Effects of vitamin D supplementation on endothelial function: a systematic review and meta-analysis of randomised clinical trials

The effect of vitamin D supplementation on endothelial function: An umbrella review of interventional meta-analyses

AIMS

There is no consensus in the existing literature regarding the effect of vitamin D supplementation on endothelial function. This umbrella review aimed to assess meta-analyses of randomized controlled trials (RCTs) conducted in this field.

DATA SYNTHESIS

We systematically searched English-language databases, including PubMed, Embase, Scopus, and Web of Science, up to January 2024. Flow-Mediated Dilation (FMD), Pulse Wave Velocity (PWV), and Augmentation Index (AIx) were the primary endpoints evaluated. A total of 16 meta-analyses were included in the review. The results indicated that vitamin D supplementation significantly improved FMD as assessed by Standardized Mean Difference (SMD) (SMD = 0.72, 95 % CI: 0.34, 1.11; p < 0.001; I2 = 79.4 %, p < 0.001) and Weighted Mean Difference (WMD) (WMD = 1.91; 95 % CI: 0.66, 3.16; p = 0.003; I2 = 94.5 %, p < 0.001). PWV also showed a modest but significant improvement (SMD = -0.06, 95 % CI: -0.12, -0.00; p = 0.03; I2 = 0.0 %, p = 0.66). However, vitamin D had no significant impact on AIx based on SMD (SMD = -0.03, 95 % CI: -0.13, 0.06; p = 0.48; I2 = 0.0 %, p = 0.49) or WMD (WMD = 0.02, 95 % CI: -2.22, 2.25; p = 0.98; I2 = 29.2 %, p = 0.23).

CONCLUSION

These findings suggest that vitamin D supplementation may be a beneficial intervention for improving endothelial function, particularly in populations with low FMD. The effects on PWV were modest, while AIx remained unaffected.

REGISTRATION NUMBER

PROSPERO, CRD42024451215.

Vitamin D levels and risk of ocular disorders: insights from bidirectional and multivariable Mendelian randomization analysis

Purpose

This study aimed to assess the causal relationships between vitamin D levels and ocular disorders.

Methods

Independent genetic variables were obtained from genome-wide association studies (GWAS) and publicly available databases. The summary statistics for 25-hydroxyvitamin D (25(OH)D) were obtained from two large-scale GWAS studies, with sample sizes of 324,105 and 417,580 European individuals. The genetic variants of myopia, primary open angle glaucoma (POAG), anterior iridocyclitis, senile cataract, diabetic retinopathy (DR), retinal vein occlusion (RVO), wet age-related macular degeneration (WAMD) and optic neuritis were extracted from the latest release of FinnGen consortium, which contains genome data from Finnish participants. Subsequently, Mendelian randomization (MR) analyses were conducted to obtain effect estimates. Additionally, we performed multivariable MR analysis and mediation analysis to validate the results.

Results

In the discovery dataset, genetically predicted vitamin D concentration was found to be causally associated with an increased risk of WAMD, (odd ratio (OR) = 1.35, 95% confidence interval (CI) = 1.09-1.67, P IVW = 0.005). However, no causal effects of genetically predisposed vitamin D levels on the risk of most types of ocular disorders were observed. Reverse MR revealed no causal relationships between the ocular diseases and vitamin D concentrations. The MR analyses of the validation dataset yielded consistent results. Additionally, the causal effect of vitamin D levels on the risk of WAMD remained significant after adjusting for potential confounders in the multivariable MR analysis (OR = 1.86, 95% CI = 1.26-2.73, P IVW = 0.002).

Conclusion

Our MR analysis results provide robust evidence of a causal relationship between genetically predicted 25(OH)D levels and an increased risk of WAMD in European population. These findings offer important insights into the management and control of ocular disorders.

Vitamin D and ischemic stroke - Association, mechanisms, and therapeutics

Confronting the rising tide of ischemic stroke and its associated mortality and morbidity with ageing, prevention and acute management of ischemic stroke is of paramount importance. Mounting observational studies have established a non-linear association of vitamin D status with cardiovascular diseases, including ischemic stroke. Paradoxically, current clinical trials fail to demonstrate the cardiovascular benefits of vitamin D supplementation. We aim to update recent clinical and experimental findings on the role of vitamin D in the disease course of ischemic stroke, from its onset, progression, recovery, to recurrence, and the established and alternative possible pathophysiological mechanisms. This review justifies the necessities to address stroke etiological subtypes and focus on vitamin D-deficient subjects for investigating the potential of vitamin D supplementation as a preventive and therapeutic approach for ischemic stroke. Well-powered clinical trials are warranted to determine the efficacy, safety, timing, target individuals, optimal dosages, and target 25OHD concentrations of vitamin D supplementation in the prevention and treatment of ischemic stroke.

Effect of walnut consumption on markers of endothelial function in adults: A systematic review and meta-analysis of randomized controlled trials

Findings on the effect of walnut consumption on endothelial function are conflicting. Therefore, the present systematic review and meta-analysis summarized available trials in this regard. A systematic search was performed in online databases including PubMed-Medline, Scopus, and ISI Web of Science up to October 2023. Articles that reported the effect of walnut intake on flow-mediated dilation (FMD), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and stimulus-adjusted response measure (SARM) were included. Random effects models for a weighted mean difference (WMD) or standardized mean difference (SMD) were used to test for the overall effect. Six eligible trials were analyzed (250 participants). Walnut intake significantly increased FMD (WMD: 0.94%, 95% CI: 0.12 to 1.75; p = 0.02). However, meta-analysis could not show any beneficial effect of walnut intake on ICAM-1 (SMD: -0.23, 95% CI: -0.68 to 0.22; p = 0.31), VCAM-1 (SMD: -0.02, 95% CI: -1.38 to 1.34; p = 0.97), and SARM (WMD: 0.01%, 95% CI: -0.01 to 0.04; p = 0.28). In conclusion, the present meta-analysis suggests that walnuts may reduce cardiovascular disease risk by improving FMD. However, further studies should be performed on adults to determine the effect of walnut intake on endothelial function.

Associations between Aging and Vitamin D Status with Whole-Body Nitric Oxide Production and Markers of Endothelial Function

BACKGROUND

Aging and vitamin D deficiency have been associated with reduced nitric oxide (NO) synthesis and impaired endothelial function (EF) but the evidence in humans remains weak.

OBJECTIVES

Two independent cross-sectional studies were designed to evaluate the association between age, sex, and plasma vitamin D concentrations with physiological and biochemical biomarkers of NO synthesis and EF in young and older healthy participants (Study 1) and in overweight and obese postmenopausal females (Study 2).

METHODS

In Study 1, 40 young (20-49 y) and older (50-75 y) males and females (10 participants per age and sex group) were included. Resting blood pressure and ear-to-finger peripheral pulse wave velocity (PWV) were measured. A stable-isotopic method was used to determine whole-body NO production. Plasma 25-hydroxyvitamin D (25(OH)D), nitrate, nitrite, and asymmetric dimethylarginine (ADMA) concentrations were determined. In Study 2, 80 older overweight and obese females (age 61.2 ± 6.2 y, body mass index 29.5 ± 4.4 kg/m2) were recruited. Postocclusion reactive hyperemia (PORH) and peripheral PWV were measured. Plasma concentrations of 25(OH)D, nitrate, cyclic guanosine monophosphate, 3-nitrotyrosine (3-NT), endothelin-1, vascular endothelial growth factor, and ADMA were determined.

RESULTS

In Study 1, whole-body NO production was significantly greater in young compared with older participants (0.61 ± 0.30 μmol·h-1·kg-1 compared with 0.39 ± 0.10 μmol·h-1·kg-1, P = 0.01) but there was no evidence of a sex difference (P = 0.81). Plasma 25(OH)D concentration was not associated with PWV (r = 0.18, P = 0.28) or whole-body NO production (r = -0.20, P = 0.22). Plasma ADMA concentration was associated positively with age (r = 0.35, P = 0.03) and negatively with whole-body NO production (r = -0.33, P = 0.04). In Study 2, age was associated with lower PORH (r = -0.28, P = 0.02) and greater ADMA concentrations (r = 0.22, P = 0.04). Plasma 25(OH)D concentration was inversely associated with 3-NT concentrations (r = -0.31, P = 0.004).

CONCLUSIONS

Older age was associated with lower whole-body NO production. Plasma vitamin D concentrations were not associated with NO production or markers of EF but showed a weak, significant correlation with oxidative stress in postmenopausal overweight females.

The Role of Vitamin D and Its Molecular Bases in Insulin Resistance, Diabetes, Metabolic Syndrome, and Cardiovascular Disease: State of the Art

In the last decade, an increasing awareness was directed to the role of Vitamin D in non-skeletal and preventive roles for chronic diseases. Vitamin D is an essential hormone in regulating calcium/phosphorous balance and in the pathogenesis of inflammation, insulin resistance, and obesity. The main forms of vitamin D, Cholecalciferol (Vitamin D3) and Ergocalciferol (Vitamin D2) are converted into the active form (1,25-dihydroxyvitamin D) thanks to two hydroxylations in the liver, kidney, pancreas, and immune cells. Some anti-inflammatory cytokines are produced at higher levels by vitamin D, while some pro-inflammatory cytokines are released at lower levels. Toll-Like Receptor (TLR) expression is increased, and a pro-inflammatory state is also linked to low levels of vitamin D. Regardless of how it affects inflammation, various pathways suggest that vitamin D directly improves insulin sensitivity and secretion. The level of vitamin D in the body may change the ratio of pro- to anti-inflammatory cytokines, which would impact insulin action, lipid metabolism, and the development and function of adipose tissue. Many studies have demonstrated an inverse relationship between vitamin D concentrations and pro-inflammatory markers, insulin resistance, glucose intolerance, metabolic syndrome, obesity, and cardiovascular disease. It is interesting to note that several long-term studies also revealed an inverse correlation between vitamin D levels and the occurrence of diabetes mellitus. Vitamin D supplementation in people has controversial effects. While some studies demonstrated improvements in insulin sensitivity, glucose, and lipid metabolism, others revealed no significant effect on glycemic homeostasis and inflammation. This review aims to provide insight into the molecular basis of the relationship between vitamin D, insulin resistance, metabolic syndrome, type 1 and 2 diabetes, gestational diabetes, and cardiovascular diseases.

Mechanisms Suggesting a Relationship between Vitamin D and Erectile Dysfunction: An Overview

Vitamin D deficiency (VDD) and erectile dysfunction (ED) heavily burden the male population. The higher prevalence of both conditions in the elderly suggests a possible relationship between the two conditions. In addition, in vitro, animal, and human studies have revealed several mechanisms that may relate VDD to ED. The main mechanism by which vitamin D might exert its action on sexual function appears to be through the regulation of endothelial function. Indeed, VDD correlates with several markers of endothelial function. The action of vitamin D on the endothelium would be exercised both indirectly through its intervention in inflammatory processes and through the production of oxygen free radicals, and directly through the regulation of vascular stiffness, the production of nitric oxide, and the regulation of vessel permeability. Furthermore, the ubiquitous distribution of the vitamin D receptor in the human body means that this hormone can also exert a beneficial effect on erectile function by interfering with those comorbidities significantly associated with ED, such as hypertension, diabetes mellitus, hypercholesterolemia, chronic kidney disease, and hypogonadism. In this review, we thoroughly and carefully presented the evidence and mechanisms that would appear to relate vitamin D levels to erectile function. Furthermore, we have summarized the meta-analytic evidence for and against this association to provide a true representation of this topic. Data published to date suggest that low levels of vitamin D could contribute to worsening erectile function through several mechanisms. Therefore, vitamin D levels should be measured in patients with ED and maintained at adequate levels by specific supplementation in case of deficiency. However, the low quality and heterogeneity of clinical trials evaluating the effects of vitamin D administration on erectile function and ED-associated comorbidities do not allow for a univocal conclusion, and indicate the need for further studies to analyze these aspects.

Circulating microRNAs as potential biomarkers of early vascular damage in vitamin D deficiency, obese, and diabetic patients

Vitamin D3 deficiency, obesity, and diabetes mellitus (DM) have been shown to increase the risk of cardiovascular diseases (CVDs). However, the early detection of vascular damage in those patients is still difficult to ascertain. MicroRNAs (miRNAs) are recognized to play a critical role in initiation and pathogenesis of vascular dysfunction. Herein, we aimed to identify circulating miRNA biomarkers of vascular dysfunction as early predictors of CVDs. We have recruited 23 middle-aged Emiratis patients with the following criteria: A healthy control group with vitamin D ≥ 20ng, and BMI < 30 (C1 group = 11 individuals); A vitamin D deficiency (Vit D level ≤ 20 ng) and obese (BMI ≥ 30) group (A1 group = 9 patients); A vitamin D deficiency, obese, plus DM (A2 group = 3 patients). Arterial stiffness via pulse wave velocity (PWV) was measured and the whole transcriptome analysis with qPCR validation for miRNA in plasma samples were tested. PWV relative to age was significantly higher in A1 group 19.4 ± 4.7 m/s and A2 group 18.3 ± 1.3 m/s compared to controls 14.7 ± 2.1 m/s (p < 0.05). Similar patterns were also observed in the Augmentation pressure (AP) and Alx%. Whole RNA-Sequencing revealed miR-182-5p; miR-199a-5p; miR-193a-5p; and miR-155-5p were differentially over-expressed (logFC > 1.5) in high-risk patients for CVDs vs healthy controls. Collectively, our result indicates that four specific circulating miRNA signature, may be utilized as non-invasive, diagnostic and prognostic biomarkers for early vascular damage in patients suffering from vitamin D deficiency, obesity and DM.

Hypovitaminosis D and Metabolic Syndrome in Postmenopausal Women

Metabolic syndrome (MetSyn) is a precursor for several cardiometabolic diseases. The prevalence of MetSyn is higher in postmenopausal women compared to premenopausal women. The role of vitamin D in postmenopausal women is not clearly understood. Hypovitaminosis D is more prevalent in postmenopausal women compared to premenopausal women. For this review, Pubmed, Cochrane, SCOPUS, Embase, and Google Scholar databases were searched up to August 2022. Findings from one randomized controlled trial (RCT) and ten cross-sectional studies were included in this review. Several cross-sectional studies (8 out of 10 reviewed) unequivocally demonstrated an inverse association between serum 25-hydroxyvitamin D concentrations and MetSyn. However, RCTs are severely lacking in the effect of vitamin D intake on the biomarkers of MetSyn and the prevalence of MetSyn. Therefore, caution should be used in recommending mega doses of vitamin D supplements for postmenopausal women because of the potential adverse effects associated with this vitamer.

The impacts of vitamin D supplementation in adults with metabolic syndrome: A systematic review and meta-analysis of randomized controlled trials

Background: Studies have shown the association of vitamin D status with the development of metabolic syndrome (MetS), which has attracted an extensive research interest with inconsistent results. Therefore, we hypothesized that vitamin D supplementation (VDS) will benefit adults with MetS.

Aims: To test our hypothesis, we performed a meta-analysis to evaluate the effect of VDS on MetS in adults using relevant biomarkers such as anthropometric parameters, blood pressure, blood lipid profile, glycemia, oxidative stress and vitamin D toxicity (VDT).

Methods: Randomized controlled trials published in PubMed, Web of Science, embase and the Cochrane Library between 2012 and 2022 on the effect of VDS on MetS in adults were searched. The language was limited to English. A meta-analysis performed using RevMan 5.4 and Stata 14.0 software, sensitivity analysis, and evaluation of the risk of bias and general quality of the resulting evidence were conducted.

Results: Eventually, 13 articles were included in this meta-analysis. Overall, VDS significantly increased the endline serum 25-hydroxyvitamin D levels as compared to the control [MD:17.41, 95% CI (14.09, 20.73), p < 0.00001]. VDS did not affect waist circumference, body mass index, body fat percentage and VDT biomarkers, but decreased waist-to-hip ratio and blood pressure (p < 0.01). VDS significantly decreased fasting plasma glucose (FPG) [MD: 3.78; 95% CI (−6.52, −1.03), p = 0.007], but did not affect the levels of blood high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglyceride (TG). Pooled estimate of nine papers indicated a significant reduction of fasting insulin (FI) (p = 0.006), and homeostasis model assessment of insulin resistance (p = 0.0001). The quantitative insulin check index levels were moderately increased (p = 0.007) without any impact on the glycosylated hemoglobin type A1C (HbA1c). For the oxidative stress parameters, VDS significantly lowered the levels of malondialdehyde and hypersensitive C-reactive protein (p < 0.05).

Conclusion: Results of this meta-analysis demonstrate that VDS only reduces insulin resistance and hypertension but not the blood lipid profile and HbA1c. It appears that the evidence for the benefit of VDS in adults with MetS is inconclusive. Further clinical studies are still needed.

Persistent or new symptoms 1 year after a single high dose of vitamin D3 in patients with moderate to severe COVID-19

Purpose

The aim of this study was to investigate the reported persistent or new symptoms 1 year after a single dose of 200,000 IU of vitamin D₃ and hospitalization in patients with moderate to severe COVID-19.

Methods

This is a post-hoc, exploratory analysis from a multicenter, double-blind, placebo-controlled, randomized clinical trial from two hospitals in São Paulo, Brazil, registered in ClinicalTrials.gov, NCT04449718. Discharged patients were followed for up to 1 year and evaluated by telephone interviews at 6 and 12 months. The primary and secondary outcomes were previously published. These post-hoc exploratory secondary outcomes are the persistent or new symptoms and quality of life (QoL) at the post-viral stage of COVID-19. Generalized estimating equations (GEE) for repeated measures with Bonferroni’s adjustment were used for testing outcomes.

Results

Between 2 June and 27 August 2020, we randomized 240 patients of which 144 were included in this study [the vitamin D₃ (n = 71) or placebo (n = 73) group]. The mean (SD) age was 54.3 (13.1) years, and body mass index (BMI) was 32.4 (6.5) kg/m². Fever demonstrated a significant main effect of time (P < 0.001) with a reduction from baseline to 6 (52–0) and 12 months (52–0). No significant differences between groups were observed for fever, cough, fatigue, fever, myalgia, joint pain, runny nose, nasal congestion, sore throat, hypertension, diabetes, cardiovascular disease, rheumatic disease, asthma, chronic obstructive pulmonary, chronic kidney disease, QoL, and new or persistent symptoms up to 1-year of follow-up.

Conclusion

The findings do not support the use of 200,000 IU of vitamin D₃ compared to placebo for the management of persistence or new symptoms, and QoL reported by moderate to severe patients after hospitalization for COVID-19.

The Endothelium and COVID-19: An Increasingly Clear Link Brief Title: Endotheliopathy in COVID-19

The endothelium has a fundamental role in the cardiovascular complications of coronavirus disease 2019 (COVID-19). Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) particularly affects endothelial cells. The virus binds to the angiotensin-converting enzyme 2 (ACE-2) receptor (present on type 2 alveolar cells, bronchial epithelial cells, and endothelial cells), and induces a cytokine storm. The cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 have particular effects on endothelial cells-leading to endothelial dysfunction, endothelial cell death, changes in tight junctions, and vascular hyperpermeability. Under normal conditions, apoptotic endothelial cells are removed into the bloodstream. During COVID-19, however, endothelial cells are detached more rapidly, and do not regenerate as effectively as usual. The loss of the endothelium on the luminal surface abolishes all of the vascular responses mediated by the endothelium and nitric oxide production in particular, which results in greater contractility. Moreover, circulating endothelial cells infected with SARS-CoV-2 act as vectors for viral dissemination by forming clusters that migrate into the circulation and reach distant organs. The cell clusters and the endothelial dysfunction might contribute to the various thromboembolic pathologies observed in COVID-19 by inducing the formation of intravascular microthrombi, as well as by triggering disseminated intravascular coagulation. Here, we review the contributions of endotheliopathy and endothelial-cell-derived extracellular vesicles to the pathogenesis of COVID-19, and discuss therapeutic strategies that target the endothelium in patients with COVID-19.

Mechanisms Involved in the Relationship between Vitamin D and Insulin Resistance: Impact on Clinical Practice

Recent evidence has revealed anti-inflammatory properties of vitamin D as well as extra-skeletal activity. In this context, vitamin D seems to be involved in infections, autoimmune diseases, cardiometabolic diseases, and cancer development. In recent years, the relationship between vitamin D and insulin resistance has been a topic of growing interest. Low 25-hydroxyvitamin D (25(OH)D) levels appear to be associated with most of the insulin resistance disorders described to date. In fact, vitamin D deficiency may be one of the factors accelerating the development of insulin resistance. Vitamin D deficiency is a common problem in the population and may be associated with the pathogenesis of diseases related to insulin resistance, such as obesity, diabetes, metabolic syndrome (MS) and polycystic ovary syndrome (PCOS). An important question is the identification of 25(OH)D levels capable of generating an effect on insulin resistance, glucose metabolism and to decrease the risk of developing insulin resistance related disorders. The benefits of 25(OH)D supplementation/repletion on bone health are well known, and although there is a biological plausibility linking the status of vitamin D and insulin resistance supported by basic and clinical research findings, well-designed randomized clinical trials as well as basic research are necessary to know the molecular pathways involved in this association.

A Randomized Double-Blind Placebo-Controlled Trial Evaluating the Efficacy of Oral Cholecalciferol in Improving Renal and Vascular Functions in Vitamin D-Deficient Patients With Type 2 Diabetes Mellitus

This study was performed to evaluate the efficacy of cholecalciferol in improving renal and vascular functions in vitamin D-deficient patients with type 2 diabetes mellitus (T2DM) along with chronic kidney disease (CKD). One hundred patients (18 - 65 years), having T2DM along with CKD (stage IIIA and IIIB) and hypovitaminosis D were randomized (1:1) to receive either oral cholecalciferol 60,000 IU (Group A) or placebo (Group B) weekly for 8 weeks along with standard background treatment. They were followed up for another 24 weeks. Various parameters of renal and vascular functions were compared. Except for serum calcium and phosphate levels which were significantly higher in Group A (p < 0.001), there was no significant difference in any of the biochemical or vascular parameters between the two groups at 8 weeks. There were comparable changes in urinary albumin-creatinine ratio and carotid-femoral pulse wave velocity in the two groups at 8 and 24 weeks. There was no improvement in any of the vascular parameters from the corresponding baseline values in the two groups at 8 and 32 weeks. No improvement in renal and vascular functions was observed following treatment with oral cholecalciferol in patients with T2DM and CKD.

Effect of vitamin D supplementation on microvascular reactivity in obese adolescents: A randomized controlled trial

BACKGROUND AND AIM

Childhood obesity is associated with vitamin D (VD) deficiency and vascular dysfunction. Considering evidence indicates that VD may improve vascular function, this study, for the first time, assessed the effect of VD supplementation on microvascular reactivity in obese adolescents (OA).

METHODS AND RESULTS

This randomized controlled trial included 26 OA, receiving fruit juice with (n = 13) or without VD (4000 IU/d; n = 13) over a 3-month lifestyle program, as well as 23 normal-weight adolescents (controls). The primary outcome was the pre-to-post-program change in microvascular reactivity determined by laser speckle contrast imaging with acetylcholine and sodium nitroprusside iontophoresis. Changes in 25 hydroxyvitamin D (25(OH)D), flow-mediated dilation (FMD), nitrate-mediated dilation (NMD), insulin resistance (HOMA-IR) and inflammatory markers (C-reactive protein [CRP]) were monitored. At inclusion, in comparison to controls, OA exhibited lower total and free 25(OH)D, impaired microvascular responses, and impaired FMD, but similar NMD. After the lifestyle program, total and free 25(OH)D increased in all OA, with a greater increase in those receiving VD supplements. HOMA-IR and CRP decreased in all OA. Neither FMD nor NMD were altered in either group. Endothelium-dependent microvascular reactivity only increased in the VD-supplemented group, reaching values comparable to that of controls. Similar results were found when analyzing only OA with a VD deficiency at baseline.

CONCLUSION

VD supplementation during a lifestyle program attenuated microvascular dysfunction in OA without altering macrovascular function.

REGISTRATION NUMBER FOR CLINICAL TRIAL

NCT02400151.

Role of Vitamin D in the Metabolic Syndrome

The prevalence of hypovitaminosis D has risen in developed countries over the past few years in association with lifestyle changes and an increase in unhealthy habits. Vitamin D deficiency has been implicated in various diseases, including metabolic syndrome (MetS), which is clinically defined by a set of metabolic and vascular disorders. The objective of this study was to review scientific evidence on the relationship between MetS and vitamin D deficiency to support the development of prevention strategies and health education programs. An inverse relationship has been reported between plasma vitamin D concentrations and the features that define MetS, i.e., elevated serum concentrations of glucose, total cholesterol, low-density lipoproteins, triglycerides, glycosylated hemoglobin, and a high body mass index. Numerous studies have described the benefits of vitamin D supplementation to improve outcomes in individuals with MetS. Interventions to maintain optimal vitamin D concentrations are proposed as a preventive strategy against MetS.

The effect of PCOS status on atherosclerosis markers and cardiovascular disease risk factors in young women with vitamin D deficiency

OBJECTIVE

To investigate whether polycystic ovary syndrome (PCOS) had further deteriorating influence on endothelial function or cardiometabolic parameters in women with vitamin D deficiency during reproductive age.

STUDY DESIGN

The study group was composed of women with PCOS and vitamin D deficiency and insufficiency between the ages of 18 and 35 years. Age and body mass index (BMI)-matched women were chosen as controls. Serum 25(OH) Vit D levels below 20 ng/mL were considered as vitamin D deficiency. The cutoff level of vitamin D insufficiency was suggested at 30 ng/mL. Serum FSH, LH, estradiol, testosterone, DHEA-S, fasting glucose, total cholesterol, HDL, LDL, triglyceride levels were analyzed. Carotid artery intima-media thickness (CIMT) was measured, and the flow-mediated vasodilation (FMD) was calculated.

RESULTS

CIMT and FMD values in both vitamin D deficiency and insufficiency subgroups showed no significant difference between PCOS and non-PCOS groups. There was a weak negative correlation between BMI, waist/hip ratio, CRP, and 25(OH) Vitamin D.

CONCLUSION

PCOS is a heterogeneous disease with different combinations of the diagnostic components. Vitamin D is an important variable for a healthy cardiovascular system. We did not find any difference in early atherosclerotic markers and cardiometabolic features between PCOS and non-PCOS group with Vitamin D deficiency.

The joint effect of energy reduction with calcium supplementation on the risk factors of type 2 diabetes in the overweight population: a two-year randomized controlled trial

Both excessive energy intake and low calcium intake are inversely associated with the aging-related diseases, particularly for type 2 diabetes mellitus(T2DM). This study examined whether energy reduction coupled with calcium supplementation aided in the prevention of T2DM among the overweight population. A randomized controlled trial(RCT) of 1021 overweight participants was performed, in which participants were randomly assigned to 4 groups: 1) energy-reduction group(ERG), 2) calcium supplementation group(CSG), 3) energy-reduction with calcium supplementation group(ER-CSG), 4) control group(CG). Nutritional habits, anthropometric and diabetes-related indicators were measured at baseline and each follow-up time. To analyze the separate effects of dietary energy reduction and calcium supplementation, ERG and ER-CSG were integrated into ERGs. Similarly, CSG and ER-CSG were integrated into CSGs. Compared to the non-energy-reduction groups(NERGs), ERGs had lower values of ΔBMI(-0.9kg/m²), ΔFSG (-0.34mmol/L), ΔHbA1c(0.16%), and ΔHOMA-IR(-0.13), and higher value of ΔGutt index(-5.82). Compared to the non-calcium supplementation groups(NCSGs), the ΔGutt index(-5.46) in CSGs showed a significant decrease. Moreover, these risk factors for T2DM were most effectively ameliorated in ER-CSG group with the decreased values of ΔFSG(-0.42mmol/L), ΔGutt index(-0.73), and the slowest increasing rate value of Δ2h-glucose(0.37mmol/L). This RCT demonstrated that energy-reduction with calcium supplementation was a useful dietary intervention strategy for preventing the development of T2DM in the overweight population.

Vitamin D and Its Role in the Lipid Metabolism and the Development of Atherosclerosis

Vitamin D, a crucial hormone in the homeostasis and metabolism of calcium bone, has lately been found to produce effects on other physiological and pathological processes genomically and non-genomically, including the cardiovascular system. While lower baseline vitamin D levels have been correlated with atherogenic blood lipid profiles, 25(OH)D supplementation influences the levels of serum lipids in that it lowers the levels of total cholesterol, triglycerides, and LDL-cholesterol and increases the levels of HDL-cholesterol, all of which are known risk factors for cardiovascular disease. Vitamin D is also involved in the development of atherosclerosis at the site of the blood vessels. Deficiency of this vitamin has been found to increase adhesion molecules or endothelial activation and, at the same time, supplementation is linked to the lowering presence of adhesion surrogates. Vitamin D can also influence the vascular tone by increasing endothelial nitric oxide production, as seen in supplementation studies. Deficiency can lead, at the same time, to oxidative stress and an increase in inflammation as well as the expression of particular immune cells that play a pivotal role in the development of atherosclerosis in the intima of the blood vessels, i.e., monocytes and macrophages. Vitamin D is also involved in atherogenesis through inhibition of vascular smooth muscle cell proliferation. Furthermore, vitamin D deficiency is consistently associated with cardiovascular events, such as myocardial infarction, STEMI, NSTEMI, unstable angina, ischemic stroke, cardiovascular death, and increased mortality after acute stroke. Conversely, vitamin D supplementation does not seem to produce beneficial effects in cohorts with intermediate baseline vitamin D levels.

Vitamin D Supplementation in Diabetic Foot Ulcers: A Current Perspective

INTRODUCTION

Diabetic foot ulcer (DFU) is a major complication of diabetes mellitus, as it can physically and emotionally impact the person. Its management can be challenging and expensive, depending on the severity of the wound and the presence of infection.

BACKGROUND

The fat-soluble molecule, vitamin D, has gained great importance ever since its pleiotropism has been recognized. Its efficacy could be attributed to the presence of vitamin D receptors in most of the body tissues. Vitamin D plays a significant role in cell proliferation, differentiation, and immune modulation. It modulates the T and B cells resulting in the suppression of the immunoglobulins, autoimmunity, and inflammation.

METHODS

We performed a literature search with the objective to highlight the role of vitamin D in peripheral vascular disease and peripheral neuropathy, which are the major risk factors for DFU, as well as evidences of its role in wound healing and management of DFU.

RESULTS

Preclinical and clinical studies have shown that vitamin D influences multiple phases of wound healing and thereby accelerates the process. It modulates various cells involved in proliferation and remodelling phases. Vitamin D also enhances the expression of antimicrobial peptides that help to eliminate the microbes, as well as suppress the proinflammatory responses while enhancing the anti-inflammatory responses.

CONCLUSION

This review concludes vitamin D to have a protective role in the immune and vascular system, improve glycaemic outcomes, and wound healing. Therefore, vitamin D could be a preferred adjuvant in the management of DFU.

Dietary vitamin D intake, cardiovascular disease and cardiometabolic risk factors: a sex-based analysis from the ATTICA cohort study

BACKGROUND

The present study aimed to evaluate the association between dietary vitamin D intake and 10-year first fatal/nonfatal cardiovascular disease (CVD), conventional CVD risk factors and surrogate markers related to inflammation, coagulation, insulin resistance, liver and renal function.

METHODS

The ATTICA study was conducted during 2001-2012 including 1514 men and 1528 women (aged >18 years) from the greater Athens area, Greece. Dietary assessment was based on a validated semi-quantitative food frequency questionnaire. Daily intake of vitamin D was calculated using a standardised food database. Follow-up (2011-2012) was achieved in 2020 participants (n = 317 cases).

RESULTS

Ranking from first to third vitamin D tertile, CVD events were 24%, 17% and 12% for men (P = 0.002) and 14%, 10% and 11% for women (P = 0.59). Inverse associations between vitamin D and CVD in total sample [hazard ratio (HR) = 0.76 95% confidence interval (CI) = 0.60-0.97] and in men (HR = 0.66 95% CI = 0.49-0.89) were observed, and lost after adjusting for inflammation/coagulation markers; for women, no significant trends were observed. Regarding 10-year onset of conventional risk factors, inverse associations of vitamin D with hypertension in men (HR = 0.62 95% CI = 0.39-0.99) and transition to metabolically unhealthy status in women (HR = 0.69 95% CI = 0.51-0.93) were observed. Significant inverse associations for C-reactive protein, interleukin-6 and fibrinogen in both sexes, whereas these were revealed only in women for insulin resistance.

CONCLUSIONS

Contradicting the neutral/modest associations in vitamin-D supplementation trials, increased food-generated vitamin D may protect against hard and intermediate CVD endpoints, implying different paths between sexes.

Inflammation and Premature Ageing in Chronic Kidney Disease

Persistent low-grade inflammation and premature ageing are hallmarks of the uremic phenotype and contribute to impaired health status, reduced quality of life, and premature mortality in chronic kidney disease (CKD). Because there is a huge global burden of disease due to CKD, treatment strategies targeting inflammation and premature ageing in CKD are of particular interest. Several distinct features of the uremic phenotype may represent potential treatment options to attenuate the risk of progression and poor outcome in CKD. The nuclear factor erythroid 2-related factor 2 (NRF2)-kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1 (KEAP1) signaling pathway, the endocrine phosphate-fibroblast growth factor-23-klotho axis, increased cellular senescence, and impaired mitochondrial biogenesis are currently the most promising candidates, and different pharmaceutical compounds are already under evaluation. If studies in humans show beneficial effects, carefully phenotyped patients with CKD can benefit from them.

Vitamin D and Endothelial Function

Vitamin D is known to elicit a vasoprotective effect, while vitamin D deficiency is a risk factor for endothelial dysfunction (ED). ED is characterized by reduced bioavailability of a potent endothelium-dependent vasodilator, nitric oxide (NO), and is an early event in the development of atherosclerosis. In endothelial cells, vitamin D regulates NO synthesis by mediating the activity of the endothelial NO synthase (eNOS). Under pathogenic conditions, the oxidative stress caused by excessive production of reactive oxygen species (ROS) facilitates NO degradation and suppresses NO synthesis, consequently reducing NO bioavailability. Vitamin D, however, counteracts the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase which produces ROS, and improves antioxidant capacity by enhancing the activity of antioxidative enzymes such as superoxide dismutase. In addition to ROS, proinflammatory mediators such as TNF-α and IL-6 are risk factors for ED, restraining NO and eNOS bioactivity and upregulating the expression of various atherosclerotic factors through the NF-κB pathway. These proinflammatory activities are inhibited by vitamin D by suppressing NF-κB signaling and production of proinflammatory cytokines. In this review, we discuss the diverse activities of vitamin D in regulating NO bioavailability and endothelial function.

Vitamin D, Marine n-3 Fatty Acids, and Primary Prevention of Cardiovascular Disease Current Evidence

Whether marine omega-3 fatty acid (n-3 FA) or vitamin D supplementation can prevent cardiovascular disease (CVD) in general populations at usual risk for this outcome is unknown. A major goal of VITAL (Vitamin D and Omega-3 Trial) was to fill this knowledge gap. In this article, we review the results of VITAL, discuss relevant mechanistic studies regarding n-3 FAs, vitamin D, and vascular disease, and summarize recent meta-analyses of the randomized trial evidence on these agents. VITAL was a nationwide, randomized, placebo-controlled, 2×2 factorial trial of marine n-3 FAs (1 g/d) and vitamin D3 (2000 IU/d) in the primary prevention of CVD and cancer among 25 871 US men aged ≥50 and women aged ≥55 years, including 5106 blacks. Median treatment duration was 5.3 years. Supplemental n-3 FAs did not significantly reduce the primary cardiovascular end point of major CVD events (composite of myocardial infarction, stroke, and CVD mortality; hazard ratio [HR], 0.92 [95% CI, 0.80-1.06]) but were associated with significant reductions in total myocardial infarction (HR, 0.72 [95% CI, 0.59-0.90]), percutaneous coronary intervention (HR, 0.78 [95% CI, 0.63-0.95]), and fatal myocardial infarction (HR, 0.50 [95% CI, 0.26-0.97]) but not stroke or other cardiovascular end points. For major CVD events, a treatment benefit was seen in those with dietary fish intake below the cohort median of 1.5 servings/wk (HR, 0.81 [95% CI, 0.67-0.98]) but not in those above (P interaction=0.045). For myocardial infarction, the greatest risk reductions were in blacks (HR, 0.23 [95% CI, 0.11-0.47]; P interaction by race, 0.001). Vitamin D supplementation did not reduce major CVD events (HR, 0.97 [95% CI, 0.85-1.12]) or other cardiovascular end points. Updated meta-analyses that include VITAL and other recent trials document coronary risk reduction from supplemental marine n-3 FAs but no clear CVD risk reduction from supplemental vitamin D. Additional research is needed to determine which individuals may be most likely to derive net benefit from supplementation. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01169259.

Effect of vitamin D supplementation on endothelial function - An updated systematic review with meta-analysis and meta-regression

BACKGROUND AND AIMS

Atherogenesis and endothelial dysfunction contribute to cardiovascular risk and vitamin D has been implemented in endothelial repair. This systematic review, meta-analysis and meta-regression aims to establish the effect of vitamin D supplementation on endothelial function.

METHODS AND RESULTS

To conduct the systematic review we searched the Cochrane Library of Controlled Trials, PubMed, ProQuest and EMBASE for randomized controlled trials that investigated the effects of vitamin D supplementation on flow-mediated dilation (FMD%), pulse wave velocity (PWV), and central augmentation index (AIx). Meta-analysis was based on a random effects model and inverse-variance methods to calculate either mean difference (MD) or standardized mean difference (SMD) as effects sizes. This was followed by meta-regression investigating the effect of baseline vitamin D concentrations, vitamin D dosing and study duration. Risk of bias was assessed using the JADAD scale and funnel plots. We identified 1056 studies of which 26 studies met inclusion criteria for quantitative analysis. Forty-two percent of the 2808 participants had either deficient or insufficient levels of vitamin D. FMD% (MD 1.17% (95% CI -0.20, 2.54), p = 0.095), PWV (SMD -0.09 m/s (95% CI -0.24, 0.07), p = 0.275) and AIx (SMD 0.05% (95% CI -0.1, 0.19), p = 0.52) showed no improvement with vitamin D supplementation. Sub-analysis and meta-regression revealed a tendency for AIx and FMD% to increase as weekly vitamin doses increased; no other significant relationships were identified.

CONCLUSIONS

Vitamin D supplementation showed no improvement in endothelial function. More evidence is required before recommendations for management of endothelial dysfunction can be made.

A single injection of vitamin D3 improves insulin sensitivity and β-cell function but not muscle damage or the inflammatory and cardiovascular responses to an acute bout of resistance exercise in vitamin D-deficient resistance-trained males

Vitamin D deficiency is now a recognised problem affecting multiple physiological functions. The aim of the present study was to evaluate the effect of a single dose of vitamin D3 injection on the inflammatory, muscular damage, metabolic and cardiovascular responses to an acute bout of resistance exercise (RE) in vitamin D-deficient resistance-trained males. Blood samples from fourteen vitamin D-deficient resistance-trained males were obtained during two separate trials: lower vitamin D (LVD) and higher vitamin D (HVD, after vitamin D3 injection). Metabolic, inflammatory, muscle damage and cardiovascular markers were evaluated at baseline, immediately and 1 h after RE. There were significant trial-by-time interactions for insulin and homeostatic model assessment of insulin resistance (HOMA-IR) which significantly (P < 0·05) declined for 1 h after RE in the HVD trial compared with the LVD trial. Homeostasis model assessment of β-cell function (HOMA-β) declines at 1 h post-RE in the HVD trial. There was also a time effect for blood sugar which significantly (P < 0·05) decreased and for creatine kinase, lactate dehydrogenase and IL-6 which increased significantly 1 h post-RE in both trials. There were no significant changes in other inflammatory and cardiovascular markers following both trials. A single injection of vitamin D3 improved insulin resistance and β-cell function following RE in previously vitamin D-deficient resistance-trained males. Conversely, the injection did not change muscle damage and the inflammatory response to acute RE. Intramuscular vitamin D replacement may have key implications for the promotion of glucose metabolism and lowering the risk of diabetes in vitamin D-deficient individuals.

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.

Vitamin D and cardiovascular disorders

Vitamin D is necessary for bone health but may also have many extra-skeletal effects. The vitamin D endocrine system has major effects on gene and protein expression in many cells and tissues related to the cardiovascular system. In addition, many preclinical studies in animals with vitamin D deficiency or genetically silenced expression of the vitamin D receptor or vitamin D metabolizing enzymes suggest that the absence of vitamin D action may result in cardiovascular events. This includes dysfunctions of endothelial cells, thereby accelerating the process of atherosclerosis, hypertension or abnormal coagulation, ultimately resulting in higher risks for all major cardiovascular or cerebrovascular events. A wealth of observational studies in different parts of the world have fairly consistently found a strong association between a poor vitamin D status and surrogate markers or hard cardiovascular events. A few Mendelian randomization studies did, however, not find a link between genetically lower serum 25OHD concentrations and cardiovascular events. Finally, many RCTs could not demonstrate a consistent effect on surrogate markers, and a limited number of RCTs did so far not find whatever effect on hard cardiovascular endpoints such as myocardial ischemia or infarction, stroke, or cardiovascular death. In conclusion, preclinical data generated a plausible hypothesis of a link between vitamin D status and extra-skeletal events, including cardiovascular endpoints. Whether the vitamin D endocrine system is redundant for the human vascular system or whether the RCTs have not been optimally designed to answer the research question is thus not yet settled.

Vitamin D Improves Nitric Oxide-Dependent Vasodilation in Adipose Tissue Arterioles from Bariatric Surgery Patients

There is a high prevalence of vitamin-D deficiency in obese individuals that could be attributed to vitamin-D sequestration in the adipose tissue. Associations between vitamin-D deficiency and unfavorable cardiometabolic outcomes were reported. However, the pathophysiological mechanisms behind these associations are yet to be established. In our previous studies, we demonstrated microvascular dysfunction in obese adults that was associated with reduced nitric oxide (NO) production. Herein, we examined the role of vitamin D in mitigating microvascular function in morbidly obese adults before and after weight loss surgery. We obtained subcutaneous (SAT) and visceral adipose tissue (VAT) biopsies from bariatric patients at the time of surgery (n = 15) and gluteal SAT samples three months post-surgery (n = 8). Flow-induced dilation (FID) and acetylcholine-induced dilation (AChID) and NO production were measured in the AT-isolated arterioles ± NO synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME), hydrogen peroxide (H2O2) inhibitor, polyethylene glycol-modified catalase (PEG-CAT), or 1,25-dihydroxyvitamin D. Vitamin D improved FID, AChID, and NO production in AT-isolated arterioles at time of surgery; these effects were abolished by L-NAME but not by PEG-CAT. Vitamin-D-mediated improvements were of a higher magnitude in VAT compared to SAT arterioles. After surgery, significant improvements in FID, AChID, NO production, and NO sensitivity were observed. Vitamin-D-induced changes were of a lower magnitude compared to those from the time of surgery. In conclusion, vitamin D improved NO-dependent arteriolar vasodilation in obese adults; this effect was more significant before surgery-induced weight loss.

Emerging role of vitamin D in autoimmune diseases: An update on evidence and therapeutic implications

Vitamin D plays a key role in in calcium homeostasis and, thus, provides an important support in bone growth by aiding in the mineralization of the collagen matrix. However, vitamin D performs various immunomodulatory, anti-inflammatory, antioxidant and anti-fibrotic actions. Autoimmune diseases result from an aberrant activation of the immune system, whereby the immune response is directed against harmless self-antigens. Does vitamin D play a role in the pathophysiology of autoimmune diseases? And, if so, what is its role? In the last decade, researchers' interest in vitamin D and its correlations with autoimmune diseases has considerably increased. We conducted a literature review, covering the period January 1, 2009 through March 30, 2019, in PubMed. We analyzed more than 130 studies in order to find a correlation between vitamin D levels and its effect upon several autoimmune diseases. The analysis demonstrated an inverse association between vitamin D and the development of several autoimmune diseases, such as SLE, thyrotoxicosis, type 1 DM, MS, iridocyclitis, Crohn's disease, ulcerative colitis, psoriasis vulgaris, seropositive RA, polymyalgia rheumatica. International multicenter study could allow us to confirm the data already present in the literature in the single clinical studies and to evaluate when to effectively supplement vitamin D in patients who do not take corticosteroids.

Vitamin D intervention does not improve vascular regeneration in diet-induced obese male mice with peripheral ischemia

Vitamin D appears to either promote or inhibit neovascularization in a disease context-dependent manner. The effects of vitamin D, alone or in combination with niacin, on endothelial cell (EC) angiogenic function and on revascularization in obese animals with peripheral ischemia are unknown. Here, we report that supplementation of high palmitate medium with vitamin D, niacin or both vitamins increased EC tube formation, which relies primarily on cell migration, and also maintained tube stability over time. Transcriptomic analyses revealed that both vitamins increased stress response and anti-inflammatory gene expression. However, vitamin D decreased cell cycle gene expression and inhibited proliferation, while niacin induced stable expression of miR-126-3p and -5p and maintained cell proliferation in high palmitate. To assess vascular regeneration, diet-induced obese mice received vitamin D, niacin or both vitamins following hind limb ischemic injury. Niacin, but not vitamin D or combined treatment, improved recovery of hind limb use. Histology of tibialis anterior sections revealed no improvements in revascularization, regeneration, inflammation or fibrosis with vitamin D or combined treatment. In summary, although both vitamin D and niacin increased angiogenic function of EC cultures in high fat, only niacin improved recovery of hind limb use following ischemic injury in obese mice. It is possible that inhibition of cell proliferation by vitamin D in high-fat conditions limits vascular regeneration and recovery from peripheral ischemia in obesity.

Is there a relationship between vitamin D nutritional status and metabolic syndrome in childhood acute lymphoblastic leukemia survivors? A PETALE study

BACKGROUND

Treatment of childhood acute lymphoblastic leukemia (cALL) has reached unprecedented success leading to survival rates reaching 90%. This is regrettably linked to increased risk of developing long-term health-related sequels into early adulthood.

OBJECTIVE

This study aims at assessing the relationship between the vitamin D status and metabolic biomarkers in PETALE, a well-characterized cohort of cALL survivors.

RESULTS

We demonstrate that 15.9% of the study participants exhibited 3 or more metabolic syndrome (MetS) risk factors. We also show a direct relationship between s25OHD₃ and plasma HDL-Cholesterol concentrations in female but not male participants.

CONCLUSION

Our data, from a metabolically well-described cohort, support a modest role for vitamin D in lipid metabolism in childhood leukemia survivors. The major outcome of this study is the strong association between HDL-Cholesterol concentration and s25OHD₃ only in female subjects, thereby conveying vitamin D a gender-specific cardio-protective effect. cALL survivors represent a population at higher risk for secondary diseases. For this reason thorough nutritional evaluation, including vitamin D should be part of the regular follow-up.

Eshak E, Kinuta M, Nagao M, Cui R, Imano H, Ohira T, Iso H. Association between vitamin B group supplementation with changes in % flow-mediated dilatation and plasma homocysteine levels: a randomized controlled trial

There is limited evidence examining the association between B vitamin supplementation and improved endothelial function via lowering plasma homocysteine levels. This study investigated whether low-dose B vitamin supplementation improves endothelial dysfunction in Japanese adults with one or more components of metabolic syndrome. A randomized, controlled, crossover trial, without a washout period or blinding of subjects, was conducted from May-September, 2010. The subjects were 127 Japanese men and women aged 40-65 years who had at least one component of metabolic syndrome without medication. Participants took a supplement drink for two months but were divided into early intervention or later intervention groups. The flow-mediated dilatation, plasma homocysteine level, serum B-vitamins, and vitamin C levels were measured. A significant increase in serum B vitamins and vitamin C levels, and a reduction in plasma homocysteine levels were observed. The mean serum homocysteine level pre- and post-intervention was 9.8 and 8.2 µmol/L in the early intervention group and 10.8 and 7.4 µmol/L in the later intervention group (p<0.01). However, no significant changes in flow-mediated dilatation was found. Low-dose multivitamin supplementation including B vitamins is associated with a significant reduction in plasma homocysteine levels among patients with one or more components of metabolic syndrome. This study was registered at the University Hospital Medical Information Network (UMIN) centre, and has the identifier UMIN000004436.

Human health in relation to exposure to solar ultraviolet radiation under changing stratospheric ozone and climate

The Montreal Protocol has limited increases in the UV-B (280-315 nm) radiation reaching the Earth's surface as a result of depletion of stratospheric ozone. Nevertheless, the incidence of skin cancers continues to increase in most light-skinned populations, probably due mainly to risky sun exposure behaviour. In locations with strong sun protection programs of long duration, incidence is now reducing in younger age groups. Changes in the epidemiology of UV-induced eye diseases are less clear, due to a lack of data. Exposure to UV radiation plays a role in the development of cataracts, pterygium and possibly age-related macular degeneration; these are major causes of visual impairment world-wide. Photodermatoses and phototoxic reactions to drugs are not uncommon; management of the latter includes recognition of the risks by the prescribing physician. Exposure to UV radiation has benefits for health through the production of vitamin D in the skin and modulation of immune function. The latter has benefits for skin diseases such as psoriasis and possibly for systemic autoimmune diseases such as multiple sclerosis. The health risks of sun exposure can be mitigated through appropriate sun protection, such as clothing with both good UV-blocking characteristics and adequate skin coverage, sunglasses, shade, and sunscreen. New sunscreen preparations provide protection against a broader spectrum of solar radiation, but it is not clear that this has benefits for health. Gaps in knowledge make it difficult to derive evidence-based sun protection advice that balances the risks and benefits of sun exposure.

The effects of vitamin D supplementation on endothelial activation among patients with metabolic syndrome and related disorders: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

The current systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to summarize the effect of vitamin D supplementation on endothelial activation among patients with metabolic syndrome and related disorders.

METHODS

Cochrane library, Embase, PubMed, and Web of Science database were searched to identify related RCTs published before 30th April 2018. The heterogeneity among the included studies was assessed using Cochran's Q test and I-square (I2) statistic. Data were pooled by using the random-effect model and standardized mean difference (SMD) was considered as summary effect size.

RESULTS

Fourteen clinical trials that contained a total of 1253 participants were included in the current meta-analysis. Vitamin D supplementation significantly decreased von willebrand factor (vWF) (SMD -0.27; 95% CI, - 0.46, - 0.08; P = 0.006; I2:40.5%). However, we found no significant impact of vitamin D supplementation on intercellular adhesion molecule 1(ICAM-1) (SMD -1.96; 95% CI, - 4.02, 0.09; P = 0.06; I2:97.4%), vascular celladhesion molecule 1 (VCAM-1) (SMD -0.50; 95% CI, - 1.19, 0.19; P = 0.15; I2:91.2%), on E-selectin (SMD -0.04; 95% CI, - 0.36, 0.28; P = 0.81; I2:78.8%) and endothelin (SMD -0.49; 95% CI, - 1.18, 0.19; P = 0.15; I2:90.5%). The pooled data from trials of vitamin D supplementation with dosage of ≤4000 IU/day (- 0.37, 95% CI: -0.65, - 0.10, I2: 73.5%) significantly reduced vWF concentrations, while there was no effect of vitamin D supplementation on vWF concentrations among trials with the dosage of intervention > 4000 IU/day (- 0.17, 95% CI: -0.43, 0.10, I2: 0.0%). VWF concentrations significantly reduced in pooled data from trials with duration study ≤8 weeks (- 0.37, 95% CI: -0.67, - 0.07, I2: 60.6%), but there was no effect of vitamin D supplementation on vWF concentrations among trials with > 8 weeks (- 0.20, 95% CI: -0.45, 0.05, I2: 0.0%). While there was no effect of vitamin D supplementation on vWF concentrations among trials with total sample size of ≤60 patients (- 0.03, 95% CI: -0.42, 0.36, I2: 0.0%), vWF concentrations in trials with more than 60 patients decreased significantly (- 0.34, 95% CI: -0.56, - 0.12, I2: 60.9%).

CONCLUSIONS

Overall, the current meta-analysis demonstrated that vitamin D supplementation to patients with metabolic syndrome and related disorders resulted in an improvement in vWF, but did not affect ICAM-1, VCAM-1, E-selectin and endothelin levels.

Vitamin D and cardiovascular disease

Vitamin D, a soluble steroid hormone synthesized in the skin after sun exposure, plays a crucial role in calcium metabolism and is also involved in cardiovascular pathophysiology. The aim of this review is to summarize the available evidence (a) on the association between endogenous vitamin D status and cardiovascular disease, and (b) on the effect of vitamin D supplementation on cardiovascular outcomes. Most studies have shown an inverse association between vitamin D levels and cardiovascular outcomes. Randomized controlled trials, however, do not consistently support a beneficial effect of vitamin D administration on cardiovascular health. Population characteristics, comorbid conditions such as diabetes, the overall population prevalence of cardiovascular disease, vitamin D status and the regimen of vitamin D supplementation may account for the conflicting results.

Effect of Vitamin D Supplementation on Markers of Vascular Function: A Systematic Review and Individual Participant Meta-Analysis

Background

Low 25‐hydroxyvitamin D levels are associated with an increased risk of cardiovascular events, but the effect of vitamin D supplementation on markers of vascular function associated with major adverse cardiovascular events is unclear.

Methods and Results

We conducted a systematic review and individual participant meta‐analysis to examine the effect of vitamin D supplementation on flow‐mediated dilatation of the brachial artery, pulse wave velocity, augmentation index, central blood pressure, microvascular function, and reactive hyperemia index. MEDLINE, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, and http://www.ClinicalTrials.gov were searched until the end of 2016 without language restrictions. Placebo‐controlled randomized trials of at least 4 weeks duration were included. Individual participant data were sought from investigators on included trials. Trial‐level meta‐analysis was performed using random‐effects models; individual participant meta‐analyses used a 2‐stage analytic strategy, examining effects in prespecified subgroups. 31 trials (2751 participants) were included; 29 trials (2641 participants) contributed data to trial‐level meta‐analysis, and 24 trials (2051 participants) contributed to individual‐participant analyses. Vitamin D3 daily dose equivalents ranged from 900 to 5000 IU; duration was 4 weeks to 12 months. Trial‐level meta‐analysis showed no significant effect of supplementation on macrovascular measures (flow‐mediated dilatation, 0.37% [95% confidence interval, −0.23 to 0.97]; carotid‐femoral pulse wave velocity, 0.00 m/s [95% confidence interval, −0.36 to 0.37]); similar results were obtained from individual participant data. Microvascular function showed a modest improvement in trial‐level data only. No consistent benefit was observed in subgroup analyses or between different vitamin D analogues.

Conclusions

Vitamin D supplementation had no significant effect on most markers of vascular function in this analysis.

Vitamin D Deficiency, Supplementation, and Cardiovascular Health

Vitamin D has been traditionally recognized as a vitamin quintessential for bone-mineral health. In the past 2 decades, numerous experimental and observational studies have highlighted the role of vitamin D in immunity, metabolic syndrome (obesity and diabetes), cancers, renal disease, memory, and neurological dysfunction. In this article, we review important studies that focused on the impact of vitamin D on blood pressure, myocardial infarction, peripheral arterial disease, heart failure, and statin intolerance. Amidst the current pool of ambiguous evidence, we intend to discuss the role of vitamin D in "high-value cardiovascular health care".

Effect of vitamin D supplementation on non-skeletal disorders: a systematic review of meta-analyses and randomised trials

Randomised trials reported up to Dec 31, 2012, did not confirm that vitamin D supplementation could protect from non-skeletal health conditions affecting adults, as was expected on the basis of data from observational studies. To examine whether the more recently published meta-analyses and trials would change past conclusions, we systematically reviewed meta-analyses of vitamin D supplementation and non-skeletal disorders published between Jan 1, 2013, and May 31, 2017, that included study participants of all ages, including pregnant women. We also searched for randomised trials not included in meta-analyses. We identified 87 meta-analyses, of which 52 were excluded because they contained less recent literature or were of suboptimal quality. We retrieved 202 articles on trials that were not included in meta-analyses. Recent meta-analyses reinforce the finding that 10-20 μg per day of vitamin D can reduce all-cause mortality and cancer mortality in middle-aged and older people. Although vitamin D doses were greater than those assessed in the past, we found no new evidence that supplementation could have an effect on most non-skeletal conditions, including cardiovascular disease, adiposity, glucose metabolism, mood disorders, muscular function, tuberculosis, and colorectal adenomas, or on maternal and perinatal conditions. New data on cancer outcomes were scarce. The compilation of results from 83 trials showed that vitamin D supplementation had no significant effect on biomarkers of systemic inflammation. The main new finding highlighted by this systematic review is that vitamin D supplementation might help to prevent common upper respiratory tract infections and asthma exacerbations. There remains little evidence to suggest that vitamin D supplementation has an effect on most conditions, including chronic inflammation, despite use of increased doses of vitamin D, strengthening the hypothesis that low vitamin D status is a consequence of ill health, rather than its cause. We further hypothesise that vitamin D supplementation could exert immunomodulatory effects that strengthen resistance to acute infections, which would reduce the risk of death in debilitated individuals. We identified many meta-analyses of suboptimal quality, which is of concern. Future systematic reviews on vitamin D should be based on data sharing so that data for participants with the same outcomes measured in the same way can be pooled to generate stronger evidence.

Effectiveness of Vitamin D Supplementation for Cardiovascular Health Outcomes

There is a plausible physiological theory, supported by many observational studies, that vitamin D supplementation should be effective for improving cardiovascular end points, such as blood pressure (BP), large artery stiffness, atherosclerosis, endothelial function and clinical events. However, results from randomised controlled trials (RCTs) have been inconsistent. In this review, we evaluated the evidence regarding the effectiveness of vitamin D supplementation for cardiovascular surrogate and hard clinical end points. RCTs were assessed in terms of sample size, duration of supplementation, baseline vitamin D level inclusion criteria (i.e., absence of vitamin D deficiency), dosage of vitamin D and population under investigation. Forty-five RCTs were identified. Eight RCTs with BP and 6 RCTs with large artery stiffness as the end points were found to comply with guidelines for the optimal design of clinical trials evaluating nutrient effects. Only 2 of the RCTs with an optimal design were effective in decreasing BP with vitamin D supplementation, although these were of moderate sample size (<150) and very short duration (8 weeks for both), whilst no RCT was effective in reducing large artery stiffness. Similar results were observed for atherosclerotic and endothelial function markers as end points. Only 1 RCT reported cardiovascular events as an end point and found neither increased nor decreased incident cardiovascular events over 7 years of follow-up. In conclusion, results from published RCTs indicate that vitamin D supplementation is ineffective in improving cardiovascular health among various patient populations, including in the presence or absence of vitamin D deficiency.

Low vitamin D serum levels in diffuse systemic sclerosis: a correlation with worst quality of life and severe capillaroscopic findings

OBJECTIVE

The aim of this study was to analyze the correlation of vitamin D levels with clinical parameters, bone mineral density (BMD), quality of life (QoL) and nailfold capillaroscopy (NC) in patients with diffuse systemic sclerosis (SSc).

METHODS

Thirty-eight female patients with diffuse SSc were analyzed regarding 25-hydroxyvitamin D (25OHD) serum levels. At inclusion, organ involvement, autoantibodies, modified Rodnan skin score (mRSS), Medsger Disease Severity Index (MDSI), body mass index (BMI), BMD, NC, Short-Form-36 Questionnaire (SF-36), and Health Assessment Questionnaire (HAQ), were performed through a standardized interview, physical examination and electronic chart review.

RESULTS

Mean 25OHD serum level was 20.66±8.20ng/mL. Eleven percent of the patients had 25OHD levels ≤10ng/mL, 50% ≤20ng/mL and 87% ≤30ng/mL. Vitamin D serum levels were positively correlated with BMI (r=0.338, p=0.038), BMD-total femur (r=0.340, p=0.037), BMD-femoral neck (r=0.384, p=0.017), SF-36-Vitality (r=0.385, p=0.017), SF-36-Social Function (r=0.320, p=0.050), SF-36-Emotional Role (r=0.321, p=0.049) and SF-36-Mental Health (r=0.531, p=0.0006) and were negatively correlated with HAQ-Reach (r=-0.328, p=0.044) and HAQ-Grip Strength (r=-0.331, p=0.042). A negative correlation with NC-diffuse devascularization (p=0.029) and NC-avascular area (p=0.033) was also observed.

CONCLUSION

The present study provides novel evidence demonstrating that low levels of 25OHD have a negative impact in diffuse SSc QoL and further studies are needed to define whether vitamin D supplementation can improve health related QoL in these patients. The additional observation of a correlation with severe NC alterations suggests a possible role of 25OHD in the underlying SSc vascular involvement.