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Publication Date: 08 Nov 2011
Journal: International Journal of Tryptophan Research
doi: 10.4137/IJTR.S7986
Background: Stochastic resonance therapy (SRT) is used for rehabilitation of patients with various neuropsychiatric diseases. An alteration in tryptophan metabolism along the kynurenine pathway has been identified in the central and peripheral nervous systems in patients with neuroinflammatory and neurodegenerative diseases and during the aging process. This study investigated the effect of SRT as an exercise activity on serum tryptophan metabolites in healthy subjects.
Methods: Serum L-tryptophan, L-kynurenine, kynurenic acid, and anthranilic acid levels were measured one minute before SRT and at one, 5, 15, 30, and 60 minutes after SRT. We found that SRT affected tryptophan metabolism. Serum levels of L-tryptophan, L-kynurenine, and kynurenic acid were significantly reduced for up to 60 minutes after SRT. Anthranilic acid levels were characterized by a moderate, non significant transient decrease for up to 15 minutes, followed by normalization at 60 minutes. Tryptophan metabolite ratios were moderately altered, suggesting activation of metabolism after SRT. Lowering of tryptophan would generally involve activation of tryptophan catabolism and neurotransmitter, protein, and bone biosynthesis. Lowering of kynurenic acid by SRT might be relevant for improving symptoms in patients with neuropsychiatric disorders, such as Parkinson's disease, Alzheimer's disease, schizophrenia, and depression, as well as certain pain conditions.
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Posted by Abdulla A-B Badawy - 09:49,November 11, 2011
I have 2 questions to ask and 1 comment to make in relation to your interesting paper.
(1) May I ask why you did not measure free serum Trp, as it has been reported to be increased after exercise, as a result of elevation of non-esterified fatty acids (NEFA) following stimulation of lipolysis by exercise. When free Trp is increased significantly and in a sustained way, the total Trp is also decreased, due to increased entry of Free Trp into tissues coupled with rapid equilibration between the free and albumin-bound fractions. The small (13%) decrease in total Trp observed at 1h after SRT is consistent with this possibility.
(2) As far as I know, the effect of SRT on serum free Trp has not been investigated. Could SRT actually decrease free Trp, rather than increase it, by altering albumin binding through changes in albumin conformation, or simply by decreasing NEFA or even by possibly altering calcium uptake by bone tissue?
(3) The decreases in serum Trp, kynurenine and kynurenic acid observed in your work suggest that less Trp is being metabolised along the kynurenine pathway, i.e. the flux of Trp down the pathway is impaired by the shortage of available Trp. If Trp oxidation along the kynurenine pathway was enhanced, one would expect an elevation of serum kynurenine to occur along with the decrease in serum Trp. Although the kynurenine aminotransferase reaction is a minor one under normal conditions, it is still possible that a small decrease in kynurenine may result in the small decrease in kynurenic acid observed.
I suggest an alternative interpretation of the present findings, namely that SRT decreases Trp oxidation along the kynurenine pathway.
I would be interested to read your comments.
With best regards,
Abdulla Badawy”