Evaluation and Comparison of Vitamin D Responsive Gene Expression in Ovine, Canine and Equine Kidney.
Authors: Azarpeykan Sara, Dittmer Keren E, Marshall Jonathan C, Perera Kalyani C, Gee Erica K, Acke Els, Thompson Keith G
Journal: PloS one
Summary
# Editorial Summary: Vitamin D and Calcium Regulation in Equine Kidney Researchers compared how nine key genes involved in vitamin D signalling and calcium transport are expressed across equine, ovine and canine kidneys, using quantitative PCR analysis of post-mortem renal tissue from 10 horses, 10 sheep and 5 dogs. All genes studied (including TRPV5, TRPV6, calmodulin-binding proteins, PMCA, NCX1, and the vitamin D metabolising enzymes CYP27B1 and CYP24A1) were present in kidney tissue across all three species, though expression levels and inter-gene correlations varied considerably between species. Most notably, equine kidneys showed consistently strong correlations between the vitamin D receptor (VDR) and all other vitamin D-responsive transcripts—a pattern not observed in sheep or dogs—suggesting a particularly coordinated vitamin D signalling system in horses. The findings are clinically significant because they indicate that despite horses typically having low circulating vitamin D metabolites and high urinary calcium excretion, vitamin D still plays a meaningful regulatory role in equine renal calcium handling, potentially through species-specific mechanisms. This fundamental research highlights why extrapolating vitamin D supplementation recommendations from other species to horses may be inappropriate, and suggests the need for further investigation into equine-specific vitamin D physiology to inform nutrition and management strategies.
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Practical Takeaways
- •Horses have fundamentally different vitamin D and calcium metabolism compared to other species—research from small animals or ruminants may not apply directly to equine nutrition and health management.
- •Despite horses typically having lower serum vitamin D levels than other species, vitamin D metabolism remains active and important for calcium regulation, suggesting careful dietary mineral balance is essential.
- •The unique correlations in equine gene expression suggest horses may have evolved specialized mechanisms for managing high urinary calcium losses; this has implications for understanding equine kidney function and mineral supplementation strategies.
Key Findings
- •All nine vitamin D responsive and calcium transporting genes were expressed in equine kidney tissue, with TRPV6, calD9k/calD28k, and PMCA as primary active transport pathways.
- •Equine kidney showed strong correlation between VDR and all other vitamin D responsive transcripts, unlike sheep and dogs which showed variable correlations.
- •CYP27B1 and CYP24A1 expression patterns differed significantly in horses compared to other species, suggesting unique vitamin D metabolism regulation despite low serum vitamin D concentrations.
- •Vitamin D plays a significant functional role in equine calcium metabolism independent of low serum 1,25(OH)2D concentration, indicating species-specific differences in mineral homeostasis.