Combination of microbiome and metabolome to analyze the cross-synergism mechanism of inulin and gut microbiota in vitro and vivo

Inulin can regulate the intestinal micro-ecological balance, but there are few studies on the changes of intestinal microbiota and its metabolites in vitro and vivo , SCFAs and amino acids in particular. In this study, the human fecal microbiota glycolysis model and a mouse model were used to study the mechanism of inulin on intestinal microecology. Combined with metabolism of microbiome and metabolome , the cross-synergism mechanism of inulin-micribiota-metabolites-metabolism was investigated. The results revealed that after inulin was fermented by human intestinal microbiota , the relative abundance of Lactobacillus , Bifidobacterium , Prevotella , Catenibacterium , and Agathobacter increased. In vivo , the concentration of SCFAs increased after inulin was fermented, and the abundance of Parabacteroides , Muribaculaceae and Alloprevotella increased. Both in vivo and in vitro experiments revealed that inulin can regulate the expression of 5 genes involved in Valine , leucine and isoleucine degradation. In addition, the metabolome results confirmed that Valine, leucine and isoleucine degradation, Tyrosine metabolism, and Synthesis and degradation of ketone bodies are regulatory pathways of inulin. More importantly, L−tryptophan, tyrosine, L−fucose, L−ornithine, D−fructose, D−erythrose, and pyruvic acid are hallmark metabolites of inulin metabolized by gut microbiota. The cross-synergism network greatly indicated the microbiota ( Streptococcus , Lactobacillus , Muribaculaceae), metabolites ( l -tryptophan, pyruvic acid), and metabolism (Lysine degradation, Tryptophan metabolism , Synthesis and degradation of ketone bodies) may be the key factors involved in the mechanisms regulating the in vitro and vivo effects of inulin.