There is a growing interest in the role of gut bacteria in inflammatory disorders such as MS. Gut bacteria (also referred to as our microbiome) play a crucial role in our digestive tracts by assisting with digestion of our food and producing beneficial chemicals for the body to use. However, this may just be the tip of the iceberg and the complete and complex picture of the role gut bacteria play only just beginning to be revealed.
Previously it has been shown that there are potential differences in gut bacteria between those with MS and those without MS. Now two studies published by two collaborating groups in the prestigious journal Proceedings of the National Academy of Sciences (here and here) have revealed more about the link between gut bacteria and MS.
The first study led by Hartmut Wekerle at the Max Planck Institute of Neurobiology, Germany, examined 34 pairs of identical twins where one had MS and the other didn’t. They compared the gut bacteria between the twins however they were unable to identify any obvious differences between the siblings. There were greater differences between different families than between each twin pair, which highlights the stronger influence of diet and geography in influencing our gut bacteria.
However, when the researchers took samples of gut bacteria from 5 pairs of twins (where one had MS and the other didn’t) and transplanted those bacteria into mice with a predisposition to an MS-like illness, they found that more mice developed an MS like disease if they had received the gut bacteria from the twin with MS. However, it is important to note, that receiving gut bacteria from the healthy twin did not prevent MS.
The scientists also looked at how the gut bacteria influenced the immune system in these mice. They didn’t detect any difference in the numbers of different types of immune cells. However, the mice that received gut bacteria from the people with MS showed lower levels of an immune system chemical called IL-10. IL-10 is known to play a ’calming’ regulatory role in the immune system.
These results suggest that there are some differences in gut bacteria in those with MS, and these bacteria can influence the immune system in a way that promotes MS-like inflammation.
The second study led by Sergio Baranzini at the University of California San Francisco examined the gut bacteria of 71 people with MS and 71 people without MS. While their study showed some similar findings to the German group, they did find that there were a couple of specific bacterial families which were altered in people with MS.
They then exposed healthy immune cells grown in the test-tube to extracts taken from these types of bacteria that were more common in the people with MS. This caused an increase in the types of immune cells that cause inflammation and a decrease in cells which are responsible for suppressing the immune system.
As with the German study, the scientists then transplanted gut bacteria from people with MS or without MS into mice which had an MS-like disease and they found that the bacteria from people with MS lead to a more severe disease.