Identification of a potential gene expression biomarker signature in bovine liver to detect the abuse of growth promoters.

The misuse of anabolic agents in animal husbandry is a ubiquitous problem. The ban of growth promoters in food producing animals in the European Union is well controlled, but there are still application regimes, such as new designed drugs or hormone cocktails, that are difficult to detect. Therefore, the idea of identifying molecular biomarkers that are based on the physiological effect of treatment has come into focus. In a previous study we identified mRNA biomarker candidates in liver samples that enable the separation of untreated animals from animals treated with a combination of androgens plus estrogens. In the present study those candidates were validated in calves treated with a combination of progesterone plus estradiol or clenbuterol, respectively. Therefore, the candidate genes were quantified in liver samples of those calves via RT-qPCR. Using dynamic principal component analysis (PCA), a signature of 11 genes could be selected. This set of genes enabled the separation of treated and control animals independent of the applied drug. Additional quantification of these genes in a set of control samples from another animal trial resulted in a PCA that also showed a separation of those samples from treated animals. This study showed that gene expression biomarkers have a high potential to enable the detection of physiological changes caused by the application of growth-promoting substances independent of the given drug, but further studies are necessary to broaden the spectrum of anabolic substance groups for which those biomarker candidates can be used.