February 2018    
  Gut feelings  
  Biologists and physicians study the interplay of circadian rhythms and the microbiome.  
  (Illustration courtesy UChicago Medicine)  
  What can fat and sleepy mice tell us about human health? A lot, it would seem.  
  Humans, mice, and even plants--everything biological--have circadian rhythms that follow a roughly 24-hour cycle, regulated by certain genes. These biological clocks, ticking in every cell, influence a range of physiological processes, such as metabolism. And in turn, these rhythms can be disrupted by biological activities, like changes in eating and sleeping.  
  The microbiome fits into this feedback loop, with microbial activity changing and being changed by circadian rhythms. Eugene Chang, MD'76--the Martin Boyer Professor of Medicine and a researcher in the new Duchossois Family Institute--explores the complex and multidirectional relationship between the microbiome and the biological clock.  
  Gut microbes can't see the sun, so what controls their clocks? In 2015 Chang and postdoctoral scholar Vanessa Leone determined that diet was one part of the answer. They conducted an experiment changing what, when, and how much different mice ate and then analyzing their microbiome fluctuations.  
  Mice fed a high-fat diet had less microbial variation throughout the day, which altered their bacterial waste products, which in turn affected circadian clock genes in the liver--one of the main organs for fat metabolism. Those mice gained weight.  
  The experiment also included germ-free mice, born and raised in a sterile environment and lacking any gut microbes. Sterile mice fed high-fat food also had a disrupted cycle but did not gain weight.  
  Another experiment Chang and Leone contributed to approached the issue from the sleep angle. They disrupted mice circadian rhythms by waking them repeatedly, in the same way humans are awakened by sleep apnea. The sleepy mice showed increased appetite, lowered insulin sensitivity, and fat accumulation. They also showed changes in their microbiome--in both the type of bacteria present and their waste products.  
  Then bacteria from the sleep-deprived mice were transferred to germ-free mice. Although they didn't gain weight, they ate more and developed insulin resistance despite being well rested. While the mechanisms underlying these relationships are still unclear, the results suggest that perhaps a healthy meal and a good night's sleep are in order for humans as well as mice.  
  An animation shows how we're more bacteria than human.  
  Five more things about sleep and the microbiome  
The 2017 Nobel Prize in Physiology or Medicine was awarded to three geneticists for their discovery that circadian rhythms are controlled by specific genes.
The circadian clock of cyanobacteria--one of Earth's most ancient life forms--is set by metabolism, not light.
Bacteria from jet-lagged humans made healthy mice gain weight.
Circadian disruptions, like those from shift work, are detrimental to metabolic health.
Eating before bed is not necessarily a bad thing.
  Let sleeping dogs lie  
  Augusta "Gus" Morales hard at work making his family healthy.  
  Is sharing a bed with your pooch bad for your health? It depends.  
  Are you allergic? Many dog lovers are and take meds or just deal, but the bed is best kept an allergen-free space.  
  Are you a light sleeper? Restless pets can disrupt your sleep, leading to a variety of sleep-deprivation problems.  
  Is your dog germy? (Yes, your dog is.) Exposure to outside germs may bolster your immune system,* so most healthy people can safely snuggle up.  
  *UChicago microbial ecologist Jack Gilbert, who conducted a study that showed dogs can increase a home's microbial diversity, adopted a shelter dog based on his results. His kids named him Captain Beau Diggely.  
  In case you missed it  
Brain on love: Stephanie Cacioppo studies the neuro nature of romance.
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  Support UChicago Medicine.  
  Good things come to those who share! Forward µChicago to a friend and be entered to win a prize. Congratulations to last month's contest winner, Buddy Brownstein.

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