Effects of Nutrition Relevant Mixtures of Phytoestrogens on Steroidogenesis, Aromatase, Estrogen, and Androgen Activity

Abstract

Phytoestrogens (PEs) are naturally occurring plant components produced in a large range of plants. They can induce biologic responses in vertebrates by mimicking or modulating the action or production of endogenous hormones. This study examined mixtures of 12 food relevant PEs for effects on steroid hormone production, aromatase activity, estrogenic activity, and for interaction with the androgen receptor. The results show that a mixture of all tested PEs increased estradiol production and decreased testosterone production in H295R human adrenal corticocarcinoma cells, indicating an induced aromatase activity. Furthermore, exposure of the H295R cells to isoflavonoids caused a decrease in testosterone production, and various mixtures of PEs significantly stimulated MCF-7 human breast adenocarcinoma cell growth and induced aromatase activity in JEG-3 choriocarcinoma cells. The estrogenic effect in the MCF7 cells of the isoflavonoid mixture and coumestrol was supported by an observed increase in progesterone receptor protein expression as well as a decreased ERα expression. Overall, the results support that nutrition-relevant concentrations of PEs both alone and in mixtures possess various endocrine disrupting effects, all of which need to be considered when assessing the effects on human health.

ACKNOWLEDGMENTS

This study was supported by the Danish Research Agency in the project DAN-ED: Endocrine disrupters in food and environment: exposure routes and impact on humans no. 2107-05-0006. We are indebted to Morten Andreasen and Birgitte Møller Plesning for excellent technical assistance in the steroid synthesis assay (H295R) and androgen receptor (AR) reporter gene assay, respectively, and to Birgitte Sloth Andersen and Birgit Reiter for technical assistance in the aromatase analyses and the MCF-7 cell proliferation and Western analyses, respectively.

Notes

^a Abbreviations are as follows: PSC, solvent positive control; IC₅₀, inhibitory concentration of 50%; PEs, phytoestrogens. The aromatase activity was measured in human JEG-3 choriocarcinoma cells as described in Materials and Methods. The PSC was cells + substrate: labeled and unlabeled 4-AD (see Methods). In parallel, the 4-AOD was added and used as an aromatase inhibitor control at 10 μ M (100% effective concentration) and 10 nM (IC₅₀). Means and SD are shown for n = 3–6.

*, Significantly different (P < 0.05) from the respective PSC control in the Mann–Whitney test.