Gut Microbes Important For Normal Sleep

by Pooja Shete on Dec 3 2020 3:41 PM

Gut Microbes Important For Normal Sleep
With the holiday season approaching, many people ask the question what is the relationship between food and sleep. Researchers at the University of Tsukuba in Japan led by Professor Masashi Yanagisawa studied the role of bacterial microbes in the gut. They performed a detailed study in mice that showed the extent to which bacteria can change the environment and contents of the intestines, which have a effect on behaviors like sleep.
The researchers depleted the intestinal microorganisms of the mice by giving them a powerful cocktail of antibiotics for four weeks. Comparison of the intestinal content between these mice and control mice (not given antibiotics) was done.

Microorganisms help in the digestion, which breaks food down into smaller pieces called metabolites. Significant differences between the metabolites were found in the microbiota-depleted mice and the control mice.

Professor Yanagisawa said, "We found more than 200 metabolite differences between mouse groups. About 60 normal metabolites were missing in the microbiota-depleted mice, and the others differed in the amount, some more and some less than in the control mice."

The next goal of the team was to determine the function of these metabolites. Using a method called metabolome set enrichment analysis, it was observed that the biological pathways which were affected by the antibiotic treatment were those involved in producing neurotransmitters. Neurotransmitters are molecules used by the nerves to communicate with each other.

The tryptophan-serotonin pathway, (produces serotonin that is important for well-being and mood) was shut and the microbiota-depleted mice had no serotonin but had high levels of tryptophan as they could not metabolize tryptophan to produce serotonin. Deficiency of vitamin B6 metabolites was also seen in these mice which accelerates the production of serotonin and dopamine.

Brain activity using EEG (Electroencephalogram) was used to analyze the sleeping pattern of the mice and it was observed that when compared to control mice, microbiota-depleted mice had more REM and non-REM sleep at night. Microbiota-depleted mice frequently switched between the sleep-wake stages than the control mice.

The lack of serotonin is responsible for the abnormal sleep but the exact mechanism is not known.

Professor Yanagisawa said, "We found that microbe depletion eliminated serotonin in the gut, and we know that serotonin levels in the brain can affect sleep/wake cycles. Thus, changing which microbes are in the gut by altering diet has the potential to help those who have trouble sleeping."