Functional vitamin D receptor (VDR) in the t-tubules of cardiac myocytes: VDR knockout cardiomyocyte contractility

Potential role of vitamin D deficiency on Fabry cardiomyopathy

Patients with Fabry disease frequently develop left ventricular (LV) hypertrophy and renal fibrosis. Due to heat intolerance and an inability to sweat, patients tend to avoid exposure to sunlight. We hypothesized that subsequent vitamin D deficiency may contribute to Fabry cardiomyopathy. This study investigated the vitamin D status and its association with LV mass and adverse clinical symptoms in patients with Fabry disease. 25-hydroxyvitamin D (25[OH]D) was measured in 111 patients who were genetically proven to have Fabry disease. LV mass and cardiomyopathy were assessed by magnetic resonance imaging and echocardiography. In cross-sectional analyses, associations with adverse clinical outcomes were determined by linear and binary logistic regression analyses, respectively, and were adjusted for age, sex, BMI and season. Patients had a mean age of 40 ± 13 years (42% males), and a mean 25(OH)D of 23.5 ± 11.4 ng/ml. Those with overt vitamin D deficiency (25[OH]D ≤ 15 ng/ml) had an adjusted six fold higher risk of cardiomyopathy, compared to those with sufficient 25(OH)D levels >30 ng/ml (p = 0.04). The mean LV mass was distinctively different with 170 ± 75 g in deficient, 154 ± 60 g in moderately deficient and 128 ± 58 g in vitamin D sufficient patients (p = 0.01). With increasing severity of vitamin D deficiency, the median levels of proteinuria increased, as well as the prevalences of depression, edema, cornea verticillata and the need for medical pain therapy. In conclusion, vitamin D deficiency was strongly associated with cardiomyopathy and adverse clinical symptoms in patients with Fabry disease. Whether vitamin D supplementation improves complications of Fabry disease, requires a randomized controlled trial.

Pediatric cardiomyopathies: causes, epidemiology, clinical course, preventive strategies and therapies

Pediatric cardiomyopathies, which are rare but serious disorders of the muscles of the heart, affect at least one in every 100,000 children in the USA. Approximately 40% of children with symptomatic cardiomyopathy undergo heart transplantation or die from cardiac complications within 2 years. However, a significant number of children suffering from cardiomyopathy are surviving into adulthood, making it an important chronic illness for both pediatric and adult clinicians to understand. The natural history, risk factors, prevalence and incidence of this pediatric condition were not fully understood before the 1990s. Questions regarding optimal diagnostic, prognostic and treatment methods remain. Children require long-term follow-up into adulthood in order to identify the factors associated with best clinical practice including diagnostic approaches, as well as optimal treatment approaches. In this article, we comprehensively review current research on various presentations of this disease, along with current knowledge about their causes, treatments and clinical outcomes.

A review of vitamin D status and CVD

Beyond the well-accepted effects on the skeleton, low vitamin D status has been linked to increased risk of several non-skeletal disease, including CVD. If low serum 25-hydroxyvitamin D (25(OH)D) concentration is causally linked to risk of CVD then this is important not only because low vitamin D status is quite common particularly in winter in countries above 40°N, but also of key relevance is the fact that such low vitamin D status can be improved by food-based strategies. The overarching aim of the present paper is to review the current evidence-base to support a link between low vitamin D status and CVD risk. The review initially briefly overviews how mechanistically vitamin D may play a role in CVD and then reviews the current available evidence-base to support a link between low vitamin D status and CVD risk, with particular emphasis on data from the randomised control trials, cohort studies and recent meta-analysis data as well as to the conclusions of a number of authoritative agencies/bodies. Finally, the review summarises current serum 25(OH)D concentrations within a select number of adult populations in the context of different definitions of vitamin D status proposed recently, and then briefly highlights food-based strategies for increasing vitamin D intake and status. In conclusion, at present the data for a causal link between low vitamin D status and CVD are mixed and ambiguous; however, should causality be affirmed by ongoing and future studies, there are food-based strategies for enhanced vitamin D status in the population which could ultimately lower risk of CVD.

Vitamin D and the heart

Vitamin D receptors (VDR) are found in cells throughout the cardiovascular system. A variety of experimental studies indicate that the liganded VDR may play an important role in controlling cardiac hypertrophy and fibrosis, regulating blood pressure, and suppressing the development of atherosclerosis. Some, but not all, observational studies in humans provide support for these experimental findings, raising the possibility that vitamin D or its analogs might prove useful therapeutically in the prevention or treatment of cardiovascular disease.

Vitamin D deficiency in surgical congenital heart disease: prevalence and relevance

Vitamin D is a pleiotropic hormone important for the proper functioning of multiple organ systems. An emerging body of adult and pediatric critical care literature strongly suggests that vitamin D deficiency contributes to secondary organ pathophysiology, prolongs ICU stay, and worsens outcome in critically ill populations. Recent clinical studies suggest that a significant number of children with congenital heart disease (CHD) have post-operative vitamin D deficiency which appears to be associated with greater cardiovascular dysfunction. Altogether the cumulative body of literature suggests that peri-operative optimization of vitamin D status has the potential to speed recovery and/or improve outcome. This review describes the epidemiological and basic science research linking vitamin D deficiency to post-operative organ dysfunction. Furthermore, the available supplementation approaches are reviewed in the context of prevention of post-operative vitamin D deficiency and avoidance of toxicity in the majority of CHD patients. Finally, knowledge gaps regarding vitamin D supplementation are identified and the next stages for research are outlined.

Vitamin D levels are associated with cardiac autonomic activity in healthy humans

Vitamin D deficiency (≤50nmol/L 25-hydroxy vitamin D) is a cardiovascular (CV) risk factor that affects approximately one billion people worldwide, particularly those affected by chronic kidney disease (CKD). Individuals with CKD demonstrate abnormal cardiac autonomic nervous system activity, which has been linked to the significant rates of CV-related mortality in this population. Whether vitamin D deficiency has a direct association with regulation of cardiac autonomic activity has never been explored in humans. Methods: Thirty-four (34) healthy, normotensive subjects were studied and categorized based on 25-hydroxy vitamin D deficiency (deficient vs. non-deficient, n = 7 vs. 27), as well as 1,25-dihydroxy vitamin D levels (above vs. below 25th percentile, n = 8 vs. 26). Power spectral analysis of electrocardiogram recordings provided measures of cardiac autonomic activity across low frequency (LF) and high frequency (HF, representative of vagal contribution) bands, representative of the sympathetic and vagal limbs of the autonomic nervous system when transformed to normalized units (nu), respectively, as well as overall cardiosympathovagal balance (LF:HF) during graded angiotensin II (AngII) challenge (3 ng/kg/min × 30 min, 6 ng/kg/min × 30 min). Results: At baseline, significant suppression of sympathovagal balance was observed in the 25-hydroxy vitamin D-deficient participants (LF:HF, p = 0.02 vs. non-deficient), although no other differences were observed throughout AngII challenge. Participants in the lowest 1,25-dihydroxy VD quartile experienced significant withdrawal of inhibitory vagal control, as well as altered overall sympathovagal balance throughout AngII challenge (HF, mean difference = −6.98 ± 3 nu, p = 0.05; LF:HF, mean difference = 0.34 ± 0.1, p = 0.043 vs. above 25th percentile). Conclusions: Vitamin D deficiency is associated with suppression of resting cardiac autonomic activity, while low 1,25-dihydroxy vitamin D levels are associated with unfavourable cardiac autonomic activity during an acute AngII stressor, offering a potential pathophysiological mechanism that may be acting to elevate CV risk in in populations with low vitamin D status.

Chaperone properties of pdia3 participate in rapid membrane actions of 1α,25-dihydroxyvitamin d3

Protein disulfide isomerase family A, member 3 (Pdia3) mediates many of the plasma membrane (PM)-associated rapid responses to 1α,25-dihydroxyvitamin D3 (1α,25[OH]2D3). It is not well understood how Pdia3, which is an endoplasmic reticulum (ER) chaperone, functions as a PM receptor for 1α,25(OH)2D3. We mutated 3 amino acids (K214 and R282 in the calreticulin interaction site and C406 in the isomerase catalytic site), which are important for Pdia3's ER chaperone function, and examined their role in responses to 1α,25(OH)2D3. Pdia3 constructs with and without the ER retention signal KDEL were used to investigate the PM requirement for Pdia3. Finally, we determined whether palmitoylation and/or myristoylation were required for Pdia3-mediated responses to 1α,25(OH)2D3. Overexpressing the Pdia3 R282A mutant in MC3T3-E1 cells increased PM phospholipase A2-activating protein, Rous sarcoma oncogene (c-Src), and caveolin-1 but blocked increases in 1α,25(OH)2D3-stimulated protein kinase C (PKC) seen in cells overexpressing wild-type Pdia3 (Pdia3Ovr cells). Cells overexpressing Pdia3 with K214A and C406S mutations had PKC activity comparable to untreated controls, indicating that the native response to 1α,25(OH)2D3 also was blocked. Overexpressing Pdia3[-KDEL] increased PM localization and augmented baseline PKC, but the stimulatory effect of 1α,25(OH)2D3 was comparable to that seen in wild-type cultures. In contrast, 1α,25(OH)2D3 increased prostaglandin E2 in Pdia3[±KDEL] cells. Although neither palmitoylation nor myristoylation was required for PM association of Pdia3, myristoylation was needed for PKC activation. These data indicate that both the chaperone functional domains and the subcellular location of Pdia3 control rapid membrane responses to 1α,25(OH)2D3.

Mineral metabolism abnormalities and vitamin D receptor activation in cardiorenal syndromes

Over the last decade, it has become increasingly clear that the cardiovascular and renal systems are interdependent. Primary disorders of either system have been shown to disturb the other system. As a result, a class of cardiorenal syndromes (CRS) has been identified wherein a vicious cycle is established as an acute/chronic dysfunction of either the kidney or the heart exacerbates the loss of function in the other organ. Progressive loss of kidney function observed in patients with CRS (mostly types 2 and 4) leads to reduced production of calcitriol (active vitamin D) and an imbalance in calcium and phosphorus levels, which are correlated with increased rates of cardiovascular events and mortality. In addition, hypocalcemia can lead to prolonged and excessive secretion of parathyroid hormone (PTH), eventually leading to development of secondary hyperparathyroidism. Therefore, based on this important mechanism of organ damage, one of the major goals of therapy for patients with CRS is to restore regulatory control of PTH. Although administration of calcitriol increases serum calcium levels and reduces PTH levels, it is also associated with elevated serum levels of calcium-phosphorus product. Therefore, compounds that selectively activate vitamin D receptors, potentially reducing calcium × phosphate toxicity, are likely to enhance cardiorenal protection and provide significant clinical benefit.

Use of vitamin D in various disorders

Approximately 1 billion people worldwide have been identified as vitamin D deficient in the 21st century, and the number is on the rise; non-classical actions of vitamin D were initially recognized around 30 y ago when receptors for vitamin D were detected in neoplastic cells lines. The aim of this review is to provide a brief overview of the non-classical actions of vitamin D. Reports describing the associations of non skeletal actions of vitamin D, especially pertaining to the immune system, inflammatory disorders, cancers and cardiovascular disease have been summarized in this paper. Reports support a role for the active form of vitamin D in mediating normal function of both the innate and adaptive immune systems. Studies also suggest a link between vitamin D deficiency and autoimmune diseases, such as rheumatoid arthritis, systemic sclerosis, systemic lupus erythematosus and type 1 diabetes. There is believed to be an inverse association between serum 25-hydroxyvitamin D concentrations and the incidence of colorectal cancer, sporadic colorectal adenoma and breast cancer. Vitamin D deficiency has been linked with various cardiovascular diseases such as hypertension, myocardial infarction, and stroke. Several epidemiological and genetic studies suggest a strong association between vitamin D and non skeletal acute and chronic disorders. However, currently, robust clinical data are still lacking to support raising intake requirements and target vitamin D plasma levels. Nonetheless, the high prevalence of vitamin D deficiency is alarming and requires implementation of clear supplementation guidelines.

Relationship between vitamin D status and left ventricular geometry in a healthy population: results from the Baltimore Longitudinal Study of Aging

OBJECTIVES

The effects of vitamin D on the heart have been studied in patients with cardiac disease, but not in healthy persons. We investigated the relation between vitamin D status and left ventricular (LV) structure and function in community-dwelling subjects without heart disease.

DESIGN

The relationship between concentrations of 25-hydroxyvitamin D [25(OH)D], a marker of vitamin D reserve, and LV transthoracic echocardiography measures was analysed in 711 participants in the Baltimore Longitudinal Study of Aging who were without cardiac disease.

RESULTS

Mean 25(OH)D in the study population was 32.3 ± 11.4 ng mL(-1) ; only 15.5% of subjects had moderate or severe vitamin D deficiency [25(OH)D < 20 ng mL(-1) ]. Adjusting for age, body mass index, cardiovascular disease risk factors, physical activity, calcium and parathyroid hormone, 25(OH)D was positively correlated with LV thickness (β 0.095, SE 0.039, P < 0.05) and LV mass index (β 7.5, SE 2.6, P < 0.01). A significant nonlinear relation between 25(OH)D and LV concentric remodelling was observed. LV remodelling was more likely in participants with 25(OH)D levels <30 ng mL(-1) [odds ratio (OR) 1.24; 95% confidence interval (CI) 0.83-1.85] or ≥38 ng mL(-1) (OR 1.73; 95% CI 1.13-2.65), compared with those with 30-37 ng mL(-1) 25(OH)D. Consistently, LV relative wall thickness was significantly lower (P for trend=0.05), and LV diastolic internal diameter index (P for trend<0.05) and end-diastolic volume index (P for trend<0.05) were significantly higher in subjects with 30-37 ng mL(-1) 25(OH)D compared to the rest of the study population. There was a significant interaction between 25(OH)D and hypertension on the risk of LV hypertrophy (P < 0.05).

CONCLUSIONS

In a population-based sample of predominantly vitamin D-sufficient subjects without heart disease, LV geometry was most favourable at intermediate 25(OH)D concentrations.

Vitamin D in human reproduction: a narrative review

BACKGROUND

Special attention has been given to the effect of vitamin D supplementation on fertility outcomes in both sexes.

AIMS

The purpose of this narrative review was to elucidate the role of vitamin D in male and female reproduction, providing current evidence from both animal and human studies.

MATERIALS AND METHODS

Using PubMed and Medline, we searched for publications during the last 30 years regarding the role of vitamin D in human reproduction.

RESULTS

Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the reproductive system in both genders. In women, vitamin D status has been associated with in vitro fertilization (IVF) outcome, features of polycystic ovarian syndrome (PCOS) and endometriosis. Although several data converge towards a beneficial effect of vitamin D supplementation in metabolic disturbances in women with PCOS, a significant knowledge gap precludes the establishment of a clear cause-effect relationship. In men, vitamin D status has been associated with semen quality and sperm count, motility and morphology. There is evidence for a favourable effect of vitamin D supplementation on semen quality, testosterone concentrations and fertility outcomes.

DISCUSSION

Studies with superior methodological characteristics are needed in order to establish a role for vitamin D on the treatment of female and male infertility.

CONCLUSIONS

Recent data on vitamin D provide new insights in the complex pathogenesis and treatment of infertility.

Gastric acid, calcium absorption, and their impact on bone health

Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.

Update on diastolic heart failure or heart failure with preserved ejection fraction in the older adults

Nearly half of all heart failure (HF) patients have diastolic HF (DHF) or clinical HF with normal or near-normal left ventricular ejection fraction (LVEF). Although the terminology has not been clearly defined, it is increasingly being referred to as HF with preserved ejection fraction (HFPEF). The prevalence of HFPEF increases with age, especially among older women. Identifying HFPEF is important because the etiology, pathogenesis, prognosis, and optimal management may differ from that for systolic HF (SHF) or HF with reduced ejection fraction. The clinical presentation of HF is similar for both SHF and HFPEF. As in SHF, HFPEF is a clinical diagnosis. Once a clinical diagnosis of HF has been made, the presence of HFPEF can be established by confirming a normal or near-normal LVEF, often by an echocardiogram. HFPEF is often associated with a history of hypertension, concentric left ventricular hypertrophy, vascular stiffness, and left ventricular diastolic dysfunction. As in SHF, HFPEF is also associated with poor outcomes. While therapies with angiotensin-converting enzyme inhibitors and beta-blockers improve outcomes in SHF, there is currently no such evidence of their benefits in older HFPEF patients. In this review recent advances in the diagnosis and management of HFPEF in older adults are discussed.

Vitamin D and hypertension: an update and review

PURPOSE OF REVIEW

Vitamin D deficiency and hypertension are highly prevalent. This review will discuss the association between vitamin D deficiency and blood pressure.

RECENT FINDINGS

During the past several years multiple prospective cohorts and randomized studies have been published. Recent studies have focused mostly on 25-hydroxy vitamin D, but a small number of trials used active vitamin D analog compounds.

SUMMARY

Data from cross-sectional studies report that low 25-hydroxy vitamin D is associated with higher systolic blood pressure and higher incidence of hypertension. Large observational studies show a weaker, yet similar association, but they have not largely accounted for the change in vitamin D levels over time. Randomized control trials conflict with observational data probably due to differences in populations studied, doses of vitamin D used, and unmeasured confounders. Further research is needed before clinical practice recommends vitamin D prescription as treatment for hypertension in the general population.

Hypocalcemic rachitic cardiomyopathy in infants

Hypocalcemic cardiomyopathy in infants is characterized by heart failure in a previously normal infant with hypocalcemia without organic cardiac lesion. Vitamin D deficiency rickets is increasing in Middle East. In a six month study 136 cases of rickets were diagnosed in the main Children's Hospital in Almadinah but none of them showed evidence of cardiomyopathy. Concerned of missing this serious complication of rickets we searched pub med and present this review article.

RESULTS

61 cases of hypocalcemic cardiomyopathy were reported as case reports with two series of 16 and 15 cases from London and Delhi, respectively. The major features of these cases: the age ranged from one month to 15 months with a mean age of 5 months. All presented with heart failure and hypocalcemia. There was a minor feature of rickets in a few of the cases. All had high alkaline phosphatase. Echocardiology evidence of cardiomyopathy was found in all. Most of them responded to calcium, vitamin D and cardiotonic and diuretics.

DISCUSSION

We concentrated on pathogenesis of this hypocalcemic cardiomyopathy and reviewed the literature. The evidence available supports that the most likely cause of cardiomyopathy is hypocalcemia. Hypovitamin D also contributes but hyperparathyroidism might have a protective role as we did not detect any evidence of cardiomyopathy with hyperparathyroidism and florid features of rickets.

CONCLUSION

We need to look out for cardiomyopathy among infants with hypocalcemia. For prevention maternal supplementation during pregnancy and lactation with up to 2000 units of vitamin D and 400 units for their infants.

Vitamin D, effects on brain development, adult brain function and the links between low levels of vitamin D and neuropsychiatric disease

Increasingly vitamin D deficiency is being associated with a number of psychiatric conditions. In particular for disorders with a developmental basis, such as autistic spectrum disorder and schizophrenia the neurobiological plausibility of this association is strengthened by the preclinical data indicating vitamin D deficiency in early life affects neuronal differentiation, axonal connectivity, dopamine ontogeny and brain structure and function. More recently epidemiological associations have been made between low vitamin D and psychiatric disorders not typically associated with abnormalities in brain development such as depression and Alzheimer's disease. Once again the preclinical findings revealing that vitamin D can regulate catecholamine levels and protect against specific Alzheimer-like pathology increase the plausibility of this link. In this review we have attempted to integrate this clinical epidemiology with potential vitamin D-mediated basic mechanisms. Throughout the review we have highlighted areas where we think future research should focus.

Cardiovascular disease in chronic kidney disease: untying the Gordian knot

Chronic kidney disease (CKD) affects around 10-13% of the general population, with only a small proportion in end stage renal disease (ESRD), either on dialysis or awaiting renal transplantation. It is well documented that CKD patients have an extremely high risk of developing cardiovascular disease (CVD) compared with the general population, so much so that in the early stages of CKD patients are more likely to develop CVD than they are to progress to ESRD. Various pathophysiological pathways and explanations have been advanced and suggested to account for this, including endothelial dysfunction, dyslipidaemia, inflammation, left ventricular hypertrophy and cardiac autonomic dysfunction. In this review, we try to understand and further explore the link between CKD and CVD, as well as offering interventional advice where available, while exposing the current lack of RCT-based research and trial evidence in this area. We also suggest pragmatic Interim measures we could take while we wait for definitive RCTs.

Relationship of BsmI polymorphism of vitamin D receptor gene with left ventricular hypertrophy and atherosclerosis in hemodialysis patients

BACKGROUND

Left ventricular hypertrophy (LVH) is a common manifestation of cardiovascular disease and has an important prognostic value in patients with end-stage renal disease (ESRD). Vitamin D receptor (VDR) has been intensively investigated, and one of these (BsmI) already has been associated with survival in the dialysis population.

OBJECTIVE

The aim of this study was to investigate the role of VDR polymorphism (BsmI) on the development of ventricular hypertrophy and atherosclerosis in hemodialysis patients. Subject and methods. The subjects were 80 patients with end-stage renal disease on maintenance hemodialysis, and 40 healthy controls. Clinical and laboratory parameters, including genetic variation in VDR gene (BsmI), were assessed. In addition, echocardiography and intima-media thickness were performed for all subjects.

RESULTS

There was no significant difference in the distribution of BsmI genotypes either in patients or in the control group. The frequency of the B allele of BsmI polymorphism (41.6%) in dialysis patients was similar to that of healthy control subjects (39.2%). Patients with BB genotype had significantly lower serum concentrations of 25-hydroxy vitamin D compared to both Bb and bb genotypes. The number of B alleles was positively correlated with left ventricular mass index (LVMI), but not with intima-media thickness.

CONCLUSION

These results suggest that the B alleles of the BsmI polymorphism could be considered as novel markers of altered vitamin D signaling in ESRD patients, and this alteration in BB genotype produces an increase in left ventricle mass.

Vitamin D reduces left atrial volume in patients with left ventricular hypertrophy and chronic kidney disease

BACKGROUND

Left atrial enlargement, a sensitive integrator of left ventricular diastolic function, is associated with increased cardiovascular morbidity and mortality. Vitamin D is linked to lower cardiovascular morbidity, possibly modifying cardiac structure and function; however, firm evidence is lacking. We assessed the effect of an activated vitamin D analog on left atrial volume index (LAVi) in a post hoc analysis of the PRIMO trial (clinicaltrials.gov: NCT00497146).

METHODS AND RESULTS

One hundred ninety-six patients with chronic kidney disease (estimated glomerular filtration rate 15-60 mL/min per 1.73 m(2)), mild to moderate left ventricular hypertrophy, and preserved ejection fraction were randomly assigned to 2 μg of oral paricalcitol or matching placebo for 48 weeks. Two-dimensional echocardiography was obtained at baseline and at 24 and 48 weeks after initiation of therapy. Over the study period, there was a significant decrease in LAVi (-2.79 mL/m(2), 95% CI -4.00 to -1.59 mL/m(2)) in the paricalcitol group compared with the placebo group (-0.70 mL/m(2) [95% CI -1.93 to 0.53 mL/m(2)], P = .002). Paricalcitol also attenuated the rise in levels of brain natriuretic peptide (10.8% in paricalcitol vs 21.3% in placebo, P = .02). For the entire population, the change in brain natriuretic peptide correlated with change in LAVi (r = 0.17, P = .03).

CONCLUSIONS

Forty-eight weeks of therapy with an active vitamin D analog reduces LAVi and attenuates the rise of BNP. In a population where only few therapies alter cardiovascular related morbidity and mortality, these post hoc results warrant further confirmation.

Correction of vitamin D deficiency in critically ill patients - VITdAL@ICU study protocol of a double-blind, placebo-controlled randomized clinical trial

BACKGROUND

Vitamin D deficiency is associated with multiple adverse health outcomes including increased morbidity and mortality in the general population and in critically ill patients. However, no randomized controlled trial has evaluated so far whether treatment with sufficiently large doses of vitamin D can improve clinical outcome of patients in an intensive care setting.

METHODS/DESIGN

The VITdAL@ICU trial is an investigator-initiated, non-commercial, double-blind, placebo-controlled randomized clinical trial. This study compares high-dose oral cholecalciferol (vitamin D3) versus placebo treatment in a mixed population of 480 critically ill patients with low 25-hydroxyvitamin-D levels at study enrollment (≤ 20ng/ml). Following an initial loading dose of 540,000 IU of vitamin D3, patients receive 90,000 IU of vitamin D3 on a monthly basis for 5 months. The study is designed to compare clinical outcome in the two study arms with the primary endpoint being length of hospital stay. Secondary endpoints include among others length of ICU stay, the percentage of patients with 25(OH)D levels > 30 ng/ml at day 7, ICU and hospital mortality and duration of mechanical ventilation. We describe here the VITdAL@ICU study protocol for the primary report.

DISCUSSION

This trial is designed to evaluate whether high-dose vitamin D3 is able to improve morbidity and mortality in a mixed population of adult critically ill patients and correct vitamin D deficiency safely.

TRIAL REGISTRATION

ClinicalTrials: NCT01130181.

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.

Discovery of novel vitamin D receptor interacting proteins that modulate 1,25-dihydroxyvitamin D3 signaling

The nuclear vitamin D receptor (VDR) modulates gene transcription in 1,25-dihydroxyvitamin D(3) (1,25D) target tissues such as kidney, intestine, and bone. VDR is also expressed in heart, and 1,25D deficiency may play a role in the acceleration of cardiovascular disease. Employing a yeast two-hybrid system and a human heart library, using both a 1,25D-independent and 1,25D-dependent screen, we discovered six candidate VDR interacting proteins (VIPs). These novel VIPs include CXXC5, FASTK, NR4A1, TPM2, MYL3 and XIRP1. Mammalian two-hybrid assays as well as GST pull-downs were used to confirm VIP-VDR interaction, and the combination of these two assays reveals that CXXC5, XIRP1, FASTK and NR4A1 interactions with VDR may be modulated by 1,25D. The functional effects of these VIPs on 1,25D-mediated gene expression were explored in transcriptional assays employing three separate and distinct 1,25D-responsive element (VDRE)-driven luciferase reporter genes in transfected Caco-2 and HEK-293 cells, and in a C2C12 myoblast line. FASTK and TPM2 activated expression in all cell line and promoter contexts, while CXXC5 and XIRP1 exhibited differing effects depending on the cell line and promoter employed, suggesting promoter and cell-specific effects of these unique VIPs on VDR signaling. Further evaluation of the interaction between CXXC5 and VDR revealed that CXXC5 acts in a dose-dependent manner to stimulate VDR-mediated transcription on select VDREs. Identification of novel heart VIPs and their influence on VDR activity may increase our understanding of how vitamin D impacts cardiac physiology and may facilitate development of VDR/VIP drug analogs to combat heart disease.

Vitamin D status in critically ill children

BACKGROUND

Hypovitaminosis D is an independent risk factor for cardiovascular disease, muscle weakness, impaired metabolism, immune dysfunction, and compromised lung function. Hypovitaminosis D is common in critically ill adults and has been associated with adverse outcomes. The prevalence of hypovitaminosis D and its significance in critically ill children are unclear.

METHODS

We performed a prospective study to determine the prevalence of hypovitaminosis D in 316 critically ill children, and examined its association with physiological and biochemical variables, length of pediatric intensive care unit (PICU) stay, and hospital mortality.

RESULTS

The prevalence of hypovitaminosis D [25(OH)D(3) <50 nmol/L] was 34.5 %. Hypovitaminosis D was more common in postoperative cardiac patients than in general medical ICU patients (40.5 versus 22.6 %, p = 0.002), and the cardiac patients had a higher inotrope score [2.5 (1.9-3.3) versus 1.4 (1.1-1.9), p = 0.006]. Additionally, ionized calcium within the first 24 h was lower in patients with 25(OH)D(3) <50 nmol/L [1.07 (0.99-1.14) mmol/L] compared with patients with normal vitamin D(3) [1.17 (1.14-1.19) mmol/L, p = 0.02]. Hypovitaminosis D was not associated with longer PICU stay or increased hospital mortality.

CONCLUSIONS

Hypovitaminosis D is common in critically ill children, and is associated with higher inotropes in the postoperative cardiac population, but not with PICU length of stay or hospital survival.

Risk factors for vitamin D deficiency and relationship with cardiac biomarkers, inflammation and immune restoration in HIV-infected youth

BACKGROUND

Vitamin D deficiency is common in HIV-infected individuals. In adults, traditional and HIV-related factors play a role in vitamin D status, and deficiency appears to impair immune restoration and exacerbate HIV complications, like cardiovascular disease (CVD). This study sought to determine factors contributing to vitamin D status in HIV-infected youth and investigate the relationship with CVD risk, inflammation and immune restoration.

METHODS

HIV-infected subjects (1-25 years old) were enrolled prospectively along with healthy controls that were group-matched by age, sex and race. HIV data were collected for the HIV-infected group, while traditional risk factors, including vitamin D intake, sun exposure, skin pigmentation, physical activity level and body mass index (BMI) were collected for both groups. Fasting lipids, plasma 25-hydroxyvitamin D (25[OH]D), and inflammation markers were measured.

RESULTS

In total, 200 HIV-infected subjects and 50 controls were enrolled. HIV group had 53% male, 95% Black and a mean age of 17.2 ±4.6 years. There was no difference in 25(OH)D between groups; 77% of HIV+ and 74% of controls had 25(OH)D<20 ng/ml. Only Fitzpatrick skin type was independently associated with 25(OH)D. No HIV variables were associated with 25(OH)D, even when HIV sub-populations were examined. Inflammation, CVD risk factors and immune restoration were not independently associated with 25(OH)D.

CONCLUSIONS

Vitamin D deficiency is common among HIV-infected youth. However, HIV factors, CVD risk, inflammation and immune restoration do not appear to have the same relationship with vitamin D as has been shown in adults. Supplementation trials are needed to determine if increasing 25(OH)D concentrations could better elucidate these relationships.

Vitamin D supplementation in infants with chronic congestive heart failure

Increased circulating proinflammatory cytokines may contribute to the pathogenesis of congestive heart failure (CHF). In vitro studies have suggested that vitamin D suppresses proinflammatory cytokines and increases anti-inflammatory cytokines. The aim of this work was to evaluate the effect of vitamin D supplementation on renin-angiotensin system cytokines as well as different clinical, biochemical, and echocardiographic variables in infants with chronic CHF. This was a double-blind, placebo-controlled intervention study and included 80 infants with CHF. The intervention consisted of either giving Vitamin D(3) oral drops (group I) or placebo oral drops (group II). In both study groups, baseline 25-hydroxyvitamin D [25(OH)D] concentrations were below the lower end of the reference range. After 12 weeks of intervention, vitamin D supplementation for group I infants caused significant improvement of HF score, left-ventricular (LV) end-diastolic diameter, LV end-systolic diameter, LV ejection fraction%, and myocardial performance index together with markedly increased serum 25(OH)D and interleukin (IL)-10 and decreased PTH, IL-6, and TNF-α compared with the placebo group; these differences were statistically significant (p < 0.001). Vitamin D supplementation has great benefits as an anti-inflammatory agent in infants with CHF. It helps acceleration of the clinical improvement and cytokine profile balance.

Vitamin D deficiency exacerbates experimental stroke injury and dysregulates ischemia-induced inflammation in adult rats

Vitamin D deficiency (VDD) is widespread and considered a risk factor for cardiovascular disease and stroke. Low vitamin D levels are predictive for stroke and more fatal strokes in humans, whereas vitamin D supplements are associated with decreased risk of all-cause mortality. Because VDD occurs with other comorbid conditions that are also independent risk factors for stroke, this study examined the specific effect of VDD on stroke severity in rats. Adult female rats were fed control or VDD diet for 8 wk and were subject to middle cerebral artery occlusion thereafter. The VDD diet reduced circulating vitamin D levels to one fifth (22%) of that observed in rats fed control chow. Cortical and striatal infarct volumes in animals fed VDD diet were significantly larger, and sensorimotor behavioral testing indicated that VDD animals had more severe poststroke behavioral impairment than controls. VDD animals were also found to have significantly lower levels of the neuroprotective hormone IGF-I in plasma and the ischemic hemisphere. Cytokine analysis indicated that VDD significantly reduced IL-1α, IL-1β, IL-2, IL-4, IFN-γ, and IL-10 expression in ischemic brain tissue. However, ischemia-induced IL-6 up-regulation was significantly higher in VDD animals. In a separate experiment, the therapeutic potential of acute vitamin D treatments was evaluated, where animals received vitamin D injections 4 h after stroke and every 24 h thereafter. Acute vitamin D treatment did not improve infarct volume or behavioral performance. Our data indicate that VDD exacerbates stroke severity, involving both a dysregulation of the inflammatory response as well as suppression of known neuroprotectants such as IGF-I.

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 in relation to myocardial structure and function after eight years of follow-up: the Hoorn study

BACKGROUND AND AIMS

To investigate associations between baseline serum 25-hydroxyvitamin D [25(OH)D] levels and myocardial structure and function after 8 years of follow-up in older Dutch subjects.

METHODS

We included 256 subjects of the Hoorn Study, a population-based cohort. They underwent a standardized 2-dimensional echocardiogram at baseline between 2000 and 2001, and again between 2007 and 2009. We studied the association of 25(OH)D quartiles with echocardiographic measures of the left ventricular mass index (LVMI), left ventricular systolic function and markers of diastolic function using linear regression analyses.

RESULTS

At baseline, subjects had a mean age of 67.4 ± 5.2 years and 41.4% had prior cardiovascular disease (CVD). Low serum 25(OH)D levels were only associated with higher LVMI at 8-year follow-up in subjects without prior CVD and in subjects with low kidney function (median estimated glomerular filtration rate ≤77.5 ml/min/1.73m(2)). The associations attenuated after adjustments for parathyroid hormone (PTH), which was associated with higher LVMI (g/m(2.7)) in subjects with low kidney function (regression coefficient highest quartile 6.3, 95% CI: 0.2, 12.5).

CONCLUSION

This study showed no strong associations of 25(OH)D with myocardial structure and function. However, PTH - a possible modifiable mediator in the relation between 25(OH)D and myocardial structure - was positively associated with LVMI in subjects with low kidney function.

Vitamin D3 and the risk of CVD in overweight and obese women: a randomised controlled trial

Evidence indicates that vitamin D deficiency contributes to CVD. We investigated the effect of vitamin D3 supplementation on cardiovascular risk factors in women. Healthy premenopausal overweight and obese women (n 77; mean age 38 (sd 8·1) years) were randomly allocated to the vitamin D (25 μg/d as cholecalciferol) or the placebo group in a double-blind manner for 12 weeks. Blood pressure, serum lipoproteins, apolipoproteins and anthropometric parameters were recorded. Dietary intake was recorded using 24 h food recall and FFQ. Physical activity was assessed by the International Physical Activity Questionnaire. Mean total cholesterol concentrations increased in the vitamin D group (0·08 (sd 0·56) mmol/l) but declined in the placebo group (0·47 (sd 0·58) mmol/l), and a significant effect was observed (P ≤ 0·001). In the vitamin D group, mean HDL-cholesterol concentration increased, whereas it decreased in the placebo group (0·07 (sd 0·2) v. - 0·03 (sd 0·2) mmol/l; P = 0·037). Mean apoA-I concentration increased in the vitamin D group, although it decreased in the placebo group (0·04 (sd 0·39) v. - 0·25 (sd 0·2) g/l; P ≤ 0·001). Mean LDL-cholesterol:apoB-100 ratio augmented in the vitamin D group, while this ratio declined in the placebo group (0·11 (sd 0·6) v. - 0·19 (sd 0·3); P = 0·014). Body fat mass was significantly decreased in the vitamin D group more than the placebo group ( - 2·7 (sd 2) v. - 0·4 (sd 2) kg; P ≤ 0·001). The findings showed that supplementation with vitamin D3 can significantly improve HDL-cholesterol, apoA-I concentrations and LDL-cholesterol:apoB-100 ratio, which remained significant in the multivariate model including anthropometric, dietary and physical activity measures.

Extraskeletal benefits and risks of calcium, vitamin D and anti-osteoporosis medications

Drugs used for the prevention and the treatment of osteoporosis exert various favourable and unfavourable extra-skeletal effects whose importance is increasingly recognized notably for treatment selection.

INTRODUCTION

The therapeutic armamentarium for the prevention and the treatment of osteoporosis is increasingly large, and possible extra-skeletal effects of available drugs could influence the choice of a particular compound.

METHODS

The present document is the result of a national consensus, based on a systematic and critical review of the literature.

RESULTS

Observational research has suggested an inverse relationship between calcium intake and cardiovascular diseases, notably through an effect on blood pressure, but recent data suggest a possible deleterious effect of calcium supplements on cardiovascular risk. Many diverse studies have implicated vitamin D in the pathogenesis of clinically important non-skeletal functions or diseases, especially muscle function, cardiovascular disease, autoimmune diseases and common cancers. The possible effects of oral or intravenous bisphosphonates are well-known. They have been associated with an increased risk of oesophageal cancer or atrial fibrillation, but large-scale studies have not found any association with bisphosphonate use. Selective oestrogen receptor modulators have demonstrated favourable or unfavourable extra-skeletal effects that vary between compounds. Strontium ranelate has a limited number of non-skeletal effects. A reported increase in the risk of venous thromboembolism is not found in observational studies, and very rare cases of cutaneous hypersensitivity reactions have been reported. Denosumab has been introduced recently, and its extra-skeletal effects still have to be assessed.

CONCLUSION

Several non-skeletal effects of bone drugs are well demonstrated and influence treatment choices.

Vitamin D3 deficiency differentially affects functional and disease outcomes in the G93A mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by motor neuron death in the central nervous system. Vitamin D supplementation increases antioxidant activity, reduces inflammation and improves motor neuron survival. We have previously demonstrated that vitamin D(3) supplementation at 10× the adequate intake improves functional outcomes in a mouse model of ALS.

OBJECTIVE

To determine whether vitamin D deficiency influences functional and disease outcomes in a mouse model of ALS.

METHODS

At age 25 d, 102 G93A mice (56 M, 46 F) were divided into two vitamin D(3) groups: 1) adequate (AI; 1 IU D(3)/g feed) and 2) deficient (DEF; 0.025 IU D(3)/g feed). At age 113 d, tibialis anterior (TA), quadriceps (quads) and brain were harvested from 42 mice (22 M and 20 F), whereas the remaining 60 mice (34 M and 26 F) were followed to endpoint.

RESULTS

During disease progression, DEF mice had 25% (P=0.022) lower paw grip endurance AUC and 19% (P=0.017) lower motor performance AUC vs. AI mice. Prior to disease onset (CS 2), DEF mice had 36% (P=0.016) lower clinical score (CS) vs. AI mice. DEF mice reached CS 2 six days later vs. AI mice (P=0.004), confirmed by a logrank test which revealed that DEF mice reached CS 2 at a 43% slower rate vs. AI mice (HR= .57; 95% CI: 0.38, 1.74; P=0.002). Body weight-adjusted TA (AI: r=0.662, P=0.001; DEF: r=0.622, P=0.006) and quads (AI: r=0.661, P=0.001; DEF: r=0.768; P<0.001) weights were strongly correlated with age at CS 2.

CONCLUSION

Vitamin D(3) deficiency improves early disease severity and delays disease onset, but reduces performance in functional outcomes following disease onset, in the high-copy G93A mouse.

Vitamin D is linked to carotid intima-media thickness and immune reconstitution in HIV-positive individuals

BACKGROUND

Patients with HIV infection are at increased risk of cardiovascular disease (CVD). Vitamin D insufficiency has been associated with increased CVD risk in non-HIV populations. This study sought to determine the relationship between vitamin D status and markers of CVD and HIV-related factors in HIV-positive patients.

METHODS

Patients with HIV infection on antiretroviral therapy and healthy controls were prospectively enrolled. Fasting lipids, glucose, insulin, inflammatory markers (soluble tumour necrosis factor-α receptor I, interleukin-6 and high-sensitivity C-reactive protein) and endothelial markers (soluble intercellular adhesion molecule-1 and soluble vascular cell adhesion molecule-1) were measured. Fasting 25-hydroxyvitamin D (25(OH)D) was measured from stored serum samples. The internal carotid artery and common carotid artery (CCA) intima-media thickness (IMT) were measured in a subset of HIV-positive patients. Baseline cross-sectional data were analysed.

RESULTS

A total of 149 HIV-positive patients (56 with carotid IMT) and 34 controls were included. Controls had higher adjusted mean 25(OH)D levels than HIV-positive patients (P=0.02). In multivariable linear regression among the HIV-positive patients, 25(OH)D was positively associated with CD4(+) T-cell restoration after antiretroviral therapy (ΔCD4 = current - nadir CD4(+) T-cell; P<0.01), but was not associated with inflammatory or endothelial markers. In multivariable logistic regression, odds of having CCA IMT above the median were more than 10× higher in those with lower 25(OH)D levels (OR=10.62, 95% CI 1.37-82.34; P<0.01).

CONCLUSIONS

Vitamin D status in HIV-positive patients was positively associated with improved immune restoration after antiretroviral therapy and negatively associated with CCA IMT. These findings suggest that vitamin D may play a role in HIV-related CVD and in immune reconstitution after antiretroviral therapy.

Bile acids regulate cardiovascular function

Research over the last decade has uncovered roles for bile acids (BAs) that extend beyond their traditional functions in regulating lipid digestion and cholesterol metabolism. BAs are now recognized as signaling molecules that interact with both plasma membrane and nuclear receptors. Emerging evidence indicates that by interacting with these receptors, BAs regulate their own synthesis, glucose and energy homeostasis, and other important physiological events. Herein, we provide a comprehensive review of the actions of BAs on cardiovascular function. In the heart and the systemic circulation, BAs interact with plasma membrane G-protein-coupled receptors, for example, TGR5 and muscarinic receptors, and nuclear receptors, for example, the farnesoid (FXR) and pregnane (PXR) xenobiotic receptors. BA receptors are expressed in cardiovascular tissue, however, the mechanisms underlying BA-mediated regulation of cardiovascular function remain poorly understood. BAs reduce heart rate by regulating channel conductance and calcium dynamics in sino-atrial and ventricular cardiomyocytes and regulate vascular tone via both endothelium-dependent and -independent mechanisms. End-stage liver disease, obstructive jaundice, and intrahepatic cholestasis of pregnancy are prominent conditions in which elevated serum BAs alter vascular dynamics. This review focuses on BAs as newly recognized signaling molecules that modulate cardiovascular function.

Vitamin d and stage 5 chronic kidney disease: a new paradigm?

Vitamin D receptor agonists (VDRA) are currently recommended for the treatment of secondary hyperparathyroidism in stage 5 CKD. They are considered to be contraindicated in the presence of low or normal (for a dialysis patient) levels of PTH due to the risk of developing adynamic bone disease, with consequent vascular calcification. However, these recommendations are increasingly at odds with the epidemiological evidence, which consistently shows a large survival advantage for patients treated with low-dose VDRAs, regardless of plasma calcium, phosphate, or PTH. A large number of pleiotropic effects of vitamin D have been described, including inhibition of renin activity, anti-inflammation, and suppression of vascular calcification stimulators and stimulation of vascular calcification inhibitors present in the uremic milieu. Laboratory studies suggest that a normal cellular vitamin D level is necessary for normal cardiomyocyte and vascular smooth muscle function. While pharmacological doses of VDRA can be harmful, the present evidence suggests that the level of 1,25-dihydroxycholecalciferol should also be more physiological in stage 5 CKD, and that widespread use of low-dose VDRA would be beneficial. A randomized controlled trial to test this hypothesis is warranted.

Differential effects of vitamin d receptor agonists on gene expression in neonatal rat cardiomyocytes

PURPOSE

Vitamin D receptor (VDR) activation is associated with cardiovascular benefits in chronic kidney disease patients, but whether VDR's hormone and prehormone exhibit similar effects requires more studies.

METHODS

Neonatal rat cardiomyocytes were treated with VDR agonists (calcitriol and/or paricalcitol) and the prehormone calcidiol in the presence of aldo (1 μM). The expression of VDR target genes were determined by real-time PCR and Western blotting. The expression and activity of CYP27B1 (the enzyme responsible for converting calcidiol to calcitriol) was measured.

RESULTS

Treating cells with aldo (1 μM) for 24 h significantly reduced the VDR mRNA (29%) and protein levels (>90%). Calcitriol and calcidiol induced VDR expression in the presence of aldo with EC(50) at 0.3 and 7,952 nM, respectively. Calcitriol, paricalcitol and calcidiol stimulated CYP24A1 (EC(50) at 6.4, 4.5 and 992 nM, respectively) and suppressed NPPB expression (IC(50) at 1.9, 0.1 and 210 nM, respectively) in the presence of 1 μM aldo. Neonatal rat cardiomyocytes expressed CYP27B1 and converted calcidiol to calcitriol at a low rate (~10% in 24 h).

CONCLUSIONS

VDR hormone calcitriol and its analog paricalcitol exhibit more potent effects than the prehormone calcidiol in cardiomyocytes.

The renin-angiotensin system, blood pressure, and heart structure in patients with hereditary vitamin D-resistance rickets (HVDRR)

Vitamin D deficiency has been linked to hypertension and an increased prevalence of cardiovascular risk factors and disease. Studies in vitamin D receptor knockout (VDR KO) mice revealed an overstimulated renin-angiotensin system (RAS) and consequent high blood pressure and cardiac hypertrophy. VDR KO mice correspond phenotypically and metabolically to humans with hereditary 1,25-dihydroxyvitamin D-resistant rickets (HVDRR). There are no data on the cardiovascular system in human HVDRR. To better understand the effects of vitamin D on the human cardiovascular system, the RAS, blood pressure levels, and cardiac structures were examined in HVDRR patients. Seventeen patients (9 males, 8 females, aged 6 to 36 years) with hereditary HVDRR were enrolled. The control group included age- and gender-matched healthy subjects. Serum calcium, phosphorous, creatinine, 25-hydroxyvitamin D [25(OH)D],1,25-dihydroxyvitamin D(3) [1,25(OH)(2) D(3) ], parathyroid hormone (PTH), plasma rennin activity (PRA), aldosterone, angiotensin II (AT-II), and angiotensin-converting enzyme (ACE) levels were determined. Ambulatory 24-hour blood pressure measurements and echocardiographic examinations were performed. Serum calcium, phosphorus, and alkaline phosphatase values were normal. Serum 1,25(OH)(2) D(3) and PTH but not PRA and ACE levels were elevated in the HVDRR patients. AT-II levels were higher than normal in the HVDRR patients but not significantly different from those of the controls. Aldosterone levels were normal in all HVDRR patients. No HVDRR patient had hypertension or echocardiographic pathology. These findings reveal that 6- to 36-year-old humans with HVDRR have normal renin and ACE activity, mild but nonsignificant elevation of AT-II, normal aldosterone levels, and no hypertension or gross heart abnormalities.

Vitamin D receptor (VDR)-mediated actions of 1α,25(OH)₂vitamin D₃: genomic and non-genomic mechanisms

The conformationally flexible secosteroid, 1α,25(OH)₂vitamin D₃ (1α,25(OH)₂D₃) initiates biological responses via binding to the vitamin D receptor (VDR). The VDR contains two overlapping ligand binding sites, a genomic pocket (VDR-GP) and an alternative pocket (VDR-AP), that respectively bind a bowl-like ligand configuration (gene transcription) or a planar-like ligand shape (rapid responses). When occupied by 1α,25(OH)₂D₃, the VDR-GP interacts with the retinoid X receptor to form a heterodimer that binds to vitamin D responsive elements in the region of genes directly controlled by 1α,25(OH)₂D₃. By recruiting complexes of either coactivators or corepressors, activated VDR modulates the transcription of genes encoding proteins that promulgate the traditional genomic functions of vitamin D, including signaling intestinal calcium and phosphate absorption to effect skeletal and calcium homeostasis. 1α,25(OH)₂D₃/VDR control of gene expression and rapid responses also delays chronic diseases of aging such as osteoporosis, cancer, type-1 and -2 diabetes, arteriosclerosis, vascular disease, and infection.

Vitamin D in fetal brain development

In this review we will provide a concise summary of the evidence implicating a role for vitamin D in the developing brain. Vitamin D is known to affect a diverse array of cellular functions. Over the past 10 years data has emerged implicating numerous ways in which this vitamin could also affect the developing brain including its effects on cell differentiation, neurotrophic factor expression, cytokine regulation, neurotransmitter synthesis, intracellular calcium signaling, anti-oxidant activity, and the expression of genes/proteins involved in neuronal differentiation, structure and metabolism. Dysfunction in any of these processes could adversely affect development. Although there are many ways to study the effects of vitamin D on the developing CNS in vivo, we will concentrate on one experimental model that has examined the impact of the dietary absence of vitamin D in utero. Finally, we discuss the epidemiological data that suggests that vitamin D deficiency either in utero or in early life may have adverse neuropsychiatric implications.

Assessment and modification of cardiovascular disease risk in the HIV-infected individual

HIV-infected patients are living decades longer than before owing to combination antiretroviral therapy. However, complications are emerging in this population at rates higher than the general population, including cardiovascular disease (CVD). HIV-infected patients have many traditional risk factors that account for a significant part of their increased risk of CVD. However, HIV factors, including complications from antiretroviral therapy and increased inflammation associated with chronic HIV infection, also play a role. Clinicians need to be ever-vigilant to calculate and help attenuate any modifiable CVD risk factors for each HIV-infected individual.

Vitamin D receptor activator reduces oxidative stress in hemodialysis patients with secondary hyperparathyroidism

Treatment with a vitamin D receptor activator (VDRA) has survival benefits probably related to its effects beyond the traditional role in mineral metabolism. We hypothesized that VDRA reduces oxidative stress in hemodialysis (HD) patients. To test this hypothesis, we investigated the effect of VDRA on the oxidative status of albumin in HD patients with secondary hyperparathyroidism. Eleven HD patients with secondary hyperparathyroidism were treated with calcitriol at an intravenous dose of 1.5 µg/week for four weeks. Serum intact parathyroid hormone, calcium and phosphorus were monitored and we measured the amount of oxidized albumin and albumin hydroperoxides form before and after calcitriol treatment. The ratio of oxidized to un-oxidized albumin was determined as a representative marker of oxidative stress. The radical scavenging activity of albumin was also evaluated. After four weeks of calcitriol therapy, there were no significant changes in serum intact parathyroid hormone, calcium, or phosphorus levels; however, the ratio of oxidized to un-oxidized albumin was markedly decreased and serum thiol content was significantly increased after calcitriol treatment. Furthermore, the radical scavenging activity of albumin was greater after calcitriol treatment compared with that of untreated albumin. Our data suggest that intravenous calcitriol treatment reduces oxidative stress and strengthens antioxidant defenses by inhibiting albumin oxidation in HD patients with secondary hyperparathyroidism.

Vitamin D, chronic kidney disease and survival: a pluripotent hormone or just another bone drug?

It is now about 40 years ago that the mechanism of renal 1-α-hydroxylation of vitamin D was discovered and characterized. After this seminal observation, the key role of the active vitamin D derivative 1, 25-(OH)2-vitamin D (calcitriol) in calcium homeostasis and bone mineralization, and its specific role in the course of chronic kidney disease (CKD) and renal osteopathy, was unraveled step by step, while the precursor 25-OH-vitamin D (calcidiol) was gradually ignored. Calcitriol and its synthetic analogue alfa-calcidol became the first-line standard drug to tackle secondary hyperparathyroidism (sHPT) in CKD. Potential side-effects, including hypercalcemia, hyperphosphatemia, and vascular calcification, were partly abrogated by developing less calcemic substances such as paricalcitol or maxacalcitol. Thus, TIME Magazine surprised when nominating vitamin D, with regard to its newly discovered pleiotropic actions, as one of the "top medical breakthroughs" in the December issue of 2007. This vote was driven by novel and spectacular insights into the pivotal regulatory role of vitamin D with regard to autoimmune diseases, immune defense, cancer development and progression, and cardiovascular function and disease. More than 30 cell types express the vitamin D receptor (VDR), and more than ten organs in addition to the kidney are capable of paracrine 1-α-hydroxylation. More than 200 genes are under the control of calcitriol. A MEDLINE search performed in December 2009 focusing on the keywords "vitamin D-and-kidney-and-2009" yielded 523 hits. This review intends to give a subjective and CKD-related update on novel biological and clinical insights with relevance to the steroid hormone vitamin D.

Vitamin D deficiency and toxicity in chronic kidney disease: in search of the therapeutic window

Both vitamin D deficiency and vitamin D toxicity are associated with cardiovascular complications in chronic kidney disease (CKD). Clinical and experiment data indicate that the association of vitamin D levels with cardiovascular disease is best illustrated as a biphasic, or U-shaped, curve. Children and adolescents with CKD need vitamin D due to the demands of a growing skeleton, to prevent renal rickets. However, this therapy carries the risk of severe side effects and chronic toxicity. Observational studies show that vitamin D deficiency and toxicity are frequently present in patients with CKD. In view of the importance of cardiovascular complications for the long-term survival of young patients, these findings demand a judicious use of vitamin D preparations. In clinical practice, the therapeutic window is rather small, presenting a therapeutic challenge to avoid both vitamin D deficiency and toxicity.

Vitamin D deficiency and myocardial diseases

Vitamin D deficiency is common among patients with myocardial diseases because sun-induced vitamin D production in the skin and dietary intake of vitamin D is often insufficient. Knockout mice for the vitamin D receptor develop myocardial hypertrophy and dysfunction. It has also been shown that children with rickets who suffered from severe heart failure could be successfully treated with supplementation of vitamin D plus calcium. In adults, almost all patients with heart failure exhibit reduced 25-hydroxyvitamin D levels, which are used to classify the vitamin D status. In prospective studies, vitamin D deficiency was an independent risk factor for mortality, deaths due to heart failure and sudden cardiac death. Several vitamin D effects on the electrophysiology, contractility, and structure of the heart suggest that vitamin D deficiency might be a causal factor for myocardial diseases. Data from interventional trials, however, are rare and urgently needed to elucidate whether vitamin D supplementation is useful for the treatment of myocardial diseases. In our opinion, the current knowledge of the beneficial effects of vitamin D on myocardial and overall health strongly argue for vitamin D supplementation in all vitamin D-deficient patients with or at high risk for myocardial diseases.

Vitamin D and cardiovascular disease risk: emerging evidence

PURPOSE OF REVIEW

Vitamin D deficiency is common throughout the world, with a particularly high prevalence in northern latitudes and colder climates. Although the best known sequelae of vitamin D deficiency involve the musculoskeletal system, a growing body of evidence suggests that vitamin D status may influence cardiovascular health as well. This review focuses on recent studies linking vitamin D and cardiovascular disease risk, emphasizing the potential relevance to primary prevention.

RECENT FINDINGS

There is strong experimental evidence that vitamin D status may influence cardiovascular structure and function. The number of clinical studies has steadily grown in recent years, with the largest number comprising observational studies showing associations between low vitamin D status, the presence of various cardiovascular risk factors, and adverse cardiovascular outcomes. A few small, randomized, controlled studies have been published, but these have been largely inconclusive.

SUMMARY

Despite substantial clinical evidence linking vitamin D deficiency with increased cardiovascular risk, it remains to be established whether this represents a causal association. Further study is needed with prospective, randomized controlled trials before vitamin D supplementation can be routinely recommended for the primary or secondary prevention of cardiovascular disease.

High prevalence of vitamin D deficiency and its association with left ventricular dilation: an echocardiography study in elderly patients with chronic heart failure

BACKGROUND AND AIMS

Vitamin D deficiency has been associated with chronic heart failure (CHF). We evaluated vitamin D levels in relationship with New York Heart Association (NYHA) classes, N-terminal pro-brain natriuretic peptide (NT-proBNP) values and left ventricular (LV) measures in ≥60 year old patients with stable CHF. Differently from previous investigations, LV function was assessed by transthoracic echocardiography, to provide easily reproducible results.

METHODS AND RESULTS

The study was performed at geographic latitude 44° N, from March to May and from September to November 2008. Acute HF and diseases or drugs altering vitamin D status were exclusion criteria. NYHA scores and 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D and NT-proBNP concentrations were assessed in 90 (45 F, 45 M) Caucasian patients with CHF secondary to hypertension and/or coronary artery disease. Vitamin D levels were also measured in 31 subjects without heart disease (controls). LV echocardiography was performed in 52 (26 F, 26 M) representative patients. Vitamin D concentrations were significantly lower in CHF cases than in controls. Among subject with CHF, 97.8% presented vitamin D deficiency (25(OH)D<75 nmol/L), being severe (<25 nmol/L) in 66.7%. LV end-diastolic and end-systolic diameters were significantly longer, LV end-diastolic and end-systolic volumes bigger and fractional shortening lower in CHF patients with 25(OH)D<25 nmol/L than with 25(OH)D≥25 nmol/L (p<0.05). Log-values of 25(OH)D were negatively correlated with LV end-systolic diameter and volume (r=-0.28; p<0.05). On subgroup analysis, these results persisted only in male patients.

CONCLUSIONS

In elderly CHF patients, vitamin D deficiency was highly prevalent and often severe. This first addressed echocardiography study showed a sex-specific association between vitamin D deficiency and LV dilation. Since further echocardiography data are easily obtainable, larger investigations are demanded.

Vitamin D receptor and enzyme expression in dorsal root ganglia of adult female rats: modulation by ovarian hormones

Vitamin D insufficiency impacts sensory processes including pain and proprioception, but little is known regarding vitamin D signaling in adult sensory neurons. We analyzed female rat dorsal root ganglia (DRG) for vitamin receptor (VDR) and the vitamin D metabolizing enzymes CYP27B1 and CYP24. Western blots and immunofluorescence revealed the presence of these proteins in sensory neurons. Nuclear VDR immunoreactivity was present within nearly all neurons, while cytoplasmic VDR was found preferentially in unmyelinated calcitonin gene-related peptide (CGRP)-positive neurons, colocalizing with CYP27B1 and CYP24. These data suggest that 1,25(OH)(2)D3 may affect sensory neurons through nuclear or extranuclear signaling pathways. In addition, local vitamin D metabolite concentrations in unmyelinated sensory neurons may be controlled through expression of CYP27B1 and CYP24. Because vitamin D deficiency appears to exacerbate some peri-menopausal pain syndromes, we assessed the effect of ovariectomy on vitamin D-related proteins. Two weeks following ovariectomy, total VDR expression in DRG dropped significantly, owing to a slight decrease in the percentage of total neurons expressing nuclear VDR and a large drop in unmyelinated CGRP-positive neurons expressing cytoplasmic VDR. Total CYP27B1 expression dropped significantly, predominantly due to decreased expression within unmyelinated CGRP-positive neurons. CYP24 expression remained unchanged. Therefore, unmyelinated CGRP-positive neurons appear to have a distinct vitamin D phenotype with hormonally-regulated ligand and receptor levels. These findings imply that vitamin D signaling may play a specialized role in a neural cell population that is primarily nociceptive.