The intestine is the “second brain” that sometimes attacks the first: as in this case. A story of biological betrayal that emerges from research on multiple sclerosis, and the “culprits” are precisely the intestinal bacteria.
In a study that could rewrite neurology textbooks, a team of German researchers analyzed identical twins to isolate the needle in the haystack: the specific microbes that could trigger the disease. And after examining 81 pairs of twins (one with MS, the other healthy), they identified two gut bacteria with an ugly face. The discovery sheds light on the nebulous area of interaction between genetic predisposition and environmental factors that has baffled scientists for decades.
The identikit of the microscopic suspects
Scientists fromLudwig Maximilian University of Munich have finally pinpointed two intestinal bacteria potentially responsible (here you can find the paper published on PNAS). As detectives finally identify the culprit after years of inconclusive investigation, researchers have pointed the finger at Eisenbergiella tayi e Lachnoclostridium, both members of the family Lachnospiraceae.
I am particularly fascinated by the methodological approach: the choice to study identical twins to eliminate the genetic variable from the equation. Same genes, same predispositions, but one twin develops multiple sclerosis and the other does not. What makes the difference? Apparently, these tiny inhabitants of our intestines.
The team identified as many as 51 different types of bacteria whose abundance varied significantly between the affected and healthy twins. A difference that cannot be coincidental (not between identical twins) and which suggests a direct role of the intestinal microbiome in the development of the disease.
The mouse test
To confirm their suspicions, the researchers did something brilliant (and a little disturbing): they transferred the intestinal microbiota twins in mice genetically predisposed to develop diseases similar to multiple sclerosis.
The results? The mice that received the bacteria from the sick twins actually developed symptoms similar to MS. Further analysis later confirmed that this was indeed the case. E. tayi e Lachnoclostridium were the main responsible.
Together with our functional studies, this supports our conclusion that these bacteria may play a crucial role as environmental triggers of human MS, although further studies will be needed to extend our current findings.
The gut-brain axis never ceases to amaze us, and it’s clear that it’s much, much more important than we previously thought.
Gut bacteria, the road to new therapies
There are limitations to the study, of course. We cannot yet say with absolute certainty that these intestinal bacteria are the sole, direct cause of multiple sclerosis in humans. Even the experiments done on mice are indicative, not definitive. It must be said.
But the direction is promising. If these intestinal bacteria are indeed involved in the onset of MS, we can think about therapies that modify the microbiome to prevent or slow the disease.
The research team concluded that this experimental strategy “could pave the way to a functional understanding of the role of the gut microbiota in multiple sclerosis.” A phrase that hides between the lines an enormous therapeutic potential.
And perhaps, in a few years, we will no longer look at these intestinal bacteria as traitors, but as targets to be hit to win an important battle.
