| Title |
Potential mechanisms of action and beneficial effects of a synbiotic containing the probiotic Bifidobacterium lactis HN019 and chicory inulin. А, fermentation of chicory inulin by gut microbiota with SCFA production. Inulin fermentation in the colon both by indigenous bifidobacteria and by the probiotic Bifidobacterium lactis HN019 strain is associated first of all with a decrease of intraluminal pH, acetate and lactate production and an increase in bifidobacteria counts (the bifidogenic effect), lactobacilli and butyrate-producing bacteria (Anaerostipes, Faecalibacterium, Anaerobutyricum). The latter use acetate and lactate for butyrate production during cross-feeding. Some commensal bacteria also produce propionate during inulin fermentation. Butyrate, acetate, and propionate are the main SCFA with anti-inflammatory, immunomodulating, and metabolic effects; they regulate energy homeostasis in colonocytes (butyrate) and facilitate the secretion of intestinal peptide hormones GLP-1 and PYY, thereby improving glucose metabolism and decreasing insulin resistance. Inulin also reduces the numbers of potential pathobionts (Bacteroides, Bilophila, Desulfovibrio), related to the proinflammatory immune response and metabolic endotoxemia, promoting a decrease in H2S production and LPS levels. Bifidobacterium lactis HN019 produces lactate and acetate, contributing to cross-feeding; it also stimulates gut motility by facilitating serotonin biosynthesis by enterochromaffin cells and fatty acid metabolism by commensals. B, immunomodulating effects of inulin and Bifidobacterium lactis HN019. Inulin regulates the differentiation and proliferation of immune cells (including Treg), reducing gut inflammation; it also augments tight junction protein expression, induces the secretion of sIgA and MUC2 by plasma and goblet cells, and promotes the secretion of IL-22 by γδ T cells and ILC3, thus supporting the intestinal barrier homeostasis. Bifidobacterium lactis HN019 suppresses pathogen colonization, including by enhancing AMP secretion; it reduces macrophage production of TNF-α and IL-6 cytokines associated with chronic inflammation and metabolic disorders; increases the activity of NK cells involved in innate immunity and enhances the phagocytic activity of polymorphonuclear leukocytes. AMP, antimicrobial peptides; ATP, adenosine triphosphate; DC, dendritic cell; EC, enterochromaffin cell; GLP-1, glucagon-like peptide 1; H2S, hydrogen sulfide; IL-6, interleukin 6; IL-22, interleukin 22; ILC3, innate lymphoid cell 3; LPS, lipopolysaccharide; MUC2, mucin 2; PYY, peptide YY; SCFA, short-chain fatty acids; sIgA, secretory immunoglobulin A; TNF-α, tumor necrosis factor α; Treg, regulatory T cell; 5-НТ, serotonin 5-hydroxytryptamine. Created with BioRender.com |