Active vitamin D increases myogenic differentiation in C2C12 cells via a vitamin D response element on the myogenin promoter.

Background: Skeletal muscle development during embryogenesis depends on proliferation of myoblasts followed by differentiation into myotubes/multinucleated myofibers. Vitamin D (VD) has been shown to affect these processes, but there is conflicting evidence within the current literature on the exact nature of these effects due to a lack of time course data. With 20%-40% of pregnant women worldwide being VD deficient, it is crucial that a clearer understanding of the impact of VD on myogenesis is gained. Methods: A detailed 8-day differentiation time course was used where C2C12 cells were differentiated in control media (2% horse serum) or with different concentrations of active VD, 1,25 (OH)2D3 (10-13 M, 10-11 M, 10-9 M or 10-7 M), and measurements were taken at 6 time points. DNA, creatine kinase and protein assays were carried out as well as quantitative PCR to determine expression of Myf5, MyoD, myogenin, MHC I, and MHC neonatal, MHC embryonic, MHC IIa, MHC IIx, and MHC IIb mRNAs. Transfections were carried out using one vector containing the myogenin promoter and another containing the same promoter with a 3 base mutation within a putative vitamin D response element (VDRE) to determine effects of 1,25 (OH)2D3 on myogenin transcription. Finally, a ChIP assay was performed to determine whether the VD receptor (VDR) binds to the putative VDRE. Results: 1,25(OH)2D3 caused an inhibition of proliferation and an increase in differentiation in C2C12 cells. Myf5, myogenin, MHC I, and MHC neonatal, MHC embryonic, MHC IIa, MHC IIx, and MHC IIb expression were all increased by 1,25(OH)2D3. Myotube size was also increased by VD. When the putative VDRE on the myogenin promoter was mutated, the increase in expression by VD was lost. ChIP analysis revealed that the VDR does bind to the putative VDRE on the myogenin promoter. Conclusion: Active VD directly increases myogenin transcription via a functional VDRE on the myogenin promoter, resulting in increased myogenic differentiation, increased expression of both the early and late MHC isoforms, and also increased myotube size. These results highlight the importance of VD status during pregnancy for normal myogenesis to occur, but further in vivo work is needed.

A Novel Immunomodulatory Mechanism by Which Vitamin D Influences Folate Receptor 3 Expression to Reduce COVID-19 Severity.

BACKGROUND/AIM: Identify potential mechanisms involving gene expression changes through which vitamin D supplementation could be beneficial in preventing adverse COVID-19 outcomes. MATERIALS AND METHODS: We performed a literature review to identify differentially expressed genes (DEGs) in the blood between severe and mild COVID-19 patients. We compared these with the top DEGs induced by 6 months of 10,000 IU/day vitamin D supplementation in healthy adults who were vitamin D deficient/insufficient. We used bioinformatic tools to look for a vitamin D response element (VDRE) in DEGs. RESULTS: FOLR3, RGS1, GPR84, and LRRN3 were the most significantly altered genes by 6 months of 10,000 IU/day vitamin D supplementation whose expression levels were also involved in COVID-19 severity. FOLR3 and GPR84 were found to be consistently up-regulated and RGS1 and LRRN3 consistently down-regulated in severe COVID-19 infection. FOLR3 and LRRN3 were down-regulated and RGS1 and GPR84 were up-regulated by 10,000 IU/day vitamin D supplementation. CONCLUSION: FOLR3 and RGS1 are expressed in neutrophils and lymphocytes, respectively. Vitamin D supplementation may decrease the neutrophil-lymphocyte ratio as has been reported in patients admitted with severe symptoms. There is evidence that vitamin D directly influences the expression of the RGS1 gene through vitamin D receptor binding. A potential negative VDRE (nVDRE) in an intron of the FOLR3 gene was found, which was homologous with two known nVDREs. Combined with other transcription factor elements near the newly identified nVDRE, these observations may explain the mechanism by which vitamin D regulates these genes, thus influencing COVID-19 outcomes.

Vitamin D Receptor/Vitamin D Response Element Directly Modulate Nestin Transcription to Ameliorate PAN-Induced Podocyte Morphological Changes.

BACKGROUND: The change of podocyte morphology is a pathologic feature of chronic kidney disease. Several studies have suggested that vitamin D plays a role in the protection of podocytes, but the underlying mechanism remains unclear. METHODS: The effects of paricalcitol on podocyte injury were tested in a puromycin aminonucleoside (PAN)-induced rat model and cultured mouse podocytes. Proteinuria, podocyte foot process (FP) effacement, and the expression of nestin and vitamin D receptor (VDR) were evaluated. VDR-siRNA or plasmids containing VDR-shRNA were transfected into podocytes to silence VDR expression. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were performed to verify the connection between VDR and nestin gene expression. RESULTS: Paricalcitol significantly alleviated proteinuria and podocyte FP effacement in PAN-induced nephrosis, which was accompanied by increased VDR expression in the glomeruli. Paricalcitol also inhibited PAN-induced nestin overexpression in the glomeruli. In an in vivo study, PAN significantly inhibited VDR protein expression, stimulated nestin protein expression, and resulted in nestin filament derangement in mouse podocytes, while paricalcitol treatment abolished these effects. In contrast, downregulation of VDR resulted in derangement and overexpression of nestin. ChIP assays demonstrated the presence of a vitamin D response element (VDRE) in the nestin promoter, and paricalcitol enhanced the binding of VDR to VDRE. Furthermore, luciferase reporter assays of the nestin promoter fragment showed that paricalcitol effectively repressed nestin reporter gene expression after PAN treatment, and mutation of VDRE abolished this effect. CONCLUSIONS: Paricalcitol directly regulates nestin transcription through the interaction of VDR/VDRE, thereby preventing morphological changes of podocytes in PAN nephropathy.

Cholecalciferol and metformin protect against lipopolysaccharide-induced endothelial dysfunction and senescence by modulating sirtuin-1 and protein arginine methyltransferase-1.

Endothelial cell activation through nuclear factor-kappa-B (NFkB) and mitogen-activated protein kinases leads to increased biosynthesis of pro-inflammatory mediators, cellular injury and vascular inflammation under lipopolysaccharide (LPS) exposure. Recent studies report that LPS up-regulated global methyltransferase activity. In this study, we observed that a combination treatment with metformin (MET) and cholecalciferol (VD) blocked the LPS-induced S-adenosylmethionine (SAM)-dependent methyltransferase (SDM) activity in Eahy926 cells. We found that LPS challenge (i) increased arginine methylation through up-regulated protein arginine methyltransferase-1 (PRMT1) mRNA, intracellular concentrations of asymmetric dimethylarginine (ADMA) and homocysteine (HCY); (ii) up-regulated cell senescence through mitigated sirtuin-1 (SIRT1) mRNA, nicotinamide adenine dinucleotide (NAD+) concentration, telomerase activity and total antioxidant capacity; and (iii) lead to endothelial dysfunction through compromised nitric oxide (NOx) production. However, these LPS-mediated cellular events in Eahy926 cells were restored by the synergistic effect of MET and VD. Taken together, this study identified that the dual compound effect inhibits LPS-induced protein arginine methylation, endothelial senescence and dysfunction through the components of epigenetic machinery, SIRT1 and PRMT1, which is a previously unidentified function of the test compounds. In silico results identified the presence of vitamin D response element (VDRE) sequence on PRMT1 suggesting that VDR could regulate PRMT1 gene expression. Further characterization of the cellular events associated with the dual compound challenge, using gene silencing approach or adenoviral constructs for SIRT1 and/or PRMT1 under inflammatory stress, could identify therapeutic strategies to address the endothelial consequences in vascular inflammation-mediated atherosclerosis.

Vitamin D signaling inhibits HBV activity by directly targeting the HBV core promoter.

Clinical and epidemiological studies support a role for vitamin D in suppressing hepatitis B virus (HBV). This antiviral role of vitamin D is widely attributed to vitamin D receptor (VDR)/retinoid X receptor-mediated regulation of host immunomodulatory genes through vitamin D response elements (VDREs) in their promoters. Here, we investigated the ability of calcitriol (1α,25-dihydroxyvitamin D3, metabolically activated vitamin D) to directly regulate HBV activity through this signaling pathway. We observed that calcitriol selectively inhibited only the HBV core promoter without affecting the HBV-PreS1, HBV-PreS2/S, or HBx promoters. We then identified a VDRE cluster in the HBV core promoter that is highly conserved across most HBV genotypes. Disruption of this VDRE cluster abrogated calcitriol-mediated suppression of the HBV core promoter. Furthermore, we showed that VDR interacts directly with the VDRE cluster in the HBV core promoter independent of retinoid X receptor. This demonstrates that calcitriol inhibits HBV core promoter activity through a noncanonical calcitriol-activated VDR pathway. Finally, we observed that calcitriol suppressed expression of the canonical HBV core promoter transcripts, pregenomic RNA, and precore RNA in multiple HBV cell culture models. In addition, calcitriol inhibited the secretion of hepatitis B "e" antigen and hepatitis B surface antigen (HBV-encoded proteins linked to poor disease prognosis), without affecting virion secretion. Our findings identify VDR as a novel regulator of HBV core promoter activity and also explain at least in part the correlation of vitamin D levels to HBV activity observed in clinical studies. Furthermore, this study has implications on the potential use of vitamin D along with anti-HBV therapies, and lays the groundwork for studies on vitamin D-mediated regulation of viruses through VDREs in virus promoters.

Vitamin D Inhibits IL-22 Production Through a Repressive Vitamin D Response Element in the il22 Promoter.

Th22 cells constitute a recently described CD4+ T cell subset defined by its production of interleukin (IL)-22. The action of IL-22 is mainly restricted to epithelial cells. IL-22 enhances keratinocyte proliferation but inhibits their differentiation and maturation. Dysregulated IL-22 production has been associated to some inflammatory skin diseases such as atopic dermatitis and psoriasis. How IL-22 production is regulated in human T cells is not fully known. In the present study, we identified conditions to generate Th22 cells that do not co-produce IL-17 from naïve human CD4+ T cells. We show that in addition to the transcription factors AhR and RORγt, the active form of vitamin D3 (1,25(OH)2D3) regulates IL-22 production in these cells. By studying T cells with a mutated vitamin D receptor (VDR), we demonstrate that the 1,25(OH)2D3-induced inhibition of il22 gene transcription is dependent on the transcriptional activity of the VDR in the T cells. Finally, we identified a vitamin D response element (VDRE) in the il22 promoter and demonstrate that 1,25(OH)2D3-VDR directly inhibits IL-22 production via this repressive VDRE.

Promoter hypermethylation regulates vitamin D receptor (VDR) expression in colorectal cancer-A study from Kashmir valley.

BACKGROUND: Colorectal carcinogenesis (CRC) is a multistep process, involving both genetic and epigenetic modifications of genes involved in diverse pathways ranging from tumor suppression to DNA mismatch repair. PURPOSE: This study was undertaken to assess the role of promoter methylation of vitamin D receptor (VDR) gene, a transcription factor with myriad biological functions, in relation to its expression and clinicopathological parameters. METHODS: Tissue specimens were taken from a total of 75 colorectal cancer cases paired with their normal surrounding epithelium and analyzed by Real-time RT-PCR for assessing the expression profile and MS-PCR for analyzing the promoter methylation status of the VDR gene. Blood sample from the same patients was drawn for vitamin D estimation. RESULTS: The frequency of promoter methylation in cancerous tissue was 37.33% against 9.33% in normal tissues (p<0.001). The hypermethylated status of VDR promoter showed significantly inverse association with its expression (p=0.008). Furthermore, when compared with the clinical parameters, methylation status of VDR promoter was significantly associated with tumor staging (p=0.008), grading (p<0.001), depth of invasion (p=0.002) and lymph node metastases (p<0.001). Univariate and multivariate analysis indicated patients with increased VDR expression (p<0.001) and decreased methylation status (p=0.012) exhibited longer overall survival. Additionally, serum 25(OH)D3 levels were not significantly associated with any of the patient characteristics. CONCLUSION: Our study, first of its kind from Kashmir, indicated that VDR shows aberrant methylation pattern in CRC with consequent loss in its expression.

Vitamin D deficiency downregulates TASK-1 channels and induces pulmonary vascular dysfunction.

Vitamin D (VitD) receptor regulates the expression of several genes involved in signaling pathways affected in pulmonary hypertension (PH). VitD deficiency is highly prevalent in PH, and low levels are associated with poor prognosis. We investigated if VitD deficiency may predispose to or exacerbate PH. Male Wistar rats were fed with a standard or a VitD-free diet for 5 wk. Next, rats were further divided into controls or PH, which was induced by a single dose of Su-5416 (20 mg/kg) and exposure to hypoxia (10% O2) for 2 wk. VitD deficiency had no effect on pulmonary pressure in normoxic rats, indicating that, by itself, it does not trigger PH. However, it induced several moderate but significant changes characteristic of PH in the pulmonary arteries, such as increased muscularization, endothelial dysfunction, increased survivin, and reduced bone morphogenetic protein (Bmp) 4, Bmp6, DNA damage-inducible transcript 4, and K+ two-pore domain channel subfamily K member 3 (Kcnk3) expression. Myocytes isolated from pulmonary arteries from VitD-deficient rats had a reduced whole voltage-dependent potassium current density and acid-sensitive (TASK-like) potassium currents. In rats with PH induced by Su-5416 plus hypoxia, VitD-free diet induced a modest increase in pulmonary pressure, worsened endothelial function, increased the hyperreactivity to serotonin, arterial muscularization, decreased total and TASK-1 potassium currents, and further depolarized the pulmonary artery smooth muscle cell membrane. In human pulmonary artery smooth muscle cells from controls and patients with PH, the active form of VitD calcitriol significantly increased KCNK3 mRNA expression. Altogether, these data strongly suggest that the deficit in VitD induces pulmonary vascular dysfunction.

The Non-Genomic Actions of Vitamin D.

Since its discovery in 1920, a great deal of effort has gone into investigating the physiological actions of vitamin D and the impact its deficiency has on human health. Despite this intense interest, there is still disagreement on what constitutes the lower boundary of adequacy and on the Recommended Dietary Allowance. There has also been a major push to elucidate the biochemistry of vitamin D, its metabolic pathways and the mechanisms that mediate its action. Originally thought to act by altering the expression of target genes, it was realized in the mid-1980s that some of the actions of vitamin D were too rapid to be accounted for by changes at the genomic level. These rapid non-genomic actions have attracted as much interest as the genomic actions and they have spawned additional questions in an already busy field. This mini-review attempts to summarise the in vitro and in vivo work that has been conducted to characterise the rapid non-genomic actions, the mechanisms that give rise to these properties and the roles that these play in the overall action of vitamin D at the cellular level. Understanding the effects of vitamin D at the cellular level should enable the design of elegant human studies to extract the full potential of vitamin D to benefit human health.

VDR/vitamin D receptor regulates autophagic activity through ATG16L1.

The Paneth cell is a unique intestinal epithelial cell that can sense the gut microbiome and secrete anti-microbial peptides, thereby playing critical roles in the maintenance of homeostasis at the intestinal-microbial interface. These roles in regulating innate immunity and intestinal microbial ecology are dependent on a functional autophagy pathway through ATG16L1. ATG16L1 is a regulator for autophagy and a risk gene for inflammatory bowel disease (IBD). We demonstrated that a low VDR/vitamin D receptor level in the intestine is associated with abnormal Paneth cells, impaired autophagy function, and imbalanced bacterial profile (dysbiosis), accompanied by a reduction of ATG16L1. We determined that VDR transcriptionally regulates ATG16L1 as a VDR target gene. Administration of the bacterial product butyrate increases intestinal VDR expression and suppresses inflammation in a colitis model. Thus, our study indicates that VDR may be a determinant of IBD risk through its actions on ATG16L1. These insights can be leveraged to define therapeutic targets for restoring Paneth cells and autophagy through VDR in chronic inflammation. It may also have applicability for infectious diseases and autoimmune diseases associated with skin or lung, where the host is in contact with bacteria.

Efeito da suplementação com vitamina D sobre adipocinas em idosos obesos com osteoporose / Effects of vitamin D supplementation on adipokines in obese osteoporotic subjects

Uma das principais consequências do envelhecimento populacional é o aumento dos índices de osteoporose, que resulta em risco aumentado de fratura, sobretudo as fraturas relacionadas com traumas de pequena intensidade. Similarmente, a obesidade está sendo diagnosticada em um percentual cada vez maior de indivíduos e, atualmente, acredita-se que mais de meio bilhão da população mundial seja obesa. A vitamina D, dentre as suas funções, desempenha um papel central na homeostase do cálcio e do fósforo e tem sua ação reduzida em indivíduos obesos, possivelmente em consequência do seu sequestro no tecido adiposo. O tecido adiposo é um órgão endócrino capaz de produzir e secretar peptídeos bioativos como leptina, fator de necrose tumoral α (TNF-α) e adiponectina que atuam simultaneamente em algumas vias de regulação do metabolismo energético e ósseo. O objetivo do presente estudo foi avaliar a resposta ao tratamento com suplementação de cálcio e vitamina D sobre marcadores sanguíneos do metabolismo ósseo e energético e do estado inflamatório crônico em 21 pacientes obesos e osteoporóticos com hipovitaminose D, em tratamento com bisfosfonatos durante 12 meses. A idade dos pacientes variou entre 63-86 anos e 20/21 eram mulheres em uso de ácido zoledrônico (47,6%) ou alendronato de sódio (52,4%). Durante o período de acompanhamento não houve alteração do estado nutricional dos pacientes, que permaneceram obesos. Após os 12 meses de tratamento os níveis séricos de vitamina D, osteoprotegerina e adiponectina aumentaram significativamente em relação à medida basal. No mesmo período e nas mesmas condições, os níveis séricos de C-telopeptídeo, fosfatase alcalina óssea, leptina e TNF-α apresentaram redução significativa em relação aos níveis basais pré-tratamento. Apesar da suplementação oral, os níveis de vitamina D mesmo tendo aumentado significativamente em relação aos valores pré-tratamento, permaneceram abaixo da faixa de referência de normalidade. O efeito anti-reabsortivo dos bisfosfonatos foi confirmado e, aparentemente, foi independente do estado de obesidade. A maior disponibilidade de reservatórios de gordura e a alta liposolubilidade da vitamina D, favorecendo o seu sequestro neste sítio, provavelmente resultou na redução da sua biodisponibilidade que poderia explicar a manutenção do estado de hipovitaminose D, a despeito da suplementação durante 12 meses com cálcio e vitamina D. Nossos resultados estão de acordo com os relatos da literatura que favorecem a hipótese de que leptina e adiponectina são sensíveis à ação da vitamina D, caracterizada por uma relação direta entre vitamina D e adiponectina e inversa entre vitamina D e leptina. A ação anti-inflamatória da 25(OH)D, avaliada através da redução dos níveis circulantes de TNF-α também pode ser sugerida a partir dos resultados do presente estudo. Estudos clínicos adicionais serão necessários para tentar elucidar os mecanismos sistêmicos, as interações e níveis circulantes ótimos de vitamina D e adipocinas em obesos e o seu papel na saúde humana

One of the main consequences of population aging is the rising in osteoporosis rates, resulting in increased risk of fracture, particularly fragility fractures. Similarly, obesity is being diagnosed in an increasing percentage of individuals, and currently it is believed that more than half a billion of the world population is obese. Vitamin D, among its many functions, plays a central role in the homeostasis of calcium and phosphorus and has an effect reduced in obese individuals possibly in consequence of sequestration in adipose tissue. The adipose tissue is an endocrine organ able to produce and secrete bioactive peptides such as leptin, tumor necrosis factor α (TNF-α) and adiponectin that simultaneously act in some pathways regulating energy and bone metabolism. The aim of this study was to evaluate the response to treatment with calcium and vitamin D supplementation on blood markers of bone and energy metabolism and a marker of chronic inflammatory state in 21 obese and osteoporotic patients with hypovitaminosis D, treated with bisphosphonates for 12 months. The patients' ages ranged from 63-86 years and 20/21 was women taking zoledronic acid (47.6%) or sodium alendronate (52.4%). During the follow-up period there was no change in the nutritional status of patients who remained obese. After 12 months of treatment serum levels of vitamin D, osteoprotegerin and adiponectin increased significantly compared to baseline values. In the same period and under the same conditions, C-telopeptide, serum bone alkaline phosphatase, leptin and TNF-α showed significant reduction compared to baseline levels. Compared to pre-treatment values, oral supplementation with vitamin D increased significantly the circulating levels that, however, remained below the normal reference range. The anti-resorptive effect of bisphosphonates was confirmed and was apparently independent of the state of obesity. The greater availability of fat reservoirs and the high lipid solubility of vitamin D, favoring its sequestration on this site, probably resulted in reduced bioavailability and thus, persistence of the state of hypovitaminosis D, despite the 12 months supplementation with calcium and vitamin D. Our results are in agreement with most reports from the literature that favor the hypothesis that leptin and adiponectin are sensitive to the action of vitamin D, characterized by a direct relationship between adiponectin and vitamin D and a negative relationship between vitamin D and leptin. The anti-inflammatory action of 25 (OH) D, as measured by the reduction in circulating levels of TNF-α, can also be suggested from the results of this study. Additional clinical studies are needed to try to elucidate the systemic mechanisms, interactions and optimal circulating levels of vitamin D and adipokines in obese and their role in human health

1α,25-dihydroxyvitamin D3 stimulates human SOST gene expression and sclerostin secretion.

Sclerostin, the SOST gene product, is a negative regulator of bone formation and a positive regulator of bone resorption. In this study, treatment of human primary osteoblasts, including cells differentiated to an osteocyte-like stage, with 1α,25-dihydroxyvitaminD3 (1,25D) resulted in the dose-dependent increased expression of SOST mRNA. A similar effect was observed in human trabecular bone samples cultured ex vivo, and in osteocyte-like cultures of differentiated SAOS2 cells. Treatment of SAOS2 cells with 1,25D resulted in the production and secretion of sclerostin protein. In silico analysis of the human SOST gene revealed a single putative DR3-type vitamin D response element (VDRE) at position -6216 bp upstream of the transcription start site (TSS). This sequence was confirmed to have strong VDRE activity by luciferase reporter assays and electrophoretic mobility shift analysis (EMSA). Sequence substitution in the VDR/RXR half-sites abolished VDRE reporter activity and binding of nuclear proteins. A 6.3 kb fragment of the human proximal SOST promoter demonstrated responsiveness to 1,25D. The addition of the evolutionary conserved region 5 (ECR5), a known bone specific enhancer region, ahead of the 6.3 kb fragment increased basal promoter activity but did not increase 1,25D responsiveness. Site-specific mutagenesis abolished the responsiveness of the 6.3 kb promoter to 1,25D. We conclude that 1,25D is a direct regulator of human SOST gene and sclerostin protein expression, extending the pathways of control of sclerostin expression. At least some of this responsiveness is mediated by the identified classical VDRE however the nature of the transcriptional regulation by 1,25D warrants further investigation.

MART-10, a novel vitamin D analog, inhibits head and neck squamous carcinoma cells growth through cell cycle arrest at G0/G1 with upregulation of p21 and p27 and downregulation of telomerase.

For the head and neck squamous cell carcinoma (HNSCC), surgery in combination with radiation therapy is the current standard treatment. However, the complex anatomy and important functions over the head and neck region often make HNSCC patients with severe comorbidities. Even after aggressive treatment, the 5year survival for HNSCC patients is only around 61%. Thus, new therapeutic regimens against HNSCC are urgently needed. 1α,25-Dihydroxyvitamin D3 [1α,25(OH)2D3] is a potent anti-tumor agent in a variety of pre-clinical studies, but its clinical application is impeded by hypercalcemic side effect. A new class of less-calcemic 1α,25(OH)2D3 analog, MART-10 (19-nor-2α-(3-hydroxypropyl)- 1α,25-Dihydroxyvitamin D3), has been shown to be much more potent than 1α,25(OH)2D3 in inhibiting cancer cell growth in vitro and in vivo without inducing hypercalcemia. In this study, we compared the antiproliferative activity of MART-10 with 1α,25(OH)2D3 and the mechanism responsible for the inhibition in FaDu and SCC-25 squamous carcinoma cells. Our results demonstrate that MART-10 is more potent than 1α,25(OH)2D3 in suppressing FaDu and SCC-25 cell growth through greater cell cycle arrest at G0/G1, accompanied by a greater downregulation of ki-67 expression and upregulation of p21 and p27. We also showed that telomerase expression in SCC-25 was suppressed to a greater extent by MART-10 than by 1α,25(OH)2D3. Thus, given the previously-proven in vivo antitumor effect and safety of MART-10 and bleak background of HNSCC, based on our current result, we concluded that MART-10 has a potential as a chemo-preventive and - therapeutic agent to treat HNSCC.

Vitamin D deficiency and severe asthma.

Vitamin D has received tremendous amount of attention recently due to the ever-increasing reports of association between vitamin D deficiency and a wide range of conditions, from cancer to fertility to longevity. The fascination of disease association with vitamin D deficiency comes from the relatively easy solution to overcome such a risk factor, that is, either by increase in sun exposure and/or diet supplementation. Many reviews have been written on a protective role of vitamin D in asthma and related morbidities; here, we will summarize the epidemiological evidence supporting a role of vitamin D against hallmark features of severe asthma, such as airway remodeling and asthma exacerbations. Furthermore, we discuss data from in vitro and in vivo studies which provide insights on the potential mechanisms of how vitamin D may protect against severe asthma pathogenesis and how vitamin D deficiency may lead to the development of severe asthma. Approximately 5-15% of asthmatic individuals suffer from the more severe forms of disease in spite of aggressive therapies and they are more likely to have irreversible airflow obstruction associated with airway remodeling. At present drugs commonly used to control asthma symptoms, such as corticosteroids, do not significantly reverse or reduce remodeling in the airways. Hence, if vitamin D plays a protective role against the development of severe asthma, then the most effective therapy may simply be a healthy dose of sunshine.

Insulin-like growth factor binding protein-3 modulates osteoblast differentiation via interaction with vitamin D receptor.

Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) is a secreted glycoprotein that reduces the bioavailability of IGFs. This glycoprotein has both IGF-dependent and -independent effects on cell growth. However, the mechanisms responsible for the IGF-independent actions of IGFBP-3 are not fully understood. In the present study, we used multiple methodologies including glutathione S-transferase pull-down assay and co-immunoprecipitation to demonstrate that IGFBP-3 can directly interact with vitamin D receptor (VDR) in vitro and in vivo. Furthermore, immunofluorescence co-localization studies showed that IGFBP-3 and VDR could co-localize in the cell nucleus. Reporter gene experiment showed that IGFBP-3 negatively regulates the growth hormone promoter activity induced by ligand-activated VDR. Moreover, real-time RT-PCR demonstrated that IGFBP-3 can inhibit the osteocalcin and CYP24a1 mRNA transcription induced by 1,25-(OH)2D3 in osteoblastic cells. Finally, alkaline phosphatase activity significantly decreased in osteoblastic cells when the cells were transfected with IGFBP-3 in the presence of 1,25-(OH)2D3. In conclusion, these studies provide evidence that overexpression of IGFBP-3 suppresses osteoblastic differentiation regulated by VDR in the presence of 1,25-(OH)2D3. These findings reveal a novel mechanism by which IGFBP-3 functions.

THE SYNERGISTIC EFFECTS OF 1?-25-DIHYDROXY VITAMIN D_3 AND TAMOXIFEN ON ER-NEGATIVE BREAST CANCER CELLS CONTAINING EXOGENOUS PVDRE-TK-ER? PLASMID IN VIVO / 营养学报

Objective:To observe the inhibitory effects of VD3 and Tamoxifen on ER-negative breast cancer cells transfected with human recombinant pVDRE-Tk-ER? eukaryotic expression plasmid in vivo. Method:A recombinant human ER? expression plasmid containing 4 copies of VDRE and Tk promoter was introduced into the ER-negative MDA-MB-231 breast cancer cell. The transformed breast cancer cells were inoculated into athymic nude mice. 4 w after tumor inoculation,mice bearing the tumor of approximately 200 mm3 were treated with 0.5?g/kg of VD3 and/or 50mg/kg of Tamoxifen(SC) for 20d. The tumor volume was precisely measured,concurrently HE stain and Ki-67 immunohistochemical(IHC) assay were performed to detect the anti-proliferative effect of Vit D3 in combination with Tamoxifen in vivo. Results:After 20d of treatment,VD3 and Tamoxifen synergistically decreased the tumor volume as compared with control group. And the IHC results also showed that the Ki-67 expression was significantly inhibited by co-treatment of VD3 and Tamoxifen,which means the arrest of cell cycle progression. Conclusion:VD3 could effectively restore the sensitivity of ER-negative breast cancer cells to Tamoxifenby inducing the expression of exogenous ER? gene through the VDRE and Tk promoter in vivo.