Fructooligosaccharide modulates the intestinal exosomal miRNAs to reshape the gut microbiota

Fructooligosaccharide (FOS), a well-recognized prebiotic, is generally considered non-absorbable in the upper gastrointestinal tract, allowing it to reach the colon and exert its prebiotic effects. In this study, we uncovered a novel function of FOS: it directly modulates the expression profile of miRNAs in exosomes derived from intestinal epithelial cells (IECs) and in the feces of antibiotic-induced pseudo-germ-free (PGF) mice, indicating that FOS-mediated regulation of intestinal exosomal miRNAs is independent of its prebiotic role. Furthermore, these miRNAs modified by FOS in turn reconstruct the gut microbial structure, notably elevating the relative abundance of <em>Eubacterium</em>, a component of the core human gut microbiome that is beneficial to gut health. Specifically, supplementation with FOS at 0.6 and 1.2 g/kg/d significantly reduced fecal miR-690 expression in PGF mice by 4.3-fold (from 768.3 ± 92.0 to 177.0 ± 87.5) and 7.8-fold (to 98.7 ± 12.4), respectively (<em>P &lt; </em>0.05). Subsequent<em> in vitro</em> co-culture experiments demonstrated that synthetic miR-690 mimics (2.5 nM) selectively inhibited the growth of <em>Eubacterium limosum</em>. Our findings provide new insights into a novel molecular mechanism by which FOS reshapes the gut microbiome through the regulation of exosomal miRNA expression in IECs.