JET LAG CAUSE OBESITY BY DISRUPTING THE DAILY RHYTHMS OF GUT MICROBES
Organisms ranging from
bacteria to humans have circadian clocks to help them synchronize their
biological activities to the time of day. A study published by Cell Press
October 16th in Cell now reveals that gut microbes in mice and humans have circadian rhythms
that are controlled by the biological clock of the host in which they reside.
Disruption of the circadian clock in the host alters the rhythms and
composition of the microbial community, leading to obesity and metabolic
problems
"These findings
provide an explanation for a long-standing and mysterious observation, namely
that people with chronically disturbed day-night cycles due to repetitive jet
lag or shift work have a tendency to develop obesity and other metabolic
complications," says senior study author Eran Elinav of the Weizmann
Institute of Science. "These surprising findings may enable us to devise
preventive treatments for these people to lower their risk for these
complications."
Disruption of the
circadian clock in humans is a hallmark of relatively recent lifestyle changes
involving chronic shift work or frequent flights across time zones. These
widespread behavioral patterns have been linked to a wide range of diseases,
including obesity, diabetes, cancer, and cardiovascular disease. But, until
now, it has not been clear how changes in circadian rhythms increase the risk
for these diseases.
In the new study,
Elinav and his team set out to determine whether gut microbes could be the
missing link. When they analyzed microbes found in fecal samples collected from
mice and humans at different times of day, they discovered rhythmic
fluctuations in the abundance of microbes and their biological activities. The
host's circadian clock and normal feeding habits were required for the
generation of these rhythmic fluctuations in the gut microbes.
When mice were
exposed to changing light-dark schedules and abnormal 24 hr feeding habits, the
microbial community lost its rhythmic fluctuations and changed in composition.
Moreover, a high-fat diet caused these jet-lagged mice to gain weight and
develop metabolic problems associated with diabetes. Similarly, jet lag in two
humans who had traveled from the United States to Israel changed the
composition of gut microbes, favoring the growth of bacteria that have been
linked to obesity and metabolic disease.
"Our findings
highlight a new therapeutic target that may be exploited in future studies to
normalize the microbiota in those people whose lifestyle involves frequent
alterations in sleep patterns, such as shift workers and very frequent
fliers," Elinav says. "Targeting the harmful changes in the
microbiota in these large human populations with probiotic or antimicrobial
therapies may reduce or even prevent their risk of developing obesity and its
complications."
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