Zearalenone and its metabolites in urine and breast cancer risk: A case-control study in Tunisia

Highlights

• Zearalenone and its five metabolites were analyzed in a population of Tunisian women.

• The association between risk of breast cancer and concentration of α-ZAL was evaluated.

• The magnitude of associations were estimated by unconditional logistic regression.

• Crude and adjusted odds ratios with 95% confidence intervals were calculated.

• Results suggest a potential role of α-ZAL in the risk of developing breast cancer.

Abstract

Zearalenone (ZON) is a non-steroidal estrogenic mycotoxin produced by Fusarium species. The exposure risk to humans and animals is the consumption of contaminated food and animal feeds. It has been reported that ZON and some of its metabolites promote the development of hormone-dependent tumors. The aim of this case-control study was to estimate exposure to ZON and its five metabolites (α-zearalenol [α-ZOL], β-zearalenol [β-ZOL], α-zearalanol [zeranol, α-ZAL], β-zearalanol [teranol, β-ZAL] and zearalanone [ZAN]) by measuring urinary concentrations of these compounds, and to evaluate the risk of breast cancer related to this exposure. Chemical analyses were carried out by liquid–liquid extraction (LLE) and ultra-high performance liquid chromatography with tandem mass spectrometry detection (UHPLC-MS/MS). Statistical analyses were performed in order to determine the association between exposure to these compounds and the development of breast cancer. Crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by unconditional logistic regression to estimate the magnitude of the associations. The obtained results (adjusted OR = 1.54, 95% CI = 1.10–2.77) suggest a potential role of α-ZAL in the risk of developing breast cancer.

Introduction

Mycotoxins are toxic secondary metabolites produced by a variety of fungal species that contaminate various agricultural commodities either before harvest or under post-harvest conditions. They are a worldwide problem because they may affect human and animal health and cause huge economic losses associated to contaminated foods, feeds and loss of animal productivity. The Food and Agriculture Organization (FAO) of the United Nations has estimated that 25% of the world’s food crops are contaminated by mycotoxins every year (Boutrif and Canet, 1998).

Among mycotoxins, zearalenone (ZON) is of major interest because, despite its low acute toxicity, it has proved to be hepatotoxic, hematotoxic, immunotoxic, genotoxic, teratogenic and carcinogenic to a number of mammalian species (Zinedine et al., 2007). ZON metabolism in humans is poorly understood (Warth et al., 2013). Animal data suggest that ZON biotransformation occurs in the liver and intestinal tissue and results in the formation of five metabolites: α-zearalenol (α-ZOL), β-zearalenol (β-ZOL), α-zearalanol (zeranol, α-ZAL), β-zearalanol (teranol, β-ZAL) and zearalanone (ZAN) (Fig. 1). These metabolites are subsequently conjugated with sulfonic or glucuronic acid and excreted in the urine (Zinedine et al., 2007). Because of its anabolic effect, α-ZAL is produced commercially and used as an animal growth promoter. In this regard, it has been widely used to fatten cattle in the U.S since 1969. However, α-ZAL has been banned in many countries, including Tunisia where it was banned in 1980 (Ben-Youssef et al.).

ZON and its metabolites can be found worldwide in a wide range of cereals including maize, sorghum, wheat, rice, barley and oats (Rashedi et al., 2012, Abia et al., 2013). However, the dietary intake of ZON and its metabolites may also occur through consumption of meat, milk and eggs from animals exposed to these toxins (Chen et al., 2013), or that have been given α-ZAL to promote their growth (Jeong et al., 2010, Zhu et al., 2012).

Recently, ZON and its metabolites have become of great interest because evidence suggests that they may play an important role in increasing the risk of hormone-dependent tumors (Tomaszewski et al., 1998, Withanage et al., 2001). In vitro studies show that these compounds enhance proliferation of estrogen receptor-positive human breast tumor cells, through estrogen-mediated pathways and by activation of gene profiles similar to those activated by natural estradiol (Khosrokhavar et al., 2009, Parveen et al., 2009). Regarding in vivo studies, exposure of female rats to environmentally relevant doses of ZON resulted in long-term changes in mammary gland development, associated with increased risk of mammary tumors (Belli et al., 2010). In addition, serum collected from heifers following one month of α-ZAL implantation stimulated MCF-7 breast cancer cell growth (Ye et al., 2010).

Despite the concerns over the potential health effects of ZON, α-ZAL and its related metabolites in humans, most studies focus on the determination of these compounds in cereals (Ghali et al., 2008, Zaied et al., 2012), feed (Krska et al., 2007) and food (Chen et al., 2013) and few studies have examined their fate in humans (Bandera et al., 2011). In addition, epidemiological studies on the potential association between urinary concentrations of ZON and ZON metabolites and breast cancer are particularly lacking. The aim of this study was therefore to measure urinary concentrations of ZON, α-ZOL, β-ZOL, α-ZAL, β-ZAL and ZAN in a population of women from Tunisia and to evaluate the correlation between concentrations and risk of breast cancer.