Transcriptomic analysis of skeletal muscle from beef cattle exposed to illicit schedules containing dexamethasone: identification of new candidate biomarkers and their validation using samples from a field monitoring trial

Abstract

Growth promoters (GPs) such as the glucocorticoid dexamethasone (DEX) and the β-adrenergic agonist clenbuterol (CLEN) are still used abusively in beef cattle production. Transcriptomic markers for indirect detection of such GPs have been discussed in either experimentally treated animals or commercial samples separately. In the present study we examine the transcriptomic signature of DEX alone or in combination with CLEN in skeletal muscle of experimentally treated beef cattle, and, furthermore, compare them with previously screened commercial samples from a field-monitoring study, as well as with proteomics data representing the same set of samples. Using DNA microarray technology, transcriptomic profiling was performed on 12 samples representing three groups of animals: DEX (0.75 mg/animal/day, n = 4), a combination of DEX (0.66 mg/animal/day) and CLEN (from 2 to 6 mg/animal/day, n = 4) and a control group (n = 4). Analyses showed the differential expression of 198 and 39 transcripts in DEX and DEX–CLEN groups, respectively. Both groups had no common modulated genes in between, neither with the proteomics data. Sixteen candidate genes were validated via qPCR. They showed high correlation with the corresponding microarray data. Principal component analysis (PCA) on both the qPCR and normalised microarray data resulted in the separation of treated animals from the untreated ones. Interestingly, all the PCA plots grouped the DEX-positive samples (experimental or commercial) apart from each other. In brief, this study provides some interesting glucocorticoid-responsive biomarkers whose expression was contradictory to what is reported in human studies. Additionally, this study points out the transcriptomic signature dissimilarity between commercial and experimentally treated animals.

Keywords:

• cattle
• clenbuterol
• dexamethasone
• microarray
• muscle

Acknowledgements

The authors acknowledge Giancarlo Biancotto (Veterinary and Public Health Institute, Legnaro, Padua, Italy) and Luca Bargelloni (Department of Comparative Biomedicine and Food Science, University of Padua) for providing animal samples (muscles) for analysis.

Additional information

Funding

This work was supported by a grant from the Regione del Veneto (‘New Genomic and Proteomic Approaches for the Screening of GPs Misuse in Beef Cattle’; DGR 2862, 20.12.2012) to C.M. and M.D. Thanks to Fatima Al Fihri Erasmus Mundus Scholarship Program, Action 2 (EMA2), Lot 1, for the full Ph.D. scholarship awarded to R.E.