesting stress-related activation of this pathway.

What biomarkers were different between sleep bruxism and combined bruxism?▼

Sleep bruxism had significantly higher cortisol, KYN, KTR, and TNF-α, and lower melatonin compared to combined bruxism, indicating a stronger stress and inflammatory link.

How were bruxism and its subtypes diagnosed in this study?▼

Bruxism was assessed using a five-item questionnaire evaluating sleep- and awake-related grinding and clenching behaviors, classifying participants as possible sleep bruxism or possible combined bruxism.

What was the sample size and study design?▼

The study included 84 individuals with possible bruxism and 84 age-matched healthy controls, using a cross-sectional observational design with morning saliva collection and ELISA analysis.

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References

1.Afşar E, Ayran Ş, Oral N, BahadırKuzzu K, Şanlı E, Avcı MA, Göz MS. "Activation of the kynurenine pathway in possible bruxism: associations with cortisol, TNF-α, and possible bruxism subtypes.." Oral and maxillofacial surgery, 2026. PMID: 42490003 DOI: 10.1007/s10006-026-01606-9

Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.