Determination of prednisolone metabolites in beef cattle

Anabolic steroids in livestock production: Background and implications for chemical food safety

The use of steroids in livestock animals is a source of concern for consumers because of the risks associated with the presence of their residues in foodstuffs of animal origin. Technological advances such as mass spectrometry have made it possible to play a fundamental role in controlling such practices, firstly for the discovery of marker metabolites but also for the monitoring of these compounds under the regulatory framework. Current control strategies rely on the monitoring of either the parent drug or its metabolites in various matrices of interest. As some of these steroids also have an endogenous status specific strategies have to be applied for control purposes. This review aims to provide a comprehensive and up-to-date knowledge of analytical strategies, whether targeted or non-targeted, and whether they focus on markers of exposure or effect in the specific context of chemical food safety regarding the use of anabolic steroids in livestock. The role of new approaches in data acquisition (e.g. ion mobility), processing and analysis, (e.g. molecular networking), is also discussed.

Sample Preparation and Analytical Methods for Steroid Hormones in Environmental and Food Samples: An Update Since 2012

Steroid hormones (SHs) have been widely used over the past few decades as both human and veterinary drugs to prevent or treat infectious diseases and anti-inflammatory benefits in clinical. Unfortunately, their residues in foodstuffs and environmental samples can produce adverse effects on human and animal life such as disrupting the endocrine system. For these reasons, sensitive, simple and efficient methods have been developed for the determination of these compounds in various matrices. This critical review summarized the articles published in the period from 2012 to 2019 and can be used to help researchers to understand development of the sample pretreatment protocols and analytical methods used to detect SHs. The developed extraction and purification techniques used for steroids in different samples, such as cloud point extraction, solid phase extraction based on different novel materials, microextraction methods, QuEChERS and other methods are summarized and discussed. Analytical methods used to quantify these compounds, such as different chromatography methods, electrochemical methods, as well as other methods, are illustrated and compared. We focused on the latest advances in SHs pretreatment, and the application of new technologies in SHs analysis.

Effects of truck transportation and slaughtering on the occurrence of prednisolone and its metabolites in cow urine, liver, and adrenal glands

Background

The recognition of illegal administration of synthetic corticosteroids in animal husbandry has been recently challenged by the case of prednisolone, whose occasional presence in the urine of bovines under strong stressful conditions was attributed to endogenous biosynthesis, not to exogenous administration. The study of the natural stress sources possibly inducing endogenous prednisolone production represents a stimulating investigation subject. The biochemical effects of transportation and slaughtering were verified in untreated cows by studying the possible occurrence of prednisolone and its metabolites in urine, liver and adrenal glands, and the cortisol/cortisone quantification.

Results

Cortisol, cortisone, prednisolone and its metabolites were measured in urine, collected at farm under natural micturition and then at the slaughterhouse. The study was performed on 15 untreated cows reared in different farms at the end of their productive cycle. 2–3 days after the first urine collection, the animals were transported by trucks to the abattoir, slaughtered, and subjected to a second urine sampling from the bladder. Specimens of liver and adrenal gland were also collected and analysed by means of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) validated method. The stressful conditions of transportation and slaughtering proved to increase considerably the urinary levels of cortisol and cortisone as compared to those collected at farm. Prednisolone was detected in the urine collected at the slaughterhouse of two cows only, at a concentration level (≈0.6 μg L^− 1) largely below the official cut off (5.0 μg L^− 1) established to avoid false non-compliances. These two animals exhibited the highest urinary cortisol levels of the series. Prednisolone and prednisone were also detected in the adrenal glands of a different cow. Prednisolone metabolites were not detected in any urine, liver, and adrenal gland sample.

Conclusion

Within the constraints of the condition adopted, this study confirms the sporadic presence of prednisolone traces (2 samples out of 15) and the consistently increased concentration of cortisone and cortisol in the urines collected from cows subjected to truck transportation and subsequent slaughtering. No prednisolone metabolites were detected in any liver and adrenal gland samples, nor in urine specimens, unlike what was previously reported for cows artificially stressed by pharmacological treatment.

Pharmacokinetic and urinary profiling reveals the prednisolone/cortisol ratio as a valid biomarker for prednisolone administration

BACKGROUND

In Europe, synthetic corticosteroids are not allowed in animal breeding for growth-promoting purposes. Nevertheless, a high prevalence of non-compliant urine samples was recently reported for prednisolone, however, without any indication of unauthorized use. Within this context, 20β-dihydroprednisolone and the prednisolone/cortisol ratio have been suggested as potential tools to discriminate between exogenous and endogenous urinary prednisolone. In this study, the validity of these strategies was verified by investigating the plasma pharmacokinetic and urinary excretion profiles of relevant glucocorticoids in bovines, subjected to exogenous prednisolone treatment or tetracosactide hexaacetate administration to induce endogenous prednisolone formation. Bovine urine and plasma samples were analysed by liquid chromatography and mass spectrometry.

RESULTS

Based on the plasma pharmacokinetics and urinary profiles, 20β-dihydroprednisolone was confirmed as the main prednisolone-derived metabolite, being detected in the biological fluids of all 12 bovines (plasma AUC0-inf of 121 h μg L-1 and urinary concentration > 0.695 μg L-1). However, this metabolite enclosed no potential as discriminative marker as no significant concentration differences were observed upon exogenous prednisolone treatment or tetracosactide hexaacetate administration under all experimental conditions. As a second marker tool, the prednisolone/cortisol ratios were assessed along the various treatments, taking into account that endogenous prednisolone formation involves the hypothalamic-pituitary-adrenal axis and is associated with an increased cortisol secretion. Significantly lower ratios were observed in case of endogenous prednisolone formation (i.e. ratios ranging from 0.00379 to 0.129) compared to the exogenous prednisolone treatment (i.e. ratios ranging from 0.0603 to 36.9). On the basis of these findings, a discriminative threshold of 0.260 was proposed, which allowed classification of urine samples according to prednisolone origin with a sensitivity of 94.2% and specificity of 99.0%.

CONCLUSION

The prednisolone/cortisol ratio was affirmed as an expedient strategy to discriminate between endogenous and exogenous prednisolone in urine. Although the suggested threshold value was associated with high specificity and sensitivity, a large-scale study with varying experimental conditions is designated to optimize this value.

Profile of the urinary excretion of prednisolone and its metabolites in finishing bulls and cows treated with a therapeutic schedule

BACKGROUND

Prednisolone was one of the first glucocorticoids to be synthesised, but it is still widely applied to cattle. Illegal uses of prednisolone include its uses for masking a number of diseases before animal sale and, at lower dosages for extended periods of time, for the improvement of feed efficiency and carcass characteristics. Since occasional presence of prednisolone has been detected at trace level in urine samples from untreated cattle, the Italian Ministry of Health introduced a provisional limit of 5 ng/mL to avoid false non-compliances. However, this limit proved ineffective in disclosing prednisolone misuse as a growth-promoter. In the present study, prednisolone acetate was administered to finishing bulls and cows according to a therapeutic protocol (2 × 0.4-0.5 mg/kg bw i.m. at 48 h interval) to further verify the practical impact of this cut-off limit and develop sound strategies to distinguish between exogenous administration and endogenous production. Urinary prednisolone, prednisone, 20β-dihydroprednisolone, 20α-dihydroprednisolone, 20β-dihydroprednisone, 6β-hydroxyprednisolone, cortisol, and cortisone were determined using a validated LC/MS-MS method.

RESULTS

The urinary excretion profile showed the simultaneous presence of prednisolone, 20β-dihydroprednisolone, and prednisone, the latter at lower concentrations, up to 33 days after the first dosing. Higher analyte levels were detected in bulls even after correction for dilution in the urine. Prednisolone concentrations below 5 ng/ml were determined in half of the samples collected at 19 days, and in all the samples obtained 26 and 33 days after the first administration. No measurable concentrations of prednisolone or its metabolites were found in the samples collected before the treatment, while cortisol and cortisone levels lower than the respective LOQs were observed upon treatment.

CONCLUSIONS

The present study confirms the criticism of the coarse quantitative approach currently adopted to ascertain illegal prednisolone administration in cattle. As previously shown for growth-promoting treatments of meat cattle, the simultaneous determination of urinary prednisolone, prednisone, 20β-dihydroprednisolone, along with cortisol and cortisone, may represent a more reliable approach to confirm the exogenous origin of prednisolone. Such a strategy would facilitate unequivocal detection of animals treated with prednisolone acetate using a therapeutical protocol, even 3 to 4 weeks after the treatment.