Voluntary training and food modulate the fecal microbiota in humans and mice. Although there are some reports of the timing effects of voluntary training and feeding on metabolism, the timing effects of these factors on microbiota have not been investigated. Therefore, we investigated the effects of the timing of voluntary training and feeding on the gut microbiota. The ICR mice were housed under conditions with an early (in the morning) or late (evening) active phase of increased physical activity. Furthermore, to investigate why voluntary training affects the gut microbiota, mice were housed in a cold environment and received propranolol administration with increased physical activity. After that, we collected cecal contents and feces and measured cecal pH. Short-chain fatty acids (SCFA) were measured from cecal contents. Microbiota was determined using sequencing of the V3-V4 region of the 16S rDNA gene. This study found that increased evening physical activity rather than morning activity decreases cecal pH, increases SCFA, and changes the microbiota. It is especially important that increased evening physical activity is induced under the post-prandial voluntary training condition. Also, we found that cold room housing, sympathetic blockade, or both suppressed the increased physical activity-induced changes in cecal pH, SCFA, and microbiota. Allobaculum responded to increased physical activity through body temperature increases and sympathetic activation. Post-prandial increased physical activity, rather than pre-prandial increased physical activity by evening voluntary wheel training, altered the microbiota composition, which may be related to the increase in body temperature and sympathetic nervous system activation.
Keywords: Body temperature; Chrono-exercise; Circadian; Microbiota; Sympathetic nervous system; Voluntary training.
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