The Gut Micro biome (GM) is the largest one that includes trillions of bacteria, fungi, and viruses that live in the intestinal tract. These bacteria have been identified to influence immunological responses linked with a variety of disorders including Rheumatoid Arthritis (RA), gastrointestinal diseases especially Irritable Bowel Syndrome (IBS), fatty liver, and asthma. Another disease that has been studied in recent years in connection with the intestinal microbiome in autoimmune Central Nervous System (CNS) disease. The global prevalence of autoimmune illnesses is quickly rising. One of the most important diseases of this group is Multiple Sclerosis (MS) with an incidence rate of 2.1 per 100,000 persons/year. The animal model of MS is Experimental Autoimmune Encephalomyelitis (EAE). Due to the importance of the intestinal microbiome in MS, various animal and human studies have evaluated this relationship. In this mini-review study, we review some of these studies.

It has been shown in the pre-clinical studies that an imbalance in the gut microbiota, called “dysbiosis”, is associated with EAE. Disruption of the intestinal microbiome in favor of pathogenic bacteria can damage the Blood-Brain Barrier (BBB) permeability and the function of microglia and myelin. Preclinical studies have shown that in EAE -induced mice, dysbiosis induce naive T-cell differentiation to Th1 and Th17 cells (which produce pro-inflammatory cytokine such as interferon (IFN)-γ) and reduce the expression of anti- inflammatory proteins and cytokines specially FoxP3+ Treg cells, IL-10 and IL-13. On the other hand, the process of differentiation of naive T cells into T cells with anti-inflammatory properties is accelerated by polysaccharide A (PSA) produced by some bacterial strains such as B. fragilis. In addition, it has been shown that the production of Short-Chain Fatty Acids (SCFA) by intestinal bacteria can improve the naive T-cell differentiation to regulatory T (Treg) and reduce the risk of EAE. Lactobacillus and Turicibacter spp. are among the bacterial strains involved in the production of SCFA.

Among the human studies, Mirza et al. in a systematic review study showed that there wasn’t any significant difference in gut microbiome alpha-diversity among the patients with MS compared to the control group. However, they found a lower relative abundance of Prevotella, Faecalibacterium prausnitzii, Bacteroides coprophilus, Bacteroides fragilis, and higher Methanobrevibacter and Akkermansia muciniphila in MS cases versus controls.

With Regards,
Joseph Kent
Journal Manager
Journal of Clinical Nutrition & Dietetics