Sunday, July 17, 2016

Wrap your brain with germs: Myelin and bacteria

One of my main areas of interest is the interaction between the brain and the gut. In trying to better understand how this can happen, a powerful animal model has been the interesting case of the germ free animal, which is born (believe it or not) without a microbiota. As one can imagine, this can lead to major effects upon digestion, but increasing evidence has also suggested that germ free animals have altered behaviour, such as changes in anxiety-like behaviour and reduced social behaviour. This suggests an impact of gut microbes on the brain, and has ignited interest in what kind of factors might be mediating this relationship.

Recent research from APC Microbiome Institute, UCC, suggests that germ-free mice have increased levels of myelin, the fatty sheath that surrounds brain cells and assists in the transmission of brain signals. This change in myelin was clearly observed in the prefrontal cortex, a region of the brain responsible for more complex cognition, including behavioural changes that have previously been shown in germ free mice. Interestingly, giving the mice a microbiota restored typical myelination, deepening the evidence for a causal link between the two, and suggesting that the effects were reversible.

The authors believe the findings could have relevance for multiple sclerosis, which is a disorder of myelination, although one would imagine translation from quite a blue-skies study like this to the clinic will clearly take time. Multiple sclerosis is also related to dysfunction of the immune system, which has been implicated as a pathway within the gut-brain axis, so perhaps this will be a key topic within future research within this area.

It was encouraging to see the findings being picked up by The Guardian and other news outlets, which will hopefully help further fire up the public imagination about the gut-brain-microbiota axis. Stay tuned next month for more on this topic!

Hoban AE, Stilling RM, Ryan FJ, Shanahan F, Dinan TG, Claesson MJ, Clarke G, Cryan JF. (2016). Regulation of prefrontal cortex myelination by the microbiota. Translational Psychiatrydoi: 10.1038/tp.2016.42.

(Banner image for this blog post is a detail from Figure 3, Hoban et al., 2016).

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