Effects of Dietary Ochratoxin A on Growth Performance and Intestinal Apical Junctional Complex of Juvenile Grass Carp (Ctenopharyngodon idella)

Negative Effects of Occurrence of Mycotoxins in Animal Feed and Biological Methods of Their Detoxification: A Review

Secondary metabolic products of molds, called mycotoxins, negatively affect animal health and production. They constitute a significant problem in veterinary and medical sciences, and their presence has been confirmed in feed all over the world. Applying appropriate agricultural practices and ensuring proper storage conditions significantly reduces the contamination of agricultural products with mycotoxins. However, this does not guarantee that raw materials are completely free from contamination. Many detoxification methods are currently used, but their insufficient effectiveness and negative impact on the quality of the raw material subjected to them significantly limits their usefulness. The positive results of eliminating mycotoxins from many products have been proven by the specific properties of microorganisms (bacteria, yeast, and fungi) and the enzymes they produce. Biological detoxification methods seem to offer the most promising opportunities to solve the problem of the presence of mycotoxins in animal food. This work, based on literature data, presents the health risks to farm animals consuming mycotoxins with feed and discusses the biological methods of their purification.

Dietary copper improves intestinal structural integrity in juvenile grass carp (Ctenopharyngodon idella) probably related to its increased intestinal antioxidant capacity and apical junction complex

This research evaluated the effects of copper (Cu) on intestinal antioxidant capacity and apical junctional complex (AJC) in juvenile grass carp. A total of 1080 healthy juvenile grass carp (11.16 ± 0.01 g) were fed six diets including different dosages of Cu, namely 0, 2, 4, 6, 8 mg/kg (Cu citrate [CuCit] as Cu source) and 3 mg/kg (CuSO4·5H2O as Cu source). The trial lasted for 9 weeks. The findings revealed that dietary optimal Cu supplementation (2.2 to 4.1 mg/kg) promoted intestinal growth, including intestinal length, intestinal length index, intestinal weight, and intestinal somatic index (P < 0.05). Furthermore, optimal Cu boosted the intestinal mucosal barrier in juvenile grass carp. On the one hand, optimal Cu reduced diamine oxidase and D-lactate levels in serum (P < 0.05), reduced levels of the oxidative damage indicators malondialdehyde, reactive oxygen species (ROS), protein carbonyl, superoxide dismutase (P < 0.05), and catalase mRNA levels were elevated (P < 0.05), thus boosting intestinal antioxidant capacity, the binding protein Keap1a/1b/Nrf2 signaling pathway might be involved. Optimal Cu had no impact on glutathione peroxidase 1b (GPx1b) gene expression (P > 0.05). On the other hand, optimal Cu increased intestinal tight junction (TJ) proteins (except for claudin 15b) and adherens junction (AJ) proteins (E-cadherin, α-catenin, β-catenin, nectin and afadin) mRNA levels (P < 0.05), which could be connected to the signaling pathway formed by the Ras homolog gene family, member A (RhoA), Rho-associated kinase (ROCK), and myosin light chain kinase (MLCK). Finally, based on serum indicator D-lactate and intestinal oxidative damage index (ROS), Cu requirement (CuCit as Cu source) for juvenile grass carp from initial weight to final weight (from 11 to 173 g) was determined to be 4.14 and 4.12 mg/kg diet, respectively. This work may provide a theoretical foundation for identifying putative Cu regulation pathways on fish intestinal health.

Dietary curcumin alleviates intestinal damage induced by ochratoxin A in juvenile grass carp (Ctenopharyngodon idella): Necroptosis and inflammatory responses

Ochratoxin A (OTA) is one of the most common pollutants in aquatic feed. As a first line of defense, intestinal barriers could be utilized against OTA in order to prevent disorders. Natural product supplementation is one of the most popular strategies to alleviate toxicity induced by mycotoxins, but there is a lack of knowledge about how it functions in the teleost intestine. In this study, 720 juvenile grass carp of about 11 g were selected and four treatment groups (control group, OTA group, curcumin [Cur] group, and OTA + Cur group) were set up to conduct a 60-day growth test. After the test, the growth performance and intestinal health related indexes of grass carp were investigated. The addition of dietary Cur could have the following main results: (1) inhibit absorption and promote efflux transporters mRNA expression, reducing the residuals of OTA, (2) decrease oxidative stress by reducing oxidative damage and enhancing the expression of antioxidant enzymes, (3) promote mitochondrial fusion proteins to inhibit the expression of mitotic proteins and mitochondrial autophagy proteins and enhance mitochondrial function, (4) reduce necroptosis-related gene expression through inhibiting the tumor necrotic factor receptor-interacting protein kinase/mixed lineage kinase domain-like pathway, (5) reduce the expression of pro-inflammatory factors by inhibiting the Toll-like receptor 4/nuclear factor-κB signaling pathway to alleviate the intestinal inflammatory response. In summary, the results suggested that Cur could alleviate OTA-induced intestinal damage by enhancing antioxidant capacity and mitochondrial function as well as reducing necroptosis and inflammation in the grass carp intestine. This study provided a theoretical basis and production implications for dietary Cur that could improve growth performance and alleviate the intestinal damage induced by OTA in fish.

Unveiling the emerging role of curcumin to alleviate ochratoxin A-induced muscle toxicity in grass carp (Ctenopharyngodon idella): in vitro and in vivo studies

BACKGROUND

Ochratoxin A (OTA), a globally abundant and extremely hazardous pollutant, is a significant source of contamination in aquafeeds and is responsible for severe food pollution. The developmental toxicity of OTA and the potential relieving strategy of natural products remain unclear. This study screened the substance curcumin (Cur), which had the best effect in alleviating OTA inhibition of myoblast proliferation, from 96 natural products and investigated its effect and mechanism in reducing OTA myotoxicity in vivo and in vitro.

METHODS

A total of 720 healthy juvenile grass carp, with an initial average body weight of 11.06 ± 0.05 g, were randomly assigned into 4 groups: the control group (without OTA and Cur), 1.2 mg/kg OTA group, 400 mg/kg Cur group, and 1.2 mg/kg OTA + 400 mg/kg Cur group. Each treatment consisted of 3 replicates (180 fish) for 60 d.

RESULTS

Firstly, we cultured, purified, and identified myoblasts using the tissue block culture method. Through preliminary screening and re-screening of 96 substances, we examined cell proliferation-related indicators such as cell viability and ultimately found that Cur had the best effect. Secondly, Cur could alleviate OTA-inhibited myoblast differentiation and myofibrillar development-related proteins (MyoG and MYHC) in vivo and in vitro and improve the growth performance of grass carp. Then, Cur could also promote the expression of OTA-inhibited protein synthesis-related proteins (S6K1 and TOR), which was related to the activation of the AKT/TOR signaling pathway. Finally, Cur could downregulate the expression of OTA-enhanced protein degradation-related genes (murf1, foxo3a, and ub), which was related to the inhibition of the FoxO3a signaling pathway.

CONCLUSIONS

In summary, our data demonstrated the effectiveness of Cur in alleviating OTA myotoxicity in vivo and in vitro. This study confirms the rapidity, feasibility, and effectiveness of establishing a natural product screening method targeting myoblasts to alleviate fungal toxin toxicity.

Effects of the Replacement of Dietary Fishmeal by the Blend of Tenebrio molitor Meal, Chlorella Meal, Clostridium Autoethanogenum Protein, and Cottonseed Protein Concentrate on Growth, Protein Utilization, and Intestinal Health of Gibel Carp (Carassius gibelio, CAS Ⅴ)

The trial was conducted to investigate the effects of the replacement of dietary fishmeal (FM) by the blend of Tenebrio molitor meal (TMM), Chlorella meal (CM), Clostridium autoethanogenum protein (CAP), cottonseed protein concentrate (CPC) on growth, protein utilization and intestinal health of gibel carp (Carassius gibelio, CAS Ⅴ). The FM-based diet was used as the control, and the blended proteins (TMM: CM: CAP: CPC) at ratios of 1 : 1:8 : 2 (BLEND A), 1 : 1:6 : 4 (BLEND B), and 1 : 1:4 : 6 (BLEND C) were used to replace FM at three levels (33%, 67%, 100%), respectively. The results showed that, compared to the control group, growth performance increased significantly when dietary FM was fully replaced by BLEND B (P < 0.05), while decreased by BLEND A (P < 0.05). The complete substitution of FM with BLEND B significantly upregulated the mRNA expression of intestinal proinflammatory cytokines, anti-inflammatory cytokines, and tight junction-related genes (P < 0.05), improving intestinal tissue morphology and health. And it also significantly increased intestinal trypsin activity (P < 0.05), upregulated the mRNA expression of amino acid sensory receptor-related and amino acid or peptide transport-related genes (P < 0.05), increased protein apparent digestibility coefficient (P < 0.05). The 100% substitution of FM with BLEND A significantly upregulated the mRNA expression of intestinal proinflammatory cytokines and downregulated the mRNA expression of anti-inflammatory cytokine il-10 (P  < 0.05), reduced intestinal villus height (P < 0.05), and decreased protein apparent digestibility coefficient (P < 0.05). In conclusion, BLEND B could completely substitute dietary FM and was beneficial to the growth and health of gibel carp. Dietary digestible essential amino acids index (DEEAI) was found as an important indicator and should be higher than 79.5% to meet the maximum growth of fish.

EFSA Panel on Contaminants in the Food Chain (CONTAM), Schrenk D, Bignami M, Bodin L, Chipman JK, del Mazo J, Grasl‐Kraupp B, Hogstrand C, Hoogenboom L(R, Leblanc J, Nielsen E, Ntzani E, Sand S, Schwerdtle T, Vleminckx C, Wallace H, Gropp J, Antonissen G, Rychen G, Gómez Ruiz JÁ, Innocenti ML, Rovesti E, Petersen A. Risks for animal health related to the presence of ochratoxin A (OTA) in feed

In 2004, the EFSA Panel on Contaminants in the Food Chain (CONTAM) adopted a Scientific Opinion on the risks to animal health and transfer from feed to food of animal origin related to the presence of ochratoxin A (OTA) in feed. The European Commission requested EFSA to assess newly available scientific information and to update the 2004 Scientific Opinion. OTA is produced by several fungi of the genera Aspergillus and Penicillium. In most animal species it is rapidly and extensively absorbed in the gastro-intestinal tract, binds strongly to plasma albumins and is mainly detoxified to ochratoxin alpha (OTalpha) by ruminal microbiota. In pigs, OTA has been found mainly in liver and kidney. Transfer of OTA from feed to milk in ruminants and donkeys as well as to eggs from poultry is confirmed but low. Overall, OTA impairs function and structure of kidneys and liver, causes immunosuppression and affects the zootechnical performance (e.g. body weight gain, feed/gain ratio, etc.), with monogastric species being more susceptible than ruminants because of limited detoxification to OTalpha. The CONTAM Panel considered as reference point (RP) for adverse animal health effects: for pigs and rabbits 0.01 mg OTA/kg feed, for chickens for fattening and hens 0.03 mg OTA/kg feed. A total of 9,184 analytical results on OTA in feed, expressed in dry matter, were available. Dietary exposure was assessed using different scenarios based on either model diets or compound feed (complete feed or complementary feed plus forage). Risk characterisation was made for the animals for which an RP could be identified. The CONTAM Panel considers that the risk related to OTA in feed for adverse health effects for pigs, chickens for fattening, hens and rabbits is low.

New perspective on mechanism in muscle toxicity of ochratoxin A: Model of juvenile grass carp (Ctenopharyngodon idella)

Ochratoxin A (OTA) is a common fungal toxin that pollutes raw materials of aquatic feeds (such as corn, soybean meal, and wheat). This study explored the effects of OTA through diet on muscle toxicity in juvenile grass carp (Ctenopharyngodon idella). The following results were obtained for the muscle. (1) With an increase in dietary OTA, the residue of OTA in muscle increased, muscle fiber diameter and density decreased, and even muscle fiber breakage. (2) OTA caused oxidative stress by downregulating GPx1 (a, b) and Trx via inhibited the PGC1-α/Nrf2 signaling pathway. (3) OTA exacerbated endoplasmic reticulum stress in the muscle by causing endoplasmic reticulum expansion (results of transmission electron microscopy) and upregulating the expression of GRP78, eIF2α, ATF6, PERK, and CHOP. (4) OTA reduced muscle fiber diameter by inhibiting protein synthesis (AKT, TOR, and S6K1) and promoting the mRNA expression of protein degradation-related genes (MURF1, MAFBX, and FoxO3a), as well as by reducing AKT and promoting the immunofluorescence expression of FoxO3. (5) OTA inhibits collagen deposition by downregulating TGF-β1, TGF-βR1, Smad2, Smad3, Smad4, CTGF, TIMP, PHD, and LOX mRNA expressions as well as the CTGF immunofluorescence expression. Moreover, based on the GSH and collagen content contents, the upper safe dose for OTA-induced toxicity was 963.6 and 1129.6 μg/kg diet, respectively. Using the example of OTA, our research has provided new insights that raise concerns about the quality of aquatic products by exploring muscle toxicity caused by mycotoxins.

Novel insights on toxicology of ochratoxin A contaminated diets to skin: Residues, mucus disruption and barrier impairment in teleost model grass carp (Ctenopharyngodon idella)

Ochratoxin A (OTA), a notorious pollutant widely present worldwide, seriously pollutes aquafeeds. This paper aims to explore the toxicity effects of OTA by the way of diet on the skin barrier in grass carp (Ctenopharyngodon idella). Results were shown as follows in the skin: (1) OTA increased the mRNA abundances of uptake transporter proteins (e.g., OAT3) and decreased efflux transporter proteins (e.g., ABCG2), which caused the accumulation of OTA in the skin of grass carp. (2) OTA upregulated the gene expression related to ROS production by enhancing the NOX (1, 2, 4) signaling pathway and decreased the ability to ROS elimination with downregulation of GPx1 (a,b), Trx by inhibiting the PGC1-α/Nrf2 signaling pathway, which caused oxidative damage to the skin. (3) OTA exacerbated apoptosis in the skin by upregulating the expression of apoptosis-related proteins mediated by ways of endoplasmic reticulum stress and mitochondrial apoptosis. Moreover, OTA down-regulated the mRNA and protein abundances of tight junction-related proteins by inhibiting the MLCK signaling pathway, which in turn disrupted the tight junctions. (4) OTA reduced the number of mucous cup cells and decreased f LZ activities and IgM contents, and finally down-regulated the mRNA abundances of mucin (2, 3), LEAP-2 (A, B), and β-defensin (1, 2, 3), which in turn resulted in impairing skin chemical barrier. Moreover, based on the antimicrobial-related indexes (LZ activities and IgM contents), the OTA-safe upper doses were 814.827 and 813.601 μg/kg.

Ochratoxin A induces locomotor impairment and oxidative imbalance in adult zebrafish

Ochratoxin A (OTA) is a mycotoxin produced by species of filamentous fungi widely found as a contaminant in food and with high toxic potential. Studies have shown that this toxin causes kidney and liver damage; however, data on the central nervous system effects of exposure to OTA are still scarce. Thus, this study aimed to investigate the effects of exposure to OTA on behavioral and neurochemical parameters in adult zebrafish. The animals were treated with different doses of OTA (1.38, 2.77, and 5.53 mg/kg) with intraperitoneal injections and submitted to behavioral evaluations in the open tank and social interaction tests. Subsequently, they were euthanized, and the brains were used to assess markers associated with oxidative status. In the open tank test, OTA altered distance traveled, absolute turn angle, mean speed, and freezing time. However, no significant effects were observed in the social interaction test. Moreover, OTA also increased glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GR) levels and decreased non-protein thiols (NPSH) levels in the zebrafish brain. This study showed that OTA can affect behavior and neurochemical levels in zebrafish.

The multiple biotoxicity integrated study in grass carp (Ctenopharyngodon idella) caused by Ochratoxin A: Oxidative damage, apoptosis and immunosuppression

Ochratoxin A (OTA) is a common hazardous food contaminant that seriously endangers human and animal health. However, limited study is focused on aquatic animal. This research investigated the multiple biotoxicity of OTA on spleen (SP) and head kidney (HK) in grass carp and its related mechanism. Our data showed that, dietary supplemented with OTA above 1209 μg/kg caused histopathological damages by decreasing the number of lymphocytes and necrotizing renal parenchymal cells. Meanwhile, OTA caused oxidative damage and reduced the isoforms mRNAs transcripts of antioxidant enzymes (e.g., GPX1, GPX4, GSTO) partly due to suppressing NF-E2-related factor 2 (Nrf2). OTA triggered apoptosis through mitochondria and death receptor pathway potentially by p38 mitogen-activated protein kinase (p38MAPK) activation. Besides, OTA exacerbated inflammation by down-regulation of anti-inflammatory factor (e.g., IL-10, IL-4) and up-regulations of pro-inflammatory factors (e.g., TNF-α, IL-6), which could be ascribed to signaling meditation of Janus kinase / signal transducer and activator of transcription (JAK/STAT). Additionally, the safe upper limits of OTA were estimated to be 677.6 and 695.08 μg/kg based on the immune-related indexes (C3 contents in the SP and LZ activities in the HK, respectively). Our study has provided a wide insight for toxicological assessment of feed pollutant in aquatic animals.

Metagenomic analysis explores the interaction of aged microplastics and roxithromycin on gut microbiota and antibiotic resistance genes of Carassius auratus

The aging process changes the physicochemical structure of microplastics and affects environmental behaviors and toxicological effects of coexisting pollutants, thereby posing ecological risks. In this study, the effects of aged polystyrene microplastics alone or in combination with the 100 μg/L roxithromycin (ROX) on intestines of Carassius auratus were investigated. The carrier effect of microplastics was enhanced by aging due to changes in functional groups and surface area, which led to an increase in the bioaccumulation of ROX. The combined exposure of aged microplastics (APS) and ROX caused more inflammatory cell infiltration and cilia defects, and significantly inhibited the activity of amylase and lipase. Metagenomic sequencing revealed that the combined exposure of microplastics and ROX increased the abundance of Gemmobacter, Bosea, Rhizobium, and Shinella and decreased the abundance of Cetobacterium and Akkermansia (p < 0.05). The presence of APS enhanced the selective enrichment of antibiotic resistance genes. What's more, the influence of microplastics and antibiotics on gut microbiota was closely related to carbohydrate metabolism and amino acid metabolism activities, as well as the abundance of baca and sul1 resistance genes. These results expand our understanding of the interaction mechanism between APS and antibiotics in real aquatic environment.

Whole transcriptome-based ceRNA network analysis revealed ochratoxin A-induced compromised intestinal tight junction proteins through WNT/Ca2+ signaling pathway

Ochratoxin A (OTA) is a widespread environmental pollutant that is a threat to humans and livestock and remains a global concern to public health. It has negative effects on both humans and animals that are in a continuously exposed environment. The compromised intestinal barrier caused by OTA has aroused widespread concern. This study aimed to investigate the mechanism of OTA-induced tight junction (TJ) protein damage and the relevant components of the intestinal barrier through in vivo whole transcriptome analysis combined with in vitro functional verification. Bioinformatics analysis in OTA-treated Balb/c mice demonstrated that regulated TJ protein related mRNAs were perturbed, and activated the WNT/Ca2+ signaling pathway possibly regulated by key lncRNAs and miRNAs. Competing endogenous RNA (ceRNA) network analysis revealed that lncRNA Zeb1 regulated FZD4 binding with WNT5a to release Ca2+ by targeting miR-1258-x and reduced the expression of TJ proteins, thus damaging the function of the intestinal barrier. An in vitro experiment with Caco-2 cells verified that an increase in Ca2+ level was involved in OTA-induced decreases in the expression of TJ proteins. Taken together, these results will help to identify targets in the intestinal barrier that are compromised by OTA, and will provide the basis for preventing the associated hazard and risk.

Effect of Dietary Tryptophan on Growth, Intestinal Microbiota, and Intestinal Gene Expression in an Improved Triploid Crucian Carp

Tryptophan (Trp) has received increasing attention in the maintenance of intestinal function. In this study, improved triploid crucian carp (ITCC) fed diets containing 6.35 g kg⁻¹ Trp had higher average daily gain (ADG) and improved villus height (VH) and crypt depth (CD) in the intestine compared to the control group. To elucidate the potential mechanisms, we used RNA sequencing (RNA-seq) to investigate changes in the intestinal transcriptome and 16S rRNA gene sequencing to measure the intestinal microbiota in response to 6.35 g kg⁻¹ Trp feeding in ITCC. Dietary Trp altered intestinal gene expression involved in nutrient transport and metabolism. Differentially expressed transcripts (DETs) were highly enriched in key pathways containing protein digestion and absorption and the AMPK signaling pathway. 16S rRNA sequencing showed that 6.35 g kg⁻¹ Trp significantly increased the abundance of the genus Cetobacterium, and the Firmicutes/Bacteroidetes ratio at the phylum level (P < 0.05). In addition, bacterial richness indices (Simpson index) significantly increased (P < 0.05) community evenness in response to 6.35 g kg⁻¹ Trp. In conclusion, appropriate dietary Trp improves the growth performance, and influences the intestinal flora of ITCC. This study might be helpful to guide the supply of dietary exogenous Trp in ITCC breeding.