Your brain is protected from toxins lurking in the bloodstream by the blood-brain barrier (BBB). Sheaths of tightly packed cells wrapped around blood vessels in the brain allow the entry of nutrients but block pathogens and harmful molecules. Now, working in mice, scientists have demonstrated that microbes in the gut play a key role in fortifying this brain blockade. In mice born and raised in sterile conditions (left), tracer molecules (yellow) – too big to breach a healthy BBB – infiltrated the brain. But the barrier worked fine in mice with normal gut microbes (middle). And when germ-free mice (right) were given bacteria, the barrier was restored. The study shows that this interplay between gut bacteria and BBB begins during gestation. If human studies produce similar results, it would raise the possibility that diet or exposure to antibiotics during pregnancy may influence the development of this all-important blockade in the foetal brain.
Written by Daniel Cossins
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