[Background] There is growing evidence that gut microbiota is altered in multiple sclerosis (MS). Microbial dysbiosis is characterized by the increase in the genera Methanobrevibacter, Akkermansia, Acinetobacter, Pseudomonas, Blautia and Ruminococcus; and decrease in Sutterella, Faecalibacterium, Prevotella, Fusobacterium, Anaerostipes, Clostridium cluster XIVa and IV, Parabacteroides and Butyricimonas. However, the understanding of how these changes affects the disease development and evolution requires the functional study of the microbiota. Microorganisms produce thousands of biologically active compounds to communicate and interact with their host. Between them could be remarked the short chain fatty acids (SCFAs) as important mediators of the interaction with the neuroendocrine and immune systems. [Aims]: Characterize the profile of fecal SCFAs in MS patients and controls and determine its relation with the fiber intake and the disease. [Methods]: A total of 20 MS patients and 20 controls participated in the study. All participants filled a complete nutritional test and provide a fecal sample. SCFAs were extracted from feces using formic acid (20%v/v) and methanol. 2-Ethylbutyric acid was used as internal control. Analysis was performed using gas chromatography and the acids acetic, propionic, butyric, isobutyric, valeric, isovaleric and caproic were determined. [Results]: The amount of total SCFAs and every single acid evaluated was lower on MS patients regardless the fiber intake. The dominant SCFAs acetic, propionic and butyric were between 20 and 30% lower in MS patients than in controls; major differences were observed on caproic acid (43%). Besides, MS patients showed an altered SCFA profile in comparison with healthy controls, characterized by the higher representation of isobutyric, acetic and isovaleric acids and lower of butyric and caproic acids. Regarding the fiber intake the most affected SCFAs were the acetic and butyric acids. Interestingly the total SCFAs in MS patients seems to diminish with the disease evolution and EDSS score. [Conclusion]: MS patient’s microbiota produces lower levels of SCFAs and presents an altered SCFAs profile. Besides, differences are more pronounced when EDSS score increases and disease progresses. Those results provide valuable information for the evaluation of SCFAs as biomarkers of the disease evolution and the establishment of nutritional patterns directed to the increase of SCFAs productio

Trabajo presentado en The 35th European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS), celebrado en Estocolmo (Suecia), del 11 al 13 de septiembre de 2019