Serum Vitamin D Metabolites and CXCL10 Concentrations Associate With Survival in Dogs With Immune Mediated Disease

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.

The effects of age, sex, breed, diet, reproductive status and housing condition on the amounts of 25(OH) vitamin D in the serum of healthy dogs: Reference values

BACKGROUND

Optimal amount of vitamin D for the proper functioning of the immune system is different from the required vitamin D amount for bones to prevent rickets. However, reports on vitamin D reference values in dogs are minimal, and there is still not enough information regarding the relationship between vitamin D and various variables such as disease, age, breed, diet type, and so on, as well as its relationship with haematological and serum biochemical parameters.

OBGECTIVES

The present study aimed to determine reference values of 25(OH) Vit D in dogs and its concentration in different groups, categorized based on age, sex, breed, housing conditions, and diet, as well as 25(OH) Vit D relationship with hematology and serum biochemistry parameters.

METHODS

In this study, 90 healthy dogs were selected to determine the reference value of 25 (OH) Vit D of serum after evaluating of their haematological and biochemical parameters to assess their general health. Dogs were divided into different groups according to above-mentioned variables. Serum 25 (OH) Vit D was subsequently measured by the ELISA method.

RESULTS

The median concentration of 25 (OH) Vit D was 52.50 ng/ml with minimum and maximum amounts of 14.00 and 155.57 ng/ml, respectively. No significant difference was observed between 25 (OH) Vit D levels in the studied dogs regarding their different age, sex, breed, diet, housing condition, and reproductive status. Serum 25 (OH) Vit D concentration is directly correlated with the number of band neutrophils (p < 0.05). We also witnessed indirect correlations between serum 25 (OH) Vit D levels and the number of blood eosinophils and serum glucose (p < 0.05).

CONCLUSION

In the present study age, sex, breed, housing condition and age had no significant effects on the amounts of 25(OH) vitamin D. According to correlations of vitamin D with MCH, band and eosinophil numbers and glucose, vitamin D may have a role in erythropoiesis and leukocytes response and also in energy metabolism in dog.

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.

Rapid improvement in vitamin D status with dietary 25-hydroxycholecalciferol in vitamin D insufficient dogs

Vitamin D insufficiency is associated with various disease processes. We determined whether consumption of a diet supplemented with HyD^®, a 25-hydroxycholecalciferol (25(OH)D₃) source, would safely increase plasma 25(OH)D₃ concentrations in Golden Retrievers with low vitamin D status. We hypothesised that dietary supplementation with HyD^® would rapidly increase and sustain plasma 25(OH)D₃ levels in healthy Golden Retrievers with low vitamin D status compared with supplementation with vitamin D₃. Of fifty-seven privately owned dogs recruited with written owner consent, eighteen dogs with low vitamin D status were identified and sorted between two groups to have similar initial plasma 25(OH)D₃ concentrations, sex distributions, ages and body weights. Dogs of each group were fed a dry dog food supplemented with either 16 μg/kg of 25(OH)D₃ as HyD^® (n 10) or 81 μg/kg of cholecalciferol (D₃) (n 8) for 4 months. Plasma 25(OH)D₃ concentrations were determined monthly. A significant time effect (P < 0⋅001) and time by group interaction (P = 0⋅0045) were found for monthly determined plasma 25(OH)D₃ concentrations. Dogs fed the HyD^®-supplemented diet experienced a 40⋅5 % rise in plasma 25(OH)D₃ values after 1 month (P < 0⋅001) and no change thereafter. Plasma 25(OH)D₃ values of dogs supplemented with vitamin D₃ did not increase (P > 0⋅05) and were less than values of dogs supplemented with HyD^® (P = 0⋅044). With few exceptions, average haematologic, biochemical and urinalyses results remained within the reference range for both groups. Dietary supplementation with HyD^® is sufficient to safely increase and sustain plasma 25(OH)D₃ levels in healthy dogs.

Serum 25-hydroxyvitamin D concentration and infectious respiratory disease complex in shelter dogs

Background

Hypovitaminosis D is a risk factor for the development of respiratory infections in humans and repletion can be protective.

Objectives

Determine if serum 25‐hydroxyvitamin (OH)D concentrations are lower in shelter dogs and if 25(OH)D concentrations are associated with clinical signs of canine infectious respiratory disease complex (CIRDC) or with time in the shelter.

Animals

One hundred forty‐six shelter dogs (clinically ill n = 36, apparently healthy n = 110) and 23 nonshelter control dogs.

Methods

Prospective cohort study. Shelter dogs were grouped as clinically ill or apparently healthy based on the presence or absence, respectively, of clinical signs associated with CIRDC. Serum 25(OH)D concentrations were measured with a competitive chemiluminesence immunoassay. Nucleic acids of agents associated with the CIRDC were amplified by polymerase chain reaction assays.

Results

The concentration of 25(OH)D was 7.3 ng/mL (4.5‐9.9, 95% confidence interval [CI]) lower in dogs with signs of CIRDC than apparently healthy shelter dogs (t(142) = 2.0, P = .04). Dogs positive for DNA of canine herpesvirus (CHV)‐1 had serum 25(OH)D concentrations 14.9 ng/mL (−3.7 to 29.6, 95% CI) lower than dogs that were negative (t(137) = 2.0, P = .04). Serum 25(OH)D concentrations in shelter dogs were not different from control dogs (t(45) = −1.4, P = .17). Serum 25(OH)D concentration was not associated with duration of time in the shelter (F(1, 140) = 1.7, P = .2, R² = 0.01).

Conclusion and Clinical Importance

Vitamin D could have a role in acute respiratory tract infections in shelter dogs.

Vitamin D Binding Protein (VDBP) and Its Gene Polymorphisms-The Risk of Malignant Tumors and Other Diseases

Vitamin D is an important component of the endocrine system that controls calcium homeostasis and bone mineralization. Because of the very short half-life of free serum vitamin D it is stabilized and transported to target tissues by being bound to the vitamin D binding protein (VDBP). The most common polymorphisms: rs4588 and rs7041 in the vitamin D binding protein gene may correlate with differences in vitamin D status in the serum. This review presents data that relate to the presence of genetic variants in the VDBP gene in correlation with certain diseases, mostly concerning cancers (breast, prostate, pancreatic, lung, colorectal, basal cell carcinoma cancer and cutaneous melanoma) or other related diseases (thyroid autoimmunity disorders, obesity, diabetes mellitus, bone metabolism, rheumatoid arthritis, ankylosing spondylitis, asthma, chronic obstructive pulmonary disease, tuberculosis and coronary artery diseases).

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.

Development and application of a LC-MS/MS assay for simultaneous analysis of 25-hydroxyvitamin-D and 3-epi-25-hydroxyvitamin-D metabolites in canine serum

Hypovitaminosis D and hypervitaminosis D are well recognised disorders in dogs. Hypovitaminosis D can occur following consumption of a diet inadequately supplemented with vitamin D or as a sequelae of severe intestinal disease. Hypervitaminosis D may occur as a result of consuming proprietary dog foods over-supplemented with vitamin D or through ingestion of vitamin D containing medicinal products or rodenticides. Consequently, there is a clear need to establish a methodology that can accurately quantify vitamin D metabolites across a broad dynamic range in dogs. The existence of C3-epimers of vitamin D metabolites has yet to be elucidated in dogs, yet are known to interfere with the analysis of vitamin D and have unknown biological activity in other species. Here, we describe the development and validation of a sensitive, specific and robust analytical liquid chromatography tandem mass spectrometry (LC-MS/MS) assay capable of separating and accurately measuring 25-hydroxyvitamin-D_2/3 (25(OH)D_2/3) and 3-epi-25-hydroxyvitamin-D_2/3 (3-epi-25(OH)D_2/3). We describe a simplified workflow utilising supported liquid extraction (SLE) without derivatization that provides good linearity (mean r > 0.996) and accuracy across a broad dynamic range of 4-500 nmol/L for D₃ metabolites and 7.8-500 nmol/L for D₂ metabolites. Upon application of this assay to 117 canine serum samples, 25(OH)D₃ was detectable in all samples with a median concentration of 82.1 nmol/L (inter-quartile range (IQR) 59.7-101.8 nmol/L). 3-epi-25(OH)D₃ could be detected in 87.2 % of the study population, with a median concentration of 5.2 nmol/L (2.4-8.1 nmol/L). However, 3-epi-25(OH)D₃ was quantified below the LLOQ in 40.2 % of these samples. 3-epi-25(OH)D₃ contributed on average 6.3 % to 25(OH)D₃ status (contribution ranges from 0 to 23.8%) and a positive correlation was detected between 25(OH)D₃ and 3-epi-25(OH)D₃ concentrations. Free 25(OH)D was also measured using an immunoassay with a median concentration of 15.2 pmol/L (12.5-23.2 pmol/L), and this metabolite was also positively correlated to both 3-epi-25(OH)D₃ and 25(OH)D₃ concentrations. D₂ metabolites were not detected in canine serum as expected. Vitamin D metabolite concentrations were variable between individuals, and research into the causes of this variation should include factors such as breed, age, sex and neuter status to determine the impact of genetic and hormonal factors. Given the clinical importance of vitamin D in dogs, and the immense potential for utilising this species as a model for human disease, further elucidation of the vitamin D pathway in this species would provide immense clinical and research benefit.