Vitamin D plays an important role in skeletal health in dogs. Due to the inability to cutaneously produce vitamin D, dogs are heavily reliant on dietary sources of vitamin D. We have previously shown that dogs with a protein losing enteropathy have significantly lower concentrations of the major vitamin D metabolite, 25 hydroxyvitamin D (25(OH)D). Furthermore, we have shown that serum 25(OH)D concentrations negatively correlate with extent of inflammation in dogs with a chronic enteropathy (CE). In addition, low vitamin D status has been found to be a negative prognostic marker in dogs with a CE.

Vitamin D influences cellular function by signalling through the vitamin D receptor (VDR). Despite the growing awareness of the potential impact gastrointestinal diseases have on vitamin D metabolism in dogs, little is known about the sites of VDR expression and whether intestinal inflammation influences VDR expression. The aim of this study was to define the non-skeletal tissues which express VDR in the dog and to investigate how extent of inflammation correlated with VDR expression in the small intestine.

Twelve non-skeletal tissues were collected prospectively from 6 dogs, euthanised for non-health related problems. These included stomach, duodenum, ileum, colon, skin, kidney, spleen, liver, mesenteric lymph node, heart and lung. VDR expression was assessed with immunohistochemistry using a Rat IgG VDR monoclonal antibody.

Thirty-five dogs diagnosed with a chronic enteropathy were prospectively enrolled and biopsies taken at endoscopy from the duodenum were evaluated for VDR expression with both immunohistochemistry and quantitative polymerase chain reaction (qPCR). Twenty-three control dogs were also prospectively enrolled without clinical signs of gastrointestinal disease.

The VDR was found to be highly expressed in the duodenum of all 6 control dogs. It was also found in the skin of these 6 dogs and in the majority of the kidney samples, and occasionally in spleen and ileum.

There was no statistical difference in the relative expression, by qPCR, of the VDR between dogs with chronic enteropathy and dogs not clinically affected. VDR expression was also not different between healthy and CE dogs when assessed by protein expression via immunohistochemistry scoring.

Our study has defined the tissues which express VDR in healthy dogs. The lack of down regulation of VDR expression in intestinal inflammation contrasts with humans and provides support for future studies which aim to investigate whether vitamin D and its analogues can be used to modulate intestinal inflammation in the dog.

Disclosures

No disclosures to report.