Forecasting levels of serum 25-hydroxyvitamin D based on dietary intake, lifestyle and personal determinants in a sample of Southern Europeans

Vitamin D is an essential nutrient to be consumed in the habitual dietary intake, whose deficiency is associated with various disturbances. This study represents a validation of vitamin D status estimation using a semi-quantitative FFQ, together with data from additional physical activity and lifestyle questionnaires. This information was combined to forecast the serum vitamin D status. Different statistical methods were applied to estimate the vitamin D status using predictors based on diet and lifestyle. Serum vitamin D was predicted using linear regression (with leave-one-out cross-validation) and random forest models. Intraclass correlation coefficients, Lin's agreement coefficients, Bland-Altman plots and other methods were used to assess the accuracy of the predicted v. observed serum values. Data were collected in Spain. A total of 220 healthy volunteers aged between 18 and 78 years were included in this study. They completed validated questionnaires and agreed to provide blood samples to measure serum 25-hydroxyvitamin D (25(OH)D) levels. The common final predictors in both models were age, sex, sunlight exposure, vitamin D dietary intake (as assessed by the FFQ), BMI, time spent walking, physical activity and skin reaction after sun exposure. The intraclass correlation coefficient for the prediction was 0·60 (95 % CI: 0·52, 0·67; P < 0·001) using the random forest model. The magnitude of the correlation was moderate, which means that our estimation could be useful in future epidemiological studies to establish a link between the predicted 25(OH)D values and the occurrence of several clinical outcomes in larger cohorts.

The effect of vitamin D supplementation on serum levels of fibroblast growth factor- 23: A systematic review and meta-analysis of randomized controlled trials

Previous studies of the effect of vtamin D on serum levels of fibroblast growth factor- 23 (FGF-23) have yeilded an inconsistent findings. This systematic review and meta-analysis of randomized controlled trials (RCTs) sought to investigate the effect of vitamin D supplementation on serum levels of FGF-23. PubMed, Scopus, ISI Web of Science, and the Cochrane Library were searched, from database inception to November 2020, for RCTs that evaluated the effects of native or active vitamin D supplementation on serum levels of FGF-23 in adults. Weighted mean difference (WMD) were calculated and random effects meta-analysis was used to estimate the overall effects. Twenty-seven trials were included in the meta-analysis. Supplementation with native vitamin D (23 studies, n = 2247 participants; weighted mean difference [WMD] = 0.5 pg/mL, 95 % CI: -0.52 to 1.51, P = 0.33; I² = 29.9 %), and active vitamin D (5 studies, n = 342 participants, WMD = 29.45 pg/mL, 95 % CI: -3.9 to 62.81, P = 0.08; I² = 99.3%) had no significant effects on serum FGF-23 concentration. In subgroup analyses, supplementation with ergocalciferol (3 studies, n = 205 participants; WMD = 18.27 pg/mL, 95 % CI: 5.36-31.17, P = 0.006), and daily dosing regimens (9 studies, n = 1374 participants; WMD = 0.41 pg/mL, 95 % CI: 0.22 to 0.59, P < 0.001) increased serum FGF-23 levels compared to control. Overall, our findings revealed no significan effect of vitamin D supplementation on serum FGF-23 concentration. However, further high quality, large-scale studies are needed to better elucidate this relationship.

Relative Efficacy of Vitamin D2 and Vitamin D3 in Improving Vitamin D Status: Systematic Review and Meta-Analysis

BACKGROUND

Widespread prevalence of vitamin D deficiency has been documented globally. Commonly used interventions to address this deficiency include supplementation and/or fortification with either ergocalciferol (vitamin D₂) or cholecalciferol (vitamin D₃), but the relative efficacy of these two vitamers is unclear. The current study aimed to evaluate the relative efficacy of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃) for raising the serum levels of vitamin D metabolites and functional indicators including serum parathyroid (PTH) levels, isometric muscle strength, hand grip strength and bone mineral density.

METHODS

Randomized and non-randomized controlled studies evaluating relative efficacy of ergocalciferol and cholecalciferol were systematically reviewed to synthesize quantitative and qualitative evidence as per the recommendations of according to "Preferred Reporting Items for Systematic reviews and Meta-analysis" guidelines. Search terms were constructed on the basis of the "participants", "intervention", "control", "outcome" and "study type" (PICOS) strategy to systematically search the popular electronic databases. Relevant data from studies meeting inclusion and exclusion criteria were extracted and analyzed. Meta-regression, subgroup and sensitivity analyses were performed to investigate the influence of study-level characteristics including intervention dosage, frequency of dosing, interval between the last dose and test for outcome assessment, participant characteristics and analytical methods.

RESULTS

Apparently healthy human participants (n = 1277) from 24 studies were included for meta-analysis. The quantitative analysis suggested higher efficacy of cholecalciferol than ergocalciferol in improving total 25(OH)D (mean difference: 15.69, 95%CI: 9.46 to 21.93 nmol/L) and reducing PTH levels, consistently across variable participant demographics, dosage and vehicle of supplementation. Meta-regression suggested smaller differences in the efficacy of cholecalciferol and ergocalciferol at lower doses. Average daily dose was the single significant predictor of effect size, as revealed by multivariate meta-regression analysis.

CONCLUSIONS

Compared to ergocalciferol, cholecalciferol intervention was more efficacious in improving vitamin D status (serum levels of total 25(OH)D and 25(OH)D₃) and regulating PTH levels, irrespective of the participant demographics, dosage and vehicle of supplementation.

Vitamin D Metabolites and Clinical Outcome in Hospitalized COVID-19 Patients

(1) Background: Vitamin D, a well-established regulator of calcium and phosphate metabolism, also has immune-modulatory functions. An uncontrolled immune response and cytokine storm are tightly linked to fatal courses of COVID-19. The present retrospective study aimed to inves-tigate vitamin D status markers and vitamin D degradation products in a mixed cohort of 148 hospitalized COVID-19 patients with various clinical courses of COVID-19. (2) Methods: The serum concentrations of 25(OH)D₃, 25(OH)D₂, 24,25(OH)₂D₃, and 25,26(OH)₂D₃ were determined by a validated liquid-chromatography tandem mass-spectrometry method in leftover serum samples from 148 COVID-19 patients that were admitted to the University Hospital of the Medical Uni-versity of Graz between April and November 2020. Anthropometric and clinical data, as well as outcomes were obtained from the laboratory and hospital information systems. (3) Results: From the 148 patients, 34 (23%) died within 30 days after admission. The frequency of fatal outcomes did not differ between males and females. Non-survivors were significantly older than survivors, had higher peak concentrations of IL-6 and CRP, and required mechanical ventilation more frequently. The serum concentrations of all vitamin D metabolites and the vitamin D metabolite ratio (VMR) did not differ significantly between survivors and non-survivors. Additionally, the need for res-piratory support was unrelated to the serum concentrations of 25(OH)D vitamin D and the two vitamin D catabolites, as well as the VMR. (4) Conclusion: The present results do not support a relevant role of vitamin D for the course and outcome of COVID-19.

Increased 1,25(OH)2-Vitamin D Concentrations after Energy Restriction Are Associated with Changes in Skeletal Muscle Phenotype

The influence of energy restriction (ER) on muscle is controversial, and the mechanisms are not well understood. To study the effect of ER on skeletal muscle phenotype and the influence of vitamin D, rats (n = 34) were fed a control diet or an ER diet. Muscle mass, muscle somatic index (MSI), fiber-type composition, fiber size, and metabolic activity were studied in tibialis cranialis (TC) and soleus (SOL) muscles. Plasma vitamin D metabolites and renal expression of enzymes involved in vitamin D metabolism were measured. In the ER group, muscle weight was unchanged in TC and decreased by 12% in SOL, but MSI increased in both muscles (p < 0.0001) by 55% and 36%, respectively. Histomorphometric studies showed 14% increase in the percentage of type IIA fibers and 13% reduction in type IIX fibers in TC of ER rats. Decreased size of type I fibers and reduced oxidative activity was identified in SOL of ER rats. An increase in plasma 1,25(OH)₂-vitamin D (169.7 ± 6.8 vs. 85.4 ± 11.5 pg/mL, p < 0.0001) with kidney up-regulation of CYP27b1 and down-regulation of CYP24a1 was observed in ER rats. Plasma vitamin D correlated with MSI in both muscles (p < 0.001), with the percentages of type IIA and type IIX fibers in TC and with the oxidative profile in SOL. In conclusion, ER preserves skeletal muscle mass, improves contractile phenotype in phasic muscles (TC), and reduces energy expenditure in antigravity muscles (SOL). These beneficial effects are closely related to the increases in vitamin D secondary to ER.

Vitamin D Status in Egyptian Children With Allergic Rhinitis

Objective: This study aimed to assess the serum levels of vitamin D in an Egyptian cohort of children with allergic rhinitis (AR) and to evaluate any correlation of vitamin D status with the disease severity. Patient and methods: One hundred twenty children with AR and 100 healthy children were included in our study. We studied the serum levels of vitamin D 25(OH)D and 1,25(OH)2D in all participants. The associations between vitamin D levels and clinical characteristics of AR were examined. Results: In AR group, the serum levels of calcium, (25(OH)D and 1,25(OH)2D levels were significantly lower (p < .0001, p < .001, and p < .0001, respectively) in AR children than in controls. Furthermore, the mean 25-OHD3 levels in patients with moderate/severe AR were significantly lower than those with mild AR (p < .001). We found significant negative correlations between mean 25(OH)D levels and total nasal symptom score (r = -.62, p = .002) and total immunoglobulin E levels (r = -.27, p = .013) in AR group. Conclusions: Vitamin D deficiency is a frequent finding among Egyptian children with AR when compared to the healthy group. A significant inverse association was observed between vitamin D levels and AR disease severity.

Association of vitamin D2 and D3 with type 2 diabetes complications

AIMS

Vitamin D measurement is a composite of vitamin D₂ (25(OH)D₂) and D₃ (25(OH)D₃) levels, and its deficiency is associated with the development of type 2 diabetes (T2DM) and diabetic complications; vitamin D deficiency may be treated with vitamin D₂ supplements. This study was undertaken to determine if vitamin D₂ and D₃ levels differed between those with and without T2DM in this Middle Eastern population, and the relationship between diabetic microvascular complications and vitamin D₂ and vitamin D₃ levels in subjects with T2DM_. METHODS: Four hundred ninety-six Qatari subjects, 274 with and 222 without T2DM participated in the study. Plasma levels of total vitamin D₂ and D₃ were measured by LC-MS/MS analysis.

RESULTS

All subjects were taking vitamin D₂ and none were taking D₃ supplements. Vitamin D₂ levels were higher in diabetics, particularly in females, and higher levels were associated with hypertension and dyslipidemia in the diabetic subjects (p < 0.001), but were not related to diabetic retinopathy or nephropathy. Vitamin D₃ levels measured in the same subjects were lower in diabetics, particularly in females (p < 0.001), were unrelated to dyslipidemia or hypertension, but were associated with retinopathy (p < 0.014). Neither vitamin D₂ nor vitamin D₃ were associated with neuropathy. For those subjects with hypertension, dyslipidemia, retinopathy or neuropathy, comparison of highest with lowest tertiles for vitamin D₂ and vitamin D₃ showed no difference.

CONCLUSIONS

In this Qatari cohort, vitamin D₂ was associated with hypertension and dyslipidemia, whilst vitamin D₃ levels were associated with diabetic retinopathy. Vitamin D₂ levels were higher, whilst vitamin D₃ were lower in diabetics and females, likely due to ingestion of vitamin D₂ supplements.

Multiple Sclerosis Patients Show Lower Bioavailable 25(OH)D and 1,25(OH)2D, but No Difference in Ratio of 25(OH)D/24,25(OH)2D and FGF23 Concentrations

Vitamin D (VitD) insufficiency is common in multiple sclerosis (MS). VitD has possible anti-inflammatory effects on the immune system. The ratio between VitD metabolites in MS patients and the severity of the disease are suggested to be related. However, the exact effect of the bone-derived hormone fibroblast-growth-factor-23 (FGF23) and VitD binding protein (VDBP) on this ratio is not fully elucidated yet. Therefore, the aim is to study differences in total, free, and bioavailable VD metabolites and FGF23 between MS patients and healthy controls (HCs). FGF23, vitD (25(OH)D), active vitD (1,25(OH)₂D), inactive 24,25(OH)D, and VDBP were measured in 91 MS patients and 92 HCs. Bioavailable and free concentrations were calculated. No difference in FGF23 (p = 0.65) and 25(OH)D/24.25(OH)₂D ratio (p = 0.21) between MS patients and HCs was observed. Bioavailable 25(OH)D and bioavailable 1.25(OH)₂D were lower (p < 0.01), while VDBP concentrations were higher in MS patients (p = 0.02) compared with HCs, specifically in male MS patients (p = 0.01). In conclusion, FGF23 and 25(OH)D/24.25(OH)₂D did not differ between MS patients and HCs, yet bioavailable VitD concentrations are of potential clinical relevance in MS patients. The possible immunomodulating role of VDBP and gender-related differences in the VD-FGF23 axis in MS need further study.

Sources of variation evaluation of 24,25(OH)2D levels and the ratio of 25OHD to 24,25(OH)2D in apparently healthy Chinese adults: a multicenter cross-sectional study

24,25(OH)₂D and the 25OHD/24,25(OH)₂D ratio have recently been shown to be useful for screening for hypercalcemia caused by CYP24A1 mutations. However, no population-based data on 24,25(OH)₂D have been published for Chinese populations, and few studies evaluated the sources of variation on 24,25(OH)₂D levels and the 25OHD/24,25(OH)₂D ratio. Hence, in 2018, we enrolled 1211 apparently healthy adults without systematic diseases from six representative cities in China (Beijing, Dongying, Guiyang, Urumqi, Shenzhen, and Qiqihar). 24,25(OH)₂D and 25OHD levels were measured using isotope dilution liquid chromatography tandem mass spectrometry. Multiple regression analysis showed that sex contributed the most to variations in 24,25(OH)₂D, 25OHD, and 25OHD/24,25(OH)₂D (rp= -0.255, -0.253, and 0.141, respectively), and age also contributed to variations in 25OHD but not 24,25(OH)₂D or 25OHD/24,25(OH)₂D. Men had significantly higher 24,25(OH)₂D and 25OHD levels than women, but had significantly lower 25OHD/24,25(OH)₂D values. Individuals from Dongying had the highest 24,25(OH)₂D and 25OHD values, whereas individuals from Urumqi had the lowest values. The median(2.5-97.5%) values for 24,25(OH)₂D, 25OHD, and 25OHD/24,25(OH)₂D were 1.2(0.36-2.65) ng/mL, 18.9(8.6-32.5) ng/mL, and 16.0 (9.8-30.8), respectively. 24,25(OH)₂D was significantly correlated with 25OHD (r = 0.838, p <  0.001), and 25OHD/24,25(OH)₂D was significantly negatively correlated with 24,25(OH)₂D (r = -0.758, P < 0.001) and 25OHD (r = -0.310, P < 0.001). In conclusion, in this nationwide, multicenter, cross-sectional study, we evaluated the levels of 24,25(OH)₂D and the 25OHD/24,25(OH)₂D ratio in the Chinese population. Sex contributed the most to variations in 24,25(OH)₂D, 25OHD, and 25OHD/24,25(OH)₂D.

[Vitamin D deficiency in Spanish population. Importance of egg on nutritional improvement]

INTRODUCTION

Vitamin D is an essential nutrient whose deficiency has been associated with the risk of various chronic diseases such as osteoporosis, hypertension, cardiovascular disease, diabetes, some types of cancer and even overweight and obesity. Although vitamin D can be synthesized at the skin from exposure to sunlight, this source is not always sufficient to meet the needs. For example, the use of sunscreen or the low exposition to the sunlight limits the syntheses. In fact, studies have found that at least half of the Spanish population has vitamin D deficits. Therefore, the dietary contribution is fundamental. Although there are different foods fortified in this vitamin, few products are natural source of it, as fatty fish and eggs. However, according to different studies carried out in the Spanish population, there is a low consumption of this food group. In this way, it would be advisable to promote egg consumption among the population, since this food, in addition to having many nutrients, contains a high amount of vitamin D, which contributes to avoid the appearance of deficiencies and the consequences health consequences that this implies.

Free versus total serum 25-hydroxyvitamin D in a murine model of colitis

Inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease have been linked to vitamin D-deficiency. Using a dextran sodium sulphate (DSS)-induced model of IBD we have shown previously that mice raised on vitamin D-deficient diets from weaning have lower serum 25-hydroxyvitamin D (25OHD) levels and develop more severe colitis compared to vitamin D-sufficient counterparts. We have also shown in vitro that immune responses to 25OHD may depend on 'free' rather than total serum concentrations of 25OHD. To investigate the possible effects of free versus total 25OHD on anti-inflammatory immune responses in vivo we have studied DSS-induced colitis in wild type C57BL/6 mice raised from weaning on diets containing vitamin D2 (D2) or vitamin D3 (D3) only (both 1000 IU/kg feed). 25OHD2 has lower binding affinity for the vitamin D binding protein than 25OHD3 which results in higher levels of free 25OHD2 relative to free 25OHD3 in mice raised on a D2-only diet. Total serum 25OHD concentrations, measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS), showed that D2 mice had significantly lower levels of 25OHD than D3 mice (6.85 ± 2.61 nmol/L vs. 49.16 ± 13.8 nmol/L for D2 and D3 respectively). Despite this, direct ELISA measurement showed no difference in free serum 25OHD levels between D2 and D3 mice (13.62 ± 2.26 pmol/L vs. 14.11 ± 2.24 pmol/L for D2 and D3 respectively). Analysis of DSS-induced colitis also showed no difference in weight loss or disease progression between D2 and D3 mice. These data indicate that despite D2-fed mice being vitamin D-deficient based on serum total 25OHD concentrations, these mice showed no evidence of increased inflammatory colitis disease relative to vitamin D-sufficient D3 mice. We therefore propose that free, rather than total serum 25OHD, may be a better marker of immune responses to vitamin D in vivo.

Rapid liquid chromatography-tandem mass spectrometry method for determination of 24,25(OH)2D and 25OHD with efficient separation of 3-epi analogs

This study establishes and validates a rapid method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) without derivatization steps to simultaneously measure of 24,25(OH)₂D₂, 24,25(OH)₂D₃, 25OHD₂, and 25OHD₃, while efficiently separating the 3-epi analogs. Samples were prepared by precipitation and liquid-liquid extraction. The linearity, precision, accuracy, recovery and matrix effect of the method were thoroughly evaluated according to the Clinical & Laboratory Standards Institute guidelines. Additionally, the four vitamin D metabolites in the serum of 38 apparently healthy Chinese volunteers were evaluated. The total analysis time was 8.0 min, with efficient separation of 3-epi 24,25(OH)₂D₃ and 3-epi 25OHD₃, without interference from isomers such as 23,25(OH)₂D₃ or 1,25(OH)₂D₂, 1,25(OH)₂D₃. Good reproducibility was obtained for all four metabolites with within-run coefficient variations (CVs) of 4.07%-6.55%, 4.26%-7.84%, 2.46%-7.21%, and 4.90%-6.87% for 25OHD₃, 25OHD₂, 24,25(OH)₂D₃, and 24,25(OH)₂D₂, respectively, and the total CVs were 4.29%-6.64%, 6.14%-7.84%, 4.33%-7.21%, 5.82%-9.90%, respectively. The limit of quantification was 0.625 ng/mL for 25OHD₃ and 25OHD₂, and 0.5 ng/mL for 24,25(OH)₂D₃ and 24,25(OH)₂D₂. The relative bias of the LC-MS/MS method compared to the certified results of SRM 972a for 25OHD₃, 25OHD₂ and 24,25(OH)₂D₃ was -2.21% to 1.01%, 3.38% to 6.73%, and -7.72% to -3.9%, respectively. The mean±SD values for 25OHD, 24,25(OH)₂D and 25OHD/24,25(OH)₂D in the volunteers were 13.5±4.4 ng/mL(range:7.6-27.5 ng/mL), 0.84±0.42 ng/mL (range:0.26-2.1 ng/mL), and 18±7(range:8-37), respectively. Thus, a simple, precise LC-MS/MS method for appropriate retention and separation of vitamin D metabolites and their epi analogs was developed.

Vitamin-D2 treatment-associated decrease in 25(OH)D3 level is a reciprocal phenomenon: a randomized controlled trial

BACKGROUND

Vitamin-D2 (D2) treatment has been associated with a decrease in 25-hydroxy (25(OH)) vitamin-D3 (D3) level, suggesting that D3 treatment would be preferred to raise total 25(OH) vitamin-D (D) level. We postulated that D2 treatment-associated decrease in 25(OH)D3 level is related to the increase in 25(OH)D level rather than being D2-specific, and thus there would be a similar D3 treatment-associated decrease in 25(OH)D2 level.

METHODS

Fifty volunteers were block-randomized to 50,000 IU D2 or placebo orally once (study-1) and fifty volunteers received 50,000 IU D2 orally once and 4 days later block-randomized to 50,000 IU D3 or placebo orally once (study-2). Interventions were concealed from volunteers and research coordinators and blindly-administered. Serum 25(OH)D2 and 25(OH)D3 levels were blindly-determined at baseline and days 14, 28, 42, and 56, post-randomization by high performance liquid chromatography assay. Results of 97 participants were analyzed. Primary outcome measure was day-28 D2-associated change in 25(OH)D3 level in study-1 and D3-associated change in 25(OH)D2 level in study-2, adjusted for baseline levels.

RESULTS

Mean (95% confidence interval) difference between the active and placebo arms in the decrease in day-28 25(OH)D3 (study-1) and 25(OH)D2 (study-2) levels was 13.2 (9.7 to 16.6) and 9.8 (5.2 to 14.4) nmol/L, respectively. Corresponding differences at day-56 were 10.8 (6.8 to 14.8) and 1.7 (- 7.6 to 11.1) nmol/L, respectively. The difference between the placebo and active arms in area-under-the-curve at day-28 (AUC₂₈) and day-56 (AUC₅₆) were 262.3 (197.8 to 326.7) and 605.1 (446.3 to 784.0) for 25(OH)D3 (study-1) and 282.2 (111.2 to 453.3) and 431.2 (179.3 to 683.2) nmol.d/L for 25(OH)D2 (study-2), respectively. There were significant correlations between day-28 changes in 25(OH)D2 and 25(OH)D3 levels in study-1 (rho = - 0.79, p < 0.001) and study-2 (rho = - 0.36, p = 0.01), and between day-28 changes in 25(OH)D2 level and baseline 25(OH)D level in study-2 (rho = - 0.42, p = 0.003).

CONCLUSIONS

Compared to placebo, D3 treatment is associated with a decrease in 25(OH)D2 level similar in magnitude to D2-treatment associated decrease in 25(OH)D3 level; however, the D3-placebo difference in 25(OH)D2 level is shorter-lasting. Changes in 25(OH)D2 and 25(OH)D3 levels are correlated with each other and with baseline 25 (OH) D levels, suggesting a common regulatory mechanism.

TRIAL REGISTRATION

ClinicalTrial.gov identifier: NCT03035084 (registered January 27, 2017).

The role of proteinuria, paricalcitol and vitamin D in the development of post-transplant diabetes mellitus

INTRODUCTION

Post-transplant diabetes mellitus (PTDM) occurs most frequently during the first year after transplantation. We focused on parameters of calcium-phosphate metabolism and proteinuria as possible new risk factors for PTDM after kidney transplantation.

MATERIALS AND METHODS

We have prospectively identified risk factors for post-transplant diabetes mellitus with follow-up of 12 months in a set of 167 patients after kidney transplantation. Patients with diabetes mellitus type 1 and type 2 as well as patients using ciclosporin A or mTOR inhibitor have been excluded from the monitoring. From the perspective of immunosuppression it was a homogeneous set of patients.

RESULTS

We identified the following independent risk factors for PTDM in our set: average proteinuria > 0.300 g/24 h (HR 3.0785, (95 % CI 1.6946-5.5927), p=0.0002), level of vitamin D<20 ng/ml (HR 5.4517, (95 % CI 2.3167-11.8209), p1.45 mmol/l (HR0.0821, (95 % CI0.0042-1.5920), p=0.0439). The lowest occurrence of PTDM and proteinuria was recorded in patients whose treatment included paricalcitol (p<0.0001) and these patients had at the same time the highest level of vitamin D (p<0.0001).

CONCLUSION

Deficit of vitamin D, proteinuria and hyperphosphatemia have been independent risk factors for the development of PTDM in our set. We identified the usage of paricalcitol as protective factor with regard to the PTDM development (Tab. 6, Fig. 4, Ref. 29).

Clinical practice guidelines for vitamin D in the United Arab Emirates

In the UAE and the Gulf region in general, there are several intricate public health issues in the context of vitamin D deficiency that needs to be addressed. Changes in lifestyle such as diet, lack of exercise, cultural habits, avoiding sun exposure due to excessive heat, and other risk factors predispose those who live in GULF countries, such as Emiratis likely to becoming vitamin D deficient. Consequently, the prevalence of vitamin D deficiency is high, and new guidelines are needed to overcome this major public health issue. Peer-reviewed papers related to guidelines and those vitamin D-related papers relevant to the Middle-Eastern region were extracted from multiple research databases using key words according to the general guidelines from the Preferred Reporting Items for Systematic Analysis. This guideline was prepared focusing on the United Arab Emirate and the Gulf populations, to overcome the high incidence of vitamin D deficiency and to improve overall health. We recommend the following vitamin D supplementations for different groups of people: (A) Breastfed infants supplement with 400 IU/day up to age 6 months, and 400-600 IU/day between 6 and 12 months, depending on daily intake of total vitamin D and sun exposure; (B) for children and adolescents of age 1-18 years supplement with 600-1000 IU/day depending on the body weight; (C) adults greater than 18 years', supplementation with 1000-2000 IU/day is recommended, while, (D) the elderly (over 65 years) should be supplemented with 2000 IU/day, throughout the year; (E) pregnant and breast feed women, 2000 IU/day from the first trimester of pregnancy. (F) Premature infants, supplementation of 400-800 IU/daystart from the first days of life. (G) For obese, individuals and those with metabolic syndrome, supplementation of 2000 IU/day (H) For individuals with dark skin complexions and for night workers, supplementation of 1000-2000 IU/day (25-50μg/day), throughout the year, depending on body weight. The goal of supplementation is to achieve and longer term maintenance of serum 25(OH)D concentration of 30-50ng/mL.

Quality assessment of vitamin D metabolite assays used by clinical and research laboratories

The Vitamin D External Quality Assessment Scheme (DEQAS) was launched in 1989 and monitors the performance of 25-hydroxyvitamin D (25-OHD) and 1,25- dihydroxyvitamin D (1,25(OH)₂D) assays. In April 2015 a pilot scheme for 24,25-dihydroxyvitamin D (24,25(OH)₂D) was introduced. The 25-OHD scheme is accuracy - based with target values assigned by the NIST Reference Measurement Procedure (RMP) for 25-OHD₂ and 25-OHD₃. A similar method is used to assign values for 3-epi-25-OHD. Five samples of human serum are distributed quarterly to over 1000 participants in 58 countries (April 2016) and clinical laboratories are expected to submit results within approximately 5 weeks. Research laboratories with assays run less frequently are not given a deadline. Archived samples with NIST- assigned values are also available. Performance is assessed on the first four samples with the fifth reserved for investigations e.g. recovery experiments or to assess the influence of other serum constituents such as lipids. DEQAS provides rapid feedback, with an on-line preliminary report available immediately after a participant submits results and a comprehensive report soon after the results deadline. In 2015, DEQAS investigations revealed that several 25-OHD immunoassays under-recovered 25-OHD₂ and 25-OHD results were falsely low on a sample with a modestly raised triglyceride concentration. An RMP for 1,25 (OH)₂D is not yet available and results are judged against the Method Mean. Free advice is available from the DEQAS Advisory Panel which includes experts on methodology and biostatistics. DEQAS collaborates closely with the Vitamin D Standardization Program (VDSP) and both organizations have successfully worked with participants and manufacturers to improve the accuracy of vitamin D assays.

Plasma transport of ergocalciferol and cholecalciferol and their 25-hydroxylated metabolites in dairy cows

In cattle, there are 2 significant forms of vitamin D: ergocalciferol (ERG) from fungi on roughage and cholecalciferol (CHO) from vitamin supplements or endogenous synthesis in the skin. The hypothesis of the present study is that vitamin D from the 3 sources is transported in different plasma fractions in the body. This is hypothesized to explain the lower efficiency of ERG compared to CHO in securing a sufficient plasma status of 25-hydroxyvitamin D and explain the inefficient excretion of dietary CHO into milk compared to endogenous CHO. Twenty vitamin D-depleted cows were assigned to 5 treatments: D2, housed indoor and fed 625-μg/d (25.000 IU) ERG; D3, housed indoor and fed 625-μg/d CHO; D2+D3, housed indoor and fed 625-μg/d ERG and 625-μg/d CHO; SUN, let out for daily pasture to facilitate CHO synthesis from sunlight; and D2+SUN, fed 625-μg/d ERG and let out for daily pasture. Blood samples were taken twice weekly and plasma fractionated by ultracentrifugation into 3 fractions: light lipoprotein (LLP), heavy lipoprotein (HLP), and protein and analyzed for content of ERG and CHO and their liver derived metabolites 25-hydroxyergocalciferol (25ERG) and 25-hydroxycholecalciferol (25CHO), respectively. Liver biopsies were taken on the last day of the study to asses gene expression related to vitamin D metabolism. During 4 wk of study, the vitamin D status in plasma increased to 19.3 to 22.8 ng/mL 25ERG in ERG-treated cows with the highest concentration in D2 (P ≤ 0.05) and to 25.0 to 33.4 ng/mL 25CHO in pasture or CHO-treated cows with the highest concentration in SUN (P ≤ 0.01). In plasma fractions, CHO was mainly found in the HLP fraction, whereas 25CHO was almost exclusively found in the protein fraction, probably due to its reported high binding affinity to vitamin D-binding protein. About 70% to 90% of 25ERG was found in the protein fraction and the remaining 25ERG was found in HLP, whereas ERG was found in both HLP and LLP fractions. In liver tissue, the expression of vitamin D-25-hydroxylase was lower in D2+D3 (P ≤ 0.05) and SUN (P ≤ 0.05) than that in the remaining groups, and the vitamin D receptor was expressed in the liver to a larger extent in D2+SUN than that in D2+D3 (P ≤ 0.05) and SUN (P ≤ 0.05). In conclusion, different plasma transport mechanisms may explain the lower physiological efficiency of ERG compared to CHO in securing the vitamin D status in plasma but do not explain the lower efficiency of synthetic CHO compared to endogenous CHO from sunlight or UV light in securing a high CHO content in milk.

Vitamin D in Chronic Kidney Disease and Dialysis Patients

Vitamin D deficiency (<20 ng/mL) and insufficiency (20–29 ng/mL) are common among patients with chronic kidney disease (CKD) or undergoing dialysis. In addition to nutritional and sunlight exposure deficits, factors that affect vitamin D deficiency include race, sex, age, obesity and impaired vitamin D synthesis and metabolism. Serum 1,25(OH)₂D levels also decrease progressively because of 25(OH)D deficiency, together with impaired availability of 25(OH)D by renal proximal tubular cells, high fibroblast growth factor (FGF)-23 and decreased functional renal tissue. As in the general population, this condition is associated with increased morbidity and poor outcomes. Together with the progressive decline of serum calcitriol, vitamin D deficiency leads to secondary hyperparathyroidism (SHPT) and its complications, tertiary hyperparathyroidism and hypercalcemia, which require surgical parathyroidectomy or calcimimetics. Kidney Disease Outcomes Quality Initiative (KDOQI) and Kidney Disease Improving Global Outcomes (KDIGO) experts have recognized that vitamin D insufficiency and deficiency should be avoided in CKD and dialysis patients by using supplementation to prevent SHPT. Many vitamin D supplementation regimens using either ergocalciferol or cholecalciferol daily, weekly or monthly have been reported. The benefit of native vitamin D supplementation remains debatable because observational studies suggest that vitamin D receptor activator (VDRA) use is associated with better outcomes and it is more efficient for decreasing the serum parathormone (PTH) levels. Vitamin D has pleiotropic effects on the immune, cardiovascular and neurological systems and on antineoplastic activity. Extra-renal organs possess the enzymatic capacity to convert 25(OH)D to 1,25(OH)₂D. Despite many unanswered questions, much data support vitamin D use in renal patients. This article emphasizes the role of native vitamin D replacement during all-phases of CKD together with VDRA when SHPT persists.

Comparison of the effects of novel vitamin D receptor analog VS-105 and paricalcitol on chronic kidney disease-mineral bone disorder in an experimental model of chronic kidney disease

When using vitamin D, the most important clinical problems are hypercalcemia, hyperphosphatemia, and vascular calcification. VS-105 is a novel vitamin D receptor (VDR) analog. In the present study, we compared the effects of VS-105 and paricalcitol on chronic kidney disease-mineral bone disorder (CKD-MBD) in a CKD rat model. We used male Sprague-Dawley (SD) rats and performed 5/6 nephrectomy at 8-9 weeks. At 10 weeks, the rats were classified into five groups and administered vehicle, low-dose paricalcitol (LP, 0.1μg/kg), high-dose paricalcitol (HP, 0.3μg/kg), low-dose VS-105 (LV, 0.2μg/kg), and high-dose VS-105 (HV, 0.6 μg/kg) three times a week for 10 weeks. There were no significant differences in blood pressure or renal function among the five groups. Alhough serum calcium levels were comparable between the LP and LV groups, they were higher in the HP group than in the HV group. Serum phosphate levels were higher in the paricalcitol-treated groups than in the VS-105-treated groups and paticularly higher in the HP group than in the other groups. The urinary excretion of phosphate was greater in the VS-105-treated groups than in the paricalcitol-treated groups. Serum parathyroid hormone (PTH) levels decreased and serum fibroblast growth factor-23 (FGF23) levels were elevated after administering paricalcitol and VS-105; however, serum FGF23 levels were remarkably elevated in the paricalcitol-treated groups. Further biochemical analyses revealed that the calcium content of the aorta was higher in the paricalcitol-treated groups than in the VS-105-treated group. VDR and Klotho expression in the kidney was significantly higher in the VS-105-treated groups than in the paricalcitol-treated groups although both agents increased these expressions. Our data suggest that VS-105 had a lesser effect on CKD-MBD than paricalcitol except in the case of serum PTH levels. The mechanism appears to be associated with the difference in VDR and Klotho expression.

Determination of human reference values for serum total 1,25-dihydroxyvitamin D using an extensively validated 2D ID-UPLC-MS/MS method

BACKGROUND

To assess a patient's vitamin D status the precursor metabolite 25-hydroxyvitamin D can be determined. However, measurement of 1,25-dihydroxyvitamin D is required when disorders of 1a-hydroxylation, extrarenal 1a-hydroxylation, or vitamin D receptor defects are suspected.

METHODS

The aim of this study was to determine reference values for 1,25-dihydroxyvitamin D₃ and D₂ using a 2D ID-UPLC-MS/MS method.

RESULTS

The LC-MS/MS method, able to measure picomolar concentrations of both 1,25-dihydroxyvitamin D₃ and D₂ in human serum, was extensively validated. Intra-assay variations were <5% and 8.5% and <7.5% and 11%, for 1,25-dihydroxyvitamin D₃ and D₂, respectively, over the whole dynamic range (3.1-376 and 3.1-652pmol/L). Limit of quantitation was 3.4pmol/L for both compounds. Our method correlated well with a published LC-MS/MS method (r=0.87) and with the average 1,25-dihydroxyvitamin D₃ results of the vitamin D External Quality Assessment Scheme (DEQAS) determined with LC-MS/MS (r=0.93). Reference ranges, determined in 96 plasma samples of healthy volunteers were 59-159pmol/L and <17pmol/L for respectively 1,25-dihydroxyvitamin D₃ and D₂. The female part of the reference group showed a statistically significant decrease of 1,25-dihydroxyvitamin D₃ concentrations with age. The presence of significantly higher average 1,25-dihydroxyvitamin D₃ levels in premenopausal women taking oral contraceptive pills compared to postmenopausal women suggests that this effect is estrogen-related, as estrogens lead to a higher vitamin D binding protein.

CONCLUSIONS

The major finding of the present study is a reference interval of 59-159pmol/L for 1,25-dihydroxyvitamin D₃ determined with a highly sensitive and precise LC-MS/MS method.

Vitamin D (25(OH)D) in patients with chronic kidney disease stages 2-5

OBJECTIVE

To establish the impact the chronic kidney disease stage has in the native vitamin D levels in patients not undergoing dialysis treatment.

METHODS

A study performed in Manizales, Colombia, a city located 2,200 meters above sea level, without important stational variations. Patients with 18 years of age or more, with chronic kidney disease stages 2 to 5 and not undergoing dialysis treatment were recruited for this study. Demographic and anthropometric variations were evaluated as well as solar exposure, CKD etiology and laboratory variables related to bone and mineral diseases. For each CKD clinical stage, correlations were evaluated for vitamin D levels, laboratory results for bone and mineral diseases, solar exposure and ethnicity.

RESULTS

Three hundred thirty-three patients were evaluated with a median age of 71 years, most of them mestizo (71%), 173 were women. The main CKD etiology was hypertensive nephropathy (32.2%). 21.1% of patients had normal vitamin D levels, 70.1% were within insufficient range and 8.8% were in deficit. A negative correlation was found between the levels of vitamin 25 (OH) D and the values for: creatinine, phosphorous, calcium x phosphorous product, PTH, 24 hours urine protein and BMI. A positive relationship was found for calcium and albumin. Positive significant statistical correlation was found for vitamin 25(OH) D levels and solar exposure for stages 3b and 4 of CKD.

CONCLUSIONS

It is common to find low levels of vitamin 25(OH) D in patients with CKD; these can contribute to the appearance of secondary hyperparathyroidism.

OBJETIVO

Establecer el impacto del estadio clínico en los niveles de vitamina D nativa en pacientes con enfermedad renal crónica (ERC) sin diálisis.

MÉTODOS

Estudio realizado en Manizales, Colombia, una ciudad tropical ubicada a 2,200 metros de altura sobre el nivel del mar, sin variaciones estacionales importantes a lo largo del año. Se incluyeron pacientes mayores de 18 años, con enfermedad renal crónica estadio 2 a 5 sin tratamiento dialítico. En ellos se evaluaron variables demográficas, antropométricas, grado de exposición solar, etiología de la enfermedad, y variables de laboratorio relacionadas con desórdenes óseos y minerales. Para cada estadío clínico se evaluó la correlación entre los niveles de vitamina D y los resultados de las pruebas de laboratorio relacionadas con desordenes óseos y minerales, exposición solar y etnia.

RESULTADOS

Se evaluaron 331 pacientes, con una edad media de 71 años, la mayoría mestizos (71%), 173 mujeres. La principal etiología de ERC fue nefropatía hipertensiva (33.2%). El 21.1% de los pacientes tenían niveles normales de vitamina D, fueron insuficientes en 70.1% y 8.8% en déficit. Se detectó correlación negativa, entre los niveles de vitamina 25(OH)D y los valores de creatinina, fósforo, producto calcio x fósforo, PTH, proteínas en orina de 24 horas e IMC. Correlación positiva para el calcio y la albumina. Se encontró significancia estadística positiva entre los niveles de vitamina 25(OH)D y la exposición solar para los estadios 3b y 4.

CONCLUSIONES

En pacientes con ERC es comun detectar bajos niveles de 25(OH)D, los cuales pueden contribuir a la generación de hiperparatiroidismo secundario.

Quantification of 1,25-Dihydroxyvitamin D2 and D3 in Serum Using Liquid Chromatography-Tandem Mass Spectrometry

1,25-Dihydroxyvitamin D is the active form of vitamin D and plays a critical role in the maintenance of calcium and phosphorous metabolism of the human body. Measurement of 1,25-dihydroxyvitamin D in serum can aid in clinical diagnosis and/or management of renal disease, sarcoidosis, and rare inherited diseases. We present here an effective and accurate method for measuring 1,25-dihydroxyvitamin D3 and 1,25-dihydroxyvitamin D2 by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) after immunoaffinity extraction. The MS/MS is operated in multiple reaction mode with positive electrospray. Quantification is based on peak area ratios of the analytes to respective deuterated internal standards. This method offered a linear range from 4.0 to 160.0 pg/mL with analytical recovery of 89.9-115.5 % for both 1,25-dihydroxyvitamin D3 and 1,25-dihydroxyvitamin D2.

The Effect of Vitamin D Supplementation on Metabolic Phenotypes in Thais with Prediabetes

OBJECTIVE

To investigate the effects of vitamin D supplement for three months on anthropometric and glucose homeostatic measures in Thai adults with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT).

MATERIAL AND METHOD

Forty-seven IFG and/or IGT subjects enrolled in the study. Subjects were randomized into three groups, control (n = 18), vitamin D₂ (20,000 IU weekly, n = 19) or vitamin D₃ (15,000 IU weekly, n = 10). Anthropometric variables were obtained at baseline and at 3-month. Oral glucose tolerance test was performed at baseline and at 3-month. Total serum 25(OH)D, 25(OH)D₃, and 25(OH)D2 were measured by LC-MS/MS. Insulin resistance (HOMA-IR) and insulin secretion index (HOMA%B) were calculated by the homeostasis model assessment.

RESULTS

The total 25(OH)D levels significantly increased from baseline in both the vitamin D₂ and the vitamin D₃ groups, while there was no change in the control group. D₃ supplementation raised 25(OH)D₃ significantly (+13.7 ± 4.9 ng/mL, p < 0.01) while D2 increased 25(OH)D2 levels (+25.9?4.2 ng/mL, p<0.001) but with a decrease in 25(OH)D3 (-13.1?3.1 ng/mL, p<0. 001). Subjects were classified into two groups, i.e., control (n = 18) and D₂ or D₃ supplementations (n = 29). After three months, waist circumference (WC) significantly decreased in subjects of vitamin D supplementation group. Body weight (BW p = 0.05), systolic blood pressure (SBP, p = 0.05), body mass index (BM, p = 0.06), and HOMA-IR (p = 0.09) also tended to decrease. Subjects with an increase of total 25(OH)D levels > 10 ng/mL (23 of 29 subjects) had significant decrease in HOMA-IR and increase in disposition index. Using robust regression analysis, we found the use of D3 was associated with a larger decrease in WC (coefficient = -3.5, p < 0.001) independent of the change in total 25(OH)D and baseline BMI. No difference between D₂ and D₃ was observed for other metabolic measures.

CONCLUSION

Weekly supplementations of vitamin D₂ (20,000 IU) or vitamin D₃ (15,000 IU) improve metabolic phenotypes in subjects with prediabetes. D₃ supplement may decrease waist circumference more than D₂ supplement.

The influence of a whole food vegan diet with Nori algae and wild mushrooms on selected blood parameters

BACKGROUND

Vegan and vegetarian diets could overcome many diseases of civilization. This study examines whether a whole food vegan diet with Nori algae and wild mushrooms can provide a sufficient quantity of critical nutrients.

METHODS

Five blood samples (Baseline to Time 5) were taken over eight months from 75 subjects (10 vegans without B12 supplementation who consumed Nori algae and wild mushrooms, 20 vegans with supplementation, 40 vegetarians, 5 meat-eaters). Blood was analyzed for blood cell counts, total vitamin B12, holotranscobalamin, homocysteine, methylmalonic acid, vitamin B6, folic acid, ferritin, TSH, zinc, creatinine, vitamin D2 and D3.

RESULTS

In the vegan group without supplementation, all means were within the tolerance (holotranscobalamin, homocystein) or normal, except for elevated methylmalonic acid and diminished vitamin D. This group developed significantly higher vitamin D2 levels. The vegan group with B12 supplementation and the vegetarian group showed normal values for all parameters.

CONCLUSIONS

Vegans following a whole food diet had a borderline supply of vitamin B12. Folic acid, vitamin B6, TSH, iron metabolism, and the blood count were in the normal range. Vegans taking dietary supplements demonstrated satisfactory overall results. An ingestion of sundried mushrooms can contribute to the supply of vitamin D.

Hypovitaminosis D in adolescent females--an analytical cohort study in the United Arab Emirates

BACKGROUND

Despite living in a sunny country, hypovitaminosis D is common in women of reproductive age in Al Ain, United Arab Emirates (UAE).

AIMS AND OBJECTIVES

To establish the prevalence of hypovitaminosis D in adolescent female Emirati nationals and its risk factors.

METHODS

This was an analytical prospective cohort study of 350 female Emirati nationals aged 11-18 years attending public schools in Al Ain. Socio-economic status, diet and amount of sun exposure were evaluated by face-to-face interviews. Serum total 25 (OH) vitamin D (D2 + D3) levels were measured by electrochemiluminescence assay. The prevalence of hypovitaminosis D was calculated and the association with risk factors analysed.

RESULTS

Data were complete for 293 girls. Only one girl [prevalence 0.3%, 95% confidence interval (CI) 0.01-1.9] had vitamin D sufficiency (serum vitamin D levels >75 nmol/L). Three girls (1.0%, 95% CI 0.2-2.9) had vitamin D insufficiency (50-75 nmol/L), 58 (19.8%, 95% CI 15.0-25.5) were deficient (27.5-50 nmol/L) and 231 (78.8%, 95% CI 68.9-89.6) had severe deficiency (<27.5 nmol/L). Serum vitamin D levels declined between the ages of 11 and 13 years before progressively rising until the age of 18 years but without regaining the levels they were at the age of 11. There was no statistically significant difference between the vitamin D status groups in age, body mass index, accommodation type, family income, percentage of surface area unexposed to the sun when outdoors, consumption of oily fish or total vitamin D intake.

CONCLUSION

The finding of a high prevalence of hypovitaminosis D in adolescent females in UAE is of serious concern for their health and that of their infants during their reproductive lives. Adolescent girls with a similar social and cultural background currently living in less sunny, industrialised countries might also be at risk.

Interpreting the Laboratory Reports for Vit D

Importance for Vit D estimation has increased in the recent years due to its link to various diseases. Measurements of Vit D by different diagnostic laboratories is however not uniform. There is variation pertaining to assay methodology and also variation in the measurement of different metabolites of Vit D. There are also various confounders which influence Vit D assays and which in most instances are overlooked. Also a matter of concern regarding Vit D assays is the lack of assay standardisation. These factors contribute to the variation in the reports generated by the diagnostic laboratories. Therefore interpretation of Vit D reports needs proper understanding of these interfering factors and further reports need to be correlated substantially with the clinical findings.

Technical and clinical evaluation of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay--comparison with marketed automated immunoassays and a liquid chromatography-tandem mass spectrometry method

BACKGROUND

The study was conducted to evaluate the technical and clinical performance of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay, and compare it with the performance of five marketed automated assays and a liquid chromatography/mass spectrometry reference method (LC-MS/MS).

METHODS

Three hundred patient serum samples were used to compare the correlation of the VITROS® 25-OH Vitamin D Total Assay with both the other immunoassays and the LC-MS/MS method, using Passing-Bablok regression and Bland-Altman analyses. Concordance of the diagnosis of vitamin D status was calculated to test the agreement between the different assays. In addition, samples containing vitamin D2 were used to test the assay's ability to detect the D2 form of the vitamin.

RESULTS AND CONCLUSIONS

These results from the VITROS® 25-OH Vitamin D Total Assay generally correlated well with those from most of the marketed immunoassays. Cross-reactivity of the D2 form was calculated as being close to 100%. Additionally, we found substantial variability in performance amongst the various assays, which suggests the need for optimisation and recalibration of commercial methods.

Case report: Three patients with substantial serum levels of 3-epi-25(OH)D including one with 3-epi-25(OH)D2 while on high-dose ergocalciferol

CONTEXT

We report the presence of substantial concentrations of 3-epi-25(OH)D3 in two patients and a third patient with 3-epi-25(OH)D2.

PATIENTS

The first patient, a 66-year-old female receiving cholecalciferol 4000 IU daily was originally found to have 53 ng/mL of 25(OH)D3 and almost an equal amount of 3-epi-25(OH)D3. Subsequently, the patient had four additional samples, each of which has similar levels of both 25(OH)D3 and 3-epi-25(OH)D3. The second patient, a 7-year-old male receiving cholecalciferol 1000 IU daily, had a 25(OH)D3 concentration of 37 ng/mL and 3-epi-25(OH)D3 of approximately 10 ng/mL. The third and most intriguing patient, a 55-year-old female was receiving ergocalciferol 50,000 IU twice weekly for approximately 3 months, at which time her serum 25(OH)D2 was 64 ng/mL and her 3-epi-25(OH)D2 was approximately 32 ng/mL. This patient's physician changed her vitamin D therapy to cholecalciferol 1000 IU daily, discontinuing ergocalciferol, and a second specimen was collected 5 months later. Analysis of this last specimen found both 25(OH)D3 and 25(OH)D2 at concentrations of 12 and 24 ng/mL respectively, plus corresponding 3-epimer peaks for both 25(OH)D3 and 25(OH)D2 observed chromatographically.

CONCLUSION

The presence of a substantial concentration of 3-epi-25(OH)D in these three patients documents that one cannot assume 3-epi is a trivial metabolite of 25(OH)D for all patients. In addition, the appearance of 3-epi-25(OH)D3 when the last patient changed her vitamin D supplementation from ergocalciferol to cholecalciferol demonstrates that the 3-epimer is probably an endogenous metabolite of 25(OH)D in humans.

Vitamin D2 supplementation amplifies eccentric exercise-induced muscle damage in NASCAR pit crew athletes

This study determined if 6-weeks vitamin D₂ supplementation (vitD₂, 3800 IU/day) had an influence on muscle function, eccentric exercise-induced muscle damage (EIMD), and delayed onset of muscle soreness (DOMS) in National Association for Stock Car Auto Racing (NASCAR) NASCAR pit crew athletes. Subjects were randomized to vitD₂ (n = 13) and placebo (n = 15), and ingested supplements (double-blind) for six weeks. Blood samples were collected and muscle function tests conducted pre- and post-study (leg-back and hand grip dynamometer strength tests, body weight bench press to exhaustion, vertical jump, 30-s Wingate test). Post-study, subjects engaged in 90 min eccentric-based exercise, with blood samples and DOMS ratings obtained immediately after and 1- and 2-days post-exercise. Six weeks vitD₂ increased serum 25(OH)D₂ 456% and decreased 25(OH)D₃ 21% versus placebo (p < 0.001, p = 0.036, respectively), with no influence on muscle function test scores. The post-study eccentric exercise bout induced EIMD and DOMS, with higher muscle damage biomarkers measured in vitD₂ compared to placebo (myoglobin 252%, 122% increase, respectively, p = 0.001; creatine phosphokinase 24 h post-exercise, 169%, 32%, p < 0.001), with no differences for DOMS. In summary, 6-weeks vitD₂ (3800 IU/day) significantly increased 25(OH)D₂ and decreased 25(OH)D₃, had no effect on muscle function tests, and amplified muscle damage markers in NASCAR pit crew athletes following eccentric exercise.

Clinical review: The role of the parent compound vitamin D with respect to metabolism and function: Why clinical dose intervals can affect clinical outcomes

CONTEXT

There is no doubt that vitamin D must be activated to the hormonal form 1,25-dihydroxyvitamin D to achieve full biological activity or that many tissues participate in this activation process-be it endocrine or autocrine. We believe that not only is 25-hydroxyvitamin D important to tissue delivery for this activation process, but also that intact vitamin D has a pivotal role in this process.

OBJECTIVE

In this review, evidence on the vitamin D endocrine/autocrine system is presented and discussed in relation to vitamin D-binding protein affinity, circulating half-lives, and enzymatic transformations of vitamin D metabolites, and how these affect biological action in any given tissue.

CONCLUSIONS

Circulating vitamin D, the parent compound, likely plays an important physiological role with respect to the vitamin D endocrine/autocrine system, as a substrate in many tissues, not originally thought to be important. Based on emerging data from the laboratory, clinical trials, and data on circulating 25-hydroxyvitamin D amassed during many decades, it is likely that for the optimal functioning of these systems, significant vitamin D should be available on a daily basis to ensure stable circulating concentrations, implying that variation in vitamin D dosing schedules could have profound effects on the outcomes of clinical trials because of the short circulating half-life of intact vitamin D.

Influence of estrogen therapy on calcium, phosphorus, and other regulatory hormones in postmenopausal women: the MESA study

BACKGROUND

Estrogen therapy (ET) is associated with lower serum calcium and phosphorus concentrations and is known to increase bone mineral density (BMD). Other biomarkers of mineral metabolism may help understand the biological basis of these actions.

METHODS

We studied 2767 postmenopausal women in the Multi-Ethnic Study of Atherosclerosis, 862 (31%) of whom were using ET. We measured serum concentrations of calcium, phosphorus, 25-hydroxyvitamin D, 24,25-dihydoxyvitamin D, and fibroblast growth factor-23 and urinary fractional excretion of calcium (FEca) and phosphorus (FEphos). We examined the associations of ET with each biomarker. In addition, we tested whether the adjustment for biomarkers attenuated the association of ET with lumbar BMD measured by abdominal computed tomography in a subset of 810 women.

RESULTS

In adjusted models, women who used ET were younger in age [62 (SD 8) vs 66 (9) y, P < .001], had lower mean serum calcium [-13 mg/dL (95% confidence interval [CI] -0.17, -0.10), P < .001] and lower FEca [-0.15% (95% CI -0.21, -0.09), P < .001]. Mean serum phosphorus was lower [-0.19 mg/dL (95% CI -0.23, -0.15), P < .001] and FEphos [0.56% (95% CI 0.16, 0.96), P = .007] was higher in women on ET. Mean 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D were higher [1.52 ng/dL (95% CI 0.57, 2.47), P = .002, and 0.26 ng/mL (95% CI 0.03, 0.48), P = .03, respectively] in women who used ET. Mean PTH and fibroblast growth factor-23 did not differ significantly by the use of ET. ET use was strongly associated with higher lumbar BMD [12.75 mg/cm³ (95% CI 7.77-17.73), P < .001]; however, mineral metabolism measures did not meaningfully alter this association.

CONCLUSIONS

In a multiethnic cohort of postmenopausal women, ET use was associated with lower serum calcium, lower FEca, lower serum phosphorus, and higher FEphos, suggesting these associations are attributable to increased calcium intake into bone and increased urinary phosphorus excretion. ET use was also associated with greater concentrations of vitamin D metabolites. ET-associated differences in these mineral metabolism measures did not meaningfully attenuate the strong association between ET use and lumbar BMD.

Bioavailability of vitamin D(2) and D(3) in healthy volunteers, a randomized placebo-controlled trial

BACKGROUND

The bioequivalence of the different forms of vitamin D, ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), has been questioned. Earlier studies have suggested that vitamin D2 is less biologically active than vitamin D3.

OBJECTIVE AND DESIGN

In a parallel study, we tested the effects of supplementation with 50-μg/d doses of vitamin D2 or D3 or a placebo over a period of 8 weeks on 25(OH)D2, 25(OH)D3, their sum 25(OH)D (primary outcome variables), and PTH in healthy volunteers applying a double-blind, randomized study design. The study was conducted during the winter of 2012 in Halle (Saale), Germany, at latitude 51°47N, when UVB irradiation is virtually absent. Blood samples for the determinations of vitamin D status and PTH were collected at baseline and after 4 and 8 weeks of supplementation.

RESULTS

In the placebo group (n = 19), 25(OH)D3 decreased from 39.4 ± 14.2 to 31.1 ± 12.4 nmol/L after 8 weeks (P < .01). In the vitamin D3 group (n = 42), the concentrations of 25(OH)D3 increased from 41.5 ± 22.8 nmol/L at baseline to 88.0 ± 22.1 nmol/L after 8 weeks (P < .01). In the group receiving vitamin D2 (n = 46), the 25(OH)D2 concentrations increased significantly, whereas the 25(OH)D3 concentration fell from 36.4 ± 13.3 nmol/L at baseline to 16.6 ± 6.3 nmol/L after 8 weeks (P < .01). The total 25(OH)D was not different between the groups at baseline but differed significantly between the groups after 4 and 8 weeks (P < .001).

CONCLUSIONS

Vitamin D3 increases the total 25(OH)D concentration more than vitamin D2. Vitamin D2 supplementation was associated with a decrease in 25(OH)D3, which can explain the different effect on total 25(OH)D.

The effects of vitamin D₂ or D₃ supplementation on glycaemic control and related metabolic parameters in people at risk of type 2 diabetes: protocol of a randomised double-blind placebo-controlled trial

BACKGROUND

The global prevalence of type 2 diabetes is increasing. Effective strategies to address this public health challenge are currently lacking. A number of epidemiological studies have reported associations between low concentrations of 25-hydroxy vitamin D and the incidence of diabetes, but a causal link has not been established. We investigate the effect of vitamin D supplementation on the metabolic status of individuals at increased risk of developing type 2 diabetes.

METHODS/DESIGN

In a randomised double-blind placebo-controlled trial individuals identified as having a high risk of type 2 diabetes (non-diabetic hyperglycaemia or positive diabetes risk score) are randomised into one of three groups and given 4 doses of either placebo, or 100,000 IU Vitamin D₂ (ergocalciferol) or 100,000 IU Vitamin D₃ (cholecalciferol) at monthly intervals. The primary outcome measure is the change in glycated haemoglobin level between baseline and 4 months. Secondary outcome measures include blood pressure, lipid levels, apolipoproteins, highly sensitive C-reactive protein, parathyroid hormone (PTH) and safety of supplementation. and C-reactive protein. The trial is being conducted at two sites (London and Cambridge, U.K.) and a total of 342 participants are being recruited.

DISCUSSION

Trial data examining whether supplementation of vitamin D improves glycaemic status and other metabolic parameters in people at risk of developing type 2 diabetes are sparse. This trial will evaluate the causal role of vitamin D in hyperglycaemia and risk of type 2 diabetes. Specific features of this trial include recruitment of participants from different ethnic groups, investigation of the relative effectiveness and safety of vitamin D₂ and D₃ and an evidence based approach to determination of the dose of supplementation.

TRIAL REGISTRATION

EudraCT2009-011264-11; ISRCTN86515510.

Long-term bioavailability after a single oral or intramuscular administration of 600,000 IU of ergocalciferol or cholecalciferol: implications for treatment and prophylaxis

CONTEXT

We previously showed that a single high dose of oral (po) cholecalciferol (D₃) sharply increases serum 25-hydroxyvitamin D [25(OH)D].

OBJECTIVE

We evaluated the long-term bioavailability and metabolism of a single po or intramuscular (im) high dose of ergocalciferol (D₂) or D₃.

DESIGN

This was a prospective intervention study.

SETTING

The study was conducted in an ambulatory care setting.

PATIENTS

Participants were 24 subjects with hypovitaminosis D.

INTERVENTIONS

A single dose of 600,000 IU of po or im D₂ or D₃ was administered.

MAIN OUTCOME MEASURES

Serum 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)₂D] were measured at baseline and at days 30, 60, 90, and 120 by RIA. Serum 1,25(OH)₂D₂, 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], 24,25-hydroxyvitamin D₂ [24,25(OH)D₂], and 24,25-hydroxyvitamin D₃ [24,25(OH)D₃] were measured by liquid chromatography-tandem mass spectrometry in a subgroup of patients receiving the po formulations.

RESULTS

The areas under the curve of 25(OH)D after D₃ were significantly higher than those after D₂ (P < .0001). Serum 25(OH)D basal difference significantly increased at day 30 with po D₂ and D₃ (P < .01 and P < .0001) and up to day 90 with po D₃ (P < .01). The im formulations produced a slow increased, and values peaked at day 120 relative to the other time points (P < .0001). We found a decrease in 1,25(OH)₂D at day 30 (P < .05) and up to day 120 (P < .001) and an increase in 1,25(OH)₂D₂ at day 30 (P < .01) and up to day 120 (P < .01) after po D₂. Oral D₂ and D₃ produced increases in 24,25(OH)D₂ and 24,25(OH)D₃, respectively, at day 30 (P < .001).

CONCLUSIONS

A po dose of 600,000 IU of D₂ or D₃ is initially more effective in increasing serum 25(OH)D than the equivalent im dose and is rapidly metabolized. Our RIA assay for 1,25(OH)₂D may not recognize 1,25(OH)₂D₂.

Mineral metabolism and cortical volumetric bone mineral density in childhood chronic kidney disease

CONTEXT

The relationships among cortical volumetric bone mineral density (CortBMD) and comprehensive measures of mineral metabolism have not been addressed in chronic kidney disease (CKD).

OBJECTIVE

The aim of the study was to identify the determinants of CortBMD in childhood CKD. A secondary objective was to assess whether CortBMD was associated with subsequent fracture.

DESIGN AND PARTICIPANTS

This prospective cohort study included 171 children, adolescents, and young adults (aged 5-21 years) with CKD stages 2-5D at enrollment and 89 1 year later.

OUTCOMES

Serum measures included vitamin D [25-hydroxyvitamin D (25[OH]D), 1,25-dihydroxyvitamin D (1,25(OH)₂D), 24,25-dihydroxyvitamin D], vitamin D-binding protein, intact PTH, fibroblast growth factor 23, calcium, and phosphorus. Tibia quantitative computed tomography measures of CortBMD were expressed as sex-, race-, and age-specific Z-scores based on 675 controls. Multivariable linear regression identified the independent correlates of CortBMD Z-scores and the change in CortBMD Z-scores.

RESULTS

Lower calcium (β = .31/1 mg/dL, P = .01) and 25(OH)D (β = .18/10 ng/mL, P = .04) and higher PTH (β = -.02/10%, P = .002) and 1,25(OH)₂D (β = -.07/10%, P < .001) were independently associated with lower CortBMD Z-scores at baseline. The correlations of total, free, and bioavailable 25(OH)D with CortBMD did not differ. Higher baseline 1,25(OH)₂D (P < .05) and greater increases in PTH (P < .001) were associated with greater declines in CortBMD Z-scores. Greater increases in calcium concentrations were associated with greater increases in CortBMD Z-scores in growing children (interaction P = .009). The hazard ratio for fracture was 1.75 (95% confidence interval 1.15-2.67; P = .009) per SD lower baseline CortBMD.

CONCLUSIONS

Greater PTH and 1,25(OH)₂D and lower calcium concentrations were independently associated with baseline and progressive cortical deficits in childhood CKD. Lower CortBMD Z-score was associated with increased fracture risk.

Serum concentrations of 1,25-dihydroxyvitamin D2 and 1,25-dihydroxyvitamin D3 in response to vitamin D2 and vitamin D3 supplementation

OBJECTIVE

The purpose of this study was to determine 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and 1,25-dihydroxyvitamin D2 [1,25(OH)2D2] levels in healthy adults consuming 1000 IU vitamin D2 or vitamin D3 per day for 11 weeks.

SUBJECTS AND DESIGN

Blood from 34 healthy male and female adults, aged 18 to 79 years, from a placebo-controlled, double-blind study who received a placebo, 1000 IU vitamin D3, or 1000 IU vitamin D2 daily for 11 weeks at end of winter was analyzed. Serum levels of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, 1,25(OH)2D2, and 1,25(OH)2D3 were determined by liquid chromatography-tandem mass spectroscopy.

RESULTS

Of the adults, 82% were vitamin D insufficient (serum 25-hydroxyvitamin D [25(OH)D <30 ng/mL]) at the start of the study. Administration of vitamin D2 and vitamin D3 induced similar increases in total 25(OH)D as well as in 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3, respectively. Compared with placebo and adjusting for baseline levels, 1000 IU daily of vitamin D2 was associated with a mean increase of 7.4 pg/mL (95% confidence interval, 4.4-10.3) in 1,25(OH)2D2, which was accompanied by a mean decrease of 9.9 pg/mL (-15.8 to -4.0) in 1,25(OH)2D3. No such differences accompanied administration of 1000 IU daily of vitamin D3.

CONCLUSION

Vitamin D2 and vitamin D3 were effective in raising and maintaining total serum concentrations of 25(OH)D. Ingestion of vitamin D2 also resulted in an increase in serum concentrations of 1,25(OH)2D2. This increase was accompanied by a comparable decrease in serum concentrations of 1,25(OH)2D3; therefore, the total 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations did not significantly change after 11 weeks compared with baseline levels. Ingestion of vitamin D3 did not alter serum concentrations of 1,25(OH)2D3 or total 1,25(OH)2D. Therefore, ingestion of 1000 IU vitamin D2 or vitamin D3 for 11 weeks was effective in raising total serum concentrations of 25(OH)D as well as sustaining serum concentrations of total 1,25(OH)2D.

Serum 24,25-dihydroxyvitamin D concentrations in osteogenesis imperfecta: relationship to bone parameters

BACKGROUND

Several studies suggest that 24,25-dihydroxyvitamin D [24,25(OH)₂D] may have an effect on bone mass and metabolism.

OBJECTIVE

We evaluated the relationship between serum 24,25(OH)₂D levels and bone density and bone metabolism in children with a primary bone disorder-osteogenesis imperfecta (OI).

MATERIALS AND METHODS

The study included 132 patients (age, 1.1 to 17.9 yr; 67 girls) with OI types I, III, or IV who had not received bisphosphonate treatment at the time of analysis.

RESULTS

Serum 24,25(OH)₂D levels were significantly higher in OI type III than in OI type I or IV. Serum 24,25(OH)₂D concentrations were positively correlated with serum 25-hydroxyvitamin D (25OHD) levels and negatively correlated with serum PTH levels, and were not correlated with serum 1α,25-dihydroxyvitamin D [1,25(OH)₂D]. The ratio between serum 24,25(OH)₂D and 25OHD was negatively correlated with age and was independent of serum 25OHD concentrations. Regression analysis revealed that OI severity (P = 0.04), serum 25OHD levels (P < 0.001), and serum PTH concentrations (P = 0.045), but not age, gender, or serum 1,25(OH)₂D, were independent predictors of serum 24,25(OH)₂D levels. No correlation was found between serum 24,25(OH)₂D levels or the ratio between serum 24,25(OH)₂D and 25OHD and lumbar spine bone mineral density z-scores or bone marker levels (serum osteocalcin and urinary collagen type I N-telopeptide) after adjusting for OI type, age, and gender.

CONCLUSION

Patients with more severe OI type had higher 24,25(OH)₂D serum levels and higher serum 24,25(OH)₂D to 25OHD ratios, suggesting an increased 25OHD-24-hydroxylase activity.

Prospective evaluation of bone markers, parathormone and 1,25-(OH)₂ vitamin D in HIV-positive patients after the initiation of tenofovir/emtricitabine with atazanavir/ritonavir or efavirenz

BACKGROUND

Increased risk of fractures and osteoporosis have been associated with the use of antiretroviral drugs. There is a paucity of prospective evaluations of bone markers after the initiation of drugs currently recommended to treat HIV infection and results on the evolution of these markers are conflicting. Lastly, the effect of tenofovir on 1,25-(OH)₂ vitamin D is uncertain.

METHODS

We performed a prospective study on the evolution of bone markers, parathormone and 1,25-(OH)₂ vitamin D before and after standard antiretroviral regimens. This was a sub-study of a trial conducted in antiretroviral-naïve patients randomized to tenofovir + emtricitabine in combination with either atazanavir/ritonavir (ATV/r) or efavirenz (EFV). Follow-up lasted 48 weeks. The following bone markers were analyzed: C-terminal cross-laps (CTx), osteocalcin (OC), osteoprotegerin (OPG), and receptor activator of nuclear factor κB ligand (RANKL). Mixed-factorial analysis of variance with random-coefficient general linear model was used to compare their trends over time and linear multivariable regression was performed with a backward selection method to assess predictors of their variations from baseline to week 48. Trends of parathormone and 1,25-(OH)₂ vitamin D were also evaluated.

RESULTS

Seventy-five patients were studied: 33 received EFV and 42 ATV/r. Significant increases were found for all markers except for RANKL. There was a significant direct association between CTx and OC increases. Multivariable analysis showed that higher glomerular filtration rate (estimated through cystatin C clearance) predicted greater OPG increase, while older age, higher HIV RNA at baseline and use of ATV/r predicted greater CTx increase. A significant increase of parathormone accompanied the evolution of the study markers. 1,25-(OH)₂ vitamin D remained stable, though a seasonality variation was demonstrated.

CONCLUSIONS

These data demonstrate CTx increase (bone resorption marker) corresponding to OC increase (bone formation marker) early upon HAART initiation. Moreover, predictors of bone marker increases have been suggested, possibly indicating that a stricter monitoring of bone health and pro-active interventions are needed in older patients, those with higher HIV RNA, prescribed ATV/r rather than EFV, and with decreased renal function at baseline. Further studies are needed to clarify the mechanisms responsible for up-regulation of bone turnover markers, as well as to understand if and what markers are best correlated or predictive of pathological fractures.

Evaluation of bone markers in hypophosphatemic rickets/osteomalacia

N-terminal propeptide of type I procollagen (PINP) is a marker of newly formed type I collagen. However, its role in hypophosphatemic rickets/osteomalacia has not yet been established. Metabolic bone markers were examined in patients with oncogenic osteomalacia (OOM) and X-linked hypophosphatemic rickets (XLH), and in healthy controls. OOM and XLH patients were found to have hypophosphatemia secondary to elevated levels of serum fibroblast growth factor 23 (FGF-23). OOM patients had reduced levels of 1,25-dihydroxy vitamin D (1,25D) compared with XLH patients and healthy controls, despite attenuation of the reduction in these levels in the XLH patients secondary to active vitamin D supplementation. In contrast to patients with XLH, OOM patients showed a significant increase in serum PINP, which is suggestive of accelerated bone matrix formation. Bone alkaline phosphatase (BAP) and the BAP/PINP ratio were also increased in OOM but not in XLH patients, suggesting the presence of a disturbance in bone mineralization in OOM. Long-term supplementation of active form vitamin D and inorganic phosphate (IP) may have attenuated the defect in bone mineralization in the XLH patients, resulting in the normalization of PINP, BAP, and the BAP/PINP ratio. The present results suggest that, as with BAP, PINP is an appropriate metabolic bone marker in the assessment of hypophosphatemic rickets/osteomalacia.

Bioavailability of vitamin D in malnourished adolescents with anorexia nervosa

CONTEXT

Young women with anorexia nervosa (AN) have a normal vitamin D status. The bioavailability of vitamin D during malnutrition is unknown.

OBJECTIVE

The objective of the study was to examine the serum response to oral ergocalciferol in AN.

DESIGN/SETTING

This was a prospective cohort study, conducted in 2007-2009 at a tertiary care center.

PATIENTS/INTERVENTIONS

Twelve adolescents with AN (age 19.6 ± 2.0 yr, body mass index 16.5 ± 1.4 kg/m²) and 12 matched healthy controls (20.0 ± 2.4 yr, 22.7 ± 1.0 kg/m²) received one baseline 50,000 IU oral dose of ergocalciferol.

MAIN OUTCOMES

Serum D₂, D₃, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D, collected before ingestion, at 6 and 24 h and weekly for 4 wk, and body composition measures were measured.

RESULTS

The AN group was severely malnourished (77.2 ± 6.3% median body weight), whereas the control group was normal weighted (106.2 ± 6.2%). From a common baseline D₂ (1.5 ± 1.6 nmol/liter, P =0.34) the groups diverged (time × group interaction P = 0.04), peaking at 70 ± 34 nmol/liter at 6 h in controls compared with 43 ± 28 nmol/liter in AN subjects (P = 0.008). The D₂ trajectories converged at 24 h (57 nmol/liter, P = 0.98) and returned to near baseline at 1 wk. Baseline D₃ was higher in AN subjects (12.1 ± 9.6 vs. 3.1 ± 2.3 nmol/liter, P < 0.001) and remained higher throughout. 25-Hydroxyvitamin D followed a common trajectory (time × group interaction P = 0.15), rising to 45 ± 10 nmol/liter at 24 h but returning to baseline by wk 3 (P = 0.36). Correlating vitamin D levels with fat measures (body mass index, body fat) produced similar findings.

CONCLUSIONS

Despite severe malnutrition, young women with AN had a similar bioavailability of oral ergocalciferol as the healthy-weighted controls. Vitamin D dosing for patients suffering from malnutrition may not differ from that for normal-weighted adolescents.

Determination of vitamins A, D and E in a small volume of human plasma by a high-throughput method based on liquid chromatography/tandem mass spectrometry

We have developed an automated high-throughput assay for the determination of vitamin A (retinol), ergocalciferol (25-OH D2), cholecalciferol (25-OH D3) and vitamin E (α-tocopherol) in a small volume of human plasma. Sample preparation involved mixing 50 μL of plasma with 100 μL of ethanol containing isotope-labelled internal standards, followed by mixing with isooctane/chloroform (3:1, 300 μL). The organic phase was evaporated, and the sample reconstituted in 50 μL methanol. The analysis was performed using reversed-phase liquid chromatography with a gradient mobile phase containing water, methanol and ammonium formate. Chromatographic run-time was 5 min, and positive mode electrospray tandem mass spectrometry (MS/MS) was used for detection. The limits of detection were 0.10 μM for all-trans retinol and 3.3 nM for 25-OH D2 and 25-OH D3. Recoveries were 91.9-105.0%, and within- and between-day coefficients of variance (CVs) 2.4-5.3 and 3.1-8.2, respectively. The assay is presently being used in large-scale studies.

Circulating 25-hydroxyvitamin D levels and frailty status in older women

CONTEXT

Vitamin D deficiency and frailty are common with aging, but the association between these conditions is uncertain.

OBJECTIVE

To determine the association between 25-hydroxyvitamin D (25(OH)D) levels and prevalent and incident frailty status among older women.

DESIGN

Cross-sectional and longitudinal analyses of a prospective cohort study.

SETTING

Four U.S. centers.

PARTICIPANTS

6307 women aged≥69 years.

MAIN OUTCOME MEASURES

Frailty status classified as robust, intermediate stage, or frail at baseline; and robust, intermediate stage, frail, or dead (all-cause mortality) at follow-up an average of 4.5 years later.

RESULTS

At baseline, there was a U-shaped association between 25(OH)D level and odds of frailty with the lowest risk among women with levels 20.0-29.9 ng/ml (referent group). Compared with this group, the odds of frailty were higher among those with levels<15.0 ng/ml [multivariable odds ratio (MOR) 1.47, 95% confidence interval (CI), 1.19-1.82], those with levels 15.0-19.9 ng/ml (MOR 1.24, 95% CI 0.99-1.54), and those with levels≥30 ng/ml (MOR 1.32, 95% CI 1.06-1.63). Among 4551 nonfrail women at baseline, the odds of frailty/death (vs. robust/intermediate) at follow-up appeared higher among those with levels 15.0-19.9 ng/ml (MOR 1.21, 95% CI 0.99-1.49), but the CI overlapped 1.0. The odds of death (vs. robust/intermediate/frail at follow-up) was higher among those with levels<15.0 ng/ml (MOR 1.40, 95% CI 1.04-1.88) and those with levels 15.0-19.9 ng/ml (MOR 1.30, 95% CI 0.97-1.75), although the latter association did not quite reach significance.

CONCLUSION

Lower (<20 ng/ml) and higher (≥30 ng/ml) levels of 25(OH)D among older women were moderately associated with a higher odds of frailty at baseline. Among nonfrail women at baseline, lower levels (<20 ng/ml) were modestly associated with an increased risk of incident frailty or death at follow-up.

Treatment and prevention of vitamin D insufficiency in cystic fibrosis patients: comparative efficacy of ergocalciferol, cholecalciferol, and UV light

BACKGROUND

The optimal treatment for correcting or preventing vitamin D insufficiency in cystic fibrosis (CF) patients has not been established.

OBJECTIVE

The aim of the study was to assess the relative efficacy of three modes of vitamin D therapy: cholecalciferol (D3), ergocalciferol (D2), and UV light in raising or maintaining 25(OH)D levels above 30 ng/ml.

DESIGN

Thirty adult CF subjects with vitamin D insufficiency were randomized into one of three treatment arms: D3, D2, or UV light. Subjects randomized to D3 or D2 ingested 50,000 IU of vitamin D weekly, and those randomized to UV exposed their skin to UV light from a lamp five times a week. Serum was collected for 25(OH)D and PTH at baseline and at 12 wk.

RESULTS

Treatment with D3 and D2 raised 25(OH)D levels significantly, from a mean of 21.2 +/- 10.18 to 47.1 +/- 20.5 ng/ml (P < 0.001) and 24.4 +/- 10.3 to 32.7+/- 9.7 ng/ml (P = 0.01), with 100% and 60% reaching 25(OH)D levels above 30 ng/ml, respectively. Treatment with UV did not raise 25(OH)D levels significantly; however, only 55% of subjects were adherent with UV therapy.

CONCLUSION

This study demonstrates that CF subjects are able to achieve or maintain optimal vitamin D status (>30 ng/ml) with two oral regimens of either D3 or D2 treatment, the former being more efficacious. A confounding variable for this observation is the fact that the D3 and D2 capsules contained different carriers, powder-based vs. oil-based, respectively. UV therapy did not alter vitamin D status, possibly due to poor adherence to UV therapy.

Ectopic thymic parathyroid adenoma and vitamin D deficiency rickets: a 5-year-follow-up case report and review of literature

Sixteen patients with primary hyperparathyroidism presenting as rickets have so far been reported in the English literature. However, no report of an ectopic thymic parathyroid adenoma presenting as rickets has been published. We report a 14-year-old Caucasian American, wheelchair-ridden male who presented with signs and symptoms suggestive of vitamin D deficiency rickets subsequently confirmed by laboratory and radiological findings. Following the intramuscular administration of 125,000 U ergocalciferol (vitamin D2), he developed hypercalcemia with persistently elevated parathyroid hormone (PTH) levels suggestive of primary hyperparathyroidism. Sestamibi scan demonstrated significant uptake in the superior chest, without uptake at the normal parathyroid glands location. Surgical exploration revealed normal parathyroid glands and a thymic mass, which was removed and confirmed by pathology to be a parathyroid adenoma. With subsequent oral ergocalciferol solution and calcium carbonate therapies, the patient's symptoms resolved, blood chemistries normalized, and radiological evidence of rickets significantly improved. To our knowledge, this is the first case of an ectopic thymic parathyroid adenoma in a patient presenting with rickets. Our patient demonstrates that hyperparathyroidism-induced hypercalcemia may be masked by severe vitamin D deficiency. Prolonged treatment with ergocalciferol after removal of the parathyroid adenoma was necessary to normalize iPTH and replenish vitamin D store.

Osteomalacia in a hemodialysis patient receiving an active vitamin D sterol

BACKGROUND

A 17-year-old Filipino male hemodialysis patient presented for renal transplant evaluation. He had significant skeletal abnormalities characterized by bone pain, an inability to walk, and secondary hyperparathyroidism despite therapy with an active vitamin D sterol (paricalcitol).

INVESTIGATIONS

The patient underwent a physical examination, and his serum levels of calcium, phosphorus, alkaline phosphatase, parathyroid hormone, aluminum and 25-hydroxycholecalciferol (25OH-vitamin D) were determined. X-rays of hips and lower extremities, MRI, and bone histomorphometry after double tetracycline labeling were performed.

DIAGNOSIS

Osteomalacia associated with low 25OH-vitamin D levels.

MANAGEMENT

Monthly therapy with ergocalciferol (vitamin D2) and discontinuation of paricalcitol.

Risk of vitamin A toxicity from candy-like chewable vitamin supplements for children

Numerous vitamin supplements are available over-the-counter to the general public. Some such supplements are available as candy-like chewable preparations to encourage consumption by children. We report 3 cases of overdose of such preparations. Each patient had taken an estimated 200,000 to 300,000 IU of vitamin A. Their circulating vitamin A (retinol and retinyl palmitate) concentrations were monitored over a 6-month period. There were no clinical or biochemical complications noted. However, there were marked increases in both retinol and retinyl palmitate concentrations above age-related reference ranges. In particular, it took 1 to 3 weeks for the serum retinol concentrations to peak and many months for them to normalize. Parents should be warned about the dangers of excessive vitamin consumption. Clinicians should be aware of the late peak in serum retinol concentrations, which may lead to late complications of vitamin A overdose.

All-trans retinoic acid antagonizes the action of calciferol and its active metabolite, 1,25-dihydroxycholecalciferol, in rats

An antagonistic interaction between retinol and calciferol has been established. However, the mechanism by which this antagonism occurs is unclear. One possibility is that retinol affects the metabolism of calciferol. To investigate this hypothesis, retinol- and calciferol-depleted rats were given various amounts of ergocalciferol, cholecalciferol, 1alpha,25-dihydroxycholecalciferol [1,25(OH)2D3], or 24,24-difluoro-1alpha,25-dihydroxycholecalciferol [24-F2-1,25(OH)2D3] in combination with various amounts of retinyl acetate or all-trans retinoic acid (ATRA) in a series of studies. Rats administered 1720 or 3440 microg retinyl acetate once every 3 d for 33 d in combination with 25.8 ng ergocalciferol or 25 ng cholecalciferol every 3 d had lower serum calcium and greater serum phosphorus concentrations than rats fed 0 or 11.4 mug retinyl acetate every 3 d. In addition, rats fed 400 microg ATRA/d in combination with 25.8 ng ergocalciferol every 3 d, 25 ng cholecalciferol every 3 d, 2-5 ng 1,25(OH)2D3/d, or 0.5-1 ng 24-F2-1,25(OH)2D3/d had significantly lower serum calcium and higher serum phosphorus concentrations than rats not given ATRA in the diet. Therefore, both retinyl acetate and ATRA are able to antagonize the action of ergocalciferol and cholecalciferol in vivo. Additionally, ATRA antagonizes the in vivo action of 1,25(OH)2D3 and an analog, 24-F2-1,25(OH)2D3, that cannot be 24-hydroxylated. Together, these results suggest that retinol does not antagonize the action of calciferol by altering the metabolism of calciferol or 1,25(OH)2D3, but does so by another mechanism.

1,24(S)-dihydroxyvitamin D2, an endogenous vitamin D2 metabolite, inhibits growth of breast cancer cells and tumors

BACKGROUND

1,24-Dihydroxyvitamin D2 (1,24(OH)2D2) is a naturally occurring metabolite of vitamin D2 with low calcemic activity and potent antiproliferative activity. We evaluated the activity of 1,24(OH)2D2 in breast cancer models.

MATERIALS AND METHODS

The antiproliferative activity of 1,24(OH)2D2 was quantitated against human and murine breast cancer cell lines. The antitumor activity of 1,24(OH)2D2 was quantitated using MCF-7 xenografts in nude mice.

RESULTS

1,24(OH)2D2 inhibited growth of vitamin D receptor (VDR)-positive, but not VDR-negative, breast cancer cells. 1,24(OH)2D2 (10 microg/kg or 50 microg/kg) reduced MCF-7 xenograft growth by 50% after five weeks. Tumor morphology in treated animals was consistent with replacement of epithelial cells by stromal tissue. Mice treated with 1,24(OH)2D2 showed no loss of body weight, hypercalcemia or kidney calcification.

CONCLUSION

1,24(OH)2D2 inhibits growth of breast cancer cells via VDR-dependent mechanisms; its complete lack of toxicity and significant antitumor activity supports further development for chemotherapeutic applications.