JUN 05, 2017 5:56 PM PDT

Unraveling the Relationship Between Metabolism and Circadian Rhythm

WRITTEN BY: Carmen Leitch

Scientists have known that there is a link between the internal clocks that keep a schedule for our body and metabolism. Researchers have been investigating that connection, and new work using both human participants and a mouse model has revealed more. Investigators using mice found that changing the circadian clock affects the body’s response to food, while the human study showed that regular mealtimes exert control over one particular body clock.

Ten young men were participants in the research, eating meals with the same nutrient and caloric content, three per day at five hour intervals for 13 days. The results showed that when the the timing of meals was disrupted, the circadian rhythm of blood sugar regulation was impacted. Reporting in Current Biology, the investigators suggest that regular meal times can help keep a person’s body on schedule. 

"A five-hour delay in meal times causes a five-hour delay in our internal blood sugar rhythms," explained Jonathan Johnston of the University of Surrey. "We think this is due to changes in clocks in our metabolic tissues, but not the 'master' clock in the brain.”

The participants started with a timed meal regimen in which they got used to eating 30 minutes after walking; then they were changed to a meal that was served five hours later for six days, after which circadian measurements were taken.

Altered meal times did not have much affect on hunger or sleepiness in the subjects, and didn't change the melatonin or cortisol, thought to be markers of the master rhythm. However, the late meals, caused a delay in blood sugar rhythms by an average of over 5 hours.

"We anticipated seeing some delays in rhythms after the late meals, but the size of the change in blood sugar rhythms was surprising," Johnston said. "It was also surprising that other metabolic rhythms, including blood insulin and triglyceride, did not change.”

Related: The Movement of gut Microbes Influences Circadian Rhythm of the Host

While there is still more a lot to learn, research like this suggests that if you’re trying to recover from jet lag or have other circadian disruptions, timed meals could be one way to get back. on track.

The investigators working with mice are studying how the microbiome and metabolism are linked. "Organisms can change how their bodies process food in different ways," said Dr. Derek O'Neill, a postdoctoral fellow in obstetrics and gynecology at Baylor. "Here, we studied two of those strategies. One involves the circadian clock, the internal mechanism that helps orchestrate body activities such as going to sleep or when to eat. Another aspect that can affect how we metabolize our food is the microbiome, the bacteria that live in the body.”

They deleted a gene from the livers of mice, Npas2, which is known to play a role in circadian rhythm. They then manipulated the diets of normal and genetically engineered mice; instead of the typical diet in which they ate as much as they wanted at night, they were only given food for four hours during the day.

In the end, the mice  all ate around the same amount of food and all lost weight. But those without liver Npas2 lost less weight than the normal mice. The findings were reported in the American Journal of Obstetrics and Gynecology.

"We speculate that our findings may lead to solutions for people who are resistant to losing weight with restricted feeding as well as the opposite situation," said Dr. Kjersti Aagaard, a professor of obstetrics and gynecology at Baylor. "This is the first scientific mechanistic study that shows clear evidence of a complex interplay between the host circadian system, the microbiome and the host metabolism when under dietary stress.”


Sources: UPI, AAAS/Eurekalert! via Cell Press, American Journal of Obstetrics and Gynecology, Current Biology, Cover image: Rich Bowen/Flickr

About the Author
Bachelor's (BA/BS/Other)
Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
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