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S Senesi, Pathophysiology Experimental Medicine and public Health, University of Siena, Siena, Italy
P Marcolongo, Pathophysiology Experimental Medicine and public Health, University of Siena, Siena, Italy
I Manini, Department of Neuroscience and Center for Stem Cell Research, University of Siena, Siena, Italy
R Fulceri, Siena, Italy
V Sorrentino, Siena, Italy
M Csala, Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
G Banhegyi, Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
A Benedetti, Pathophysiology Experimental Medicine and public Health, University of Siena, Siena, 53100, Italy

Correspondence: Angelo Benedetti, Email: benedetti{at}unisi.it

Abstract

The reductase activity of 11beta-hydroxysteroid dehydrogenase type 1 plays an important role in the growth and differentiation of adipose tissue via the prereceptorial activation of glucocorticoids. This enzyme colocalizes with hexose-6-phosphate dehydrogenase at the lumenal surface of endoplasmic reticulum membrane, and the latter enzyme provides NADPH to the former, which can thus act as an 11beta-reductase. It was suggested that, during adipogenesis, the increased expression of hexose-6-phosphate dehydrogenase causes a dehydrogenase-to-reductase switch in the activity of 11beta-hydroxysteroid dehydrogenase type 1. However, only the expression of the 11beta-hydroxysteroid dehydrogenase type 1 has been extensively studied, and little is known about the expression of hexose-6-phosphate dehydrogenase. Here we investigated the expression and the activity of hexose-6-phosphate dehydrogenase in the course of the differentiation of human adipose-derived mesenchymal stem cells and murine 3T3-L1 cells. It was found that hexose-6-phosphate dehydrogenase is already present in adipose-derived stem cells and in 3T3-L1 fibroblasts even before the induction of adipogenesis. Moreover, mRNA and protein levels, as well as the microsomal H6PDH activities remained unchanged during the differentiation. At the same time a great induction of 11beta-hydroxysteroid dehydrogenase type 1 was observed in both cell types. The observed constant expression of hexose-6-phosphate dehydrogenase suggests that 11beta-hydroxysteroid dehydrogenase type 1 acts as a reductase throughout the adipogenesis process in human adipose-derived mesenchymal stem cells and murine 3T3-L1 cells.