A DNA analysis to identify changes in the gut microbiome in people newly diagnosed with multiple sclerosis — who have yet to begin using disease-modifying therapies — showed that all, regardless of ethnic background, have an abundance of the bacteria group Clostridia compared to people without MS, a study reports.
Identifying changes in the gut microbiome — the collection of microorganisms, bacteria, viruses, and fungi present in the gastrointestinal tract — that are associated with MS may lead to new diagnostic markers, or perhaps identify an environmental root cause of the disease, its researchers said.
The study, “Gut microbiome of treatment-naïve MS patients of different ethnicities early in disease course,” was published in the journal Nature.
Growing evidence suggests that changes to the gut microbiome play a role in MS.
Studies in mice suggested that gut bacteria can influence both pro-inflammatory and anti-inflammatory responses. In one study, mice raised in a germ-free environment were resistant to MS-like disease, but became susceptible when their gut bacteria were restored.
Studies in humans have been inconclusive, as most study participants have been living with MS for a long time and have used, or are taking, disease-modifying treatments that can alter the gut microbiome.
A team of researchers at the New York University School of Medicine analyzed the gut bacteria of people in the early stages of MS who had yet to be treated, and compared findings to the gut microbiome of healthy controls to determine if there were differences associated with MS.
The researchers believe that studying the gut bacteria in people with early stage MS, who are still treatment-naïve, may provide a better understanding of how gut microbiome changes can influence, or perhaps lead to, MS.
As MS severity can vary between different ethnic backgrounds, people were recruited from three major ethnic groups in the local population: African-Americans, Hispanics, and Caucasians.
Overall, the team enrolled 45 people diagnosed with relapsing-remitting MS (RRMS) who had yet to be treated with disease-modifying or biological therapies from the NYU Multiple Sclerosis Comprehensive Care Center clinic.
Among these patients, 14 self-identified as African-Americans, 15 as Caucasians, and 16 as Hispanics. Healthy control participants were ethnically matched.
DNA sequencing was used to identify bacteria from participants’ stool samples, and microbes with similar sequences were grouped together as closely related species (genus).
The analysis revealed an increase in the population of a related group of bacteria called Clostridia in MS patients from all three ethnic groups, compared to controls. (Clostridia are typically found in the human microbiota of the gut, present primarily in the intestinal tract. The Clostridia group includes several species.)
Differences among people from different ethnic groups were also identified. In some cases, greater numbers of specific bacteria were observed in the Caucasian group only versus control, while different bacteria were more abundant in Hispanics and African-Americans groups compared to controls.
“Whether or not the differences we found in the microbiota compositions between our CA [Caucasians], HA [Hispanics], and AA [African-Americans] groups of MS patients may account for some of the differences in disease course between ethnic groups requires further study,” the researchers wrote.
An analysis to measure the variety of bacteria species within a single sample, and between different samples, found no significant difference between MS patients and controls, or between the ethnic groups, with a single exception — a greater variety of bacteria among individual samples from the Hispanic group.
As MS may be influenced by more than one group of microbes, the team examined whether MS-related differences existed in pairs or groups of bacteria found together (bacterial networks). MS patients compared to controls had a decrease in the number of bacterial networks, suggesting that the overall composition of gut bacteria differs in people with this disease.
Participants also completed a dietary survey to measure how wide a range of foods they consume, such as yogurt, probiotics, bread, red and white meat, fatty foods, and fruits and vegetables. No significant differences in diet were found among participant groups.
All three ethnic groups of MS patients analyzed had a greater relative abundance of Clostridia compared to controls, the researchers concluded. However, “further work is needed to elucidate a functional role for the increase in Clostridia representation that we and others have observed in the MS population,” they wrote.
Future “studies will help determine whether candidate species alter immune functions to contribute to early MS, which would have implications for diagnosis, prevention, and treatment of MS,” the team concluded.