Application of stable carbon isotope analysis to the detection of 17β-estradiol administration to cattle

Anabolic steroids in livestock production: Background and implications for chemical food safety

The use of steroids in livestock animals is a source of concern for consumers because of the risks associated with the presence of their residues in foodstuffs of animal origin. Technological advances such as mass spectrometry have made it possible to play a fundamental role in controlling such practices, firstly for the discovery of marker metabolites but also for the monitoring of these compounds under the regulatory framework. Current control strategies rely on the monitoring of either the parent drug or its metabolites in various matrices of interest. As some of these steroids also have an endogenous status specific strategies have to be applied for control purposes. This review aims to provide a comprehensive and up-to-date knowledge of analytical strategies, whether targeted or non-targeted, and whether they focus on markers of exposure or effect in the specific context of chemical food safety regarding the use of anabolic steroids in livestock. The role of new approaches in data acquisition (e.g. ion mobility), processing and analysis, (e.g. molecular networking), is also discussed.

Hormones residues in bovine animals: Sampling, analysis and health risk assessment

The use of hormones for breeding animal livestock has been banned since 1981 under the Council Directive 81/602/EC. So far, each country should monitor the use of anabolic hormones in animal production to protect the consumer's health against these unwanted residues. This paper presents the research results on steroid and non-steroid hormones residues carried out in Lebanon from 2018 to 2020. Using a newly developed and validated LC-MS/MS method, the detection and the quantification of hormones in bovine matrices were done. The targeted matrices were muscle, liver, kidney, and bile. A total of two-hundred and forty-seven samples were collected from different slaughterhouses located in six different cities in Lebanon. Interestingly, only four hormones were found: testosterone, progesterone, epitestosterone, and 6 propyl 2thiouracil. Based on the obtained data, the estimated daily intake, hazard quotient, and hazard index were calculated to evaluate an exposure assessment.

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.

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.

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.

Discriminating the endogenous and exogenous urinary estrogens in human by isotopic ratio mass spectrometry and its potential clinical value

Estrogens were prohibited in the food producing animals by European Union (96/22/EC directive) and added to the Report on Carcinogens in United States since 2002. Due to very low concentration in serum or urine (~pg/mL), the method of control its abuse had not been fully developed. The endogenous estrogens were separated from urines of 18 adult men and women. The exogenous estrogens were chemical reference standards and over the counter preparations. Two patients of dysfunctional uterine bleeding (DUB) administered exogenous estradiol and the urines were collected for 72 h. The urinary estrogens were separated by high-performance liquid chromatography (HPLC) and confirmed. The exogenous and exogenous estrogens were analyzed by gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) to determine the (13)C/(12)C ratio (δ(13)C‰). The δ(13)C‰ values of reference standard of E1, E2, and E3 were -29.36±0.72, -27.98±0.35, -27.62±0.51, respectively. The δ(13)C‰ values of the endogenous E1, E2, and E3 were -21.62±1.07, -22.14±0.98, and -21.88±1.16, with P<0.01 (t-test). Two DUB patients' urinary estradiol δ(13)C‰ values was depleted to -28.02±0.33 after the administration. The progesterone, 17α-hydroxyprogesterone, pregnanediol, as well as desogestrel and ethinylestradiol from contraceptives were also determined. Stable carbon isotope analysis can distinguish the endogenous and exogenous urinary estrogen in human.

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

Although substantial technical advances have been achieved during the past decades to extend and facilitate the analysis of growth promoters in cattle, the detection of abuse of synthetic analogs of naturally occurring hormones has remained a challenging issue. When it became clear that the exogenous origin of steroid hormones could be traced based on the (13)C/(12)C isotope ratio of the substances, GC/C/IRMS has been successfully implemented to this aim since the end of the past century. However, due to the costly character of the instrumental setup, the susceptibility of the equipment to errors and the complex and time consuming sample preparation, this method is up until now only applied by a limited number of laboratories. In this review, the general principles as well as the practical application of GC/C/IRMS to differentiate between endogenous steroids and exogenously synthesized homologous compounds in cattle will be discussed in detail, and will be placed next to other existing and to be developed methods based on isotope ratio mass spectrometry. Finally, the link will be made with the field of sports doping, where GC/C/IRMS has been established within the World Anti-Doping Agency (WADA) approved methods as the official technique to differentiate between exogenous and endogenous steroids over the past few years.

Carbon isotopic (13C and 14C) composition of synthetic estrogens and progestogens

RATIONALE

Steroids are potent hormones that are found in many environments. Yet, contributions from synthetic and endogenous sources are largely uncharacterized. The goal of this study was to evaluate whether carbon isotopes could be used to distinguish between synthetic and endogenous steroids in wastewater and other environmental matrices.

METHODS

Estrogens and progestogens were isolated from oral contraceptive pills using semi-preparative liquid chromatography/diode array detection (LC/DAD). Compound purity was confirmed by gas chromatography/flame ionization detection (GC/FID), gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) and liquid chromatography/mass spectrometry using negative electrospray ionization (LC/ESI-MS). The (13)C content was determined by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and (14)C was measured by accelerator mass spectrometry (AMS).

RESULTS

Synthetic estrogens and progestogens are (13)C-depleted (δ(13)C(estrogen) = -30.0 ± 0.9 ‰; δ(13)C(progestogen) = -30.3 ± 2.6 ‰) compared with endogenous hormones (δ(13)C ~ -16 to -26 ‰). The (14)C content of the majority of synthetic hormones is consistent with synthesis from C(3) plant-based precursors, amended with 'fossil' carbon in the case of EE(2) and norethindrone acetate. Exceptions are progestogens that contain an ethyl group at carbon position 13 and have entirely 'fossil' (14)C signatures.

CONCLUSIONS

Carbon isotope measurements have the potential to distinguish between synthetic and endogenous hormones in the environment. Our results suggest that (13)C could be used to discriminate endogenous from synthetic estrogens in animal waste, wastewater effluent, and natural waters. In contrast, (13)C and (14)C together may prove useful for tracking synthetic progestogens.

Endogenous steroid profiling by gas chromatography-tandem mass spectrometry and multivariate statistics for the detection of natural hormone abuse in cattle

For years it has been suspected that natural hormones are illegally used as growth promoters in cattle in the European Union. Unfortunately there is a lack of methods and criteria that can be used to detect the abuse of natural hormones and distinguish treated from non-treated animals. Pattern recognition of steroid profiles is a promising approach for tracing/detecting the abuse of natural hormones administered to cattle. Traditionally steroids are analysed in urine as free steroid after deconjugation of the glucuronide (and sulphate) conjugates. The disadvantage of this deconjugation is that valuable information about the steroid profile in the sample is lost. In this study we develop a method to analyse steroids at very low concentration levels (ng l(-1)) for the free steroid, glucuronide and sulphate conjugates in urine samples. This method was used to determine concentrations of natural (pro)hormones in a large population (n = 620) of samples from male and female bovine animals and from bovine animals treated with testosterone-cypionate, estradiol-benzoate, dihydroepiandrosterone and pregnenolone. The data acquired were used to build a statistical model applying the multivariate technique 'Soft Independent Modeling of Class Analogy' (SIMCA). It is demonstrated that by using this model the results of the urine analysis can indicate which animal may have had illegal treatment with natural (pro)hormones.

Improvement of estradiol esters monitoring in bovine hair by dansylation and liquid chromatography/tandem mass spectrometry analysis in multiple reaction monitoring and precursor ion scan modes

RATIONALE

The control of forbidden anabolic practices in cattle in the European Union has become challenging since endogenous compounds such as estradiol derivatives can potentially be used as growth promoters. Due to the great difficulty in establishing a reference threshold value for endogenous steroids, the direct detection of steroid esters in hair is an efficient strategy for the detection of 'natural' steroid abuse in cattle.

METHODS

The present study aimed to develop and validate according to the current European standards a specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) analytical strategy to monitor estrogen esters in bovine hair. The analysis was performed by positive ion electrospray ionisation (ESI+) after dansylation. Two acquisition modes were then assessed: single reaction monitoring and precursor ion scanning.

RESULTS

The results showed that the introduction of a dansylation step strongly improves the sensitivity of the detection of estradiol-17-esters by LC/(ESI+)-MS/MS. The CCα values are in the range 1-10 ng g(-1) after optimisation, except for estradiol decanoate for which the derivatisation is not efficient. In addition, this LC/MS/MS approach makes it possible to carry out a precursor ion scan to screen for the presence of these estradiol 17-esters in hair samples.

CONCLUSIONS

Based on the specific product ions, i.e. m/z 255 in native conditions or m/z 171 after dansylation, this strategy has the advantage of detecting any (un)known estradiol ester and of giving access to the [M + H](+) ion of the suspected ester through only a single analysis.

Presence and metabolism of endogenous androgenic-anabolic steroid hormones in meat-producing animals: a review

The presence and metabolism of endogenous steroid hormones in meat-producing animals has been the subject of much research over the past 40 years. While significant data are available, no comprehensive review has yet been performed. Species considered in this review are bovine, porcine, ovine, equine, caprine and cervine, while steroid hormones include the androgenic-anabolic steroids testosterone, nandrolone and boldenone, as well as their precursors and metabolites. Information on endogenous steroid hormone concentrations is primarily useful in two ways: (1) in relation to pathological versus 'normal' physiology and (2) in relation to the detection of the illegal abuse of these hormones in residue surveillance programmes. Since the major focus of this review is on the detection of steroids abuse in animal production, the information gathered to date is used to guide future research. A major deficiency in much of the existing published literature is the lack of standardization and formal validation of experimental approach. Key articles are cited that highlight the huge variation in reported steroid concentrations that can result when samples are analysed by different laboratories under different conditions. These deficiencies are in most cases so fundamental that it is difficult to make reliable comparisons between data sets and hence it is currently impossible to recommend definitive detection strategies. Standardization of the experimental approach would need to involve common experimental protocols and collaboratively validated analytical methods. In particular, standardization would need to cover everything from the demographic of the animal population studied, the method of sample collection and storage (especially the need to sample live versus slaughter sampling since the two methods of surveillance have very different requirements, particularly temporally), sample preparation technique (including mode of extraction, hydrolysis and derivatization), the end-point analytical detection technique, validation protocols, and the statistical methods applied to the resulting data. Although efforts are already underway (at HFL and LABERCA) to produce more definitive data and promote communication among the scientific community on this issue, the convening of a formal European Union working party is recommended.

Criteria to distinguish between natural situations and illegal use of boldenone, boldenone esters and boldione in cattle 2. Direct measurement of 17beta-boldenone sulpho-conjugate in calf urine by liquid chromatography--high resolution and tandem mass spectrometry

Boldenone is banned in the European Union (Directive 96/22/EC) as growth promoter for meat producing animals. Boldione (ADD), boldenone and boldenone esters (mainly the undecylenate form) are commercially available as anabolic preparations, either to the destination of human, horse or cattle. Since the late 90s, the natural occurrence of boldenone metabolites has been reported in cattle. According to EU regulation, the unambiguous demonstration of boldenone administration in bovine urine should be provided on the basis of boldenone identification in the corresponding conjugate fraction. An analytical method has been developed and validated according to current standards with main concern to the measurement of intact 17beta-boldenone-sulphate. The analytical procedure included direct extraction-purification of target analyte on octadecylsilyl cartridges and direct detection of phase II metabolite by liquid chromatography (negative electrospray), tandem mass spectrometry (QqQ) or high resolution mass spectrometry (Orbitrap). Decision limit (CCalpha) and detection capability (CCbeta) were respectively 0.2 microg L(-1) and 0.4 microg L(-1) on triple quadrupole and 0.1 microg L(-1) and 0.2 microg L(-1) on hybrid system. The method was successfully applied to the analysis of incurred samples collected in different experiments. 17beta-Boldenone-sulphate was measurable up to 36h after oral administration of boldione, and 30 days after 17beta-boldenone undecylenate intra-muscular injection. This conjugate form was never detected in non-treated animals, confirming its status of definitive candidate marker for boldenone administration in calf.

Stable isotope analysis of the bioelements: an introduction

The abundances of the stable isotopes of the bioelements are not constant. Subtle, but significant, variations may be induced by physical, physiological and biochemical processes. These variations may be detected and quantified. Often, isotope fingerprints are characteristic of certain processes and may reveal information concerning the sources and origins of compounds of interest. Moreover, natural variabilities of stable isotopes may be exploited in order to perform tracer experiments. The most accurate technology to perform stable isotope analysis is (gas) isotope ratio MS (IRMS). Compound-specific approaches employ hyphenation of GC and LC to IRMS. In these approaches, complete conversion to simple gases prior to MS is required. Analysis by stable isotope ratio spectroscopy currently approaches the accuracy of IRMS. However, for bioanalytical projects, it is still predominantly confined to material synthetically enriched with stable isotopes.

Detection of the administration of 17beta-nortestosterone in boars by gas chromatography/mass spectrometry

17beta-Nortestosterone (17betaN) is illegally used in livestock as a growth promoter and its endogenous production has been described in some animals, such as adult boars. In this paper, the metabolism of 17betaN in boars has been studied by gas chromatography/mass spectrometry (GC/MS) in order to identify markers of the exogenous administration. Administration studies of intramuscular 17betaN laurate to male pigs were performed. Free, sulphate and glucuronide fractions of the urine samples were separated and the steroids present were quantified by GC/MS. 17betaN was detected in some pre-administration samples. After administration, 17betaN, norandrosterone, noretiocholanolone (NorE), norepiandrosterone, 5beta-estrane-3alpha,17beta-diol and 5alpha-estrane-3beta,17beta-diol were detected in different fractions, being the most important metabolites, 17betaN excreted as a sulphate and free NorE. Samples collected in routine controls were also analyzed by GC/MS to identify endogenous compounds. 17betaN, norandrostenedione and estrone were detected in almost all the samples. No other 17betaN metabolites were detected. According to these results, the detection by GC/MS of some of the 17betaN metabolites described above, different from 17betaN, could be indicative of the exogenous administration of 17betaN to boars.

Improved Performance and Maintenance in Gas Chromatography/Isotope Ratio Mass Spectrometry by Precolumn Solvent Removal

The crucial step in current concepts to interface isotope ratio mass spectrometry (IRMS) to gas chromatography (GC) is efficient solvent removal. This is due to the essential postcolumn conversion of the analytes into simple gases, which is performed by either combustion or pyrolysis. The capacity of this step merely suffices to convert the analytes. Already small amounts of solvent present in the respective furnace can cause severe damage. In conventional GC/IRMS interfaces, the solvent is removed after passage of the GC column. Either back-flushing or flow diversion is employed for this purpose. Both techniques necessitate the use of numerous components such as unions, tee pieces, valves, and capillary connections. Often this results in significant deterioration of the chromatographic resolution. In contrast, accurate GC/IRMS measurements require baseline separation of adjacent peaks. Moreover, maintenance of conventional interfaces may be tedious and time consuming, mostly because the numerous connections are prone to leakage. In order to avoid these drawbacks, we propose a concept to efficiently remove the solvent before passage of the GC column. It is based on the use of a cooled injection system operated in solvent vent mode, where the solvent elimination is supported by an auxiliary pump. Most unions and tee pieces thus can be removed. The chromatographic resolution is considerably enhanced. In particular, analysis of high-boiling and polar compounds can be improved. At the same time, the maintenance of the system is significantly facilitated. Under the chosen conditions, partial losses of low-boiling analytes during solvent elimination were not associated with significant isotope fractionation.

Phytosterols and anabolic agents versus designer drugs

Cholesterol is a well-known component in fats of animal origin and it also is the precursor of natural hormones. Phytosterols appear in plants and only differ slightly in structure from cholesterol. An important difference however is the low absorption in the gut of phytosterols and their saturated derivatives, the phytostanols. As a result, there is time for all kind of reactions in faecal material inside and outside of the gut. Determination of the abuse of natural hormones may be based on gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Abuse of natural hormones changes the 13C/12C ratio of some metabolites during a relatively long time. The formation of (natural) hormones in the gut may interfere with this method. Designer drugs are mainly known from sports doping. In animal fattening, designer drugs may be used as well. Small changes in the structure of (natural) hormones may lead to a new group of substances asking for new strategies for their detection and the constatation of their abuse.

Development and application of stable carbon isotope analysis to the detection of cortisol administration in cattle

The use of anabolic agents in food-producing animals has been prohibited within the EU since 1988. The control of the illegal use of natural steroid hormones in cattle is still an exciting analytical challenge as no definitive method and nonambiguous analytical criteria are available. We have used gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) to demonstrate the administration of cortisol to cattle. The method consisted of an efficient combination between OASIS HLB solid-phase extraction (SPE), oxidation, SiOH SPE and semi-preparative high-performance liquid chromatography (HPLC) for glucocorticoid purification. By comparison of the (13)C/(12)C isotopic ratio of the oxidised product of cortisol, i.e. 5 beta-androstane-3,11,17-trione (5 beta AAT), with an endogenous reference compound (ERC), dehydroepiandrosterone (DHEA), the differentiation of cortisol metabolite origin, either endogenous or exogenous, has been achieved. After treatment of an animal, the delta(13)C(VPDB) values of 5 beta AAT reached -30 to -32 per thousand, whereas the delta(13)C(VPDB) values of DHEA remained at -25 per thousand. A significant difference in the delta(13)C(VPDB) values between DHEA and 5 beta AAT was measurable over a period of 3 days after a single administration of cortisol to the animal.

Application of stable carbon isotope analysis to the detection of testosterone administration to cattle

The use of anabolic substances is prohibited in food-producing animals throughout the European Union. No method is available to reliably detect the misuse of natural hormones in cattle. A method was developed to detect the abuse of testosterone in cattle fattening. Synthesized testosterone is rather depleted in the (13)C/(12)C ratio. Hence, the method is based on gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis of urine. To select testosterone metabolites and endogenous reference compounds (ERC), the concentration of urinary steroids of cattle was investigated. Dehydroepiandrosterone and androst-5ene-3beta,17alpha-diol were chosen as ERCs to show endogenous (13)C/(12)C ratios. Etiocholanolone and 5alpha-androstane-3beta,17alpha-diol were chosen as the most important testosterone metabolites. Other metabolites known from literature like epitestosterone were less promising. In principle, GC/C/IRMS is a nonspecific method because finally carbon dioxide is analyzed. Therefore, a dedicated cleanup procedure for the selected steroids was developed. By means of proposed confidence intervals in the isotopic composition of ERCs and metabolites, the administration of testosterone to cattle could be detected reliably. Differences of up to 11 per thousand on the delta-scale between ERC and testosterone metabolites were found after testosterone administration, whereas endogenous differences did not exceed 2 per thousand.