This study investigated the effects of solid-state fermentation with Clostridium butyricum on the microstructure of wheat bran, the release of dietary fiber and phenolic compounds, and antioxidant capacity. Compared with unfermented wheat bran, insoluble dietary fiber and phytic acid content decreased, whereas soluble dietary fiber and water-extractable arabinoxylan content increased in C. butyricum culture. Because of the increased release of phenolic compounds, such as ferulic acid and apigenin, and organic acids, such as isobutyric acid, the antioxidant capacity of the culture was considerably improved. Furthermore, the culture of C. butyricum treated with dextran sulfate sodium-induced ulcerative colitis in mice enhanced the expression of intestinal mucus and tight-junction proteins, modulating the gut microbiota structure, increasing the levels of short-chain fatty acids in the intestine, and restoring the essential functions of the gut microbiota. These anti-inflammatory effects stemmed from the combined action of various effective components.

High‐density solid‐state fermented probiotic products, combining live bacteria with microbial and substrate‐derived bioactives, offer a potential solution to address dysregulation of gut microbiota–immune homeostasis associated with inflammatory bowel disease (IBD). However, their synergistic efficacy against IBD remains elusive. Here, we discuss our high‐density solid‐state fermented Lacticaseibacillus paracasei culture (PYW) and its effects on dextran sulfate sodium (DSS)‐induced colitis. Comparison of the effects of PYW, enriched with viable cells and bioactive metabolites—obtained via fermentation with wheat bran—with those of its thermally inactivated postbiotic (SPYW) shows superior efficacy of PYW than SPYW, with a viable bacterial load of ≥ 5 × 10 ¹⁰ CFU g ⁻¹ being indispensable. PYW effectively restores microbiota structure, restructures the gut tryptophan metabolic network, enriching indole‐3‐lactic acid (ILA) and indole‐3‐acetic acid (IAA), which activate the aryl hydrocarbon receptor (AhR) signaling pathway, suppress pro‐inflammatory mediators, and strengthen mucosal barriers. Antibiotic depletion abolishes the effects of PYW, while fecal microbiota transplantation from PYW‐treated donors and exogenous ILA/IAA supplementation replicate its anti‐colitic benefits. These findings suggest that PYW alleviates colitis via microbiota‐dependent enrichment of ILA/IAA and subsequent AhR pathway activation, highlighting its potential as a probiotic therapeutic targeting the microbiota–metabolism–immunity regulatory axis in IBD.

An 8-week feeding trial was conducted to evaluate the effects of dietary fermented rapeseed meal (FRM), potassium iodide, and their interactions on growth performance, approximate composition, and antioxidant capacity in tilapia, Oreochromis niloticus (initial body weight: 3.50 ± 0.15 g). Six isonitrogenous and isolipidic diets from a 2 × 3 factorial design were formulated with two levels of FRM (25.8 and 51.6%) and three levels of potassium iodide (0, 6, and 12 mg/kg), respectively. The results indicated that dietary levels of FRM and iodine had no significant influence on the SR of tilapia but exerted significant effects on weight gain (WG), specific growth rate (SGR), feed intake (FI), hepatosomatic index, and viscerosomatic index. The WG, SGR, and FI of tilapia in the 51.6% FRM groups were significantly lower than those in other groups (p < 0.05), and iodine inclusion in the 51.6% FRM diet significantly enhanced WG, SGR, and FI of tilapia (p < 0.05). Dietary iodine significantly increased the whole-body and muscle lipid content in the tilapia (p < 0.05). The content of total bilirubin (T-Bil) and the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the tilapia serum were significantly reduced by the inclusion of 6–12 mg/kg iodine in 51.6% FRM level (p < 0.05), and the serum total triiodothyronine content was significantly elevated by the supplementation of 12 mg/kg iodine (p < 0.05). Significant interactions between dietary FRM and iodine were found in serum T-Bil content and triglyceride and AST activity (p < 0.05). Dietary supplementation of iodine in high FRM diets (51.6%) significantly increased the activities of total superoxide dismutase (T-SOD), catalase (CAT), and total antioxidant capacity (T-AOC) and decreased the content of malondialdehyde (MDA) in the liver of tilapia (p < 0.05). The activity of T-SOD, CAT, and T-AOC and the content of MDA in the liver of tilapia significantly interacted with the levels of dietary FRM and iodine (p < 0.05). Furthermore, the liver cell structure was further ameliorated, and the liver health status was significantly enhanced in each iodine treatment group.

Histamine can damage the antioxidant and immune systems in fish and crustaceans. Rutin, a natural substance with a diverse phenolic structure, has demonstrated antioxidant and anti-inflammatory properties. However, whether rutin can mitigate histamine-induced negative effects remains uninvestigated in fish models. This study investigated the effect of 0.1–100 μM rutin preincubation on histamine (29.5 mM)-induced cytotoxicity in zebrafish liver cells (ZFL) and its potential mechanisms. Results showed that 0.1–100 μM rutin significantly improved ZFL cell survival following histamine stimulation and protected cellular morphology. Rutin inhibited the adverse effects of histamine on ZFL by scavenging or suppressing the accumulation of reactive oxygen species (ROS), H₂O₂, and malondialdehyde (MDA), while increasing the activities of superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC). At the protein level, 10 μM rutin significantly promoted Nrf2 protein expression. HO-1 protein was significantly up-regulated after preincubation with 0.1–10 μM rutin, whereas IL-1β protein levels were significantly down-regulated. The mechanism may involve activation of the Nrf2 antioxidant signaling pathway and inhibition of the NF-κB inflammatory signaling pathway. In summary, within the experimental concentration range, 10 μM rutin showed the strongest inhibitory effects on histamine-induced ZFL cell death and oxidative stress. This study provides a theoretical basis and data support for evaluating rutin’s feasibility as a green aquatic feed additive.