MON-203 Local Activation of 11-Oxygenated Androgens by AKR1C3 Is the Predominant Source of Androgens in Human Female Adipose Tissue

Abstract

Polycystic ovary syndrome (PCOS) affects 10% of women and is a lifelong metabolic disorder, with increased risk of type 2 diabetes, fatty liver and cardiovascular disease. Androgen excess is an important driver of metabolic risk. Excess androgen activation in adipose tissue from PCOS women, through conversion of androstenedione (A4) to testosterone (T) by the enzyme AKR1C3, has been shown to drive insulin resistance and lipotoxicity, with insulin upregulating AKR1C3 further. Recent work has shown that 11-oxygenated androgens including 11-ketotestosterone (11KT), which binds and activates the androgen receptor with similar potency to T, constitute the majority of circulating androgens in PCOS, and that AKR1C3 can activate 11-ketoandrostenedione (11KA4) to 11KT with even higher efficiency than A4 to T. This raises the possibility that 11KT is more relevant than T in mediating excess androgen effects in PCOS. Here, we examined the contributions of classic and 11-oxygenated androgen pathways to intra-adipose androgen activation and the functional significance of the involved enzymes. To this end, we performed ex vivo primary adipose tissue incubations with corresponding subcutaneous (sc) and omental (om) adipose tissue obtained from eight women undergoing bariatric surgery (age range 32-59 years; BMI range 44-57). Incubations carried out with 100nM A4 and 11KA4, respectively, revealed significantly higher AKR1C3-mediated conversion of 11KA4 to 11KT than conversion of A4 to T, both in sc and om tissue. We observed a significant reduction of both 11KT and T generation after the addition of a selective AKR1C3 inhibitor to the primary tissue incubations. Conversely, co-incubation with a selective HSD11B1 inhibitor significantly enhanced the activation of 11KA4 to 11KT by decreasing the inactivation of 11KA4 to 11β-hydroxyandrostenedione; HSD11B1 inhibition had no impact on classic androgen pathway activation of A4 to T. Supernatants and tissues are currently undergoing investigation by mass spectrometry and NMR spectroscopy to determine the differential impact of T and 11KT generation on the adipose-specific global metabolome and lipidome. We conclude that local activation of 11-oxygenated androgens is the predominant source of androgen exposure in adipose tissue. AKR1C3 inhibition presents a promising tool to reduce androgen burden in PCOS, with effective reduction in both classic and 11-oxygenated pathway androgen biosynthesis in adipose tissue.