Plant-oriented microbiome inoculum modulates age-related maturation of gut-mucosal expression of innate immune and barrier function genes in suckling and weaned piglets.

In the immediate time after weaning, piglets often show symptoms of gut inflammation. The change to a plant-based diet, lack of sow milk and the resulting novel gut microbiome and metabolite profile in digesta may be causative factors for the observed inflammation. We used the intestinal loop perfusion assay (ILPA) to investigate jejunal and colonic expression of genes for antimicrobial secretion, oxidative stress, barrier function and inflammatory signaling in suckling and weaned piglets when exposed to 'plant-oriented' microbiome (POM) representing postweaning digesta with gut-site specific microbial and metabolite composition. Two serial ILPA were performed in two replicate batches, with 16 piglets pre- (day 24-27) and 16 piglets postweaning (day 38-41). Two jejunal and colonic loops were perfused with Krebs-Henseleit buffer (control) or with the respective POM for two hours. Afterwards, RNA was isolated from the loop tissue to determine the relative gene expression. Age-related effects in jejunum included higher expression of genes for antimicrobial secretions and barrier function as well as reduced expression of pattern-recognition receptors post- compared to preweaning (P < 0.05). Age-related effects in the colon comprised downregulation of the expression of pattern-recognition receptors post- compared to preweaning (P < 0.05). Likewise, age reduced the colonic expression of genes encoding for cytokines, antimicrobial secretions, antioxidant enzymes and tight-junction proteins post- compared to preweaning. Effect of POM in the jejunum comprised an increased the expression of toll-like receptors compared to the control (P < 0.05), demonstrating a specific response to microbial antigens. Similarly, POM administration upregulated the jejunal expression of antioxidant enzymes (P < 0.05). The POM perfusion strongly upregulated the colonic expression of cytokines and altered the expression of barrier function genes, fatty acid receptors and transporters and antimicrobial secretions (P < 0.05). In conclusion, results indicated that POM signaled via altering the expression of pattern recognition receptors in the jejunum, which in turn activated the secretory defense and decreased mucosal permeability. In the colon, POM may have acted proinflammatory via upregulated cytokine expression. Results are valuable for the formulation of transition feeds for the immediate time after weaning to maintain mucosal immune tolerance towards the novel digesta composition.