Differential estrogenic 17β-hydroxysteroid dehydrogenase activity and type 12 17β-hydroxysteroid dehydrogenase expression levels in preadipocytes and differentiated adipocytes

Estradiol (E2) is produced locally in adipose tissue and could play an important role in fat distribution and accumulation, especially in women. It is well recognized that aromatase is expressed in adipose tissue: however the identity of its estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) partner is not identified. To gain a better knowledge about the enzyme responsible for the conversion of estrone into estradiol, we determined the activity and expression levels of known estrogenic 17 beta-HSDs, namely types 1, 7 and 12 17 beta-HSD in preadipocytes before and after differentiation into mature adipocytes using an adipogenic media. Estrogenic 17 beta-HSD activity was assessed using [C-14]-labelled estrone, while mRNA expression levels of types 1, 7 and 12 17 beta-HSD were quantified using real-time PCR and protein expression levels of type 12 17 beta-HSD was determined using immunoblot analysis. The data indicate that there is a low conversion of El into E2 in preadipocytes; however this activity is increased similar to 5-fold (p < 0.0001) in differentiated adipocytes. The increased estrogenic 17 beta-HSD activity is consistent with the increase in protein expression levels of 17 beta-HSD12. (C) 2009 Elsevier Ltd. All rights reserved.