Jian Carp Research Articles

Transcriptomic profiling reveals potential regulatory genes and molecular mechanisms of residual feed intake in Jian carp (Cyprinus carpio var. Jian)

Feed efficiency is one of the most important economic traits in animal production. Improving feed efficiency through genetic selection or other approaches will reduce production costs and mitigate environmental impacts. Residual feed intake (RFI) has some advantages over traditional feed efficiency metrics as a selection criterion for improving feed efficiency, because it is not a ratio and unrelated to growth. In this study, high RFI (HRFI) and low RFI (LRFI) Jian carp (Cyprinus carpio var. Jian) were tested for feed efficiency traits and serum biochemical indices. No significant differences were observed in the growth rates between HRFI and LRFI group, but daily feed intake of LRFI was significantly lower than that of the HRFI group. The results indicated that significantly higher content of triglyceride (TG) and total cholesterol (T-CHO) in the LRFI group was significantly correlated with RFI. We also selected HRFI and LRFI carp for transcriptomic analysis to determine differentially expressed genes (DEGs) in the liver tissues of 12 individuals. A total of 830 DEGs were identified between HRFI and LRFI group, of which 486 genes were up-regulated and 344 genes were down-regulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that DEGs were mainly enriched in fatty acid metabolism, ErbB signaling pathway, phosphatidylinositol signaling system, and autophagy. Lipid metabolism and autophagy-related genes, were considered candidate genes that played a crucial role in regulating feed efficiency. Taken together, these results indicated that differences in RFI affect Jian carp metabolism and cell fate, and that alterations in fatty acid metabolism and autophagy are key physiological modes of regulation in low RFI Jian carp. Our data provide valuable candidate genes and candidate pathways, which will help to study the molecular mechanisms of feed efficiency in carp.

The protective effect of dietary extract of Astragalus membranaceus on the high stocking density, copper and trichlorfon in Jian carp (Cyprinus carpio var. Jian)

This study was designed to examine the protective effects of extract of Astragalus membranaceus (EAM) against stress, which induced by high stocking density, Cu and trichlorfon exposure in Jian carp (Cyprinus carpio var. Jian). The husbandry period (23.0 ± 1 °C) for high stocking density (0.97 fish/L) was 60 days with the initial fish weight 7.2 ± 0.2 g, and Cu (0.7 mg/L) and trichlorfon (2.2 mg/L) exposure was 4 days after feeding trial (30 days) with the initial fish weight 10.5 ± 0.3 g. Stress of high stocking density and Cu exposure decrease 48.2 % of fish weight gain and reduced 97.6 % of feed intake. Meanwhile, trichlorfon exposure induced 100 % fish rollover. High stocking densities and Cu exposure decreased activities of amylase, trypsin, as well as Na+/K+-ATPase and alkaline phosphatase and increased malonaldehyde content in fish digestive organs (P < 0.05), indicating an interruption of digestive ability and antioxidant status. Furthermore, trichlorfon exposure decreased activities of lactate dehydrogenase, superoxide dismutase, catalase, glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase in fish muscles (P < 0.05), indicating an interruption on bioenergetic homeostasis and antioxidant status. Dietary EAM supplementation relieved these detrimental effect, which induced by high stocking density, Cu and trichlorfon exposure. The optimum dietary EAM supplementation were 5.23, 4.79 and 5.12 g kg/diet for Jian carp under high stocking densities, Cu and trichlorfon exposure, respectively. Our study indicates that dietary EAM supplementation offers a feasible way for relieving the stress which induced by inappropriate high stocking densities, Cu, as well as trichlorfon.

The Extract of Astragalus membranaceus Inhibits Lipid Oxidation in Fish Feed and Enhances Growth Performance and Antioxidant Capacity in Jian Carp (Cyprinus carpio var. Jian)

In this study, a linoleic and linolenic acid were incubated with petroleum ether extract, ethyl acetate extract, acetone extract (AE) and aqueous extract of Astragalus membranaceus. The phenolic content and total antioxidant capacity (T-AOC) were determined in the extracts of Astragalus membranaceus (EAms) above. Results showed that EAms decreased the levels of malonaldehyde, conjugated diene, and peroxide value levels in material above. Of all of EAms, AE showed the strongest T-AOC and inhibitory effect on the lipid oxidation. Next, fish feeds were incubated with graded levels of AE. The results showed that AE inhibited lipid oxidation in fish feed. The appropriate dosage for reducing lipid oxidation was 6.74 g AE kg−1 feeds. The effect of EAms on the lipid oxidation may be closely associated with their phenolic content. Then, juvenile Jian carp (Cyprinus carpio var. Jian, 10.2 ± 0.3 g) were fed with diets containing graded levels of AE (0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0 g kg−1) for 60 days. Current data displayed that dietary AE increased the growth performance of fish. The optimum dosage for growth promotion was 5.15 g AE kg−1 diet. This result of AE may be ascribed to its enhancing effect on the activity of digestive and absorptive enzymes and antioxidant capacity in digestive organs of fish. Our present study indicated that EAm holds promise as a natural antioxidant for fish and their feed.

Extract of Ginkgo biloba Leaves (EGb) Decrease Lipid Oxidation in Fish Feed and Meat and Enhance Growth and Antioxidant Capacity in Jian Carp (Cyprinus carpio var. Jian)

Firstly, a linoleic and linolenic acid emulsion were incubated with petroleum ether extract, ethyl acetate extract (EAE), ethanol extract and aqueous extract of Ginkgo biloba leaves. The flavonoids content, total antioxidant capacity (T-AOC) and metal-chelating ability (MCA) were determined in EGbs above. Results showed that the extracts of Ginkgo biloba leaves (EGbs) inhibited the lipid oxidation in material above. Of all of EGbs, EAE showed the strongest T-AOC, MCA and protective effects against the lipid oxidation. Next, fish feeds were incubated with graded levels of EAE. The results showed that EAE inhibited lipid oxidation in fish feeds. The optimal inclusion levels of EAE for minimizing lipid oxidation were 4.26 g kg−1 feeds. The effect of EGbs on the lipid oxidation may be closely associated with their flavonoid content. Finally, juvenile carp (14.8 ± 0.4 g) were fed with EAE at concentrations ranging from 0.0 to 6.0 g kg−1 for 60 days. Current data displayed that dietary EAE increased the growth performance of fish. This result of EAE may be ascribed to its enhancing effect on the activity of digestive and absorptive enzymes and antioxidant capacity in digestive organs of fish. Furthermore, dietary EAE decreased the hot-drying-induced lipid oxidation in fish meat through inhibiting the induction effect of hemoglobin in erythrocytes. Our study suggests that EGb can be considered as a potential natural antioxidant for fish and fish feed.

Species-specific effects of microplastics on juvenile fishes.

Microplastics contamination have been extensively reported in aquatic ecosystem and organisms. It is wildly acknowledged that the ingestion, accumulation and elimination of microplastics in fishes are species-specific, which mainly depending on the feeding behavior. This study aimed to investigate the effects of microplastics on the morphology and inflammatory response in intestines of fishes with different feeding types. Largemouth bass (carnivorous fish), grass carp (herbivorous fish) and Jian carp (omnivorous fish) were used as organism model. The contributing concentration and size of microplastics were explored as well as the response time and legacy effect in fishes. Two different sizes of polystyrene microplastics (80nm and 8μm) were set at three concentrations. And samples were analyzed at different exposure times and depuration times. Histological analysis indicated that multiple abnormalities in intestines were presented in three species fishes after acute exposure microplastics. The mRNA abundance of immune-related genes in the intestine tissues of fishes were significantly fluctuant. There were differential expressions of genes coping with differential sizes and concentrations of microplastics exposure in different fishes. The reason for the difference effects of microplastics on fishes was still unclear but could be due to the difference in the structure and function of the digestive system. These results provided a theoretical basis to further analysis of the mechanism of fish intestinal pathology caused by microplastics.

Methanotroph (Methylococcus capsulatus, Bath) bacteria meal (FeedKind®) could effectively improve the growth, apparent digestibility coefficient, blood biochemical parameters, antioxidant indices of juvenile Jian carp (Cyprinus carpio var. Jian)

A 10-week growth study was conducted to evaluate the effects of replacement of soybean meal (SBM) with different levels of Methylococcus capsulatus (0%, 2%, 4%, 6%, 8%, 10%) meal on the growth, digestibility, intestinal development and serum biochemical indices of juvenile Jian carp. The present results showed that compared to the control group (0% M. capsulatus meal), 6%, 8%, and 10% M. capsulatus meal significantly improved the final average weight (FW), weight gain rate (WGR), specific growth rate (SGR), and decreased feed conversion rate (FCR). No significant difference was found in the survival rate (SR) in the treatment groups, and SR of each group was more than 95%. Jian carp had relatively high apparent digestibility of diets containing M. capsulatus meal, the apparent digestibility coefficient of Jian carp for dry matter, crude protein, crude lipid, energy and amino acid of M. capsulatus meal was 70.85%, 90.68%, 67.68%, 80.82%, and 88.00–91.17%, respectively. The addition of M. capsulatus meal had no adverse effect in the intestinal tissue of Jian carp juveniles, and 8% M. capsulatus meal significantly increased the villus width compared with the control group. Improved serum biochemical indices and increased antioxidant capacity of fish was noted in fish fed diets containing M. capsulatus meal. Replacement of M. capsulatus meal at the 6% level significantly decreased alanine aminotransferase (ALT) activity compared to the control group. The blood glucose (GLU) of all treatment groups had a decreasing trend, and the 8% and 10% M. capsulatus meal diets had significant effects on GLU content. Compared to the control group, 6%, 8%, and 10% M. capsulatus meal significantly decreased blood urea nitrogen (BUN) content. Compared to the control group, 6% and 8% M. capsulatus meal diets significantly increased serum total antioxidant capacity (T-AOC) of Jian carp, and 8% M. capsulatus meal diet significantly decreased malondialdehyde (MDA) activity. The study has demonstrated that the replacement of SBM with Methylococcus capsulatus shows promise as an alternative protein source in the aquaculture industry.

Interactive Effects of Microplastics and Tetracycline on Bioaccumulation and Biochemical Status in Jian Carp (Cyprinus carpio var. Jian)

Microplastics (MPs) and tetracycline (TC) are severe emerging pollutants in the aquatic environment. But there is a lack of research to investigate the interactive effects of MPs and TC in vivo. This study used Jian carp (Cyprinus carpio var. Jian) as the model organism to explore the bioaccumulation and biochemical status when exposed to MPs and TC, alone and combined. The accumulation of TC and MPs in intestine, variation of enzyme activities in intestine, and expression of immune-related genes in muscle were evaluated. Our results found the bioaccumulation of MPs was not affected by TC, but the presence of MPs would change the content of TC within 48 h. The superoxide dismutase (SOD) and lactate dehydrogenase (LDH) activity showed that TC-MP combined exposure could reduce oxidative damage to Jian carps compared to MP exposure alone. The integrated biomarker response (IBR) index showed that SOD activity was sensitive to TC-MP exposure. In addition, co-exposure to MPs and TC could alleviate the overexpression of interleukin 1 beta (IL-1β), interleukin 10 (IL-10), transforming growth factor beta (TGF-β), and toll like receptor 2 (TLR-2) induced by TC in muscles. TLR-2 gene has the potential to be the candidate gene reflecting the injury of TC exposure. In conclusion, it is inferred that co-exposure may reduce the toxicity of individual exposure in the living organisms. This study provides essential information for the risk assessment of pollution with MPs and TC, individually and combined, as well as a foundation to investigate the interactive effects of MPs and antibiotics on aquatic ecosystems.

Dietary Taraxacum mongolicum polysaccharide ameliorates the growth, immune response, and antioxidant status in association with NF-κB, Nrf2 and TOR in Jian carp (Cyprinus carpio var. Jian)

Taraxacum mongolicum polysaccharide (TMP) is a highly effective anti-inflammatory and antioxidant agent, but it has not been studied in aquatic feed. Here, the objective of this study was to evaluate the effects of dietary TMP on the growth, digestive enzyme activity, immune response, antioxidant status, and the NF-κB, Nrf2 and TOR signalling pathway-related genes in Jian carp. The juvenile fish were randomly distributed into four groups according to the TMP concentrations (0, 0.5, 1.0 and 2.0 g/kg) for 56 days. Our results indicated that the growth, enzyme activity and immune factors in fish increased in a concentration-dependent manner, and the dietary supplementation with TMP (1.0 g/kg) increased the WG, SGR, PER, amylase, lipase and protease activity. Meanwhile, the serum immune response (except for ACP) and hepatopancreas antioxidant enzyme activity were positively regulated by TMP. However, MDA, PC, COR and LDH contents were negatively correlated with the dietary supplementation with TMP. Furthermore, the trend in the expression of genes related to the NF-κB, Nrf2 and TOR signalling pathways were similar to that of the enzyme activity, which increased with the increase in dietary supplementation with TMP (except for proinflammatory factors, tgf-β and keap1). Among them, il-10, il-2, ho-1, nrf2, sod-(Cu-Zn) and gpx showed sharp increases. These results elucidate that dietary supplementation with TMP may greatly ameliorate the growth, digestive enzyme activity, immune response and antioxidant status and regulate the expression of NF-κB, Nrf2 and TOR signalling pathway-related genes in Jian carp.

Evaluation of yeast hydrolysate as a substitute to dietary fish meal of| juvenile Jian carp ( Cyprinus carpio var. Jian): Protein synthesis via TOR pathway

This study was performed to evaluate effects of fish meal replacement by yeast hydrolysate (YH) on crude protein via TOR pathway of Jian carp, Cyprinus carpio var. Jian (initial average weight 19.44 ± 0.06 g). Six hundred fish were assigned into five groups and fed with five isonitrogenous and isocaloric diets replacing fish meal by 0g/kg (G1), 10g/kg (G2), 30g/kg (G3), 50g/kg (G4) and 70g/kg YH (G5). The results showed crude protein of fish in G2 and G3 were significantly higher (p < .05) than in G1. YH significantly increased AST and ALT activities of hepatocytes (p < .05) compared with the control group, but had no effects (p > .05) on AST and ALT contents in conditioned medium of hepatocytes. Furthermore, MyoD, TOR and S6K1 mRNA levels in muscle of G2 and G3 were significantly higher than of G1 (p < .05). Meanwhile, YH significantly increased MyoD, TOR and S6K1 mRNA levels in hepatocytes compared with the control group. In conclusion, 10g/kg and 30g/kg YH increased crude protein content of muscle in fish and increased TOR pathway genes expression levels in muscle and hepatocytes.

Effect of replacing fish meal by yeast hydrolysate on growth and intestinal function of| juvenile Jian carp (Cyprinus carpio var. jian)

This experiment was performed to investigate the effects of replacing fish meal in the diet of Cyprinus carpio var. jian (average weight 19.44±0.06 g) by yeast hydrolysate (YH), on growth, intestinal histology and function. Six hundred fish were assigned into five groups and fed with five isonitrogenous and isocaloric diets replacing fishmeal by 0% (G1), 1% (G2), 3% (G3), 5% (G4) and 7% (G5) YH. YH supplementation at 3% level significantly increased average body weight, daily growth index, feed intake, condition factor, specific growth rate, intestinal villi length and digestive and brush-border enzymes activity compared to the control group (p&lt;0.05). Moreover, YH supplementation significantly increased (p&lt;0.05) intestinal lipase, γ-GT, Na+/K+-ATPase and AKP expression levels. Intestinal Claudin-7 and Occludin mRNA levels in fish of dietary group G5 were significantly higher (p&lt;0.05) than that in the control group. Replacing fish meal with 3% YH increased growth performance, intestinal digestion and absorption, as well as improved intestinal villi length without triggering any negative effects on intestinal tight junction structure. Keywords: Enzyme activities, Growth, Intestinal histology, Jian carp, Tight junction structure, Yeast hydrolysate

Characterization of a novel brain cell line from Jian carp (Cyprinus carpio var. Jian).

Jian carp (Cyprinus carpio var. Jian) is an economically important cultured fish in China. Currently, it is facing threats from infectious diseases including koi herpesvirus (KHV). Here, we established a new cell line, designated CCB-J, derived from the brain tissue of the Jian carp. CCB-J cells grew well in Leibovitz's L-15 medium containing 20% fetal bovine serum at 25°C and have been subcultured for more than 60 passages. At the 30th passage, analysis showed that the number of chromosomes was 100, which is identical to that of other carp variants. Sequencing of the 18S ribosomal DNA confirmed that CCB-J originated from Jian carp. After transfection with the pEGFP-N1 plasmid, green fluorescence was observed in CCB-J. The replication of KHV in CCB-J cells was confirmed by RT-PCR and transmission electron microscopy. The viral titers of KHV in CCB-J cells and CCB cells, which have been widely used in the study of KHV, reached 103.9 and 101.8 median tissue culture infectious dose (TCID50/mL), respectively, within 14days. The result of TaqMan PCR revealed that CCB-J cells were more sensitive to KHV than CCB cells. Meanwhile, a cytopathic effect (CPE) was also observed in the CCB-J cells in a shorter time post-infection compared with CCB cells. In summary, the CCB-J cell line will be a useful tool in the study of viral pathogenesis and vaccine research.

Diet supplemented with a novel Clostridium autoethanogenum protein have a positive effect on the growth performance, antioxidant status and immunity in juvenile Jian carp (Cyprinus carpio var. Jian)

A ten-week feeding trial was conducted to investigate the effects of the supplementation of Clostridium autoethanogenum protein (CAP) in practical diets on the growth performance, serum chemical parameters, antioxidant status and histopathological examination of the liver and midgut in juvenile Jian carp. Five isnitrogenous and isenergetic diets were formulated with graded levels of CAP (0, 50, 100, 150 and 200 g/kg) to replace plant proteins. The results showed that, final body weight, percent weight gain, specific growth rate, protein retention value, protein efficiency ratio and condition factor were significantly improved in fish fed with CAP, while feed conversion ratio was the opposite(P < 0.05). Visceral somatic index was significantly decreased in the fish fed with CAP (P < 0.05). Serum total cholesterol and total triglyceride contents were significantly increased with increasing dietary CAP levels, and serum lactate dehydrogenase showed an opposite trend (P < 0.05). Meanwhile, aspartate aminotransferase activities were significantly decreased with increasing dietary CAP levels (P < 0.05). The serum activities of the catalase were significantly increased with an increase in CAP levels (P < 0.05); however, malondialdehyde contents showed the opposite trend (P < 0.05). The mRNA expression levels of growth-related genes (PepT-1, PepT-2 and IGF-1), Nrf2 signaling pathway-related genes (Nrf2, Cu/Zn-SOD, HO-1, GPx, Mn-SOD and CAT) and TOR signaling pathway-related genes (TOR, 4E-BP2 and S6K1) were improved by the addition of dietary CAP (P < 0.05). Furthermore, from histological examination, CAP had no obvious effect on the liver and midgut. The present results indicated that CAP supplementation in practical diets has a beneficial effect on growth performance and antioxidant capacity and does not have an obvious effect on the liver and midgut in juvenile Jian carp. This study has shown the potential of converting industrial waste into a high protein feed ingredient for aquafeeds.

Effects of dietary γ‐aminobutyric acid levels on the growth, serum biochemical indexes, immune‐related signalling molecules of Jian carp

In order to evaluate the protect effects of γ-aminobutyric acid (GABA) on the growth, serum biochemical indexes, immune-related signalling molecules of Jian carp (Cyprinus carpio var. Jian), fish were randomly divided into 6 groups, which fed six diets with different GABA levels (0, 30, 60, 90, 120 and 150 mg/kg) for 8 weeks, respectively. The results indicated the following: body weight gain, specific growth rate, feed intake, feed efficiency ratio and protein efficiency ratio were significantly improved by dietary GABA supplementation, the levels of total protein, albumin, glucose and the activity of superoxide dismutase in serum responded same trend; whereas, the activities of aspartate aminotransferase, alanine aminotransferase and malondialdehyde contents were opposite. Moreover, the activities of lysozyme and alkaline phosphatase and the content of nitric oxide in head kidney and spleen showed significantly increased under GABA pre-supplementation. Furthermore, GABA pre-supplementation had significantly higher expressions of interleukin-2, interleukin 10, interferon γ and lower expressions of nuclear factor-kappa B, interleukin-1β, tumour necrosis factor α in head kidney and spleen when compared to the control group. These results indicated that GABA pre-supplementation improved the growth in Jian carp, which could be related to the activation of serum biochemical indexes and immune-related signalling molecules, showing the potential of GABA as a novel feed additive to prevent stress. The recommendation dietary GABA level for Jian carp, estimated by quadratic regression analysis based on BWG and FER, was 99.01 mg/kg and 96.75 mg/kg, respectively.

Soybean glycinin disrupted intestinal structural integrity related to aggravation of apoptosis and downregulated transcription of tight junction proteins in the intestine of juvenile grass carp (Ctenopharyngodon idella)

Glycinin is a major anti-nutritional factor of soybean. Glycinin inhibits growth and impairs intestinal health in grass carp and Jian carp, but the underlying mechanisms are largely unknown. This study used grass carp to examine whether the negative influences of dietary glycinin are related to intestinal apoptosis signalling and tight junctions (TJs). The results showed that 8% dietary glycinin caused higher diamine oxidase activities and D-lactate content in the serum than did the control, indicating impairment of intestinal structural integrity. For the apoptosis indices, in the midgut and hindgut, glycinin aggravated the DNA fragmentation phenomenon, promoted caspase-3, −8, and − 9 activities, and increased cytochrome c protein abundance in the cytoplasm (apart from mitochondria) compared to those the control. In the midgut, glycinin increased the mRNA levels of pro-apoptotic molecules, including caspase-3, tumour necrosis factor-α (TNF-α), B-cell lymphoma 2 (Bcl-2)-associated X (Bax), and apoptotic protease activating factor 1 (Apaf-1), and decreased the mRNA levels of the anti-apoptotic molecule Bcl-2 compared to those in the control. In the hindgut, glycinin increased caspase-3, −8, and − 9, TNF-α, Fas-ligand (FasL), Bax, and Apaf-1 mRNA levels and decreased Bcl-2, myeloid cell leukaemia 1 (Mcl-1), and inhibitors of apoptosis proteins (IAP) mRNA levels compared to those in the control. For TJs, compared to that in the control, glycinin reduced the mRNA abundance of barrier-forming TJs—including claudin-c in the foregut; ZO-1, ZO-2b, occludin, and claudin-7a in the midgut; and ZO-1, ZO-2b, occludin, claudin-3c, claudin-7a, claudin-7b, and claudin-11 in the hindgut. In contrast, glycinin increased the mRNA abundance of pore-forming TJs, including claudin-15a and claudin-15b, in the midgut and hindgut. As an important nuclear factor of TJ transcription, hepatic nuclear factor 4 alpha (HNF-4α) protein abundance was reduced by glycinin in the midgut and hindgut. Glutamine alleviated apoptosis in the midgut. Glycinin aggravated apoptosis associated with both extrinsic and intrinsic signalling and disrupted TJ related to HNF-4α signalling in the midgut and hindgut, ultimately disrupting the intestinal structural integrity of grass carp.

A comparative study on intestinal morphology and function of normal and injured intestines of Jian carp (Cyprinus carpio var. Jian)

This study aimed to compare the intestinal morphology, barrier function, and digestive and absorptive function of normal and injured intestines in Cyprinus carpio var. Jian. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used for gene expression analysis, and the results were correlated with intestinal morphology and plasma biochemical parameters. The normal fish intestine was filled with chyme. Furthermore, the intestine surface was glossy and intact, and no gaps were observed in the tight junction structure (TJ). The amount of chyme in the injured intestine, however, was negligible. The wall of the injured intestine thinned and started to dissolve. Furthermore, hyperemia was observed in the injured intestine, and gaps were evident in the TJ structure of the injured intestinal mucosa. The levels of both diamine oxidase and D-lactate in the injured intestine were significantly higher than those in the normal intestine (p < .05). Protease, lipase, amylase, Na+/K+-ATPase, and alkaline phosphatase (AKP) activities in the proximal intestine of normal fish were significantly higher than that in the injured intestine of fish (p < .05). Meanwhile, Lipase, Amylase, AKP, Na+/K+-ATPase and γ-GT mRNA levels in the proximal segment of the injured intestine were significantly lower than that in the normal intestine (p < .05). However, Claudin-3c, Claudin-7, Qccludin and ZO-1 mRNA levels showed the opposite results. Taken together, intestinal injury decreased digestive and absorptive function and disrupted the TJ barrier, which consequently increased the permeability of the intestinal mucosa.

Effect of dietary L-glutamate levels on growth, digestive and absorptive capability, and intestinal physical barrier function in Jian carp (Cyprinus carpio var. Jian).

The present study explored effects of L-glutamate (Glu) levels on growth, digestive and absorptive capability, and intestinal physical barrier functions of Jian carp (Cyprinus carpio). A total of 600 Jian carp (126.40 ± 0.21 g) were randomly distributed into 5 groups with 3 replicates each, fed diets containing graded levels of Glu (53.4 [control], 57.2, 60.6, 68.4, and 83.4 g/kg) for 63 d. Results showed compared with control diet, feed intake and percent weight gain (PWG) in fish fed 83.4 g of Glu/kg diet were increased and feed conversion ratio in fish fed 68.4 g of Glu/kg diet was decreased (P < 0.05). Similarly, body crude protein and lipid contents in fish fed 68.4 g of Glu/kg diet were higher (P < 0.05). The activities of trypsin and chymotrypsin in the hepatopancreas and intestine, and amylase, alkaline phosphatase (AKP), Na+, K+-ATPase (NKA), and creatine kinase (CK) in intestine were higher in fish fed 68.4 g of Glu/kg diet (P < 0.05). Dietary Glu (57.2 to 83.4 g/kg diet) decreased malondialdehyde (MDA) and protein carbonyl (PCO) contents in the intestine (P < 0.05). The activities of catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST) in the hepatopancreas and intestine were higher in fish fed 60.6 and 68.4 g of Glu/kg diets (P < 0.05). Intestinal the glutathione reductase (GR) activity and glutathione (GSH) content in fish fed 60.6, 68.4, and 83.4 g of Glu/kg diet were increased (P < 0.05). The GPx1a, GST, and nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA expressions in the intestine were up-regulated in fish fed 60.6 and 68.4 g of Glu/kg diet (P < 0.05). The zonula occludens protein-1 (ZO-1), occludin1, and claudin3 mRNA expressions were also up-regulated in fish fed 83.4 g of Glu/kg diet (P < 0.05). Fish fed 68.4 g of Glu/kg diet had higher levels of claudin 2, claudin7, and protein kinase C (PKC) mRNA (P < 0.05). These results indicated that Glu improved fish growth, digestive and absorptive ability, and intestinal physical barrier functions. Based on the quadratic regression analysis of PWG, and MDA of the hepatopancreas and intestine, the optimal dietary Glu levels were estimated to be 81.97, 71.06, and 71.36 g/kg diet, respectively.

Soybean glycinin caused NADPH-oxidase-regulated ROS overproduction and decreased ROS elimination capacity in the mid and distal intestine of juvenile grass carp (Ctenopharyngodon idella)

Soybean glycinin could increase reactive oxygen species (ROS) content and cause damage in the intestine of Jian carp. However, related mechanisms are largely unknown. To test the hypothesis that glycinin increases intestinal ROS content by increasing ROS generation and decreasing ROS elimination capacity, juvenile grass carp (Ctenopharyngodon idella) were distributed into 3 treatments, fed with control, 8% glycinin or 8% glycinin+1.2% glutamine diets for 7 weeks, and intestinal oxidative damage, ROS content, intestinal ROS generation and elimination parameters were measured. Compared with control treatment, fish fed with glycinin diet had higher ROS, protein carbonyl (PC) and malondialdehyde (MDA) in the mid intestine (MI) and distal intestine (DI) (P < 0.05) rather than proximal intestine (PI) (P ≥ 0.05). For ROS generation parameters, compared with control treatment, dietary glycinin increased NADPH oxidase (NOX) activities, NOX1 and NOX2 protein abundance, and NOX1, NOX2, NOX organizer (NOXO) 1b, NOX activator (NOXA) 1, p47phox and p67phox mRNA abundance (P < 0.05) of MI, increased NOX activities, NOX1 protein, NOXO1b, NOXA1 and p22phox mRNA abundance (P < 0.05) of DI, and decreased NOX activities and all the mRNA abundance of NOX family genes measured (P < 0.05) except NOX4, NOXO1a and p47phox in the PI (P ≥ 0.05). For ROS elimination parameters, compared with control treatment, dietary glycinin decreased total and nuclear Nrf2 protein abundance, total antioxidant capacity (T-AOC), anti-superoxide anion (ASA), anti-hydroxy radical (AHR), CuZn-SOD, catalase, glutathione (GSH) peroxidase (GPx), GSH-S-transferase (GST) and GSH reductase (GR) activities of MI (P < 0.05), total and nuclear Nrf2 protein abundance, T-AOC, ASA, AHR, CuZn-SOD, Mn-SOD, CAT, GPx and GST activities (P < 0.05) of DI and T-AOC, ASA, CuZn-SOD, Mn-SOD and catalase activities (P < 0.05) of PI. Compared with glycinin treatment, glycinin + glutamine treatment decreased ROS, PC and MDA of MI (P < 0.05) but neither in PI nor DI of grass carp (P ≥ 0.05). Concluded, this study showed that (1) glycinin increased ROS generation related to NOX signaling pathway and decreased ROS elimination capacity related to the Nrf2 translocation in the MI and DI, which lead to the increased ROS content; (2) glycinin decreased both ROS generation and ROS elimination capacity in the PI of fish, which lead to the unchanged ROS content; (3) Glutamine could protect glycinin-induced oxidative stress mainly in the MI.

Evaluation of defatted black soldier fly (Hermetia illucens L.) larvae meal as an alternative protein ingredient for juvenile Japanese seabass (Lateolabrax japonicus) diets

Defatted black soldier fly larvae meal (DBSFLM) has been shown a promising fish meal (FM) substitute in diets for turbot, rainbow trout, Jian carp, Pacific white shrimp and Atlantic salmon, but it has not been examined as an alternative protein source in Japanese seabass (Lateolabrax japonicus) diets. A 56-day feeding trial was conducted to assess the effects of partial replacement of dietary FM with DBSFLM on the growth performance, whole body composition, blood metabolites, digestive enzyme activities, hepatic and intestinal histomorphology, and lipid metabolism related genes expression of juvenile L. japonicus. Five isoproteic (39%) and isolipidic (11%) diets were formulated by replacing 0% (FM), 16% (DBSFLM16), 32% (DBSFLM32), 48% (DBSFLM48) and 64% (DBSFLM64) of fish meal. Each diet was randomly assigned to triplicate groups of 30 fish per tank. Fish were fed two times daily to apparent satiation. Results showed that growth performance, somatic indexes, hepatic and intestinal histomorphology, and the intestinal antioxidant and immunity indexes of fish were not affected (P > 0.05) by dietary treatments. Fish consuming DBSFLM48 and DBSFLM64 had higher (P < 0.05) feed intake, but lower (P < 0.05) whole body ash content and ash retention along with serum concentrations of total cholesterol, triacylglycerol, high density lipoprotein cholesterol and malondialdehyde than those fed FM. DBSFLM inclusion did not alter activities of hepatic trypsin, lipase and amylase, but increased (P < 0.05) activity of intestinal lipase for fish fed DBSFLM48 and DBSFLM64 than those fed FM. Relative genes expression were up-regulated (P < 0.05) in hepatic lipoprotein lipase for fish fed DBSFLM64 and in hormone sensitive lipase for fish fed DBSFLM32, DBSFLM48 and DBSFLM64, whereas down-regulated (P < 0.05) in fatty acid synthase for fish fed DBSFLM diets than those fed FM. It was concluded that the replacement of dietary FM with DBSFLM up to 64% level did not alter growth performance, hepatic and intestinal histomorphology of L. japonicus. The increased feed intake, reduced blood lipid and inhibited hepatic lipid deposition suggest that DBSFLM can be a desirable protein alternative source as a replacement of fish meal in L. japonicus diets.

Effect of dietary enzyme‐treated soy protein on the immunity and antioxidant status in the intestine of juvenile Jian carp ( Cyprinus carpio var. Jian)

This study was conducted to evaluate the hypothesis that enzyme-treated soy protein (ETSP) can save the fish dietary protein, and further investigated the mechanism for saving effect by studying the effects of ETSP on intestinal immune response and antioxidant status in juvenile Jian carp (Cyprinus carpio var. Jian). Compared with the high-protein diet, results showed that decreasing 2% of dietary protein increased the protein carbonyl (PC) content, decreased the anti-hydroxyl radical capacity (AHR) and superoxide dismutase (SOD) activity and increased the relative expressions of pro-inflammatory cytokine (p < 0.05). The low-protein diet might impair the intestinal health, so as to reduce fish growth performance. After adding 1.5% or 2% of ETSP to the low-protein diet, results indicated that (1) ETSP decreased the relative expressions of pro-inflammatory cytokine and increased the relative expressions of anti-inflammatory cytokine (p < 0.05). (2) ETSP decreased malondialdehyde (MDA) and PC content (p < 0.05), improved activities of antioxidant enzymes, glutathione (GSH) content, relative expressions of antioxidant enzymes and Nrf2, which were even much higher than the high-protein diet (p < 0.05). All the above data suggested that optimal level of ETSP can save 2% of fish dietary protein which might be partly attributed to improve intestinal health through regulating intestinal immunity response and antioxidant status.

MRNA and microRNA transcriptomics analyses in intermuscular bones of two carp species, rice flower carp (Cyprinus carpio var. Quanzhounensis) and Jian carp (Cyprinus carpio var. Jian)

The rice flower carp (Cyprinus carpio var. Quanzhounensis) is a bony fish (superclass Osteichthyes), with very soft bones that is a significant feature unlike the other carp species. In this study, we analyzed the mRNA and microRNA (miRNA) transcriptomes in the intermuscular bones of rice flower carp and Jian carp (Cyprinus carpio var. Jian) (a typical member of common carp in China), using Illumina RNA sequencing. We identified 55,340 genes (including 47,541 known genes and 8231 predicted new genes) and 662 miRNAs (including 595 known miRNAs and 67 novel miRNAs) in the two species. By comparing the transcriptomes of the two species, we identified 1523 differentially expressed genes (DEGs) (including 576 up - and 947 downregulated DEGs) and 352 differentially expressed miRNAs (DEMs) (including 85 up- and 267 downregulated DEMs). According to the Gene Ontology (GO) annotation, 7 DEGs and 12 DEMs were found to be involved in the regulation of bone mineralization. The results of this study improve our understanding of the mRNA and miRNA profiles of carp bones, particularly those of the rice flower carp.