Deficiency of dietary niacin impaired gill immunity and antioxidant capacity, and changes its tight junction proteins via regulating NF-κB, TOR, Nrf2 and MLCK signaling pathways in young grass carp (Ctenopharyngodon idella)

Toxic effects of combined exposure to cadmium and nitrate on intestinal morphology, immune response, and microbiota in juvenile Japanese flounder (Paralichthys olivaceus)

Cadmium (Cd2+) and nitrate (NO3-) are important environmental pollutants in the offshore marine ecological environment. However, limited research has explored their combined effects, particularly regarding their impact on the microbiota and intestinal health of marine fish. In this study, juvenile Japanese flounders (P. olivaceus) were immersed in seawater samples with different combinations of Cd2+ (0, 0.2, and 2 mg/L) and NO3- (0 and 80 mg/L NO3N) for 30 days to explore their toxic impacts on intestinal morphology, tight junction (TJ) barrier, immune response, and microbiota. Our results showed that Cd2+ or NO3- exposure alone led to histopathological damage of the gut, while their co-exposure aggravated intestinal damage. Moreover, co-exposure substantially decreased TJ-related gene expression, including occludin, claudin-10, and ZO-2, suggesting increased TJ permeability in the gut. Regarding the immune response, we observed upregulated expression of immune-related markers such as HSP40, IL-1β, TNF-α, and MT, suggesting the onset of intestinal inflammation. Furthermore, Cd2+ and NO3- exposure led to changes in intestinal microflora, characterized by decreased the abundance of Sediminibacterium and NS3a_marine_group while increasing the prevalence of pathogens or opportunistic pathogens such as Ralstonia, Proteus, and Staphylococcus. This alteration in microbiota composition increased network complexity and α-diversity, ultimately causing dysbiosis in the fish gut. Additionally, combined exposure resulted in metabolic disorders that affected the predicted functions of the intestinal microbiota. Overall, our study demonstrates that Cd2+-NO3- co-exposure amplifies the deleterious effects compared to single exposure. These findings enhance our understanding of the ecological risks posed by Cd2+-NO3- co-exposure in marine ecosystems.

Effect of Different Levels of Niacin on Serum Biochemical Parameters, Antioxidant Status, Cytokine Levels, Inflammatory Gene Expression and Colonic Microbial Composition in Weaned Piglets

Niacin plays an important role in regulating the gut health of weaned piglets. In this study, 48 25-day-old weaned piglets (7.9 ± 0.20 kg) produced by 14 sows (3 to 4 piglets per sow) were randomly divided into 4 groups with 6 replicates in each group and 2 piglets in each replicate. Each group was fed diets supplemented with 22.5 (N1), 30 (N2), 45 (N3), and 75 (N4) mg/kg of niacin, respectively. Samples were taken at 7 and 14 d, respectively. The study shows that changes in niacin levels significantly affected the content of IgG and IgM in the serum (p < 0.05). Niacin had a significant effect on antioxidant parameters such as MDA, T-SOD, and CuZn-SOD in the jejunal mucosa of weaned piglets (p < 0.05). Moreover, significant differences were observed in the expression of cytokines such as TGF-β, TNF-α, and COX2 in the jejunal mucosa (p < 0.05). The 16S rRNA sequencing analysis showed that there were significant differences in the colonic species composition, which were also accompanied by changes in the isovaleric acid content (p < 0.05). In conclusion, an appropriate increase in niacin dose based on NRC (2012) has an important role in improving the antioxidant status of weaned piglets, alleviating intestinal inflammation in piglets, improving immunity, and regulating the structure of the microbiota.

Dietary Niacin Requirement of Juvenile Chinese Mitten Crab, Eriocheir sinensis

Effects of dietary niacin on the growth performance, intestinal histomorphology, body composition, and antioxidant capacity were investigated in the present study to determine the optimum requirement of niacin for juvenile Eriocheir sinensis. All 360 crabs (initial average weight 1.14 ± 0.04 g) were randomly divided into 6 groups with 3 replicates in each group and 20 crabs in each replicate. Crabs were fed with the control diet (0.89 mg/kg) or niacin-supplemented diets (170.54 mg/kg, 347.05 mg/kg, 587.59 mg/kg, 784.85 mg/kg, and 1248.86 mg/kg) for 12 weeks (named as G1, G2, G3, G4, G5, and G6, respectively). The results showed that appropriate dietary niacin (above 347.05 mg/kg) significantly increased the weight gain rate (WGR) and specific growth rate (SGR) (p < 0.05), but did not affect the survival rate (SR), feed conversion ratio (FCR), daily feeding rate (DFR), and molting frequency (MF) of crabs (p > 0.05). The niacin content in the hepatopancreas of crabs in G1 and G2 was significantly lower than that of the other four groups (p < 0.05). Moreover, dietary niacin significantly affected the intestinal histomorphology of crabs, including the number of folds (NF), height of folds (HF), height of microvillus (HMV), and thickness of muscularis (TM) (p < 0.05). Additionally, moderate dietary niacin levels significantly affected the nonspecific immune responses of crabs, by improving the activity of catalase (CAT), glutathione s-transferase (GST), glutathione peroxidase (GSH-Px), and total superoxide dismutase (T-SOD) (p < 0.05). Based on the broken-line model analysis of SGR against dietary niacin level, the dietary niacin requirement of juvenile crabs was suggested to be 419.4 mg/kg.

GPR109A alleviate mastitis and enhances the blood milk barrier by activating AMPK/Nrf2 and autophagy

Mastitis causes great psychological and physical pain among women. Our previous studies found that niacin has anti-inflammatory effect, and the realization of this function depends on GPR109A. However, there are no previous reports about the anti-inflammatory function of GPR109A in mastitis. In our study, we observed the effect of niacin on the WT and GPR109A^-/- mice mastitis model. The results showed that administration of niacin to WT mice reduced the damage, proinflammatory mediators and protected the integrity of the blood milk barrier in mammary gland. While in GPR109A^-/- mice, there was no effect on the above indexes. In mammary epithelial cells, GPR109A was able to promote autophagy and Nrf2 nuclear import through AMPK. In LPS-induced mammary epithelial cells, niacin inhibited the LPS-induced inflammatory response and downregulation of tight junction proteins, and these effects were eliminated by knocking down GPR109A, blocking autophagy or inhibiting Nrf2 nuclear import. These results indicate that in mastitis, GPR109A promotes autophagy and Nrf2 nuclear import through AMPK, thereby inhibiting inflammatory damage to the mammary gland and repairing the blood milk barrier. Our results suggested that GPR109A may be a potential target for the treatment of mastitis.

Protective effects and potential mechanisms of (2-Carboxyethyl) dimethylsulfonium Bromide (Br-DMPT) on gill health status of on-growing grass carp (Ctenopharyngodon idella) after infection with Flavobacterium columnare

In this study, the protective effects and potential mechanisms of (2-Carboxyethyl) dimethylsulfonium Bromide (Br-DMPT) were evaluated in relation to the gill health status of on-growing young grass carp (Ctenopharyngodon idella). A total of 450 grass carp (216.49 ± 0.29 g) were randomly distributed into five treatments of three replicates each (30 fish per replicate) and were fed diets supplemented with gradational Br-DMPT (0-520.0 mg/kg levels) for 60 days. Subsequently, the fish were challenged with Flavobacterium columnare for 3 days, and the gills were sampled to evaluate antioxidant status and immune responses evaluation. Our results showed that, when compared to the control group, dietary supplementation with appropriate Br-DMPT levels resulted in the following: (1) decreased gill rot morbidity and improved gill histological symptoms after exposure to F. columnare (P < 0.05); (2) improved activities and gene expression levels (except GSTP2 gene) of antioxidant enzymes and decreased oxidative damage parameter values (reactive oxygen species, malondialdehyde and protein carbonyl) (P < 0.05), which may be partially associated with the nuclear factor-erythroid 2-related factor 2 (Nrf2) signalling pathway (P < 0.05); (3) increased lysozyme (LZ) and acid phosphatase (ACP) activities and complement 3 (C3), C4 and immunoglobulin M (IgM) contents, and upregulated genes expressions of antibacterial peptides (liver-expressed antimicrobial peptide-2A, -2B, hepcidin, β-defensin and mucin2) (P < 0.05); (4) upregulated gene expressions of anti-inflammatory cytokines (except IL--4/13B) that may be partially to the TOR/(S6K1, 4E-BP1) signalling pathway, and downregulated gene expressions of pro-inflammatory cytokines (except IL-12P35) may be partially to the IKK β, γ/IκBα/NF-kB) signalling pathway (P < 0.05). Taken together, our results indicate that dietary supplementation with appropriate amounts of Br-DMPT may effectively protect on-growing grass carp from F. columnare by strengthening gill antioxidant capacity and immunity. Furthermore, based on measures of combatting gill rot, antioxidant indices (MDA) and immune indices (LZ), the dietary Br-DMPT supplementation levels for on-growing grass carp are recommended to be 291.14, 303.38 and 312.01 mg/kg diet, respectively.

Amelioration of hexavalent chromium-induced bioaccumulation, oxidative stress, tight junction proteins and immune-related signaling factors by Allium mongolicum Regel flavonoids in Ctenopharyngodon idella

Chromium (Cr) is the most common heavy metal and that becomes toxic when present at higher concentrations in aquatic environments. Allium mongolicum Regel flavonoids (AMRF) has been documented to possess detoxification, antioxidant and anti-inflammatory properties. The aim of this study was to explore the potential of dietary AMRF and Cr exposure on bioaccumulation, oxidative stress, and immune response in Ctenopharyngodon idella. After acclimation, 360 fish were randomly distributed into six groups. The fish were fed with diets supplemented with Cr and/or AMRF for 4 weeks (28 days), the Cr concentrations were 0, 120, and 240 mg/kg and the concentrations of AMRF were 0 or 40 mg/kg, respectively. The results shown that Cr accumulation in the kidney, liver, spleen, intestine and gill were significantly increased following Cr exposure, dietary AMRF supplementation attenuated the increased in Cr accumulation. Dietary AMRF supplementation significantly reduced the levels of malondialdehyde (MDA) and protein carbonyl (PC) in liver, spleen and gill compared with the same Cr dose groups. When fish were supplemented with AMRF significantly increased lysozyme activity (LZM), complement 3 (C3) in kidney and intestine compared with the same Cr dose groups. Serum glutamic oxalate transaminase (GOT) and glutamic pyruvate transaminase (GPT) were significantly increased following exposure to Cr. Dietary AMRF supplementation significantly decreased GOT and GPT activity in the serum. In addition, AMRF supplementation can decrease the expression of inflammatory (NF-κB p65, TNF-α and IL-1β) and increased the expression of tight junction proteins (occludin and ZO-1) following Cr exposure in C. idella. These results indicate that AMRF has the potential to alleviate the effects of Cr toxicity in C. idella.

In vitro antioxidants and hepatoprotective effects of Pleurotus tuber-regium on carbon tetrachloride-treated rats

Objectives This study has characterized the phytoconstituents and evaluated the in vitro antioxidant and hepatoprotective effects of Pleurotus tuber-regium induced by carbon tetrachloride (CCl4). In vitro antioxidant assay of ethanol extract of P. tuber-regium and gas chromatography-mass spectrometry analyses to identify the phytoconstituents were carried out. Methods Sixty rats were divided into six groups of 10 animals in each group and treated as follows for 13 weeks. Group I (control) received 3 mL/kg olive oil intraperitoneal twice weekly in addition to feed and water ad libitum. Group II received CCl4 3 mL/kg twice weekly. Groups III, IV and V received 100, 200 and 500 mg/kg wild edible P. tuber-regium mixed with feed by ingestion daily in addition to 3 mL/kg CCl4 twice weekly, respectively. Group VI received 500 mg P. tuber-regium daily. Liver and body weights were recorded. Liver function tests, oxidative stress biomarkers, bilirubin, ascorbic acid and α-tocopherol were assayed. Histopathology of the liver was carried out. The gas chromatography-mass spectroscopy analysis yielded 10 antioxidants. Results CCl4 increased the levels of alanine transaminase, aspartate transaminase, alkaline phosphatase, bilirubin and malondialdehyde from 24±1.778 iu/L, 53±3.7 iu/L, 257±19 iu/L, 0.45±0.03 mg/dL and 1.90±0.42 μmol/L in the control group to 48±2.5 iu/L, 81±2.10 iu/L, 495±38 iu/L, 1.20±0.09 mg/dL and 14.0±2.6 μmol/L in the treated group, respectively. Conclusions P. tuber-regium prevented the necrosis, edema and vein congestion observed in the CCl4-only group. P. tuber-regium is effective in protecting the liver against CCl4-induced damage.

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.

Effect of Dietary Niacin Supplementation on Growth Performance, Nutrient Digestibility, Hematology, and Lipoprotein Concentrations of Young Turkeys, Meleagris gallopavo

The growth performance, nutrient digestibility, hematology, serum chemistry, and lipoprotein concentrations of turkey (Meleagris gallopavo) poults fed diets supplemented with high or recommended concentrations of niacin were investigated in this study. A total of 120 four-week-old turkey poults were randomly divided into three treatment groups with five replicates of eight birds in each group. The poult diets were supplemented with 0.0, 60, and 180 mg/kg niacin in the three treatments, termed control, recommended niacin supplementation (RNS), and high niacin supplementation (HNS), respectively. The study lasted for four weeks. The results showed that the HNS treatment reduced the feed intake and increased the body weight gain of poults. The apparent, nitrogen-corrected, and true metabolizable energy contents were the highest in the HNS-group turkey poults (P<0.05). The red and white blood cell counts and hemoglobin concentration of the turkeys improved with increasing niacin supplementation (P<0.01). The serum constituents, including the serum protein and globulin, were significantly increased (P<0.05), while the uric acid and creatinine contents were significantly reduced in the HNS-group turkeys. Similarly, the HNS-group turkeys exhibited significantly reduced alanine aminotransferase (ALT) and alkaline phosphatase (ALP) contents, while the RNS-group turkeys had the least aspartate aminotransferase (AST) content. In addition, the HNS-group turkeys had the least serum low-density lipoprotein (LDL), triglyceride, and total cholesterol concentrations and the highest serum high-density lipoprotein (HDL) (P<0.01) concentrations. In conclusion, the supplementation of 180 mg/kg niacin in the diet reduced the feed intake and serum ALT, ALP, LDL, triglyceride, and cholesterol contents and increased the body weight gain, metabolizable energy, and HDL concentration in turkeys. This study showed that niacin supplementation could reduce the fat content without compromising the body weight gain and increase stress resistance in turkey poults.

Dietary threonine deficiency depressed the disease resistance, immune and physical barriers in the gills of juvenile grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare

This study was conducted to investigate the effects of dietary threonine on the disease resistance, gill immune and physical barriers function of juvenile grass carp (Ctenopharyngodon idella). A total of 1080 juveniles were fed six iso-nitrogenous diets containing graded levels of threonine (3.99-21.66 g kg^-1 diet) for 8 weeks, and then challenged with Flavobacterium columnare. Results showed that threonine deficiency (3.99 g kg^-1 diet): (1) increased the gill rot morbidity after exposure to F. columnare; (2) attenuated the gill immune barrier function by decreasing antimicrobial substances production, up-regulating the mRNA levels of pro-inflammatory cytokines (except IL-12p40), and down-regulating the anti-inflammatory cytokines partly due to the modulation of NF-κB and TOR signaling. (3) disrupt the gill tight junction complexes by down-regulating TJs (claudin-3, -b, -c, 12, occludin, ZO-1 and ZO-2) and up-regulating TJs (claudin-7a, -7b) as well as related signaling molecule myosin light chain kinase mRNA levels (P < 0.05). (4) exacerbated the gill apoptosis by up-regulating cysteinyl aspartic acid-protease-3, 8, 9, c-Jun N-terminal kinases and mediating apoptosis related factors mRNA levels (P < 0.05); (5) exacerbated oxidative injury with increased reactive oxygen species, malondialdehyde and protein carbonyl contents (P < 0.05), decreased the antioxidant related enzymes activities and corresponding mRNA levels (except glutathione peroxidase-1b and glutathione-S-transferase-omega 2) as well as glutathione contents (P < 0.05) partly ascribe to the abridgement of NF-E2-related factor 2 signaling [Nrf2/Keap1a (not Keap1b)] in fish gill. Overall, threonine deficiency depressed the disease resistance, and impaired immune and physical barriers in fish gill. Finally, based on the gill rot morbidity and biochemical indices (immune indices LA activity and antioxidant indices MDA content), threonine requirements for juvenile grass carp (9.53-53.43 g) were estimated to be 15.32 g kg^-1 diet (4.73 g 100 g^-1 protein), 15.52 g kg^-1 diet (4.79 g 100 g^-1 protein), 15.46 g kg^-1 diet (4.77 g 100 g^-1 protein), respectively.

Role of MiRNAs in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD), mainly including Crohn's disease and ulcerative colitis, are characterized by chronic inflammation of the gastrointestinal tract. Despite improvements in detection, drug treatment and surgery, the pathogenesis of IBD has not been clarified. A number of miRNAs have been found to be involved in the initiation, development and progression of IBD, and they may have the potential to be used as biomarkers and therapeutic targets. Here, we have summarized the recent advances about the roles of miRNAs in IBD and analyzed the contribution of miRNAs to general diagnosis, differential diagnosis and activity judgment of IBD. Furthermore, we have also elaborated the promising role of miRNAs in IBD-related cancer prevention and prognosis prediction.

Gill structural integrity changes in fish deficient or excessive in dietary isoleucine: Towards the modulation of tight junction protein, inflammation, apoptosis and antioxidant defense via NF-κB, TOR and Nrf2 signaling pathways

This study firstly aimed to test the impact of dietary isoleucine (Ile) on tight junction protein, inflammation, apoptosis, antioxidant defense and related signaling molecule gene expression in the gill of fish. Young grass carp (Ctenopharyngodon idella) (weighing 256.8 ± 3.5 g) were fed six diets containing graded levels of Ile, namely, 3.8, 6.6, 9.3, 12.5, 15.2 and 18.5 g/kg diet for 8 weeks. The results firstly revealed that Ile deficiency down-regulated the mRNA expressions of claudin-3, claudin-b, claudin-c, occludin and zonula occludens-1 (ZO-1) and up-regulated the mRNA expression of claudin-12, which led to the intercellular structure damage of fish gill. These effects were partially ascribed to the up-regulation of pro-inflammatory cytokines [interleukin 1β (IL-1β), interleukin 8 (IL-8) and tumor necrosis factor-α (TNF-α)] mRNA expressions that referring to up-regulated nuclear factor κB P65 (NF-κB P65) mRNA expression and down-regulated inhibitor factor κBα (IκBα) mRNA expression, and the down-regulation of anti-inflammatory cytokines [interleukin 10 (IL-10) and transforming growth factor β1 (TGF-β1)] mRNA expressions that referring to the down-regulated TOR and S6K1 mRNA expression. Interestingly, no change in claudin 15 mRNA level was observed among every treatment. At the same time, the results firstly indicated that Ile deficiency also resulted in the cellular structure damage of fish gill: (1) DNA fragmentation partially due to the up-regulation of caspase-3, caspase-8 and caspase-9 mRNA expression; (2) increase in protein carbonyl (PC), malondialdehyde (MDA) and ROS contents, which may be partially attributed to the impaired antioxidant defense [indicated by decreased glutathione (GSH) level and depressed anti-superoxide anion (ASA), anti-hydroxyl radical (a-HR), copper/zinc superoxide dismutase (Cu/Zn-SOD), catalase (CAT) and glutathione peroxidase (GPx) activities] that referring to the down-regulation of corresponding antioxidant enzyme mRNA expressions and the related signaling molecules Nrf2 mRNA expression. Ile excess caused similar negative effects that observed in Ile-deficient group, whereas these negative effects were reversed with appropriate Ile supplementation. In conclusion, our results indicated that Ile deficiency or excess disrupted the structural integrity of fish gill, partially due to the trigger of apoptosis, the impairment of antioxidant defense, and the regulation of tight junction protein, inflammatory cytokines, apoptosis-related, antioxidant enzymes and related signaling molecules mRNA expressions in the fish gill.