Gut microbes affect brain damage after stroke

The right concoction of gut microbes may reduce brain damage after stroke, according to a new study.

The communities of microorganisms that live in our gut and on our skin – also known as our microbiome – can affect digestion and wellbeing, as well as our immune responses. However, our understanding of the gut’s effect on a stroke-affected brain is hazy.

So researchers in New York tested how changes in gut microbiome affected mice that had suffered a stroke. Their findings, published in Nature Medicine, suggest that the right mix of microbes in a mouse’s gut can increase the number of good, anti-inflammatory immune cells, and reduce brain injury following a stroke.

Josef Anrather from the Weill Cornell Medical College in New York and colleagues altered the gut bacteria in groups of test mice with antiobiotics, while a control group was given a placebo. All mice then experienced induced stroke, and their immune responses were tested to compare the effects of the microbial change.

The researchers suspected that adjustments to gut flora might affect immune responses, which could be decrease symptoms sustained after a stroke.

In the mice given antibiotics, researchers saw the balance shift to more regulatory T cells – a type of white blood cell with anti-inflammatory properties. They also saw fewer pro-inflammatory cells that travel to the brain after stroke. These changes successfully reduced brain injury in the test mice.

Their adjusted gut flora was transferred from mouse to mouse using faecal transplants, and the effect was the same: more anti-inflammatory T cells in the gut and fewer pro-inflammatory cells travelling to the brain after stroke.

The surprising discovery, the researchers say, is that different kinds of intestinal immune cells travel to the stroke-affected brain. But they do admit more research is needed to work out whether this link between gut and brain is the same in humans as in mice.

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