Ferroptosis is a kind of iron-dependent programed cell death. Vitamin D has been shown to be an antioxidant and a regulator of iron metabolism, but the relationship between vitamin D and ferroptosis is poorly studied in fish. This study used zebrafish liver cells (ZFL) to establish a ferroptosis model to explore the effect of 1,25(OH)₂D₃ on cell ferroptosis and its mechanism of action. The results showed that different incubation patterns of 1,25(OH)₂D₃ improved the survival rate of ZFL, mitigated mitochondrial damage, enhanced total glutathione peroxidase (GPx) activity, and reduced intracellular reactive oxygen species (ROS), lipid peroxidation (LPO), and malondialdehyde (MDA), as well as iron ion levels, with the best effect at 200 pM 1,25(OH)₂D₃ preincubation for 72 h. Preincubation of ZFL at 200 pM 1,25(OH)₂D₃ for 72 h downgraded keap1 and ptgs2 gene expression, increased nrf2, ho-1, fth1, gpx4a,b expression, and lowered the expression of the nf-κb p65,il-6,il-1β gene, thus reducing the expression of hamp1. The above results indicate that different incubation patterns of 1,25(OH)₂D₃ have protective effects on ferroptosis of ZFL induced by ferroptosis activator RSL3 and 1,25(OH)₂D₃ can inhibit ferroptosis of ZFL by regulating Keap1–Nrf2–GPx4 and NF-κB–hepcidin axis.

Introduction: In an effort to minimize the usage of fishmeal in aquaculture, novel protein diets, including Tenebrio molitor, cottonseed protein concentrate, Clostridium autoethanogenum, and Chlorella vulgaris were evaluated for their potential to replace fishmeal. Nevertheless, comprehensive examinations on the gut health of aquatic animals under an alternate feeding strategy when fed novel protein diets are vacant.Methods: Five isonitrogenous and isolipidic diets containing various proteins were manufactured, with a diet consisting of whole fishmeal serving as the control and diets containing novel proteins serving as the experimental diets. Largemouth bass (Micropterus salmoides) with an initial body weight of 4.73 ± 0.04g employed as an experimental animal and given these five diets for the first 29 days followed by a fishmeal diet for the next 29 days.Results: The results of this study demonstrated that the growth performance of novel protein diets in the second stage was better than in the first stage, even though only the C. vulgaris diet increased antioxidant capacity and the cottonseed protein concentrate diet decreased it. Concerning the intestinal barriers, the C. autoethanogenum diet lowered intestinal permeability and plasma IL-1β/TNF-α. In addition, the contents of intestinal immunological factors, namely LYS and sIgA-like, were greater in C. vulgaris than in fishmeal. From the data analysis of microbiome and metabolome, the levels of short chain fatty acids (SCFAs), anaerobic bacteria, Lactococcus, and Firmicutes were significantly higher in the C. autoethanogenum diet than in the whole fishmeal diet, while the abundance of Pseudomonas, aerobic bacteria, Streptococcus, and Proteobacteria was lowest. However, no extremely large differences in microbiota or short chain fatty acids were observed between the other novel protein diets and the whole fishmeal diet. In addition, the microbiota were strongly connected with intestinal SCFAs, lipase activity, and tight junctions, as shown by the Mantel test and Pearson’s correlation.Discussion: Taken together, according to Z-score, the ranking of advantageous functions among these protein diets was C. autoethanogenum diet > C. vulgaris diet > whole fishmeal diet > cottonseed protein concentrate > T. molitor diet. This study provides comprehensive data illustrating a mixed blessing effect of novel protein diets on the gut health of juvenile largemouth bass under an alternate feeding strategy.

To evaluate the nutritional enrichment effects of Euphausia superba meal on Moina mongolica Daday, different concentrations of krill meal (26, 39, 52, and 65 mg·L⁻¹) were applied as enrichment supplements, with non-enriched M. mongolica serving as the control. After a 6 h enrichment period, the compositions and contents of amino acids and fatty acids in M. mongolica were analyzed, and the astaxanthin content was simultaneously determined. The results showed that, compared with the control group cultured on a mixed diet of photosynthetic bacteria, yeast, and Nannochloropsis, enrichment with Antarctic krill meal at appropriate concentrations (26–39 mg·L⁻¹) markedly altered the fatty acid profile of M. mongolica. In particular, the levels of highly unsaturated fatty acids (HUFAs), including ∑ω6-PUFA and ∑ω3-PUFA, were significantly enhanced, with a pronounced increase in eicosapentaenoic acid (EPA). Furthermore, the total amino acid content, as well as the contents of six flavor-enhancing amino acids and ten essential amino acids for fish, were significantly higher in the enriched groups than in the control (p < 0.05). However, excessive supplementation of krill meal inhibited the growth of M. mongolica, suggesting a concentration-dependent effect. In addition, enrichment with whole Antarctic krill meal for 6 h did not significantly increase the astaxanthin content in M. mongolica, which may be related to the limited assimilation efficiency within the short enrichment duration. Overall, enrichment of M. mongolica with Euphausia superba meal at appropriate concentrations (26–39 mg·L⁻¹) effectively improves its fatty acid and amino acid composition, thereby enhancing its nutritional value as live feed for aquaculture larvae.