Detection of LongR(3) -IGF-I, Des(1-3)-IGF-I, and R(3) -IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes.
Des(1-3)-IGF-I and R(3)-IGF-I can be detected in rats for up to 24 hours after a single injection, while LongR(3)-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. The dose administered was 100 μg/kg, and the detection was assessed up to 36 hours post-injection. The study found that Des(1-3)-IGF-I and R(3)-IGF-I were detectable until 24 hours, while LongR(3)-IGF-I was undetectable 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 need for reliable detection methods for IGF-1 variants in anti-doping contexts. Prior studies have indicated that IGF-1 can be misused in sports, but effective detection methods remain a challenge. This study is significant as it explores advanced techniques to improve detection accuracy.
Methods
The study utilized high-resolution mass spectrometry combined with immunopurification techniques. The specific population or sample size is not reported in the abstract. The primary outcome measure was the detection limit of various IGF-1 variants in urine samples.
Results
The study reports detection limits for LongR(3)-IGF-I at 0.5 ng/mL, Des(1-3)-IGF-I at 0.1 ng/mL, and R(3)-IGF-I at 0.2 ng/mL in urine samples. No p-values or confidence intervals are provided.
Interpretation
The findings suggest that the detection limits for these IGF-1 variants are relatively low, which may enhance anti-doping efforts. However, the clinical significance of these detection limits is unclear, and the study does not provide information on the prevalence of these variants in actual doping cases. Limitations include the absence of a detailed sample size and potential confounding factors related to the detection methods.
Key findings
- LongR(3)-IGF-I detected at 0.5 ng/mL in urine samples.
- Des(1-3)-IGF-I detected at 0.1 ng/mL in urine samples.
- R(3)-IGF-I detected at 0.2 ng/mL in urine samples.
Limitations
- Not reported sample size.
- Focus on detection methods, not clinical outcomes.
- No p-values or confidence intervals provided.
- Single-method study, limiting generalizability.