Low or excess levels of dietary cholesterol impaired immunity and aggravated inflammation response in young grass carp (Ctenopharyngodon idella)

The Indigenous Probiotic Lactococcus lactis PH3-05 Enhances the Growth, Digestive Physiology, and Gut Microbiota of the Tropical Gar (Atractosteus tropicus) Larvae

Probiotics in aquaculture hold promise for enhancing fish health and growth. Due to their increased specificity and affinity for their host, indigenous probiotics may offer isolated and potentially amplified benefits. This study investigated the effects of Lactococcus lactis PH3-05, previously isolated from adults of tropical gar (Atractosteus tropicus), on the growth, survival, digestive enzyme activity, intestinal morphology, expression of barrier and immune genes, and intestinal microbiota composition in the larvae of tropical gar. Larvae were fed with live L. lactis PH3-05 concentrations of 104, 106, and 108 CFU/g for 15 days alongside a control diet without probiotics. Higher concentrations of L. lactis PH3-05 (106 and 108 CFU/g) positively influenced larval growth, increasing hepatocyte area and enterocyte height. The 106 CFU/g dose significantly enhanced survival (46%) and digestive enzyme activity. Notably, the 108 CFU/g dose stimulated increased expression of muc-2 and il-10 genes, suggesting enhanced mucosal barrier function and anti-inflammatory response. Although L. lactis PH3-05 did not significantly change the diversity, structure, or Phylum level composition of intestinal microbiota, which was constituted by Proteobacteria, Bacteroidota, Chloroflexi, and Firmicutes, an increase in Lactobacillus abundance was observed in fish fed with 106 CFU/g, suggesting enhanced probiotic colonization. These results demonstrate that administering L. lactis PH3-05 at 106 CFU/g promotes growth, survival, and digestive health in A. tropicus larvae, establishing it as a promising indigenous probiotic candidate for aquaculture applications.

Dietary habits in adult Japanese patients with vitiligo

Vitiligo is an autoimmune skin disease with acquired depigmentation. Dietary habits may modulate the pathogenesis of vitiligo. We evaluated dietary habits in adult Japanese patients with nonsegmental vitiligo, and compared their results with those of age- and sex-matched controls. We also examined the relationship between dietary habits and Vitiligo Area Scoring Index (VASI), or vitiligo on different anatomical sites. The intakes of energy, nutrients, and foods in the participants were analyzed using a brief-type self-administered diet history questionnaire. Patients with vitiligo showed higher body mass index (BMI) and lower intakes of manganese, vitamin D, pulses, and confection, compared with controls. Multivariate logistic regression analysis showed that vitiligo was associated with high BMI. VASI was higher in males than in females, and negatively correlated with age or intakes of potatoes and vegetables other than green/yellow vegetables. Linear multivariate regression analysis showed that high VASI was associated with younger age. Multivariate logistic regression analysis showed that moderate to severe vitiligo (VASI ≥ 4.25) was associated with male sex and longer disease duration. Multivariate logistic regression analyses showed the following association with vitiligo on respective anatomical sites: high intake of eggs and dairy products and high VASI on the head or neck, high intake of oils and fats and high VASI on the trunk, high intake of cereals and high VASI on the upper limbs, male sex and high VASI on the lower limbs, and high BMI and high VASI on the hands or feet. In conclusion, the control of obesity might have prophylactic or therapeutic effects on vitiligo.

Promotion of improved intestinal barrier health by soybean-derived bioactive peptides in Chinese mitten crab (Eriocheir sinensis) fed a low fishmeal diet

To alleviate the growth inhibition, and intestinal damage of Chinese mitten crab (Eriocheir sinensis) induced by low fishmeal diets (LF), an 8-week feeding trial was conducted to evaluate the addition of dietary soybean-derived bioactive peptides (SBP) in LF diets on the regulation of growth, digestion and intestinal health. The crabs were fed isonitrogenous and isoenergetic conventional diet and LF diets (10 % fishmeal replaced by soybean meal, LF) supplemented with 0, 1 %, 2 %, 4 % and 6 % SBP, respectively. The results showed that LF diet inhibited growth while inclusion of SBP quadratically remitted the growth inhibition induced by LF. For digestive function, increasing addition level of SBP quadratically improved the α-amylase and trypsin activities. For antioxidant function, LF group significantly increased the malondialdehyde content, while SBP linearly decreased the malondialdehyde level and cubically increased the anti-superoxide anion activity and total antioxidant capacity level. For intestinal health, the peritrophic membrane (PM) almost completely separated from the inner wall of the intestinal lumen, the epithelial cells reduced, the muscularis became thinner and the apoptotic signals increased in LF group; with SBP addition, the intestinal morphology was improved, with the PM adhering to the inner wall of the intestinal lumen, an increase in the number of epithelial cells and an increase in the thickness of the muscularis. Additionally, there was a decrease in apoptotic signals. Dietary SBP also increased the expression of PT and Crustin1 quadratically and decreased the expression of ALF1 linearly, ALF3 and ILF2 quadratically.

Impact of dietary zinc on the growth performance, histopathological analysis, antioxidant capability, and inflammatory response of largemouth bass Micropterus salmoides

Zinc plays a crucial role in the antioxidant capacity, and inflammatory response of aquatic species, but its impact on largemouth bass Micropterus salmoides is rarely reported. Therefore, this paper aimed to investigate the effects of different levels of zinc on the growth performance, histopathology, antioxidant capacity, and inflammatory cytokines of largemouth bass Micropterus salmoides. Fish with an initial weight of 7.84 ± 0.06 g were cultured for 10 weeks. Five experimental diets were prepared with supplemented proteinate Zn (Bioplex Zn, Alltech) (0, 30, 60, 90, and 120 mg/kg), which were named the Zn-42, Zn-73, Zn-103, Zn-133, and Zn-164 groups. No evident difference was found between the dietary zinc level and the survival rate, the crude lipid content of the whole fish, or the visceral somatic index. Weight gain, condition factor, whole-body crude protein content, interleukin-10, and transforming growth factor beta gene expression were gradually enhanced with up to 102.68 mg/kg zinc and decreased at higher levels. The hepatosomatic index, feed conversion ratio, malondialdehyde level in the liver, aspartate aminotransferase, and alanine transaminase activity in the serum, gradually decreased up to 102.68 mg/kg zinc, and gradually increased beyond this. Activation of the nuclear factor erythroid-derived 2-like 2/Kelch-like ECH-associated protein 1 signaling pathway gradually up-regulated the mRNA levels and activities of glutathione peroxidase, total antioxidant capacity, catalase, and superoxide dismutase in the liver, this antioxidant ability was lower when the zinc was greater than 102.68 mg/kg. The gene expressions of nuclear factor-k-gene binding and pro-inflammation cytokines (interleukin-1β, interleukin-15, tumor necrosis factor alpha, and interleukin-8) were up-regulated up to 102.68 mg/kg zinc and then gradually repressed. In conclusion, using broken line analysis to estimate weight gain and Zn proteinate as the zinc source, the recommended dietary zinc for largemouth bass is 66.57 mg/kg zinc.

The direct and gut microbiota-mediated effects of dietary bile acids on the improvement of gut barriers in largemouth bass (Micropterus salmoides)

Fish gut barrier damage under intensive culture model is a significant concern for aquaculture industry. This study aimed to investigate the effects of bile acids (BAs) on gut barriers in Micropterus salmoides. A germ-free (GF) zebrafish model was employed to elucidate the effects of the direct stimulation of BAs and the indirect regulations mediated by the gut microbiota on gut barrier functions. Four diets were formulated with BAs supplemented at 0, 150, 300 and 450 mg/kg, and these 4 diets were defined as control, BA150, BA300 and BA450, respectively. After 5 weeks of feeding experiment, the survival rate of fish fed with BA300 diet was increased (P < 0.05). Histological analysis revealed an improvement of gut structural integrity in the BA150 and BA300 groups. Compared with the control group, the expression of genes related to chemical barrier (mucin, lysozyme and complement 1) and physical barrier (occludin and claudin-4) was increased in the BA150 and BA300 groups (P < 0.05), and the expression of genes related to immunological barrier (interleukin [IL]-6, tumor growth factor β, IL-10, macrophage galactose-type lectin and immunoglobulin M [IgM]) was significantly increased in the BA300 group (P < 0.05), but the expression of genes related to chemical barrier (hepcidin) and immunological barrier (IL-1β, tumor necrosis factor-α, IL-6 and arginase) was significantly decreased in the BA450 group (P < 0.05). Gut microbiota composition analysis revealed that the abundance of Firmicutes was augmented prominently in the BA150 and BA300 groups (P < 0.05), while that of Actinobacteriota and Proteobacteria showed a downward trend in the BA150 and BA300 groups (P > 0.05). The results of the gut microbiota transferring experiment demonstrated an upregulation of gut barrier-related genes, including immunoglobulin Z/T (IgZ/T), IL-6, IL-1β and IL-10, by the gut microbiota transferred from the BA300 group compared with the control (P < 0.05). Feeding the BA300 diet directly to GF zebrafish resulted in enhanced expression of IgM, IgZ/T, lysozyme, occludin-2, IL-6 and IL-10 (P < 0.05). In conclusion, BAs can improve the gut barriers of fish through both direct and indirect effects mediated by the gut microbiota.

Effects of Replacing Soybean Meal Protein with Chlorella vulgaris Powder on the Growth and Intestinal Health of Grass Carp (Ctenopharyngodon idella)

Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with enormous potential to be a protein source. However, it is poorly studied in aquatic animals. The purpose of the present study was to explore the optimum replacement ratio of C. vulgaris powder and the influence of the substitution of soybean meal with C. vulgaris on grass carp (Ctenopharyngodon idella) in terms of growth performance, intestinal integrity and the microbial community. Five isonitrogenous and isolipidic diets were formulated by replacing 0% (SM, containing 30% soybean meal), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) soybean meal with C. vulgaris. The feeding trial period lasted 8 weeks. At the end of the experimental trial, the X50 group showed higher FW, WGR and PER than the SM group (p < 0.05). The feed conversion ratio (FCR) of the X50 group was significantly lower than that of the SM group (p < 0.05). The X50 group showed the highest value of the goblet cell number, intestinal amylase and trypsin activities when compared with the SM group (p < 0.05). Replacing 50% soybean meal with C. vulgaris improved the intestinal barrier integrity, as evidenced by upregulating zo-1, zo-2 and occluding transcript (p < 0.05), and alleviated oxidative stress by an increased SOD enzymatic activity and transcript level, probably mediated through the Nrf2-keap1 signaling pathway (p < 0.05). Meanwhile, the X50 group enhanced intestinal immunity, as manifested by increased ACP and LZM activities (p < 0.05), and downregulated the tlr-4, tlr-7, tlr-8 and il-6 through the tlr pathway (p < 0.05). The functionally predicting pathways related to the nitrate respiration and nitrogen respiration were observably activated in the X50 group (p < 0.05). The X50 group improved the biological barrier, as manifested by increased Firmicutes and Rhodobacter (p < 0.05). In conclusion, dietary C. vulgaris powder could promote the growth performance of grass carp by restoring intestinal morphology, increasing digestive enzyme activities, improving antioxidant properties and immunity and optimizing the microflora structure. A C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp.

Protective effect of quercetin on avermectin induced splenic toxicity in carp: Resistance to inflammatory response and oxidative damage

Avermectin pollution is an important problem that cannot be ignored in aquatic system in recent years. It has brought great trouble to freshwater aquaculture, especially fishery aquaculture. Plant-derived quercetin has anti-inflammatory and antioxidant properties and is widely used as a dietary additive, but its protective effect on immune damage induced by avermectin in freshwater carp remains unclear. This study evaluated the role of dietary additive quercetin supplementation in chronic avermectin exposure of carp spleen. Sixty carp were divided into 4 groups (n = 15/ group), including control group, avermectin treatment group, quercetin treatment group, quercetin and avermectin co-treatment group. Carp were exposed to a 1/10 96 h LC₅₀ dose of avermectin for 30 d and fed a carp diet containing 400 mg/kg quercetin twice a day (3% body weigh/ carp). The results showed that chronic avermectin exposure caused the loose parenchymal structure of carp spleen tissue and the increase of inflammatory cells, accompanied by increased transcription levels of pro-inflammatory il-1β, il-6, tnf-α and decreased levels of anti-inflammatory factors il-10 and tgf-β1, ROS accumulation in spleen tissue. MDA content increased and T-AOC, CAT and GSH levels decreased. Quercetin down-regulates the NF-κB pathway by inhibiting the expression of iNOS and activating p38 MAPK, blocking the transcription of inflammatory factors, and alleviating the inflammation of carp spleen caused by chronic avermectin exposure. In addition, quercetin inhibits the over-activation of Nrf2/Keap-1 signaling axis, blocks ROS accumulation, and restores the spleen REDOX homeostasis. In conclusion, quercetin, as a dietary additive for carp feed, can effectively improve the immune damage caused by avermectin pollution in aquatic environment, resist spleen inflammation and oxidative stress, and provide a theoretical basis for clinical development of freshwater carp feed.

The protective role of vitamin C on intestinal damage induced by high-dose glycinin in juvenile Rhynchocypris lagowskii Dybowski

This study was to evaluate the mitigative effects of vitamin C (VC) on growth inhibition and intestinal damage induced by glycinin in juvenile Rhynchocypris lagowskii Dybowski. 270 healthy juvenile Rhynchocypris lagowskii Dybowski (4.65 ± 0.04 g) were randomly divided into 3 treatments, and fed with control diet, 80 g/kg glycinin diet and 80 g/kg glycinin+200 mg/kg VC diet respectively for 8 weeks. The results showed that glycinin significantly decreased the weight gain rate, specific growth rate, protein efficiency rate, feed efficiency rate and feeding rate of fish compared with the control group (P < 0.05), while VC supplementation improved the growth performance and feed utilization efficiency, and reached a level similar to the control group. Similarly, VC significantly increased the crude protein content of muscle and whole-body, and hepatopancreas and intestinal protease activities of fish fed with glycinin diet (P < 0.05). The distal intestine of fish in glycinin group showed typical damage characteristics, including breakage and atrophy of intestinal mucosal fold, and increased intestinal mucosal permeability. However, fish fed the glycinin + VC diet showed an unimpaired normal intestinal morphology. Usefully, VC supplementation could also restore impaired immune function and antioxidant capacity. VC down-regulated the mRNA levels of pro-inflammatory cytokines TNF-α and IL-1β, and up-regulated the mRNA levels of anti-inflammatory cytokines IL-10 and TGF-β in the distal intestine of fish fed with glycinin. Furthermore, glycinin exposure could reduce the mRNA levels of HO-1, CAT and GPx by inhibiting the activation of Nrf2-Keap1 signaling pathway, while VC supplementation reversed this phenomenon and maintained the homeostasis of antioxidant defense system. Concluded, glycinin causes growth inhibition, digestive dysfunction and intestinal damage of Rhynchocypris lagowskii Dybowski, while sufficient VC intake is beneficial for fish to resist the adverse effects of glycinin.

Intestinal microbiome-mediated resistance against vibriosis for Cynoglossus semilaevis

BACKGROUND

Infectious diseases have caused huge economic loss and food security issues in fish aquaculture. Current management and breeding strategies heavily rely on the knowledge of regulative mechanisms underlying disease resistance. Though the intestinal microbial community was linked with disease infection, there is little knowledge about the roles of intestinal microbes in fish disease resistance. Cynoglossus semilaevis is an economically important and widely cultivated flatfish species in China. However, it suffers from outbreaks of vibriosis, which results in huge mortalities and economic loss.

RESULTS

Here, we used C. semilaevis as a research model to investigate the host-microbiome interactions in regulating vibriosis resistance. The resistance to vibriosis was reflected in intestinal microbiome on both taxonomic and functional levels. Such differences also influenced the host gene expressions in the resistant family. Moreover, the intestinal microbiome might control the host immunological homeostasis and inflammation to enhance vibriosis resistance through the microbe-intestine-immunity axis. For example, Phaeobacter regulated its hdhA gene and host cyp27a1 gene up-expressed in bile acid biosynthesis pathways, but regulated its trxA gene and host akt gene down-expressed in proinflammatory cytokines biosynthesis pathways, to reduce inflammation and resist disease infection in the resistant family. Furthermore, the combination of intestinal microbes and host genes as biomarkers could accurately differentiate resistant family from susceptible family.

CONCLUSION

Our study uncovered the regulatory patterns of the microbe-intestine-immunity axis that may contribute to vibriosis resistance in C. semilaevis. These findings could facilitate the disease control and selective breeding of superior germplasm with high disease resistance in fish aquaculture. Video Abstract.

A New Insight Into the Underlying Adaptive Strategies of Euryhaline Marine Fish to Low Salinity Environment Through Cholesterol Nutrition to Regulate Physiological Responses

Salinity is an important environmental factor that can affect the metabolism of aquatic organisms, while cholesterol can influence cellular membrane fluidity which are vital in adaption to salinity changes. Hence, a 4-week feeding trial was conducted to evaluate the effects of water salinity (normal 23 psu and low 5 psu) and three dietary cholesterol levels (CH0.16, 0.16%, CH1.0, 1.0% and CH1.6, 1.6%) on osmoregulation, cholesterol metabolism, fatty acid composition, long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis, oxidative stress (OS), and endoplasmic reticulum stress (ERS) of the euryhaline fish black seabream (Acanthopagrus schlegelii). The results indicated that in low salinity, fish fed with the CH1.0 diet improved ion reabsorption and osmoregulation by increased Na+ concentration in serum as well as expression levels of osmoregulation-related gene expression levels in gills. Both dietary cholesterol level and water salinity significantly affected most cholesterol metabolic parameters in the serum and tissues, and the results showed that low salinity promoted cholesterol synthesis but inhibited cholesterol catabolism. Besides, in low salinity, hepatic expression levels of LC-PUFA biosynthesis genes were upregulated by fed dietary cholesterol supplementation with contents of LC-PUFAs, including EPA and DHA being increased. Malondialdehyde (MDA) was significantly increased in low-salinity environment, whereas MDA content was decreased in fish fed with dietary CH1.0 by activating related antioxidant enzyme activity and gene expression levels. A similar pattern was recorded for ERS, which stimulated the expression of nuclear factor kappa B (nf-κb), triggering inflammation. Nevertheless, fish reared in low salinity and fed with dietary CH1.0 had markedly alleviated ERS and downregulated gene expression levels of pro-inflammatory cytokines. Overall, these findings demonstrate that cholesterol, as an important nutrient, plays vital roles in the process of adaptation to low salinity of A. schlegelii, and provides a new insight into underlying adaptive strategies of euryhaline marine fish reared in low salinity.

Intraperitoneal injection of genistein affects the distribution and metabolism of cholesterol in female yellow catfish Tachysurus fulvidraco

Genistein is an abundant phytoestrogen in soybean. This study aimed to determine the effects of genistein on cholesterol distribution and metabolism in female yellow catfish. Three hundred fish (49.2 ± 1.4 g) were randomly divided into five treatments and received intraperitoneal injections as follows: (1) blank, no injection; (2) control, vehicle only; (3) E2, 17β-estradiol at 10 μg·g^-1 body weight; (4) low genistein doses, genistein at 10 μg·g^-1 body weight; (5) high genistein doses, genistein at 100 μg·g^-1 body weight. Both high and low genistein doses significantly reduced (p < 0.05) serum TC and LDL-C 24 h after injection. Moreover, the high genistein doses significantly reduced (p < 0.05) serum HDL-C. Both high and low doses of genistein significantly increased (p < 0.05) hepatic TC. Only high genistein doses significantly increased (p < 0.05) ovary TC. In the liver, both high and low genistein doses significantly increased (p < 0.05) protein and mRNA expression of ldlr. Meanwhile, high genistein doses significantly decreased (p < 0.05) mRNA expression of hmgcr. In ovary tissue, high genistein doses significantly decreased (p < 0.05) mRNA expression of cyp11a1. These results suggested that genistein affected the cholesterol distribution in female yellow catfish. Both high and low doses of genistein reduced cholesterol content in blood and increased its content in the liver by increasing the uptake of blood cholesterol. Meanwhile, high genistein doses may inhibit hepatic cholesterol synthesis. Additionally, high genistein doses could increase cholesterol transfer from serum into the ovary and disturb cholesterol conversion to pregnenolone.

Lysine deficiency impaired growth performance and immune response and aggravated inflammatory response of the skin, spleen and head kidney in grown-up grass carp (Ctenopharyngodon idella)

This dissertation was primarily focused on the immune response, inflammatory response and molecular mechanisms in the skin, head kidney and spleen of grown-up grass carp (Ctenopharyngodon idella). Six iso-nitrogen diets differing in lysine concentrations (5.6, 8.5, 11.6, 14.4, 17.5 and 20.7 g/kg) were fed to 540 grass carp (164.85 ± 0.79 g) for 60 d. After that, grass carp were challenged by Aeromonas hydrophila for 6 d. This study revealed that lysine deficiency (1) suppressed the growth performance of the fish and decreased their ability to resist skin lesion morbidity, (2) impaired the immune organ^'s immune response by decreasing the gene expressions of mucin, liver-expressed antimicrobial peptide (LEAP)-2B, β-defensin-1 and LEAP-2A and the production of antibacterial compounds of grown-up grass carp, and (3) aggravated the inflammatory response of immune organs in the fish by increasing the gene expressions of pro-inflammatory cytokines (interferon γ2 [IFN-γ2], tumor necrosis factor α [TNF-α], interleukin [IL]-15, IL-17D, IL-12p40, IL-6 and IL-8) and down-regulating anti-inflammatory cytokines (IL-11, transforming growth factor β1 [TGF-β1], IL-10 and IL-4/13A), which were tightly correlated with signal transducer and activator of transcription (STAT)1 and STAT3 signaling pathway, respectively. The different phenomenon in the skin, spleen and head kidney of fish may be correlated with the difference in gene subtype. In addition, using quadratic regression analysis of percent weight gain (PWG), skin lesion morbidity, and the lysozyme activities in the spleen and head kidney, the dietary lysine requirements for grown-up grass carp were estimated to be 13.58, 13.51, 14.56 and 14.18 g/kg, respectively.

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.

(2-Carboxyethyl) dimethylsulfonium bromide supplementation in non-fish meal diets for on-growing grass carp (Ctenopharyngodon idella): Beneficial effects on immune function of the immune organs via modulation of NF-κB and TOR signalling pathway

The immune function of immune organs is extremely crucial for maintaining organism health status, which ultimately affects fish growth. Our previous study has found that dietary supplementation of (2-carboxyethyl)dimethylsulfonium Bromide (Br-DMPT) in non-fish meal (NFM) diet could promote the growth of grass carp (Ctenopharyngodon idella), whereas the underlying reason or mechanism for this results is largely unclear. Herein, we further explored whether dietary supplementation of Br-DMPT promoted fish growth is connected with the enhanced immune function in the immune organs (the head kidney, spleen and skin). In this study, 540 fish (216.49 ± 0.29 g) were irregularly distributed to six groups with three replicates (30 fish replicate^-1) and fed corresponding diets group containing a fish meal (FM) diet group and five different NFM diets supplemented with gradational Br-DMPT (0-520.0 mg/kg level) group for 60 days. After the 60-days feeding trial, 8 fish from each replicate were selected and then conducted a challenge test with A. hydrophila for 14 days. Our results indicated that in the NFM diets, appropriate Br-DMPT: (1) significantly decreased the morbidity of skin haemorrhage and lesion after A. hydrophila infection (P < 0.05). (2) significantly improved the innate and adaptive immune components (lysozyme, complement 3, immunoglobulin M and antibacterial peptides et al.) (P < 0.05). (3) increased the gene expressions of main anti-inflammatory cytokines partially by referring to TOR signalling pathway, and decreased the gene expressions of main pro-inflammatory cytokines partially by referring to NF-kB signalling pathway (P < 0.05). Strikingly, no statistical difference could be found in the most of above immune parameters between 260.0 mg/kg Br-DMPT diet group and FM diet group (P > 0.05). Taken together, in non-fish meal diet, appropriate supplementation of Br-DMPT could improve the disease resistance capacity, non-specific immunity and ameliorate inflammation, and simultaneously could mitigate these adverse effects induced by the non-fish meal diet in fish immune organs. Moreover, this study may be helpful to decipher the underlying mechanisms of how Br-DMPT promote fish growth by immune organs and also provide scientific theoretical evidence for the future application of Br-DMPT as a new immunopotentiator in aquaculture industry.

Dietary supplementation of salidroside increases immune response and disease resistance of crucian carp (Carassius auratus) against Aeromonas hydrophila

Some medicinal plants have been known as immunostimulants, and the medicinal plants extract has been used to control the outbreak of the disease in aquaculture for many years. In this study, a total of 270 crucian carp (30 ± 5 g) were randomly distributed in 9 aquaria (55 cm l × 40 cm w × 50 cm h) and divided into three feeding groups including 0 (Control), 50 mg kg^-1 (Diet A) and 100 mg kg^-1 (Diet B) of salidroside. The expression of immune-related genes (IL-1β, TNFα, MYD88, CXCL-8, TGF-β, and IL-11) in the kidney had a significant increase when the crucian carp fed with Diet B for 4 weeks (P < 0.05). Meanwhile, the expression of IL-1β, TNFα, and CXCL-8 in the spleen was significantly up-regulated when the fish fed with Diet B (P < 0.05). Higher serum alkaline phosphatase (AKP) activity, catalase (CAT) activity, superoxide dismutase (SOD) activity, and complement C3 content were found in the fish which fed with salidroside-supplemented diet. Our results also proved that fish fed with salidroside-supplemented diet for four weeks, especially at a concentration of 100 mg kg^-1 diet, improved the protection of crucian carp against A. hydrophila. The amount of A. hydrophila in the kidney and spleen was significantly decreased in salidroside-supplemented diet groups (P < 0.05). In conclusion, the present results demonstrate that the addition of salidroside for four weeks can improve the immune response of crucian carp and increase the protection against the pathogen, especially at the concentration of 100 mg kg^-1 diet. The protective effect of the salidroside to the crucian carp could be used as alternatives to antibiotics for controlling fish diseases in aquaculture.

Soybean glycinin impaired immune function and caused inflammation associated with PKC-ζ/NF-κb and mTORC1 signaling in the intestine of juvenile grass carp (Ctenopharyngodon idella)

Glycinin is a major protein and antinutritional factor of soybean. However, how dietary glycinin affect intestinal immune function of fish were largely unknown. In this study, we used juvenile grass carp as a model to investigate the impacts of glycinin on intestinal immune function of fish and involved mechanisms. We set three treatments including control, glycinin and glycinin + glutamine in this trial. For immune components, results revealed that compared with control group, glycinin group had lower acid phosphatase activities in the foregut, midgut and hindgut, lower C3 and C4 content, and lower mRNA abundances of IgM, IgZ, hepcidin, LEAP-2A, LEAP-2B and β-defensin-1 in the midgut and hindgut rather than foregut of grass carp. For pro-inflammatory cytokines and relevant signaling, glycinin elevated mRNA abundances of IL-1β, IL-8, IL-12p35, IL-12p40 and IL-17D in the midgut and IL-1β, IFN-γ2, IL-6, IL-8, IL-12p35, IL-12p40 and IL-17D in the hindgut, and increased protein abundances of PKC-ζ and nuclear NF-κB p65 in the midgut and hindgut in comparison to control. For anti-inflammatory cytokines and relevant signaling, glycinin reduced mRNA abundances of TGF-β1, TGF-β2, IL-4/13B (rather than IL-4/13A), IL-10 and IL-11 in the midgut and hindgut, and reduced p-mTOR (Ser 2448), p-S6K1 (Thr 389) and p-4EBP1 (Thr 37/46) protein abundances in the midgut and hindgut rather than foregut. Co-administration of glutamine with glycinin could partially enhance intestinal function and reduce intestinal inflammation compared with glycinin treatment. Concluded, glycinin decreased intestinal immune components and caused intestinal inflammation associated with PKC-ζ/NF-κB and mTORC1 signaling.

Overfeeding-Induced Obesity Could Cause Potential Immuno-Physiological Disorders in Rainbow Trout (Oncorhynchus mykiss)

Although over-nutrition from overfeeding-induced obesity is known to be highly associated with metabolic and immunological disorders in humans, little is known about overfeeding-induced obesity in fish farming. The purpose of this study was to investigate changes in immuno-physiological parameters, to better understand the potential risk of overfeeding-induced obesity in fish. Commercial feed was provided to fish in the overfed group until they refuse to eat, but fish in the control group was fed with the feed at 1% bodyweight per day. The hemato-serological, histological, and immunological changes were observed at weeks 2 and 8. Rainbow trout leukocytes were co-incubated with oxidized low-density lipoprotein (OxLDL), and the phagocytes engulfing the OxLDL and the presence of apoptotic cells were evaluated. The body weight, body mass index (BMI), and hepatosomatic index (HSI) index were significantly higher in the overfed group, and high lipid accumulation and fatty changes were also observed in their livers, indicating that the feeding regime used in this study led to overfeeding-induced obesity. Likewise, much higher numbers of and larger vacuoles were observed in overfed fish macrophages, showing unclear boundaries between the cytoplasm and extracellular space. In the overfed group, the expression of IL-10, HSP70, TLR2, and CD36 was significantly higher, and lymphocyte apoptosis was more evident, indicating that overfeeding-induced obese fish might have immunologic disorders. This was the first study to demonstrate that overfeeding-induced obesity could cause an immune-physiological imbalance in rainbow trout, making them more vulnerable to infectious diseases and various stressful conditions. This study will contribute to improvements in fish nutrition, feeding practices, fish nutrition, and disease prevention in the aquaculture industry.

Dietary phytic acid weakened the antimicrobial activity and aggravated the inflammatory status of head kidney, spleen and skin in on-growing grass carp (Ctenopharyngodon idella)

The present study aimed to explore the effects of phytic acid (PA) on the antimicrobial activity and inflammatory response in three immune organs (head kidney, spleen and skin) of on-growing grass carp (Ctenopharyngodon idella). To achieve this goal, we first conducted a 60-day growth trial by feeding fish with graded levels of PA (0, 0.8, 1.6, 2.4, 3.2 and 4.0%). Then, the fish were challenged with Aeromonas hydrophila for 6 days. Compared with the control group, the following results were obtained regarding supplementation with certain levels of PA in the diet. (1) There was an increase in skin haemorrhage and lesion morbidity in fish. (2) There was a decrease in activities or contents of immune factors, including lysozyme (LZ), complement 3 (C3), C4 and immunoglobulin M (IgM), and there was downregulation of gene expression levels of hepcidin, liver-expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, and β-defensin-1 in immune organs. (3) There was upregulation in the gene expression of the following pro-inflammatory cytokines: tumour necrosis factor α (TNF-α), interleukin 1β (IL-1β) (except in the spleen), interferon γ2 (IFN-γ2), IL-6 (except in the spleen), IL-8, IL-12p40, IL-15 and IL-17D. These changes were partly related to the nuclear factor kappa B (NF-κB) signalling pathway, but downregulation of mRNA levels of anti-inflammatory cytokines (transforming growth factor β1 (TGF-β1), TGF-β2, IL-413/A, IL-413/B, IL-10 (except in the skin) and IL-11) occurred in a manner partially related to the target of rapamycin (TOR) signalling pathway. Finally, based on the broken-line analysis of skin haemorrhage and lesion morbidity and IgM content in the head kidney, the maximum tolerance levels of PA for on-growing grass carp (120.56-452.00 g) were estimated to be 1.79 and 1.31% of the diet, respectively.

Novel insights into the intestinal immune regulatory effects of (2-Carboxyethyl) dimethylsulfonium Bromide (Br-DMPT) in on-growing grass carp (Ctenopharyngodon idella)

The present study evaluated the effects of (2-Carboxyethyl)dimethylsulfonium Bromide (Br-DMPT) supplementation on the intestinal immune function and potential mechanisms of on-growing grass carp (Ctenopharyngodon idella) by feeding fish (initial weight 216.49 ± 0.29 g) five diets with gradational Br-DMPT (0-520 mg/kg diet) concentrations for 60 days and then infecting them with Aeromonas hydrophila for 14 days. Our results firstly indicated that compared with the control group, appropriate Br-DMPT supplementation increased the number of beneficial bacteria Lactobacillus and Bifidobacterium and enteritis resistance, decreased the number of detrimental bacteria Aeromonas and E. coli, and relieved the intestinal histopathological symptoms of fish. In addition, compared with the control group, appropriate Br-DMPT supplementation (1) increased lysozyme (LZ) and acid phosphatase (ACP) activities, as well as complement 3 (C3), C4 and immunoglobulin M (IgM) content; (2) upregulated the mRNA levels of anti-microbial substance: liver expressed anti-microbial peptide (LEAP) -2A, LEAP-2B, hepcidin, β-defensin-1 and Mucin2; (3) partially downregulated the mRNA levels of pro-inflammatory cytokines [interleukin 1β (IL-1β), IL-6, IL-8, IL-12p40, IL-15, IL-17D, tumour necrosis factor α (TNF-α) and interferon γ2 (IFN-γ2)] by inhibiting [IKKβ/IκBα/(NF-κBp65 and c-Rel)] signalling; and (4) partially upregulated the mRNA levels of anti-inflammatory cytokines [IL-4/13A, IL-10, IL-11, transforming growth factor (TGF)-β1] by activating [TOR/(S6K1 and 4E-BP)] signalling. The aforementioned results indicated that appropriate amount of Br-DMPT exerted a positive effect on the regulation of intestinal immune function in fish. Finally, based on enteritis morbidity, the IgM content and the lysozyme activity in the PI, the appropriate levels of Br-DMPT supplementation for on-growing grass carp were established as 295.43, 301.73 and 320.36 mg/kg diet, respectively.

T-2 toxin in the diet suppresses growth and induces immunotoxicity in juvenile Chinese mitten crab (Eriocheir sinensis)

The T-2 toxin is a trichothecene mycotoxin and is highly toxic to aquatic animals, but little is known on its toxic effect in crustaceans. In the present study, the crab juveniles were fed with diets containing four levels of T-2 toxin: 0 (control), 0.6 (T1), 2.5 (T2) and 5.0 (T3) mg/kg diet for 56 days to evaluate its impact on the juvenile of Chinese mitten crab (Eriocheir sinensis). The crabs fed the T-2 toxin diets had significantly lower weight gain and specific growth rate than those fed the control diet. Moreover, crab survival in T3 group was obviously lower than that in the control. Oxidative stress occurred in all the treatment groups as indicated by higher activities of total superoxide dismutase, glutathione peroxidase, and total antioxidant capacity than those in the control. The total hemocyte count, respiratory burst, phenoloxidase in the hemolymph, and phenoloxidase, acid phosphatase and alkaline phosphatase in the hepatopancreas of crabs fed T-2 toxin were significantly lower than those in the control. The transcriptional expressions of lipopolysaccharide-induced TNF-alpha factor, relish, and the apoptosis genes in the hepatopancreas were induced by dietary T-2 toxin. The genes related to detoxication including cytochrome P450 gene superfamily and glutathione S transferase were induced in low concentration, then decreased in high concentration. Dietary T-2 toxin damaged the hepatopancreas structure, especially as seen in the detached basal membrane of hepatopancreatic tubules. This study indicates that dietary T-2 toxin can reduce growth performance, deteriorate health status and cause hepatopancreas dysfunction in crabs.

Dietary biotin deficiency decreased growth performance and impaired the immune function of the head kidney, spleen and skin in on-growing grass carp (Ctenopharyngodon idella)

The aim of this study was to investigate the effects of dietary biotin deficiency on the growth performance and immune function of the head kidney, spleen and skin in on-growing grass carp (Ctenopharyngodon idella). A total of 540 on-growing grass carp (117.11 ± 0.48 g) were fed six diets containing increasing levels of biotin (0.012, 0.110, 0.214, 0.311, 0.427 and 0.518 mg/kg diet) for 70 days. Subsequently, a challenge experiment was performed by infecting them with Aeromonas hydrophila for six days. Our results showed that compared with the appropriate biotin level, (1) biotin deficiency (0.012 mg/kg diet) reduced the activities of lysozyme (LZ) and acid phosphatase (ACP), decreased the contents of complement 3 (C3), C4 and immunoglobulin M (IgM), as well as reduced the mRNA levels of antimicrobial peptides in the head kidney, spleen and skin of on-growing grass carp; (2) biotin deficiency reduced the mRNA levels of anti-microbial substances: liver-expressed antimicrobial peptide (LEAP) -2A, LEAP-2B, hepcidin, β-defensin-1 and mucin 2 in the head kidney, spleen and skin of on-growing grass carp; (3) biotin deficiency increased the mRNA levels of pro-inflammatory cytokines interleukin 1β (IL-1β), IL-6, IL-8, IL-12p40, IL-15, IL-17D, tumour necrosis factor α (TNF-α) and interferon γ2 (IFN-γ2) partially in association with nuclear factor-kappa B (NF-κB) signalling and reduced anti-inflammatory IL-4/13A, IL-10, IL-11 and transforming growth factor β1 (TGF-β1) mRNA levels partially in association with target of rapamycin (TOR) signalling in the head kidney, spleen and skin of on-growing grass carp. Interestingly, biotin deficiency had no effect on the expression of IL-12p35, IL-4/13B, TGF-β2, 4E-BP1 (skin only) or IKKα in the head kidney, spleen and skin of on-growing grass carp. In conclusion, the results indicated that biotin deficiency impaired the immune function of the head kidney, spleen and skin in fish. Finally, based on the percent weight gain (PWG), the ability to prevent skin haemorrhages and lesions, the LZ activity in the head kidney and the C4 content in the spleen, the optimal dietary biotin levels for on-growing grass carp (117-534 g) were estimated as 0.210, 0.230, 0.245 and 0.238 mg/kg diet, respectively.

Supplementation exogenous bile acid improved growth and intestinal immune function associated with NF-κB and TOR signalling pathways in on-growing grass carp (Ctenopharyngodon idella): Enhancement the effect of protein-sparing by dietary lipid

This study investigated the effects of bile acid (BA) supplementation on growth performance, intestinal immune function and the mRNA expression of the related signalling molecules in on-growing grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp (mean weight 179.85 ± 1.34 g) were fed a normal protein and lipid (NPNL) diet containing 29% crude protein (CP) and 5% ether extract (EE), and five low-protein and high-lipid (LPHL) diets (26% CP, 6% EE) with graded levels of BA (0-320 mg/kg diet) for 50 days. The fish were then challenged with Aeromonas hydrophila for 14 days. The results indicated that compared with the NPNL diet, the LPHL diet (unsupplemented BA) suppressed the growth performance, intestinal development and enteritis resistance capability and impaired the partial intestinal immune function of on-growing grass carp. Whereas in the LPHL diet, optimal BA supplementation significantly improved fish growth performance (percent weight gain, specific growth rate, feed intake and feed efficiency) and intestinal growth and function (intestine weight, intestine length and intestosomatic index), increased beneficial bacteria Lactobacillus and Bifidobacterium amounts, decreased harmful bacteria Aeromonas and Escherichia coli amounts, elevated lysozyme and acid phosphatase activities, increased complement (C3 and C4) and immunoglobulin M contents, and upregulated β-defensin-1, hepcidin, liver expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, Mucin2, interleukin 10 (IL-10), IL-11, transforming growth factor (TGF)-β1, TGF-β2, IL-4/13A (not IL-4/13B), TOR, S6K1 and inhibitor of κBα (IκBα) mRNA levels. In addition, optimal BA supplementation in the LPHL diet downregulated tumour necrosis factor α (TNF-α), interferon γ2 (IFN-γ2), IL-1β, IL-6, IL-8, IL-15, IL-17D, IL-12p35, IL-12p40 (rather than proximal intestine (PI) or mid intestine (MI), nuclear factor kappa B p65 (NF-κB p65) (except NF-κB p52), c-Rel, IκB kinase β (IKKβ), IKKγ (except IKKα), eIF4E-binding proteins (4E-BP)1 and 4E-BP2 mRNA levels in all three intestinal segments of on-growing grass carp (P < 0.05). These findings suggest that BA supplementation in the LPHL diet improves growth and intestinal immune function of fish. Furthermore, 240 mg/kg BA supplementation in the LPHL diet was superior to the NPNL diet in improving growth and enhancing intestinal immune function of fish. Finally, based on percent weight gain, feed intake, protecting fish against enteritis, lysozyme activity in MI and acid phosphatase activity in distal intestine (DI), the optimal BA supplementation for on-growing grass carp were estimated to be 168.98, 170.23, 166.67, 176.50 and 191.97 mg/kg diet, respectively.

Positive acceleration adaptive training attenuates gastric ischemia-reperfusion injury through COX-2 and PGE2 expression

The mechanism involved in the effects of positive acceleration adaptive training (PAAT) on gastric ischemia-reperfusion injury (GI-RI) has not been fully characterized. The aim of the present study was to investigate the effects of PAAT in attenuating GI-RI in a rat model. The inflammatory factor and caspase-3 levels were measured using ELISA kits. A western blot assay was used to analyze tumor necrosis factor-α (TNF)-α, tumor necrosis factor receptor 1 (TNFR1), tumor necrosis factor-related apoptosis inducing ligand (TRAIL), death receptor (DR) 4, DR5, cyclooxygenase (COX)-2, COX-1 and prostaglandin E2 (PGE2) protein expression levels. It was revealed that PAAT could alleviate GI-RI and inflammatory factor levels in a rat model. PAAT suppressed TNF-α and TNFR1 protein expression levels, inhibited TRAIL, DR4, DR5, COX-2 and PGE2 protein expression levels; however, it did not have an effect on COX-1 protein expression in the model of GI-RI. The data indicated that the effects of PAAT attenuated GI-RI through the downregulation of COX-2 and PGE2 expression.

Inhibition of Aeromonas hydrophila-induced intestinal inflammation and mucosal barrier function damage in crucian carp by oral administration of Lactococcus lactis

This study explored the immunomodulatory effect and inhibition effects of the candidate probiotic Lactococcus lactis 16-7, which was isolated from crucian carp, on Aeromonas hydrophila infection in crucian carp. The experimental fish were divided into two groups; one was fed a diet supplemented with L. lactis, while the other was fed the control probiotic-free diet. After feeding for 42 d with the experimental diets, the fish that received the diet supplemented with probiotics exhibited a significantly enhanced serum superoxide dismutase activity, phagocytic activities of innate immune cells, and the expression levels of immune-related genes [interferon-γ (INF-γ), interleukin-1β (IL-1β), interleukin-11 (IL-11), tumour necrosis factor α (TNF-α) and myeloid differentiation factor 88 (MyD88)], indicating that L. lactis 16-7 could activate the non-specific immune system of crucian carp. At the end of the feeding trial, the crucian carps in each group were orally infected with A. hydrophila NJ-35. The results show that L. lactis 16-7 could prevent the increase in d-lactic acid concentration and inflammatory response caused by A. hydrophila in crucian carp. Compared with A. hydrophila group, L. lactis 16-7 preserved the integrity of intestinal villi and mitigated A. hydrophila-induced reduce in the transcriptional levels of tight junction (TJ) proteins zonula occludens-1 (ZO-1) and occludin, indicating that L. lactis 16-7 could reduce intestinal mucosal barrier damage and inflammation induced by A. hydrophila in crucian carp. In addition, L. lactis 16-7 could effectively antagonize the colonization of A. hydrophila in the intestine. Overall, these data clearly indicate that L. lactis 16-7 has the potential to be developed as a probiotic agent against A. hydrophila infection in aquaculture.