Scientists Offer a New Explanation for Long Covid

(CTN News) – After discovering that serotonin levels were lower in persons with the complex ailment, a team of scientists has proposed a new explanation for some cases of extended Covid.

Researchers at the University of Pennsylvania published a study in the journal Cell on Monday that suggests that serotonin suppression is driven by the virus’s persistence in the gut.

Memory issues, as well as other neurological and cognitive effects of prolonged COVID-19, may be attributable to low serotonin levels, they suggest.

Why It Matters: New ways to diagnose and treat long Covid.

Important discoveries for a disorder that manifests in various ways and is sometimes undetectable by conventional diagnostic techniques like X-rays have been made in this and other recent research demonstrating different biochemical alterations in the bodies of patients with chronic Covid.

The findings may pave the way for effective treatments, such as serotonin-enhancing drugs. According to the study’s authors, the molecular route they detail may bring together several competing hypotheses on what causes extended Covid, including the virus’s persistence, inflammation, abnormal blood clotting, and autonomic nerve system dysfunction.

According to the study’s co-author and assistant professor of microbiology at Penn’s Perelman School of Medicine, Christoph Thaiss: “All these different hypotheses might be connected through the serotonin pathway.”

Second, “even if not everybody experiences difficulties in the serotonin pathway, at least a subset might respond to therapies that activate this pathway,” he explained.

According to Yale University immunologist Akiko Iwasaki, “this is an excellent study that identifies lower levels of circulating serotonin as a mechanism for long Covid.”

Her group and their colleagues at the Icahn School of Medicine at Mount Sinai recently published a study that linked elevated cortisol levels to some cases of extended Covid. These investigations may shed light on distinct forms of extended Covid or varying biological signs at various stages of the disease.

The Back Story: A series of disruptions set off by bits of virus in the gut.

After three months and twenty-two months of infection, 58 patients with extended Covid were studied by analyzing their blood.

These findings were compared to those obtained from analyzing the blood of 30 participants who had no symptoms after recovering from Covid and 60 patients in the acute phase of coronavirus infection.

The levels of serotonin and other metabolites are altered immediately following a coronavirus infection, as is the case following other viral infections, according to the study’s principal author and assistant professor of microbiology at the Perelman School of Medicine, Maayan Levy.

However, she noted that serotonin was the only major chemical whose levels did not return to pre-infection levels in persons with chronic Covid.

Some of the long-term Covid patients had virus particles detected in their stool tests. By combining patient data with findings from mouse and human gut model studies, the team was able to identify a potential route behind some cases of prolonged Covid.

The thought is this: Interferons are infection-fighting proteins produced by the immune system in response to viral leftovers. Inflammation triggered by interferons hinders tryptophan absorption, which is necessary for serotonin production in the intestines. Serotonin circulation could be hindered by blood clots that occur during a coronavirus infection.

Researchers found that low serotonin levels disrupted the vagus nerve system, which normally relays information from the body to the brain. Depleted serotonin has been linked to memory impairments and other cognitive issues in persons with extended Covid. Serotonin plays a role in short-term memory.

Specifically, “they showed that one-two-three punch to the serotonin pathway then leads to vagal nerve dysfunction and memory impairment,” Dr. Iwasaki stated.

Exceptions exist. Due to the study’s small sample size, its results need be verified by future studies. Dr. Levy speculated that this would mean that serotonin depletion only occurs in people whose long Covid contains several major symptoms in people who participated in other long Covid studies in which some patients had milder symptoms.

What’s Next: A clinical trial of Prozac.

To better diagnose long Covid, researchers are looking for biomarkers or measurable biological changes. According to Dr. Thaiss, the current study suggests three: low serotonin, high levels of interferons, and the presence of viral leftovers in feces.

Most professionals agree that there will not be a single biomarker for the disorder but rather that multiple signs will emerge, some of which may change depending on the nature of the symptoms.

Several potential therapies for extended Covid are currently being tested in clinical trials. Clinical trials with fluoxetine (Prozac) and tryptophan (an amino acid that the body converts into serotonin) were announced by doctors Levy and Thaiss.

Dr. Levy speculated that “if we supplement serotonin or prevent the degradation of serotonin,” it would be possible to restore some of the vagal signals, so enhancing memory and cognition.

New Scientific Insights

Immune System Dysregulation

Scientists have recently uncovered that Long Covid may be linked to the dysregulation of the immune system. The body’s immune response, which is crucial in fighting off infections, appears to become imbalanced in Long Covid patients, leading to prolonged symptoms.

Lingering Viral Particles

Researchers have also found that viral particles can persist in certain tissues, even after the virus is no longer detectable in the bloodstream. This may trigger an ongoing inflammatory response, contributing to the symptoms of Long Covid.

Microvascular Damage

A further explanation for Long Covid lies in microvascular damage. Some patients show signs of microclots and vascular damage that can disrupt the normal function of vital organs, leading to prolonged health issues.

Brain Inflammation

Long Covid can also impact the brain. In some cases, it’s been associated with brain inflammation, which may contribute to the cognitive issues and brain fog experienced by affected individuals.

Coping Strategies

Supportive Therapies

While scientific understanding of Long Covid is still evolving, various supportive therapies, such as physical therapy, cognitive-behavioral therapy, and symptom-specific treatments, have shown promise in helping patients manage their symptoms.

Patient Advocacy

Patients and advocacy groups have played a crucial role in raising awareness about Long Covid and pushing for further research and medical recognition of this condition.

Conclusion

Long Covid remains a medical enigma, but the latest scientific discoveries are shedding light on its potential causes and mechanisms. It is crucial to continue researching and supporting those affected by this condition as we work towards a better understanding and improved treatment options.