Investigation of the effects of zearalenone and its metabolites in the genes related to energy metabolism in vitro: relation with the epigenetic alterations

Zearalenone (ZEA), produced by various Fusarium species, is a non-steroidal estrogenic mycotoxin. It contaminates cereals such as corn, wheat, oat and soybean and water, therefore it has negative effects on human health. In doctorate thesis, the effects of ZEA and its metabolite α-ZOL on epigenetic modifications and metabolic pathways have been investigated in HepG2 cells in order to elucidate the possible relationship between metabolic dysfunctions. According to the MTT and NRU tests, the IC50 values were determined as 143.35 and 60.45 for ZEA and 111.42 and 35.73 µM for α-ZOL, respectively. At the concentrations of 1-50 µM of ZEA and α-ZOL exposures for 24 h were significantly increased cell proliferation by BrdU assay in the rates of 7.2-41.71% for ZEA, 11.78-44.33% for α-ZOL, respectively, compared to the control. 50 µM of ZEA and α-ZOL exposure significantly increased levels of ROS generation in the rates of 48.1% and 49.6%, respectively, compared to the control. ZEA caused an increase in global DNA methylation levels at 1.46 and 2.54 fold after 10 and 50 µM of ZEA exposure and at 1.53-1.58 fold after 1-50 µM α-ZOL exposure. 1-50 µM of ZEA and α-ZOL exposure caused alterations in PPARɣ expressiom and promoter DNA methylation significantly. Besides, 1-50 µM of ZEA and α-ZOL exposure showed significant alterations in the expression levels of nuclear receptor genes (AhR, LXRα, PPARα, PPARγ), carbohydrate-lipid metabolism related genes (L-fabp, LDLR, GAPDH, Glut2, Igf-1, Akt1, HK2), and oxidative stress genes (HO1, Hsp70, Nrf2). In addition, 1-50 µM of ZEA and α-ZOL exposure resulted in significant changes in global histone modifications (H3K27me, H3K9me3, H3K9ac) by western blot technique. It is expected that results from this thesis will contribute to better understanding of key molecular events in the toxicity of endocrine disrupting chemicals for risk assessment process. Key Words: Zearalenone; α-zearalenol; epigenetic mechanisms; nuclear receptor genes; carbohydrate and lipid metabolism; oxidative damage.