The Interplay Between Sleep and Gut Microbiota
What causes us to sleep? Recent research suggests that the answer lies not only in our brains but also in their dynamic relationship with the microorganisms residing in our intestines.
Research Insights from Washington State University
New findings from Washington State University (WSU) indicate a shift in the understanding of sleep, demonstrating that peptidoglycan—a substance found in the cell walls of bacteria—naturally exists in the brains of mice and is closely linked to sleep cycles.
Revisiting Established Hypotheses
This research supports a broader hypothesis that has been under development at WSU, suggesting that sleep is a result of communication between the body’s sleep regulatory systems and the diverse microbial communities inhabiting our bodies.
PhD candidate Erika English, lead author of two recently published scientific papers, commented, “This added a new dimension to what we already know.”
The Holobiont Condition
The emerging perspective of sleep arising from this “holobiont condition” aligns with accumulating evidence that gut microbiomes play critical roles in various functions such as cognition, appetite regulation, and libido. This paradigm shift challenges traditional brain-centric models and has significant implications for our understanding of evolution, free will, and the development of future treatments for sleep disorders.
Peptidoglycan’s Role in Sleep Regulation
Recent discoveries regarding peptidoglycan (PG) bolster this hypothesis by suggesting a potential regulatory function for bacterial cell wall products in sleep regulation. While PG has been shown to induce sleep in animal studies, previous consensus held that it did not naturally migrate to the brain.
English’s research revealed that PG, along with its receptor molecules involved in PG signaling, is present in various brain regions—levels of which fluctuate with the time of day and in response to sleep deprivation.
Collaboration of Contributing Factors
These findings were detailed in the July edition of Frontiers in Neuroscience, co-authored by longtime WSU sleep researcher and Regents Professor James Krueger. English is also the lead author of a paper in the journal Sleep Medicine Reviews discussing the “holobiont condition” hypothesis of sleep.
This work synthesizes two key perspectives: one emphasizes that sleep regulation is primarily managed by the brain and neurological systems, while the other focuses on “local sleep,” which posits that sleep results from accumulating sleep-like states among smaller cellular networks throughout the body—a phenomenon observed in vitro.
As these localized sleep-regulated states accumulate, the body transitions from wakefulness toward sleep.
Integrating Microbial and Host Responses
The new hypothesis proposes that sleep results from the interplay between the body and its resident microorganisms—two independent systems that profoundly influence one another.
“It’s not one or the other; it’s both. They must work together,” English remarked. “Sleep is a process occurring at various rates across different cellular and tissue levels, arising from extensive coordination.”
Emerging Links Between Microbiome and Behavior
Initial evidence indicates that gut microbiota significantly influence cognition and fundamental behaviors, challenging the established view of human neurology as a solely top-down process. Instead, this perspective foregrounds a bottom-up model driven by microorganisms that evolved alongside their hosts, guiding the hosts’ cognitive and behavioral responses.
Krueger noted, “We inhabit a community of microbes that possess a far longer evolutionary history than any mammal, bird, or insect—billions of years longer. We believe that the evolution of sleep began with the basic activity/inactivity cycles of bacteria, with molecules driving that cycle related to those influencing cognition today.”
Looking Ahead: Exploring Microbial Communication
English’s work extends established connections between bacteria and sleep, revealing that sleep patterns impact gut microbiome function and that bacterial infections can increase sleep duration.
With an eagerness to explore further, English stated, “As the understanding of the importance of microbes in health continues to evolve, it presents an exciting opportunity to enhance our knowledge of the communication networks between humans and their microbiota.”
Key Health Takeaway
The intricate relationship between gut microbiota and brain function suggests that understanding this interplay could open new avenues for addressing sleep disorders and enhancing overall health.
