The application of in vitro technologies to study the metabolism of the androgenic/anabolic steroid stanozolol in the equine

Rapid investigating of phase I metabolites of SR9009 in vitro horse liver microsomes via feature-based molecular networking approach: Potential applications in doping control

SR9009, a peroxisome proliferator-activated receptor δ (PPARδ) agonist, is known for its potential benefits in energy homeostasis. It failed to receive the United States Food and Drug Administration (USFDA) approval and its illegal distribution has raised concerns. As a result, it has been classified as a prohibited substance by the World Anti-Doping Agency and the International Federation of Horseracing Authorities (IFHA). This study emphasizes the application of the in-silico molecular networking technology to analyze phase I drug metabolites in horses, distinguishing it from conventional methodologies in forensic science. Feature-based molecular networking (FBMN) analysis identified 15 metabolites, with novel major N-dealkylated metabolite (-C8H7NO4S), indicative of diverse metabolic modifications in horse liver microsomes incubation assay. Additionally, a proposed metabolic pathway of SR9009 in the in vitro assay was outlined, including the previously known dehydroxylated metabolite. Finally, the metabolic pathways included in this study were as follows: hydroxylation, dehydrogenation, N-dealkylation dihydroxylation, and combinations. Molecular networking provided insights into MS spectra connectivity, facilitating rapid interpretation and accurate detection of previously undiscovered metabolites. In conclusion, this study contributes to the understanding of SR9009 metabolism in horses and underscores the importance of advanced analytical techniques, such as molecular networking, in enhancing the accuracy and efficiency of metabolite analysis for forensic and doping control purposes.

Doping control of estra-4,9-diene-3,17-dione in horses

Estra-4,9-diene-3,17-dione (dienedione) is an anabolic-androgenic steroid (AAS) available on the market as a dietary supplement for bodybuilding. It is prohibited in both human and equine sports due to its potential performance-enhancing effect. With the rare presence of the 4,9-diene configuration in endogenous steroids, dienedione has been considered as a synthetic AAS. Nevertheless, the reoccurring detection of dienedione in entire male horse urine samples led to the investigation of its possible endogenous nature in horses, and its endogenous nature in entire male horses has been recently confirmed and reported by the authors' laboratory. While dienedione is not detected in castrated horses (geldings), it is essential to study its elimination and identify its metabolites for its effective control. To study the elimination and biotransformation of dienedione, administration experiments were performed by giving three castrated horses (geldings) each single oral dose of 1500 mg of dienedione powder for seven consecutive days. The postulated in vivo metabolites included 17-hydroxyestra-4,9-dien-3-one (M1a and M1b), hydroxylated dienedione (M2a, M2b, M3a, M3b, M4, M5) and hydroxylated M1 (M6a, M6b, M7a, M7b, M8a and M8b), formed from hydroxylation and reduction of dienedione. To control the misuse of dienedione in geldings, M3a and M3b are the potential targets that gave the longest detection time, which could be detected for up to 2-5 days in urine and 0.4-4 days in plasma.

Investigations into the concentration and metabolite profiles of stanozolol and LGD-4033 in blood plasma and seminal fluid using liquid chromatography high-resolution mass spectrometry

Potential scenarios as to the origin of minute amounts of banned substances detected in doping control samples have been a much-discussed problem in anti-doping analysis in recent years. One such debated scenario has been the contamination of female athletes' urine with ejaculate containing doping agents and/or their metabolites. The aim of this work was to obtain complementary information on whether relevant concentration ranges of doping substances are excreted into the ejaculate and which metabolites can be detected in the seminal fluid (sf) and corresponding blood plasma (bp) samples. A method was established to study the concentration and metabolite profiles of stanozolol and LGD-4033-substances listed under anabolic substances (S1) on the World Anti-Doping Agency's Prohibited List-in bp and sf using liquid chromatography high-resolution mass spectrometry (LC-HRMS). For sf and bp, methods for detecting minute amounts of these substances were developed and tested for specificity, recovery, linearity, precision, and reliability. Subsequently, sf and bp samples from an animal administration study, where a boar orally received stanozolol at 0.33 mg/kg and LGD-4033 at 0.11 mg/kg, were measured. The developed assays proved appropriate for the detection of the target substances in both matrices with detection limits between 10 and 40 pg/mL for the unmetabolized drugs in sf and bp, allowing to estimate the concentration of stanozolol in bp (0.02-0.40 ng/mL) and in sf (0.01-0.25 ng/mL) as well as of LGD-4033 in bp (0.21-2.00 ng/mL) and in sf (0.03-0.68 ng/mL) post-administration. In addition, metabolites resulting from different metabolic pathways were identified in sf and bp, with sf resembling a composite of the metabolic profile of bp and urine.

Equine metabolism of the selective androgen receptor modulator YK-11 in urine and plasma following oral administration

YK-11 is a steroidal selective androgen receptor modulator, a compound class prohibited in both equine racing and human sports because of their potentially performance enhancing properties. YK-11 is easily accessible via internet-based supplement vendors making this compound a possible candidate for doping; however, its phases I and II metabolism has not yet been reported in the horse. The purpose of this study was to investigate the in vivo metabolites of YK-11 in urine and plasma following oral administration with three daily doses of 50 mg to two Thoroughbred horses. In vitro incubations with equine liver microsomes/S9 were also performed for use as metabolite reference materials; however, this resulted in the formation of 79 metabolites with little overlap with the in vivo metabolism. In plasma, parent YK-11 and seven phase I metabolites were detected, with five of them also observed in vitro. They were present nonconjugated in plasma, with one metabolite also indicating some glucuronide conjugation. In urine, 11 phase I metabolites were observed, with four of them also observed in vitro and six of them also detected in plasma. Nine metabolites were excreted non-conjugated in urine, with two of them also indicating some sulfate conjugation. Two minor metabolites were detected solely as sulfate conjugates. The most abundant analytes in urine were a mono-O-demethylated breakdown product and di-O-demethylated YK-11. The most abundant analytes in plasma were two isomers of the breakdown product with an additional hydroxylation reaction, which also provided the longest detection time in both matrices.

Development of a Standardized Microflow LC Gradient to Enable Sensitive and Long-Term Detection of Synthetic Anabolic-Androgenic Steroids for High-Throughput Doping Controls

Synthetic androgenic anabolic steroids (AAS) are banned compounds and considered as major threats by both racing and sports international authorities. Hence, doping control laboratories are continually looking into analytical improvements to increase their detection capabilities, notably by means of emerging technologies. To enhance analytical performances for the detection of synthetic AAS such as stanozolol, specific chromatographic procedures have been developed using recent quaternary liquid chromatography technology originally designed for high-throughput standardized proteomics connected to mass spectrometry. Applying the newly designed elution procedures described in this paper to the analyses of stanozolol and its metabolites in complex matrixes revealed improved sensitivity compared to previously described high-throughput methods. Indeed, we report the consistent and reliable detection of 16β-hydroxy-stanozolol down to 10 pg/mL in equine urine and being detectable up-to 3 months after a microdosing administration. Furthermore, a five months long elimination of stanozolol and its metabolites could be monitored on horse mane sections after a single dose administration. Our work highlights novel solutions to detect AAS with improved sensitivity. The application of such developments constitutes new landmarks for doping control laboratories and could be extended to other targeted compounds in residue analysis, toxicology, and metabolomics. Based on this work, the developed chromatographic method is now freely available within the Evosep Plus program.

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

Despite the impressive innate physical abilities of horses, camels, greyhounds, or pigeons, doping agents might be administered to these animals to improve their performance. To control these illegal practices, anti-doping analytical methodologies have been developed. This review compiles the analytical methods that have been published for the detection of prohibited substances administered to animals involved in sports over 30 years. Relevant papers meeting the search criteria that discussed analytical methods aiming to detect and/or quantify doping substances in animal biological matrices published from 1990 to 2019 were considered. A total of 317 studies were included, of which 298 were related to horses, demonstrating significant advances toward the development of doping detection methods for equine sports. However, analytical methods for the detection of doping agents in sports involving other species are lacking. Due to enhanced accuracy and specificity, chromatographic analysis coupled to mass spectrometry detection is preferred over immunoassays. Regarding biological matrices, blood and urine remain the first choice, although alternative biological matrices, such as hair and feces, have been considered. With the increasing number and type of drugs used as doping agents, the analytes addressed in the published papers are diverse. It is very important to continue to detect and quantify these drugs, recognizing those that are most frequently used, in order to punish the abusers, protect animals' health, and ensure a healthier and genuine competition.

Equine metabolism of the selective androgen receptor modulator AC-262536 in vitro and in urine, plasma and hair following oral administration

AC-262536 is one of a number of selective androgen receptor modulators that are being developed by the pharmaceutical industry for treatment of a range of clinical conditions including androgen replacement therapy. Though not available therapeutically, selective androgen receptor modulators are widely available to purchase online as (illegal) supplement products. The growth- and bone-promoting effects, along with fewer associated negative side effects compared with anabolic-androgenic steroids, make these compounds a significant threat with regard to doping control in sport. The aim of this study was to investigate the metabolism of AC-262536 in the horse following in vitro incubation and oral administration to two Thoroughbred horses, in order to identify the most appropriate analytical targets for doping control laboratories. Urine, plasma and hair samples were collected and analysed for parent drug and metabolites. Liquid chromatography-high-resolution mass spectrometry was used for in vitro metabolite identification and in urine and plasma samples. Nine phase I metabolites were identified in vitro; four of these were subsequently detected in urine and three in plasma, alongside the parent compound in both matrices. In both urine and plasma samples, the longest detection window was observed for an epimer of the parent compound, which is suggested as the best target for detection of AC-262536 administration. AC-262536 and metabolites were found to be primarily glucuronide conjugates in both urine and plasma. Liquid chromatography-tandem mass spectrometry analysis of post-administration hair samples indicated incorporation of parent AC-262536 into the hair following oral administration. No metabolites were detected in the hair.

Investigations into the analysis of intact drug conjugates in animal sport doping control - Development and assessment of a rapid and economical approach for screening greyhound urine

Animal sport doping control laboratories are constantly reviewing ways in which they can improve their service offering whilst ensuring that they remain economically viable. This paper describes the development and assessment of a rapid and economical method for the detection of intact glucuronide conjugates of three anabolic steroids and their metabolites along with three corticosteroids in canine urine. The analysis of intact drug conjugates for animal sport doping control is generally not performed routinely as it presents a number of analytical challenges, not least of which is the lack of availability of appropriate reference standards. Here, we report the development of a UHPLC-MS/MS method using APCI in the negative ion mode for the detection of intact phase II conjugates, including the importance of in vitro incubations in order to provide appropriate reference materials. Cross-validation of the developed method demonstrated that the detection capability of the intact phase II conjugates of stanozolol, boldenone, nandrolone, and their metabolites along with the corticosteroids dexamethasone and methylprednisolone was equivalent to that achieved in routine race-day screens. The new process has been in operation for approximately 2 years and has been used to analyze in excess of 13500 canine urine samples, resulting in a number of positive screening findings. To the best of our knowledge, this is the first reported use of a routine screen for intact drug conjugates within animal sport doping control.

In vitro simulation of the equine hindgut as a tool to study the influence of phytosterol consumption on the excretion of anabolic-androgenic steroids in horses

Traditionally, steroids other than testosterone are considered to be synthetic, anabolic steroids. Nevertheless, in stallions, it has been shown that β-Bol can originate from naturally present testosterone. Other precursors, including phytosterols from feed, have been put forward to explain the prevalence of low levels of steroids (including β-Bol and ADD) in urine of mares and geldings. However, the possible biotransformation and identification of the precursors has thus far not been investigated in horses. To study the possible endogenous digestive transformation, in vitro simulations of the horse hindgut were set up, using fecal inocula obtained from eight different horses. The functionality of the in vitro model was confirmed by monitoring the formation of short-chain fatty acids and the consumption of amino acids and carbohydrates throughout the digestion process. In vitro digestion samples were analyzed with a validated UHPLC-MS/MS method. The addition of β-Bol gave rise to the formation of ADD (androsta-1,4-diene-3,17-dione) or αT. Upon addition of ADD to the in vitro digestions, the transformation of ADD to β-Bol was observed and this for all eight horses' inocula, in line with previously obtained in vivo results, again confirming the functionality of the in vitro model. The transformation ratio proved to be inoculum and thus horse dependent. The addition of pure phytosterols (50% β-sitosterol) or phytosterol-rich herbal supplements on the other hand, did not induce the detection of β-Bol, only low concentrations of AED, a testosterone precursor, could be found (0.1 ng/mL). As such, the digestive transformation of ADD could be linked to the detection of β-Bol, and the consumption of phytosterols to low concentrations of AED, but there is no direct link between phytosterols and β-Bol.

Advances in the detection of designer steroids in anti-doping

The abuse of unknown designer androgenic anabolic steroids (AAS) is considered to be an issue of significant importance, as AAS are the choice of doping preference according to World Anti-doping Agency statistics. In addition, unknown designer AAS are preferred since the World Anti-doping Agency mass spectrometric identification criteria cannot be applied to unknown molecules. Consequently, cheating athletes have a strong motive to use designer AAS in order to both achieve performance enhancement and to escape from testing positive in anti-doping tests. To face the problem, a synergy is required between the anti-doping analytical science and sports anti-doping regulations. This Review examines various aspects of the designer AAS. First, the structural modifications of the already known AAS to create new designer molecules are explained. A list of the designer synthetic and endogenous AAS is then presented. Second, we discuss progress in the detection of designer AAS using: mass spectrometry and bioassays; analytical data processing of the unknown designer AAS; metabolite synthesis; and, long-term storage of urine and blood samples. Finally, the introduction of regulations from sports authorities as preventive measures for long-term storage and reprocessing of samples, initially reported as negatives, is discussed.

Impact of the emergence of designer drugs upon sports doping testing

Historically, dope-testing methods have been developed to target specific and known threats to the integrity of sport. Traditionally, the source of new analytical targets for which testing was required were derived almost exclusively from the pharmaceutical industry. More recently, the emergence of designer drugs, such as tetrahydrogestrinone that are specifically intended to evade detection, or novel chemicals intended to circumvent laws controlling the sale and distribution of recreational drugs, such as anabolic steroids, stimulants and cannabinoids, have become a significant issue. In this review, we shall consider the emergence of designer drugs and the response of dope-testing laboratories to these new threats, in particular developments in analytical methods, instrumentation and research intended to detect their abuse, and we consider the likely future impact of these approaches.

Challenges and benefits of endogenous steroid analysis by LC–MS/MS

Quantification of endogenous hormonal steroids and their precursors is essential for diagnosing a wide range of endocrine disorders. Historically, these analyses have been carried out using immunoassay, but such methods are problematic, especially for low-concentration analytes, due to assay interference by other endogenous steroids. MS offers improved specificity over immunoassay and can be highly sensitive. GC–MS, with use of stable isotopically labeled internal standards, is considered the ‘gold standard’ method for serum steroid analysis. GC–MS is the method of choice for profiling steroid metabolites in urine, but these techniques are not appropriate for routine use in clinical laboratories owing to a need for extensive sample preparation, as well as analytical expertise. LC–MS/MS compares well to GC–MS in terms of accuracy, precision and sensitivity, but allows simplified sample preparation. While most publications have featured only one or a limited number of steroids, we consider that steroid paneling (which we propose as the preferred term for multitargeted steroid analysis) has great potential to enable clinicians to make a definitive diagnosis. It is adaptable for use in a number of matrices, including serum, saliva and dried blood spots. However, LC–MS/MS-based steroid analysis is not straightforward, and understanding the chemical and analytical processes involved is essential for implementation of a robust clinical service. This article discusses specific challenges in the measurement of endogenous steroids using LC–MS/MS, and provides examples of the benefits it offers.

In vitro metabolism of tiletamine, zolazepam and nonbenzodiazepine sedatives: Identification of target metabolites for equine doping control

Within horseracing, the detection of prohibited substance doping often requires urine analysis; hence, it is necessary to understand the metabolism of the drugs in question. Here, the previously unknown equine metabolism of eight sedatives is reported in order to provide information on target metabolites for use in doping control. Phase I metabolite information was provided by incubation with equine liver S9 fraction. In vitro techniques were chosen in order to reduce the ethical and financial issues surrounding the study of so many compounds, none of which are licensed for use in horses in the UK. Several metabolites of each drug were identified using liquid chromatography-high resolution mass spectrometric (LC-HRMS) analysis on an LTQ-Orbitrap. Further structural information was obtained by tandem mass spectrometry (MS/MS) analysis; allowing postulation of the structure of some of the most abundant in vitro metabolites. The most abundant metabolites of alpidem, etifoxine, indiplon, tiletamine, zaleplon, zolazepam, zolpidem, and zopiclone related to hydroxylation/N-oxidation, deethylation, demethylation, deethylation, hydroxylation/N-oxidation, demethylation, hydroxylation/N-oxidation and hydroxylation/N-oxidation, respectively. In many cases, further work would be required to fully elucidate the precise positioning of the functional groups involved. The results of this study provide metabolite information that can be used to enhance equine anti-doping screening methods. However, the in vitro metabolites identified are at present only a prediction of those that may occur in vivo. In the future, any positive findings of these drugs and/or their metabolites in horse urine samples could help validate these findings and/or refine the choice of target metabolites.

Metabolism of anabolic steroids and their relevance to drug detection in horseracing

The fight against doping in sport using analytical chemistry is a mature area with a history of approximately 100 years in horseracing. In common with human sport, anabolic/androgenic steroids (AASs) are an important group of potential doping agents. Particular issues with their detection are extensive metabolism including both phase I and phase II. A number of the common AASs are also endogenous to the equine. A further issue is the large number of synthetic steroids produced as pharmaceutical products or as 'designer' drugs intended to avoid detection or for the human supplement market. An understanding of the metabolism of AASs is vital to the development of effective detection methods for equine sport. The aim of this paper is to review current knowledge of the metabolism of appropriate steroids, the current approaches to their detection in equine sport and future trends that may affect equine dope testing.

Use of in vitro technologies to study phase II conjugation in equine sports drug surveillance

Background: Within equine drug surveillance, there is significant interest in analyzing intact phase II conjugates of drugs in urine, but progress has been limited by a lack of reference material. Method: In this study, in vitro techniques using equine liver fractions were employed to produce glucuronide and sulfate conjugates of stanozolol, 16β-hydroxystanozolol and nandrolone, the glucuronide conjugate of morphine and the glutathione metabolite of chlordinitrobenzene for the first time in equine sports drug surveillance. Results: The glucuronide conjugate of the synthetic progestagen altrenogest was also produced in vitro, removing the requirement for sample hydrolysis during routine urinalyses. Conclusion: These results highlight the potential of in vitro studies for the production of phase II reference material, allowing the development of assays based on intact conjugates.