The Effects of Naringin on Antioxidant Function, Intestinal Barrier and Immune Response in Broilers Challenged with Lipopolysaccharide

This study aimed to investigate the effects of naringin (NG) on growth performance, antioxidant status, intestinal barrier function, and immune stress in broilers challenged with lipopolysaccharide (LPS). A total of 144 one-day-old Ross 308 broiler chicks were randomly allocated into 2 treatment groups, with six replicates per group and 12 birds per replicate. The groups consisted of a control group (fed a basal diet) and an NG group (fed the basal diet supplemented with 200 mg/kg NG). The trial lasted 21 days; to evaluate the impact of NG on the late-stage growth performance of broilers, the rearing trial continued until 35 days. Body weight was recorded on days 21 and 35 to evaluate growth performance. A 2 × 2 factorial design was implemented in which broilers were challenged with or without LPS, and their diets were supplemented with or without NG. On day 21, two birds per replicate were intraperitoneally injected with 0.5 mg/kg body weight (BW) LPS, while another two birds received an equal volume of saline, in each group of 12 birds. Birds were slaughtered 3 h post-injection for sample collection. Dietary NG supplementation had no significant effect on growth performance (<i>p</i> > 0.05). However, NG markedly improved plasma liver function markers following LPS challenge (<i>p</i> < 0.05). NG significantly increased hepatic glutathione peroxidase (GSH-Px) activity, duodenal and ileal catalase (CAT) activity, and ileal GSH-Px activity (<i>p</i> < 0.05) while reducing malondialdehyde (MDA) levels in the liver, duodenum, jejunum, and ileum, as well as hydrogen peroxide (H₂O₂) levels in the jejunum and ileum (<i>p</i> < 0.05). Dietary NG supplementation significantly upregulated the relative mRNA expression of <i>Toll-like receptor 4 (TLR4)</i> and <i>interferon-gamma (IFN-γ)</i> in the liver (<i>p</i> < 0.05) and attenuated the LPS-induced upregulation of <i>tumor necrosis factor-alpha (TNF-α)</i> mRNA expression in the jejunum (<i>p</i> < 0.05). NG reduced serum diamine oxidase (DAO) levels (<i>p</i> < 0.05), increased villus height in the duodenum and jejunum (<i>p</i> < 0.05), and increased the villus-height-to-crypt-depth (VH/CD) ratio in the jejunum (<i>p</i> < 0.05). Moreover, NG markedly upregulated the relative mRNA expression of <i>zonula occludens-1 (ZO-1)</i> and <i>occludin</i> in the duodenum while drastically downregulating the relative expression of <i>mucin-2</i> in the duodenum and ileum (<i>p</i> < 0.05). NG further reduced <i>mucin-2</i> expression in the jejunum and mitigated the LPS-induced downregulation of <i>ZO-1</i> in the ileum (<i>p</i> < 0.05). In addition, NG significantly upregulated the expression of <i>X-linked inhibitor of apoptosis protein (XIAP)</i> and <i>B-cell lymphoma 2 (Bcl-2)</i> and downregulated the expression of <i>matrix metalloproteinase-13 (MMP-13)</i> in the liver of LPS-challenged broilers (<i>p</i> < 0.05). Conclusions: Dietary NG supplementation alleviated LPS-induced intestinal and hepatic injury in broilers. NG attenuated the adverse effects of LPS challenge on intestinal barrier function and enhanced antioxidant capacity in broilers by modulating intestinal tight junction expression and antioxidant enzyme activity. NG may serve as a promising eco-friendly additive to enhance resilience against immune stress in broilers.