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Vitamin D Binding Protein-Macrophage Activating Factor (DBP-maf) Inhibits Angiogenesis and Tumor Growth in Mice Vitamin D binding protein-macrophage activating factor (DBP-maf) inhibits angiogenesis and tumor growth in mice. Kisker O, Onizuka S, Becker CM, Fannon M, Flynn E, D'Amato R, Zetter B, Folkman J, Ray R, Swamy N, Pirie-Shepherd S. Neoplasia. 2003 Jan-Feb;5(1):32-40. PMID: 12659668 Taken together, these data suggest that DBP-maf is an antiangiogenic molecule that can act directly on endothelium as well as stimulate macrophages to attack both the endothelial and tumor cell compartment of a growing malignancy.

BACKGROUND: To determine the effect of vitamin D binding protein (DBP) genotypes on 25-hydroxyvitamin D [25(OH)D] changes with vitamin D supplements, we studied 98 adults receiving 600 or 4000 IU/d vitamin D(3) for one year. METHODS: The DBP functional variant, T436K, was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: Mean 25(OH)D increases were 97% for TT (n=48), 151% for TK (n=31) and 307% (n=6) for KK genotypes (p=.004). CONCLUSIONS: As with baseline 25(OH)D, T436K genotype predicts 25(OH)D changes after long-term vitamin D supplementation. Common genetic variants of the vitamin D binding protein (DBP) predict differences in response of serum 25-hydroxyvitamin D [25(OH)D] to vitamin D supplementation. Fu L, Yun F, Oczak M, Wong BY, Vieth R, Cole DE. Clin Biochem. 2009 Jul;42(10-11):1174-7. Epub 2009 Mar 18. PMID: 19302999

In conclusion, genetic variations of DBP are associated with insulin resistance in Japanese with normal glucose tolerance, which might contribute to the development of type 2 diabetes. Variations in vitamin D-binding protein (group-specific component protein) are associated with fasting plasma insulin levels in Japanese with normal glucose tolerance. Hirai M, Suzuki S, Hinokio Y, Hirai A, Chiba M, Akai H, Suzuki C, Toyota T. J Clin Endocrinol Metab. 2000 May;85(5):1951-3. PMID: 10843180

Role of vitamin D in the pathogenesis of type 2 diabetes mellitus. Palomer X, González-Clemente JM, Blanco-Vaca F, Mauricio D. Diabetes Obes Metab. 2008 Mar;10(3):185-97. Review. PMID: 18269634 DOI: 10.1111/j.1463-1326.2007.00710.x Vitamin D deficiency has been shown to alter insulin synthesis and secretion in both humans and animal models. It has been reported that vitamin D deficiency may predispose to glucose intolerance, altered insulin secretion and type 2 diabetes mellitus. Vitamin D replenishment improves glycaemia and insulin secretion in patients with type 2 diabetes with established hypovitaminosis D, thereby suggesting a role for vitamin D in the pathogenesis of type 2 diabetes mellitus.

Also known as group specific protein (Gc), vitamin D binding protein (VDBP) is a 52Kda protein that binds monomeric actin in addition to vitamin D. The protein is 458 residues in length (Cooke, 1986), and forms three domains, the first of which contains the sterol binding site

Back to the future: a new look at 'old' vitamin D. Chun RF, Adams JS, Hewison M. J Endocrinol. 2008 Aug;198(2):261-9. Epub 2008 May 21. PMID: 18495944 DOI: 10.1677/JOE-08-0170

Bioactive vitamin D or calcitriol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone. More recently, it has become clear that receptors for vitamin D are present in a wide variety of cells, and that this hormone has biologic effects which extend far beyond control of mineral metabolism. The active form of vitamin D binds to intracellular receptors that then function as transcription factors to modulate gene expression. Like the receptors for other steroid hormones and thyroid hormones, the vitamin D receptor has hormone-binding and DNA-binding domains. The vitamin D receptor forms a complex with another intracellular receptor, the retinoid-X receptor, and that heterodimer is what binds to DNA. In most cases studied, the effect is to activate transcription, but situations are also known in which vitamin D suppresses transcription. Each of the forms of vitamin D is hydrophobic, and is transported in blood bound to carrier proteins. The major carrier is called, appropriately, vitamin D-binding protein. The halflife of 25-hydroxycholecalciferol is several weeks, while that of 1,25-dihydroxycholecalciferol is only a few hours. The vitamin D receptor binds several forms of cholecalciferol. Its affinity for 1,25-dihydroxycholecalciferol is roughly 1000 times that for 25-hydroxycholecalciferol, which explains their relative biological potencies