Combination of Gut Microorganisms Can Worsen Multiple Sclerosis Symptoms

A combination of certain gut microorganisms were found to exacerbate the symptoms of multiple sclerosis (MS) in a mouse model, according to a new study published in Nature.

MS is an autoimmune disease in which the immune system attacks the myelin that covers the nerve cells of the brain and spinal cord. This process, known as demyelination, affects how quickly neurons communicate with each other and with muscles. This causes a variety of symptoms that include tremors, weak muscles, numbness, and the inability to walk.

Gut microorganisms were already known to affect MS symptoms, but how bacteria in the intestines affects myelin, the brain and spinal cord is not known. Researchers at the RIKEN Center for Integrative Medical Sciences used a mouse model to investigate the connection. The mice experienced similar demyelination of the spinal cord, resulting from autoimmune attacks by T cells that produce the cytokine IL-17A.

Researchers found that giving mice the antibiotic ampicillin reduced demyelination and prevented the activation of a particular type of T cell. Only ampicillin reduced symptoms in mice, according to the study.

The only bacteria nearly completely deleted in ampicillin-treated mice was a new strain known as OTU002. Mice with this bacterium had more severe symptoms than germ-free mice. However, the symptoms in mice with only this bacterium were not as bad as the regular model mice, meaning there must be more than 1 culprit, according to the study.

A bacterium known as Lactobacillus reuteri was found to have co-colonized with OTU002 in mice with the worse symptoms.

"Other studies have focused on fecal microbes, or a single microbe, in patients with multiple sclerosis or in model mice…Our data emphasize the necessity of considering the synergistic effects of intestinal microbes on autoimmune diseases and give hope to people looking for effective treatments for multiple sclerosis," first author Eiji Miyauchi, MD, said in a press release.

Reference:

Tag team gut bacteria worsen symptoms of multiple sclerosis (Press release) Japan, August 26, 2020, EurekAlert! Accessed August 26, 2020