Effects of dietary butylated hydroxytoluene on aflatoxin B1-relevant metabolic enzymes in turkeys

Chicken CYP1A5 is able to hydroxylate aflatoxin B1 to aflatoxin M1

Aflatoxin B1 (AFB1), a naturally-occurring mycotoxin, can cause severe toxicological and carcinogenic effects in livestock and humans. Given that the chicken is one of the most important food-producing animals, knowledge regarding AFB1 metabolism and enzymes responsible for AFB1 transformation in the chicken has important implications for chicken production and food safety. Previously, we have successfully expressed chicken CYP1A5 and CYP3A37 monooxygenases in E. coli, and reconstituted them into a functional CYP system consisting of CYP1A5 or CYP3A37, CPR and cytochrome b5. In this study, we aimed to investigate the roles of CYP1A5 and CYP3A37 in the bioconversion of AFB1 to AFM1. Our results showed that chicken CYP1A5 was able to hydroxylate AFB1 to AFM1. The formation of AFM1 followed the typical Michaelis-Menten kinetics. The kinetics parameters of Vmax and Km were determined as 0.83 ± 0.039 nmol/min/nmol P450 and 26.9 ± 4.52 μM respectively. Docking simulations further revealed that AFB1 adopts a "side-on" conformation in chicken CYP1A5, facilitating the hydroxylation of the C9a atom and the production of AFM1. On the other hand, AFB1 assumes a "face-on" conformation in chicken CYP3A37, leading to the displacement of the C9a atom from the heme iron and explaining the lack of AFM1 hydroxylation activity. The results demonstrate that chicken CYP1A5 possesses efficient hydroxylase activity towards AFB1 to form AFM1.

The ameliorative effects of Nigella sativa, thymoquinone, and bentonite against aflatoxicosis in broilers via AFAR and Nrf2 signalling pathways, and down-regulation of caspase-3

1. Aflatoxins' (AFs) are metabolites which especially have toxic effects on proteins, and are detoxified by the aflatoxin-B₁ aldehyde reductase (AFAR) pathway. In this pathway, the aldo-keto reductase family 7, member A2 (AKR7A2) enzyme is controlled by nucleic-related erythroid factor 2 (Nrf2) plays an active role. However, data on the efficacy of this critical pathway in broilers is limited.2. The aim of the following study was the changes in the expression levels of AKR7A2, Nrf2, and caspase-3, and the effects of Nigella sativa seeds (NS), thymoquinone (TMQ), and bentonite (BNT) on expression were investigated in broilers exposed to AFs.3. One-hundred broilers were divided into ten groups (control (CNT); AF; NS; TMQ; BNT; AF+TMQ; AF+NS; AF+BNT; AF+BNT+NS; AF+BNT+TMQ) and fed for 28 d. AF. TMQ, NS and BNT were added to diets at levels of 2 mg/kg, 300 mg/kg, 50 g/kg and 10 g/kg respectively.4. The addition of AF to the diet decreased AKR7A2 and Nrf2 levels dramatically, but increased caspase-3 (P<0.01). TMQ, NS and BNT additions to the diet eliminated all negative effects caused by AF (P<0.01); and AKR7A2 and Nrf2 were further raised in TMQ and NS groups when compared to the control group. TMQ and NS showed a positive effect on detoxification parameters when given together with BNT.5. Supplementation with NS and TMQ enhanced AF detoxification via the AFAR pathway, by increasing AKR7A2 and Nrf2 levels, in addition to reducing hepatocyte apoptosis.

The Mechanism Underlying the Extreme Sensitivity of Duck to Aflatoxin B1

Most metabolites of aflatoxin B1 (AFB1), especially exo-AFB1-8,9-epoxide (AFBO), can induce the production of reactive oxygen species (ROS) to vary degrees, causing oxidative stress and liver damage, and ultimately induce liver cancer in humans and animals. Duck is one of the most sensitive animals to AFB1, and severe economic losses are caused by duck AFB1 poisoning every year, but the exact mechanism of this high sensitivity is still unclear. This review highlights significant advances in our understanding of the AFB1 metabolic activation, like cytochrome P450s (CYPs), and AFB1 metabolic detoxification, like glutathione S-transferases (GSTs) in poultry. In addition, AFB1 may have other metabolic pathways in poultry, such as the mutual conversion of AFB1 and aflatoxicol (AFL) and the process of AFBO to produce AFB1-8,9-dihydrodiol (AFB1-dhd) and further metabolize it into detoxification substances. This review also summarized some exogenous regulatory substances that can alleviate AFB1-induced oxidative stress.

Methionine alleviates aflatoxinb1-induced broiler chicks embryotoxicity through inhibition of caspase-dependent apoptosis and enhancement of cellular antioxidant status

Practical methods for preventing embryotoxicity in chickens that are caused by aflatoxin-B1 (AFB1) are currently rare. Binding absorbers are commonly used in feeding stuff to reduce laying hens' exposure to off-contaminated diets, thus reducing residue exposure to fertilized eggs. Nonetheless, several adsorbents have been shown to affect the use of nutrients and the absorption of minerals in poultry. Thus, seeking an effective strategy to counter or control embryotoxicity in broiler chicks caused by AFB1 is a problem. A total of 180 embryonated eggs were injected with 36 ng AFB1 with or without 5.90 mg L-methionine (Met) 30 embryonated eggs each, followed by incubation in an incubator until hatching time. The in ovo injection of Met significantly reduced toxicity caused by AFB1 in broiler embryos by enhancing the liver and kidney functions, lipid profiles, and alleviated oxidative stress during the incubation period. Furthermore, the relative gene expressions (SSTR5, TSH-β, Bcl-2, GSH-Px, GST-a, and SOD in the liver) were up-regulated with in ovo injection of AFB1+Met compared to AFB1 alone. Moreover, there was a dowin-regulated trend in Bax, Caspases-3, Caspases-7, Caspases-9, CYP1A1, CYP2H1, and P53 gene expression with in ovo injection of AFB1+Met compared to AFB1 alone. The in ovo injection of Met led to less apoptotic cells in liver tissues. Such results might be necessary for the poultry industry as it is focused on managing the embryotoxicity of AFB1, which affecting poultry production and welfare. Results from this study demonstrated that in ovo Met injection could alleviate AF-induced toxicity in chicken embryos.

The efficiency of synthetic polymers to ameliorate the adverse effects of Aflatoxin on plasma biochemistry, immune responses, and hepatic genes expression in ducklings

To evaluate the effect of molecularly imprinted polymers as a synthetic polymer (TMU95) and commercial toxin binder (CTB) on aflatoxins (AFs) toxic effects on hepatic gene expression, and the biochemical and immunological parameters in ducklings, 240 four-day-old ducklings were randomly allocated into six groups with four replicates of 10 ducklings per each. The experimental groups were as follows: Negative control (basal diet without any additive or AFs), Negative control + TMU95 (5 g/kg feed), Negative control + CTB (Zarinbinder, Vivan Group, Mashhad, Iran. 5 g/kg feed), Positive control (0.2 mg AFs/kg feed), Positive control + TMU95 (5 g/kg feed), and Positive control + CTB (5 g/kg feed). On day 14, livers were collected (8 per treatment) to evaluate change in the expression of genes involved in AFs biotransformation (cytochrome P450 1A1 and 2H1) and antioxidant function (glutathione S-transferase). Several biochemical biomarkers and immune responses were also recorded. Compared with the negative control group AFs treatment significantly decreased plasma total cholesterol, triglyceride and increased the aspartate-aminotransferase (AST), alanine-aminotransferase (ALT) and alkaline phosphatase (ALP) activity (P ≤ 0.01). Cellular immune responses to the phytohemagglutinin-and 2, 4-dinitro 1-chlorobenzene skin test were significantly influenced by dietary aflatoxins (P ≤ 0.01) but a humoral immune response to Newcastle disease virus/vaccine was not affected (P ≥ 0.01). Compared with negative control group, the genes associated with AFs biotransformation were downregulated, whereas the gene associated with the antioxidant function was upregulated in birds fed AFs. The CTB supplement in contaminated feed could alleviate AFs adverse effects on cellular immunity, ALT concentration, and cytochrome P450 2H1 gene expression partially, whereas TMU95 could not ameliorate the adverse effects of AFs on the traits studied, except for ALP. The data suggest that TMU95 may alleviate some of the toxic effects of aflatoxins in duckling and it might prove to be beneficial in the reduction of aflatoxicosis adverse effect in poultry when used in combination with other aflatoxin management practices.

Effect of probiotic supplement on aflatoxicosis and gene expression in the liver of broiler chicken

The present study aimed to investigate the toxic effect of aflatoxin B1 (AFB1) and the effectiveness of a biological mycotoxin binder (Nutritox^®) in detoxifying aflatoxicosis. Ninety one-day-old chicks were chosen and divided into 3 groups. The first group received standard basal diet only, the second group received a basal diet with AFB1 (0.25 mg/kg diet), and the third group received a basal diet with AFB1 (0.25 mg/kg diet) and Nutritox^® (1 kg/ton diet). AFB1 feed contamination significantly reduced growth performance and deteriorated FCR. Moreover, it significantly increased serum AST, ALT, and malondialdehyde and significantly decreased serum total protein, albumin, globulin, SOD, CAT activities and glutathione peroxidase gene expression as well. Aflatoxin residues were detected in the liver tissues. Furthermore, the liver and kidney of AFB1 treated group showed pathological changes. The supplementation of Nutritox^® significantly reduced aflatoxin levels in the liver and counteracted the negative effects of AFB1.

Detoxification, metabolism, and glutathione pathway activity of aflatoxin B1 by dietary lactic acid bacteria in broiler chickens

Lactic acid bacteria (LAB) and the glutathione (GSH) pathway are protective against aflatoxin, but information on the effect of LAB on aflatoxin metabolism and GSH activity in farm animals is scarce. This study aimed to investigate the effects of LAB and aflatoxin B (AFB) on growth performance, aflatoxin metabolism, and GSH pathway activity using 480 male Arbor Acres broiler chickens from d 1 to 35 of age. Diets were arranged in a 2 × 2 factorial design, including AFB at 0 or 40 µg/kg of feed and LAB at 0 or 3 × 10 cfu/kg of feed, and the LAB was a mixture of equal amounts of , , and . The results showed that there were highly significant ( < 0.01) effects of AFB toxicity, LAB protection, and their interaction on ADFI, ADG, and G:F of broilers during d 1 to 35. Compared with the AFB diet, the LAB diet reduced ( < 0.05) the residues of AFB in the liver, kidney, serum, ileal digesta, and excreta on d 14 by 121.5, 80.6, 43.7, 47.0, and 26.5%, respectively, and on d 35 by 40.6, 60.2, 131.7, 37.9, and 32.9%, respectively, whereas the LAB diet increased ( < 0.05) the contents of aflatoxin M, a metabolite of AFB, in the liver, kidney, serum, and ileal digesta on d 14 by 98.2, 154.2, 168.6, 19.1, and 34.1%, respectively, and in the kidney and serum on d 35 by 32.6 and 142.2%, respectively. For the activity of the GSH pathway in the liver and duodenal mucosa, there were significant ( ≤ 0.01) effects of LAB and AFB on reduced GSH, glutathione S-transferases (GST), and glutathione reductase (GR) on d 14 and 35; compared with the control diet, the LAB diet increased ( < 0.05) GSH, GST, and GR by a range of 11.6 to 86.1%, and compared with the AFB diet, the LAB diet increased ( < 0.05) GSH, GST, and GR by a range of 24.1 to 146.9%. In the liver, there were interactions ( < 0.05) on GSH and GST on d 14 and on GSH on d 35; in the mucosa, interactions were significant ( ≤ 0.01) on GSH and GR on d 14 and on GST on d 35. It can be concluded that LAB is effective in the detoxification of AFB by modulating toxin metabolism and activating the GSH pathway in animals.

Growth Inhibition and DNA Damage Induced by X-Phenols in Yeast: A Quantitative Structure-Activity Relationship Study

Phenolic compounds and their derivatives are ubiquitous constituents of numerous synthetic and natural chemicals that exist in the environment. Their toxicity is mostly attributed to their hydrophobicity and/or the formation of free radicals. In a continuation of the study of phenolic toxicity in a systematic manner, we have examined the biological responses of Saccharomyces cerevisiae to a series of mostly monosubstituted phenols utilizing a quantitative structure-activity relationship (QSAR) approach. The biological end points included a growth assay that determines the levels of growth inhibition induced by the phenols as well as a yeast deletion (DEL) assay that assesses the ability of X-phenols to induce DNA damage or DNA breaks. The QSAR analysis of cell growth patterns determined by IC₅₀ and IC₈₀ values indicates that toxicity is delineated by a hydrophobic, parabolic model. The DEL assay was then utilized to detect genomic deletions in yeast. The increase in the genotoxicity was enhanced by the electrophilicity of the phenolic substituents that were strong electron donors as well as by minimal hydrophobicity. The electrophilicities are represented by Brown's sigma plus values that are a variant of the Hammett sigma constants. A few mutant strains of genes involved in DNA repair were separately exposed to 2,6-di-tert-butyl-4-methyl-phenol (BHT) and butylated hydroxy anisole (BHA). They were subsequently screened for growth phenotypes. BHA-induced growth defects in most of the DNA repair null mutant strains, whereas BHT was unresponsive.

Hepatic Transcriptome Responses of Domesticated and Wild Turkey Embryos to Aflatoxin B₁

The mycotoxin, aflatoxin B₁ (AFB₁) is a hepatotoxic, immunotoxic, and mutagenic contaminant of food and animal feeds. In poultry, AFB₁ can be maternally transferred to embryonated eggs, affecting development, viability and performance after hatch. Domesticated turkeys (Meleagris gallopavo) are especially sensitive to aflatoxicosis, while Eastern wild turkeys (M. g. silvestris) are likely more resistant. In ovo exposure provided a controlled AFB₁ challenge and comparison of domesticated and wild turkeys. Gene expression responses to AFB₁ in the embryonic hepatic transcriptome were examined using RNA-sequencing (RNA-seq). Eggs were injected with AFB₁ (1 μg) or sham control and dissected for liver tissue after 1 day or 5 days of exposure. Libraries from domesticated turkey (n = 24) and wild turkey (n = 15) produced 89.2 Gb of sequence. Approximately 670 M reads were mapped to a turkey gene set. Differential expression analysis identified 1535 significant genes with |log₂ fold change| ≥ 1.0 in at least one pair-wise comparison. AFB₁ effects were dependent on exposure time and turkey type, occurred more rapidly in domesticated turkeys, and led to notable up-regulation in cell cycle regulators, NRF2-mediated response genes and coagulation factors. Further investigation of NRF2-response genes may identify targets to improve poultry resistance.

2,6-Di-Tert-Butyl-Hydroxytoluene and Its Metabolites in Foods

2,6-Di-tert-butyl-hydroxytoluene (BHT, E-321) is a synthetic phenolic antioxidant which has been widely used as an additive in the food, cosmetic, and plastic industries for the last 70 y. Although it is considered safe for human health at authorized levels, its ubiquitous presence and the controversial toxicological data reported are of great concern for consumers. In recent years, special attention has been paid to these 14 metabolites or degradation products: BHT-CH₂ OH, BHT-CHO, BHT-COOH, BHT-Q, BHT-QM, DBP, BHT-OH, BHT-OOH, TBP, BHQ, BHT-OH(t), BHT-OH(t)QM, 2-BHT, and 2-BHT-QM. These derived compounds could pose a human health risk from a food safety point of view, but they have been little studied. In this context, this review deals with the occurrence, origin, and fate of BHT in foodstuffs, its biotransformation into metabolites, their toxicological implications, their antioxidant and prooxidant properties, the analytical determination of metabolites in foods, and human dietary exposure. Moreover, noncontrolled additional sources of exposure to BHT and its metabolites are highlighted. These include their carryover from feed to fish, poultry and eggs, their presence in smoke flavorings, their migration from plastic pipelines and packaging to water and food, and their presence in natural environments, from which they can reach the food chain.

Aflatoxicosis chemoprevention by probiotic Lactobacillius and lack of effect on the major histocompatibility complex

Turkeys are extremely sensitive to aflatoxin B1 (AFB1) which causes decreased growth, immunosuppression and liver necrosis. The purpose of this study was to determine whether probiotic Lactobacillus, shown to be protective in animal and clinical studies, would likewise confer protection in turkeys, which were treated for 11 days with either AFB1 (AFB; 1 ppm in diet), probiotic (PB; 1 × 10(11) CFU/ml; oral, daily), probiotic + AFB1 (PBAFB), or PBS control (CNTL). The AFB1 induced drop in body and liver weights were restored to normal in CNTL and PBAFB groups. Hepatotoxicity markers were not significantly reduced by probiotic treatment. Major histocompatibility complex (MHC) genes BG1 and BG4, which are differentially expressed in liver and spleens, were not significantly affected by treatments. These data indicate modest protection, but the relatively high dietary AFB1 treatment, and the extreme sensitivity of this species may reveal limits of probiotic-based protection strategies.

Heterologous expression and functional characterization of avian mu-class glutathione S-transferases

Hepatic glutathione S-transferases (GSTs: EC2.5.1.1.8) catalyze the detoxification of reactive electrophilic compounds, many of which are toxic and carcinogenic intermediates, via conjugation with the endogenous tripeptide glutathione (GSH). Glutathione S-transferase (GST)-mediated detoxification is a critical determinant of species susceptibility to the toxic and carcinogenic mycotoxin aflatoxin B1 (AFB1), which in resistant animals efficiently detoxifies the toxic intermediate produced by hepatic cytochrome P450 bioactivation, the exo-AFB1-8,9-epoxide (AFBO). Domestic turkeys (Meleagris gallopavo) are one of the most sensitive animals known to AFB1, a condition associated with a deficiency of hepatic GST-mediated detoxification of AFBO. We have recently shown that unlike their domestic counterparts, wild turkeys (Meleagris gallopavo silvestris), which are relatively resistant, express hepatic GST-mediated detoxification activity toward AFBO. Because of the importance of GSTs in species susceptibility, and to explore possible GST classes involved in AFB1 detoxification, we amplified, cloned, expressed and functionally characterized the hepatic mu-class GSTs tGSTM3 (GenBank accession no. JF340152), tGSTM4 (JF340153) from domestic turkeys, and a GSTM4 variant (ewGSTM4, JF340154) from Eastern wild turkeys. Predicted molecular masses of tGSTM3 and two tGSTM4 variants were 25.6 and 25.8kDa, respectively. Multiple sequence comparisons revealed four GSTM motifs and the mu-loop in both proteins. tGSTM4 has 89% amino acid sequence identity to chicken GSTM2, while tGSTM3 has 73% sequence identity to human GSTM3 (hGSTM3). Specific activities of Escherichia coli-expressed tGSTM3 toward 1-chloro-2,4-dinitrobenzene (CDNB) and peroxidase activity toward cumene hydroperoxide were five-fold greater than tGSTM4 while tGSTM4 possessed more than three-fold greater activity toward 1,2-dichloro-4-nitrobenzene (DCNB). The two enzymes displayed equal activity toward ethacrynic acid (ECA). However, none of the GSTM proteins had AFBO detoxification capability, in contrast to recombinant alpha-class GSTs shown in our recent study to possess this important activity. In total, our data indicate that although turkey hepatic GSTMs may contribute to xenobiotic detoxification, they probably play no role in detoxification of AFBO in the liver.

Effect of the combined probiotics with aflatoxin B₁-degrading enzyme on aflatoxin detoxification, broiler production performance and hepatic enzyme gene expression

In order to degrade aflatoxin B₁ (AFB₁), AFB₁-degrading microbes (probiotics) such as Lactobacillus casei, Bacillus subtilis and Pichia anomala, and the AFB₁-degrading enzyme from Aspergillus oryzae were selected and combined to make feed additive. Seventy-five 43-day-old male Arbor Acres broilers were randomly divided into 5 groups, 15 broilers for each group. The broilers were given with 5 kinds of diets such as the basal diet, 400 μg/kg AFB₁ supplement without feed additive, and 200, 400, 800 μg/kg AFB₁ supplement with 0.15% feed additive. The feeding experimental period was 30 d, which was used to determine production performance of broilers. In addition, serum, liver and chest muscle were selected for measuring AFB₁ residues, gene expressions, microscopic and antioxidant analyses. The results showed that adding 0.15% feed additive in broiler diets could significantly relieve the negative effect of AFB₁ on chicken's production performance and nutrient metabolic rates (P<0.05). It could also improve AFB₁ metabolism, hepatic cell structure, antioxidant activity, and many hepatic enzyme gene expressions involved in oxidoreductase, apoptosis, cell growth, immune system and metabolic process (P<0.05). It could be concluded that the feed additive was able to degrade AFB₁ and improve animal production.

Alpha-class glutathione S-transferases in wild turkeys (Meleagris gallopavo): characterization and role in resistance to the carcinogenic mycotoxin aflatoxin B1

Domestic turkeys (Meleagris gallopavo) are one of the most susceptible animals known to the toxic effects of the mycotoxin aflatoxin B₁ (AFB₁), a potent human hepatocarcinogen, and universal maize contaminant. We have demonstrated that such susceptibility is associated with the inability of hepatic glutathione S-transferases (GSTs) to detoxify the reactive electrophilic metabolite exo-AFB₁-8,9-epoxide (AFBO). Unlike their domestic counterparts, wild turkeys, which are relatively AFB₁-resistant, possess hepatic GST-mediated AFBO conjugating activity_. Here, we characterized the molecular and functional properties of hepatic alpha-class GSTs (GSTAs) from wild and domestic turkeys to shed light on the differences in resistance between these closely related strains. Six alpha-class GST genes (GSTA) amplified from wild turkeys (Eastern and Rio Grande subspecies), heritage breed turkeys (Royal Palm) and modern domestic (Nicholas strain) turkeys were sequenced, and catalytic activities of heterologously-expressed recombinant enzymes determined. Alpha-class identity was affirmed by conserved GST domains and four signature motifs. All GSTAs contained single nucleotide polymorphisms (SNPs) in their coding regions: GSTA1.1 (5 SNPs), GSTA1.2 (7), GSTA1.3 (3), GSTA2 (3), GSTA3 (1) and GSTA4 (2). E. coli-expressed GSTAs possessed varying activities toward GST substrates 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (ECA), cumene hydroperoxide (CHP). As predicted by their relative resistance, livers from domestic turkeys lacked detectable GST-mediated AFBO detoxification activity, whereas those from wild and heritage birds possessed this critical activity, suggesting that intensive breeding and selection resulted in loss of AFB₁-protective alleles during domestication. Our observation that recombinant tGSTAs detoxify AFBO, whereas their hepatic forms do not, implies that the hepatic forms of these enzymes are down-regulated, silenced, or otherwise modified by one or more mechanisms. These data may inform of possible molecular mechanisms of resistance to AFB₁, and may also have the benefit of identifying genetic markers which could be used to enhance AFB₁ resistance in modern domestic strains.

Functional characterization of alpha-class glutathione s-transferases from the Turkey (meleagris gallopavo)

Six Alpha-class glutathione S-transferase (GST) subunits were cloned from domestic turkey livers, which are one of the most susceptible animals known to the carcinogenic mycotoxin aflatoxin B₁. In most animals, GST dysfunction is a risk factor for susceptibility toward AFB₁, and we have shown that turkeys lack GSTs with affinity toward the carcinogenic intermediate exo-aflatoxin B(1)-8-9-epoxide (AFBO). Conversely, mice are resistant to AFB₁ carcinogenesis, due to high constitutive expression of mGSTA3 that has high affinity toward AFBO. When expressed in Escherichia coli, all six tGSTA subunits possessed conjugating activities toward substrates 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (ECA), and cumene hydroperoxide (CHP) with tGSTA1.2 appearing most active. Interestingly, tGSTA1.1, which lacks one of the four Alpha-class signature motifs, possessed enzymatic activities toward all substrates. All had comparable activities toward AFBO conjugation, an activity absent in turkey liver cytosols. E. coli-expressed mGSTA3 conjugated AFBO with more than 3-fold greater activity than that of tGSTAs and had higher activity toward GST prototype substrates. Mouse hepatic cytosols had approximately 900-fold higher catalytic activity toward AFBO compared with those from turkey. There was no apparent amino acid profile in tGSTAs that might correspond to specificity toward AFBO, although tGSTA1.2, which had slightly higher AFBO-trapping ability, shared Tyr¹⁰⁸ with mGSTA3, a residue postulated to be critical for AFBO trapping activity in mammalian systems. The observation that recombinant tGSTAs detoxify AFBO, whereas their hepatic forms do not, implies that the hepatic forms of these enzymes are silenced by one or more regulatory mechanisms.

Aflatoxin B1 in poultry: toxicology, metabolism and prevention

Aflatoxins (AF) are ubiquitous in corn-based animal feed and causes hepatotoxic and hepatocarcinogenic effects. The most important AF in terms of toxic potency and occurrence is aflatoxin B1 (AFB1). Poultry, especially turkeys, are extremely sensitive to the toxic and carcinogenic action of AFB1, resulting in millions of dollars in annual losses to producers due to reduced growth rate, increased susceptibility to disease, reduced egg production and other adverse effects. The extreme sensitivity of turkeys and other poultry to AFB1 is associated with efficient hepatic cytochrome P450-mediated bioactivation and deficient detoxification by glutathione S-transferases (GST). Discerning the biochemical and molecular mechanisms of this extreme sensitivity of poultry to AFB1, will contribute in the development of novel strategies to increase aflatoxin resistance. Since AFB1 is an unavoidable contaminant of corn-based poultry feed, chemoprevention strategies aimed at reducing AFB1 toxicity in poultry and in other animals have been the subject of numerous studies. This brief review summarizes many of the key recent findings regarding the action of aflatoxins in poultry.

Hepatic retention and toxicological responses during feeding and depuration periods in Atlantic salmon ( Salmo salar ) fed graded levels of the synthetic antioxidant, butylated hydroxytoluene

The human safety aspects of seafood production require the expansion of vital knowledge of both nutrients and possible contaminants along the entire production chain. Thus, production of safer seafood can be achieved by using feed materials that are low in contaminants, while maintaining balanced nutrition, in order to secure optimal fish and consumer health. Our understanding of primary responses of fish health and production related diseases, as well as biological processes that influence carry-over and lowering of contaminants in farmed fish, will contribute to a sustainable production of safer seafood products. Therefore, we have studied the liver deposition and toxicological effects in salmon fed graded levels of BHT during a 12-week feeding followed by a 2-week depuration period using chemical, molecular, and catalytic assays. In general, our data showed that BHT was significantly retained in the liver and selectively modulated toxicological responses in the xenobiotic biotransformation pathways during the feeding period. Specifically, BHT produced consistent dose- and time-specific gene expression patterns for AhR2alpha, AhR2beta, CYP1A1, CYP3A, UGT1, and GSTpi. The effect of BHT on the gene expression of biotransformation enzyme did not parallel enzyme activity levels, suggesting a possible inhibition by parent BHT or its metabolites. As a safety precaution, the production of farmed Atlantic salmon in Norway requires a mandatory 2-week depuration period prior to slaughtering and market delivery to ensure the elimination of veterinary medicaments, additives, and other undesirable components. Comparison of feeding and depuration periods showed that BHT was highly retained in fish liver, as only 8-13% of fed BHT was eliminated during the 2-week depuration period. This is just a part of the total concentration in the whole fish, since BHT may have been distributed and accumulated in other organs. Since BHT or its metabolites putatively inhibited biotransformation enzymes and affected metabolism of the compound, they may have potential for toxicological and adverse health effects for both fish and fish consumers through carry-over processes from the fish products.