Episode 7 of The Microbiome Podcast: Gut bacteria and circadian clocks with Drs. Eugene Chang and Vanessa Leone

On the seventh episode of The Microbiome Podcast we had a great conversation with Drs. Eugene Chang and Vanessa Leone from the University of Chicago. Drs. Chang and Leone found that bacteria in the gut influence the circadian clock in mice.  They discovered that altering the diet of the mouse by introducing a high-fat diet caused conventionally raised mice to have a disrupted circadian clock and became obese. They looked at what genes were expressed in the liver and found that the genes expressed varied widely from mice that were germ-free and those that were normal and conventionally raised.  We talked with them about this work and what influence this could have on humans and on our eating and sleeping patterns.

Listen to the podcast here on our website, here on iTunes, and here on Stitcher.

Below are more detailed show notes:

• Two scientific talks that David saw in New York City. First (0:37), a talk by AMI Scientific Advisory Board member Marty Blaser about antibiotics and obesity. We then (1:23) discussed a talk by Chris Mason about the microbiome and his study on the microbes in the NYC transit system. Dr. Mason published his slides on twitter so if you’re interested in seeing his slides, you can see them here.
• (2:26) Dr. Tim Spector from Kings College London had his son eat only McDonalds for 10 days straight. His son lost approximately 40% of the bacterial diversity in his gut. Read more about it here.
• (3:40) The British Gut Project that Dr. Tim Spector leads, a partner of The American Gut Project. Check out the British Gut Project.
• (5:37) A company called Biomecite Diagnostics that licensed technology from The University of Maryland School of Medicine to develop molecular diagnostics to detect inflammatory bowel diseases like Crohn's disease and ulcerative colitis. Read more here. 
• (6:10) We gave an overview of diurnal changes, circadian clock, and the microbiome.
• (9:21) We began the interview with Drs. Chang and Vanessa Leone and discussed their paper that found that cirdcadian clocks were influenced by gut microbes. Read the paper in Cell Host and Microbe. Read our blog post about this work.     
• (11:47) Dr. Leone discussed a few seminal papers from 2014 about diurnal changes. Read this paper about jet-lag and the microbiome. 
• (34:15) After the interview with Drs. Chang and Leone we talked about our own sleep patterns.
• (37:18) We gave our own opinions on Deflategate and Bill goes on a little rant about the Patriots, Tom Brady, and deflated footballs.

Obesity and the daily cycle of the microbiome

We recently wrote a blog about an article discussing how sleeping patterns affected the microbiome and may contribute to obesity, but what about eating patterns?  A paper published last week in Cell Metabolism aimed to answer this question. 

Three groups of mice were used in the experiment.  The first group of mice was given unlimited access to a high fat diet.  These mice ate their food all day and night.  The second group of mice mice was given a high fat diet but restricted to eat for only 8 hours per day.  The final group of mice was given unlimited access to normal food.  These mice tended to eat for only 8 hours per day, so they were actually no different than a group of mice restricted to eating normal food for 8 hours per day.  The researchers measured all of the mice’s microbiomes, weights, cholesterol, and other metabolites at various time points throughout the day.

Most shockingly, they found that by restricting the mice to a high fat diet for only 8 hours per day decreased their obesity and cholesterol and these mice were indiscriminant from mice eating normally.  The mice that ate the high fat diet at all hours were obese, and had high cholesterol.  When investigating the mice’s stool, the scientists discovered that the stool of mice with restricted eating times was of higher caloric density than mice eating a high fat diet at all times.  This means that mice that eat the high fat diet at any time extract more calories from their food than those mice that restrict their eating.  They also discovered that while all mice that ate a high fat diet had similar microbiomes, the mice that only ate for 8 hours had many cyclic bacteria that would flourish and dissipate depending on the feeding schedule, whereas there were less cyclic bacteria in the mice that ate at all times.  Furthermore, there seemed to be a decrease in one bacteria associated with obesity, Lactococcus, in the mice with restricted eating times, even with the high fat diet, whereas these bacteria flourished in mice that ate the high fat diet at all times. 

From a microbiome science standpoint, this study demonstrates the need to consider diurnal cycles when making microbiome measurements.  From a nutrition standpoint it makes one reconsider the benefits of eating many small meals a day versus fasting.   If nothing else, the study demonstrates how complex the microbiome, diet, and obesity puzzle really is, and how much we have yet to understand.