Yeast found in the gut linked to asthma
Yeast has joined the list of gut microbes that play a role in driving diseases like asthma.
In a study of babies in Equador, the presence of a particular type of yeast in the gut appears to be a strong predictor that they will develop asthma in childhood. The new research by Brett Finlay, Co-Director of the Humans & the Microbiome program and a microbiologist at the University of British Columbia, is the first to find an association between yeast and asthma.
“Early life microbes really set you up or not to get early life asthma,” Finlay told reporters at the American Association for the Advancement of Science (AAAS) meeting in Boston Feb. 17. “By one year of age it’s too late.”
In 2015, Finlay identified four gut bacteria that seem to prevent asthma in Canadian children: Lachnospira, Veillonella, Faecalibacterium, and Rothia. Children with fewer of these bacteria during their first 100 days of life were at a higher risk of asthma by age five. Furthermore, when researchers implanted feces containing these bacteria in mice that did not previously have them, the mice appeared to be protected from asthmatic symptoms. This suggests there is a causal link between the loss of these microbes and asthma.
Finlay wondered whether this asthma-gut bacteria link was specific to Canadian children or common across the globe. In a follow-up study, microbiologists examined feces from 100 children in rural Ecuador with comparable asthma rates. Researchers found that while the four gut bacteria play a role in preventing asthma in Ecuador, it was the presence of a type of yeast known as Pichia that was more strongly linked to asthma. Instead of helping to prevent asthma, however, the presence of Pichia in those early days puts children at risk.
“It’s different microbes in different places but it makes sense,” Finlay says. “This pre-life microbial exposure is important for shaping the immune system and how you get asthma, and now we can add yeast to the list.”
Most research on the microbiome – the microbes that live in the gut – has been focused on bacteria rather than fungi, like yeast. Not only are fungi harder to sequence, they are also less common in the gut than bacteria and viruses. But thanks to new technologies, Finlay’s colleagues were able to sequence fungi in the Ecuador study. Now they will re-examine the Canadian samples and look for the presence of yeast in the gut of infants.
With these technological advances Finlay hopes scientists can better understand how yeast affects asthma. One hypothesis is that fungi interact with the bacteria involved with producing short-chain fatty acids. These fatty acids have been measured in kids and seem to affect how the cell’s immune system functions.
“We know that microbes in the gut play a role in many diseases, and I think that as we look into these yeast there will be many other examples,” he says.
“They’re there, we’ve figured that out, but now we need to figure out what they do.”
Finlay presented his research as part of a session entitled “Microbes and Humans: Effects on Health, Disease, and Society” with Humans & the Microbiome program Co-Director Janet Rossant (Hospital for Sick Children), Senior Fellow Eran Elinav (Weizmann Institute of Science) and Ana Duggan of Senior Fellow Hendrik Poinar’s lab (McMaster University). They were among several CIFAR researchers who participated in the 2017 AAAS meeting.
Banner image: In a study of babies in Ecuador, the presence of a particular type of yeast in the gut (Pichia) appears to be a strong predictor that they will develop asthma in childhood. (credit: Rozlyn Boutin)