Reveal the correlation of colonic microbiota composition with immune response in weaned piglets fed with Garlic essential oil by metagenomic analysis. Metagenomic analysis reveals the correlation of colonic microbiota composition with immune response in weaned piglets fed with Garlic essential oil

The present study aimed to use metagenomic analysis to reveal the correlation of colonic microbiota composition and immune response in weaned piglets with dietary Garlic essential oil (GEO). Twelve weaned piglets were randomly divided into control group and experimental group that fed either a basal diet (CON group), or a basal diet supplemented with 1.5 g/kg GEO (GEO group). The result showed that GEO supplementation increased serum immunoglobulin and anti-inflammatory cytokine level but decreased serum proinflammatory cytokine content. In addition, our data also revealed that GEO down-regulated anti-inflammation pathways and anti-inflammation cytokine mRNA expressions in the jejunum mucosa, while up-regulated immune pathway and immune cytokine mRNA expressions in the ileum mucosa. Additionally, it was observed higher short chain fatty acid (SCFA) levels of the colonic contents in the GEO compared with the control group, and the mRNA expressions of G-protein coupled receptors were up-regulated in both jejunum and ileum mucosa. What’s more, the metagenomic analysis demonstrated that GEO supplementation altered the overall structure of colonic microbiota as evidenced by β diversities analysis. In addition, GEO increased the abundance of beneficial bacteria, while decreased the abundance of harmful bacteria in both phylum and species level. What’s more, the main function pathway of virulence factor (VFDB) enriched in GEO group were beneficial pathways related to immune response, while the main function pathway of VFDB enriched in CON group were pathways involved in inflammation. Furthermore, Spearman correlation analysis indicated a significant correlation between altered microbiota genera vs serum cytokine levels and microbiota genera vs volatile fatty acids production. In conclusion, metagenomic analysis and correlation analysis results uncovered that immune regulation effects of GEO may be associated with the dynamic shift in microbiota composition, microbial metabolites and VFDB functional pathway in response to diet.