Detection of LongR<sup>3</sup> -IGF-I, Des(1-3)-IGF-I, and R<sup>3</sup> -IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes.
The study found that Des(1-3)-IGF-I and R<sup>3</sup>-IGF-I can be detected in rats for up to 24 hours after a single injection, while LongR<sup>3</sup>-IGF-I is undetectable after 4 hours.
Where it sits
this study against the rest of the igf-1 des (des(1-3) igf-1) corpusSummary and findings
This study aimed to validate a detection method for IGF-I analogs and evaluate their detectability after intramuscular administration in rats. A single dose of 100 μg/kg was administered, and detection was assessed for up to 36 hours. The study found that Des(1-3)-IGF-I and R<sup>3</sup>-IGF-I were detectable until 24 hours, while LongR<sup>3</sup>-IGF-I was not detectable after 4 hours.
Abstract
Insulin-like growth factor-I (IGF-I) and its analogs LongR<sup>3</sup> -IGF-I, Des(1-3)-IGF-I, and R<sup>3</sup> -IGF-I are prohibited substances in sport. Although they were never approved for use in humans, they are readily available as black market products for bodybuilding and can be used to enhance physical performance. This study's aims were to validate a fast and sensitive detection method for IGF-I analogs and to evaluate their detectability after intramuscular administration in rats. The sample preparation consisted of an immunopurification on MSIA™ microcolumns using a polyclonal anti-human-IGF-I antibody. The target substances were then directly analyzed by nano-liquid chromatography coupled with high-resolution mass spectrometry. Abundant signs of lower quality, oxidized peptide forms were found in black market products, justifying the need to monitor at least both the native and mono-oxidized forms. The analytical performance of this method (linearity, carry over, detection limits, precision, specificity, recovery, and matrix effect) was studied by spiking the analogs into human serum. Following a single intramuscular administration (100 μg/kg) in rats, detection was evaluated up to 36 h after injection. While unchanged Des(1-3)-IGF-I and R<sup>3</sup> -IGF-I were detected until 24 h after administration, LongR<sup>3</sup> -IGF-I disappeared rapidly after 4 h. Des(1)-LongR<sup>3</sup> -IGF-I, a new N-terminal Long-R<sup>3</sup> -IGF-I degradation product, was detected in addition to Des(1-10)-LongR<sup>3</sup> -IGF-I and Des(1-11)-LongR<sup>3-</sup> IGF-I: the latter was detected up to 16 h. The same products were found after in vitro incubation of the analogs in human whole blood, suggesting that observations in rats may be extrapolated to humans and that the validated method may be applicable to antidoping testing.
Background
The paper addresses the detection of IGF-I analogs, which are prohibited in sports and often misused for performance enhancement. Prior research has indicated the presence of these substances in black market products, but their detection methods require validation. This study is significant as it explores a new detection method that could be useful in antidoping contexts.
Methods
The study utilized a detection method involving immunopurification on MSIA™ microcolumns and high-resolution mass spectrometry. The population model consisted of rats, with a sample size not reported in the abstract. A single intramuscular dose of 100 μg/kg was administered, and detection was evaluated up to 36 hours post-injection.
Results
Des(1-3)-IGF-I and R<sup>3</sup>-IGF-I were detected until 24 hours after administration, while LongR<sup>3</sup>-IGF-I was no longer detectable after 4 hours. Additionally, degradation products such as Des(1)-LongR<sup>3</sup>-IGF-I were identified, with Des(1-11)-LongR<sup>3</sup>-IGF-I detectable for up to 16 hours.
Interpretation
The findings indicate that while some IGF-I analogs can be detected for extended periods, the rapid disappearance of LongR<sup>3</sup>-IGF-I may limit its utility in antidoping testing. The study's rodent model may confound the applicability of results to humans, and the clinical significance of these detection times remains uncertain.
Key findings
- Des(1-3)-IGF-I and R<sup>3</sup>-IGF-I detected until 24 h after administration, n=not reported in abstract.
- LongR<sup>3</sup>-IGF-I disappeared rapidly after 4 h, n=not reported in abstract.
- Des(1)-LongR<sup>3</sup>-IGF-I detected in addition to Des(1-10)-LongR<sup>3</sup>-IGF-I and Des(1-11)-LongR<sup>3</sup>-IGF-I.
- Des(1-11)-LongR<sup>3</sup>-IGF-I was detected up to 16 h, n=not reported in abstract.
Limitations
- rodent model, limited to n=not reported in abstract
- substances not approved for human use
- short follow-up period of 36 hours
- potential confounding from black market product quality