Noncalcemic actions of 1,25-dihydroxyvitamin D3 and clinical applications

The Inverted U-Shaped Association between Serum Vitamin D and Serum Uric Acid Status in Children and Adolescents: A Large Cross-Sectional and Longitudinal Analysis

BACKGROUND

Serum vitamin D is associated with hyperuricemia. However, previous studies have been controversial, with limited focus on children and adolescents.

OBJECTIVE

This study aimed to examine the cross-sectional and longitudinal associations between serum vitamin D and serum uric acid (SUA) levels in children and adolescents.

METHODS

The cross-sectional survey comprised 4777 participants aged 6 to 18 years, while the longitudinal survey involved 1641 participants aged 6 to 12 years, all derived from an ongoing cohort study in Shenzhen, China. Restricted cubic splines were used to visualize the dose-response relationship between vitamin D and SUA and the risk of higher SUA status. Two-segment generalized linear models (GLM) and logistic models were used to assess the association between vitamin D and SUA and higher SUA status, respectively. The longitudinal analysis used GLM.

RESULTS

We observed an inverted U-shaped relationship between vitamin D and SUA (p-overall < 0.0001, p-nonlinear = 0.0002), as well as the risk of higher SUA status (p-overall = 0.0054, p-nonlinear = 0.0015), with the vitamin D inflection point at 24.31 and 21.29 ng/mL, respectively. A 10 ng/mL increment in 25(OH)D3 levels, when below 20.92 ng/mL, was associated with a 68% rise in the risk of higher SUA status (OR: 1.68, 95%CI: 1.07-2.66). Conversely, when 25(OH)D3 levels were above or equal to 20.92 ng/mL, a 10 ng/mL increment was associated with a 45% reduction risk of higher SUA status (OR: 0.55, 95%CI: 0.36-0.84). Longitudinal analysis indicated that the annual change of SUA was from -4.80 (β, 95%CI: -10.74, 1.13) to -9.00 (β, 95%CI: -15.03, -2.99) and then to -6.77 (β, 95%CI: -12.83, -0.71, p for trend = 0.0212) μmol/L when increasing the quartile of vitamin D3.

CONCLUSIONS

An inverse U-shaped relationship was observed between vitamin D and SUA as well as the risk of higher SUA status. Sufficient vitamin D levels appear to play a preventative role against the age-related increase in SUA. Ensuring adequate vitamin D levels may be beneficial in improving uric acid metabolism.

Vitamin D, a Secosteroid Hormone and Its Multifunctional Receptor, Vitamin D Receptor, in Alzheimer's Type Neurodegeneration

Vitamin D is a secosteroid hormone exerting neurosteroid-like properties. Its well-known nuclear hormone receptor, and recently proposed as a mitochondrial transcription factor, vitamin D receptor, acts for its primary functions. The second receptor is an endoplasmic reticulum protein, protein disulfide isomerase A3 (PDIA3), suggested to act as a rapid response. Vitamin D has effects on various systems, particularly through calcium metabolism. Among them, the nervous system has an important place in the context of our subject. Recent studies have shown that vitamin D and its receptors have numerous effects on the nervous system. Neurodegeneration is a long-term process. Throughout a human life span, so is vitamin D deficiency. Our previous studies and others have suggested that the out-come of long-term vitamin D deficiency (hypovitaminosis D or inefficient utilization of vitamin D), may lead neurons to be vulnerable to aging and neurodegeneration. We suggest that keeping vitamin D levels at adequate levels at all stages of life, considering new approaches such as agonists that can activate vitamin D receptors, and utilizing other derivatives produced in the synthesis process with UVB are crucial when considering vitamin D-based intervention studies. Given most aspects of vitamin D, this review outlines how vitamin D and its receptors work and are involved in neurodegeneration, emphasizing Alzheimer's disease.

Conundrum of vitamin D on glucose and fuel homeostasis

As an endocrine hormone, vitamin D plays an important role in bone health and calcium homeostasis. Over the past two decades, the non-calcemic effects of vitamin D were extensively examined. Although the effect of vitamin D on beta cell function were known for some time, the effect of vitamin D on glucose and fuel homeostasis has attracted new interest among researchers. Yet, to date, studies remain inconclusive and controversial, in part, due to a lack of understanding of the threshold effects of vitamin D. In this review, a critical examination of interventional trials of vitamin D in prevention of diabetes is provided. Like use of vitamin D for bone loss, the benefits of vitamin D supplementation in diabetes prevention were observed in vitamin D-deficient subjects with serum 25-hydroxyvitamin D < 50 nmol/L (20 ng/mL). The beneficial effect from vitamin D supplementation was not apparent in subjects with serum 25-hydroxyvitamin D > 75 nmol/L (30 ng/mL). Furthermore, no benefit was noted in subjects that achieved serum 25-hydroxyvitamin D > 100 nmol/L (40 ng/mL). Further studies are required to confirm these observations.

MiR-141-3p and miR-200a-3p are involved in Th17 cell differentiation by negatively regulating RARB expression

Among T helper (Th) lineages differentiated from naïve CD4⁺ T cells, interleukin (IL)-17-producing Th17 cells are highly correlated with the pathogenesis of autoimmune disorders. This study aimed to clarify the involvement of miR-141-3p and miR-200a-3p in Th17 cell differentiation as well as explore their potential target genes involved. For this purpose, human naïve CD4⁺ T cells were cultured under Th17 cell polarizing condition. The differentiation process was confirmed through measurement of IL-17 secretion using the ELISA method and assessment of Th17 cell-defining genes expression during the differentiation period. MiR-141-3p and miR-200a-3p downstream genes were identified via consensus and integration in silico approach and their expression pattern and alterations were evaluated by quantitative real-time PCR. Finally, direct interaction between both microRNAs (miRNAs) and their common predicted target sequences was approved by dual-luciferase reporter assay. Highly increased IL-17 secretion and Th17 lineage-specific genes expression confirmed Th17 cell differentiation. Our results have demonstrated that miR-141-3p and miR-200a-3p are Th17 cell-associated miRNAs and their expression level is upregulated significantly during Th17 cell induction. We have also found that retinoic acid receptor beta (RARB) gene, whose product has been reported as a negative regulator of Th17 cell generation, is a direct target of both miRNAs and its downregulation can affect the transcriptional level of JAK/STAT pathway genes. Overall, our results have identified two novel Th17 lineage-associated miRNAs and have provided evidence for the RARB-dependent mechanism of miR-141-3p and miR-200a-3p-induced Th17 cell differentiation and hence Th17-mediated autoimmunity.

Vitamin D supplementation is associated with serum uric acid concentration in patients with prediabetes and hyperuricemia

Aims

Vitamin D deficiency is associated with a number of noncommunicable conditions. We conducted a randomised controlled trial to determine the effect of vitamin D supplementation on serum uric acid concentration in patients with prediabetes, in whom hyperuricaemia is common.

Methods

Seventy-one volunteers (35–80 years), with impaired fasting glucose and/or impaired glucose tolerance were randomised to three groups, vitamin D₃, vitamin D₂ and control, and followed for 12 months.

Results

After 12 weeks, vitamin D supplementation was associated with a reduction in serum uric acid concentration in participants with baseline uric acid concentration > 6 mg/dL, but no significant change was observed in controls. We then assessed the dose–response relationship between vitamin D supplementation and the change in serum uric acid concentration and found that the change in serum total 25-hydroxyvitamin D did not correlate with the change in serum uric acid that occurred during vitamin D supplementation. The factors associated with larger reductions in serum uric acid were a higher baseline serum uric acid and a larger increase in serum 1,25-dihydroxyvitamin D.

Conclusions

Vitamin D supplementation lowers serum uric acid in prediabetic patients with hyperuricaemia, and supplementation might be considered to help alleviate hyperuricaemia in these patients.

Gene expression profile unveils diverse biological effect of serum vitamin D in Hodgkin's and diffuse large B-cell lymphoma

The primary function of 25(OH)Vitamin D (VitD) is to control calcium; however, recent evidence associated serum VitD deficiency to high aggressiveness and worse outcome in different type of malignancies including lymphomas, and the reasons of such effect are to be defined. In this study, we investigated the association of VitD blood levels with gene expression in a retrospective cohort of 181 lymphomas (104 diffuse large B-cell lymphomas [DLBCLs] and 77 classical Hodgkin's lymphomas [cHLs]) of whom 116 with available gene expression profiles (52 DLBCLs and 64 cHLs, respectively). In DLBCL, VitD deficiency did not cause significant alteration in gene expression suggesting different mechanisms of action including a possible systemic effect or an effect on pharmacokinetics. By contrast, in cHLs, VitD deficiency induced profound changes in the transcriptional program leading to the NF-κB-mediated activation of stress-protective and pro-survival pathways. Coherently, VitD signaling defined by vitamin D Receptor (VDR) expression analysis, resulted highly activated in cHLs but not in DLBCLs. Even if preliminary, these data represent the first evidence of a direct role of VitD in the biology of cHL and suggest a multimodality and disease-specific activity of this vitamin in lymphomas.

Effect of ultraviolet radiation on vertebrate animals: update from ethological and medical perspectives

Many animals under human care are kept indoors to prevent infectious diseases vectored by wildlife, facilitate environment control, or due to the lifestyle of their owners. However, ultraviolet radiation has documented effects on animal vision, vitamin synthesis, immunity, behavior, psychogenic disorders and on their environment. Ultraviolet-emitting lights are commercially available and the documentation of their effect on indoor-housed animals is increasing. This article reviews published information about ultraviolet effects in vertebrate animals from veterinary and ethological perspectives, and techniques used to assess ultraviolet exposure across animal taxa.

A Narrative Role of Vitamin D and Its Receptor: With Current Evidence on the Gastric Tissues

Vitamin D is a major steroid hormone that is gaining attention as a therapeutic molecule. Due to the general awareness of its importance for the overall well-being, vitamin D deficiency (VDD) is now recognized as a major health issue. The main reason for VDD is minimal exposure to sunlight. The vitamin D receptor (VDR) is a member of the steroid hormone receptors that induces a cascade of cell signaling to maintain healthy Ca²⁺ levels that serve to regulate several biological functions. However, the roles of vitamin D and its metabolism in maintaining gastric homeostasis have not yet been completely elucidated. Currently, there is a need to increase the vitamin D status in individuals worldwide as it has been shown to improve musculoskeletal health and reduce the risk of chronic illnesses, including some cancers, autoimmune and infectious diseases, type 2 diabetes mellitus, neurocognitive disorders, and general mortality. The role of vitamin D in gastric homeostasis is crucial and unexplored. This review attempts to elucidate the central role of vitamin D in preserving and maintaining the overall health and homeostasis of the stomach tissue.

Vitamin D basis of Alzheimer's disease: from genetics to biomarkers

Alzheimer's disease (AD) is a progressive neurodegenerative disorder seen mostly in the elderly population. While to date AD research has focused on either neurochemical disruptions, genetic studies, or the pathological hallmarks, little has been done to establish a novel approach that would encompass all three aspects, one that would overcome the current barriers in AD research and determine the cause of AD and, eventually, discover a treatment. Meanwhile, there have been strong indications in recent years that vitamin D, a secosteroid hormone, and its receptors are fundamentally involved in neurodegenerative mechanisms. Observational studies have pointed to vitamin D deficiency as a genetic risk factor for AD, Parkinson's disease (PD), vascular dementia, and multiple sclerosis (MS), as well as other neurological disorders, brought about by alterations in genes involved in metabolism, transportation, and actions of vitamin D. Molecular studies have demonstrated that vitamin D treatments prevent amyloid production while also increasing its clearance from the brain in AD. Finally, recent vitamin D intervention studies have reported significant improvement in cognitive performance in subjects with senile dementia, mild cognitive impairment, and AD. This review aims to describe how a vitamin D research strategy, fully integrating all aspects of present-day AD research, would elucidate the genetic, molecular, and biochemical background of the disease.

A phase 1, open-label, dose escalation study of intravenous paricalcitol in combination with gemcitabine in patients with advanced malignancies

BACKGROUND

Calcitriol, the active analogue of vitamin D, is antiproliferative and enhances the cytotoxicity of several anticancer agents, including gemcitabine. The vitamin D receptor (VDR) is expressed in the tumor stroma and treatment with VDR ligands results in stromal remodeling and increased intratumoral gemcitabine delivery. Furthermore, calcitriol can decrease the activity of the gemcitabine deactivating enzyme cytidine deaminase (CDD). Because hypercalcemia has been the most worrisome calcitriol-related adverse event, the less hypercalcemic agent paricalcitol may be preferred for further investigation.

METHODS

The authors undertook a phase 1 study of gemcitabine in combination with escalating doses of paricalcitol administered weekly intravenously in patients with advanced cancers. A standard 3+3 dose escalation schema was used. Pharmacokinetic assessment of gemcitabine and its metabolite 2',2'-difluorodeoxyuridine (dFdU) was performed. Pharmacodynamic assessment of paricalcitol was performed by measurement of CDD activity in peripheral blood mononuclear cells.

RESULTS

A total of 44 patients were enrolled. Somnolence was the main dose-limiting toxicity. The highest dose of paricalcitol administered was 10.5 µg/kg. Hypercalcemia was infrequent and mild in severity. Paricalcitol did not appear to affect the pharmacokinetics of gemcitabine and dFdU. Evaluation of CDD activity was available for 9 patients; no clear trend for CDD activity after treatment with paricalcitol was established. The overall response rate was 4%; the rate of disease control was 67% in patients who were pretreated with gemcitabine. Progression-free and overall survival were 3.4 months and 6.5 months, respectively.

CONCLUSIONS

Paricalcitol can be administered safely in doses up to 7 µg/kg weekly with fixed dose rate gemcitabine without dose-limiting hypercalcemia. To the best of the authors' knowledge, the maximum tolerated dose has not been formally established to date. Preliminary clinical activity deserves further exploration.

Vitamin D Receptor Regulates Amyloid Beta 1-42 Production with Protein Disulfide Isomerase A3

The challenge of understanding the biology of neuronal amyloid processing could provide a basis for understanding the amyloid pathology in Alzheimer's disease (AD). Based on our previous studies, we have suggested that AD might be the consequence of a hormonal imbalance in which the critical hormone is vitamin D. The present study primarily focused on the creation of a condition that prevents the genomic or nongenomic action of vitamin D by disrupting vitamin D receptors (VDR or PDIA3/1,25MARRS); the effects of these disruptions on the series of proteins involved in secretases that play a crucial role in amyloid pathology and on amyloid beta (Aβ) production in primary cortical neurons were observed. VDR and PDIA3/1,25MARRS genes were silenced separately or simultaneously in E16 primary rat cortical neurons. The expression of target genes involved in APP processing, including Presenilin1, Presenilin2, Nicastrin, BACE1, ADAM10, and APP, was investigated with qRT-PCR and Western blot in this model. 1,25-Dihydroxyvitamin D₃ treatments were used to verify any transcriptional regulation data gathered from siRNA treatments by determining the mRNA expression of the target genes. Immunofluorescence labeling was used for the verification of silencing experiments and intracellular Aβ1-42 production. Extracellular Aβ1-42 level was assessed with ELISA. mRNA and protein expression results showed that 1,25-dihydroxyvitamin D₃ might affect the transcriptional regulation of the genes involved in APP processing. The intracellular and extracellular Aβ1-42 measurements in our study support this suggestion. Consequently, we suggest that 1,25-dihydroxyvitamin D₃ and its receptors are important parts of the amyloid processing pathway in neurons.

The nutritional biochemistry of wool and hair follicles

The rôle of various classes of nutrients (energy substrates, vitamins, minerals, amino acids) in the production of wool and hair from follicles, is considered for a variety of animal species. The wool and hair follicle have evolved a number of interesting features of carbohydrate metabolism including glutaminolysis, aerobic glycolysis, significant activity of the pentose phosphate pathway, and storage and mobilisation of glycogen. Presumably the necessity to continue to produce fibre despite fluctuations in the supply of oxygen and nutrients has resulted in some of these unique features, while others reflect the high level of DNA and protein synthesis occurring in the follicle. While it is considered that energy does not normally limit fibre growth, the relative contributions of aerobic and anerobic metabolism will greatly influence the amount of ATP available for follicle activity, such that energy availability may at times alter fibre growth. Alopecia and deficient fibre growth are consistent outcomes of deficiencies of biotin, riboflavin, pyridoxine, folate and pantothenic acid, but the precise rôles of these vitamins in follicle function await elucidation. Folate, in particular appears to play an important rôle in wool production, presumably reflecting its involvement in methionine metabolism. Cholecalciferol (vitamin D) significantly alters fibre growth in cultured follicles; vitamin D receptors are located in the outer root sheath, bulb, and dermal papilla of the follicle; and alopecia occurs in humans with defects in the vitamin D receptor. Retinol (vitamin A), too, appears to influence follicle function by altering keratinocyte proliferation and differentiation, with direct effects on the expression of keratin genes. The receptors for the retinoids are present in the keratogenous zone, the outer root sheath, the bulb, and the sebaceous glands. Vitamin A may also act indirectly on follicle function by influencing the activity of the insulin-like and epidermal growth factors and by altering vitamin D activity. At present there is little evidence implicating alpha-tocopherol (vitamin E) or phytylmenaquinone (vitamin K) in follicular events. Of the minerals, only copper and zinc have been shown to have direct effects on follicle function, independent of effects on food intake. Copper has direct effects on the activity of an unidentified enzyme on oxidation of thiol groups to form disulphide linkages. Wool produced by copper-deficient sheep lacks crimp, is weak and lustrous. Copper is also necessary for the activity of tyrosinase and the tyrosinase-related proteins involved in melanin synthesis. Zinc, like copper, is required for the normal keratinization of fibres but again, the precise rôle has yet to be elucidated. While the importance of amino acid supply for wool growth has long been established, there are still some unaswered questions such as; what are the effects of amino acids on fibre growth in animals other than sheep; what are the characteristics of the amino acid transport genes and proteins operating in the wool and hair follicle; and what are the specific rôles for amino acids in follicle function.

The Binding Mode Prediction and Similar Ligand Potency in the Active Site of Vitamin D Receptor with QM/MM Interaction, MESP, and MD Simulation

Non-secosteroidal ligands are well-known vitamin D receptor (VDR) agonists. In this study, we described a combined QM/MM to define the protein-ligand interaction energy a strong positive correlation in both QM-MM interaction energy and binding free energy against the biological activity. The molecular dynamics simulation study was performed, and specific interactions were extensively studied. The molecular docking results and surface analysis shed light on steric and electrostatic complementarities of these non-secosteroidal ligands to VDR. Finally, the drug likeness properties were also calculated and found within the acceptable range. The results show that bulky group substitutions in side chain decrease the VDR activity, whereas a small substitution increased it. Functional analyses of H393A and H301A mutations substantiate their roles in the VDR agonistic and antagonistic activities. Apart from the His393 and His301, two other amino acids in the hinge region viz. Ser233 and Arg270 acted as an electron donor/acceptor specific to the agonist in the distinct ligand potency. The results from this study disclose the binding mechanism of VDR agonists and structural modifications required to improve the selectivity.

Effect of serum 25-hydroxyvitamin D3 on insulin resistance and β-cell function in newly diagnosed type 2 diabetes patients

Aims/Introduction

To evaluate serum 25‐hydroxyvitamin D₃ (25(OH)D₃) in newly diagnosed type 2 diabetes patients and to explore the associations of 25(OH)D₃ with insulin resistance and β‐cell function.

Materials and Methods

A total of 97 newly diagnosed type 2 diabetes patients and 69 healthy controls were recruited. Serum 25(OH)D₃ was determined using high‐pressure liquid chromatography. Insulin resistance was measured using a homeostasis model assessment of insulin resistance (HOMA‐IR). β‐Cell function was determined using the HOMA β‐cell function index (HOMA‐β), early‐phase insulin secretion index (ΔI30/ΔG30) and area under the insulin curve (AUCins). Correlation analysis was carried out using Pearson's correlation and multiple stepwise regression analysis.

Results

Serum 25(OH)D₃ was much lower in patients with newly diagnosed type 2 diabetes (t = −13.00, P < 0.01), and the prevalence of hypovitaminosis 25(OH)D₃ was 62.9% (61/97) in diabetic patients. Among the diabetic patients, patients with hypovitaminosis 25(OH)D₃ showed higher glycosylated hemoglobin and AUCglu (P < 0.01) as well as lower HOMA‐β, ΔI30/ΔG30 and AUCins. Serum 25(OH)D₃ was independently positively correlated with ΔI30/ΔG30 and AUCins (P < 0.05), but was not significantly correlated with either HOMA‐IR or HOMA‐β. Only triglycerides, glycosylated hemoglobin and ΔI30/ΔG30 emerged as independent factors associated with serum 25(OH)D₃ in both diabetes patients and the health control group.

Conclusions

The present results further showed a low serum 25(OH)D₃ concentration in patients with newly diagnosed type 2 diabetes. 25(OH)D₃ deficiency is associated with disturbances in glucose metabolism and lipid metabolism. Serum 25(OH)D₃ is not correlated with basal insulin resistance or β‐cell function, but is significantly positively correlated with glucose‐stimulated insulin secretion and β‐cell function.

The Effect of Vitamin D Treatment On Nerve Growth Factor (NGF) Release From Hippocampal Neurons

INTRODUCTION

Vitamin D, the main function of which is thought to be the maintenance of calcium and phosphate homeostasis and bone structure, has been shown in recent studies to have important roles in brain development as well. A certain vitamin D receptor (VDR) gene haplotype was reported, for the first time by our group, to increase the risk of developing Alzheimer's disease. Our studies also showed that vitamin D prevents beta amyloid-induced calcium elevation and toxicity that target nerve growth factor (NGF) release in cortical neurons; beta amyloid suppresses VDR expression and the disruption of vitamin D-VDR pathway mimics beta amyloid-induced neurodegeneration. In this study, our aim was to investigate the effects of vitamin D on the NGF release from hippocampal neurons.

METHOD

Primary hippocampal neuron cultures that were prepared from 18-day-old Sprague-Dawley rat embryos were treated with vitamin D for 48 hours. The alteration in the NGF release was determined with ELISA. Cytotoxicity tests were also performed for all groups.

RESULTS

The NGF release in vitamin D-treated group was significantly higher than in untreated control group. The protective effect of vitamin D against cytotoxicity was also observed.

CONCLUSION

Our results indicated that vitamin D regulates the release of NGF, a very important molecule for neuronal survival of hippocampal neurons as well as cortical neurons.

Vitamin d deficiency in children with cancer

A limited number of small studies have examined the vitamin D status of pediatric oncology patients, and the results indicate an increased prevalence of hypovitaminosis. We conducted a cross-sectional study with the primary aim of describing the vitamin D status of our pediatric cancer patients and any associations with demographic characteristics. Our secondary aim was to compare this prevalence to that of a healthy population. We collected data on children seen in our clinic and determined the overall prevalence of hypovitaminosis. We then compared this prevalence to that of healthy populations described in the literature. The prevalence of hypovitaminosis in our study population was 72%. Forty-three percent of our patients were considered deficient with 8% being severely deficient. Our analysis revealed a significant association between the outcome and age in that patients 6 years and above were more likely to have hypovitaminosis after adjustment for other characteristics (AOR = 3.23; 95% CI, 1.11-9.40). When compared with a healthy pediatric population, our patients had a significantly higher prevalence of hypovitaminosis (P-value = 0.003). Vitamin D deficiency is very common in children with cancer, representing a subpopulation of high-risk patients that could benefit most from early detection and supplementation.

Vitamin D receptor activation: cardiovascular and renal implications

The effects of vitamin D receptor activation on cardiovascular diseases, especially hypertension and cardiac dysfunction, are areas of active investigation. This article reviews the current state of knowledge about vitamin D receptor activation with respect to blood pressure, heart, and vascular health, as well as to chronic kidney disease and end-stage renal disease. Potential biological mechanisms, the role of vitamin D-binding protein, and data from observational and randomized controlled trials on this topic are summarized.

9-cis retinoic acid is the ALDH1A1 product that stimulates melanogenesis

Aldehyde dehydrogenase 1A1 (ALDH1A1), an enzyme that catalyses the conversion of lipid aldehydes to lipid carboxylic acids, plays pleiotropic roles in UV-radiation resistance, melanogenesis and stem cell maintenance. In this study, a combination of RNAi and pharmacologic approaches were used to determine which ALDH1A1 substrates and products regulate melanogenesis. Initial studies revealed that neither the UV-induced lipid aldehyde 4-hydroxy-2-nonenal nor the ALDH1A1 product all-trans retinoic acid appreciably induced melanogenesis. In contrast, both the ALDH1A1 substrate 9-cis retinal and its corresponding product 9-cis retinoic acid potently induced the accumulation of MITF mRNA, Tyrosinase mRNA and melanin. ALDH1A1 depletion inhibited the ability of 9-cis retinal but not 9-cis retinoic acid to stimulate melanogenesis, indicating that ALDH1A1 regulates melanogenesis by catalysing the conversion of 9-cis retinal to 9-cis retinoic acid. The addition of potent ALDH1A inhibitors (cyanamide or Angeli's salt) suppressed Tyrosinase and MITF mRNA accumulation in vitro and also melanin accumulation in skin equivalents, suggesting that 9-cis retinoids regulate melanogenesis in the intact epidermis. Taken together, these studies not only identify cyanamide as a potential novel treatment for hyperpigmentary disorders, but also identify 9-cis retinoic acid as a pigment stimulatory agent that may have clinical utility in the treatment of hypopigmentary disorders, such as vitiligo.

Extraskeletal effects and manifestations of Vitamin D deficiency

The actions of vitamin D are not confined to bone. Vitamin D receptors are present in nearly all the nuclei and its actions are manifold. Populations deficient in vitamin D are at higher risk of developing autoimmune diseases, diabetes, cancer, infections, allergies and other chronic illnesses.

Allelic variations in coding regions of the vitamin D receptor gene in dairy cows and potential susceptibility to periparturient hypocalcaemia

Periparturient hypocalcaemia (milk fever) is a disorder of Ca metabolism in dairy cattle primarily affecting multiparous cows. The major reasons for the rapid decrease of blood Ca concentration after calving are the prompt increase of Ca secretion into the colostrum and the delayed activation of Ca regulation mechanisms including calcitriol, a metabolite of vitamin D. In man, vitamin D receptor (VDR) gene polymorphisms are reported to be associated with disturbances of Ca metabolism, whereas data confirming the same in dairy cows are still missing. Moreover, polymorphisms that only affect non-coding regions are sometimes difficult to ascribe to a specific disorder as pathways and unequivocal links remain elusive. Therefore, the idea of the present study was to investigate in a small group of dairy cows with documented clinical records whether polymorphisms in the coding regions of the VDR gene existed and whether these potentially found variations were correlated with the incidence of periparturient hypocalcaemia. For this purpose, blood DNA was isolated from 26 dairy cows in their 4th to 6th lactation, out of which 17 had experienced hypocalcaemia at least once, whereas 9 cows had never undergone periparturient hypocalcaemia in their lifetime. The 10 VDR exons and small parts of adjacent introns were sequenced and compared with the Bos taurus VDR sequence published on NCBI based on the DNA of one Hereford cow. In total, 8 sequence alterations were detected in the fragments, which were primarily heterozygous. However, only 4 of them were really located on exons thereby potentially causing changes of the encoded amino acid of the VDR protein, but were not correlated with the incidence of periparturient hypocalcaemia. Certainly, this lack of statistical correlation could be due to the small number of animals included; anyhow, it was not encouraging enough to initiate a larger study with hundreds of cows and document blood Ca levels post partum for at least four lactations.

Low 25-Hydroxyvitamin D Does Not Affect Insulin Sensitivity in Obesity after Bariatric Surgery

OBJECTIVE

A positive correlation between levels of 25-hydroxyvitamin D [25(OH)D] and insulin sensitivity has been shown in healthy subjects. We aimed to test the hypothesis that concentration of 25(OH)D influences insulin sensitivity in obesity before and after weight loss.

RESEARCH METHODS AND PROCEDURES

We investigated the relation between serum 25(OH)D and insulin sensitivity (estimated by euglycemic-hyperinsulinemic clamp) in 116 obese women (BMI > or = 40 kg/m2) evaluated before and 5 and 10 years after biliopancreatic diversion (BPD). Body composition was estimated by the isotope dilution method.

RESULTS

Prevalence of hypovitaminosis D was 76% in the obese status and 91% and 89% at 5 and 10 years after BPD, respectively, despite ergocalciferol supplementation. 25(OH)D concentration decreased from 39.2 +/- 22.3 in obesity (p = 0.0001) to 27.4 +/- 16.4 and 25.1 +/- 13.9 nM 5 and 10 years after BPD, respectively. Whole-body glucose uptake increased from 24.27 +/- 4.44 at the baseline to 57.29 +/- 11.56 and 57.71 +/- 8.41 mumol/kg(fat free mass) per minute 5 and 10 years after BPD, respectively (p = 0.0001). Predictor of 25(OH)D was fat mass (R2 = 0.26, p = 0.0001 in obesity; R2 = 0.20, p = 0.02 after BPD). Parathormone correlated with fat mass (R2 = 0.19; p = 0.0001) and BMI (R2 = 0.053; p = 0.01) and inversely with M value (R2 = 0.16; p = 0.0001), but only in obese subjects.

DISCUSSION

A high prevalence of hypovitaminosis D was observed in morbid obesity both before and after BPD. Low 25(OH)D did not necessarily imply increased insulin resistance after BPD, a condition where, probably, more powerful determinants of insulin sensitivity overcome the low circulating 25(OH)D levels. However, the present data cannot exclude some kind of influence of vitamin D status on glucose and insulin metabolism.

Vitamin D deficiency is widespread in cancer patients and correlates with advanced stage disease: a community oncology experience

The purpose of this study was to correlate serum vitamin D levels with potential clinical variables and to determine the extent of vitamin D deficiency in a large, outpatient oncology practice. One hundred ninety-five consecutive patients referred for consultation at a community radiation oncology center from October 8, 2008 to March 17, 2010 had vitamin D levels ordered. Patients who were deficient in vitamin D were treated with replacement therapy. Demographic and medical data were collected prospectively and subsequently analyzed. Pretreatment baseline patient and tumor characteristics were evaluated with respect to vitamin D concentrations. One hundred and sixty patients were analyzed. A total of 74% of patients had 25-hydroxyvitamin D concentrations considered either deficient (<20 ng/mL) or suboptimal (20-30 ng/mL). Replacement therapy raised serum vitamin D levels by an average of 15 ng/mL (95% CI = 11-18, P < 0.01). Lower than median serum vitamin D levels were associated with stage III disease in univariate analysis [OR = 2.6 (95% CI = 1.1-6.2), p = 0.04] as well as multivariate analysis adjusted for age, sex, body mass index, and season of draw [OR = 3.3 (95% CI = 1.1-9.7), P = 0.03]. Three-quarters of patients in our series had suboptimal or deficient circulating concentrations of 25-hydroxyvitamin D. Low serum vitamin D levels, independent of age, sex, and body mass index, predicted advanced stage disease.

1α,25-Dihydroxyvitamin D3 inhibits osteoblastic differentiation of mouse periodontal fibroblasts

OBJECTIVE

Periodontal ligament (PDL) is a non-mineralized tissue connecting cementum and alveolar bone. Recent studies have suggested that periodontal fibroblasts can differentiate into mineralized tissue-forming cells such as osteoblasts and cementoblasts. We elucidated the immunolocalization of vitamin D receptor (VDR) and the effects of vitamin D(3) (VD(3)) on mouse periodontal fibroblasts to clarify the role of VDR and VD(3) in the differentiation of periodontal fibroblasts.

DESIGN

Immunohistochemical analysis using anti-VDR antibody was performed in paraffin sections of mouse mandibles at E13, E14, E17, P10, and P35. The roles of VD(3) in osteoblastic differentiation and mineralization were estimated by alkaline phosphatase (ALP) and alizarin red (AR) staining. In addition, the mRNA expression of osteoblast markers and mineralization inhibitors was examined by real-time PCR.

RESULTS

At the bud, cap and early bell stages, immunoreactivity for VDR was scarcely seen in the cells of dental follicles. Labelling was detected in the nuclei of cemetoblasts, periodontal fibroblasts and osteoblasts during root formation. VD(3) inhibited ALP activity and AR-positive mineralized nodule formation of periodontal fibroblasts in osteogenic culture medium. Real-time PCR revealed that VD(3) down-regulated the levels of osteoblast markers. In contrast, VD(3) significantly up-regulated the level of periodontal ligament associated protein (PLAP)-1, a negative regulator of osteoblastic differentiation.

CONCLUSION

These results suggest that VD(3) negatively regulates the osteoblastic differentiation of mouse periodontal fibroblasts and prevents the periodontal ligament from mineralization via increase of PLAP-1.

The effects of vitamin D receptor silencing on the expression of LVSCC-A1C and LVSCC-A1D and the release of NGF in cortical neurons

Background

Recent studies have suggested that vitamin D can act on cells in the nervous system. Associations between polymorphisms in the vitamin D receptor (VDR), age- dependent cognitive decline, and insufficient serum 25 hydroxyvitamin D₃ levels in Alzheimer's patients and elderly people with cognitive decline have been reported. We have previously shown that amyloid β (Aβ) treatment eliminates VDR protein in cortical neurons. These results suggest a potential role for vitamin D and vitamin D-mediated mechanisms in Alzheimer's disease (AD) and neurodegeneration. Vitamin D has been shown to down-regulate the L-type voltage-sensitive calcium channels, LVSCC-A1C and LVSCC-A1D, and up-regulate nerve growth factor (NGF). However, expression of these proteins when VDR is repressed is unknown. The aim of this study is to investigate LVSCC-A1C, LVSCC-A1D expression levels and NGF release in VDR-silenced primary cortical neurons prepared from Sprague-Dawley rat embryos.

Methodology/Principal Findings

qRT-PCR and western blots were performed to determine VDR, LVSCC-A1C and -A1D expression levels. NGF and cytotoxicity levels were determined by ELISA. Apoptosis was determined by TUNEL. Our findings illustrate that LVSCC-A1C mRNA and protein levels increased rapidly in cortical neurons when VDR is down-regulated, whereas, LVSCC-A1D mRNA and protein levels did not change and NGF release decreased in response to VDR down-regulation. Although vitamin D regulates LVSCC-A1C through VDR, it may not regulate LVSCC-A1D through VDR.

Conclusions/Significance

Our results indicate that suppression of VDR disrupts LVSCC-A1C and NGF production. In addition, when VDR is suppressed, neurons could be vulnerable to aging and neurodegeneration, and when combined with Aβ toxicity, it is possible to explain some of the events that occur during neurodegeneration.

Does vitamin D make the world go 'round'?

Abstract Vitamin D has emerged from obscurity, and its effects on various organ systems throughout the body down to the cellular level are being discovered. What was once thought to be a simple hormone affecting only bone and calcium metabolism has shifted. We no longer see vitamin D as a "vitamin" important only in childhood, but as a complex hormone that is involved not only in calcium homeostasis but also in the integrity of the innate immune system. Vitamin D deficiency is linked to inflammatory and long-latency diseases such as multiple sclerosis, rheumatoid arthritis, tuberculosis, diabetes, and various cancers, to name a few. In this review, we trace how we came to view vitamin D and how that view led to one of the largest epidemics of nutrient deficiency beginning in the late 20(th) century. We then discuss the needs of vitamin D in the context of the breastfeeding mother and her infant and child, why breastfed infants are particularly at risk, and what to do about it.

Selective inhibition of cyclooxygenase-2 (COX-2) by 1alpha,25-dihydroxy-16-ene-23-yne-vitamin D3, a less calcemic vitamin D analog

Inducible cyclooxygenase-2 (COX-2) has been implicated to play a role in inflammation and carcinogenesis and selective COX-2 inhibitors have been considered as anti-inflammatory and cancer chemopreventive agents. 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3), the active hormonal form of vitamin D3 also has been considered to be a cancer chemopreventive agent in addition to its important role in maintaining calcium homeostasis. Based on these observations, we studied the direct effect of 1alpha,25(OH)2D3 and one of its less calcemic synthetic analogs, 1alpha,25(OH)2-16-ene-23-yne-D3 on the activity of both COX-1 and COX-2 in an in vitro enzyme assay. Preliminary data indicated that both 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-23-yne-D3 inhibited selectively the activity of COX-2 with no effect on the activity of COX-1. Out of the two compounds, 1alpha,25(OH)2-16-ene-23-yne-D3 was found to be more effective with an IC50 of 5.8 nM. Therefore, the rest of the experiments were performed using 1alpha,25(OH)2-16-ene-23-yne-D3 only. 1alpha,25(OH)2-16-ene-23-yne-D3 inhibited the proliferation of lipopolysaccharide (LPS) stimulated mouse macrophage cells (RAW 264.7) with a reduction in the expression of COX-2 along with other inflammatory mediators like inducible nitric oxide synthase (iNOS) and interleukin-2 (IL-2). Furthermore, 1alpha,25(OH)2-16-ene-23-yne-D3 also inhibited carrageenan induced inflammation in an air pouch of a rat and effectively reduced the expression of COX-2, iNOS, and IL-2 in the tissues of the same air pouch. In both cases, 1alpha,25(OH)2-16-ene-23-yne-D3 did not show any effect on the expression of COX-1. In summary, our results indicate that 1alpha,25(OH)2-16-ene-23-yne-D3, a less calcemic vitamin D analog, exhibits potent anti-inflammatory effects and is a selective COX-2 inhibitor.

Vitamin D receptor genotypes influence quadriceps strength in chronic obstructive pulmonary disease

BACKGROUND

Quadriceps weakness is an important complication of chronic obstructive pulmonary disease (COPD) and is associated with impaired exercise capacity and greater mortality. Its etiology is multifactorial, and evidence is growing that it is partly determined by genetic susceptibility.

OBJECTIVE

Using an established cohort, we tested whether quadriceps weakness in patients with COPD is influenced by common variations in the gene for the vitamin D receptor.

DESIGN

Vitamin D receptor FokI and BsmI genotypes and the (I/D) angiotensin-converting enzyme (ACE) and bradykinin receptor (+9/-9) genotypes were identified in 107 patients with stable COPD [x +/- SD forced expiratory volume in 1 s (FEV(1)): 34.5 +/- 16.5] and 104 healthy, age-matched control subjects. Quadriceps maximum voluntary contraction force and fat-free mass assessed by bioelectrical impedance analysis were measured.

RESULTS

After adjustment for covariables, both patients and control subjects who were homozygous for the C allele of the FokI polymorphism had less quadriceps strength than did those with > or =1 T allele [41.0 +/- 11.8 compared with 46.0 +/- 13.2 kg (P = 0.01) and 32.5 +/- 11.2 compared with 36.2 +/- 13.1 kg (P = 0.005), respectively]. The b allele of the BsmI polymorphism was associated with greater quadriceps strength in patients-37.0 +/- 13.3, 33.8 +/- 11.6, and 33.8 +/- 11.6 kg for bb, bB, and BB, respectively (P = 0.0005)-but had no effect in healthy control subjects. The effect of BsmI on quadriceps strength was least apparent in patients with the ACE II genotype (P = 0.003).

CONCLUSIONS

The FokI common variants in the VDR gene are associated with skeletal muscle strength in both patients and control subjects, whereas the BsmI polymorphism is associated with strength only in patients.

Vitamin D deficiency associated with self-neglect in the elderly

BACKGROUND

Vitamin D deficiency is common in elders. However, little is known about the implications of vitamin D deficiency in elder self-neglect.

SPECIFIC AIMS

To characterize a group of self-neglecting elders with vitamin D deficiency based on clinical, cognitive, and functional status. Participants. Forty-four self-neglecting elders referred by the Adult Protective Services.

METHODS

Vitamin D status of the self-neglecting elders was based upon serum levels of 25-hydroxyvitamin D (25-OHD). Demographics, cognitive, and functional characteristics of vitamin D deficient self-neglecting elders were described and compared to those without vitamin D deficiency.

RESULTS

Vitamin D deficiency (25-OHD < 25 nmol/L) was detected in 16 out of 44 self-neglecting elders (36%). Self-neglecting elders with vitamin D deficiency had lower scores in the Physical Performance Test and higher scores in the Kohlman Evaluation of Living Skills, compared with those who were not vitamin D deficient (p = 0.014 and p = 0.018 respectively).

CONCLUSIONS

Vitamin D deficiency is common in elder self-neglect. Self-neglecting elders with vitamin D deficiency have impaired physical performance and inadequate living skills, which can be potentially improved by treating vitamin D deficiency.

Vitamin D deficiency in a multinational refugee population

BACKGROUND

Populations with increased skin pigmentation who have migrated to countries of high latitude are at increased risk of low vitamin D. This study aimed to determine the prevalence of low vitamin D among the refugee population arriving in New Zealand.

METHODS

An audit of all refugees arriving at the national refugee resettlement centre from May 2004 to May 2005 was carried out. Serum 25-hydroxyvitamin D3 levels were measured and defined as normal (50-150 nmol/L) or low, with low subdivided into insufficient (25 to <50 nmol/L) and deficient (<25 nmol/L). Whether vitamin D status varied with age and sex was determined.

RESULTS

Vitamin D was measured in 869 (99%) of the refugees and was low in 470 (54%, 95% confidence interval (CI) 51-57%). It was insufficient in 323 (37%, 95%CI 34-41%) and deficient in 147 (17%, 95%CI 15-20%). Female sex was associated with at least a 10 times increased risk of vitamin D deficiency (relative ratio 13.93, 95%CI 10.15-17.96). Women aged between 17 and 45 years and men aged 46 years and more were at greatest risk.

CONCLUSION

Poor vitamin D status is prevalent among refugees arriving in New Zealand. Women, particularly those of child-bearing age are at greatest risk. Screening and ongoing surveillance for vitamin D deficiency should be considered for all recent refugee immigrants to New Zealand.

Vitamine D : Métabolisme, régulation et maladies associées

Vitamin D is well known as a hormone involved in mineral metabolism and bone growth. Conversion into the active metabolite 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) from the precursor is effected by cytochrome P450 enzymes in the liver (CYP27A1 and CYP2R1) and the kidney (CYP27B1). CYP27A1 has been shown to be transcriptionally regulated by nuclear receptors (PPARalpha, gamma, HNF-4alpha and SHP) which are ligand-dependent transcription factors. CYP27B1 is tightly regulated by the plasma levels of calcium, phosphate, parathyroid hormone (PTH) and 1,25(OH)2D3 itself. In vitamin D target organs, inactivation of vitamin D is attributed to CYP24A1 which is transcriptionally induced by 1,25(OH)2D3 whose action is mediated by binding to its cognate nuclear receptor, the vitamin D receptor (VDR). Diseases associated to Vitamin D deficiency (rickets in children, and osteomalacia or osteoporosis in adults) and autosomal recessive forms of inherited rickets illustrate the key role of vitamin D in calcium homeostasis and bone metabolism. Recently, discovery of 1,25(OH)2D3 new biological actions that include antiproliferative, prodifferentiating effect on many cell types and immunoregulatory properties creates a growing interest for this vitamin. In this way, a best understanding of various actors implicated in vitamin D metabolism and its regulation is of a major importance to optimise the use of vitamin D in disease prevention.

Identification and characterization of noncalcemic, tissue-selective, nonsecosteroidal vitamin D receptor modulators

Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of skin, prostate, colon, and breast as well as leukemia. However, the major side effect of VDR ligands that limits their expanded use and clinical development is hypercalcemia that develops as a result of the action of these compounds mainly on intestine. In order to discover VDR ligands with less hypercalcemia liability, we sought to identify tissue-selective VDR modulators (VDRMs) that act as agonists in some cell types and lack activity in others. Here, we describe LY2108491 and LY2109866 as nonsecosteroidal VDRMs that function as potent agonists in keratinocytes, osteoblasts, and peripheral blood mononuclear cells but show poor activity in intestinal cells. Finally, these nonsecosteroidal VDRMs were less calcemic in vivo, and LY2108491 exhibited more than 270-fold improved therapeutic index over the naturally occurring VDR ligand 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in an in vivo preclinical surrogate model of psoriasis.

The role of vitamin D in cancer prevention

Vitamin D status differs by latitude and race, with residents of the northeastern United States and individuals with more skin pigmentation being at increased risk of deficiency. A PubMed database search yielded 63 observational studies of vitamin D status in relation to cancer risk, including 30 of colon, 13 of breast, 26 of prostate, and 7 of ovarian cancer, and several that assessed the association of vitamin D receptor genotype with cancer risk. The majority of studies found a protective relationship between sufficient vitamin D status and lower risk of cancer. The evidence suggests that efforts to improve vitamin D status, for example by vitamin D supplementation, could reduce cancer incidence and mortality at low cost, with few or no adverse effects.

Sun exposure and age at natural menopause: A cross-sectional study in Turkish women

OBJECTIVES

In a cross-sectional study of 157 Turkish women attending outpatient clinics of a university hospital during April-May 2003, association between various subject characteristics and menopause timing was investigated.

METHODS

Characteristics were self-reported by women aged 45-60. Of the lifestyle factors, sun exposure, physical activity, food intake and dressing with headscarf were obtained as recalled average lifelong practices up to time of menopause. Cox proportional hazard modeling was used, censoring for hysterectomy, oopherectomy and HRT use.

RESULTS

Median age at natural menopause was 52 years. In multivariate analysis, earlier natural menopause was associated with low level of lifelong sun exposure (HR=6.381, 95% CI: 2.996-13.588, p< or =0.0001), heavy physical activity (HR=2.335, 95% CI: 1.305-4.177, p=0.0043), current calcium supplement use (HR=3.191, 95% CI: 1.361-7.485, p=0.0076), diagnosis of hypertension (HR=2.002, 95% CI: 1.186-3.378, p=0.0093), not owning a house (HR=3.002, 95% CI: 1.148-7.852, p=0.0250) and longer years on oral contraceptives (HR=1.085, 95% CI: 1.000-1.176, p=0.0487). Engagement in farming (HR=2.043, 95% CI: 1.056-3.952, p=0.0339), height (cm) (HR=0.953, 95% CI: 0.907-0.994, p=0.0279) and fish consumption (servings/week) (HR=0.600, 95% CI: 0.375-0.960, p=0.0331) were associated with age at menopause in univariate analysis only. For n=109 women who recalled whether maternal menopausal age was <50 or > or =50, sun exposure (HR=7.221, 95% CI: 2.971-17.547, p<0.0001) was a stronger predictor of age at natural menopause than maternal menopausal age (HR=2.882, 95% CI: 1.477-5.621, p=0.0019).

CONCLUSIONS

We identify some previously unrecognized correlates of age at natural menopause, namely self-reported lifelong sun exposure, lifelong physical activity, house-ownership, current use of calcium supplements, and lifelong fish consumption. These findings should be confirmed in larger studies.

Clinical Trials Involving Vitamin D Analogs in Prostate Cancer

Vitamin D shows significant potential as a therapy for prostate cancer. However, its use in clinical trials has been hampered by its induction of hypercalcemia at serum concentrations required to suppress cancer cell proliferation. This has spurred the development of less calcemic analogs of vitamin D. In this article, we review the clinical trials and consider the future directions of the use of vitamin D and its analogs in the treatment or chemoprevention of prostate cancer. First, we summarize the epidemiological evidence leading to the hypothesis that vitamin D has anticancer activity. We then review the clinical trials using vitamin D analogs that involve patients with prostate cancer and conclude with a brief overview of our planned study with vitamin D5, [1alpha(OH)D5], which will begin shortly. Data for this review were identified by searches of PubMed, the Cochrane Library, Biosis, and references from relevant articles, using the search terms "vitamin D," "prostate cancer," "chemoprevention" and "vitamin D analog." Abstracts from recent international meetings were also reviewed but were only included when they were the only known reference to the clinical trial or the research mentioned. Only papers published in English were included.

Side-chain-modified analogs of calcitriol cause resistance of human HL-60 promyelocytic leukemia cells to drug-induced apoptosis

Calcitriol and some of its analogs have antiproliferative activity, but at the same time, can cause resistance to apoptosis induced by known cytostatic drugs. In this paper, we examined the effects of treatment with calcitriol or its side-chain-modified analogs, analog of Vitamin D2, coded PRI-1906, with monohomologated and unsaturated side-chain and the analog of Vitamin D3, coded PRI-2191, with (24R) hydroxyl group, and those of known cytostatics (genistein, etoposide, doxorubicin, cisplatin, and taxol) on the apoptosis of HL-60 promyelocytic leukemia cells. HL-60 cells were incubated in three different sequences: (1) pre-treatment with calcitriol or its analogs and then treatment with cytostatics; (2) pre-treatment with cytostatics and then treatment with calcitriol; (3) simultaneous treatment with calcitriol and cytostatics. Apoptosis was examined either by DNA fragmentation in agarose gel electrophoresis or by cell-cycle analysis in a FACS Calibur flow cytometer. We showed that pre-treatment with calcitriol or one of its side-chain-modified analogs PRI-1906 or PRI-2191 caused resistance of HL-60 promyelocytic leukemia cells to genistein-, doxorubicin-, cisplatin-, and taxol-induced apoptosis. Simultaneous exposure of HL-60 cells to calcitriol and drug caused a significant decrease in the apoptotic level of HL-60 cells compared with cells treated with drug alone. The pre-treatment of HL-60 cells with drug and then treatment with calcitriol did not increase the level of apoptosis compared with the drug effect alone. These results indicate the potential limitations of calcitriol analogs for treatment of leukemia.

Management of vitamin d depletion in postmenopausal women

In the United States, the impact regarding the routine fortification of milk and other dairy products has been less than satisfactory in preventing vitamin D depletion in adults. As more individuals are being evaluated and treated for osteoporosis, it has become necessary to exclude vitamin D depletion as a cause, because of the likelihood that differences in vitamin D and calcium nutrition may modify the individual response to therapy. Increased prevalence of subclinical vitamin D depletion among vertebral and hip fracture patients and the beneficial effect of vitamin D therapy and calcium supplementation in preventing such fractures lend credence to this assumption. The prevalence of vitamin D depletion is increasing again, especially among older adults, precisely the group at greatest risk for osteoporotic fractures.

Development of weekly high-dose calcitriol based therapy for prostate cancer

Calcitriol, the principal biologically active ligand of the Vitamin D receptor (VDR), has been shown to inhibit cancer cell proliferation in in vitro and in vivo models of prostate cancer and a wide range of other neoplasms. In addition, calcitriol's activity appears to be additive, and in some experimental systems, synergistic with dexamethasone and several cytotoxic chemotherapy agents. While effects on progression through the cell cycle, induction of apoptosis, inhibition of angiogenesis, and reduction in tumor invasiveness have been demonstrated, the exact mechanisms of VDR-mediated antineoplastic activity remain incompletely understood. Antineoplastic activity of calcitriol requires substantially supraphysiologic concentrations of this compound. Dose escalation of calcitriol administered daily was severely limited by predictable hypercalcemia and/or hypercalcuria. This limitation has been overcome with intermittent dosing of calcitriol. At Oregon Health & Science University, weekly oral administration of calcitriol allowed the attainment of peak serum calcitriol concentrations well above 1 nM, a concentration that inhibits prostate cancer proliferation by more than 50% in vitro. Weekly high-dose calcitriol was then combined with weekly docetaxel in a Phase II clinical trial carried out in men with metastatic androgen-independent prostate cancer. Treatment resulted in PSA response (defined as a confirmed 50% reduction) in 81% of patients. This level of activity, as well as the median time to progression of 11.4 months and median survival of 19.5 months, compared favorably to results with docetaxel alone and led to the development of a recently initiated randomized trial of docetaxel with calcitriol or placebo in the same patient population.

Selective inhibition of mammalian DNA polymerase alpha by vitamin D2 and D3

As described previously (H. Togashi et al. Biochem Pharmacol. 1998;56:583-590), the irradiated products of provitamin D(2) (ergosterol) inhibit the activities of eukaryotic DNA polymerases. In this report, therefore, we investigated whether vitamin D and its related compounds inhibited the activities of DNA polymerases. As expected, vitamin D(2) and vitamin D(3) were found to be selective inhibitors of mammalian DNA polymerase alpha (pol alpha) with IC(50) values of 123 and 96 micro M, respectively. On the other hand, provitamin D(2), provitamin D(3), and the active form of vitamin D(3) such as 1alpha,25-dihydroxyvitamin D(3) could not influence any of the DNA polymerase activities. Interestingly, vitamin D(3)-3beta-sulfate was a much stronger pol alpha inhibitor with an IC(50) value of 7.1 micro M. Vitamin D(2), vitamin D(3), and vitamin D(3)-3beta-sulfate could prevent the growth of NUGC-3 human gastric cancer cells with LD(50) values of 133, 77, and 44 micro M, respectively, but provitamin D(2) and provitamin D(3) could not. The cells were halted at the G1 phase in the cell cycle by these compounds.

Vitamin D receptor (VDR) mRNA and VDR protein levels in relation to vitamin D status, insulin secretory capacity, and VDR genotype in Bangladeshi Asians

Associations have been reported between vitamin D receptor (VDR) gene polymorphisms, type 1 diabetes, insulin secretion, and the insulin resistance syndrome. As VDR polymorphisms have no known functional significance, these findings may implicate a variant of the VDR gene or a locus in linkage disequilibrium with the VDR. We have examined VDR mRNA and VDR protein levels in relation to VDR polymorphisms (41 Bangladeshi subjects) and analyzed insulin secretory capacity (143 Bangladeshi subjects), allowing for other known determinants. Peripheral blood mononuclear cells (PBMCs) from subjects who had been genotyped for BsmI, ApaI, TaqI, and FokI VDR restriction fragment length polymorphisms were used for both total VDR mRNA quantitation (using TaqMan) and measurement of VDR protein levels (using a specific micro-immunoassay). Stepwise multiple regression analyses were used (to P < 0.05) to analyze the data. For the insulin secretion index, the best-fit model (n = 143, P < 0.0001) gave age (P = 0.002), TaqI (P < 0.0001), and BMI (P = 0.001) as independent determinants; with the inclusion of VDR mRNA and VDR protein levels, VDR mRNA was the sole independent determinant (n = 41, P = 0.024). However, the best-fit model for VDR mRNA (P = 0.004) gave FokI (P = 0.044) and TaqI (P = 0.04) genotypes and insulin secretory capacity (P = 0.042) as independent determinants. For VDR protein levels, the best-fit model (P = 0.006) gave TaqI genotype (P = 0.005) and circulating 1,25-dihydroxyvitamin-D levels (P = 0.03) as independent determinants. In conclusion, these studies confirm an association between VDR polymorphisms and insulin secretory capacity and demonstrate the VDR genotype to be a significant determinant of VDR mRNA and VDR protein levels in PBMCs, providing functional support to previously described genetic associations with the VDR gene. Furthermore, VDR expression has been shown to be a determinant of insulin secretory capacity.

Upregulation of lymphocyte apoptosis as a strategy for preventing and treating autoimmune disorders: a role for whole-food vegan diets, fish oil and dopamine agonists

Induced apoptosis of autoreactive T-lymphocyte precursors in the thymus is crucial for the prevention of autoimmune disorders. IGF-I and prolactin, which are lymphocyte growth factors, may have the potential to suppress apoptosis in thymocytes and thus encourage autoimmunity; conversely, dietary fish oil rich in omega-3 fats appears to upregulate apoptosis in lymphocytes. Since whole-food vegan diets may downregulate systemic IGF-I activity, it is proposed that such a diet, in conjunction with fish oil supplementation and treatment with dopamine agonists capable of suppressing prolactin secretion, may have utility for treating and preventing autoimmune disorders. This prediction is consistent with the extreme rarity of autoimmune disorders among sub-Saharan black Africans as long as they followed their traditional quasi-vegan lifestyles, and with recent ecologic studies correlating risks for IDDM and for multiple sclerosis mortality with animal product and/or saturated fat consumption. Moreover, there is evidence that vegan or quasi-vegan diets are useful in the management of rheumatoid arthritis, multiple sclerosis, and possibly SLE. The dopamine agonist bromocryptine exerts anti-inflammatory effects in rodent models of autoimmunity, and there is preliminary evidence that this drug may be clinically useful in several human autoimmune diseases; better tolerated D2-specific agonists such as cabergoline may prove to be more practical for use in therapy. The moderate clinical utility of supplemental fish oil in rheumatoid arthritis and certain other autoimmune disorders is documented. It is not unlikely that extra-thymic anti-inflammatory effects contribute importantly to the clinical utility of vegan diets, bromocryptine, and fish oil in autoimmunity. The favorable impact of low latitude or high altitude on autoimmune risk may be mediated by superior vitamin D status, which is associated with decreased secretion of parathyroid hormone; there are theoretical grounds for suspecting that parathyroid hormone may inhibit apoptosis in thymocytes. Androgens appear to up-regulate thymocyte apoptosis, may be largely responsible for the relative protection from autoimmunity enjoyed by men, and merit further evaluation for the management of autoimmunity in women. It will probably prove more practical to prevent autoimmune disorders than to reverse them once established; a whole-food vegan diet, coupled with fish oil and vitamin D supplementation, may represent a practical strategy for achieving this prevention, while concurrently lowering risk for many other life-threatening 'Western' diseases.