Identification by a proteomic approach of a plasma protein as a possible biomarker of illicit dexamethasone treatment in veal calves

Transcriptional Biomarkers and Immunohistochemistry for Detection of Illicit Dexamethasone Administration in Veal Calves

Corticosteroids such as Dexamethasone (DEX) are commonly licensed for therapy in meat animals due to their known pharmacological properties. However, their misuse aimed to achieve anabolic effects is often found by National Residues Control Plans. The setup of a complementary “biomarker based” methods to unveil such illicit practices is encouraged by current European legislation. In this study, the combined use of molecular and histological quantitative techniques was applied on formalin fixed paraffin embedded (FFPE) muscle samples to assess the effects of illicit DEX treatment on veal calves. A PCR array, including 28 transcriptional biomarkers related to DEX exposure, was combined with a histochemical analysis of muscle fiber. An analysis based on unsupervised (PCA) and supervised (PLS-DA and Kohonen’s SOM) methods, was applied in order to define multivariate models able to classify animals suspected of illicit treatment by DEX. According to the conventional univariate approach, a not-significant reduction in type I fibres was recorded in the DEX-treated group, and only 12 out of 28 targeted genes maintained their expected differential expression, confirming the technical limitations of a quantitative analysis on FFPE samples. However, the multivariate models developed highlighted the possibility to establish complementary screening strategies, particularly when based on transcriptional biomarkers characterised by low expression profiles.

Validation of serum paraoxonase/arylesterase 1 (PON1) as a protein marker of illicit dexamethasone treatment in veal calves

The illicit use of dexamethasone and other glucocorticoids for cattle fattening in livestock production has been widely described; evidence for illegal treatments can be obtained by direct or indirect detection. In our previous study, we applied two-dimensional electrophoresis (2DE) to identify plasma protein markers of dexamethasone administration in veal calves. Comparison of 2DE maps obtained from blood samples before and after treatment showed the disappearance of two protein spots identified as serum paraoxonase/arylesterase 1 precursor (PON1). In the present study, we validated PON1 as a marker by analysing a larger number of samples treated with dexamethasone for illicit use. Analysis of samples from experimental treatment with other glucocorticoids, androgens and oestrogens confirmed that their influence on PON1 could be excluded. The specificity of the PON1 protein marker was verified on expected negative field samples to exclude interfering factors. However, there is poor statistical evidence to support a significant association between the outcome of PON1 and the considered variables. The results on field samples were compared with histological examination of the thymus as a biomarker of corticosteroid treatment monitored in the Italian histological plan for the control of growth promoters in animals. Two suspect cases were identified from two Piedmont farms where other animals had tested positive at histological examination. In conclusion, the absence of PON1 in the plasma of veal calves can indirectly reveal illicit dexamethasone treatment in individual animals and so identify suspect farms for further investigation. It is effective in a period ranging from 3 to about 10 days from illicit treatment, covering a time span that goes beyond the limits of official chemical controls and preceding histological controls on the thymus of slaughtered animals. PON1 detection in plasma can be coupled with other tests to identify illegal dexamethasone use on veal calf farms.

Anabolic treatments in bovines: quantification of plasma protein markers of dexamethasone administration

The aim of this study was to profile plasma proteome responses in bulls experimentally treated with dexamethasone at anabolic dosage. Illicit use of active substances in animal husbandry remains a matter of concern in Europe. Corticosteroids are probably one of the most widespread growth promoter family illegally used in beef cattle and veal calves. Testing for corticosteroids relies on detection of drug residues or their metabolites in biological fluids or tissues. Their indirect detection by mapping altered physiological parameters may overcome limits linked to route of administration, dosage, biotransformation and elimination kinetics that can lower residual drug concentration, hampering official controls. A set of 11 proteins proposed in literature as potential markers of anabolic treatments with dexamethasone, was quantified in bovine plasma by targeted proteomics based on liquid chromatography-high resolution tandem mass spectrometry. Among investigated proteins, sex hormone-binding globulin (SHBG), histidine-rich glycoprotein (HRG) and paraoxonase-1 (PON1) were found to be biomarkers of treatment. To investigate further such biomarkers, an additional group of veal calves was experimentally treated with dexamethasone at anabolic. These animals also demonstrated a significant alteration in SHBG, HRG and PON1 concentration, suggesting that quantification of plasma markers have the potential to detect animals illegally exposed to dexamethasone.

Regucalcin expression profiles in veal calf testis: validation of histological and molecular tests to detect sex steroids illicit administration

Background

Sex steroids administration in meat producing animals is forbidden within the EU to preserve consumers’ safety, but continuous monitoring to identify resurgence of their misuse is needed. Among biomarkers related to sex steroids abuse in veal calves the regucalcin (RGN) mRNA perturbations in testis have been described in RNAlater samples. To setup novel diagnostic method, to update current tests available in National Residue Control Plans (NRCPs) and in legal dispute when illicit practices on farm animals are suspected, the reliability of RGN profiling was assessed by histological and molecular techniques.

Methods

Formalin fixed paraffin embedded (FFPE) testis samples, chosen being the most effective preservation strategy adopted by histological NRCPs and allowing easier retrospective analysis if required by legal disputes, were analyzed from veal calves treated with nandrolone, 17β-estradiol and a cocktail of the two hormones. RGN levels were determined by quantitative Real Time PCR and Immunohistochemistry assays. Test performances were assessed and compared by multiple ROC curves.

Results

Both tests resulted sensitive and specific, allowing to enrich, in future field investigation, novel integrated diagnostic protocols needed to unveil sex steroid abuse.

Discussion

Developed RT-qPCR and IHC methods confirmed RGN as a useful and robust biomarker to detect illegal administration of sex steroid hormones in veal calves. The developed methods, successfully applied to ten years old FFPE blocks, could allow both retrospective analysis, when supplementary investigations are requested by authorities, and future implementation of current NRCPs.

TMT-Based Proteomics Profiling of Bovine Liver Underscores Protein Markers of Anabolic Treatments

Illegal use of growth promoter compounds in food production exposes consumers to health risk. Surveillance of such practices is based on direct detection of drugs or related metabolites by HPLC-MS/MS. Screening strategies focusing on indirect biological responses are considered promising tools to improve surveillance. In this study, an untargeted shotgun proteomics approach based on tandem mass tags (TMTs) is carried out to identify proteins altered in bovine liver after different anabolic treatments. Three controlled pharmacological treatments with dexamethasone, a combination of dexamethasone and clenbuterol, or a combination of sexual steroids (trenbolone and estradiol) are analyzed. Untargeted TMT analysis of liver digests by high resolution MS allowed for the relative quantification of proteins. Thanks to partial least squarediscriminant analysis, a set of proteins capable to classify animals treated with dexamethasone alone (11 proteins), or in combination with clenbuterol (13 proteins) are identified. No significant difference is found upon administration of sexual steroids. After relative quantification of candidate markers by parallel reaction monitoring (PRM), two predictive models are trained to validate protein markers. Finally, an independent animal set of control bulls and bulls treated with dexamethasone is analyzed by PRM to further validate a predictive model giving an accuracy of 100%.

Canonical discriminant analysis and meat quality analysis as complementary tools to detect the illicit use of dexamethasone as a growth promoter in Friesian bulls

A screening method based on meat quality parameters and production traits for detecting the effects of illegal administration of dexamethasone in Friesian bulls was assessed. Twenty finishing bulls were divided into an untreated control group (n=8) and two treatment groups receiving dexamethasone orally at dosages of 1.4 (n=6) or 0.7 (n=6)mg per head per day for 60 days. The animals were slaughtered 26days after cessation of treatment. Thirty-six parameters were measured on live animals, carcasses and samples of the longissimus thoracis muscle. The production traits were similar between groups, but there were significant differences in meat quality between treatment groups. The higher dosage of dexamethasone improved meat tenderness, while the lower dosage resulted in more saturated red meat, with increased meat cooking shrinkage and cooking loss. The use of a portable 'electronic nose' as a screening tool was not successful in discriminating between treated and untreated meat. These results indicate that a multivariable approach using canonical discriminant analysis may be a complementary tool to identify meat from animals illegally treated with dexamethasone, based on several parameters (meat flavour, cooking and thawing loss, tenderness, colour and live weight gain), which are part of the normal analysis of meat quality.

Proteomics in food: Quality, safety, microbes, and allergens

Food safety and quality and their associated risks pose a major concern worldwide regarding not only the relative economical losses but also the potential danger to consumer's health. Customer's confidence in the integrity of the food supply could be hampered by inappropriate food safety measures. A lack of measures and reliable assays to evaluate and maintain a good control of food characteristics may affect the food industry economy and shatter consumer confidence. It is imperative to create and to establish fast and reliable analytical methods that allow a good and rapid analysis of food products during the whole food chain. Proteomics can represent a powerful tool to address this issue, due to its proven excellent quantitative and qualitative drawbacks in protein analysis. This review illustrates the applications of proteomics in the past few years in food science focusing on food of animal origin with some brief hints on other types. Aim of this review is to highlight the importance of this science as a valuable tool to assess food quality and safety. Emphasis is also posed in food processing, allergies, and possible contaminants like bacteria, fungi, and other pathogens.