Hypoglycin A Concentrations in Maple Tree Species in the Netherlands and the Occurrence of Atypical Myopathy in Horses

Plants Causing Toxic Myopathies

Boxelder and sycamore maple contain hypoglycin A (HGA), the toxic metabolite of which, MCPA-CoA, inhibits fatty acid β-oxidation, causing seasonal pasture myopathy (SPM) or atypical myopathy (AM), respectively. White snakeroot and rayless goldenrod contain multiple benzofuran ketones (BFKs). The identity/toxicity of BFKs appear variable, possibly involving interactions between toxins/toxic metabolites, but ultimately inhibit cellular energy metabolism. Unthrifty horses grazing sparse pastures during the fall appear predisposed to these plant-associated, frequently fatal, toxic myopathies. Toxidromes are characterized by varying degrees of rhabdomyolysis and cardiac myonecrosis, with plant toxins remaining toxic in hay and being excreted in milk.

Do Poisonous Plants in Pastures Communicate Their Toxicity? Meta-Study and Evaluation of Poisoning Cases in Central Europe

One of the possible roles of secondary plant metabolites, including toxins, is facilitating plant-animal communication. Lethal cases of pasture poisoning show that the message is not always successfully conveyed. As the focus of poisoning lies in the clinical aspects, the external circumstances of pasture poisoning are widely unknown. To document poisoning conditions in cattle, sheep, goats, and horses on pastures and to compile a checklist of plants involved in either poisoning or co-existence (zero poisoning), published case reports were evaluated as primary sources. The number of affected animal individuals was estimated within abundance classes from 0 to more than 100. The checklist of poisonous plants comprised 52 taxa. Of these, 13 taxa were deemed safe (no reference was found indicating poisoning), 11 taxa were associated with evidence-based zero poisoning (positive list), and 28 taxa were associated with poisoning (negative list). Nine plant taxa caused poisoning in more than 100 animal individuals. Zero poisoning accounted for 40% and poisoning accounted for 60% of a total of 85 cases. Poisoning was most often associated with a limited choice of feed (24.7%), followed by overgrazing (12.9%), seasonally scarce feed (10.6%), and co-ingestion of grass (4.7%). Hunger interferes with plant-animal co-existence, while zero poisoning improves it. In conclusion, poisonous plants in pastures may communicate their toxicity if the animals have enough alternative feed plants. An individual animal might utterly perceive the communication of toxicity by the plant species but be forced to ignore the message owing to a limited choice of feed options.

Hypoglycin A in Acer genus plants

Hypoglycin A (HGA) is an amino acid occuring in the Sapindaceae family. Ingestion of certain Acer genus plants belonging to this family has been connected with atypical myopathy (AM) or seasonal pasture myopathy (SPM). To date, all cases of AM/SPM have been associated with sycamore (Acer pseudoplatanus) and boxelder maple (Acer negundo). The aim of this work was to determine and compare HGA in sycamore, boxelder and silver maple (Acer saccharinum), the trees known for HGA content, whose occurence is quite common in the Czech Republic. In sycamore and boxelder maple the effect of location, weather condition and sampling season was evaluated. The other aim was screening for presence of HGA in 12 other species of Acer genus which are grown as ornamental trees in Europe. The determination of HGA was conducted using ultra - high performance liquid chromatography - tandem mass spectrometry (LC/MS). HGA was detected in all samples of sycamore, boxelder and silver maple except for eight leave samples of boxelder maple. In the case of sycamore maple, the highest concentrations of HGA (median) were found in seedlings (770 mg/kg) followed by samaras (130 mg/kg) and by leaves (48 mg/kg) and inflorescences (24 mg/kg). In boxelder maple, significantly higher concentrations of HGA (median) were found in seedlings (550 mg/kg) compared with samaras (45 mg/kg), leaves (14 mg/kg) and inflorescences (24 mg/kg). According to the results the seedlings could pose a significant risk of poisoning, although other factors such as accessibility and palatability of other parts, especially samaras, should be considered. No significant differences of HGA concentrations in silver maple (56 mg/kg) were found between samaras, leaves and inflorescences. HGA was also identified in sugar maple (Acer saccharum), Japanese maple (Acer palmatum), trident maple (Acer buergerianum), paperbark maple (Acer griseum) and Himalayan maple (Acer oblongum). Although silver maple and other ornamental maples have not been reported to cause AM/SPM, the possibility of intoxication in animals can not be excluded.

Tissue Specific Distribution and Activation of Sapindaceae Toxins in Horses Suffering from Atypical Myopathy

Equine atypical myopathy is caused by hypoglycin A (HGA) and methylenecyclopropylglycine (MCPrG), the known protoxins of sycamore maple (Acer pseudoplatanus). Various tissues from five atypical myopathy cases were analyzed but only HGA was found. Whether deamination of MCPrG has already occurred in the intestine as the first stage of metabolization has not been investigated. Activation of the protoxins to methylenecyclopropylacetyl (MCPA)-CoA and methylenecyclopropylformyl (MCPF)-CoA, respectively, occurred mainly in the skeletal muscles, as evidenced by very high concentrations of MCPA-carnitine and MCPF-carnitine in this tissue. Inhibition of the acyl-CoA dehydrogenases of short- and medium-chain as well as branched-chain fatty acids by the toxins led to a strong increase in the corresponding acylcarnitines, again preferentially in skeletal muscles. An accumulation of the long-chain acylcarnitines beyond the level of the control samples could not be detected in the tissues. As a high amount of HGA was always found unmetabolized in the organs, we speculate that targeting the interruption of further metabolization might be a way to stop the progression of intoxication. Inhibition of the mitochondrial branched-chain amino acid aminotransferase, i.e., the first enzyme responsible for the activation of sycamore maple protoxins, could be a therapeutic approach.

A sensitive LC-MS/MS method for the quantification of the plant toxins hypoglycin A and methylenecyclopropylglycine and their metabolites in cow's milk and urine and application to farm milk samples from Germany

Hypoglycin A (HGA) and its homologue methylenecyclopropylglycine (MCPrG) are present in ackee and lychee as well as seeds, leaves, and seedlings of some maple (Acer) species. They are toxic to some animal species and humans. The determination of HGA, MCPrG, and their glycine and carnitine metabolites in blood and urine is a useful tool for screening for potential exposure to these toxins. In addition, HGA, MCPrG, and/or their metabolites have been detected in milk. In this work, simple and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methods without derivatization were developed and validated for the quantification of HGA, MCPrG, and their metabolites in cow's milk and urine. An extraction procedure from milk samples has been developed, whereas a dilute-and-shoot approach was implemented for urine samples. For quantification, the MS/MS analysis was performed in multiple reaction monitoring mode. The methods were validated according to the European Union guidelines using blank raw milk and urine as matrices. The limit of quantification presented here for HGA in milk (1.12 µg/L) is noticeably lower than the lowest published limit of detection (9 µg/L). Acceptable values for recovery (89-106% and 85-104% in milk and urine, respectively) and precision (≤ 20%) were obtained for all the quality control levels. The stability of HGA and MCPrG in frozen milk over a period of 40 weeks has been demonstrated. The method was applied to 68 milk samples from 35 commercial dairy farms and showed the absence of any quantifiable amounts of HGA, MCPrG, and their metabolites.

Co-Occurrence of Hypoglycin A and Hypoglycin B in Sycamore and Box Elder Maple Proved by LC-MS/MS and LC-HR-MS

Hypoglycin A (HGA) and methylenecyclpropylglycine (MCPrG) are formed by some maple trees (Acer species) and have been associated with incidences of atypical myopathy among horses in pastures. In this work, a simple and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method without derivatization was developed for the quantification of HGA and MCPrG in maple samples and validated according to EU guidelines. The LOQ presented here for HGA (16.4 µg/kg) is considerably lower than the lowest published LOQ (500 µg/kg). This method confirms that sycamore and box elder maple contain considerable amounts of HGA and MCPrG. In addition, the presence of the dipeptides hypoglycin B and γ-glutamyl-MCPrG in these two maple species is shown using high-resolution MS. This is the first report on the presence of these dipeptides in maple since 1973. The presence of HGB and γ-glutamyl-MCPrG could change the way we understand animal intoxication following the ingestion of maple.

Acer pseudoplatanus: A Potential Risk of Poisoning for Several Herbivore Species

Acer pseudoplatanus is a worldwide-distributed tree which contains toxins, among them hypoglycin A (HGA). This toxin is known to be responsible for poisoning in various species, including humans, equids, Père David's deer and two-humped camels. We hypothesized that any herbivore pasturing with A. pseudoplatanus in their vicinity may be at risk for HGA poisoning. To test this hypothesis, we surveyed the HGA exposure from A. pseudoplatanus in species not yet described as being at risk. Animals in zoological parks were the major focus, as they are at high probability to be exposed to A. pseudoplatanus in enclosures. We also searched for a toxic metabolite of HGA (i.e., methylenecyclopropylacetyl-carnitine; MCPA-carnitine) in blood and an alteration of the acylcarnitines profile in HGA-positive animals to document the potential risk of declaring clinical signs. We describe for the first instance cases of HGA poisoning in Bovidae. Two gnus (Connochaetes taurinus taurinus) exposed to A. pseudoplatanus in their enclosure presented severe clinical signs, serum HGA and MCPA-carnitine and a marked modification of the acylcarnitines profile. In this study, even though all herbivores were exposed to A. pseudoplatanus, proximal fermenters species seemed less susceptible to HGA poisoning. Therefore, a ruminal transformation of HGA is hypothesized. Additionally, we suggest a gradual alteration of the fatty acid metabolism in case of HGA poisoning and thus the existence of subclinical cases.

In Vitro Assays for the Assessment of Impaired Mitochondrial Bioenergetics in Equine Atypical Myopathy

Equine atypical myopathy is a seasonal intoxication of grazing equids. In Europe, this poisoning is associated with the ingestion of toxins contained in the seeds and seedlings of the sycamore maple (Acer pseudoplatanus). The toxins involved in atypical myopathy are known to inhibit ß-oxidation of fatty acids and induce a general decrease in mitochondrial respiration, as determined by high-resolution respirometry applied to muscle samples taken from cases of atypical myopathy. The severe impairment of mitochondrial bioenergetics induced by the toxins may explain the high rate of mortality observed: about 74% of horses with atypical myopathy die, most within the first two days of signs of poisoning. The mechanism of toxicity is not completely elucidated yet. To improve our understanding of the pathological process and to assess therapeutic candidates, we designed in vitro assays using equine skeletal myoblasts cultured from muscle biopsies and subjected to toxins involved in atypical myopathy. We established that equine primary myoblasts do respond to one of the toxins incriminated in the disease.

Atypical myopathy in 2 Bactrian camels

Atypical myopathy (AM) is an acute seasonal rhabdomyolysis seen primarily in equids, caused by the ingestion of sycamore maple samaras containing hypoglycin A (HGA) and methylenecyclopropyl-glycine (MCPG). Toxic metabolites inhibit acyl-CoA dehydrogenases and enoyl-CoA hydratases, causing selective hyaline degeneration of type I muscle fibers. Two zoo-kept Bactrian camels (Camelus bactrianus) with a fatal course of AM had sudden onset of muscle pain and weakness, recumbency, and dysphagia, accompanied by increased serum creatine kinase activity and detection in serum of HGA, MCPG, and metabolites. Medical treatment was ineffective. At postmortem examination, sycamore maple tree material was found within the first gastric compartment of the 2-y-old gelding. Although musculature was macroscopically normal, histologically, monophasic hyaline degeneration was marked within type I fibers of intercostal and hypoglossal muscles of the gelding, and in neck, tongue, and masticatory muscles of the cow. The ingestion of sycamore maple material can cause AM in Bactrian camels, and trees of the Sapindaceae family should be avoided in enclosures.

Hypoglycin A absorption in sheep without concurrent clinical or biochemical evidence of disease

BACKGROUND

Hypoglycin A (HGA) intoxication after ingestion of Acer spp. tree material has never been confirmed in domesticated ruminants despite their similar grazing habitats.

OBJECTIVES

To investigate whether sheep have low HGA bioavailability caused by rumen HGA breakdown.

ANIMALS

Stomach and rumen fluid samples from 5 adult horses and 5 adult sheep respectively. Residual serum samples from 30 ewes and lambs.

METHODS

Experimental and retrospective cohort study. Hypoglycin A concentration was quantified in horse gastric and sheep ruminal samples after in vitro incubation with Acer pseudoplatanus seeds. Serum samples from grazing sheep (n = 20) and nursing lambs (n = 10) obtained before and after their release onto pastures with and without Sycamore seedlings were analyzed for HGA and methylenecyclopropyl-acetic acid carnitine, and serum biochemistry.

RESULTS

Neither ovine rumen nor equine gastric fluid affected HGA content in samples incubated for up to 2 hours. Despite HGA's detection in serum from sheep (n = 13/15; median, 23.71 ng/mL; range, 5.62-126.4 ng/mL) grazing contaminated pastures and in their nursing lambs (n = 2/5; median, 12.5 ng/mL; range, 8.82-15.67 ng/mL), there was no apparent clinical or subclinical disease.

CONCLUSIONS AND CLINICAL IMPORTANCE

Any reduced sensitivity to HGA intoxication in sheep seems unrelated to ruminal degradation. Serum HGA concentrations in sheep were similar to those of subclinically affected atypical myopathy horses. Any reduced sensitivity of sheep to HGA might be related to greater metabolic resistance rather than selective grazing habits or lower bioavailability. Hypoglycin A was found in nursing lambs, suggesting that HGA is excreted in milk.

Detection of maple toxins in mare's milk

Background

Plants from the Sapindaceae family that are consumed by horses (maple) and humans (ackee and litchi) are known to contain the toxins hypoglycin A and methylenecyclopropylglycine which cause seasonally occurring myopathy in horses and entero‐encephalopathic sickness in humans. Vertical transmission of these toxins from a mare to her foal has been described once. However the mare's milk was not available for analysis in this case. We investigated mare's milk in a similar case.

Objective

We hypothesized that hypoglycin A and methylenecyclopropylglycine, like other amino acids' are secreted into the milk.

Animals

Mare with atypical myopathy.

Methods

A sample of the mare's milk and 6 commercial horse milk samples were extracted with a methanolic standard solution and analyzed for hypoglycin A, methylenecyclopropylglycine, and metabolites using tandem mass spectrometry after column chromatographic separation.

Results

There were hypoglycin A (0.4 μg/L) and the associated metabolites methylenecyclopropylacetyl glycine and carnitine (18.5 and 24.6 μg/L) plus increased concentrations of several acylcarnitines in the milk. The milk also contained methylenecyclopropylformyl glycine and carnitine (0.8 and 60 μg/L). The latter substances were also detected in 1 of 6 commercial horse milk samples.

Conclusions and Clinical Importance

Transmission of the maple toxins can occur through mare's milk. Vertical transmission of Sapindacea toxins might also have importance for human medicine, for example, after consumption of ackee or litchi.

Detection of hypoglycin A and MCPA-carnitine in equine serum and muscle tissue: Optimisation and validation of a LC-MS-based method without derivatisation

BACKGROUND

Measurement of hypoglycin A (HGA) and its toxic metabolite, methylenecyclopropylacetic acid (MCPA), in equine serum confirms a diagnosis of atypical myopathy (AM), a pasture-associated toxic rhabdomyolysis with high mortality linked to the ingestion of Acer trees plant material. Supportive diagnostic tests include plasma acyl-carnitine profiling and urine organic acid testing, but these are not specific for AM. Previously reported HGA and MCPA analytical techniques used liquid chromatography-mass spectrometry (LC-MS) with a derivatising step, but the latter prolongs testing and increases costs.

OBJECTIVES

To develop a rapid LCMS method for detection of serum and tissue HGA and MCPA that enables expedited diagnosis for horses with AM.

STUDY DESIGN

Analytical test validation.

METHODS

Validation parameters to industry standards using as criteria precision, accuracy, linearity, reproducibility and stability in analyte-spiked samples were calculated on 9-calibration points and 3 different validation concentrations in both serum and muscle tissue.

RESULTS

The test was successfully validated for the detection of HGA and MCPA-carnitine in equine serum and muscle. Test linearity was excellent (r²  = .999), accuracy was very good for both analytes (93%-108%), precision did not exceed 10% coefficient of variation and reproducibility met the requirements of the Horwitz equation. Stability was unaffected by storage at a range of temperatures.

MAIN LIMITATIONS

The spectrum of the tested analytes was limited to only two relevant analytes in favour of a quick and easy analysis. Linearity of the muscle method was not evaluated as calibration curves were not produced in this matrix.

CONCLUSION

We report an optimised, simplified and validated method for detection of HGA and MCPA-carnitine in equine serum and muscle suitable for rapid diagnosis of suspected AM cases. The serum-based test should also enable risk assessment of toxin exposure in cograzing horses and assessment of horses with undiagnosed myopathies, while the tissue detection test should help to confirm cases post-mortem and to determine toxin distribution, metabolism and clearance across different tissues.

Optimised method for determination hypoglycine A in maple plant material by multidimensional gas chromatography/mass spectrometry

In 2018, more than 50 cases of horse death by equine atypical myopathy (AM) were reported in the Czech Republic. This disease is often associated with the toxin hypoglycine A (HGA), which is found in several maple plant materials. To monitor this toxin in products of these trees that grow in or around horse pastures, a rapid and inexpensive analytical method that can provide the required accuracy is needed. Until now, maple samples have been prepared for gas chromatography using time-consuming methods, with preparation processes taking longer than 1 h. In this work, a shorter method (25 min) with an accuracy of 90-94 %, reproducibility of 2-5%, precision of 3-9%, and linearity, with an R² of 0.999, is presented. This sample preparation consists of a procedure without an SPE extraction step and consumes a lower volume of solvent during the extraction. The limit of quantitation for HGA in plant material was improved from 0.5 μg/g of plant material in previous studies to 0.2 μg/g. The method was validated according to the guideline CD 2002/657/EC and ISO 17025, and was found to have good performance characteristics. This simple and rapid method was tested for the monitoring of hypoglycine A level in maple sycamore plant material (seeds, seedlings, and leaves) during the entire growth of the trees.

Answers to the Frequently Asked Questions Regarding Horse Feeding and Management Practices to Reduce the Risk of Atypical Myopathy

Simple Summary

Equine atypical myopathy is a severe intoxication of grazing equids resulting from the ingestion of samaras or seedlings of trees from the Acer species. The sycamore maple (Acer pseudoplatanus) is involved in European cases whereas the box elder (Acer negundo) is recognized as the cause of this seasonal pasture myopathy in the Unites States of America. In Europe, young and inactive animals with a thin to normal body condition and no feed supplementation, except for hay in autumn, are at higher risk. The risk is also associated with full time pasturing in a humid environment. Indeed, dead leaves piling up in autumn as well as, the presence of trees and/or woods presumably exposes the horses to the sycamore maple. This manuscript answers the most frequently asked questions arising from the equine field about feeding and management of equines to reduce the risk of atypical myopathy. All answers are based on data collected from 2006 to 2019 by the “Atypical Myopathy Alert Group” (AMAG, Belgium) and the “Réseau d’épidémiosurveillance en Pathologie équine” (RESPE, France) as well as on a review of the most recent literature.

Abstract

In 2014, atypical myopathy (AM) was linked to Acer pseudoplatanus (sycamore maple) in Europe. The emergence of this seasonal intoxication caused by a native tree has raised many questions. This manuscript aims at answering the five most frequently asked questions (FAQs) regarding (1) identification of toxic trees; reduction of risk at the level of (2) pastures and (3) equids; (4) the risk associated with pastures with sycamores that have always been used without horses being poisoned and (5) the length of the risk periods. Answers were found in a literature review and data gathered by AM surveillance networks. A guide is offered to differentiate common maple trees (FAQ1). In order to reduce the risk of AM at pasture level: Avoid humid pastures; permanent pasturing; spreading of manure for pasture with sycamores in the vicinity and avoid sycamore maple trees around pasture (FAQ2). To reduce the risk of AM at horse level: Reduce pasturing time according to weather conditions and to less than six hours a day during risk periods for horses on risk pasture; provide supplementary feeds including toxin-free forage; water from the distribution network; vitamins and a salt block (FAQ3). All pastures with a sycamore tree in the vicinity are at risk (FAQ4). Ninety-four percent of cases occur over two 3-month periods, starting in October and in March, for cases resulting from seeds and seedlings ingestion, respectively (FAQ5).

Potential new sources of hypoglycin A poisoning for equids kept at pasture in spring: a field pilot study

Equine atypical myopathy in Europe results from hypoglycin A (HGA) exposure through the ingestion of samaras or seedlings of the sycamore maple tree. This pilot study aimed at better defining sources of HGA intoxication in spring. Samaras fallen on the ground and then seedlings were collected at two-week intervals from sycamore, Norway, and field maple trees over the spring 2016. In early April, rainwater from wet seedlings collected after a rainy night was harvested to be analysed. Mid-May, samaras of the box elder, common ash, and inflorescences of sycamore maples were collected on the tree. Quantification of HGA in samples was performed using high performance thin layer chromatography. Hypoglycin A was detected in all samples from sycamore including rainwater but tested negative for Norway, field maples. The samaras of the box elder found in the present study area did not contain a seed within their husk and thus tested negative. From the maximum HGA concentrations found, it may be extrapolated that at some periods and locations, about 20 g of samaras, 50 seedlings, 150 g of inforescences or 2 liters of water that has been in contact with seedlings would contain the maximum tolerated dose per day for a horse.

Atypical myopathy-associated hypoglycin A toxin remains in sycamore seedlings despite mowing, herbicidal spraying or storage in hay and silage

BACKGROUND

Several pasture management strategies have been proposed to avoid hypoglycin A (HGA) intoxication in horses, but their efficacy has never been investigated.

OBJECTIVES

To evaluate the effect of mowing and herbicidal spraying on HGA content of sycamore seedlings and the presence of HGA in seeds and seedlings processed within haylage and silage.

STUDY DESIGN

Experimental study.

METHODS

Groups of seedlings were mowed (n = 6), sprayed with a dimethylamine-based (n = 2) or a picolinic acid-based herbicide (n = 1). Seedlings were collected before intervention, and at 48 h, 1 and 2 weeks after. Cut grass in the vicinity of mowed seedlings was collected pre-cutting and after 1 week. Seeds and seedling (n = 6) samples processed within haylage and silage were collected. HGA concentration in samples was measured using a validated LC-MS-based method.

RESULTS

There was no significant decline in HGA content in either mowed or sprayed seedlings; indeed, mowing induced a temporary significant rise in HGA content of seedlings. HGA concentration increased significantly (albeit to low levels) in grass cut with the seedlings by 1 week. HGA was still present in sycamore material after 6-8 months storage within either hay or silage.

MAIN LIMITATIONS

Restricted number of herbicide compounds tested.

CONCLUSIONS

Neither mowing nor herbicidal spraying reduces HGA concentration in sycamore seedlings up to 2 weeks after intervention. Cross contamination is possible between grass and sycamore seedlings when mowed together. Mowing followed by collection of sycamore seedlings seems the current best option to avoid HGA toxicity in horses grazing contaminated pasture. Pastures contaminated with sycamore material should not be used to produce processed hay or silage as both seedlings and seeds present in the bales still pose a risk of intoxication.

Newborn foal with atypical myopathy

The case of atypical myopathy (AM) in newborn Haflinger foal with clinical signs of depression and weakness appearing 6 hours after birth resulting in recumbency 12 hours after birth is described. The foal's dam was diagnosed with AM in the 6th month of gestation based on clinical signs of a myopathy, elevated serum activity of creatine kinase, metabolomic analysis and the presence of methylenecyclopropyl acetyl carnitine (MCPA‐carnitine) in the blood. At the time of delivery, the mare was grazing on a pasture near sycamore trees but was free of clinical signs of AM. Metabolomic analysis of the foal's blood revealed increased concentrations of acylcarnitines and MCPA‐carnitine consistent with metabolic profiles of blood from AM affected horses. Two theories could explain this observation (a) hypoglycin A or its metabolites accumulated in the mare's placenta with consequent transfer to fetus or (b) these compounds were secreted into mare's milk.

Free Radical Scavenging Capacity, Carotenoid Content, and NMR Characterization of Blighia sapida Aril Oil

Blighia sapida aril oil is rich in monounsaturated fatty acids but is however currently not utilized industrially. The oil was characterized utilizing nuclear magnetic resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). A spectrophotometric assay was conducted to determine the free radical scavenging properties and carotenoid content of the oil. Chemical shifts resonating between δ 5.30 and 5.32 in the ¹H NMR are indicative of olefinic protons present in ackee aril oil which are due to the presence of oleic acid. A peak at 3006 cm⁻¹ in the FTIR spectra confirms the high levels of monounsaturation. The oil has a free radical scavenging activity of 48%  ± 2.8% and carotenoid content of 21 ± 0.2 ppm.

Detection of equine atypical myopathy-associated hypoglycin A in plant material: Optimisation and validation of a novel LC-MS based method without derivatisation

Hypoglycin A (HGA) toxicity, following ingestion of material from certain plants, is linked to an acquired multiple acyl-CoA dehydrogenase deficiency known as atypical myopathy, a commonly fatal form of equine rhabdomyolysis seen worldwide. Whilst some plants are known to contain this toxin, little is known about its function or the mechanisms that lead to varied HGA concentrations between plants. Consequently, reliable tools to detect this amino acid in plant samples are needed. Analytical methods for HGA detection have previously been validated for the food industry, however, these techniques rely on chemical derivatisation to obtain accurate results at low HGA concentrations. In this work, we describe and validate a novel method, without need for chemical derivatisation (accuracy = 84-94%; precision = 3-16%; reproducibility = 3-6%; mean linear range R2 = 0.999). The current limit of quantitation for HGA in plant material was halved (from 1μg/g in previous studies) to 0.5μg/g. The method was tested in Acer pseudoplatanus material and other tree and plant species. We confirm that A. pseudoplatanus is most likely the only source of HGA in trees found within European pastures.

Identification of hypoglycin A binding adsorbents as potential preventive measures in co-grazers of atypical myopathy affected horses

BACKGROUND

Intestinal absorption of hypoglycin A (HGA) and its metabolism are considered major prerequisites for atypical myopathy (AM). The increasing incidence and the high mortality rate of AM urgently necessitate new therapeutic and/or preventative approaches.

OBJECTIVES

To identify a substance for oral administration capable of binding HGA in the intestinal lumen and effectively reducing the intestinal absorption of the toxin.

STUDY DESIGN

Experimental in vitro study.

METHODS

Substances commonly used in equine practice (activated charcoal composition, di-tri-octahedral smectite, mineral oil and activated charcoal) were tested for their binding capacity for HGA using an in vitro incubation method. The substance most effective in binding HGA was subsequently tested for its potential to reduce intestinal HGA absorption. Jejunal tissues of 6 horses were incubated in Ussing chambers to determine mucosal uptake, tissue accumulation, and serosal release of HGA in the presence and absence of the target substance. Potential intestinal metabolism in methylenecyclopropyl acetic acid (MCPA)-conjugates was investigated by analysing their concentrations in samples from the Ussing chambers.

RESULTS

Activated charcoal composition and activated charcoal were identified as potent HGA binding substances with dose and pH dependent binding capacity. There was no evidence of intestinal HGA metabolism.

MAIN LIMITATIONS

Binding capacity of adsorbents was tested in vitro using aqueous solutions, and in vivo factors such as transit time and composition of intestinal content, may affect adsorption capacity after oral administration.

CONCLUSIONS

For the first time, this study identifies substances capable of reducing HGA intestinal absorption. This might have major implications as a preventive measure in cograzers of AM affected horses but also in horses at an early stage of intoxication.

Acylcarnitines profile best predicts survival in horses with atypical myopathy

Equine atypical myopathy (AM) is caused by hypoglycin A intoxication and is characterized by a high fatality rate. Predictive estimation of survival in AM horses is necessary to prevent unnecessary suffering of animals that are unlikely to survive and to focus supportive therapy on horses with a possible favourable prognosis of survival. We hypothesized that outcome may be predicted early in the course of disease based on the assumption that the acylcarnitine profile reflects the derangement of muscle energetics. We developed a statistical model to prognosticate the risk of death of diseased animals and found that estimation of outcome may be drawn from three acylcarnitines (C2, C10:2 and C18 -carnitines) with a high sensitivity and specificity. The calculation of the prognosis of survival makes it possible to distinguish the horses that will survive from those that will die despite severe signs of acute rhabdomyolysis in both groups.

Equine atypical myopathy in the UK: Epidemiological characteristics of cases reported from 2011 to 2015 and factors associated with survival

BACKGROUND

Equine atypical myopathy (AM) is a toxic rhabdomyolysis associated with ingestion of hypoglycin A, derived typically in Europe, from Acer pseudoplatanus tree. Despite the wide distribution of this tree species in the UK, the number of cases reported annually varies, and there has been an apparent increase in prevalence in recent years. Although AM was first recognised in the UK, epidemiological studies have never been conducted focused solely on this country.

OBJECTIVES

To describe the spatiotemporal distribution, presentation, treatment and outcome of AM cases reported in the UK.

STUDY DESIGN

Retrospective case series.

METHODS

British AM cases reported to the atypical myopathy alert website, between 2011 and 2015 were included (n = 224). Data were obtained via standardised epidemiological questionnaires from owners and veterinarians. Factors associated with survival were assessed using logistic regression.

RESULTS

Most cases reported were from England (87.9%). Survival was 38.6% (n = 73/189). Clinical factors associated with reduced odds of survival included, hypothermia (odds ratio [OR] 0.18; 95% confidence interval [CI] 0.06-0.57; P = 0.01), bladder distension (OR 0.11; CI 0.02-0.59; P = 0.01), tachycardia (OR 0.97; CI 0.94-0.99; P = 0.04) and serum creatine kinase activity >100,000 IU/L (OR 0.17; CI 0.04-0.68; P = 0.01) in the univariable analysis as well as recumbency. The latter was the only sign retained in multivariable analysis (OR = 0.19; CI 0.06-0.62; P = 0.006). Administration of vitamins during the disease was associated with survival (OR 3.75; CI 1.21-11.57; P = 0.02).

MAIN LIMITATIONS

Reporting cases to the Atypical Myopathy Alert Group is voluntary; therefore, under-reporting will result in underestimation of AM cases; furthermore, direct owner-reporting could have introduced misdiagnosis bias.

CONCLUSION

Some areas of the UK reported AM cases more commonly. Clinical signs such as recumbency, rectal temperature, distended bladder and serum creatine kinase activity might be useful prognostic indicators though should be considered in the context of the clinical picture. Treatment with vitamins increases odds of survival.

Mitochondrial function is altered in horse atypical myopathy

Equine atypical myopathy in Europe is a fatal rhabdomyolysis syndrome that results from the ingestion of hypoglycin A contained in seeds and seedlings of Acer pseudoplatanus (sycamore maple). Acylcarnitine concentrations in serum and muscle OXPHOS capacity were determined in 15 atypical myopathy cases. All but one acylcarnitine were out of reference range and mitochondrial respiratory capacity was severely decreased up to 49% as compared to 10 healthy controls. The hallmark of atypical myopathy thus consists of a severe alteration in the energy metabolism including a severe impairment in muscle mitochondrial respiration that could contribute to its high death rate.