Although serotonin is widely associated with feelings of happiness, a study suggests it may be associated with the severity of COVID-19.
New research supports previous findings that selective serotonin reuptake inhibitors may reduce severe COVID-19 symptoms, identifying an important link between serotonin cells in the gut and COVID-19.1 The findings were published in the research journal Gut.
“Our study adds further evidence that COVID-19 is far more likely to infect cells in the gut and increase serotonin levels through direct effects on specific gut cells, potentially worsening disease outcomes,” study senior author Damien Keating, deputy director of the Flinders Health and Medical Research Institute and head of the Gut Sensory Systems research group, said in a press release.1
COVID-19 can cause gastrointestinal issues, with symptoms worsening with the severity of the illness. Additionally, more than half of the body’s serotonin is produced in the gut and levels increase with disease severity. However, increasing serotonin levels can catalyze gut issues by pushing our body’s immune response into overdrive, possibly affecting patient outcomes.1
The study authors sought to identify whether COVID-19 was transmitted through the gut. Further, they aimed to find the genes associated with viral transmission through the gut.1
The investigators analyzed the genome sequences of thousands of intestinal cells lining the gut wall. They discovered that the specialized gut cells that produce serotonin were the only type of intestinal cell to express all 3 gene receptors associated with COVID-19.1
While genes linked to COVID-19 were found in various types of intestinal cells lining the gut wall, serotonin cells expressed all 3 receptors vs the expression of only 2 receptors among other intestinal cells, Keating said in the press release.1
Previous research out of Julius-Maximilians-Universität Würzburg (JMU) suggests that the antidepressant fluoxetine mitigated COVID-19 severity by trapping the virus in cell lysosomes—or small vesicles that house digestive processes by activating or suppressing the acid ceramidases enzyme group. This process increases ceramide and lipid concentrations in the body, which traps the virus and ultimately prevents it from spreading.2
"The enzyme ceramidase is a new, completely unexpected target structure for antiviral therapy," said professor Jochen Bodem from the JMU Institute of Virology and Immunobiology, in a press release.2
The Flinders research supports growing clinical evidence that antidepressants that block serotonin transport throughout the body may be a beneficial treatment, according to Keating.1
“As COVID-19 continues to circulate, further research will be required to advance our understanding of the gut’s role in this virus and continue to find treatment options to work alongside vaccinations,” Keating said in the press release.1