Novel protein markers of androgen activity in humans: proteomic study of plasma from young chemically castrated men
Abstract
Background
Reliable biomarkers ofv androgen activity in humans are lacking. The aim of this study was, therefore, to identify new protein markers of biological androgen activity and test their predictive value in relation to low vs. normal testosterone values and some androgen deficiency linked pathologies.
Methods
Blood samples from 30 healthy GnRH-antagonist treated males were collected at three time points: a) before GnRH antagonist administration; b) 3 weeks later, just before testosterone undecanoate injection, and c) after additional 2 weeks. Subsequently they were analysed by mass spectrometry to identify potential protein biomarkers of testosterone activity. Levels of proteins most significantly associated with testosterone fluctuations were further tested in a cohort of 75 hypo- and eugonadal males suffering from infertility. Associations between levels of those markers and cardio-metabolic parameters, bone mineral density as well as androgen receptor CAG repeat lengths, were explored.
Results
Using ROC analysis, 4-hydroxyphenylpyruvate dioxygenase (4HPPD), insulin-like growth factor-binding protein 6 (IGFBP6) and fructose-bisphosphate aldolase (ALDOB), as well as a Multi Marker Algorithm, based on levels of 4HPPD and IGFBP6, were shown to be best predictors of low (< 8 nmol/L) vs. normal (> 12 nmol/L) testosterone. They were also more strongly associated with metabolic syndrome and diabetes than testosterone levels. Levels of ALDOB and 4HPPD levels also showed association with AR CAG-repeat lengths.
Conclusions
We identified potential new protein biomarkers of testosterone action. Further investigations to eluciadate their clinical potential are warranted.
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