Investigating the biosynthesis and metabolism of 11β-hydroxyandrostenedione

Abstract

The "rediscovery" 11β-hydroxyandrostenedione (11OHA4) placed the spotlight on this unique adrenal-derived hormone with researchers and clinicians once again focusing on the steroid's presence in endocrine pathology. Little was known about the steroid other than its chemical characterisation and that a mitochondrial cytochrome P450 enzyme catalysed the 11β-hydroxylation of 11OHA4. The fact that neither the biosynthesis nor metabolism of 11OHA4 had been fully characterised presented an ideal opportunity to investigate the metabolic pathways. In addition, methodologies and analytical tools have improved vastly since 11OHA4 was first identified in the 1950s. Cell models, recombinant DNA technology and steroid quantification using liquid chromatography mass spectrometry have greatly facilitated investigations in the field of steroidogenesis. Evident from the structure is that 11OHA4 can be metabolised by hydroxysteroid dehydrogenases and reductases acting on the C4/C5 double bond and on functional moieties at specific carbons on the cyclopentane-perhydro-phenanthrene backbone of the steroid. In this chapter, the biosynthesis and metabolism of 11OHA4 is followed using two strategies that complement each another; (i) human cell models either transiently transfected with recombinant DNA or expressing endogenous steroidogenic enzymes and (ii) steroid identification and quantification using high resolution mass spectrometry. These methodologies have proven invaluable in the determination of 11OHA4's metabolic route. Both strategies are presented with the focus on the accurate identification and quantification of steroids using UHPLC-MS/MS and UPC²-MS/MS. The protocols described in this chapter lay a sound foundation which can aid the researcher and be adapted and implement in future studies.

Keywords: 11-ketotestosterone (11KT); 11β-hydroxyandrosterone (11OHAST); 11β-hydroxyetiocholanolone; Adrenal cytochrome P450; Androgen excess; LC–MS method development and validation; Liquid chromatography–mass spectrometry (LC–MS); Qualifier:quantifier; Steroid extraction; Steroid mass transitions (MRM).