Cardiovascular changes associated with intravenous administration of fumonisin B1 in horses

Assessment of information as regards the toxicity of fumonisins for pigs, poultry and horses

In 2018, the EFSA Panel on Contaminants in the Food Chain (CONTAM) adopted a Scientific Opinion on the risks for animal health related to the presence of fumonisins, their modified forms and hidden forms in feed. A no observed adverse effect level (NOAEL) of 1 mg/kg feed was established for pigs. In poultry a NOAEL of 20 mg/kg feed and in horses a reference point for adverse animal health effect of 8.8 mg/kg feed was established, referred to as NOAEL. The European Commission (EC) requested EFSA to review the information regarding the toxicity of fumonisins for pigs, poultry and horses and to revise, if necessary, the established NOAELs. The EFSA CONTAM Panel considered that the term reference point (RP) for adverse animal health effects better reflects the uncertainties in the available studies. New evidence which had become available since the previous opinion allowed to revise an RP for adverse animal health effects for poultry from 20 mg/kg to 1 mg/kg feed (based on a LOAEL of 2.5 mg/kg feed for reduced intestinal crypt depth) and for horses from 8.8 to 1.0 mg/kg feed (based on case studies on equine leukoencephalomalacia (ELEM)). For pigs, the previously established NOAEL was confirmed as no further studies suitable for deriving an RP for adverse animal health effects could be identified. Based on exposure estimates performed in the previous opinion, the risk of adverse health effects of feeds containing FB1-3 was considered a concern for poultry, when taking into account the RP of 1 mg/kg feed for intestinal effects. For horses and other solipeds, the risk is considered low, although a large uncertainty associated with exposure was identified. The same conclusions apply to the sum of FB1-3 and their hidden forms.

Association between forage mycotoxins and liver disease in horses

Background

Outbreaks of liver disease in horses are common but the etiology of most remains unknown. Forage mycotoxins have been suspected to be a cause.

Objectives

To examine the association between outbreaks of liver disease and the presence of mycotoxins in forage stored on the same premises.

Animals

Premises were identified where ≥4 horses were contemporaneously affected by liver disease, and a control group was formed from premises where ≥4 horses had been examined and found to have no evidence of liver disease.

Methods

Forage was collected from 29 case and 12 control premises. The forage was analyzed for mycotoxin content using a liquid chromatography/mass spectrometry method, targeting 54 mycotoxins. The presence and distribution of mycotoxins between case and control samples was compared.

Results

Mycotoxins were found in 23/29 (79%) case samples and 10/12 (83%) control samples (P > .99; relative risk, 0.93; 95% confidence interval [CI], 0.64‐1.75). Median (interquartile range [IQR]) total mycotoxin concentration was similar in case and control samples (85.8 μg/kg [1.6‐268] vs. 315 μg/kg [6.3‐860]; P = .16). Ten mycotoxins were found exclusively in case premises comprising fumonisin B1, 15‐acetyldeoxynivalenol, deoxynivalenol, zearalenone, aflatoxins B1 and G1, methylergonovine, nivalenol, verruculogen, and wortmannin. The median (IQR) concentration of fumonisin B1 was significantly higher in case versus control samples (0 μg/kg [0‐81.7] vs. 0 μg/kg [0‐0]; P = .04).

Conclusions and Clinical Importance

Several mycotoxins with known hepatotoxic potential were found, alone or in combination, exclusively at case premises, consistent with the hypothesis that forage‐associated mycotoxicosis may be a cause of outbreaks of liver disease in horses in the United Kingdom.

Occurrence of fumonisin-producing black aspergilli in Australian wine grapes: effects of temperature and water activity on fumonisin production by A. niger and A. welwitschiae

Black aspergilli are some of the most common mycotoxigenic fungi in vineyards worldwide. The aims of this research were to assess the occurrence of fumonisin-producing black aspergilli in Australian wine grapes and the effects of environmental factors on fumonisin production by A. niger and A. welwitschiae (syn. A. awamori). Thirty-eight Aspergillus isolates (black aspergilli) were collected from six wine grape varieties grown in Australian vineyards. LC-MS/MS analysis of culture extracts revealed that six isolates produced fumonisins FB₂ and FB₄. Molecular data revealed that all fumonisin-producing isolates were A. niger and A. welwitschiae. None of the reference isolates, A. carbonarius, A. tubingensis, A. japonicus, and A. foetidus, were positive for fumonisin production. The effects of temperature and water activity on the growth and production of fumonisins were studied using two A. niger and an isolate of A. welwitschiae on synthetic grape juice medium (SGJM) at 20 °C, 25 °C, 30 °C, and 35 °C, and 0.92 a_w, 0.95 a_w, and 0.98 a_w levels. All isolates produced FB₂ and FB₄ at 0.95 a_w and 0.98 a_w and 20 °C, 25 °C, and 30 °C. The highest growth rate observed was 14.89 mm/day for A. welwitschiae at 0.98 a_w and 35 °C, whereas the highest fumonisin production observed was 25.3 mg/kg at 0.98 a_w and 20 °C for A. welwitschiae. None of the isolates produced fumonisins at 35 °C at any water activity levels. To our knowledge, this is the first report on the occurrence of fumonisin-positive isolates of Aspergillus from Australian wine grapes and the impact of the environmental factors on fumonisin production by A. welwitschiae.

Research Progress on Fumonisin B1 Contamination and Toxicity: A Review

Fumonisin B1 (FB1), belonging to the member of fumonisins, is one of the most toxic mycotoxins produced mainly by Fusarium proliferatum and Fusarium verticillioide. FB1 has caused extensive contamination worldwide, mainly in corn, rice, wheat, and their products, while it also poses a health risk and is toxic to animals and human. It has been shown to cause oxidative stress, endoplasmic reticulum stress, cellular autophagy, and apoptosis. This review focuses on the current stage of FB1 contamination, its toxic effects of acute toxicity, immunotoxicity, organ toxicity, and reproductive toxicity on animals and humans. The potential toxic mechanisms of FB1 are discussed. One of the main aims of the work is to provide a reliable reference strategy for understanding the occurrence and toxicity of FB1.

Mycotoxin Production in Fusarium According to Contemporary Species Concepts

Fusarium is one of the most important genera of plant-pathogenic fungi in the world and arguably the world's most important mycotoxin-producing genus. Fusarium species produce a staggering array of toxic metabolites that contribute to plant disease and mycotoxicoses in humans and other animals. A thorough understanding of the mycotoxin potential of individual species is crucial for assessing the toxicological risks associated with Fusarium diseases. There are thousands of reports of mycotoxin production by various species, and there have been numerous attempts to summarize them. These efforts have been complicated by competing classification systems based on morphology, sexual compatibility, and phylogenetic relationships. The current depth of knowledge of Fusarium genomes and mycotoxin biosynthetic pathways provides insights into how mycotoxin production is distributedamong species and multispecies lineages (species complexes) in the genus as well as opportunities to clarify and predict mycotoxin risks connected with known and newly described species. Here, we summarize mycotoxin production in the genus Fusarium and how mycotoxin risk aligns with current phylogenetic species concepts.

Echocardiographic assessment of left ventricular systolic function in neonatal calves with naturally occurring sepsis or septic shock due to diarrhea

Sepsis is associated with clinically relevant cardiovascular changes. The objectives of this study were to evaluate the clinical value of echocardiography for monitoring left ventricular (LV) systolic function in septic calves. A prospective longitudinal study was performed using a convenience sample. Twenty septic calves and 10 healthy calves were enrolled in the study. Arterial blood pressure (BP) was measured and M-mode echocardiography performed to characterize LV systolic function; the latter included measurement of ejection fraction, EF; stroke volume, SVI and cardiac output indexed to body weight, CI; E-point of septal separation, EPSS; pre-ejection period, PEP; ejection time, LVET; ratio of PEP to LVET; velocity of circumferential shortening, Vcf, LV end-diastolic volume index (LVEDVI) and LV end-systolic volume index (LVESVI) on admission and 6, 24, 48 and 72 h later in septic calves and once in healthy calves. Admission data were compared using the Mann-Whitney U test and P < .05 was considered significant. Decreased preload and afterload were present in septic calves, as indicated by marked decreases in BP, LVEDVI, LVESVI, SVI, CI, EPSS when compared to healthy calves. Systolic function appeared adequate in septic calves, based on EF and FS compared to control calves. There was no difference in heart rate, LVET, PEP:LVET, or Vcf between septic and health calves. We conclude that circulatory dysfunction, rather than systolic dysfunction predominates in septic calves. Positive associations on admission between CI and LVEDVI, LVESVI, and SVI support this conclusion. Echocardiographic determination of LVEDVI and CI appears useful in directing treatment in septic calves.

Mycotoxin exposure and adverse reproductive health outcomes in Africa: a review

It is well established that mycotoxin exposure can have adverse effects on reproductive health resulting to poor reproductive potential. The most studied mycotoxin in relation to poor reproductive health in humans is aflatoxin, although fumonisins, trichothecenes and zearalenone have also been reported to impair reproductive function and cause abnormal foetal development. These potent fungal toxins contaminate many food products making them a prominent agricultural, food safety and public health challenge, especially in Africa due to little or lack of mycotoxin regulation in agricultural products. Neonates can be exposed to aflatoxins in utero, as the toxins pass from mother to the foetus through the placenta. This exposure may continue during breast feeding, to the introduction of weaning foods, and then foods taken by adults. The consequences of aflatoxin exposure in mothers, foetus and children are many, including anaemia in pregnancy, low birth weight, interference with nutrient absorption, suppression of immune function, child growth retardation and abnormal liver function. In males, reports have indicated a possible relationship between aflatoxin exposure and poor sperm quality culminating in infertility. Maternal exposure to fumonisin during early pregnancy has been associated with increased risk of neural tube defects among newborns in regions where maize is the common dietary staple with the possibility of chronic fumonisin exposure. Furthermore, zearalenone has been linked to precocious puberty and premature thelarche in girls, correlating with extremely high serum oestrogen levels. This review presents an overview of the several reports linking aflatoxins, fumonisins, trichothecenes, and zearalenone exposure to poor reproductive health outcomes in Africa, with emphasis on birth outcomes, foetal health and infertility.

Fusarium Molds and Mycotoxins: Potential Species-Specific Effects

This review summarizes the information on biochemical and biological activity of the main Fusarium mycotoxins, focusing on toxicological aspects in terms of species-specific effects. Both in vitro and in vivo studies have centered on the peculiarity of the responses to mycotoxins, demonstrating that toxicokinetics, bioavailability and the mechanisms of action of these substances vary depending on the species involved, but additional studies are needed to better understand the specific responses. The aim of this review is to summarize the toxicological responses of the main species affected by Fusarium mycotoxins.

Risks for animal health related to the presence of fumonisins, their modified forms and hidden forms in feed

Fumonisins, mycotoxins primarily produced by Fusarium verticillioides and Fusarium proliferatum, occur predominantly in cereal grains, especially in maize. The European Commission asked EFSA for a scientific opinion on the risk to animal health related to fumonisins and their modified and hidden forms in feed. Fumonisin B1 (FB 1), FB 2 and FB 3 are the most common forms of fumonisins in feedstuffs and thus were included in the assessment. FB 1, FB 2 and FB 3 have the same mode of action and were considered as having similar toxicological profile and potencies. For fumonisins, the EFSA Panel on Contaminants in the Food Chain (CONTAM) identified no-observed-adverse-effect levels (NOAELs) for cattle, pig, poultry (chicken, ducks and turkeys), horse, and lowest-observed-adverse-effect levels (LOAELs) for fish (extrapolated from carp) and rabbits. No reference points could be identified for sheep, goats, dogs, cats and mink. The dietary exposure was estimated on 18,140 feed samples on FB 1-3 representing most of the feed commodities with potential presence of fumonisins. Samples were collected between 2003 and 2016 from 19 different European countries, but most of them from four Member States. To take into account the possible occurrence of hidden forms, an additional factor of 1.6, derived from the literature, was applied to the occurrence data. Modified forms of fumonisins, for which no data were identified concerning both the occurrence and the toxicity, were not included in the assessment. Based on mean exposure estimates, the risk of adverse health effects of feeds containing FB 1-3 was considered very low for ruminants, low for poultry, horse, rabbits, fish and of potential concern for pigs. The same conclusions apply to the sum of FB 1-3 and their hidden forms, except for pigs for which the risk of adverse health effect was considered of concern.

Fusarium Species and Their Associated Mycotoxins

The genus Fusarium includes numerous toxigenic species that are pathogenic to plants or humans, and are able to colonize a wide range of environments on earth. The genus comprises around 70 well-known species, identified by using a polyphasic approach, and as many as 300 putative species, according to phylogenetic species concepts; many putative species do not yet have formal names. Fusarium is one of the most economically important fungal genera because of yield loss due to plant pathogenic activity; mycotoxin contamination of food and feed products which often render them unaccep for marketing; and health impacts to humans and livestock, due to consumption of mycotoxins. Among the most important mycotoxins produced by species of Fusarium are the trichothecenes and the fumonisins. Fumonisins cause fatal livestock diseases and are considered potentially carcinogenic mycotoxins for humans, while trichothecenes are potent inhibitors of protein synthesis. This chapter summarizes the main aspects of morphology, pathology, and toxigenicity of the main Fusarium species that colonize different agricultural crops and environments worldwide, and cause mycotoxin contamination of food and feed.

Impact of two mycotoxins deoxynivalenol and fumonisin on pig intestinal health

Mycotoxins are secondary metabolites of fungi that grow on a variety of substrates. Due to their high consumption of cereals and their sensitivity, pigs are highly impacted by the presence of mycotoxins. At the European level, regulations and recommendations exist for several mycotoxins in pig feed. Among these toxins, fumonisin B₁ (FB₁), and deoxynivalenol (DON) have a great impact on the intestine and the immune system. Indeed, the intestine is the first barrier to food contaminants and can be exposed to high concentrations of mycotoxins upon ingestion of contaminated feed. FB₁ and DON alter the intestinal barrier, impair the immune response, reduce feed intake and weight gain. Their presence in feed increases the translocation of bacteria; mycotoxins can also impair the immune response and enhance the susceptibility to infectious diseases. In conclusion, because of their effect on the intestine, FB₁ and DON are a major threat to pig health, welfare and performance.

Fumonisin B₁ (FB₁) Induces Lamellar Separation and Alters Sphingolipid Metabolism of In Vitro Cultured Hoof Explants

One of the most important hoof diseases is laminitis. Yet, the pathology of laminitis is not fully understood. Different bacterial toxins, e.g. endotoxins or exotoxins, seem to play an important role. Additionally, ingestion of mycotoxins, toxic secondary metabolites of fungi, might contribute to the onset of laminitis. In this respect, fumonsins are of special interest since horses are regarded as species most susceptible to this group of mycotoxins. The aim of our study was to investigate the influence of fumonisin B₁ (FB₁) on primary isolated epidermal and dermal hoof cells, as well as on the lamellar tissue integrity and sphingolipid metabolism of hoof explants in vitro. There was no effect of FB₁ at any concentration on dermal or epidermal cells. However, FB₁ significantly reduced the separation force of explants after 24 h of incubation. The Sa/So ratio was significantly increased in supernatants of explants incubated with FB₁ (2.5–10 µg/mL) after 24 h. Observed effects on Sa/So ratio were linked to significantly increased sphinganine concentrations. Our study showed that FB₁ impairs the sphingolipid metabolism of explants and reduces lamellar integrity at non-cytotoxic concentrations. FB₁ might, therefore, affect hoof health. Further in vitro and in vivo studies are necessary to elucidate the effects of FB₁ on the equine hoof in more detail.

Commentary

Veterinary pathologists working as toxicologic pathologists in academic settings fill many vital roles, such as diagnosticians, educators, and/or researchers. These individuals have spent years investigating pathology problems that mainly or exclusively focus on the reactions of cells, organs, or systems to toxic materials. Thus, academic toxicologic pathologists are uniquely suited both to help trainees understand toxicity as a cause of pathology responses and also to provide expert consultation on toxicologic pathology. Most toxicologic pathologists in academia are employed at colleges of medicine or veterinary medicine, even though specific toxicologic pathology faculty appointments are uncommon in Europe and North America. Academic toxicologic pathologists typically receive lower financial compensation than do toxicologic pathologists in industry, but academic positions generally provide alternative rewards, such as higher workplace autonomy and scheduling flexibility, professional enrichment through student interactions, and enhanced opportunities for collaborative research and advanced diagnostic investigations. Regular participation by academic toxicologic pathologists in professional training opportunities (eg, as pathology and toxicology instructors in medical and veterinary medical courses, graduate programs, and residencies) offers an important means of engendering interest and inspiring veterinarians to select toxicologic pathology and toxicology as their own areas of future expertise.

Occurrence, Rapid Analysis, and Detoxification of Fumonisins in Maize and its Feeds: Review

Maize (Zea mays L.) is one of the main cereals as a source of food, forage and processed products for industry, especially for feeds. However, in worldwide approximately 25% of crops are affected by mycotoxins annually, especially in feeds with fumonisins(FUM). Moreover, the exact mechanism of FUM toxicity is not completely established. This paper gives an overview about the occurrence, toxicity, rapid non-invasive analysis, and detoxification of FUM in maize and its feeds. Due to economic losses engendered by FUM and its impact on animal and human health, several strategies for detecting mycotoxins with non-invasive methods and detoxifying contaminated feeds have been described.

Mycobiota and mycotoxins in malted barley and brewer's spent grain from Argentinean breweries

AIMS

To evaluate mycobiota and aflatoxins B(1) (AFB(1)), B(2) (AFB(2)), G(1) (AFG(1)), G(2) (AFG(2)) and fumonisin B(1) (FB(1)) contamination in different malted barley types and brands and brewer's grain collected from a major Argentinean brewery.

METHODS AND RESULTS

Total fungal counts were performed using the plate count method. Aflatoxin B(1), AFB(2), AFG(1), AFG(2) and Zearalenone (ZEA) analyses were performed by thin-layer chromatography (TLC). Fumonisin B(1) was determined by HPLC. Eighty-three percentage of the malted barley (100% M1, 50% M2 and 100% M3) and 61% of brewer's grain samples had a count >1 × 10(4) CFU g(-1). Yeasts were isolated from all malt and brewer's grain samples. Genera containing some of the most important mycotoxin producer species--Fusarium ssp., Aspergillus ssp., Penicillium ssp. and Alternaria ssp.--were isolated from the analysed samples, along with other environmental saprophytic fungi such as Geotrichum ssp., Mucorales and Cladosporium ssp. All samples were contaminated with 104-145 μg kg(-1) FB(1). Eighteen per cent of brewer's grain samples were contaminated with 19-44.52 μg kg(-1) AFB(1). Aflatoxin B(2), AFG(1), AFG(2) and ZEA were not detected in any of the analysed samples.

CONCLUSIONS

Fungal and mycotoxin contamination in malt and brewer's grain is an actual risk for animal and human health.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study may be useful for assessing the risk of mycotoxins in Argentinean beers and especially in animal feeds.

Comparative analysis of the mycobiota and mycotoxins contaminating corn trench silos and silo bags

BACKGROUND

Silage is one of the most important feed sources for bovines. Mycotoxin contamination of feedstuffs is a worldwide concern. The aim of this study was to compare mycobiota and levels of aflatoxin B₁ (AFB₁), fumonisin B₁ (FB₁), deoxynivalenol (DON), zearalenone (ZEA) and patulin (PAT) in corn trench silos and silo bags.

RESULTS

Dry matter was higher in trench silos. Counts varied from not detected to 10⁸ CFU g⁻¹ in both trench silos and silo bags. Isolation frequencies of Aspergillus spp. and Fusarium spp. were higher in trench silos, whereas Penicillium spp. was higher in silo bags. Silo bags showed less diversity than trench silos. Strains isolated produced AFB₁, FB₁ and PAT. In trench silos, AFB₁ was the only mycotoxin detected (1-160 µg kg⁻¹). In silo bags AFB₁ levels varied from 5.8 to 47.4 µg kg⁻¹. DON was detected in two silo bag samples.

CONCLUSION

When handling is adequate the reduction of mould and mycotoxin contamination in silo bags is considerable. This study will enable estimation of the mycotoxicological risk of different ensiling practices and determination of the most adequate method to minimize economic losses and reduce hazard to animal and human health.

Endurance exercise is associated with increased plasma cardiac troponin I in horses

REASON FOR PERFORMING STUDY

Information is lacking regarding the influence of long distance exercise on the systemic concentration of cardiac troponin I (cTnI) in horses.

OBJECTIVES

To determine if the concentration of cTnI in horses competing in 80 and 160 km endurance races increases with exercise duration and if cTnI concentrations can be correlated with performance data.

METHODS

Blood samples for the measurement of cTnI and 3 min electrocardiogram recordings were obtained from horses prior to, during and after completion of 80 and 160 km endurance races at 3 ride sites during the 2004 and 2005 American Endurance Ride Conference competition seasons.

RESULTS

Full data sets were obtained from 100 of the 118 horses. Endurance exercise was associated with a significant increase in cTnI over baseline in both distance groups. Failure to finish competition (poor performance) was also associated with an increased cTnI concentration over baseline at the time of elimination when data from both distances were combined. Other than one horse that developed paroxysmal atrial fibrillation, no arrhythmias were noted on the 3 minute ECG recordings that were obtained after endurance exercise in either distance group.

CONCLUSIONS

Systemic concentrations of cTnI increase in endurance horses competing in both 80 and 160 km distances. Although final cTnI concentrations were significantly increased over their baseline values in horses that failed to finish competition, the degree of increase was not greater than the increase over baseline seen in the horses that successfully completed competition. The clinical significance of increased cTnI in exercising horses could not be ascertained from the results of this study.

POTENTIAL RELEVANCE

These data indicate that cardiac stress may occur in horses associated with endurance exercise. Future studies utilising echocardiograpy to assess cardiac function in horses with increased cTnI are warranted.

Oxidative Stress Induced by Fumonisin B1in Continuous Human and Rodent Neural Cell Cultures

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium verticillioides, which is a common infectant of corn and other cereal grains. Of concern to human health is also a possible airborne exposure to FB1-producing strains of F. verticillioides, which may grow in moisture-damaged buildings. In this study, we have characterized oxidative stress-related parameters induced by FB1 in three different neural cell lines, human SH-SY5Y neuroblastoma, rat C6 glioblastoma and mouse GT1-7 hypothalamic cells. The cells were exposed to graded doses of FB1 between 0.1 and 100 microM for 0-144 h after which the production of reactive oxygen species (ROS), lipid peroxidation, intracellular glutathione (GSH) levels and cell viability were measured. FB1 caused a dose-dependent increase of ROS production in C6 glioblastoma and GT1-7 hypothalamic cells but was without an effect in SH-SY5Y cells. Decreased GSH levels, increased MDA-formation, indicative of lipid peroxidation and necrotic cell death were observed in all cell lines after incubation with FB1. These findings indicate that FB1 induces oxidative stress in human, rat and mouse neural cell cultures.

Sphingolipids as determinants of apoptosis and chemoresistance in the MCF-7 cell model system

An estimated 182,640 women and 1,990 men were diagnosed with breast cancer in 2008, and approximately 40,480 women and 450 men died from the disease. Thus, continued mechanistic studies are needed to understand the causes and develop additional therapeutics for this complicated disease. The MCF-7 cell system is one of the most recognized models for estrogen receptor (ER)-positive breast cancer and has generated approximately 13,000 publications cited in PubMed to date. A number of clues for biological mechanisms related to apoptotic/anti-apoptotic pathways and chemoresistance were elucidated and summarized in our previous review. The focus of this review is new knowledge of the central role of sphingolipid signaling in apoptotic mechanisms in estrogen receptor-positive breast cancer. The ultimate goal is to target crucial steps in survival signaling pathways that may ultimately provide additional translational solutions to the successful pharmacologic treatment of breast cancer.

A review of the toxic effects and mechanisms of action of fumonisin B1

Fumonisin B(1) (FB(1)) is a mycotoxin produced by the fungus Fusarium verticillioides, which commonly infects corn and other agricultural products. Fusarium species can also be found in moisture-damaged buildings, and, therefore, exposure of humans to Fusarium mycotoxins including FB(1) may take place. FB(1) bears a clear structural similarity to the cellular sphingolipids, and this similarity has been shown to disturb the metabolism of sphingolipids by inhibiting the enzyme ceramide synthase leading to accumulation of sphinganine in cells and tissues. FB(1) is neurotoxic, hepatotoxic, and nephrotoxic in animals, and it has been classified as a possible carcinogen to humans. The cellular mechanisms behind FB(1)-induced toxicity include the induction of oxidative stress, apoptosis, and cytotoxicity, as well as alterations in cytokine expression. The effects of FB(1) on different parameters vary markedly depending on what types of cells are studied or what species they originate from. These aspects are important to consider when evaluating the toxic potential of FB(1).

Maternal fumonisin exposure as a risk factor for neural tube defects

Fumonisins are mycotoxins produced by the fungus F. verticillioides, a common contaminant of maize (corn) worldwide. Maternal consumption of fumonisin B(1)-contaminated maize during early pregnancy has recently been associated with increased risk for neural tube defects (NTDs) in human populations that rely heavily on maize as a dietary staple. Experimental administration of purified fumonisin to mice early in gestation also results in an increased incidence of NTDs in exposed offspring. Fumonisin inhibits the enzyme ceramide synthase in de novo sphingolipid biosynthesis, resulting in an elevation of free sphingoid bases and depletion of downstream glycosphingolipids. Increased sphingoid base metabolites (i.e., sphinganine-1-phosphate) may perturb signaling cascades involved in embryonic morphogenesis by functioning as ligands for sphingosine-1-P (S1P) receptors, a family of G-protein-coupled receptors that regulate key biological processes such as cell survival/proliferation, differentiation and migration. Fumonisin-induced depletion of glycosphingolipids impairs expression and function of the GPI-anchored folate receptor (Folr1), which may also contribute to adverse pregnancy outcomes. NTDs appear to be multifactorial in origin, involving complex gene-nutrient-environment interactions. Vitamin supplements containing folic acid have been shown to reduce the occurrence of NTDs, and may help protect the developing fetus from environmental teratogens. Fumonisins appear to be an environmental risk factor for birth defects, although other aspects of maternal nutrition and genetics play interactive roles in determining pregnancy outcome. Minimizing exposures to mycotoxins through enhanced agricultural practices, identifying biomarkers of exposure, characterizing mechanisms of toxicity, and improving maternal nutrition are all important strategies for reducing the NTD burden in susceptible human populations.

Acute effects of short duration, maximal exercise on cardiac troponin I in healthy horses

This study evaluated the effects of exercise on cardiac troponin I (cTnI) concentrations in healthy, adult horses.

Fifteen fit, healthy horses determined to have a normal cardiovascular system completed a standardized exercise test on a high-speed treadmill. Heparinized blood was collected for plasma cTnI concentrations before maximal exercise, and 1, 3, 6, 9, 12 and 24 h post-exercise. The cTnI concentrations were measured with a commercial system (Stratus CS, Dade Behring, Inc.). Results were analysed by a multivariate ANOVA, where indicatedpost hocanalysis was done by Tukey–Kramer HSD and significance was placed atp < 0.05.

All horses had elevations in cTnI concentrations after maximal exercise. Values for cTnI trended higher at 3 h (0.066 ± 0.011 ng ml− 1) and 6 h (0.062 ± 0.011 ng ml− 1) post-exercise compared with pre-exercise (0.039 ± 0.007 ng ml− 1), although this did not reach statistical significance. Mean cTnI concentrations were within our normal reference range at all time points, although four individuals were above our normal range after exercise.

These data show that short-term, high-intensity exercise induces a small rise in plasma cTnI in normal horses. This should be kept in mind when evaluating cTnI concentrations in horses that have recently completed intense exercise. In addition, these data suggest that 3–6 h after intense exercise may be the optimal time for measurement of cTnI concentrations in horses with suspected exercise-induced myocardial damage.

Effects of exogenous sphinganine, sphingosine, and sphingosine-1-phosphate on relaxation and contraction of porcine thoracic aortic and pulmonary arterial rings

Fumonisin mycotoxicosis in pigs causes a decrease in mean aortic pressure, an increase in mean pulmonary arterial pressure, and increases in serum concentrations of sphinganine (3.2 microM) and sphingosine (1.4 microM). To determine a causal relationship between the hemodynamic changes and sphingolipid alterations, we examined the in vitro effects of sphinganine, sphingosine, and sphingosine-1-phosphate on porcine aortic and pulmonary arterial rings. Both sphinganine and sphingosine relaxed un-contracted and phenylephrine-contracted aortic rings at > or = 10 microM and > or = 1 microM, respectively. Sphingosine (> or = 10 microM) relaxed un-contracted and phenylephrine-contracted pulmonary arterial rings, whereas sphingosine-1-phosphate (10 microM) contracted pulmonary arterial rings. Sphingosine (3 microM) also impaired the contractile response of pulmonary artery rings to 60 mM KCl. The results suggested that the systemic hypotension caused by fumonisin is mediated, in part, by increases in serum sphinganine and sphingosine concentrations, and the pulmonary hypertension is mediated, in part, by increased sphingosine-1-phosphate concentrations.

Liquid chromatographic determination of fumonisins B1, B2, and B3 in corn silage

Corn silage was dried, ground, and then extracted with 0.1 M ethylenediaminetetraacetic acid. The filtrate was applied to a FumoniTest immunoaffinity column. Fumonisins were derivatized with naphthalene-2,3-dicarboxaldehyde, separated on a C(18) liquid chromatographic column, and detected by fluorescence. The detection limits for fumonisin B(1), fumonisin B(2), and fumonisin B(3) were 50, 25, and 25 ng/g of dried silage, respectively. Recoveries of fumonisin B(1), fumonisin B(2), and fumonisin B(3) from wet and dried corn silage spiked over the range of 100-5000 ng/g averaged 91-106%. The method was applied to corn silage samples collected from the midwestern area of the United States during 2001-2002. Of 89 corn silage samples, fumonisin B(1), fumonisin B(2), and fumonisin B(3) were found in 86 (97%), 64 (72%), and 51 (57%) of the samples. The mean positive levels of fumonisin B(1), fumonisin B(2), and fumonisin B(3) were 615, 93, and 51 ng/g, respectively, in dried silage. This suggests that fumonisins may be frequent low level contaminants in corn silage.

Fumonisin-induced blockade of ceramide synthase in sphingolipid biosynthetic pathway alters aortic input impedance spectrum of pigs

The sphingolipid signaling pathway appears to play an important role in regulating vascular tone. We examined the effect of fumonisin B(1), a fungal toxin in corn that blocks ceramide synthase in the sphingolipid signaling pathway, on the ascending aortic impedance spectrum of pigs. Sixteen pigs were fed culture material containing fumonisin B(1) (20 mg/kg body wt) (n = 7) or a control diet (n = 9) daily for 3 days and then instrumented under alpha-chloralose anesthesia for measurement of ascending aortic pressure and flow. Fumonisin ingestion increased serum sphinganine and sphingosine concentrations. Fumonisin ingestion also decreased cardiac output and characteristic impedance and increased the frequency of the first minimum impedance modulus, systemic vascular resistance, and the terminal, first, and second harmonic reflection coefficients, without changing mean arterial pressure. Thus blockade of ceramide synthase is accompanied by decreased vascular tone in systemic conduit arteries and increased vascular tone in systemic resistance vessels. The results indicate that the sphingolipid signaling pathway influences vascular tone in alpha-chloralose-anesthetized pigs.