Metabolism of Zearalenone in the Rumen of Dairy Cows with and without Application of a Zearalenone-Degrading Enzyme.

The mycotoxin zearalenone (ZEN) is a frequent contaminant of animal feed and is well known for its estrogenic effects in animals. Cattle are considered less sensitive to ZEN than pigs. However, ZEN has previously been shown to be converted to the highly estrogenic metabolite α-zearalenol (α-ZEL) in rumen fluid in vitro. Here, we investigate the metabolism of ZEN in the reticulorumen of dairy cows. To this end, rumen-fistulated non-lactating Holstein Friesian cows (n = 4) received a one-time oral dose of ZEN (5 mg ZEN in 500 g concentrate feed) and the concentrations of ZEN and ZEN metabolites were measured in free rumen liquid from three reticulorumen locations (reticulum, ventral sac and dorsal mat layer) during a 34-h period. In all three locations, α-ZEL was the predominant ZEN metabolite and ß-zearalenol (ß-ZEL) was detected in lower concentrations. ZEN, α-ZEL and ß-ZEL were eliminated from the ventral sac and reticulum within 34 h, yet low concentrations of ZEN and α-ZEL were still detected in the dorsal mat 34 h after ZEN administration. In a second step, we investigated the efficacy of the enzyme zearalenone hydrolase ZenA (EC 3.1.1.-, commercial name ZENzyme®, BIOMIN Holding GmbH, Getzersdorf, Austria) to degrade ZEN to the non-estrogenic metabolite hydrolyzed zearalenone (HZEN) in the reticulorumen in vitro and in vivo. ZenA showed a high ZEN-degrading activity in rumen fluid in vitro. When ZenA was added to ZEN-contaminated concentrate fed to rumen-fistulated cows (n = 4), concentrations of ZEN, α-ZEL and ß-ZEL were significantly reduced in all three reticulorumen compartments compared to administration of ZEN-contaminated concentrate without ZenA. Upon ZenA administration, degradation products HZEN and decarboxylated HZEN were detected in the reticulorumen. In conclusion, endogenous metabolization of ZEN in the reticulorumen increases its estrogenic potency due to the formation of α-ZEL. Our results suggest that application of zearalenone hydrolase ZenA as a feed additive may be a promising strategy to counteract estrogenic effects of ZEN in cattle.

Zearalenone and Metabolites in Livers of Turkey Poults and Broiler Chickens Fed with Diets Containing Fusariotoxins.

Zearalenone (ZEN) and metabolites were measured in livers of turkeys and broilers fed a control diet free of mycotoxins, a diet that contained 0.5 mg/kg ZEN (ZEN diet), and a diet that contained 0.5, 5, and 20 mg/kg of ZEN, fumonisins, and deoxynivalenol, respectively (ZENDONFB diet). The feed was individually distributed to male Grade Maker turkeys from the 55th to the 70th day of age and to male Ross chickens from the 1st to the 35th day of age, without any signs of toxicity. Together, the free and conjugated forms of ZEN, α- and ß-zearalenols (ZOLs), zearalanone (ZAN), and α- and ß-zearalanols (ZALs) were measured by UHPLC-MS/MS with [13C18]-ZEN as an internal standard and immunoaffinity clean-up of samples. ZAN and ZALs were not detected. ZEN and ZOLs were mainly found in their conjugated forms. α-ZOL was the most abundant and was found at a mean concentration of 2.23 and 1.56 ng/g in turkeys and chickens, respectively. Consuming the ZENDONFB diet significantly increased the level of total metabolites in the livers of chickens. Furthermore, this increase was more pronounced for the free forms of α-ZOL than for the conjugated forms. An investigation of the presence of ZEN and metabolites in muscle with the methods validated for the liver failed to reveal any traces of these contaminants in this tissue. These results suggest that concomitant dietary exposure to deoxynivalenol (DON) and fumonisins (FB) may alter the metabolism and persistence of ZEN and its metabolites in the liver.

ZEN and the art of breast health maintenance.

Zearalenone (ZEN) is a non-steroidal mycoestrogen that widely contaminates agricultural products. ZEN and its derivatives share similar molecular mechanisms and activity with estrogens and interact with ERα and ERß leading to changes in the reproductive system in both animals and humans. The reduced form of ZEN, α-ZEA ralenol, has been used as an anabolic agent for animals and also proposed as hormonal replacement therapy in postmenopausal women. Furthermore, both zearelanol ZEN and derivatives have been patented as oral contraceptives. ZEN has been widely used in the United States since 1969 to improve fattening rates in cattle by increasing growth rate and feed conversion efficiency. Evidence of human harm from this practice is provided by observations of central precocious puberty. As a result, this practice has been banned by the European Union. As ZEN has been associated with breast enlargement in humans, it has been included in many bust-enhancing dietary supplements but epidemiological evidence is lacking with regard to breast cancer risk. Extensive work with human breast cancer cell lines has shown estrogenic stimulation in those possessing ER but a reduction in DMBA-induced breast cancers in rodents given ZEN. Protein disulfide isomerase provides a molecular biomarker of dietary exposure to ZEN and its derivatives allowing the detection and control of harmful food intake. The interaction of ZEN with anti-estrogens, anticancer agents and antioxidants requires further investigation.