Butyrate Enhances Sleep
The short chain fatty acid butyrate promotes sleep, according to a new study.
A growing body of research is illuminating the fundamental role that the microbiome plays in our lives. The gut microbiome plays a fundamental role in the development of a healthy immune system, and microbiome dysbiosis has been linked to a plethora of diseases including IBD, metabolic disease, heart disease and rheumatoid arthritis.
The components of bacterial cells, such as lipopolysaccharide (LPS; a component of the bacterial cell wall), and the metabolites made by bacteria are primarily responsible for exerting these effects.
In a new study published in the journal Scientific Reports, scientists report that a key short chain fatty acid (butyrate) produced by bacteria induces sleep in mice and rats.
Sleep is impacted by a variety of signals such as satiety (feeling full), hormones, and proinflammatory signals. Importantly, gut bacteria can affect our behavior and signaling to the brain through the gut-brain axis
The brain sleep mechanisms and the gut flora are linked through a dynamic bidirectional relationship. Depleting gut bacteria has been shown to reduce sleep, while disruption of the normal sleep cycle (i.e., from jet lag) causes intestinal dysbiosis.
These links prompted scientists to ask whether the metabolites made by good bacteria (from the breakdown of fiber) affect sleep.
To test this, the researchers investigated the effects of oral administration and injection of sodium butyrate and tributyrin, a butyrate-yielding prodrug, in mice and rats.
The scientists found that oral administration of butyrate (as sodium butyrate or tributyrin) robustly induced sleep in the animals. However, injecting butyrate directly into the blood had no effect on sleep. The scientists think that this happens because the butyrate acts on the liver on its way out of the gut, which then induces sleep.
Sleep responses to systemic bacterial infection are linked to inflammation. Butyrate is produced by bacteria in the intestines, and it has potent anti-inflammatory properties. Butyrate suppresses inflammation in the colon and liver and the production of proinflammatory molecules in response to LPS. Therefore, it seems that system-wide proinflammatory signals related to bacterial infections negatively affect sleep, whereas bacterial-derived anti-inflammatory signals from the intestinal tract have the potential to positively influence sleep.
Szentirmai É., et al. Scientific Reports. 2019 May 7;9(1):7035. doi: 10.1038/s41598-019-43502-1.