Past, present and future of mass spectrometry in the analysis of residues of banned substances in meat-producing animals

A mesoporous graphene @ zirconium-based metal–organic frameworks as a matrix and an adsorbent for steroid detection using surface-assisted laser desorption/ionization time-of-flight mass spectrometry

Endocrine-disrupting chemicals (EDCs) in environmental water samples, a rapid, sensitive, and high-throughput method should be developed. In this study, an in situ-synthesized composite material of three-dimensional mesoporous graphene (3D-MG) and zirconium-based metal-organic frameworks (MOFs), denoted as MG@UiO-66, was used as both the adsorbent and matrix in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) for steroid detection. Both graphene-based materials and MOFs have proven to be ineffective in detecting steroids as a matrix; however, their composites can detect steroids with higher sensitivity and lower interference. After screening different types of MOFs, a composite of UiO-66 and 3D-MG was selected as the new matrix for steroid detection. The combination of 3D-MG and UiO-66 further enhanced the ability of the material to enrich steroids, and reduced the limit of detection (LOD) of steroids. The method was evaluated for linearity, LODs, limit of quantitation (LOQs), reproducibility, and precision under optimized conditions. The results showed that the linear relationships of three steroids are kept in the range of 0-300 nM/L with a correlation coefficient r ≥ 0.97. The LODs and LOQs of the steroids were in the range of 3-15 and 10-20 nM/L, respectively. Recoveries (n = 5) of 79.3-97.2% were obtained at three spiked levels in the blank water samples. This fast and efficient method of using SALDI-TOF MS can be extended to detect the steroids in EDCs in environmental water samples.

Nandrolone and estradiol biomarkers identification in bovine urine applying a liquid chromatography high-resolution mass spectrometry metabolomics approach

With the aim of specifically investigating patterns associated with three steroid treatments (17β-nandrolone, 17β-estradiol, and 17β-nandrolone + 17β-estradiol) in bovine, an reversed phase liquid chromatography (RPLC)-electrospray ionization (ESI)(+/-)-high-resolution mass spectrometry (HRMS) study was conducted to characterize the urinary profiles of involved animals. Although specific fingerprints with strong differences could be highlighted between urinary metabolite profiles within urine samples collected on control and treated animals, it appeared further that significant discriminations could also be observed between steroid treatments, evidencing thus specific patterns and candidate biomarkers associated to each treatment. An MS-2 structural elucidation step enabled level-1 identification of two biomarkers mainly involved in energy pathways, in relation to skeletal muscle functioning. These results make it possible to envisage a global strategy for the detection of anabolic practices involving steroids, while at the same time providing clues as to the compounds used, which would facilitate the confirmation stage to follow.

Determination of residues of pesticides, anabolic steroids, antibiotics, and antibacterial compounds in meat products in Oman by liquid chromatography/mass spectrometry and enzyme-linked immunosorbent assay

BACKGROUND AND AIM

Meat is a rich source of many nutrients and plays a vital role in human life however, meat safety is one of the top priorities of great concern for consumers today. More than 90% of human exposure to harmful materials is due to consumption of contaminated meat products. This study was designed to compare four valid analytical methods for the determination of organochlorine pesticides 2,4 D (2,4-dichlorophenoxyacetic acid), dichlorodiphenyldichloroethylene/dichlorodiphenyltrichloroethane, alachlor, organophosphate, anabolic steroids (progesterone, testosterone, and estrogen), antibiotics (tetracycline, sulfonamides, gentamycin, and cephalexin), antibacterial compounds (Macrolide, ß-Lactam, Chloramphenicol, Sulphur drugs, and Gentamicin) residues in 135 beef, buffalo, and sheep meat samples (fresh, frozen meats, minced, and sausage samples) of local, regional, and international brands available in Omani markets.

MATERIALS AND METHODS

Triplicate meat samples from each brand within each species were extracted with acetonitrile and purified with acetonitrile-saturated n-hexane to remove all impurities. To dry the sample after heating, the residue was passed across a Sep-Pak C18 cartridge for sample cleaning before gas chromatography (GC) (Brand GCMS-QP2010 Plus) coupled with different detectors, including a mass spectrometer or GC-electron capture detector (GC-ECD). Liquid chromatography/mass spectrometry (LC-MS) was also employed for the quantification of the residues in meat products. Enzyme-linked immunosorbent assay (ELISA) kits were employed to assess veterinary drug residues, anabolic steroids, and pesticides. The CHARM II instrument was employed to detect chloramphenicol, gentamicin, sulfa-drug, ß-lactam, and macrolide residues in meat and meat product samples.

RESULTS

A thin-layer chromatographic (TLC) method should be considered as another method of choice to determine concentrations of veterinary drugs and anabolic steroids. The TLC results were validated by LC-MS. The three described methods permit the multi-residue analysis of anabolic steroid residue levels of 0.06-1.89 ppb in meat product samples. There were three violative residues of anabolic steroids in red meat products that were above the maximum residue limits (MRLs). Although, the levels of organochlorine pesticides and antibiotic concentrations in meat products were below the MRLs, the long-term consumption is considered a health hazard and will affect the wellbeing of consumers.

CONCLUSION

The four techniques (GC, high-performance liquid chromatography, ELISA and CHARM II) provided results that were reliable and precise for the detection of chessssmical residues in meat and meat products.

A novel tool to screen for treatments with clenbuterol in bovine: Identification of two hepatic markers by metabolomics investigation

Surveillance of illegal use of growth promoters such as β₂-agonists in food producing animals rely on the detection of drug residues by LC-MS/MS. Screening strategies focusing on indirect physiological responses following administration of active compounds are promising approaches to strengthen existing targeted methods and ensure food safety. A metabolomics analysis based on LC-HRMS was carried out on liver extracts from bulls experimentally treated with clenbuterol combined with dexamethasone (n = 8) to mimic a potential anabolic practice, and control animals (n = 8). Nicotinic acid and 5'-deoxy-5'-methylthioadenosine were identified as biomarkers of treatment. Ratio values of such markers to others of the same metabolic pathways (nicotinamide or methionine) were used to develop a classification model to assign animals as treated with clenbuterol or non-treated. The classification model was tested on an external validation set comprising 74 animals either treated with different anabolic compounds (β₂-agonists, sexual steroids, corticosteroid), or non-treated, showing 100% sensitivity and specificity.

Hormones and Hormonal Anabolics: Residues in Animal Source Food, Potential Public Health Impacts, and Methods of Analysis

The demand for nutritious food, especially food of animal origin, is globally increasing due to escalating population growth and a dietary shift to animal source food. In order to fulfill the requirements, producers are using veterinary drugs such as hormones and hormone-like anabolic agents. Hormones such as steroidal (estrogens, gestagens, and androgens), nonsteroidal, semisynthetic, and synthetic or designer drugs are all growth-promoting and body-partitioning agents. Hence, in food animal production practice, farm owners use these chemicals to improve body weight gain, increase feed conversion efficiency, and productivity. However, the use of these hormones and hormonal growth-promoting agents eventually ends up with the occurrence of residues in the animal-originated food. The incidence of hormone residues in such types of food and food products beyond the tolerance acts as a risk factor for the occurrence of potential public health problems. Currently, different international and national regulatory bodies have placed requirements and legislative frameworks, which enable them to implement residue monitoring test endeavors that safeguard the public and facilitate the trading activity. To make the tests on the animal-origin food matrix, there are different sample extraction techniques such as accelerated solvent extraction, supercritical fluid extraction, solid phase extraction, solid-phase microextraction, and hollow-fiber liquid-phase microextraction. After sample preparation steps, the analytes of interest can be assayed by screening and confirmatory methods of analysis. For screening, immunological tests such as ELISA and radioimmunoassay are used. Detection and determination of the specific residues will be done by chromatographic or instrumental analysis. Mainly, among high-performance liquid chromatography, liquid chromatography with mass spectrometry (LC-MS, LC-MS/MS), and gas chromatography with mass spectrometry (GC-MS and GC-MS/MS) methods, LC-MS/MS is being preferred because of easier sample preparation without a derivatization step and high detection and quantification capacity.

Inhibition of pancreatic lipase by environmental xenoestrogens

Environmental xenoestrogens are the most accessible endocrine disrupting chemicals that have been reported with harmful effects on human health. Although the influences of xenoestrogens on the endocrine system have been extensively studied, it remains unclear whether these xenoestrogens can affect the digestive system in mammals. This study aimed to investigate the inhibitory effects and the underlying mechanism of six non-steroidal synthetic estrogens (including hexestrol, diethylstilbestrol, dienestrol, bisphenol A, bisphenol AF and bisphenol Z) on pancreatic lipase (PL), a key digestive enzyme responsible for lipid digestion and absorption in mammals. The results clearly demonstrated that hexestrol, diethylstilbestrol and dienestrol exhibited strong inhibition on PL, with the IC₅₀ values of less than 1.0 μM. Further investigations elucidated that these three synthetic estrogens functioned as mixed inhibitors of PL, with the K_i values of less than 1 μM. Moreover, molecular dynamics simulations showed that diethylstilbestrol and its analogues might block the binding of substrate on PL via occupying the portal to the active site of PL and thereby inhibit the hydrolytic activity of this key enzyme. Collectively, these results suggested that diethylstilbestrol and its analogues were potent PL inhibitors, which might play a profound role in lipid absorption and weight gain in mammals.

AgNPs/QDs@GQDs nanocomposites developed as an ultrasensitive impedimetric aptasensor for ractopamine detection

Developing easy-to-use and miniaturized sensors for in-field monitoring of targets which is related to human health is necessary. Ractopamine (RAC) is a feed additive with serious side effects that is forbidden in many countries. This study reports the fabrication of an impedimetric aptasensor for ultrasensitive and selective detection of the RAC in human biological fluids. Accordingly, an efficient nanocomposites was synthesized by a beneficial combination of graphene quantum dots (GQDs), quantum dots (QDs) and silver nanoparticles (AgNPs) for modifying a glassy carbon electrode (GCE). This nanocomposite is promising to present a synergistic effect in the increase of the active surface area of the modified electrode to more load the biocapture of the target. Next, the RAC-binding aptamer (Apt) was attached to the AgNPs/QDs@GQDs/GCE surface and a sensitive layer for the RAC detection was embedded. A RAC-Apt complex was formed upon adding the RAC and the changes of the electrochemical behavior were studied by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS). Under optimal conditions, the charge transfer resistance (R_ct) value was increased linearly with increasing of the RAC concentrations in the range of 1 fM to 901.4 nM. Limit of detection (LOD) was calculated to be 330 aM which is superior by other reported electrochemical methods in the RAC sensing. The applicability of the aptasensor was tested in human urine and blood serum as the real samples and satisfactory results of specificity were achieved. It seems that the proposed strategy not only provides a new ultrasensitive strategy for RAC detection but also expands the application of the sensing interface to develop other aptasensors by changing the Apt sequence.

TMT-Based Proteomics Profiling of Bovine Liver Underscores Protein Markers of Anabolic Treatments

Illegal use of growth promoter compounds in food production exposes consumers to health risk. Surveillance of such practices is based on direct detection of drugs or related metabolites by HPLC-MS/MS. Screening strategies focusing on indirect biological responses are considered promising tools to improve surveillance. In this study, an untargeted shotgun proteomics approach based on tandem mass tags (TMTs) is carried out to identify proteins altered in bovine liver after different anabolic treatments. Three controlled pharmacological treatments with dexamethasone, a combination of dexamethasone and clenbuterol, or a combination of sexual steroids (trenbolone and estradiol) are analyzed. Untargeted TMT analysis of liver digests by high resolution MS allowed for the relative quantification of proteins. Thanks to partial least squarediscriminant analysis, a set of proteins capable to classify animals treated with dexamethasone alone (11 proteins), or in combination with clenbuterol (13 proteins) are identified. No significant difference is found upon administration of sexual steroids. After relative quantification of candidate markers by parallel reaction monitoring (PRM), two predictive models are trained to validate protein markers. Finally, an independent animal set of control bulls and bulls treated with dexamethasone is analyzed by PRM to further validate a predictive model giving an accuracy of 100%.

Chemiluminescent detection integrated with microdialysis sampling for label-free measuring the affinity of ractopamine monoclonal antibody

A novel label-free protocol was developed for measuring the affinity between ractopamine and its monoclonal antibody (McAb) based on microdialysis (MD) on-line sampling integrated with flow injection chemiluminescent detection. In this study, unbound ractopamine was sampled by MD probe from homogeneous immunoreaction equilibrious systems, and then real-time quantified using flow injection chemiluminescent detection. The quantified concentrations of unbound ractopamine in the immunoreaction equilibrious systems were treated with Scatchard analysis and Klotz analysis to obtain the affinity constant. The mean recovery of MD probe for sampling ractopamine was found to be 24.2%. The affinity constants calculated by Scatchard analysis and Klotz analysis both were 1.0 × 10⁶ M^-1, indicating that the investigated ractopamine mouse McAb was a medium-affinity antibody. The result showed good agreement with that obtained from thiocyanate elution test. This protocol for measuring antibody affinity is free of protein conjugation of hapten and enzyme labeling of McAb. Therefore it avoids affinity decrease resulting from steric hindrance, occupancy of the antigenic determinants, and deactivation of antibody, which has been frequently encountered in the reported conventional approaches. It opens up a new pathway for direct measurement of antibody affinity with a facile, rapid, accurate and low-cost approach.

New surveillance concepts in food safety in meat producing animals: the advantage of high throughput 'omics' technologies - A review

The misuse of anabolic hormones or illegal drugs is a ubiquitous problem in animal husbandry and in food safety. The ban on growth promotants in food producing animals in the European Union is well controlled. However, application regimens that are difficult to detect persist, including newly designed anabolic drugs and complex hormone cocktails. Therefore identification of molecular endogenous biomarkers which are based on the physiological response after the illicit treatment has become a focus of detection methods. The analysis of the ‘transcriptome’ has been shown to have promise to discover the misuse of anabolic drugs, by indirect detection of their pharmacological action in organs or selected tissues. Various studies have measured gene expression changes after illegal drug or hormone application. So-called transcriptomic biomarkers were quantified at the mRNA and/or microRNA level by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) technology or by more modern ‘omics’ and high throughput technologies including RNA-sequencing (RNA-Seq). With the addition of advanced bioinformatical approaches such as hierarchical clustering analysis or dynamic principal components analysis, a valid ‘biomarker signature’ can be established to discriminate between treated and untreated individuals. It has been shown in numerous animal and cell culture studies, that identification of treated animals is possible via our transcriptional biomarker approach. The high throughput sequencing approach is also capable of discovering new biomarker candidates and, in combination with quantitative RT-qPCR, validation and confirmation of biomarkers has been possible. These results from animal production and food safety studies demonstrate that analysis of the transcriptome has high potential as a new screening method using transcriptional ‘biomarker signatures’ based on the physiological response triggered by illegal substances.

An ssDNA library immobilized SELEX technique for selection of an aptamer against ractopamine

An improved SELEX technique was developed for selecting aptamers against ractopamine (RAC) by immobilizing ssDNA library on the magnetic beads. After sixteen selection rounds, a highly enriched ssDNA pool was sequenced and nine families were grouped according to their homology and secondary structures analysis. One representative aptamer candidate from each family was picked out for binding affinity identification by graphene oxide (GO) adsorption platform. The aptamer RAC-6 was demonstrated as the optimal aptamer with high specificity and dissociation constant (K_d) value of 54.22 ± 8.02 nM. To prove the potential application of aptamer RAC-6 in the quantitative determination of RAC, a fluorescent bioassay with aptamer RAC-6 was developed. The linear range for RAC was from 0.10 ng/mL to 100 ng/mL and the limit of detection was as low as 0.04 ng/mL. Furthermore, the method was validated for the analysis of RAC spiked real samples, and the recoveries were between 82.57% and 104.65%.

Semiquantitative immunohistochemical detection of progesterone receptors in male accessory sex glands as a screening assay for anabolic steroid use in bulls

We investigated the immunohistochemical expression of progesterone receptors (PRs) in the prostate and bulbourethral glands of thirty-two 10–14-mo-old Charolais bulls following treatment with a low dosage of estrogens. Animals were divided into 2 groups: 16 animals (group T) were treated for 71 d with a therapeutic dose of trenbolone acetate and estradiol by subcutaneous implant, 16 animals (group C) received no treatment. Urine samples were collected both at the beginning of the trial and 9 times during the study. A semiquantitative analysis of immunohistochemistry (IHC) was performed by counting the number of positive cells in 10 randomly selected high-power fields (hpf). Both groups showed no significant histologic lesions. IHC examination showed positive cells in the epithelium of both glands, with different patterns of distribution between groups. In group C, IHC-positive cells per hpf varied from 0 to 40 in the prostate and from 0 to 32 in the bulbourethral gland. In group T, positive cells varied from 0 to 85 per hpf in the prostate and from 0 to 75 in the bulbourethral gland. The treated group showed significantly higher median numbers of positively stained cells in both organs than the controls (  p < 0.001). Chemical analysis of the urine samples confirmed that the experimental treatment mimics continuous, low-dose administration of anabolic steroids. IHC quantification showed good sensitivity with a high predictive power to correctly classify treated animals and could be used as a preliminary screening test in bulls.

Urinary Concentrations of Steroids in Bulls under Anabolic Treatment by Revalor-XS® Implant

Despite the European ban of using anabolics in food-producing animals, growth promoters might still be illegally used in the European Union. To control the food chain and guarantee consumers' health, there is a need of highly sensitive analytical methods for the identification of marker residues of such treatments. In the present study, a group of bulls (n = 16) received trenbolone acetate (200 mg) and estradiol (40 mg) by a commercial ear implant during a time range of 71 days, and a second group (n = 16) was kept for control. The aim of the research was to measure the residual urinary concentrations of the administered drugs (β-trenbolone and β-estradiol), their main metabolites (α-trenbolone and α-estradiol), and possible alterations of the urinary profile of other endogenous hormones metabolically related. The analytical method was based on liquid chromatography-tandem mass spectrometry. Results showed average urinary concentrations of α-trenbolone and α-estradiol during treatment in the range of (0.81 ÷ 2.1) ng mL^-1 and (0.96 ÷ 4.4) ng mL^-1, respectively, whereas β-trenbolone and β-estradiol exhibit urinary concentrations lower than 0.22 ng mL^-1 in both cases. Data obtained from the urinary profiles of endogenous steroids indicate that they could be useful to indirectly detect the ongoing treatment.

The transcriptome of muscle and liver is responding differently to a combined trenbolone acetate and estradiol implant in cattle

We investigated the transcriptomic signature of some anabolic steroids in cattle. Our main objective was to evaluate the effect of a combined trenbolone acetate (TBA, 200mg) and estradiol-17β (E2, 40 mg) implant (Revalor-XS®, REV) on the transcriptome of muscle (target tissue for anabolic steroids) and liver (main biotransformation site). Transcriptomic profiling was performed on 60 samples (30 per tissue) representing 2 groups of animals: REV (sustained release implant for 71 days, n=15), and a control group (CTR, n=15). The analyses (REV vs. CTR) evidenced the differential expression of 431 (down-regulated) and 503 transcripts (268 up-regulated and 235 down-regulated) in muscle and liver tissues, respectively. Functional annotation showed the enrichment of several ion transport systems (cation, metal ion and potassium ion transport) in muscle, while revealing the enrichment of carbohydrate, protein and glycoprotein metabolism and biosynthesis mechanisms in the liver. Both tissues had 20 genes commonly expressed in-between. Seven randomly-selected genes showed positive correlation with their corresponding microarray data upon a qPCR cross-validation step. In muscle, but not the liver, Principal Component Analysis (PCA) on the microarray data resulted in the separation of treated animals from the untreated ones (first 2 components=97.87%.). Overall, the identification of different genes, pathways and biological processes has illustrated the distinctive transcriptomic profile of muscle and liver in response to anabolic steroids. Moreover, it is becoming more clear that anabolic steroids are working through a complex interaction of numerous pathways and processes incorporating different tissues.

Simultaneous detection of flumethasone, dl-methylephedrine, and 2-hydroxy-4,6-dimethylpyrimidine in porcine muscle and pasteurized cow milk using liquid chromatography coupled with triple-quadrupole mass spectrometry

A simple analytical method based on liquid chromatography coupled with triple-quadrupole mass spectrometry was developed for detection of the veterinary drugs flumethasone, dl-methylephedrine, and 2-hydroxy-4,6-dimethylpyrimidine in porcine muscle and pasteurized cow milk. The target drugs were extracted from samples using 10mM ammonium formate in acetonitrile followed by clean-up with n-hexane and primary secondary amine sorbent (PSA). The analytes were separated on an XBridge™ hydrophilic interaction liquid chromatography (HILIC) column using 10mM ammonium formate in ultrapure water and acetonitrile. Good linearity was achieved over the tested concentrations in matrix-fortified calibrations with correlation coefficients (R(2))≥0.9686. Recovery at two spiking levels ranged between 73.62-112.70% with intra- and inter-day precisions of ≤20.33%. The limits of quantification ranged from 2-10ng/g in porcine muscle and pasteurized cow milk. A survey of market samples showed that none of them contained any of the target analytes. Liquid-liquid purification using n-hexane in combination with PSA efficiently removed the interferences during porcine and milk sample extraction. The developed method is sensitive and reliable for detection of the three target drugs in a single chromatographic run. Furthermore, it exhibits high selectivity and low quantification limits for animal-derived food products destined for human consumption.

Regucalcin Expression as a Diagnostic Tool for the Illicit Use of Steroids in Veal Calves

It has been previously demonstrated that sex steroid hormone treatment down-regulates regucalcin gene expression in the accessory sex glands and testis of prepubertal and adult male bovines. The aim of this study was to investigate whether low doses of sex steroid hormones combined with other drugs significantly affect regucalcin gene expression in the accessory sex glands and testis of veal calves. The regucalcin expression was down-regulated in the bulbo-urethral glands of estrogen-treated calves, whereas it was up-regulated in the prostate of estrogen-treated calves. Only the testis of androgen-treated calves showed a down-regulation of the regucalcin expression. Thus, the administration of sex steroid hormones, even in low doses and combined with other molecules, could affect regucalcin expression in target organs. Particularly, the specific response in the testis suggests regucalcin expression in this organ as a first molecular biomarker of illicit androgen administration in bovine husbandry.

Determination of ketosteroid hormones in meat by liquid chromatography tandem mass spectrometry and derivatization chemistry

A method for the determination and quantification of ketosteroid hormones in meat by mass spectrometry, based on the derivatization of the carbonyl moiety of steroids by O-methylhydroxylamine, is presented. The quantitative assay is performed by means of multiple-reaction-monitoring (MRM) scan mode and using the corresponding labelled species, obtained by reaction with d 3-methoxylamine, as internal standard. The accuracy of the method was established by evaluating artificially spiked samples, obtaining values in the range 90-110%. Recovery tests were performed on blank matrix samples spiked with non-natural steroids including trenbolone and melengestrol acetate. The latter experiment revealed that the yield of the extraction processes was approximately 60%. Good values of LOQ and LOD were achieved, making this method competitive with current hormone assay methods.

Metabolism of androstenone, 17β-estradiol and dihydrotestosterone in primary cultured pig hepatocytes and the role of 3β-hydroxysteroid dehydrogenase in this process

Steroids metabolism plays an important role in mammals and contributes to quality of pig meat. The main objective of this study was to identify metabolites of androstenone, 17β-estradiol and dihydrotestosterone using primary cultured pig hepatocytes as a model system. The role of 3β-hydroxysteroid dehydrogenase (3βHSD) in regulation of steroid metabolism was also validated using trilostane, a specific 3βHSD inhibitor. Steroid glucuronide conjugated metabolites were detected by liquid chromatography time of flight mass spectrometry (LC-TOF-MS). 3βHSD enzyme was essential for metabolism of androstenone to 5α-androst-16-en-3β-ol, which then formed androstenone glucuronide conjugate. Metabolism of 17β-estradiol was accompanied by formation of glucuronide-conjugated estrone and glucuronide-conjugated estradiol. The ratio of the two metabolites was around 5∶1. 3βHSD enzyme was not involved in 17β-estradiol metabolism. 5α-Dihydrotestosterone-17β-glucuronide was identified as a dihydrotestosterone metabolite, and this metabolism was related to 3βHSD enzyme activity as demonstrated by inhibition study.

Analysis of estrogens and estrogen mimics in edible matrices--a review

This review provides a brief survey of the biological effects of selected endocrine-disrupting compounds that are formed after internal exposure of organisms. Further, the present analytical methods available for the determination of these compounds in foodstuffs are critically evaluated. The attention is primarily devoted to the methods for sample pretreatment, which are the main source of errors and are usually the most time-consuming step of the whole analysis. This review is focused on selected natural and synthetic estrogens, estrogen conjugates, and chemical additives used in the plastic industry that can act as estrogen mimics.

Excretion profile of corticosteroids in bovine urine compared with tissue residues after therapeutic and growth-promoting administration of dexamethasone

The illicit use of dexamethasone as growth-promoting agent in animal breeding is still practiced within the EU constituting a health risk for meat consumers. An experimental study was developed to assess dexamethasone urinary excretion and tissue distribution (liver, kidney, and muscle) in male calves after therapeutic and growth-promoting administration. Urine and tissue samples collected from treated and untreated bovines were also investigated for the presence of other natural and synthetic corticosteroids (prednisolone, prednisone, hydrocortisone, and cortisone), in order to study a possible correlation with dexamethasone administration and to clarify prednisolone origin. Analyses were performed by a multi-residue LC-MS/MS method developed and validated according to the Commission Decision 2002/657/EC. The results confirm the rapid rate of dexamethasone urinary excretion, irrespective of the dosage, the duration and the route of administration, and the disappearance of cortisone and hydrocortisone during the treatment. Dexamethasone was distributed to the tissues where the elimination rate proceeded relatively slower as suggested by the presence of residues one month after the withdrawal of the therapeutic treatment. An increase in the number of positive findings for prednisolone, in association with higher levels of cortisone and hydrocortisone, was observed in urine samples collected from slaughterhouse rather than those collected at the farm. Prednisone residues were found only in one urine sample that showed the highest levels of prednisolone, hydrocortisone, and cortisone. The occurrence of prednisolone residues in urine and even in tissue samples confirms the endogenous nature of this molecule.

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.

Investigation of testosterone, androstenone, and estradiol metabolism in HepG2 cells and primary culture pig hepatocytes and their effects on 17βHSD7 gene expression

Steroid metabolism is important in various species. The accumulation of androgen metabolite, androstenone, in pig adipose tissue is negatively associated with pork flavor, odour and makes the meat unfit for human consumption. The 17β-hydroxysteroid dehydrogenase type 7 (17βHSD7) expressed abundantly in porcine liver, and it was previously suggested to be associated with androstenone levels. Understanding the enzymes and metabolic pathways responsible for androstenone as well as other steroids metabolism is important for improving the meat quality. At the same time, metabolism of steroids is known to be species- and tissue-specific. Therefore it is important to investigate between-species variations in the hepatic steroid metabolism and to elucidate the role of 17βHSD7 in this process. Here we used an effective methodological approach, liquid chromatography coupled with mass spectrometry, to investigate species-specific metabolism of androstenone, testosterone and beta-estradiol in HepG2 cell line, and pig cultured hepatocytes. Species- and concentration-depended effect of steroids on 17βHSD7 gene expression was also investigated. It was demonstrated that the investigated steroids can regulate the 17βHSD7 gene expression in HepG2 and primary cultured porcine hepatocytes in a concentration-dependent and species-dependent pattern. Investigation of steroid metabolites demonstrated that androstenone formed a 3′-hydroxy compound 3β-hydroxy-5α-androst-16-ene. Testosterone was metabolized to 4-androstene-3,17-dione. Estrone was found as the metabolite for β-estradiol. Inhibition study with 17βHSD inhibitor apigenin showed that apigenin didn’t affect androstenone metabolism. Apigenin at high concentration (50 µM) tends to inhibit testosterone metabolism but this inhibition effect was negligible. Beta-estradiol metabolism was notably inhibited with apigenin at high concentration. The study also established that the level of testosterone and β-estradiol metabolites was markedly increased after co-incubation with high concentration of apigenin. This study established that 17βHSD7 is not the key enzyme responsible for androstenone and testosterone metabolism in porcine liver cells.

Immunodetection of 17β-estradiol in serum at ppt level by microcantilever resonators

To date control strategies in detecting anabolic agents for promoting growth of food producing animals are mainly related to screening techniques based on immunochemical and physiochemical methods, whose major limit is represented by relative low analytical sensitivity. As a consequence, consumers are currently exposed to molecules with potential carcinogenic effects such as 17β-estradiol, the most powerful substance with estrogenic effect. Therefore, high analytical sensitivity screening and confirmatory methods are required, coupling easiness of use and efficiency. We here report on the immunodetection of 17β-estradiol in serum by antibody-immobilized microcantilever resonators, an innovative biosensing platform able to quantify an adsorbed target mass (such as cells, nucleic acids, biomolecules, etc.) thanks to a shift in resonance frequency. Our tool based on microcantilever resonator arrays has shown to be capable of discriminating treated and untreated animals, showing the ability of detecting traces of 17β-estradiol in serum at concentrations lower than the present accepted physiological serum concentration threshold value (40 ppt) and commercial ELISA tests (25 ppt). The method exhibits a limit of detection of 20 ppt and a limited cross-reactivity with high concentrations (10 ppb) of similar molecules (testosterone).

Progesterone receptor up-regulation: a diagnostic tool for the illicit use of oestrogens in adult beef cattle

The monitoring of gene regulation via mRNA levels to detect anabolic sex steroid administration in cattle is a novel approach to detecting the illicit treatment of livestock in meat production. A previous study revealed that progesterone receptor (PR) gene expression levels were increased in the bulbourethral glands and prostates of 17β-oestradiol-treated prepubertal calves, suggesting that the PR can be used as a specific molecular biomarker for oestrogen treatment. The aim of this study was to verify the specificity and applicability of the PR to detect the illegal use of 17β-oestradiol in sexually mature beef cattle. Accessory sex glands were sampled from 42 male beef cattle that were divided into six experimental groups, including two control groups, K1 and K2. Group A cattle were treated with 17β-oestradiol (five weekly intramuscular doses of 20 mg), and group B cattle were treated with dexamethasone (40 daily doses of 0.7 mg per os). Group C cattle received an implant of Revalor-200 (200 mg of trenbolone acetate and 20 mg of 17β-oestradiol), and group D cattle received Revalor-200 plus dexamethasone (0.7 mg daily per os). 17β-Oestradiol, either alone or in combination with other steroids, up-regulated the PR gene and protein expression, even in the absence of detectable histological changes in the accessory sex glands, confirming the high sensitivity of PR gene expression as an indirect diagnostic screening tool to detect illicit oestrogen treatment in sexually mature male bovine.

5α-Estrane-3β,17β-diol and 5β-estrane-3α,17β-diol: definitive screening biomarkers to sign nandrolone abuse in cattle?

17β-Nandrolone (17β-NT) is one of the most frequently misused anabolic steroids in meat producing animals. As a result of its extensive metabolism combined with the possibility of interferences with other endogenous compounds, detection of its illegal use often turns out to be a difficult issue. In recent years, proving the illegal administration of 17β-NT became even more challenging since the presence of endogenous presence of 17β-NT or some of its metabolite in different species was demonstrated. In bovines, 17α-NT can occur naturally in the urine of pregnant cows and recent findings reported that both forms can be detected in injured animals. Because efficient control must both take into account metabolic patterns and associated kinetics of elimination, the purpose of the present study was to investigate further some estranediols (5α-estrane-3β,17β-diol (abb), 5β-estrane-3α,17β-diol (bab), 5α-estrane-3β,17α-diol (aba), 5α-estrane-3α,17β-diol (aab) and 5β-estrane-3α,17α-diol (baa)) as particular metabolites of 17β-NT on a large number of injured (n=65) or pregnant (n=40) bovines. Whereas the metabolites abb, bab, aba and baa have previously been detected in urine up to several days after 17β-NT administration, the present study showed that some of the isomers abb (5α-estrane-3β,17β-diol) and bab (5β-estrane-3α,17β-diol) could not be detected in injured or pregnant animals, even at very low levels. This result may open a new way for the screening of anabolic steroid administration considering these 2 estranediols as biomarkers to indicate nandrolone abuse in cattle.

Disturbance in sex-steroid serum profiles of cattle in response to exogenous estradiol: a screening approach to detect forbidden treatments

Estradiol benzoate (EB) has been one of the most widely used estrogenic agents in animal husbandry, as a way of exogenously introducing the natural hormone estradiol-17β into the animal organism. Estradiol was previously employed to induce anabolic effects or reproductive improvements in cattle. However, the employment of EB in European countries has been permanently forbidden by Directive 2008/97/EC to guarantee consumers' health. Despite this prohibition, the control of estradiol-17β and its esters continues to be a difficult task for residue-monitoring plans in European Communities because official analyses of natural thresholds for hormones in cattle have not yet been established, leading to a lack of confirmation for any exogenous administration of natural hormones. Several researchers have worked on excretion profiles of metabolites, variation in specific hormonal ratios and metabolomic fingerprints after hormonal treatments. This research focuses on the possible existence of disturbances in the serum profile of animals treated with EB in terms of steroid sex hormones (androgens, oestrogens and progestogens), by investigating the serum levels of several of these hormones. The serum samples were collected from three groups of cows: one treated with an intramuscular injection of EB, one treated with a combination of intravaginal EB and progesterone and a control (non-treated) group. The samples have been analysed by a validated high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method, and 17 natural hormones were identified and quantified. Subsequently, data from the serum profiles were submitted for statistic and multivariate analysis, and it was possible to observe a manifest variation between animal groups. The obtained results can help in the development of a viable screening tool for monitoring purposes in cattle.