Endocrine Abstracts

The adrenal steroid dehydroepiandrosterone (DHEA) and its sulphate ester, DHEAS have been shown to oppose the effects of glucocorticoids, thereby producing beneficial effects on insulin sensitivity in rodent models of diabetes and obesity and in hypoadrenal patients. Glucocorticoids, key regulators of adipose differentiation and insulin sensitivity, are reactivated locally by 11β-hydroxysteroid dehydrogenase type (11β-HSD1) oxoreductase activity, which increases with adipocyte differentiation. DHEA has recently been shown to inhibit differentiation and 11β-HSD1 oxoreductase activity in murine 3t3-L1 adipocytes, although the underlying mechanism remains elusive. In this study, using a human subcutaneous cell line, Chub-s7, which expresses 11β-HSD1 upon differentiation, we examined the effects of DHEA, DHEAS and the DHEA metabolite androstenediol. RT-PCR analysis revealed the expression of OATP-C and OATP-D, required for the active cross-membrane influx of DHEAS, a prerequisite for its intracellular conversion to DHEA. Enzymatic activity assays demonstrated significant conversion of DHEAS to DHEA and further to androstenediol, consistent with the observed enzyme expression pattern. Preadipocyte proliferation, assessed by tritiated thymidine uptake was significantly inhibited by DHEA (10 μM) (100 μM, 7 days 39% of ctl, P<0.05) and to a lesser extent by androstenediol (100 μM, 7 days 66% of ctl, P<0.05), but not by DHEAS. This inhibitory effect was not reversible by co-incubation with the androgen receptor antagonist flutamide. FACS analysis revealed this inhibition to occur via cell cycle arrest in G1 phase (ctl G1 vs 25 μM G1 P=0.034). DHEA and androstenediol but not DHEAS significantly inhibited preadipocyte differentiation as assessed by markers of early (LPL) and terminal (G3PDH) adipocyte differentiation (LPL day 14 10 μM, DHEA 0.3-fold P<0.05, Δ5diol 0.5-fold P<0.05; G3PDH day 21 10 μM, DHEA 0.25-fold P<0.05, Δ5diol 0.4-fold P<0.05). 11β-HSD1 oxoreductase activity in differentiated adipocytes was significantly inhibited by DHEA (≥10 μM) (10 μM, 20% of ctl, P<0.001). In addition, DHEA significantly increased insulin dependent (1 μM 1.9-fold P<0.05) and independent (1 μM 2.9-fold P<0.05) glucose uptake in a dose dependent manner. These findings demonstrate that DHEA directly opposes glucocorticoid effects in human preadipocytes, which might explain previously documented in vivo anti-adipogenic effects of DHEA.