Protective effect of sialyllactose on the intestinal epithelium in weaned pigs upon enterotoxigenic Escherichia coli challenge

Abstract

Sialyllactose (SL), one of the most abundant oligosaccharides present in porcine breast milk, has been implicated in many biological functions, including the prebiotic and immune-modulating effects. This study was conducted to investigate the influences of dietary SL supplementation on intestinal barrier functions exposure to enterotoxigenic Escherichia coli (ETEC) in a porcine model. Thirty-two pigs were assigned to four treatments, fed with basal or SL-containing (5.0 g kg⁻¹) diet, and orally infused with ETEC or culture medium. SL supplementation significantly reduced the diarrhea incidence and the abundance of E. coli in feces (P < 0.05). Interestingly, SL attenuated ETEC-induced intestinal epithelium injury as indicated by the decreased serum concentrations of diamine oxidase (DAO) and D-lactate and reduced the number of apoptotic cells in the jejunal epithelium (P < 0.05). Moreover, SL not only elevated the abundance of the tight-junction protein ZO-1 in the duodenal and ileal epithelium but also elevated the antioxidant capacity and the number of SIgA positive cells in the jejunal epithelium upon the ETEC challenge (P < 0.05). Importantly, SL decreased the expression levels of inflammation-related genes such as the tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), myeloid differentiation factor 88 (MyD88) in the duodenum, and ileum upon ETEC challenge (P < 0.05). SL also significantly elevated the expression levels of two critical antioxidant genes such as the nuclear factor erythroid-2 related factor 2 (Nrf-2) and kelch-like ECH-associated protein 1 (KEAP-1) in the jejunum (P < 0.05). These results suggested that SL can alleviate ETEC-induced intestinal epithelium injury, which is associated with suppressed inflammation, improved intestinal immunity, antioxidant capacity, and improved intestinal epithelial functions.