FUT3 and multiple sclerosis: Changes in the composition of the microbiota caused by FUT3 gene polymorphisms, including a reduction in the population of SCFA-producing bacteria, may result in reduced SCFA secretion, leading to the decreased bactericidal activity of caproic acid, limited differentiation of Th1 and Th17 cells, and weakened self-renewal and differentiation processes of intestinal stem cells supported by valeric acid, consequently modulating the immune response relevant to the pathophysiology of multiple sclerosis [11,48,49,50].