Abstract

Dehydroepiandrosterone (DHEA) and 3β-hydroxy-5α-androstan-17-one (epiandrosterone, EpiA) are both precursors for 7α- and 7β-hydroxylated metabolites in the human brain. These 7-hydroxylated derivatives were shown to exert anti-glucocorticoid and neuroprotective effects. When these steroids are administered per os to humans, the first organ encountered is the liver, where extensive metabolism takes place. The objective of this work was to assess the cofactor dependence and metabolism of DHEA, EpiA, and their 7-hydroxylated derivatives in S9 fractions of human liver, using a radiolabeled steroid substrate for quantification and gas chromatography-mass spectrometry for identification. The best transformation yields were obtained with NADPH and were larger in female than in male. Results showed that both DHEA and EpiA mainly transformed into their 17β-hydroxylated derivatives, 7- or 16α-hydroxylated metabolites under NAD(P)H conditions, and 5α-androstane-3,17-dione for EpiA under NAD(P)⁺ conditions. In turn, 7α-hydroxy-DHEA and 7β-hydroxy-DHEA were partly transformed into each other via a 7-oxo-DHEA intermediate and were reduced into the 17β-hydroxy derivative, respectively. The same type of transformations occurred for 7α-hydroxy-EpiA and 7β-hydroxy-EpiA, except that no 7-oxo-EpiA intermediate was obtained. These findings determine the presence of enzymes responsible for the 7α- and 16α-hydroxylation in the human liver, the 11β-hydroxysteroid dehydrogenase type 1 responsible for the oxidoreduction of the 7-hydroxylated substrates, and the 17β-hydroxysteroid dehydrogenase responsible for the reduction of 17-oxo-steroids into 17β-hydroxysteroids.