Endocrine Abstracts

According to the world Health Organization, about 422 million people worldwide have diabetes mellitus (DM), and this number is growing rapidly. DM, mainly type 2, is associated with insulin resistance, which involves reduced expression of glucose transporter GLUT4 (Slc2a4 gene). It is known that estrogen can modulate glycemic homeostasis and seems to involve changes in the Slc2a4/GLUT4 expression. There has been an increased interest in plant-derived phytoestrogens, which can bind to estrogen receptors (ESR1 and ESR2), mimicking or inhibiting some estrogen effects. It is believed that these compounds have beneficial health properties, acting against various diseases, however, that must be carefully analyzed. Phytoestrogens can have different affinity for ESR1 or ESR2 and can reveal variable estrogen or antiestrogen effects. Little is known about the effect of phytoestrogens upon the GLUT4 expression, and about their possible role in cellular glucose disposal. The present study investigates the effects of some abundant phytoestrogens, isoflavones genistein (G) and daidzein (D), as compared to estradiol (E2), upon the Slc2a4 mRNA and GLUT4 expression (respectively by RT-qPCR and Western blotting), in isolated adipocytes. Differentiated 3T3-L1 cells were cultivated for 24 h with 10 nM of E2, G and D, alone or in combination. Alone, E2, G and D showed a similar increase (by ~50%, P<0.05) in the expression of both Slc2a4 mRNA and GLUT4 protein, as compared to untreated cells. Besides, in combination with E2, both G and D promoted an additional increase (P<0.005) in the Slc2a4 mRNA, which was not accompanied by a similar increase in GLUT4, suggesting the presence of a posttranscriptional regulation. Based on these results, we conclude that phytoestrogens genistein and daidzein can increase Slc2a4/GLUT4 expression as efficiently as estradiol does. These results indicate that, concerning the adipocyte capacity of glucose uptake, the isoflavones studied can effectively substitute estradiol.