Grass Carp Ctenopharyngodon Idella Research Articles

Phagocytic Plasma Cells in Teleost Fish Provide Insights into the Origin and Evolution of B Cells in Vertebrates.

Teleost IgM+ B cells can phagocytose, like mammalian B1 cells, and secrete Ag-specific IgM, like mammalian B2 cells. Therefore, teleost IgM+ B cells may have the functions of both mammalian B1 and B2 cells. To support this view, we initially found that grass carp (Ctenopharyngodon idella) IgM+ plasma cells (PCs) exhibit robust phagocytic ability, akin to IgM+ naive B cells. Subsequently, we sorted grass carp IgM+ PCs into two subpopulations: nonphagocytic (Pha-IgM+ PCs) and phagocytic IgM+ PCs (Pha+IgM+ PCs), both of which demonstrated the capacity to secrete natural IgM with LPS and peptidoglycan binding capacity. Remarkably, following immunization of grass carp with an Ag, we observed that both Pha-IgM+ PCs and Pha+IgM+ PCs could secrete Ag-specific IgM. Furthermore, invitro concatenated phagocytosis experiments in which Pha-IgM+ PCs from an initial phagocytosis experiment were sorted and exposed again to beads confirmed that these cells also have phagocytic capabilities, thereby suggesting that all teleost IgM+ B cells have phagocytic potential. Additionally, we found that grass carp IgM+ PCs display classical phenotypic features of macrophages, providing support for the hypothesis that vertebrate B cells evolved from ancient phagocytes. These findings together reveal that teleost B cells are a primitive B cell type with functions reminiscent of both mammalian B1 and B2 cells, providing insights into the origin and evolution of B cells in vertebrates.

Uncovering the freezing energy release of salted grass carp (Ctenopharyngodon idella) flesh: Effects of water state and protein structure on the thermal properties

The effect of NaCl content on the protein structures, water status and thermal properties of grass carp flesh, along with its relationship with energy required for freezing was investigated to improve the quality of frozen flesh and to reduce energy consumption for freezing. Adding salt prompted the shifting of the secondary structure of α-helix to β-sheet, β-turn and random coil. The interaction between water molecules and hydrophilic groups in the unfolded protein structure increased nonfreezing water content, which decreased specific heat capacity, thermal conductivity of sample during freezing. The lowest energy required (235.69 kJ/kg) for freezing was found in 7% NaCl salted sample, indicating a 38.39% reduction compared to the unsalted sample. Few pores between muscle fibers were observed in the 3% and 5% NaCl salted sample. Therefore, an optimal salt concentration improved quality of frozen flesh and reduced the energy required for freezing, promoting energy-efficient freezing of aquatic products.

Metformin improves insulin resistance, liver healthy and abnormal hepatic glucolipid metabolism via IR/PI3K/AKT pathway in Ctenopharyngodon idella fed a high-carbohydrate diet

The effects and underlying mechanisms of metformin which can improve glucose homeostasis of fish have rarely been explored. This experiment aimed to explore the influence of metformin on growth performance, body composition, liver health, hepatic glucolipid metabolic capacity and IR/PI3K/AKT pathway in grass carp (Ctenopharyngodon idella) fed high-carbohydrate diets. A normal diet (Control) and high carbohydrate diets with metformin supplementation (0.00 %, 0.20 %, 0.40 %, 0.60 % and 0.80 %) were configured. Six groups of healthy fish were fed with the experimental diet for eight weeks. The results showed that the growth performance of grass carp was impaired in high carbohydrate diet. Impairment of IR/PI3K/AKT signalling pathway reduced insulin sensitivity, while hepatic oxidative stress damage and decreased immunity affected liver metabolic function. The glycolysis and lipolysis decrease while the gluconeogenesis and fat synthesis increase, which triggers hyperglycaemia and lipid deposition in the body. Metformin supplementation restored the growth performance of grass carp. Metformin improved IR/PI3K/AKT pathway signalling and alleviated insulin resistance, while liver antioxidant capacity and immunity were enhanced resulting in the restoration of liver health. The elevation of glycolysis and lipolysis maintains glycaemic homeostasis and reduces lipid deposition, respectively. These results suggest that metformin supplementation restores liver health and activates the IR/PI3K/AKT signalling pathway, ameliorating insulin resistance and glucose-lipid metabolism disorders caused by a high-carbohydrate diet. As judged by HOMA-IR, the optimum supplementation level of metformin in grass carp (C. idella) fed a high-carbohydrate diet is 0.67 %.

Feasibility evaluation of cottonseed protein concentrate to replace soybean meal in the diet of juvenile grass carp (Ctenopharyngodon idellus): Growth performance, antioxidant capacity, intestinal health and microflora composition

An investigation into the replacement of soybean meal (SBM) with cottonseed protein concentrate (CPC) in the diet of grass carp feed (Ctenopharyngodon idellus) was carried out. During a 56-day feeding trial, 750 grass carp were fed five experimental diets (isonitrogenous and isolipidic) with different levels of CPC: SBM (control group), CPC25, CPC50, CPC75, and CPC100, corresponding to dietary SBM replacements levels of 0%, 25%, 50%, 75%, and 100%. The results showed that dietary CPC inclusion significantly increased FW, WGR, and PER (P < 0.05) except CPC100 groups, which did not differ with SBM group (P > 0.05). FCR was remarkably increased when SBM replacement levels reached up to 100% (P < 0.05). Based on broken-line regression analysis of WGR against the dietary replacement of SBM with CPC, the optimal replacement level of SBM with CPC was estimated to be 75.11% for juvenile grass carp. Muscle texture parameters hardness, gumminess and chewiness were apparently elevated (P < 0.05), demonstrated an improved flesh quality followed CPC added. The CPC inclusion groups showed significantly higher serum IgM, C3 amd C4 contents, as well as ACP and AKP activities than SBM group except CPC100 groups (P < 0.05). The hepatic antioxidant capacity was enhanced followed CPC inclusion verified at enzymatic and transcriptional levels (P < 0.05). The intestinal inflammation was relieved evidenced by the down-regulated il-β, il-6 and tnf-α expressive abundance mediated through NF-κB pathway (P < 0.05). Additionally, the intestinal mucosal barrier function was enhanced by the up-regulation of tight junction proteins (occludin, claudin12, zo-1, and zo-2). The intestinal lipase and trypsin activities in CPC50 and CPC75 and intestinal folds height in CPC25, CPC50 and CPC75 were advanced (P < 0.05). The gut microbiota revealed no significant differences in the alpha diversity indices across treatments (P > 0.05). While the key bacteria of Aeromonas in the CPC100 group was increased leading intestinal dysbacteriosis. Besides, the ME1 of the microbial network has a negative correlation with pro-inflammatory gens and a positive correlation with antioxidant gens and tight linking proteins (P < 0.05). Summarily, CPC could partially replace SBM with positive influences on growth, antioxidant capacity, immunity, and intestinal microbiota in grass carp.

Influence of microplastic pollution on the toxicity of potamodromous fish grass carp (Ctenopharyngodon idellus) and its swimming capacity

Microplastics (MPs), as a ubiquitous environmental contaminant in marine and freshwater systems, produced a significant influence on the physiological characteristics of aquatic organisms, and inevitably posed unknown effects on their swimming capacity. Herein, we evaluated the MPs accumulation in potamodromous fish, Ctenopharyngodon idellus, and their potential effects on oxidative stress, neurotoxicity, gut microbial diversity, and swimming capability through a toxic-control experiment. Juvenile fish were exposed to 5 µm polystyrene-MPs (PS-MPs) for 6 days at concentrations of 0.1, 1, and 10 mg/L. Exposure to PS-MPs resulted in significant inhibition of acetylcholinesterase (AChE) in the brain of fish, with significant increases in superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels at 1 and 10 mg/L exposures. Meanwhile, MPs altered grass carp gut microbiota and reduced the Shannon diversity index. In addition, MPs significantly increased induced swimming speed by observing the flow rate at which grass carp happened to produce a reverse current behavioral response. The 1 and 10 mg/L of MPs treatments can significantly reduce the critical swimming speed of grass carp, meaning that the completion of the life history of grass carp may be delayed. Furthermore, there were significant correlations between biomarkers and indicators of swimming capacity. Therefore, the present study suggests that MPs produced a negative effect on the physiological properties of fish, reducing the swimming capacity of migratory fish.

Effects of polystyrene microspheres on the swimming behavior and metabolism of grass carp (Ctenopharyngodon idella)

Microplastics (MPs) are a heterogeneous class of pollutants fouling aquatic environments and they are hazardous to aquatic organisms. This study investigated the size-dependent effects of polystyrene microspheres (PSMPs) on the swimming ability, metabolism, and oxidative stress of juvenile grass carp (Ctenopharyngodon idella). Test fish were exposed to four sizes of PSMPs (0.07, 0.5, 5, and 20-μm), and swimming ability was tested after different exposure times (2, 7, and 15 days). To measure the effect on swimming ability, critical swimming speed (Ucrit) was determined, and to assess metabolic effects, oxygen consumption (MO2), routine metabolic rate (RMR), maximum oxygen consumption (MMR), and excess post-exercise oxygen consumption (EPOC) were determined. To assess the effects on oxidative stress, the activities of two antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) were determined in the liver and gills of test fish. After exposure to 20 μm PSMPs, there was a significant drop in Ucrit compared to the control group (P<0.05), with decreases of 22% on Day 2 and Day 7, and 21% on Day 15. The RMR and MMR increased significantly (P<0.05), the RMR by 23.9% on Day 2 and the MMR by 17.2% on Day 2 and on Day 15, 44.7% and 20.0% respectively. The EPOC decreased with exposure time, by 31% (0.07-μm), 45%-(0.5-μm), 49% (5-μm), and 57% (20-μm) after 15 days. Exposure to the larger PSMPs increased CAT and SOD activity more than the smaller PSMPs and the increases began with SOD activity in the gills. The larger PSMPs were consistently more harmful to juvenile grass carp than the smaller PSMPs. Our results clearly show that PSMPs have detrimental effects on juvenile grass carp and provide additional scientific evidence that environmental monitoring and regulation of microplastic pollution is necessary.

Whole-genome resequencing of grass carp (Ctenopharyngodon idella) for genome-wide association study on GCRV resistance

Grass carp (Ctenopharyngodon idella) is a highly productive freshwater fish species that annually contributes significant economic value to the aquaculture industry. However, its production is frequently affected by grass carp haemorrhagic disease (GCHD), which is caused by grass carp reovirus (GCRV). To elucidate the molecular mechanism of GCRV resistance in C. idella, whole-genome resequencing of both susceptible and resistant C. idella was conducted, yielding a total of 3,941,776 high quality single nucleotide polymorphisms (SNPs). A genome-wide association study (GWAS) then identified five significant SNPs, located on chromosomes 2, 3, 5, 6 and 10, associated with the trait of GCRV resistance. An integrative analysis of the GWAS and a previous transcriptome study was performed, and five common genes were identified, including b4galt2 (β-1,4-galactosyltransferase 2), kif2c (Kinesin family member 2C), jmjd8 (JmjC domain containing 8), selenom (Selenoprotein M), and znfx1 (Zinc finger NFX1-type containing 1). This study serves as a valuable basis for implementing marker-assisted selection (MAS) to improve GCRV resistance in C. idella breeding programs, and provides insight into developing methods to control the spread of GCHD.

Evaluation of soybean meal replacement by Clostridium autoethanogenum protein in diets for juvenile grass carp (Ctenopharyngodon idellus)

An investigation into the possible substitution of Clostridium autoethanogenum protein (CAP) for soybean meal (SBM) in the diet of grass carp (Ctenopharyngodon idellus) was carried out. During a 56-day feeding trial, 750 grass carp were fed five experimental diets with different levels of CAP: SBM (control group), CAP25, CAP50, CAP75, and CAP100, corresponding to dietary SBM replacements levels of 0%, 25%, 50%, 75%, and 100%. The results showed that dietary CAP significantly increased FW, WGR, and PER in CAP25 group (P < 0.05), but complete substitution showed the opposite trend (P < 0.05). The liver antioxidant capacity was improved in CAP25 group manifested by the enhanced SOD, GPx and CAT activities, reduced ROS, and MDA contents, and the up-regulated cuznsod, mnsod, gpx1, gpx4, gsto and gr transcript levels mediated by Keap1-Nrf2 signaling pathway (P < 0.05). The intestinal inflammation was relieved in CAP25 group evidenced by the down-regulated il-β, il-6 and tnf-α expressive abundance through NF-κB pathway (P < 0.05). Additionally, the intestinal mucosal barrier function was enhanced by the upregulation of tight junction proteins (occludin, zo-1 and zo-2) in the CAP25 group. Whereas the intestinal folds showed varying degrees of breakage in CAP100 group. The increased amylase and lipase activities, intestinal folds height, and goblet cell numbers were found in CAP25 group (P < 0.05). The gut microbiota revealed no significant differences in the alpha diversity indices across treatments (P > 0.05). Besides, the abundance of Bacteroides in the CAP25 group was increased, while the abundance of Erysipelatoclosridium in the CAP100 group was increased. Summarily, CAP could replace 25% of SBM with positive influences on growth, antioxidant capacity, immunity and intestinal microbiota for juvenile grass carp. Conversely, high levels of CAP impaired intestinal physical barrier and caused intestinal microbiota disturbance, resulting in negatively affect the growth performance.

Co-exposure of decabromodiphenyl ethane and polystyrene nanoplastics damages grass carp (Ctenopharyngodon idella) hepatocytes: Focus on the role of oxidative stress, ferroptosis, and inflammatory reaction

Decabromodiphenyl ethane (DBDPE) and polystyrene nanoplastics (PS-NPs) are emerging pollutants that seriously threaten the ecological safety of the aquatic environment. However, the hepatotoxicity effect of their combined exposure on aquatic organisms has not been reported to date. In, this study, the effects of single or co-exposure of DBDPE and PS-NPs on grass carp hepatocytes were explored and biomarkers related to oxidative stress, ferroptosis, and inflammatory cytokines were evaluated. The results show that both single and co-exposure to DBDPE and PS-NPs caused oxidative stress. Oxidative stress was induced by increasing the contents of pro-oxidation factors (ROS, MDA, and LPO), inhibiting the activity of antioxidant enzymes (CAT, GPX, T-SOD, GSH, and T-AOC), and downregulating the mRNA expressions of antioxidant genes (GPX1, GSTO1, SOD1, and CAT); the effects of combined exposure were stronger overall. Both single and co-exposure to DBDPE and PS-NPs also elevated Fe2+ content, promoted the expressions of TFR1, STEAP3, and NCOA4, and inhibited the expressions of FTH1, SLC7A11, GCLC, GSS, and GPX4; these effects resulted in iron overload-induced ferroptosis, where co-exposure had stronger adverse effects on ferroptosis-related biomarkers than single exposure. Moreover, single or co-exposure enhanced inflammatory cytokine levels, as evidenced by increased mRNA expressions of IL-6, IL-12, IL-17, IL-18, IL-1β, TNF-α, IFN-γ, and MPO. Co-exposure exhibited higher expression of pro-inflammatory cytokines compared to single exposure. Interestingly, the ferroptosis inhibitor ferrostatin-1 intervention diminished the above changes. In brief, the results suggest that DBDPE and PS-NPs trigger elevated levels of inflammatory cytokines in grass crap hepatocytes. This elevation is achieved via oxidative stress and iron overload-mediated ferroptosis, where cytotoxicity was stronger under co-exposure compared to single exposure. Overall, the findings contribute to elucidating the potential hepatotoxicity mechanisms in aquatic organisms caused by co-exposure to DBDPE and PS-NPs.

GMPR2-MDA5 interaction bridged the cell junction and anti-GCRV immune

As a consequence of increased vascular endothelial permeability and vascular injury caused by GCRV (grass carp reovirus) infection, grass carp (Ctenopharyngodon idellus) could suffer from hemorrhagic disease and even death. MDA5 is a key RNA sensor that stimulates type I interferon as well as regulates vascular permeability. The guano monophosphate ductase 2 (GMPR2) plays a key role in regulating the permeability of vascular endothelial cells. This study examined the interaction between grass carp MDA5 and GMPR2 and their antiviral effects. GMPR2 interacted directly with MDA5 and promoted its protein level, whilst MDA5 conversely inhibited the GMPR2 protein expression. The expression of GCRV VP7 protein was inhibited by the increased levels of MDA5 and GMPR2. In addition, the cell junction molecule Claudin7b which is closely related to the change in vascular permeability, was inhibited by both MDA5 and GMPR2. Finally, in GMPR2 knockout zebrafish, the mRNA level of MDA5 was significantly down-regulated, which validated the positive functional relationship of GMPR2 on MDA5. Consistent changes of the Claudin 7b and VP7 protein levels were observed in the GMPR2 and MDA5 overexpression groups. In summary, MDA5-GMPR2 interaction affecting GCRV replication might through cell junction molecule Claudin7b. The results from this study provided systematic support for revealing the genetic basis of cell permeability change as well as the hemorrhagic diseases in grass carp.

Identification and functional analyses of CD4-1+ cells in grass carp (Ctenopharyngodon idella)

In mammals, CD4 is found to be expressed on T cells and innate immune cells, however, teleost cells bearing CD4 have not been well identified and characterized. In this study, we identified two different CD4-1+ cell subsets in grass carp (Ctenopharyngodon idella): CD4-1+ lymphocytes (Lym) and CD4-1+ myeloid cells (Mye), both of which had the highest proportions in the head kidney. The mRNA expression analysis showed that CD4-1, CD4-2, TCRβ, CD3γ/δ, and LCK1 are highly expressed in CD4-1+ Lym and also expressed in CD4-1+ Mye. Furthermore, we found that CD4-1+ Lym have a Lym morphology and highly express T-cell cytokines, suggesting that they are CD4+ T cells equivalent to mammalian Th cells. On the other hand, CD4-1+ Mye were found to have a morphology of macrophage and highly express macrophage marker gene MCSFR, indicating that they are macrophages. In addition, functional analysis revealed that CD4-1+ Mye possess phagocytic ability and great antigen-processing ability. Taken together, our study sheds further light on the composition and function of CD4+ cells in teleost fish.

Unveiling the emerging role of curcumin to alleviate ochratoxin A-induced muscle toxicity in grass carp (Ctenopharyngodon idella): in vitro and in vivo studies

BackgroundOchratoxin A (OTA), a globally abundant and extremely hazardous pollutant, is a significant source of contamination in aquafeeds and is responsible for severe food pollution. The developmental toxicity of OTA and the potential relieving strategy of natural products remain unclear. This study screened the substance curcumin (Cur), which had the best effect in alleviating OTA inhibition of myoblast proliferation, from 96 natural products and investigated its effect and mechanism in reducing OTA myotoxicity in vivo and in vitro.MethodsA total of 720 healthy juvenile grass carp, with an initial average body weight of 11.06 ± 0.05 g, were randomly assigned into 4 groups: the control group (without OTA and Cur), 1.2 mg/kg OTA group, 400 mg/kg Cur group, and 1.2 mg/kg OTA + 400 mg/kg Cur group. Each treatment consisted of 3 replicates (180 fish) for 60 d.ResultsFirstly, we cultured, purified, and identified myoblasts using the tissue block culture method. Through preliminary screening and re-screening of 96 substances, we examined cell proliferation-related indicators such as cell viability and ultimately found that Cur had the best effect. Secondly, Cur could alleviate OTA-inhibited myoblast differentiation and myofibrillar development-related proteins (MyoG and MYHC) in vivo and in vitro and improve the growth performance of grass carp. Then, Cur could also promote the expression of OTA-inhibited protein synthesis-related proteins (S6K1 and TOR), which was related to the activation of the AKT/TOR signaling pathway. Finally, Cur could downregulate the expression of OTA-enhanced protein degradation-related genes (murf1, foxo3a, and ub), which was related to the inhibition of the FoxO3a signaling pathway.ConclusionsIn summary, our data demonstrated the effectiveness of Cur in alleviating OTA myotoxicity in vivo and in vitro. This study confirms the rapidity, feasibility, and effectiveness of establishing a natural product screening method targeting myoblasts to alleviate fungal toxin toxicity.Graphical

The role of pantothenic acid in alleviating hypoxia-induced liver injury of sub-adult grass carp (Ctenopharyngodon idellus): Possible mechanisms and implication

In aquaculture, hypoxia poses a significant threat to fish growth and survival. Despite this, there is limited research on the impact of pantothenic acid (PA) in enhancing the anti-hypoxia stress capability of fish. The primary objective of this study was to explore the effects and potential mechanisms of PA in alleviating hypoxia-induced liver injury in sub-adult grass carp. To achieve this, six experimental diets containing varying levels of PA (0.08, 11.95, 24.95, 37.95, 50.95, and 63.95 mg/kg) were formulated and administered to grass carp (initial weight 696.22 ± 2.45 g) for 63 days. Following the dietary intervention, the fish were segregated into hypoxia and control groups and treated for 96 h. The findings revealed that optimal PA levels could enhance the growth performance of sub-adult grass carp and ameliorate the adverse impacts of hypoxia. First, optimal PA levels reduced serum levels of glutamate-oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT), and lactate dehydrogenase (LDH), as well as mitigated hepatocyte vacuolization, improved liver and mitochondrial morphology, thereby alleviating hypoxia-induced liver injury. Furthermore, optimal PA levels were associated with increased contents of serum cortisol, glucose, liver glycogen, pyruvate, and the activities of Pantothenate kinase 2 (PanK2) and coenzyme A (CoA), while liver lactate content and LDH activity were reduced, indicating improvements in energy metabolism and PA utilization, potentially mediated by the down-regulation of hypoxia-inducible factor-1α (HIF-1α) mRNA level. Moreover, optimal PA levels decreased reactive oxygen species (ROS) and malondialdehyde (MDA) levels, enhanced liver antioxidant capacity, down-regulated autophagy-related gene mRNA levels, and up-regulated autophagy receptor protein 62 (p62) protein level, suggesting a reduction in oxidative damage and autophagy. Finally, a rise in levels of mitochondrial quality control-related mRNAs such as mitofusin 1/2 (MFN1/2), dynamin-related protein-1 (DRP-1), and nuclear respiratory factor 1/2 (Nrf-1/2) was observed, together with increment in the protein levels of PTEN induced putative kinase 1 (PINK1), BCL-2 interacting protein 3 (BNIP3) and FUN14 domain-containing protein 1 (FUNDC1). These alterations hinted at the role of PA in preserving mitochondrial homeostasis. In conclusion, PA exhibited a protective role against hypoxia-induced liver injury by enhancing liver energy metabolism, bolstering antioxidant defenses, suppressing autophagy, and maintaining mitochondrial homeostasis. Through an assessment of percentage weight gain (PWG) and liver ROS level, the requirements of PA for promoting growth and resilience to hypoxia-induced liver injury in sub-adult grass carp were determined to be 37.44 mg/kg and 42.57 mg/kg, respectively.

Selection of texture-associated biomarkers in chilled and iced grass carp (Ctenopharyngodon idella) fillets via DIA-based proteomics

Consumers care about the texture of fresh fish flesh, but a rapid quantitative analytical method for this has not been properly established. In this study, texture-associated biomarkers were selected by DIA-based proteomics for possible future application. Results indicated a significant decline in texture and moisture characteristics with extended storage under chilled and iced conditions, and flesh quality was categorized into three intervals. A total of 8 texture-associated biomarkers were identified in the chilled storage group, and 3 distinct ones in the iced storage group. Biomarkers were further refined based on their expression levels. Isobutyryl-CoA dehydrogenase, mitochondrial and [Phosphatase 2A protein]-leucine-carboxy methyltransferase were identified as effective texture-associated biomarkers for chilled fish, and Staphylococcal nuclease domain-containing protein 1 for iced fish. This study provided suitable proteins as indicators of fresh fish flesh texture, which could help establish a rapid and convenient texture testing method in future studies.

In vitro susceptibility of grass carp fish (Ctenopharyngodon idella) to oxidized myosin on structural change of protein secondary structure associated with reactive oxygen species (ROS) treatment

This study aimed to investigate the in vitro susceptibility of grass carp (Ctenopharyngodon idella) oxidized myosin, with the treatment of H2O2 levels being 0, 25, 50, and 100 μmol/L, respectively. The results showed that in vitro oxidation of myosin, reactive oxidative species promoted protein modifications that propagated the conformation changes on myosin secondary structure, leading to a significant increase (P < 0.05) in the protein carbonyl content in the high oxidation treatment, when compared to the low and medium treatments. The results of the Western blot analysis and sodium-polyacrylamide amide-dodecyl sulfate gel electrophoresis demonstrated that in vitro oxidation actively promoted the degradation of protein molecular weight and Desmin (53 kDa) deterioration in the sample with the highest concentration treatment of H2O2. Circular dichroism spectra showed a decrease in α-helix content from 70.1% to 29.8% and an increase in β-sheet percentage from 5.6% to 17.4%. Meanwhile, cysteine and methionine as the free amino acids were most susceptible to oxidative change due to their high sensitivity to the reaction of the sulfur group of amino acids. Protein degradation induced by oxidation resulted in significant changes to the protein secondary structure, as evidenced by the observation of oxidized myosin under different H2O2 levels.

Microelements, Fatty Acid Profile, and Selected Biomarkers in Grass Carp (Ctenopharyngodon idella) Muscle Tissue: Seasonal Variations and Health Risk Assessment

AbstractThe study assesses associations between microelement levels, fatty acid composition, and oxidative stress markers in grass carp muscle in the summer and autumn seasons. Additionally, various factors were considered, including the estimated daily intake (EDI), target hazard quotient (THQ), total THQ (TTHQ), and metal pollution index (MPI), to evaluate potential health risks for consumers. The microelements (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, Se, Sr, and Zn) were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and total mercury was determined using cold-vapor atomic absorption spectroscopy (CV-AAS). Fatty acid profiling was realized using gas chromatography (GC) detection with a flame ionization detector (FID). The overall tendency of microelement levels was as follows: Fe &gt; Zn &gt; Al &gt; Sr &gt; Ba &gt; Ni &gt; Se &gt; Cr&gt; Cu &gt; Mn &gt; Pb &gt; As &gt; Li &gt; Hg; &lt;LOQ (below limit of quantification): Cd, and Co. The correlation analysis between concentrations of trace elements (Al, Ba, Cr, Cu, Mn, Li, Sr, Zn, and Hg) and the fatty acids (C16:0, C16:1, C18:1n9c, C18:2n6c, C20:4n6c, EPA, and DHA), as well as between Al, Ba, Fe, or Hg and oxidative stress markers (superoxide dismutase—SOD, glutathione peroxidase—GPx, or total antioxidant status—TAS), revealed statistically significant interactions in different seasons. THQ values were lower than 1; TTHQ values ranged from 0.27 to 0.76. The main toxic elements forming TTHQ were Hg and Ni (49%). The calculated health risk assessment indices indicate a low concentration of observed elements and low risks associated with the consumption of grass carp muscle from the tested location, although concentrations and THQ of mercury and nickel may be of slight concern.

New insights into resveratrol attenuates hepatotoxicity in emamectin benzoate-exposed grass carp (Ctenopharyngodon idella) via NO system/NF-κB signaling pathway

Emamectin benzoate (EMB) is extensively used as a crop protection agent. Overuse of EMB poses a serious threat to the quality of water and non-target organisms in the environment. Resveratrol (RES) is a natural phytoalexin with the function of anti-oxidation and anti-inflammation. Nonetheless, it is unclear whether EMB affects the expression of cytokines and induces autophagy, apoptosis, and necroptosis of hepatocytes (L8824 cell) in grass carp (Ctenopharyngodon idella), and whether RES has an attenuate function in this process. Therefore, we established the L8824 cells model of EMB exposure and treated it with RES. The results showed that compared with the control (CON) group, EMB exposure significantly increased the nitric oxide (NO) content, inducible nitric oxide synthase (iNOS) activity, and the expression of iNOS and phosphorylated nuclear factor kappa B (p-NF-κB) (P < 0.05). In addition, compared with the CON group, the results of flow cytometry and dansylcadaverine (MDC) staining showed a significant increase in apoptosis and autophagy in the EMB-exposed group (P < 0.05) with the activation of the B-cell lymphoma-2 (Bcl-2)/Bcl-2 associated X (Bax)/cysteine-aspartic acid protease 3 (Caspase-3)/cysteine-aspartic acid protease 9 (Caspase-9) pathway and microtubule-associated protein light chain 3 (LC3)/sequestosome 1 (p62)/Beclin1 pathway. EMB exposure significantly increased the mRNA and protein expression of receptor-interacting protein 1 (RIPK1)/receptor-interacting protein 3 (RIPK3)/mixed the lineage kinase domain-like (MLKL) pathway (P < 0.05). Moreover, EMB exposure significantly increased the expression of genes related to immunity (immunoglobulin G (IgG), immunoglobulin M (IgM), and immunoglobulin D (IgD), and antimicrobial peptide-related genes expression including β-defensin and hepcidin) (P < 0.05). The addition of RES significantly diminished autophagy, apoptosis, necroptosis, and immunity-related gene expression by inhibiting iNOS activity, NO content, and the protein expression of iNOS and p-NF-κB. In conclusion, RES attenuated autophagy, apoptosis, and necroptosis in EMB-exposed L8824 cells via suppression of the NO system/NF-κB signaling pathway.

Identification of novel SNPs and candidate genes significantly affecting growth in grass carp (Ctenopharyngodon idella) through GWAS analysis

Grass carp (Ctenopharyngodon idella) is one of the most important cultivated fish species in the global freshwater aquaculture with fast growth, low cost of production and delicious meat. A breeding program to improve economically important growth traits in grass carp would benefit from effective molecular markers. Although a genetic linkage map of grass carp has been constructed, and quantitative trait loci (QTL) mapping and a genome-wide association study (GWAS) have been conducted, the effective number of SNP markers and genes currently available for breeding is still very limited. In this study, we conducted a GWAS based on re-sequencing of individuals to identify genomic regions and candidate genes potentially associated with various growth traits of grass carp, including body weight (BW), body length (BL) and body height (BH). A total of 4,854,366 high-quality SNPs were identified and located on 24 chromosomes. Among them, 31 SNPs were identified as being associated with growth traits, including 8 SNPs on chromosomes 1, 2, 10, 13, 14, 17 and 22 associated with BW, 21 SNPs on chromosomes 2, 4, 5, 8, 10, 13, 14, 15, 17, 23 and 24 correlated with BL, and 18 SNPs on chromosomes 2, 9, 10, 13, 14, 17, 23 and 24 related to BH. In addition, 13 of these SNPs were simultaneously associated with two or three growth traits. Within a 48 kb range upstream and downstream of these significant SNPs, 120 candidate genes were identified to be associated with the QTLs. Most of these genes were related to growth and development, fat metabolism, bone mineralization and differentiation, vascular development, and feeding regulation. Notably, the genes pwp1, cers5, chrebp, lsr, ctnnbip1, smoc2, ano6 and cckrb were specifically associated with growth, fat, bone formation and feeding. Our findings would provide a foundation for molecular marker-assisted selection, genomic selection, and functional analysis of growth traits in grass carp.

Ecological inferences on invasive carp survival using hydrodynamics and egg drift models

Bighead carp (Hypophthalmichthys nobilis), silver carp (H. molitrix), black carp (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella), are invasive species in North America. However, they hold significant economic importance as food sources in China. The drifting stage of carp eggs has received great attention because egg survival rate is strongly affected by river hydrodynamics. In this study, we explored egg-drift dynamics using computational fluid dynamics (CFD) models to infer potential egg settling zones based on mechanistic criteria from simulated turbulence in the Lower Missouri River. Using an 8-km reach, we simulated flow characteristics with four different discharges, representing 45–3% daily flow exceedance. The CFD results elucidate the highly heterogeneous spatial distribution of flow velocity, flow depth, turbulence kinetic energy (TKE), and the dissipation rate of TKE. The river hydrodynamics were used to determine potential egg settling zones using criteria based on shear velocity, vertical turbulence intensity, and Rouse number. Importantly, we examined the difference between hydrodynamic-inferred settling zones and settling zones predicted using an egg-drift transport model. The results indicate that hydrodynamic inference is useful in determining the ‘potential’ of egg settling, however, egg drifting paths should be taken into account to improve prediction. Our simulation results also indicate that the river turbulence does not surpass the laboratory-identified threshold to pose a threat to carp eggs.

Isalo scorpion cytotoxic peptide‐strengthened immune function through the JAKs/STATs signaling pathway of the immune organ of grass carp (Ctenopharyngodon idella) challenged with Aeromonas hydrophila

AbstractTo investigate the impact of Isalo scorpion cytotoxic peptide (IsCT) on the immune function of immune organ (head kidney, spleen, and skin) of grass carp (Ctenopharyngodon idella), 540 fish (136.88 ± 0.72 g) were supplied with a different amount of IsCT (0, 0.6, 1.2, 1.8, 2.4, and 3.0 mg/kg diet) through a period of 60 days. Afterward, 24 fish were randomly selected from each group and were inoculated with Aeromonas hydrophila for a period of 6 days. Our findings suggested that appropriate IsCT complementation: (1) attenuated skin morbidity and histopathological structural changes in the head kidney and spleen (p &lt; 0.05), which ensured the structural integrity of the immune organs; (2) increased the activity and expression of immune substances (p &lt; 0.05), which in turn increased the function of the immune organs, promoting immune responses; (3) through the regulation of the Janus kinase/signal transducers and activators of transcription (JAKs/STATs) signaling pathway, the mRNA expression of anti‐inflammatory cytokines increased and the mRNA expression of pro‐inflammatory cytokines decreased, which in turn increased the function of the immune organs, reducing the inflammatory response (p &lt; 0.05). However, the addition of IsCT did not affect the expression of IL‐12p35, STAT2, and STAT3a in the immune organ. Ultimately, this study provided evidence that IsCT enhanced immune function via the JAKs/STATs signaling pathway in the immune organ in grass carp after challenged with Aeromonas hydrophila.