Transfer of gut bacteria affects brain function and nerve fiber insulation
Quick hide, shut your windows and lock your doors, are you alone? No, you aren’t that’s the problem and what’s worse, you are being controlled. This isn’t a plot for the latest thriller, this is the findings of a new study and adds to growing number of studies showing that our bacteria is more of us than we realize. In fact, the study found that specific combinations of gut bacteria produce substances that affect myelin content and cause social avoidance behaviors in mice.
The research has — not so creepy mind control-esque — practical applications. It suggests that targeting intestinal bacteria, or their metabolites, could be one way to treat debilitating psychiatric disorders and demyelinating diseases, like multiple sclerosis. Which is a not so fun autoimmune disorder characterized by damage to myelin, the insulating sheath around the axons of nerve cells that allows for faster electrical impulse conduction.
A little side note, myelination is critical for everyday brain and nerve function. Myelin is like the plastic around electrical cords, if it wasn’t there, or if it was very thin, you would have some serious troubles.
Damaged myelin results in altered synaptic transmission and clinical symptoms like you know, pain, anguish, hurt, oh and loss of signal between nerves. Previous research found a thinning of myelin and a reduction of myelinated fibers in preclinical models of depression. This actually helped give a biological insight for the high rate of depression in MS patients.
This current study found bacteria-derived gut metabolites that can affect myelin content in the brains of mice and induce depression-like symptoms.
Researchers transferred fecal (see: poop, its okay you can laugh…) bacteria from the gut of depressed mice to genetically distinct mice exhibiting non-depressed behavior. The study found that the transfer of this microbiota was sufficient to induce social withdrawal behaviors and change the expression of myelin genes and myelin content in the brains of the recipient mice.
“Our findings will help in the understanding of microbiota in modulating multiple sclerosis,” says Patrizia Casaccia, MD, PhD.
“The study provides a proof of principle that gut metabolites have the ability to affect myelin content irrespective of the genetic makeup of mice. We are hopeful these metabolites can be targeted for potential future therapies.”
In an effort to define the mechanism of gut-brain communication, researchers identified bacterial communities associated with increased levels of cresol, a substance that has the ability to pass the blood-brain barrier. When the precursors of myelin-forming cells were cultured in a dish and exposed to cresol, they lost their ability to form myelin, thereby suggesting that a gut-derived metabolite impacted myelin formation in the brain.
Of course, further study is needed to translate these findings to humans. Also, to identify bacterial populations with the potential to boost myelin production which may help treat people with MS or even depression.
Gacias, M., Gaspari, S., Mae-Santos, P., Tamburini, S., Andrade, M., Zang, F., Shen, N., Tolstikov, V., Kiebish, M., Dupree, J., Zachariou, V., Clemente, J., & Casaccia, P. (2016). Microbiota-driven transcriptional changes in prefrontal cortex override genetic differences in social behavior eLife, 5 DOI: 10.7554/eLife.13442