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 that gut bacteria play is only 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 – available 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, among whom one had MS and the other didn’t. Upon comparing the gut bacteria between the twins, they were unable to identify any obvious differences between the siblings. In fact, 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. It is important to note, though, 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 a couple of specific bacterial families that 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 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 responsible for suppressing the immune system.

As with the German study, the scientists then transplanted gut bacteria from people with or without MS into mice that had an MS-like disease, and found that the bacteria from people with MS led to a more severe disease.

These studies provide evidence that there may be subtle differences in gut bacteria between people with MS and people who do not have MS. They also provide evidence that these differences can affect the immune system in mice in a way that may influence the severity of MS.

There are still some differences between the results of these two studies, which need to be resolved through further research. While there is great interest in how we may be able to manipulate our gut microbiome to treat or prevent disease, this research shows that we still have a way to go before we have a complete picture of how much influence our microbiome may have in MS, and exactly how we might use this knowledge to treat MS.

With thanks to MS Research Australia – the lead provider of research summaries on our website.