Dietary mycotoxin exposure and human health risks: A protocol for a systematic review

BACKGROUND

Mycotoxins are toxic fungal secondary metabolites that contaminate a wide spectrum of essential foods worldwide, such as grain-based products, nuts and spices, causing adverse health effects pertaining to their carcinogenic, nephrotoxic and hepatotoxic nature, among others.

AIM

The aim of this systematic review (SR) is to systematically search for, appraise and synthesize primary research evidence to identify what is known about dietary mycotoxin-related health effects and what remains unknown, as well as the uncertainty around findings and the recommendations for the future.

SEARCH STRATEGY AND ELIGIBILITY CRITERIA

Search strategies, as well as eligibility criteria were structured according to a predefined PECO (population, exposure, comparison, and outcome) research question and developed in an iterative scoping process. Several bibliographic databases, including Embase, Cochrane Library, Pubmed, Web of Science Core Collection and Scopus, will be searched. Primary research on any measured or modelled dietary exposure to a single or multiple mycotoxins, and adverse human health outcomes (i.e. cancer, non-carcinogenic diseases, and reproductive & developmental adverse outcomes) will be included, and references will be imported into Covidence. In vitro, ex vivo, in silico, animal and review studies, as well as expert's opinions, secondary literature, conference abstracts, presentations, posters, book chapters, dissertations and studies involving non-dietary mycotoxin exposure, will be excluded.

STUDY SELECTION

Two independent reviewers will screen titles and abstracts, and review full-texts. Any disagreements will be resolved by a third reviewer based on two-third majority.

DATA EXTRACTION

Data from retained eligible studies will be extracted by the principal reviewer, and peer-checked by a second reviewer.

STUDY QUALITY ASSESSMENT

Eligible studies will be evaluated for risk of bias (Overall High-Quality Assessment Tool, OHAT) and certainty of evidence (Grading of Recommendations Assessment, Development and Evaluation, GRADE).

EVIDENCE SYNTHESIS

A detailed summary of the included studies will be provided within a tabular format and narratively discussed. Heat maps will be constructed to provide information on available knowledge (gaps), and a meta-analysis may be performed based on the variability in predefined PECO elements and depending on the heterogeneity of studies.

CONCLUSION

This protocol describes the methodology for the conduct of a SR on mycotoxin-related human health risks, that could guide future research and inform regulatory decisions, as emphasized by the European Commission within the field of regulatory risk assessment for emerging chemicals.

The potential of lactic acid bacteria isolated from ikan budu (fermented fish) to inhibit the growth of pathogenic fungi and detoxify aflatoxin B1

Background and Aim

Market demand for safe feed and food supply and consumer preferences for safe and healthy products are increasing. Control measures to counter threats to the feed supply need to be implemented as early as possible to prevent economic losses. Mycotoxins produced by certain groups of fungi are a problem that can disrupt the feed supply or pose a threat to the health of animals and humans. Biological control to detoxify contaminated feed ingredients can be carried out on a large scale economically. For example, lactic acid bacteria (LAB) can act as biological agents for eliminating mycotoxins. This study aimed to clarify the value of screening LAB to inhibit Aspergillus flavus growth and detoxify aflatoxin B1 (AFB1).

Materials and Methods

In this study, using a completely randomized design with three replications, five isolates of LAB (LA.1, LA.6, LA.8, LA.12, and LA.22) along with their supernatants were tested qualitatively and quantitatively for their ability to counter mycotoxins using A. flavus and corn kernels. The isolates with the best activity were identified by sequencing 16S rDNA.

Results

The results showed that the five LAB isolates can inhibit the growth of A. flavus and detoxify AFB1. Among these isolates, LA.12 showed the best performance, followed by LA.22, LA.8, LA.6, and then LA.1. The sequencing results confirmed that LA.12 was Lactobacillus harbinensis strain 487.

Conclusion

All of the isolates in this study have the potential as biological agents for detoxifying AFB1, with isolate LA.12 appearing to be the most promising biodetoxification agent for feed (AFB1 in corn) based on its ability to inhibit pathogenic fungi.

Mycotoxin risks are lower in biotech corn

Mycotoxins are food contaminants that occur when toxigenic fungi colonize crops. Unfortunately, corn, a major staple crop worldwide, is highly susceptible to mycotoxin contamination. Some mycotoxins, most notably aflatoxin, cause human cancer and other harmful effects such as immunotoxicity and growth impairment. Hence, many nations have set food-safety standards on mycotoxins. Aside from regulations, good agricultural and manufacturing practices lower mycotoxin risks. Agricultural biotechnology has made notable advances in reducing mycotoxins recently. While transgenic Bt corn has been known for years to reduce the mycotoxin fumonisin, new studies have shown its benefit in reducing aflatoxin as well. Other transgenic and RNA-interference corn hybrids target mycotoxin reduction specifically, and gene editing through clustered regularly interspaced short palindromic repeat systems has focused on preventing mycotoxin biosynthesis.

Meta-analysis of the effects of mycotoxins and yeast cell wall extract supplementation on the performance, livability, and environmental sustainability of broiler production

The effect of mycotoxins (MT) on broiler performance without or with the inclusion of yeast cell wall extract (YCWE, Mycosorb, Alltech, Inc., KY) was evaluated in a random-effects meta-analysis. Data was extracted from 25 research experiments with a total of 10,307 broilers. Broilers fed MT had lower (P < 0.001) body weight gain (BWG, −217 g), reduced feed intake (FI, −264 g), increased feed conversion ratio (FCR, 0.12), and greater mortality by 2.01%. Inclusion of YCWE improved (P < 0.001) BWG (59 g) and FI (65 g), lowered FCR (−0.05), and reduced mortality by 1.74%. Additionally, change in European Production Efficiency Factor (EPEF) was assessed. Feeding MT lowered (P < 0.001) EPEF while YCWE increased (P < 0.001) EPEF. Finally, the carbon footprint of production was evaluated. Control fed birds produced an estimated 1.93 kg CO2-equivalent/kg liveweight (LW), while MT fed broilers produced 2.13 kg CO2-equivalent/kg LW and YCWE inclusion lowered this to 2.03 kg CO2-equivalent/kg LW which resulted in −25 tonnes less CO2-equivalent output per 100,000 birds with YCWE. In conclusion, mycotoxins can play a role in reducing broiler performance and farm production output, as well as increase the carbon footprint. Inclusion of YCWE in feed under a mycotoxin challenge can improve broiler performance and output, as well as lower carbon footprint, which could play a role in farm efficiency, profitability, and environmental sustainability.

Antifungal Peptides and Proteins to Control Toxigenic Fungi and Mycotoxin Biosynthesis

The global challenge to prevent fungal spoilage and mycotoxin contamination on food and feed requires the development of new antifungal strategies. Antimicrobial peptides and proteins (AMPs) with antifungal activity are gaining much interest as natural antifungal compounds due to their properties such as structure diversity and function, antifungal spectrum, mechanism of action, high stability and the availability of biotechnological production methods. Given their multistep mode of action, the development of fungal resistance to AMPs is presumed to be slow or delayed compared to conventional fungicides. Interestingly, AMPs also accomplish important biological functions other than antifungal activity, including anti-mycotoxin biosynthesis activity, which opens novel aspects for their future use in agriculture and food industry to fight mycotoxin contamination. AMPs can reach intracellular targets and exert their activity by mechanisms other than membrane permeabilization. The mechanisms through which AMPs affect mycotoxin production are varied and complex, ranging from oxidative stress to specific inhibition of enzymatic components of mycotoxin biosynthetic pathways. This review presents natural and synthetic antifungal AMPs from different origins which are effective against mycotoxin-producing fungi, and aims at summarizing current knowledge concerning their additional effects on mycotoxin biosynthesis. Antifungal AMPs properties and mechanisms of action are also discussed.

Management strategies for aflatoxin risk mitigation in maize, dairy feeds and milk value chains—case study Kenya

Widespread aflatoxin contamination of a great number of food and feed crops has important implications on global trade and health. Frequent occurrence of aflatoxin in maize and milk poses serious health risks to consumers because these commodities are staple foods in many African countries. This situation calls for development and implementation of rigorous aflatoxin control measures that encompass all value chains, focusing on farms where food and feed-based commodities prone to aflatoxin contamination are cultivated. Good agricultural practices (GAP) have proven to be an effective technology in mitigation and management of the aflatoxin risk under farm conditions. The prevailing global climate change is shown to increase aflatoxin risk in tropical and subtropical regions. Thus, there is an urgent need to devise and apply novel methods to complement GAP and mitigate aflatoxin contamination in the feed, maize and milk value chains. Also, creation of awareness on aflatoxin management through training of farmers and other stakeholders and enforcement of regular surveillance of aflatoxin in food and feed chains are recommended strategies. This literature review addresses the current situation of aflatoxin occurrence in maize, dairy feeds and milk produced and traded in Kenya and current technologies applied to aflatoxin management at the farm level. Finally, a case study in Kenya on successful application of GAP for mitigation of aflatoxin risk at small-scale farms will be reviewed.

Selection and characterization of two monoclonal antibodies specific for the Aspergillus flavus major antigenic cell wall protein Aflmp1

Aspergillus flavus is a major fungal pathogen of plants and an opportunistic pathogen of humans. In addition to the direct impact of infection, it produces immunosuppressive and carcinogenic aflatoxins. The early detection of A. flavus is therefore necessary to diagnose and monitor fungal infection, to prevent aflatoxin contamination of food and feed, and for effective antifungal therapy. Aspergillus-specific monoclonal antibodies (mAbs) are promising as diagnostic and therapeutic reagents for the tracking and treatment of Aspergillus infections, respectively. However, A. flavus has a complex cell wall composition and dynamic morphology, hindering the discovery of mAbs with well-characterized targets. Here we describe the generation and detailed characterization of mAb5.52 (IgG2aκ) and mAb17.15 (IgG1κ), which bind specifically to the highly immunogenic cell wall antigen A. flavus mannoprotein 1 (Aflmp1). Both mAbs were generated using hybridoma technology following the immunization of mice with a recombinant truncated version of Aflmp1 (ExD, including the homologous CR4 domain) produced in bacteria. We show that mAb5.52 and mAb17.15 bind specifically to A. flavus and A. parasiticus cell wall fragments (CWFs), with no cross-reaction to CWFs from other fungal pathogens. Immunofluorescence microscopy revealed that both mAbs bind to the surface of Aspergillus hyphae and that mAb17.15 also binds to spores. The epitope for both mAbs is localized within the CR4 region of the Aflmp1 protein. These Aspergillus-specific mAbs may be useful for the early detection of fungal infection in food/feed crops, for serodiagnosis in patients with invasive aspergillosis caused by A. flavus infection and for the development of antibody-expressing disease-resistant crops.

Degradation and Detoxification of Aflatoxin B1 by Tea-Derived Aspergillus niger RAF106

Microbial degradation is an effective and attractive method for eliminating aflatoxin B1 (AFB1), which is severely toxic to humans and animals. In this study, Aspergillus niger RAF106 could effectively degrade AFB1 when cultivated in Sabouraud dextrose broth (SDB) with contents of AFB1 ranging from 0.1 to 4 μg/mL. Treatment with yeast extract as a nitrogen source stimulated the degradation, but treatment with NaNO₃ and NaNO₂ as nitrogen sources and lactose and sucrose as carbon sources suppressed the degradation. Moreover, A. niger RAF106 still degraded AFB1 at initial pH values that ranged from 4 to 10 and at cultivation temperatures that ranged from 25 to 45 °C. In addition, intracellular enzymes or proteins with excellent thermotolerance were verified as being able to degrade AFB1 into metabolites with low or no mutagenicity. Furthermore, genomic sequence analysis indicated that the fungus was considered to be safe owing to the absence of virulence genes and the gene clusters for the synthesis of mycotoxins. These results indicate that A. niger RAF106 and its intracellular enzymes or proteins have a promising potential to be applied commercially in the processing and industry of food and feed to detoxify AFB1.

The Impact of Bt Corn on Aflatoxin-Related Insurance Claims in the United States

Previous field studies have reached no collective consensus on whether Bt corn, the most commonly planted transgenic crop worldwide, has significantly lower aflatoxin levels than non-Bt isolines. Aflatoxin, a mycotoxin contaminating corn and other commodities, causes liver cancer in humans and can pose severe economic losses to farmers. We found that from 2001-2016, a significant inverse correlation existed between Bt corn planting and aflatoxin-related insurance claims in the United States, when controlling for temperature and drought. Estimated benefits of aflatoxin reduction resulting from Bt corn planting are about $120 million to $167 million per year over 16 states on average. These results suggest that Bt corn use is an important strategy in reducing aflatoxin risk, with corresponding economic benefits. If the same principles hold true in other world regions, then Bt corn hybrids adapted to diverse agronomic regions may have a role in reducing aflatoxin in areas prone to high aflatoxin contamination, and where corn is a dietary staple.

Restricting mycotoxins without killing the producers: a new paradigm in nano-fungal interactions

Over the past several years, numerous studies have demonstrated the feasibility of using engineered nanoparticles as antifungals, especially against those fungal pathogens that produce mycotoxins and infect plants, animals, and humans. The high dosage of nanoparticles has been a concern in such antifungal applications due to the potential toxicological and ecotoxicological impacts. To address such concerns, we have recently introduced the idea of inhibiting mycotoxin biosynthesis using low doses of engineered nanoparticles. At such low doses these particles are minimally toxic to humans and the environment. From our studies we realize that for the effective use of nanotechnology to intervene in the biology of fungal pathogens and for an accurate evaluation of the impacts of the increasingly growing nanomaterials in the environment on fungi and their interacting biotic partners, there is a pressing need for a rigorous understanding of nano-fungal interactions, which is currently far from complete. In this minireview, we build on the available evidence from nano-bio interaction research and our recent interaction studies with Aspergillus cells and engineered silver nanoparticles to introduce a potential theoretical model for nano-fungal interactions. The aim of the proposed model is to provide an initial insight on how nanoparticle uptake and their transformation inside fungal cells, possibly influence the production of mycotoxins and other secondary metabolites of filamentous fungi .

Modelling Fungal Growth, Mycotoxin Production and Release in Grana Cheese

No information is available in the literature about the influence of temperature (T) on Penicillium and Aspergillus spp. growth and mycotoxin production on cheese rinds. The aim of this work was to: (i) study fungal ecology on cheese in terms of T requirements, focusing on the partitioning of mycotoxins between the rind and mycelium; and (ii) validate predictive models previously developed by in vitro trials. Grana cheese rind blocks were inoculated with A. versicolor, P. crustosum, P. nordicum, P. roqueforti, and P. verrucosum, incubated at different T regimes (10–30 °C, step 5 °C) and after 14 days the production of mycotoxins (ochratoxin A (OTA); sterigmatocystin (STC); roquefortine C (ROQ-C), mycophenolic acid (MPA), Pr toxin (PR-Tox), citrinin (CIT), cyclopiazonic acid (CPA)) was quantified. All the fungi grew optimally around 15–25 °C and produced the expected mycotoxins (except MPA, Pr-Tox, and CIT). The majority of the mycotoxins produced remained in the mycelium (~90%) in three out of five fungal species (P. crustosum, P. nordicum, and P. roqueforti); the opposite occurred for A. versicolor and P. verrucosum with 71% and 58% of STC and OTA detected in cheese rind, respectively. Available predictive models fitted fungal growth on the cheese rind well, but validation was not possible for mycotoxins because they were produced in a very narrow T range.

Fungal Pathogens of Maize Gaining Free Passage Along the Silk Road

Silks are the long threads at the tips of maize ears onto which pollen land and sperm nuclei travel long distances to fertilize egg cells, giving rise to embryos and seeds; however fungal pathogens also use this route to invade developing grain, causing damaging ear rots with dangerous mycotoxins. This review highlights the importance of silks as the direct highways by which globally important fungal pathogens enter maize kernels. First, the most important silk-entering fungal pathogens in maize are reviewed, including Fusarium graminearum, Fusarium verticillioides, and Aspergillus flavus, and their mycotoxins. Next, we compare the different modes used by each fungal pathogen to invade the silks, including susceptible time intervals and the effects of pollination. Innate silk defences and current strategies to protect silks from ear rot pathogens are reviewed, and future protective strategies and silk-based research are proposed. There is a particular gap in knowledge of how to improve silk health and defences around the time of pollination, and a need for protective silk sprays or other technologies. It is hoped that this review will stimulate innovations in breeding, inputs, and techniques to help growers protect silks, which are expected to become more vulnerable to pathogens due to climate change.

Overview of the activities of the European Food Safety Authority on mycotoxins in food and feed

Mycotoxins are widely occurring in foods and feeds and dietary exposure to them can induce various types of adverse health effects in humans and animals. Since its establishment in 2002, the European Food Safety Authority (EFSA) has assessed risks of dietary exposure to mycotoxins for public health and for the health of farm and companion animals on the request of the European Commission and has assessed safety and efficacy of feed additives for the reduction of contamination of feed by mycotoxins within the European Union authorisation process for feed additives. Over 40 scientific opinions on risks of mycotoxins for human and animal health and other reports on mycotoxins have been issued by the authority for the use of the European risk managers. Mycotoxins belong to one of the important areas of the EFSA work. Occurrence data on mycotoxins submitted to EFSA by the European national food safety bodies and research institutions have been collected in the EFSA databases and have informed its scientific opinions and reports on mycotoxins. Similarly, many EFSA-funded projects conducted by the European research organisations, not only to generate data on occurrence, but also data on toxicity of mycotoxins, have provided valuable information for the risk assessments of EFSA. Aflatoxin and deoxynivalenol are the mycotoxins, for which EFSA has delivered most of its scientific mycotoxin opinions. Very recently also modified forms of mycotoxins have been included in the EFSA risk assessments. In this review paper an overview of many different EFSA activities on mycotoxins is given. It also includes a brief description how EFSA develops its scientific opinions and works.

Occurrence of aflatoxin B1 in Triticum species inoculated with Aspergillus flavus

Effects of climate change, global trade and technological changes in processing industries cause higher occurrence of Aspergillus flavus and aflatoxin B1 (AFB1) in cereal crops. Four Triticum species: common wheat (Triticum aestivum L.), spelt (T. aestivum ssp. spelta L.), Khorasan wheat (Triticum turgidum ssp. turanicum Jakubz.) and hybrid wheat (T. aestivum L.– F1) were examined for their response to A. flavus infection and production of AFB1. The grains were obtained from control and artificially field inoculated wheat with A. flavus isolates (No. 1 and No. 2) in the 2016 vegetation season in the region of Vojvodina (Northern province of Serbia). Spelt wheat showed the strongest response to the infection in comparison to other analysed wheat species due to specific physico-chemical characteristics of the hull. The weakest response to A. flavus infections was noted in Khorasan wheat. The highest AFB1 level (256 μg/kg) was observed in the dehulled spelt grains, in comparison to other species where the AFB1 in dehulled grains was not detected. The levels of AFB1 in spelt were about three times higher in hulls (648 and 97.3 μg/kg, respectively) in comparison to grains (256 and 30.7 μg/kg, respectively) in two inoculation treatments (A. flavus No. 1 and No. 2, respectively). In order to investigate the impact of wheat hulls on development of A. flavus, including the biosynthesis of toxic fungal metabolites, physico-chemical and structural properties of different Triticum spp. hulls were characterised. The highest value of the water absorption index and total dietary fibre were observed in spelt hulls in comparison to other wheat species. Additionally, the height value distribution of the fossilized stomatal apparatus of hulls indicates the diversity of spelt wheat compared to other wheat species.

The Mycotox Charter: Increasing Awareness of, and Concerted Action for, Minimizing Mycotoxin Exposure Worldwide

Mycotoxins are major food contaminants affecting global food security, especially in low and middle-income countries. The European Union (EU) funded project, MycoKey, focuses on “Integrated and innovative key actions for mycotoxin management in the food and feed chains” and the right to safe food through mycotoxin management strategies and regulation, which are fundamental to minimizing the unequal access to safe and sufficient food worldwide. As part of the MycoKey project, a Mycotoxin Charter (charter.mycokey.eu) was launched to share the need for global harmonization of mycotoxin legislation and policies and to minimize human and animal exposure worldwide, with particular attention to less developed countries that lack effective legislation. This document is in response to a demand that has built through previous European Framework Projects—MycoGlobe and MycoRed—in the previous decade to control and reduce mycotoxin contamination worldwide. All suppliers, participants and beneficiaries of the food supply chain, for example, farmers, consumers, stakeholders, researchers, members of civil society and government and so forth, are invited to sign this charter and to support this initiative.

Mycotoxins – climate impact and steps to prevention based on prediction

Although mycotoxins occur worldwide and represent a global public health threat, their prevalence and quantities in food and feed may vary due to geographic and climatic differences. Also, in accordance with climate change, outside temperatures that are anticipated to rise and rainfall patterns modify the usual mycotoxicological scheme transforms and unexpectedly extreme events happen in practice more often. Such weather conditions increase fungal occurrence and mycotoxin concentrations in crops. Consequently, the risk to human and animal health grows, and strategies to alleviate adverse effects become more complex. This also elevates economic losses. Therefore, the task of mycotoxin prediction has been put in front of the multidisciplinary scientific community recently, and a targeted prevention has become more important. This paper is a review of the latest achievements in this field prepared with the aim to summarize and integrate available data.

The ameliorative effect of Aspergillus awamori on aflatoxin B1-induced hepatic damage in rabbits

This study was conducted to investigate the effect of dietary supplementation of Aspergillus awamori on aflatoxin B1 (AFB1)-induced liver damage in rabbits. Administration of AFB1 (0.3 mg/kg diet) led to a significant reduction in body weight, body weight gain, total feed intake, total serum proteins, albumin, high density lipoprotein-cholesterol, phagocytic activity, phagocytic index, and the antioxidant enzyme, glutathione peroxidase (GPx). Moreover, AFB1 administration was associated with a significant increase in feed conversion ratio, lipid peroxidation and serum levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, lactate dehydrogenase and total bilirubin. In addition, livers of AFB1-supplemented animals showed fatty degeneration with vacuolisation, focal areas of necrosis, mononuclear cells infiltration hyperplasia of bile ducts and sinusoids. A significant increase in the hepatic expression of the biotransformation gene (Cyp3A6), stress-sensitive genes (HO1 and SOD1), and inflammation-related genes (IL6, TNFa, NF-kB, and Cox2) was also observed. Supplementation of the diets with 0.05, 0.1 or 0.15% A. awamori ameliorated all AFB1 deleterious effects with the best improvement observed at the lowest concentration. This is the first investigation to report that supplementation of rabbit diets with A. awamori has an ameliorative effect against AFB1-induced liver damage possibly through preventing hepatic oxidative stress, promoting the antioxidant defence systems, and inhibiting expression of Cyp3A6, HO1, SOD1, IL6, TNFa, NF-kB, and Cox2. Therefore, A. awamori could be used as a potential preventive or therapeutic agent for aflatoxicosis.

Aflatoxins contamination of maize in Serbia: the impact of weather conditions in 2015

In recent years climate changes recorded in temperate regions of Europe have led to aflatoxin (AF) contamination of maize. Thus, the aim of this study was to investigate the influence of weather conditions on levels of aflatoxin B₁ (AFB1), aflatoxin B₂ (AFB2), aflatoxin G₁ (AFG1) and aflatoxin G₂ (AFG2) in 180 maize samples collected from the main maize-growing regions (Western Bačka, North Banat, South Banat and Central Serbia) in Serbia after harvest in 2015. The concentrations of AFs were determined by a validated HPLC method with post-column derivatisation and fluorescence detection (HPLC-FLD). The presence of AFB1, AFB2, AFG1 and AFG2 was detected in 57.2%, 13.9%, 5.6% and 2.8% of maize samples in the concentration ranges of 1.3-88.8 µg kg^-1, 0.60-2.8 µg kg^-1, 1.8-28.5 µg kg^-1 and 2.1-7.5 µg kg^-1 respectively. The recorded smaller amount of precipitation and especially higher air temperatures during the summer of 2015 were favourable for AF production, which resulted in 32.2% and 21.1% of samples being unsuitable for human consumption, since AFB1 and the sum of AFs concentrations were above 5.0 and 10.0 µg kg^-1 respectively. Furthermore, the findings in this study indicate that the microclimate conditions in the investigated regions had a great influence on the contamination frequency of maize with AFs. The highest percentage of samples unsuitable for human consumption, considering both AFB1 and total AFs content were 72.5% and 51.5% respectively from Central Serbia, whilst the lowest percentages of 15.6% and 6.2% respectively were found in Western Bačka. These findings confirmed that maize should be continuously monitored in order to protect human and animal health from the harmful effects caused by AFs contamination.