Abstract
Dogs and cats have differences in vitamin D metabolism compared to other mammalian species, as they are unable to perform vitamin D cutaneous synthesis through sun exposure. Therefore, they are dependent on the dietary intake of this nutrient. The classic functions of vitamin D are to stimulate intestinal calcium and phosphate absorption, renal calcium and phosphate reabsorption and regulate bone mineral metabolism. Thus, it is an important nutrient for calcium and phosphorus homeostasis. This review highlights the evidence of the direct and indirect actions of vitamin D on bone mineral metabolism, the consequences of nutritional imbalances of this nutrient in small animals, as well as differences in vitamin D metabolism between different size dogs.
Highlights
Vitamin D is an essential nutrient for dogs and cats since they are unable to synthesize vitaminD3 through skin sun exposure; it is essential that they receive this nutrient in their diet [1,2].vitamin D has two nonactive forms in nature: cholecalciferol or vitamin D3, and ergocalciferol or vitamin D2
It is believed that the inability to synthesize vitamin D3 in the skin in dogs and cats is related to the evolutionary aspect that once, in nature, these animals consumed preys which stores vitamin D3 in the liver and adipose tissue
In situations of high serum phosphate concentrations, there is an increase in synthesis and release of FGF-23, an important peptide produced by osteoblasts and mainly by osteocytes, with hypophosphatemic action, so that it stimulates renal phosphorus excretion, increases 24hydroxylase activity, decreases 1α-hydroxylase activity and, decreases calcitriol synthesis, since this hormone has the function of intestinal phosphorus absorption and tubular reabsorption of inorganic phosphate [61,64,65]
Summary
Vitamin D is an essential nutrient for dogs and cats since they are unable to synthesize vitamin. Calcitriol acts in the parathyroid gland regulating parathyroid hormone (PTH) secretion All these functions can indirectly regulate bone growth and mineralization. Excessive vitamin D is harmful and causes of hypervitaminosis D in small animals This can be due to commercial food formulation miscalculation [21,22,23,24], accidental consumption of rodenticides [25,26,27,28,29], consumption of certain plants that may contain calcitriol glycosides (such as jessamine [30]) and the use of topical ointments for psoriasis treatment, which are based on vitamin D analogs such as calcipotriol and maxacalcitol [31,32,33,34]. This review aims to summarize the current knowledge about the direct and indirect role of vitamin D in bone metabolism, as well as discussing the negative effects of vitamin D deficiency and excess in dogs’ and cats’ bone health
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