Assessment of endogenous 25-hydroxyvitamin D serum concentrations by liquid chromatography-tandem mass spectrometry in various animal species

Serum 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D are decreased in dogs with sinonasal aspergillosis

Canine sinonasal aspergillosis (SNA) is a poorly understood disease and remains a challenge to treat. Hypovitaminosis D is associated with many infectious diseases in humans and Vitamin D (VitD) deficiency in experimental mice decreases resistance to Aspergillus fumigatus. The objective of this study was to determine whether dogs with SNA have different VitD metabolite concentrations compared to healthy dogs (HD) and dogs with other nasal conditions and if those concentrations change after cure for SNA dogs. Twenty-two dogs with SNA, 12 HD, 9 dogs with lymphoplasmacytic rhinitis (LPR) and 10 dogs with nasal neoplasia (NN) were included. Serum 25-hydroxyvitamin D2 (25(OH)D2), 25-hydroxyvitamin D3 (25(OH)D3), 24,25-dihydroxyvitamin D3 (24,25(OH)2D3), 3-epimer-25-hydroxyvitamin D3 (3-epi-25(OH)D3) concentrations were measured by a certified liquid chromatography tandem mass spectrometry method at time of diagnosis or revisit. Twelve SNA dogs were available for serial blood collection until cure. Serum 25(OH)D and 24,25(OH)2D3 were lower in dogs with SNA (mean ± standard deviation; 23 ng/ml ± 7.3 and 10.2 ng/ml ± 4.2, respectively) than in HD (34.1 ng/ml ± 7.5; P = 0.007 and 18.2 ng/ml ± 5.4; P = 0.002) while there was no difference among the other groups. Cured SNA dogs had higher serum 25(OH)D concentrations (27.7 ng/ml ± 9.4) compared to before treatment (23.1 ng/ml ± 7.7; P = 0.0002). These results further support the rationale that VitD may play a role in the complex SNA pathophysiology. Whether lower VitD status contributes to the development of the disease or is a consequence of it is unknown.

A Novel UHPLC-MS/MS Method for the Measurement of 25-Hydroxyvitamin D3 in Canine Serum and Its Application to Healthy Dogs

Several studies have shown the importance of vitamin D3 supplementation in small animals. In dogs, a low vitamin D3 status is associated not only with bone metabolism but also with different kinds of disorders, such as congestive heart failure, gastrointestinal diseases, chronic kidney diseases, and some types of cancer. However, it is crucial to maintain balance and monitor the introduction of this essential nutrient through the diet because over-supplementation can result in toxicity. Due to the clinical importance of assessing the vitamin D3 status in small animal patients, a quick, simple, and highly performing analytical method for its measurement is needed. In this study, we describe the development of a novel liquid chromatography-tandem mass spectrometry method for 25-hydroxyvitamin D3 quantification in canine serum. The approach was successfully validated following current European guidelines, proving excellent linearity (R2 always ≥0.996), accuracy (always within ±13%) and precision (always <10%). The application of the validated approach to samples collected from 40 healthy dogs made possible the definition of a reliable reference interval for 25-hydroxyvitamin D3, the main biomarker of vitamin D3. In addition, variations below 5% in the results obtained quantifying the same samples using a water-based calibration curve demonstrated that a surrogate matrix may be used without affecting data accuracy. Thanks to its simplicity, the proposed technique represents a useful tool for supporting clinical routine and investigating correlations between serum concentrations of this metabolite and multiple diseases. Additionally, it could enable the monitoring of supplementation in small animal patients in veterinary clinical practice.

Vitamin D metabolism and disorders in dogs and cats

Vitamin D plays an important role in regulating calcium metabolism and in the development and maintenance of skeletal health of companion animals. There is also a growing interest in understanding the role vitamin D plays in non-skeletal health in both human and veterinary patients. This review provides an update of our current understanding of vitamin D biology in dogs and cats and gives an overview of how vitamin D metabolism can be assessed in companion animals. Congenital and acquired vitamin D disorders are then summarised before the review concludes with a summary of recent studies which have explored the role of vitamin D in the development and outcomes of non-skeletal diseases of dogs and cats.

Vitamin D Metabolism and Profiling in Veterinary Species

The demand for vitamin D analysis in veterinary species is increasing with the growing knowledge of the extra-skeletal role vitamin D plays in health and disease. The circulating 25-hydroxyvitamin-D (25(OH)D) metabolite is used to assess vitamin D status, and the benefits of analysing other metabolites in the complex vitamin D pathway are being discovered in humans. Profiling of the vitamin D pathway by liquid chromatography tandem mass spectrometry (LC-MS/MS) facilitates simultaneous analysis of multiple metabolites in a single sample and over wide dynamic ranges, and this method is now considered the gold-standard for quantifying vitamin D metabolites. However, very few studies report using LC-MS/MS for the analysis of vitamin D metabolites in veterinary species. Given the complexity of the vitamin D pathway and the similarities in the roles of vitamin D in health and disease between humans and companion animals, there is a clear need to establish a comprehensive, reliable method for veterinary analysis that is comparable to that used in human clinical practice. In this review, we highlight the differences in vitamin D metabolism between veterinary species and the benefits of measuring vitamin D metabolites beyond 25(OH)D. Finally, we discuss the analytical challenges in profiling vitamin D in veterinary species with a focus on LC-MS/MS methods.

The Validation of Quantitative Mass Spectrometry Assays for Clinical Chemistry Assessments in Animal Models

Mass spectrometry (MS) has become a key platform in the clinical pathology laboratory and is being used more frequently for clinical pathology assessments in preclinical species for drug development studies. MS assays are being utilized for some traditional clinical pathology end points as well as novel biomarker analyses. For effective deployment in drug development toxicology studies, assays must be validated for use, and these validations are not very different from other bioanalytical platforms commonly found in the clinical pathology laboratory. Validations for MS assays include accuracy and precision assessments, analyte stability evaluations, carryover determinations, and recovery measures. The MS platform does present some unique challenges that should be considered, including ion suppression and availability of reference standards with MS data. Understanding the caveats of the MS platform is important for thorough validations and effective deployment.