Use of isotope ratio mass spectrometry to differentiate between endogenous steroids and synthetic homologues in cattle: a review

RNAseq Analysis of Livers from Pigs Treated with Testosterone and Nandrolone Esters: Selection and Field Validation of Transcriptional Biomarkers

The use of anabolic-androgenic steroids (AASs) as growth promoters in farm animals is banned in the European Union, representing both an illicit practice and a risk for consumer health. However, these compounds are still illegally administered, often in the form of synthetic esters. This work aimed to characterize significant coding RNA perturbations related to the illicit administration of testosterone and nandrolone esters in fattening pigs. A total of 27 clinically healthy 90-day-old pigs were randomly assigned to test and control groups. Nine animals were treated with testosterone esters (Sustanon®) and other nine with nandrolone esters (Myodine®). At the end of the trial, liver samples were collected and analyzed using RNAseq, allowing the identification of 491 differentially expressed genes (DEGs). The transcriptional signature was further characterized by a smaller sub-cluster of 143 DEGs, from which a selection of 16 genes was made. The qPCR analysis confirmed that the identified cluster could still give good discrimination between untreated gilt and barrows compared to the relative testosterone-treated counterparts. A conclusive field survey on 67 liver samples collected from pigs of different breeds and weight categories confirmed, in agreement with testosterone residue profiles, the specificity of selected transcriptional biomarkers, showing their potential applications for screening purposes when AAS treatment is suspected, allowing to focus further investigations of competent authorities and confirmatory analysis where needed.

Carbon isotope ratios of endogenous steroids in Belgian Blue and Holstein cattle: Method development, reference population studies and application to steroid misuse control

RATIONALE

The misuse of growth promoters in livestock and breeding animals is prohibited according to the laws of the European Union. Among these growth promoters, the detection of endogenous steroids like testosterone, estradiol or progesterone remains especially challenging as concentration-based urinary thresholds may not provide conclusive results due to large inter-individual variations. In addition to the detection of intact steroid esters in blood or hair, carbon isotope ratio (CIR) determination of urinary steroids has commonly been the method of choice.

METHODS

A comprehensive sample clean-up procedure was developed and validated, which enables for the first time simultaneous CIR measurements of testosterone metabolites (17α-hydroxyandrost-4-en-3-one, 3α-hydroxy-5β-androstan-17-one and 5α-androstane-3β,17α-diol), the estradiol metabolite 17α-estradiol (ESTR) and the progesterone metabolite 5β-pregnane-3α,20α-diol (PD) from a single urine specimen. As endogenous reference compounds 3β-hydroxyandrost-5-en-17-one and 5-androstene-3β,17α-diol (5EN) were chosen. The method was validated by means of linear mixing models and a reference population encompassing n = 53 Belgian Blue and Holstein cattle was investigated to enable the calculation of population-based Δ¹³ C thresholds.

RESULTS

The combined measurement uncertainty determined for the Δ¹³ C-values of all steroids under investigation was found to be <0.8 ‰. Within the reference population studies, 5EN was demonstrated to be the most promising endogenous reference compound resulting in comparably low Δ-values and accompanying thresholds. For PD, a surprisingly high number of samples (n = 9) yielded significantly ¹³ C-depleted values and ESTR was only detectable in n = 13 samples. Proof-of-concept was accomplished by investigating two post-administration samples.

CONCLUSIONS

This first comprehensive investigation on the CIRs of endogenous urinary steroids demonstrated once more the potential of isotope ratios in aiding discrimination between endogenously produced and exogenously administered steroids. By means of the reference population-derived CIRs, it is possible to apply cattle-specific thresholds to differentiate between treated and non-treated animals.

Applicability of an innovative steroid-profiling method to determine synthetic growth promoter abuse in cattle

A robust LC-MS/MS method was developed to quantify a large number of phase I and phase II steroids in urine. The decision limit is for most compounds lower than 1ngml^-1 with a measurement uncertainty smaller than 30%. The method is fully validated and was applied to assess the influence of administered synthetic steroids and beta-agonists on the steroidogenesis. From three animal experiments, clenbuterol, diethylstilbestrol and stanozolol, the steroid profiles in urine of bovine animals were compared before and after treatment. It was demonstrated that the steroid profiles were altered due to these treatments. A predictive multivariate model was built to identify deviations from normal population steroid profiles. The abuse of synthetic steroids can be detected in urine samples from bovine animals using this model. The samples from the animal experiments were randomly analysed using this method and predictive model. It was shown that these samples were predicted correctly in the exogenous steroids group.

Development of LC-MS/MS Confirmatory Method for the Determination of Testosterone in Bovine Serum

Introduction

In the European Union the use of steroid growth promoters is prohibited under Council Directive 96/22/EC. For effective control of illegal use of natural steroids, highly sensitive analytical methods are required, because sex hormones can be present in very low concentrations in biological samples. The aim of the study was to develop a confirmatory method for the detection of testosterone in bovine serum at ppt level.

Material and Methods

17β-testosterone and internal standards of 17%-testosterone-d2 were extracted from serum samples with a mixture of tert-butyl methyl ether/petroleum ether and were directly analysed by an LC/MS/MS on QTRAP 5500 instrument with a TurboIon-Spray source operating in a positive ionisation mode. Chromatographic separation was achieved on the analytical column Inertsil® ODS-3 with an isocratic elution using mobile phase consisting of acetonitrile, methanol, and water. Method validation has been carried out in accordance with the Commission Decision 2002/657/EC.

Results

The method was characterised by good recovery (82%) and precision (R.S.D 17 %). Decision limit (CCα) and detection capability (CCβ) was 0.05 μg L⁻¹ and 0.09 μg L⁻¹ respectively. The method met the criteria set out in Commission Decision 2002/657/EC for the purpose of confirmation in terms of retention time and ion ratio in the whole range of its application.

Conclusions

The developed method is specific and sensitive, suitable for measuring the natural level of testosterone in blood of cattle and for use in routine control programme for the detection of this hormone in bovine serum.

Abuse of anabolic agents in beef cattle: Could bile be a possible alternative matrix?

European Union prohibited the use of anabolic agents in food producing animals since 1988. An efficient control of abuses is guaranteed not only by highly performing analytical methods, but also by knowledge of metabolic pathways, kinetics of elimination and tissue distribution. To obtain data concerning metabolites production and accumulation in bile, two typical growth promoting treatments are carried out in cattle. In the first study, sixteen beef cattle were implanted with trenbolone acetate and estradiol. In the second one, three animals were implanted with zeranol and three were fed a diet containing zearalenone. Methods based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) were developed and validated to quantify the analytes of interest. The results evidenced that the biliary concentrations of the marker residues were always higher than those determined at the same time in urine and liver which are the matrices generally collected within the official monitoring programmes.

Levels of the natural hormones 17β-oestradiol and testosterone in serum of cattle: results from population studies in Poland

Introduction: The present study is a comprehensive overview of the natural occurrence of 17β-oestradiol and testosterone in serum of cattle in Poland. Material and Methods: The serum samples (n = 826) were collected from cattle within five years. The samples were examined for the presence of oestradiol and testosterone using ELISA or gas chromatography with mass spectrometry. Results: In 98 samples (24%) 17β-oestradiol was detected above decision limits of applied methods, including five samples over the recommended concentration of 0.1 μg L-1. Of the serum samples taken from cows (≤18 months of age), 95 and 99 percentiles of the animals had 17β-oestradiol concentration below 0.027 and 0.086 μg L-1 and of samples from cows over 18 months of age - below 0.059 and 0.125 μg L-1 respectively. Calculated values for bulls (≤18 months of age) were 0.025 and 0.034 μg L-1 and for the animals older than 18 months of age - 0.035 and 0.041 μg L-1. The natural presence of testosterone was detected in 201 serum samples (48.7%). According to the obtained data, 95% and 99% of cows (≤18 months of age) serum samples had testosterone concentration below 0.05 and 0.23 μg L-1 and the animals over 18 months of age - 0.30 and 0.49 μg L-1, respectively. For bulls these values did not depend on the age of the animals and were in the ranges of 5 - 6.3 μg L-1 (95%) and 11.4 - 12.1 μg L-1 (99%). Conclusion: Our study showed that the threshold values for these hormones in plasma of cattle designated years ago are correct, but they need to be supplemented for animals older than 18 months.

The use of gas chromatography-mass spectrometry/combustion/isotope ratio mass spectrometry to demonstrate progesterone treatment in bovines

Currently, no analytical method is available to demonstrate progesterone administration in biological samples collected in rearing animals, and therefore, tracking the abuse of this popular growth promoter is arduous. In this study, a method is presented to reveal progesterone (PG) treatment on the basis of carbon isotope measurement of 5β-pregnane-3α, 20α-diol (BAA-PD), a major PG metabolite excreted in bovine urine, by gas chromatography-mass spectrometry/combustion/isotope ratio mass spectrometry (GC-MS/C/IRMS). 5-Androstene-3β,17α-diol (AEdiol) is used as endogenous reference compound. Intermediate precisions (n=11) of 0.56‰ and 0.68‰ have been determined for AEdiol and BAA-PD, respectively. The analytical method was used for the very first time to successfully differentiate urine samples collected in treated and untreated animals.

Simultaneous Detection of Androgen and Estrogen Abuse in Breeding Animals by Gas Chromatography-Mass Spectrometry/Combustion/Isotope Ratio Mass Spectrometry (GC-MS/C/IRMS) Evaluated against Alternative Methods

The administration of synthetic homologues of naturally occurring steroids can be demonstrated by measuring (13)C/(12)C isotopic ratios of their urinary metabolites. Gas chromatography-mass spectrometry/combustion/isotope ratio mass spectrometry (GC-MS/C/IRMS) was used in this study to appraise in a global approach isotopic deviations of two 17β-testosterone metabolites (17α-testosterone and etiocholanolone) and one 17β-estradiol metabolite (17α-estradiol) together with those of 5-androstene-3β,17α-diol as endogenous reference compound (ERC). Intermediate precisions of 0.35‰, 1.05‰, 0.35‰, and 0.21‰, respectively, were observed (n = 8). To assess the performance of the analytical method, a bull and a heifer were treated with 17β-testosterone propionate and 17β-estradiol-3-benzoate. The sensitivity of the method permitted the demonstration of 17β-estradiol treatment up to 24 days. For 17β-testosterone treatment, the detection windows were 3 days and 24 days for the bull and the heifer, respectively. The capability of GC-MS/C/IRMS to demonstrate natural steroid abuse for urinary steroids was eventually compared to those of mass spectrometry (LC-MS/MS) when measuring intact steroid esters in blood and hair.

Evaluation of the discriminative potential of a novel biomarker for estradiol treatments in bovine animals

The endogenous occurrence of natural hormones obstructs the application of classical targeted methods as confirmatory options. In the case of estradiol, the ultimate confirmation of its exogenous administration relies on gas chromatography coupled to combustion/isotope ratio mass spectrometry (GC-C/IRMS). A serum dipeptide composed of pyroglutamic acid and phenylalanine was identified as a potential biomarker of estradiol treatments in adult cows. To evaluate its potential to pinpoint suspicious samples, samples from prepubertal females under different estrogenic treatments have been analyzed. The results confirmed the up-regulation of the dipeptide in adult bovines. The 2-week-old females exhibited short-lasting responses only in a few animals. The 6-month-old female showed a delayed but clear increase on the biomarker level. The composition of the anabolic preparations, the dose, and/or the administration route are possible additional reasons for the reduced response in young animals. A comparison to previous results reported by various researchers is included.

Application of gas chromatography-mass spectrometry/combustion/isotope ratio mass spectrometry (GC-MS/C/IRMS) to detect the abuse of 17β-estradiol in cattle

Although the ability to differentiate between endogenous steroids and synthetic homologues on the basis of their (13)C/(12)C isotopic ratio has been known for over a decade, this technique has been scarcely implemented for food safety purposes. In this study, a method was developed using gas chromatography-mass spectrometry/combustion/isotope ratio mass spectrometry (GC-MS/C/IRMS) to demonstrate the abuse of 17β-estradiol in cattle, by comparison of the (13)C/(12)C ratios of the main metabolite 17α-estradiol and an endogenous reference compound (ERC), 5-androstene-3β,17α-diol, in bovine urine. The intermediate precisions were determined as 0.46 and 0.26‰ for 5-androstene-3β,17α-diol and 17α-estradiol, respectively. This is, to the authors' knowledge, the first reported use of GC-MS/C/IRMS for the analysis of steroid compounds for food safety issues.