Maria J. Groot

Metabolomics Approach to Anabolic Steroid Urine Profiling of Bovines Treated with Prohormones

In livestock production, illegal use of natural steroids is hard to prove because metabolites are either unknown or not significantly above highly fluctuating endogenous levels. In this work we outlined for the first time a metabolomics based strategy for anabolic steroid urine profiling. Urine profiles of controls and bovines treated with the prohormones dehydroepiandrosterone (DHEA) and pregnenolone were analyzed with ultraperformance liquid chromatography in combination with time-of-flight accurate mass spectrometry (UPLC-TOFMS). The obtained full scan urinary profiles were compared using sophisticated preprocessing and alignment software (MetAlign) and multivariate statistics, revealing hundreds of mass signals which were differential between untreated control and prohormone-treated animals. Moreover, statistical testing of the individual accurate mass signals showed that several mass peak loadings could be used as biomarkers for DHEA and pregnenolone abuse. In addition, accurate mass derived elemental composition analysis and verification by standards or Orbitrap mass spectrometry demonstrated that the observed differential masses are most likely steroid phase I and glucuronide metabolites excreted as a direct result from the DHEA and pregnenolone administration, thus underlining the relevance of the findings from this untargeted metabolomics approach. It is envisaged that this approach can be used as a holistic screening tool for anabolic steroid abuse in bovines and possibly in sports doping as well.

Evidence of the indirect hormonal activity of prohormones using liver S9 metabolic bioactivation and an androgen bioassay.

Prohormones such as dehydroepiandrosterone (DHEA) are steroid precursors that do not show hormonal activity by themselves. Abuse of these prohormones in cattle fattening is hard to prove because of strong in vivo metabolism and the difficulty to detect metabolites which are not significantly above endogenous levels. The aim of the present work was to develop an in vitro assay capable of detecting the indirect hormonal activity of prohormones that might be present in feed supplements and injection preparations. Sample extracts were incubated with a bovine liver S9 fraction in order to mimic the in vivo metabolic activation. Subsequently incubated extracts were exposed to a highly androgen-specific yeast bioassay to detect hormonal activity. Metabolic activation of DHEA, 4-androstene-3,17-dione (4-adione) and 5-androstene-3,17-diol (5-adiol) resulted in an increased androgenic activity caused by the formation of the active androgen 17β-testosterone (17β-T), as shown by ultra-performance liquid chromatography and time-of-flight mass spectrometry with accurate mass measurement. The developed in vitro system successfully mimics the hydroxysteroid dehydrogenase (HSD)- and cytochrome P450-mediated in vivo metabolic transitions, thus allowing assessment of both bioactivity and chemical identification without the use of animal experiments. Screening of unknown supplement samples claimed to contain DHEA resulted in successful bioactivation and positive screening results according to the androgen yeast biosensor.

Bovine liver slices: A multifunctional in vitro model to study the prohormone dehydroepiandrosterone (DHEA).

Biotransformation of inactive prohormones like dehydroepiandrosterone (DHEA) can lead to the formation of potent androgens and subsequent androgenic responses in target tissues. In the present study, precision-cut bovine liver slices were used to study the effects of DHEA on the metabolite, transcript and androgenic activity level. Bovine liver slices were exposed for 6h to various concentrations of DHEA. Changes in androgenic activity of the DHEA containing cell culture media were measured using a yeast androgen bioassay and metabolites were identified using ultra performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS), while gene expression in the DHEA-treated liver slices was examined using bovine microarrays and compared with the profile as obtained with 17ß-testosterone (17ß-T). An increase in androgenic activity was observed in the bioassay upon testing of samples from incubations of DHEA with liver slices and the formation of 4-androstenedione (4-AD), 5-androstene-3ß,17ß-diol, 17ß-T, 7α-hydroxy-DHEA, 7-keto-DHEA and 17α-T could be confirmed by UPLC-TOFMS analysis. Exposure of liver slices to DHEA and the strong androgen 17ß-T resulted in the identification of significantly up- and down-regulated genes and revealed similar gene expression profiles for both compounds. The results indicate that DHEA itself is biologically not very active, but is rapidly converted by the liver slices into the more androgen active compounds 4-AD and 17ß-T. Moreover, the present data highlight the multi-functionality of bovine liver slices as an in vitro bioactivation model, allowing the assessment of androgen activity or gene expression as effect-based endpoints for prohormone exposure.

Screening for estrogen residues in calf urine: Comparison of a validated yeast estrogen bioassay and gas chromatography-tandem mass spectrometry

Within the European Union, the control for residues of illegal hormones in food-producing animals is based on urine analysis for a few target analytes using gas chromatography/mass spectrometry and/or liquid chromatography–tandem mass spectrometry. Recently, we developed a robust yeast bioassay screening tool for estrogens, which was validated as a qualitative screening method in accordance with EC decision 2002/657/EC. In this study, we present long-term performance data and a comparison of urine data obtained with this bioassay, and data from an established gas chromatography–tandem mass spectrometry (GC/MS/MS) confirmatory analysis method. More than 120 calf urine samples from a controlled reference experiment were analysed using both protocols. According to the GC/MS/MS method, only the natural estrogens 17α-estradiol and estrone were present in the non-compliant samples. The bioassay was less sensitive than GC/MS/MS for the relatively weak estrogenic compound 17α-estradiol, in accordance with expectations. Assuming that application of the mass spectrometric method is considered beyond reasonable doubt, the bioassay performed very well: only 5.6% of the calf urine samples found compliant in GC/MS/MS were screened false suspect in the bioassay screening method. The bioassay results of non-compliant urine samples under routine conditions were as predicted, taking into account the relative estrogenicity of the natural estrogens 17α-estradiol and estrone vs. 17β-estradiol. Only one sample was screened false negative for 17α-estradiol and estrone. Application of this fast and simple estrogen bioassay in routine surveillance and control can significantly reduce GC/MS/MS sample workload and allow higher percentages of animals to be screened for potential hormone abuse.

Bioassay based screening of steroid derivatives in animal feed and supplements

Receptor binding transcription activation bioassays are valuable tools for the screening of steroid hormones in animal feed and supplements. However, steroid derivatives often lack affinity for their cognate receptor and do not show any direct hormonal activity by themselves. These compounds are thus not detected by these kinds of bioassays and need a bioactivation step in order to become active, both in vivo and in vitro. In this study a comparison was made between different in vitro activation methods for hormone esters and hormone glycosides. Testosterone acetate and testosterone decanoate were chosen as model compounds for the hormone esters, representing the broad range of steroid esters of varying polarities, while genistin was used as a substitute model for the steroid-glycosides. Concerning bioactivation of the steroids esters, the efficiency for alkaline hydrolysis was 90-100% and much better as compared to enzymatic deconjugation by esterase. As a result 1 μg testosterone ester per gram of animal feed could easily be detected by a yeast androgen bioassay. When comparing different enzyme fractions for deglycosilation, genistin was shown to be deconjugated most efficiently by β-glucuronidase/aryl sulfatase from Helix pomatia, resulting in a significant increase of estrogenic activity as determined by a yeast estrogen bioassay. In conclusion, chemical and enzymatic deconjugation procedures for ester and glycoside conjugates respectively, resulted in a significant increase in hormonal activity as shown by the bioassay readouts and allowed effective screening of these derivatives in animal feed and feed supplements.

Possible contamination with clenbuterol from treated veal calves to untreated pen mates.

To investigate whether clenbuterol-treated calves could contaminate untreated pen mates, three animal experiments were performed. (1) One calf of a pen of five was treated with clenbuterol by injection (Ventipulmin injection, REG NL 2532, 2.5 mL/100 kg) twice a day for 10 days. (2) In two pens, one animal was treated with clenbuterol via oral administration (Ventipulmin syrup, REG NL 2532, 4 mL/125 kg) for 4 weeks. (3) In two pens, one animal was treated with clenbuterol via the milk (Ventipulmin, REG NL 2532, 2.5 mL/100 kg body weight) twice a day for 10 days. Here, the animal was set apart during treatment, cleaned and put back into the group. Levels of clenbuterol were analysed in hair and urine with LC-MS/MS. Clenbuterol administered by injection could not be transferred from treated to untreated calves. In the second experiment, all pen mates were found positive for clenbuterol in the hair. This contamination was probably due to licking the mouth of the treated animal or saliva from the treated animal spoiling the floor. In the third experiment, no pen mates were found positive for clenbuterol in the hair. Clenbuterol was found in the urine and hair of only treated animals.

Illegal treatment of barrows with nandrolone ester: effect on growth, histology and residue levels in urine and hair

The effect of 17β-19-nortestosterone (17βNT) treatment of barrows on residue levels and growth was evaluated. Five barrows were treated three times during the fattening period with 17βNT phenylpropionate (Nandrosol, nandrolone phenylpropionate 50 mg/ml,1 mg/kg body weight). Another five barrows were untreated and five boars (untreated) were kept as positive control. Boars and treated barrows showed a 13 and 9% improvement in growth compared to untreated barrows, with mean final body weights of 121.6, 117.8 and 109.0 kg, respectively. The bulbourethral glands of the treated barrows were three times heavier than untreated barrows. The histology of the prostate and bulbourethral gland of the treated barrows was comparable to the boars, whereas the control barrows showed atrophic glands. Levels of 17βNT ester in hair from treated barrows were high, whereas boars and untreated barrows did not show levels above LLQ. It is concluded that analysis of hair can detect illegal treatment with 17βNT ester in barrows. The size of the bulbourethral gland can also be used for screening in the slaughterhouse.

Transfer of pyrrolizidine alkaloids from various herbs to eggs and meat in laying hens

ABSTRACT To investigate the potential transfer of pyrrolizidine alkaloids (PAs), laying hens were fed for 14 days with diets containing 0.5% of dried common ragwort, common groundsel, narrow-leaved ragwort or viper’s bugloss, or 0.1% of common heliotrope. This resulted in total PA levels in feed of respectively 5.5, 11.1, 53.1, 5.9 and 21.7 mg kg–1, with varying composition. PAs were transferred to eggs, in particular yolk, with steady-state levels of respectively 12, 21, 216, 2 and 36 µg kg–1. Overall transfer rates for the sum of PAs were estimated between 0.02% and 0.23%, depending on the type of PAs in the feed. In animals slaughtered shortly after the last exposure, levels in meat were slightly lower than those in eggs, levels in livers somewhat higher. When switched to clean feed, levels in eggs gradually decreased, but after 14 days were still above detection limits in the hens exposed to higher PA levels. Similar was the case for meat and especially kidneys and livers. It is concluded that the intake of PA containing herbs by laying hens may result in levels in eggs and meat that could be of concern for consumers, and as such should be avoided.

Effect of oxygen concentration and selected protocol factors on viability and gene expression of mouse liver slices

Precision cut liver slices (PCLSs) are widely used as a model to study hepatotoxicity. For culturing of PCLS diverse protocols are used which could affect slices viability and results. We aimed to identify the most optimal culture protocol for mouse PCLS. Slices were cultured for 24h under different concentrations of serum, glucose, insulin, and oxygen. Thereafter, slices viability was assessed by biochemical methods. Transcriptome analysis was performed to identify changes introduced by culture at different oxygen concentrations (20%, 40%, 60%, and 80% of oxygen). Medium composition did not affect the slices viability. Although metabolic competence was unaffected by oxygen concentrations, culturing at 80% of oxygen yielded slices with the best biochemical characteristics. The comparison of uncultured vs. cultured slices revealed 2524 genes to be differentially expressed. Genes involved in drug metabolism, peroxisomal and mitochondrial functions were down-regulated while several adaptive/stress response processes were up-regulated. Moreover, 80% of oxygen was the most favorable condition with respect to maintenance of expression of genes involved in drug and energy metabolism. The outcome of this study indicates that mouse PCLS are a valuable tool in research on hepatic functions and toxicity, particularly if they are cultured under a controlled oxygen concentration of 80%.

Veterinary treatment of cows with isoxsuprine for a caesarian section may temporarily lead to residues in hair of both cow and calf

Isoxsuprine is a beta-agonist that can be used for growth promotion in cattle, but it is also used as registered veterinary medicine. To investigate if veterinary treatment of cows could lead to residues of isoxsuprine in the hair of their newborn calves, an animal experiment was performed. Four cows, treated on veterinary indication with isoxsuprine lactate (Duphaspasmin) before a caesarian section, were included in the experiment. Hair samples from cows and from their calves were analyzed. The animals were shaved every week for 16 weeks and levels of isoxsuprine were measured in hair. In the cows, the levels of isoxsuprine were highest (>15 µg/kg) just after administration of the isoxsuprine lactate. After two weeks in two cows, a sort of plateau was reached and then the levels decreased. After approximately 10-15 weeks the levels were around the CCα level of the method used (0.5 µg/kg). In calves, for the first two weeks after birth, no isoxsuprine was found above CCα level in three of the four animals. At about 20-30 days old, a maximum concentration of 4 µg/kg was found. Then the levels dropped again under the CCα level, after 60 days no levels above CCα level were found. In one animal, the levels never reached CCα level. We conclude that veterinary treatment of cows with isoxsuprine may temporarily lead to low levels of isoxsuprine in the hair of their newborn calves which can be measured for a maximum of 60 days after birth.