You might wonder what connection there could possibly be between the brain, the gut, and the vagus nerve. It turns out there’s a direct link.
To recap, the vagus nerve is the longest nerve in the autonomic nervous system. It runs from the brain through the neck to the gastrointestinal tract, heart, and lungs.
An international team of molecular biologists found that sleep deprivation sends abnormal signals from the brain to the gut via the vagus nerve. That triggers a release of serotonin, which can kill intestinal stem cells.
Research indicates sleep deprivation disrupts intestinal stem cell function. Consequently, this increases the risk of developing inflammatory bowel diseases (IBD), such as ulcerative colitis and Crohn’s disease.
What Did the Scientists Discover?
In a study published in the journal Cell Stem Cell, researchers examined the multi-step mechanism by which abnormal signals travel from the brain’s sleep center to gut cells. This disrupted signaling reduces the regenerative capacity of the gut lining.
To understand how a lack of sleep affects the gut, the team focused on its stem cells. These cells play a crucial role in maintaining gut health, specifically preserving the integrity of the intestinal lining.
During the study, researchers deprived laboratory mice of sleep for two days and then found signs of oxidative stress in their guts. The mice that were sleep-deprived had nearly half the number of stem cells compared to well-rested mice. Additionally, the sleep-deprived rodents showed a reduced ability to regenerate after damage.
“This clearly demonstrated how quickly and severely sleep disruption can harm the gut,” said study co-author Zhengchuan Yu, a molecular biologist at China Agricultural University.
Further investigation into the molecular changes revealed increased levels of serotonin in the guts of sleep-deprived mice.
Serotonin is critical for signaling the gut to release digestive juices and for controlling the muscle contractions that move food through the digestive system. However, prolonged exposure to high levels of serotonin can lead to diarrhea, inflammatory bowel diseases, and tumor development in the gut. Therefore, strict regulation of serotonin levels is essential for intestinal health.
But How Do Brain Signals Related to Sleep Deprivation Reach the Gut?
The team hypothesized those signals travel along the vagus nerve, which normally connects the gut and the brain.
To test their theory, researchers examined the effects of sleep deprivation in mice with damaged vagus nerves. These animals maintained normal serotonin levels. Moreover, they had more intestinal stem cells than sleep-deprived rodents with intact vagus nerves.
Interestingly, blocking signals from the vagus nerve protected the gut from the consequences of sleep disruption.
Researchers also identified the chemical messenger acetylcholine as the primary signaling molecule released by the vagus nerve; it triggers the release of serotonin.
“Every component of this cascade is important for potential therapy,” said study co-author Maxim Pliakus, a cell biologist at the University of California, Irvine, in an interview with Live Science. He noted that the team plans to study this cascade using miniature gut models—organoids.
The researchers aim to develop treatments for gut dysfunction in patients with insomnia by focusing primarily on the vagus nerve.
Experts estimate that sleep deprivation affects about 10 percent of the adult population worldwide. In addition to seriously disrupting daily life, chronic sleep disturbances are linked to a rise in chronic diseases, including diabetes, hypertension, major depressive disorder, and inflammatory bowel diseases.
