The bacteria in our microbiota also regulate our sleep

Sleep is a complex process. And this essential phase for the organism is too often abused due to our rhythms of life. However, it is during sleep that our body regenerates itself, that our memories are fixed, that our body is updated to better face a new day. Researchers from the University of Tsukuba (Japan) have discovered that our sleep also depends on bacteria and microorganisms present in our digestive tract, because they are the ones that regulate serotonin, which is essential for maintaining a good circadian cycle. Their research findings were published on November 11, 2020 in the journal Scientific reports.

The interest of microorganisms in our microbiota

To fully understand the situation, the researchers gave the mice antibiotics for four weeks. Although antibiotics are known to help our body defend itself, they can also kill some bacteria in our digestive tract, which weaken the microbiota.

The researchers compared the intestinal contents of these mice released from these microorganisms with that of control mice that have the same diet. During digestion, food breaks down and becomes metabolites or small molecules. “We found over 200 differences in metabolites between groups of mice. About 60 normal metabolites were missing in the microbiota-free mice, and the rest differed in quantity, some more and some less than in the control mice.“Says Masashi Yanagisawa, a professor at Tsukuba University.

Once this observation was made, the researchers tried to understand the usefulness of these metabolites. By analyzing the enrichment of all metabolites, they found that the biological pathways most affected by antibiotic treatment were those involved in the production of neurotransmitters. Therefore, the tryptophan-serotonin pathway was nearly blocked in mice lacking the microbiota. This shows that without the proper gut microorganisms, the mice could not make serotonin from the tryptophan they ate. Similarly, these mice had a deficiency in vitamin B6 metabolites, which accelerate the production of serotonin and dopamine.

Serotonin, a sleep regulator

Finally, the mice underwent an electroencephalogram in order to see their brain activity during sleep. Compared to control mice, the paradoxical sleep of microbiota-free rodents was more disturbed. The number of REM sleep episodes was highest during the day and night, while the number of non-REM sleep episodes was highest during the day. In other words, mice lacking the microbiota alternated between sleep and wake phases more frequently than others.

“We have found that depletion of microbes eliminates serotonin in the gut, and we know that serotonin levels in the brain can affect sleep / wake cycles., souligne Masashi Yanagisawa. Hence, changing the microbes in the gut by changing the diet can help those who have trouble sleeping.. “