Many adults struggle with daytime sleepiness and nighttime insomnia, impairing memory, mood, and focus. Several factors regulate sleep and wake activities, including central and peripheral circadian rhythms and timing of meals. These rhythms also regulate the diurnal activities of the gut microbiota. New research reports that antibiotics, which can alter the gut microbial population, may disrupt normal sleep cycles in mice due to changes in neurotransmitters.
The human gut is an important site for the production and metabolism of neurotransmitters like serotonin. Neurotransmitters in the gut regulate digestive processes, communicate with the brain directly through the enteric nervous system, and interact with the microbiome. Serotonin is important for regulating sleep/wake cycles, and too little serotonin may decrease sleep quality.
The scientists gave mice water containing broad spectrum antibiotics for four weeks to deplete their gut microbiota or normal drinking water. They used implantable electrodes to collect detailed sleep pattern data in the mice and measured concentrations of metabolites in the animals' guts and feces.
The authors reported significant alterations in metabolites related to vitamin, amino acid, and neurotransmitter metabolism in mice whose microbiota had been depleted with antibiotics. These mice exhibited less time in deep sleep during the day (when these nocturnal animals should be sleeping) and more time in deep sleep during the night. They also experienced frequent transitions between rapid eye movement (REM) sleep and non-REM deep sleep, an indicator of decreased sleep quality. The authors suggested this may have been caused by lower levels of serotonin in the gut due to depletion of vitamin B6, a necessary cofactor for producing serotonin.
This research could have important implications for human health. The authors noted that other research has demonstrated the ability of some prebiotics (fiber and nutrients that are beneficial for the gut microbiota) to improve sleep in humans.