Effects of Selected Phytoestrogens and Their Mixtures on the Function of the Thyroid Hormone and the Aryl Hydrocarbon Receptor

Abstract

Phytoestrogens (PEs) are natural plant components, which can induce biologic responses in vertebrates by mimicking or blocking the actions of natural hormones or influencing the hormone production in the body. This study investigated the effect of different mixtures composed of food-relevant PEs on the thyroid hormone (TH) system assessing the proliferation of the 3,3′,5-triiodi-L-thryonine (T3) dependent rat pituitary GH3 cells using the T-screen assay, and the effect on the aryl hydrocarbon receptor (AhR) transactivation using an AhR-luciferase reporter gene assay. Most tested PEs and their mixtures showed effect on both the TH and AhR system. Single isoflavonoid metabolites and their mixture and coumestrol induced GH3 cell growth and AhR transactivity dose-dependently. Isoflavonoid metabolites elicited an additive effect on the T3-dependent GH3 cell growth, and a synergistic effect on the AhR transactivity. In conclusion, nutrition-relevant PEs, alone and in mixture may possess endocrine-disrupting potential by interfering with TH and AhR functions, 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 Disruptors in Food and Environment: Exposure Routes and Impact on Human No. 2170-05-0006.

We thank the DAN-ED team for scientific support and good collaboration. A special thanks to Christine Nellemann, Anne Marie Vinggaard, and Anne Lykkesfeldt.