Study: Gut microbiota impacts the progression of brain lesions after stroke

Stroke-induced inflammation is both a blessing and a curse. Some of the inflammatory processes help heal the damaged brain after treatment, but others severely damage neurons and whole-body function. In the research world, this observation has kicked off a long-distance race to find a solution that would both hinder ‘bad’ inflammation and promote its ‘good’ counterpart.

Corinne Benakis, neurobiologist at the Institute for Stroke and Dementia Research, has something of a head start on her peers. Her research has found that the gut microbiota – beneficial bacteria living in symbiosis in our gut – has an impact on the progression of brain lesions after stroke.

Benakis’ research started bearing fruit in 2016, when she published a research paper in Nature Medicine demonstrating how the gut microbiota can modulate the inflammatory response in case of stroke, alongside project leader Arthur Liesz.

The gut contains the largest number of immune cells in the body, whose function is tightly regulated by the beneficial bacteria living in symbiosis in our gut. This so-called microbiota can ‘talk’ to immune cells, activate them and define whether they’ll become good or bad. We used an experimental model for stroke and induced a lesion in the brain, and we found that a stroke changes the type of bacteria in the gut. Immune cells become bad pro-inflammatory cells, travel from the gut to the brain and start causing more damage,”

Corinne Benakis, neurobiologist at the Institute for Stroke and Dementia Research

Probiotics and postbiotics for the brain

Benakis found that by using antibiotics, they could deplete some types of microbes in the gut and promote the overgrowth of others. By doing so, they were able to induce anti-inflammatory cells in the gut and protect the brain from stroke injury. Since then, the MetaBiota team has been taking on a new challenge: investigating the complex crosstalk between gut microbes and these immune cells.

The research in itself is groundbreaking. By combining experimental models and analysis tools from the fields of microbiology, immunology and neuroscience, it provides much-needed understanding of the complex interactions between the brain and the gut. And it could mean a lot for patients, too.

“It brings new therapeutic perspectives,” Benakis explains. “About 14 million people suffer a stroke each year worldwide. It’s one of the leading causes of death amongst the elderly and the leading cause of long-term disability, with very limited therapeutic options. The very concept that gut microbiota composition can be modulated to improve the outcome of stroke is extremely promising. You could imagine treatments that give patients a cocktail of beneficial bacteria or beneficial molecules produced by bacteria – known as probiotics and postbiotics respectively – through dietary interventions. These could protect the brain and improve recovery after stroke.”

While this all sounds exciting, there is still much to uncover before treatments like this can be administered to patients. As Benakis points out, “it is still not known which types of gut bacteria participate in the intestinal immune changes after stroke. We also don’t know which microbial cues influence the immune cells in the gut after stroke. But we can hope to get there, now that MetaBiota has revealed critical pathways of communication between gut bacteria and the immune cells that critically influence the outcome of stroke.”

Benakis has now obtained a position as junior team leader at the Institute for Stroke and Dementia Research. She hopes her findings will soon translate into clinical settings and will notably focus on investigating the value of microbiome changes in stroke patients as disease-related biomarkers.

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