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The Many Neuroprogressive Actions of Tryptophan Catabolites (TRYCATs) that may be Associated with the Pathophysiology of Neuro-Immune Disorders.
Morris, Gerwyn, Carvalho, André F, Anderson, George et al. · Current pharmaceutical design · 2016 · DOI
Quick Summary
When the body has chronic inflammation and immune activation, it breaks down an amino acid called tryptophan differently than usual, creating byproducts called TRYCATs. Some of these byproducts can damage nerve cells and mitochondria (the energy factories in cells), while others may protect the brain but at the cost of causing brain fog and emotional problems. This review examines how this abnormal tryptophan breakdown might contribute to ME/CFS and other neurological conditions.
Why It Matters
ME/CFS patients frequently experience cognitive dysfunction, neuroinflammation, and mitochondrial dysfunction. This review proposes a unifying biochemical mechanism—dysregulated tryptophan catabolism—that could explain multiple pathological features of ME/CFS and suggests specific biomarkers and potential therapeutic targets worth investigating in patient cohorts.
Observed Findings
- Chronic immune activation and elevated pro-inflammatory cytokines activate the IDO enzyme and upregulate the TRYCAT pathway
- Quinolinic acid functions as a potent neurotoxin that inhibits mitochondrial ATP production, increases oxidative/nitrosative stress, and acts as an NMDA receptor agonist
- Kynurenic acid acts as an antagonist of NMDA and glutamate receptors and engages neuroprotective receptors (alpha7 nicotinic acetylcholine, aryl hydrocarbon receptors)
- Different TRYCATs possess distinct neurotoxic or neuroprotective properties through pro-oxidant and antioxidant mechanisms
Inferred Conclusions
- Dysregulated tryptophan catabolism via the TRYCAT pathway may contribute to neuroinflammation and neuroprogression in ME/CFS and related neuro-immune disorders
- An imbalance between neurotoxic TRYCATs (e.g., quinolinic acid) and neuroprotective TRYCATs (e.g., kynurenic acid) could explain cognitive dysfunction, mitochondrial impairment, and neuronal damage
- The TRYCAT pathway represents a mechanistic link between systemic immune activation and central nervous system pathology in chronic illness
Remaining Questions
- Are TRYCAT pathway metabolites actually elevated in cerebrospinal fluid or serum of ME/CFS patients, and do levels correlate with symptom severity or cognitive dysfunction?
- Which factors determine the balance between production of neurotoxic versus neuroprotective TRYCATs in ME/CFS, and can this balance be therapeutically modulated?
What This Study Does Not Prove
This is a mechanistic review, not an empirical study with ME/CFS patient data; it does not prove that elevated TRYCATs actually occur in ME/CFS patients or that they cause disease in this population. The review cannot establish causation or rule out that TRYCAT elevation is secondary to other primary pathological processes. No clinical trials or outcome data are presented.
Tags
Symptom:Cognitive DysfunctionFatigue
Biomarker:CytokinesMetabolomicsBlood Biomarker
Method Flag:Exploratory Only
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