Endocrine Abstracts

The vitamin D endocrine system (D-endo) is essential for calcium and bone homeostasis. Absence of a functional VDR or CYP27B1 creates a severe rachitic bone and growth plate phenotype in humans and mice as in severe vitamin D deficiency. The intestine is the key target for VDR as a high calcium intake or selective VDR rescue in the intestine restores a normal bone and growth plate phenotype. Selective absence of VDR in osteoblasts does not create a bone phenotype when calcium ...

The vitamin D endocrine system (D-endo) is essential for calcium and bone homeostasis. The vitamin D receptor, VDR, is ubiquitously expressed and about 3% of the mouse or human genome is regulated by D-endo. VDR knock-out mice show impaired striated muscle maturation and selective VDR deficiency in heart muscle cause cardiomyopathy. Muscle weakness may be severe in patients with severe chronic renal failure combined with vitamin D deficiency or in subjects with congenital CYP2...

Ligand activated VDR regulates about 3% the mouse genome. Its classical function is to regulate calcium and bone homeostasis. 1,25-(OH)2D is essential for transepithelial calcium transport in the intestine (by an epithelial calcium channel, TRPV6) and in the kidney (TRPV5). Normal osteoclastogenesis and bone resorption as well as bone mineralisation is possible in the absence of VDR when VDR KO men or animals receive a high calcium diet. VDR.1α,25-(OH)2</s...

Vitamin D is a substrate for the active hormone, 1α, 25-dihydroxyvitamin D3, which binds to a single vitamin D receptor (VDR) belonging to the class of nuclear transcription factors.Ligand activated VDR regulates about 3 % the mouse/human genome and has a wide variety of physiologic actions. Its regulates calcium and bone homeostasis by increasing transepithelial calcium transport (intestine, kidney) and regulates the functions of bone an...

The calcium-sensing receptor (CaSR) plays a central role in regulating parathyroid hormone (PTH) secretion in response to changes in extracellular calcium. The CaSR is a G-protein-coupled receptor and ligand binding results in stimulation of phospholipase C (PLC) activity, causing accumulation of inositol 1,4,5-triphosphate (IP3) and the rapid release of calcium ions from intracellular stores. Given the pivotal role of the CaSR in calcium homeostasis, we decided to ...

Background: Total 25 hydroxyvitamin D (25(OH)D) and total 1.25 dihydroxyvitamin D (1.25(OH)2D) are associated with all-cause mortality. The free hormone hypothesis postulates that only the free vitamin D fraction can exert its biological function. Recently some studies suggested that free 25(OH)D levels might be a better predictor for clinical outcomes, including mortality.Objective: To study the association between total and free 25(OH)D and ...

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) influences the differentiation and cytokine secretion of various immune cell types. These immune modulating effects of 1,25(OH)2D3 are mediated through the nuclear vitamin D receptor (VDR). In the immune system, the 1,25(OH)2D3/VDR complex interacts with promoter vitamin D responsive elements (VDRE), or interferes with the signalling of other transcription factor...