A study from the University of Pennsylvania reveals that a drop in serotonin levels could be responsible for the neurological symptoms of long Covid.
- Components of the SARS-CoV-2 virus remain in the gut of some long-term Covid patients, causing persistent inflammation and an immune system response.
- Inflammation leads to a reduction in the absorption of the amino acid tryptophan in the gastrointestinal tract. Which in turn leads to a drop in serotonin levels.
- This decrease in serotonin could be the cause of neurological symptoms of long Covid such as memory loss or brain fog.
According to Public Health Francearound 2 million people have a post-Covid-19 condition END 2022. This disorder, known as long Covid, is characterized by persistent symptoms such as brain fog, fatigue or memory loss several months after SARS-CoV-2 infection. Its exact origin still remains mysterious.
However, researchers from the School of Medicine Perelman from the University of Pennsylvania have recently made a significant advance in understanding the neurological symptoms of the disease: some patients have low serotonin levels.
Long Covid: components of SARS-CoV-2 in the intestine cause inflammation
By studying blood and stool samples from people suffering from long Covid, scientists discovered that components of SARS-CoV-2 persist in the intestines of some of them. These virus fragments activate the immune system. The latter then releases proteins, called interferons, to fight the virus. They cause inflammation which reduces the absorption of the amino acid tryptophan in the gastrointestinal tract. However, tryptophan is a component of several neurotransmitters, including serotonin.
“Researchers have found that when tryptophan absorption is reduced by persistent viral inflammation, serotonin is depleted. (Low serotonin) leads to disruption of vagus nerve signaling, which in turn can cause several symptoms associated with long Covid, such as memory loss”specifies press release from the American establishment published on October 16, 2023.
Long Covid: low serotonin level, biomarker of the disease
“Doctors treating patients with long Covid rely on these patients’ self-reports to determine whether their symptoms are improving. Now our research shows that there are biomarkers that we may be able to use to offer patients treatments or clinical trials that address the specific causes of their long Covid symptoms and more effectively assess their progress.”explains co-lead author, Pr Sarah Cherry.
Additionally, animal tests have shown that serotonin levels can be restored and memory impairments can be reversed through treatment with serotonin precursors or selective serotonin inhibitors. recapture serotonin (SSRIs). This discovery opens the way to the development of new treatments and improved diagnosis of long Covid.
“Long Covid varies from patient to patient, and we do not fully understand what causes the differences in symptoms”explains the co-lead author, Pr Christopher Thaiss in a press release. “Our study provides a unique opportunity for further research to determine how many people with long Covid are affected by the pathway linking viral persistence, serotonin deficiency and vagus nerve dysfunction and to discover additional targets for treatments through the different symptoms that patients have.“
