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Tributyrin, a Source of Butyric Acid, Modulates the Intestinal Health of Weaning Pigs
Aim of this study was to evaluate the intestinal architecture and expression of inflammatory and tight junction markers in piglets fed with tributyrin as dietary source of butyric acid. Twenty-one weaned pigs (n = 7), received a basal diet (control) or the diet supplemented with tributyrin or its encapsulated form at 1750 mg/kg (TB and m-TB, respectively), both providing 960 mg/kg of butyric acid equivalents. After 21 days, pigs were euthanized to collect duodenum, jejunum, ileum, and colon samples for histo-morphology, and cytokines and tight junction markers m-RNA analysis. Data were analyzed with 1-way ANOVA. Compared to control, m-TB induced deeper crypts in the duodenum (P=0.09) and significantly reduced villi:crypts in the ileum (P=0.04); goblet cells tended to be reduced by TB in duodenal villi (2.4 fold, P=0.09), by both TB and m-TB in ileal villi (1.8-2.2 fold, respectively; P=0.06), and by m-TB in colonic crypts (P=0.08). Compared to control, TB tended to have higher TNF-α expression in the duodenum and ileum (P=0.06 and P=0.10), and higher IFN-γ level in the jejunum (P=0.04), whereas in the colon m-TB down regulated IFN-γ and IL-1β level (2.2 fold and 1.7 fold; P=0.06). Jejunal claudin-1 mRNA was reduced in m-TB compared to control (2.4 fold; P=0.05). Similarly, in the colon claudin-1 mRNA was numerically lower in m-TB (2.1 fold) than in control group. Ileal occludin mRNA was reduced in both groups receiving tributyrin compared to control (1.6-2.2 fold for TB and m-TB; P<0.01). In the colon occludin mRNA was down regulated in m-TB compared to control (1.4 fold; P<0.05). The supplementation of tributyrin in the diet reduced the mucous-secreting goblet cells in a tract specific manner, tributyrin affecting the upper intestine while the microencapsulated form acting in the lower gut. The differential expression of cytokines in the upper and lower intestine by TB and m-TB, would suggest a differential modulation of cellular turnover and epithelial differentiation that would reflect differences in the anatomy and functionality of the gut segments. Nevertheless, the reduced expression of pro-inflammatory cytokines observed in the colon of m-TB indicate a reduced inflammation by butyric acid released via microencapsulated tributyrin. This beneficial effect mediated by m-TB would be substantiated by the parallel reduction of tight junction proteins gene expression in the hindgut probably indicating, by a mechanism of negative feed-back, a relatively higher abundance of these proteins and a tighter intestinal epithelium.
Keywords:
Tributyrin
Microencapsulation
Weaning piglet