Vitamin D Metabolism and Profiling in Veterinary Species

Abstract

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.

Low serum vitamin D concentrations in Spring-born dairy calves are associated with elevated peripheral leukocytes

“…Furthermore, their dynamics after sun exposure or Vit D supplementation are yet to be explored 48 . Therefore, a comprehensive study of the Vit D metabolome beyond 25OHD is necessary to gain a more comprehensive understanding of the role of Vit D in health and disease 49 .…”

The effect of season, management and endocrinopathies on vitamin D status in horses

“…2 In humans and other domestic herbivores, vitamin D 3 , synthesised in the skin, makes up most of the total vitamin D measured in plasma. 3 Horses, like other herbivores, source vitamin D 2 from their forage-based diet but it is unclear whether they can synthesise vitamin D 3 . 1 Our understanding of vitamin D biology in horses and ponies is very limited with few equine-specific peerreviewed publications in the last 30 years.…”

Case Report: A Case Series Linked to Vitamin D Excess in Pet Food: Cholecalciferol (Vitamin D3) Toxicity Observed in Five Cats

“…In this case series, acute dietary vitamin D3 toxicosis has been described in five young cats. Although not common, dietary vitamin D3 toxicity has even been reported in domestic cats and captive felids (tigers and lynxes) recently, thereby resulting in renal failure and widespread mineralization in various organs ( 4 , 5 , 12 , 13 , 20 , 21 ).…”

“…Domestic cats can utilize vitamin D2, but to a lesser extent than vitamin D3, due to a lower affinity of vitamin D binding proteins to vitamin D2 metabolites compared to vitamin D3 ( 4 ). Nevertheless, as is the case for most terrestrial carnivores, they do not synthesize vitamin D3 by way of the skin and, therefore, they are dependent on the dietary intake of vitamin D ( 5 , 6 ). Vitamin D3 is rapidly absorbed after ingestion and is firstly converted to 25-hydroxyvitamin D3 [25(OH)D3] by 25-hydroxylase in the liver, but it becomes metabolically active when converted to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] by 1-α-hydroxylase in the kidney ( 7 ).…”