Quercetin Attenuates Oxidative Stress and Immune Inflammation via Modulating Heme and ROS Pathways in Rats Fed Protein-Oxidized Soybean Meal.

Dietary protein oxidation impairs animal health, yet effective interventions remain limited. This study investigated whether quercetin (Q) supplementation protects against protein-oxidized soybean meal (OS)-induced oxidative stress and inflammatory injury in rats. A 2 × 2 factorial experiment was conducted with 48 three-week-old Sprague-Dawley rats randomly assigned to four dietary treatments (n = 12): fresh soybean meal (FS), FS + 400 mg/kg Q, OS, and OS + 400 mg/kg Q for 28 days. Serum biochemistry, intestinal and hepatic histology, antioxidant status, inflammatory markers, and transcriptomic pathways were analyzed. As a result, OS feeding elevated serum glucose and urea nitrogen, induced duodenal, jejunal and hepatic lesions, reduced total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) activity, glutathione (GSH) level, increased reactive oxygen species (ROS) and malondialdehyde (MDA) content (p < 0.05), and increased IgG and IL-6 levels (p < 0.05). Transcriptomic analysis revealed upregulation of heme biosynthesis and ROS synthesis pathways in jejunum and liver (p < 0.05). Q supplementation mitigated these adverse effects by improving antioxidant status, reducing inflammatory lesions, downregulating heme and ROS pathways, and normalizing the expression of key genes (Ccl20, RT1-M2) and protein (Ccl20) in jejunum (p < 0.05), and key genes (Duox1, Cyp4a2) and protein (Duox1) in liver (p < 0.05). These findings demonstrate that Q alleviates OS-induced oxidative stress, inflammation, and tissue damage through the modulation of heme and ROS pathways.