Dietary choline regulates antibacterial activity, inflammatory response and barrier function in the gills of grass carp (Ctenopharyngodon idella)

Proteomics and metabolomics analysis of American shad (Alosa sapidissima) liver responses to heat stress

The dramatic changes in the global climate pose a major threat to the survival of many organisms, including fish. To date, the regulatory mechanisms behind the physiological responses of fish to temperature changes have been studied, and a comprehensive analysis of the regulatory mechanisms of temperature tolerance will help to propose effective strategies for fish to cope with global warming. In this study, we investigated the expression profiles of proteins and metabolites in liver tissues of American shad (Alosa sapidissima) corresponding to different water temperatures (24 °C, 27 °C and 30 °C) at various times (1-month intervals) under natural culture conditions. Proteomic analysis showed that the expression levels of the heat shock protein family (e.g. HSPE1, HSP70, HSPA5 and HSPA.1) increase significantly with temperature and that many differentially expressed proteins were highly enriched especially in pathways related to the endoplasmic reticulum, oxidative phosphorylation and glycolysis/gluconeogenesis processes. In addition, the results of conjoint metabolomics and proteomics analysis suggested that the contents of several important amino acids and chemical compounds, including L-serine, L-isoleucine, L-cystine, choline and betaine, changed significantly under high-temperature environmental stress, affecting the metabolic levels of starch, amino acid and glucose, which is thought to represent a possible energy conservation method for A. sapidissima to cope with rapid changes in external temperature. In summary, our findings demonstrate that living under high temperatures for a long period of time leads to different physiological defense responses in A. sapidissima, which provides some new ideas for analyzing the molecular regulatory patterns of adaptation to high temperature and also provides a theoretical basis for the subsequent improvement of fish culture in response to global warming.

Dietary choline activates the Ampk/Srebp signaling pathway and decreases lipid levels in Pacific white shrimp (Litopenaeus vannamei)

An 8-week feeding trial was conducted in Pacific white shrimp (Litopenaeus vannamei) to evaluate the effects of dietary choline supplementation on choline transport and metabolism, hepatopancreas histological structure and fatty acid profile, and regulation of lipid metabolism. Six isonitrogenous and isolipidic diets were formulated to contain different choline levels of 2.91 (basal diet), 3.85, 4.67, 6.55, 10.70 and 18.90 g/kg, respectively. A total of 960 shrimp (initial weight, 1.38 ± 0.01 g) were distributed randomly into twenty-four 250-L cylindrical fiber-glass tanks, with each diet assigned randomly to 4 replicate tanks. The results indicated that dietary choline significantly promoted the deposition of choline, betaine and carnitine (P < 0.05). The diameters and areas of R cells, total lipid and triglyceride contents in hepatopancreas, and triglyceride and non-esterified fatty acid contents in hemolymph were negatively correlated with dietary choline level. The contents of functional fatty acids in hepatopancreas, the activity of acetyl-CoA carboxylase (Acc), and the mRNA expression of fas, srebp and acc were highest in shrimp fed the diet containing 4.67 g/kg choline, and significantly higher than those fed the diet containing 2.91 g/kg, the lowest level of choline (P < 0.05). The number of R cells, content of very low-density lipoprotein (VLDL), activities of carnitine palmitoyl-transferase (Cpt1), lipoprotein lipase and hepatic lipase, and the mRNA expression levels of cpt1, fabp, fatp, ldlr, and ampk in hepatopancreas increased significantly as dietary choline increased (P < 0.05). In addition, hepatopancreas mRNA expression levels of ctl1, ctl2, oct1, badh, bhmt, ck, cept, and cct were generally up-regulated as dietary choline level increased (P < 0.01). In conclusion, dietary choline promoted the deposition of choline and its metabolites by up-regulating genes related to choline transport and metabolism. Moreover, appropriate dietary choline level promoted the development of hepatopancreas R cells and maintained the normal accumulation of lipids required for development, while high dietary choline not only promoted hepatopancreas lipid export by enhancing VLDL synthesis, but also promoted fatty acid β-oxidation and inhibited de novo fatty acid synthesis by activating the Ampk/Srebp signaling pathway. These findings provided further insight and understanding of the mechanisms by which dietary choline regulated lipid metabolism in L. vannamei.

An emerging role of arecoline on growth performance, intestinal digestion and absorption capacities and intestinal structural integrity of adult grass carp (Ctenopharyngodon idella)

Arecoline is an alkaloid with important pharmacological effects in the plant areca nut, which has been demonstrated to be an agonist of muscarinic receptors (M receptor). This study explored the influences of dietary arecoline on growth performance, intestinal digestion and absorption abilities, antioxidant capacity, and the apical junction complex (AJC) of adult grass carp (Ctenopharyngodon idella). Adult grass carp (608 to 1512 g) were fed at 6 graded levels of dietary arecoline (0, 0.5, 1.0, 1.5, 2.0, and 2.5 mg/kg diet) for 9 weeks. The results suggested that appropriate dietary supplementation of arecoline (1.0 mg/kg) increased growth parameters and intestinal growth in adult grass carp (P < 0.05), enhanced digestion and absorption capacities (P < 0.05), up-regulated muscarinic receptor 3 (M3) mRNA level (P < 0.05), increased the content of neuropeptide fish substance P (P < 0.05), improved antioxidant capacity by activating the Keap1a/Nrf2 signaling pathway (P < 0.05), reduced intestinal mucosal permeability (P < 0.05), and increased mRNA levels of tight junction (TJ) and adherent junction AJ-related proteins in fish by inhibiting the RhoA/ROCK signaling pathway (RhoA/ROCK/MLCK/NMII) (P < 0.05). In addition, the appropriate arecoline supplementation for adult grass carp was determined to be 1.20, 1.21, 1.07, and 1.19 mg/kg based on percentage weight gain, lipase activity, serum diamine oxidase, and protein carbonyl, respectively. Overall, to the best of our knowledge, we investigated for the first time the effects and possible mechanisms of dietary arecoline on intestinal digestive and absorptive capacities and structural integrity in fish and evaluated the appropriate level of supplementation.

Dietary Soybean Lecithin Improves Growth, Immunity, Antioxidant Capability and Intestinal Barrier Functions in Largemouth Bass Micropterus salmoides Juveniles

This study evaluated the effects of dietary soybean lecithin (SBL) on the growth, haematological indices, immunities, antioxidant capabilities, and inflammatory and intestinal barrier functions because little information of dietary SBL could be obtained in juvenile largemouth bass (Micropterus salmoides). The fish were fed identical diets except for SBL added at 0, 2, 4 and 8%. It was found that 4 and 8% SBL significantly increased fish weight gain and daily growth rate (p < 0.05), while 4% SBL was optimal for enhancing RBC, HGB, PLT, MCV, MCH, WBC and MON in blood, and ALB and ALP in serum (p < 0.05). SBL (4%) also significantly elevated the antioxidant enzymes activities of T-SOD, CAT, GR, GPx, GST and T-AOC and GSH contents; increased mRNA transcription levels of Nrf2, Cu/Zn-SOD, CAT, GR, GST3 and GPx3; and decreased MDA contents. Keap1a and Keap1b levels were markedly down-regulated (p < 0.05). SBL (4%) significantly enhanced levels of the immune factors (ACP, LZM and C3) and the mRNA expression levels of innate immune-related genes (C3, C4, CFD, HEPC and MHC-I) compared with the control groups (0%) (p < 0.05). SBL (4%) significantly increased IgM and T-NOS in the intestine (p < 0.05) and significantly decreased levels of TNF-α, IL-8, IL-1β and IFN-γ and increased TGF-β1 at both transcription and protein levels in the liver and intestine (p < 0.05). The mRNA expression levels of MAPK13, MAPK14 and NF-κB P65 were significantly decreased in the intestine in the 4% SBL groups (p < 0.05). Histological sections also demonstrated that 4% SBL protected intestinal morphological structures compared with controls. This included increased intestinal villus height and muscular thickness (p < 0.05). Furthermore, the mRNA expression levels of the intestinal epithelial cell tight junction proteins (TJs) (ZO-1, claudin-3, claudin-4, claudin-5, claudin-23 and claudin-34) and mucin-5AC were significantly up-regulated in the 4% SBL groups compared with the controls (p < 0.05). In conclusion, these results suggested that 4% dietary SBL could not only improve growth, haematological indices, antioxidant capabilities, immune responses and intestinal functions, but also alleviate inflammatory responses, thereby providing reference information for the feed formulations in cultured largemouth bass.

Serial Extraction Technique of Rich Antibacterial Compounds in Sargassum cristaefolium Using Different Solvents and Testing their Activity

Background:

Sargassum cristaefolium, as one of the brown seaweeds locally found in Indonesia, is extracted using the serial technique employing different solvents.

Methods:

S. cristaefolium powder (50 mesh) was extracted with three different solvents, including hexane, ethyl acetate, and methanol. S. cristaefolium powder residue was dried prior to serial re-extraction using different solvents. Three serial extracts were obtained and named as 1-stage extract, 2-stage extract, and 3-stage extract. Besides, a single-step extract (i.e., extraction using only methanol) was produced to be compared with three serial extracts in antibacterial activity tests (against E. coli and S. aureus). The three serial extracts were detected for their antibacterial compounds using GC-MS, LC-HRMS, and FT-IR.

Results:

The 3-stage extract exhibited the highest extraction yield. On S. aureus, the inhibition zone in all extracts was not significantly different. On E.coli, the highest inhibition zone (5.42±0.14 mm) was of the 3-stage extract; indeed, it was higher than both antibiotic and a single- step extract. Antibacterial compounds, such as phenol, 9-Tricosene(Z)-, palmitic acid, and oleamide, were present in all extracts. Other antibacterial compound types, both the 1-stage and 2-stage extracts, contained 7 types, whilst the 3-stage extract contained the most types (11 types). Particularly, hexyl cinnamic aldehyde, betaine and several cinnamic aldehyde groups were detected only in the 3-stage extract comprising the dominant area. The carboxylic acid groups were detected in all extracts to confirm the fatty acid structure.

Conclusions:

The serial extraction technique could produce the 3-stage extract which exhibited the strongest antibacterial activity and contained the richest antibacterial compounds.

Short-term exposure to polymethylmethacrylate nanoplastics alters muscle antioxidant response, development and growth in Sparus aurata

Polymethylmethacrylate (PMMA) plastic fragments have been found abundant in the environment, but the knowledge regarding its effects on the physiology of aquatic animals is still poorly studied. Here the short-term (96 h) effects of waterborne exposure to PMMA nanoplastics (PMMA-NPs) on the muscle of gilthead sea bream (Sparus aurata) fingerlings was evaluated at a concentration range that includes 0.001 up to 10 mg/L. The expression of key transcripts related to cell stress, tissue repair, immune response, antioxidant status and muscle development, together with several biochemical endpoints and metabolic parameters. Results indicate that exposure to PMMA-NPs elicit mildly antioxidant responses, enhanced the acetylcholinesterase (AChE) activity, and inhibited key regulators of muscle development (growth hormone receptors ghr-1/ghr-2 and myostatin, mstn-1 transcripts). However, no effects on pro-inflammatory cytokines (interleukin 1β, il1β and tumor necrosis factor α, tnfα) expression nor on the levels of energetic substrates (glucose, triglycerides and cholesterol) were found.

Molecular cloning and expression mechanism of Mnp65 in Megalobrama amblycephala response to Aeromonas hydrophilia challenge

p65 is one of the important subunits of the inflammation-related transcription factor NF-κB. In the present study, we cloned and identified the p65 from Megalobrama amblycephala (Mnp65) by homologous cloning and RACE technique. The full-length Mnp65 cDNA consisted of 2331 bp, and included one open reading frame encoding a 604-amino acid putative protein. The protein sequence included a DNA binding motif, a well conserved N-terminal Rel-homology domain (RHD), and a C-terminal IG-like plexins transcription (IPT). Mnp65 was closely related with the other p65 proteins of Cypriniformes and clearly distinct from that of Perciformes and Salmoniformes in terms of sequence homology. Mnp65 homodimer may interact with IκBα in the IPT domain based on the predicted 3D structure of IκBα/Mnp65 complex. Mnp65 was ubiquitously expressed in M. amblycephala tissues, and the highest levels were detected in muscle and liver. Intragastric infection with Aeromonas hydrophila caused respiratory burst and cytokine storm from 8 h to 48 h, showing significantly higher level of respiratory burst activities and significantly high cytokines levels, such as TNF-α, IL-1β, IL-6, IL-8 etc., compared to 0 h. In addition, the bacterial challenge downregulated the IkBα, and upregulated Mnp65 and TNF-α in the liver. IkBα-Mnp65 was regulated by the negative feedback of cytokine storm, to increase IkBα and decrease Mnp65. Then cytokine storm was relieved at 96 h. Finally, severe intestinal inflammation was observed from 24 h to 48 h after infection, characterized by extensive villous necrosis, epithelial hyperplasia and lymphocyte infiltration, all of which were relieved at 96 h. Taken together, Mnp65 plays a crucial role in the physiological response of teleost fish to bacterial infection.

Dietary Choline-Enhanced Skin Immune Response of Juvenile Grass Carp Might Be Related to the STAT3 and NF-kB Signaling Pathway (Ctenopharyngodon idella)

To investigate the effects and potential mechanisms of dietary choline on immune function in the skin of juvenile grass carp (Ctenopharyngodon idella), fish were fed different diets containing different levels of choline (142. 2, 407.4, 821.6, 1215.8, 1589.3, and 1996.6 mg/kg) for 70 d and then sampled after a 6-d challenge test. The results exhibited that dietary choline (1) advanced the contents of phosphatidylcholine (PC), betaine, and choline in grass carp skin (P < 0.05) and upregulated the mRNA abundance of choline transporter high-affinity choline transporter 1 (CHT1), choline transporter-like protein 1 (CTL1), and choline transporter-like protein 5 (CTL5), indicating that dietary choline could increase the contents of choline which might be connected with choline transporters in the grass carp skin; (2) receded skin rot symptom after infection with A. hydrophila (Aeromonas hydrophila), increased the levels of IgM, C4, and C3 and the activities of acid phosphatase (ACP) and lysozyme (LZ), raised mucin2, β-defensin, hepcidin, and LEAP-2B mRNA abundance (rather than LEAP-2A), downregulated pro-inflammatory cytokine mRNA abundance (IFN-γ2, IL-15, TNF-α, IL-6, IL-12P40, and IL-1β) in skin of juvenile grass carp (P < 0.05), and upregulated anti-inflammatory cytokine mRNA abundance (IL-10, IL-4/13A, TGF-β1, IL-11, and IL-4/13B) in grass carp skin (P < 0.05), demonstrating that choline enhanced the skin immune function; and (3) downregulated the mRNA abundance of IKKγ, NF-κBp52, IKKβ, c-Rel, NF-κBp65, STAT3b2, STAT3b1, JAK1, and JAK2 as well as protein level of NF-κBp65, p-STAT3 Tyr705, and p-STAT3 Ser727 in nucleus and inhibited the mRNA and protein level of IkBα (P < 0.05), indicating that choline-enhanced immune function might be relevant to the JAK1, 2 /STAT3, and NF-κB signaling pathway in fish skin. In conclusion, choline enhanced the skin immune function which might be related to JAK1, 2/STAT3, and NF-κB signaling molecules in fish. Furthermore, based on immune indices of grass carp (9.28-108.97 g) skin (C3 and IgM contents as well as ACP activities), the choline requirements were estimated to be 1475.81, 1364.24, and 1574.37 mg/kg diet, respectively.

The growth performance and non-specific immunity of juvenile grass carp (Ctenopharyngodon idella) affected by dietary alginate oligosaccharide

The effects of alginate oligosaccharides (AOs) on the growth performance and non-specific immunity of juvenile grass carp (Ctenopharyngodon idella) were investigated by performing a 60-day feeding trial. Four trial diets were formulated and supplemented with different doses of AOs (0, 100, 200 and 400 mg/kg). Triplicate groups of grass carp were fed with one of the diets twice daily. The grass carps fed with diets containing an appropriate dose of AOs for 60 days exhibited higher survival rates; body weight gains; specific growth rates; resistance to Aeromonas hydrophila; superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities; and serum total protein, lysozyme, alkaline phosphatase, complement C3, complement C4 and interleukin-10 expression levels and lower feed conversion ratios and malondialdehyde, alanine aminotransferase, aspartate aminotransferase, IL-1β expression, IL-8 expression and tumor necrosis factor-α expression levels than the control group (p < 0.05). Based on the effects of AOs on growth performance and survival percent, the optimum dose of AOs was 200 mg/kg. Results indicate that AOs as a dietary supplement enhances the growth performance and non-specific immunity of grass carps and their resistance to diseases.

Supplemental Choline Modulates Growth Performance and Gut Inflammation by Altering the Gut Microbiota and Lipid Metabolism in Weaned Piglets

BACKGROUND

Whether dietary choline and bile acids affect lipid use via gut microbiota is unclear.

OBJECTIVES

This study aimed to investigate the effect of choline and bile acids on growth performance, lipid use, intestinal immunology, gut microbiota, and bacterial metabolites in weaned piglets.

METHODS

A total of 128 weaned piglets [Duroc × (Landrace × Yorkshire), 21-d-old, 8.21 ± 0.20 kg body weight (BW)] were randomly allocated to 4 treatments (8 replicate pens per treatment, each pen containing 2 males and 2 females; n = 32 per treatment) for 28 d. Piglets were fed a control diet (CON) or the CON diet supplemented with 597 mg choline/kg (C), 500 mg bile acids/kg (BA) or both (C + BA) in a 2 × 2 factorial design. Growth performance, intestinal function, gut microbiota, and metabolites were determined.

RESULTS

Compared with diets without choline, choline supplementation increased BW gain (6.13%), average daily gain (9.45%), gain per feed (8.18%), jejunal lipase activity (60.2%), and duodenal IL10 gene expression (51%), and decreased the mRNA abundance of duodenal TNFA (TNFα) (40.7%) and jejunal toll-like receptor 4 (32.9%) (P < 0.05); additionally, choline increased colonic butyrate (29.1%) and the abundance of Lactobacillus (42.3%), while decreasing the bile acid profile (55.8% to 57.6%) and the abundance of Parabacteroides (75.8%), Bacteroides (80.7%), and unidentified-Ruminococcaceae (32.5%) (P ≤ 0.05). Compared with diets without BA, BA supplementation decreased the mRNA abundance of colonic TNFA (37.4%), NF-κB p65 (42.4%), and myeloid differentiation factor 88 (42.5%) (P ≤ 0.01); BA also increased colonic butyrate (20.9%) and the abundance of Lactobacillus (39.7%) and Faecalibacterium (71.6%) and decreased that of Parabacteroides (67.7%) (P < 0.05).

CONCLUSIONS

Choline supplementation improved growth performance and prevented gut inflammation in weaned piglets by altering gut microbiota and lipid metabolism. BA supplementation suppressed intestinal inflammation with no effect on growth performance, which was associated with changed gut microbiota and metabolites.

The regulatory effects of pyridoxine deficiency on the grass carp (Ctenopharyngodon idella) gill barriers immunity, apoptosis, antioxidant, and tight junction challenged with Flavobacterium columnar

The effects of dietary pyridoxine (PN) on the gill immunity, apoptosis, antioxidant and tight junction of grass cap (Ctenopharyngodon idella) were investigated in this study. Fish were fed semi-purified diets containing graded levels of PN for 10 weeks, and then challenged with Flavobacterium columnare by bath immersion exposure for 3 days. The results indicated that compared with the optimal PN level, PN deficiency resulted in a decline in the antimicrobial compound production of gill. In addition, PN deficiency up-regulated the pro-inflammatory cytokines and down-regulated the anti-inflammatory cytokines gene expression, which might be associated with the enhanced nuclear factor κB p65 and the inhibited target of rapamycin signalling pathways, respectively, suggesting that PN deficiency could impair gill immune barrier function. Furthermore, PN deficiency (1) induced cell apoptosis, which may be partly associated with the (apoptotic protease activating factor-1, Bcl-2 associated X protein)/caspase-9 and c-Rel/tumor necrosis factor α (rather than FasL)/caspase-8 mediated apoptosis pathway. (2) Inhibited Kelch-like ECH-associating protein 1a/NF-E2-related factor 2 mRNA expression, decreased the mRNA expression and activities of antioxidant enzymes, increased the levels of reactive oxygen species, protein carbonyl and malondialdehyde. (3) Increased the mRNA expression level of myosin light chain kinase, which may be result in the down-regulation of tight junction complexes such as zonula occludens 1, occludin and claudins (expect claudin-12 and claudin-15). These results suggest that PN deficiency could impair gill physical barrier function. In summary, dietary PN deficiency could cause the impairment of gill barrier function associated with immunity, apoptosis, antioxidant and tight junction, which may result in the increased the susceptibility of fish to pathogenic bacteria. Moreover, based on the gill rot morbidity, LZ activity and MDA content, the dietary PN requirements for grass cap were estimated to be 4.85, 4.78 and 4.77 mg kg^-1 diet, respectively.

Integrated omics analysis of sweat reveals an aberrant amino acid metabolism pathway in Vogt-Koyanagi-Harada disease

Vogt-Koyanagi-Harada (VKH) disease is an autoimmune disease leading to visual impairment. Its pathogenic mechanisms remain poorly understood. Our purpose was to investigate the distinctive protein and metabolic profiles of sweat in patients with VKH disease. In the present study, proteomics and metabolomics analysis was performed on 60 sweat samples (30 VKH patients and 30 normal controls) using liquid chromatography tandem mass spectrometry. Parallel reaction monitoring (PRM) analysis was used to validate the results of our omics analysis. In total, we were able to detect 716 proteins and 175 metabolites. Among them, 116 proteins (99 decreased and 17 increased) were observed to be significantly different in VKH patients when compared to controls. Twenty-one differentially expressed metabolites were identified in VKH patients, of which 18 included choline, L-tryptophan, betaine and L-serine were reduced, while the rest were increased. Our multi-omics strategy reveals an important role for the amino acid metabolic pathway in the pathogenesis of VKH disease. Significant differences in proteins and metabolites were identified in the sweat of VKH patients and, to some extent, an aberrant amino acid metabolism pathway may be a pathogenic factor in the pathogenesis of VKH disease.

Dietary choline supplementation attenuated high-fat diet-induced inflammation through regulation of lipid metabolism and suppression of NFκB activation in juvenile black seabream (Acanthopagrus schlegelii)

The present study aimed to investigate whether dietary choline can regulate lipid metabolism and suppress NFκB activation and, consequently, attenuate inflammation induced by a high-fat diet in black sea bream (Acanthopagrus schlegelii). An 8-week feeding trial was conducted on fish with an initial weight of 8·16 ± 0·01 g. Five diets were formulated: control, low-fat diet (11 %); HFD, high-fat diet (17 %); and HFD supplemented with graded levels of choline (3, 6 or 12 g/kg) termed HFD + C1, HFD + C2 and HFD + C3, respectively. Dietary choline decreased lipid content in whole body and tissues. Highest TAG and cholesterol concentrations in serum and liver were recorded in fish fed the HFD. Similarly, compared with fish fed the HFD, dietary choline reduced vacuolar fat drops and ameliorated HFD-induced pathological changes in liver. Expression of genes of lipolysis pathways were up-regulated, and genes of lipogenesis down-regulated, by dietary choline compared with fish fed the HFD. Expression of nfκb and pro-inflammatory cytokines in liver and intestine was suppressed by choline supplementation, whereas expression of anti-inflammatory cytokines was promoted in fish fed choline-supplemented diets. In fish that received lipopolysaccharide to stimulate inflammatory responses, the expression of nfκb and pro-inflammatory cytokines in liver, intestine and kidney were all down-regulated by dietary choline compared with the HFD. Overall, the present study indicated that dietary choline had a lipid-lowering effect, which could protect the liver by regulating intrahepatic lipid metabolism, reducing lipid droplet accumulation and suppressing NFκB activation, consequently attenuating HFD-induced inflammation in A. schlegelii.

The growth performance and nonspecific immunity of juvenile grass carp (Ctenopharyngodon idella) affected by dietary Porphyra yezoensis polysaccharide supplementation

This study aims to investigate the effects of dietary Porphyra yezoensis polysaccharides (PPs) on growth performance and nonspecific immunity of juvenile grass carp (Ctenopharyngodon idella). Four hundreds of juvenile grass carps were randomly divided into four groups, i.e. one control group received basal diet and three treatment groups received diets supplemented with three different levels of PPs (1, 3, and 5 g kg^-1) and tested for growth performance, survival percent, intestine digestive-enzyme activities, superoxide dismutase (SOD) activity, catalase (CAT) activity, glutathione peroxidase (GPx) activity, serum total protein, lysozyme, alkaline phosphatase, complement C3 and complement C4 and resistance to Aeromonas hydrophila of juvenile grass carp. After 60 days of feeding, the diet supplemented with an appropriate dose of PPs significantly increased growth performance, survival percent, intestine digestive-enzyme activities, SOD activity, CAT activity, GPx activity, serum lysozyme, alkaline phosphatase, complement C3, and complement C4 and resistance to Aeromonas hydrophila of juvenile grass carp compared with the control group and the optimum dose of PPs was found to be 3 g kg^-1. Results showed that dietary PPs can improve growth performance and nonspecific immunity of juvenile grass carps and can thus be used as a diet supplement for them.

Effects of dietary soybean lecithin on growth performance, blood chemistry and immunity in juvenile stellate sturgeon (Acipenser stellatus)

An eleven weeks feeding trial was conducted to determine the effects of different levels of dietary soybean lecithin (SBL) on growth performance, blood chemistry and immunity in juvenile stellate sturgeon (Acipenser stellatus). Fish were fed seven isoproteic (44% crude protein) and isolipidic (17% crude fat) diets containing graded levels of SBL: 0 (control), 1, 2, 4, 6, 8 and 10%. Results showed that dietary SBL supplementation significantly improved the final body weight (BW) and weight gain (WG). Fish fed 6% SBL showed the highest BW and WG values in comparison to fish fed the control diet (P < 0.05), whereas increasing SBL levels above 6% had little practical benefit in terms of somatic growth performance. The inclusion of SBL in diets significantly improved the immune response as data from lysozyme, total Ig levels, alternative complement, phagocytic and bactericidal activities indicated (P < 0.05). The broken-line regression analysis of immunological variable revealed that depending on the parameter considered, the optimal SBL levels in diets for stellate sturgeon juveniles varied. In particular, dietary SBL levels requirements in stellate sturgeon when considering the phagocytic activity rate were determined at 3.3%, whereas 4.1-4.2% were recommended when considering data from lysozyme, alternative complement and bactericidal activities. In contrast, the highest minimum dietary SBL content was estimated at 6.9% when data from total Ig levels were considered. These results indicated that dietary PLs are required for boosting innate immunity in stellate sturgeon, although their minimal level changed depending on the immunological parameter considered. Therefore, we assume that SBL levels comprised between 3.3 and 6.9% may be used as a prophylactic measure to improve the health status in stellate sturgeon. Red blood cell count, hemoglobin and hematocrit levels increased with increasing dietary SBL levels, especially in those sturgeons fed the diet with 6% SBL (P < 0.05). In addition, white blood cell counts significantly increased as dietary SBL levels increased from 4 to 8% in comparison to the control group. Blood biochemistry was also affected by different dietary SBL levels. In particular, significantly higher levels of glucose, cholesterol, HDL and triglycerides were detected in fish fed >6%, >4%, >2% and 2% SBL, respectively (P < 0.05). Based on somatic growth parameters, blood chemistry and systemic immunity parameters, diets containing ca. 6% SBL are recommended for juvenile stellate sturgeon.

Plasma immune protein analysis in the orange-spotted grouper Epinephelus coioides: Evidence for altered expressions of immune factors associated with a choline-supplemented diet

This study aimed to unravel the regulatory roles of choline in activating immune responses and disease resistance of the orange-spotted grouper Epinephelus coioides. Fish were fed a choline-supplemented diet at 1 g kg^-1 of feed for 30 days. Fish fed a fish meal basal diet without choline-supplement served as controls. At the end of the feeding trial, fish were challenged with Vibrio alginolyticus. Meanwhile, plasma proteomics of fish in each group were also evaluated by two-dimensional gel electrophoresis (2-DE), and differentially expressed proteins were identified by tandem mass spectrophotometry (MS/MS), then a Western blot analysis or real-time polymerase chain reaction was used to confirm differential expressions of immune-enhancing proteins. Results showed that choline significantly increased survival of E. coioides 48 days after being injected with V. alginolyticus. From maps of plasma proteins, a comparative analysis between the control and choline groups revealed that 111 spots matched, with 26 altered expression spots in the choline group. Of these 26 spots, 16 were upregulated and 10 downregulated. After protein identification by reverse-phase nano-high-performance liquid chromatography-electrospray ionization MS/MS analysis, eight of 26 proteins were found to be immune-related proteins, all of which were upregulated, including complement 3 (C3), alpha-2-macroglobulin-P-like isoform (A2M), fibrinogen beta chain precursor (FBG), and immunoglobulin heavy constant mu (Ighm) proteins. Expression of the A2M protein and A2M enzyme activity in plasma of fish fed choline significantly increased compared to the control group. Additionally, A2M messenger (m)RNA transcripts were also upregulated in the liver and kidneys. Significantly higher C3 expressions at both the mRNA and protein levels were detected in the liver of fish in the choline group. Moreover, FBG gene expressions in the liver and kidneys significantly increased, while Ighm increased in the kidneys and spleen of fish in the choline group. Our results suggest that dietary administration of choline can protect grouper against bacterial infections through activating the complement system, thereby inducing antiprotease activity and natural antibodies that play important roles in the innate immune system of fish.

Effect of dietary phosphorus deficiency on the growth, immune function and structural integrity of head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella)

This study evaluates the effects of dietary phosphorus on the growth, immune function and structural integrity (head kidney, spleen and skin) of young grass carp (Ctenopharyngodon idella) that were fed graded levels of available phosphorus (0.95-8.75 g/kg diet). Results indicated that phosphorus deficiency decreased the growth performance of young grass carp. In addition, the results first demonstrated that compared with the optimal phosphorus level, phosphorus deficiency depressed the lysozyme (LZ) and acid phosphatase (ACP) activities and the complement 3 (C3), C4 and immunoglobulin M (IgM) contents, and down-regulated the mRNA levels of antimicrobial peptides, anti-inflammatory cytokines, inhibitor of κBα (IκBα) and target of rapamycin (TOR), whereas it up-regulated pro-inflammatory cytokines, nuclear factor kappa B (NF-κB) p65 and NF-κB p52 mRNA levels to decrease fish head kidney and spleen immune functions. Moreover, phosphorus deficiency up-regulated the mRNA levels of Kelch-like-ECH-associated protein 1a (Keap1a), Fas ligand (FasL), apoptotic protease activating factor-1 (Apaf-1), Bcl-2 associated X protein (Bax), caspase -2, -3, -7, -8 and -9, p38 mitogen-activated protein kinase (MAPK) and myosin light chain kinase (MLCK), whereas it depressed the glutathione (GSH) contents and antioxidant enzymes activities, and down-regulated the mRNA levels of antioxidant enzymes, NF-E2-related factor 2 (Nrf2), B-cell lymphoma protein-2 (Bcl-2), myeloid cell leukemia-1 (Mcl-1) and tight junction complexes to attenuate fish head kidney and spleen structural integrity. In addition, phosphorus deficiency increased skin hemorrhage and lesions morbidity. Finally, based on the percent weight gain (PWG) and the ability to combat skin hemorrhage and lesions, the dietary available phosphorus requirements for young grass carp (254.56-898.23 g) were estimated to be 4.10 and 4.13 g/kg diet, respectively. In summary, phosphorus deficiency decreases the growth performance, and impairs immune function and structural integrity in the head kidney, spleen and skin of young grass carp.

Dietary vitamin C deficiency depressed the gill physical barriers and immune barriers referring to Nrf2, apoptosis, MLCK, NF-κB and TOR signaling in grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare

This study explored the effects of vitamin C on the physical barriers and immune barriers, and relative mRNA levels of signaling molecules in the gill of grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare. The results indicated that compared with optimal vitamin C supplementation, vitamin C deficiency (2.9 mg/kg diet) (1) increased reactive oxygen species, malondialdehyde and protein carbonyl (PC) contents (P < 0.05), decreased the copper/zinc superoxide dismutase, manganese superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities and mRNA levels (P < 0.05), and glutathione and vitamin C contents (P < 0.05), down-regulated NF-E2-related factor 2 mRNA level (P < 0.05), and up-regulated Kelch-like ECH-associating protein (Keap) 1a (rather than Keap1b) mRNA level (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency induced oxidative injury in fish gill; (2) up-regulated caspase-3, -7, -8, -9, Fas ligand, B-cell lymphoma protein 2 associated X protein, apoptotic protease activating factor-1 mRNA levels (P < 0.05), and down-regulated inhibitor of apoptosis protein and B-cell lymphoma-2 (rather than myeloid cell leukemia-1) mRNA level (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency aggravated cell apoptosis in fish gill; (3) up-regulated pore-forming TJs Claudin-12, 15a, -15b, and related signaling molecules myosin light chain kinase, p38 mitogen-activated protein kinase (rather than c-Jun N-terminal kinases) mRNA levels (P < 0.05), and down-regulated barrier-forming TJs Occludin, zonula occludens (ZO) 1, ZO-2, Claudin-c, -3c, -7a, -7b mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency disrupted tight junctional complexes in fish gill; (4) decreased lysozyme and acid phosphatase (ACP) activities, and complement 3 (C3), C4 and IgM contents (P < 0.05), down-regulated the mRNA levels of antimicrobial peptides liver expressed antimicrobial peptide (LEAP) 2A, LEAP-2B, Hepcidin, β-defensin mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency decrease fish gill immune function; (5) down-regulated the mRNA levels of anti-inflammatory cytokines-related factors interleukin 10 (IL-10), IL-11, transforming growth factor (TGF) β1, TGF-β2, inhibitor of κBa and eIF4E-binding protein 1 (4E-BP1) (rather than 4E-BP2) (P < 0.05), and up-regulated pro-inflammatory cytokines-related factors interferon γ2, IL-1β, IL-6, IL-8, IL-12 P35, IL-12 P40, nuclear factor κB (NF-κB) p65 (rather than NF-κB p52), IκB kinases (IKK) (only IKKα and IKKγ), target of rapamycin and ribosomal protein S6 kinase 1 mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency aggravated fish gill inflammation. In conclusion, vitamin C deficiency disrupted physical barriers and immune barriers, and regulated relative mRNA levels of signaling molecules in fish gill. The vitamin C requirement for against gill rot morbidity of grass carp (264-1031 g) was estimated to be 156.0 mg/kg diet. In addition, based on the gill biochemical indices (antioxidant indices MDA, PC and vitamin C contents, and immune indices LA and ACP activity) the vitamin C requirements for grass carp (264-1031 g) were estimated to be 116.8, 156.6, 110.8, 57.8 and 134.9 mg/kg diet, respectively.