The host’s immune system and gut microbiome engage in continuous interactions, maintaining the balance of normal bodily functions. This dynamic two-way relationship suggests that altering the gut microbiome could influence immune function and the host’s susceptibility to infections.
Synbiotics, which combine live microorganisms like probiotics with substances like prebiotics that are specifically consumed by these microorganisms, have emerged as potential regulators of both the gut microbiome and the immune system. They are increasingly popular among the general population as tools to enhance immune function. However, there is limited scientific evidence regarding the impact of synbiotics on the immune system in healthy individuals, and this knowledge gap holds significant implications. Additionally, we still have a limited understanding of whether changes in the microbiome induced by synbiotic supplementation play a role in its immune-modulating properties.
Researchers from University of Science and Technology, Wuhan conducted a double-blind, randomized, placebo-controlled study in 106 healthy adults, recently published in Gut Microbes. The aim was to define whether synbiotic supplementation could induce alternations in immune parameters among healthy adults and whether these alternations associated with gut microbiota variations could be triggered by synbiotic supplementation.
Participants were randomly assigned to receive either synbiotics (containing Bifidobacterium lactis HN019 1.5 × 108 CFU/d, Lactobacillus rhamnosus HN001 7.5 × 107 CFU/d, and fructooligosaccharide 500 mg/d) or placebo for 8 weeks. Immune parameters and gut microbiota composition were measured at baseline, mid, and end of the study. Compared to the placebo group, participants receiving synbiotic supplementation exhibited greater reductions in plasma C-reactive protein and interferon-gamma, along with larger increases in plasma interleukin (IL)-10 and stool secretory IgA (sIgA). Additionally, synbiotic supplementation led to an enrichment of beneficial bacteria (Clostridium_sensu_stricto_1, Lactobacillus, Bifidobacterium, and Collinsella) and several functional pathways related to amino acids and short-chain fatty acids biosynthesis, whereas reduced potential pro-inflammatory Parabacteroides compared to baseline. Importantly, alternations in anti-inflammatory markers (IL-10 and sIgA) were significantly correlated with microbial variations triggered by synbiotic supplementation. Stratification of participants into two enterotypes based on pre-treatment Prevotella-to-Bacteroides (P/B) ratio revealed a more favorable effect of synbiotic supplements in individuals with a higher P/B ratio.
In conclusion, this study suggested the beneficial effects of synbiotic supplementation on immune parameters, which were correlated with synbiotics-induced microbial changes and modified by microbial enterotypes. In particular, synbiotic supplementation increased beneficial bacteria, decreased pro-inflammatory biomarkers and increased anti-inflammatory cytokine. These findings provided direct evidence supporting the personalized supplementation of synbiotics for immunomodulation, even if additional randomized controlled trials with larger numbers of participants are needed to confirm these findings.
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