Vitamin D Receptor Expression in Dogs

Collaborative Metabolism: Gut Microbes Play a Key Role in Canine and Feline Bile Acid Metabolism

Bile acids, produced by the liver and secreted into the gastrointestinal tract, are dynamic molecules capable of impacting the overall health of dogs and cats in many contexts. Importantly, the gut microbiota metabolizes host primary bile acids into chemically distinct secondary bile acids. This review explores the emergence of new literature connecting microbial-derived bile acid metabolism to canine and feline health and disease. Moreover, this review highlights multi-omic methodologies for translational research as an area for continued growth in veterinary medicine aimed at accelerating microbiome science and medicine as it pertains to bile acid metabolism in dogs and cats.

Expression of vitamin D receptor, CYP24A1, and CYP27B1 in normal and inflamed canine pancreases

Vitamin D plays a role in anti-inflammatory processes, and the alteration of its metabolism is associated with the inflammatory processes of pancreatitis. This study was performed to evaluate the expression of the vitamin D receptor (VDR) and the two major enzymes that regulate vitamin D metabolism, 1α-hydroxylase (CYP27B1) and 24-hydroxylase (CYP24A1), in the canine pancreas and to compare their degrees of immunoreactivity between normal and inflamed pancreases. Five normal and inflamed pancreatic tissues each were obtained from six dogs. The expression of VDR, CYP24A1, and CYP27B1 were determined immunohistochemically, and the degree of immunostaining was assessed semiquantitatively. The VDR was expressed in the ducts, acini, and islets of Langerhans of normal pancreases and in the ducts and acini of inflamed ones. There was a significant difference in the immunoreactivity score for VDR in the islets of Langerhans between normal (median, 3 [interquartile range, 2-7.5] score) and inflamed pancreatic tissues (0 [0-0.5] score, p = 0.03). CYP24A1 was expressed in the ducts and islets of Langerhans in both normal and inflamed pancreases, whereas CYP27B1 was expressed in the ducts and acini in only some normal and inflamed pancreatic tissues. This study showed that VDR expression decreased in inflamed pancreases and demonstrated CYP24A1 and CYP27B1 expression in the canine pancreas for the first time. These findings indicate that the pancreas could regulate the metabolism and biological activity of vitamin D and suggest that a decrease in these might be related to the pathophysiology of pancreatitis.

Serum 25-hydroxyvitamin D, vitamin D receptor, and vitamin D binding protein concentrations in dogs with acute pancreatitis compared to healthy control dogs

BACKGROUND

Previous studies have documented vitamin D imbalance in dogs with acute pancreatitis (AP), but no studies have investigated serum vitamin D receptor (VDR) and vitamin D-binding protein (VDBP) concentrations.

OBJECTIVES

Compare serum 25-hydroxyvitamin D (25[OH]D), VDR, and VDBP concentrations in healthy dogs and dogs with AP and identify correlations between these concentrations with ionized calcium, C-reactive protein (CRP), and canine-specific pancreatic lipase (Spec cPL) concentrations.

ANIMALS

Twenty-two dogs with AP and 20 healthy control dogs.

METHODS

Prospective cross-sectional study. Serum 25(OH)D concentrations were measured using a chemiluminescence immunoassay, and VDR and VDBP concentrations were measured using a ELISA kit designed for dogs.

RESULTS

Serum concentrations of 25(OH)D were lower in dogs with AP (mean ± SD, 66.1 ± 39.2 ng/mL) than in controls (96.8 ± 30.4 ng/mL; P = .01), and VDR concentrations were lower in dogs with AP (5.3 ± 3.5 ng/mL) than in controls (7.4 ± 2.5 ng/mL; P = .03). No difference was observed in serum VDBP concentrations between the groups. Serum VDR concentrations differed between survivors (median [interquartile range] = 6.6 [4.3-8.2] ng/mL) and nonsurvivors (2.7 [0.5-3.5] ng/mL; P = .01). Negative correlations were observed among serum VDR, CRP (rs  = -0.55), and Spec cPL (rs  = -0.47) concentrations in dogs with AP.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with AP had lower serum 25(OH)D and VDR concentrations than controls. Additionally, our study suggests a potential role of VDR expression in the inflammatory process of AP in dogs.

Feline precision medicine using whole-exome sequencing identifies a novel frameshift mutation for vitamin D-dependent rickets type 2

OBJECTIVES

A 14-week-old female domestic longhair kitten presented with shifting lameness and disproportionately smaller size compared with a co-housed littermate.

METHODS

Hematology and serum biochemical testing were conducted to investigate causes for delayed growth, and radiographs of the appendicular skeleton were obtained.

RESULTS

The afflicted kitten had marked hypocalcemia, mild hypophosphatemia and substantial elevations in alkaline phosphatase activity, as well as pathognomonic radiographic findings consistent with rickets. Skeletal changes and hypocalcemia prompted testing of concentrations of parathyroid hormone (PTH) and vitamin D metabolites. Endocrine testing demonstrated significant increases in serum concentrations of PTH and 1,25-dihydroxycholecalciferol (calcitriol), supporting a diagnosis of vitamin D-dependent rickets type 2. Provision of analgesia, supraphysiologic doses of calcitriol and calcium carbonate supplementation achieved normalization of the serum calcium concentration and restoration of normal growth, although some skeletal abnormalities persisted. Once skeletally mature, ongoing calcitriol supplementation was not required. Whole-exome sequencing (WES) was conducted to identify the underlying DNA variant. A cytosine deletion at cat chromosome position B4:76777621 in VDR (ENSFCAT00000029466:c.106delC) was identified and predicted to cause a stop codon in exon 2 (p.Arg36Glufs*18), disrupting >90% of the receptor. The variant was unique and homozygous in this patient and absent in the sibling and approximately 400 other cats for which whole-genome and whole-exome data were available.

CONCLUSIONS AND RELEVANCE

A unique, heritable form of rickets was diagnosed in a domestic longhair cat. WES identified a novel frameshift mutation affecting the gene coding for the vitamin D3 receptor, determining the likely causal genetic variant. Precision medicine techniques, including whole-exome and whole-genome sequencing, can be a standard of care in cats to identify disease etiologies, and to target therapeutics and personalize treatment.

Genomic analysis of 1,25-dihydroxyvitamin D3 action in mouse intestine reveals compartment and segment-specific gene regulatory effects

1,25-dihydroxyvitamin D (VD) regulates intestinal calcium absorption in the small intestine (SI) and also reduces risk of colonic inflammation and cancer. However, the intestine compartment-specific target genes of VD signaling are unknown. Here, we examined VD action across three functional compartments of the intestine using RNA-seq to measure VD-induced changes in gene expression and Chromatin Immunoprecipitation with next generation sequencing to measure vitamin D receptor (VDR) genomic binding. We found that VD regulated the expression of 55 shared transcripts in the SI crypt, SI villi, and in the colon, including Cyp24a1, S100g, Trpv6, and Slc30a10. Other VD-regulated transcripts were unique to the SI crypt (162 up, 210 down), villi (199 up, 63 down), or colon (102 up, 28 down), but this did not correlate with mRNA levels of the VDR. Furthermore, bioinformatic analysis identified unique VD-regulated biological functions in each compartment. VDR-binding sites were found in 70% of upregulated genes from the colon and SI villi but were less common in upregulated genes from the SI crypt and among downregulated genes, suggesting some transcript-level VD effects are likely indirect. Consistent with this, we show that VD regulated the expression of other transcription factors and their downstream targets. Finally, we demonstrate that compartment-specific VD-mediated gene expression was associated with compartment-specific VDR-binding sites (<30% of targets) and enrichment of intestinal transcription factor-binding motifs within VDR-binding peaks. Taken together, our data reveal unique spatial patterns of VD action in the intestine and suggest novel mechanisms that could account for compartment-specific functions of this hormone.

Regulatory domains controlling high intestinal vitamin D receptor gene expression are conserved in mouse and human

Vitamin D receptor (VDR) levels are highest in the intestine where it mediates 1,25 dihydroxyvitamin D-induced gene expression. However, the mechanisms controlling high intestinal VDR gene expression are unknown. Here, we used Assay for Transposase-Accessible Chromatin using Sequencing (ATAC-Seq) to identify the regulatory sites controlling intestine-specific Vdr gene expression in the small intestine (villi and crypts) and colon of developing, adult, and aged mice. We identified 17 ATAC peaks in a 125 kb region from intron 3 to −55.8 kb from exon 1 of the Vdr gene. Interestingly, many of these peaks were missing/reduced in the developing intestine. Chromatin ImmunoPrecipitation-Sequencing (ChIP-Seq) peaks for intestinal transcription factors (TFs) were present within the ATAC peaks and at HiChIP looping attachments that connected the ATAC/TF ChIP peaks to the transcription start site and CCCTF-binding factor sites at the borders of the Vdr gene regulatory domain. Intestine-specific regulatory sites were identified by comparing ATAC peaks to DNAse-Seq data from other tissues that revealed tissue-specific, evolutionary conserved, and species-specific peaks. Bioinformatics analysis of human DNAse-Seq peaks revealed polymorphisms that disrupt TF-binding sites. Our analysis shows that mouse intestinal Vdr gene regulation requires a complex interaction of multiple distal regulatory regions and is controlled by a combination of intestinal TFs. These intestinal regulatory sites are well conserved in humans suggesting that they may be key components of VDR regulation in both mouse and human intestines.

Vitamin D and Gut Health

Vitamin D is a conditionally required nutrient that can either be obtained from skin synthesis following UVB exposure from the diet. Once in the body, it is metabolized to produce the endocrine hormone, 1,25 dihydroxyvitamin D (1,25(OH)2D), that regulates gene expression in target tissues by interacting with a ligand-activated transcription factor, the vitamin D receptor (VDR). The first, and most responsive, vitamin D target tissue is the intestine. The classical intestinal role for vitamin D is the control of calcium metabolism through the regulation of intestinal calcium absorption. However, studies clearly show that other functions of the intestine are regulated by the molecular actions of 1,25(OH)2 D that are mediated through the VDR. This includes enhancing gut barrier function, regulation of intestinal stem cells, suppression of colon carcinogenesis, and inhibiting intestinal inflammation. While research demonstrates that there are both classical, calcium-regulating and non-calcium regulating roles for vitamin D in the intestine, the challenge facing biomedical researchers is how to translate these findings in ways that optimize human intestinal health.

Antimicrobial peptides in domestic animals and their applications in veterinary medicine

Antimicrobial peptides (AMPs) are molecules with a broad-spectrum activity against bacteria, fungi, protozoa, and viruses. These peptides are widely distributed in insects, amphibians and mammals. Indeed, they are key molecules of the innate immune system with remarkable antimicrobial and immunomodulatory activity. Besides, these peptides have also shown regulatory activity for gut microbiota and have been considered inductors of growth performance. The current review describes the updated findings of antimicrobial peptides in domestic animals, such as bovines, goats, sheep, pigs, horses, canines and felines, analyzing the most relevant aspects of their use as potential therapeutics and their applications in Veterinary medicine.

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 receptor (VDR) expression in different molecular subtypes of canine mammary carcinoma

BACKGROUND

The molecular-based classification of canine mammary carcinomas (CMCs) has been the focus of much current research. Both in canines and humans, the triple-negative (TN) molecular subtype of mammary cancer is defined by a lack of expression of progesterone receptor (PR), oestrogen receptor (ER) and HER2. It has a poor prognosis; no effective targeted therapy is available. Vitamin D displays anticarcinogenic properties, and the expression of its receptor (VDR) has been found in different molecular subtypes, being about 30-40 % of TN breast cancer (TNBC) positive to it. We assessed the VDR expression in the different molecular subtypes of 58 CMCs from 45 female dogs using an immunohistochemical panel for the molecular classification of included: PR, ER, HER2, cytokeratin (CK) 5, CK14, and Ki67. In addition, we studied the relationship among the molecular subtypes of CMCs and clinicopathologic parameters.

RESULTS

Investigation showed VDR positivity in 45.0 % of the triple-negative CMCs (TNCMCs), 27.3 % of luminal B and 19.0 % of luminal A. Luminal A was the most molecular subtype represented of the total tumours (36.2 %), followed of TNCMCs (34.5 %), luminal B (20.7 %) and HER2-overexpression (10.3 %). Both HER2-overexpression and TNCMC subtypes were positively related to lymphatic invasion (P = 0.028), simple histologic subtype (P = 0.007), a higher histological grade (P = 0.045) and a trend to higher proliferation index (P = 0.09).

CONCLUSIONS

The highest VDR expression was observed in TNCMC, being almost half of them (45 %) positive to this receptor. VDR expression was absent in HER2-overexpression tumours and low in luminal A and B molecular subtypes.

Relationship between vitamin D status and clinical outcomes in dogs with a cranial cruciate ligament rupture

Cranial cruciate ligament rupture (CCLR) is one of the most common orthopaedic disorders diagnosed in dogs yet the factors which influence postoperative clinical outcomes are poorly understood. Low vitamin D status has been linked to poorer clinical outcomes in human patients undergoing elective orthopaedic surgery. The aim of this study was to examine the relationship between pre-operative vitamin D status, as defined by serum 25 hydroxyvitamin D (25(OH)D) concentrations, and initial disease severity and clinical outcomes in dogs undergoing surgical treatment for a CCLR. Serum 25(OH)D concentrations were measured in 44 dogs with a CCLR on the day before surgery. C-reactive protein concentrations were measured at a median time of 1 day post-surgery and the patient's clinical and radiographic response to CCLR surgical treatment was assessed at a median timepoint of 60 days post-surgery. Serum 25(OH)D concentrations in dogs with a CCLR was not significantly different to a population of healthy dogs (median 74.1 nmol/L and 88.40 nmol/L, respectively). There was no significant correlation between pre-operative serum 25(OH)D concentrations and length of pre-diagnosis clinical signs, pre-operative lameness scores or day 1 post-operative CRP concentrations. Thirty nine of the 44 dogs were re-examined at a median 60 days post-surgery. There was no relationship between the day 60 lameness scores and pre-operative serum 25(OH)D concentrations. In summary, we discovered that the vitamin D status of dogs with a CCLR was not significantly lower than healthy dogs and pre-operative serum 25(OH)D concentrations were not correlated to either pre-surgical disease severity or post-operative clinical outcomes.

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.

Vitamin D Metabolism and Its Role in Mineral and Bone Disorders in Chronic Kidney Disease in Humans, Dogs and Cats

Some differences regarding Vitamin D metabolism are described in dogs and cats in comparison with humans, which may be explained by an evolutionary drive among these species. Similarly, vitamin D is one of the most important regulators of mineral metabolism in dogs and cats, as well as in humans. Mineral metabolism is intrinsically related to bone metabolism, thus disturbances in vitamin D have been implicated in the development of chronic kidney disease mineral and bone disorders (CKD-MBD) in people, in addition to dogs and cats. Vitamin D deficiency may be associated with Renal Secondary Hyperparathyroidism (RSHPT), which is the most common mineral disorder in later stages of CKD in dogs and cats. Herein, we review the peculiarities of vitamin D metabolism in these species in comparison with humans, and the role of vitamin D disturbances in the development of CKD-MBD among dogs, cats, and people. Comparative studies may offer some evidence to help further research about vitamin D metabolism and bone disorders in CKD.

Effects of surgery on free and total 25 hydroxyvitamin D concentrations in dogs

Background

It is unclear whether a low total 25(OH)D concentration is a cause or consequence of illnesses. To address this knowledge gap, studies measuring free and total 25(OH)D during the evolution and resolution of an inflammatory process are required.

Objectives

Serum total and free 25(OH)D concentrations would transiently decline after cruciate surgery in dogs.

Animals

Seventeen client‐owned dogs with a spontaneous cranial cruciate ligament rupture (CCLR).

Methods

A longitudinal cohort study involving the measurement of serum concentrations of total and free 25(OH)D, total calcium, creatinine, albumin, phosphate, C‐reactive protein and plasma ionized calcium, at 1 day before and a median time of 1 and 60 days after surgical treatment of CCLR.

Results

Median serum concentrations of total 25(OH)D before surgery (80.3 nmoL/L [range, 43.5‐137.3]) significantly declined immediately after surgery; (64.8 nmoL/L [range, 36.3‐116.5] 1 day after surgery, P < .005) before increasing to become nonsignificantly different from concentrations before surgery at day 60 after surgery (median 78.0 nmoL/L [range, 24.2‐115.8], P = .14). In contrast, median free 25(OH)D concentrations before surgery (7.6 pg/mL [range, 3.8‐12.2]) significantly increased immediately after surgery (9.2 pg/mL [range, 5.2‐15.7], P < .05) before declining to become nonsignificantly different from before surgery concentrations at day 60 after surgery (median 6.2 pg/mL [range, 4.0‐15.8], P = .37).

Conclusion and Clinical Importance

This study reveals the difficulties of assessing vitamin D status in dogs following elective surgery.

Elucidating potential molecular signatures through host-microbe interactions for reactive arthritis and inflammatory bowel disease using combinatorial approach

Reactive Arthritis (ReA), a rare seronegative inflammatory arthritis, lacks exquisite classification under rheumatic autoimmunity. ReA is solely established using differential clinical diagnosis of the patient cohorts, where pathogenic triggers linked to enteric and urogenital microorganisms e.g. Salmonella, Shigella, Yersinia, Campylobacter, Chlamydia have been reported. Inflammatory Bowel Disease (IBD), an idiopathic enteric disorder co-evolved and attuned to present gut microbiome dysbiosis, can be correlated to the genesis of enteropathic arthropathies like ReA. Gut microbes symbolically modulate immune system homeostasis and are elementary for varied disease patterns in autoimmune disorders. The gut-microbiota axis structured on the core host-microbe interactions execute an imperative role in discerning the etiopathogenesis of ReA and IBD. This study predicts the molecular signatures for ReA with co-evolved IBD through the enveloped host-microbe interactions and microbe-microbe 'interspecies communication', using synonymous gene expression data for selective microbes. We have utilized a combinatorial approach that have concomitant in-silico work-pipeline and experimental validation to corroborate the findings. In-silico analysis involving text mining, metabolic network reconstruction, simulation, filtering, host-microbe interaction, docking and molecular mimicry studies results in robust drug target/s and biomarker/s for co-evolved IBD and ReA. Cross validation of the target/s or biomarker/s was done by targeted gene expression analysis following a non-probabilistic convenience sampling. Studies were performed to substantiate the host-microbe disease network consisting of protein-marker-symptom/disease-pathway-drug associations resulting in possible identification of vital drug targets, biomarkers, pathways and inhibitors for IBD and ReA.Our study identified Na(+)/H(+) anti-porter (NHAA) and Kynureninase (KYNU) to be robust early and essential host-microbe interacting targets for IBD co-evolved ReA. Other vital host-microbe interacting genes, proteins, pathways and drugs include Adenosine Deaminase (ADA), Superoxide Dismutase 2 (SOD2), Catalase (CAT), Angiotensin I Converting Enzyme (ACE), carbon metabolism (folate biosynthesis) and methotrexate. These can serve as potential prognostic/theranostic biomarkers and signatures that can be extrapolated to stratify ReA and related autoimmunity patient cohorts for further pilot studies.

Glucocorticoid metabolism and the action of 11 beta-hydroxysteroid dehydrogenase 2 in canine congestive heart failure

The enzyme 11-beta-hydroxysteroid dehydrogenase isoenzyme 2 (11BHSD2) is responsible for converting the active glucocorticoid cortisol to inactive cortisone and in the renal medulla protects the mineralocorticoid receptor (MR) from activation by cortisol. Derangements in 11BHSD2 activity can result in reduced conversion of cortisol to cortisone, activation of the MR by cortisol and, consequently, sodium and water retention. The objective of this study was to examine glucocorticoid metabolism in canine congestive heart failure (CHF), specifically to evaluate whether renal 11BHSD2 activity and expression were altered. Dogs were prospectively recruited into one of two phases; the first phase (n=56) utilized gas chromatography-tandem mass spectrometry to examine steroid hormone metabolites normalised to creatinine in home-caught urine samples. Total serum cortisol was also evaluated. The second phase consisted of dogs (n=18) euthanased for refractory CHF or for behavioural reasons. Tissue was collected from the renal medulla for examination by quantitative reverse transcription polymerase chain reaction, immunohistochemistry and protein immune-blotting. Heart failure did not change urinary cortisol:cortisone ratio (P=0.388), or modify renal expression (P=0.303), translation (P=0.427) or distribution of 11BHSD2 (P=0.325). However, CHF did increase excretion of 5α-tetrahydrocortisone (P=0.004), α-cortol (P=0.002) and α-cortolone (P=0.009). Congestive heart failure modifies glucocorticoid metabolism in dogs by increasing 5α-reductase and 20α-hydroxysteroid dehydrogenase activity. Differences between groups in age, sex and underlying disease processes may have influenced these results. However, 11BHSD2 does not appear to be a potential therapeutic target in canine CHF.

Vitamin D metabolism in dogs and cats and its relation to diseases not associated with bone metabolism

Due to the presence of receptors in the cells of numerous body tissues, vitamin D is associated with several physiological functions that go beyond calcium and phosphorus homoeostasis and control of bone metabolism in the body. In humans, several studies have associated lower vitamin D concentrations with numerous diseases, such as cancer, heart disease, autoimmune diseases and infectious diseases, and also with an increase in the total mortality rate of the population. Recently, this nutrient started to gain importance in veterinary medicine, and several articles have shown a correlation between low vitamin D status and diseases unrelated to bone metabolism. The present review aims to highlight the recent publications that investigated this relationship, bringing the evidence that exists so far in dogs and cats.

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

Background: Low vitamin D increases the risk of immune-mediated disease (IMD) in human beings and rodent models. Vitamin D metabolites, particularly 1,25(OH)2D3, modulate gene expression of immune cells and may attenuate immune pathways that drive IMD.

Hypothesis/objectives: Our primary hypothesis was that serum 25(OH)D3 and 1,25(OH)2D3, are reduced in patients with IMD and associate with poorer outcomes. We secondarily hypothesized serum 24,25(OH)2D3 would not be associated with disease or outcome. We also measured serum CXCL10 concentrations to determine if an increase occurs in dogs with IMD and in association with poorer survival.

Animals: We enrolled dogs diagnosed with IMD (n = 29) and healthy control dogs (n = 9) in the study with informed client consent.

Methods: Serum was collected and stored at −80°C until analyses. Serum vitamin D metabolites were measured by LC-MS/MS by an accredited laboratory. A commercially available canine-specific ELISA kit measured serum CXCL10.

Results: Serum 25(OH)D3 and 1,25(OH)2D3 were significantly reduced in dogs (n = 25) with IMD. Serum CXCL10 concentrations undetectable in all controls, and were 30 times higher overall in IMD dogs (n = 25; P = 0.004). CXL10 was, however, undetectable in 40% of dogs with IMD. Of the 60% of IMD dogs with increased CXCL10 concentrations, 5/25 had concentrations at the upper limit of quantification. The survival of those five dogs was significantly (P = 0.049) shorter (72 days) than all other dogs with IMD with measured CXCL10 concentrations. The median survival time (MST) for dogs with 25(OH)D3 concentrations ≤ the median was 106 days, while dogs with concentrations of 25(OH)D3 > the median did not achieve an MST.

Conclusions and clinical importance: Serum 25(OH)D3 and 1,25(OH)2D3, but not 24,25(OH)2D3 levels are reduced dogs with IMD. Vitamin D metabolites and CXCL10 may be useful prognostic markers and may be targets for adjunct therapy in canine IMD. These data support the future investigation of vitamin D analogs in the treatment of canine IMD.