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Integrated rice–aquatic animal farming has become a vital strategy for enhancing food security. To assess the effects of integrated rice–giant river prawn (Macrobrachium rosenbergii) farming (IRPF) on agricultural ecosystems, we used 16S rRNA gene sequencing to analyze soil bacterial communities in comparison with traditional rice monoculture (RM). Our study revealed that the IRPF did not significantly affect the diversity of the soil bacterial community. However, during the initial culture stage, IRPF markedly increased the relative abundance of the phylum candidate division NC10 and the genus Candidatus Methylomirabilis, enhancing nitrogen-cycling-related functions within the bacterial community. Additionally, IRPF reduced the complexity and stability of these communities in the early to middle culture stages. While stochastic processes usually dominate the assembly of these communities, IRPF restricted bacterial migration and reduced the influence of these stochastic processes. Furthermore, IRPF had a significant impact on environmental factors within paddy soils, strongly correlating with shifts in bacterial communities, particularly through variations in soil nitrite concentration. In conclusion, the influence of IRPF on the bacterial community in paddy soils was primarily observed during the early and middle culture stages, and the impacts of IRPF on the soil bacterial community were primarily driven by environmental changes, especially soil nitrite concentration. These findings provide theoretical insights and a reference for understanding the microbiological impacts of different integrated rice–fish farming systems on agricultural ecosystems.

The application of cottonseed protein concentrate (CPC) is an effective strategy to moderate the shortage of fish meal (FM) for the aquafeed industry. However, little attention has been paid to the effects of replacing fishmeal with CPC on cyprinid fish. This study used common carp (Cyprinus carpio) as the biological model and assessed the potential of applying CPC as a substitute for fishmeal in the diet of common carp. The proportion of fish meal substituted with CPC in the six diets was 0% (CPC0), 25% (CPC25), 50% (CPC50), 75% (CPC75), and 100% (CPC100). Each diet was fed to three replicate groups of common carp (4.17 ± 0.02 g) for 56 days. Results revealed that the CPC50 group significantly increased the growth indexes via up-regulating the genes of the GH/IGF axis and the TOR pathway. The intestinal digestive ability was also elevated in the CPC50 group via markedly increasing intestinal villus height, protease and lipase activities in the whole intestine, and the amylase activity of the foregut and midgut. The CPC50 group captured significantly higher activities and gene expressions of antioxidant enzymes and lower malonaldehyde contents via evoking the Nrf2/Keap1 signal pathway. The CPC50 group enhance the intestinal mechanical barrier via up-regulating the gene expressions of tight junction proteins and heighten the intestinal biological barrier by increasing the probiotics (Lactococcus) and decreasing the harmful bacteria (Enterococcus). But excessive substitution levels (75% and 100%) would compromise growth performance, intestinal antioxidant capacity, and immune function. The optimum substitution level was estimated to be 46.47%, 47.72%, and 46.43% using broken-line regression analyses based on mass gain rate, protein efficiency ratio, and feed conversion rate. Overall, the fishmeal in common carp feed could be substituted up to 50% by CPC without negative influence on growth, feed utilization, and or intestinal health.

Vitamin C (VC) can be used to increase disease resistance in practice in intensive aquaculture. But it is still unconfirmed whether VC could alleviate inflammation and what dosage is suitable. This study investigated the effects of dietary VC on the immunity and enteritis of juvenile blunt snout bream (Megalobrama amblycephala) challenged with Aeromonas hydrophila. The fish were fed with VC levels ranging from 25.35 to 2231.98 mg/kg for 60 days. After that, fish fed with 150.65 mg/kg, 573.79 mg/kg, and 2231.98 mg/kg VC were challenged with A. hydrophila orally to simulate enteritis. The results showed that 285.39 and 573.79 mg/kg dietary VC significant improved growth performance and feed utilization. Dietary VC (573.79 and 1133.79 mg/kg) significantly enhanced the serum immune parameters, antioxidant enzymes’ activities, and relative gene expressions of ikbα and cat in the liver in the 60-day feeding trail. The survival rate was significantly higher in 573.79 mg/kg dietary VC group than the other two treatments. Cytokines were activated after the bacteria challenge. Dietary 573.79 mg/kg VC caused significantly higher TNF-α level at 12 hpi and maintained a high level of IL-8 at 48 to 72 h compared to other treatments. In conclusion, more than 500 mg/kg VC was needed to maintain the health of blunt snout bream juveniles. Suitable VC would activate cytokines to increase disease resistance along with antioxidant enzymes.

To investigate the impact of dietary inclusion of ferulic acid (FA) on growth performance, physiological and biochemical functions and hepato-intestinal health, three iso-nitrogenous and iso-lipidic diets supplemented with 0 mg/kg, 100 mg/kg, and 200 mg/kg FA were fed to Megalobrama amblycephala (9.75 ± 0.04 g) for 8 weeks. The growth performance, physiological and biochemical parameters, antioxidant capacity and the expression of genes were assessed on 4th and 8th week. The results indicated that 100 mg/kg FA inclusion significantly enhanced the weight gain rate (on week 4 and 8), feed intake (on 4th week), protein efficiency ratio (on week 8) and condition factor (on week 4) (P

An 8-week feeding trial was conducted to evaluate the effects of dietary krill oil (KO), fish oil (FO) and soybean oil (SO) on growth, nutritional quality and flavor of the edible meat of the oriental river prawns (Macrobrachium nipponense). The results revealed that SO and KO diets promoted the growth performance (P < 0.05). The activity of alanine aminotransferase in hemolymph of the FO group was significantly lower than that in the SO group (P

DL-methionyl–DL-methionine (AQUAVI® Met-Met) (Met-Met) (0.10%, 0.20%, 0.30%, and 0.40%) or DL-methionine (DL-Met) (0.10%, 0.20%, 0.30%, and 0.40%) were added to a low-fishmeal diet in an attempt to reduce fishmeal in the diet of Micropterus salmoides (M. salmoides). The fish were randomly allocated into ten experimental groups (n = 100), each with 4 replicates of 25 fish (16.39 ± 0.01 g) each. Compared to 25% FM, 0.40% of DL-Met and 0.10% of Met-Met promoted growth, and 0.10% of Met-Met decreased FCR. Compared to 25% FM, the supplementation of Met-Met or DL-Met improved the intestinal antioxidant capacity by upregulating the NF-E2-related factor 2-mediated antioxidant factors and enzyme activities and nuclear factor kappa-B-mediated anti-inflammatory factors while downregulating the pro-inflammatory factors, thereby exerting anti-inflammatory effects. Moreover, 0.10% of the Met-Met diet affected the Firmicutes-to-Bacteroidota ratio, increased the levels of Proteobacteria, changed the composition of intestinal flora (Roseburia, Lachnospiraceae_NK4A136_group, and unclassified_Oscillospiraceae), and enhanced intestinal dominant bacteria (Caldicoprobacter, Pseudogracilibacillus, and Parasutterella), leading to improved gut health. In summary, the supplementation of DL-Met or Met-Met alleviated the adverse effect of fishmeal reduction (from 40 to 25%) on the growth performance and intestinal health of M. salmoides.

The present study assessed the protective effects and underlying mechanisms of mulberry leaf polysaccharides (MLPs) against hydrogen peroxide (H2O2)-induced oxidative stress injury in the peripheral blood leukocytes (PBLs) of Megalobrama amblycephala. Five treatment groups were established in vitro: the NC group (PBLs incubated in an RPMI-1640 complete medium for 4 h), the HP group (PBLs incubated in an RPMI-1640 complete medium for 3 h, and then stimulated with 100 μM of H2O2 for 1 h), and the 50/100/200-MLP pre-treatment groups (PBLs were pre-treated with MLPs (50, 100, and 200 μg/mL) for 3 h, and then stimulated with 100 μM of H2O2 for 1 h). The results showed that MLP pre-treatment dose-dependently enhanced PBLs’ antioxidant capacities. The 200 μg/mL MLP pre-treatment effectively protected the antioxidant system of PBLs from H2O2-induced oxidative damage by reducing the malondialdehyde content and lactic dehydrogenase cytotoxicity, and increasing catalase and superoxide dismutase activities (p < 0.05). The over-production of reactive oxygen species, depletion of nicotinamide adenine dinucleotide phosphate, and collapse of the mitochondrial membrane potential were significantly inhibited in the 200-MLP pre-treatment group (p < 0.05). The expressions of endoplasmic reticulum stress-related genes (forkhead box O1α (foxO1α), binding immunoglobulin protein (bip), activating transcription factor 6 (atf6), and C/EBP-homologous protein (chop)), Ca2+ transport-related genes (voltage-dependent anion-selective channel 1 (vdac1), mitofusin 2 (mfn2), and mitochondrial Ca2+ uniporter (mcu)), and interleukin 6 (il-6) and bcl2-associated x (bax) were significantly lower in the 200-MLP pre-treatment group than in the HP group (p < 0.05), which rebounded to normal levels in the NC group (p > 0.05). These results indicated that MLP pre-treatment attenuated H2O2-induced PBL oxidative damage in the M. amblycephala by inhibiting endoplasmic reticulum stress and maintaining mitochondrial function. These findings also support the possibility that MLPs can be exploited as a natural dietary supplement for M. amblycephala, as they protect against oxidative damage.

To investigate the effects of different levels of fermented antarctic krill shell (FAKS) on the growth performance, hemolymph biochemistry, hepatopancreatic antioxidant capacity, and digestive enzyme activities of Macrobrachium nipponense, five isonitrogenous and isoenergetic experimental diets containing different proportions of FAKS (0 %, 0.25 %, 0.5 %, 1.0 %, 2.0 %) were fed to M. nipponense for 8 weeks. The results showed the weight gain rate (WGR), specific growth rate (SGR), head-to-body ratio (H/S), and head-to-tail ratio (H/T) increased first and then decreased with higher proportions of FAKS. The FAKS1.0 group exhibited the highest values, and significantly higher than that of the FAKS0 group (P

Background: The regulation of target gene mRNA mediated by microRNA may play an important role in glucose metabolism in fish. Previous research findings of our research group revealed that Momordica charantia saponin (MS) administration in a high-starch diet could improve insulin resistance of common carp through renovating insulin signaling pathways, whose fundamental mechanisms have remained unknown by far. To reveal this potential mechanism, we aimed to investigate the difference in miRNA and mRNA expression profiles between common carp fed with high-starch diets containing MS (HS_MS1 and HS_MS2) and common carp fed with high-starch (HS) diets.Results: Through miRNA deep-sequencing, 10 significantly differentially expressed miRNAs in HC and HS_MS1, including one upregulated and nine downregulated miRNAs, were identified, whereas 10 significantly differentially expressed miRNAs in HC and HS_MS2, including four upregulated and six downregulated miRNAs, were identified. These miRNAs may not only be involved in the regulation of insulin signaling pathways and insulin resistance in common carp but also be the markers for liver insulin resistance in MS therapy for the remission of insulin resistance. This study identified 10 potential known miRNAs, namely, ccr-miR-10b, ccr-miR-122, ccr-miR-143, ccr-miR-146a, ccr-miR-155, ccr-miR-16c, ccr-miR-200a, ccr-miR-29a, ccr-miR-34, and ccr-miR-375, as candidates participating in modulating the liver insulin resistance. According to the biopathway enrichment analysis of the 252 target genes using the KEGG classical biopathway database, the relative expression levels of gsk3bb, pik3r1, and pik3r3b were analyzed using RNA-seq. Compared to the HC group, a significant decrease in the relative expression levels of pik3r1 and pik3r3b was observed in HS_MS1 and HS_MS2 groups (p < 0.05). This study raised a presumption of the presence of ccr-miR-29a targeting pik3r1 or ccr-miR-143 targeting pik3r3 playing likely roles in Momordica charantia saponins remitting the liver insulin resistance.Conclusion: The findings will further deepen the understanding of the carbohydrate metabolism of common carp and provide an important scientific basis for the application of Momordica saponins as functional nutrients to alleviate insulin resistance of fish in fish culture.

The study aims to investigate the effects of dietary Astragalus membranaceus extract (AME) and Eucommia ulmoides leaf extract (ELE) supplementation on the growth performance, blood biochemistry, and antioxidant capacity of gibel carp (Carassius auratus gibelio var. CAS V, 10.01 g ± 0.24 g). Six experimental diets supplemented were marked as A0E0 (basic diet, 0% AME and 0% ELE), A0E0.1 (0% AME and 0.1% ELE), A0.02E0, A0.02E0.05, A0.02E0.1, A0.02E0.2 (0.02% AME with 0%, 0.05%, 0.1%, and 0.2% ELE). After 8 weeks, A0.02E0 diet significantly increased the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), and decreased the glucose (GLU), triglyceride content (TG), and total cholesterol (TC) of the plasma, the malonaldehyde (MDA) content of the liver, the A0E0.1 group significantly increased the total protein (TP) and albumin (ALB) content of the plasma, decreased the alanine aminotransferase (ALT) content of the plasma when compared with A0E0 group (Independent T-test: P

To investigate the mechanisms through which ferrous ion (Fe2+) addition improves the utilization of a cottonseed meal (CSM) diet, two experimental diets with equal nitrogen and energy content (low-cottonseed meal (LCM) and high-cottonseed meal (HCM) diets, respectively) containing 16.31% and 38.46% CSM were prepared. Additionally, the HCM diet was supplemented with graded levels of FeSO4·7H2O to establish two different Fe2+ supplementation groups (HCM + 0.2%Fe2+ and HCM + 0.4%Fe2+). Juvenile Ctenopharyngodon idellus (grass carps) (5.0 ± 0.5 g) were fed one of these four diets (HCM, LCM, HCM + 0.2%Fe2+ and HCM + 0.4%Fe2+ diets) for eight weeks. Our findings revealed that the HCM diet significantly increased lipid peroxide (LPO) concentration and the expression of lipogenic genes, e.g., sterol regulatory element binding transcription factor 1 (srebp1) and stearoyl-CoA desaturase (scd), leading to excessive lipid droplet deposition in the liver (p < 0.05). However, these effects were significantly reduced in the HCM + 0.2%Fe2+ and HCM + 0.4%Fe2+ groups (p < 0.05). Plasma high-density lipoprotein (HDL) concentration was also significantly lower in the HCM and HCM + 0.2%Fe2+ groups compared to the LCM group (p < 0.05), whereas low-density lipoprotein (LDL) concentration was significantly higher in the HCM + 0.2%Fe2+ and HCM + 0.4%Fe2+ groups than in the LCM group (p < 0.05). Furthermore, the plasma levels of liver functional indices, including alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and glucose (GLU), were significantly lower in the HCM + 0.4%Fe2+ group (p < 0.05). Regarding the expression of genes related to iron transport regulation, transferrin 2 (tfr2) expression in the HCM group and Fe2+ supplementation groups were significantly suppressed compared to the LCM group (p < 0.05). The addition of 0.4% Fe2+ in the HCM diet activated hepcidin expression and suppressed ferroportin-1 (fpn1) expression (p < 0.05). Compared to the LCM group, the expression of genes associated with ferroptosis and inflammation, including acyl-CoA synthetase long-chain family member 4b (acsl4b), lysophosphatidylcholine acyltransferase 3 (lpcat3), cyclooxygenase (cox), interleukin 1β (il-1β), and nuclear factor kappa b (nfκb), were significantly increased in the HCM group (p < 0.05), whereas Fe2+ supplementation in the HCM diet significantly inhibited their expression (p < 0.05) and significantly suppressed lipoxygenase (lox) expression (p < 0.05). Compared with the HCM group without Fe2+ supplementation, Fe2+ supplementation in the HCM diet significantly upregulated the expression of genes associated with ferroptosis, such as heat shock protein beta-associated protein1 (hspbap1), glutamate cysteine ligase (gcl), and glutathione peroxidase 4a (gpx4a) (p < 0.05), and significantly decreased the expression of the inflammation-related genes interleukin 15/10 (il-15/il-10) (p < 0.05). In conclusion, FeSO4·7H2O supplementation in the HCM diet maintained iron transport and homeostasis in the liver of juvenile grass carps, thus reducing the occurrence of ferroptosis and alleviating hepatic lipid deposition and inflammatory responses caused by high dietary CSM contents.

Abstract A 75-day rearing trial was designed to study the response of juvenile Megalobrama amblycephala to dietary methionine (Met) levels. Three practical diets with graded Met levels (0.40%, 0.84% and 1.28% dry matter) were prepared to feed the juvenile fish. The results showed that the 0.84% Met diet significantly improved the growth compared with 0.40% diets. Compared with 0.84% and 1.28% Met, 0.40% Met significantly increased the hepatic lipid content, while decreasing the muscular lipid and glycogen contents. 0.40% Met decreased the protein levels of phospho-Eukaryotic initiation factor 4E binding protein-1 (p-4e-bp1), 4e-bp1 and Ribosomal protein S6 kinase 1 in the liver, compared with 0.84% diet, while an increasing trend was observed in the muscle. Met supplementation tended to decrease and increase lipid synthesis in the liver and muscle, respectively, via changing mRNA levels of sterol regulatory element-binding protein 1, fatty acid synthetase and acetyl-CoA carboxylase. 1.28% dietary Met promoted fatty acid β-oxidation and lipolysis in both the liver and muscle by increasing carnitine palmitoyl transferase 1, peroxisome proliferator activated receptor alpha, lipoprotein lipase and lipase mRNA levels. Compared with 0.40% and 0.84% dietary Met, 1.28% Met enhanced the mRNA levels of hepatic gluconeogenesis related genes phosphoenolpyruvate carboxykinase (pepck), and glucose-6-phosphatase, and muscular glycolysis related genes phosphofructokinase (pfk), and pyruvate kinase (pk). The mRNA levels of hepatic pfk, pk and glucokinase were markedly downregulated by 1.28% Met compared with 0.84% level. Muscular pepck, glycogen synthase, and hepatic glucose transporters 2 mRNA levels were induced by 1.28% Met. Generally, deficient Met level decreased the growth of juvenile Megalobrama amblycephala, and the different nutrient metabolism responses to dietary Met were revealed in the liver and muscle.

Endogenous water pollution and excessive nitrogen in ponds have always been prominent problems threatening aquaculture. To solve this problem, a 70-day indoor simulation experiment was conducted. The snail Bellamya purificata was stocked at four different densities: 0, 15, 30, and 60 individuals/tank, represented as CON (control), LD (low density), MD (medium density), and HD (high density), respectively, to investigate the effects of B. purificata on the nitrogen occurrence forms and bacterial communities in the sediment. At the end of the experiment, the nitrate concentration was significantly higher, while the total nitrogen content was significantly lower in the MD group than in the other three groups. Ammonia monooxygenase activity was significantly lower in the CON group than in the other three groups, and hydroxylamine oxidase activity was significantly higher in the HD group than in the other three groups. The CON and MD groups showed the highest and lowest values in nitrate reductase activity, respectively. The hydroxylamine reductase activity decreased significantly with increasing density. Through 16S ribosomal RNA (rRNA) high-throughput sequencing, significantly affected bacterial communities by B. purificata were found. Alpha diversity results showed that, a significantly lower Shannon index was observed in the MD group than in the other three groups. The LD and MD groups showed the highest and lowest Chao1 index values, respectively. Phyla Nitrospinae and family Nitrosomonadaceae were significantly enriched in the HD and MD groups, respectively. Redundancy analysis (RDA) indicated a significant correlation between differential bacterial taxa and TN content. Predicted functional analysis based on FAPROTAX (Functional annotation of prokaryotic taxa) database showed that functional groups aerobic ammonia oxidation and aerobic nitrite oxidation were significantly enriched in the MD group. Overall, B. purificata significantly altered the bacterial community composition, increased hydroxylamine oxidase and ammonia monooxygenase activities, enhanced the bacterial nitrification process, and promoted the transformation of total nitrogen to nitrate. Moreover, B. purificata stocked at 30 and 60 individuals/tank appeared to have a significant promotion effect on the bacterial community and nitrogen occurrence forms in the sediment. Hence, co-culturing B. purificata may be a feasible and effective ecological restoration method to alleviate excess nitrogen and reduce water eutrophication.

To reveal the hepatic nutritional metabolism and gill immune responses adapted to cold stress in genetically improved farmed tilapia, four libraries were constructed and sequenced using Illumina sequencing technology. The results showed that sequencing generated a total of 556,770,992 raw reads, and approximately 40.9–45.6 M clean reads were obtained from each library. In the liver, 3757 differentially expressed genes (DEGs) were identified under cold stress, among which 1764 genes were upregulated and 1993 genes were downregulated. In the gill, a total of 3933 differentially expressed genes (DEGs) were identified under cold stress, among which 1847 genes were upregulated and 2086 genes were downregulated. Twenty-two DEGs were randomly selected for quantitative RT–PCR (qRT–PCR) analysis, and the results confirmed the reliability of the transcriptome analysis. Furthermore, the DEGs were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, and the results showed that most of the DEGs were involved in protein, lipid and carbohydrate metabolism in the liver and immune and apoptotic pathways in the gill. Moreover, plasma total protein (TP) and triglyceride (TG) contents were significantly lower, and plasma glucose (GLU), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly higher at lower temperatures compared with the control. In summary, these results indicated that cold stress activates hepatic gluconeogenesis and inhibits lipolysis to provide energy to the body, while reducing the efficiency of protein synthesis. Furthermore, the immune and apoptotic pathways were activated in the gill to enhance anti-apoptotic capacity when exposed to cold stress.

An M. salmoides fish meal diet was supplemented with 0 (CHL0, Control), 38 (CHL38), 76 (CHL76), 114 (CHL114), and 152 (CHL152) mg/kg C. vulgaris for 60 days, and their serum and intestinal samples were analyzed. The results showed that the albumin (ALB) and total protein (TP) contents were observably enhanced in the CHL76 group compared with the Control group. The intestinal glutathione (GSH) and glutathione peroxidase (GSH-Px) contents were enhanced significantly in the CHL76 group, while the total antioxidant capacity (T-AOC) was enhanced in the CHL38 group, compared with the Control group. However, supplementation of >76 g/kg C. vulgaris significantly inhibited the superoxide dismutase (SOD) activity in the intestines of M. salmoides. Moreover, the malondialdehyde (MDA) content was observably dropped in the CHL-supplemented groups compared with the Control group. Transcriptome analysis of the CHL76 and Control groups displayed a total of 1384 differentially expressed genes (DEGs). KEGG analysis revealed that these DEGs were enriched in apoptosis, cytokine–cytokine receptor interaction, tight junction (TJ), and phagosome signaling pathways, which were associated with improved intestinal immunity in the CHL76 group. Additionally, the DEGs enriched in the above pathways were also correlated with the antioxidant parameters, such as catalase (CAT), GSH, GSH-Px, SOD, T-AOC, and MDA. Therefore, our study found that dietary supplementation of C. vulgaris effectively enhanced the intestinal antioxidant capacity of M. salmoides by increasing antioxidant enzyme activity and decreasing MDA content. Additionally, dietary supplementation of C. vulgaris improved the intestinal immune status of M. salmoides by reducing proapoptotic and proinflammatory factors, increasing intestinal TJs- and phagosome-related genes expressions, and increasing the serum ALB and TP contents. Lastly, quadratic regression analysis of the serum biochemical indices (ALB and TP) and intestinal antioxidant parameters (GSH-Px and GSH) revealed that the optimal supplemental level of C. vulgaris in the M. salmoides diet was 58.25–77.7 g/kg.

Abstract Fish has poor utilization capacity for glucose metabolism. The possible reasons are related to the core regulatory elements of glucose metabolism: transport proteins. Studies on the species and functions of Sglt1 in aquatic animals are scarce, therefore further studies are needed. In this study, the full length of blunt snout bream (Megalobrama amblycephala) sglt1 (Masglt1) was 2965 bp including 5′-UTR region of 168 bp and a 3′-UTR region of 820 bp. Masglt1 have a highest sequence homology in Cypriniformes fish. MaSglt1 protein was identified as a transmembrane protein with 14 α-helix structures locating plasma membrane by the methods of predicted tertiary structure and immunohistochemical staining. MaSglt1 protein has a hollow channel forms which could be specifically coupled with two Na+ ions to recognize glucose and carry out transmembrane transport. High sglt1 mRNA was found in the intestine and kidney. The mRNA levels of intestinal sglt1 had a positive correlation with dietary starch levels at 3 h after feeding, and the mRNA was significantly higher than that at 24 h, however, the mRNA levels of renal sglt1 presented results opposite to those of intestinal sglt1. The mRNA levels of renal sglt1 had a positive correlation with dietary starch levels at 24 h after feeding, and the expression was significantly higher than that at 3 h. These results confirmed that Masglt11 was mainly found in the intestine and kidney and was located in the cell membrane, playing a role in glucose homeostasis.

Momordica charantia saponins (MCS) was supplemented to a high-starch diet to ssess the effect on the growth performance, glucose homeostasis modulating factors concerning the attenuated hyperglycemia, hyperlipemia and insulin resistance. Five iso-nitrogenous (30.48%) and iso-lipidic (5.41%) diets were formulated containing 30% starch (control group, HS), and were supplemented with 100 mg/kg (HS-MCS100), 400 mg/kg (HS-MCS400), 1600 mg/kg (HS-MCS1600) and 6400 mg/kg (HS-MCS6400) MCS on the basis of the HS diet. 450 common carp weighing (6.43 ± 0.02) g were randomly divided into 5 groups, with three replicates in each group and 30 fish in each replicate. Results revealed that dietary MCS effectively enhanced the growth and feed efficiency and significantly attenuated the glucose homeostasis and insulin resistance triggered by the HS diet. Moreover, 1600 mg/kg of MCS administration fulfilled more efficient and significant improvement of weight gain rate (WGR), specific growth rate (SGR), feed conversion rate (FCR), protein efficiency ratio (PER), protein and lipid deposition in the whole body. Alterations of serum biochemical indices revealed that 1600 mg/kg of MCS administration remarkably suppressed the hyperglycemia and hyperlipemia and elevated the insulin sensitivity. Enzyme activity and gene expression analysis of glycometabolism indicated that 1600 mg/kg of MCS administration could attenuate the hepatopancreas insulin resistance by enhancing glycolysis ability, promoting the glycogen synthesis and inhibiting the gluconeogenesis through activating PI3K/AKT signaling pathway. On all accounts detail, appropriate MCS administration have potential value in the alleviation of insulin resistance, thereby effectually maintain the glucose homeostasis and giving play to growth promoting effect for common carp fed with a high-carbohydrate diet.

This study aimed to determine whether water temperature and dietary protein levels played a role in regulating the growth and nutritional metabolism of juvenile grass carp (4.47 ± 0.01 g). Six dietary protein levels (18.20%, 24.32%, 30.60%, 36.42%, 43.27%, 49.49%) and two levels of water temperature (23 ℃ and 28 ℃) were used with a 6 × 2 experimental design method. After 60 days, the results demonstrated that appropriate dietary protein levels (30.60%, 23 ℃; 36.42%, 28 ℃) significantly increased the specific growth rate and weight gain rate of grass carp and significantly decreased the feed conversion ratio (P

The present study explored the effects of ferulic acid (FA) supplementation in cottonseed meal (CSM)-based diets on grass carp growth performance, feed utilization, liver antioxidation status, and intestinal physical barrier function. Here, four experimental diets supplemented with FA at graded levels (0, 50, 100 and 200 mg/kg) and CSM as the main protein source (384.6 g/kg feed) for an 8-week feeding trial. Our results indicated that 200 mg/kg FA supplementation in a CSM-based diet significantly improved growth performance [including final body weight (FBW), weight gain rate, and specific growth rate] and feed utilization [including feed conversion ratio and protein efficiency ratio] in grass carp (p < 0.05). The results of polynomial regression analysis based on FBW recommended that the optimal dose for FA supplementation was 204 mg/kg. Compared with that no FA supplementation, 200 mg/kg FA supplementation significantly reduced liver malondialdehyde levels and increased glutathione reductase activities (p < 0.05) and 100 mg/kg FA supplementation significantly increased liver total superoxide dismutase activities and reduced blood alanine transaminase levels (p < 0.05). Compared with the control group, 100 mg/kg FA supplementation also led to significantly increased mRNA expression of zo-1, zo-2, occludin, claudin-b, claudin-3, claudin-7a, and claudin-12, encoding intestinal tight junction proteins (p < 0.05). Notably, FA supplementation could reduce lipid deposition by regulating bile acid (BA) secretion. In this study, 100 and 200 mg/kg FA supplementation significantly increased blood and liver total BA levels, respectively (p < 0.05); 100 mg/kg FA also significantly activated mRNA expressions of fxr and cyp7a1 (p < 0.05). Furthermore, the whole-body composition results presented that FA treatment relieved lipid deposition, particularly 50 and 200 mg/kg FA supplementation (p < 0.05). Moreover, triglyceride and total cholesterol levels were significantly lower and high-density lipoprotein levels were significantly higher with 200 mg/kg FA supplementation than with no FA supplementation (p < 0.05). Taken together, the results indicated that FA may be a beneficial feed additive to boost fish growth performance and increase CSM utilization.

To evaluate the interactive effect of inclusion levels (IL) and preparation methods (PM) of myo-inositol (MI) on growth performance, hepatic antioxidant capacity and lipid metabolism of Cyprinus carpio var. jian, five isonitrogenous and isoenergetic diets were formulated at a high level of dietary fat content (11.3%, HF basic diet), supplemented with 400 mg/kg or 800 mg/kg of enzyme biocatalysis MI (E-MI) (400E-MI, 800E-MI) and chemical acid hydrolysis MI (C-MI) (400 C-MI, 800 C-MI). 300 healthy C. Carpio var. jian (1.5 ± 0.1 g) were randomly fed one of the five experimental diets in triplicates (20 fish per tank) for 66 days. After the 66 days feeding trial, the growth performance, plasma biochemistry, hepatic antioxidant enzyme activities, and gene expressions related to lipid metabolism were determined. Two-way ANOVA analysis showed that PM and IL of dietary MI had an interactive effect on growth performance, antioxidant capacity and lipid metabolism of C. Carpio var. jian. The IL significantly affected protein deposition rate (PDR), activities of hepatic CAT, T-SOD and GPx (P

This study assessed the potential applicability of Moringa oleifera leaf meal (MO) and fermented Moringa oleifera leaf meal (FMO) as feed supplements for aquatic animals. Five experimental diets, including the basal diet (control), 2.2% and 4.4% MO-supplemented diets (MO2 and MO4), and 2.2% and 4.4% FMO-supplemented diets (FMO2 and FMO4), were prepared for feeding Megalobrama amblycephala juveniles. After the eight-week feeding trial, the growth performance, muscle nutritional composition, plasma and hepatic biochemistry indicators were measured. The results demonstrated that MO and FMO had no detrimental effects on the growth performance of M. amblycephala juveniles. The muscle crude protein, crude lipid, and total free amino acids contents were significantly enhanced in the FMO4 group (p < 0.05). The liver acetyl-CoA carboxylase α mRNA level was significantly increased and the lipoprotein lipase mRNA level was markedly reduced in the FMO4 group (p < 0.05). Therefore, the FMO4 group exhibited a significant increase in plasma low-density lipoprotein cholesterol and triglyceride levels (p < 0.05). Compared to the control group, total superoxide dismutase and catalase activities were significantly increased in the FMO4 group (p < 0.05). The FMO2 and FMO4 groups exhibited an anti-inflammatory response by inhibiting the expression levels of toll-like receptor 4, nuclear factor-kappa B, and tumor protein P53 mRNA (p < 0.05). In conclusion, the 4.4% FMO treatment increased muscle crude protein content, enhanced lipogenesis, and improved the hepatic antioxidant abilities of M. amblycephala juveniles, while 2.2% FMO and 4.4% FMO improved the liver anti-inflammatory capacities.

To investigate the effects of replacing fishmeal with Spirulina (Arthrospira) platensis, juvenile blunt snout bream (Megalobrama amblycephala) (bodyweight 21.60 ± 0.44 g) were fed with six diets containing 0%(SP0), 0.75%(SP0.75), 1.5%(SP1.5), 3%(SP3), 6%(SP6), and 9.5%(SP9.5) of S. platensis for 65 days. It was found S. platensis improved growth performance, that the weight gain rate (WGR), protein efficiency ratio (PER) were highest following 3.0% S. platensis, and the feed conversion ratio (FCR) was lowest. Besides, the WGR of SP3 group was significantly higher than SP6 and SP9.5 groups, while the PER and FCR were significantly different from the SP6 group. S. platensis affected the apparent digestibility of crude lipid, which was higher in the SP9.5 group than the control and the SP0.75 groups, but the digestibility of methionine and cysteine were lowest in SP9.5 group. As for the muscle compositions, serine was significantly elevated in the SP1.5 group than the control group, and glycine was significantly increased in the SP3 group. The contents of lysine and valine in whole fish were significantly higher in the SP1.5 group than the SP0.75 group. The content of complement 4 in plasma was significantly lower in control group than the SP1.5–9.5 groups. The plasma aspartate transaminase activities and the malondialdehyde contents of SP6 and SP9.5 groups were significantly higher than the SP1.5 group. The liver peroxidase activity and total antioxidant capacity of SP9.5 group were significantly lower than control group. In summary, the inclusion of S. platensis could improve lipid digestion and immune response of M. amblycephala. 3.0% S. platensis inclusion in the diet (replacing 33.25% fishmeal) achieved the best growth performance and feed utilisation.

The aim was to evaluate the effects of increasing bacterial protein meal (BPM) (M. capsulatus, Bath) as a fishmeal replacer in the diets of GIFT. A total of 540 juveniles (initial weight 3 g) were allocated randomly to 18 outdoor floating cages (1 m 1 m 1 m) at 30 fish/cage for 56 days with diets (0, 17, 34, 51, 68 and 85 g/kg) prepared in triplicate. Weight gain rate, specific growth rate, feed intake, feed conversation ratio, and survival rate were not significantly affected across all diets (P > 0.05). Immunoglobulin M and albumin were significantly increased with an increase in BPM, while alanine transaminases, aspartate transaminases, and alkaline phosphatase showed no significant difference (P > 0.05). The activities of catalase, superoxide dismutase, glutathione peroxidase and glutathione showed no significant difference (P > 0.05). Meanwhile, total antioxidant capacity increased significantly, while malondialdehyde showed an opposite trend (P 0.05). However, nuclear factor-kappa B, tumor necrosis factor-α, interfelony, interleukin 8, interleukin 10 and interleukin 16 decreased significantly (P 0.05). In conclusion, our study has demonstrated that M. capsulatus Bath could improve the immune response without affecting the growth and antioxidant capacity in GIFT juveniles.

A 7-week rearing trial was designed to investigate the effects of Eucommia ulmoides leaf extract (ELE) on growth performance, body composition, antioxidant capacity, immune response, and disease susceptibility of diet-fed GIFT. The results showed that dietary ELE did not affect growth performance or whole-body composition (p > 0.05). Compared with the control group, plasma ALB contents increased in the 0.06% dietary ELE group (p < 0.05), and plasma ALT and AST activities decreased in the 0.08% dietary ELE group (p < 0.05). In terms of antioxidants, compared with GIFT fed the control diet, 0.06% dietary ELE upregulated the mRNA expression levels of Nrf2 pathway-related antioxidant genes, including CAT and SOD (p < 0.05), and 0.06% and 0.08% dietary ELE upregulated the mRNA levels of Hsp70 (p < 0.05). In terms of immunity, 0.06% dietary ELE suppressed intestinal TLR2, MyD88, and NF-κB mRNA levels (p < 0.05). Moreover, the mRNA levels of the anti-inflammatory cytokines TGF-β and IL-10 were upregulated by supplementation with 0.04% and 0.06% dietary ELE (p < 0.05). In terms of apoptosis, 0.06% and 0.08% ELE significantly downregulated the expression levels of FADD mRNA (p < 0.05). Finally, the challenge experiment with S. agalactiae showed that 0.06% dietary ELE could inhibit bacterial infection, and significantly improve the survival rate of GIFT (p < 0.05). This study demonstrated that the supplementation of 0.04–0.06% ELE in diet could promote intestinal antioxidant capacity, enhance the immune response and ultimately improve the disease resistance of GIFT against Streptococcus agalactiae.

The present study investigates the effects of dietary protein levels on glucolipid metabolism, immune function, and resistance to Streptococcus agalactiae of genetically improved farmed tilapia (GIFT) exposed to high temperature. Six practical diets were prepared to feed 360 fish (initial weight 43.78 ± 0.12 g) with graded protein levels (26.45%, 29.28%, 31.69%, 33.68%, 36.18%, and 38.75% dry matter). The results showed that 26.45% dietary protein significantly improved glycolysis by increasing PK mRNA levels, while the 29.28% and 31.69% dietary protein levels promoted gluconeogenesis by increasing PEPCK and G6Pase mRNA levels. For lipid metabolism, 26.45% dietary protein enhanced lipid synthesis by increasing PPAR-γ, SREBP1c, and FAS mRNA levels, while 31.69% dietary protein enhanced the level of lipolysis by increasing the PPAR-α and CPT1 mRNA levels. The highest plasma TG and TC contents were observed in the 29.28% and 31.69% dietary protein groups, respectively. In terms of antioxidants and immunity, the 31.69% dietary protein level activated the expression levels of HSP90 mRNA, thus increasing the expression levels of antioxidant-related genes (CAT, SOD, and GPx), and upregulating the anti-inflammatory factor IL-10 mRNA levels. In addition, regarding the antioxidant enzymes, the highest GSH content was found in the 29.28% dietary protein group, while the 31.69% dietary protein group had the maximum GSH-Px activity. The lowest plasma ALT and AST activities were observed in the 31.69% dietary protein group. Ultimately, the survival rate of juvenile GIFT fed 31.69% dietary protein was highest after a Streptococcus agalactiae challenge. Overall, 29.28–31.69% dietary protein was recommended in the diet of GIFT in a high-temperature environment.

The present study aimed to assess the role of tributyrin (TB) in regulating the growth and health status of juvenile blunt snout bream (Megalobrama amblycephala) through an 8-week feeding experiment. Six groups were fed experimental diets with added TB percentages of 0% (control group), 0.03%, 0.06%, 0.09%, 0.12% and 0.15%. The present results showed that TB supplementation in feed had some positive impacts on FW, WG, FCR and SGR, and the best results were found in the 0.06% TB group (P0.05). TB supplementation in feed increased antioxidant capacity and immunological capacity and attenuated the inflammatory response by increasing the activity of T-SOD, GPx, CAT and the levels of anti-inflammatory cytokines (IL-10 and TGF-β) and decreasing the levels of MDA and anti-inflammatory cytokines (TNF-α) (P0.05). The possible mechanism was that TB activated PI3K/Akt/Nrf2 and inhibits the NF-κB signaling pathway, further regulating the mRNA levels of key genes with antioxidant capacity and the inflammatory response; for example, it increased the mRNA levels of Nrf2, Cu/Zn-SOD, HO-1, CAT, Akt, PI3K, GPx, IL-10, and TGF-β and decreased the mRNA levels of NF-κB and TNF-α (P0.05). Evidence was presented that TB supplementation decreased the mortality rate caused by Aeromonas hydrophila challenge. In pathological examination, TB supplementation prevented hepatic and intestinal damage. Generally, TB supplementation improved the growth performance of juvenile blunt snout bream. Furthermore, TB supplementation activated PI3K/Akt/Nrf2 and inhibited the NF-κB signaling pathway, regulating health status and preventing hepatic and intestinal damage.

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.

A 60-day feeding trial was carried out to investigate the effects of the dietary carbohydrate-to-lipid ratio (CHO:L) on growth performance, plasma parameters and hepatic antioxidant status in ide (Leuciscus idus). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO:L ratios from 0.79 to 15.29. The final weight, weight gain (WG) and feed conversion ratio (FCR) were affected by the dietary CHO:L ratio, and the optimal values were found in fish fed a diet with a 3.66 ratio (P < 0.05). The hepatosomatic index and glycogen content were positively related to the dietary CHO:L ratio, and the whole body lipid content decreased with the increasing dietary CHO:L ratio (P < 0.05). Plasma alanine aminotransferase and aspartic transaminase activities and total protein, albumin, total triglyceride and glucose contents were similar among dietary treatment groups (P> 0.05). The lowest total cholesterol content was observed in fish fed with highest dietary CHO:L ratio (P < 0.05). Significantly lower malondialdehyde contents were observed in fish fed diets with 2.23 and 3.66 CHO: L ratios than in those fed diets with 0.79 or 15.29 CHO:L ratios. The highest values of superoxide dismutase, glutathione peroxidase and catalase activities, total antioxidant capacity and glutathione content were found in fish fed a diet with a 2.23 CHO:L ratio. The present results indicated that diets with a CHO:L ratio 2.23 is optimal for juvenile ide antioxidant status, and the optimal dietary CHO：L ratio was calculated to be 2.96 and 2.79, respectively, based on the broken-line regression analysis of WG or FCR.

An 8-week rearing trial was designed to appraise the dietary lysine levels on intestinal antioxidant capacity and immunity of grass carp fry. Six practical diets were prepared with graded levels of lysine (1.44, 1.79, 1.97, 2.44, 2.56 and 2.87% dry matter), and these diets were fed to grass carp fry. The results showed that the activities of intestinal antioxidant factors including catalase and glutathione peroxidase were markedly improved by the 2.44% dietary lysine compared with the control diet (1.44% dietary lysine) (P < 0.05). In terms of antioxidants, compared with the control diet, the 2.44% diet markedly upregulated the mRNA expression levels of target of rapamycin, S6 kinase1 and nuclear factor erythroid 2-related factor 2 pathway-related antioxidant genes, containing catalase and glutathione peroxidase 1α (P < 0.05) and downregulated the mRNA levels of Kelch-like ECH-associated protein 1 (P > 0.05). The mRNA levels of 4E-binding protein 2 showed the opposite trend compared with those of target of rapamycin, and the minimum value was observed in the group of 1.97% dietary lysine (P < 0.05). In terms of immunity, compared with the 1.44% diet, the 2.44% diet markedly suppressed the intestinal p38 mitogen-activated protein kinase and interferon γ2 mRNA levels (P < 0.05). Moreover, nuclear factor-kappa B p65, tumor necrosis factor α, interleukin 6, interleukin 8, and interleukin 15 mRNA levels all exhibited the same trend as p38 mitogen-activated protein kinase and interferon γ2; however, the difference among all the lysine treatments groups was not significant (P > 0.05). The anti-inflammatory cytokines transforming growth factor β2 and interleukin 4/13B mRNA levels in the intestine were remarkably upregulated by high dietary lysine levels (2.56 and 2.87%) (P < 0.05), and when the dietary lysine level reached 2.44%, the interleukin 4/13A mRNA levels were strikingly increased (P < 0.05). Overall, the data suggested that 2.44% dietary lysine could strengthen the immune and antioxidant capacities of grass carp fry via activating the target of rapamycin (TOR) signaling pathway, and suppressing the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway, which then improve the survival rate.

Dietary oxidized lipids are key perpetrator to accumulate excessive reactive oxygen species (ROS) that induce oxidative stress for animals. Immoderate oxidative stress dysregulates cell fate, perturbs cellular homeostasis, thereby interrupts metabolism and normal growth. Therefore, a 12-week feeding trial with fish oil (FO, control group), oxidized fish oil (OF), and emodin-supplemented (OF+E) diets was conducted to evaluate the therapeutic mechanism of emodin on metabolic and oxidative resistance in Megalobrama amblycephala liver. Morphologically, emodin remits oxidized fish oil-induced cellular constituents damage, evidenced by lipid droplets enlargement and accumulation, mitochondria rupture, and nucleus aggregation, which were functionally related to oxidative stress, metabolism, and cell fate determination. Consecutively, glucose, lipid, and amino acid metabolism were retained under emodin stimulation. Specifically, fatty acid metabolic genes optimized fatty acid utilization and metabolism, featured as total saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) alternation. Physiologically, inflammation, autophagy, apoptosis, as well as antioxidant capacity were alleviated by emodin. Interactively, fatty acid metabolism was correlated with antioxidant capacity; while the crosstalk and dynamic equilibrium between apoptosis and autophagy determine the cell fate under oxidative stress amelioration. Synergistically, Nrf2 and Notch signaling were active to antioxidant defense. In particular, oxidative stress blocked the crosstalk between Notch and Nrf2 signaling, while emodin rescued Notch-Nrf2 interaction to ameliorate oxidative stress. In conclusion, these results suggest that elevated ROS levels by oxidative stress activates Notch and Nrf2 signaling but intercepts Notch-Nrf2 crosstalk to stimulate cell fate and antioxidant program; dietary emodin alleviates oxidative stress and returns overall ROS levels to a moderate state to maintain homeostatic balance. The crosstalk between Notch and Nrf2 signaling might be the potential therapeutic target for emodin to ameliorate oxidative stress and metabolic disorder in M. amblycephala liver.

Facilitative glucose transporter 4 (GLUT4) plays a central role in mediating insulin function to increase glucose uptake in glucose metabolism homeostasis. In this study, the function and localization of GLUT4 in blunt snout bream (Megalobrama amblycephala) were first investigated, and then, the response measured as carbohydrate level, was analyzed. The results showed that the cDNA sequence of GLUT4 in blunt snout bream (MaGLUT4, GenBank accession no: MT447093) was 2868 bp in length, and the corresponding mRNA contained a 5′-UTR region of 513 bp and a 3′-UTR region of 837 bp. MaGLUT4 had an open reading frame of 1518 bp and was encoded by 505 amino acids. Its theoretical isoelectric point and molecular weight was 6.41 and 55.47 kDa, respectively. A comparison of these characteristics with BLASTP results from the NCBI database showed that MaGLUT4 had the highest homology with Cypriniformes fish, with MaGLUT4 and GLUT4 of other Cypriniformes clustered in the phylogenetic tree with other GLUT1–4 amino acid sequences. Compared with the results from the homo_sapiens and mus_musculus data sets, some mutations were observed in the GLUT4 amino acid sequence of these aquatic animals, including an FQQI mutation to FQQL, LL mutation to MM, and TELEY mutation to TELDY. MaGLUT4 was constitutively expressed in the muscle, intestine, and liver, with the highest mRNA level observed in muscle. Furthermore, the predicted tertiary structure and results of immunohistochemical staining showed that MaGLUT4 was a transmembrane protein primarily located in the plasma membrane, where it accounts for 60.9% of the total expressed, according to an analysis of subcellular localization. Blood glucose level peaked within 1 h, and the insulin level peaked at 6 h, while the mRNA and protein levels of GLUT4 showed an upward trend with an increase in feeding time and decreased sharply after 12 h. These results confirmed that MaGLUT4 was mainly distributed in muscles and crosses the cell membrane. The changes in the insulin, mRNA, and protein levels of MaGUT4 lagged far behind changes in blood glucose levels. This delay in insulin level changes and GLUT4 activation might be the important reasons for glucose intolerance of this fish species.

The goal of this study was to investigate the effects of dietary Cu on growth, antioxidant capacity and immune responses in juvenile blunt snout bream with histological examination. Fish were fed three practical diets containing graded copper levels ranging from 1.43 mg/kg-9.13 mg/kg for 10 weeks. The control diet (1.43 mg/kg) significantly improved the growth performance of blunt snout bream (P < 0.05). The 5.21 mg/kg dietary copper significantly increased immunoglobin M (IgM) and complement 3 (C3) content and significantly decreased the activity of alanine transaminase (ALT) in plasma (P < 0.05). The diets containing 5.21 and 9.13 mg/kg copper significantly increased albumin (ALB) content and significantly decreased triglyceride (TG) content (P < 0.05). Dietary copper supplementation improved antioxidant capacity and decrease the content of malondialdehyde (MDA) by regulating the activities of catalase (CAT), total superoxide dismutase (T-SOD) and copper zinc superoxide dismutase (Cu/Zn-SOD) (P < 0.05). With respect to the mRNA levels, the 5.21 mg/kg dietary copper significantly lowered the Kelch-like ECH associated protein 1 (Keap1) mRNA levels and significantly increased the nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA levels (P < 0.05). Furthermore, significant improvements in Cu/Zn-SOD, CAT and heat stress protein 70 (HSP70) mRNA levels were observed in fish fed the 5.21 and 9.13 mg/kg dietary coppers. The relative expression of HO-1 was significantly enhanced in fish fed the 5.21 mg/kg dietary copper (P < 0.05). Dietary copper supplementation affected nuclear factor-kappa B (NF-κB) expression, which further decreased the mRNA levels of pro-inflammatory cytokines, including tumour necrosis factor-alpha (TNF-α), interleukin 8 (IL-8) and interleukin 1β (IL-1β), and increased the mRNA levels of anti-inflammatory cytokines, including interleukin 10 (IL-10). With respect to histological examination, there were no obvious pathological differences among the three groups. Overall, our study indicated that suitable dietary copper supplementation could improve growth performance and antioxidant capacity and weaken the inflammatory response in blunt snout bream.

We hypothesized that the mitogenome of Gammarus lacustris (GL), native to the Qinghai-Tibet Plateau, might exhibit genetic adaptations to the extreme environmental conditions associated with high altitudes (greater than 3000 m). To test this, we also sequenced the mitogenome of Gammarus pisinnus (GP), whose native range is close to the Tibetan plateau, but at a much lower altitude (200–1500 m). The two mitogenomes exhibited conserved mitochondrial architecture, but low identity between genes (55% atp8 to 76.1% cox1). Standard (homogeneous) phylogenetic models resolved Gammaridae as paraphyletic, but ‘heterogeneous’ CAT-GTR model as monophyletic. In indirect support of our working hypothesis, GL, GP and Gammarus fossarum exhibit evidence of episodic diversifying selection within the studied Gammaroidea dataset. The mitogenome of GL generally evolves under a strong purifying selection, whereas GP evolves under directional (especially pronounced in atp8) and/or relaxed selection. This is surprising, as GP does not inhabit a unique ecological niche compared to other gammarids. We propose that this rapid evolution of the GP mitogenome may be a reflection of its relatively recent speciation and heightened non-adaptive (putatively metabolic rate-driven) mutational pressures. To test these hypotheses, we urge sequencing mitogenomes of remaining Gammarus species populating the same geographical range as GP.

Abstract This study evaluated the mechanisms governing insulin resistance, glucose metabolism and lipogenesis in juvenile fish fed with graded levels of dietary arginine. The results showed that, compared with the control group (0.87%), 2.31% dietary arginine level resulted in the upregulation of the relative gene expression of IRS-1, PI3K and Akt in the insulin signaling pathway, while 2.70% dietary arginine level led to inhibition of these genes. 1.62% dietary arginine level upregulated glycolysis by increasing GK mRNA level; 2.70% dietary arginine level upregulated gluconeogenesis and resulted in high plasma glucose content by increasing PEPCK and G6P mRNA level. Furthermore, 2.70% dietary arginine level significantly lowered GLUT2 and increased PK mRNA levels. 1.62% dietary arginine level significantly upregulated ACC, FAS and G6PDH mRNA levels in the fat synthesis pathway and resulted in high plasma TG content. These results indicate that 1.62% dietary arginine level improves glycolysis and fatty acid synthesis in juvenile blunt snout bream. However, 2.70% dietary arginine level results in high plasma glucose, which could lead to negative feedback of insulin resistance, including inhibition of IRS-1 mRNA levels and activation of gluconeogenesis-related gene expression. This mechanism seems to be different from mammals at the molecular level.

Hypoxia has important effects on biological activity in crustaceans, and modulation of energy metabolism is a crucial aspect of crustaceans’ ability to respond to hypoxia. The adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) enzyme is very important in cellular energy homeostasis; however, little information is known about the role of AMPK in the response of prawns to acute hypoxia. In the present study, three subunits of AMPK were cloned from the oriental river prawn, Macrobrachium nipponense. The full-length cDNAs of the α, β, and γ AMPK subunits were 1,837, 3,174, and 3,773 bp long, with open reading frames of 529, 289, and 961 amino acids, respectively. Primary amino acid sequence alignment of these three subunits revealed conserved similarity between the functional domains of the M. nipponense AMPK protein with AMPK proteins of other animals. The expression of the three AMPK subunits was higher in muscle tissue than in other tissues. Furthermore, the mRNA expression of AMPKα, AMPKβ, and AMPKγ were significantly up-regulated in M. nipponense muscle tissue after acute hypoxia. Probing with a phospho-AMPKα antibody revealed that AMPK is phosphorylated following hypoxia; this phosphorylation event was found to be essential for AMPK activation. Levels of glucose and lactic acid in hemolymph and muscle tissue were significantly changed over the course of hypoxia and recovery, indicating dynamic changes in energy metabolism in response to hypoxic stress. The activation of AMPK by hypoxic stress in M. nipponense was compared to levels of muscular AMP, ADP, and ATP, as determined by HPLC; it was found that activation of AMPK may not completely correlate with AMP:ATP ratios in prawns under hypoxic conditions. These findings confirm that the α, β, and γ subunits of the prawn AMPK protein are regulated at the transcriptional and protein levels during hypoxic stress to facilitate maintenance of energy homeostasis.

Hypoxia represents a major physiological challenge for prawns and is a problem in aquaculture. Therefore, an understanding of the metabolic response mechanism of economically important prawn species to hypoxia and re-oxygenation is essential. However, little is known about the intrinsic mechanisms by which the oriental river prawn Macrobrachium nipponense copes with hypoxia at the metabolic level. In this study, we conducted gas chromatography-mass spectrometry-based metabolomics studies and assays of energy metabolism-related parameters to investigate the metabolic mechanisms in the hepatopancreas of M. nipponense in response to 2.0 O2/L hypoxia for 6 and 24 h, and reoxygenation for 6 h following hypoxia for 24 h. Prawns under hypoxic stress displayed higher glycolysis-related enzyme activities and lower mRNA expression levels of aerobic respiratory enzymes than those in the normoxic control group, and those parameters returned to control levels in the reoxygenated group. Our results showed that hypoxia induced significant metabolomic alterations in the prawn hepatopancreas within 24 h. The main metabolic alterations were depletion of amino acids and 2-hydroxybutanoic acid and accumulation of lactate. Further, the findings indicated that hypoxia disturbed energy metabolism and induced antioxidant defense regulation in prawns. Surprisingly, recovery from hypoxia (i.e., reoxygenation) significantly affected 25 metabolites. Some amino acids (valine, leucine, isoleucine, lysine, glutamate, and methionine) were markedly decreased compared to the control group, suggesting that increased degradation of amino acids occurred to provide energy in prawns at reoxygenation conditions. This study describes the acute metabolomic alterations that occur in prawns in response to hypoxia and demonstrates the potential of the altered metabolites as biomarkers of hypoxia.

The effects of high carbohydrate diet on growth, serum physiological response, and hepatic heat shock protein 70 expression in Wuchang bream were determined at 25°C and 30°C. At each temperature, the fish fed the control diet (31% CHO) had significantly higher weight gain, specific growth rate, protein efficiency ratio and hepatic glucose-6-phosphatase activities, lower feed conversion ratio and hepatosomatic index (HSI), whole crude lipid, serum glucose, hepatic glucokinase (GK) activity than those fed the high-carbohydrate diet (47% CHO) (p

The effect of dietary carbohydrate (CHO) level on serum physiological response, hepatic antioxidant abilities and heat shock protein 70 (HSP70) expression of Wuchang bream (Megalobrama amblycephala) was studied. Two isonitrogenous (28.56% crude protein) and isolipidic (5.28% crude lipid) diets were formulated to contain 30% or 53% wheat starch. Diets were fed for 90 days to fish in triplicate tanks (28 fish per tank). At the end of feeding trial, significantly higher serum triglyceride level, insulin level, cortisol level, and malondialdehyde (MDA) content were observed in fish fed the 53% CHO diet, while significantly lower serum total protein content, alkaline phosphatase activity, superoxide dismutase activity and total antioxidative capacity were found in fish fed the 53% CHO diet compared with those fed the 30% diet. The relative level of hepatic heat shock protein 70 mRNA was significantly higher in the 53% CHO group than that in the 30% CHO at 6, 12 and 48 h after feeding. Ingestion of 53% dietary CHO impacts the nonspecific immune ability and causes metabolic stress in Megalobrama amblycephala.

The lethal concentration of water-borne copper in Chinese mitten crab Eriocheir sinensis larvae was tested by exposing the animals to 0, 0.1, 0.2, 0.3, 0.5 and 0.8 mg Cu L-1 at 20°C for 96 h. The 96-h median lethal concentration (LC50) and its corresponding 95% confident interval was estimated on zoea 1 larvae and megalopa larvae, respectively. Acute dissolved copper toxicity was higher for zoea 1 larvae (0.16 mg L-1) than for megalopa larvae (0.21 mg L-1). The antioxidant status, metallothionein-I mRNA expression and physiological response of the crab to copper toxicity was further investigated by exposing the megalopa larvae to 0, 0.08 and 0.16 mg Cu L-1 for 96 h. The superoxide dismutase activity, catalase activity, glutathione S-transferase (GST) activity and lipid peroxidation content of megalopa larvae increased concomitantly with the exposure time and copper concentration. MT-I mRNA expression levels were positively correlated with both the concentration and duration of copper exposure. The oxygen consumption and respiratory quotient of megalopa larvae in response to 0.16 mg L-1 copper were significantly higher than those in the control group after 96 h of exposure (P < 0.05). The results of this study highlight the potential effects of copper as a common stressor in E. sinensis larvae. MT-I and GST appear to be suitable biomarkers of environmental copper exposure stress in E. sinensis larvae

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