Design, synthesis, and biological activity of D-bishomo-1α,25-dihydroxyvitamin D analogs and their crystal structures with the vitamin D nuclear receptor.

The biologically active metabolite of vitamin D - calcitriol - is a hormone involved in the regulation of calcium-phosphate homeostasis, immunological processes and cell differentiation, being therefore essential for the proper functioning of the human body. This suggests many applications of this steroid in the treatment of diseases such as rickets, psoriasis and some cancers. Unfortunately, using therapeutic doses of calcitriol is associated with high concentrations of this compound which causes hypercalcemia.

Antibody production in mice requires neither vitamin D, nor the vitamin D receptor.

The vitamin D receptor as well as its ligand have been localized to various immune tissues and cells. These observations have led researchers to hypothesize a role for vitamin D in the immune system. However, a specific role for vitamin D in immunity has yet to be clearly delineated.

Vitamin D receptor absence does not enhance intestinal tumorigenesis in ApcPirc/+rats.

Epidemiological observations have prompted some to posit that elevated circulating vitamin D is responsible for reduced colon cancer in individuals residing near the equator. We have previously demonstrated that vitamin D has no effect on colon cancer in two rodent models of intestinal tumorigenesis. We have now extended this line of inquiry to ask whether ablation of vitamin D receptor (VDR) affects tumorigenesis.

Vitamin D esters are the major form of vitamin D produced by UV irradiation in mice.

The primary source of vitamin D3 for humans is that produced in skin by ultraviolet irradiation. Ultraviolet (UV) B (UVB, 280-310 nm) light causes the isomerization of 7-dehydrocholesterol (7-DHC) to pre-vitamin D3 that is thermally isomerized to vitamin D3. In addition to free vitamin D3, it has been previously reported that esterified vitamin D3 is also found in the skin of rats irradiated with UVB.

Vitamin D binding protein greatly improves bioactivity but is not essential for orally administered vitamin D.

Vitamin D is a prohormone that is essential for calcium homeostasis. It is naturally produced in the skin by ultraviolet-B (UVB) irradiation of 7-dehydrocholesterol. In the absence of skin production, vitamin D can also be obtained from oral sources.

Novel superagonist analogs of 2-methylene calcitriol: Design, molecular docking, synthesis and biological evaluation.

A new series of highly biologically active (20S,22R)-1α,25-dihydroxy-22-methyl-2-methylene-vitamin D analogs, possessing different side chains, have been efficiently prepared as potential agents for medical therapy. Design of these synthetic targets was based on the analysis of the literature data and molecular docking experiments. The synthetic strategy involved Sonogashira coupling of the known A-ring dienyne with the C,D-ring enol triflates, obtained from the corresponding Grundmann ketones.

Synthesis and Biological Activity of 2,22-Dimethylene Analogues of 19-Norcalcitriol and Related Compounds.

Continuing our search for vitamin D analogues, we explored the modification of the steroidal side chain and inserted a methylene moiety in position C-22 together with either lengthening the side chain or introducing a ring at the terminal end. Our conformational studies confirmed that the presence of a methylene group attached to C-22 restricts the conformational flexibility of the side chain, which can result in changes in biological characteristics of a molecule. All synthesized 1α,25-dihydroxy-2,22-dimethylene-19-norvitamin D analogues proved equal to calcitriol in their ability to bind to the vitamin D receptor, and most of them exert significantly higher differentiation and transcriptional activity than calcitriol.

Vitamin D binding protein is required to utilize skin-generated vitamin D.

Vitamin D is produced in the skin following exposure to sunlight. Ultraviolet (UV) B (UVB, 280-310 nm) results in isomerization of 7-dehydrocholesterol to previtamin D that spontaneously isomerizes to vitamin D. This pool of skin-derived vitamin D is the major source of vitamin D for animals.

UV light suppression of EAE (a mouse model of multiple sclerosis) is independent of vitamin D and its receptor.

Vitamin D and sunlight have each been reported to protect against the development of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS). To date, the contribution of each has been unclear as ultra violet (UV) exposure also causes the generation of vitamin D in the skin. To examine whether the UV based suppression of EAE results, at least, in part from the production of vitamin D, we studied the effect of UV light on EAE in mice unable to produce 7-dehydroxycholesterol (7-DHC), the required precursor of vitamin D.

Vitamin D is not required for adaptive immunity to listeria.

Although ex vivo research suggests that vitamin D may play a role in innate and adaptive immunity, clear in vivo evidence is lacking. We have tested whether severe vitamin D deficiency alters the ability of mice to resist infection by Listeria. Our results show that vitamin D deficiency does not affect the LD of naïve mice in response to Listeria.

A New 1,25 Dihydroxy Vitamin D Analog with Strong Bone Anabolic Activity in OVX Rats with Little or no Bone Resorptive Activity.

A new 1α,25-dihydroxy vitamin D analog (2-methylene-22(E)-(24R)-22-dehydro-1α,24,25-trihydroxy-19-norvitamin D or WT-51) has been tested as a possible therapeutic for osteoporosis. It is 1/10th as active as 1,25(OH) D in binding affinity for the vitamin D receptor but is at least 200 times more active than 1,25(OH) D and equal to that of 2MD (2-methylene-19-nor-(20S)-1α,25(OH) D , an analog previously tested in postmenopausal women), in supporting bone formation by isolated osteoblasts in culture. However, in contrast to 2MD, it is virtually inactive on bone resorption in vivo.

Vitamin D assays and the definition of hypovitaminosis D: results from the First International Conference on Controversies in Vitamin D.

The First International Conference on Controversies in Vitamin D was held in Pisa, Italy, 14-16 June 2017. The meeting's purpose was to address controversies in vitamin D research, review the data available, to help resolve them, and suggest a research agenda to clarify areas of uncertainty. The serum 25-hydroxyvitamin D [25(OH)D] concentration [i.

Vitamin D deficiency in the rat does not exacerbate colonic tumorigenesis, while low dietary calcium might be protective.

Human studies have shown that individuals with colon cancer tend to have lower serum 25-hydroxy-vitamin D [25(OH)D] levels compared with healthy controls, but whether this link is causative, a result of the disease or an indicator of another factor altogether has yet to be demonstrated. In humans, vitamin D, calcium and UV exposure are inextricably linked; therefore, understanding the individual and combined roles of each of these will require animal models specifically designed to address these questions. To begin to untangle this network, our group has employed the rat, which contains a truncating mutation in the gene, leading to the development of colonic tumors.

Differential activity of 2-methylene-19-nor vitamin D analogs on growth factor gene expression in rhino mouse skin and comparison to all-trans retinoic acid.

While all 2-methylene-19-nor analogs of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) tested produce an increase in epidermal thickness in the rhino mouse, only a subset reduce utricle size (comedolysis). All-trans retinoic acid (atRA) also causes epidermal thickening and a reduction in utricle size in the rhino mouse. We now report that 2-methylene-19-nor-(20S)-1α-hydroxybishomopregnacalciferol (2MbisP), a comedolytic analog, increases epidermal thickening more rapidly than does atRA, while both reduce utricle area at an equal rate.

Pharmacokinetics of a New Oral Vitamin D Receptor Activator (2-Methylene-19-Nor-(20S)-1α,25-Dihydroxyvitamin D) in Patients with Chronic Kidney Disease and Secondary Hyperparathyroidism on Hemodialysis.

Background: 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D (DP001 or 2MD) is a novel, potent 1α-hydroxylated vitamin D analog that binds to the vitamin D receptor and suppresses parathyroid hormone synthesis and secretion with potential for an improved safety profile compared to existing active vitamin D analogs. The purpose of this study was to evaluate the pharmacokinetics of DP001 given orally after hemodialysis.

Methods: DP001 (550 ng) was given orally to 11 hemodialysis patients with secondary hyperparathyroidism after each dialysis session (3 times/week) for 4 weeks.

Analysis of the binding sites of vitamin D 1α-hydroxylase (CYP27B1) and vitamin D 24-hydroxylase (CYP24A1) for the design of selective CYP24A1 inhibitors: Homology modelling, molecular dynamics simulations and identification of key binding requirements.

A homology model of human CYP27B1 was built using MOE and was further optimised by molecular dynamics simulations of the hCYP27B1 homology model and a hCYP27B1-SDZ-88357 complex. Docking results from the hCYP27B1-SDZ-88357 complex showed amino acids Arg107, Asn387 and Asp320 have an important role in binding interaction, with Asp320 part of the important acid-alcohol pair situated in the I-helix with the conserved sequence (A/G) GX (E/D) (T/S), which assumes an essential role in the binding of an oxygen molecule for catalysis. Additional docking experiments with selective hCYP27B1 or hCYP24A1 inhibitors using both the hCYP27B1 model and a triple mutant hCYP24A1 model provided further support for the importance of H-bonding interactions with the three identified active site amino acids.

Salate derivatives found in sunscreens block experimental autoimmune encephalomyelitis in mice.

UV light suppresses experimental autoimmune encephalomyelitis (EAE), a widely used animal model of MS, in mice and may be responsible for the decreased incidence of MS in equatorial regions. To test this concept further, we applied commercially available sunblock preparations to mice before exposing them to UV radiation. Surprisingly, some of the sunblock preparations blocked EAE without UV radiation.

Synthesis, molecular modelling and CYP24A1 inhibitory activity of novel of (E)-N-(2-(1H-imidazol-1-yl)-2-(phenylethyl)-3/4-styrylbenzamides.

CYP24A1 (25-hydroxyvitamin D-24-hydroxylase) is a useful enzyme target for a range of medical conditions including cancer, cardiovascular and autoimmune disease, which show elevated CYP24A1 levels and corresponding reduction of calcitriol (the biologically active form of vitamin D). A series of (E)-N-(2-(1H-imidazol-1-yl)-2-(phenylethyl)-3/4-styrylbenzamides have been synthesised using an efficient synthetic route and shown to be potent inhibitors of CYP24A1 (IC 0.11-0.

Design, synthesis and biological properties of seco-d-ring modified 1α,25-dihydroxyvitamin D analogues.

As a continuation of our efforts directed to the structure-activity relationship studies of vitamin D compounds, we present in this paper the synthesis of new analogues of 1α,25-(OH)D characterized by numerous structural modifications, especially a cleaved D ring. Total synthesis of the CD fragment required for the construction of the target vitamins was based on the Stork approach. The structure of the key intermediate - bicyclic hydroxy lactone - was established by crystallographic and electronic circular dichroism (ECD) spectral analysis.

Suppression of experimental autoimmune encephalomyelitis by ultraviolet light is not mediated by isomerization of urocanic acid.

Background: Ultraviolet B irradiation confers strong resistance against experimental autoimmune encephalomyelitis, a model of multiple sclerosis. This protection by ultraviolet B is independent of vitamin D production but causes isomerization of urocanic acid, a naturally occurring immunosuppressant.

Methods: To determine whether UCA isomerization from trans to cis is responsible for the protection against experimental autoimmune encephalomyelitis afforded by ultraviolet B, trans- or cis-urocanic acid was administered to animals and their disease progression was monitored.

2MD (DP001), a Single Agent in the Management of Hemodialysis Patients: A Randomized Trial.

Background: Vitamin D analogs and calcimimetics are used to manage secondary hyperparathyroidism (SHPT) in dialysis patients. DP001 is an oral vitamin D analog that suppresses parathyroid hormone (PTH) in uremic rats, osteopenic women, and hemodialysis patients. The safety and effectiveness of DP001 suppressing PTH in dialysis patients previously managed with active vitamin D with or without a calcimimetic are presented.

D-seco-Vitamin D analogs having reversed configurations at C-13 and C-14: Synthesis, docking studies and biological evaluation.

Prompted by results of molecular modeling performed on the seco-d-ring-vitamins D, we turned our attention to such analogs, having reversed configurations at C-13 and C-14, as the next goals of our studies on the structure-activity relationship for vitamin D compounds. First, we developed an efficient total synthesis of the "upper" C/seco-d-ring fragment with a 7-carbon side chain. Then, we coupled it with A-ring fragments using Sonogashira or Wittig-Horner protocol, providing the targeted D-seco analogs of 1α,25-dihydroxyvitamin D and 1α,25-dihydroxy-19-norvitamin D possessing a vinyl substituent at C-14 and a double bond between C-17 and C-20.

The association of mineral metabolism with vascular access patency.

Background: Declining kidney function leads to progressively dysregulated mineral homeostasis and contributes to vascular calcification and a pro-inflammatory milieu, both of which play a critical role in loss of dialysis vascular access patency. We designed this study to examine the relationship between markers of bone and mineral metabolism, vitamin D replacement medications, and vascular access outcomes. We hypothesized that higher levels of calcium, phosphorous, parathyroid hormone (PTH), and albumin are independently associated with vascular access patency and that vitamin D supplementation is associated with lower risk of access failure.

The absence of 25-hydroxyvitamin D3-1α-hydroxylase potentiates the suppression of EAE in mice by ultraviolet light.

Ultraviolet B (UVB) light suppresses the development of multiple sclerosis (MS) in patients and experimental autoimmune encephalomyelitis (EAE) in mice. Although vitamin D3 is produced by ultraviolet light, the suppression of EAE by narrow band UVB (NBUVB) is independent of vitamin D3. However, it is possible that the NBUVB suppression of EAE can be further influenced by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3).

Use of 2MD, a Novel Oral Calcitriol Analog, in Hemodialysis Patients with Secondary Hyperparathyroidism.

Background: Use of existing therapies for secondary hyperparathyroidism (SHPT), such as calcitriol or paricalcitol, is frequently limited by the development of hypercalcemia. 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D3 (2MD; DP001) is a novel and a more potent vitamin D receptor activator (VDRA) that more selectively localizes in the parathyroid gland, and has a wider therapeutic margin in the uremic rat model than calcitriol and paricalcitol.

Design, Setting, Participants, And Measurements: Hemodialysis patients were enrolled and dosed with 110, 220, 330, 440, or 550 ng of 2MD orally thrice weekly for 4 weeks.