Microbial molecules in our blood may influence how our cells function

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David Galas

David Galas

By Klara Hanincova, Ph.D.

Scientists in Seattle have found small molecules from bacteria, fungi and other organisms in human blood that could be influencing how our bodies function.

It has been known for some time that our cells release small molecules, call microRNAs (miRNAs), that can then be taken up by other cells and influence their function by altering their protein production.

A team of researchers at Seattle’s Northwest Diabetes Research Institute led by David Galas Ph.D. was trying to better understand just how this miRNA-mediated communication between cells takes place.

As a first step, they set out to identify all the different types of miRNAs they could find circulating in human blood using a new sequencing technology.

To their surprise they found that many of the miRNAs they identified could not be matched to the human genome suggesting that they were not of a human origin.

The finding “was completely unexpected,” said Dr. Galas. “A large fraction of miRNAs that we could not map to the human genome originated from bacteria, fungi, plants and even other animal species.”

Much work remains to be done before the function of foreign miRNAs circulating in our blood is fully understood, but based on their laboratory experiments the team already has some indications.

The foreign miRNAs they found, just like those produced by our own cells, appear to be protected from degradation in the blood and are capable of influencing the behavior of human cells in culture.

“This strongly suggests that at least some of the exogenous miRNAs are functional in the human body,” said Dr. Galas.

A number of the identified foreign miRNAs seemed to come from the microorganisms that normally live in our guts, and are collectively known as the gut microbiome.

The researchers hypothesize that these microbes could be using their own miRNAs to communicate with our bodies.

“One way of thinking about this is that, if miRNAs are indeed involved in cell communication, bacteria could be using them to hack into our computer system and possibly alter its behavior” said Dr. Galas.

The delicately balanced gut microbiome is known to be important to human health and has been found to change during various diseases including obesity, diabetes and asthma.

Hence the team further speculates that the miRNAs from our gut microorganisms circulating in our blood could be a sign of disease or even be a cause of some disorders.

The discovery of miRNAs from other species in our blood opens the door to vast uncharted research territory. As for Dr. Galas and his team, the immediate next step would be to look for correlations between microbiome in the gut and miRNAs in the blood.

Their long-term objective is to understand how changes in the microbiome influence host physiology, and what role miRNAs play in this process. “It is going to be a few more years before we really figure out what is going on,” said Dr Galas.

Klara Hanincova, Ph.D. is a scientist specializing in vector-borne disease and a freelance writer based in Seattle, WA. 

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