What if the key to brain youth was found in the intestines? This is the lead followed by a new study carried out by American and Italian researchers, reports Popular Mechanics. Transplanting feces from young mice into old mice would indeed restore the ability of their brains to form new connections.
To fully understand the issue of this work, we must first talk about amblyopia. This phenomenon occurs when the brain favors one eye over the other, a condition that affects nearly 100 million people worldwide. In children, it is enough to cover the dominant eye for a few weeks, forcing the brain to create new neuronal connections. This works because children’s brains are still very malleable: this is called neuroplasticity.
We have known for several years that the billions of bacteria that inhabit our intestines influence the functioning of the brain. This microbiome is involved in certain mental disorders such as depression, anxiety and even Alzheimer’s disease. The researchers therefore wanted to know if it could also play a role in neuroplasticity.
Young stools for a young brain
The team first gave a group of mice antibiotics for ten days to destroy the good bacteria in their gut. A second group received no treatment. All the mice then had one eye covered for three days: all the conditions for amblyopia were met. Result: only mice whose microbiome was intact showed neuroplasticity. Destroying good gut bacteria was enough to block the brain’s ability to adapt.
With this result, the researchers took a further step: if a healthy microbiome preserves neuroplasticity, can it be restored by transplanting the microbiome of a young mouse into an older mouse? Concretely, the researchers took the feces of a young mouse, rich in beneficial bacteria, and introduced them into the digestive system of an adult mouse, to recolonize its intestines with a younger microbiome.
One group of adult mice therefore received stools from young donors, another group received stools from older donors. Then all groups were subjected to the same covered eye test. Again, neuroplasticity was only observed in mice that received young stools. In other words, transplanting a young microbiome into an aging brain was enough to make it more malleable again.
The gap between mice and humans remains considerable, and researchers have yet to identify precisely which bacteria are responsible for this effect, and by what mechanism they act on the brain. But the results open up a serious avenue: what if, to keep a young brain, you first had to take care of your intestines?
