Fujian Fisheries Research Institute

This study aimed to investigate the effects of sodium hypochlorite (NaClO) bleaching on the quality of Basa (Pangasius bocourti) fish maw (BFM) and the formation of semicarbazide (SEM). Production of SEM increased (p < 0.05) when NaClO concentration, soaking temperature, or duration were increased. Notably, increasing NaClO solution pH also enhanced SEM formation. Soaking BFM in NaClO with available chlorine concentrations of 500, 700, and 1000 mg/L generated 0.05, 0.07, and 0.09 μg/kg SEM at pH 3 compared to 0.70, 1.19, and 2.34 μg/kg SEM at pH 11, respectively. NaClO improved BFM texture by creating a tight, fibrous structure, but also damaged the secondary structure and α-chains of collagen. Untargeted metabolomics showed that NaClO treatment significantly upregulated lipid metabolism pathways (biosynthesis of unsaturated fatty acids, linoleic acid metabolism, and glycerophospholipid metabolism) and elevated degradation of arginine, proline, and urocanic acid. This was associated with the accumulation of nitrogen-containing precursors in the urea cycle, which then reacted with NaClO, generating substantial SEM. Controlled SEM-generating reactions experiments confirmed that SEM was produced from reaction of urea and NaClO. This study elucidates the mechanism of SEM formation and identifies key factors influencing SEM levels, thereby providing a theoretical foundation for safe processing and quality control of fish maw.

A 60-day feeding trial was conducted to evaluate the effects of iron-porphyrin (FePh) supplementation (0, 50, 100, 150, and 200mg/kg Fe3⁺) compared with 50mg/kg FeSO4 in juvenile Epinephelus cyanopodus (16.12 ± 0.15g). The results demonstrated that FePh at 100mg/kg maximized the growth performance (P < 0.05), while 50mg/kg FePh surpassed FeSO4 in enhancing intestinal barrier integrity and growth. FePh improved systemic iron metabolism by elevating elevated transferrin and hepcidin levels (P < 0.05), with 50mg/kg FePh significantly increasing hemoglobin and serum iron (P < 0.05). Antioxidant capacity was significantly enhanced (T-AOC and SOD in serum and gills), alongside the upregulation of immune markers (C3, C4, and IgM). FePh also improved intestinal morphology (GC, MP, VL) and intestinal microbiota (P < 0.05). Serum aminotransferase (ALT and AST) levels decreased with elevated activity of antioxidant enzymes. Transcriptomic analysis revealed that FePh suppressed ferroptosis-related genes acsl4 and fth1, while activating iron-regulation genes slc7a11, slc3a2, and hmox1. In conclusion, FePh effectively improved the growth of juvenile E. cyanopodus; enhanced antioxidant capacity, non-specific immunity, and iron metabolism; maintained the stability of the intestinal mucosal barrier to promote intestinal health; and regulated the expression of key genes in the ferroptosis pathway to protect liver health. The optimal FePh inclusion level was 50-100mg/kg, demonstrating superior efficacy over inorganic iron for sustainable grouper aquaculture.

This study aimed to investigate the effects of betaine supplementation in a high-carbohydrate diet on the intestinal health of juvenile largemouth bass ( Micropterus salmoides ). Six diets were formulated: a low-carbohydrate diet (8% corn starch), a high-carbohydrate diet (20% corn starch), and the HC diet supplemented with 0.5%, 1.0%, 1.5%, or 2.0% betaine (HCB1–HCB4). A total of 270 juvenile largemouth bass with an initial body weight of 4.34 ± 0.11 g were subjected to a 56-day feeding trial. The experimental results showed that 0.5% betaine significantly improved the weight gain rate (WGR) and specific growth rate (SGR) of juvenile largemouth bass. In terms of antioxidant capacity, the levels of total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) in the intestine were markedly enhanced in the HCB groups, while 1.0% betaine significantly elevated intestinal glutathione (GSH) levels (P &lt; 0.05). Regarding intestinal histomorphology, betaine supplementation improved the intestinal histological structure, significantly upregulated the expression levels of zonula occludens-1 (ZO-1) and Occludin in the intestine, and notably augmented intestinal Claudin-1 expression in the 1% and 1.5% betaine groups (P &lt; 0.05). Furthermore, betaine reduced intestinal mucosal permeability, as evidenced by a significant decrease in serum diamine oxidase (DAO) levels (P &lt; 0.05). Additionally, betaine alleviated intestinal inflammation: specifically, 0.5% and 1% betaine markedly suppressed the expression of nuclear factor kappa-B (NF-κB), interleukin-8 (IL-8), and cyclooxygenase-2 (COX-2), while the expression level of interleukin-10 (IL-10) was significantly upregulated in the HCB groups (P &lt; 0.05). Concomitantly, supplementation with 0.5% betaine significantly boosted the relative abundance of Actinobacteria, whereas supplementation with 1% and 1.5% betaine significantly decreased the relative abundances of Proteobacteria and Enterobacteriaceae (P &lt; 0.05). In conclusion, dietary supplementation with 0.5%–1.5% betaine can significantly improve the intestinal health of juvenile largemouth bass.

Calcium and magnesium are essential mineral elements for animal growth and development, playing crucial roles in skeletal formation, particularly in the molting process of crustaceans. However, their interaction is still poorly elucidated. This study investigated the effects of dietary calcium and magnesium levels on the growth performance, tissue deposition of calcium and magnesium, exoskeleton development, and molting performance of Chinese mitten crab (Eriocheir sinensis). A 2 × 4 factorial design was adopted to formulate eight experimental diets, comprising two targeted calcium levels (1% and 2%) and four targeted magnesium levels (0.15%, 0.3%, 0.45%, and 0.6%). These diets were fed to crabs with an initial body weight of 40.46 ± 0.47 g for a 10-week period. The results showed that increased dietary calcium levels significantly reduced the weight gain rate (WGR), hepatosomatic index (HSI), carapace hardness, tissue (hepatopancreas, intestine, and muscle) calcium content, the expressions of genes related to calcium and magnesium absorption in the hepatopancreas, and the expressions of genes associated with molting and exoskeleton development. In contrast, it decreased the levels of molting hormone in hemolymph, chitinase (CHI) activity in the epidermis, and the expressions of genes encoding the molting hormone receptor and CHI in the hepatopancreas. The highest WGR was observed at a magnesium level of 0.6%, which also significantly enhanced carapace hardness and methyl farnesoate (MF) content in hemolymph, but significantly suppressed the expressions of chitin synthase genes in the hepatopancreas. Moreover, at 1% calcium level groups, increased dietary magnesium levels significantly upregulated the expressions of magnesium absorption-related genes. At 2% calcium level groups, with increasing dietary magnesium levels, the expressions of intestinal calcium absorption-related genes initially decreased then increased, while those of hepatopancreas calcium absorption-related genes significantly increased. Furthermore, significant interactive effects between dietary calcium and magnesium levels were observed on WGR, carapace hardness, collagen fiber content, CHI activity, and molting hormone levels in hemolymph. In conclusion, the interaction between dietary calcium and magnesium levels significantly influenced the growth performance, exoskeleton development, and molting of E. sinensis. An increase in dietary calcium levels should be accompanied by an appropriate elevation in magnesium levels in formulated feeds for this species.

Metabolites, once viewed mainly as energy substrates or structural precursors, are now increasingly recognized as key extracellular signaling mediators that regulate diverse physiological processes. This review synthesizes and systematizes current knowledge on metabolite-mediated signaling through G-protein-coupled receptors (GPCRs) in teleosts and, importantly, highlights new conceptual links between specific metabolite–GPCR axes and key physiological functions relevant to aquaculture. By integrating evidence across metabolite–GPCRs axes, including succinate–SUCNR1, aromatic amino acids (tryptophan and phenylalanine)–GPR142, basic amino acids (L-arginine)–GPRC6A, and lactate–GPR81. We clarify how metabolite–receptor interactions have the potential to modulate glucose homeostasis, immune responses, energy metabolism, and stress coping. A major contribution of this review is illustrating how metabolites act not only as nutrients but also as extracellular signaling molecules governing core physiological processes via GPCRs. Particularly from an evolutionary perspective, compared with peptide-activated GPCRs, metabolite-sensing GPCRs are relatively conserved across different species, suggesting that relevant findings from biomedical research could be translated to aquaculture applications. Therefore, understanding GPCR-mediated metabolite sensing provides a molecular foundation for improving nutrient formulation, developing functional feeds, and designing selective breeding strategies in precision aquaculture.

<i>Polygonatum sibiricum</i> has long been a popular functional food in Asia, known for its anti-inflammatory properties. However, its efficacy in alleviating colitis has yet to be investigated. This study aimed to explore the therapeutic potential of <i>P. sibiricum</i> polysaccharides (PSP) in dextran sulfate sodium (DSS)-induced colitis, focusing on the related pyroptosis mechanisms. Scanning electron microscopy (SEM) analysis showed that PSP possesses a smooth surface with no pore structure and a dense, lamellar structure adorned with numerous spherical entities. PSP treatment significantly reduced colitis symptoms and decreased pro-inflammatory cytokines, likely through suppression of the Toll like receptor 4 (TLR4)/nuclear factor κB (NF-κB) signaling pathway. Additionally, PSP attenuated NOD-like receptor protein 3 (NLRP3)/apoptosis-associated speck-like protein containing a CARD (ASC)/Caspase-1/Gasdermin D (GSDMD)-mediated pyroptosis and mitochondria damage in the colon, while enhanced the expression of tight junction and adherens junction proteins. Microbiota sequencing showed that PSP increased the abundance of phylum Bacteroidota and genus such as g_unclassified_f_Muribaculaceae, <i>Lactobacillus</i>, Clostridia_UCG-014, and Lachnospiraceae_NK4A136_group, while decreased the phylum Proteobacteria and the genus <i>Enterobacter</i>, <i>Escherichia-Shigella</i>, and <i>Blautia</i>. In conclusion, this study demonstrates that PSP exerts the potential therapeutic role against colitis, which was mediated by the regulation of gut microbiota and the inhibition of colonic NLRP3/ASC/Caspase-1/GSDMD signaling pathway.