VDR-mediated gene expression patterns in resting human coronary artery smooth muscle cells

Confronting the global obesity epidemic: investigating the role and underlying mechanisms of vitamin D in metabolic syndrome management

The escalating prevalence of MetS, driven by global obesity trends, underscores the urgent need for innovative therapeutic strategies. To gain a deeper understanding of the therapeutic potential of vitamin D in addressing MetS, we embarked on a targeted literature review that thoroughly examines the scientific underpinnings and pivotal discoveries derived from pertinent studies, aiming to unravel the intricate mechanisms through which vitamin D exerts its effects on MetS and its components. This article explores the multifunctional role of vitamin D in the management of MetS, focusing on its regulatory effects on insulin sensitivity, lipid metabolism, inflammation, and immune response. Through an extensive review of current research, we unveil the complex mechanisms by which vitamin D influences MetS components, highlighting its potential as a therapeutic agent. Our analysis reveals that vitamin D's efficacy extends beyond bone health to include significant impacts on cellular and molecular pathways critical to MetS. We advocate for further research to optimize vitamin D supplementation as a component of precision medicine for MetS, considering the safety concerns related to dosage and long-term use.

Role of Vitamin D Deficiency in the Pathogenesis of Cardiovascular and Cerebrovascular Diseases

Deficiency in vitamin D (VitD), a lipid-soluble vitamin and steroid hormone, affects approximately 24% to 40% of the population of the Western world. In addition to its well-documented effects on the musculoskeletal system, VitD also contributes importantly to the promotion and preservation of cardiovascular health via modulating the immune and inflammatory functions and regulating cell proliferation and migration, endothelial function, renin expression, and extracellular matrix homeostasis. This brief overview focuses on the cardiovascular and cerebrovascular effects of VitD and the cellular, molecular, and functional changes that occur in the circulatory system in VitD deficiency (VDD). It explores the links among VDD and adverse vascular remodeling, endothelial dysfunction, vascular inflammation, and increased risk for cardiovascular and cerebrovascular diseases. Improved understanding of the complex role of VDD in the pathogenesis of atherosclerotic cardiovascular diseases, stroke, and vascular cognitive impairment is crucial for all cardiologists, dietitians, and geriatricians, as VDD presents an easy target for intervention.

Ablation of Vitamin D Signaling Compromises Cerebrovascular Adaptation to Carotid Artery Occlusion in Mice

Vitamin D insufficiency has been associated with increased incidence and severity of cerebrovascular disorders. We analyzed the impact of impaired vitamin D signaling on the anatomical and functional aspects of cerebrovascular adaptation to unilateral carotid artery occlusion (CAO), a common consequence of atherosclerosis and cause of ischemic stroke. Cerebrocortical blood flow (CoBF) showed a significantly increased drop and delayed recovery after CAO in mice carrying a functionally inactive vitamin D receptor (VDR) with the most sustained perfusion deficit in the temporal cortex. To identify the cause(s) for this altered adaptation, the extent of compensatory blood flow increase in the contralateral carotid artery and the morphology of pial collaterals between the anterior and middle cerebral arteries were determined. Whereas VDR deficiency had no significant influence on the contralateral carotid arterial blood flow increase, it was associated with decreased number and increased tortuosity of pial anastomoses resulting in unfavorable changes of the intracranial collateral circulation. These results indicate that VDR deficiency compromises the cerebrovascular adaptation to CAO with the most sustained consequences in the temporal cortex. The dysregulation can be attributed to the altered development and function of pial collateral circulation whereas extracranial vessels may not be impaired.

Effect of 9 months of vitamin D supplementation on arterial stiffness and blood pressure in Graves' disease: a randomized clinical trial

PURPOSE

Risk of cardiovascular disease (CVD) is increased in Graves' disease (GD). CVD is predicted by increased pulse wave velocity (PWV) and blood pressure (BP). GD and these risk factors are all associated with lower levels of vitamin D. We aimed to assess the effect of supplemental vitamin D on PWV and BP in GD.

METHODS

In a double-blinded trial, newly diagnosed GD patients were randomized to vitamin D3 70 µg/day (n = 44) or placebo (n = 42) as add-on to anti-thyroid medication. At baseline, 3 and 9 months PWV, BP and wave analysis were performed in office and 24 h setting. Between-group differences in change at 9 months were analyzed using linear mixed modelling. In subanalysis, effect of intervention in regard to baseline vitamin D insufficiency (25(OH)D < 50 nmol/L) was investigated. (The DAGMAR study, clinicaltrials.gov ID NCT02384668).

RESULTS

PWV was unaffected by intervention in main analysis. However in the subanalysis, comparing the response to intervention in the vitamin D insufficient (n = 28) and the vitamin D replete patients, supplemental vitamin D induced a significant decrease in office PWV of 1.2 (95% CI: -2.3; -0.1) m/s compared to placebo. Of notice, baseline PWV was non-significantly higher among the vitamin D insufficient as compared to the replete participants. In response to vitamin D, office central systolic BP (-3.9 (95% CI: -7.5; -0.3) and brachial mean BP (-3.3 (95% CI: -6.5; -0.3) declined whereas 24 h measurements were unaffected.

CONCLUSIONS

High-dose vitamin D supplementation did not affect PWV. We observed significant reduction in office but not 24 h BP. Subanalysis showed a clinically relevant PWV reduction among vitamin D insufficient participants, although regression towards the mean might contribute to findings. Further studies on supplemental vitamin D in GD should focus on patients with vitamin D insufficiency.

The intestinal vitamin D receptor in inflammatory bowel disease: inverse correlation with inflammation but no relationship with circulating vitamin D status

BACKGROUND

The intestinal vitamin D receptor (VDR) remains poorly characterized in patients with inflammatory bowel disease (IBD).

METHODS

Colonoscopic biopsies and intestinal resection specimens from the terminal ileum, ascending and sigmoid colon, from patients with and without IBD, were analyzed for VDR mRNA quantification by polymerase chain reaction, and protein localization and semi-quantification by immunohistochemistry. The relationship between VDR and intestinal inflammation, serum 25(OH)D and oral vitamin D intake was elicited.

RESULTS

A total of 725 biopsies from 20 patients with Crohn's disease (CD), 15 with ulcerative colitis (UC) and 14 non-IBD controls who underwent colonoscopy were studied. VDR gene expression and protein staining intensity was similar across all three groups, and across the intestinal segments. Sigmoid colon VDR mRNA expression inversely correlated with faecal calprotectin (r = -0.64, p = 0.026) and histological score (r = -0.67, p = 0.006) in UC, and histological score (r = -0.58, p = 0.019) in patients with CD. VDR staining intensity was higher in quiescent than diseased segments. No relationship with serum 25(OH)D or oral vitamin D intake was noted. Immunohistochemical staining of 28 intestinal resection specimens from 15 patients (5 each with CD, UC and non-IBD controls) showed diffuse VDR staining in the mucosa, submucosa and circular muscle.

CONCLUSIONS

VDR transcript expression and protein staining intensity are inversely related to inflammation in IBD, but unrelated to serum 25(OH)D, and similar to non-IBD controls. Strategies to upregulate intestinal VDR, potentially translating to modulation of disease activity, require investigation.

Vitamin D Receptor Activators

The fields for clinical employment of vitamin D analogs are growing and under active evaluation in different medical specialties, ranging from dermatology to immunology and oncology. In this review we provide a brief description of the drugs that have been developed more specifically for the treatment of secondary hyperparathyroidism (SH) associated with uremia.

Vitamin D and regulation of vascular cell function

Vitamin D deficiency is linked to pathogenesis of many diseases including cardiovascular, cancer, and various eye diseases. In recent years, important roles for vitamin D in regulation of immune function, inflammation, angiogenesis, and aging have been demonstrated. Thus, vitamin D and its analogs have been evaluated for the treatment of various types of cancer and chronic diseases. We have previously shown that the active form of vitamin D [1,25(OH)₂D₃] is a potent inhibitor of angiogenesis. This activity is consistent with the important role proposed for vitamin D and its analogs in the mitigation of tumor growth through inhibition of angiogenesis. Here, we review the important nutritional value of vitamin D and the abnormalities linked to its deficiency. We will explore its potential role as a regulator of angiogenesis and vascular cell function and the role vitamin D receptor (VDR) expression plays in these activities during vascular development and neovascularization. Our studies have established an important role for 1,25(OH)₂D₃ and VDR in the regulation of perivascular supporting cell function. In addition, the interaction of 1,25(OH)₂D₃ and VDR is essential for these activities and inhibition of neovascularization. Delineating the signaling pathways involved and identification of genes that are the target of 1,25(OH)₂D₃ regulation in vascular cells will allow us to identify novel pathways that are targets for regulation of vascular function and angiogenesis.

Non-skeletal health effects of vitamin D supplementation: A systematic review on findings from meta-analyses summarizing trial data

BACKGROUND

A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D (25OHD) levels on non-skeletal outcomes. We performed a systematic quantitative review on characteristics of randomized clinical trials (RCTs) included in meta-analyses (MAs) on non-skeletal effects of vitamin D supplementation.

METHODS AND FINDINGS

We identified systematic reviews (SR) reporting summary data in terms of MAs of RCTs on selected non-skeletal outcomes. For each outcome, we summarized the results from available SRs and scrutinized included RCTs for a number of predefined characteristics. We identified 54 SRs including data from 210 RCTs. Most MAs as well as the individual RCTs reported null-findings on risk of cardiovascular diseases, type 2 diabetes, weight-loss, and malignant diseases. Beneficial effects of vitamin D supplementation was reported in 1 of 4 MAs on depression, 2 of 9 MAs on blood pressure, 3 of 7 MAs on respiratory tract infections, and 8 of 12 MAs on mortality. Most RCTs have primarily been performed to determine skeletal outcomes, whereas non-skeletal effects have been assessed as secondary outcomes. Only one-third of the RCTs had low level of 25OHD as a criterion for inclusion and a mean baseline 25OHD level below 50 nmol/L was only present in less than half of the analyses.

CONCLUSIONS

Published RCTs have mostly been performed in populations without low 25OHD levels. The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels.

High concentration calcitriol induces endoplasmic reticulum stress related gene profile in breast cancer cells

Calcitriol, the active form of vitamin D, is known for its anticancer properties including induction of apoptosis as well as the inhibition of angiogenesis and metastasis. Understanding the mechanisms of action for calcitriol will help with the development of novel treatment strategies. Since vitamin D exerts its cellular actions via binding to its receptor and by altering expressions of a set of genes, we aimed to evaluate the effect of calcitriol on transcriptomic profile of breast cancer cells. We previously demonstrated that calcitriol alters endoplasmic reticulum (ER) stress markers, therefore in this study we have focused on ER-stress-related genes to reveal calcitriols action on these genes in particular. We have treated breast cancer cell lines MCF-7 and MDA-MB-231 with previously determined IC50 concentrations of calcitriol and evaluated the transcriptomic alterations via microarray. During analysis, only genes altered by at least 2-fold with a P value < 0.05 were taken into consideration. Our findings revealed an ER-stress-associated transcriptomic profile induced by calcitriol. Induced genes include genes with a pro-survival function (NUPR1, DNAJB9, HMOX1, LCN2, and LAMP3) and with a pro-death function (CHOP (DDIT3), DDIT4, NDGR1, NOXA, and CLGN). These results suggest that calcitriol induces an ER-stress-like response inducing both pro-survival and pro-death transcripts in the process.

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'.

Does sufficient evidence exist to support a causal association between vitamin D status and cardiovascular disease risk? An assessment using Hill's criteria for causality

Serum 25-hydroxyvitamin D (25(OH)D) levels have been found to be inversely associated with both prevalent and incident cardiovascular disease (CVD) risk factors; dyslipidemia, hypertension and diabetes mellitus. This review looks for evidence of a causal association between low 25(OH)D levels and increased CVD risk. We evaluated journal articles in light of Hill's criteria for causality in a biological system. The results of our assessment are as follows. Strength of association: many randomized controlled trials (RCTs), prospective and cross-sectional studies found statistically significant inverse associations between 25(OH)D levels and CVD risk factors. Consistency of observed association: most studies found statistically significant inverse associations between 25(OH)D levels and CVD risk factors in various populations, locations and circumstances. Temporality of association: many RCTs and prospective studies found statistically significant inverse associations between 25(OH)D levels and CVD risk factors. Biological gradient (dose-response curve): most studies assessing 25(OH)D levels and CVD risk found an inverse association exhibiting a linear biological gradient. Plausibility of biology: several plausible cellular-level causative mechanisms and biological pathways may lead from a low 25(OH)D level to increased risk for CVD with mediators, such as dyslipidemia, hypertension and diabetes mellitus. Experimental evidence: some well-designed RCTs found increased CVD risk factors with decreasing 25(OH)D levels. Analogy: the association between serum 25(OH)D levels and CVD risk is analogous to that between 25(OH)D levels and the risk of overall cancer, periodontal disease, multiple sclerosis and breast cancer.

CONCLUSION

all relevant Hill criteria for a causal association in a biological system are satisfied to indicate a low 25(OH)D level as a CVD risk factor.

The future of vitamin D analogs

The active form of vitamin D₃, 1,25-dihydroxyvitamin D₃, is a major regulator of bone and calcium homeostasis. In addition, this hormone also inhibits the proliferation and stimulates the differentiation of normal as well as malignant cells. Supraphysiological doses of 1,25-dihydroxyvitamin D₃ are required to reduce cancer cell proliferation. However, these doses will lead in vivo to calcemic side effects such as hypercalcemia and hypercalciuria. During the last 25 years, many structural analogs of 1,25-dihydroxyvitamin D₃ have been synthesized by the introduction of chemical modifications in the A-ring, central CD-ring region or side chain of 1,25-dihydroxyvitamin D₃ in the hope to find molecules with a clear dissociation between the beneficial antiproliferative effects and adverse calcemic side effects. One example of such an analog with a good dissociation ratio is calcipotriol (Daivonex®), which is clinically used to treat the hyperproliferative skin disease psoriasis. Other vitamin D analogs were clinically approved for the treatment of osteoporosis or secondary hyperparathyroidism. No vitamin D analog is currently used in the clinic for the treatment of cancer although several analogs have been shown to be potent drugs in animal models of cancer. Transcriptomics studies as well as in vitro cell biological experiments unraveled basic mechanisms involved in the antineoplastic effects of vitamin D and its analogs. 1,25-dihydroxyvitamin D₃ and analogs act in a cell type- and tissue-specific manner. Moreover, a blockade in the transition of the G0/1 toward S phase of the cell cycle, induction of apoptosis, inhibition of migration and invasion of tumor cells together with effects on angiogenesis and inflammation have been implicated in the pleiotropic effects of 1,25-dihydroxyvitamin D₃ and its analogs. In this review we will give an overview of the action of vitamin D analogs in tumor cells and look forward how these compounds could be introduced in the clinical practice.

Diagnosis of Arterial Media Calcification in Chronic Kidney Disease

PURPOSE

Arterial media calcification (AMC) is often the only vascular calcification (VC) present in young patients with chronic renal failure and its presence is associated with higher mortality rates. Currently, X-ray imaging (as a standard approach) is able to show AMC in areas without diffuse overlapping arterial intimal calcification (AIC), but X-ray imaging only allows us to identify this lesion when the vessel is widely calcified. The aim of this study was to evaluate the possibility of using ultrasonography as opposed to X-rays to visualize AMC in patients with chronic renal failure. Patients and Methods: In this cross-sectional study, we examined 105 patients (chronic kidney disease stage IV: 19 patients, hemodialysis: 48 patients, renal transplant: 26 patients; mean age: 54 ± 14 years; 65 males and 40 females); B-mode ultrasonography was performed to detect AMC or AIC on the superficial femoral artery (SFA). As a control, plain radiography of the thigh was performed in all patients.

RESULTS

Upon ultrasonography investigation, 12 subjects were excluded due to diffuse VC on the SFA that did not permit a distinction between AMC and AIC. In the remaining 93 patients, AMC was detected on the SFA in 43 patients using ultrasonography and in 20 patients using the standard approach. The sensitivity and specificity of the standard approach for the detection of AMC on the SFA were 47 and 100%, respectively. The positive and negative predictive values of the standard approach were 1 and 0.68, respectively.

CONCLUSION

Ultrasonography is able to detect AMC better than the X-ray approach, focusing on individuals at higher risk.

Vitamin D receptor activation and cardiovascular disease

Vitamin D has been recently associated with several renal, cardiovascular and inflammatory diseases, beyond mineral metabolism and bone health. This is due in part to widespread expression of vitamin D receptor (VDR) on tissues and cells such as heart, kidney, immune cells, brain and muscle. In chronic kidney disease (CKD) and other chronic disorders, vitamin D deficiency [serum 25(OH)D <20 ng/mL] is very common and is associated with adverse outcomes. Paricalcitol, a selective activator of VDR, has demonstrated in several experimental and clinical studies of diabetic and non-diabetic CKD a favourable profile compared to other VDR activators, alone or as add-on to standard therapy. These beneficial effects are mediated by different actions such as reduction of oxidative stress, inflammation, downregulation of cardiac and renal renin expression, downregulation of calcifying genes and direct vascular protective effects. Furthermore, paricalcitol beneficial effects may be independent of baseline serum parathyroid hormone (PTH), calcium and phosphate levels. These benefits should be confirmed in large and well-designed ongoing clinical trials.

Increased endothelin-1 responsiveness in human coronary artery smooth muscle cells exposed to 1,25-dihydroxyvitamin D3

Low blood concentrations of 25-hydroxyvitamin D3 are associated with increased mortality, while some studies suggest improved cardiovascular outcomes with vitamin D3 supplementation in chronic kidney disease. However, the physiological effects of vitamin D3 on the cardiovascular system remain poorly understood making it difficult to determine whether vitamin D3 supplementation might provide cardiovascular benefit or even cause harm. Thus here we investigated the effects of chronic 1,25-dihydroxyvitamin D3 treatment on intracellular signaling in human coronary artery smooth muscle cells (HCASMCs) and found that 1,25-dihydroxyvitamin D3 significantly potentiated endothelin (ET-1) signaling. Specifically, 1,25-dihydroxyvitamin D3 (24-h pretreatment) caused a more than threefold enhancement in both ET-1-induced intracellular calcium mobilization and extracellular signal-regulated kinase (ERK) activation. This 1,25-dihydroxyvitamin D3-elicited signaling enhancement was not observed for either vasopressin or carbachol. With the use of endothelin receptor (ETR) isoform-selective antagonists, ETRA was found to be primarily responsible for the 1,25-dihydroxyvitamin D3-induced ET-1 responsiveness and yet ETRA mRNA expression and protein abundance were unaltered following 1,25-dihydroxyvitamin D3 treatment. While there was an increase in ETRB mRNA expression in response to 1,25-dihydroxyvitamin D3, the protein abundance of ETRB was again unchanged. Finally, ETRA/ETRB heterodimerization was not detected in HCASMCs in either the absence or presence of 1,25-dihydroxyvitamin D3. Together, these data show for the first time that 1,25-dihydroxyvitamin D3 enhances endothelin responsiveness in HCASMCs and that the effect is mediated through ETRA.

Protective role of the vitamin D receptor

Vitamin D receptor (VDR) is found in most tissues, not just those participating in the classic actions of vitamin D such as bone, gut, and kidney. The nonclassic actions are therefore potential targets for the active metabolite of vitamin D, 1,25(OH)₂D₃. This review is intended to highlight the actions of VDR in role of protection. Medline is searched for articles describing actions of VDR on secondary hyperparathyroidism, diabetic nephropathy, hypertension and atherosclerosis. VDR exerts its protective activities through the following mechanisms: inhibition of renin-angiotensin system (RAS); regulation of proliferation and differentiation; reduction of proteinuria; anti-inflammation and anti-fibrosis. The nonclassic actions of VDR provide a number of potential new clinical applications for 1,25(OH)₂D₃ and its analogs. We believe 1,25(OH)₂D₃/VDR can be of particular value in the prevention of kidney-related diseases.

Decreased expression of vitamin D receptors in neointimal lesions following coronary artery angioplasty in atherosclerotic swine

Background

Inflammatory cytokines, such as TNF-α, play a key role in the pathogenesis of occlusive vascular diseases. Activation of vitamin D receptors (VDR) elicits both growth-inhibitory and anti-inflammatory effects. Here, we investigated the expression of TNF-α and VDR in post-angioplasty coronary artery neointimal lesions of hypercholesterolemic swine and examined the effect of vitamin D deficiency on the development of coronary restenosis. We also examined the effect of calcitriol on cell proliferation and effect of TNF-α on VDR activity and expression in porcine coronary artery smooth muscle cells (PCASMCs) in-vitro.

Methodology/Principal Findings

Expression of VDR and TNF-α and the effect of vitamin D deficiency in post-angioplasty coronary arteries were analyzed by immunohistochemistry and histomorphometry. Cell proliferation was examined by thymidine and BrdU incorporation assays in cultured PCASMCs. Effect of TNF-α-stimulation on the activity and expression of VDR was analyzed by luciferase assay, immunoblotting and immunocytochemistry. In-vivo, morphometric analysis of the tissues revealed typical lesions with significant neointimal proliferation. Histological evaluation showed expression of smooth muscle α-actin and significantly increased expression of TNF-α in neointimal lesions. Interestingly, there was significantly decreased expression of VDR in PCASMCs of neointimal region compared to normal media. Indeed, post-balloon angioplasty restenosis was significantly higher in vitamin D-deficient hypercholesterolemic swine compared to vitamin D-sufficient group. In-vitro, calcitriol inhibited both serum- and PDGF-BB-induced proliferation in PCASMCs and TNF-α-stimulation significantly decreased the expression and activity of VDR in PCASMCs.

Conclusions/Significance

These data suggest that significant downregulation of VDR in proliferating smooth muscle cells in neointimal lesions could be due to atherogenic cytokines, including TNF-α. Vitamin D deficiency potentiates the development of coronary restenosis. Calcitriol has anti-proliferative properties in PCASMCs and these actions are mediated through VDR. This could be a potential mechanism for uncontrolled growth of neointimal cells in injured arteries leading to restenosis.

Vitamin D and diabetes

There is no doubt that vitamin D deficiency is the cause of several metabolic bone diseases, but vitamin D status is also linked to many major human diseases including immune disorders. Mounting data strengthen the link between vitamin D and diabetes, in particular T1D and T2D. Despite some inconsistencies between studies that associate serum 25(OH)D levels with the risk of developing T1D or T2D, there seems to be an overall trend for an inverse correlation between levels of 25(OH)D and both disorders. There is also compelling evidence that 1,25(OH)2D regulates b-cell function by different mechanisms, such as influencing insulin secretion by regulating intracellular levels of Ca2+, increasing β-cell resistance to apoptosis, and perhaps also increasing β-cell replication. The capacity of vitamin D, more specifically 1,25(OH)2D, to modulate immune responses is of particular interest for both the therapy and prevention of diabetes. In the case of T1D, vitamin D supplementation in prediabetic individuals could help prevent or reduce the initiation of autoimmune processes possibly by regulating thymic selection of the T-cell repertoire, decreasing the numbers of autoreactive T cells, and inducing Treg cells. Although immune modulation is generally discussed for the treatment of T1D, it is also relevant for T2D. Indeed, recent studies have shown that T2D patients have increased systemic inflammation and that this state can induce β-cell dysfunction and death. Supplementation trials with regular vitamin D for the protection against the development of T1D and T2D have generated some contradictory data, but many weaknesses can be identified in these trials as most were underpowered or open-labeled. However, the overwhelming strength of preclinical data and of the observational studies make vitamin D or its analogues strong candidates for the prevention or treatment of diabetes or its complications. However, proof of causality needs well-designed clinical trials and if positive, adequate dosing, regimen, and compound studies are needed to define the contribution of vitamin D status and therapy in the global diabetes problem. There are many confounding factors that need to be taken into consideration when translating successful vitamin D therapies in animal models into humans, for example, gender, age, lifestyle, and genetic background. To come to solid conclusions on the potential of vitamin D or its analogues in the prevention of or therapy for all forms of diabetes, it is clear that large prospective trials with carefully selected populations and end points will be needed, but should also receive high priority.

Vitamin D receptor activators inhibit vascular smooth muscle cell mineralization induced by phosphate and TNF-α

BACKGROUND

Vascular calcification is a highly regulated process. Tumor necrosis factor-α (TNF-α) has been shown to accelerate the highly regulated osteogenic process in vascular smooth muscle cells (VSMCs). Vitamin D receptor activators (VDRAs) have been associated with beneficial cardiovascular outcomes in patients with chronic kidney disease. We examined whether maxacalcitol, a vitamin D(3) analog, exhibits a suppressive effect on VSMC mineralization induced by phosphate and TNF-α.

METHODS

Human VSMCs were treated with either vehicle, maxacalcitol (10(-9) to 10(-7) M), or calcitriol (10(-9) to 10(-7) M) in 2.5 mM of phosphate media with TNF-α (1 ng/mL) for 9 days. VSMC mineralization was determined and expression of genes associated with the osteogenic process was examined by real-time reverse transcription-polymerase chain reaction. Expression of matrix metalloproteinase-2 (MMP-2) messenger RNA (mRNA) in VSMCs and MMP-2 protein in media was also analyzed.

RESULTS

Vehicle-treated VSMCs exhibited massive mineralization, which was inhibited by maxacalcitol in a concentration-dependent manner. Calcitriol also inhibited the mineralization. While vehicle-treated VSMCs exhibited increased mRNA expression of genes associated with the osteogenic process (Cbfa1/Runx2 and osteocalcin) compared with VSMCs grown in normal media without TNF-α (control), maxacalcitol and calcitriol suppressed the increase in mRNA species. Furthermore, vehicle-treated VSMCs exhibited increased MMP-2 mRNA and protein in the media that were suppressed notably by maxacalcitol.

CONCLUSIONS

Both the VDRAs abrogated the acceleration of the osteogenic process induced by phosphate and TNF-α in VSMCs, which was linked to inhibition of mineralization in VSMCs. MMP-2 blockade by VDRAs may contribute to an inhibitory effect on vascular calcification.

Markers of bone metabolism in premature myocardial infarction (≤ 40 years of age)

INTRODUCTION

Acute myocardial infarction (AMI) at young age is a rare disease with a poor prognosis. Bone metabolism parameters such as 1,25 (OH)₂ vitamin D₃, 25 (OH) vitamin D₃ and osteocalcin have been recently implicated in the development of coronary heart disease (CHD). We evaluated the role of these serum markers in a study population of very young AMI survivors (≤ 40 years).

METHODS AND RESULTS

We prospectively enrolled 302 subjects into our multi-center case control study, including 102 young myocardial infarction patients (≤ 40 years) and 200 control subjects who were frequency-matched on gender and age in an approximate 2:1 ratio per case patient. In the adjusted logistic regression analysis, we used baseline laboratory measurements for the first analysis (acute phase analysis) and measurements from one-year follow-up visits (stable phase analysis). In both, elevated levels of 25 (OH) vitamin D₃ (acute phase: OR per IQR 2.02, 95% CI 1.13-3.58, p = 0.017; stable phase: OR 4.07, 95% CI 1.8-9.21, p = 0.001) and 1,25 (OH)₂ vitamin D₃ (acute phase: OR 2.82, 95% CI 1.7-4.7, p < 0.001; stable phase: OR 4.57, 95% CI 2.31-9.05, p < 0.001) were associated with premature AMI. Conversely, osteocalcin was inversely associated with premature myocardial infarction (acute phase: OR 0.53, 95% CI 0.28-1.03, p = 0.059; stable phase: OR 0.26, 95% CI 0.12-0.6, p < 0.001). The observed associations were independent of the acute phase of myocardial infarction.

CONCLUSION

In our study, elevated levels of 25 (OH) vitamin D₃ and 1,25 (OH)₂ vitamin D₃, as well as decreased levels of osteocalcin were associated with myocardial infarction in very young patients. The precise mechanism and implications of these findings will have to be elucidated in future studies.

Chondro/osteoblastic and cardiovascular gene modulation in human artery smooth muscle cells that calcify in the presence of phosphate and calcitriol or paricalcitol

Vitamin D sterol administration, a traditional treatment for secondary hyperparathyroidism, may increase serum calcium and phosphorus, and has been associated with increased vascular calcification (VC). In vitro studies suggest that in the presence of uremic concentrations of phosphorus, vitamin D sterols regulate gene expression associated with trans-differentiation of smooth muscle cells (SMCs) to a chondro/osteoblastic cell type. This study examined effects of vitamin D sterols on gene expression profiles associated with phosphate-enhanced human coronary artery SMC (CASMC) calcification. Cultured CASMCs were exposed to phosphate-containing differentiation medium (DM) with and without calcitriol, paricalcitol, or the calcimimetic R-568 (10(-11)-10(-7) M) for 7 days. Calcification of CASMCs, determined using colorimetry following acid extraction, was dose dependently increased (1.6- to 1.9-fold) by vitamin D sterols + DM. In contrast, R-568 did not increase calcification. Microarray analysis demonstrated that, compared with DM, calcitriol (10(-8) M) + DM or paricalcitol (10(-8) M) + DM similarly and significantly (P < 0.05) regulated genes of various pathways including: metabolism, CYP24A1; mineralization, ENPP1; apoptosis, GIP3; osteo/chondrogenesis, OPG, TGFB2, Dkk1, BMP4, BMP6; cardiovascular, HGF, DSP1, TNC; cell cycle, MAPK13; and ion channels, SLC22A3 KCNK3. R-568 had no effect on CASMC gene expression. Thus, SMC calcification observed in response to vitamin D sterol + DM may be partially mediated through targeting mineralization, apoptotic, osteo/chondrocytic, and cardiovascular pathway genes, although some gene changes may protect against calcification. Further studies to determine precise roles of these genes in development of, or protection against VC and cardiovascular disease are required.

Global maternal early pregnancy peripheral blood mRNA and miRNA expression profiles according to plasma 25-hydroxyvitamin D concentrations

OBJECTIVE

We investigated associations of early pregnancy maternal vitamin D concentrations with differential gene expression and post-transcription regulation.

METHOD

Plasma 25-hydroxyvitamin D (25[OH]D) was measured among participants of a nested case-control study. Participants with low (<25.5 ng/ml) and high (≥31.7 ng/ml) 25[OH]D were identified among controls. Peripheral blood messenger RNA (mRNA) (N = 21) and microRNA (miRNA) (N = 13) expression studies were conducted among participants with low and high 25[OH]D concentrations. Differential expression between low/high groups were evaluated using Student's t-test, fold change, and SAM comparisons. We further investigated functions and functional relationships of differentially expressed mRNAs and targets of differentially expressed miRNAs.

RESULTS

Three hundred and five genes (299 upregulated and 6 downregulated) and 11 miRNAs (10 downregulated and 1 upregulated) were differentially expressed among participants with low 25[OH]D compared with those who had high 25[OH]D. Genes that participate in a wide range of cellular functions, including organ and system development (e.g. angiogenesis), inflammation and metabolic processes (e.g. carbohydrate/lipid metabolism), as well as miRNAs that target these genes were differentially expressed among women with low 25[OH]D compared with those with high 25[OH]D.

CONCLUSION

Early pregnancy plasma 25[OH]D concentrations are associated with maternal peripheral blood gene expression and post-transcription regulation.

Vitamin D and diabetes

Type 1 (T1D) and type 2 (T2D) diabetes are considered multifactorial diseases in which both genetic predisposition and environmental factors participate in their development. Many cellular, preclinical, and observational studies support a role for vitamin D in the pathogenesis of both types of diabetes including: (1) T1D and T2D patients have a higher incidence of hypovitaminosis D; (2) pancreatic tissue (more specifically the insulin-producing beta-cells) as well as numerous cell types of the immune system express the vitamin D receptor (VDR) and vitamin D-binding protein (DBP); and (3) some allelic variations in genes involved in vitamin D metabolism and VDR are associated with glucose (in)tolerance, insulin secretion, and sensitivity, as well as inflammation. Moreover, pharmacologic doses of 1,25-dihydroxyvitamin D (1,25(OH)(2)D), the active form of vitamin D, prevent insulitis and T1D in nonobese diabetic (NOD) mice and other models of T1D, possibly by immune modulation as well as by direct effects on beta-cell function. In T2D, vitamin D supplementation can increase insulin sensitivity and decrease inflammation. This article reviews the role of vitamin D in the pathogenesis of T1D and T2D, focusing on the therapeutic potential for vitamin D in the prevention/intervention of T1D and T2D as well as its complications.

25-Hydroxyvitamin D and pre-clinical alterations in inflammatory and hemostatic markers: a cross sectional analysis in the 1958 British Birth Cohort

BACKGROUND

Vitamin D deficiency has been suggested as a cardiovascular risk factor, but little is known about underlying mechanisms or associations with inflammatory or hemostatic markers. Our aim was to investigate the association between 25-hydroxyvitamin D [25(OH)D, a measure for vitamin D status] concentrations with pre-clinical variations in markers of inflammation and hemostasis.

METHODOLOGY/PRINCIPAL FINDINGS

Serum concentrations of 25(OH)D, C-reactive protein (CRP), fibrinogen, D-dimer, tissue plasminogen activator (tPA) antigen, and von Willebrand factor (vWF) were measured in a large population based study of British whites (aged 45 y). Participants for the current investigation were restricted to individuals free of drug treated cardiovascular disease (n = 6538). Adjusted for sex and month, 25(OH)D was inversely associated with all outcomes (p < or =0.015 for all), but associations with CRP, fibrinogen, and vWF were explained by adiposity. Association with tPA persisted after full adjustment (body mass index, waist circumference, physical activity, TV watching, smoking, alcohol consumption, social class, sex, and month), and average concentrations were 18.44% (95% CI 8.13, 28.75) lower for 25(OH)D > or =75 nmol/l compared to < 25 nmol/l. D-dimer concentrations were lower for participants with 25(OH)D 50-90 nmol/l compared to others (quadratic term p = 0.01). We also examined seasonal variation in hemostatic and inflammatory markers, and evaluated 25(OH)D contribution to the observed patterns using mediation models. TPA concentrations varied by season (p = 0.02), and much of this pattern was related to fluctuations in 25(OH)D concentrations (p < or =0.001). Some evidence of a seasonal variation was observed also for fibrinogen, D-dimer and vWF (p < 0.05 for all), with 25(OH)D mediating some of the pattern for fibrinogen and D-dimer, but not vWF.

CONCLUSIONS

Current vitamin D status was associated with tPA concentrations, and to a lesser degree with fibrinogen and D-dimer, suggesting that vitamin D status/intake may be important for maintaining antithrombotic homeostasis.

Vitamin D and vascular calcification in chronic kidney disease

Vascular calcification is frequently observed and is closely associated with cardiovascular mortality in patients with chronic kidney disease (CKD). Vascular calcification is largely divided into two types. One is atherosclerotic intimal layer calcification and the other is medial layer calcification (Monckeberg's calcification). The latter is more common in patients with CKD than in general population. Evidence is growing that vascular calcification is a regulated active process as well as a passive process resulting from elevated serum phosphate (P) and an increase in the calcium phosphate (Ca x P) product leading to oversaturated plasma. Proving the active process, in vitro studies have demonstrated that the transformation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells is a crucial mechanism in the progression of vascular calcification. Reduction of the activity of systemic and local inhibitors has also been recognized to be important. The link between vitamin D and vascular calcification is complex. Experimental and clinical researches have revealed that both vitamin D excess and vitamin D deficiency have been shown to be associated with vascular calcification in uremic milieu. On the other hand, although there are some biases, recent large observational studies have demonstrated that vitamin D has beneficial effects on the mortality of patients with CKD independent of serum Ca, P, and parathyroid hormone levels, likely due to its activation of the vitamin D receptor in vasculature and cardiac myocytes. Further prospective studies are necessary to evaluate the direct effect of vitamin D on vascular calcification in order to improve the cardiovascular health of patients with CKD.

Potential for vitamin D receptor agonists in the treatment of cardiovascular disease

Vitamin D(3) is made in the skin and modified in the liver and kidney to form the active metabolite, 1,25-dihydroxyvitamin D(3) (calcitriol). Calcitriol binds to a nuclear receptor, the vitamin D receptor (VDR), and activates VDR to recruit cofactors to form a transcriptional complex that binds to vitamin D response elements in the promoter region of target genes. During the past three decades the field has focused mainly on the role of VDR in the regulation of parathyroid hormone, intestinal calcium/phosphate absorption and bone metabolism; several VDR agonists (VDRAs) have been developed for the treatment of osteoporosis, psoriasis and hyperparathyroidism secondary to chronic kidney disease (CKD). Emerging evidence suggests that VDR plays important roles in modulating cardiovascular, immunological, metabolic and other functions. For example, data from epidemiological, preclinical and clinical studies have shown that vitamin D and/or 25(OH)D deficiency is associated with increased risk for cardiovascular disease (CVD). However, VDRA therapy seems more effective than native vitamin D supplementation in modulating CVD risk factors. In CKD, where decreasing VDR activation persists over the course of the disease and a majority of the patients die of CVD, VDRA therapy was found to provide a survival benefit in both pre-dialysis and dialysis CKD patients. Although VDR plays an important role in regulating cardiovascular function and VDRAs may be potentially useful for treating CVD, at present no VDRA is approved for CVD, and also no serum markers, beside parathyroid hormone in CKD, exist to indicate the efficacy of VDRA in CVD.

Vitamin D and human health: lessons from vitamin D receptor null mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. The precise mode of action and the full spectrum of activities of the vitamin D hormone, 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], can now be better evaluated by critical analysis of mice with engineered deletion of the vitamin D receptor (VDR). Absence of a functional VDR or the key activating enzyme, 25-OHD-1alpha-hydroxylase (CYP27B1), in mice creates a bone and growth plate phenotype that mimics humans with the same congenital disease or severe vitamin D deficiency. The intestine is the key target for the VDR because high calcium intake, or selective VDR rescue in the intestine, restores a normal bone and growth plate phenotype. The VDR is nearly ubiquitously expressed, and almost all cells respond to 1,25-(OH)(2)D exposure; about 3% of the mouse or human genome is regulated, directly and/or indirectly, by the vitamin D endocrine system, suggesting a more widespread function. VDR-deficient mice, but not vitamin D- or 1alpha-hydroxylase-deficient mice, and man develop total alopecia, indicating that the function of the VDR and its ligand is not fully overlapping. The immune system of VDR- or vitamin D-deficient mice is grossly normal but shows increased sensitivity to autoimmune diseases such as inflammatory bowel disease or type 1 diabetes after exposure to predisposing factors. VDR-deficient mice do not have a spontaneous increase in cancer but are more prone to oncogene- or chemocarcinogen-induced tumors. They also develop high renin hypertension, cardiac hypertrophy, and increased thrombogenicity. Vitamin D deficiency in humans is associated with increased prevalence of diseases, as predicted by the VDR null phenotype. Prospective vitamin D supplementation studies with multiple noncalcemic endpoints are needed to define the benefits of an optimal vitamin D status.

Vitamin D and kidney disease

Abnormalities in vitamin D metabolism play a major role in the pathogenesis of secondary hyperparathyroidism in chronic kidney disease. The gradual and progressive decline in 1,25-dihydroxyvitamin D in the course of chronic kidney disease is the result of several mechanisms that limit the ability of the failing kidney to maintain the levels of 1,25-dihydroxyvitamin D despite increasing levels of parathyroid hormone. Recent observations have indicated that chronic kidney disease seems to be associated with a high incidence of nutritional vitamin D insufficiency or deficiency as manifested by decreased levels of 25-hydroxyvitamin D. This contributes to the inability to maintain the levels of 1,25-dihydroxyvitamin D; therefore, current practice guidelines suggest repleting vitamin D status by the administration of native vitamin D as a first step in the therapy of the abnormalities of bone and mineral metabolism in chronic kidney disease. The efficacy of this therapy is extremely variable, and active vitamin D sterols may be required, especially as kidney disease progresses. The importance of the abnormal vitamin D metabolism is being investigated vigorously in view of the observations that vitamin D may have important biologic actions in many tissues in addition to bone and parathyroid. Thus, observational data have suggested potential survival benefits of vitamin D sterol administration in this clinical setting, and experimental data have suggested a potential beneficial effect of vitamin D sterols on the progression of kidney disease. Further work is required to define the mechanisms involved and to examine the effects of vitamin D therapy on outcomes in randomized, controlled trials.

Elevated phosphorus modulates vitamin D receptor-mediated gene expression in human vascular smooth muscle cells

Clinical observations show that an increase in serum inorganic phosphorus (Pi) is linked to higher cardiovascular (CV) mortality, while vitamin D receptor (VDR) agonist therapy is associated with survival benefit in stage 5 chronic kidney disease. Smooth muscle cells (SMCs) play an important role in CV pathophysiology, but the interaction between Pi and the VDR signaling pathway in SMCs is not known. Real-time RT-PCR studies revealed that elevated Pi (2.06 mM) modulated VDR-mediated regulation of a panel of genes including thrombomodulin and osteopontin in SMCs. DNA microarray results demonstrated that increasing Pi from 0.9 to 2.06 mM exerted a widespread modulating effect on VDR-mediated gene expression. A total of 325 target genes were affected by paricalcitol at 0.9 mM Pi, with 195 up- and 130 downregulated. The number of target genes affected by paricalcitol at 2.06 mM Pi decreased to 86, with 55 up- and 31 downregulated. VDR-mediated gene expression in As4.1 cells (a juxtaglomerular cell-like cell line derived from kidney tumors in SV40 T-antigen transgenic mice) and peroxisome proliferator-activated receptor (PPAR)gamma-mediated gene expression in SMCs were also altered by elevated Pi, suggesting that the observation is not unique to VDR in SMCs. Mechanism analysis showed that elevated Pi had no significant effect on VDR or PPARgamma protein level but altered the cytosolic vs. nuclear distribution of NF-kappaB or nuclear receptor corepressor 1 (NCoR1). Our results demonstrate for the first time that elevated Pi affects VDR-mediated gene expression in human coronary artery SMCs and the effect is not limited to VDR in SMCs.