In vitro metabolic studies using homogenized horse liver in place of horse liver microsomes

Investigation of in vitro generated metabolites of LGD-4033, a selective androgen receptor modulator, in homogenized camel liver for anti-doping applications

RATIONALE

The use of selective androgen receptor modulators (SARM) in sports is prohibited by the World Anti-Doping Agency (WADA) due to their potential as performance-enhancing drugs, offering an unfair advantage. LGD-4033 is a SARM known for its similarities to anabolic steroids and can be easily purchased online, leading to increased availability and misuse. Adverse analytical findings have revealed the presence of SARMs in dietary supplements. Although LGD-4033 misuse has been reported in human sports over the years, concerns also arise regarding its illicit use in animal sports, including camel racing. Although various studies have investigated the metabolism of LGD-4033 in humans, horse, and other species, there is limited research specifically dedicated to racing camels.

METHODS

This study focuses on the in vitro metabolism of LGD-4033 in homogenized camel liver using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) to identify and characterize the metabolites.

RESULTS

The findings indicated the presence of 12 phase I metabolites and 1 phase II metabolite. Hydroxylation was responsible for the formation of the main phase I metabolites that were identified. A glucuronic acid conjugate of the parent drug was observed in this study, but no sulfonic acid conjugate was found. The possible chemical structures of these metabolites, along with their fragmentation patterns, were identified using MS.

CONCLUSIONS

These findings provide valuable insights into the metabolism of LGD-4033 in camels and aid in the development of effective doping control methods for the detection of SARMs in camel racing.

Comprehensive metabolic study of IOX4 in equine urine and plasma using liquid chromatography/electrospray ionization Q Exactive high-resolution mass spectrometer for the purpose of doping control

IOX4 is a hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitor, which was developed for the treatment of anemia by exerting hematopoietic effects. The administration of HIF-PHD inhibitors such as IOX4 to horses is strictly prohibited by the International Federation of Horseracing Authorities and the Fédération Équestre Internationale. To the best of our knowledge, this is the first comprehensive metabolic study of IOX4 in horse plasma and urine after a nasoesophageal administration of IOX4 (500 mg/day, 3 days). A total of four metabolites (three mono-hydroxylated IOX4 and one IOX4 glucuronide) were detected from the in vitro study using homogenized horse liver. As for the in vivo study, post-administration plasma and urine samples were comprehensively analyzed with liquid chromatography/electrospray ionization high-resolution mass spectrometry to identify potential metabolites and determine their corresponding detection times. A total of 10 metabolites (including IOX4 glucuronide, IOX4 glucoside, O-desbutyl IOX4, O-desbutyl IOX4 glucuronide, four mono-hydroxylated IOX4, N-oxidized IOX4, and N-oxidized IOX4 glucoside) were found in urine and three metabolites (glucuronide, glucoside, and O-desbutyl) in plasma. Thus, the respective quantification methods for the detection of free and conjugated IOX4 metabolites in urine and plasma with a biphase enzymatic hydrolysis were developed and applied to post-administration samples for the establishment of elimination profiles of IOX4. The detection times of total IOX4 in urine and plasma could be successfully prolonged to at least 312 h.

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.

Metabolic studies of selective androgen receptor modulators RAD140 and S-23 in horses

This paper describes the studies of the in vitro biotransformation of two selective androgen receptor modulators (SARMs), namely, RAD140 and S-23, and the in vivo metabolism of RAD140 in horses using ultra-high performance liquid chromatography-high resolution mass spectrometry. in vitro metabolic studies of RAD140 and S-23 were performed using homogenised horse liver. The more prominent in vitro biotransformation pathways for RAD140 included hydrolysis, hydroxylation, glucuronidation and sulfation. Metabolic pathways for S-23 were similar to those for other arylpropionamide-based SARMs. The administration study of RAD140 was carried out using three retired thoroughbred geldings. RAD140 and the majority of the identified in vitro metabolites were detected in post-administration urine samples. For controlling the misuse of RAD140 in horses, RAD140 and its metabolite in sulfate form gave the longest detection time in hydrolysed urine and could be detected for up to 6 days post-administration. In plasma, RAD140 itself gave the longest detection time of up to 13 days. Apart from RAD140 glucuronide, the metabolites of RAD140 described herein have never been reported before.

Detection of bioactive peptides including gonadotrophin-releasing factors (GnRHs) in horse urine using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC/HRMS)

The use of bioactive peptides as a doping agent in both human and animal sports has become increasingly popular in recent years. As such, methods to control the misuse of bioactive peptides in equine sports have received attention. This paper describes a sensitive accurate mass method for the detection of 40 bioactive peptides and two non-peptide growth hormone secretagogues (< 2 kDa) at low pg/mL levels in horse urine using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC/HRMS). A simple mixed-mode cation exchange solid-phase extraction (SPE) cartridge was employed for the extraction of 42 targets and/or their in vitro metabolites from horse urine. The final extract was analyzed using UHPLC/HRMS in positive electrospray ionization (ESI) mode under both full scan and data independent acquisition (DIA, for MS² ). The estimated limits of detection (LoD) for most of the targets could reach down to 10 pg/mL in horse urine. This method was validated for qualitative detection purposes. The validation data, including method specificity, method sensitivity, extraction recovery, method precision, and matrix effect were reported. A thorough in vitro study was also performed on four gonadotrophin-releasing factors (GnRHs), namely leuprorelin, buserelin, goserelin, and nafarelin, using the S9 fraction isolated from horse liver. The identified in vitro metabolites have been incorporated into the method for controlling the misuse of GnRHs. The applicability of this method was demonstrated by the identification of leuprorelin and one of its metabolites, Leu M4, in urine obtained after intramuscular administration of leuprorelin to a thoroughbred gelding (castrated horse).

In vitro phase I metabolism of selective estrogen receptor modulators in horse using ultra-high performance liquid chromatography-high resolution mass spectrometry

Selective estrogen receptor modulators (SERMs) are chemicals that possess the anti-oestrogenic activities that are banned 'in' and 'out' of competition by the World Anti-Doping Agency (WADA) in human sports, and by the International Federation of Horseracing Authorities (IFHA) in horseracing. SERMs can be used as performance-enhancing drugs to boost the level of androgens or to compensate for the adverse effects as a result of extensive use of androgenic anabolic steroids (AASs). SERMs have indeed been abused in human sports; hence, a similar threat can be envisaged in horseracing. Numerous analytical findings attributed to the use of SERMs have been reported by WADA-accredited laboratories, including 42 cases of tamoxifen and 2 cases of toremifene in 2014. This paper describes the identification of the in vitro phase I metabolites of tamoxifen and toremifene using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS), with an aim to identify potential screening targets for doping control in equine sports. A total of 13 and 11 in vitro metabolites have been identified for tamoxifen and toremifene, respectively, after incubation with homogenized horse liver. The more prominent in vitro biotransformation pathways include N-desmethylation, hydroxylation, and carboxylation. In addition, this is the first report of some novel metabolites for both tamoxifen and toremifene with hydroxylation occurring at the N-methyl moiety. To our knowledge, this is the first study of the phase I metabolism of tamoxifen and toremifene in horses using homogenized horse liver. Copyright © 2017 John Wiley & Sons, Ltd.

Metabolic studies of prostanozol with the uPA-SCID chimeric mouse model and human liver microsomes

Anabolic androgenic steroids are prohibited by the World Anti-Doping Agency because of their adverse health and performance enhancing effects. Effective control of their misuse by detection in urine requires knowledge about their metabolism. In case of designer steroids, ethical objections limit the use of human volunteers to perform excretion studies. Therefore the suitability of alternative models needs to be investigated. In this study pooled human liver microsomes (HLM) and an uPA(+/+)-SCID chimeric mouse model were used to examine the metabolism of the designer steroid prostanozol as a reference standard. Metabolites were detected by GC-MS (full scan) and LC-MS/MS (precursor ion scan). In total twenty-four prostanozol metabolites were detected with the in vitro and in vivo metabolism studies, which could be grouped into two broad classes, those with a 17-hydroxy- and those with a 17-keto-substituent. Major first phase metabolic sites were tentatively identified as C-3'; C-4 and C-16. Moreover, 3'- and 16β-hydroxy-17-ketoprostanozol could be unequivocally identified, since authentic reference material was available, in both models. Comparison with published data from humans showed a good correlation, except for phase II metabolism. As metabolites were in contrast to the human studies predominantly present in the free fraction. Two types of metabolites ((di)hydroxylated prostanozol metabolites) that have not been described before could be confirmed in a real positive doping control sample. Hence, the results provide further evidence for the applicability of chimeric mice and HLM to perform metabolism studies of designer steroids.

Metabolic study of androsta-1,4,6-triene-3,17-dione in horses using liquid chromatography/high resolution mass spectrometry

Androsta-1,4,6-triene-3,17-dione (ATD) is an irreversible steroidal aromatase inhibitor and is marketed as a supplement. It has been reported to effectively reduce estrogen biosynthesis and significantly increase the levels of endogenous steroids such as dihydrotestosterone and testosterone in human. ATD abuses have been reported in human sports. Its metabolism in human has been studied, and the in vitro metabolic study of ATD in horses has been reported, however, little is known about its biotransformation and elimination in horses. This paper describes the in vitro and in vivo metabolism studies of ATD in horses, with an objective of identifying the target metabolites with the longest detection time for controlling ATD abuse. In vitro metabolism studies of ATD were performed using homogenized horse liver. ATD was found to be extensively metabolized, and its metabolites could not be easily characterized by gas chromatography/mass spectrometry (GC/MS) due to insufficient sensitivity. Liquid chromatography/high resolution mass spectrometry (LC/HRMS) was therefore employed for the identification of in vitro metabolites. The major biotransformations observed were combinations of reduction of the olefin groups and/or the keto group at either C3 or C17 position. In addition, mono-hydroxylation in the D-ring was observed along with reduction of the olefin groups and/or the keto group at C17 position. Fourteen in vitro metabolites, including two epimers of androsta-1,4,6-trien-17-ol-3-one (M1a, M1b), androsta-4,6-diene-3,17-dione (M2), boldione (M3), androsta-4,6-diene-17β-ol-3-one (M4), androsta-4,6-diene-3-ol-17-one (M5), boldenone and epi-boldenone (M6a, M6b), four stereoisomers of hydroxylated androsta-1,4,6-trien-17-ol-3-one (M7a to M7d), and two epimers of androsta-1,4-diene-16α,17-diol (M8a, M8b), were identified. The identities of all metabolites, except M1a, M5, M7a to M7d, were confirmed by matching with authentic reference standards using LC/HRMS. For the in vivo metabolism studies, two thoroughbred geldings were each administered with 800 mg of ATD by stomach tubing. ATD, and twelve out of the fourteen in vitro metabolites, including M1a, M1b, M2, M4, M5, M6, M7a to M7d, M8a and M8b, were detected in post-administration urine. Two additional urinary metabolites, namely stereoisomers of hydroxylated androsta-4,6-dien-17-ol-3-one (M9a, M9b), were tentatively identified by mass spectral interpretation. Elevated level of testosterone was also observed. In post-administration blood samples, only the parent drug, M1b and M2 were identified. This study showed that the detection of ATD administration would be best achieved by either monitoring the metabolites M1b (androsta-1,4,6-trien-17β-ol-3-one) or M4 (both excreted as sulfate conjugates) in urine, which could be detected for up to a maximum of 77 h post-administration. The analyte of choice for plasma is M1b, which could be detected for up to 28 h post administration.

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.