Gut Bacteria that May Cause Stroke

New research published in Nature has added convincing data to the theory that the gut bacteria biome may influence our health in many more ways than was previously known – and not just in the stomach.

Researchers at the University of Pennsylvania were studying a rare genetic disorder that causes cerebral cavernous malformations where bubbles filled with blood protrude from vessels in the brain and could leak or pop at any time. Although they identified 3 different gene mutations linked to the disorder, it wasn’t until they moved their lab out of one building and into another that they made the unlikely link between the gene mutation, the brain disorder and gut bacteria.

In the course of their study, students followed a research protocol that deleted specific genes in the study mice using a drug injection. Once the gene was deleted, the mice would begin to develop the brain malformations. Occasionally the injection would cause an abscess and then bacteria from the gut would leak into the bloodstream of the mice. But after they moved buildings, only the mice who developed abscesses then went on to develop the brain malformations. Other mice, even though they had the same gene deletion, did not develop the blood bubbles.

Finally, the doctors discovered that a lipopolysaccharide, carried on the cell walls of Gram-negative bacteria, was signaling the brain to produce the blood bubbles. If antibiotics were administered to the mice to kill the Gram-negative bacteria, no blood bubbles would form. Similar results were found with a fecal transplant to replace the gut bacteria, but the researchers were not able to prevent bubbles that had already formed.


The next step for the researchers is to investigate whether the same findings in the mice hold true among human subjects. For this, the researchers have looked to a specific population in New Mexico where there is a high incidence of the mutated gene. They have begun to collect fecal samples which will be tested for differences in gut bacteria and compared with those of the mice.

Quoted in the New York Times, Dr. David Relman, professor of microbiology and immunology at Stanford explained that researchers “need to be thinking more broadly about the indirect role of the microbiome.”

To learn more about the microbiome, check out this video.

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Laurie Breen

Laurie Breen is a freelance writer well-versed in research communications and grant writing. She received her Bachelors Degree in Psychology from Smith College and has worked previously at the University of Queensland's Centre for Clinical Research in Brisbane, Australia. Her favorite conversational topic is "antibiotic-resistant bacteria," making her a big hit at parties.