Dietary lipids provide energy for growth and development and provide fatty acids necessary for normal structure and biological function. However, oxidized lipids cause oxidative stress and intestinal damage. An 8-week feeding trial with fresh fish oil (FFO, control group), oxidized fish oil (OFO), and taurine-supplemented diets (OFOT, OFO + 0.2% of taurine) was conducted to evaluate the protective effect of taurine on oxidized fish-oil-induced liver oxidative stress and intestine impairment in juvenile Ictaluruspunctatus. The results showed that (1) Growth performance was significantly lower in fish fed OFO than in those fed other diets, whereas the opposite occurred in the hepatosomatic index. (2) OFO-feeding significantly increased lipid deposition compared with the FFO group. The addition of taurine ameliorated the OFO-induced increase in lipid vacuolization in the liver, significantly upregulated lpl mRNA expression, and downregulated fas and srebp1 mRNA expression. (3) OFO-feeding significantly reduced oxidative damage of liver. Compared with the OFO group, the OFOT group remarkably upregulated antioxidant enzyme mRNA expression through the Nrf2-Keap1 signaling pathway based on the transcriptional expression. (4) OFO diets induced intestinal physical and immune barrier damage. Compared with the OFO group, OFOT diets remarkably downregulated il-1β, il-6, tnf-α, and il-8 mRNA expression and upregulated tgf-β mRNA expression through the NF-κB signaling pathway. Besides, the addition of taurine to OFO diets significantly upregulated zo-2 and zo-1 mRNA expression, and downregulated claudin-15 and claudin-12 mRNA expression. In conclusion, oxidized-fish-oil diets can cause negative physiological health effects in Ictaluruspunctatus, while adding taurine can increase growth and antioxidant ability, reduce lipid deposition, and improve intestinal health.

An 8-week feeding trial with high-carbohydrate- and 100, 200 and 300 mg/kg mulberry leaf flavonoids (MLF)-supplemented diets (HCF1, HCF2 and HCF3, respectively) was conducted to evaluate the protective effect of MLF on oxidized high-carbohydrate-induced glucose metabolism disorder, liver oxidative damage and intestinal microbiota disturbance in Monopterus albus. The results showed that HC diets had significant negative effects on growth, glucose metabolism, liver antioxidant and immunity, as well as intestinal microbiota, in comparison to CON diets. However, WGR and SR in the HCF3 group dramatically increased compared to the HC group. With the increase of MLF in the HC diet, the activities of glycolysis and antioxidant enzymes in the liver tended to increase, while the changes of gluconeogenesis-related enzyme activities showed the opposite trend and significantly changed in the HCF3 group. Additionally, MLF supplementation dramatically increased the mRNA expression involved in glycolysis, antioxidative enzymes and anti-inflammatory cytokines in comparison with the HC group. Furthermore, gluconeogenesis and pro-inflammatory cytokine genes’ expression dramatically decreased. Furthermore, the proportion of Clostridium and Rhodobacter in the HC group dramatically declined, and the proportion of Lactococcus dramatically increased, compared to the HC group. In addition, 300 mg/kg MLF supplementation significantly improved the species composition and homeostasis of intestinal microbiota. These results indicate that MLF can alleviate the negative effects of low growth performance, glucose metabolism disorder, liver oxidative damage and intestinal microbiota disturbance caused by HC diets, and the relief of MLF is dose-related.

The intake of high-fat diets (HFD) has been shown to diminish the muscle quality of aquatic animals. Sanguinarine, as an excellent additive, exhibits the capability to reduce fat deposition and alleviate inflammation. However, its role in the muscle quality reduction caused by HFD remains unclear. An eight-week trial was conducted to investigate the impacts of dietary supplementation of sanguinarine at 1200 μg/kg (HFDS; crude fat = 10%) on the muscle quality of grass carp (Ctenopharyngodon idellus) in comparison to a basic diet (CON, crude fat = 5%). Each group had 3 replicates, with 40 fish per replicate. This experiment employed one-way ANOVA and Duncan's multiple comparisons of the means. The results showed that the HFD exhibited lower growth performance, reduced protein deposition, myofiber diameter, and muscle hardness, coupled with higher levels of fat deposition and inflammation when compared with the CON. However, HFDS improved growth performance (P < 0.05), fat metabolism (ppar-α ( P = 0.001), lpl (P < 0.001), atgl (P < 0.001), and cpt1 (P = 0.001) expression exhibited a significant elevation), protein deposition (the protein and mRNA levels of AKT (P = 0.004), PI3K (P = 0.027), TOR (P = 0.005), and P70S6K (P = 0.007) demonstrated a marked increase), myofiber diameter, muscle hardness, and the total content of eicosapentaenoic acid and docosahexaenoic acid. Furthermore, the HFDS reduced oxidative damage caused by fat deposition by significantly downregulating nf-κb (P < 0.001), il-1β (P < 0.001), il-6 (P < 0.001), il-8 (P = 0.003), and tnf-α (P < 0.001) expression and markedly upregulated nrf2 (P < 0.001), gpx4 (P < 0.001), cat (P < 0.001), sod (P < 0.001), and gr (P = 0.003) expression. The findings from this study suggest that sanguinarine has the potential to alleviate the adverse effects of HFD on growth and muscle quality, providing a theoretical foundation for its practical implementation.

An eight-week trial was conducted to investigate the effects of sanguinarine supplementation (600 μg and 1200 μg/kg) in high-fat (crude fat: 10%) diets (HF) on the intestinal physiological function of Ctenopharyngodon idellus (initial weight 50.21 ± 0.68 g), based on a basic diet (5% crude fat, CON), which were named HFLS and HFHS, respectively. The results showed that the HF diet significantly impaired the intestinal immune and physical barrier function, and disrupted the balance of the intestinal microbiota in grass carp. Compared to the HF diet, sanguinarine supplementation significantly improved the levels of serum C4, C3, AKP, IgA, and IgM, and enhanced the intestinal antioxidant capacity (gr, CuZnsod, gpx4, cat, gsto, and nrf2 expression were significantly up-regulated). Sanguinarine significantly down-regulated the expression of claudin-15 and up-regulated the expression of claudin-b, claudin-c, occludin, and zo-1 by inhibiting MLCK signaling molecules. Additionally, sanguinarine significantly down-regulated the expression of il-6, il-1β, and tnf-α and up-regulated the expression of il-10, tgf-β2, and tgf-β1 by inhibiting NF-κB signaling molecules, thereby alleviating intestinal inflammation caused by HF diets. Furthermore, compared to the HF diet, the abundance of Fusobacterium and Cetobacterium in the HFHS diet increased significantly, while the abundance of Firmicutes and Streptococcus showed the opposite trend. In conclusion, the HF diet had a negative impact on grass carp, while sanguinarine supplementation enhanced intestinal antioxidant ability, alleviated intestinal barrier damage, and ameliorated the homeostasis of the intestinal microbiota.

An eight-week feeding experiment was conducted to evaluate the effects of replacing fish meal with stickwater hydrolysate (SWH) or stickwater hydrolysate meal (SWM) on the growth, serum biochemical parameters, intestinal digestive enzyme activity, and muscle quality of yellow catfish (Tachysurus fulvidraco). The control diet (CON) contained 30% fish meal and the remaining five diets were substituted for fish meal with 2.5% (SWM2.5), 5% (SWM5) SWM, and 5% (SWH5), 10% (SWH10), and 15% (SWH15) SWH, respectively. The results showed that there were no significant differences in weight gain rate, feed conversion rate, survival rate, hepatosomatic index, and viscerosomatic index among the groups. The substitution of fish meal with SWH significantly augmented the serum triglyceride and total cholesterol levels, whereas urea nitrogen content exhibited a reduction proportional to the replacement ratio. The incorporation of SWH led to a notable rise in glutamate-pyruvate transaminase activity, albeit with a gradual decline as the substitution ratio escalated. Relative to the CON group, the SWH5 group displayed a significant reduction in serum superoxide dismutase activity and a significant elevation in serum catalase activity. The substitution of fish meal with SWM yielded noticeable increments in the activities of complement 3, immunoglobulin M, and alkaline phosphatase. Neither SWH nor SWM exerted a substantial influence on intestinal amylase activity. Regarding muscle characteristics, neither SWH nor SWM showed a marked effect on hardness and springiness; however, adhesiveness, cohesiveness, gumminess, and chewiness properties exhibited enhancement as the proportion of fish meal replacement increased. In conclusion, within this experimental context, substituting fish meal with SWH and SWM did not adversely impact the growth and meat quality of yellow catfish. Specifically, replacing 15% fish meal with stickwater hydrolysate and 5% fish meal with stickwater hydrolysate meal contributed to an enhanced immune capacity in yellow catfish to a certain extent.