Yellow Catfish Pelteobagrus Fulvidraco Research Articles

Pathogen identification and epidemic factor analysis of yellow catfish, Pelteobagrus fulvidraco, red lower jaw disease

Since 2020, another type of epidemic disease, ‘red lower jaw disease’ (RLJD), has broken out in yellow catfish Pelteobagrus fulvidraco every spring in China, causing large-scale deaths and significant economic losses. This new disease has the characteristics of strong infectivity, high mortality and a single host. To prevent and control RLJD, epidemiological investigation, transmission electron microscopy (TEM), virome sequencing, Koch's rule verification and epidemic factor investigation were studied in this article. The clinical symptoms of diseased yellow catfish were pale gill filaments, hyperaemia and swelling of the spleen and kidney. TEM results revealed that a large number of 35–40 nm spherical virus particles without envelope structure were found in the cytoplasm of spleen cells. The liver, spleen and kidney of the diseased fish had serious lesions. After virome sequencing, the calicivirus reads in the unique virus reads accounted for 99.5% of the unique virus reads in the diseased fish, which provided a relevant reference value for identifying the pathogen of RLJD. The full-length sequence of yellow catfish calicivirus (YCCV) obtained at 7405 bp, including the RNA-helicase domain, RdRp-1 domain and d1iqqa domain. At the same time, both PCR and TaqMan fluorescence quantitative PCR detection method of YCCV were established. Through the artificial infection test, YCCV was verified as the pathogen for RLJD. It was also found that YCCV mainly harmed the fish within 1 year, whereas the fish above 2 years had good resistance. The water temperature of the RLJD outbreak was mainly concentrated at 18 °C–24 °C. In the current study, after YCCV was verified as the pathogen of RLJD, epidemic factors including fish age and water temperature were studied, to the best of our knowledge, for the first time to provide a relevant theoretical basis for the pathogenic mechanism and prevention and control measures of yellow catfish RLJD.

Enhancement of autophagy can alleviate oxidative stress, inflammation, and apoptosis induced by ammonia stress in yellow catfish Pelteobagrus fulvidraco

Ammonia in aquatic environments is toxic to fish, directly impacting their growth performance and development. Activation of autophagy can facilitate intracellular component renewal and enhance an organism's adaptability to adverse environments. Therefore, this study investigates the impact of autophagy on the yellow catfish under acute ammonia stress. In this study, the yellow catfish intraperitoneally injected with 0.9 % sodium chloride were placed with 0 (CON group) and 125 (HA group) mg/L T-AN (Total ammonia nitrogen) dechlorinated water. The yellow catfish intraperitoneally injected with 30 mg/kg fish CQ (Chloroquine, HA + CQ group) and 1.5 mg/kg fish RAPA (rapamycin, HA + RAPA group) were placed in dechlorinated water containing 125 mg/L T-AN. The results showed that activation of autophagy by injecting with RAPA can alleviate oxidative stress (catalase, superoxide dismutase, total antioxidant capacity significantly increased, H2O2 content significantly decreased), and inflammatory response (pro-inflammatory factors TNF-α, MyD88, IL 1-β gene expression decreased significantly), apoptosis (baxa, Bcl2, Tgf-β, Smad2, Caspase3, Caspase 9 gene expression decreased significantly) induced by ammonia stress. In addition, activation of autophagy in yellow catfish can enhance ammonia detoxification by promoting the urea cycle and synthesis of glutamine (the mRNA level of CPS Ⅰ, ARG, OTC, ASS, ASL, and GS increased in the HA + RAPA group). The data above demonstrates that activating autophagy can alleviate oxidative stress, inflammatory responses, and cell apoptosis induced by ammonia stress. Therefore, enhancing autophagy is proposed as a potential strategy to mitigate the detrimental impacts of ammonia stress on yellow catfish.

Different Responses of Histology, Antioxidant, and Inflammation in Gill and Kidney of Yellow Catfish Pelteobagrus fulvidraco under Three Dietary Fat Levels

This experiment investigated the influences of different dietary fat levels on histology, oxidative status, and immune response in gill and kidney of yellow catfish (Pelteobagrus fulvidraco). Three diets with different fat levels of 63.1 g/kg (low-fat, LF), 93.3 g/kg (medium-fat, MF), and 153.2 g/kg (high-fat, HF) were prepared to feed yellow catfish. The experiment continued for 56 days, and at the end of the experiment, gill and kidney tissues were sampled. As a result, both gill and kidney showed different degrees of tissue damage in HF group in terms of histology observation. HF increased the malondialdehyde content in gill but showed no effect on kidney, indicating that gill is more susceptible to injury than kidney under high-energy intake conditions. Additionally, HF diet significantly increased the activities of total-superoxide dismutase and catalase to eliminate excess peroxides both in gill and kidney. Moreover, HF diet significantly upregulated the expressions of pro-inflammatory cytokines (il6 and tnfα) and downregulated the expression of anti-inflammatory cytokines (il10), indicating that HF-diet-induced inflammatory response both in gill and kidney. These findings reveal the potential regulatory approach for fish gill and kidney health by dietary fat level, which will help to understand the adverse impacts of dietary lipid imbalance on the health of fish.

Effects of three short-chain fatty acids on growth, intestinal microbiota composition, and ammonia tolerance of juvenile yellow catfish Pelteobagrus fulvidraco

The objective of this research was to examine how the growth, ammonia tolerance, and intestinal microbiota composition of juvenile yellow catfish are affected by dietary supplementation of isobutyric acid (IBA), isovaleric acid (IVA), and 2-methylbutyric acid (2-MBA). During the 8-week trial, four groups were fed the basal diet (Control), and the basal diet supplementation with 0.25% IBA, IVA and 2-MBA, respectively. The research shows that the yellow catfish in the IBA and 2-MBA groups had a higher weight gain rate and specific growth rate than the control group, but feed conversion ratio has the opposite trend. Dietary supplementation of IBA and 2-MBA can significantly improve digestive enzymes activities (α-amylase, lipase, and trypsin) in intestinal tract and blood health (serum albumin increased, alanine transaminase and aspartate transaminase decreased). The up-regulation of IGF-1, Myod, and MyoG gene mRNA expression levels occurred significantly in the muscle tissue of the IBA, IVA, and 2-MBA groups, but IL 1 and IL8 genes in intestinal tract were significantly down-regulated. Supplementation of IBA, IVA and 2-MBA significantly increased the relative abundance of Candidatus Arthromitus, while decreased the relative abundance of Achromobacter, most notably in IBA group. After 96-h ammonia stress, cumulative mortality in IBA group was the lowest. Supplementing the diet of yellow catfish with IBA or 2-MBA can enhance their growth, digestive enzyme activity, and blood health status. Additionally, IBA can improve ammonia tolerance, which may be related to the increase abundance of Candidatus Arthromitus in intestine.

Effects of dietary sodium acetate on growth, intestinal microbiota composition, and ammonia tolerance of juvenile yellow catfish Pelteobagrus fulvidraco

Short-chain fatty acids (SCFAs), such as acetates, play a role in modifying metabolic disorders and regulating the homeostasis of the organism. In this study, the impact of dietary sodium acetate (SA) on growth, intestinal microbiota composition, and ammonia tolerance of yellow catfish. During a 56-day study, four groups of yellow catfish weighing an average of 2.72 ± 0.11 g were provided with diets containing varying proportions of SA. The diets included 0%, 0.1%, 0.2%, and 0.4% SA. Each batch consisted of three replicates, with each replicate containing 40 fish. The results indicated that dietary supplemented with 0.2% SA had significantly higher weight gain and specific growth rates than those in 0% and 0.1% groups. The feed efficiency ratio in 0% groups was significantly the highest. Dietary SA can significantly increase the activities of intestinal lipase, amylase, and pepsin, and the contents of liver total protein, immunoglobulin M, and 50% hemolytic complement, while decreasing the contents of liver triglyceride, glucose, high-density lipoprotein cholesterol, aspartate aminotransferase, alanine aminotransferase, tumor necrosis factor-α, interleukin-1, and interleukin-8, and the activities of liver superoxide dismutase, and catalase. In addition, dietary SA significantly increased the relative abundance of beneficial bacteria (Achromobacter) and production of butyrate, meanwhile decreasing the harmful bacterial (Rhodobacter) abundance. After the challenge, cumulative mortality in fish fed 0% SA diets was higher than in fish fed 0.1–0.5% SA diets after 96 h ammonia stress. Correlation analysis showed that the SA induced the enhancement of the metabolic efficiency of carbohydrates, amino acids, and lipids were also associated with the increased relative abundance of Achromobacter. In general, SA can function as a beneficial additive for enhancing growth, intestinal health, and ammonia tolerance in yellow catfish.

Effects of dietary lipid levels on fiber quality, lipidomic profiles, antioxidant and inflammation responses in muscle of yellow catfish Pelteobagrus fulvidraco

The present study explore the impacts of dietary lipid levels on fiber quality, lipidomic profiles, antioxidant and inflammation responses in muscle of yellow catfish. For this purpose, yellow catfish were fed with low-fat (LF), medium-fat (MF) and high-fat (HF) three different lipid levels diets for 8 weeks, and at the end of the feeding trial, muscle tissues were taken for analysis. We found that HF diet increased lipid deposition, lipogenesis and decreased fatty acid oxidation in muscle of yellow catfish. HF diet induced oxidative stress and inflammatory response in muscle therefore suppressed the proliferation and differentiation of myofibril. Lipidomic analysis detected 229 differentially abundant lipids (DALs) among three groups, and PCs, TGs/DGs and PEs as the predominant lipid species. Moreover, HF diet significantly decreased the abundance of SHP, LPE, PC, PE, PI, PG and PS species. Overall, these findings revealed that dietary lipid levels influence lipid metabolism and muscle quality by affecting lipid profile and oxidative stress status in muscle of yellow catfish, which provided novel insight into the lipid nutrition of freshwater fish.

Sodium butyrate improves the growth performance, intestinal immunity, and ammonia tolerance of yellow catfish Pelteobagrus fulvidraco by increasing the relative abundance of Candidatus_Arthromitus

The study aimed to analyze the effect of dietary sodium butyrate (SB) on intestinal digestive enzyme activity, liver physiological status, immune parameter, intestinal microbiota structure and composition, and ammonia tolerance in yellow catfish. Over the course of an 8-week experiment, four separate groups including 480 healthy male yellow catfish (1.52 ± 0.66 g) were fed diets containing varying concentrations of SB: 0, 0.05, 0.1, and 0.2%. Following this, an acute ammonia stress experiment that lasted for 96-h was conducted. The study showed that dietary supplementation of SB can improve growth performance and feed utilization (weight gain rate increased from 163.66 to 226.1%; specific growth rate increased from 1.73 to 2.11%/d; feed conversion rate decreased from 2.02 to 1.34), and increase intestinal digestive enzyme activity (lipase increased from 22.66 to 41.46 U/mg prot; amylase increased from 0.38 to 0.46 U/mg prot; pepsin increased from 10.13 to 12.83 U/mg prot). Plasma total protein (from 510.79 to 523.02 μg/mL), 50% hemolytic complement (from 35.46 to 40.46 U/mL), and immunoglobulin M (from 0.45 to 0.48 g/L) increased as dietary SB levels. On the contrary, plasma glucose (from 6.2 to 3.39 mmol/mL), high-density lipoprotein cholesterol (from 0.38 to 0.25 mmol/mL), aspartate aminotransferase (from 55.66 to 37.36 U/L), alanine aminotransferase (from 358.82 to 283.25 U/L), superoxide dismutase (from 163.84 to 147.13 U/mL), catalase (from 152.89 to 135.07 U/mL), tumor necrosis factor-α (from 67.58 to 62.13 pg/mL), interleukin-1 (from 40.07 to 30.96 pg/mL), and interleukin-8 (from 57.16 to 52.16 pg/mL) decreased with dietary SB levels. In addition, dietary supplementation of 0.2% SB significantly increased the relative abundance of Candidatus_Arthromitus in intestine by approximately 22-fold. To sum up, the utilization of SB has potential to enhance fish growth performance, elevate its physiological status, and improve its ability to tolerate acute ammonia toxicity. This is achievable by increasing the prevalence of Candidatus_Arthromitus in the intestine.

Characterization and expression analysis of seven lipid metabolism-related genes in yellow catfish Pelteobagrus fulvidraco fed high fat and bile acid diet

SREBPs, such as SREBP1 and SREBP2, were the key transcriptional factors regulating lipid metabolism. The processing of SREBPs involved many genes, such as scap, s1p, s2p, cideb. Here, we deciphered the full-length cDNA sequences of scap, srebp1, srebp2, s1p, s2p, cideb and cidec from yellow catfish Pelteobagrus fulvidraco. Their full-length cDNA sequences ranged from 1587 to 3884 bp, and their ORF length from 1191 to 2979 bp, encoding 396–992 amino acids. Some conservative domains were predicted, including the multiple transmembrane domains in SCAP, the bHLH-ZIP domain in SREBP1 and SREBP2, the ApoB binding region, ER targeting region and LD targeting region in CIDEb, the LD targeting region in the CIDEc, the conserved catalytic site and processing site in S1P, and the transmembrane helix domain in S2P. Their mRNA expression could be observed in the heart, spleen, liver, kidney, brain, muscle, intestine and adipose, but varied with tissues. The changes of their mRNA expression in responses to high-fat (HFD) and bile acid (BA) diets were also investigated in the brain, heart, intestine, kidney and spleen tissues. In the brain, HFD significantly increased the mRNA expression of seven genes (scap, srebp1, srebp2, s1p, s2p, cideb and cidec), and the BA attenuated the increase of scap, srebp1, srebp2, s1p, s2p, cideb and cidec mRNA expression induced by HFD. In the heart, HFD significantly increased the mRNA abundances of six genes (srebp1, srebp2, scap, s2p, cideb and cidec), and BA attenuated the increase of their mRNA abundances induced by HFD. In the intestine, HFD increased the cideb, s1p and s2p mRNA abundances, and BA attenuated the HFD-induced increment of their mRNA abundances. In the kidney, HFD significantly increased the scap, cidec and s1p mRNA expression, and BA diet attenuated the increment of their mRNA expression. In the spleen, HFD treatment increased the scap, srebp2, s1p and s2p mRNA expression, and BA diet attenuated HFD-induced increment of their mRNA expression. Taken together, our study elucidated the characterization, expression profiles and transcriptional response of seven lipid metabolic genes, which would serve as the good basis for the further exploration into their function and regulatory mechanism in fish.

Effects of dietary supplementation with manganese dioxide nanoparticles on growth, Mn metabolism and kidney health of yellow catfish Pelteobagrus fulvidraco

The present study was performed to investigate yellow catfish manganese (Mn) requirement with Mn dioxide nanoparticles (MnO2NPs) as Mn source, and to evaluate effects of dietary Mn on growth performance, Mn metabolism and kidney health. Using MnO2NPs as the Mn sources, six experimental diets were formulated with dietary Mn levels at 1.67, 4.35, 7.37, 13.63, 26.06 and 50.37 mg Mn/kg diet, respectively, and fed to yellow catfish for 8 weeks. Yellow catfish growth performance and feed intake were the highest in the group of 13.63 mg Mn/kg diet, and the lowest in the group of 1.67 mg Mn/kg diet; and the feed conversion rate showed opposite trend with growth performance. Dietary Mn addition increased Mn content in the whole body, kidney and serum. The mRNA abundances of dmt1, zip8 and znt10 increased with the increase of dietary Mn level. Yellow catfish fed high dietary MnO2NPs level had higher mRNA abundances of dynamin1, dynamin2, cav1, cltc and eps15. Dietary Mn excess damaged the kidney histology. Yellow catfish fed the 13.63 mg Mn/kg diet had higher T-AOC, T-SOD, Mn-SOD, CAT activities, and mRNA levels of sod1, sod2 and cat (antioxidant response), but lower mRNA abundances of grp78, ire1, perk and atf4 (endoplasmic reticulum stress), tnfα, il1β and il6 (inflammatory response). The broken-line analysis of WG and the linear regression of whole-body Mn retention against dietary Mn levels showed that optimal Mn requirement was 12.57 mg Mn/kg diet and 8.33 mg Mn/kg diet, respectively, with MnO2NPs as Mn source. For the first time, we explored the effects of dietary MnO2 nanoparticles on growth performance, Mn uptake and metabolism, antioxidant responses, endoplasmic reticulum stress and inflammatory responses of the kidney, and determined the optimal dietary Mn requirement of yellow catfish fed MnO2 nanoparticles-added diet.

Dietary chenodeoxycholic acid attenuates high-fat diet-induced growth retardation, lipid accumulation and bile acid metabolism disorder in the liver of yellow catfish Pelteobagrus fulvidraco.

This experiment was conducted to investigate whether dietary chenodeoxycholic acid (CDCA) could attenuate high-fat (HF) diet-induced growth retardation, lipid accumulation and bile acid (BA) metabolism disorder in the liver of yellow catfish Pelteobagrus fulvidraco. Yellow catfish (initial weight: 4·40 (sem 0·08) g) were fed four diets: the control (105·8 g/kg lipid), HF diet (HF group, 159·6 g/kg lipid), the control supplemented with 0·9 g/kg CDCA (CDCA group) and HF diet supplemented with 0·9 g/kg CDCA (HF + CDCA group). CDCA supplemented in the HF diet significantly improved growth performance and feed utilisation of yellow catfish (P < 0·05). CDCA alleviated HF-induced increment of hepatic lipid and cholesterol contents by down-regulating the expressions of lipogenesis-related genes and proteins and up-regulating the expressions of lipololysis-related genes and proteins. Compared with the control group, CDCA group significantly reduced cholesterol level (P < 0·05). CDCA significantly inhibited BA biosynthesis and changed BA profile by activating farnesoid X receptor (P < 0·05). The contents of CDCA, taurochenodeoxycholic acid and glycochenodeoxycholic acid were significantly increased with the supplementation of CDCA (P < 0·05). HF-induced elevation of cholic acid content was significantly attenuated by the supplementation of CDCA (P < 0·05). Supplementation of CDCA in the control and HF groups could improve the liver antioxidant capacity. This study proved that CDCA could improve growth retardation, lipid accumulation and BA metabolism disorder induced by HF diet, which provided new insight into understanding the physiological functions of BA in fish.

MiR-20a-5p targeting mfn2-mediated mitochondria-lipid droplet contacts regulated differential changes in hepatic lipid metabolism induced by two Mn sources in yellow catfish

Understanding the hazards of different forms of metal elements provided innovative insights into their toxicity and environmental risk assessment. To date, few studies had been conducted to investigate the differential effects and mechanisms of MnO2 NPs and MnSO4, two widely distributed environmental pollutants, on hepatic toxicity and lipid metabolism since lipid metabolism-relevant parameters were broadly used as biomarkers for risk assessment of hazardous contaminants. Thus, using yellow catfish Pelteobagrus fulvidraco, an ecologically and economically important freshwater fish as the model, the present study investigated the differential effects and mechanisms of MnO2 NPs and MnSO4 influencing hepatic lipid metabolism. Compared to MnSO4, MnO2 NPs increased hepatic Mn content, induced lipotoxicity, up-regulated the mRNA expression of lipogenic genes, increased peridroplet mitochondrial (PDM) contents, intensified the contact between mitochondria and lipid droplets (LDs), and downregulated miR-20a-5p abundance. Importantly, miR-20a-5p targeted mfn2, which mediated the contact between mitochondria and LDs and influenced changes in lipid metabolism induced by MnO2 NPs. Mechanistically, the direct Mfn2-Plin2 binding and Mfn2 GTPase activity promoted the MnO2 NPs-induced interactions between mitochondria and LDs, which in turn influenced MnO2 NPs-induced changes in hepatic lipid metabolism. For the first time, our findings indicated the significant differences between the changes in body metabolism induced by nanoparticles and inorganic elements, which helped to illuminate different mechanisms governing the responses of aquatic vertebrates to hazardous metal pollutants (MnO2 NPs and MnSO4).

Molecular Identification and Expression Analysis of an Intelectin Gene in the Yellow Catfish Pelteobagrus fulvidraco (Siluriformes: Bagridae)

Intelectins (ITLNs) are a family of calcium-dependent lectins with carbohydrate-binding capacity, are distributed across various vertebrates, and play an important role in the innate immune response against pathogen infection. The yellow catfish Pelteobagrus fulvidraco (Siluriformes: Bagridae) is an economically important fish in China. The aim of this study was to quantify the gene expression of ITLN in response to pathogen-associated molecular patterns (PAMPs) stimulation. Here, the ITLN gene of P. fulvidraco was characterized and named PfITLN. The full-length cDNA of PfITLN was 1132 bp, including a 5’-untranslated region (UTR) of 140 bp, a 3’-UTR of 110 bp, and an open reading frame (ORF) of 882 bp encoding a polypeptide of 293 amino acids, which contains a signal peptide and two fibrinogen-related domains (FReDs). PfITLN had a molecular weight of 32.39 kDa with a theoretical pI of 5.03. The deduced PfITLN amino acid sequence had 81%, 64%, and 55% homology with Ictalurus furcatus, Danio rerio, and Homo sapiens, respectively. Moreover, the predicted tertiary protein structure of PfITLN was highly similar to that of other animals, and phylogenetic analysis showed that the PfITLN protein was close to those of other Teleostei. Real-time quantitative reverse transcription-PCR (qRT-PCR) analysis showed PfITLN expression in all examined tissues, with the highest abundance seen in the liver, followed by the head kidney, spleen, trunk kidney, and muscle. After PAMP infection with lipopolysaccharide (LPS) and polyriboinosinic polyribocytidylic acid (poly I:C), the expression levels of PfITLN were significantly upregulated at different time points. These results suggested that PfITLN might be involved in innate immunity.

Molecular characterization, spatiotemporal expression patterns of fatty acid elongase (elovl8) gene, and its transcription changes in response to different diet stimuli in yellow catfish (Pelteobagrus fulvidraco)

Elongase of very long-chain fatty acid 8 (Elovl8) is a new member identified in the Elovl family that is involved in the synthesis of highly unsaturated fatty acids (HUFAs). However, the evolutionary and physiological roles of this enzyme are still largely unknown. In the present study, the elovl8 gene was identified and characterized from yellow catfish Pelteobagrus fulvidraco, and then its evolutionary and molecular characteristics as well as transcriptional changes in response to various nutritional status were determined. Results showed that the open reading frame (ORF) of elovl8 was 795 bp in length, encoding a protein of 264 amino acids. Multiple sequences alignment showed that the yellow catfish Elovl8 was highly conserved with other homologs in teleosts, sharing similar structural characteristics (including six conserved transmembrane α-helical domains, four conserved elongase motifs, and three highly conserved cysteine residues). Meanwhile, comparisons of genetic synteny confirmed that the elovl8 gene identified from the yellow catfish was the homolog of elovl8b in other teleosts, and thus, the elovl8a gene was lost in the genome of the yellow catfish. Gene structure analysis revealed that the elovl8b gene contained eight exons and seven introns, which was highly conserved in teleosts, implying the functional conservation among various fish species. Tissue distribution analysis detected by real-time quantitative PCR (RT-qPCR) showed that the elovl8 gene was extensively expressed in all detected tissues except eyes, with high expression levels in the intestine and liver. Temporal expression analysis revealed that the expression level of elovl8 was stably expressed in the early 12 h after fertilization, and then dramatically decreased at 24, 48, 72, and 96 h after fertilization, implying that elovl8 is required for HUFA biosynthesis in the early development stages. Functional experiments showed that the expression of the elovl8 gene was stimulated after feeding with egg yolk but was not obviously affected after feeding with halogenated worms, indicating that diets full of HUFAs can inhibit the expression of elovl8 in yellow catfish. Our findings will help us to better understand the evolutionary and functional characteristics of elovl8 in teleosts, and lay a solid basis for investigating the regulation mechanism of HUFA biosynthesis.

Interactive effect of dietary vitamin D3 and zinc (Zn) on growth performance, Zn metabolism, and intestinal health of yellow catfish Pelteobagrus fulvidraco

Both vitamin D3 (VD3) and zinc (Zn) are essential micronutrients to fish, and VD3 can regulate Zn uptake and metabolism in various animals. However, the interactive effect of VD3 and Zn on growth performance, Zn metabolism, and intestinal health remains largely unknown in fish. The study formulated four experimental diets to culture yellow catfish, i.e., basic VD3 addition without extra Zn addition (control), basic VD3 addition with extra Zn addition (Zn group), high VD3 addition without extra Zn addition (VD3 group), and high VD3 and Zn addition (Zn + VD3 group). Four experimental groups contain Zn and VD3 contents at 41.15 mg/kg + 1027 IU/kg (control), 94.77 mg/kg + 1033 IU/kg (Zn group), 41.04 mg/kg + 16,047 IU/kg (VD3 group), and 94.89 mg/kg + 16,109 IU/kg (Zn + VD3 group), respectively. The experiment continued for 10 weeks. Dietary Zn and VD3 interacted to affect specific growth rate (SGR), Zn content and mRNA expression of Zn metabolism (zip4, zip9, zip14, znt1, znt2, mtf-1, and mt), SUMOylation-relevant genes (sae1, ubc9, pias1, sumo1, senp2, and senp5), tight junction-relevant genes (claudin-4, zo1, zo2, zo3, and jam2a), antioxidant (nrf2 and cat) and inflammatory genes (il1b and il8). Compared to the control, high dietary Zn addition increased intestinal mRNA expression of zip4, znt1, znt2, mt, sae1, ubc9, pias1, sumo1, claudin4, zo1, zo2, and jam2a and il1b, and Zn contents, but decreased mRNA expression of zip9, senp2, senp5, nrf2 and cat. Compared to high Zn addition in the diets, Zn and VD3 co-addition increased SGR, Zn contents, and mRNA expression of zip4, znt1, znt2, mt, mtf-1, senp2, senp5, claudin4, zo1, zo2, zo3, jam2a, nrf2 and cat, but decreased mRNA expression of zip9, zip14, sae1, ubc9, pias1, sumo1 and il1b. Dietary Zn and VD3 co-addition interacted to influence Cu/Zn-SOD, CAT and GPx activities, T-AOC, MDA content. Compared to control, high dietary Zn addition decreased intestinal Cu/Zn-SOD, CAT, GPx activities and T-AOC but increased MDA content. Compared to extra Zn addition in the diets, Zn and VD3 co-addition increased Cu/Zn-SOD, CAT and GPx activities as well as T-AOC but decreased MDA content. Based on these observations, our study indicated that high dietary Zn addition influenced Zn metabolism and SUMOylation modification, damaged the tight junction, induced oxidative stress and inflammatory responses in the intestine, and dietary vitamin D3 addition promoted growth performance and alleviated high dietary Zn-induced negative effects on the intestine of yellow catfish. Significance of relevanceOur study elucidated the innovative insights into the interaction of Zn and VD3 in fish, which provided the important references for dietary Zn and VD3 addition in aquafeeds.

Characterization of fifteen key genes involved in iron metabolism and their responses to dietary iron sources in yellow catfish Pelteobagrus fulvidraco

BackgroundIron is an essential metal element for organisms, whose metabolism is regulated by many genes and also dietary iron sources. However, the characterization, distribution and the responses of iron metabolism-related genes to different iron sources were not clear in fish. MethodsThe full-length cDNA sequences of fifteen iron metabolism-relevant genes (tf, tfr1, hp, fpn1, ho1, ho2, tfr2, hjv, hepcidin, fth, ftl, ftm, irp1, irp2 and hif2α.) were obtained via 3′ and 5′ RACE PCR from yellow catfish, a widely distributed freshwater teleost in China and other Asian countries. Their molecular characterizations were analyzed via the bioinformatic methods. Real-time quantitative PCR was used to explore their mRNA distribution in nine tissues. Their mRNA expression responses in four tissues (heart, brain, kidney and gill) were explored in yellow catfish fed diets with five iron sources, including ferrous sulfate (FeSO4), ferrous bisglycinate (Fe-Gly), ferrous chloride (FeCl2), ferric citrate (Fe-CA) and ferric oxide nanoparticles (Fe2O3NPs). ResultsCompared with mammals and other teleost, these members shared similar domains. Their mRNAs were expressed in nine tested tissues, but mRNA levels varied. Yellow catfish fed the diets containing Fe-Gly and Fe2O3NPs had higher iron contents in heart, brain, kidney and gill. Meantime, different dietary iron sources addition affected their mRNA expression differentially in brain, heart, kidney and gill. It should be pointed out that only three biological replicate tanks were used in the present feeding treatment, and more biological replicate tanks (more than five) should be emphasized in further researches. ConclusionTaken together, our study identified fifteen iron metabolism-relevant genes, explored their mRNA expression in nine tissues, and their mRNA expression in the responses to different dietary iron sources in four tissues, indicating their important regulatory function in iron metabolism and homeostasis.

Effects of ammonia and roxithromycin exposure on skin mucus microbiota composition and immune response of juvenile yellow catfish Pelteobagrus fulvidraco

As an inevitable factor in aquaculture, ammonia plays a critical role in macrolide antibiotic resistance, leading to accumulating of antibiotic-resistant bacteria in fish skin mucus. In this study, four experimental groups were implemented to test the effects of ammonia alone or in combination with roxithromycin for 28 days on skin mucus microbial composition and the immune response of yellow catfish: CON (control), AN (50.00 mg L−1 total ammonia nitrogen, TA-N), ROX (100 μg L−1 roxithromycin), and HR (50.00 mg L−1 TA-N, 100 μg L−1 ROX). This study demonstrated that ammonia or roxithromycin exposure resulted in increased plasma ammonia content and decreased total antioxidant capacity. Compared with AN group, the combined exposure of ammonia and roxithromycin inhibited the skin mucus immune response. Microbial composition analysis showed that combined exposure of ammonia and roxithromycin had no significant effect on skin mucus α-diversity as compared with CON group. The abundance of Cetobacterium, Rhizobiales_Incertae_Sedis_uncultured and Acinetobacter was increased significantly with the combined effect of ammonia and roxithromycin, these bacteria may be potentially antibiotic-resistant. As compared with CON group, the combined exposure of ammonia and roxithromycin did not affect skin goblet cell counts. This study suggests that combined exposure to ammonia and ROX increases the risk of the emergence of antibiotic-resistant bacteria.

MnO2 nanoparticles and MnSO4 differentially affected hepatic lipid metabolism through miR-92a/acsl3-dependent de novo lipogenesis in yellow catfish Pelteobagrusfulvidraco

With the increasing production and use of MnO2 NPs and MnSO4 in various fields, their discharge into the aquatic environment is inevitable, which poses potential threats to aquatic organisms and humans. However, to date, few studies have been conducted to investigate the potential mechanism of the toxicity of MnO2 NPs, and a comprehensive understanding of the differences between this mechanism and the toxicity mechanism of inorganic Mn (MnSO4) is still lacking. Since lipid metabolism-relevant parameters have been widely recognized as novel biomarkers for risk assessment of environmental contaminants, the present study investigated the differential mechanisms of how MnO2 NPs and MnSO4 affect hepatic lipid metabolism in a freshwater fish yellow catfish. Compared to MnSO4, dietary MnO2 NPs caused liver injury, increased hepatic lipid accumulation and induced lipotoxicity, and up-regulated mRNA expression of de novo lipogenic genes. Moreover, MnO2 NPs downregulated the expression of miR-92a and miR-92b-3p, microRNAs involved in regulation of lipid metabolism, in the liver. Mechanistically, we found that acls3, an acetyl-coenzyme A synthetase, is target gene of miR-92a, and miR-92a-acsl3-dependent de novo lipogenesis contributes to lipid accumulation and lipotoxicity induced by MnO2 NPs. Collectively, these findings provided novel insights into mechanism whereby miRNAs mediate nanoparticles- and inorganic Mn-induced hepatic lipotoxicity and changes of lipid metabolism in vertebrates. Our findings also shed new perspective for ecotoxicity and ecological risk of MnO2 NPs and MnSO4 in aquatic environment.

Haemolytic Bacillus subtilis, a potential pathogen of hemorrhage disease in farmed yellow catfish Pelteobagrus fulvidraco

The hemorrhagic disease has become a major bottleneck in yellow catfish Pelteobagrus fulvidraco aquaculture. Yet scarce information is available on Bacillus subtilis as a pathogen of hemorrhagic disease in cultured yellow catfish. In this study, a virulent isolate, temporarily named HS5, was isolated from hemorrhagic disease-infected cultured yellow catfish, and was identified phenotypically and molecularly as B. subtilis. In addition, isolate HS5 showed an LD50 value of 5.20×106 CFU/ml in yellow catfish, exhibited beta-haemolytic activity, harbored the virulent entFM gene, and displayed high susceptibility to enrofloxacin and florfenicol in aquaculture use. To the best of our knowledge, this is the first report of B. subtilis as a pathogen of hemorrhagic disease in farmed yellow catfish.

Effects of dietary leucine on growth, antioxidant capacity, immune response, and inflammation in juvenile yellow catfish Pelteobagrus fulvidraco.

The experiment was conducted to investigate the effects of dietary leucine on growth, antioxidant capacity, immune response, and inflammation in juvenile yellow catfish. Five diets were formulated to contain five dietary leucine levels: 12.00 (control), 19.00, 26.00, 33.00, and 40.00gkg-1. Each diet was randomly assigned to triplicate groups of 30 juvenile fish (5.02 ± 0.15g) twice daily to apparent satiation for 56days. Weight gain rate, specific growth rate, and activities of liver superoxide dismutase, glutathione peroxidase, and serum lysozyme, as well as immunoglobulin M content, significantly increased with increase in dietary leucine levels up to 26.00gkg-1, but those values decreased significantly with a further increase in dietary leucine. On the contrary, the lowest malondialdehyde content was found in 26.00 and 33.00gkg-1 leucine groups. The expression levels of IGF 1 and MYF 5 genes in muscle were significantly upregulated with increase in dietary leucine levels up to 26.00gkg-1, but the expression of MSTN level showed the opposite trend. The lowest expression levels of IL 8 and TNFɑ genes in the liver were found in 26.00gkg-1 leucine groups. The quadratic regression analysis on weight gain, specific growth rate, and feed conversion ratio against dietary leucine levels indicated that the optimal dietary leucine requirement was estimated to be 26.84-27.00gkg-1of the dry diet.

Interactive influences of dietary selenium and oxidized fish oil on growth, nutritional composition, muscle development, antioxidant responses and selenoprotein expression in the muscle of yellow catfish Pelteobagrus fulvidraco

The current study is conducted to determine the influences of dietary selenium (Se) and oxidized fish oil (OFO) on growth, nutritional composition, muscle development, antioxidant responses and selenoprotein expression in the muscle of yellow catfish. We used the 2 × 2 factorial experimental design, which included two dietary Se levels at 0.25 (adequate) and 0.5 (high) mg Se/kg diets, and each Se level had fresh fish oil (FFO) and OFO, respectively. The experiment continued for 10 weeks. Compared to FFO group, dietary OFO reduced final body weight (FBW), specific growth rate (SGR) and weight gain (WG), and the contents of n-6 polyunsaturated fatty acid (PUFA), 18: 2n-6, 20: 4n-6, n-3 PUFA, 20: 5n-3, 22: 6n-3 and total PUFA, the diameters of muscle fibers >80 μm, mRNA expression of mef2d, myf5, myod, s6kb and mTOR, and the ratio of p-mTOR to mTOR protein expression, but increased feed conversion rate (FCR), muscle lipid content, malic enzyme (ME) and isocitrate dehydrogenase (ICDH) activities, the number of the muscle fiber with the diameter lower than 50 μm; high dietary Se addition alleviated OFO- induced variations of these indices mentioned above. Dietary OFO also reduced muscle catalase (CAT) and glutathione peroxidase (GPX) activities and total antioxidant capacity (AOC), and mRNA expression of gpx1, gpx2, gpx3, selenoe, selenok and selenos, but increased total superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and NRF2 protein expression, and high dietary Se addition alleviated OFO-induced changes of these parameters involved in antioxidant responses and selenoprotein expression in the muscle of yellow catfish. Based on these observations above, dietary Se addition alleviated OFO-induced lipogenesis, and reversed the OFO-induced inhibition of muscle growth and development, and oxidative damage of muscle. Our study provides new mechanistic insights into the Se and OFO interaction in fish. Statement of relevanceThe biological basis through which dietary OFO and Se diets interacted to affect muscle metabolism and physiology is scarce. Our study indicated that dietary Se could alleviate OFO-induced negative effects on muscle metabolism and physiology, which will be helpful to the feed formulation and fish farm.