Insulin-like growth factor-I (IGF-I) misuse in athletes and potential methods for detection

Synthetic Peptides in Doping Control: A Powerful Tool for an Analytical Challenge

Peptides are very diverse molecules that can participate in a wide variety of biological processes. In this way, peptides are attractive for doping, since these molecules can activate or trigger biological processes that can improve the sports performance of athletes. Peptide molecules are found in the official World Anti-Doping Agency lists, mainly in sections S2, S4, and S5. In most cases, these molecules have a very short half-life in the body and/or are identical to natural molecules in the body, making it difficult to analyze them as performance-enhancing drugs. This article reviews the role of peptides in doping, with special emphasis on the peptides used as reference materials, the pretreatment of samples in biological matrices, the instrumentation, and the validation of analytical methodologies for the analysis of peptides used in doping. The growing need to characterize and quantify these molecules, especially in complex biological matrices, has generated the need to search for robust strategies that allow for obtaining sensitive and conclusive results. In this sense, strategies such as solid phase peptide synthesis (SPPS), seeking to obtain specific peptides, metabolites, or isotopically labeled analogs, is a key tool for adequate quantification of different peptide molecules in biological matrices. This, together with the use of optimal methodologies for sample pretreatment (e.g., SPE or protein precipitation), and for subsequent analysis by high-resolution techniques (mainly hyphenated LC-HRMS techniques), have become the preferred instrumentation to meet the analytical challenge involved in the analysis of peptides in complex matrices.

Performance-enhancing drugs and the Olympics

The rules of fair play in sport generally prohibit the use of performance-enhancing drugs (PEDs). The World Anti-Doping Agency (WADA) oversees global antidoping regulations and testing for elite athletes participating in Olympic sports. Efforts to enforce antidoping policies are complicated by the diverse and evolving compounds and strategies employed by athletes to gain a competitive edge. Now between the uniquely proximate 2021 Tokyo and 2022 Beijing Olympic Games, we discuss WADA's efforts to prevent PED use during the modern Olympic Games. Then, we review the major PED classes with a focus on pathophysiology, complexities of antidoping testing, and relevant toxicities. Providers from diverse practice environments are likely to care for patients using PEDs for a variety of reasons and levels of sport; these providers should be aware of common PED classes and their risks.

IGF-I and IGFBP-1 in Relation to Body Composition and Physical Performance in Female Olympic Athletes

INTRODUCTION

Insulin- like growth factor-I (IGF-I) is an anabolic hormone that may affect athletic performance in female athletes, and insulin-like growth factor binding protein-1 (IGFBP-1) is an important regulator of bioactive IGF-I. There is limited knowledge of the role of endogenous IGF-I and IGFBP-1 for body composition and physical performance in female elite athletes.

PURPOSE

To examine IGF-I, age adjusted IGF-I (IGFSD), IGFBP-1 and insulin in female Olympic athletes compared with controls and different sport categories, and in relation to body composition and physical performance in the athletes.

METHODS

Female athletes (n=103) and untrained controls (n=113) were included in this cross-sectional study. Body composition was established by dual-energy X-ray absorptiometry. Serum IGF-I and IGFBP-1 were analyzed by radioimmunoassay and IGFSD was calculated. Insulin was analyzed by electrochemiluminescence immunoassay. Athletes were offered to participate in standardized physical fitness tests.

RESULTS

The athletes demonstrated significantly higher IGF-I, IGFSD and IGFBP-1 and lower insulin levels than controls (p<0.05, p<0.05, p<0.01, p<0.001 respectively). Power athletes had significantly higher IGFSD compared to both endurance and technical athletes (p<0.05, p<0.01, respectively). In athletes and controls combined, significant positive correlations were found between IGF variables and higher bone mineral density (BMD) and lean mass and lower fat percent. IGF-I was positively correlated with squat jump (r_s = 0.28, p<0.05) and IGFBP-1 correlated positively with squats (r_s =0.35, p<0.05).

CONCLUSION

We found higher IGF-I, IGFSD and IGFBP-1 in female athletes than controls, and the highest IGFSD in power athletes. IGF-I and IGFBP-1 were related to increased BMD and lean mass and lower fat percent, as well as were positively associated with physical fitness tests. Future studies are needed to elucidate if these results reflect adaptive responses to physical activity or genetic predisposition.

The Use and Abuse of Growth Hormone in Sports

GH is banned by the World Anti-Doping Agency as a performance-enhancing anabolic agent. Doping with GH likely began in the early 1980s and became more prevalent with the advent of recombinant technology well before any scientific evidence of benefit. The expectation that GH improves physical function stems from its anabolic and lipolytic properties. Athletic performance depends on muscle strength and the energy required to power muscle function. In recreational athletes, GH selectively improves anaerobic sprint capacity but has not been proven to significantly enhance muscle strength, power, or maximum rate of oxygen consumption. GH is secreted as a family of isoform peptides in a pulsatile manner reflecting intermittent secretion and rapid clearance. Its anabolic actions are largely mediated by IGF-I, which stimulates whole-body protein synthesis, including skeletal muscle and collagen proteins. Two methods have been validated for detecting GH abuse in athletes. The first (the isoform method) is based on distinguishing pure recombinant 22-kDa GH from the heterogeneous isoforms secreted from the pituitary. The second (the marker method) is based on measuring blood levels of GH-responsive proteins, specifically IGF-I and the N-terminal propeptide of type III collagen (P-III-NP). Only a handful of athletes have been caught since the implementation of GH doping tests in 2004. The low rate likely reflects the limitation of in-competition testing using current methods. Improved detection rates may be achieved by more out-of-competition testing, introducing athletes' biological passports, and the development of novel methods. Governance, operational, technical, and political factors influence the effectiveness of an anti-doping program.

Use of growth hormone, IGF-I, and insulin for anabolic purpose: Pharmacological basis, methods of detection, and adverse effects

Hormones with anabolic properties such as growth hormone (GH), insulin-like growth factor-1 (IGF-I), and insulin are commonly abused among professional and recreational athletes to enhance physical ability. Performance enhancing drugs (PEDs) such as these are also commonly used by recreational athletes to improve body aesthetics. The perception of increased muscle mass due to supraphysiologic hormone supplementation, or doping, is widespread among PED users despite a paucity of evidence-based data in humans. Even still, athletes will continue to abuse PEDs in hopes of replicating anecdotal results. It is important to educate the general public and potential treating physicians of the risks of PED use, including the dangers of polypharmacy and substance dependence. It will also be important for the research community to address the common challenges associated with studying PED use such as the ethical considerations of PED administration, the general reticence of the PED-using community to volunteer information, and the constant need to improve or create new detection methods as athletes continually attempt to circumvent current methods. This review highlights the anabolic mechanisms and suggestive data implicating GH, IGF-I, and insulin for use as PEDs, the specific detection methods with cutoff ranges that may be utilized to diagnose abuse of each substance, and their respective side effects.

Determination of LongR3-IGF-I, R3-IGF-I, Des1-3 IGF-I and their metabolites in human plasma samples by means of LC-MS

According to the regulations of the World Anti-Doping Agency (WADA), growth promoting peptides such as the insulin-like growth factor-I (IGF-I) and its synthetic analogues belong to the class of prohibited compounds. While several assays to quantify endogenous IGF-I have been established, the potential misuse of synthetic analogues such as LongR³-IGF-I, R³-IGF-I and Des1-3-IGF-I remains a challenge and superior pharmacokinetic properties have been described for these analogues. Within the present study, it was demonstrated that the target peptides can be successfully detected in plasma samples by means of magnetic beads-based immunoaffinity purification and subsequent nanoscale liquid chromatographic separation with high resolution mass spectrometric detection. Noteworthy, the usage of a specific antibody for LongR³-IGF-I enables the determination in low ng/mL levels despite the presence of an enormous excess of endogenous human IGF-I. In addition, different metabolism studies (in-vitro and in-vivo) were performed using sophisticated strategies such as incubation with skin tissue microsomes, degradation in biological fluids (for all analogues), and administration to rats (for LongR³-IGF-I). Herewith, several C-and N-terminally truncated metabolites were identified and their relevancy was additionally confirmed by in-vivo experiments with rodents. Especially for LongR³-IGF-I, a metabolite ((Des1-11)-LongR³-IGF-I) was identified that prolonged the detectability in-vivo by a factor of approximately 2. The method was validated for qualitative interpretation considering the parameters specificity, identification capability, recovery (26-60%), limit of detection (0.5ng/mL), imprecision (<25%), linearity, stability, and matrix effects. A stable isotope labelled (¹⁵N)-IGF-I was used as internal standard to control all sample preparation steps.

Novel markers to detect recombinant human insulin-like growth factor-I (rhIGF-I)/rhIGF binding protein-3 (rhIGFBP-3) misuse in athletes

Insulin-like growth factor-I (IGF-I) is abused by elite athletes for its metabolic and anabolic effects. We have previously shown that it is possible to detect IGF-I misuse by measuring serum IGF-I and procollagen type III amino-terminal propeptide (P-III-NP) but a pilot study suggested measuring IGF-II, IGF binding protein-2 (IGFBP-2) and acid-labile subunit (ALS) may improve the detection of IGF-I administration. The aim of the study was to assess this in a randomized controlled trial. Twenty-six female and 30 male recreational athletes were randomized to 28 days' treatment with placebo or recombinant human (rh)IGF-I/rhIGF binding protein-3 (IGFBP-3) complex (30 mg/day or 60 mg/day), followed by 56 days' washout. IGF-II, IGFBP-2 and ALS (women only) were measured using commercial immunoassays. IGFBP-2 increased and IGF-II decreased in response to both low and high dose rhIGF-I/rhIGFBP-3 in both women and men while ALS decreased in women in response to high dose rhIGF-I/rhIGFBP-3. Two days after discontinuing treatment, significant differences remained between the three treatment groups in IGFBP-2 and IGF-II, but not ALS. Thereafter there were no significant differences between the three treatment groups in any of the markers. Combining IGF-I with IGF-II and/or IGFBP-2 improved the performance of the test to detect rhIGF-I/rhIGFBP-3 administration in both women and men. Copyright © 2016 John Wiley & Sons, Ltd.