Effects of a 1-year supplementation with cholecalciferol on interleukin-6, tumor necrosis factor-alpha and insulin resistance in overweight and obese subjects

The Role of Vitamin D in the Prevention of Type 2 Diabetes: To D or Not to D?

Evidence on biological plausibility from mechanistic studies and highly consistent data from observational studies raise the possibility that optimizing vitamin D status may reduce the risk of type 2 diabetes. However, the observational nature of cohort studies precludes a definitive assessment of cause and effect because residual confounding or reverse causation cannot be excluded. Confounding is especially problematic with studies of vitamin D because blood 25-hydoxyvitamin D concentration is not only an excellent biomarker of vitamin D status, reflecting intake or biosynthesis, but also an excellent marker of good overall health. Results from underpowered trials and post hoc analyses of trials designed for nondiabetic outcomes do not support a role of vitamin D supplementation for prevention of type 2 diabetes among people with normal glucose tolerance. Whether vitamin D supplementation may have a role in the prevention of diabetes in high-risk populations remains to be seen. Adequately powered, randomized trials in well-defined populations (e.g., prediabetes) are ongoing and expected to establish whether vitamin D supplementation lowers risk of diabetes.

High Dose Supplementation of Vitamin D Affects Measures of Systemic Inflammation: Reductions in High Sensitivity C-Reactive Protein Level and Neutrophil to Lymphocyte Ratio (NLR) Distribution

The prevalence of Vitamin D deficiency is increasing worldwide, which has be shown to be associated with increased risk of cardiovascular disease (CVD), autoimmune disease, and metabolic syndrome. These conditions are also associated with a heightened state of inflammation. The aim of the current study was to evaluate the effect of vitamin D supplementation on serum C-Reactive Protein (CRP) level and Neutrophil-to-lymphocyte ratio (NLR) distribution in a large cohort of adolescent girls. A total of 580 adolescent girls were recruited follow by evaluation of CRP and hematological parameters before and after supplementation with vitamin D supplements as 9 of 50000 IU cholecalciferol capsules for 9 weeks taken at weekly intervals. At baseline, serum hs-CRP level was 0.9 (95%CI: 0.5-1.8), while this value after intervention was reduced to 0.8 (95%CI: 0.3-1.6; P = 0.007). Similar results were also detected for NLR (e.g., NLR level was 1.66 ± 0.72 and 1.53 ± 0.67, P = 0.002, before and after therapy with compliance rate of >95.2%). Moreover, we found an association between hs-CRP and BMI, triglyceride, white blood cell count, and lymphocytes. Interestingly we observed a significant reduction in neutrophil count and CRP level after high dose vitamin D supplementation. Our findings showed that the high dose supplementation of vitamin D affects measures of systemic inflammation: reductions in High Sensitivity C-Reactive Protein level and Neutrophil-to-lymphocyte ratio (NLR) distribution. J. Cell. Biochem. 118: 4317-4322, 2017. © 2017 Wiley Periodicals, Inc.

Vitamin D supplementation has no effect on insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults: a randomized placebo-controlled trial

Background: Vitamin D supplementation has been proposed as a potential strategy to prevent type 2 diabetes. Existing clinical trials have been limited by short duration, low doses of vitamin D, variability in participants' vitamin D-deficiency status, and the use of surrogate measures of body composition, insulin sensitivity, and insulin secretion.Objective: To address existing knowledge gaps, we conducted a double-blind, randomized, placebo-controlled trial to investigate whether vitamin D supplementation that is provided in a sufficient dose and duration to vitamin D-deficient individuals would improve insulin sensitivity or secretion as measured with the use of gold-standard methods. We hypothesized that vitamin D supplementation would improve insulin sensitivity and secretion compared with placebo.Design: Sixty-five overweight or obese, vitamin D-deficient (25-hydroxyvitamin D [25(OH)D] concentration ≤50 nmol/L) adults were randomly assigned to receive either a bolus oral dose of 100,000 IU cholecalciferol followed by 4000 IU cholecalciferol/d or a matching placebo for 16 wk. Before and after the intervention, participants received gold-standard assessments of body composition (via dual X-ray absorptiometry), insulin sensitivity (via hyperinsulinemic-euglycemic clamps), and insulin secretion [via intravenous-glucose-tolerance tests (IVGTTs)].Results: Fifty-four participants completed the study [35 men and 19 women; mean ± SD age: 31.9 ± 8.5 y; body mass index (in kg/m²): 30.9 ± 4.4]. 25(OH)D increased with vitamin D supplementation compared with placebo (57.0 ± 21.3 compared with 1.9 ± 15.1 nmol/L, respectively; P = 0.02). Vitamin D and placebo groups did not differ in change in insulin sensitivity (0.02 ± 2.0 compared with -0.03 ± 2.8 mg · kg^-1 · min^-1, respectively; P = 0.9) or first-phase insulin secretion (-21 ± 212 compared with 24 ± 184 mU/L, respectively; P = 0.9). Results remained nonsignificant after adjustment for age, sex, percentage of body fat, sun exposure, physical activity, and dietary vitamin D intake (P > 0.1).Conclusions: Vitamin D supplementation does not improve insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults, despite using high-dose vitamin D supplementation and robust endpoint measures. Therefore, it is unlikely that vitamin D supplementation would be an effective strategy for reducing diabetes risk even in vitamin D-deficient populations. This trial was registered at clinicaltrials.gov as NCT02112721.

Celiac disease is associated with reduced bone mineral density and increased FRAX scores in the US National Health and Nutrition Examination Survey

We investigated the association between celiac disease (CD) and bone mass density (BMD) and risk of osteoporotic fractures in the general US population. In children and men ≥18 years, CD was associated with reduced BMD, and in men ≥40 years, CD was associated with increased risk of osteoporotic fractures.

INTRODUCTION

Celiac disease (CD) is an autoimmune condition, characterized by inflammation of the small intestine. CD has an increasing prevalence, and if unrecognized or untreated, CD can lead to complications from malabsorption and micronutrient deficiencies. We aimed to study whether CD is an independent predictor of reduced bone mineral density (BMD) and FRAX scores in the general US population.

METHODS

We used data from the National Health and Nutrition Examination Survey, 2009-2010 and 2013-2014. CD was defined by positive tissue transglutaminase IgA antibody test. Multivariable models of BMD and FRAX scores were adjusted for BMI, serum 25-hydroxyvitamin D, vitamin D and calcium supplements, milk intake, serum calcium, and smoking status, when available.

RESULTS

In children, aged 8-17 years, CD was associated with decreased Z-scores, by 0.85 for hip and 0.46 for spine (both P < 0.001). In men aged ≥ 18 years, CD was associated with 0.06 g/cm² decrease in BMD in hip and with 0.11 g/cm² decrease in BMD in spine (P = 0.08 and P < 0.001, respectively). In women, there were no statistically significant differences in the multiple-adjusted model. In men aged ≥ 40 years, CD predicted FRAX scores, resulting in increased scores by 2.25 % (P = 0.006) for hip fracture and by 2.43 % (P = 0.05) for major osteoporotic fracture. CD did not predict FRAX scores in women aged ≥40 years.

CONCLUSION

CD is independently associated with reduced BMD in children and adults aged ≥18 years and is an independent risk factor of osteoporotic fractures in men aged ≥40 years.

Vitamin D and Weight Cycling: Impact on Injury, Illness, and Inflammation in Collegiate Wrestlers

This study explored the link between vitamin D status and frequency of skin infections, inflammation, and injury in college wrestlers during an academic year. Methods: Serum 25-hydroxyvitamin D (25(OH)D) (n = 19), plasma cytokine (TNF-α, IL-6, IL-10) (n = 18) concentrations, and body weight/composition were measured and injury/illness/skin infection data were collected in fall, winter, and spring. Results: In the fall, 74% of wrestlers had vitamin D concentrations <32 ng/mL which increased to 94% in winter and spring. Wrestlers lost an average of 3.4 ± 3.9 kg (p < 0.001) during the season with corresponding decreases in fat mass and increases in lean mass (p < 0.01). An inverse association between 25(OH)D concentrations and total body mass and body fat percentage was observed at all-time points (p < 0.01). Concentrations of cytokines were highly variable among individuals and did not change across time (p > 0.05). Correlations between vitamin D status, cytokines, or frequency of illness, injury, or skin infections were not observed. Conclusions: A high prevalence of vitamin D insufficiency (<32 ng/mL) and deficiency (<20 ng/mL) was observed in wrestlers and was associated with higher adiposity. It remains unclear if higher vitamin D status would reduce injury, illness, and skin infection risk.

Effects of vitamin D supplementation on glycated haemoglobin and fasting glucose levels in hypertensive patients: a randomized controlled trial

AIM

To investigate the efficacy of vitamin D supplementation on glycaemic control.

METHODS

The Styrian Vitamin D Hypertension Trial was a single-centre, double-blind, placebo-controlled study conducted between 2011 and 2014 at the Medical University of Graz, Austria. We enrolled 200 people with arterial hypertension and 25-hydroxyvitamin D [25(OH)D] concentrations <30 ng/mL. Study participants were randomized to receive either 2800 IU of vitamin D or placebo per day for 8 weeks. The present study was a post hoc analysis that incorporated an analysis of covariance (ancova) approach, while adjusting for baseline differences.

RESULTS

A total of 185 participants [mean ± standard deviation age, 60.1 ± 11.3 years; 47% women; mean 25(OH)D 21.2 ± 5.6 ng/mL, mean glycated haemoglobin (HbA1c) 44.8 ± 11.8 mmol/mol and mean body mass index 30.4 ± 5.4 kg/m(2) ] completed the trial. ancova showed a mean treatment effect [95% confidence interval (CI)] on HbA1c of -3.52 (-6.7 to -0.34) mmol/mol (p = .045). There was no difference in fasting glucose -4.7 mg/dL (95% CI -16.3 to 6.9; p = .426).

CONCLUSIONS

Vitamin D supplementation in obese hypertensive patients with low 25(OH)D reduces HbA1c levels. This finding warrants further investigation into potential vitamin D effects on glucose homeostasis.

Effects of vitamin D supplementation on metabolic indices and hs-CRP levels in gestational diabetes mellitus patients: a randomized, double-blinded, placebo-controlled clinical trial

BACKGROUND/OBJECTIVES

Vitamin D plays an important role in the etiology of gestational diabetes mellitus (GDM). This study evaluated the effect of vitamin D supplementation on metabolic indices and hs-C-reactive protein (CRP) levels in GDM patients.

SUBJECTS/METHODS

The study was a randomized, placebo-controlled, double-blinded clinical trial. Seventy-six pregnant women with GDM and gestational age between 24-28 weeks were assigned to receive four oral treatments consisting of 50,000 IU of vitamin D3 (n = 38) or placebo (n = 38) once every 2 weeks for 2 months. Fasting blood glucose (FG), insulin, HbA1c, 25-hydroxyvitamin D, lipid profile, hs-CRP, and homeostasis model assessment-insulin resistance (HOMA-IR) were measured before and after treatment. Independent and paired t-tests were used to determine intra- and intergroup differences, respectively. ANCOVA was used to assess the effects of vitamin D supplementation on biochemical parameters.

RESULTS

Compared with the placebo group, in the vitamin D group, the serum level of 25-hydroxyvitamin D increased (19.15 vs. -0.40 ng/ml; P < 0.01) and that of FG (-4.72 vs. 5.27 mg/dl; P = 0.01) as well as HbA1c (-0.18% vs. 0.17%; P = 0.02) decreased. Improvements in the lipid profiles were observed in the vitamin D group, but without statistical significance. Significant increases in concentrations of hs-CRP, FG, HbA1c, total cholesterol, and LDL cholesterol were observed in the placebo group. No significant change in fasting insulin and HOMA-IR was observed in either group.

CONCLUSIONS

In GDM patients, vitamin D supplementation improved FG and HbA1c but had no significant effects on lipid profile or hs-CRP.

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.

Free 25-hydroxyvitamin D is low in obesity, but there are no adverse associations with bone health

BACKGROUND

The mechanism and clinical significance of low circulating 25-hydroxyvitamin D [25(OH)D] in obese people are unknown. Low total 25(OH)D may be due to low vitamin D-binding proteins (DBPs) or faster metabolic clearance. However, obese people have a higher bone mineral density (BMD), which suggests that low 25(OH)D may not be associated with adverse consequences for bone.

OBJECTIVE

We sought to determine whether 1) vitamin D metabolism and 2) its association with bone health differ by body weight.

DESIGN

We conducted a cross-sectional observational study of 223 normal-weight, overweight, and obese men and women aged 25-75 y in South Yorkshire, United Kingdom, in the fall and spring. A subgroup of 106 subjects was also assessed in the winter. We used novel techniques, including an immunoassay for free 25(OH)D, a stable isotope for the 25(OH)D3 half-life, and high-resolution quantitative tomography, to make a detailed assessment of vitamin D physiology and bone health.

RESULTS

Serum total 25(OH)D was lower in obese and overweight subjects than in normal-weight subjects in the fall and spring (geometric means: 45.0 and 40.8 compared with 58.6 nmol/L, respectively; P < 0.001) but not in the winter. Serum 25(OH)D was inversely correlated with body mass index (BMI) in the fall and spring and in the winter. Free 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)2D] were lower in obese subjects. DBP, the DBP genotype, and the 25(OH)D3 half-life did not differ between BMI groups. Bone turnover was lower, and bone density was higher, in obese people.

CONCLUSIONS

Total and free 25(OH)D and 1,25(OH)2D are lower at higher BMI, which cannot be explained by lower DBP or the shorter half-life of 25(OH)D3 We speculate that low 25(OH)D in obesity is due to a greater pool of distribution. Lower 25(OH)D may not reflect at-risk skeletal health in obese people, and BMI should be considered when interpreting serum 25(OH)D as a marker of vitamin D status.

Effect of Vitamin D3 Supplementation on Inflammatory Markers and Glycemic Measures among Overweight or Obese Adults: A Systematic Review of Randomized Controlled Trials

BACKGROUND

Obesity induced low-grade chronic inflammation disrupts proper immune and metabolic function. Vitamin D deficiency increases inflammation, which is associated with cardiometabolic risk. This systematic review examines the association between oral vitamin D (VD) supplementation and circulating inflammatory biomarkers and glycemic outcomes from randomized controlled trials (RCTs) of overweight and/or obese adults.

METHODS

MEDLINE OVID, EMBASE and the Cochrane Central Register of Controlled Trials were searched according to a predefined protocol. Eligible RCTs included adults randomized to receive either oral VD or placebo. Two reviewers independently assessed RCTs for inclusion. Bias was assessed using the Cochrane Collaboration risk of bias tool. Mean differences were calculated comparing end-of-study sample means between the independent VD and placebo groups.

RESULTS

Eleven unique RCTs met inclusion criteria from a total of 3,383 identified citations, including 79 screened articles and 14 full text data extractions. Inflammatory and glycemic measures were reported in 7 and 10 RCTs, respectively. Most trial findings were non-significant with considerable heterogeneity in design, participants and outcomes. All but one trial was rated as either high or unclear risk of bias. Two RCTs reported significant changes in inflammatory biomarkers; however, the mean difference between groups was not statistically significant: C-reactive protein 0.19 mg/L (p = 0.88); Tumor Necrosis Factor -0.54 pg/ml (p = 0.20). Two other trials found significant mean differences in fasting plasma glucose -0.32 mmol/L (p = 0.03), Hemoglobin A1c -0.13% (p = 0.04), and Homeostatic Model Assessment -0.86 (p = 0.02) following VD supplementation.

CONCLUSIONS

Overall, there is no clear established benefit of VD supplementation on inflammatory biomarkers among overweight/obese adults. Baseline serum VD possibly influences the effect of VD repletion on inflammatory markers. Risk of bias was present in most studies, thus supporting the need for higher quality studies in this area to more conclusively understand the role VD supplementation has on inflammatory pathways.

Serum 25-hydroxyvitamin D concentrations and cardiometabolic risk factors in adolescents and young adults

Evidence associating serum 25-hydroxyvitamin D (25(OH)D) concentrations and cardiometabolic risk factors is inconsistent and studies have largely been conducted in adult populations. We examined the prospective associations between serum 25(OH)D concentrations and cardiometabolic risk factors from adolescence to young adulthood in the West Australian Pregnancy Cohort (Raine) Study. Serum 25(OH)D concentrations, BMI, homoeostasis model assessment for insulin resistance (HOMA-IR), TAG, HDL-cholesterol and systolic blood pressure (SBP) were measured at the 17-year (n 1015) and 20-year (n 1117) follow-ups. Hierarchical linear mixed models with maximum likelihood estimation were used to investigate associations between serum 25(OH)D concentrations and cardiometabolic risk factors, accounting for potential confounders. In males and females, respectively, mean serum 25(OH)D concentrations were 73·6 (sd 28·2) and 75·4 (sd 25·9) nmol/l at 17 years and 70·0 (sd 24·2) and 74·3 (sd 26·2) nmol/l at 20 years. Deseasonalised serum 25(OH)D3 concentrations were inversely associated with BMI (coefficient −0·01; 95 % CI −0·03, −0·003; P=0·014). No change over time was detected in the association for males; for females, the inverse association was stronger at 20 years compared with 17 years. Serum 25(OH)D concentrations were inversely associated with log-HOMA-IR (coefficient −0·002; 95 % CI −0·003, −0·001; P<0·001) and positively associated with log-TAG in females (coefficient 0·002; 95 % CI 0·0008, 0·004; P=0·003). These associations did not vary over time. There were no significant associations between serum 25(OH)D concentrations and HDL-cholesterol or SBP. Clinical trials in those with insufficient vitamin D status may be warranted to determine any beneficial effect of vitamin D supplementation on insulin resistance, while monitoring for any deleterious effect on TAG.

Effect of vitamin D supplementation on inflammation: protocol for a systematic review

INTRODUCTION

The extraskeletal role of vitamin D is being increasingly recognised. This has important clinical implications, as vitamin D deficiency has reached epidemic proportions worldwide. Vitamin D has proposed anti-inflammatory properties, yet the role of vitamin D supplementation in reducing inflammation remains largely unknown. The purpose of this review is to investigate the impact of vitamin D supplementation on inflammation, and to identify relevant knowledge gaps in the field.

METHODS AND ANALYSIS

Medline, CINAHL, EMBASE and All EBM will be systematically searched for randomised controlled trials (RCTs) and systematic reviews of RCTs, comparing vitamin D supplementation with placebo, usual care or other pharmacological or non-pharmacological interventions. One reviewer will assess articles for eligibility according to prespecified selection criteria, after which 2 independent reviewers will perform data extraction and quality appraisal. Meta-analyses will be conducted where appropriate.

ETHICS AND DISSEMINATION

Formal ethical approval is not required as no primary data is collected. This systematic review will identify potential clinical implications of vitamin D deficiency and supplementation, and will be disseminated through a peer-reviewed publication and at conference meetings, to inform future research on the efficacy of vitamin D supplementation for inflammation and inflammatory diseases.

PROSPERO REGISTRATION NUMBER

CRD42016037104.

Metabolic effects of vitamin D supplementation in vitamin D deficient patients (a double-blind clinical trial)

BACKGROUND

Vitamin D has recently been given a lot of attention for its role in controlling insulin secretion. Many studies have spoken of its role in weight management, blood sugar control and many other metabolic variables.

PATIENT AND METHODS

In a randomized double-blind clinical trial, 210 people with vitamin D deficiency were randomly allocated into two groups receiving vitamin D (50,000 units per week) or placebo for 8 weeks.

RESULTS

Vitamin D levels were significantly increased in the group receiving vitamin D supplementation (13.7±5.2 unit increase versus 0.8±2.8). The increased levels of vitamin D lead to significant changes in fasting insulin levels (6.8±8.1 unit reduction versus 2.3±3.7), a 2-h insulin (31.1±34.9 unit reduction versus 4.5±24.6) and Homeostasis Model Assessment (HOMA) indices.

CONCLUSION

Correction of vitamin D deficiency leads to increased insulin sensitivity that was significantly able to maintain glucose in the normal range with lower levels of insulin.

Vitamin D and Immune Response: Implications for Prostate Cancer in African Americans

Prostate cancer (PCa) is the most common cancer among men in the U.S. African American (AA) men have a higher incidence and mortality rate compared to European American (EA) men, but the cause of PCa disparities is still unclear. Epidemiologic studies have shown that vitamin D deficiency is associated with advanced stage and higher tumor grade and mortality, while its association with overall PCa risk is inconsistent. Vitamin D deficiency is also more common in AAs than EAs, and the difference in serum vitamin D levels may help explain the PCa disparities. However, the role of vitamin D in aggressive PCa in AAs is not well explored. Studies demonstrated that the active form of vitamin D, 1,25-dihydroxyvitamin D, has anti-inflammatory effects by mediating immune-related gene expression in prostate tissue. Inflammation also plays an important role in PCa pathogenesis and progression, and expression of immune-related genes in PCa tissues differs significantly between AAs and EAs. Unfortunately, the evidence linking vitamin D and immune response in relation to PCa is still scarce. This relationship should be further explored at a genomic level in AA populations that are at high risk for vitamin D deficiency and fatal PCa.

Causes of Vitamin D Deficiency and Effect of Vitamin D Supplementation on Metabolic Complications in Obesity: a Review

Obese subjects are often characterized by low plasma 25-hydroxy-vitamin D (25OHD) levels. Many explanations for this association have been proposed. Low plasma 25OHD is associated with obesity-related comorbidities such as insulin resistance, type 2 diabetes mellitus, and low-grade inflammation. In this review, we discuss the proposed mechanisms for low 25OHD in obesity and explore the results of recent RCTs on vitamin D (VD) supplementation on obesity and its metabolic complications such as insulin resistance and type 2 diabetes. Although the results from these clinical randomized controlled trials vary, the general picture is that VD treatment of obese individuals does not seem to be an effective treatment of obesity-related metabolic complications.

The effect of vitamin D supplementation on insulin and glucose metabolism in overweight and obese individuals: systematic review with meta-analysis

The aim of this systematic review was to assess the effect of vitamin D supplementation on glucose and insulin metabolism in overweight and obese subjects. The search process was based on the selection of publications listed in the databases: PubMed, Scopus, Web of Knowledge, Embase and the Cochrane library that met the inclusion criteria. Twelve randomized controlled trials were included. The analysed population consisted of 1181 individuals with BMIs >23 kg/m2. Changes in the concentration of 25(OH)D, fasting glucose, insulin and the HOMA-IR index were assessed. In the meta-regression analysis, a restricted maximum likelihood method was applied. To combine individual study results, a meta-analysis was performed. Vitamin D supplementation did not have an effect on glucose concentrations, insulin level and HOMA-IR values when the supplemented dose, time of supplementation and baseline of 25(OH)D concentration were taken under consideration in subgroup-analysis. This meta-analysis provides evidence that vitamin D supplementation has no significant effect on glucose and insulin metabolism in overweight and obese individuals.

Vitamin D and cardiovascular risk among adults with obesity: a systematic review and meta-analysis

BACKGROUND

Obesity is a risk factor for both vitamin D deficiency and cardiovascular disease. A link between vitamin D status optimisation and improved cardiometabolic profile among adults with obesity could inform public health initiatives.

METHODS

PubMed, Embase and Web of Science were searched for interventional studies examining the effects of vitamin D status improvement on cardiovascular risk factors (anthropometric measures, lipid profile, blood pressure, glucose tolerance) among nondiabetic adults with obesity.

RESULTS

Seventeen publications reporting results from 11 different studies were included. Number of participants ranged from 34 to 1179 subjects. Duration was between 6 weeks and 4 years. Vitamin D was administered as a supplement in ten studies (1000 IU daily to 120 000 IU fortnightly). In one study, participants were advised to increase sunlight exposure and dietary vitamin D intake. The random and fixed-effects meta-analysis showed that vitamin D significantly increased systolic blood pressure and LDL-C levels. The fixed-effects model also indicated a significant decrease in triglyceride levels, which was not evident using the random-effects model. Caution should be given to these results given the small number of studies used and the high heterogeneity between studies for the two latter outcomes. Additionally, a subset of eligible studies with compatible data presentation was included in the meta-analysis.

CONCLUSION

This systematic review highlights a paucity of interventional studies examining the effects of vitamin D status improvement on cardiovascular risk factors among otherwise healthy adults with obesity. Large-scale studies at pharmacologically relevant doses and with sufficient duration are warranted.

Effect of vitamin D supplementation on selected inflammatory biomarkers in older adults: a secondary analysis of data from a randomised, placebo-controlled trial

Observational studies have suggested that 25-hydroxyvitamin D (25(OH)D) levels are associated with inflammatory markers. Most trials reporting significant associations between vitamin D intake and inflammatory markers used specific patient groups. Thus, we aimed to determine the effect of supplementary vitamin D using secondary data from a population-based, randomised, placebo-controlled, double-blind trial (Pilot D-Health trial 2010/0423). Participants were 60- to 84-year-old residents of one of the four eastern states of Australia. They were randomly selected from the electoral roll and were randomised to one of three trial arms: placebo (n 214), 750 μg (n 215) or 1500 μg (n 215) vitamin D3, each taken once per month for 12 months. Post-intervention blood samples for the analysis of C-reactive protein (CRP), IL-6, IL-10, leptin and adiponectin levels were available for 613 participants. Associations between intervention group and biomarker levels were evaluated using quantile regression. There were no statistically significant differences in distributions of CRP, leptin, adiponectin, leptin:adiponectin ratio or IL-10 levels between the placebo group and either supplemented group. The 75th percentile IL-6 level was 2·8 pg/ml higher (95 % CI 0·4, 5·8 pg/ml) in the 1500 μg group than in the placebo group (75th percentiles:11·0 v. 8·2 pg/ml), with a somewhat smaller, non-significant difference in 75th percentiles between the 750 μg and placebo groups. Despite large differences in serum 25(OH)D levels between the three groups after 12 months of supplementation, we found little evidence of an effect of vitamin D supplementation on cytokine or adipokine levels, with the possible exception of IL-6.

Mechanistic Effects of Calcitriol in Cancer Biology

Besides its classical biological effects on calcium and phosphorus homeostasis, calcitriol, the active vitamin D metabolite, has a broad variety of actions including anticancer effects that are mediated either transcriptionally and/or via non-genomic pathways. In the context of cancer, calcitriol regulates the cell cycle, induces apoptosis, promotes cell differentiation and acts as anti-inflammatory factor within the tumor microenvironment. In this review, we address the different mechanisms of action involved in the antineoplastic effects of calcitriol.

Vitamin D and inflammation

Several studies found an inverse relationship between 25-hydroxyvitamin D [25(OH)D] and markers of inflammation. A controversy exists as to whether vitamin D lowers inflammation or whether inflammation lowers 25(OH)D concentrations. Certainly 25(OH)D concentrations fall after major surgery. However, is this due to inflammation lowering 25(OH)D or is 25(OH)D being metabolically cleared by the body to quell inflammation. We searched the literature and found 39 randomized controlled trials (RCT) of vitamin D and markers of inflammation. Seventeen found significantly reduced inflammatory markers, 19 did not, one was mixed and one showed adverse results. With few exceptions, studies in normal subjects, obesity, type 2 diabetics, and stable cardiovascular disease did not find significant beneficial effects. However, we found that 6 out of 7 RCTS of vitamin D3 in highly inflammatory conditions (acute infantile congestive heart failure, multiple sclerosis, inflammatory bowel disease, cystic fibrosis, SLE, active TB and evolving myocardial infarction) found significant reductions. We found baseline and final 25(OH)D predicted RCTs with significant reduction in inflammatory markers. Vitamin D tends to modestly lower markers of inflammation in highly inflammatory conditions, when baseline 25(OH)D levels were low and when achieved 25(OH)D levels were higher. Future inquiries should: recruit subjects with low baseline 25(OH)D levels, subjects with elevated markers of inflammation, subjects with inflammatory conditions, achieve adequate final 25(OH)D levels, and use physiological doses of vitamin D. We attempted to identify all extant randomized controlled trials (RCTs) of vitamin D that used inflammatory markers as primary or secondary endpoints.

Glucose Metabolism Effects of Vitamin D in Prediabetes: The VitDmet Randomized Placebo-Controlled Supplementation Study

Epidemiological evidence suggests a role for vitamin D in type 2 diabetes prevention. We investigated the effects of vitamin D3 supplementation on glucose metabolism and inflammation in subjects with prediabetes. A 5-month randomized, double-blind, placebo-controlled intervention with three arms (placebo, 40 μg/d, or 80 μg/d vitamin D3) was carried out among sixty-eight overweight (BMI 25-35) and aging (≥60 years) subjects from Finland, with serum 25-hydroxyvitamin D3 [25(OH)D3] < 75 nmol/L and either impaired fasting glucose or impaired glucose tolerance. Analyses included 66 subjects who completed the trial. Glucose metabolism was evaluated by fasting and 2-hour oral glucose tolerance test-derived indices and glycated hemoglobin. Inflammation was evaluated by high-sensitive C-reactive protein and five cytokines. Although a dose-dependent increase in serum 25(OH)D3 over the supplementation period was observed (P trend < 0.001), there were no other statistically significant differences in changes in the 13 glucose homeostasis indicators between the study groups other than increase in the 120 min glucose concentration (P trend = 0.021) and a decreasing trend both in 30 min plasma insulin (P trend = 0.030) and glycated hemoglobin (P trend = 0.024) concentrations. A borderline statistically significant decreasing trend in interleukin-1 receptor antagonist concentration was observed (P = 0.070). Vitamin D3 supplementation does not improve glucose metabolism in ageing subjects with prediabetes but may have modest anti-inflammatory effects.

Calcium-vitamin D cosupplementation influences circulating inflammatory biomarkers and adipocytokines in vitamin D-insufficient diabetics: a randomized controlled clinical trial

CONTEXT

To the best of our knowledge, no study has examined the effects of vitamin D-calcium cosupplementation on inflammatory biomarkers and adipocytokines in vitamin D-insufficient type 2 diabetics.

OBJECTIVE

This study was performed to assess the effects of vitamin D and calcium supplementation on inflammatory biomarkers and adipocytokines in vitamin D-insufficient people with type 2 diabetes.

METHODS

Totally, 118 diabetic patients were enrolled in this randomized, placebo-controlled clinical trial. After matching for age, sex, body mass index, type and dose of hypoglycemic agents, and duration of diabetes, subjects were randomly assigned into 4 groups receiving the following: 1) 50000 IU/wk vitamin D + calcium placebo; 2) 1000 mg/d calcium + vitamin D placebo; 3) 50 000 IU/wk vitamin D + 1000 mg/d calcium; or 4) vitamin D placebo + calcium placebo for 8 weeks. Blood sampling was done for the quantification of inflammatory biomarkers and adipocytokines at the study baseline and after 8 weeks of intervention.

RESULTS

Calcium (changes from baseline: -75 ± 19 ng/ml, P = .01) and vitamin D alone (-56 ± 19 ng/mL, P = .01) and joint calcium-vitamin D supplementation (-92 ± 19 ng/mL, P = .01) resulted in a significant reduction in serum leptin levels compared with placebo (-9 ± 18 ng/mL). This was also the case for serum IL-6, such that calcium (-2 ± 1 pg/mL, P < .001) and vitamin D alone (-4 ± 1 pg/mL, P < .001) and their combination (-4 ± 1 pg/mL, P < .001) led to significant reductions compared with placebo (3 ± 1 pg/mL). After adjustment for potential confounders, individuals in the calcium (-3.1 ± 1.3, P < .05), vitamin D (-3.1 ± 1.3, P < .05), and joint calcium-vitamin D groups (-3.4 ± 1.3, P < .05) had greater reductions in serum TNF-α concentrations compared with placebo (0.1 ± 1.2). Individuals who received joint calcium-vitamin D supplements tended to have a decrease in serum high-sensitivity C-reactive protein levels compared with placebo after controlling for baseline levels (-1.14 ± 0.25 vs 0.02 ± 0.24 ng/mL, P = .09).

CONCLUSION

Joint calcium-vitamin D supplementation might improve systemic inflammation through decreasing IL-6 and TNF-α concentrations in vitamin D-insufficient people with type 2 diabetes.

Clinical review: Effect of vitamin D3 supplementation on improving glucose homeostasis and preventing diabetes: a systematic review and meta-analysis

CONTEXT

Observational studies report consistent associations between low vitamin D concentration and increased glycemia and risk of type 2 diabetes, but results of randomized controlled trials (RCTs) are mixed.

OBJECTIVE

The objective of the study was to systematically review RCTs that report on the effects of vitamin D supplementation on glucose homeostasis or diabetes prevention.

DATA SOURCES

Sources of data for the study were MEDLINE, EMBASE, SCOPUS, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, Health Technology Assessment, and Science Citation Index from inception to June 2013.

STUDY SELECTION

Study selection was trials that compared vitamin D3 supplementation with placebo or a non-vitamin D supplement in adults with normal glucose tolerance, prediabetes, or type 2 diabetes.

DATA EXTRACTION AND SYNTHESIS

Two reviewers collected data and assessed trial quality using the Cochrane Risk of Bias tool. Random-effects models were used to estimate mean differences (MDs) and odds ratios. The main outcomes of interest were homeostasis model assessment of insulin resistance, homeostasis model assessment of β-cell function, hemoglobin A1c levels, fasting blood glucose, incident diabetes, and adverse events.

DATA SYNTHESIS

Thirty-five trials (43 407 patients) with variable risk of bias were included. Vitamin D had no significant effects on insulin resistance [homeostasis model assessment of insulin resistance: MD -0.04; 95% confidence interval (CI) -0.30 to 0.22, I-squared statistic (I(2)) = 45%], insulin secretion (homeostasis model of β-cell function: MD 1.64; 95% CI -25.94 to 29.22, I(2) = 40%), or hemoglobin A1c (MD -0.05%; 95% CI -0.12 to 0.03, I(2) = 55%) compared with controls. Four RCTs reported on the progression to new diabetes and found no effect of vitamin D (odds ratio 1.02; 95% CI 0.94 to 1.10, I(2) = 0%). Adverse events were rare, and there was no evidence of publication bias.

CONCLUSIONS

Evidence from available trials shows no effect of vitamin D3 supplementation on glucose homeostasis or diabetes prevention. Definitive conclusions may be limited in the context of the moderate degree of heterogeneity, variable risk of bias, and short-term follow-up duration of the available evidence to date.

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

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

CONCLUSION

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

Does vitamin D improve liver enzymes, oxidative stress, and inflammatory biomarkers in adults with non-alcoholic fatty liver disease? A randomized clinical trial

The aim of this study was to investigate the effects of vitamin D supplementation on serum aminotransferases, insulin resistance, oxidative stress, and inflammatory biomarkers in adult patients with non-alcoholic fatty liver disease (NAFLD). Fifty-three patients with NAFLD were enrolled in a parallel, double-blind, placebo-controlled study. The patients were randomly allocated to receive either one oral pearl consisting of 50,000 IU vitamin D3 (n = 27) or a placebo (n = 26), every 14 days for 4 months. Serum aminotransferases, high-sensitive C-reactive protein (hs-CRP), tumor necrosis factor α, malondialdehyde (MDA), total antioxidant capacity, transforming growth factor β1, as well as grade of hepatic steatosis and homeostasis model assessment of insulin resistance were assessed pre- and post-intervention. In patients who received vitamin D supplement compared to the controls, the median of serum 25(OH)D3 significantly increased (16.2 vs. 1.6 ng/ml, P < 0.001). This increase accompanied by significant decrease in serum MDA (-2.09 vs. -1.23 ng/ml, P = 0.03) and near significant changes in serum hs-CRP (-0.25 vs. 0.22 mg/l, P = 0.06). These between-group differences remained significant even after controlling for baseline covariates. Other variables showed no significant changes. Improved vitamin D status led to amelioration in serum hs-CRP and MDA in patients with NAFLD. This might be considered as an adjunctive therapy to attenuate systemic inflammation and lipid peroxidation alongside other treatments for NAFLD patients.

The role of vitamin D in human fracture healing: a systematic review of the literature

INTRODUCTION

Vitamin D is essential for bone mineralization and for the subsequent maintenance of bone quality. Mineralization is part of hard callus formation and bone remodelling, processes, which are part of fracture healing. We provide a comprehensive review of the literature to summarize and clarify if possible, the cellular effects of vitamin D and its clinical involvement in the process of fracture healing in human.

MATERIAL AND METHODS

We conducted a literature search in PubMed, Embase (OVID version), and Web of Science.

RESULTS

A total of 75 in vitro and 30 in vivo studies were found with inconsistent results about the cellular effect of vitamin D on fracture involved inflammatory cells, cytokines, growth factors, osteoblasts, osteoclasts and on the process of mineralization. With only five in vitro studies performed on material derived from a fracture site and one in vivo study in fracture patients, the exact cellular role remains unclear. Seven studies investigated the circulating vitamin D metabolites in fracture healing. Although it appears that 25(OH)D and 24,25(OH)2D3 are not affected by the occurrence of a fracture, this might not be the case with serum concentrations of 1,25(OH)2D3. The potential clinical effect of vitamin D deficiency is only described in one case series and three case controlled studies, where the results tend to show no effect of a vitamin D deficiency. No clinical studies were found investigating solely vitamin D supplementation. Two clinical studies found a positive effect of vitamin D supplementation and calcium, of increased bone mineral density or respectively increased fracture callus area at the fracture site. One study found indirect evidence that vitamin D and calcium promoted fracture healing.

CONCLUSION

Despite these results, and the presumed beneficial effect of vitamin D supplementation in deficient patients, clinical studies that address the effects of vitamin D deficiency or supplementation on fracture healing are scarce and remain inconclusive. We conclude that vitamin D has a role in fracture healing, but the available data are too inconsistent to elucidate how and in what manner.

Vitamin D and cardiovascular disease

Vitamin D plays a classical hormonal role in skeletal health by regulating calcium and phosphorus metabolism. Vitamin D metabolites also have physiological functions in nonskeletal tissues, where local synthesis influences regulatory pathways via paracrine and autocrine mechanisms. The active metabolite of vitamin D, 1α,25-dihydroxyvitamin D, binds to the vitamin D receptor that regulates numerous genes involved in fundamental processes of potential relevance to cardiovascular disease, including cell proliferation and differentiation, apoptosis, oxidative stress, membrane transport, matrix homeostasis, and cell adhesion. Vitamin D receptors have been found in all the major cardiovascular cell types including cardiomyocytes, arterial wall cells, and immune cells. Experimental studies have established a role for vitamin D metabolites in pathways that are integral to cardiovascular function and disease, including inflammation, thrombosis, and the renin-angiotensin system. Clinical studies have generally demonstrated an independent association between vitamin D deficiency and various manifestations of degenerative cardiovascular disease including vascular calcification. However, the role of vitamin D supplementation in the management of cardiovascular disease remains to be established. This review summarizes the clinical studies showing associations between vitamin D status and cardiovascular disease and the experimental studies that explore the mechanistic basis for these associations.

Mean platelet volume and vitamin D level

BACKGROUND

Vitamin D deficiency and a high mean platelet volume (MPV) are related to cardiovascular disease. We investigated whether vitamin D deficiency is associated with high MPV.

METHODS

This study included 434 patients without chronic disease who were not taking vitamin D or calcium supplements. Vitamin D was measured by chemiluminescent microparticle immunoassay on the Architect-I2000 system (Abbott Diagnostics, USA), and MPV was measured on the Cell-Dyn Ruby analyzer (Abbott Diagnostics). Patients were divided into Groups 1 (138 [men/women, 46/92]), 2 (148 [men/women, 54/94]), and 3 (148 [men/women, 50/98]) according to vitamin D levels of <10 ng/mL, 10-20 ng/mL, and >20 ng/mL, respectively.

RESULTS

The vitamin D level in Group 1 (7.7±1.9 ng/mL) was lower than that in Group 2 (15.1±1.6 ng/mL, P<0.001) and Group 3 (25.6±6.3 ng/mL, P<0.001). The MPV in Group 3 (7.5±1.0 fL) was lower than that in Group 1 (8.1±1.1 fL, P<0.001) and Group 2 (7.9±1.0 fL, P=0.009). Linear regression analysis showed that low levels of vitamin D (β=-0.109, P=0.019) was independently associated with increased MPV.

CONCLUSIONS

There was a strong association between a low vitamin D level and a high MPV; therefore, vitamin D deficiency may be associated with increased MPV.

Mean platelet volume and vitamin D level

BACKGROUND

Vitamin D deficiency and a high mean platelet volume (MPV) are related to cardiovascular disease. We investigated whether vitamin D deficiency is associated with high MPV.

METHODS

This study included 434 patients without chronic disease who were not taking vitamin D or calcium supplements. Vitamin D was measured by chemiluminescent microparticle immunoassay on the Architect-I2000 system (Abbott Diagnostics, USA), and MPV was measured on the Cell-Dyn Ruby analyzer (Abbott Diagnostics). Patients were divided into Groups 1 (138 [men/women, 46/92]), 2 (148 [men/women, 54/94]), and 3 (148 [men/women, 50/98]) according to vitamin D levels of <10 ng/mL, 10-20 ng/mL, and >20 ng/mL, respectively.

RESULTS

The vitamin D level in Group 1 (7.7±1.9 ng/mL) was lower than that in Group 2 (15.1±1.6 ng/mL, P<0.001) and Group 3 (25.6±6.3 ng/mL, P<0.001). The MPV in Group 3 (7.5±1.0 fL) was lower than that in Group 1 (8.1±1.1 fL, P<0.001) and Group 2 (7.9±1.0 fL, P=0.009). Linear regression analysis showed that low levels of vitamin D (β=-0.109, P=0.019) was independently associated with increased MPV.

CONCLUSIONS

There was a strong association between a low vitamin D level and a high MPV; therefore, vitamin D deficiency may be associated with increased MPV.

Vitamin-D supplementation in prediabetes reduced progression to type 2 diabetes and was associated with decreased insulin resistance and systemic inflammation: an open label randomized prospective study from Eastern India

Vitamin-D supplementation in vitamin-D insufficient/deficient prediabetes individuals is associated with significantly lower progression to diabetes (6/55 vs. 13/49; p=0.04) and higher reversal to normoglycemia (23/55 vs. 10/49; p=0.02), associated with decreased insulin resistance and systemic inflammation (TNFα and IL6). Baseline vitamin-D and 2h blood glucose independently predicted progression to diabetes.

Impact of new vitamin D data on future studies and treatment

PURPOSE OF REVIEW

This review evaluates recently published data on clinical effects of vitamin D supplementation, focusing on randomized, placebo-controlled trials and nontraditional actions on the cardiovascular and immune systems.

RECENT FINDINGS

Several randomized trials evaluating vitamin D therapy have recently emerged, in both the general population and in individuals with chronic kidney disease (CKD). In the former, measurable effects on cardiovascular risk factors have not been detected, with the possible exception of a modest reduction in blood pressure. Studies aimed at boosting immunity have demonstrated efficacy only in specific, high-risk populations. In CKD, the benefits of nutritional vitamin D appear largely limited to earlier stages of disease. Benefits of active vitamin D agents, outside of their known effects on mineral metabolism, have also thus far eluded detection. One possible exception that has accumulated supportive evidence is the link between active vitamin D analogs and decreased proteinuria. Large-scale clinical trials, now underway, will be critical to understanding of the potential benefits and hazards of vitamin D treatment.

SUMMARY

New trials evaluating the effects of vitamin D supplementation have failed to reveal any robust clinical benefits beyond its known actions on mineral and bone disease.

Ability of vitamin D to reduce inflammation in adults without acute illness

In vitro studies and some clinical studies suggest that vitamin D plays an important role in reducing inflammation. The objective of this review was to examine recent evidence that vitamin D status influences the level of inflammation in adults without acute illness or injury. Five large cross-sectional studies and two randomized controlled trials are the focus of this review. Associations between 25-hydroxyvitamin D (25OHD) and inflammation markers are significant and inverse in study populations with low 25OHD levels (<21 ng/mL). They are also inverse in adults with relatively high inflammation levels. These associations in the few available randomized controlled vitamin D intervention trials have been null; this may be because they were not examined in populations with sufficiently low levels of 25OHD or high levels of inflammation.

Does insulin resistance in type 2 diabetes alter vitamin D status?

AIMS

Data on changes of vitamin D due to insulin resistance are conflicting. We assessed vitamin D concentrations and parameters of glycemia and mineral homeostasis in patients with insulin resistant type 2 diabetes and in matched normal controls.

METHODS

Sixty-nine patients with type 2 diabetes and 60 matched normal control subjects were studied. After an overnight fast, blood was collected for measuring the parameters of glycemia (glucose, insulin and HbA1c), mineral profile (corrected calcium, phosphate and alkaline phosphatase), total 25(OH) vitamin D and parathyroid hormone (PTH) levels.

RESULTS

Patients had significantly elevated fasting glucose (P=0.0001), insulin (P=0.0003) and HbA1c (P=0.0005) than the controls had. They had significantly raised calculated insulin resistance compared with control subjects (P=0.0001). Patients and controls had similar levels of serum corrected calcium and ALP, whereas serum phosphate was significantly lower in the patients compared with controls (P=0.001). Patients and controls had similar levels of 25(OH)D, but the levels of 25(OH)D in both were in the deficiency range. Intact PTH was similar in the patients and controls. Levels of 25(OH)D did not demonstrate any relation with fasting insulin, insulin resistance, or HbA1c, but correlated negatively with intact PTH (r=-0.4, P=0.02).

CONCLUSION

This study demonstrated prevalent vitamin D deficiency in insulin resistant type 2 diabetic and normal subjects. Insulin resistance did not influence the status of vitamin D.

The role of vitamin D deficiency in cardiovascular disease: where do we stand in 2013?

The high worldwide prevalence of vitamin D deficiency is largely the result of low sunlight exposure with subsequently limited cutaneous vitamin D production. Classic manifestations of vitamin D deficiency are linked to disturbances in bone and mineral metabolism, but the identification of the vitamin D receptor in almost every human cell suggests a broader role of vitamin D for overall and cardiovascular health. The various cardiovascular protective actions of vitamin D such as anti-diabetic and anti-hypertensive effects including renin suppression as well as protection against atherosclerosis and heart diseases are well defined in previous experimental studies. In line with this, large epidemiological studies have highlighted vitamin D deficiency as a marker of cardiovascular risk. However, randomized controlled trials (RCTs) on vitamin D have largely failed to show its beneficial effects on cardiovascular diseases and its conventional risk factors. While most prior vitamin D RCTs were not designed to assess cardiovascular outcomes, some large RCTs have been initiated to evaluate the efficacy of vitamin D supplementation on cardiovascular events in the general population. When considering the history of previous disappointing vitamin RCTs in general populations, more emphasis should be placed on RCTs among severely vitamin D-deficient populations who would most likely benefit from vitamin D treatment. At present, vitamin D deficiency can only be considered a cardiovascular risk marker, as vitamin D supplementation with doses recommended for osteoporosis treatment is neither proven to be beneficial nor harmful in cardiovascular diseases.

So depression is an inflammatory disease, but where does the inflammation come from?

BACKGROUND

We now know that depression is associated with a chronic, low-grade inflammatory response and activation of cell-mediated immunity, as well as activation of the compensatory anti-inflammatory reflex system. It is similarly accompanied by increased oxidative and nitrosative stress (O&NS), which contribute to neuroprogression in the disorder. The obvious question this poses is 'what is the source of this chronic low-grade inflammation?'

DISCUSSION

This review explores the role of inflammation and oxidative and nitrosative stress as possible mediators of known environmental risk factors in depression, and discusses potential implications of these findings. A range of factors appear to increase the risk for the development of depression, and seem to be associated with systemic inflammation; these include psychosocial stressors, poor diet, physical inactivity, obesity, smoking, altered gut permeability, atopy, dental cares, sleep and vitamin D deficiency.

SUMMARY

The identification of known sources of inflammation provides support for inflammation as a mediating pathway to both risk and neuroprogression in depression. Critically, most of these factors are plastic, and potentially amenable to therapeutic and preventative interventions. Most, but not all, of the above mentioned sources of inflammation may play a role in other psychiatric disorders, such as bipolar disorder, schizophrenia, autism and post-traumatic stress disorder.

Vitamin D supplementation affects serum high-sensitivity C-reactive protein, insulin resistance, and biomarkers of oxidative stress in pregnant women

Unfavorable metabolic profiles and oxidative stress in pregnancy are associated with several complications. This study was conducted to determine the effects of vitamin D supplementation on serum concentrations of high-sensitivity C-reactive protein (hs-CRP), metabolic profiles, and biomarkers of oxidative stress in healthy pregnant women. This randomized, double-blind, placebo-controlled clinical trial was conducted in 48 pregnant women aged 18-40 y old at 25 wk of gestation. Participants were randomly assigned to receive either 400 IU/d cholecalciferol supplements (n = 24) or placebo (n = 24) for 9 wk. Fasting blood samples were taken at study baseline and after 9 wk of intervention to quantify serum concentrations of hs-CRP, lipid concentrations, insulin, and biomarkers of oxidative stress. After 9 wk of intervention, the increases in serum 25-hydroxyvitamin D and calcium concentrations were greater in the vitamin D group (+3.7 μg/L and +0.20 mg/dL, respectively) than in the placebo group (-1.2 μg/L and -0.12 mg/dL, respectively; P < 0.001 for both). Vitamin D supplementation resulted in a significant decrease in serum hs-CRP (vitamin D vs. placebo groups: -1.41 vs. +1.50 μg/mL; P-interaction = 0.01) and insulin concentrations (vitamin D vs. placebo groups: -1.0 vs. +2.6 μIU/mL; P-interaction = 0.04) and a significant increase in the Quantitative Insulin Sensitivity Check Index score (vitamin D vs. placebo groups: +0.02 vs. -0.02; P-interaction = 0.006), plasma total antioxidant capacity (vitamin D vs. placebo groups: +152 vs. -20 mmol/L; P-interaction = 0.002), and total glutathione concentrations (vitamin D vs. placebo groups: +205 vs. -32 μmol/L; P-interaction = 0.02) compared with placebo. Intake of vitamin D supplements led to a significant decrease in fasting plasma glucose (vitamin D vs. placebo groups: -0.65 vs. -0.12 mmol/L; P-interaction = 0.01), systolic blood pressure (vitamin D vs. placebo groups: -0.2 vs. +5.5 mm Hg; P-interaction = 0.01), and diastolic blood pressure (vitamin D vs. placebo groups: -0.4 vs. +3.1 mm Hg; P-interaction = 0.01) compared with placebo. In conclusion, vitamin D supplementation for 9 wk among pregnant women has beneficial effects on metabolic status.

Optimal vitamin D status: a critical analysis on the basis of evidence-based medicine

CONTEXT

Public health authorities around the world recommend widely variable supplementation strategies for adults, whereas several professional organizations, including The Endocrine Society, recommend higher supplementation.

METHODS

We analyzed published randomized controlled clinical trials to define the optimal intake or vitamin D status for bone and extraskeletal health.

CONCLUSIONS

The extraskeletal effects of vitamin D are plausible as based on preclinical data and observational studies. However, apart from the beneficial effects of 800 IU/d of vitamin D3 for reduction of falls in the elderly, causality remains yet unproven in randomized controlled trials (RCTs). The greatest risk for cancer, infections, cardiovascular and metabolic diseases is associated with 25-hydroxyvitamin D (25OHD) levels below 20 ng/mL. There is ample evidence from RCTs that calcium and bone homeostasis, estimated from serum 1,25-dihydroxyvitamin D and PTH, calcium absorption, or bone mass, can be normalized by 25OHD levels above 20 ng/mL. Moreover, vitamin D supplementation (800 IU/d) in combination with calcium can reduce fracture incidence by about 20%. Such a dose will bring serum levels of 25OHD above 20 ng/mL in nearly all postmenopausal women. Based on calculations of the metabolic clearance of 25OHD, a daily intake of 500-700 IU of vitamin D3 is sufficient to maintain serum 25OHD levels of 20 ng/mL. Therefore, the recommendations for a daily intake of 1500-2000 IU/d or serum 25OHD levels of 30 ng or higher for all adults or elderly subjects, as suggested by The Endocrine Society Task Force, are premature. Fortunately, ongoing RCTs will help to guide us to solve this important public health question.

Serum 1,25-dihydroxyvitamin D: an outcome prognosticator in human sepsis

In sepsis, the vitamin D active metabolite 1,25-dihydroxyvitamin D (1,25(OH)₂D) may play a crucial role by its action to produce cathelicidin and improve endothelial barrier function, such that a deficiency in 1,25(OH)₂D is associated with poor outcome. To test our hypothesis, we performed analysis of stored plasma samples from a prospective observational study in 91 patients with sepsis, age of 59.1+/−2.0 years, 52.7% females, and 11.0% deaths at 30 days. Vitamin D status, including 25-hydroxyvitamin D (25(OH)D), 1,25(OH)₂D, 24,25-dihydroxyvitamin D (24,25(OH)₂D), and parathyroid hormone (PTH), were measured daily over 3 days after hospital admission. At baseline, 1,25(OH)₂D was significantly different between survivors vs. non-survivors. But there was no significant difference in 25(OH)D, 24,25(OH)₂D, and PTH. In a multivariable binomial logistic regression model, age, total calcium and 1,25(OH)₂D were significant predictors of 30-day mortality. Kaplan Meier analysis showed that patients with mean 1,25(OH)₂D measured over 3 days of < = 13.6 pg/mL had 57.1% 30-day survival compared to 91.7% in patients with 1,25 (OH)₂D level >13.6 pg/mL (p<0.01). From repeated measures regression analysis, there was significant increase in 1,25(OH)₂D for increases in 25(OH)D in both survivors and non-survivors. However, compared to survivors, the low 25(OH)D in non-survivors was insufficient to account for the larger decrease in 1,25(OH)₂D, indicating a dysfunctional 1α-hydroxylase. Additionally, there was a significant negative correlation between PTH and 1,25(OH)₂D in both survivors and non-survivors, suggesting a severe impairment in the effect of PTH to increase renal 1α-hydroxylase activity. In conclusion, low 1,25(OH)₂D levels are associated with increased 30-day mortality in sepsis patients, likely due to impaired 25(OH)D hydroxylation and PTH insensitivity. Our data also suggest that the active metabolite 1,25(OH)₂D may be an important therapeutic target in the design of sepsis clinical trials.

Role of vitamin D in the development of insulin resistance and type 2 diabetes

Vitamin D deficiency is mainly a consequence of insufficient sunlight induced vitamin D production in the skin and has been associated with various chronic diseases including type 2 diabetes. Experimental data have shown that vitamin D is important for glucose induced insulin secretion, improves insulin resistance, and exerts anti-inflammatory actions. Epidemiological studies have largely documented that a poor vitamin D status is associated with higher risk of insulin resistance and type 2 diabetes. The majority of randomized controlled trials (RCTs) in healthy or prediabetic individuals have, however, failed to demonstrate relevant vitamin D effects on insulin resistance or diabetes incidence. In patients with type 2 diabetes, a few RCTs reported some moderate effects of vitamin D on glycemic control and insulin resistance. While these findings warrant further in-depth studies, the current evidence is insufficient to recommend vitamin D supplementation for the prevention or treatment of type 2 diabetes.