Protective Effects of Dietary Epigallocatechin-3-Gallate in Weaned Pigs Exposed to Oxidative Stress

Abstract

Epigallocatechin-3-gallate (EGCG), a major catechin in green tea, possesses antioxidant and immunomodulatory properties. We hypothesized that dietary EGCG supplementation before oxidative challenge would attenuate Diquat-induced redox disturbance and help maintain intestinal epithelial integrity and immune-related homeostasis in weaned pigs. To test this hypothesis, 32 weaned piglets were assigned to a 2 × 2 factorial arrangements involving dietary EGCG supplementation (0 or 50 mg/kg) and saline or Diquat challenge (10 mg/kg body weight). Dietary EGCG increased serum superoxide dismutase activity and immunoglobulin A, G, and M concentrations and decreased serum IL-1β, whereas Diquat decreased superoxide dismutase activity and immunoglobulin concentrations and increased TNF-α (p < 0.05). A significant EGCG × Diquat interaction was detected for serum total antioxidant capacity (p = 0.020), which was increased by EGCG in Diquat-challenged pigs (Sidak-adjusted p = 0.001). Significant interactions were also observed for duodenal and jejunal ZO-1 immunoreactivity, jejunal sIgA immunoreactivity, and jejunal epithelial apoptosis (p < 0.05). Under Diquat challenge, EGCG increased ZO-1 and sIgA immunoreactivity and reduced TUNEL-positive staining (adjusted p < 0.05). Intestinal gene-expression responses were segment dependent: EGCG was associated with increased IL-10 and FOXP3 expression and with reduced expression of IL-17, IL-22, RORγT, STAT3, caspase-3, caspase-9, and BAX in several intestinal segments, particularly in Diquat-challenged pigs. Collectively, the observed findings indicate associations between dietary EGCG supplementation and systemic antioxidant and immune indices, epithelial barrier-related characteristics, immune-cell phenotypes, and mucosal transcriptional responses. Given the number of outcomes examined and the absence of a global multiplicity adjustment, these findings should be interpreted as exploratory and do not establish a specific protective mechanism.