Recent findings suggest that fragments of bacteria moving from the gut to the brain might significantly influence sleep. This points to the possibility that some of the most ancient microorganisms in our bodies play a crucial role in signaling when we should sleep.
These fragments are composed of a substance known as peptidoglycan, which is derived from bacterial cell walls found in the digestive tract. Previous studies on animals have indicated that peptidoglycan can penetrate the central nervous system and potentially affect behavior.
In this new research, neuroscientists Erika English and James Krueger from Washington State University conducted tests on mice, revealing that peptidoglycan levels in the brain fluctuate throughout the day, peaking in the evening and being lowest in the morning.
When subjected to sleep deprivation, the levels of peptidoglycan in different brain areas deviated from normal, and there were observable changes in the activity of related genes.
These results imply that molecules emitted by our gut bacteria might not only influence our sleep patterns but could also be affected by our sleep. While there’s still much to uncover, this presents compelling evidence of a connection.
“We have a whole community of microbes living within us,” Krueger states. “These microbes have a vastly older evolutionary history than mammals, birds, or insects—billions of years older.”
“We believe sleep evolution began long ago with the activity cycles of bacteria, and that the molecules involved are similar to those impacting cognition today.”
This research supports a hypothesis at WSU, suggesting our microbiome significantly affects sleep regulation, as well as factors like appetite and sex drive.
The concept is referred to as the “holobiont condition” of sleep, positing that individual microbes and the brain work in tandem to regulate our need for rest and wakefulness.
“It’s not simply one or the other, it’s both,” English explains. “They need to collaborate.”
“Sleep is indeed a process that operates at various speeds depending on cellular and tissue organization, and it emerges from extensive coordination.”
An increasing number of studies are illustrating how the gut and brain cooperate to sustain overall health. For instance, particular microbial compositions have been linked to insomnia and neurodegenerative conditions, showcasing the intricate relationship between these systems.
Advancements continue in pinpointing the various influences on our sleep needs, including peptidoglycan—along with factors like daylight exposure and circadian rhythms.
“With the growing acknowledgment of microbes’ importance for both health and disease, it’s an exciting time to delve deeper into how we interact with our microbes and vice versa,” English adds.
The findings have been published in Frontiers in Neuroscience.
