Vitamin D, Shedding Light on the Development of Disease in Peripheral Arteries

Gut microbiota's causative relationship with peripheral artery disease: a Mendelian randomization study

Introduction

The relationship between gut microbiota and peripheral artery disease (PAD) remains understudied. While traditional risk factors like smoking and hyperlipidemia are well-understood, our study aims to determine the potential causative association of gut microbiota with PAD using Mendelian Randomization.

Methods

Data from the International MiBioGen Consortium and the FinnGen research project were used to study 211 bacterial taxa. Instrumental variables, comprising 2079 SNPs, were selected based on significance levels and linkage disequilibrium. Analyses were conducted utilizing the inverse-variance weighted (IVW) method and other statistical MR techniques to mitigate biases, processed in R (v4.3.1) with the TwosampleMR package.

Results

Three bacterial taxa, namely genus Coprococcus2, RuminococcaceaeUCG004, and RuminococcaceaeUCG010, emerged as protective factors against PAD. In contrast, family. FamilyXI and the genus Lachnoclostridium and LachnospiraceaeUCG001 were identified as risk factors.

Conclusion

Our findings hint at a causative association between certain gut microbiota and PAD, introducing new avenues for understanding PAD's etiology and developing effective treatments. The observed associations now warrant further validation in varied populations and detailed exploration at finer taxonomic levels.

Phosphate in Cardiovascular Disease: From New Insights Into Molecular Mechanisms to Clinical Implications

Hyperphosphatemia is a common feature in patients with impaired kidney function and is associated with increased risk of cardiovascular disease. This phenomenon extends to the general population, whereby elevations of serum phosphate within the normal range increase risk; however, the mechanism by which this occurs is multifaceted, and many aspects are poorly understood. Less than 1% of total body phosphate is found in the circulation and extracellular space, and its regulation involves multiple organ cross talk and hormones to coordinate absorption from the small intestine and excretion by the kidneys. For phosphate to be regulated, it must be sensed. While mostly enigmatic, various phosphate sensors have been elucidated in recent years. Phosphate in the circulation can be buffered, either through regulated exchange between extracellular and cellular spaces or through chelation by circulating proteins (ie, fetuin-A) to form calciprotein particles, which in themselves serve a function for bulk mineral transport and signaling. Either through direct signaling or through mediators like hormones, calciprotein particles, or calcifying extracellular vesicles, phosphate can induce various cardiovascular disease pathologies: most notably, ectopic cardiovascular calcification but also left ventricular hypertrophy, as well as bone and kidney diseases, which then propagate phosphate dysregulation further. Therapies targeting phosphate have mostly focused on intestinal binding, of which appreciation and understanding of paracellular transport has greatly advanced the field. However, pharmacotherapies that target cardiovascular consequences of phosphate directly, such as vascular calcification, are still an area of great unmet medical need.

The relationship between the level of vitamin D and ruptured intracranial aneurysms among patients with high sun exposure

Non-traumatic subarachnoid hemorrhage (SAH) accounts for 3-5% of acute strokes. Intracranial aneurysm is the most common cause of non-traumatic SAH. Vitamin D influences the cardiovascular system, including the formation and rupture of cerebral aneurysms. To evaluate the serum vitamin D level in patients living in the tropical zone who suffered aneurysmal subarachnoid hemorrhage and its correlation with demographic and neurological characteristics. This is an analytical cross-sectional study to assess the serum level of vitamin D in a study population of 99 patients treated and diagnosed with aSAH in a public hospital in Recife-PE over a period of 12 months. In the study sample, composed of individuals with high sun exposure due to the lifestyle they lead in a tropical region, we observed hypovitaminosis D (85.9%), with a median of 19.9 ng/ml, although the majority of individuals are skin with high concentration of melanin (Fitzpatrick skin type IV and V). In addition, rates of sun exposure are high to all patients (Solar Index 9.03 P50). Most individuals were female (79.8%); there was no statistical difference in solar exposure/solar index between genders. As for the neurological repercussions, there was no statistical relevance in the clinical prognostic scales evaluated. As the sample was composed mainly of individuals whose economic activity is agriculture, the values of solar index found are vastly higher than those of other studies conducted in high latitude regions. In line with the literature review, some aspects were raised with the objective of justifying such findings that go from the base of the poor diet of these individuals, the increase of melanin in the skin and genetic alterations that directs us to possible mechanisms of natural photoprotection to high sun exposure. Thus, we had a vast majority (85%) of hypovitaminosis D, which in fact makes us wonder if there is any influence of calcitriol on vitamin D receptors in vascular walls and in the cardiovascular system as a whole, which influence bleeding events of this nature. As for the neurological repercussions, measured using assessment scales (Glasgow coma scale, WFNS scale, Hunt-Hess and Fisher's tomographic scale) there was no significant difference in the results. As it is only a descriptive study, the causal relationship of the facts cannot be established. However, in a population exposed to high sun exposure and affected by aneurysmal SAH, there is a significant rate of hypovitaminosis D, which supports the hypothesis that vitamin D plays a role in vascular pathologies, such as cerebral aneurysms and SAH.

The Role of Polymorphism in the Endothelial Homeostasis and Vitamin D Metabolism Genes in the Severity of Coronary Artery Disease

Coronary artery disease (CAD) remains one of the leading causes of cardiovascular morbidity and mortality worldwide. The maintenance of endothelial homeostasis and vitamin D metabolism play an important role in CAD pathogenesis. This study aimed to determine the association of endothelial homeostasis and vitamin D metabolism gene polymorphism with CAD severity. A total of 224 low-risk patients (SYNTAX score ≤ 31) and 36 high-risk patients (SYNTAX score > 31) were recruited for this study. The serum level of E-, L- and P-selectins; endothelin; eNOS; 25OH; and 1.25-dihydroxy vitamin D was measured using an enzyme-linked immunosorbent assay (ELISA). Polymorphic variants in SELE, SELP, SELPLG, END1, NOS3, VDR and GC were analyzed using a polymerase chain reaction (PCR). We found no differences in the serum levels of the studied markers between high- and low-risk patients. Three polymorphic variants associated with CAD severity were discovered: END1 rs3087459, END1 rs5370 and GC rs2298849 in the log-additive model. Moreover, we discovered a significantly decreased serum level of 1.25-dihydroxy vitamin D in high-risk CAD patients with the A/A-A/G genotypes of the rs2228570 polymorphism of the VDR gene, the A/A genotype of the rs7041 polymorphism of the GC gene and the A/A genotype of the rs2298849 polymorphism of the GC gene.

Relationship between serum 25-hydroxyvitamin D and target organ damage in children with essential hypertension

Researchers have shown that 25-hydroxyvitamin D (25[OH] D), a kind of active vitamin D in the human body, plays a role in cardiovascular disease (CVD). Low serum 25(OH) D levels have been found to be associated with elevated blood pressure (BP) in adults. However, measurement of 25(OH) D in hypertensive children has not been documented. The aim of this study was to investigate the relationship between 25(OH) D and target organ damage (TOD) in children with essential hypertension. We recruited a total of 346 children with essential hypertension and analyzed the correlation between serum 25(OH) D and TOD. Serum 25(OH) D concentration was significantly lower in the TOD than in the no-TOD group (t = 2.416, P = 0.016), as well as significantly lower in the two-organ damage than in the single-organ damage group (t = 3.140, P = 0.002). Pearson’s correlation coefficient (PCC) indicated that serum 25(OH) D levels were negatively correlated with left ventricular mass index (LVMI; r = −0.110, P = 0.041) and albuminuria (r = −0.120, P = 0.026). Linear- regression analysis showed that 25(OH) D was a risk factor for left ventricular hypertrophy (LVH; β ± s.e. =−0.074 ± 0.036; 95% confidence interval [CI], − 0.145 to –0.003; P < 0.001) and renal damage (β ± s.e.= −0.018 ± 0.008; 95% CI, − 0.035 to –0.002; P = 0.004). In total, our data revealed that serum 25(OH) D was independently associated with hypertensive cardiac and renal damage, meaning that it was a risk factor for LVH and albuminuria in childhood hypertension.

Relationship of serum vitamin D deficiency with coronary artery disease severity using multislice CT coronary angiography

AIM

To assess the relationship between vitamin D deficiency and severity of coronary artery disease using multislice CT coronary angiography.

METHODS

100 patients diagnosed with coronary artery disease during multislice CT coronary angiography were subjected to full evaluation of coronary artery disease severity followed by measurement of serum vitamin D level.

RESULTS

The mean value of serum vitamin D level was 13.35±7.49ng/ml. 76% of the patients had vitamin D deficiency (<20ng/ml). 41% of the patients had single vessel disease, 28% had two vessel diseases, and 31% had multi-vessel disease. Patients with vitamin D deficiency had higher degree of coronary stenosis, higher coronary Ca score (p<0.001) and higher number of affected vessels compared with normal vitamin D level subgroup (p<0.001). Vitamin D level showed a significant negative correlations with age (r=-0.290, p=0.003), coronary Ca score (r=-0.630, p<0.001) and severity of coronary lesions. Multivariate linear regression analysis showed that dyslipidemia and vitamin D level were independent predictors of percent severity of coronary stenosis.

CONCLUSION

In addition to traditional cardiovascular risk factors, vitamin D deficiency looks to be independent predictor of coronary artery disease severity including percent stenosis, number of the affected vessels as well as degree of coronary calcification.

Factors affecting vitamin D status in outpatients with abdominal aortic aneurysm and peripheral artery disease- a single centre study

BACKGROUND AND AIMS

Vitamin D (VD) deficiency is considered an important risk factor for the development of atherosclerosis and aortic aneurysms. The deficiency is claimed to enhance degeneration and remodeling of collagen and elastin fibers in the artery wall, leading to its weakening and progressive dilatation. This study aimed to assess vitamin D status, in outpatients with abdominal aneurysms (AAA) and peripheral artery disease (PAD) not treated with VD, and factors affecting serum 25-OH-D levels.

METHODS AND RESULTS

This cross-sectional study involved 59 outpatients with AAA and 150 with PAD. AAA was defined as local dilation of the aorta diameter >30 mm in imaging. None of the patients was prescribed VD containing medicines. Serum 25-OH, iPTH, phosphorus and calcium levels were assessed in all study participants. VD status was categorized according to commonly used cut-offs for serum 25-OH-D (<20 ng/mL - deficiency, <30 ng/mL -insufficiency). Serum 25-OH-D levels were similar in patient with AAA and PAD [1-3Q: 26.2 (18.8-37.6) vs 21.8 (15.9-31.4) ng/mL; p = 0.30], with deficiency noted in 25.4% with AAA and 41.8% with PAD (p < 0.05). Multiple regression analysis revealed that VD deficiency was explained by past stroke episodes [OR = 2.80 (95%CI: 1.22-6.41)]. Secondary hyperparathyroidism was diagnosed in 1.7% of patients with AAA and 1.9% with PAD.

CONCLUSIONS

The frequency of VD deficiency in outpatient with AAA is not greater than in those with PAD. Past stroke episode is associated with an increased occurrence of VD deficiency in both outpatients with AAA and PAD other than sun exposure and diet.

Association of Bone Mineral Density, Vitamin D, and Serum Calcium in Intracranial Aneurysm

Aims

The objective of this study is to understand the association between bone mineral density (BMD), serum calcium, and Vitamin D in s (IA) patients.

Subjects and Methods

A total of 100 patients with IA diagnosed at the department of neurosurgery between January 2019 and December 2019 were reviewed and analyzed in this study. Computed tomography angiography was used to confirm and locate the site of aneurysms. BMD, serum calcium, and Vitamin D levels were measured.

Statistical Analysis Used

Linear or logistic regression statistical models were applied to found the association between BMD and IA size. To confirm the statistical significance, P < 0.05 (twos-tailed) was considered as statistically significant.

Results

Of the studied 100 patients, 61 patients were female and 39 were male. According to the age group, patients were divided into five categories: below 30, 31-40, 41-50, 51-60, and ≥60 years. The most common site of aneurysm observed to be the anterior communicating artery (Acom); 39.25% of the patients had Acom aneurysm followed by the middle cerebral artery (18.69%). This clearly shows that the occurrence of aneurysm is more prominent in anterior circulation as compared to posterior circulation. The results showed that there is a negative linear correlation between BMD and size of aneurysm (P = 0.00043, r =-0.12). Sex-specific analysis showed that females have lower mean BMD value as compared to males (i.e., females 0.785 ± 0.13; males 0.887 ± 0.13; P = 0.0003). We also found that the multiplicity of IAs also shows an association with BMD (i.e. mean BMD: 0.825 ± 0.14, whereas BMD of patients with multiple aneurysms was 0.747 ± 0.08; P = 0.05). Of 100 patients, 66 were observed calcium deficient (normal range: 8.8-10.2 mg/dl). The obtained mean value of calcium was 8.56 ± 0.859 standard deviation (SD), i.e., below the normal range of calcium. In the case of Vitamin D, 85% of the patients were observed Vitamin D deficient, whereas 14 patients showed Vitamin D insufficiency and merely 1 patient has Vitamin D sufficiency. The mean 25-hydroxy Vitamin D level obtained in our study was 14.57 ± 5.60 (SD), which is considered as Vitamin D deficiency.

Conclusions

The size and multiplicity of IA can be associated with BMD, calcium, and Vitamin D. The results from the research provide evidence of common pathophysiology between the development of IA and these factors.

Arterial Stiffness: A Focus on Vascular Calcification and Its Link to Bone Mineralization

This review focuses on the association between vascular calcification and arterial stiffness, highlighting the important genetic factors, systemic and local microenvironmental signals, and underlying signaling pathways and molecular regulators of vascular calcification. Elevated oxidative stress appears to be a common procalcification factor that induces osteogenic differentiation and calcification of vascular cells in a variety of disease conditions such as atherosclerosis, diabetes mellitus, and chronic kidney disease. Thus, the role of oxidative stress and oxidative stress-regulated signals in vascular smooth muscle cells and their contributions to vascular calcification are highlighted. In relation to diabetes mellitus, the regulation of both hyperglycemia and increased protein glycosylation, by AGEs (advanced glycation end products) and O-linked β-N-acetylglucosamine modification, and its role in enhancing intracellular pathophysiological signaling that promotes osteogenic differentiation and calcification of vascular smooth muscle cells are discussed. In the context of chronic kidney disease, this review details the role of calcium and phosphate homeostasis, parathyroid hormone, and specific calcification inhibitors in regulating vascular calcification. In addition, the impact of the systemic and microenvironmental factors on respective intrinsic signaling pathways that promote osteogenic differentiation and calcification of vascular smooth muscle cells and osteoblasts are compared and contrasted, aiming to dissect the commonalities and distinctions that underlie the paradoxical vascular-bone mineralization disorders in aging and diseases.

Calcitriol modulates cholesteryl ester transfer protein (CETP) levels and lipid profile in hypercholesterolemic male rabbits: A pilot study

Vitamin D3 efficacy against cardiovascular disease prevention has been reported in many experimental studies. We aimed to investigate the effect of the calcitriol or active form of Vitamin D3 (1, 25(OH) 2D3) on serum cholesteryl ester transfer protein (CETP) levels in a rabbit model of atherosclerosis. New Zealand white male rabbits were fed with 1% cholesterol diet and randomly assigned into two groups (n = 6). The case group was administrated with 50000 calcitriol (IU/kg/per wk) and the control group which administrated with calcitriol solvent (sesame oil) for 2 months. Then, after two months the lipid profile, CETP and 25OHD3 levels were measured. The serum concentration of CETP was increased after treatment with calcitriol in case group as compared to the control group (41.75 ± 3.19 vs. 34.5 ± 2.3, ng/ml, P < 0.05). We also observed higher levels of the 25OHD3 in the calcitriol group at the 1^st month (16.3 ± 1.64 vs. 12.8 ± 1.33 ng/ml) and the 2^nd month (19.5 ± 2.14 vs. 12.5 ± 1.25 ng/ml) as compared with the control group. the significant increase in the level of HDL-C was observed in the case group than the control group (P < 0.01). In addition, serum levels of LDL- Cholesterol (LDL-C), Triglyceride (TG) were reduced after assessment at 1^st and 2^nd month after administration of calcitriol. Our research indicated the significant anti-atherogenic effects of calcitriol in the rabbit model of atherosclerosis. However, increased in CETP levels by calcitriol may know as an additional way, which interfere with the anti-atherogenic effects of calcitriol.

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.

Vitamin D as A Protector of Arterial Health: Potential Role in Peripheral Arterial Disease Formation

Atherosclerotic occlusive diseases and aneurysms that affect large and medium-sized arteries outside the cardiac and cerebral circulation are collectively known as peripheral arterial disease (PAD). With a rise in the rate of aging population worldwide, the number of people diagnosed with PAD is rapidly increasing. The micronutrient vitamin D is an important steroid hormone that acts on many crucial cellular mechanisms. Experimental studies suggest that optimal levels of vitamin D have beneficial effects on the heart and blood vessels; however, high vitamin D concentrations have been implicated in promoting vascular calcification and arterial stiffness. Observations from various clinical studies shows that deficiency of vitamin D has been associated with a greater risk of PAD. Epidemiological studies have often reported an inverse relation between circulating vitamin D status measured in terms of 25-hydroxivitamin D [25(OH)D] levels and increased cardiovascular disease risk; however, randomized controlled trials did not show a consistent positive effect of vitamin D supplementation on cardiovascular disease risk or events. Even though PAD shares all the major risk factors with cardiovascular diseases, the effect of vitamin D deficiency in PAD is not clear. Current evidence suggests a strong role of vitamin D in promoting genomic and epigenomic changes. This review summarises the current literature that supports the notion that vitamin D deficiency may promote PAD formation. A better understanding of underlying pathological mechanisms will open up new therapeutic possibilities which is the main unmet need in PAD management. Furthermore, epigenetic evidence shows that a more holistic approach towards PAD prevention that incorporates a healthy lifestyle, adequate exercise and optimal nutrition may be more effective in protecting the genome and maintaining a healthy vasculature.

Vitamin D-binding protein and vitamin D receptor genotypes and 25-hydroxyvitamin D levels are associated with development of aortic and mitral valve calcification and coronary artery diseases

To assess the association between vitamin D-Binding Protein (VDBP rs7041T>G) and vitamin D receptor (VDR rs1544410G>A) gene polymorphisms with susceptibility to cardiovascular diseases in population from west of Iran. Two hundred forty-nine individuals with cardiovascular disease (92 with aortic and Mitral Valves Calcification (AMVC) and 157 with Coronary Artery Diseases (CAD) that their diseases were confirmed by echocardiography and angiography and unrelated 182 healthy controls (gender and age-matched) were selected for this case-control study. The VDR 1544410G>A, and VDBP 7041T>G genotyping were detected by PCR-RFLP, serum vitamin D and lipid concentrations were measured by ELISA and enzyme assay, respectively. The VDR rs1544410G>A gene is a strong risk factor for CAD (OR = 1.28, p = 0.002) and the dominant genotype (T/G+G/G) of VDBP 7041 T>G SNP plays a protective role (OR = 0.67, p = 0.003) in AMVC development in studied population. In addition, lower level of vitamin D strongly increased the risk of CAD (15 ± 11.02 vs. 21.3 ± 18 μg/L, p = 0.043) and AMVC (12.1 ± 13.1 vs.21.3 ± 18 μg/L, p = 0.014) development in individuals carrying T/T genotype of VDBP 7041 T>G gene polymorphism. There was a strong interaction between A allele VDR rs1544410 and G allele of VDBP rs7041 genes in a protective role (OR = 0.74, p = 0.044) in AMVC patients). CAD and AMVC patients were deficient in vitamin D, i.e. their level of vitamin D was strongly lower than that in the control group. Our findings for the first time indicated that there is a strong association between vitamin D deficiency, lipid profile and the VDR rs1544410G>A and rs7T41>G VDBP genes polymorphisms. These interactions may be one of the important factors for CAD and AMVC incidence.

The Modulatory Action of Vitamin D on the Renin-Angiotensin System and the Determination of Hepatic Insulin Resistance

Vitamin D deficiency or hypovitaminosis D is associated with increased risks of insulin resistance, type 2 diabetes mellitus (T2DM) and its related non-alcoholic fatty liver disease (NAFLD). Meanwhile, inappropriate over-activation of the renin–angiotensin system (RAS) in the liver leads to the hepatic dysfunction and increased risk of T2DM, such as abnormalities in lipid and glucose metabolism. Our previous findings have shown that calcitriol, an active metabolite of vitamin D, reduces hepatic triglyceride accumulation and glucose output in diabetic db/db mice and human hepatocellular cell HepG2 cells under insulin-resistant conditions. Notwithstanding the existence of this evidence, the protective action of vitamin D in the modulation of overexpressed RAS-induced metabolic abnormalities in the liver under insulin resistance remains to be elusive and investigated. Herein, we have reported the potential interaction between vitamin D and RAS; and its beneficial effects on the expression and function of the RAS components in HepG2 cells and primary hepatocytes under insulin-resistance states. Our study findings suggest that hormonal vitamin D (calcitriol) has modulatory action on the inappropriate upregulation of the hepatic RAS under insulin-resistant conditions. If confirmed, vitamin D supplementation might provide a nutraceutical potential as a cost-effective approach for the management of hepatic metabolic dysfunction as observed in T2DM and related NAFLD.

Vitamin D and Atherosclerotic Cardiovascular Disease

CONTEXT

A large body of experimental and observational data has implicated vitamin D deficiency in the development of cardiovascular disease. However, evidence to support routine vitamin D supplementation to prevent or treat cardiovascular disease is lacking.

EVIDENCE ACQUISITION

A comprehensive literature review was performed using Pubmed and other literature search engines.

EVIDENCE SYNTHESIS

Mounting epidemiological evidence and data from Mendelian randomization studies support a link between vitamin D deficiency and adverse cardiovascular health outcomes, but randomized trial evidence to support vitamin D supplementation is sparse. Current public health guidelines restrict vitamin D intake recommendations to the maintenance of bone health and prevention of fractures. Two recently published large trials (VITAL and ViDA) that assessed the role of moderate-to-high dose vitamin D supplementation as primary prevention for cardiovascular outcomes in the general population had null results, and previous randomized trials have also been generally negative. These findings from general population cohorts that are largely replete in vitamin D may not be applicable to chronic kidney disease (CKD) populations, in which the use of active (1α-hydroxylated) vitamin D compounds is prevalent, or to other high-risk populations. Additionally, recent trials in the CKD population, and trials using vitamin D analogues have been limited.

CONCLUSIONS

Current randomized trials of vitamin D supplementation do not support benefits for cardiovascular health, but the evidence remains inconclusive. Additional randomized trials assessing larger numbers of participants with low baseline vitamin D levels, having longer follow-up periods, and testing higher vitamin D dosages, are needed to guide clinical practice.

Effects of vitamin D supplementation along with endurance physical activity on lipid profile in metabolic syndrome patients: A randomized controlled trial

BACKGROUND AND OBJECTIVES

This study was conducted to determine the effects of vitamin D supplementation along with endurance physical activity on lipid profile among metabolic syndrome patients.

MATERIALS AND METHODS

In a parallel randomized placebo controlled trial, 70 metabolic syndrome patients, were randomly assigned into three groups. Biochemical tests were assessed as baseline and after 12 weeks of intervention. Statistical analysis was performed using SPSS version 20.

RESULTS

The mean vitamin D levels was increased significantly in both vitamin D and vitamin D plus physical activity groups (P value < 0.05). No significant change was observed in the placebo group. Additionally, there was a significant decrease in total cholesterol and LDL-C in vitamin D plus physical activity group (P value < 0.05). No significant differences in changes of triglycerides and HDL-C among the three groups (P value > 0.05). While, in vitamin D group a decreased in total cholesterol, HDL-C, LDL-C and increase in triglycerides were observed, but did not reach a statistically significant.

CONCLUSION

Daily supplementation of vitamin D for 12 weeks, along with moderate endurance physical activity, significantly increase vitamin D concentration and induce a significant reduction in lipid profile in metabolic syndrome patients.

Vitamin D and macrophage polarization in epicardial adipose tissue of atherosclerotic swine

Vitamin D functions as a potent immunomodulator by interacting with many immune cells however, its role in regulating inflammation in the epicardial adipose tissue (EAT) is unclear. In the EAT of atherosclerotic microswine that were fed with deficient, sufficient or supplemented levels of vitamin D, we evaluated the phenotype of the macrophages. Vitamin D treatment was continued for 12 months and serum 25(OH)D levels were measured regularly. Infiltration of M1/M2 macrophage was investigated by immunostaining for CCR7 and CD206, respectively in conjunction with a pan macrophage marker CD14. Significant difference in the number of CCR7+ cells was observed in the EAT from vitamin D-deficient swine compared to vitamin D-sufficient or -supplemented swine. Expression of CD206 correlated with high levels of serum 25(OH)D indicating a significant increase in M2 macrophages in the EAT of vitamin D-supplemented compared to -deficient swine. These findings suggest that vitamin D-deficiency exacerbates inflammation by increasing pro-inflammatory M1 macrophages, while vitamin D-supplementation attenuates the inflammatory cytokines and promotes M2 macrophages in EAT. This study demonstrates the significance of vitamin D mediated inhibition of macrophage mediated inflammation in the EAT during coronary intervention in addition to its immunomodulatory role. However, additional studies are required to identify the cellular mechanisms that transduce signals between macrophages and smooth muscle cells during restenosis in the presence and absence of vitamin D.

Atmospheric Pressure Variation is a Delayed Trigger for Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

There is an ongoing search for conditions that induce spontaneous subarachnoid hemorrhage (SAH). The seasonal pattern of SAH is shown in a large meta-analysis of the literature, but its explanation remains undecided. There is a clear need for sound meteorologic data to further elucidate the seasonal influence on SAH. Because of the stable and densely monitored atmospheric situation in the north of the Netherlands, we reviewed our unique cohort on the seasonal incidence of SAH and the association between SAH and local atmospheric changes.

METHODS

Our observational cohort study included 1535 patients with spontaneous SAH admitted to our neurovascular center in the north of the Netherlands between 2000 and 2015. Meteorologic data could be linked to the day of the ictus. To compare SAH incidences over the year and to test the association with meteorologic conditions, incidence rate ratios (IRRs) with corresponding 95% confidence intervals (CIs) were used, calculated by Poisson regression analyses.

RESULTS

Atmospheric pressure variations were significantly associated with aneurysmal SAH. In particular, the pressure change on the second and third day before the ictus was independently correlated to a higher incidence of aneurysmal SAH (IRR, 1.11; 95% CI, 1.00-1.23). The IRR for aneurysmal SAH in July was calculated 0.67 (95% CI, 0.49-0.92) after adjustment for temperature and atmospheric pressure changes.

CONCLUSIONS

Atmospheric pressure variations are a delayed trigger for aneurysmal SAH. Also, a significantly decreased incidence of aneurysmal SAH was noted in July.

Serum 25-Hydroxyvitamin D3 Levels Are Associated with Carotid Intima-Media Thickness and Carotid Atherosclerotic Plaque in Type 2 Diabetic Patients

Objective. To investigate the relationship between serum 25-hydroxyvitamin D3 [25(OH)D3] levels and carotid intima-media thickness (IMT) as well as carotid atherosclerotic plaque in patients with type 2 diabetes mellitus (T2DM). Methods. 314 patients with T2DM were enrolled in this study. The clinical data and laboratory examinations of subjects were recorded, such as serum 25(OH)D3, hemoglobin A1c (HbA1c), serum lipids, fasting blood glucose (FBG), and other biochemical parameters. Color Doppler ultrasound was used to measure carotid IMT and carotid atherosclerotic plaques. Patients were divided into four quartile groups according to the serum 25(OH)D3 levels from low to high: group Q1~group Q4. Results. From group Q1 to group Q4, carotid IMT and the incidence of plaque were gradually reduced. Serum 25(OH)D3 levels were lower in the plaque group compared with the nonplaque group (P < 0.01). Serum 25(OH)D3 levels were negatively correlated with the carotid IMT (r = -0.4, P < 0.01). Multiple linear stepwise regression analysis showed that serum 25(OH)D3 was independently associated with carotid IMT (β = -0.009, P < 0.01). Logistic regression analysis showed that serum 25(OH)D3 levels were independently associated with the presence of carotid plaque in T2DM (OR = 0.95; 95%CI: 0.92~0.98, P = 0.004). Conclusions. Low vitamin D status may contribute to the incidence of carotid atherosclerosis in type 2 diabetic patients.

Vitamin D Receptor Activation Reduces Angiotensin-II-Induced Dissecting Abdominal Aortic Aneurysm in Apolipoprotein E-Knockout Mice

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a vascular disorder characterized by chronic inflammation of the aortic wall. Low concentrations of vitamin D3 are associated with AAA development; however, the potential direct effect of vitamin D3 on AAA remains unknown. This study evaluates the effect of oral treatment with the vitamin D3 receptor (VDR) ligand, calcitriol, on dissecting AAA induced by angiotensin-II (Ang-II) infusion in apoE(-/-) mice.

APPROACH AND RESULTS

Oral treatment with calcitriol reduced Ang-II-induced dissecting AAA formation in apoE(-/-) mice, which was unrelated to systolic blood pressure or plasma cholesterol concentrations. Immunohistochemistry and reverse-transcription polymerase chain reaction analysis demonstrated a significant increase in macrophage infiltration, neovessel formation, matrix metalloproteinase-2 and matrix metalloproteinase-9, chemokine (CCL2 [(C-C motif) ligand 2], CCL5 [(C-C motif) ligand 5], and CXCL1 [(C-X-C motif) ligand 1]) and vascular endothelial growth factor expression in suprarenal aortic walls of apoE(-/-) mice infused with Ang-II, and all were significantly reduced by cotreatment with calcitriol. Phosphorylation of extracellular signal-regulated kinases 1/2, p38 mitogen-activated protein kinase, and nuclear factor-κB was also decreased in the suprarenal aortas of apoE(-/-) mice cotreated with calcitriol. These effects were accompanied by a marked increase in VDR-retinoid X receptor (RXR) interaction in the aortas of calcitriol-treated mice. In vitro, VDR activation by calcitriol in human endothelial cells inhibited Ang-II-induced leukocyte-endothelial cell interactions, morphogenesis, and production of endothelial proinflammatory and angiogenic chemokines through VDR-RXR interactions, and knockdown of VDR or RXR abolished the inhibitory effects of calcitriol.

CONCLUSIONS

VDR activation reduces dissecting AAA formation induced by Ang-II in apoE(-/-) mice and may constitute a novel therapeutic strategy to prevent AAA progression.

Increased Incidence of Hypovitaminosis D Among Patients Requiring Treatment for Cerebral Aneurysms

OBJECTIVE

Aneurysmal subarachnoid hemorrhage management is hampered by our incomplete understanding of what variables promote aneurysm formation, growth, and rupture. Because hypovitaminosis D has been identified as a risk factor for other vascular diseases, we examined its association with cerebral aneurysms requiring treatment.

METHODS

We retrospectively reviewed charts of patients with cerebral aneurysms with recorded 25-hydroxy vitamin D levels undergoing treatment at our institution from May 2010 to May 2015. We compared these patients with a group of patients without aneurysms. We used multivariable Poisson regression and backward elimination to identify factors associated with cerebral aneurysms, with a threshold P < 0.20. A propensity-matching algorithm was used, incorporating all factors with P < 0.10 in our regression model.

RESULTS

Patients in the aneurysm group were older than those in the control group (P = 0.001) and more likely to be female (P = 0.004), to be tobacco users (P < 0.001), and to have a diagnosis of hypertension (P = 0.001), but ethnicity, body mass index, and diabetes rates did not differ. Vitamin D levels in the aneurysm group were lower than in the control group (23.3 ± 12.3 vs. 28.7 ± 14.1 ng/mL, P = 0.001), and the patients were more likely to be vitamin D deficient (P = 0.028). Multivariable Poisson regression demonstrated that vitamin D level, tobacco use, age, and sex were significantly associated with aneurysms requiring treatment (P < 0.05). The propensity-matching algorithm confirmed a significant difference in vitamin D levels between the aneurysm and control groups (P = 0.01).

CONCLUSIONS

Patients with cerebral aneurysms requiring treatment have a significantly higher incidence of hypovitaminosis D compared with patients in a control group.

High prevalence of vitamin D deficiency and lack of association with subclinical atherosclerosis in asymptomatic patients with Type 1 Diabetes Mellitus from a Mediterranean area

AIMS

Several studies linked vitamin D deficiency with coronary artery disease (CAD). The aim of this study was to evaluate the relationship between the concentrations of 25-hydroxyvitamin D (25OHD) and the presence of early atherosclerosis in asymptomatic Type 1 Diabetes (T1D) patients with no previous history of ischemic heart disease.

METHODS

One hundred and forty-five patients with T1D (age 37.8 ± 8 years, 57 % male, all Caucasian, disease duration 20.6 ± 8.3 years, HbA1c 7.6 ± 1.4 % (60.2 ± 11.1 mmol/mol), body mass index (BMI) 25.2 ± 3.5 kg/m2, 52.4 % smokers, 23 % retinopathy, 10 % nephropathy) and 48 controls matched for age, sex, BMI and smoking habit were studied. 25OHD deficiency was defined for values ≤20 ng/mL. A sun exposure questionnaire, carotid ultrasonography to determine carotid intima-media thickness (CIMT) and the presence of atheroma plaques and cardiac computed tomography for evaluation of calcium artery calcification (CACS) were performed.

RESULTS

T1D subjects showed a high proportion of 25OHD deficiency (43.2 % vs. 21.7 %, p = 0.032). Of all, 82 % of T1D patients and 92 % of controls had a calcium score of 0. CIMT was greater in patients with T1D (0.55 ± 0.14 mm vs 0.48 ± 0.15, p = 0.01) compared with controls. T1D subjects showed no differences in the results of CACS or CIMT according to the vitamin D concentrations.

CONCLUSIONS

T1D patients have lower concentrations and twice more prevalence of 25OHD deficiency than controls. There was no association between 25OHD concentrations and subclinical CAD.

Vitamin D and atherosclerosis

PURPOSE OF REVIEW

To provide an overview of the association between vitamin D deficiency and atherosclerosis.

RECENT FINDINGS

Vitamin D exerts protective effects on atherosclerosis through multiple mechanisms. It has been shown to protect against endothelial dysfunction, vascular smooth muscle cell proliferation and migration, and modulation of the immune system, as well as the inflammatory response. In addition, vitamin D has been shown to have systemic effects on insulin resistance, dyslipidemia, and hypertension.

SUMMARY

Vitamin D deficiency is widely prevalent in the United States and worldwide. Although deficiency of this fat-soluble vitamin is usually associated with musculoskeletal disorder, it is associated with a wide range of disease processes that include multiple organ systems. Recently, there has been mounting evidence linking vitamin D deficiency to cardiovascular disease and atherosclerosis.

Links between Vitamin D Deficiency and Cardiovascular Diseases

The aim of the present paper was to review the most important mechanisms explaining the possible association of vitamin D deficiency and cardiovascular diseases, focusing on recent experimental and clinical data. Low vitamin D levels favor atherosclerosis enabling vascular inflammation, endothelial dysfunction, formation of foam cells, and proliferation of smooth muscle cells. The antihypertensive properties of vitamin D include suppression of the renin-angiotensin-aldosterone system, renoprotective effects, direct effects on endothelial cells and calcium metabolism, inhibition of growth of vascular smooth muscle cells, prevention of secondary hyperparathyroidism, and beneficial effects on cardiovascular risk factors. Vitamin D is also involved in glycemic control, lipid metabolism, insulin secretion, and sensitivity, explaining the association between vitamin D deficiency and metabolic syndrome. Vitamin D deficit was associated in some studies with the number of affected coronary arteries, postinfarction complications, inflammatory cytokines and cardiac remodeling in patients with myocardial infarction, direct electromechanical effects and inflammation in atrial fibrillation, and neuroprotective effects in stroke. In peripheral arterial disease, vitamin D status was related to the decline of the functional performance, severity, atherosclerosis and inflammatory markers, arterial stiffness, vascular calcifications, and arterial aging. Vitamin D supplementation should further consider additional factors, such as phosphates, parathormone, renin, and fibroblast growth factor 23 levels.

Vitamin D and endothelial vasodilation in older individuals: data from the PIVUS study

CONTEXT

Vitamin D plays a role in a wide range of extraskeletal processes, including vascular function. Endothelial dysfunction is a predictor of cardiovascular disease, especially in older subjects. However, the relationship between vitamin D levels and indexes of endothelial vasodilation has never been fully addressed in older individuals.

OBJECTIVE

The objective of this study was to examine the association between vitamin D and endothelial function in a large community-based sample of older subjects.

METHODS

This cross-sectional study involved 852 community-dwelling men and women aged 70 years from the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS), with complete data on vascular function and 25-hydroxyvitamin D. We evaluated endothelium-dependent vasodilation by an invasive forearm technique with acetylcholine, endothelium-independent vasodilation by sodium nitroprussiate, flow-mediated vasodilation, and the pulse wave analysis (reflectance index). Vitamin D levels were measured by chemiluminescence. We used multivariate regression models adjusted for body mass index (model 1) and for multiple confounders (high-sensitivity C-reactive protein, insulin, total cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, smoking, sex hormones, season of blood collection, hypertension, diabetes, cardiovascular medications and diseases, statin usage, plasma calcium and calcium intake, PTH, physical exercise, liver and kidney function tests, albumin; model 2).

RESULTS

In women, but not in men, vitamin D levels were positively associated with endothelium-independent vasodilation in both model 1 (β ± SE = 1.41 ± 0.54; P = .001), and model 2 (β ± SE = 2.01 ± 0.68; P = .003).We found no significant relationship between vitamin D levels and endothelium-dependent vasodilation, flow-mediated vasodilation, and reflectance index in both sexes.

CONCLUSIONS

In older women, but not in men, vitamin D is positively and independently associated with EIDV.

Vitamin D deficiency is independently associated with the extent of coronary artery disease

BACKGROUND

Vitamin D (25-OH D3) deficiency represents a rising social and economic problem in Western countries. Vitamin D has been recently reported to modulate inflammatory processes, endothelium and smooth muscle cell proliferation and even platelet function, thus potentially modulating atherothrombosis. Great interest has been addressed on its impact on cardiovascular outcome, with contrasting results. The aim of current study was to evaluate the relationship between 25-OH D3 and the extent of coronary artery disease (CAD) in a consecutive cohort of patients undergoing coronary angiography.

MATERIALS AND METHODS

Patients undergoing elective coronary angiography were included in a cross-sectional study. Fasting samples were collected for 25-OH D3 levels assessment. Significant CAD was defined as at least 1 vessel stenosis > 50%, while severe CAD as left main and/or trivessel disease, as evaluated by quantitative coronary angiography.

RESULTS

Hypovitaminosis D was observed in 70·4% of 1484 patients. Patients were divided according to vitamin D tertiles (< 9·6; 9·6-18·4; ≥ 18·4). Lower vitamin D levels were associated with age, female gender (P < 0·001), renal failure (P = 0·05), active smoking (P = 0·001), acute coronary syndrome at presentation (P < 0·001), therapy with calcium antagonists (P = 0·02) and diuretics (P < 0·001), less beta-blockers (P = 0·02) and statins (P = 0·001) use. Vitamin D was directly related to haemoglobin (P < 0·001) and inversely with platelet count (P = 0·002), total and low-density-lipoprotein cholesterol (P = 0·002 and P < 0·001) and triglycerides (P = 0·01). Vitamin D did not influence angiographic features of coronary lesions, but was associated with higher prevalence of left main or right CAD (P = 0·03). Vitamin D deficiency was significantly associated with higher prevalence of CAD (adjusted OR [95%CI] = 1·32[1·1-1·6], P = 0·004) and severe CAD (adjusted OR [95%CI] = 1·18[1-1·39], P = 0·05).

CONCLUSION

Hypovitaminosis D was observed in the vast majority of patients undergoing coronary angiography. Vitamin D deficiency is significantly associated with the prevalence and extent of CAD, especially for patients with values < 10 ng/mL. Therefore, future large studies are needed to evaluate whether vitamin D supplementation may prevent CAD and its progression.

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

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

The role of vitamin D in blood pressure, endothelial and renal function in postmenopausal women

BACKGROUND

Vitamin D is a pro-hormone that plays an essential role in the vasculature and in kidney function.

AIMS

To review the extra-skeletal effects of vitamin D on blood pressure, endothelial and renal function with emphasis on recent findings in postmenopausal women.

METHODS

Included in this review was a PubMed database search for English language articles through March 2013. This review discussed the physiology and definition of vitamin D deficiency, the recent evidence for the role vitamin D in blood pressure, vascular and renal function.

RESULTS

Experimental and epidemiological data suggest that vitamin D plays an important role in the vasculature and in kidney function. Low vitamin D concentrations appear to significantly associate with hypertension, endothelial and renal dysfunction. However, the results of clinical trials have generally been mixed. Studies specifically conducted among postmenopausal women are limited and findings are still inconsistent.

CONCLUSIONS

Definitive studies are warranted to elucidate the effects of vitamin D supplementation on vascular and renal function and a more detailed work is needed to outline the route, duration and optimal dose of supplementation. It is premature to recommend vitamin D as a therapeutic option in the improvement of vascular and renal function at the current stage.

Is hypovitaminosis D associated with abdominal aortic aneurysm, and is there a dose-response relationship?

OBJECTIVE

This study aims to investigate the association between plasma 25-hydroxyvitamin D (25(OH)D) concentrations with the presence of abdominal aortic aneurysm (AAA) and aortic diameter.

DESIGN

An observational study of 4233 community-dwelling men aged 70-88 years, who participated in a randomised controlled trial of screening for AAA.

METHODS

Infrarenal aortic diameter measured by ultrasound and 25(OH)D by immunoassay.

RESULTS

A total of 311 men (7.4%) with AAA (defined as aortic diameter ≥ 30 mm) comprised the study. Multivariable models were adjusted for age, smoking, cardiovascular disease, hypertension, diabetes, dyslipidaemia, body mass index and serum creatinine concentration. Amongst men with the lowest 25(OH)D quartile of values compared with the highest quartile, the adjusted odds ratio of having an AAA increased in a graded fashion from 1.23 (95% confidence interval (CI) 0.87-1.73) for AAA ≥ 30 mm to 5.42 (95% CI 1.85-15.88) for AAA ≥ 40 mm. Similarly, there was a dose-response relationship between 25(OH)D concentrations and the size of the AAA: every 10-nmol l(-1) decrease in 25(OH)D levels was associated with 0.49 mm (95% CI 0.11-0.87) increase in mean aortic diameter.

CONCLUSIONS

Low vitamin D status is associated with the presence of larger AAA in older men, and there is a graded inverse relationship between 25(OH)D concentrations and AAA diameter. Further research is needed to clarify the mechanisms underlying these associations.

Vitamin D supplementation in older adults: searching for specific guidelines in nursing homes

BACKGROUND

The prevalence of vitamin D insufficiency is very high in the nursing home (NH) population. Paradoxically, vitamin D insufficiency is rarely treated despite of strong clinical evidence and recommendations for supplementation. This review aims at reporting the current knowledge of vitamin D supplementation in NH and proposing recommendations adapted to the specificities of this institutional setting.

DESIGN

Current literature on vitamin D supplementation for NH residents was narratively presented and discussed by the French Group of Geriatrics and Nutrition.

RESULT

Vitamin D supplementation is a safe and well-tolerated treatment. Most residents in NH have vitamin D insufficiency, and would benefit from vitamin D supplement. However, only few residents are actually treated. Current specific and personalized protocols for vitamin D supplementation may not be practical for use in NH settings (e.g., assessment of serum vitamin D concentrations before and after supplementation). Therefore, our group proposes a model of intervention based on the systematic supplementation of vitamin D (1,000 IU/day) since the patient's admission to the NH and throughout his/her stay without the need of a preliminary evaluation of the baseline levels. Calcium should be prescribed only in case of poor dietary calcium intake.

CONCLUSION

A population-based rather than individual-based approach may probably improve the management of vitamin D insufficiency in the older population living in NH, without increasing the risks of adverse health problems. The clinical relevance and cost effectiveness of this proposal should be assessed under NH real-world conditions to establish its feasibility.

Vitamin D and risk of future hypertension: meta-analysis of 283,537 participants

The evidence on the association between baseline vitamin D status and risk of incident hypertension in general populations is limited and has not been reliably quantified. We conducted a systematic review and meta-analysis of published prospective studies evaluating the associations of baseline vitamin D status (circulating 25-hydroxyvitamin D [25(OH)D] levels and dietary vitamin D intake) with risk of hypertension. Eligible studies were identified in a literature search of MEDLINE, EMBASE, and Web of Science up to November 2012. Pooled relative risks (RRs) with 95% confidence intervals were calculated using random effects models. Generalized least-squares trend estimation was used to assess dose-response relationships. Of the 2,432 articles reviewed for eligibility, eight unique prospective cohorts with aggregate data on 283,537 non-overlapping participants and 55,816 incident hypertension cases were included. The RRs (95% CIs) for hypertension in a comparison of extreme thirds of baseline levels of vitamin D were 0.70 (0.58, 0.86) for seven studies that measured blood 25(OH) D levels and 1.00 (0.95, 1.05) for four studies that assessed dietary vitamin D intake. The pooled RR of incident hypertension per 10 ng/mL increment in baseline 25(OH)D levels was 0.88 (0.81, 0.97) in dose-response analysis. Evidence was lacking of heterogeneity among studies that measured blood 25(OH) D levels and those that assessed dietary vitamin D status. Studies are needed to determine whether the association of vitamin D with hypertension represents a causal association and also to determine whether vitamin D therapy may be beneficial in the prevention or the treatment of hypertension.

Hypovitaminosis D and peripheral arterial disease: emerging link beyond cardiovascular risk factors

Vitamin D has received increasing interest for its beneficial effect on health. Beyond its conventional role in bone metabolism, emerging evidence suggests a possible link between low vitamin D levels and cardiovascular disease (CVD), including peripheral arterial disease (PAD), and cardiovascular risk factors. Vitamin D interacts either directly with the vascular tree or indirectly through its association with cardiovascular risk factors, but the exact mechanism remains controversial. This review outlines the association between hypovitaminosis D and PAD. Both entities are quite prevalent in the general population and, therefore, their potential association might have important clinical implications. Whether vitamin D deficiency represents a novel risk factor for PAD/CVD, and whether vitamin D supplementation would reduce the burden of CVD still remains to be answered. Until then, vitamin D intake is not recommended for PAD/CVD prevention. Outdoor physical activity, coupled with adequate but safe sun exposure, is a healthy lifestyle practice suggested for the prevention of both PAD and hypovitaminosis D.

Vitamin d: popular cardiovascular supplement but benefit must be evaluated

Vitamin D deficiency is prevalent in the United States. Understanding any relationship between this deficiency and cardiovascular disease is essential. Vitamin D, as used, refers to both D(2) and D(3); both are present in over-the-counter supplements, whereas D(2) is the prescription product in the United States. In the liver, both D(2) and D(3) are converted to 25-hydroxyvitamin D, the major circulating metabolite that is measured to assess activity. The actual active form at a cellular level is 1,25-dihydroxyvitamin D; however, it does not correlate well with overall activity. Estimated vitamin D deficiency is, at times, more than 50%. Despite absence of placebo-controlled randomized trials, much information associates vitamin D deficiency with cardiovascular risk and supports benefit from vitamin D supplementation. There are also reports that explain how this benefit from vitamin D may occur. Vitamin D appears to cause only minimal changes in low- and high-density lipoprotein levels. Therefore, any cardiovascular benefit that may exist from vitamin D probably has an explanation other than an effect on levels of these lipoproteins. There is more association of vitamin D deficiency with metabolic syndrome components such as an increase in blood pressure, elevated plasma triglycerides, and impaired insulin metabolism. Possible documentation of cardiovascular benefit from vitamin D includes some evidence for endothelial stabilization and decreased inflammation in arteries. If the clinician decides that recommendation of vitamin D supplementation is warranted, it is reassuring that toxicity is rare. Furthermore, this toxicity involves doses exceeding those of most clinical trials and mainly has involved hypercalcemia. Vitamin D supplementation is easy and can be taken as a dose of 2000 IU daily on an indefinite basis. In 1997, the Food and Nutrition Board of the U.S. Institute of Medicine considered this the safe tolerable upper limit, but this is not based on current evidence. Some practitioners, especially endocrinologists, recommend vitamin D at a dose of 50,000 IU per week for 8 weeks, repeated if necessary to achieve a normal level of vitamin D. It appears appropriate to assess low vitamin D as a possible cardiovascular risk factor, but potential benefit of supplementation must be weighed against the current absence of definitive outcomes studies.

Vitamin D receptor activation and prevention of arterial ageing

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

Vitamin D status and peripheral arterial disease: evidence so far

Background

Vitamin D deficiency has recently been implicated as a contributory factor in the development of peripheral arterial disease (PAD).

Methods

A review of the published literature on PAD and vitamin D was undertaken using Medline, PubMed, and Embase, and cross-referenced. All relevant published papers on the subject were reviewed.

Results

Published studies have shown that there is a significant association between vitamin D and PAD. Populations with lower vitamin D levels are more likely to develop PAD in a graded manner. Higher amputation rates are also observed among patients with PAD and lower vitamin D levels. In addition, vitamin D deficiency is significantly associated with increased risk of cardiovascular adverse events. This was also observed in the mouse model where low vitamin D led to the development of atherosclerosis.

Conclusion

This study shows that vitamin D deficiency could be an independent risk factor for the development of PAD and that this risk factor is easily correctable. Further studies should look into the effects of vitamin D supplementation in patients with PAD.

Vitamin D in chronic heart failure

Recent evidence suggests a number of mechanisms whereby vitamin D may positively influence the pathophysiology of heart failure. These include actions on the renin-angiotensin system, calcium handling, reduction of proinflammatory cytokines, and improvements in endothelial function and blood pressure. Observational data suggest that low vitamin D levels are common in patients with heart failure and are associated with worse exercise capacity and natriuretic peptide levels. Little interventional data are currently available, but evidence to date does not support vitamin D supplementation, even in patients with low vitamin D levels. Further studies are needed to establish whether larger doses of vitamin D given over a longer period of time can reduce symptoms, hospitalization, and mortality in heart failure.

Vitamin D and metabolic health with special reference to the effect of vitamin D on serum lipids

Considering that the vitamin D receptor as well as the 1-α-hydroxylase enzyme that converts 25-hydroxyvitamin D (25(OH)D) to its active form 1,25-dihydroxyvitamin D have been found in tissues throughout the body, it is likely that vitamin D is important for more than the calcium balance. Accordingly, low serum levels of 25(OH)D have been associated with mortality, cardiovascular disease, type 2 diabetes, hypertension and obesity. Low serum levels of 25(OH)D have also been associated with an unfavourable lipid profile, which could possible explain the relation with cardiovascular disease and mortality. However, the relation between vitamin D and lipids have so far received little attention and is therefore the main focus of the present review. A PubMed search identified 22 cross-sectional studies where serum levels of 25(OH)D and lipids were related and that included a minimum of 500 subjects, and 10 placebo-controlled double-blind intervention studies with vitamin D where more than 50 subjects were included. In all the cross-sectional studies serum 25(OH)D was positively associated with high-density lipoprotein cholesterol (HDL-C) resulting in a favourable low-density lipoprotein cholesterol (LDL-C) (or total cholesterol) to HDL-C ratio. There was also a uniform agreement between studies on a negative relation between serum 25(OH)D and triglycerides (TG). On the other hand, the intervention studies gave divergent results, with some showing a positive and some a negative effect of vitamin D supplementation. However, none of the intervention studies were specifically designed for evaluating the relation between vitamin D and lipids, none had hyperlipemia as an inclusion criterion, and none were sufficiently powered. In only one study was a significant effect seen with an 8% (0.28 mmol/L) increase in serum LDL-C and a 16% (0.22 mmol/L) decrease in serum TG in those given vitamin D as compared to the placebo group. Accordingly, the effect of vitamin D supplementation on serum lipids is at present uncertain. Considering the numerous other promising vitamins and minerals that when properly tested have been disappointing, one should wait for the results of forthcoming vitamin D intervention studies before drawing conclusions on potential beneficial effects of vitamin D.

Effects of vitamin D on the peripheral adaptive immune system: a review

Epidemiological studies have shown that a poor vitamin D status is associated with an increased risk of several diseases, including autoimmune diseases. The immune regulatory function of vitamin D is thought to have an important role in these associations. Cells of the adaptive immune system have shown to be direct targets of the vitamin D metabolites. Besides being direct targets, cells of the adaptive immune system express the enzymes involved in the metabolism of vitamin D, enabling them to locally convert 25(OH)D into its active metabolite 1,25(OH)2D. In this review, the effects of vitamin D on cells of the adaptive immune system are described. Experimental data in vitro show that vitamin D skews cells of the adaptive immune system toward a more tolerogenic status which might be exploited in the treatment of autoimmune diseases. However, it should be noticed that in vivo effects may differ from in vitro effects due to the cross-talk between different vitamin D sensitive cells, but data support the view that vitamin D is positively involved in maintaining or restoring immune homeostasis. Upcoming vitamin D supplementation trials will further elucidate the in vivo effects of vitamin D on the immune system and its potency to serve as an immune regulating agent in autoimmune diseases.

Vitamin D hormone: a multitude of actions potentially influencing the physical function decline in older persons

Vitamin D, a secosteroid (pro)-hormone, has been traditionally considered as a key regulator of bone metabolism, and calcium and phosphorous homeostasis through a negative feedback with the parathyroid hormone. However, during the last 20 years, the role played by vitamin D has been largely revised by recognizing its pleiotropic action on a wide spectrum of systems, apparatuses and tissues. Thus, vitamin D has growingly been involved as a primary determinant of biological modifications and specific clinical conditions. The effect of vitamin D on skeletal muscle and related outcomes (including physical function decline and disability) is surely one of the most relevant to study in the context of global aging. In the present review, the subclinical and clinical consequences of vitamin D deficiency/insufficiency, extremely frequent conditions in older age, are described. Special focus is given to skeletal muscle and physical function. Limitations of available scientific evidence on the topic are also discussed.