Quantification of urinary AICAR concentrations as a matter of doping controls

Quantification of AICAR and study of metabolic markers after administration

Objectives: AICAR (5-amino-4-imidazolecarboxyamide ribonucleoside) was reported as the first pharmacological AMPK (adenosine 5'-monophosphate (AMP)-activated protein kinase) activator, and it has been confirmed to exhibit a significant endurance enhancement effect and prohibited for doping by the World Anti-Doping Agency. Due to the fact that the human body can produce such substances, in order to ensure fairness in sports competition, methods for rapid detection and multi-type identification of AICAR drugs taken orally should be established. Methods: to assess AICAR levels, a new rapid, sensitive, efficient, and selective method was reported for the quantitative detection of AICAR in urine using LC-MS/MS. The method was validated for quantitative purposes based on the elemental selectivity, intra- (1.0-15.6%) and inter-day precision (1.3-16.3%), accuracy (99.9-112.8%), matrix effects (88.9-103.6%), recovery (87.4-106.5%), and stability at four different concentrations. The calibration curve was linear over a wide concentration range of 10-10,000 ng mL-1 with a high coefficient of determination (R 2 > 0.998). The limit of detection (LOD) and limit of quantification (LOQ) for the experiment were determined to be 1 and 10 ng mL-1, respectively. Simultaneously, metabolomics analysis was used to obtain the metabolic fingerprint of different populations and biomarkers to distinguish administration cases through partial least squares discriminant analysis (PLS-DA) and a receiver operating characteristic (ROC) curve. Results: the method enables easy quantitation for LC-MS/MS analysis with the best recovery yield maintained, and the method was applied to 122 Asian biological samples with an average concentration of 1310.5 ± 1031.4 ng mL-1. Through drug metabolism research, 734 and 294 variables were extracted for data analysis respectively in the positive and negative ion modes, and more than 100 metabolites with significant up- and down-regulation were found after the test. Conclusions: this research developed a fast, precise, effective, and specific approach for the qualitative and quantitative identification of AICAR in urine. Meanwhile, administration metabolism studies found that there were significant changes in AICAR levels and other compounds, such as PC types PC(18:1/16:0), PC(16:0/18:0), and PC(16:0/16:0), PE types PE(18:0/20:4), and LPE-type 18:1, which could better distinguish samples before and after AICAR administration. The analysis provides a multi-perspective reference for WADA to determine a positive criterion.

Urinary concentrations of AICAR and mannitol in athlete population

Both AICAR and mannitol are prohibited for use in sports, but no decisive criteria that would guide anti-doping laboratories on data interpretation have been established so far. In an attempt to help harmonize reporting and management of analytical findings, reference population data collected for US athletes are presented. Upon analysis of 12 377 samples, mean urinary AICAR concentration was found to be 647 ± 365 ng/mL with median value of 574 ng/mL, 99th percentile at 1786 ng/mL and 99.7th percentile at 2151 ng/mL. Based on these results, we suggest that any sample with AICAR concentration greater than 2000 or 2500 ng/mL be analyzed by carbon isotope ratio mass spectrometry to establish the origin. Urinary mannitol concentrations demonstrate larger variation with the mean value of 72 ± 140 μg/mL and median at 41 μg/mL (n = 6407). While the 99.7th percentile for mannitol was measured to be 1094 μg/mL, the population data alone is not sufficient to suggest a threshold value. It is also shown that the use of mannitol as a sweetener in amounts of up to 20 g per day results in a urinary concentration of about 14 mg/mL. As only intravenous mannitol is prohibited in sports, controlled excretion studies are needed to see whether intravenous administration could in fact be discriminated from dietary intake. An important observation is that mannitol present in mg/mL quantities significantly increases urine specific gravity, which makes a widely accepted normalization approach not applicable.

Synthesis of 13 C-labeled 5-aminoimidazole-4-carboxamide-1-β-D-[13 C5 ] ribofuranosyl 5'-monophosphate

5-Aminoimidazole-4-carboxamide-1-β-D-[¹³ C₅ ] ribofuranosyl 5'-monophosphate ([¹³ C₅ ribose] AICAR-PO₃ H₂ ) (6) has been synthesized from [¹³ C₅ ]adenosine. Incorporation of the mass-label into [¹³ C₅ ribose] AICAR-PO₃ H₂ provides a useful standard to aid in metabolite identification and quantification in monitoring metabolic pathways. A synthetic route to the ¹³ C-labeled compound has not been previously reported. Our method employs a hybrid enzymatic, and chemical synthesis approach that applies an enzymatic conversion from adenosine to inosine followed by a ring-cleavage of the protected inosine. A direct phosphorylation of the resulting 2',3'-isopropylidine acadesine (5) was developed to yield the title compound in 99% purity following ion exchange chromatography.

Urine levels of 5-aminoimidazole-4-carboxamide riboside (AICAR) in patients with type 2 diabetes

AIMS

5-Aminoimidazole-4-carboxamide riboside (AICAR) is an endogenous activator of AMPK, a central regulator of energy homeostasis. Loss and/or reduction of AMPK signaling plays an important role in the development of insulin resistance in type 2 diabetes. The loss of AMPK in diabetes could be due to a loss of AICAR. The aim of this study was to characterize urine levels of AICAR in diabetes and determine whether an association exists with respect to late complications, e.g., retinopathy, nephropathy and neuropathy.

METHODS

Urine AICAR was measured by liquid chromatography tandem mass spectrometry in 223 patients consisting of 5 healthy controls, 63 patients with pre-diabetes, 29 patients with newly diagnosed type 2 diabetes and 126 patients with long-standing type 2 diabetes. For statistical analyses, nonparametric Kruskal-Wallis test, one-way ANOVA and multivariate regression analysis were performed to investigate the associations of urinary AICAR excretion within different groups and different clinical parameters.

RESULTS

The mean urine AICAR for all 223 patients was 694.7 ± 641.1 ng/ml. There was no significant difference in urine AICAR between the control and patients with diabetes (592.3 ± 345.1 vs. 697.1 ± 646.5 ng/ml). No association between any of the biochemical and/or clinical parameters measured and urine AICAR was found, with the exception of age of patient (R = - 0.34; p < 0.01) and estimated glomerular filtration rate (R = 0.19; p = 0.039). These results were confirmed additionally by linear regression analysis.

CONCLUSIONS

Clinical diabetes is not associated with a change in endogenous AICAR levels. Loss of AICAR may therefore not be a mechanism by which AMPK signaling is reduced in diabetes.

Implementation of AICAR analysis by GC-C-IRMS for anti-doping purposes

AICAR (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside), is a naturally occurring substance which is part to the World Anti-Doping Agency (WADA) Prohibited List. It is claimed to improve physical performance when administered as a supplement. As for other endogenous compounds such as steroids, the gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis remains an efficient tool to differentiate endogenous substances from exogenous ones. A protocol was described in the literature for the analysis of AICAR by GC-C-IRMS. The aim of the present study was to implement this protocol in our laboratory and to propose solutions to avoid the difficulties encountered. The first point discussed in this study is the derivatization step. Due to the structure of the AICAR molecule, conventional derivatization for GC-C-IRMS such as acetylation could not be applied and silylation was preferred. The improvement of the derivatives stability was achieved thanks to several derivatization conditions tested. This adjustment led to a reproducible derivatization pattern with the 3-TMS form as major derivative product. The second point discussed in this study is the diminution of extracts' background noise. Indeed, the implementation of the published protocol was not easy due to high performance liquid chromatography (HPLC) problems encountered when concentrated urine was injected into our system. Also, too many interferences in the endogenous reference compound fractions were observed. The addition of both a wash step before the HPLC purification and a HPLC purification step for the endogenous reference compound (ERC) fraction allowed us to increase the robustness of the method. This study presents the modified protocol compared to the original protocol as well as the evaluation of the whole method performances. Copyright © 2017 John Wiley & Sons, Ltd.

Doping control study of AICAR in post-race urine and plasma samples from horses

Acadesine, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, commonly known as AICAR, is a naturally occurring adenosine monophosphate-activated protein kinase (AMPK) activator in many mammals, including humans and horses. AICAR has attracted considerable attention recently in the field of doping control because of a study showing the enhancement of endurance performance in unexercised or untrained mice, resulting in the term 'exercise pill'. Its use has been classified as gene doping by the World Anti-Doping Agency (WADA), and since it is endogenous, it may only be possible to control deliberate administration of AICAR to racehorses after establishment of an appropriate threshold. Herein we report our studies of AICAR in post-race equine urine and plasma samples including statistical studies of AICAR concentrations determined from 1,470 urine samples collected from thoroughbreds and standardbreds and analyzed in Australia, France, and Hong Kong. Quantification methods in equine urine and plasma using liquid chromatography-mass spectrometry were developed by the laboratories in each country. An exchange of spiked urine and plasma samples between the three countries was conducted, confirming no significant differences in the methods. However, the concentration of AICAR in plasma was found to increase upon haemolysis of whole blood samples, impeding the establishment of a suitable threshold in equine plasma. A possible urine screening cut-off at 600 ng/mL for the control of AICAR in racehorses could be considered for adoption. Application of the proposed screening cut-off to urine samples collected after intravenous administration of a small dose (2 g) of AICAR to a mare yielded a short detection time of approximately 4.5 h. Copyright © 2017 John Wiley & Sons, Ltd.

Emerging drugs affecting skeletal muscle function and mitochondrial biogenesis - Potential implications for sports drug testing programs

RATIONALE

A plethora of compounds potentially leading to drug candidates that affect skeletal muscle function and, more specifically, mitochondrial biogenesis, has been under (pre)clinical investigation for rare as well as more common diseases. Some of these compounds could be the object of misuse by athletes aiming at artificial and/or illicit and drug-facilitated performance enhancement, necessitating preventive and proactive anti-doping measures.

METHODS

Early warnings and the continuous retrieval and dissemination of information are crucial for sports drug testing laboratories as well as anti-doping authorities, as they assist in preparation of efficient doping control analytical strategies for potential future threats arising from new therapeutic developments. Scientific literature represents the main source of information, which yielded the herein discussed substances and therapeutic targets, which might become relevant for doping controls in the future. Where available, mass spectrometric data are presented, supporting the development of analytical strategies and characterization of compounds possibly identified in human sports drug testing samples.

RESULTS & CONCLUSIONS

Focusing on skeletal muscle and mitochondrial biogenesis, numerous substances exhibiting agonistic or antagonistic actions on different cellular 'control centers' resulting in increased skeletal muscle mass, enhanced performance (as determined with laboratory animal models), and/or elevated amounts of mitochondria have been described. Substances of interest include agonists for REV-ERBα (e.g. SR9009, SR9011, SR10067, GSK4112), sirtuin 1 (e.g. SRT1720, SRT2104), adenosine monophosphate-activated protein kinase (AMPK, e.g. AICAR), peroxisome proliferator-activated receptor (PPAR)δ (e.g. GW1516, GW0742, L165041), and inhibitory/antagonistic agents targeting the methionine-folate cycle (MOTS-c), the general control non-derepressible 5 (GCN5) acetyl transferase (e.g. CPTH2, MB-3), myostatin (e.g. MYO-029), the myostatin receptor (bimagrumab), and myostatin receptor ligands (e.g. sotatercept, ACE-031). In addition, potentially relevant drug targets were identified, e.g. with the sarcoplasmic transmembrane peptide myoregulin and the nuclear receptor corepressor 1 (NCOR-1). The antagonism of these has shown to result in substantially enhanced physical performance in animals, necessitating the monitoring of strategies such as RNA interference regarding these substances. Most drug candidates are of lower molecular mass and comprise non-natural compositions, facts which suggest approaches for their qualitative identification in doping control samples by mass spectrometry. Electrospray ionization/collision-induced dissociation mass spectra of representatives of the aforementioned substances and selected in vitro derived phase-I metabolites support this assumption, and test methods for a subset of these have been recently established. Expanding the knowledge on analytical data will further facilitate the identification of such analytes and related compounds in confiscated material as well as sports drug testing specimens.

Methotrexate reduces HbA1c concentration but does not produce chronic accumulation of ZMP in patients with rheumatoid or psoriatic arthritis

OBJECTIVES

The mechanism by which methotrexate (MTX) improves glucose homeostasis in patients with rheumatoid (RA) and psoriatic arthritis (PsA) remains undetermined. Animal studies indicate a role for intracellular accumulation of 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranosyl 5'-monophosphate (ZMP) but this has not been directly demonstrated in humans. We explored whether accumulation of ZMP is associated with improvements in glucose homeostasis during MTX therapy.

METHOD

MTX-naïve, non-diabetic RA (n = 16) and PsA (n = 10) patients received uninterrupted MTX treatment for 6 months. To evaluate whether ZMP accumulated during MTX therapy, we measured the concentration of ZMP in erythrocytes and the concentration of its dephosphorylated derivative 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) in urine using liquid chromatography mass spectrometry (LC-MS/MS). To assess glucose homeostasis, we determined the concentration of glycated haemoglobin (HbA1c) and homeostasis model assessment of insulin resistance [HOMA-IR: fasting glucose (mmol/L) × fasting insulin (μU/mL)/22.5].

RESULTS

Erythrocyte ZMP and urinary AICAR concentrations did not increase during 6 months of MTX therapy. HbA1c concentration was reduced from 5.80 ± 0.29% at baseline to 5.51 ± 0.32% at 6 months (p < 0.001), while HOMA-IR remained unaltered. Reduction in HbA1c concentration was not associated with increased ZMP or AICAR concentrations.

CONCLUSIONS

MTX therapy probably does not produce a chronic increase in erythrocyte ZMP or urinary AICAR concentrations. Collectively, our data do not support the hypothesis that MTX improves glucose homeostasis through chronic accumulation of ZMP.

Mass spectrometric characterization of a prolyl hydroxylase inhibitor GSK1278863, its bishydroxylated metabolite, and its implementation into routine doping controls

Drug candidates, which have the potential of enhancing athletic performance represent a risk of being misused in elite sport. Therefore, there is a need for early consideration by anti-doping authorities and implementation into sports drug testing programmes. The hypoxia-inducible factor (HIF) or prolyl hydroxylase inhibitor (PHI) GSK1278863 represents an advanced candidate of an emerging class of therapeutics that possess substantial potential for abuse in sport due to their capability to stimulate the biogenesis of erythrocytes and, consequently, the individual's oxygen transport capacity. A thorough characterization of such analytes by technologies predominantly used for doping control purposes and the subsequent implementation of the active drug and/or its main urinary metabolite(s) are vital for comprehensive, preventive, and efficient anti-doping work. In the present study, the HIF PHI drug candidate GSK1278863 (comprising a 6-hydroxypyrimidine-2,4-dione nucleus) and its bishydroxylated metabolite M2 (GSK2391220A) were studied regarding their mass spectrometric behaviour under electrospray ionization (ESI-MS/MS) conditions. Synthesized reference materials were used to elucidate dissociation pathways by means of quadrupole/time-of-flight high resolution/high accuracy tandem mass spectrometry, and their detection from spiked urine and elimination study urine samples under routine doping control conditions was established using liquid chromatography-electrospray ionization-tandem mass spectrometry with direct injection. Dissociation pathways to diagnostic product ions of GSK1278863 (e.g. m/z 291, 223, and 122) were proposed as substantiated by determined elemental compositions and MS(n) experiments as well as comparison to spectra of the bishydroxylated analogue M2. An analytical assay based on direct urine injection using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was developed for the simultaneous determination of GSK1278863 in combination with its bishydroxylated metabolite M2. Validation parameters including limit of detection (0.5-1 ng/mL), linearity, specificity, ion suppression/enhancement (<10%), intra- and inter-day precision (6-22%) were determined, demonstrating the fitness-for-purpose of the assay for doping control screening of urine samples for the presence of the drug candidate and its main metabolite and for expanding current anti-doping efforts to this new class of therapeutics. However, administration study urine sample analysis suggested the use of M2 rather than the intact drug due to extensive metabolic conversion. Copyright © 2015 John Wiley & Sons, Ltd.

"Dilute-and-inject" multi-target screening assay for highly polar doping agents using hydrophilic interaction liquid chromatography high resolution/high accuracy mass spectrometry for sports drug testing

In the field of LC-MS, reversed phase liquid chromatography is the predominant method of choice for the separation of prohibited substances from various classes in sports drug testing. However, highly polar and charged compounds still represent a challenging task in liquid chromatography due to their difficult chromatographic behavior using reversed phase materials. A very promising approach for the separation of hydrophilic compounds is hydrophilic interaction liquid chromatography (HILIC). Despite its great potential and versatile advantages for the separation of highly polar compounds, HILIC is up to now not very common in doping analysis, although most manufacturers offer a variety of HILIC columns in their portfolio. In this study, a novel multi-target approach based on HILIC high resolution/high accuracy mass spectrometry is presented to screen for various polar stimulants, stimulant sulfo-conjugates, glycerol, AICAR, ethyl glucuronide, morphine-3-glucuronide, and myo-inositol trispyrophosphate after direct injection of diluted urine specimens. The usage of an effective online sample cleanup and a zwitterionic HILIC analytical column in combination with a new generation Hybrid Quadrupol-Orbitrap® mass spectrometer enabled the detection of highly polar analytes without any time-consuming hydrolysis or further purification steps, far below the required detection limits. The methodology was fully validated for qualitative and quantitative (AICAR, glycerol) purposes considering the parameters specificity; robustness (rRT < 2.0%); linearity (R > 0.99); intra- and inter-day precision at low, medium, and high concentration levels (CV < 20%); limit of detection (stimulants and stimulant sulfo-conjugates < 10 ng/mL; norfenefrine; octopamine < 30 ng/mL; AICAR < 10 ng/mL; glycerol 100 μg/mL; ETG < 100 ng/mL); accuracy (AICAR 103.8-105.5%, glycerol 85.1-98.3% at three concentration levels) and ion suppression/enhancement effects.

Gene doping in sport - perspectives and risks

In the past few years considerable progress regarding the knowledge of the human genome map has been achieved. As a result, attempts to use gene therapy in patients' management are more and more often undertaken. The aim of gene therapy is to replace defective genes in vivo and/or to promote the long-term endogenous synthesis of deficient protein. In vitro studies improve the production of human recombinant proteins, such as insulin (INS), growth hormone (GH), insulin-like growth factor-1 (IGF-1) and erythropoietin (EPO), which could have therapeutic application. Unfortunately, genetic methods developed for therapeutic purposes are increasingly being used in competitive sports. Some new substances (e.g., antibodies against myostatin or myostatin blockers) might be used in gene doping in athletes. The use of these substances may cause an increase of body weight and muscle mass and a significant improvement of muscle strength. Although it is proven that uncontrolled manipulation of genetic material and/or the introduction of recombinant proteins may be associated with health risks, athletes are increasingly turning to banned gene doping. At the same time, anti-doping research is undertaken in many laboratories around the world to try to develop and refine ever newer techniques for gene doping detection in sport. Thanks to the World Anti-Doping Agency (WADA) and other sports organizations there is a hope for real protection of athletes from adverse health effects of gene doping, which at the same time gives a chance to sustain the idea of fair play in sport.

AMPK activation: a therapeutic target for type 2 diabetes?

Type 2 diabetes (T2D) is a metabolic disease characterized by insulin resistance, β-cell dysfunction, and elevated hepatic glucose output. Over 350 million people worldwide have T2D, and the International Diabetes Federation projects that this number will increase to nearly 600 million by 2035. There is a great need for more effective treatments for maintaining glucose homeostasis and improving insulin sensitivity. AMP-activated protein kinase (AMPK) is an evolutionarily conserved serine/threonine kinase whose activation elicits insulin-sensitizing effects, making it an ideal therapeutic target for T2D. AMPK is an energy-sensing enzyme that is activated when cellular energy levels are low, and it signals to stimulate glucose uptake in skeletal muscles, fatty acid oxidation in adipose (and other) tissues, and reduces hepatic glucose production. There is substantial evidence suggesting that AMPK is dysregulated in animals and humans with metabolic syndrome or T2D, and that AMPK activation (physiological or pharmacological) can improve insulin sensitivity and metabolic health. Numerous pharmacological agents, natural compounds, and hormones are known to activate AMPK, either directly or indirectly - some of which (for example, metformin and thiazolidinediones) are currently used to treat T2D. This paper will review the regulation of the AMPK pathway and its role in T2D, some of the known AMPK activators and their mechanisms of action, and the potential for future improvements in targeting AMPK for the treatment of T2D.

Determination of ¹³C/¹² C ratios of endogenous urinary 5-amino-imidazole-4-carboxamide 1β-D-ribofuranoside (AICAR)

RATIONALE

AICAR (5-aminoimidazole-4-carboxamide 1β-D-ribofuranoside) is prohibited in sport according to rules established by the World Anti-Doping Agency. Doping control laboratories identify samples where AICAR abuse is suspected by measuring its urinary concentration and comparing the observed level with naturally occurring concentrations. As the inter-individual variance of urinary AICAR concentrations is large, this approach requires a complementary method to unambiguously prove the exogenous origin of AICAR. Therefore, a method for the determination of carbon isotope ratios (CIRs) of urinary AICAR has been developed and validated.

METHODS

Concentrated urine samples were fractionated by means of liquid chromatography for analyte cleanup. Derivatization of AICAR yielding the trimethylsilylated analog was necessary to enable CIR determinations by gas chromatography/combustion/isotope ratio mass spectrometry. The method was tested for its repeatability and stability over time and a linear mixing model was applied to test for possible isotopic discrimination. A reference population of n = 63 males and females was investigated to calculate appropriate reference limits to differentiate endogenous from exogenous urinary AICAR. These limits were tested by an AICAR elimination study.

RESULTS

The developed method fulfills all the requirements for adequate sports drug testing and was found to be fit for purpose. The investigated reference population showed a larger variability in the CIR of AICAR than of the endogenous steroids. Nevertheless, the calculated thresholds for differences between AICAR and endogenous steroids can be applied straightforwardly to evaluate suspicious doping control samples with the same statistical confidence as established e.g. for testosterone misuse. These thresholds enabled the detection of a single oral AICAR administration for more than 40 h.

CONCLUSIONS

Determination of thee CIRs is the method of choice to distinguish between an endogenous and an exogenous source of urinary AICAR. The developed method will enable investigations into doping control samples with elevated urinary concentrations of AICAR and clearly differentiate between naturally produced/elevated and illicitly administered AICAR.

From gene engineering to gene modulation and manipulation: can we prevent or detect gene doping in sports?

During the last 2 decades, progress in deciphering the human gene map as well as the discovery of specific defective genes encoding particular proteins in some serious human diseases have resulted in attempts to treat sick patients with gene therapy. There has been considerable focus on human recombinant proteins which were gene-engineered and produced in vitro (insulin, growth hormone, insulin-like growth factor-1, erythropoietin). Unfortunately, these substances and methods also became improper tools for unscrupulous athletes. Biomedical research has focused on the possible direct insertion of gene material into the body, in order to replace some defective genes in vivo and/or to promote long-lasting endogenous synthesis of deficient proteins. Theoretically, diabetes, anaemia, muscular dystrophies, immune deficiency, cardiovascular diseases and numerous other illnesses could benefit from such innovative biomedical research, though much work remains to be done. Considering recent findings linking specific genotypes and physical performance, it is tempting to submit the young athletic population to genetic screening or, alternatively, to artificial gene expression modulation. Much research is already being conducted in order to achieve a safe transfer of genetic material to humans. This is of critical importance since uncontrolled production of the specifically coded protein, with serious secondary adverse effects (polycythaemia, acute cardiovascular problems, cancer, etc.), could occur. Other unpredictable reactions (immunogenicity of vectors or DNA-vector complex, autoimmune anaemia, production of wild genetic material) also remain possible at the individual level. Some new substances (myostatin blockers or anti-myostatin antibodies), although not gene material, might represent a useful and well-tolerated treatment to prevent progression of muscular dystrophies. Similarly, other molecules, in the roles of gene or metabolic activators [5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR), GW1516], might concomitantly improve endurance exercise capacity in ischaemic conditions but also in normal conditions. Undoubtedly, some athletes will attempt to take advantage of these new molecules to increase strength or endurance. Antidoping laboratories are improving detection methods. These are based both on direct identification of new substances or their metabolites and on indirect evaluation of changes in gene, protein or metabolite patterns (genomics, proteomics or metabolomics).

Genes in sport and doping

Genes control biological processes such as muscle production of energy, mitochondria biogenesis, bone formation, erythropoiesis, angiogenesis, vasodilation, neurogenesis, etc. DNA profiling for athletes reveals genetic variations that may be associated with endurance ability, muscle performance and power exercise, tendon susceptibility to injuries and psychological aptitude. Already, over 200 genes relating to physical performance have been identified by several research groups. Athletes’ genotyping is developing as a tool for the formulation of personalized training and nutritional programmes to optimize sport training as well as for the prediction of exercise-related injuries. On the other hand, development of molecular technology and gene therapy creates a risk of non-therapeutic use of cells, genes and genetic elements to improve athletic performance. Therefore, the World Anti-Doping Agency decided to include prohibition of gene doping within their World Anti-Doping Code in 2003. In this review article, we will provide a current overview of genes for use in athletes’ genotyping and gene doping possibilities, including their development and detection techniques.

Quantification of AICAR-ribotide concentrations in red blood cells by means of LC-MS/MS

AICAR (5-amino-4-imidazolecarboxyamide ribonucleoside) arguably provides performance-enhancing properties even in the absence of physical exercise and, therefore, the substance is banned in elite sports since 2009. Due to the natural presence of AICAR in human blood and urine, uncovering the misuse by direct qualitative analysis is not possible. Entering the circulation, the riboside is immediately incorporated into red blood cells (RBCs) and transformed into the corresponding ribotide (5'-monophosphate) form. Within the present study, an analytical method was developed to determine AICAR-ribotide concentrations in RBC concentrates by means of liquid chromatography-tandem mass spectrometry. The method was validated enabling quantitative result interpretation considering the parameters specificity, precision (intra- and interday), linearity, recovery, accuracy (LOD/LOQ), stability and ion suppression. By analysing 99 RBC samples of young athletes, normal physiological levels of AICAR-ribotide were determined (10-500 ng/mL), and individual levels were found to be stable for several days. Employing in vitro incubation experiments with AICAR riboside in fresh whole blood samples, the ribotide concentrations were observed to increase significantly within 30 min from baseline to 1-10 μg/mL. These levels are considered conserved for the lifetime of the erythrocyte and, thus, the results of the in vitro model strongly support the hypothesis that measuring abnormally high AICAR-ribotide concentrations in RBC of elite athletes has the potential to uncover the misuse of this substance for a long period of time.

A HPLC method for simultaneous determination of 5-aminoimidazole-4-carboxamide riboside and its active metabolite 5-aminoimidazole-4-carboxamide ribotide in tumor-bearing nude mice plasma and its application to pharmacokinetics study

A HPLC method with on-line solid phase extraction (SPE) and column switching was developed for simultaneous determination of 5-aminoimidazole-4-carboxamide riboside (AICA riboside) and its active metabolite 5-aminoimidazole-4-carboxamide ribotide (AICA ribotide) in nude mice plasma. Plasma sample was deproteinized by adding a half volume of 10% trichloroacetic acid (TCA), and the resulting supernatant was extracted with diethyl ether to remove TCA. 50 μl aqueous fraction was injected onto a WAX-1 SPE column, and AICA ribotide was trapped on the SPE column, while AICA riboside was eluted from the SPE column. The chromatographic separation of AICA riboside was achieved on CG16 column, and separation of AICA ribotide was performed on HILIC-10 and WAX-1 column. The columns temperature was maintained at 40 °C, and the optimal detection wavelength was 268 nm for both AICA riboside and AICA ribotide. The total analytical run time was 40 min. The proposed method was linear over the range of 0.1-500 μg/ml for AICA riboside and 0.03-50 μg/ml for AICA ribotide. The lower limit of quantification (LLOQ) was 100 and 30 ng/ml for AICA riboside and AICA ribotide, respectively. The sensitivity, accuracy and precision of this method were within acceptable limits during validation period. The method was successfully applied to investigate the pharmacokinetics characteristics of AICA riboside and its active metabolite AICA ribotide in nude mice bearing MCF-7 cell xenografts.

Evolving concepts and techniques for anti-doping

Technical advances are being made in many areas of biotechnology and genetics that are facilitating the detection of doping in sport. These improvements have been catalyzed by the need to counter the ever-increasing sophistication of the community of athletes and their retinues who are intent on the illicit use of physical, pharmacological and genetic tools and methods to enhance athletic performance, in contravention of established international ethical and legal standards and of international treaty. The methods described in this article present a partial and general picture of only some of these advances.

Trafficking of drug candidates relevant for sports drug testing: detection of non-approved therapeutics categorized as anabolic and gene doping agents in products distributed via the Internet

Identifying the use of non-approved drugs by cheating athletes has been a great challenge for doping control laboratories. This is due to the additional complexities associated with identifying relatively unknown and uncharacterized compounds and their metabolites as opposed to known and well-studied therapeutics. In 2010, the prohibited drug candidates and gene doping substances AICAR and GW1516, together with the selective androgen receptor modulator (SARM) MK-2866 were obtained by the Cologne Doping Control Laboratory from Internet suppliers and their structure, quantity, and formulation elucidated. All three compounds proved authentic as determined by liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry and comparison to reference material. While AICAR was provided as a colourless powder in 100 mg aliquots, GW1516 was obtained as an orange/yellow suspension in water/glycerol (150 mg/ml), and MK-2866 (25 mg/ml) was shipped dissolved in polyethylene glycol (PEG) 300. In all cases, the quantified amounts were considerably lower than indicated on the label. The substances were delivered via courier, with packaging identifying them as containing 'amino acids' and 'green tea extract', arguably to circumvent customs control. Although all of the substances were declared 'for research only', their potential misuse in illicit performance-enhancement cannot be excluded; moreover sports drug testing authorities should be aware of the facile availability of black market copies of these drug candidates.