The Impact of Triptorelin on Hormone Levels in Human and Its Metabolite Confirmation Using Liquid Chromatography-Ion Trap/Time-of-Flight Mass Spectrometry (LC/MS-IT-TOF) and Liquid Chromatography-Orbitrap (LC-Orbitrap) for Doping Control Analysis

Triptorelin, a synthetic gonadotrophin-releasing hormone (GnRH), is mainly used in the clinical treatment of prostate cancer. The mechanism initially stimulates luteinizing hormone (LH) and testosterone secretion followed by suppression, resulting in a reduction in cancer progression. However, GnRHs are prohibited in doping control because of the indirect surge of LH and testosterone. Therefore, GnRH analog detection and confirmation are enforced by World Anti-Doping Agency (WADA) requirements. The effects of triptorelin on LH and endogenous steroid levels in urine and serum of five prostate cancer patients taking triptorelin for the first time were investigated and compared with leuprorelin. The samples were collected at 0.0 h, 3.0 h, 6.0 h, 1 month, and 3 months later after drug administration. The effect of triptorelin on LH levels was measured using a sandwich enzyme-linked immunoassay (ELISA). Testosterone and endogenous steroid levels were monitored using gas chromatography coupled with mass spectrometry (GC/MS). Triptorelin showed an advantage over leuprorelin on LH and testosterone suppression, which is preferable to use for prostate cancer treatment. In this study, triptorelin (5-10), a unique in vivo metabolite, was found in urine and serum and verified with synthetic triptorelin (5-10). The metabolite was analyzed using liquid chromatography combined with Orbitrap (LC-Orbitrap) and liquid chromatography coupled with ion trap/time-of-flight mass spectrometry (LC/MS-IT-TOF). When triptorelin levels are undetectable, the presence of triptorelin (5-10) in human urine can be used as evidence that triptorelin is being misused in doping control.

The sensitive detection of low molecular mass peptide drugs in dried blood spots by solid-phase extraction and LC-HRMS

Dried blood spot (DBS) technique has become a new popular topic in anti-doping field in recent years due to its advantages of sample stability and easy operation. It can be employed as a supplementary method to routine urine analysis. However, the small volume of DBS samples (usually 10-20 μL) significantly reduces the application value of this technique. Therefore, the development of sensitive detection methods for the analysis of prohibited substances in DBS is particularly important. In this study, based on the characteristics of low molecular mass peptide (LMMP) drugs, systematic optimization strategies were utilized for the first time to establish a sensitive detection method for LMMPs in DBS. Without using DMSO to enhance mass spectrometry ionization efficiency of peptides, the limits of detection (LOD) ranged between 0.05 and 3.74 ng/mL, significantly better than the previously reported method (0.5-20 ng/mL). This method was validated according to the guidelines of the World Anti-Doping Agency (WADA), and corresponding post-administration study was conducted, demonstrating that the method could be applied to routine analysis of LMMP drugs in DBS. Moreover, since DMSO is not involved, this method also has the potential to simultaneously detect both LMMP and small molecular drugs.

Characterization and preparation of food-derived peptides on improving osteoporosis: A review

Osteoporosis is a systemic bone disease characterized by reduced bone mass and deterioration of the microstructure of bone tissue, leading to an increased risk of fragility fractures and affecting human health worldwide. Food-derived peptides are widely used in functional foods due to their low toxicity, ease of digestion and absorption, and potential to improve osteoporosis. This review summarized and discussed methods of diagnosing osteoporosis, treatment approaches, specific peptides as alternatives to conventional drugs, and the laboratory preparation and identification methods of peptides. It was found that peptides interacting with RGD (arginine-glycine-aspartic acid)-binding active sites in integrin could alleviate osteoporosis, analyzed the interaction sites between these osteogenic peptides and integrin, and further discussed their effects on improving osteoporosis. These may provide new insights for rapid screening of osteogenic peptides, and provide a theoretical basis for their application in bone materials and functional foods.

The Finding of New In Vivo Metabolite Triptorelin (5-10) in Human Urine Using Liquid Chromatography Coupled with Ion Trap/Time-of-Flight Mass Spectrometry with Dimethyl Sulfoxide Additives in the Mobile Phase

Triptorelin and leuprorelin are synthetic gonadotrophin-releasing hormones (GnRH) that are on the World Anti-Doping Agency (WADA) list of prohibited substances. To investigate the possible in vivo metabolites of triptorelin and leuprorelin in humans compared to previously reported in vitro metabolites, excreted urine from five patients treated with either triptorelin or leuprorelin was analyzed by liquid chromatography coupled with ion trap/time-of-flight mass spectrometry (LC/MS-IT-TOF). The addition of dimethyl sulfoxide (DMSO) to the mobile phase was found to enhance the detection sensitivity of certain GnRH analogs. The method was validated, and the limit of detection (LOD) was found at 0.02-0.08 ng/mL. Using this method, a novel new metabolite of triptorelin was discovered in the urine of all subjects up to 1 month after triptorelin administration, but it was not observed in the urine of subjects before drug administration. The limit of detection was estimated to be 0.05 ng/mL. The structure of the metabolite, triptorelin (5-10), is proposed from bottom-up mass spectrometry analysis. The discovery of in vivo triptorelin (5-10) can possibly be used as supporting evidence of triptorelin misuse in athletes.

Advances and perspectives in the analytical technology for small peptide hormones analysis: A glimpse to gonadorelin

In the last twenty years, we have witnessed an important evolution of bioanalytical approaches moving from conventional lab bench instrumentation to simpler, easy-to-use techniques to deliver analytical responses on-site, with reduced analysis times and costs. In this frame, affinity reagents production has also jointly advanced from natural receptors to biomimetic, abiotic receptors, animal-free produced. Among biomimetic ones, aptamers, and molecular imprinted polymers (MIPs) play a leading role. Herein, our motivation is to provide insights into the evolution of conventional and innovative analytical approaches based on chromatography, immunochemistry, and affinity sensing referred to as peptide hormones. Indeed, the analysis of peptide hormones represents a current challenge for biomedical, pharmaceutical, and anti-doping analysis. Specifically, as a paradigmatic example, we report the case of gonadorelin, a neuropeptide that in recent years has drawn a lot of attention as a therapeutic drug misused in doping practices during sports competitions.

A biomimetic enzyme-linked immunosorbent assay (BELISA) for the analysis of gonadorelin by using molecularly imprinted polymer-coated microplates

An original biomimetic enzyme-linked immunoassay (BELISA) to target the small peptide hormone gonadorelin is presented. This peptide has been recently listed among the substances banned in sports by the World Antidoping Agency (WADA) since its misuse by male athletes triggers testosterone increase. Hence, in response to this emerging issue in anti-doping controls, we proposed BELISA which involves the growth of a polynorepinephrine (PNE)-based molecularly imprinted polymer (MIP) directly on microwells. PNE, a polydopamine (PDA) analog, has recently displayed impressive performances when it was exploited for MIP preparation, giving even better results than PDA. Gonadorelin quantification was accomplished via a colorimetric indirect competitive bioassay involving the competition between biotinylated gonadorelin linked to the signal reporter and the unlabeled analyte. These compete for the same MIP binding sites resulting in an inverse correlation between gonadorelin concentration and the output color signal (λ = 450 nm). A detection limit of 277 pmol L-1 was achieved with very good reproducibility in standard solutions (avCV% = 4.07%) and in urine samples (avCV% = 5.24%). The selectivity of the assay resulted adequate for biological specimens and non-specific control peptides. In addition, the analytical figures of merit were successfully validated by mass spectrometry, the reference anti-doping benchtop platform for the analyte. BELISA was aimed to open real perspectives for PNE-based MIPs as alternatives to antibodies, especially when the target analyte is a poorly or non-immunogenic small molecule, such as gonadorelin. Biomimetic enzyme-linked immunosorbent assay (BELISA).

The pharmacokinetics of buserelin after intramuscular administration in pigs and cows

BACKGROUND

Buserelin is a luteinizing hormone releasing hormone (LHRH) agonist used for the treatment of hormone-dependent diseases in males and females. However, the pharmacokinetics of buserelin in pigs and cows are not fully understood. This study was designed to develop a sensitive method to determine the concentration of buserelin in blood plasma and to investigate the pharmacokinetic parameters after intramuscular (i.m.) administration in pigs and cows.

RESULTS

A sensitive and rapid stability method based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed. The pharmacokinetic parameters of buserelin after i.m. administration were studied in five pigs and five cows at a single dose of 1 mg per pig and 3 mg per cow. The plasma kinetics were analyzed by WinNonlin 8.1.0 software using a non-compartmental model. The mean concentration area under the curve (AUC0-t) was 25.02 ± 6.93 h × ng/mL for pigs and 5.63 ± 1.86 h × ng/mL for cows. The maximum plasma concentration (Cmax) and time to reach the maximum concentration (tmax) were 10.99 ± 2.04 ng/mL and 0.57 ± 0.18 h for pigs and 2.68 ± 0.36 ng/mL and 1.05 ± 0.27 h for cows, respectively. The apparent volume of distribution (Vz) in pigs and cows was 80.49 ± 43.88 L and 839.88 ± 174.77 L, respectively. The elimination half-time (t1/2), and clearance (CL) were 1.29 ± 0.40 h and 41.15 ± 11.18 L/h for pigs and 1.13 ± 0.3 h and 545.04 ± 166.40 L/h for cows, respectively. No adverse effects were observed in any of the animals.

CONCLUSION

This study extends previous studies describing the pharmacokinetics of buserelin following i.m. administration in pigs and cows. Further studies investigating other factors were needed to establish therapeutic protocol in pigs and cows and to extrapolate these parameters to others economic animals.

Doping control analysis of small peptides in human urine using LC-HRMS with parallel reaction monitoring mode: screening and confirmation

This study described a reliable analytical method, which combines solid-phase extraction (SPE) with liquid chromatography-high resolution mass spectrometry (LC-HRMS) employing the parallel reaction monitoring (PRM) mode, for screening 41 small peptides and 3 non-peptide growth hormone secretagogues in human urine. Additionally 36 small peptides and 3 non-peptide growth hormone secretagogues were also confirmed in the same way. For the whole screening procedure, the PRM mode was applied to the HRMS detection of small peptides, which reduces the background noise from matrix compounds to a large extent and thus improves the selectivity and reliability of the peptide analytes. Meanwhile, competent chromatographic separation was achieved within a total runtime of 14 minutes, indicating an improvement in the detection efficiency. Moreover, the PRM mode could also be applied to the confirmation procedure due to its strong identification power with a low risk of generating false positives or negatives and good selectivity. Validation was performed according to the relevant World Anti-Doping Agency (WADA) criteria, including selectivity and reliability, limit of detection (LOD), limit of identification (LOI), recovery, extraction stability and carryover. The LODs of the peptide analytes ranged between 0.20 ng mL^-1 and 0.92 ng mL^-1 in urine, while their LOIs ranged between 0.20 ng mL^-1 and 2.00 ng mL^-1, which met the corresponding Minimum Required Performance Levels (MRPLs) as defined by WADA. The developed method furnished the rapid and sensitive detection of small peptides in urine for more than 5000 samples with no false-positive or false-negative, indicating that it is an eligible method for doping control analysis.

Gonadorelins adherence in prostate cancer: A time-series analysis of England's national prescriptions during the COVID-19 pandemic (from Jan 2019 to Oct 2020)

Objective

To examine the effect of the COVID‐19 pandemic on gonadorelin analogue prescription for community patients in England.

Materials and methods

We included data from all primary‐care patients who had relevant prescriptions dispensed in the community in England. Descriptive statistics and interrupted time series analysis over 22 months (15 months before and 7 months after lockdown) was evaluated.

Results

A total of 22 months’ worth of data were analyzed (or 1 041 638 total items, monthly average 47 347 items). Goserelin; leuprorelin, and triptorelin are the medicines most used by total quantity in the study period. Simple descriptive statistics show that mean values have declined during the pandemic. The Interrupted Time Series (ARIMA Modeling) shows declining trends.

After the pandemic's onset, we observe a statistically significant downward trend for goserelin (P = .017) and leuprorelin (P = .014). As these are the major constituents of the model, we interpret this overall data as showing a significant downward category trend. Aside from linearity, a significant step change was noted for leuprorelin (P = .029) showing an increase in prescription items with a similar effect that is close to being statistically significant for goserelin (P = .051).

The actual cost of medicines shows minimal variation suggesting that prices of individual medicines have remained stable. The regional data showed variation but this was not statistically significant. In all cases, the Oct‐20 figures are lower “year on year.” This novel work reports the impact of a global pandemic on prescription volumes of prostate cancer (PCa) medicines.

Conclusions

A worrying decrease in prescription medicines raises concerns for the care of PCa patients. We encourage diagnosed patients to discuss their planned care with their doctor.

Recent advances in identifying and utilizing metabolites of selected doping agents in human sports drug testing

Probing for evidence of the administration of prohibited therapeutics, drugs and/or drug candidates as well as the use of methods of doping in doping control samples is a central assignment of anti-doping laboratories. In order to accomplish the desired analytical sensitivity, retrospectivity, and comprehensiveness, a considerable portion of anti-doping research has been invested into studying metabolic biotransformation and elimination profiles of doping agents. As these doping agents include lower molecular mass drugs such as e.g. stimulants and anabolic androgenic steroids, some of which further necessitate the differentiation of their natural/endogenous or xenobiotic origin, but also higher molecular mass substances such as e.g. insulins, growth hormone, or siRNA/anti-sense oligonucleotides, a variety of different strategies towards the identification of employable and informative metabolites have been developed. In this review, approaches supporting the identification, characterization, and implementation of metabolites exemplified by means of selected doping agents into routine doping controls are presented, and challenges as well as solutions reported and published between 2010 and 2020 are discussed.

Sensitive 'two-steps' competitive assay for gonadotropin-releasing hormone detection via SPR biosensing and polynorepinephrine-based molecularly imprinted polymer

The work reports an innovative bioassay for the detection of gonadorelin in urine, a gonadotropin-releasing hormone agonist widely used in fertility medicine and to treat hormonal dysfunctions. Gonadorelin is also a synthetic hormone listed by the World Anti-Doping Agency (WADA) and of interest in anti-doping controls. The main novelty relies on the development of a biocompatible, stable, and low-cost biomimetic receptor alternative to classic antibodies. Starting from norepinephrine monomer, a highly selective and sensitive molecularly imprinted polymer (MIP) was developed and optimized for optical real-time and label-free SPR biosensing. The selectivity has been addressed by testing a series of peptides, from high to low similarity, both in terms of molecular weight and primary sequence. Due to the very low molecular weight of gonadorelin (1182 Da), a 'two-steps' competitive assay was developed. Particular attention has been paid to the design of the competitor and its binding affinity constant towards the MIP, being a key step for the success of the competitive strategy. The SPR assay was first optimized in standard conditions and finally applied to untreated urine samples, achieving the sensitivity required by WADA guidelines. The MIP, tested in parallel with a monoclonal antibody, gave comparable results in terms of affinity constants and selectivity towards possible interfering analytes. However, the biomimetic receptor appears clearly superior in terms of sensitivity and reproducibility. This, together with its preparation simplicity, the extremely low-cost of the monomer and its reusability for hundreds of measurements, make polynorepinephrine-based MIPs powerful rivals to immune-based approaches in the near future for similar applications.

Hepatic in vitro metabolism of peptides; Comparison of human liver S9, hepatocytes and Upcyte hepatocytes with cyclosporine A, leuprorelin, desmopressin and cetrorelix as model compounds

The number of approved peptide therapeutics has increased significantly in recent years. Peptide therapeutics have many advances over small molecule drugs, such as higher affinity to target and lower toxicity profiles. Although peptide-like drugs are mainly metabolized/catabolized in the body for smaller peptides and amino acids, metabolite identification still has an essential part of in their development, especially if their structure contains modified amino acids, and also to identify the metabolic soft spots enabling modification to more stable sequence. The use of human derived in vitro systems is an important tool when investigating metabolism of peptide drugs, and comparison of results by various hepatic systems was investigated here. Peptides were incubated in several different in vitro human liver-derived subcellular and cellular incubation systems, i.e. liver S9 fraction, suspended cryo-preserved human primary hepatocytes and plated Upcyte hepatocytes. Samples were collected at different time points and analysed by UPLC/HR-MS-method developed for the purpose. Both substrate disappearance and metabolite formation were monitored, and the systems were compared. S9 fraction formed the highest number of metabolites for leuprorelin and cetrorelix, while for desmopressin and cyclosporin, primary hepatocytes and liver S9 produced similar metabolite profiles. Interestingly, not only cyclosporin, but also leuprorelin and cetrorelix showed metabolites whose formation was CYP (NADPH) dependent in liver S9. For leuprorelin and cetrorelix, the metabolites that showed NADPH dependency with liver S9, were not detected with hepatocytes, even though for leuprorelin these reactions played a major role in liver S9. The hydrolytic metabolic reactions were very similar between liver S9 and hepatocytes, i.e. the metabolite profiles in hepatocytes matched better with liver S9 profiles without NADPH, which may be caused by cell uptake rate limitation with hepatocytes, or then hydrolytic processes are more stressed in peptide metabolism with hepatocytes, in comparison to CYP-mediated processes.

Doping control analysis of small peptides: A decade of progress

Small peptides are handled in the field of sports drug testing analysis as a separate group doping substances. It is a diverse group, which includes but is not limited to growth hormone releasing-factors and gonadotropin-releasing hormone analogues. Significant progress has been achieved during the past decade in the doping control analysis of these peptides. In this article, achievements in the application of liquid chromatography-mass spectrometry-based methodologies are reviewed. To meet the augmenting demands for analyzing an increasing number of samples for the presence of an increasing number of prohibited small peptides, testing methods have been drastically simplified, whilst their performance level remained constant. High-resolution mass spectrometers have been installed in routine laboratories and became the preferred detection technique. The discovery and implementation of metabolites/catabolites in testing methods led to extended detection windows of some peptides, thus, contributed to more efficient testing in the anti-doping community.

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).

Interpol review of toxicology 2016-2019

This review paper covers the forensic-relevant literature in toxicology from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20.Papers%202019.pdf.

Identification of metabolites of peptide-derived drugs using an isotope-labeled reporter ion screening strategy

Background

Peptide-derived drugs represent an emerging class of prohibited substances in professional sports and, thus, in modern doping controls. After parental administration (e.g. subcutaneous, intravenous), these drugs undergo various metabolic processes, which degrade them to biologically active or inactive peptides. Knowledge about these metabolic processes and the hereby produced metabolites plays a key role in successful doping controls due to the effective design of analytical assays under consideration of optimal analytical targets. Unfortunately, the complexity of biological matrix (e.g. blood or urine) complicates the immediate identification of relevant metabolites due to the enormous excess of naturally occurring peptides and their degradation products.

Methods

In this study, a strategy employing in-vitro metabolism of stable isotope-labeled peptides producing characteristic reporter ions derived from labeled immonium ions is shown. The in-vitro experiments were performed with human skin tissue microsomes (S9), and model drugs representing prohibited peptide hormones were synacthen, insulin, and corticorelin (respectively, their stable isotope-labeled analogs). After generic sample preparation, the metabolites were identified by means of liquid chromatography (LC) coupled to high-resolution mass spectrometry (MS) in an untargeted approach.

Results and conclusions

For all three model peptides, several metabolic products were readily identified. While insulin and corticorelin were found to be comparably stable, synacthen was fully degraded, yielding a plethora of metabolic products. A proof of concept concerning the transferability of the obtained data was accomplished by analyzing plasma samples collected post-administration of recombinant human insulin, corroborating the presence of a skin protease-indicative insulin metabolite in vivo.

Food-derived antithrombotic peptides: Preparation, identification, and interactions with thrombin

Thromboembolism and its sequelae have been the leading causes of morbidity and mortality throughout the world. Food-derived antithrombotic peptides, as potential ingredients in health-promoting functional foods targeting thrombus, have attracted increasing attention because of their high biological activities, low toxicity, and ease of metabolism in the human body. This review presents the conventional workflow of preparation, isolation and identification of antithrombotic peptides from various kinds of food materials. More importantly, to analyze the antithrombotic effects and mechanism of antithrombotic peptides, methods for interaction of anticoagulant peptides and thrombin, the main participant in thrombosis, were analyzed from biochemistry, solution chemistry and crystal chemistry. The present study is intended to highlight the recent advances in research of food-derived antithrombotic peptide as a novel vehicle in the field of food science and nutrition. Future outlooks are highlighted with the aim to suggest a research line to be followed in further studies with the introduced research approach.