Microbial Dysbiosis and Lack of SCFAs Production on the Gut of Multiple Sclerosis Patients in a Spanish Cohort

Multiple Sclerosis (MS) is a heterogeneous disease on its clinic and evolution, on which the myelin sheath of the axons is attacked by the own immune system. The origin of MS is still unknown; however, genetic, epigenetic and environmental factors seem to be implicated in its development. In the last years, much effort has been made to describe the gut microbiota dysbiosis of MS patients. Nevertheless, differences in geographical location, diets and lifestyles have made this goal difficult to achieve; therefore, the role of the bacterial dysbiosis in the MS is unclear. The microbiota produces thousands of biologically active substances among which are notable the Short Chain Fatty Acids (SCFAs) excretion. These metabolites are the main mediators of the interaction with the immune and neuroendocrine systems; in consequence, their analysis in the MS could be of great interest. Our work reveal that the gut microbiota of the Spanish cohort of MS patients is characterized by an increment in members of the phylum Proteobacteria, especially marked on those patients that are not receiving any disease modifying treatment. Regarding SCFAs production, a lack in total SCFAs excretion and an altered profile of SCFAs in MS patients, (characterized by a decrease of butyric acid production) could be observed. This alteration is more evident when patients with an Expanded Disability Status Scale (EDSS) score higher than 1 were considered, also presenting a significative reduction of caproic acid and an increase of acetic acid excretion.