Objective: To determine the potential of the tryptophan:kynurenine ratio (trp/kyn) as a marker for the responsiveness of Parkinson’s symptoms to treatment by photobiomodulation

Background:

The therapeutic use of laser, termed photobiomodulation (PBM), has increased over the last 60 years since Andre Mester first determined that low doses of non-thermal laser could effectively increase the rate of wound healing and hair regrowth. The clinical evidence for PBM to treat wounds, attenuate pain and enhance tendon and muscle injury recovery has been well documented. There is also increasing evidence for the use of PBM for neurodegenerative diseases including Parkinson’s disease, and Alzheimer’s disease. The necessity of understanding mechanisms of action of, and the responsiveness and non-responsiveness to treatment is becoming increasingly important. Trp/kyn has been suggested as a biomarker to assess progression in a number of diseases, including aging, metabolic diseases, inflammatory diseases, and type 2 diabetes. The kynurenine pathway is also being seen as increasingly important in Parkinson’s disease pathogenesis and may be an indicator of neuroinflammation.

As part of a series of small proof-of-concept studies that examined the use of PBM for the alleviation of Parkinson’s symptoms, we investigated trp/kyn in a subset of participants, both those with Parkinson’s disease and in healthy control participants. The positive response to PBM treatment including improved motor and non-motor symptoms and microbiome changes have been previously reported.

Method: 10 participants with Parkinson’s disease and 3 healthy controls were treated with PBM, either with a transcranial LED helmet (3 Parkinson’s participants) or a transabdominal laser device (remaining participants); 3 times per week for 12 weeks.  The tryptophan and kynurenine concentrations were measured from blood samples by HPLC.

Results: 6 of 7 participants with Parkinson’s disease and 2 of 3 healthy controls showed an improvement in trp/kyn ratio after 12 weeks of PBM.

Conclusion: These results send a signal that the trp/kyn ratio might be a biomarker for the effective treatment of Parkinson’s symptoms by PBM, and indicate that a larger study for Parkinson’s disease treatment with PBM is warranted to assess the utility of this potential biomarker.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/parkinsons-disease-symptoms-mitigated-by-photobiomodulation-the-potential-of-the-tryptophan-kynurenine-ratio-as-a-marker-for-responsiveness-to-therapy/