Inhibition of the glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 drives concurrent 11-oxygenated androgen excess

Aldo-keto reductase 1C3 (AKR1C3) is a key enzyme in the activation of both classic and 11-oxygenated androgens. In adipose tissue, AKR1C3 is co-expressed with 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), which catalyzes not only the local activation of glucocorticoids but also the inactivation of 11-oxygenated androgens, and thus has the potential to counteract AKR1C3. Using a combination of in vitro assays and in silico modeling we show that HSD11B1 attenuates the biosynthesis of the potent 11-oxygenated androgen, 11-ketotestosterone (11KT), by AKR1C3. Employing ex vivo incubations of human female adipose tissue samples we show that inhibition of HSD11B1 results in the increased peripheral biosynthesis of 11KT. Moreover, circulating 11KT increased 2-3 fold in individuals with type 2 diabetes after receiving the selective oral HSD11B1 inhibitor AZD4017 for 35 days, thus confirming that HSD11B1 inhibition results in systemic increases in 11KT concentrations. Our findings show that HSD11B1 protects against excess 11KT production by adipose tissue, a finding of particular significance when considering the evidence for adverse metabolic effects of androgens in women. Therefore, when targeting glucocorticoid activation by HSD11B1 inhibitor treatment in women, the consequently increased generation of 11KT may offset beneficial effects of decreased glucocorticoid activation.

The glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 catalyzes the activation of testosterone

Testosterone biosynthesis from its precursor androstenedione is thought to be exclusively catalysed by the 17β-hydroxysteroid dehydrogenases-HSD17B3 in testes, and AKR1C3 in the ovary, adrenal and peripheral tissues. Here we show for the first time that the glucocorticoid activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1) can also catalyse the 17β-reduction of androstenedione to testosterone, using a combination of in vitro enzyme kinetic assays, mathematical modelling, and molecular docking analysis. Furthermore, we show that co-expression of HSD11B1 and AKR1C3 increases testosterone production several-fold compared to the rate observed with AKR1C3 only, and that HSD11B1 is likely to contribute significantly to testosterone production in peripheral tissues.