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Brain depends on gut bacteria for protection

Life Science

Published Dec 03, 2014

With the abundance of information available about eating right, no one could question the capacity of your brain to protect your digestive tract. But a recent study shows that the intestines may in turn be protecting the brain, long before you’re old enough to surf health and nutrition websites.

An image showing the uptake of the substance, Raclopride, in the brain of bacteria-free versus conventional mice. (Photo: Miklos Toth)

An international research team has found that in mice, there is a connection between exposure to intestinal flora during gestation and the development of the brain’s protective cells.

One of the researchers, Hans Herbert, a professor in biotechnology at KTH Royal Institute of Technology, says that understanding the link between gut bacteria and the development of what is known as the blood-brain barrier could “have important significance for the prevention and treatment of neurological disorders such as autism in humans.”

The blood-brain barrier is a layer of cells that line the blood vessels throughout the brain. This layer is held together by tight junctions that prevent small molecules from diffusing through the gaps between the cells. The barrier serves as a filter to prevent harmful substances from passing into the brain tissue from the bloodstream.

Herbert and other researchers have shown that mice deprived of exposure to natural intestinal flora – or gut bacteria – during the fetal development period had higher permeability of the blood-brain barrier than mice exposed to maternal gut bacteria.

The “leakiness” of the blood-brain barrier continued even into adulthood for the bacteria-free mice. This permeability was associated with a lower incidence of the proteins that make up the blood-brain barrier.

Hans Herbert in the lab. (Photo: Staffan Larsson)

But when these adult mice were exposed to gut bacteria, the permeability of the blood-brain barrier decreased and the presence of the proteins increased.

The researchers concluded that communication between flora in the intestine and the blood-brain barrier begins during gestation and that it then continues throughout life.

Herbert says the findings may be significant for understanding how neurological disorders develop. “There are hypotheses about how changes in the presence of gut microbiota can lead to problems in the function of the brain and nervous system. It also has been hypothesized that autism is related to the blood-brain barrier function,” he says.

The project was a collaboration between Karolinska Institute in Stockholm and research groups in New York and Singapore, in addition to KTH. Hebert and KTH researchers Kjell Hultenby and Harriet Nilsson contributed through the electron microscopy study of specific protein complexes in the blood-brain barrier.

The results were published November 19, 2014 in the journal Science Translational Medicine.

For more information, contact Hans Herbert at 08 - 790 94 66 or .

Peter Larsson/David Callahan

The gut microbiota influences the blood-brain barrier permeability in mice. Science Translational Medicine , 19 November 2014: Vol. 6, Issue 263, p. 263fs46.

For more information, contact Hans Herbert at +46 8 - 790 94 66 or .