Characterization and identification of a C-terminal amidated mechano growth factor (MGF) analogue in black market products.
BACKGROUND
Mechano growth factor (MGF) is a splice variant of insulin-like growth factor that possesses anabolic properties and has not yet been approved for therapeutic use. Nevertheless, it is readily available on the black market. Although the World Anti-Doping Agency (WADA) has banned the use of MGF in sports, no routinely performed methods have been reported for its detection. In this work, two preparations from the black market containing an unknown MGF analogue were characterized.


METHODS
Mass spectrometry characterizations of unknown preparations and a reference human MGF were performed on an Orbitrap and a triple quadrupole mass spectrometers after separation by liquid chromatography. High accuracy measurements allowed protein identification from full scan MS data, and low-resolution full scan MS/MS provided further information on fragmentation.


RESULTS
HCD scans of the analytes showed the presence of common b series product ions in the black market preparations and the human MGF reference standard, but all the y series ions starting from (y(1))(+) exhibited a difference of 1 m/z unit in nominal mass. This difference was demonstrated to be due to a C-terminal amidation of MGF. High-resolution data demonstrated that the black market products were both C-terminal amidated analogues of human MGF. In addition, low-resolution MS/MS characterization revealed a potentially diagnostic transition (m/z 717.8 → 431.1) for the discrimination of C-amidated MGF from the endogenous form.


CONCLUSIONS
Qualitative identification of a MGF C-terminal amidated analogue in two black market products was successfully achieved. This report demonstrates that illegal MGF preparations are commercially available for use as doping agent in sports.
Doping Control Laboratory, Ghent University (UGent), Technologiepark 30-B, 9052, Zwijnaarde, Belgium. simone.esposito@ugent.be
Simone
S
Esposito
Koen
K
Deventer
Peter
P
Van Eenoo
D000577:Amides / Q000737:chemistry; D000595:Amino Acid Sequence; D002853:Chromatography, Liquid / Q000379:methods; D006801:Humans; D013287:Illicit Drugs / Q000737:chemistry*; D007334:Insulin-Like Growth Factor I / Q000737:chemistry* / Q000302:isolation & purification; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D015813:Substance Abuse Detection / Q000379:methods
D000577:Amides; D013287:Illicit Drugs; D007334:Insulin-Like Growth Factor I