Background: Hypovitaminosis D is associated with insulin resistance and an increased risk of type 1 and type 2 diabetes mellitus (DM) in humans. In dogs, its role in autoimmune and inflammatory diseases is well established, but its association with DM remains unclear.
Objectives: This study aimed to assess whether controlled diabetic dogs exhibit alterations in serum vitamin D status. Animals: Twenty-seven diabetic dogs, free from other diseases, and 19 healthy dogs were included.
Methods: Diabetic dogs underwent a 60-day stabilization period with NPH insulin and a diet formulated for diabetic dogs. After stabilization, all dogs received the same diet for two months. Healthy dogs were fed the same diet for 60 days. Serum 25-hydroxyvitamin(OH)D3 (calcidiol) and 24,25-dihydroxyvitamin(OH)2D3 were analyzed. Wilcoxon or t-tests compared diabetic and healthy dogs.
Results: No significant differences were found in age or median serum calcidiol concentrations between groups (p = 0.09). However, diabetic dogs had significantly higher mean serum 24,25(OH)2D3 concentrations than healthy dogs (p = 0.007). Conclusions and Clinical Importance: This is the first study standardizing diet to evaluate vitamin D metabolism in diabetic dogs, revealing alterations distinct from human type 1 DM, which is linked to hypovitaminosis D. However, our findings align with juvenile insulin-dependent diabetes in humans, where increased calcidiol and 24,25(OH)2D3 are also observed. The elevated 24,25(OH)2D3 may result from mitochondrial stimulation of 24-hydroxylase by DM metabolites, as reported in insulin-deficient rats.
