Lipid metabolism disorders, lymphocytes cells death, and renal toxicity induced by very low levels of deoxynivalenol and fumonisin b1 alone or in combination following 7 days oral administration to mice

Gut ribotoxic stress responses facilitate dyslipidemia via metabolic reprogramming: an environmental health prediction

Rationale: The gut and its accessory organ, the liver, are crucial determinants of metabolic homeostasis via the regulation of circulating lipids for cardiovascular health. In response to environmental insults, cells undergo diverse adaptation or pathophysiological processes via stress-responsive eukaryotic initiation factor 2 alpha (eIF2α) kinase signaling and subsequent cellular reprogramming. We noted that patients with inflammatory gut distress display enhanced levels of ribosomal stress-responsive eIF2α kinase, which is notably associated with lipid metabolic process genes. Based on an assumption that eukaryotic ribosomes are a promising stress-responsive module for molecular reprogramming, chemical ribosome-inactivating stressors (RIS) were assessed for their involvement in enterohepatic lipid regulation. Methods: Experimental assessment was based on prediction using the clinical transcriptome and single-cell RNA-sequencing analysis of inflammatory bowel diseases and obesity. The prediction was verified using RIS exposure models of mice, gut organoids, and intestinal cells. The lipidomic profiling was performed to address RIS-induced intracellular fat alterations. Biochemical processes of the mechanisms were evaluated using RT-PCR, western blot analysis, luciferase reporter assays, and confocal microscopy of genetically ablated or chemically inhibited mice, organoids, and cells. Results: Chemical RIS including deoxynivalenol promoted enterohepatic lipid sequestration while lowering blood LDL cholesterol in normal and diet-induced obese mice. Although ribosomal stress caused extensive alterations in cellular lipids and metabolic genes, the cholesterol import-associated pathway was notably modulated. In particular, ribosomal stress enhanced gut levels of the low-density lipoprotein receptor (LDLR) via both transcriptional and post-transcriptional regulation. Subsequently, LDLR facilitated enterohepatic cholesterol accumulation, leading to dyslipidemia in response to ribosomal stress. Moreover, genetic features of stress-responsive LDLR modulators were consistently proven in the inflammation- and obesity-associated gut model. Conclusion: The elucidated ribosome-linked gut lipid regulation provides predictive insights into stress-responsive metabolic rewiring in chronic human diseases as an environmental health prediction.

Metabolic Disruption by Naturally Occurring Mycotoxins in Circulation: A Focus on Vascular and Bone Homeostasis Dysfunction

Naturally occurring food/feed contaminants have become a significant global issue due to animal and human health implications. Despite risk assessments and legislation setpoints on the mycotoxins' levels, exposure to lower amounts occurs, and it might affect cell homeostasis. However, the inflammatory consequences of this possible everyday exposure to toxins on the vascular microenvironment and arterial dysfunction are unexplored in detail. Circulation is the most accessible path for food-borne toxins, and the consequent metabolic and immune shifts affect systemic health, both on vascular apparatus and bone homeostasis. Their oxidative nature makes mycotoxins a plausible underlying source of low-level toxicity in the bone marrow microenvironment and arterial dysfunction. Mycotoxins could also influence the function of cardiomyocytes with possible injury to the heart. Co-occurrence of mycotoxins can modulate the metabolic pathways favoring osteoblast dysfunction and bone health losses. This review provides a novel insight into understanding the complex events of coexposure to mixed (low levels) mycotoxicosis and subsequent metabolic/immune disruptions contributing to chronic alterations in circulation.

Dodecanol, metabolite of entomopathogenic fungus Conidiobolus coronatus, affects fatty acid composition and cellular immunity of Galleria mellonella and Calliphora vicina

One group of promising pest control agents are the entomopathogenic fungi; one such example is Conidiobolus coronatus, which produces a range of metabolites. Our present findings reveal for the first time that C. coronatus also produces dodecanol, a compound widely used to make surfactants and pharmaceuticals, and enhance flavors in food. The main aim of the study was to determine the influence of dodecanol on insect defense systems, i.e. cuticular lipid composition and the condition of insect immunocompetent cells; hence, its effect was examined in detail on two species differing in susceptibility to fungal infection: Galleria mellonella and Calliphora vicina. Dodecanol treatment elicited significant quantitative and qualitative differences in cuticular free fatty acid (FFA) profiles between the species, based on gas chromatography analysis with mass spectrometry (GC/MS), and had a negative effect on G. mellonella and C. vicina hemocytes and a Sf9 cell line in vitro: after 48 h, almost all the cells were completely disintegrated. The metabolite had a negative effect on the insect defense system, suggesting that it could play an important role during C. coronatus infection. Its high insecticidal activity and lack of toxicity towards vertebrates suggest it could be an effective insecticide.

Genotoxicity of three mycotoxin contaminants of rice: 28-day multi-endpoint assessment in rats

Deoxynivalenol (DON), zearalenone (ZEN), and fumonisin B₁ (FB₁), as the main mycotoxins contaminating rice, often coexist in food. Thus, we have measured the genotoxicity of the three rice fungal contaminants, singly and in different combinations, with a 28-day multi-endpoint (Pig-a assay + in vivo micronucleus [MN] test + comet assay) genotoxicity platform. Male Sprague-Dawley rats received the agents orally via gavage for 28 consecutive days, before performing the abovementioned tests. Results indicated that low dose of a single mycotoxin did not show significant genotoxicity. However, some of these mycotoxins in combination induced significant genotoxicity in the peripheral blood and tissues, at sacrifice. In the peripheral blood, the binary combination of DON and FB₁ significantly induced MN. In the liver, ZEN might aggravate the DNA-damaging effects of DON and FB₁. Therefore, the genotoxicity of sub-chronic exposure to mycotoxins in combination cannot be ignored.

The Effects of Mixed Fusarium Mycotoxins at EU-Permitted Feed Levels on Weaned Piglets' Tissue Lipids

At exactly the individual permitted EU-tolerance dietary limits, fumonisins (FB: 5 mg/kg diet) and mixed fusariotoxins (DZ: 0.9 mg deoxynivalenol + 0.1 mg zearalenone/kg diet, and FDZ: 5 mg fumonisins + 0.9 mg deoxynivalenol + 0.1 mg zearalenone/kg diet) were administered to piglets (n = 6/group) for three weeks. Bodyweights of intoxicated piglets increased, while feed conversion ratios decreased. In FDZ, both the absolute and relative weight of the liver decreased. In the renal-cellular membrane, the most pronounced alterations were in FDZ treatment, followed by individual FB exposure. In both treatments, high proportions of C20:0 and C22:0 with low fatty acid (FA) unsaturation were found. In hepatocyte phospholipids, FDZ toxins exerted antagonistic interactions, and FB had the strongest increasing effect on FA monounsaturation. Among all investigated organs, the spleen lipids were the least responsive, in which FDZ expressed synergistic reactions on C20:0 (↑ FDZ vs. FB) and C22:0 (↓ FDZ vs. DZ). The antioxidant defense of the kidney was depleted (↓ glutathione concentration by FB-exposure). Blood plasma indicated renal injury (profound increase of urea and creatinine in FB vs. DZ and FDZ). FB strongly increased total-cholesterol and low density lipoprotein concentrations, whereas FDZ synergistically increased gamma-glutamyltransferase, alkaline-phosphatase, calcium and phosphorus levels. Summarized, individual and combined multiple fusariotoxins modified the membrane lipid profile and antioxidant defense of splanchnic organs, and serum biochemicals, without retarding growth in piglets.

A preliminary study on changes in heat shock protein 70 levels induced by Fusarium mycotoxins in rats: in vivo study

The heat shock protein (Hsp70) level was assessed after 14 days of oral gavage-exposure to fumonisin B₁ (FB₁: 150 µg/animal/day), deoxynivalenol (DON: 30 µg/animal/day) and zearalenone (ZEN: 150 µg/animal/day), alone or in combinations (in additive manner: FD = FB₁ + DON, FZ = FB₁ + ZEN, DZ = DON + ZEN and FDZ = FB₁ + DON + ZEN) in the liver, kidneys and lung of 24 adult male Wistar rats (n = 3/group). The liver was the most responsive tissue, as compared with kidney and lung. Except of DZ-treatment, mycotoxins elevated the Hsp70 levels in livers. The highest Hsp70-levels (≈ twofold) were in the DON, FD, FZ and FDZ treatments (additive effects). In the kidney, alterations (↑ ≈ twofold) were detected in ZEN, FD, FZ and DZ treatments. The least responsive organ was the lung (↑ only in FDZ, antagonistic effect). DON and ZEA exposures have altered the reduced glutathione concentration (↓) and glutathione peroxidase activity (↓) in the blood serum. The serum malondialdehyde level increased only after exposure to FD (synergistic effect), as compared with the DZ group (antagonistic effect). When the blood clinical chemistry was assessed, significant alterations were in alanine aminotransferase (80% increase in FDZ, antagonistic effect) and total protein (↓ ZEN). Results varied according to the organ, toxin type and interactions. Furthermore, oxidative stress was not the only key player behind the Hsp70 increase, in which another mechanism is suggested.

The mycotoxin deoxynivalenol activates GABAergic neurons in the reward system and inhibits feeding and maternal behaviours

Deoxynivalenol (DON) or vomitoxin, is a trichothecene mycotoxin produced mainly by Fusarium graminearum and culmorum. Mycotoxins or secondary metabolic products of mold fungi are micro-pollutants, which may affect human and animal health. The neuronal and behavioural actions of DON were analysed in the present study. To address, which neurons can be affected by DON, the neuronal activation pattern following intraperitoneal injection of DON (1 mg/kg) was investigated in adult male rats and the results were confirmed in mice, too. DON-induced neuronal activation was assessed by c-Fos immunohistochemistry. DON injection resulted in profound c-Fos activation in only the elements of the reward system, such as the accumbens nucleus, the medial prefrontal cortex, and the ventral tegmental area. Further double labelling studies suggested that GABAergic neurons were activated by DON treatment. To study the behavioural relevance of this activation, we examined the effect of DON on feed intake as an example of reward-driven behaviours. Following DON injection, feed consumption was markedly reduced but returned to normal the following day suggesting an inhibitory action of DON on feed intake without forming taste-aversion. To further test how general the effect of DON on goal-directed behaviours is, its actions on maternal behaviour was also examined. Pup retrieval latencies were markedly increased by DON administration, and DON-treated mother rats spent less time with nursing suggesting reduced maternal motivation. In a supplementary control experiment, DON did not induce conditioned place preference arguing against its addictive or aversive actions. The results imply that acute uptake of the mycotoxin DON can influence the reward circuit of the brain and exert inhibitory actions on goal-directed, reward-driven behaviours. In addition, the results also suggest that DON exposure of mothers may have specific implications.

Porcine Hepatic Response to Fumonisin B1 in a Short Exposure Period: Fatty Acid Profile and Clinical Investigations

Scarce studies have investigated the impact of fumonisin B1 (FB1) on the hepatic tissue fatty acid (FA) profile, and no study is available on piglets. A 10-day in vivo experiment was performed on seven piglets/group: control and FB1-fed animals (diet was contaminated with fungal culture: 20 mg FB1/kg diet). Independent sample t-test was carried out at p < 0.05 as the significance level. Neither growth, nor feed efficiency, was affected. The hepatic phospholipid (PL) fatty acids (FAs) were more susceptible for FB1, while triglyceride (TG) was less responsive. The impact of FB1 on hepatic PL polyunsaturated fatty acids (PUFAs) was more pronounced than on saturated fatty acids. Among all PUFAs, predominant ones in response were docosapentaenoicacid (DPA) (↓), docosahexaenoic DHA (↓) and arachidonic acids (↑). This led to a higher omega-6:omega-3 ratio, whereas a similar finding was noted in TGs. Neither total saturation (SFA) nor total monousaturation (MUFA) were affected by the FB1 administration. The liver showed an increase in malondialdehyde, as well as antioxidant capacity (reduced glutathione and glutathione peroxidase). The plasma enzymatic assessment revealed an increase in alkaline phosphatase (ALP), while alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), and gamma-glutamyltransferase (GGT) were not influenced. The microscopic sections provided evidence of vacuolar degeneration of the hepatocytes' cytoplasm, but it was not severe. Furthermore, the lung edema was developed, while the kidney was not affected. In conclusion, regarding FB1-mediated hepatotoxicity in piglets, the potential effect of slight hepatotoxicity did not compromise growth performance, at least at the dose and exposure period applied.

Behavioural and metabolomic changes from chronic dietary exposure to low-level deoxynivalenol reveal impact on mouse well-being

The mycotoxin deoxynivalenol (DON) has a high global prevalence in grain-based products. Biomarkers of exposure are detectable in most humans and farm animals. Considering the acute emetic and chronic anorexigenic toxicity of DON, maximum levels for food and feed have been implemented by food authorities. The tolerable daily intake (TDI) is 1 µg/kg body weight (bw)/day for the sum of DON and its main derivatives, which was based on the no-observed adverse-effect level (NOAEL) of 100 µg DON/kg bw/day for anorexic effects in rodents. Chronic exposure to a low-DON dose can, however, also cause inflammation and imbalanced neurotransmitter levels. In the present study, we therefore investigated the impact of a 2-week exposure at the NOAEL in mice by performing behavioural experiments, monitoring brain activation by c-Fos expression, and analysing changes in the metabolomes of brain and serum. We found that DON affected neuronal activity and innate behaviour in both male and female mice. Metabolite profiles were differentiable between control and treated mice. The behavioural changes evidenced at NOAEL reduce the safety margin to the established TDI and may be indicative of a risk for human health.

Interaction between the three frequently co-occurring Fusarium mycotoxins in rats

To test the complex, acute biochemical effects of combined, naturally co-occurring fusariotoxins, a 5-day rat study was performed. Mycotoxin treatment was invented by intraperitoneal injection: FB₁ (F): 9 µg/animal/day (approx. 30 µg/kg bw/day), DON (D): 16.5 µg/animal/day (approx. 55 µg/kg bw/day) and ZEN (Z): 12.75 µg/animal/day (approx. 42.5 µg/kg bw/day). The binary groups (FB₁ and DON [FD], FB₁ and ZEN [FZ] and DON and ZEN [DZ]) as well as the ternary (FB₁ , DON and ZEN [FDZ]) group were dosed at the same combined level as the individual mycotoxins. Body weight, feed intake and mortality were not affected by any of the treatments. FB₁ and DON in combination (FD) increased the plasma aspartate aminotransferase activity synergistically (compared to the individual FB₁ and DON). In the liver, both the total glutathione (GSH) and the glutathione peroxidase (GPx) activity were increased (p < 0.05) by the binary FB₁ and ZEN (FZ) and the DON and ZEN (DZ) groups as well as the ternary FB₁ , DON and ZEA group (FDZ) compared to the control. The GSH level of the ternary group was significantly increased compared to the FB₁ group, whereas the GPx activity of the ternary group was significantly increased compared to all three the individual mycotoxin groups. The Bliss independence method revealed synergism between DON and ZEN (DZ), as well as FB₁ and DON (FD) on liver GPx activity. None of the toxins alone or in combination exerted strong genotoxicity on lymphocytes, neither on the gross histopathological characteristics. However, even at these low levels acute exposure of more than one of these mycotoxins (FB₁ , DON and ZEN) affected metabolic and detoxification changes.

Appropriateness to set a group health-based guidance value for fumonisins and their modified forms

The EFSA Panel on Contaminants in the Food Chain (CONTAM) established a tolerable daily intake (TDI) for fumonisin B1 (FB 1) of 1.0 μg/kg body weight (bw) per day based on increased incidence of megalocytic hepatocytes found in a chronic study with mice. The CONTAM Panel considered the limited data available on toxicity and mode of action and structural similarities of FB 2-6 and found it appropriate to include FB 2, FB 3 and FB 4 in a group TDI with FB 1. Modified forms of FBs are phase I and phase II metabolites formed in fungi, infested plants or farm animals. Modified forms also arise from food or feed processing, and include covalent adducts with matrix constituents. Non-covalently bound forms are not considered as modified forms. Modified forms of FBs identified are hydrolysed FB 1-4 (HFB 1-4), partially hydrolysed FB 1-2 (pHFB 1-2), N-(carboxymethyl)-FB 1-3 (NCM-FB 1-3), N-(1-deoxy-d-fructos-1-yl)-FB 1 (NDF-FB 1), O-fatty acyl FB 1, N-fatty acyl FB 1 and N-palmitoyl-HFB 1. HFB 1, pHFB 1, NCM-FB 1 and NDF-FB 1 show a similar toxicological profile but are less potent than FB 1. Although in vitro data shows that N-fatty acyl FBs are more toxic in vitro than FB 1, no in vivo data were available for N-fatty acyl FBs and O-fatty acyl FBs. The CONTAM Panel concluded that it was not appropriate to include modified FBs in the group TDI for FB 1-4. The uncertainty associated with the present assessment is high, but could be reduced provided more data are made available on occurrence, toxicokinetics and toxicity of FB 2-6 and modified forms of FB 1-4.

Individual and Combined Effects of Fumonisin B₁, Deoxynivalenol and Zearalenone on the Hepatic and Renal Membrane Lipid Integrity of Rats

(1) Background and (2) Methods: A 14-day in vivo, multitoxic (pure mycotoxins) rat experiment was conducted with zearalenone (ZEA; 15 μg/animal/day), deoxynivalenol (DON; 30 μg/animal/day) and fumonisin B₁ (FB₁; 150 μg/animal/day), as individual mycotoxins, binary (FD, FZ and DZ) and ternary combinations (FDZ), via gavage in 1 mL water boluses. (3) Results: Body weight was unaffected, while liver (ZEA↑ vs. DON) and kidney weight (ZEA↑ vs. FDZ) increased. Hepatocellular membrane lipid fatty acids (FAs) referred to ceramide synthesis disturbance (C20:0, C22:0), and decreased unsaturation (C22:5 n3 and unsat. index), mainly induced by DON and to a lesser extent by ZEA. The DON-FB₁ interaction was additive on C20:0 in liver lipids. In renal phospholipids, ZEA had the strongest effect on the FA profile, affecting the saturated (C18:0) and many n6 FAs; ZEA was in an antagonistic relationship with FB₁ (C18:0) or DON (C18:2 n6, C20:1 n9). Hepatic oxidative stress was the most expressed in FD (reduced glutathione and glutathione peroxidase), while the nephrotoxic effect was further supported by lipid peroxidation (malondialdehyde) in the DON treatment. (4) Conclusions: In vivo study results refer to multiple mycotoxin interactions on membrane FAs, antioxidants and lipid peroxidation compounds, needing further testing.

Rapid Assessment of the Toxicity of Fungal Compounds Using Luminescent Vibrio qinghaiensis sp. Q67

Most tropical fruits after harvest are very perishable because of fungal infection. Since some pathogenic fungi can produce hazardous compounds such as mycotoxins, novel rapid and effective methods to assess those hazardous compounds are urgently needed. Herein we report that Vibrio qinghaiensis sp. Q67, a luminescent bacterium, can be used to rapidly assess the toxicities of mycotoxins and cultures from mycotoxin-producing pathogens. A good correlation (R² > 0.98) between concentrations of the mycotoxins (fumonisin B1, deoxynivalenol, zearalenone, ochratoxin A, patulin, and citrinin) and the luminous intensity of V. qinghaiensis sp. Q67 was obtained. Furthermore, significant correlations (R² > 0.96) between the amount of mycotoxin and the luminous intensity from the cultures of 10 major mycotoxin-producing pathogens were also observed. In addition, Fusarium proliferatum (half-maximal inhibitory concentration (IC₅₀) = 17.49%) exhibited greater luminescence suppression than Fusarium semitectum (IC₅₀ = 92.56%) or Fusarium oxysporum (IC₅₀ = 28.61%), which was in agreement with the existing higher levels of fumonisin B1, fumonisin B2, and deoxynivalenol, which were measured by high-performance liquid chromatography-tandem mass spectrometry. These results suggest that V. qinghaiensis sp. Q67 is a promising alternative for the rapid evaluation of the toxicity of fungal mycotoxins.

Mycotoxin contamination in laboratory rat feeds and their implications in animal research

Compound feed is particularly vulnerable to multi-mycotoxin contamination. A method for the determination of 12 mycotoxins; enniatins A, A1, B, B1; aflatoxins B1, B2, G1, G2; OTA; ZEA; T-2 and HT-2 by liquid chromatography-tandem mass spectrometry has been developed and applied for the analysis of laboratory rat commercial feeds. The method trueness was checked by recovery assays at three different spiked levels (n = 9). Recoveries ranged from 73% to 112%, and the intra-day and inter-day precision were lower than 9% and 13%, respectively. Limits of quantitation were lower than 15 μg/kg. Twenty-seven laboratory rats feed samples showed multi-contamination by at least three up to six different mycotoxins. ENNs B and B1, followed by ZEA were the most prevalent mycotoxins. T-2, HT-2, and OTA were not detected. ZEA showed the highest concentration levels reaching 492 μg/kg. The results underline the importance of implementing mycotoxin regular surveillance programs for laboratory animal feeds.