Racial differences in the association of serum 25-hydroxyvitamin D concentration with coronary heart disease events

The Role of Vitamin D in CKD Stages 3 to 4: Report of a Scientific Workshop Sponsored by the National Kidney Foundation

Deficiency of 25-hydroxyvitamin D (25[OH]D) is common in patients with chronic kidney disease stages 3 and 4 and is associated with poor outcomes. However, the evaluation and management of vitamin D deficiency in nephrology remains controversial. This article reports on the proceedings from a "controversies conference" on vitamin D in chronic kidney disease that was sponsored by the National Kidney Foundation. The report outlines the deliberations of the 3 work groups that participated in the conference. Until newer measurement methods are widely used, the panel agreed that clinicians should classify 25(OH)D "adequacy" as concentrations > 20ng/mL without evidence of counter-regulatory hormone activity (ie, elevated parathyroid hormone). The panel also agreed that 25(OH)D concentrations < 15ng/mL should be treated irrespective of parathyroid hormone level. Patients with 25(OH)D concentrations between 15 and 20ng/mL may not require treatment if there is no evidence of counter-regulatory hormone activity. The panel agreed that nutritional vitamin D (cholecalciferol, ergocalciferol, or calcifediol) should be supplemented before giving activated vitamin D compounds. The compounds need further study evaluating important outcomes that observational studies have linked to low 25(OH)D levels, such as progression to end-stage kidney disease, infections, fracture rates, hospitalizations, and all-cause mortality. We urge further research funding in this field.

The Role of Vitamin D and Oxidative Stress in Chronic Kidney Disease

Chronic kidney disease (CKD) is a major non-communicable disease associated with high rates of premature morbidity and mortality. The prevalence of hypovitaminosis D (deficiency of 25(OH)D or 25D) is greater in racial/ethnic minorities and in patients with CKD than the general population. Low 25D is associated with bone and mineral disorders as well as immune, cardiometabolic and cardiovascular (CV) diseases. Thus, it has been suggested that low 25D contributes to the poor outcomes in patients with CKD. The prevalence of hypovitaminosis D rises progressively with advancing severity of kidney disease with over 30% of patients with CKD stage 3 and 70% patients with CKD stage 5 estimated to have low levels of 25D. This report describes several of the abnormal physiologic and counter-regulatory actions related to low 25D in CKD such as those in oxidative stress and inflammatory systems, and some of the preclinical and clinical evidence, or lack thereof, of normalizing serum 25D levels to improve outcomes in patients with CKD, and especially for the high risk subset of racial/ethnic minorities who suffer from higher rates of advanced CKD and hypovitaminosis D.

Update on Chronic Kidney Disease Mineral and Bone Disorder in Cardiovascular Disease

Chronic kidney disease mineral and bone disorder (MBD) encompasses changes in mineral ion and vitamin D metabolism that are widespread in the setting of chronic kidney disease and end-stage renal disease. MBD components associate with cardiovascular disease in many epidemiologic studies. Through impacts on hypertension, activation of the renin-angiotensin-aldosterone system, vascular calcification, endothelial function, and cardiac remodeling and conduction, MBD may be a direct and targetable cause of cardiovascular disease. However, assessment and treatment of MBD is rife with challenges owing to biological tensions between its many components, such as calcium and phosphorus with their regulatory hormones fibroblast growth factor 23 and parathyroid hormone; fibroblast growth factor 23 with its co-receptor klotho; and vitamin D with control of calcium and phosphorus. These complex interactions between MBD components hinder the simple translation to clinical trials, which ultimately are needed to prove the benefits of treating MBD. Deeper investigation using precision medicine tools and principles, including genomics and individualized risk assessment and therapy, may help move the field closer toward clinical applications. This review provides a high-level overview of conventional and precision epidemiology in MBD, potential mechanisms of cardiovascular disease pathogenesis, and guiding therapeutic principles for established and emerging treatments.

MANAGEMENT OF ENDOCRINE DISEASE: Therapeutics of Vitamin D

OBJECTIVE

The central role of vitamin D in bone health is well recognized. However, controversies regarding its clinical application remain. We therefore aimed to review the definition of hypovitaminosis D, the skeletal and extra-skeletal effects of vitamin D and the available therapeutic modalities.

DESIGN

Narrative and systematic literature review.

METHODS

An international working group that reviewed the current evidence linking bone and extra-skeletal health and vitamin D therapy to identify knowledge gaps for future research.

RESULTS

Findings from observational studies and randomized controlled trials (RCTs) in vitamin D deficiency are discordant, with findings of RCTs being largely negative. This may be due to reverse causality with the illness itself contributing to low vitamin D levels. The results of many RCTs have also been inconsistent. However, overall evidence from RCTs shows vitamin D reduces fractures (when administered with calcium) in the institutionalized elderly. Although controversial, vitamin D reduces acute respiratory tract infections (if not given as bolus monthly or annual doses) and may reduce falls in those with the lowest serum 25-hydroxyvitamin D (25OHD) levels. However, despite large ongoing RCTs with 21 000–26 000 participants not recruiting based on baseline 25OHD levels, they will contain a large subset of participants with vitamin D deficiency and are adequately powered to meet their primary end-points.

CONCLUSIONS

The effects of long-term vitamin D supplementation on non-skeletal outcomes, such as type 2 diabetes mellitus (T2DM), cancer and cardiovascular disease (CVD) and the optimal dose and serum 25OHD level that balances extra-skeletal benefits (T2DM) vs risks (e.g. CVD), may soon be determined by data from large RCTs.

Rationale and design of a placebo controlled randomized trial to assess short term, high-dose oral cholecalciferol on select laboratory and genomic responses in African Americans with hypovitaminosis D

Cardiovascular Disease (CVD) and related disorders remain a leading cause of health disparities and premature death for African Americans. Hypovitaminosis D is disproportionately prevalent in African Americans and has been linked to CVD and CVD risk factors including hypertension, diabetes and obesity. Thus, hypovitaminosis D may represent a common pathway influencing CV risk factors in a select subgroup of persons. The purpose of this paper is to report the study design of a prospective eight week prospective double-blind randomized, placebo-controlled trial (n = 330 allocated 2:1 to intervention vs. control) to assess the effect of placebo vs. high-dose oral cholecalciferol (100,000 IU vitamin D3 at baseline and week 2) on 6-week change of select biologic cardiometabolic risk factors (including parathyroid hormone to assess biologic activity, pro-inflammatory/pro-thrombotic/fibrotic markers, insulin sensitivity and vitamin D metabolites) and their relationship to vitamin D administration and modification by vitamin D receptor polymorphisms in overweight, hypertensive African Americans with hypovitaminosis D. Findings from this trial will present insights into potential causal links between vitamin D repletion and mechanistic pathways of CV disease, including established and novel genomic markers.

Vitamin D deficiency and risk of cardiovascular diseases: a narrative review

Vitamin D, a fat-soluble prohormone, has wide-ranging roles in the regulation of many physiological processes through their interactions with the vitamin D receptors (VDR). It plays a major role in bones and calcium metabolism. Vitamin D deficiency is not uncommon and it has been associated with many health-related issues, including skeletal and non-skeletal complications. The association of low vitamin D and cardiovascular diseases and risk factors has been explored in both animal and human studies. However, studies and trials on the effect of vitamin D supplementation on cardiovascular risk factors and hypertension are conflicting with inconsistent results. Therefore, large, well-powered randomized controlled trials are warranted. If successful, supplementation with easy and low-cost vitamin D can impact our health positively. Here, we summarized the evidence for the association of vitamin D, cardiovascular diseases and risk factors, including coronary artery diseases, stroke, and hypertension, and mortality, with special consideration to resistant hypertension.

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.

Cholecalciferol Supplementation Promotes Bone Turnover in Chinese Adults with Vitamin D Deficiency

BACKGROUND

Bone turnover markers (BTMs) are proposed as alternative indicators for bone mineral density in diagnosis and management of osteoporosis. However, little is known about the effects of vitamin D supplementation on BTMs in nonwhite populations.

OBJECTIVE

We aimed to investigate the responses in BTMs after vitamin D supplementation in Asians.

METHODS

In this secondary data analysis of a randomized, double-blind, placebo-controlled trial, 448 Chinese adults [mean ± SD age: 31.9 ± 8.0 y; mean ± SD body mass index (kg/m2): 22.1 ± 2.6; 69% were women] with vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] <50 nmol/L) received 2000 IU/d cholecalciferol or placebo for 20 wk. Serum concentrations of 25(OH)D, parathyroid hormone (PTH), calcium, and markers of bone formation and resorption were measured at weeks 0 and 20. Intention-to-treat analysis was applied, and between-group differences were compared by general linear models with adjustments.

RESULTS

Cholecalciferol supplementation increased the serum bone alkaline phosphatase (BALP) concentration (+1.7 ± 1.9 µg/L) significantly more than placebo (+1.1 ± 1.7 µg/L; P = 0.004), but not circulating concentrations of procollagen type I N-terminal propeptide (PINP), β-isomerized C-terminal telopeptide of type I collagen (β-CTX), or tartrate-resistant acid phosphatase 5b (TRAP5b) (P ≥ 0.53). Notably, a pooled analysis indicated that changes in serum 25(OH)D were positively associated with changes in serum BALP, PINP, and TRAP5b (r = 0.07-0.16, P ≤ 0.02), but inversely with changes in PTH (r = -0.15, P < 0.001). Among cholecalciferol-treated participants, individuals who achieved serum 25(OH)D ≥75 nmol/L had greater increases in serum β-CTX (224% compared with 146%; P = 0.02) and TRAP5b (22.2% compared with 9.1%; P = 0.007), but smaller decreases in serum calcium (-1.3% compared with -1.9%; P = 0.005) and calcium-phosphorus product (-2.6% compared with -3.3%; P = 0.02) compared with those with serum 25(OH)D <75 nmol/L.

CONCLUSIONS

Daily supplementation with 2000 IU cholecalciferol for 20 wk may promote bone formation in Chinese adults with vitamin D deficiency. More studies are needed to elucidate the potential clinical implications of BTMs.This trial was registered at clinicaltrials.gov as NCT01998763.

Measurement of Vitamin D for Epidemiologic and Clinical Research: Shining Light on a Complex Decision

Vitamin D is a fat-soluble vitamin that is synthesized in the skin with exposure to sunlight or is ingested from dietary supplements or food. There has been a dramatic increase in research on vitamin D, linking it with health outcomes as varied as reproductive function, infection, cardiovascular disease, and cancer. The study of vitamin D has generated much excitement, partly because there is an ideal intervention: Low levels may be common and can be remedied with widely available supplements. Determination of vitamin D status is complex and has advanced dramatically in the past 5 years. In this paper, we begin by describing important considerations for measurement of total 25-hydroxyvitamin D (25(OH)D), the biomarker traditionally assessed in epidemiologic studies. While 25(OH)D remains the most commonly measured biomarker, emerging evidence suggests that other related analytes may contribute to the characterization of an individual's vitamin D status (e.g., vitamin D-binding protein, bioavailable and free 25(OH)D, the C-3 epimer of 25(OH)D, 1,25-dihydroxyvitamin D, and 24,25-dihydroxyvitamin D). The measurement of these analytes is also complex, and there are important considerations for deciding whether their measurement is warranted in new research studies. Herein we discuss these issues and provide the reader with an up-to-date synthesis of research on vitamin D measurement options and considerations.

Transethnic Evaluation Identifies Low-Frequency Loci Associated With 25-Hydroxyvitamin D Concentrations

Context

Vitamin D inadequacy is common in the adult population of the United States. Although the genetic determinants underlying vitamin D inadequacy have been studied in people of European ancestry, less is known about populations with Hispanic or African ancestry.

Objective

The Trans-Ethnic Evaluation of Vitamin D (TRANSCEN-D) genomewide association study (GWAS) consortium was assembled to replicate genetic associations with 25-hydroxyvitamin D [25(OH)D] concentrations from the Study of Underlying Genetic Determinants of Vitamin D and Highly Related Traits (SUNLIGHT) meta-analyses of European ancestry and to identify genetic variants related to vitamin D concentrations in African and Hispanic ancestries.

Design

Ancestry-specific (Hispanic and African) and transethnic (Hispanic, African, and European) meta-analyses were performed with Meta-Analysis Helper software (METAL).

Patients or Other Participants

In total, 8541 African American and 3485 Hispanic American (from North America) participants from 12 cohorts and 16,124 European participants from SUNLIGHT were included in the study.

Main Outcome Measures

Blood concentrations of 25(OH)D were measured for all participants.

Results

Ancestry-specific analyses in African and Hispanic Americans replicated single nucleotide polymorphisms (SNPs) in GC (2 and 4 SNPs, respectively). An SNP (rs79666294) near the KIF4B gene was identified in the African American cohort. Transethnic evaluation replicated GC and DHCR7 region SNPs. Additionally, the transethnic analyses revealed SNPs rs719700 and rs1410656 near the ANO6/ARID2 and HTR2A genes, respectively.

Conclusions

Ancestry-specific and transethnic GWASs of 25(OH)D confirmed findings in GC and DHCR7 for African and Hispanic American samples and revealed findings near KIF4B, ANO6/ARID2, and HTR2A. The biological mechanisms that link these regions with 25(OH)D metabolism warrant further investigation.

Vitamin D Levels, Body Composition, and Metabolic Factors in Asian Indians: Results from the Metabolic Syndrome and Atherosclerosis in South Asians Living in America Pilot Study

BACKGROUND/AIMS

Asian Indians have a high prevalence of vitamin D deficiency and metabolic syndrome. Vitamin D deficiency is associated with an increased risk of cardiovascular disease and diabetes.

METHODS

We performed a cross-sectional study of 150 Asian Indians (50% male) from the San Francisco Bay Area. We assessed the association between 25-OH vitamin D (25-OHD) levels and vitamin D deficiency with body composition (anthropometric and radiographic measures) and metabolic outcomes.

RESULTS

In both men and women, the presence of vitamin D deficiency was associated with higher systolic (p = 0.004) and diastolic (p = 0.01) blood pressure, and fasting glucose (p = 0.01). Only in women, vitamin D deficiency status was associated with higher body mass index (BMI), waist-to-hip ratio, visceral fat area, and hepatic fat content after adjusting for age, income, and physical activity level. In women, 25-OHD was also associated with fasting glucose after adjusting for age, income, and physical activity and further adjusting for BMI and waist circumference (β -2.1, 95% CI -0.86 to -0.01, p = 0.04). This association between vitamin D deficiency and metabolic parameters was not significant in men.

CONCLUSIONS

A lower level of 25-OHD and vitamin D deficiency were associated with higher levels of metabolic factors among Asian Indians. Our findings suggest that 25-OHD metabolism may differ by the distribution of adipose tissue and involve previously unexplored pathways accounting for the variability in the role of vitamin D in cardiovascular disease.

Plasma 25-hydroxyvitamin D concentration and subsequent risk of total and site specific cancers in Japanese population: large case-cohort study within Japan Public Health Center-based Prospective Study cohort

OBJECTIVE

To evaluate the association between pre-diagnostic circulating vitamin D concentration and the subsequent risk of overall and site specific cancer in a large cohort study.

DESIGN

Nested case-cohort study within the Japan Public Health Center-based Prospective Study cohort.

SETTING

Nine public health centre areas across Japan.

PARTICIPANTS

3301 incident cases of cancer and 4044 randomly selected subcohort participants.

EXPOSURE

Plasma concentration of 25-hydroxyvitamin D measured by enzyme immunoassay. Participants were divided into quarters based on the sex and season specific distribution of 25-hydroxyvitamin D among subcohorts. Weighted Cox proportional hazard models were used to calculate the multivariable adjusted hazard ratios for overall and site specific cancer across categories of 25-hydroxyvitamin D concentration, with the lowest quarter as the reference.

MAIN OUTCOME MEASURE

Incidence of overall or site specific cancer.

RESULTS

Plasma 25-hydroxyvitamin D concentration was inversely associated with the risk of total cancer, with multivariable adjusted hazard ratios for the second to fourth quarters compared with the lowest quarter of 0.81 (95% confidence interval 0.70 to 0.94), 0.75 (0.65 to 0.87), and 0.78 (0.67 to 0.91), respectively (P for trend=0.001). Among the findings for cancers at specific sites, an inverse association was found for liver cancer, with corresponding hazard ratios of 0.70 (0.44 to 1.13), 0.65 (0.40 to 1.06), and 0.45 (0.26 to 0.79) (P for trend=0.006). A sensitivity analysis showed that alternately removing cases of cancer at one specific site from total cancer cases did not substantially change the overall hazard ratios.

CONCLUSIONS

In this large prospective study, higher vitamin D concentration was associated with lower risk of total cancer. These findings support the hypothesis that vitamin D has protective effects against cancers at many sites.

Association of vitamin D deficiency and VDBP gene polymorphism with the risk of AMI in a Pakistani population

Objective

To investigate the relationship of vitamin D deficiency and risk of AMI in a Pakistani population, and to find out any association between vitamin D binding protein (VDBP) genotypes and risk of AMI in this population.

Methods

In a comparative cross-sectional study, 246 patients (age: 20-70 years; 171 males and 75 females) with first AMI were enrolled with informed consent. Similarly, 345 healthy adults (230 males and 115 females) were enrolled as controls. Their fasting serum samples were analyzed for 25 (OH) vitamin D, lipids and other biomarkers using kit methods, while DNA was analyzed for VDBP genotypes using PCR-RFLP based methods. Chi-squared test and logistic regression were used for association of vitamin D deficiency and VDBP genotypes with AMI.

Results

Mean serum concentration of 25(OH) vitamin D was significantly lower in AMI patients compared to healthy subjects (p=0.015) and percent vitamin D deficiency was higher in AMI patients compared to healthy subjects (p=0.003). VDBP IF-IF genotype was positively associated with the risk of AMI in subject above 45 years after adjusting for potential confounders [OR = 9.86; 95% CI=1.16 to 83.43].

Conclusion

Vitamin D deficiency and VDBP IF-IF genotype are associated with AMI in Pakistani adults.

Vitamin D, Calcium, and Cardiovascular Disease: A"D"vantageous or "D"etrimental? An Era of Uncertainty

While the function of vitamin D in regulating calcium homeostasis is well established, there has been growing interest in its role in the prevention of numerous chronic diseases, including cardiovascular disease (CVD). There is mounting epidemiological evidence suggesting that vitamin D deficiency is linked to increased CVD risk. However, the results of previous vitamin D supplementation trials have yielded mixed results in regards to cardiovascular health, and the results of ongoing large-scale randomized controlled trials are not yet available. Further complicating the issue, calcium supplementation, which is often prescribed concurrently with vitamin D, has been associated with increased CVD risk in some (but not all) studies. Thus, it is currently unclear whether vitamin D supplements, particularly for those that are deficient, can help prevent the development of CVD. In addition, there has not been uniform consensus regarding the threshold of 25-hydroxyvitamin D levels that constitutes "sufficiency" across organizational guidelines. This review will provide an update on the most recent evidence regarding the effects of vitamin D and calcium supplements on CVD clinical outcomes, summarize ongoing vitamin D trials, and discuss the current but remarkably disparate recommendations regarding vitamin D deficiency screening and supplementation.

Biomarkers of Key Biological Pathways in CVD

This review provides background on the laboratory design for MESA (Multi-Ethnic Study of Atherosclerosis) as well as the approach used in MESA to select biomarkers for measurement. The research related to the multitude of circulating and urinary biomarkers of inflammation and other novel and emerging biological pathways in MESA is summarized by domain, or pathway, represented by the biomarker. The contributions of MESA biomarkers to our knowledge of these key pathways in the development and progression of atherosclerosis, cardiovascular disease, diabetes, kidney disease, and pulmonary disease are highlighted, as are the contributions of MESA to recommendations for clinical use of several of these biomarkers. In addition, contributions of MESA to multicohort genomics consortia and current collaborations in transomics and metabolomics are noted.

Racial Variations in the Markers of Mineral Bone Disorders in CKD Patients in South Africa

Introduction

Several studies showed that serum intact parathyroid hormone (PTH), phosphate, and vitamin D levels differ across races. These comparative studies were largely carried out between Caucasians and black Americans. However, little is known of the existence of these associations in an African population with chronic kidney disease (CKD).

Methods

This cross-sectional multicenter study involved 293 CKD patients from 3 renal units in Johannesburg, South Africa.

Results

The 293 CKD patients (208 blacks, 85 whites) had an overall mean age of 51.1 ± 13.6 years, and black patients were significantly younger than the white patients (48.4 ± 13.6 years vs. 57.1 ± 15.5 years; P < 0.001). Compared with whites, blacks had higher median intact PTH (498 [range: 37–1084] pg/ml vs. 274 [range: 131–595] pg/ml; P = 0.03), alkaline phosphatase (122 [range: 89–192] U/L vs. 103 [range: 74–144] U/L; p = 0.03), and mean 25 OH vitamin D₃ (26.8 ± 12.7 ng/ml vs. 22.7 ± 12.2 ng/ml, P = 0.01) levels, whereas their median fibroblast growth factor (FGF) level was 23 (100 [range: 34–639] pg/ml vs. 233 [range: 80–1370] pg/ml; P = 0.002), and their mean serum phosphate (1.3 ± 0.5 vs. 1.5 ± 0.5; P = 0.001) levels were significantly lower. In multivariable analyses, black race was independently associated with increased log PTH (β = 0.488, P = 0.01) and decreased log FGF-23 (β = −0.636, P = 0.02). Similarly, blacks had a 3.08 times higher likelihood (95% confidence interval: 1.51–6.30; P = 0.002) of developing severe hyperparathyroidism than whites.

Conclusion

This study highlighted the existence of racial differences in the circulating markers of mineral bone disorders in an African CKD population.

Vitamin D Status and Kidney Function Decline in HIV-Infected Men: A Longitudinal Study in the Multicenter AIDS Cohort Study

Vitamin D may play an important role in a range of disease processes. In the general population, lower vitamin D levels have been associated with kidney dysfunction. HIV-infected populations have a higher risk of chronic kidney disease. Few studies have examined the link between lower vitamin D levels and kidney function decline among HIV-infected persons. We investigated the associations of serum 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] with kidney function decline in a cohort of HIV-infected white and black men under highly active antiretroviral therapy treatment in the vitamin D ancillary study of the Multicenter AIDS Cohort Study. The associations of 25(OH)D and 1,25(OH)2D with annual change in estimated glomerular filtration rate (eGFR) were evaluated using linear mixed effects models. This study included 187 whites and 86 blacks with vitamin D measures and eGFR ≥60 ml/min/1.73 m2 at baseline. Over a median follow-up of 8.0 years, lower 25(OH)D levels were significantly associated with faster eGFR decline in whites (adjusted annual change in eGFR, tertile 1: -2.06 ml/min/1.73 m2 vs. tertile 3: -1.23 ml/min/1.73 m2, p trend .03), while no significant association was detected in blacks. Lower 1,25(OH)2D was associated with faster kidney function decline in both whites and blacks, although the estimates were not statistically significant. In conclusion, lower 25(OH)D levels were significantly associated with faster eGFR decline in a cohort of HIV-infected white men, but not in those with black ancestry. Further research is warranted to investigate the association of 25(OH)D and 1,25(OH)2D with kidney function decline in larger and ethnically diverse populations.

Independent and Synergistic Associations of Biomarkers of Vitamin D Status With Risk of Coronary Heart Disease

OBJECTIVE

To comprehensively evaluate the independent associations and potential interactions of vitamin D-related biomarkers including total and bioavailable 25-hydroxyvitamin D (25OHD), VDBP (vitamin D binding protein), and parathyroid hormone (PTH) with risk of coronary heart disease (CHD).

APPROACH AND RESULTS

We prospectively identified incident cases of nonfatal myocardial infarction and fatal CHD among women in the Nurses' Health Study during 20 years of follow-up (1990-2010). Using risk-set sampling, 1 to 2 matched controls were selected for each case. The analysis of 25OHD and PTH included 382 cases and 575 controls; the analysis of VDBP included 396 cases and 398 controls. After multivariate adjustment, plasma levels of total 25OHD, bioavailable 25OHD, and PTH were not significantly associated with CHD risk. VDBP was associated with a lower CHD risk with an extreme-quartile odds ratio of 0.60 (95% confidence interval, 0.39-0.92; P trend=0.02). When examining the biomarkers jointly, a significant, inverse association between 25OHD and CHD was observed among participants with higher PTH levels (P for interaction=0.02). The odds ratio (95% confidence interval) comparing the highest quartile of 25OHD to lowest was 0.43 (0.23-0.82; P trend=0.003) when PTH levels were above population median (35.3 pg/mL), whereas among the rest of participants the corresponding odds ratio (95% confidence interval) was 1.28 (0.70-2.36; P trend=0.43).

CONCLUSIONS

Our data suggest that higher 25OHD levels were associated with a lower CHD risk when PTH levels were high, whereas no association was observed for participants with low PTH levels. VDBP but not bioavailable 25OHD was independently associated with lower CHD risk.

Relation of Serum Vitamin D to Risk of Mitral Annular and Aortic Valve Calcium (from the Multi-Ethnic Study of Atherosclerosis)

Serum 25-hydroxyvitamin D [25(OH)D] concentration has been identified as a possible modifiable risk factor for cardiovascular disease (CVD). We hypothesized that serum 25(OH)D concentration would be associated with calcifications of the left-sided heart valves, which are markers of CVD risk. Aortic valve calcium (AVC) and mitral annular calcium (MAC) were quantified from cardiac computed tomography scans performed on 5,530 Multi-Ethnic Study of Atherosclerosis participants at the baseline examination (2000 to 2002) and at a follow-up visit at either Examination 2 (2002 to 2004) or Examination 3 (2004 to 2005). 25(OH)D was measured from serum samples collected at the baseline examination. Using relative risk regression, we evaluated the multivariable-adjusted risk of prevalent and incident AVC and MAC in this ethnically diverse population free of clinical CVD at baseline. The mean age of participants was 62 ± 10 years; 53% were women, 40% white, 26% black, 21% Hispanic, and 12% Chinese. Prevalent AVC and MAC were observed in 12% and 9% of study sample, respectively. There were no significant associations between 25(OH)D and prevalent AVC or MAC. Over a mean follow-up of 2.5 years, 4% developed incident AVC and 5% developed incident MAC. After adjusting for demographic variables, each 10 ng/ml higher serum 25(OH)D was associated with a 15% (relative risk 0.85, 95% confidence interval 0.74 to 0.98) lower risk of incident MAC but not AVC. However, this association was no longer significant after adjusting for lifestyle and CVD risk factors. Results suggest a possible link between serum 25(OH)D and the risk for incident MAC, but future studies with longer follow-up are needed to further test this association.

Associations of Vitamin D-Binding Globulin and Bioavailable Vitamin D Concentrations With Coronary Heart Disease Events: The Multi-Ethnic Study of Atherosclerosis (MESA)

CONTEXT

Low 25-hydroxyvitamin D [25(OH)D] is associated with coronary heart disease (CHD) in people who are white and Chinese but not black or Hispanic. Vitamin D binding globulin (VDBG) avidly binds 25(OH)D, reducing its bioavailability, and differs in isoform and concentration by race.

OBJECTIVE

Evaluate associations of VDBG with CHD and whether accounting for VDBG or estimating bioavailable 25(OH)D explains the heterogeneity of the association of 25(OH)D with CHD.

DESIGN AND SETTING

We conducted a case-cohort study within the Multi-Ethnic Study of Atherosclerosis. Participants with an incident CHD event over 12 years of follow-up (n = 538) and a randomly assigned subcohort (n = 999) were included. We measured baseline 25(OH)D, VDBG, and isoforms using mass spectrometry and estimated bioavailable 25(OH)D from published equations.

RESULTS

VDBG was associated with an increased risk of CHD [hazard ratio, 1.77 (95% confidence interval, 1.46 to 2.14) per standard deviation increment, P < 0.0001], without evidence of heterogeneity by race or isoform (each P for interaction > 0.1). Low total 25(OH)D was differentially associated with CHD events, by race, with or without adjustment for VDBG (P for interaction = 0.04 or 0.05, respectively). Associations of 25(OH)D with CHD were strengthened with adjustment for VDBG among participants who were white or Chinese, and bioavailable 25(OH)D was associated with CHD events only among white participants.

CONCLUSIONS

High VDBG concentration was associated with CHD events in all racial and ethnic groups. Incorporation of VDBG strengthened existing associations of 25(OH)D with CHD but did not explain racial heterogeneity in associations of 25(OH)D with CHD.

Serum Phosphate Is Associated With Fracture Risk: The Rotterdam Study and MrOS

Extreme phosphate levels (P) have been associated with mineralization defects and increased fracture risk. Whether P within normal range is related to bone health in the general population is not well understood. To investigate the association of P with bone mineral density (BMD) and fracture risk, we assessed two population-based cohorts: the Dutch Rotterdam Study (RS-I, RS-II, RS-III; n = 6791) and the US Osteoporotic Fractures in Men (MrOS; n = 5425) study. The relationship of P with lumbar spine (LS) and femoral neck (FN) BMD was tested in all cohorts via linear models; fracture risk was tested in RS-I, RS-II, and MrOS through Cox models, after follow-up of 8.6, 6.6, and 10.9 years, respectively. Adjustments were made for age, body mass index, smoking, serum levels of calcium, potassium, 25-hydroxyvitamin D, estimated glomerular filtration rate (eGFR), FN-BMD, prevalent diabetes, and cardiovascular disease. Additional adjustments were made for phosphate intake, parathyroid hormone, and fibroblast growth factor 23 levels in MrOS. We further stratified by eGFR. Results were pooled through study-level meta-analyses. Hazard ratios (HR) and betas (β) (from meta-analyses) are expressed per 1 mg/dL P increase. P was positively associated with fracture risk in men and women from RS, and findings were replicated in MrOS (pooled HR all [95% CI]: 1.47 [1.31-1.65]). P was associated with fracture risk in subjects without chronic kidney disease (CKD): all (1.44 [1.26-1.63]) and in men with CKD (1.93 [1.42-2.62]). P was inversely related to LS-BMD in men (β: -0.06 [-0.11 to -0.02]) and not to FN-BMD in either sex. In summary, serum P was positively related to fracture risk independently from BMD and phosphate intake after adjustments for potential confounders. P and LS-BMD were negatively related in men. Our findings suggest that increased P levels even within normal range might be deleterious for bone health in the normal population. © 2017 American Society for Bone and Mineral Research.

Physical Activity, Vitamin D, and Incident Atherosclerotic Cardiovascular Disease in Whites and Blacks: The ARIC Study

CONTEXT

Physical activity (PA) is associated with 25-hydroxyvitamin D [25(OH)D] levels. Both are associated with atherosclerotic cardiovascular disease (ASCVD), but their joint association with ASCVD risk is unknown.

OBJECTIVE

To examine the relationship between PA and 25(OH)D, and assess effect modification of 25(OH)D and PA with ASCVD.

DESIGN

Cross-sectional and prospective study.

SETTING

Community-dwelling cohort.

PARTICIPANTS

A total of 10,342 participants free of ASCVD, with moderate- to vigorous-intensity PA assessed (1987 to 1989) and categorized per American Heart Association (AHA) guidelines (recommended, intermediate, or poor).

MAIN OUTCOME MEASURES

Serum 25(OH)D levels (1990 to 1992) and ASCVD events (i.e., incident myocardial infarction, fatal coronary disease, or stroke) through 2013.

RESULTS

Participants had mean age of 54 years, and were 57% women, 21% black, 30% 25(OH)D deficient [<20 ng/mL (<50 nmol/L)], and <40% meeting AHA-recommended PA. PA was linearly associated with 25(OH)D levels in whites. Whites meeting recommended PA were 37% less likely to have 25(OH)D deficiency [relative risk, 0.63 (95% confidence interval [CI], 0.56, 0.71)]; there was no significant association in blacks. Over 19.3 years of follow-up, 1800 incident ASCVD events occurred. Recommended PA was associated with reduced ASCVD risk [hazard ratio [HR], 0.78 (95% CI, 0.65, 0.93) and 0.76 (95% CI, 0.62, 0.93)] among participants with intermediate [20 to <30 ng/mL (50 to <75 nmol/L)] and optimal [≥30 ng/mL (≥75 nmol/L)] 25(OH)D, respectively, but not among those with deficient 25(OH)D (P for interaction = 0.04).

CONCLUSION

PA is linearly associated with higher 25(OH)D levels in whites. PA and 25(OH)D may have synergistic beneficial effects on ASCVD risk.

Serum 25-hydroxyvitamin D and the risk of cardiovascular disease: dose-response meta-analysis of prospective studies

Background: During the past decade, an increasing number of prospective studies have focused on the association between vitamin D and cardiovascular disease (CVD). However, the evidence on the relation between serum 25-hydroxyvitamin D [25(OH)D] and the risk of overt CVD is inconclusive.Objective: We performed a dose-response meta-analysis to summarize and prospectively quantify the RR of low serum 25(OH)D concentration and total CVD (events and mortality).Design: We identified relevant studies by searching PubMed and EMBASE up to December 2015 and by hand-searching reference lists. Prospective studies based on the general population and reported RRs and 95% CIs were included. A random-effects model was used to calculate the pooled RRs. Nonlinear association was assessed by using restricted cubic spline analyses.Results: A total of 34 publications with 180,667 participants were eligible for the meta-analysis. We included 32 publications (27 independent studies) for total CVD events and 17 publications (17 independent studies) for CVD mortality. We observed an inverse association between serum 25(OH)D and total CVD events and CVD mortality, and the pooled RRs per 10-ng/mL increment were 0.90 (95% CI: 0.86, 0.94) for total CVD events and 0.88 (95% CI: 0.80, 0.96) for CVD mortality. A nonlinear association was detected for total CVD events (P-nonlinear < 0.001) and CVD mortality (P-nonlinear = 0.022).Conclusion: Serum 25(OH)D concentration was inversely associated with total CVD events and CVD mortality from the observed studies.

LOWER SERUM 25-HYDROXYVITAMIN D IS ASSOCIATED WITH OBESITY BUT NOT COMMON CHRONIC CONDITIONS: AN OBSERVATIONAL STUDY OF AFRICAN AMERICAN AND CAUCASIAN MALE VETERANS

OBJECTIVE

The study examined whether vitamin D insufficiency is a predictor of prevalent and/or incident common chronic conditions in African American men (AAM) and Caucasian American men (CAM).

METHODS

A total of 1,017 men were recruited at an urban VA medical center and followed prospectively for a mean of 5.4 years. Prevalent and incident chronic conditions evaluated were: obesity, type 2 diabetes, cancer, depression, dementia, and cardiovascular disease (CVD, including coronary artery disease [CAD], cerebrovascular accident [CVA], and congestive heart failure [CHF]). Univariate and multivariate regressions were performed to examine the association between 25-hydroxyvitamin D (25[OH]D) and these chronic illnesses.

RESULTS

This analysis was limited to 955 men (65.5% AAM, 27.2% CAM, 6.4% Hispanic) who had at least 1 year of follow-up (range, 1.0 to 7.1 years). Univariate analysis of the entire group showed that 25(OH)D correlated negatively with body mass index (BMI). There was no correlation between 25(OH)D and prevalent CVD (including separate analyses for CAD, CVA, and CHF), cancer, depression, dementia, all-cause mortality, or incident cancer, CAD, or CVA. Independent predictors of prevalent common conditions included increasing age, BMI, smoking, alcohol and polysubstance use, but not 25(OH)D levels.

CONCLUSION

The study does not support previously suggested associations of low vitamin D levels with prevalent common chronic conditions or increased risk for cancer, CAD, and CVA in a population of men with high burden of chronic disease. The finding that smoking and alcohol and polysubstance use are predictors of chronic conditions is an important reminder for addressing these risks during patient encounters.

ABBREVIATIONS

AAM = African American men BMI = body mass index CAD = coronary artery disease CAM = Caucasian American men CHF = congestive heart failure CI = confidence interval CVA = cerebrovascular accident CVD = cardiovascular disease HTN = hypertension OR = odds ratio T2DM = type 2 diabetes mellitus VAMC = Veteran Administration Medical Center 25(OH)D = 25-hydroxyvitamin D.

Standardized serum 25-hydroxyvitamin D concentrations are inversely associated with cardiometabolic disease in U.S. adults: a cross-sectional analysis of NHANES, 2001-2010

BACKGROUND

Previously reported associations between vitamin D status, as measured by serum 25-hydroxyvitamin D [25(OH)D] concentrations, and cardiometabolic risk factors were largely limited by variability in 25(OH)D assay performance. In accordance with the Vitamin D Standardization Program, serum 25(OH)D measurement was recently standardized in the National Health and Nutrition Examination Survey (NHANES) to reduce laboratory and method related differences in serum 25(OH)D results. We evaluated the overall and ethnic-specific associations between the newly standardized serum 25(OH)D concentrations and cardiometabolic risk in U.S. adults.

METHODS

This study examined standardized 25(OH)D data from five cycles of the NHANES (2001-2010). The total sample included 7674 participants (1794 Mexican-Americans, 4289 non-Hispanic whites, and 1591 non-Hispanic blacks) aged ≥ 20 years who were examined in the morning after overnight fasting. Serum 25(OH)D was directly measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 2007-2010, and was predicted from LC-MS/MS equivalents for 2001-2006. Serum 25(OH)D levels were categorized into quartiles (<43.4, 43.4-58.6, 58.7-74.2, ≥74.3 nmol/L). Cardiometabolic risk was defined by the homeostatic model assessment of insulin resistance (HOMA-IR), metabolic syndrome (MetS), and Framingham cardiovascular disease (CVD) risk. Prevalence ratios and 95% confidence intervals were calculated using modified Poisson regression.

RESULTS

After full adjustment for confounders, serum 25(OH)D ≥74.3 nmol/L was associated with lower cardiometabolic risk compared to 25(OH)D <43.4 nmol/L in the overall sample [HOMA-IR: 0.70 (0.59, 0.84); MetS: 0.82 (0.74, 0.91); CVD risk: 0.78 (0.66, 0.91)]. These associations remained significant in Mexican-Americans [HOMA-IR: 0.54 (0.35, 0.82); MetS: 0.73 (0.55, 0.96)], non-Hispanic whites [HOMA-IR: 0.81 (0.68, 0.96); MetS: 0.84 (0.73, 0.95); CVD risk: 0.78 (0.64, 0.93)]; and in non-Hispanic blacks [HOMA-IR: 0.67 (0.45, 0.99); MetS: 0.75 (0.56, 0.97); CVD risk: 0.58 (0.41, 0.81)].

CONCLUSIONS

Low vitamin D status is a significant risk factor for cardiometabolic disease in U.S. adults based on standardized serum 25(OH)D results, irrespective of ethnic background. Future studies using standardized 25(OH)D data are needed to confirm these results, particularly amongst U.S. blacks with 25(OH)D concentrations above 75 nmol/L.

Serum 25-hydroxyvitamin D is associated with incident peripheral artery disease among white and black adults in the ARIC study cohort

BACKGROUND AND AIMS

Low 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with peripheral artery disease (PAD). Prevalence of low 25(OH)D and PAD differ between whites and blacks. However, these associations have not been studied prospectively or in a population based cohort. We tested the hypothesis that low 25(OH)D is associated with greater risk of incident PAD in white and black adults.

METHODS

25(OH)D was measured in serum collected at ARIC visit 2 (1990-1992). We followed 11,789 ARIC participants free of PAD at visit 2 through 2011 for incident PAD events. 25(OH)D (ng/mL) was categorized as deficient (<20), insufficient (20 to <30) or sufficient (≥30). PAD was defined by an ankle brachial index (ABI) of <0.9 at ARIC visits 3 or 4 or a hospital diagnosis with an ICD-9 code indicating PAD during follow-up. Analysis used multivariable-adjusted Cox proportional hazards regressions.

RESULTS

Over a mean follow-up of 17.1 years, 1250 incident PAD events were identified. 22% of whites and 61% of blacks were 25(OH)D deficient. After adjustment for demographic characteristics, the hazard ratio (95% CI) of PAD in participants with deficient versus sufficient 25(OH)D was 1.49 (1.26, 1.76). Inclusion of BMI, physical activity, and smoking status attenuated the association [1.25 (1.06, 1.48)]. The association between 25(OH)D and PAD was qualitatively stronger in blacks (p for interaction = 0.20).

CONCLUSIONS

Deficient 25(OH)D was associated with increased risk of PAD in black and white participants. Whether treatment of low vitamin D through supplementation or modest sunlight exposure prevents PAD is unknown.

Vitamin D and Cardiovascular Disease: Can Novel Measures of Vitamin D Status Improve Risk Prediction and Address the Vitamin D Racial Paradox?

PURPOSE OF REVIEW

To provide a state-of-the-art update on some emerging measures of vitamin D status and discuss how assessment of these key vitamin D metabolites might improve prognostication of risk for cardiovascular disease (CVD) outcomes.

RECENT FINDINGS

Vitamin D deficiency is a highly prevalent condition and relatively easy to treat with supplementation and/or modest sunlight exposure. A substantial body of experimental and epidemiological evidence suggest that vitamin D deficiency is a risk factor for CVD. Most epidemiologic studies to date have focused on total 25-hydroxyvitamin D [25(OH)D] concentrations, which is the established marker of vitamin D stores. However, there is emerging evidence that other novel markers of vitamin D metabolism may better characterize 'true' vitamin D status. Some key novel measures include bioavailable 25(OH)D, free 25(OH)D, 1-25 dihydroxyvitamin D, 24,25-dihydroxyvitamin D3 [24,25(OH)₂D3], and ratio of 24,25(OH)₂D3 to 25(OH)D [the vitamin D metabolic ratio]. Utilization of these biomarkers may enhance understanding of the association between vitamin D and CVD risk, and may provide explanation for the observation that 25(OH)D is a stronger CVD risk factor in whites than blacks.

SUMMARY

Novel measures of vitamin D status could potentially change clinical practice regarding how patients are currently screened for vitamin D status and defined as vitamin D deficient or not. However, whether measuring any of these alternate markers of vitamin D status can provide further insight regarding CVD risk beyond the traditionally measured 25(OH)D concentrations is uncertain at this time. This is an area where further research is strongly needed.

High Serum Alkaline Phosphatase, Hypercalcaemia, Race, and Mortality in South African Maintenance Haemodialysis Patients

Objective. To determine the association between serum total alkaline phosphatase (TAP) and mortality in African maintenance haemodialysis patients (MHD). Patients and Methods. The study enrolled a total of 213 patients on MHD from two dialysis centers in Johannesburg between January 2009 and March 2016. Patients were categorized into a low TAP group (≤112 U/L) versus a high TAP group (>112 U/L) based on a median TAP of 112 U/L. Results. During the follow-up period of 7 years, there were 55 (25.8%) deaths. After adjusting for cofounders such as age, other markers of bone disorder, and comorbidity (diabetes mellitus), patients in the high TAP group had significantly higher risk of death compared to patients in the low TAP group (hazard ratio, 2.50; 95% CI 1.24-5.01, P = 0.01). Similarly, serum calcium >2.75 mmol/L was associated with increased risk of death compared to patients within levels of 2.10-2.37 mmol/L (HR 6.34, 95% CI 1.40-28.76; P = 0.02). The HR for death in white patients compared to black patients was 6.88; 95% CI 1.82-25.88; P = 0.004. Conclusion. High levels of serum alkaline phosphatase, hypercalcaemia, and white race are associated with increased risk of death in MHD patients.

Gender and Racial/Ethnic Disparities: Cumulative Screening of Health Risk Indicators in 20-50 Year Olds in the United States

This study explored potential gender and racial/ethnic disparities in overall health risk related to 24 health risk indicators selected across six domains: socioeconomic, health status and health care, lifestyle, nutritional, clinical, and environmental. Using the 2003-2006 National Health and Nutrition Examination Surveys (NHANES), it evaluated cross-sectional data for 5,024 adults in the United States. Logistic regression models were developed to estimate prevalence odds ratios (PORs) adjusted for smoking, health insurance status, and age. Analyses evaluated disparities associated with 24 indicator variables of health risk, comparing females to males and four racial/ethnic groups to non-Hispanic Whites. Non-Hispanic Blacks and Mexican Americans were at greater risk for at least 50% of the 24 health risk indicators, including measures of socioeconomic status, health risk behaviors, poor/fair self-reported health status, multiple nutritional and clinical indicators, and blood lead levels. This demonstrates that cumulative health risk is unevenly distributed across racial/ethnic groups. A similarly high percentage (46%) of the risk factors was observed in females. Females as compared to males were more likely to have lower income, lower blood calcium, poor/fair self-reported health, more poor mental health days/month, higher medication usage and hospitalizations, and higher serum levels of some clinical indicators and blood cadmium. This analysis of cumulative health risk is responsive to calls for broader-based, more integrated assessment of health disparities that can help inform community assessments and public health policy.

Assessment of vitamin D status – a changing landscape

In recent years it has been shown that vitamin D deficiency is associated with an increased incidence as well as the progression of a broad range of diseases including osteoporosis, rickets, cardiovascular disease, autoimmune disease, multiple sclerosis and cancer. Consequently, requests for the assessment of vitamin D status have increased dramatically. Despite significant progress in the analysis of vitamin D metabolites and an expansion of our pathophysiological knowledge of vitamin D, the assessment of vitamin D status remains a challenging and partially unresolved issue. Current guidelines from scientific bodies recommend the measurement of 25-hydroxy vitamin D (25-OHD) in blood as the preferred test. However, growing evidence indicates significant limitations of this test, including analytical aspects and interpretation of results. In addition, the relationships between 25-OHD and various clinical indices, such as bone mineral density and fracture risk, are rather weak and not consistent across races. Recent studies have systematically investigated new markers of vitamin D status including the vitamin D metabolite ratio (VMR) (ratio between 25-OHD and 24,25-dihydroxy vitamin D), bioavailable 25-OHD [25-OHD not bound to vitamin D binding protein (DBP)], and free 25-OHD [circulating 25-OHD bound to neither DBP nor albumin (ALB)]. These parameters may potentially change how we will assess vitamin D status in the future. Although these new biomarkers have expanded our knowledge about vitamin D metabolism, a range of unresolved issues regarding their measurement and the interpretation of results prevent their use in daily practice. It can be expected that some of these issues will be overcome in the near future so that they may be considered for routine use (at least in specialized centers). In addition, genetic studies have revealed several polymorphisms in key proteins of vitamin D metabolism that affect the circulating concentrations of vitamin D metabolites. The affected proteins include DBP, 7-dehydrocholesterol synthase and the vitamin D receptor (VDR). Here we aim to review existing knowledge regarding the biochemistry, physiology and measurement of vitamin D. We will also provide an overview of current and emerging biomarkers for the assessment of vitamin D status, with particular attention methodological aspects and their usefulness in clinical practice.

Effects of Genetic and Nongenetic Factors on Total and Bioavailable 25(OH)D Responses to Vitamin D Supplementation

CONTEXT

Little is known about how genetic and nongenetic factors modify responses of vitamin D supplementation in nonwhite populations.

OBJECTIVE

To investigate factors modifying 25-hydroxyvitamin D [25(OH)D] and bioavailable 25(OH)D [25(OH)DBio] responses after vitamin D3 supplementation.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION

In this 20-week, randomized, double-blinded, placebo-controlled trial, 448 Chinese with vitamin D deficiency received 2000 IU/d vitamin D3 or placebo.

MAIN OUTCOME MEASURES

Serum 25(OH)D, vitamin D-binding protein (VDBP), parathyroid hormone (PTH) and calcium were measured, and 25(OH)DBio was calculated based on VDBP levels. Six common polymorphisms in vitamin D metabolism genes were genotyped.

RESULTS

Between-arm net changes were +30.6 ± 1.7 nmol/L for 25(OH)D, +2.7 ± 0.2 nmol/L for 25(OH)DBio, and -5.2 ± 1.2 pg/mL for PTH, corresponding to 70% [95% confidence interval (CI), 62.8% to 77.2%] net reversion rate for vitamin D deficiency at week 20 (P < 0.001). Only 25(OH)DBio change was positively associated with calcium change (P < 0.001). Genetic factors (GC-rs4588/GC-rs7041, VDR-rs2228570, and CYP2R1-rs10741657; P ≤ 0.04) showed stronger influences on 25(OH)D or 25(OH)DBio responses than nongenetic factors, including baseline value, body mass index, and sex. An inverse association of PTH-25(OH)D was demonstrated only at 25(OH)D of <50.8 (95% CI, 43.6 to 59.0) nmol/L.

CONCLUSIONS

Supplemented 2000 IU/d vitamin D3 raised 25(OH)D and 25(OH)DBio but was unable to correct deficiency in 25% of Chinese participants, which might be partially attributed to the effect of genetic modification. More studies are needed to elucidate appropriate vitamin D recommendations for Asians and the potential clinical implications of 25(OH)DBio.

The effects of vitamin D on severity of coronary artery atherosclerosis and lipid profile of cardiac patients

INTRODUCTION

A deficiency of 25-hydroxyvitamin D (25(OH)D) (the standard biomarker for vitamin D status) can have multiple impacts on the cardiovascular system. The aim of the study was to assess of the influence of 25(OH)D on severity of coronary atherosclerosis and lipid profile.

MATERIAL AND METHODS

The study involved prospectively 637 patients subject to coronary catheterization. The stage of coronary atherosclerosis was assessed using the Coronary Artery Surgery Study score (CASSS). Plasma concentration of 25(OH)D was measured using an electrochemiluminescent immunoassay. The levels of total cholesterol (TC), high-density cholesterol (HDL-C) and triglycerides (TG) were measured using the enzymatic method, and the concentration of low-density cholesterol (LDL-C) was calculated with the Friedewald equation.

RESULTS

The average level of 25(OH)D was 15.85 ng/ml. A higher level of 25(OH)D was observed in men (16.28 ng/ml vs. 15.1 ng/ml; p = 0.027). The study did not reveal any significant correlation between the level of 25(OH)D and severity of coronary atherosclerosis. It was observed however that the increase of 25(OH)D level results in an increased number of patients without significant lesions in the coronary arteries. In the whole group of women and men in the age group of 70-80 years an inverse relationship was observed between the level of 25(OH) and the severity of coronary atherosclerosis. The whole study group showed a statistically significant inverse correlation of the 25(OH)D level with TC (p = 0.0057), LDL-C (p = 0.00037) and TG (p = 0.00017).

CONCLUSIONS

Women and men over 70 years showed an inverse correlation of the 25(OH)D level and the stage of coronary atherosclerosis. Deficiency of 25(OH)D affects the levels of TC, LDL-C and TG.

25-Hydroxyvitamin D Levels and Markers of Subclinical Myocardial Damage and Wall Stress: The Atherosclerosis Risk in Communities Study

BACKGROUND

Low 25-hydroxyvitamin D (25[OH]D) is associated with increased cardiovascular disease risk. Less known is whether 25(OH)D deficiency contributes to subclinical myocardial damage and wall stress (high-sensitivity cardiac troponin T [hs-cTnT] and N-terminal pro-brain natriuretic peptide [NT-proBNP]) or whether associations vary among subgroups.

METHODS AND RESULTS

Overall, 11 311 Atherosclerosis Risk in Communities participants without prevalent cardiovascular disease had 25(OH)D, hs-cTnT, and NT-proBNP measured at baseline (1990-1992), and 8990 had measurements of hs-cTnT and NT-proBNP repeated 6 years later. We examined associations of deficient 25(OH)D (<20 ng/mL) with prevalent elevated hs-cTnT (≥14 ng/L) and NT-proBNP (≥100 pg/mL), change in hs-cTnT and NT-proBNP, and incident elevated hs-cTnT and NT-proBNP. We tested for interactions by age (<56 and ≥56 years), sex, and race. In fully adjusted models, 25(OH)D was not associated with prevalent elevated hs-cTnT and NT-proBNP. Deficient 25(OH)D, however, was associated with increased 6-year change in hs-cTnT (β=0.54 ng/L [95% CI 0.08-1.01]) but not change in NT-proBNP. Deficiency in 25(OH)D was not associated with incident elevated hs-cTnT in the overall cohort but was associated with incident elevated hs-cTnT in younger but not older adults (relative risk 2.18 [95% CI 1.21-3.94] versus 0.78 [95% CI 0.56-1.08], respectively; P=0.01 for interaction by age). Deficient 25(OH)D was also associated with incident elevated NT-proBNP in men but not women (P=0.01 for interaction by sex).

CONCLUSIONS

Vitamin D deficiency was associated with increased 6-year change in hs-cTnT levels. Hypothesis-generating differences in associations by age and sex, but not race, were observed. If these associations are causal, further research is needed to understand mechanisms by which low 25(OH)D confers increased risk in these subgroups and whether treating deficient 25(OH)D can prevent myocardial damage and wall stress.

Consistent ethnic specific differences in diabetes risk and vitamin D status in the National Health and Nutrition Examination Surveys

Previous findings from the Third National Health and Nutrition Examination Survey (NHANES III), a representative sample of the US population carried out in 1988-1994, showed an inverse association between diabetes risk and serum concentrations of 25-hydroxyvitamin D (25(OH)D) in non-Hispanic whites and Mexican-Americans but not in non-Hispanic blacks. The study aim was to determine if this same pattern in ethnic variation occurred in more recent NHANES surveys. Cross-sectional data came from the NHANES carried out from 1988 to 1994 (NHANES III) and from 2001 to 2006 (NHANES 01-06). The analysis included 11,331 people (5641 non-Hispanic white, 2714 non-Hispanic black and 2976 Mexican American) without known diabetes mellitus, fasting for ≥8h and aged ≥20 years, with available measurements of 25(OH)D, fasting glucose, fasting insulin and body mass index (BMI). Adjusting for age, gender, BMI, leisure time physical activity and season, higher levels of 25(OH)D were associated with decreased fasting glucose, decreased fasting insulin, and decreased diabetes risk in both non-Hispanic whites and Mexican Americans for both surveys and when combined. When combining NHANES III and NHANES 01-06 the odds ratio (95% confidence interval) for having diabetes was 0.28 (0.19, 0.41) in the highest 25(OH)D quartile compared to the lowest quartile in non-Hispanic whites, and 0.13 (0.06, 0.28) in Mexican Americans (both p<0.0001); but 1.54 (0.62, 3.82) in non-Hispanic blacks, among whom 25(OH)D was not associated with fasting glucose, fasting insulin, or diabetes risk (p>0.05). There was a significant interaction between non-Hispanic whites and Mexican Americans combined, compared with non-Hispanic blacks, when 25(OH)D was regressed against fasting glucose (p=0.016) but not against fasting insulin (p>0.05). The major finding in both NHANES surveys of consistent inverse associations between serum 25(OH)D concentrations and diabetes risk in non-Hispanic whites and Mexican Americans, but not in non-Hispanic blacks, suggests this finding is unlikely due to chance.

Vitamin D deficiency and incident stroke risk in community-living black and white adults

BACKGROUND

Black individuals are at greater risk of stroke and vitamin D deficiency than white individuals. Epidemiologic studies have shown that low 25-hydroxyvitamin D concentrations are associated with increased risk of stroke, but these studies had limited representation of black individuals.

METHODS

We examined the association of 25-hydroxyvitamin D with incident stroke in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a cohort of black and white adults ≥45 years of age. Using a case-cohort study design, plasma 25-hydroxyvitamin D was measured in 610 participants who developed incident stroke (cases) and in 937 stroke-free individuals from a stratified cohort random sample of REGARDS participants (comparison cohort).

RESULTS

In multivariable models adjusted for socio-demographic factors, co-morbidities and laboratory values including parathyroid hormone, lower 25-hydroxyvitamin D concentrations were associated with higher risk of stroke (25-hydroxyvitamin D >30 ng/mL reference; 25-hydroxyvitamin D concentrations 20-30 ng/mL, hazard ratio 1.33, 95% confidence interval (95% CI) 0.89,1.96; 25-hydroxyvitamin D <20 ng/mL, hazard ratio 1.85, 95% CI 1.17, 2.93). There were no statistically significant differences in the association of lower 25-hydroxyvitamin D with higher risk of stroke in black vs. white participants in fully adjusted models (hazard ratio comparing lowest vs. highest 25-hydroxyvitamin D category 2.62, 95% CI 1.18, 5.83 in blacks vs. 1.64, 95% CI 0.83, 3.24 in whites, P(interaction) = 0.82). The associations were qualitatively unchanged when restricted to ischemic or hemorrhagic stroke subtypes or when using race-specific cut-offs for 25-hydroxyvitamin D categories.

CONCLUSIONS

Vitamin D deficiency is a risk factor for incident stroke and the strength of this association does not appear to differ by race.

Serum vitamin D status and bacterial vaginosis prevalence and incidence in Zimbabwean women

BACKGROUND

Bacterial vaginosis, a highly prevalent vaginal condition, is correlated with many adverse reproductive outcomes. In some studies, low vitamin D status (measured as serum 25-hydroxyvitamin D, 25[OH]D) has been associated with increased prevalence of bacterial vaginosis.

OBJECTIVES

We examined the cross-sectional association between vitamin D status and prevalence of bacterial vaginosis, separately for pregnant and nonpregnant women. Using prospectively collected data, we also characterized the effect of time-varying vitamin D status on incident bacterial vaginosis.

STUDY DESIGN

We quantified 25(OH)D in stored sera collected quarterly from 571 Zimbabwean women participating in the Hormonal Contraception and Risk of HIV Acquisition Study. The analysis was restricted to women not using hormonal contraception. We characterized associations between vitamin D insufficiency (defined as 25[OH]D ≤ 30 ng/mL vs > 30 ng/mL) and prevalence of bacterial vaginosis among nonpregnant women at the enrollment visit and among pregnant women at the first follow-up visit that pregnancy was detected. Among women who were negative for bacterial vaginosis at enrollment (n = 380), we also assessed the effect of time-varying vitamin D status on incident bacterial vaginosis. We used the Liaison 25(OH)D total assay to measure 25(OH)D. Bacterial vaginosis was diagnosed via Nugent score.

RESULTS

At enrollment, the prevalence of bacterial vaginosis was 31% and overall median 25(OH)D was 29.80 ng/mL (interquartile range, 24.70-34.30 ng/mL): 29.75 ng/mL (interquartile range, 25.15-33.95 ng/mL) among women with bacterial vaginosis, and 29.90 ng/mL (interquartile range, 24.70-34.50 ng/mL) among women without bacterial vaginosis. Among pregnant women, the prevalence of bacterial vaginosis was 27% and overall median 25(OH)D was 29.90 ng/mL (interquartile range, 24.10-34.00 ng/mL): 30.80 ng/mL (interquartile range, 26.10-36.90 ng/mL) among women with bacterial vaginosis, and 29.10 ng/mL (interquartile range, 23.80-33.45 ng/mL) among women without bacterial vaginosis. Vitamin D levels ≤ 30 ng/mL were not associated with a prevalence of bacterial vaginosis in nonpregnant women (adjusted prevalence ratio, 1.04; 95% confidence interval, 0.81-1.34) or pregnant women (adjusted prevalence ratio, 0.88, 95% confidence interval, 0.51-1.54). Vitamin D levels ≤ 30 ng/mL were similarly not associated with incident bacterial vaginosis (adjusted hazard ratio, 0.98, 95% confidence interval, 0.73-1.31). Our findings were robust to alternative specifications of vitamin D status including using a cut point for vitamin D deficiency of < 20 ng/mL vs ≥ 20 ng/mL and modeling 25(OH)D as a continuous variable.

CONCLUSION

Among reproductive-age Zimbabwean women, insufficient vitamin D was not associated with increased bacterial vaginosis prevalence or incidence. Given established associations between bacterial vaginosis and poor reproductive outcomes, identification of factors leading to high bacterial vaginosis prevalence is urgently needed.

Vitamin D deficiency is independently associated with greater prevalence of erectile dysfunction: The National Health and Nutrition Examination Survey (NHANES) 2001-2004

BACKGROUND AND AIMS

Erectile dysfunction (ED) and atherosclerotic cardiovascular disease (ASCVD) share many common risk factors, and vascular ED is a marker for increased ASCVD risk. Low 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with increased ASCVD risk, but less is known regarding the relationship of low 25(OH)D with ED. We determined whether 25(OH)D deficiency is associated with ED independent of ASCVD risk factors.

METHODS

We performed cross-sectional analyses of 3390 men aged ≥20 years free of ASCVD who participated in NHANES 2001-2004. Serum 25(OH)D was measured by the DiaSorin radioimmunoassay; deficiency was defined as levels <20 ng/ml (<50 nmol/L). Self-reported ED, assessed by a single validated question, was defined as men who reported being "never" or "sometimes able" to maintain an erection. We assessed the relationship between 25(OH)D deficiency and ED prevalence using adjusted Poisson regression methods.

RESULTS

After accounting for NHANES sampling, the weighted prevalence of 25(OH)D deficiency and of ED were 30% and 15.2%, respectively. 25(OH)D levels were lower in men with vs. those without ED (mean 22.8 vs 24.3 ng/mL, respectively; p = 0.0005). After adjusting for lifestyle variables, comorbidities, and medication use, men with 25(OH)D deficiency had a higher prevalence of ED compared to those with levels ≥30 ng/ml (Prevalence Ratio 1.30, 95% CI 1.08-1.57).

CONCLUSION

In this cross-sectional analysis of a representative sample of U.S. men, vitamin D deficiency was associated with an increased prevalence of ED independent of ASCVD risk factors. Additional research is needed to evaluate whether treating vitamin D deficiency improves erectile function.

Increased Bone Resorption: A Possible Pathophysiological Link Between Hypovitaminosis D and Peripheral Arterial Disease

OBJECTIVE/BACKGROUND

Vitamin D deficiency has been associated with the prevalence and severity of peripheral arterial disease (PAD); nevertheless, data on bone turnover in patients with PAD is lacking. The present study investigates a possible relationship between the markers of bone turnover and the presence and severity of PAD.

METHODS

The study examined 143 patients, with a mean ± SD age of 75.3 ± 8.5 years (range 50.0-93.0 years), of both sexes, admitted to a department of internal medicine. All patients underwent ankle brachial index (ABI) assessment by Doppler velocimetry. Serum levels of 25(OH) vitamin D and two markers of bone turnover, C-terminal telopeptide of type I collagen (sCTX) and bone isoenzyme of alkaline phosphatase, were measured. The differences between patients with normal ABI and patients with PAD were analyzed. Pearson and Spearman correlation coefficients were calculated and independent predictors were identified through a stepwise linear regression analysis. Odds ratios were calculated with a logistic regression model.

RESULTS

Compared with patients with a normal ABI (≥0.90), patients with PAD (ABI < 0.90) presented with significantly lower levels of 25(OH) vitamin D (12.2 ± 9.6 ng/mL vs. 16.7 ± 8.7 ng/mL; p = .006) and a significantly higher concentration of sCTX (1.1 ± 0.7 ng/mL vs. 0.6 ± 0.4 ng/mL; p < .001). There was a positive correlation between ABI and serum concentration of 25 (OH) vitamin D (r = 0.3; p < .001), whereas ABI was inversely correlated with the concentration of sCTX (r = -0.358; p < .001). At logistic regression analysis, age, cigarette smoking, and both vitamin D and sCTX were independent predictors of an ABI < 0.90.

CONCLUSION

These results support the hypothesis that hypovitaminosis D and increased bone turnover are risk factors for the presence and severity of PAD. Furthermore, the presence of PAD, even if asymptomatic and diagnosed by a reduced ABI, could identify a population at risk for osteoporosis and osteomalacia.

Vitamin D status of black and white Americans and changes in vitamin D metabolites after varied doses of vitamin D supplementation

BACKGROUND

Controversy exists over the disparate circulating 25-hydroxyvitamin D [25(OH)D] concentrations between black and white Americans.

OBJECTIVE

We sought to determine whether there are differences in total and directly measured free 25(OH)D concentrations between black and white American adults and how daily supplementation with cholecalciferol changes these concentrations.

DESIGN

Cross-sectional and longitudinal analyses were conducted with the use of data from 2 placebo-controlled, randomized trials at 2 academic medical centers in the United States: CaDDM (Calcium and Vitamin D in Type 2 Diabetes) and DDM2 (Vitamin D for Established Type 2 Diabetes). A total of 208 subjects with pre- or well-controlled diabetes with a mean age of 59.1 y and mean body mass index (BMI; in kg/m(2)) of 31.6 were randomly assigned to receive daily cholecalciferol supplementation at 1 of 2 doses (2000 or 4000 IU) or a matching placebo for 16 wk. We measured serum total 25(OH)D, vitamin D-binding protein (DBP) by 2 different immunoassays (with the use of monoclonal or polyclonal antibodies), parathyroid hormone, and albumin. Free 25(OH)D concentration was directly measured and calculated.

RESULTS

Blacks had lower total 25(OH)D concentrations than whites [adjusted median: 20.3 ng/mL (95% CI: 16.2, 24.5 ng/mL) compared with 26.7 ng/mL (95% CI: 25.2, 28.1 ng/mL), respectively; P = 0.026)], and a higher proportion of blacks had total 25(OH)D concentrations <20 ng/mL (46% compared with 19%, respectively; P < 0.001). Directly measured free 25(OH)D concentrations were lower in blacks than in whites [adjusted median: 4.5 ng/mL (95% CI: 3.7, 5.4 ng/mL) compared with 5.7 ng/mL (95% CI: 5.4, 5.9 ng/mL), respectively; P = 0.044] and were strongly correlated with total 25(OH)D without an effect of race. DBP was lower in blacks when measured by the monoclonal but not the polyclonal antibody immunoassay. Cholecalciferol supplementation increased total and measured free 25(OH)D concentrations proportionally to the dose and without a difference between races.

CONCLUSIONS

The relation between free and total 25(OH)D did not vary systematically by race in this multiracial population with pre- or well-controlled diabetes. The results need to be replicated in additional cohorts before concluding that the clinical assessment of vitamin D status in blacks and whites should follow a single standard. The CaDDM and DDM2 trials were registered at clinicaltrials.gov as NCT00436475 and NCT01736865, respectively.

A Significant Positive Association of Vitamin D Deficiency with Coronary Artery Calcification among Middle-aged Men: For the ERA JUMP Study

OBJECTIVE

Although a significant positive association of vitamin D deficiency with coronary heart disease has been demonstrated in cross-sectional as well as prospective studies, only a few studies have examined the association of vitamin D deficiency with subclinical atherosclerosis. We examined whether vitamin D deficiency is associated with subclinical atherosclerosis, as measured by coronary artery calcification (CAC) in asymptomatic adults.

METHODS

In a population-based cross-sectional study, 195 men aged 40 to 49 years without cardiovascular disease were randomly selected (98 Caucasian and 97 Japanese American men). Liquid chromatography-tandem mass spectrometry was utilized to measure serum vitamin D. CAC was examined by electron beam computed tomography using standardized protocols and read centrally at the University of Pittsburgh using Agatston's methods. To investigate an association between vitamin D deficiency (defined as 25-hydroxyvitamin D [25(OH)D] < 20 ng/mL) and CAC (defined as Agatston score ≥ 10), we utilized multivariable logistic regression models.

RESULTS

Prevalence of CAC and vitamin D deficiency was 27.2% and 10.3%, respectively. Participants with CAC were significantly older, had significantly higher body mass index (BMI), and had higher rates of smoking. Those with CAC were 3.31 times likely to be vitamin D deficient, after adjusting for traditional cardiovascular risk factors (odds ratio [OR] = 3.31, 95% confidence interval [CI], 1.12-9.77).

CONCLUSIONS

In this population-based study of healthy middle-aged men, vitamin D deficiency had a significant positive association with the presence of CAC.

Associations of Serum 25-Hydroxyvitamin D With Hemostatic and Inflammatory Biomarkers in the Multi-Ethnic Study of Atherosclerosis

CONTEXT

Mechanisms explaining documented associations of 25-hydroxyvitamin D [25(OH)D] deficiency with increased risks of cardiovascular disease (CVD) and venous thromboembolism may relate to adverse hemostatic and inflammatory responses.

OBJECTIVE

To evaluate whether 25(OH)D deficiency is associated with a prothrombotic and proinflammatory biological profile.

DESIGN

Cross-sectional analyses.

SETTING

The Multi-Ethnic Study of Atherosclerosis, a multicenter prospective cohort of American adults.

PARTICIPANTS

Up to 6554 adults free of CVD.

MAIN OUTCOME MEASURES

Ten hemostatic biomarkers (D-dimer, fibrinogen, factor VIII, plasmin-antiplasmin, and homocysteine [n = 6443]; von Willebrand factor, soluble tissue factor, plasminogen activator inhibitor-1 (PAI-1), total tissue factor pathway inhibitor (TFPI), and soluble thrombomodulin [n = 814]), and three inflammatory biomarkers (IL-6, C-reactive protein [n = 6443], and TNF-α soluble receptor [n = 3802]).

RESULTS

Among 6443 subjects (46.6% men; mean age, 62.1 years; mean body mass index, 28.3 kg/m(2)) of White (37.8%), Black (27.2%), Chinese (12.2%), and Hispanic (21.8%) race/ethnicity, mean 25(OH)D was 25.3 ng/mL. After multiple adjustment, 25(OH)D concentrations were associated with concentrations of IL-6 and homocysteine and also with concentrations of PAI-1 and TFPI: per 10 ng/mL decrement in 25(OH)D, 5.1% higher IL-6 (95% confidence interval [CI], 3.4-6.9; P < .001); 3.7% higher homocysteine (95% CI, 3.0-4.3; P < .001); 7.0% higher PAI-1 (95% CI, 0.9-13.6; P = .025); and 2.1% higher TFPI (95% CI, 0.0-4.2; P = .047), without racial/ethnic heterogeneity. No significant associations were observed for other hemostatic and inflammatory biomarkers.

CONCLUSIONS

Increased inflammation as reflected by higher circulating IL-6 and increased homocysteine concentrations may represent mechanisms linking 25(OH)D deficiency to greater risks of CVD and perhaps venous thromboembolism. Low concentrations of 25(OH)D were also associated with PAI-1 and TFPI concentrations, but not with other hemostatic biomarkers.

Serum vitamin D levels correlate to coronary artery disease severity: a retrospective chart analysis

BACKGROUND

The pro-atherosclerotic nature of vitamin D deficiency has been shown to increase cardiovascular events. We further emphasized and evaluated the severity of coronary artery disease (CAD) with varying levels of vitamin D in relation to age, gender, ethnicity and baseline confounders.

METHODS

A retrospective, single-center study of 9,399 patients admitted between 2005 and 2014 for chest pain who underwent coronary angiography. Patients without a vitamin D level, measured as 25-dihydroxyvitamin D (25[OH]D) were excluded from our study. 25(OH)D deficiency and insufficiency were defined by having serum concentration levels of less than 20 ng/ml and 20 to 29.9 ng/ml, respectively, while normal levels were defined as greater than or equal to 30 ng/ml. We assessed levels of 25(OH)D and extent of coronary disease with coronary angiography as obstructive CAD (left main stenosis of ≥50% or any stenosis of ≥70%), non-obstructive CAD (≥1 stenosis ≥20% but no stenosis ≥70%) and normal coronaries (no stenosis >20%).

RESULTS

Among 9,399 patients, 1,311 qualified, of which 308 patients (23%) had normal 25(OH)D levels, 552 patients (42%) had 25(OH)D deficiency and 451 patients (35%) had 25(OH)D insufficiency. In an analysis of the extent of coronary disease, we identified 20% of patients having normal coronaries, 55% having obstructive CAD and 25% having non-obstructive CAD. Baseline clinical risk factors and co-morbidities did not differ between the groups. Patients with normal 25(OH)D levels were found to have normal coronaries compared to patients with 25(OH)D deficiency or insufficiency (OR: 7, 95% CI: 5.2 - 9.5, p < 0.0001). Comparing patients with normal 25(OH)D levels, patients with 25(OH)D deficiency or insufficiency (<29 ng/ml), 62% were found to have obstructive CAD (n = 624, OR: 2.9, 95% CI: 2.3-3.7, p < 0.0001) and 25% had non-obstructive CAD (n = 249, OR: 1.5, 95% CI: 1.1-2, p = 0.02).

CONCLUSION

Normal coronaries and CAD were shown to correlate with normal and low levels of 25(OH)D, respectively. There is an inverse relationship between the percentage of coronary artery occlusion and serum 25(OH)D concentrations. Vitamin D may provide benefits in risk stratification of patients with CAD and serve as a possible risk factor.

Vitamin D and cardiovascular disease prevention

Vitamin D is a precursor of the steroid hormone calcitriol that is crucial for bone and mineral metabolism. Both the high prevalence of vitamin D deficiency in the general population and the identification of the vitamin D receptor in the heart and blood vessels raised interest in the potential cardiovascular effects of vitamin D. Experimental studies have demonstrated various cardiovascular protective actions of vitamin D, but vitamin D intoxication in animals is known to induce vascular calcification. In meta-analyses of epidemiological studies, vitamin D deficiency is associated with an increased cardiovascular risk. Findings from Mendelian randomization studies and randomized, controlled trials (RCTs) do not indicate significant effects of a general vitamin D supplementation on cardiovascular outcomes. Previous RCTs, however, were not adequately designed to address extraskeletal events, and did not focus on vitamin D-deficient individuals. Therefore, currently available evidence does not support cardiovascular benefits or harms of vitamin D supplementation with the commonly used doses, and whether vitamin D has cardiovascular effects in individuals with overt vitamin D deficiency remains to be evaluated. Here, we provide an update on clinical studies on vitamin D and cardiovascular risk, discuss ongoing vitamin D research, and consider the management of vitamin D deficiency from a cardiovascular health perspective.

The cross-sectional relationships of dietary and serum vitamin D with cardiometabolic risk factors: Metabolic components, subclinical atherosclerosis, and arterial stiffness

OBJECTIVE

There has been increasing interest in non-skeletal interactions between vitamin D insufficiency, which is common, and cardiovascular event and cardiovascular disease (CVD) risk factors.

METHODS

To evaluate cross-sectional associations between dietary and serum vitamin D status and metabolic abnormalities and arterial changes among 1054 adults aged ≥40 y (404 men and 650 women) in a rural area of South Korea. Study subjects were divided into three groups according to dietary vitamin D intake (tertiles) measured by food frequency questionnaire and serum 25(OH)D levels (≤20, 21-29, and ≥30 ng/mL). Metabolic components (blood pressure, lipid profiles, and glycemic index) and arterial changes (brachial ankle pulse wave velocity [baPWV] and carotid artery intima-media wall thickness [cIMT]) were measured.

RESULTS

Dietary vitamin D was inversely associated with diastolic blood pressure (DBP) and baPWV among men, but the association disappeared after multinutrient supplement users were excluded. Among women, there was an inverse association between dietary vitamin D and triacylglycerol (TG) levels. However, serum 25(OH)D showed a significant positive relationship with HDL cholesterol in both men and women, while a positive linear trend or nonlinear trend with serum 25(OH)D levels was shown in TG levels among men and in systolic blood pressure (SBP), DBP, total cholesterol, and baPWV among women. The positive relationship between serum 25(OH)D with baPWV disappeared after adjustment for blood pressure.

CONCLUSIONS

Serum 25(OH)D may be favorably related to HDL cholesterol. However, serum 25(OH)D may not favorably related to subclinical atherosclerosis and arterial stiffness measured by cIMT and baPWV. The positive relationship between 25(OH)D and baPWV is likely to be mediated by blood pressure.

Measurement by a Novel LC-MS/MS Methodology Reveals Similar Serum Concentrations of Vitamin D-Binding Protein in Blacks and Whites

BACKGROUND

Vitamin D deficiency is associated with poor bone health and other adverse health outcomes; however, the associations are greatly attenuated in black vs white individuals. One possible explanation for this attenuation is different concentrations of bioavailable vitamin D metabolites in plasma, which are estimated with equations that include the total concentration of vitamin D binding globulin (VDBG) and haplotype-specific dissociation constants.

METHODS

We developed a method to quantify VDBG with LC-MS/MS that could also identify the haplotypes/isoforms of VDBG present. We validated the method according to recent recommendations for publications of biomarker studies. We determined serum VDBG concentrations in samples from the Atherosclerosis Risk in Communities cohort and compared the results with a widely used monoclonal immunoassay.

RESULTS

With 10 μL of serum or plasma, the lower limit of quantification for the assay (<20% CV) was 71 μg/mL. The assay was linear from 62 to 434 μg/mL, with total imprecision of 7.3-9.0% CV at approximately 250 μg/mL. Significant hemolysis interfered with quantification. The identification of isoforms was 97% concordant with genotyping (κ coefficient). Method comparison with immunoassay revealed significant isoform-specific effects in the immunoassay. Mean concentrations (SD) of VDBG by mass spectrometry were similar in whites and blacks [262 (25) vs 266 (35) μg/mL, respectively; P = 0.43].

CONCLUSIONS

Validated mass spectrometric methods for the quantification of proteins in human samples can provide additional information beyond immunoassay. Counter to prior observations by immunoassay, VDBG concentrations did not vary by race.

Early pregnancy vitamin D status and risk for adverse maternal and infant outcomes in a bi-ethnic cohort: the Behaviors Affecting Baby and You (B.A.B.Y.) Study

Vitamin D deficiency is common during pregnancy and higher in Hispanic as compared with non-Hispanic white women. However, the association between vitamin D deficiency and adverse pregnancy outcomes remains unclear and may vary across ethnic groups, in part because of genetic variation in the metabolism of vitamin D. Few studies have included Hispanic women. Therefore, we investigated this association among 237 participants in the Behaviors Affecting Baby and You Study, a randomised trial of an exercise intervention among ethnically diverse prenatal care patients in Massachusetts. Baseline serum 25-hydroxyvitamin D (25(OH)D) was measured at 15·2 (sd 4·7) weeks' gestation. Information on adverse pregnancy outcomes was abstracted from medical records. Mean 25(OH)D was 30·4 (sd 12·0) ng/ml; 53·2 % of participants had insufficient (<30 ng/ml) and 20·7 % had deficient (<20 ng/ml) 25(OH)D levels. After adjusting for month of blood draw, gestational age at blood draw, gestational age at delivery, age, BMI and Hispanic ethnicity, women with insufficient and deficient vitamin D had infants with birth weights 139·74 (se 69·16) g (P=0·045) and 175·52 (se 89·45) g (P=0·051) lower compared with women with sufficient vitamin D levels (≥30 ng/ml). Each 1 ng/ml increase in 25(OH)D was associated with an increased risk for gestational diabetes mellitus among Hispanic women only (relative risk 1·07; 95 % CI 1·03, 1·11) in multivariable analysis. We did not observe statistically significant associations between maternal vitamin D status and other pregnancy outcomes. Our findings provide further support for an adverse impact of vitamin D deficiency on birth weight in Hispanic women.