Objective: Our aim was to study the possible synergic action of one prebiotic with increasing dietary doses of a probiotic strain of Bifidobacterium animalis on the translocation of bifidobacteria and on Toll-like receptor (TLR) gene expression in different organs of weaned piglets.
Methods: Sixty-four pigs, reared from 21 to 35 d of age, were fed eight different diets according to a 2 x 4 factorial design: a control diet or the control diet supplemented with three different levels of B. animalis (10(7), 10(9), 10(11) colony-forming units/d), crossed with 0% or 2% sugar beet fructo-oligosaccharides. Pigs were then sacrificed, and the jejunum mucosa, ileocecal lymph nodes, and liver were sampled to determine the presence of Bifidobacterium spp. DNA and to quantify the expression of TLR2-, TLR4-, and tumor necrosis factor-alpha-encoding genes.
Results: We found Bifidobacterium spp. genus-specific DNA in lymph nodes of subjects from all dietary treatments, including the control diet, but it increased with the bifidobacteria oral dose (P = 0.065). The linear effect of the dose of B. animalis on the expression of the TLR2-encoding gene in the lymph nodes was observed when fructo-oligosaccharides were added to the diet (P < 0.05). Tumor necrosis factor-alpha-encoding gene expression was positively correlated with TLR4- and TLR2-encoding gene expressions (P < 0.001 and P < 0.01, respectively) and negatively correlated with bifidobacteria DNA (P < 0.05). Moreover, the expression of the TLR4-encoding gene showed a positive correlation with TLR2-encoding gene expression (P < 0.001). In contrast, there was no correlation between expressions of the TLR2- and TLR4-encoding genes with the bifidobacteria DNA.
Conclusion: Soon after weaning, the translocation of the commensal bacteria in the ileocecal lymph nodes is a physiologic process. Moreover, diet affects the expression of the TLR2-encoding gene.