What is already known on this topic
Multiple sclerosis affects 2.5 million people worldwide, but little is known about its causes and which factors shape the course of the disease.
What this research adds
By analyzing the gut microbes of a mouse model of multiple sclerosis, researchers have found differences in the microbiota composition between mice that show acute flare-ups followed by periods of remission and mice that experience an increase in disability without periods of remission.
The study suggests that the composition of the gut microbiota could determine remittance or pro-inflammatory conditions in a multiple sclerosis model.
Multiple sclerosis affects 2.5 million people worldwide, but little is known about its causes and which factors shape the course of the disease. Now, researchers have found that the composition of the gut microbiota could determine remittance or pro-inflammatory conditions in a mouse model of multiple sclerosis.
The results, published in Scientific Reports, show for the first time that gut microbes may determine the susceptibility to different forms of multiple sclerosis. The condition is an autoimmune disorder that strips away nerve cells’ protective covers, leading to muscle weakness, blindness, and even death.
Scientists think that the disease starts when genetically predisposed people encounter an as-yet-unknown environmental trigger, and previous studies have identified particular bacteria present in increased amounts in the guts of people with multiple sclerosis. But why some individuals experience acute flare-ups followed by periods of remission while others show an increase in disability without periods of remission is poorly understood.
So Alexa Orr Gandy and her colleagues at the University of South Carolina School of Medicine used a mouse model of multiple sclerosis to assess the role of gut microbiota in determining whether mice would develop the chronic-progressive or the relapse-remitting form of the disease.
Different disease courses
Bacteria belonging to the phylum Bacteroidetes, including Bacteroidaceae, Porphyromonadaceae, and Prevotellaceae, were underrepresented in healthy mice and only present in mice that developed the relapse-remitting form of multiple sclerosis. Some as-yet-unclassified species of Parabacteroides were exclusively present in relapse-remitting mice, and members of the Tenericutes phylum were also more abundant in the relapsing-remitting group than in healthy mice.
In line with previous reports, bacteria belonging to the phylum Verrucomicrobia, in particular the microbe Akkermansia muciniphila, were present only in the chronic-progressive group. While bacteria of the Rickenellaceae family were found in feces from mice that developed the chronic-progressive form of the disease, they were also abundant in relapse-remitting mice.
The researchers were able to identify differentially abundant gut bacteria that may serve as biomarkers for multiple sclerosis. For example, Akkermansia muciniphila, members of the Peptococcaceae family, and unclassified species of the Lachnospiraceae family were identified as biomarkers of the chronic-progressive disease course.
Bacteria belonging to the Bacteroidales family, unclassified genera from the Rikencellaceae family, and Bacteroides acidifaciens were identified as biomarkers of the relapse-remitting disease course.
Dorea and Lactobacillus bacteria were instead identified as biomarkers of healthy mice.
Although more work is needed to understand how the gut microbiota shapes the course of the disease in mice and people, the findings suggest that different gut bacteria could determine an individual’s susceptibility to chronic-progressive or relapse-remitting forms of multiple sclerosis.