The prevalence of multiple sclerosis (MS) has been increasing over the past two decades, especially in certain areas, such as the Mediterranean regions and Japan. This increase might be attributed to an altered microbiota and metabolic status in accordance with a change in food habits. Studies on an animal model of MS have led to the hypotheses suggesting the pathogenic role of altered gut microbiota and cellular metabolism of immune cells in MS. Recent studies showed that patients with MS have a distinct gut microbiota composition compared with healthy controls. Furthermore, accumulating evidence highlights the critical role of dysregulated immune cell metabolism in autoimmunity. Regarding neuromyelitis optica (NMO), its microbiome has been reported to have distinct features in comparison with healthy controls and MS. Interestingly, molecular mimicry between aquaporin 4 and components of Clostridium perfringens, the second most significantly enriched taxon in NMO, is suggested. CD4 + T cells recognizing the dominant aquaporin 4 T-cell epitope show the T helper 17 cell phenotype, and show cross-reactivity to a homologous peptide sequence in NMO patients. These results raise the possibility that commensal bacteria in NMO patients might be involved in aquaporin 4 autoantibody production. In the present review, we introduce the current advances in the research of food habit and microbiota in MS and NMO in terms of intestinal immunity and immune-metabolic interactions. In addition, we discuss the potential perspective of diet therapy and probiotics in terms of prophylactic or therapeutic treatment options for MS and NMO.
Multiple sclerosis and environmental factorsMultiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system, and is characterized by inflammatory demyelination and secondary neurodegeneration. 1 MS is a leading cause of disability in young adults, affecting an estimated 2.5 million people worldwide. Myelin-reactive CD4 + cells are thought to play the main pathogenic role in relapsing-remitting MS (RRMS). 1 Although the etiology of MS is not fully understood, genetic studies have shown that human leukocyte antigen (HLA) alleles, including DRB1*1501, are related to susceptibility to MS. 2,3 These major histocompatibility complex class II genes are involved in antigen presentation to CD4 + T cells, which leads to autoimmunity in the central nervous system. Recently, genome-wide association studies have shown that several other genes involved in the immune response, including those related to major histocompatibility complex class I, are also related genes of MS, supporting the notion that this disease is fundamentally an immune-mediated disease. 4 Recent research has shown that environmental factors play important roles in the pathogenesis of MS in addition to genetic factors. One of the most important environmental factors is geographical location, with a higher disease incidence being noted at higher latitudes. 5 This north-south gradient has been hypothesized to be attributabl...