Vitamin D signaling is modulated on multiple levels in health and disease

Evaluation of the effects of vitamin D analogs, bevacizumab, and radiotherapy in uveal melanoma cells

Due to the lack of a definitive effective treatment method that provides a complete cure and increases survival rates in uveal melanoma, the search for alternative treatments at the molecular level continues. In this context, we aimed to comparatively analyze the therapeutic effects of 25-hydroxyvitamin D3 (D2), 1a, 25-dihydroxyvitamin D3 (D3), bevacizumab and radiotherapy (RT) in a uveal melanoma cell line (MP41). Cytotoxicity was evaluated using XTT cell proliferation kit and Xcelligence cell analyzer system. RT dose was determined after a clonogenic assay. Annexin V/PI staining and Western blot analyses for caspase-3, -8, and -9 were performed to analyze apoptosis. Additionally, cell cycle analyses were also conducted. As a result, we found that D2 and D3 did not show cytotoxic effects, while bevacizumab and RT showed time and dose-dependent cytotoxicity. IC50 concentration of bevacizumab was 6.945 mg/mL. Radiotherapy and bevacizumab significantly reduced cell survival and induced apoptosis when administered both as monotherapy and in combination. A significant increase in caspase proteins was detected at high bevacizumab concentrations. However, the combination of bevacizumab and radiotherapy caused a substantial decrease in caspase-3, -8 and -9 expressions. No significant difference in cell cycle distribution was detected in any treatment. Our results showed that bevacizumab inhibited MP41 cell proliferation and had an additive effect when administered with RT. In conclusion, our study offers a different perspective on the treatment of uveal melanoma, and these results, when supported by animal experiments and clinical studies in the future, might be a new step in the treatment of this challenging ocular tumor.

Neuroprotective and therapeutic effects of calcitriol in rotenone-induced Parkinson’s disease rat model

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Treatment of PD is challenging, as current treatment strategies are only symptomatic and do not stop disease development. Recent studies reported neuroprotective effects of calcitriol in PD through its antioxidant and anti-inflammatory properties. The exact pathomechanisms of PD are not yet fully understood. So, investigation of different molecular pathways is challenging. Sirtuin-1 (Sirt1) modulates multiple physiological processes, including programmed cell death, DNA repair, and inflammation. Furthermore, defective autophagy is considered a key pathomechanism in PD as it eliminates protein aggregation and dysfunctional cell organelles. The present study investigated the involvement of autophagy and Sirt1/NF-κB molecular pathway in rotenone-induced PD and explored the protective and restorative effects of calcitriol through these mechanisms. Therefore, behavioral tests were used to test the effect of calcitriol on motor disability and equilibrium. Furthermore, the histological and neuronal architecture was assessed. The expression of genes encoding neuroinflammation and autophagy markers was determined by qPCR while their protein levels were determined by Western blot analysis and immune-histochemical staining. Our results indicate that behavioral impairments and dopaminergic neuron depletion in the rotenone-induced PD model were improved by calcitriol administration. Furthermore, calcitriol attenuated rotenone-induced neuroinflammation and autophagy dysfunction in PD rats through up-regulation of Sirt1 and LC3 and down-regulation of P62 and NF-κB expression levels. Thus, calcitriol could induce a neuro-protective and restorative effect in the rotenone-induced PD model by modulating autophagy and Sirt1/NF-κB pathway.

The role of vitamin D and vitamin D deficiency in orthopaedics and traumatology-a narrative overview of the literature

Vitamin D is considered to play an important role in musculoskeletal health. It’s classical function is the regulation of calcium and phosphate homeostasis, thus ensuring a balanced bone metabolism that is characterised by an equal amount of bone resorption and bone formation. In the past decades, a plethora of pre-clinical and clinical studies reporting on potential health-beneficial properties of vitamin D have emerged. Moreover, there is an abundance of reports highlighting vitamin D deficiency and insufficiency in patients with almost innumerable diseases. Further, it is estimated that more than one billion people globally are affected by insufficient vitamin D levels. As such, research on vitamin D has been particularly popular over the past years. In orthopaedics and traumatology, most studies describe favourable effects of vitamin D in general. However, the relative importance of vitamin D is oftentimes debated. In this narrative review of the literature, we consider first, the properties of vitamin D and how vitamin D, vitamin D deficiency and the vitamin D receptor (VDR) impact on musculoskeletal health. Secondly, we provide an overview of studies reporting the prevalence of vitamin D deficiency in traumatology and diverse orthopaedic diseases including bone oncology. Lastly, we emphasise recent findings and touch on future perspectives in vitamin D research.

The MUC5B-associated variant rs35705950 resides within an enhancer subject to lineage- and disease-dependent epigenetic remodeling

The G/T transversion rs35705950, located approximately 3 kb upstream of the MUC5B start site, is the cardinal risk factor for idiopathic pulmonary fibrosis (IPF). Here, we investigate the function and chromatin structure of this –3 kb region and provide evidence that it functions as a classically defined enhancer subject to epigenetic programming. We use nascent transcript analysis to show that RNA polymerase II loads within 10 bp of the G/T transversion site, definitively establishing enhancer function for the region. By integrating Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) analysis of fresh and cultured human airway epithelial cells with nuclease sensitivity data, we demonstrate that this region is in accessible chromatin that affects the expression of MUC5B. Through applying paired single-nucleus RNA- and ATAC-seq to frozen tissue from IPF lungs, we extend these findings directly to disease, with results indicating that epigenetic programming of the –3 kb enhancer in IPF occurs in both MUC5B-expressing and nonexpressing lineages. In aggregate, our results indicate that the MUC5B-associated variant rs35705950 resides within an enhancer that is subject to epigenetic remodeling and contributes to pathologic misexpression in IPF.

Does vitamin D deficiency predict tumour malignancy in patients with bone tumours? Data from a multi-center cohort analysis

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Vitamin D deficiency is common in patients with bone tumours.

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Potential association between pre-diagnostic vitamin D status and tumour malignancy in patients with bone tumours.

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25(OH)D status should routinely be assessed and monitored in patients with bone tumours.

Vitamin D deficiency is a global health concern that is estimated to afflict over one billion people globally. The major role of vitamin D is that of a regulator of calcium and phosphate metabolism, thus, being essential for proper bone mineralisation. Concomitantly, vitamin D is known to exert numerous extra-skeletal actions. For example, it has become evident that vitamin D has direct anti-proliferative, pro-differentiation and pro-apoptotic actions on cancer cells. Hence, vitamin D deficiency has been associated with increased cancer risk and worse prognosis in several malignancies. We have recently demonstrated that vitamin D deficiency promotes secondary cancer growth in bone. These findings were partly attributable to an increase in bone remodelling but also through direct effects of vitamin D on cancer cells. To date, very little is known about vitamin D status of patients with bone tumours in general. Thus, the objective of this study was to assess vitamin D status of patients with diverse bone tumours. Moreover, the aim was to elucidate whether or not there is an association between pre-diagnostic vitamin D status and tumour malignancy in patients with bone tumours.

In a multi-center analysis, 25(OH)D, PTH and calcium levels of 225 patients that presented with various bone tumours between 2017 and 2018 were assessed. Collectively, 76% of all patients had insufficient vitamin D levels with a total mean 25(OH)D level of 21.43 ng/ml (53.58 nmol/L). In particular, 52% (117/225) of patients were identified as vitamin D deficient and further 24% of patients (55/225) were vitamin D insufficient. Notably, patients diagnosed with malignant bone tumours had significantly lower 25(OH)D levels than patients diagnosed with benign bone tumours [19.3 vs. 22.75 ng/ml (48.25 vs. 56.86 nmol/L); p = 0.04).

In conclusion, we found a widespread and distressing rate of vitamin D deficiency and insufficiency in patients with bone tumours. However, especially for patients with bone tumours sufficient vitamin D levels seem to be of great importance. Thus, we believe that 25(OH)D status should routinely be monitored in these patients. Collectively, there should be an increased awareness for physicians to assess and if necessary correct vitamin D status of patients with bone tumours in general or of those at great risk of developing bone tumours.

The relationships of vitamin D, vitamin D receptor gene polymorphisms, and vitamin D supplementation with Parkinson's disease

In recent years, many studies have investigated the correlations between Parkinson's disease (PD) and vitamin D status, but the conclusion remains elusive. The present review focuses on the associations between PD and serum vitamin D levels by reviewing studies on the associations of PD with serum vitamin D levels and vitamin D receptor (VDR) gene polymorphisms from PubMed, Web of Science, Cochrane Library, and Embase databases. We found that PD patients have lower vitamin D levels than healthy controls and that the vitamin D concentrations are negatively correlated with PD risk and severity. Furthermore, higher vitamin D concentrations are linked to better cognitive function and mood in PD patients. Findings on the relationship between VDR gene polymorphisms and the risk of PD are inconsistent, but the FokI (C/T) polymorphism is significantly linked with PD. The occurrence of FokI (C/T) gene polymorphism may influence the risk, severity, and cognitive ability of PD patients, while also possibly influencing the effect of Vitamin D3 supplementation in PD patients. In view of the neuroprotective effects of vitamin D and the close association between vitamin D and dopaminergic neurotransmission, interventional prospective studies on vitamin D supplementation in PD patients should be conducted in the future.

Differentially expressed serum proteins associated with calcium regulation and hypocalcemia in dairy cows

Objective

Hypocalcemia is an important metabolic disease of dairy cows during the transition period, although the effect of hypocalcemia on biological function in dairy cows remains unknown.

Methods

In this study, proteomic, mass spectrum, bioinformatics and western blotting were employed to identify differentially expressed proteins related to serum Ca concentration. Serum samples from dairy cows were collected at three time points: 3rd days before calving (day −3), the day of calving (day 0), and 3rd days after calving (day +3). According to the Ca concentration on day 0, a total of 27 dairy cows were assigned to one of three groups (clinical, subclinical, and healthy). Samples collected on day −3 were used for discovery of differentially expressed proteins, which were separated and identified via proteomic analysis and mass spectrometry. Bioinformatics analysis was performed to determine the function of the identified proteins (gene ontology and pathway analysis). The differentially expressed proteins were verified by western blot analysis.

Results

There were 57 differential spots separated and eight different proteins were identified. Vitamin D-binding protein precursor (group-specific component, GC), alpha-2-macroglobulin (A2M) protein, and apolipoprotein A-IV were related to hypocalcemia by bioinformatics analysis. Due to its specific expression (up-regulated in clinical hypocalcemia and down-regulated in subclinical hypocalcemia), A2M was selected for validation. The results were consistent with those of proteomic analysis.

Conclusion

A2M was as an early detection index for distinguishing clinical and subclinical hypocalcemia. The possible pathogenesis of clinical hypocalcemia caused by GC and apolipoprotein A-IV was speculated. The down-regulated expression of GC was a probable cause of the decrease in calcium concentration.

Low vitamin D-modulated calcium-regulating proteins in psoriasis vulgaris plaques: S100A7 overexpression depends on joint involvement

Psoriasis is an inflammatory skin disease with or without joint involvement. In this disease, the thickened epidermis and impaired barrier are associated with altered calcium gradients. Calcium and vitamin D are known to play important roles in keratinocyte differentiation and bone metabolism. Intracellular calcium is regulated by calcium-sensing receptor (CASR), calcium release-activated calcium modulator (ORAI) and stromal interaction molecule (STIM). Other proteins modulated by vitamin D play important roles in calcium regulation e.g., calbindin 1 (CALB1) and transient receptor potential cation channel 6 (TRPV6). In this study, we aimed to investigate the expression of calcium-regulating proteins in the plaques of patients with psoriasis vulgaris with or without joint inflammation. We confirmed low calcium levels, keratinocyte hyperproliferation and an altered epidermal barrier. The CASR, ORAI1, ORAI3, STIM1, CALB1 and TRPV6 mRNA, as well as the sterol 27-hydroxylase (CYP27A1), 25-hydroxyvitamin D3 1-α-hydroxylase (CYP27B1) and 1,25-dihydroxyvitamin D3 24-hydroxylase (CYP24A1) protein levels were low in the plaques of patients with psoriasis. We demonstrated S100 calcium-binding protein A7 (S100A7) overexpression in the plaques of patients with psoriasis vulgaris with joint inflammation, compared with those without joint involvement. We suggest an altered capacity to regulate the intracellular Ca2+ concentration ([Ca2+]i), characterized by a reduced expression of CASR, ORAI1, ORAI3, STIM1, CALB1 and TRPV6 associated with diminished levels of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], which may be associated with an altered balance between keratinocyte proliferation and differentiation in the psoriatic epidermis. Additionally, differences in S100A7 expression depend on the presence of joint involvement.

Serum 25-Hydroxyvitamin D Levels and the Risk of Dysplasia and Esophageal Adenocarcinoma in Patients with Barrett's Esophagus

BACKGROUND

To date, there are no studies reporting an association between vitamin D and Barrett's esophagus (BE), the precursor for esophageal adenocarcinoma (EAC).

AIMS

Our aim was to study the association between serum 25-hydroxyvitamin D (25(OH)D) levels and prevalence and incidence of dysplasia/EAC in BE.

METHODS

Patients from our BE Registry cohort seen between 2000 and 2012 who had serum 25(OH)D levels measured were included. Age, gender, race, BE length, hiatal hernia size, and histological findings were recorded. Patients without high-grade dysplasia (HGD)/EAC at or within 1 year of index biopsy and who had follow-up endoscopies and 25(OH)D levels were studied for incidence of dysplasia/EAC.

RESULTS

Among 429 patients with BE, the mean 25(OH)D level was 72 ± 31.2 nmol/L. Hundred and one (23.6 %) patients had deficiency (<50 nmol/L), 149 (34.7 %) had insufficiency (50-74.9 nmol/L), and 179 (41.7 %) had normal levels of 25(OH)D. There was no association between serum 25(OH)D levels and dysplasia (p = 0.90). In the incidence cohort of 246 patients with median follow-up of 46 months, there were 34 cases of low-grade dysplasia, 12 of HGD, and 5 of EAC. Change in 25(OH)D levels did not impact progression to dysplasia/EAC (every 5 nmol/L increase from baseline, hazard ratio 0.98; p = 0.62).

CONCLUSIONS

Serum 25(OH)D levels were low in 58.3 % of our BE cohort. There was no association between 25(OH)D levels and prevalence or incidence of HGD/EAC in patients with BE. Further long-term studies are needed to study the association between vitamin D status and progression of dysplasia in BE.

Differential antitumor effects of vitamin D analogues on colorectal carcinoma in culture

Colorectal cancer (CRC) is an emerging global problem with the rapid increase in its incidence being associated with an unhealthy lifestyle. Epidemiological studies have shown that decreased levels of vitamin D3 significantly increases the risk of CRC. Furthermore, negative effects of vitamin D3 deficiency can be compensated by appropriate supplementation. Vitamin D3 was shown to inhibit growth and induce differentiation of cancer cells, however, excessive vitamin D3 intake leads to hypercalcemia. Thus, development of efficient vitamin D3 analogues with limited impact on calcium homeostasis is an important scientific and clinically relevant task. The aims of the present study were to compare the antiproliferative potential of classic vitamin D3 metabolites (1α,25(OH)2D3 and 25(OH)D3) with selected low calcemic analogues (calcipotriol and 20(OH)D3) on CRC cell lines and to investigate the expression of vitamin D-related genes in CRC cell lines and clinical samples. Vitamin D3 analogues exerted anti-proliferative effects on all CRC cell lines tested. Calcipotriol proved to be as potent as 1α,25(OH)2D3 and had more efficacy than 20-hydroxyvitamin D3. In addition, the analogs tested effectively inhibited the formation of colonies in Matrigel. The expression of genes involved in 1α,25(OH)2D3 signaling and metabolism varied in cell lines analysed, which explains in part their different sensitivities to the various analogues. In CRC biopsies, there was decreased VDR expression in tumor samples in comparison to the surgical margin and healthy colon samples (p<0.01). The present study indicates that vitamin D3 analogues which have low calcemic activity, such as calcipotriol or 20(OH)D3, are very promising candidates for CRC therapy. Moreover, expression profiling of vitamin D-related genes is likely to be a powerful tool in the planning of anticancer therapy. Decreased levels of VDR and increased CYP24A1 expression in clinical samples underline the importance of deregulation of vitamin D pathways in the development of CRC.

Vitamin D

Interest in vitamin D and the VDR gene is increasing as putative roles in human health and evolutionary processes are explored. This review looks beyond the classic biochemistry that links vitamin D to calcium homeostasis; it explores how vitamin D interacts with light in a broader perspective than simple skin photosynthesis. It examines how the vitamin influences circadian rhythm, and how it may have helped drive the evolution of skin pigmentation. To this end, the nutrient–nutrient relationship with folate is also explored. The VDR gene is additionally examined as a factor in the evolutionary selection of skin depigmentation at higher latitudes to allow vitamin D synthesis. Evidence is given to show that VDR polymorphisms exhibit a latitudinal gradient in allele prevalence consistent with such a paradigm. Overall, the review examines new evo-devo ideas that link light-sensitive vitamins to human health/phenotype, both within and across the lifecycle.

Different vitamin D receptor agonists exhibit differential effects on endothelial function and aortic gene expression in 5/6 nephrectomized rats

Endothelial dysfunction, common in chronic kidney disease (CKD), significantly increases cardiovascular disease risk in CKD patients. This study investigates whether different vitamin D receptor agonists exhibit different effects on endothelial function and on aortic gene expression in an animal CKD model. The 5/6 nephrectomized (NX) rat was treated with or without alfacalcidol (0.02, 0.04 and 0.08μg/kg), paricalcitol (0.04 and 0.08μg/kg), or VS-105 (0.004, 0.01 and 0.16μg/kg). All three compounds at the test doses suppressed serum parathyroid hormone effectively. Alfacalcidol at 0.08μg/kg raised serum calcium significantly. Endothelial function was assessed by pre-contracting thoracic aortic rings with phenylephrine, followed by treatment with acetylcholine or sodium nitroprusside. Uremia significantly affected endothelial-dependent aortic relaxation, which was improved by all three compounds in a dose-dependent manner with alfacalcidol and paricalcitol exhibiting a lesser effect. DNA microarray analysis of aorta samples revealed that uremia impacted the expression of numerous aortic genes, many of which were normalized by the vitamin D analogs. Real-time RT-PCR analysis confirmed that selected genes such as Abra, Apoa4, Fabp2, Hsd17b2, and Hspa1b affected by uremia were normalized by the vitamin D analogs with alfacalcidol exhibiting less of an effect. These results demonstrate that different vitamin D analogs exhibit different effects on endothelial function and aortic gene expression in 5/6 NX rats. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Comparative portal hypotensive effects as propranolol of vitamin D₃ treatment by decreasing intrahepatic resistance in cirrhotic rats

BACKGROUND AND AIM

Vitamin D₃ improves portal hypertension (PH) through the activation of vitamin D receptor (VDR) and calcium-sensing receptor (CaSR) in cirrhotic rats. Propranolol is a non-selective β-blocker that is recommended for the treatment of PH. The present study aims to investigate the detail systemic and hepatic mechanisms of vitamin D₃ and propranolol, alone or in combination, in cirrhotic rats.

METHODS

Common bile duct-ligated and thioacetamide cirrhotic rats were treated with vehicle, propranolol (30 mg/kg/day), vitamin D₃ (0.5 μg/100 g/day, twice weekly), or propranolol + vitamin D₃, separately.

RESULTS

Significantly, propranolol and vitamin D₃ produced a similar magnitude of reduction in portal venous pressure (PVP) in cirrhotic rats through different mechanisms: whereas propranolol decreased PVP by reducing splanchnic hyperemia and cardiac index, vitamin D₃ decreased PVP by decreasing intrahepatic resistance (IHR). However, propranolol + vitamin D₃ did not further decrease PVP in cirrhotic rats. Notably, a marked decrease in hepatic VDR and CaSR expressions was noted in cirrhotic human/rat livers compared with non-cirrhotic human/rat livers. In cirrhotic rats, vitamin D₃ administration decreasing IHR by inhibiting the renin-angiotensin system, hepatic oxidative stress, inflammation/fibrosis, angiotensin II (ANGII) production, CaSR-mediated ANGII hyperresponsiveness, ANGII-induced hepatic stellate cells contraction, and correcting hepatic endothelial dysfunction through upregulation of hepatic VDR, CaSR, and endothelial nitric oxide synthase expressions.

CONCLUSION

Chronic vitamin D₃ treatment alone results in comparative portal hypotensive effects as propranolol alone in cirrhotic rats with PH. Taken together, chronic vitamin D₃ administration was an ideal alternative strategy to effectively improve PH without unwanted systemic side-effects.

The Effect of Short Term Vitamin D Supplementation on the Inflammatory and Oxidative Mediators of Arterial Stiffness

BACKGROUND

Vitamin D deficiency has been implicated as a potential risk factor for cardiovascular disease. The high rate of vitamin D deficiency (<30 ng/ml) exhibited by African Americans may account for some of the excess prevalence of cardiovascular morbidity and mortality in this vulnerable US population. Vitamin D supplementation may reduce the risk of cardiovascular disease by ameliorating the onset and progression of arterial stiffness, a strong predictor of cardiovascular mortality, usually assessed by pulse wave velocity and augmentation index. Very few prospective studies have evaluated the effect of vitamin D supplementation on the inflammatory and oxidative stress mediators of arterial stiffness.

METHOD

In a double blind randomized placebo controlled study we evaluated the effect of a monthly dose of 100,000IU of vitamin D3 for three months on the level of serum 25(OH)D, intact parathyroid hormone (PTH), urinary isoprostane, adipocyte cytokine expression and arterial stiffness among 130 overweight and obese (BMI > 25) African Americans with elevated blood pressure (130 - 150/85 - 100 mmHg) and low serum vitamin D level (10 - 25 ng/ml).

RESULTS

There was a significant increase in the serum 25(OH)D levels to a mean level of 34.5 ng/ml (SD = 7.1) with the intervention (p < 0.001). The increase in 25(OH)D levels was associated with a significant decrease in the serum level of intact PTH (p = 0.02), mean urinary isoprostane (p = 0.02) and adipocyte cytokine expression. Although the increase in the 25(OH)D levels was not associated with any significant change in the Pulse Wave Velocity (PWV) in the overall study sample, it was associated with a significant decrease in the augmentation index among the participants with the highest tertile of urinary isoprostane (p = 0.007).

CONCLUSION

We concluded that vitamin D supplementation increased serum 25(OH)D levels, decreased intact PTH level and the levels of select inflammatory and oxidative stress mediators of arterial stiffness. Longer term prospective studies are warranted to evaluate the effect of high dose vitamin D supplementation on arterial stiffness.

Vitamin D in heart failure

Evidence linking vitamin D to cardiovascular (CV) health has accumulated in recent years: numerous epidemiologic studies report deficiency as a significant CV risk factor, and rodent models suggest that active vitamin D can modulate critical remodeling processes, including cardiac hypertrophy and extracellular matrix remodeling. The presence of vitamin D signaling machinery within the human heart implies a direct role for this hormone in cardiac physiology and may explain associations between vitamin D status and CV outcomes. Heart failure (HF) represents a growing social and economic burden worldwide. Myocardial remodeling is central to HF development, and in the context of emerging evidence supporting mechanistic involvement of vitamin D, this review provides critical appraisal of scientific literature related to the role of vitamin D in CV disease, including data from epidemiologic and supplementation studies, as well as novel findings from animal models and in vitro work. Although associative data linking vitamin D and CV outcomes and evidence supporting a role for vitamin D in relevant pathogenic processes are both substantial, there are limited mechanistic data to indicate vitamin D supplementation as a viable therapeutic adjunct for the prevention of HF development following myocardial injury.

Vitamin D supplementation and lipid profile: what does the best available evidence show?

Vitamin D supplements have increasingly been used for the treatment and prevention of osteoporosis. Historically, effects of the vitamin on the cardiovascular (CV) system have been proposed and demonstrated in the literature, including benefits on serum lipids. Although observational studies support an association between increased serum vitamin D levels and a favorable lipid profile, interventional studies have shown no effects. This review presents and analyzes all the related randomized controlled trials (RCTs) identified in the literature from 1987 to present. A systematic literature search was conducted via MEDLINE, Cochrane Library and EMBASE and, out of 19 relevant RCTs identified, only one reported benefits of vitamin D supplementation on lipid profile parameters, while the rest showed no effects or even adverse outcomes, which are highlighted by the only meta-analysis in the field. Attempts to explain the paradox of beneficial findings of observational studies versus discouraging results of interventional studies have been made and the most popular suggests that high serum vitamin D concentrations may not be the cause of good health but its outcome instead, as healthy people are more likely to stay outdoors longer and have better eating habits. For definitive answers to be given, large, well-designed RCTs need to be conducted that will take into account and adjust for dietary consumption as well as serum calcium and parathyroid hormone levels, both of which have been shown to be associated with the CV system. Until then, recommendations for vitamin D supplementation should not change.

Vitamin D modulates prostaglandin E2 synthesis and degradation in human lung fibroblasts

Vitamin D insufficiency has been increasingly recognized in the general population worldwide and has been associated with several lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), and respiratory tract infections. Fibroblasts play a critical role in tissue repair and remodeling, which is a key feature of COPD and asthma. Fibroblasts modulate tissue repair by producing and modifying extracellular matrix components and by releasing mediators that act as autocrine or paracrine modulators of tissue remodeling. The current study was designed to investigate if vitamin D alters fibroblast release of key autocrine/paracrine repair factors. First, we demonstrated that human fetal lung (HFL)-1 cells express the vitamin D receptor (VDR) and that vitamin D, 25-hydroxyvitamin D [25(OH)D], or 1,25-dihydroxyvitamin D [1,25(OH)2D] induce VDR nuclear translocation and increase VDR-DNA binding activity. We next demonstrated that vitamin D, 25(OH)D, and 1,25(OH)2D significantly reduced prostaglandin (PG)E2 production by human lung fibroblasts (HFL-1) but had no effect on transforming growth factor β1, vascular endothelial growth factor, or fibronectin production. Vitamin D, 25(OH)D, and 1,25(OH)2D significantly inhibited IL-1β-induced microsomal PGE synthase (mPGES)-1 expression; in contrast, all three forms of vitamin D stimulated 15-hydroxy PG dehydrogenase, an enzyme that degrades PGE2. Cyclooxygenase-1 and -2 and the other two PGE2 synthases (mPGES-2 and cytosolic PGE synthase) were not altered by vitamin D, 25(OH)D, or 1,25(OH)2D. Finally, the effect of PGE2 inhibition by 25(OH)D was observed in adult lung fibroblasts. These findings suggest that vitamin D can regulate PGE2 synthesis and degradation and by this mechanism can modulate fibroblast-mediated tissue repair function.

Vitamin D, folate, and potential early lifecycle environmental origin of significant adult phenotypes

Solar radiation early in pregnancy interacts with light sensitive vitamins to influence an embryo's genetic profile. This influences both adult disease risk and may play a role in the evolution of skin colour.

Background and objectives: Vitamin D and folate are highly UV sensitive, and critical for maintaining health throughout the lifecycle. This study examines whether solar irradiance during the first trimester of pregnancy influences vitamin D receptor (VDR) and nuclear folate gene variant occurrence, and whether affected genes influence late-life biochemical/clinical phenotypes.

Methodology: 228 subjects were examined for periconceptional exposure to solar irradiance, variation in vitamin D/folate genes (polymerase chain reaction (PCR)), dietary intake (food frequency questionnaire (FFQ)) and important adult biochemical/clinical phenotypes.

Results: Periconceptional solar irradiance was associated with VDR-BsmI (P = 0.0008^wk7), TaqI (P = 0.0014^wk7) and EcoRV (P = 0.0030^wk6) variant occurrence between post-conceptional weeks 6–8, a period when ossification begins. Similar effects were detected for other VDR gene polymorphisms. Periconceptional solar irradiance was also associated with 19 bp del-DHFR (P = 0.0025^wk6), and to a lesser extent C1420T-SHMT (P = 0.0249^wk6), a folate-critical time during embryogenesis. These same genes were associated with several late-life phenotypes: VDR-BsmI, TaqI and ApaI determined the relationship between dietary vitamin D and both insulin (P < 0.0001/BB, 0.0007/tt and 0.0173/AA, respectively) and systolic blood pressure (P = 0.0290/Bb, 0.0299/Tt and 0.0412/AA, respectively), making them important early and late in the lifecycle. While these and other phenotype associations were found for the VDR variants, folate polymorphism associations in later-life were limited to C1420T-SHMT (P = 0.0037 and 0.0297 for fasting blood glucose and HbA1c levels, respectively). We additionally report nutrient–gene relationships with body mass index, thiol/folate metabolome, cognition, depression and hypertension. Furthermore, photoperiod at conception influenced occurrence of VDR-Tru9I and 2R3R-TS genotypes (P = 0.0120 and 0.0360, respectively).

Conclusions and implications: Findings identify environmental and nutritional agents that may interact to modify gene–phenotype relationships across the lifecycle, offering new insight into human ecology. This includes factors related to both disease aetiology and the evolution of skin pigmentation.

PRIMOS: an integrated database of reassessed protein-protein interactions providing web-based access to in silico validation of experimentally derived data

Steady improvements in proteomics present a bioinformatic challenge to retrieve, store, and process the accumulating and often redundant amount of information. In particular, a large-scale comparison and analysis of protein-protein interaction (PPI) data requires tools for data interpretation as well as validation. At this juncture, the Protein Interaction and Molecule Search (PRIMOS) platform represents a novel web portal that unifies six primary PPI databases (BIND, Biomolecular Interaction Network Database; DIP, Database of Interacting Proteins; HPRD, Human Protein Reference Database; IntAct; MINT, Molecular Interaction Database; and MIPS, Munich Information Center for Protein Sequences) into a single consistent repository, which currently includes more than 196,700 redundancy-removed PPIs. PRIMOS supports three advanced search strategies centering on disease-relevant PPIs, on inter- and intra-organismal crosstalk relations (e.g., pathogen-host interactions), and on highly connected protein nodes analysis ("hub" identification). The main novelties distinguishing PRIMOS from other secondary PPI databases are the reassessment of known PPIs, and the capacity to validate personal experimental data by our peer-reviewed, homology-based validation. This article focuses on definite PRIMOS use cases (presentation of embedded biological concepts, example applications) to demonstrate its broad functionality and practical value. PRIMOS is publicly available at http://primos.fh-hagenberg.at.

Uric acid suppresses 1 alpha hydroxylase in vitro and in vivo

OBJECTIVE

Patients with gout have lower calcitriol levels that improve when uric acid is lowered. The mechanism of these observations is unknown. We hypothesized that uric acid inhibits 1-αhydroxylase.

MATERIALS AND METHODS

In vivo, Sprague Dawley rats were randomized to control (n = 5), allantoxanamide (n=8), febuxostat (n=5), or allantoxanamide+febuxostat (n = 7). Vitamin D, PTH, and 1-αhydroxylase protein were evaluated. In order to directly evaluate the effect of uric acid on 1-αhydroxylase, we conducted a series of dose response and time course experiments in vitro. Nuclear factor κ-B (NFκB) was inhibited pharmacologically. Finally, to evaluate the potential implications of these findings in humans, the association between uric acid and PTH in humans was evaluated in a cross-sectional analysis of data from the NHANES (2003-2006); n = 9773.

RESULTS

1,25(OH)2D and 1-αhydroxylase protein were reduced in hyperuricemic rats and improved with febuxostat treatment. Uric acid suppressed 1-αhydroxylase protein and mRNA expression in proximal tubular cells. This was prevented by NFκB inhibition. In humans, for every 1mg/dL increase in uric acid, the adjusted odds ratio for an elevated PTH (>65 pg/mL) was 1.21 (95% C.I. 1.14, 1.28; P<0.0001), 1.15 (95% C.I. 1.08, 1.22; P<0.0001), and 1.16 (95% C.I. 1.03, 1.31; P = 0.02) for all subjects, subjects with estimated GFR ≥ 60, and subjects with estimated GFR <60 mL/min/1.73 m(2) respectively.

CONCLUSION

Hyperuricemia suppresses 1-αhydroxylase leading to lower 1,25(OH)2D and higher PTH in rats. Our results suggest this is mediated by NFκB. The association between uric acid and PTH in NHANES suggests potential implications for human disease.

Reprint of: Vitamin D receptor activation and prevention of arterial ageing

In chronic kidney disease (CKD) patients, cardiovascular (CV) morbidity and mortality rate is higher than in the general population, because of frequently concomitant hypertension, peripheral vascular disease, heart failure, vascular calcification (VC), diabetes and mineral bone disease. Recently, another important factor associated to CV risk in CKD has been deeply investigated: vitamin D deficiency. Vitamin D Receptors (VDRs) are present in several systems and tissues and VDR activation is associated to positive effects, resulting in better blood pressure control and prevention of diabetic nephropathy. Unfortunately, the natural, non-selective vitamin D receptor activator (VDRA), calcitriol, is associated to higher serum calcium and phosphate levels, thus worsening CV risk in CKD. Recent data showed that the selective VDRA paricalcitol might have ameliorative CV effects. The potential positive impact of the use of paricalcitol on diabetic nephropathy, cardiac disease, hypertension, and VC may open new paths in the fight against CV disease in CKD patients.

Peroxisome proliferator-activated receptor and vitamin d receptor signaling pathways in cancer cells

Peroxisome proliferator-activated receptors (PPARs) are members of the superfamily of nuclear hormone receptors, which respond to specific ligands such as polyunsaturated fatty acids by altering gene expression. Three subtypes of this receptor have been discovered, each evolving to achieve different biological functions. Like other nuclear receptors, the transcriptional activity of PPARs is affected not only by ligand-stimulation, but also by cross-talk with other molecules. For example, both PPARs and the RXRs are ligand-activated transcription factors that coordinately regulate gene expression. In addition, PPARs and vitamin D receptor (VDR) signaling pathways regulate a multitude of genes that are of importance for cellular functions including cell proliferation and cell differentiation. Interaction of the PPARs and VDR signaling pathways has been shown at the level of molecular cross-regulation of their transcription factor. A variety of ligands influencing the PPARs and VDR signaling pathways have been shown to reveal chemopreventive potential by mediating tumor suppressive activities in human cancers. Use of these compounds may represent a potential novel strategy to prevent cancers. This review summarizes the roles of the PPARs and the VDR in pathogenesis and progression of cancer.

Effects of calcium and vitamin D supplementation on crypt morphology in normal colon mucosa: A randomized clinical trial

Calcium and vitamin D modify the molecular phenotypic profiles of colon crypts in the normal colorectal mucosa of colorectal adenoma patients, but their effects on crypt morphology (length, perimeter, and area) are unknown. We analyzed data from a previously conducted pilot, randomized, double-blind, placebo-controlled 2 × 2 factorial chemoprevention clinical trial of supplemental calcium 2000 mg/d and vitamin D3 800 IU/d, alone and in combination, versus placebo over 6 mo. Colorectal crypt length, perimeter, and area in the normal-appearing rectal mucosa were quantified by image analysis. The mean crypt length increased by 1% (P=0.92) in the calcium group, and decreased by 2% (P=0.69) and 4% (P=0.40) in the vitamin D and calcium plus vitamin D groups, respectively, relative to the placebo group. The mean crypt perimeter decreased by 2% (P=0.70) and 4% (P=0.40) in the vitamin D and calcium plus vitamin D groups, respectively, relative to the placebo group, but did not change appreciably in the calcium group. The mean crypt area decreased by 2% (P=0.74), 5% (P=0.41) and 7% (P=0.30) in the calcium, vitamin D and calcium plus vitamin D groups, respectively, relative to the placebo group. Calcium and/or vitamin D3 supplementation do not appear to appreciably change crypt morphology in the normal colorectal mucosa of sporadic adenoma patients. These results, taken together with previous findings, support the use of molecular phenotypic over morphologic pre-neoplastic biomarkers of risk for colorectal neoplasms.

Synthesis of 14-epi-2α-hydroxypropoxy-1α,25-dihydroxy-19-nortachysterol and its hVDR binding

Recently, we evaluated a novel skeleton in the vitamin D family, 14-epi-1α,25(OH)2-19-nortachysterol, and discovered its unique binding configuration in the human vitamin D receptor (VDR) with the C5,6- and C7,8-s-trans triene configuration. Because of its unprecedented form, this skeleton has a promising characteristic profile for clinical use, and also the synthesis of its derivatives should be versatile. Therefore, we synthesized the novel analog, 2α-hydroxypropoxy substituted 14-epi-1α,25(OH)2-19-nortachysterol, and evaluated its human VDR binding affinity. Although this substitution is one of the promising modification of vitamin D3 such as eldecalcitol (ED-71), it had negative effects on the binding affinity, and the compound showed lower affinity than 1α,25(OH)2D3 and its parent compound, 14-epi-1α,25(OH)2-19-nortachysterol. It was thought that the unprecedented binding configuration of this skeleton should not allow the terminal hydroxyl group of the 2α-substituent to construct effective hydrogen bond networks around the amino acid residues in the binding pocket. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Vitamin D metabolism and effects on pluripotency genes and cell differentiation in testicular germ cell tumors in vitro and in vivo

Testicular germ cell tumors (TGCTs) are classified as either seminomas or nonseminomas. Both tumors originate from carcinoma in situ (CIS) cells, which are derived from transformed fetal gonocytes. CIS, seminoma, and the undifferentiated embryonal carcinoma (EC) retain an embryonic phenotype and express pluripotency factors (NANOG/OCT4). Vitamin D (VD) is metabolized in the testes, and here, we examined VD metabolism in TGCT differentiation and pluripotency regulation. We established that the VD receptor (VDR) and VD-metabolizing enzymes are expressed in human fetal germ cells, CIS, and invasive TGCTs. VD metabolism diminished markedly during the malignant transformation from CIS to EC but was reestablished in differentiated components of nonseminomas, distinguished by coexpression of mesodermal markers and loss of OCT4. Subsequent in vitro studies confirmed that 1,25(OH)(2)D(3) (active VD) downregulated NANOG and OCT4 through genomic VDR activation in EC-derived NTera2 cells and, to a lesser extent, in seminoma-derived TCam-2 cells, and up-regulated brachyury, SNAI1, osteocalcin, osteopontin, and fibroblast growth factor 23. To test for a possible therapeutic effect in vivo, NTera2 cells were xenografted into nude mice and treated with 1,25(OH)(2)D(3), which induced down-regulation of pluripotency factors but caused no significant reduction of tumor growth. During NTera2 tumor formation, down-regulation of VDR was observed, resulting in limited responsiveness to cholecalciferol and 1,25(OH)(2)D(3) treatment in vivo. These novel findings show that VD metabolism is involved in the mesodermal transition during differentiation of cancer cells with embryonic stem cell characteristics, which points to a function for VD during early embryonic development and possibly in the pathogenesis of TGCTs.

Deciphering the calcitriol-induced transcriptomic response in keratinocytes: presentation of novel target genes

Numerous studies to date have been aimed at unraveling the large suite of calcitriol (1α,25-dihydroxyvitamin D(3)) response genes in diverse tissues including skin, where this hormone is involved in regulating keratinocyte proliferation, differentiation, permeability barrier formation, innate immunity promotion, antimicrobial peptide production, and wound healing. However, the various approaches differ considerably in probed cell types, scale, throughput, and statistical reliability and do, of note, not reveal much overlap. To further expand our knowledge on presently elusive targets and characterize the extent of fragmentation of existing datasets, we have performed whole-transcriptome microarray examinations of calcitriol-treated human primary keratinocytes. Out of 28,869 genes investigated, we uncovered 86 differentially expressed (67 upregulated and 19 downregulated) candidates that were functionally clustered into five annotation categories: response to wounding, protease inhibition, secondary metabolite biosynthesis, cellular migration, and amine biosynthetic processes. A complementary RTq-PCR study of 78 nominees selected thereof demonstrated significant differential expression of 55 genes (48 upregulated and seven downregulated) within biological replicates. Our hit list contains nine previously authenticated targets (16.36%, proof of concept) and 46 novel genes (83.6%) that have not yet been explicitly described as being differentially regulated within human primary keratinocytes. Direct vitamin D receptor response element predictions within the regulatory promoter regions of 50 of the RTq-PCR-validated targets agreed with known biological functionality and corroborated our stringent data validation pipeline. Altogether, our results indicate the value of continuing these kinds of gene expression studies, which contribute to an enhanced comprehension of calcitriol-mediated processes that may be dysregulated in human skin pathophysiology.

The world pandemic of vitamin D deficiency could possibly be explained by cellular inflammatory response activity induced by the renin-angiotensin system

This review attempts to show that there may be a relationship between inflammatory processes induced by chronic overstimulation of the renin-angiotensin system (RAS) and the worldwide deficiency of vitamin D (VitD) and that both disorders are probably associated with environmental factors. Low VitD levels represent a risk factor for several apparently different diseases, such as infectious, autoimmune, neurodegenerative, and cardiovascular diseases, as well as diabetes, osteoporosis, and cancer. Moreover, VitD insufficiency seems to predispose to hypertension, metabolic syndrome, left ventricular hypertrophy, heart failure, and chronic vascular inflammation. On the other hand, inappropriate stimulation of the RAS has also been associated with the pathogenesis of hypertension, heart attack, stroke, and hypertrophy of the left ventricle and vascular smooth muscle cells. Because VitD receptors (VDRs) and RAS receptors are almost distributed in the same tissues, a possible link between VitD and the RAS is even more plausible. Furthermore, from an evolutionary point of view, both systems were developed simultaneously, actively participating in the regulation of inflammatory and immunological mechanisms. Changes in RAS activity and activation of the VDR seem to be inversely related; thus any changes in one of these systems would have a completely opposite effect on the other, making it possible to speculate that the two systems could have a feedback relationship. In fact, the pandemic of VitD deficiency could be the other face of increased RAS activity, which probably causes lower activity or lower levels of VitD. Finally, from a therapeutic point of view, the combination of RAS blockade and VDR stimulation appears to be more effective than either RAS blockade or VDR stimulation individually.

Vitamin D: metabolism, molecular mechanisms, and mutations to malignancies

The potential protective effects of vitamin D against cutaneous carcinogenesis are still poorly understood. The inhibition, by vitamin D, of various cancers in in vitro and in vivo models has triggered detailed investigation of vitamin D effects on neoplastic behavior. Recent studies highlight that such neoplastic features as the tumor microenvironment, angiogenesis, DNA mutagenesis, and apoptosis are all connected to vitamin D metabolic pathways. This review discusses these connections. Vitamin D modulation of the cell cycle, DNA repair and apoptosis via its receptors (VDRs) may have a suppressive effect on skin cancer as some studies suggest. The regulation of multiple tumor signaling pathways by vitamin D may have an implication in cutaneous carcinogenesis and tumor progression to malignancy.

22-Oxacalcitriol prevents progression of peritoneal fibrosis in a mouse model

OBJECTIVE

Vitamin D plays an important role in calcium homeostasis and is used to treat secondary hyperparathyroidism among dialysis patients. The biologic activity of vitamin D and its analogs is mediated by vitamin D receptor (VDR), which is distributed widely throughout the body. Recent papers have revealed that low vitamin D levels are correlated with severe fibrosis in chronic diseases, including cystic fibrosis and hepatitis. The aim of the present study was to evaluate the protective effects of vitamin D against the progression of peritoneal fibrosis.

METHODS

Peritoneal fibrosis was induced by injection of chlorhexidine gluconate (CG) into the peritoneal cavity of mice every other day for 3 weeks. An analog of vitamin D, 22-oxacalcitriol (OCT), was administered subcutaneously daily from initiation of the CG injections. The peritoneal tissue was excised at 3 weeks. Changes in morphology were assessed by hematoxylin and eosin staining. Expression of VDR, alpha smooth muscle actin (as a marker of myofibroblasts), type III collagen, transforming growth factor β(TGF-β), phosphorylated Smad2/3, F4/80 (as a marker of macrophages), and monocyte chemoattractant protein-1 (MCP-1) was examined by immunohistochemistry. Southwestern histochemistry was used to detect activated nuclear factor κB (NF-κB).

RESULTS

In the CG-injected mice, immunohistochemical analysis revealed expression of VDR in mesothelial cells, myofibroblasts, and macrophages in the thickened submesothelial zone. Treatment with OCT significantly prevented peritoneal fibrosis and reduced the accumulation of type III collagen in CG-treated mice. Among the markers of fibrosis, the numbers of myofibroblasts, cells positive for TGF-β, and cells positive for phosphorylated Smad2/3 were significantly decreased in the OCT-treated group compared with the vehicle-treated group. Furthermore, OCT suppressed inflammatory mediators of fibrosis, as shown by the reduced numbers of activated NF-κB cells, macrophages, and MCP-1-expressing cells.

CONCLUSIONS

Our results indicate that OCT attenuates peritoneal fibrosis, an effect accompanied by reduced numbers of myofibroblasts, infiltrating macrophages, and TGF-β-positive cells, suggesting that vitamin D has potential as a novel therapeutic agent for preventing peritoneal sclerosis.

Determination of vitamin D in relation to body mass index and race in a defined population of black and white women

OBJECTIVE

To examine the contributions of obesity and race to levels of 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) in a defined cohort of black and white women.

METHODS

An interventional study was conducted from October 2004 to March 2008, among 219 healthy female volunteers. Serum 25(OH)D and PTH levels were determined in 117 African American women and 102 white women and the results were compared with body mass index (BMI), percentage body fat, serum lipids, and PTH levels.

RESULTS

Black women had lower median levels of 25(OH)D compared with white women (27.3 nmol/L vs 52.4 nmol/L; P<0.001). Serum levels of 25(OH)D below 50 nmol/L were found in 98% of black women and 45% of white women (P<0.001). The differences between the racial groups in the levels of 25(OH)D persisted despite adjustments for body weight, percentage body fat, and BMI. Black women had higher median serum levels of PTH than white women (31.9 pg/mL vs 22.3 pg/mL; P<0.01).

CONCLUSION

African American women are at significant risk for low vitamin D levels. Studies are needed to determine if low vitamin D status in young African American women is associated with a greater risk for vitamin D-related chronic diseases that can be reduced with vitamin D supplementation.

New vitamin D analogs as potential therapeutics in melanoma

Extensive evidence shows that the active form of vitamin D3--1α,25-dihydroxyvitamin D3--plays an important role in cancer prevention, has tumorostatic activity and may potentially be used in therapy for melanoma. Vitamin D3 and its analogs (secosteroids) exert multiple effects on cancer cells, including inhibition of cell growth and induction of differentiation. Activity of secosteroids depends on multiple cellular factors, including expression of the vitamin D receptor. Despite its endogenous origin, the key drawback for the use of pharmacologically effective doses of 1α,25-dihydroxyvitamin D3 is its hypercalcemic effect leading to profound toxicity. The solution may lie in properties of vitamin D3 analogs with modified side chains, which demonstrate low calcemic activity but conserve the anti-tumor properties. Noncalcemic vitamin D compounds were found to be potent in multiple studies that mandate further clinical testing. Finally, recent studies revealed alternative metabolic pathways for secosteroids and new targets in the cells, which opens up new therapeutic possibilities.

DDX5 is a multifunctional co-activator of steroid hormone receptors

The vitamin D receptor (VDR), an evolutionarily conserved member of the nuclear receptor superfamily, links the metabolically activated vitamin D ligand, calcitriol, with its vitamin D-responsive target genes that are implicated in diverse physiological processes. By genome-wide protein-protein interaction screening of a keratinocyte cDNA library using VDR as bait, we found that the DEAD box RNA helicase p68, also referred to as DDX5, directly interacts with VDR. Domain analysis reveals that the ligand-binding domain of VDR is responsible for the binding, an interaction typical of NR co-activators. Interestingly, the VDR interacting domain of DDX5 lacks a LXXLL-motif and interaction analysis of helix 12 VDR mutants E420K, E420Q and L417S, known to decrease binding affinity of LxxLL motif-containing co-activators showed no change in their interactions. As further support that this novel interactor might be involved in vitamin D-stimulated transcriptional regulation, we demonstrate that VDR and DDX5 co-localize within the nuclei of HaCaT keratinocytes and sub-cellular protein fractions. In vivo validation studies demonstrate, that overexpression of DDX5 has the capability to enhance both, calcitriol-dependent transcription of known response genes and an extrachromosomal DR3-type reporter response. In agreement with this, shRNA based knock-down of DDX5 in keratinocytes compensates for this particular response. Finally, our findings reveal parallels between the VDR-DDX5 interaction and the well-characterized interaction between DDX5 and human estrogen receptor α and the androgen receptor, thus underscoring the physiological significance of the novel protein-protein interaction.

Vitamin d receptor gene variants and esophageal adenocarcinoma risk: a population-based case-control study

PURPOSE

Polymorphisms in the vitamin D receptor (VDR) gene may be of etiological importance in determining cancer risk. The aim of this study was to assess the association between common VDR gene polymorphisms and esophageal adenocarcinoma (EAC) risk in an all-Ireland population-based case-control study.

METHODS

EAC cases and frequency-matched controls by age and gender recruited between March 2002 and December 2004 throughout Ireland were included. Participants were interviewed, and a blood sample collected for DNA extraction. Twenty-seven single nucleotide polymorphisms in the VDR gene were genotyped using Sequenom or TaqMan assays while the poly(A) microsatellite was genotyped by fluorescent fragment analysis. Unconditional logistic regression was applied to assess the association between VDR polymorphisms and EAC risk.

RESULTS

A total of 224 cases of EAC and 256 controls were involved in analyses. After adjustment for potential confounders, TT homozygotes at rs2238139 and rs2107301 had significantly reduced risks of EAC compared with CC homozygotes. In contrast, SS alleles of the poly(A) microsatellite had significantly elevated risks of EAC compared with SL/LL alleles. However, following permutation analyses to adjust for multiple comparisons, no significant associations were observed between any VDR gene polymorphism and EAC risk.

CONCLUSIONS

VDR gene polymorphisms were not significantly associated with EAC development in this Irish population. Confirmation is required from larger studies.

Vitamin D metabolism, functions and needs: from science to health claims

BACKGROUND

Vitamin D is a nutrient long considered as essential for skeletal health but is now attracting interest from medical and nutritional communities as knowledge emerges of its biological function and its association with decreased risk of many chronic diseases.

RESULTS

A question emerges: How much more vitamin D do we need for these new functions of vitamin D? This review discusses vitamin D physiology and hypovitaminosis D and presents two vitamin D dietary policies: that according to regulatory authorities and that of nutrition scientists. Scientific evidence suggests that 25(OH)D serum levels should be over 75 nmol/L; otherwise, there is no beneficial effect of vitamin D on long-latency diseases. Current regulatory authority recommendations are insufficient to reach this level of adequacy. Observational and some prospective data show that vitamin D has a role in the prevention of cancer as well as immunity, diabetes and cardiovascular and muscle disorders, which supports the actions of 1α,25(OH)2D at cellular and molecular levels. The recent assessments done by the European Food Safety Authority should lead to new health claims.

CONCLUSIONS

Vitamin D, through food fortification and supplementation, is a promising new health strategy and thus provides opportunities for food industry and nutrition researchers to work together towards determining how to achieve this potential health benefit.

Understanding complexity in neurodegenerative diseases: in silico reconstruction of emergence

Healthy functioning is an emergent property of the network of interacting biomolecules that comprise an organism. It follows that disease (a network shift that causes malfunction) is also an emergent property, emerging from a perturbation of the network. On the one hand, the biomolecular network of every individual is unique and this is evident when similar disease-producing agents cause different individual pathologies. Consequently, a personalized model and approach for every patient may be required for therapies to become effective across mankind. On the other hand, diverse combinations of internal and external perturbation factors may cause a similar shift in network functioning. We offer this as an explanation for the multi-factorial nature of most diseases: they are "systems biology diseases," or "network diseases." Here we use neurodegenerative diseases, like Parkinson's disease (PD), as an example to show that due to the inherent complexity of these networks, it is difficult to understand multi-factorial diseases with simply our "naked brain." When describing interactions between biomolecules through mathematical equations and integrating those equations into a mathematical model, we try to reconstruct the emergent properties of the system in silico. The reconstruction of emergence from interactions between huge numbers of macromolecules is one of the aims of systems biology. Systems biology approaches enable us to break through the limitation of the human brain to perceive the extraordinarily large number of interactions, but this also means that we delegate the understanding of reality to the computer. We no longer recognize all those essences in the system's design crucial for important physiological behavior (the so-called "design principles" of the system). In this paper we review evidence that by using more abstract approaches and by experimenting in silico, one may still be able to discover and understand the design principles that govern behavioral emergence.

Vitamin D receptor activation and prevention of arterial ageing

In chronic kidney disease (CKD) patients, cardiovascular (CV) morbidity and mortality rate is higher than in the general population, because of frequently concomitant hypertension, peripheral vascular disease, heart failure, vascular calcification (VC), diabetes and mineral bone disease. Recently, another important factor associated to CV risk in CKD has been deeply investigated: vitamin D deficiency. Vitamin D Receptors (VDRs) are present in several systems and tissues and VDR activation is associated to positive effects, resulting in better blood pressure control and prevention of diabetic nephropathy. Unfortunately, the natural, non-selective vitamin D receptor activator (VDRA), calcitriol, is associated to higher serum calcium and phosphate levels, thus worsening CV risk in CKD. Recent data showed that the selective VDRA paricalcitol might have ameliorative CV effects. The potential positive impact of the use of paricalcitol on diabetic nephropathy, cardiac disease, hypertension, and VC may open new paths in the fight against CV disease in CKD patients.

Prediagnostic 25-hydroxyvitamin D, VDR and CASR polymorphisms, and survival in patients with colorectal cancer in western European ppulations

BACKGROUND

Individuals with higher blood 25-hydroxyvitamin D [25(OH)D] levels have a lower risk of developing colorectal cancer (CRC), but the influence of 25(OH)D on mortality after CRC diagnosis is unknown.

METHODS

The association between prediagnostic 25(OH)D levels and CRC-specific (N = 444) and overall mortality (N = 541) was prospectively examined among 1,202 participants diagnosed with CRC between 1992 and 2003 in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Multivariable Cox proportional hazards models were used to calculate HRs and corresponding 95% CIs according to 25(OH)D quintiles and genetic variation within the VDR and CASR genes. Potential dietary, lifestyle, and metabolic effect modifiers were also investigated.

RESULTS

There were 541 deaths, 444 (82%) due to CRC. Mean follow-up was 73 months. In multivariable analysis, higher 25(OH)D levels were associated with a statistically significant reduction in CRC-specific (P(trend) = 0.04) and overall mortality (P(trend) = 0.01). Participants with 25(OH)D levels in the highest quintile had an adjusted HR of 0.69 (95% CI: 0.50-0.93) for CRC-specific mortality and 0.67 (95% CI: 0.50-0.88) for overall mortality, compared with the lowest quintile. Except for a possible interaction by prediagnostic dietary calcium intake (P(interaction) = 0.01), no other potential modifying factors related to CRC survival were noted. The VDR (FokI and BsmI) and CASR (rs1801725) genotypes were not associated with survival.

CONCLUSIONS

High prediagnostic 25(OH)D levels are associated with improved survival of patients with CRC.

IMPACT

Our findings may stimulate further research directed at investigating the effects of blood vitamin D levels before, at, and after CRC diagnosis on outcomes in CRC patients.

Effects of supplemental vitamin D and calcium on biomarkers of inflammation in colorectal adenoma patients: a randomized, controlled clinical trial

Vitamin D and calcium affect several pathways involved in inflammation, tumor growth, and immune surveillance relevant to carcinogenesis. Also, epidemiologic evidence indicates that calcium and vitamin D may reduce risk for developing colorectal adenomas and cancer. To investigate the effects of calcium and vitamin D on biomarkers of inflammation in colorectal adenoma patients, we conducted a pilot, randomized, double-blind, placebo-controlled, 2 × 2 factorial clinical trial (n = 92) of 2 g/d calcium and/or 800 IU/d vitamin D(3) supplementation versus placebo over 6 months. Plasma concentrations of proinflammatory markers [C-reactive protein (CRP), TNF-α, interleukin (IL)-6, IL-1β, and IL-8] and an anti-inflammatory marker (IL-10) were measured using ELISAs. After 6 months of treatment, in the vitamin D(3) supplementation group, CRP decreased 32% overall (P = 0.11), 37% in men (P = 0.05), and 41% among non-nonsteroidal anti-inflammatory drug (NSAID) users (P = 0.05) relative to placebo. In the vitamin D(3) supplementation group, TNF-α decreased 13%, IL-6 32%, IL-1β 50%, and IL-8 15%; in the calcium supplementation group, IL-6 decreased 37%, IL-8 11%, and IL-1β 27%. Although these changes were not statistically significant, a combined inflammatory markers z-score decreased 77% (P = 0.003) in the vitamin D(3) treatment group overall, 83% (P = 0.01) among men, and 48% among non-NSAID users (P = 0.01). There was no evidence of synergy between vitamin D(3) and calcium or effects on IL-10. These preliminary results are consistent with a pattern of reduction in tumor-promoting inflammation biomarkers with vitamin D(3) or calcium supplementation alone and support further investigation of vitamin D(3) as a chemopreventive agent against inflammation and colorectal neoplasms.

Vitamin d receptor activators and clinical outcomes in chronic kidney disease

Vitamin D deficiency appears to be an underestimated risk factor for cardiovascular disease in patients with chronic kidney disease. Evidence from both basic science and clinical studies supports the possible protective role of vitamin D beyond its effect on mineral metabolism. Toxicity of pharmacologic doses of active vitamin D metabolites, in particular calcitriol, is mainly due to the possibility of positive calcium and phosphorus balance. Therefore, vitamin D analogs have been developed, which suppress PTH secretion and synthesis with reduced calcemic and phosphatemic effects. Observational studies suggest that in hemodialysis patients the use of a vitamin D receptor (VDR) activator, such as calcitriol, doxercalciferol, paricalcitol, or alfacalcidol, is associated with a reduced mortality when compared with nonusers of any VDR activator. In this article the existing literature on the topic is reviewed, although a more robust answer to the question of whether or not VDR activators have beneficial effects in hemodialysis patients will hopefully come from a randomized controlled trial.

Design principles of nuclear receptor signaling: how complex networking improves signal transduction

Nuclear receptors often function in the cytoplasm.

A triple conveyor belt pumps ligand (signal) into the nucleus and onto the DNA.

The active export of importins enhances signaling to the nucleus.

Sharing a single nuclear pore may reduce rather than increase crosstalk.

Nuclear receptors (NRs) derive their family name from the early observation that they are located in the nucleus, despite responding to extracellular signals such as hormones (e.g., cortisol) (Fanestil and Edelman, 1966). According to the ‘classical' paradigm of NR signaling, the NR resides in the nucleus, attached to a DNA response element, waiting for its ligand to bind. The actual systems have multiple additional features (reviewed in Cutress et al, 2008; Cao et al, 2009; Levin, 2009a; Bunce and Campbell, 2010), such as that NRs shuttle between the nucleus and the cytoplasm (Von Knethen et al, 2010) and ligand addition changes receptor location dynamically (Pratt et al, 1989; Liu and DeFranco, 2000; Kumar et al, 2004, 2006; Tanaka et al, 2005; Heitzer et al, 2007; Prüfer and Boudreaux, 2007; Ricketson et al, 2007; Cutress et al, 2008): Figure 1 summarizes the current understanding of the topology of the reaction networks involved in NR signaling, in systems biological graphical notation (SBGN), with NR activation, importin-α and -β binding, nuclear pore complex (NPC)-mediated import, recycling of importins, NR binding to target promoter sequences, exportin-mediated nuclear export of the NR, exportin cycling and free energy-driven Ran recycling. This topology is surprisingly complex when compared with the ‘classical' paradigm. To address to what extent this extra complexity is just detail or contributes essential functionality, we have simulated the dynamics of the NR transcriptional response in maximally realistic mathematical models of increasingly complex designs.

The calculations revealed significant disadvantages of the classical and simplest mechanism for endocrine NR-mediated signaling, i.e., the one with localization of the NR exclusively on the DNA (design 1 in Figure 2A): the transcriptional response was very low (Figure 2B). A high concentration of free NR in the nucleus (design 2) improved sensitivity, but made the responsiveness much slower (Figure 2B). If the NR was equally distributed between the nucleus and the cytoplasm without the NR being able to traverse the nucleocytoplasmic membrane (design 3), then, although the NR diffuses more slowly than the much smaller ligand molecule, the higher concentration of the NR increased flux from the plasma membrane to the nuclear membrane; the steady state was reached faster (Figure 2B and C; compare design 3 relative to design 2). Enabling the NR to traverse the nucleocytoplasmic membrane (design 4), further accelerated the response (Figure 2B and C).

Designs 1–4 considered the permeation of the NR through the nuclear membrane to be passive, implying an import/export activity ratio of 1. When varying the import to export activity ratio (design 5), a trade-off between the fast responsiveness of design 4 and the high sensitivity of design 2 was calculated (Figure 2B). In order to maximize responsiveness, core-NR should be concentrated in the cytoplasm, whereas to gain sensitivity, liganded NR should be concentrated in the nucleus. This suggested that performance could be improved by making nuclear import and export selective for liganded over unliganded NR (design 6; Figure 2A). Indeed, retention of core-NR in the cytoplasm provided high influx of ligand into the nucleus (Figure 2D), and also the highest concentration of ligand in the nucleus (Figure 2C): Apart from its classical receptor role in transcription regulation, the NR may function as (part of) an active pump for its ligand, resembling a triple conveyor belt: importins and exportins cycle as conveyor belts and drive the cycling of the third conveyor belt consisting of the NR that pumps ligand into the nucleus.

Two other striking features of the NR signaling network (Figure 1) are related to the facts that the energy of GTP hydrolysis is coupled to an active export of importins rather than to direct active import of NR and that the same NPC is used for all transport processes. At first sight, the former may waste free energy and the latter might cause fragility due to interferences between different NRs and other signaling pathways. However, our models show that active nuclear export of importins is a design preventing NR sequestration in the nucleus by nuclear importins and, equally paradoxically, the transport of all cargo through the same NPC makes the transport of any particular cargo robust with respect to perturbations in the availability of any other cargo.

Our calculations also predict that there is an optimal ratio of nuclear to cytoplasmic fractions of the NR (Figure 2G) that depends on the specific properties of the ligand and on the transcription activation requirements. This may help to explain the observation that different NRs have different predominant intracellular localizations. Our model calculations are thereby in line with many experimental observations, but specific cases of NR signaling may only exhibit a subset of all features. Our models can aid in identifying which subsets are important in any particular case of NR signaling, as we demonstrate for an example.

In this study, we have shown that complex networks of biochemical and signaling reactions can harbor subtle design principles that can be understood rationally in terms of simplified but not simple models (which are available to the reader).

The topology of nuclear receptor (NR) signaling is captured in a systems biological graphical notation. This enables us to identify a number of ‘design' aspects of the topology of these networks that might appear unnecessarily complex or even functionally paradoxical. In realistic kinetic models of increasing complexity, calculations show how these features correspond to potentially important design principles, e.g.: (i) cytosolic ‘nuclear' receptor may shuttle signal molecules to the nucleus, (ii) the active export of NRs may ensure that there is sufficient receptor protein to capture ligand at the cytoplasmic membrane, (iii) a three conveyor belts design dissipating GTP-free energy, greatly aids response, (iv) the active export of importins may prevent sequestration of NRs by importins in the nucleus and (v) the unspecific nature of the nuclear pore may ensure signal-flux robustness. In addition, the models developed are suitable for implementation in specific cases of NR-mediated signaling, to predict individual receptor functions and differential sensitivity toward physiological and pharmacological ligands.

Nutrigenomics, vitamin D and cancer prevention

Although there is growing epidemiological, preclinical and clinical evidence suggesting that low vitamin D intake, exposure and/or status is associated with an increased risk of various types of cancer, the optimum amount needed remains controversial. Furthermore, there is evidence that a U- or J-shaped response curve exist between 25(OH)D and certain cancers. Increasing information about the impact of genetic variation, especially polymorphisms that influence absorption, transport, metabolism and associated molecular targets, should help clarify inconsistencies in the data regarding vitamin D's effect on cancer risk. Rather than focusing on the main effects of a few variants of these genes alone, future studies need to consider gene-nutrient or environmental interactions. Nutrigenomics should clarify who might benefit and be placed at risk because of vitamin D exposure.

Vitamin D-mediated induction of innate immunity in gingival epithelial cells

Human gingival epithelial cells (GEC) produce peptides, such as β-defensins and the cathelicidin LL-37, that are both antimicrobial and that modulate the innate immune response. In myeloid and airway epithelial cells, the active form of vitamin D(3) [1,25(OH)(2)D(3)] increases the expression and antibacterial activity of LL-37. To examine the activity of vitamin D on the innate immune defense of the gingival epithelium, cultured epithelial cells were treated with either 10(-8) M 1,25(OH)(2)D(3) or ethanol for up to 24 h. A time-dependent induction of LL-37 mRNA up to 13-fold at 24 h in both standard monolayer and three-dimensional cultures was observed. Induction of the vitamin D receptor and the 1-α-hydroxylase genes was also observed. The hydroxylase was functional, as LL-37 induction was observed in response to stimulation by 25(OH)D(3). Through microarray analysis of other innate immune genes, CD14 expression increased 4-fold, and triggering receptor expressed on myeloid cells-1 (TREM-1) was upregulated 16-fold after 24 h of treatment with 1,25(OH)(2)D(3). TREM-1 is a pivotal amplifier of the innate immune response in macrophages, leading to increased production by inflammatory response genes. Activation of TREM-1 on the GEC led to an increase in interleukin-8 (IL-8) mRNA levels. Incubation of three-dimensional cultures with 1,25(OH)(2)D(3) led to an increase in antibacterial activity against the periodontal pathogen Aggregatibacter actinomycetemcomitans when the bacteria were added to the apical surface. This study is the first to demonstrate the effect of vitamin D on antibacterial defense of oral epithelial cells, suggesting that vitamin D(3) could be utilized to enhance the innate immune defense in the oral cavity.