Even gut microbes have a routine. Like clockwork, they start their day in one part of the intestinal lining, move a few micrometers to the left, maybe the right, and then return to their original position. New research in mice now reveals that the regular timing of these small movements can influence a host animal's circadian rhythms by exposing gut tissue to different microbes and their metabolites as the day goes by. Disruption of this dance can affect the host. The study appears December 1 in Cell.
"This research highlights how interconnected the behavior is between prokaryotes and eukaryotes, between mammalian organisms and the microbes that live inside them," says Eran Elinav, an immunologist at the Weizmann Institute of Science, who led the work with co-senior author Eran Segal, a computational biologist also at the Weizmann. "These groups interact with and are affected by each other in a way that can't be separated."
The new study had three major findings:
Previous work by Elinav and Segal revealed that our biological clocks work in tandem with the biological clocks in our microbiota and that disrupting sleep-wake patterns and feeding times in mice induced changes in the microbiome in the gut.
"Circadian rhythms are a way of adapting to changes in light and dark, metabolic changes, and the timing of when we eat," says Segal. "Other studies have shown the importance of the microbiome in metabolism and its effect on health and disease. Now, we've shown for the first time how circadian rhythms in the microbiota have an effect on circadian rhythms in the host."
The investigators say their work has potential implications for human health in two important ways. First of all, because drugs ranging from acetaminophen to chemotherapy are metabolized in the liver, understanding -- and potentially being able to manipulate -- the circadian rhythms of our microbiota could affect how and when medications are administered.
Second, understanding more about this relationship could help to eventually intervene in health problems like obesity and metabolic syndrome, which are more common in people whose circadian rhythms are frequently disrupted due to shift work or jet lag.
"What we learned from this study is that there's a very tight interconnectivity between the microbiome and the host. We should think of it now as one supraorganism that can't be separated," Segal says. "We have to fully integrate our thinking with regard to any substance that we consume."
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