Metabolomic and immune alterations in long COVID patients with chronic fatigue syndrome.
Saito, Suguru, Shahbaz, Shima, Luo, Xian et al. · Frontiers in immunology · 2024 · DOI
Quick Summary
This study looked at blood samples from people with long COVID who have ME/CFS-like symptoms and compared them to people who recovered from COVID, people with acute COVID, and people who never had COVID. Researchers found that long COVID patients had unusual chemical patterns in their blood, higher levels of inflammation-promoting substances, and lower energy molecules (ATP). They also discovered that two specific chemicals (sarcosine and serine) were reduced in long COVID patients and connected to depression, anxiety, and brain fog.
Why It Matters
Understanding the metabolic and inflammatory patterns in ME/CFS-like long COVID is crucial for developing targeted treatments and biomarkers for disease diagnosis and monitoring. The identification of potentially modifiable metabolites like sarcosine and serine offers a research pathway for novel therapeutic interventions. This work helps legitimize ME/CFS symptoms as having measurable biological underpinnings rather than being purely psychological.
Observed Findings
Elevated plasma pro-inflammatory biomarkers (IL-1α, IL-6, TNF-α, Flt-1, sCD14) in long COVID patients compared to other groups.
Reduced ATP levels in long COVID patients, suggesting energy metabolism impairment.
Significantly decreased sarcosine and serine concentrations in long COVID patients.
Inverse correlation between sarcosine/serine levels and severity of depression, anxiety, and cognitive dysfunction scores.
Persistent metabolomic abnormalities in long COVID patients 12 months after acute infection onset, with approximately 70% female predominance.
Inferred Conclusions
Long COVID patients with ME/CFS-like symptoms exhibit persistent metabolomic dysregulation and sustained inflammation months after acute SARS-CoV-2 infection.
Reduced sarcosine and serine may play a role in neuropsychiatric symptoms (depression, anxiety, cognitive dysfunction) in long COVID.
Supplementation with sarcosine or serine may have potential therapeutic value for long COVID patients, warranting further investigation.
Remaining Questions
Does sarcosine or serine supplementation actually improve symptoms, and what would be optimal dosing and duration?
Are the metabolomic abnormalities the cause of symptoms or a consequence of the illness, and what is their temporal relationship to symptom onset?
What This Study Does Not Prove
This study does not prove that sarcosine or serine supplementation will improve symptoms—only that low levels correlate with cognitive and mood symptoms. It does not establish causation for the metabolomic abnormalities or whether these changes cause the illness or result from it. The cross-sectional design cannot determine if these biomarkers persist over time or if they precede or follow symptom onset.