Vitamin D3 Receptors and Metabolic Enzymes in Hen Reproductive Tissues

Abstract

In recent years, vitamin D3 has been revealed as an important regulator of reproductive processes in humans and livestock; however, its role in the female reproductive system of poultry is poorly known. The aim of this study was to examine vitamin D3 receptor (VDR and PDIA3) and metabolic enzyme (1α-hydroxylase and 24-hydroxylase) mRNA transcript and protein abundances, and protein localization within the hen ovary, oviductal shell gland, pituitary, liver, and kidney. We demonstrated, for the first time, the patterns of the relative mRNA and protein abundances of examined molecules in the ovary, dependent on follicle development and the layer of follicle wall, as well as in other examined organs. Immunohistochemically, PDIA3, 1α-hydroxylase, and 24-hydroxylase are localized in follicular theca and granulosa layers, luminal epithelium and tubular glands of the shell gland, pituitary, liver, and kidney. These results indicate that reproductive tissues have both receptors, VDR, primarily involved in genomic action, and PDIA3, probably participating in the rapid, non-genomic effect of vitamin D3. The finding of 1α-hydroxylase and 24-hydroxylase expression indicates that the reproductive system of chickens has the potential for vitamin D3 synthesis and inactivation, and may suggest that locally produced vitamin D3 can be considered as a significant factor in the orchestration of ovarian and shell gland function in hens. These results provide a new insight into the potential mechanisms of vitamin D3 action and metabolism in the chicken ovary and oviduct.

Causal association between low vitamin D and polycystic ovary syndrome: a bidirectional mendelian randomization study

“…A recent meta-analysis has shown that VD supplementation to PCOS women could decrease the occurrence rates of early miscarriage and premature delivery [ 53 ]. The nuclear receptor of VD (VDR) and 1,25(OH)2D3 membrane binding protein are expressed in both ovarian granulosa and theca cells [ 61 , 62 ]. It has been found that VD can regulate the expression of enzymes in the VDR and ovary, ultimately regulating ovarian function [ 63 ].…”

Renal Endocytic Regulation of Vitamin D Metabolism during Maturation and Aging in Laying Hens

“…In humans, in addition to Meg and CUB, 1α-hydroxylase is expressed in vitamin D target tissues, such as osteoblasts and the placenta, and the 25(OH)D 3 -DBP complex is taken up to produce 1,25(OH) 2 D 3 , indicating that 1,25(OH) 2 D 3 regulates target tissues via an autocrine or paracrine pathway independent of circulating 1,25(OH) 2 D 3 of kidney origin [28,29]. In laying hens, it has been demonstrated that vitamin D metabolizing enzymes, such as 1α-hydroxylase and 24-hydroxylase, are present in the eggshell gland and intestinal tract, in addition to the kidney [10,30]. Consequently, uptake of the 25(OH)D 3 -DBP complex by Meg and CUB in the intestinal tract, oviduct, and medullary bone of laying hens may regulate calcium metabolism via local vitamin D metabolism.…”

“…Vitamin D 3 is synthesized in the skin from 7-dehydrocholesterol by ultraviolet irradiation in sunlight or is supplemented directly from dietary sources [7]. Vitamin D 3 is transported to the liver and converted to 25-hydroxy vitamin D 3 (25(OH)D 3 ) by 25-hydroxylase (Cyp27A1), which then binds to vitamin D-binding protein (DBP), circulates in the blood, is taken up by the kidneys, and is converted to 1,25(OH) 2 D 3 by 25(OH)D 3 -1α hydroxylase (Cyp27C1 in birds, Cyp27B1 in mammals) [8][9][10]. 1,25(OH) 2 D 3 is biologically active and binds to vitamin D receptors to promote intestinal absorption and renal reabsorption of calcium, as well as the formation of medullary bone to maintain circulating calcium levels in the blood and promote eggshell formation in the oviduct [11,12].…”