Multiple sclerosis (MS) is an autoimmune disease wherein the individual’s immune system mistakenly attacks myelin – that is, the waxy coating on nerves. Myelin plays a number of roles, including protecting the nerve and speeding up transmission. Without it, communication between the brain and the rest of the body is significantly disrupted.
Symptoms of the condition include numbness or weakness, double vision, slurred speech, lack of coordination, trouble walking, and, sometimes, paralysis. Symptoms tend to come in waves, being worse during an attack, then subsiding.
There is currently no cure for MS, and treatments instead aim to speed up recovery from attacks, manage symptoms, and slow disease progression.
Gut bacteria and MS
The human gut is home to a huge number of microorganisms. In fact, researchers believe that there are as many bacteria in our guts as there are cells in our bodies. Over time, our microscopic passengers have become a vital part of the normal functioning of our body, but exactly how they influence us in health and disease is only slowly being unfurled.
Autoimmune diseases are starting to become a problem across developed countries, and they have therefore received a great deal of research of recent years. The role of gut bacteria is of particular interest.
Why gut bacteria might be different in developed countries is unknown, but there are a range of potential reasons – for example, perhaps it is due to a decreased exposure to parasites, the Western diet, or an increase in the use of antibiotics.
Because MS is characterized by an inflammatory immune attack on myelin, researchers have wondered whether altering the microbiome might influence disease progression. Is it possible to introduce a strain of bacteria, or a probiotic, that could change the microbiome and improve MS symptoms?
To answer this question, a group of researchers from the Mayo Clinic – which is based in Rochester, MN – investigated three types of microbe. They cultured bacteria from the human intestine and tested them on a mouse model of MS.
Prevotella histicola and MS
Of the three strains of bacteria, one known as Prevotella histicola effectively suppressed MS in the mice. Specifically, P. histicola produced a drop in two cell types that encourage inflammation, which are known as pro-inflammatory cytokines.
Conversely, it increased the level of certain cell types that fight disease, including dendritic cells, T cells, and a type of macrophage. Overall, inflammation and demyelination were reduced, about which the researchers are excited but cautious.
“This is an early discovery but an avenue that bears further study. If we can use the microbes already in the human body to treat human disease beyond the gut itself, we may be onto a new era of medicine. We are talking about bugs as drugs.”
Senior author Dr. Joseph Murray
Bugs as drugs, shortened by Dr. Murray to “brugs,” would mark a huge step
forward in medicine. Being able to treat a condition as complex as MS in such a simple and relatively cost-effective way would be game-changing.
The current findings knit together with other recent studies in a similar vein – for instance, studies looking at MS patients’ microbiomes have found lower levels of bacteria in the Prevotella genus. Similarly, levels of Prevotella have been shown to increase when MS patients take drugs that combat the condition.
Another neat dovetail is that Western diets promote an abundance of Bacteroides, whereas a high-fiber agrarian, or cereal-based, diet seems to encourage increased levels of Prevotella, marking another trail of clues to follow.
Although the study has concentrated on MS, the scope of these findings is much broader. First study author Ashutosh Mangalam, Ph.D. – from the University of Iowa Carver College of Medicine in Iowa City – says, “[…] it’s not just for MS, because this may have a similar modulating effect on other nervous system and autoimmune diseases.”
Across the board, gut bacteria are in the spotlight; their role in health and disease is under constant scientific scrutiny. As ever, more work will need to be done, but due to the high level of interest and the potential for groundbreaking advances, that work is likely to follow soon.