New Findings on Gut Bacteria and Multiple Sclerosis

A recent twin study has shed light on specific gut bacteria that might play a role in the onset of multiple sclerosis (MS), which is the most prevalent inflammatory condition affecting the central nervous system. By examining identical twins where only one has MS, researchers managed to rule out many genetic and environmental variables, ultimately identifying 51 types of bacteria that differed in their abundance between the twins.

Using a model with mice, the team discovered that gut bacteria from twins diagnosed with MS could trigger symptoms reminiscent of the disease. In particular, two microbes—Lachnoclostridium sp. and Eisenbergiella tayi—were highlighted as possible contributors to the disease’s development. These findings suggest potential avenues for targeted therapies focused on gut health and underscore the significance of the microbiome and lifestyle factors in MS progression.

Key Insights

• MS-Discordant Twins: Utilizing identical twins helped pinpoint microbial influences by limiting genetic and lifestyle differences.
• Evidence from Mice: Mice that received gut bacteria from MS patients exhibited symptoms associated with the disease.
• Identified Microbes: Lachnoclostridium sp. and Eisenbergiella tayi were highlighted as potential triggers for MS.

In Germany, over 280,000 individuals live with MS, and about 15,000 new cases are diagnosed each year, making MS the most widespread inflammatory disorder of the central nervous system. The disease leads to the immune system attacking the protective layer around nerve fibers, which disrupts their function.

This can result in a range of symptoms, giving rise to MS being referred to as the “disease of a thousand faces.” Individuals may experience issues like impaired vision, sensory disturbances, or even paralysis, which varies widely based on where the immune attacks occur.

However, the exact mechanisms that render immune cells dysfunctional in MS are still mostly unknown. MS is multifactorial; it doesn’t have a single cause but rather several contributing elements. Beyond genetic factors, environmental influences like smoking, deficient vitamin D levels, specific infections, and notably, gut microorganisms have all been associated with MS development.

While prior research had pointed to various bacterial strains that distinguish MS patients from healthy individuals, the implications of these differences for disease progression were not always clear. Additionally, results were often complicated by genetic variations or differing diets among participants.

Twin Study to Minimize Confounding Factors

To address these challenges, a collaborative team from various research institutions initiated a significant project focusing on twins. Identical twins, sharing nearly the same genetics, sometimes exhibit a scenario where one twin has MS while the other remains symptom-free—these are known as MS-discordant pairs.

Around 100 pairs of such twins are currently involved in the MS TWIN STUDY at the Institute of Clinical Neuroimmunology at LMU Munich, which allows for a more standardized study of the disease. Given that these twins lived together until early adulthood, their exposure to similar environmental factors adds to the controlled nature of the study.

Examining Gut Flora

The researchers analyzed stool samples from 81 twin pairs participating in the MS TWIN STUDY, comparing the gut flora between those with and without MS symptoms. Through this, they identified 51 groups of microorganisms whose abundance varied significantly.

Moreover, in an advanced step, some twin pairs consented to have samples taken from their small intestines via enteroscopy, where it is believed that interactions between microorganisms and the immune system occur. Previous studies primarily relied on stool samples, which don’t provide comprehensive insights into the gut ecosystem.

To examine whether these intestinal samples contained harmful organisms, the team utilized special germ-free transgenic mice. These mice, under normal conditions, live healthily but can develop MS-like symptoms when colonized with certain gut bacteria.

In the study, mice received samples from twins, both affected and unaffected by MS. Symptoms were notably observed in those colonized with bacteria from MS patients, suggesting that disease-triggering microorganisms are present in their intestines.

Subsequent analysis of the fecal matter from the mice pinpointed Lachnoclostridium sp. and Eisenbergiella tayi as potential contributors to MS. Their low abundance had previously limited their association with the disease to large, controlled studies. However, this innovative experimental approach allowed researchers to functionally characterize these bacteria, offering evidence for their potential pathogenicity.

While the scientists acknowledge that more microorganisms may contribute to MS, further research is necessary to construct a clearer understanding. They aim to explore the pathogenic potential of the identified bacteria more deeply, starting with mouse models and later extending to human implications.

If it turns out that relatively few microorganisms are responsible for triggering MS, it could lead to new therapeutic strategies. This study also highlights the importance of lifestyle habits in MS development, paving the way for further investigations into these effects.