Identification of potential gene expression biomarkers for the surveillance of anabolic agents in bovine blood cells

Abstract

In the EU, the use of anabolic steroids in food producing animals has been forbidden since 1988. The routine methods used in practice are based on the detection of hormonal residues. To overcome these routine methods, growth-promoting agents are sometimes administered at concentrations below the detection limit and new anabolic substances are designed. Therefore, new monitoring systems are needed to overcome the misuse of anabolic agents in meat production. In this study, a new monitoring system was applied: the quantification of mRNA gene expression changes by quantitative real time reverse transcription polymerase chain reaction (qRT-PCR). Blood was selected as ideal tissue for biomarker screening. From the literature, it is known that steroid hormones affect mRNA gene expression of the different blood cells, which can easily be taken from the living animal. In an animal trial, 18 Nguni heifers were separated to two groups of nine animals. One group served as untreated control and the other group was treated with a combination of trenbolone acetate plus estradiol for 39 days in order to allow the detection of the effect on mRNA expression in blood at three time points. Candidate genes used for developing a biomarker pattern were chosen by screening the actual literature for anabolic effects on blood cells. It could be demonstrated that the combination of trenbolone acetate plus estradiol significantly influences mRNA expression of the steroid receptors (ER-alpha and GR-alpha), the apoptosis regulator Fas, the proinflammatory interleukins IL-1alpha, IL-1beta and IL-6 and of MHCII, CK, MTPN, RBM5 and Actin-beta. Advanced statistical analysis by Principal Components Analysis (PCA) indicated that these genes represent potential biomarkers for this hormone combination in whole blood.