Vitamin D binding protein is a key determinant of 25-hydroxyvitamin D levels in infants and toddlers

Genetic influence on urinary vitamin D binding protein excretion and serum levels: a focus on rs4588 C>A polymorphism in the GC gene

Introduction

Vitamin D binding protein (VDBP) plays a crucial role in vitamin D transport and metabolism. The rs4588-A polymorphism of the GC gene, encoding VDBP, has been associated with altered serum VDBP and 25-hydroxyvitamin D (25OHD) levels. However, the mechanisms underlying these effects remain unclear. We aimed to investigate the relationship between urinary VDBP excretion and serum VDBP and 25OHD levels in individuals with and without the rs4588-A allele.

Methods

A cross-sectional study was conducted on 109 children (mean age: 11.96 years) to explore the impact of rs4588-A on vitamin D metabolism and urinary VDBP excretion. Biochemical analyses determined serum 25OHD and VDBP levels, and urinary VDBP-to-creatinine ratio (u-VDBP/Cr). Genotyping for rs4588 SNP was performed using LightSNiP assay. Statistical analyses included correlation, linear regression, and comparison between allele groups.

Results

Participants carrying the rs4588-A allele exhibited lower serum 25OHD levels compared to non-carriers (median (IQR): 11.85 (3.5) vs. 12.86 (4.9), p = 0.023). However, no statistically significant differences were observed in serum VDBP levels (126.34 ± 59.3 in rs4588-A vs. 136.49 ± 51.3 in non-rs4588-A, p = 0.141) or in u-VDBP/Cr (median (IQR): 0.4 (0.35) in rs4588-A vs. 0.386 (0.43) in non-rs4588-A, p = 0.189) between the two allele groups. A significant inverse correlation between u-VDBP/Cr and serum VDBP levels was found only in rs4588-A carriers (r = -0.367, p = 0.024). No such correlation was observed in non-carriers or the entire cohort. A linear regression analysis confirmed the impact of u-VDBP/Cr on serum VDBP levels in rs4588-A carriers (B = -0.269, t = -2.185, p = 0.035).

Conclusion

Individuals with the rs4588-A allele in the GC gene had lower serum 25OHD levels. An inverse correlation between urinary VDBP excretion and serum VDBP levels was observed, suggesting a partial role of the renal pathway in altered serum VDBP and 25OHD levels linked to the rs4588-A allele.

Single nucleotide polymorphisms in vitamin D binding protein and 25-hydroxylase genes affect vitamin D levels in adolescents of Arab ethnicity in Kuwait

Vitamin D deficiency (VDD) is widespread in the Arab world despite ample sunshine throughout the year. In our previous study, lifestyle and socio-demographic factors could explain only 45% of variability in vitamin D levels in Kuwaiti adolescents, suggesting that genetics might contribute to VDD in this region. Single nucleotide polymorphisms (SNP) in the 25-hydroxylase (CYP2R1) and the GC globulin (GC) genes have been reported to affect vitamin D levels in various ethnic groups in adults. In this study, we investigated the association of two SNPs from GC (rs4588 and rs7041) and three SNPs from CYP2R1 (rs10741657, rs11023374 and rs12794714) with vitamin D levels and VDD in a nationally representative sample of adolescents of Arab ethnicity from Kuwait. Multivariable linear regression, corrected for age, sex, parental education, governorate, body mass index, and exposure to sun, demonstrated that each of the 5 study variants showed significant associations with plasma 25(OH)D levels in one or more of the additive, recessive, and dominant genetic models - the rs10741657 under all the three models, rs12794714 under both the additive and recessive models, rs7041 under the recessive model; and rs4588 and rs11023374 under the dominant model. Minor alleles at rs4588 (T), rs7041 (A), rs11023374 (C), and rs12794714 (A) led to a decrease in plasma 25(OH)D levels - rs4588:[β (95%CI) = -4.522 (-8.66,-0.38); p=0.033]; rs7041:[β (95%CI) = -6.139 (-11.12,-1.15); p=0.016]; rs11023374:[β (95%CI) = -4.296 (-8.18,-0.40); p=0.031]; and rs12794714:[β (95%CI) = -3.498 (-6.27,-0.72); p=0.014]. Minor allele A at rs10741657 was associated with higher levels of plasma 25(OH)D levels [β (95%CI) = 4.844 (1.62,8.06); p=0.003)] and lower odds of vitamin D deficiency (OR 0.40; p=0.002). These results suggest that the CYP2R1 and GC SNP variants are partly responsible for the high prevalence of VDD in Kuwait. Genotyping these variants may be considered for the prognosis of VDD in Kuwait.

Genetic variants in the vitamin D pathway and their association with vitamin D metabolite levels: Detailed studies of an inner-city pediatric population suggest a modest but significant effect in early childhood

OBJECTIVES

In a large cohort of healthy infants and toddlers 6-36 months of age (n = 776), we have been exploring the potential role of genetic variation in predisposition to vitamin D insufficiency. The genes encoding the key cytochrome P450 hydroxylases (CYP2R1, CYP24A1, and CYP27B1) harbour recurrent mutations of uncertain effect. This study was undertaken to look for biochemically relevant associations of these variants with inter-individual differences in vitamin D metabolism in an at-risk pediatric population.

METHODS

Genotyping for CYP2R1-CT (c.-1127 C>T, rs10741657), CYP24A1-AG (c.-686A>G, rs111622401), and CYP27B1-CA (c.-1261 C>A, rs10877012) mutations were performed using SNaPshot assay, followed by Sanger sequencing confirmation. Vitamin D metabolites and vitamin D binding protein (DBP) were measured by established methods.

RESULTS

In a multivariate regression model, with corrections for co-variates, subjects with the homozygous CYP2R1-TT variant had significantly higher concentrations of 25(OH)D, free 25(OH)D, and 24,25(OH)2D levels. In subjects with the CYP24A1-AG mutation, concentrations of 25(OH)D were significantly higher.

CONCLUSIONS

The CYP2R1-TT and CYP24A1-AG variants have measurable effects on the vitamin D pathway. It seems unlikely that they will be clinically relevant in isolation, but they may be members of the large pool of infrequent mutations contributing to different risks for the vitamin D deficiency phenotype.

Vitamin D metabolic pathway genes polymorphisms and vitamin D levels in association with neonatal hyperbilirubinemia in China: a single-center retrospective cohort study

BACKGROUND

Neonatal hyperbilirubinemia (NH) is a major cause of hospitalization after birth. Previous studies indicated that vitamin D deficiency might play an important role in NH susceptibility, but the results were controversial. Meanwhile, there has been limited description of the association between vitamin D related genes single nucleotide polymorphisms (SNP) and NH susceptibility. We aimed to investigate the vitamin D metabolic pathway genes polymorphisms and vitamin D levels with NH susceptibility.

METHODS

We retrospectively analyzed the clinical data, vitamin D levels and its metabolic pathway gene polymorphisms of 187 NH neonates and 149 controls at Tianjin Children's Hospital/Tianjin University Children's Hospital between April 2019 and August 2022. Vitamin D levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, and the genetic polymorphism of NADSYN1/DHCR7, GC, CYP2R1, CYP24A1 and CYP27B1 was detected by high resolution melting (HRM) analysis.

RESULTS

The frequency of vitamin D deficiency (25(OH)D < 15 ng/mL) was significantly increased in the NH group compared to controls. TT genotype of rs12785878 and GT genotype of rs10877012 were protective factors of vitamin D deficiency and NH, and GT genotype and dominant model carriers of rs12785878 had a higher risk of severe NH than the GG genotype carriers (GT genotype: OR: 2.43; 95% CI: 1.22-4.86; P = 0.012, dominant model: OR: 1.97; 95% CI: 1.04-3.73; P = 0.037). GC gene haplotype was associated with vitamin D deficiency. No significant SNP-SNP and SNP-vitamin D levels interaction combinations were found.

CONCLUSIONS

There were associations among NH, vitamin D deficiency and NADSYN1/DHCR7 and CYP27B1 polymorphisms, TT genotype of rs12785878 and GT genotype of rs10877012 could reduce the risk of vitamin D deficiency and NH. Furthermore, rs12785878 was significantly associated with severe NH.

Association of VDBP (rs4588 and rs7041) gene polymorphisms with susceptibility to postpartum depression in South Indian population: A cross-sectional study

Low vitamin D levels have been implicated in postpartum depressive disorders (PPD). Our study aimed to demonstrate the association of Vitamin D Binding Protein (VDBP) genetic variants rs7041 and rs4588 with susceptibility to PPD and to investigate their possible relationship with serum vitamin D and VDBP levels in Indian women with PPD. A cross-sectional study involved 330 cases and 330 controls. Depressive symptoms were assessed using Edinburg Postnatal Depression Scale. Genotyping of SNPs was done by Taqman 5'allelic discrimination assay. Estimation of serum 25 hydroxyvitamin D [25(OH) D] and VDBP levels were done by ELISA. Serum total, free and bioavailable 25(OH) D levels were significantly lower in cases compared to controls, with similar levels of VDBP between the two groups. The study results showed that the VDBP rs4588 variant genotype AA was significantly associated with lower circulating levels of total 25(OH) D in cases. Also, the VDBP rs7041 variant TT genotype demonstrated significantly lower levels of total, free and bioavailable 25(OH) D levels in controls. However, VDBP rs7041 and rs4588 variants were not associated with PPD susceptibility. Also, VDBP haplotypes showed no association with PPD susceptibility. Our results demonstrated that VDBP polymorphisms rs4588 and rs7041 and their haplotypes are not associated with PPD susceptibility in the South Indian population. However, vitamin D levels were found to be influenced by the risk genotypes of VDBP SNPs rs4588 and rs7041.

Vitamin D and musculoskeletal health: outstanding aspects to be considered in the light of current evidence

Vitamin D enhances calcium absorption and bone mineralisation, promotes maintenance of muscle function, and is crucial for musculoskeletal health. Low vitamin D status triggers secondary hyperparathyroidism, increases bone loss, and leads to muscle weakness. The primary physiologic function of vitamin D and its metabolites is maintaining calcium homeostasis for metabolic functioning, signal transduction, and neuromuscular activity. A considerable amount of human evidence supports the well-recognised contribution of adequate serum 25-hydroxyvitamin D concentrations for bone homeostasis maintenance and prevention and treatment strategies for osteoporosis when combined with adequate calcium intake. This paper aimed to review the literature published, mainly in the last 20 years, on the effect of vitamin D and its supplementation for musculoskeletal health in order to identify the aspects that remain unclear or controversial and therefore require further investigation and debate. There is a clear need for consistent data to establish realistic and meaningful recommendations of vitamin D status that consider different population groups and locations. Moreover, there is still a lack of consensus on thresholds for vitamin D deficiency and optimal status as well as toxicity, optimal intake of vitamin D, vitamin D supplement alone as a strategy to prevent fractures and falls, recommended sun exposure at different latitudes and for different skin pigmentations, and the extra skeletal effects of vitamin D.

The association of vitamin D binding protein levels and genotypes with type 1 diabetes in the black South African population

BACKGROUND

Vitamin D deficiency and the vitamin D pathway have previously been associated with type 1 diabetes (T1D). The majority of vitamin D is transported through the blood bound to the vitamin D binding protein (VDBP). Two polymorphisms in the VDBP gene (rs4588 and rs7041) result in different VDBP variants and have been associated with T1D, however the results are not consistent. The association of VDBP levels and its polymorphisms with T1D have not been investigated in the black South African population. Therefore, this study aimed to determine whether rs4588, rs7041 or serum VDBP levels were associated with T1D in this population.

METHODS

Participants with type 1 diabetes and controls were recruited from the greater Johannesburg area, South Africa. Participants were genotyped for rs4588 and rs7041 using PCR-RFLP and serum VDBP levels were determined by ELISA.

RESULTS

There was no difference in VDBP allelic or genotypic frequencies between participants with T1D and controls (rs4588 C allele frequency 0.92 vs. 0.94; p = 0.390 and rs7041 T allele frequency 0.95 vs. 0.95; p = 0.890). In univariate analysis, the rs4588 CC genotype was associated with increased serum VDBP levels, however, this association was lost with multivariate analysis. The VDBP genotypes were not associated with any other study variables. In logistic regression analysis, higher VBDP levels were associated with T1D (OR: (95% CI): 6.58 (1.45-29.9); p = 0.015), and within a linear regression analysis, T1D disease status was found to be associated with 0.044 mg/ml higher VDBP levels (p = 0.028).

CONCLUSIONS

These data suggest that serum VDBP levels are positively associated with the presence of T1D in the African population. Whether VDBP lies in the causal pathway or its elevation is an effect of T1D is uncertain and requires further investigation.

Streptozotocin-induced Diabetes Represses Hepatic CYP2R1 Expression but Induces Vitamin D 25-Hydroxylation in Male Mice

Vitamin D deficiency [ie, low plasma 25-hydroxyvitamin D (25-OH-D)] associates with the prevalence of metabolic diseases including type 1 diabetes; however, the molecular mechanisms are incompletely understood. Recent studies have indicated that both fasting and metabolic diseases suppress the cytochrome P450 (CYP) 2R1, the major hepatic vitamin D 25-hydroxylase. We specifically studied the effect of a mouse model of type 1 diabetes on the regulation of Cyp2r1 and vitamin D status. We show that streptozotocin-induced diabetes in mice suppresses the expression of the Cyp2r1 in the liver. While insulin therapy normalized the blood glucose levels in the diabetic mice, it did not rescue the diabetes-induced suppression of Cyp2r1. Similar regulation of Cyp2r1 was observed also in the kidney. Plasma 25-OH-D level was not decreased and was, in contrast, higher after 4 and 8 weeks of diabetes. Furthermore, the vitamin D 25-hydroxylase activity was increased in the livers of the diabetic mice, suggesting compensation of the Cyp2r1 repression by other vitamin D 25-hydroxylase enzymes. Cyp27b1, the vitamin D 1α-hydroxylase, expression in the kidney and the plasma 1α,25-dihydroxyvitamin D level were higher after 4 weeks of diabetes, while both were normalized after 13 weeks. In summary, these results indicate that in the mouse model of type 1 diabetes suppression of hepatic Cyp2r1 expression does not result in reduced hepatic vitamin D 25-hydroxylase activity and vitamin D deficiency. This may be due to induction of other vitamin D 25-hydroxylase enzymes in response to diabetes.

Antifungal Drug Plasma Exposures: A Possible Contribution of Vitamin D-Related Gene Variants

Vitamin D (VD) seems to influence drug clearance and outcome. Antifungal drugs (AFU) are the most used azoles in clinical practice. In the literature, no data are available concerning VD’s impact on AFU therapy. The aim of this study was to analyze if VD pathway-related polymorphisms may influence voriconazole (VRC), itraconazole (ITC), and posaconazole (PSC) drug concentrations in order to identify patients with the highest probability of response and toxicity. Allelic discrimination was performed through real-time PCR, whereas drug concentrations were through liquid chromatography. A total of 636 samples of AFU-treated patients were included in the analysis. Concerning VRC, concentrations higher than the 1000 ng/mL efficacy cut-off value were predicted by Caucasian ethnicity, CYP24A1 3999, and CYP27B1 + 2838 polymorphisms, whereas levels higher than the 5000 ng/mL toxicity value by Caucasian, female sex, e.v. administration, and GC 1296. Considering PSC, concentrations higher than the 700 ng/mL efficacy cut-off value were predicted by VDR Cdx2, CYP27B1 − 1260, and GC 1296. Finally, for ITC, VDR BsmI was the only predictor of drug exposure higher than the 500 ng/mL efficacy cut-off value, whereas female sex, CYP27B1 − 1260, and VDR TaqI remained in the final regression model related to concentrations higher than the 1000 ng/mL toxicity-associated cut-off value. This is the first study reporting the influence of VD pathway-related gene SNPs on AFU exposures, efficacy, and toxicity.

Pre- and Postnatal Vitamin D Status and Allergy Outcomes in Early Childhood

The dramatic increase in the prevalence of allergic disease in recent decades reflects environmental and behavioural changes that have altered patterns of early immune development. The very early onset of allergic diseases points to the specific vulnerability of the developing immune system to environmental changes and the development of primary intervention strategies is crucial to address this unparalleled burden. Vitamin D is known to have immunomodulatory functions. While allergic disease is multifactorial, associations with reduced sunlight exposure have led to the hypothesis that suboptimal vitamin D levels during critical early periods may be one possible explanation. Interventions to improve vitamin D status, especially in early life, may be the key to allergic disease prevention.

Haplotypes in the GC, CYP2R1 and CYP24A1 Genes and Biomarkers of Bone Mineral Metabolism in Older Adults

Candidate gene studies have analyzed the effect of specific vitamin D pathway genes on vitamin D availability; however, it is not clear whether genetic variants also affect overall bone metabolism. This study evaluated the association between genetic polymorphisms in GC, CYP2R1 and CYP24A1 and serum levels of total 25(OH)D, iPTH and other mineral metabolism biomarkers (albumin, total calcium and phosphorus) in a sample of 273 older Spanish adults. We observed a significant difference between CYP2R1 rs10741657 codominant model and total 25(OH)D levels after adjusting them by gender (p = 0.024). In addition, the two SNPs in the GC gene (rs4588 and rs2282679) were identified significantly associated with iPTH and creatinine serum levels. In the case of phosphorus, we observed an association with GC SNPs in dominant model. We found a relationship between haplotype 2 and 25(OH)D levels, haplotype 4 and iPTH serum levels and haplotype 7 and phosphorus levels. In conclusion, genetic variants in CYP2R1 and GC could be predictive of 25(OH)D and iPTH serum levels, respectively, in older Caucasian adults. The current study confirmed the role of iPTH as one of the most sensitive biomarkers of vitamin D activity in vivo.

The Role of Vitamin D Supplementation in Children with Autism Spectrum Disorder: A Narrative Review

Children with autism spectrum disorder (ASD) present with persistent deficits in both social communication and interactions, along with the presence of restricted and repetitive behaviors, resulting in significant impairment in significant areas of functioning. Children with ASD consistently reported significantly lower vitamin D levels than typically developing children. Moreover, vitamin D deficiency was found to be strongly correlated with ASD severity. Theoretically, vitamin D can affect neurodevelopment in children with ASD through its anti-inflammatory properties, stimulating the production of neurotrophins, decreasing the risk of seizures, and regulating glutathione and serotonin levels. A Title/Abstract specific search for publications on Vitamin D supplementation trials up to June 2021 was performed using two databases: PubMed and Cochrane Library. Twelve experimental studies were included in the synthesis of this review. Children with ASD reported a high prevalence of vitamin D deficiency or insufficiency. In general, it was observed that improved vitamin D status significantly reduced the ASD severity, however, this effect was not consistently different between the treatment and control groups. The variations in vitamin D dose protocols and the presence of concurrent interventions might provide an explanation for the variability of results. The age of the child for introducing vitamin D intervention was identified as a possible factor determining the effectiveness of the treatment. Common limitations included a small number of participants and a short duration of follow-ups in the selected studies. Long-term, well-designed randomized controlled trials are warranted to confirm the effect of vitamin D on severity in children with ASD.

Is Bioavailable Vitamin D Better Than Total Vitamin D to Evaluate Vitamin D Status in Obese Children?

INTRODUCTION

Free hormones are biologically more active in target tissues. Thus, measurement of vitamin D taking into account bioavailability and free vitamin D may be preferable, especially when evidence is contradictory, as in obese children. In order to assess bioavailablity and free vitamin D, using a previously reported formula, vitamin D-binding protein (VDBP) level was measured and VDBP polymorphisms were also evaluated because of variations in binding affinity.

METHODS

Eighty-four obese and 78 healthy children were included. Anthropometry, calcium, phosphorus, alkaline-phosphatase, parathyroid hormone (PTH), 25 hydroxyvitamin D [25(OH)D], bioavailable-free vitamin D, and VDBP concentration and polymorphism were evaluated in the whole group.

RESULTS

Obese girls had significantly higher PTH than normal weight girls (p=0.001). Regardless of gender, obese children had significantly higher concentrations of VDBP (p=0.008) and PTH (p=0.002). When samples taken in winter were analyzed, PTH and VDBP were found to be higher and bioavailable and free vitamin D lower in the obese group. There was no difference in terms of total vitamin D between groups during the winter season.

CONCLUSION

While total, free, and bioavailable vitamin D in the obese group was similar to the control group in autumn, free and bioavailable vitamin D in the winter was lower in the obese than the control group. In addition, PTH was higher in the obese group in both autumn and winter. Therefore, more research is needed to evaluate the variability of free and bioavailable vitamin D according to body habitus, season and the effect any differences may have.

Total, bioavailable and free 25-hydroxyvitamin D levels as functional indicators for bone parameters in healthy children

Objectives

Vitamin D is essential for bone health. Not only total but also free 25-hydroxyvitamin D (25OHD) may contribute to bone mass. We sought to determine which vitamin D measure best reflected clinical and bone parameters in healthy children.

Methods

A cross-sectional study including 146 healthy children (71 boys, 9.5 ± 1.9 years) conducted at a tertiary medical center. We used a multiplex liquid chromatography-tandem mass spectrometry-based assay to simultaneously measure vitamin D metabolites. The bioavailable and free 25OHD (25OHD_BioA and 25OHD_Free) levels were calculated using the genotype-specific or genotype-constant affinity coefficients of vitamin D-binding proteins (yielding spe-25OHD_BioA, spe-25OHD_Free and con-25OHD_BioA, con-25OHD_Free respectively). The 25OHD_Free level was directly measured (m-25OHD_Free). Bone mineral content (BMC) and bone mineral density (BMD) were assessed via dual-energy X-ray absorptiometry.

Results

The total 25OHD (25OHD_Total), the two forms of 25OHD_BioA, the three forms of 25OHD_Free, and 24,25-dihydroxyvitamin D₃ levels correlated with parathyroid hormone level (all p < 0.01). Serum 25OHD_Total and m-25OHD_Free levels were influenced by age, pubertal status, season, body mass index (BMI), daylight hours, and vitamin D intake (all p < 0.05). The con-25OHD_BioA and con-25OHD_Free levels better reflected pubertal status and daylight hours than did the spe-25OHD_BioA and spe-25OHD_Free levels (both p < 0.01). The association between the 25OHD_Total level and bone parameters varied according to the BMI (interaction p < 0.05). In 109 normal-weight children, the con-25OHD_BioA and con-25OHD_Free levels correlated with total body BMC and BMD (both p < 0.05), whereas the 25OHD_Total and 24,25-dihydroxyvitamin D₃ levels were associated with total body BMC (both p < 0.05). No such association was found in overweight or obese children.

Conclusions

In healthy children, total, bioavailable, and free 25OHD levels comparably reflected lifestyle factors. In normal-weight children, the con-25OHD_BioA and con-25OHD_Free, but not m-25OHD_Free levels, reflected bone mass, as did the 25OHD_Total level.

Maternal Nutritional Status and Development of Atopic Dermatitis in Their Offspring

Atopic dermatitis (AD) is the leading chronic skin inflammatory disease and the initial manifestation of atopic march. Available evidence supports the notion that primary prevention early in life leads to a decreased incidence of AD, thus possibly decreasing the subsequent occurrence of atopic march. Nutritional status is essential to a proper functioning immune system and is valued for its important role in AD. Essential nutrients, which include carbohydrates, proteins, lipids, vitamins, and minerals, are transferred from the mother to the fetus through the placenta during gestation. Various nutrients, such as polyunsaturated fatty acids (PUFAs) and vitamin D, were studied in relation to maternal status and offspring allergy. However, no strong evidence indicates that a single nutrient or food in mothers' diet significantly affects the risk of childhood AD. In the light of current evidence, mothers should not either increase nor avoid consuming these nutrients to prevent or ameliorate allergic diseases in their offspring. Each essential nutrient has an important role in fetal development, and current government recommendations suggest specific intake amounts for pregnant women. This review discusses evidence on how various nutrients, including lipids (monounsaturated fatty acids, PUFAs, saturated fatty acids, and short-chain fatty acids), carbohydrates (oligosaccharides and polysaccharides), proteins, vitamins (A, B, C, D, and E), and trace minerals (magnesium, iron, zinc, copper, selenium, and strontium) in maternal status are associated with the development of AD and their possible mechanisms.

25-OHD response to vitamin D supplementation in children: effect of dose but not GC haplotype

OBJECTIVE

GC/DBP effects on response to vitamin D supplementation have not been well-studied. Thus we assessed free and total 25-OHD after vitamin D treatment across the six common GC haplotypes.

DESIGN

This double-blind, randomized study compared two vitamin D3 doses in healthy, urban-dwelling 6-month to 10-year-old children at-risk for vitamin D deficiency. Randomization was stratified by GC haplotype.

METHODS

Children were randomized to receive 2800 or 7000 International Units of vitamin D3 weekly. 25-OHD and 1,25(OH)2D were sampled at baseline and after 1-6 months of supplementation.

RESULTS AND CONCLUSIONS

One hundred ninety-two of 225 enrolled subjects completed the study. After one month, total 25-OHD increased with both doses and were higher with 7000 IU/week (85.5 ± 22.8 nmol/L) compared to 2800 IU/week (76.8 ± 18.0 nmol/L), despite equivalent baseline levels. No further significant increase occurred at 6 months (89.8 ± 35.5 and 74.3 ± 18.3 nmol/L, respectively). Free 25-OHD similarly changed. 25-OHD differed among GC groups at baseline. Although no significant effects of individual GC haplotypes on incremental changes were evident, a trend toward an effect of combined 'at risk' GC alleles on response was evident (P = 0.06). Total 1,25(OH)2D showed modest increases, moreso with the larger dose. In urban-dwelling children at-risk for vitamin D deficiency, 1 month of vitamin D3 2800 IU/week increased 25-OHD across all GC haplotype groups, and somewhat enhanced with 7000 IU/week with no further significant increases after 6 months of supplementation. Free 25-OHD measures offer no monitoring advantage over total 25-OHD.

Influence of vitamin D binding protein polymorphism, demographics and lifestyle factors on vitamin D status of healthy Malaysian pregnant women

BACKGROUND

Vitamin D deficiency (VDD) has been related to vitamin D binding protein (GC) gene polymorphism, demographics and lifestyle factors in different populations. However, previous studies only focused on demographic and lifestyle factors or genetic factors alone. Therefore, this cross-sectional study aimed to assess the association between GC gene polymorphism, demographics and lifestyle factors with VDD among Malaysian pregnant women.

METHOD

Information on demographic characteristics, dietary vitamin D intake from supplement and food, time spent outdoors, skin type and clothing were collected using a questionnaire. Plasma total 25-hydroxyvitamin D (25OHD) levels were measured using an Ultra-High-Performance Liquid Chromatography (UHPLC). Maternal GC single nucleotide polymorphisms (SNPs) (rs4588 and rs7041) were determined using restriction fragment length polymorphism (RFLP) technique.

RESULTS

Results showed that 50.2% of pregnant women were vitamin D deficient (25OHD < 30 nmol/L). VDD (25OHD < 30 nmol/L) was significantly associated with age, veiled clothing, maternal vitamin D intakes from both food and supplements, and GC rs7041(and GC diplotypes). In contrast to previous studies that reported for non-pregnant population, a significant positive association was found between CC genotype for SNP GC rs7041, GC 1s-1s and GC If-2 with risk of VDD (25OHD < 30 nmol/L).

CONCLUSIONS

The high prevalence of maternal VDD found in this study suggests the need for urgent development and implementation of vitamin D supplementation or fortification strategies to reduce VDD among pregnant women. The discrepancy in the association between GC rs7041 gene polymorphism and VDD reflects the variation in the factors associated with VDD in pregnancy compared to non-pregnant state.

Clinical Significance of Analysis of Vitamin D Status in Various Diseases

Vitamin D plays a role not only in the proper functioning of the skeletal system and the calcium-phosphate equilibrium, but also in the immune system, the cardiovascular system and the growth and division of cells. Although numerous studies have reported on the analysis of vitamin D status in various groups of patients, the clinical significance of measurements of vitamin D forms and metabolites remains ambiguous. This article reviews the reports analyzing the status of vitamin D in various chronic states. Particular attention is given to factors affecting measurement of vitamin D forms and metabolites. Relevant papers published during recent years were identified by an extensive PubMed search using appropriate keywords. Measurement of vitamin D status proved to be a useful tool in diagnosis and progression of metabolic syndrome, neurological disorders and cancer. High performance liquid chromatography coupled with tandem mass spectrometry has become the preferred method for analyzing the various forms and metabolites of vitamin D in biological fluids. Factors influencing vitamin D concentration, including socio-demographic and biochemical factors as well as the genetic polymorphism of the vitamin D receptor, along with vitamin D transporters and enzymes participating in vitamin D metabolism should be considered as potential confounders of the interpretation of plasma total 25(OH)D concentrations.

Obesity Represses CYP2R1, the Vitamin D 25-Hydroxylase, in the Liver and Extrahepatic Tissues

Low plasma level of 25-hydroxyvitamin D (25-OH-D), namely vitamin D deficiency, is associated with obesity and weight loss improves 25-OH-D status. However, the mechanism behind obesity-induced vitamin D deficiency remains unclear. Here, we report that obesity suppresses the expression of cytochrome P450 (CYP) 2R1, the main vitamin D 25-hydroxylase, in both mice and humans. In humans, weight loss induced by gastric bypass surgery increased the expression of CYP2R1 in the s.c. adipose tissue suggesting recovery after the obesity-induced suppression. At the same time, CYP27B1, the vitamin D 1α-hydroxylase, was repressed by the weight loss. In a mouse (C57BL/6N) model of diet-induced obesity, the plasma 25-OH-D was decreased. In accordance, the CYP2R1 expression was strongly repressed in the liver. Moreover, obesity repressed the expression of CYP2R1 in several extrahepatic tissues, the kidney, brown adipose tissue, and testis, but not in the white adipose tissue. Obesity had a similar effect in both male and female mice. In mice, obesity repressed expression of the vitamin D receptor in brown adipose tissue. Obesity also upregulated the expression of the vitamin D receptor and CYP24A1 in the s.c. adipose tissue of a subset of mice; however, no effect was observed in the human s.c. adipose tissue. In summary, we show that obesity affects CYP2R1 expression both in the mouse and human tissues. We suggest that in mouse the CYP2R1 repression in the liver plays an important role in obesity-induced vitamin D deficiency. Currently, it is unclear whether the CYP2R1 downregulation in extrahepatic tissues could contribute to the obesity-induced low plasma 25-OH-D, however, this phenomenon may affect at least the local 25-OH-D concentrations. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

In Silico Structural and Biochemical Functional Analysis of a Novel CYP21A2 Pathogenic Variant

Classical congenital adrenal hyperplasia (CAH) caused by pathogenic variants in the steroid 21-hydroxylase gene (CYP21A2) is a severe life-threatening condition. We present a detailed investigation of the molecular and functional characteristics of a novel pathogenic variant in this gene. The patient, 46 XX newborn, was diagnosed with classical salt wasting CAH in the neonatal period after initially presenting with ambiguous genitalia. Multiplex ligation-dependent probe analysis demonstrated a full deletion of the paternal CYP21A2 gene, and Sanger sequencing revealed a novel de novo CYP21A2 variant c.694–696del (E232del) in the other allele. This variant resulted in the deletion of a non-conserved single amino acid, and its functional relevance was initially undetermined. We used both in silico and in vitro methods to determine the mechanistic significance of this mutation. Computational analysis relied on the solved structure of the protein (Protein-data-bank ID 4Y8W), structure prediction of the mutated protein, evolutionary analysis, and manual inspection. We predicted impaired stability and functionality of the protein due to a rotatory disposition of amino acids in positions downstream of the deletion. In vitro biochemical evaluation of enzymatic activity supported these predictions, demonstrating reduced protein levels to 22% compared to the wild-type form and decreased hydroxylase activity to 1–4%. This case demonstrates the potential of combining in-silico analysis based on evolutionary information and structure prediction with biochemical studies. This approach can be used to investigate other genetic variants to understand their potential effects.

Vitamin D in Type 2 Diabetes: Genetic Susceptibility and the Response to Supplementation

Variants of vitamin D metabolism-genes may predispose to type 2 diabetes (T2D). This study investigated the impact of these variants on disease susceptibility, Vitamin D, parathyroid hormone, C-peptide and HbA1c levels before and after cholecalciferol supplementation in patients with T2D.Twelve polymorphisms within CYP2R1, CYP27B1, DBP, VDR and CYP24A1 were genotyped in 553 T2D patients and 916 controls. In addition 65 patients receiving either cholecalciferol or placebo were analyzed during 6 months intervention and 6 months follow-up.T2D risk alleles are VDR rs7975232 "G" (p_c=0.031), rs1544410 "G" (p_c=0.027) and CYP2R1 rs10741657 "A" (p_c=0.016). Patients with genotypes CYP27B1 rs10877012 "CC" (p_c=4x10^-5), DBP rs7041 "GG" (p_c=0.003), rs4588 "CC" (p_c = 3x10^-4), CYP24A1 rs2585426 "CG" (p_c=0.006) and rs2248137 "CG" (p_c=0.001) showed lower 25(OH)D3 and DBP rs4588 "CC" lower 1,25(OH)2D3 levels (p_c=0.005). Whereas DBP rs4588 "CC" (p_c=0.009), CYP27B1 rs10877012 "AC" (p_c=0.059), VDR rs7975323 "AG" (p_c=0.033) and rs1544410 "GG" (p_c=0.013) are associated with higher 25(OH)D3 levels at 6 months' follow-up. Significant PTH suppression was detected for CYP2R1 "AG" (p_c=0.002), DBP rs4588 "CC" (p_c<0.001), VDR rs110735810 "CT" (p_c<0.001) and CYP24A1 rs2248137 "GG" (p_c=0.021).Genetic variants of the vitamin D system predispose to type 2 diabetes and regulate - partially - vitamin D metabolism, concentrations and the vitamin D status. Vitamin D insufficiency is a T2D risk factor. The response to cholecalciferol supplementation can be measured as 25(OH)D3 increment and PTH suppression. This process is regulated by genes of the vitamin D system conferring modest T2D risk.

Association of VDBP rs4701 Variant, but not VDR/RXR-α Over-Expression with Bone Mineral Density in Pediatric Well-Chelated β-Thalassemia Patients

Background

The reduced rate of bone formation despite the availability of vitamin D has been reported in β-thalassemia. Genetic factors, together with environmental ones, could be implicated in this condition. Since vitamin D binding protein (VDBP) maintains bioavailability of vitamin D which binds to vitamin D receptor (VDR)-retinoid X receptor alpha (RXRA) heterodimer to exert its molecular actions, we speculated that vitamin D metabolic-axis expression signature and variants could be potential molecular candidates for bone turnover/disease in thalassemia. To this end, this study aims to analyze VDR/RXRA expression signature, and two VDBP variants in a pilot sample of Egyptian β-thalassemia children in correlation with bone mineral density (BMD).

Patients and methods

Forty-four well-chelated β-thalassemia children and 40 unrelated controls were enrolled. The serum bone chemistry profile was measured. Peripheral blood mononuclear cells (PBMN) VDR/RXRA expression levels were quantified by Real-Time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). VDBP rs7041 and rs4588 variants were identified by Real-Time allelic discrimination assay. All patients were subjected to lumbar-spine Dual-energy X-ray absorptiometry (DEXA).

Results

VDR/RXRA expressions were significantly higher in β-thalassemia children compared to controls (P = 0.001 and <0.001, respectively) and showed higher values in β-thalassemia major relative to β-thalassemia intermedia. Expression levels of both genes were not associated with sex or BMD. However, VDBP rs4701 genotyping revealed lower BMD-L4 and a higher frequency of osteoporosis.

Conclusions

β-Thalassemia children had higher expression levels of PBMN VDR/RXRA. VDBP rs4701 variant was associated with osteoporosis in our β-thalassemia patients on vitamin D supplementation. Further large-scale studies in other ethnic populations are warranted.

Relationship of Total and Free 25-Hydroxyvitamin D to Biomarkers and Metabolic Indices in Healthy Children

CONTEXT

Vitamin D status is usually assessed by serum total 25-hydroxyvitamin D (t25-OHD). Whether free 25-hydroxyvitamin D measures better correlate with various clinical outcomes is unclear.

OBJECTIVE

To identify correlations between t25-OHD, calculated and direct measures of free 25-OHD, and to identify associations of these measures with other outcomes in children, across the 6 common GC haplotypes.

DESIGN

Healthy urban-dwelling children underwent measurement of relevant variables.

SETTING

Academic medical center.

PARTICIPANTS

The study included 203 healthy, urban-dwelling children, aged 6 months to 10 years, predominantly of Hispanic background and representative of all common GC haplotypes.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Total and free 25-OHD and 1,25(OH)2D, calcium, phosphate, parathyroid hormone (PTH), glucose, insulin, aldosterone, and renin.

RESULTS

Mean t25-OHD [26.3 ± 6.7ng/ml; 65.8 ± 16.8nmol/L] were lowest in the GC2 genotype. Mean t1,25(OH)2D [57.6 ± 16.5pg/ml; 143.9 ± 41.3pmol/L], were lowest in GC1f/1f, GC1f/2, and GC2/2 groups. T25-OHD correlated strongly with calculated free 25-OHD (cf25-OHD) (r = 0.89) and moderately with directly measured free 25-OHD (dmf25-OHD) (r = 0.69). Cf25-OHD correlated with dmf25-OHD (r = 0.69) (P < 0.001 for all). t25-OHD inversely correlated with body mass index (BMI) (r=-0.191; P = 0.006), skin reflectometry, and systolic blood pressure. T25-OHD correlated with fasting insulin and the homeostatic model assessment for insulin resistance (HOMA-IR), however significance for these correlations was not evident after adjustment for BMI. PTH inversely correlated with all measures of 25-OHD, but most strongly with t25-OHD.

CONCLUSIONS

Measures of circulating total and free 25-OHD are comparable measures of vitamin D status in heathy children. Correlations are similar with other outcome variables, however t25-OHD remains the strongest correlate of circulating PTH and other variables. These data argue against routine refinement of the t25-OHD measure using currently available assessments of free 25-OHD.

CLINICAL TRIAL INFORMATION

Clinicaltrials.gov registration no: NCT01050387 (January 15, 2010).

Genetic Contributions to Maternal and Neonatal Vitamin D Levels

Vitamin D is essential for several physiological functions and biological processes. Increasing levels of maternal vitamin D are required throughout pregnancy as a unique source of vitamin D for the fetus, and consequently maternal vitamin D deficiency may result in several adverse outcomes in newborns. However, the genetic regulation of vitamin D in pregnancy and at birth is not yet well understood. We performed genome-wide association studies of maternal midgestational serum-derived and neonatal blood-spot-derived total 25-hydroxyvitamin D from a case-control study of autism spectrum disorder (ASD). We identified one fetal locus (rs4588) significantly associated with neonatal vitamin D levels in the GC gene, encoding the binding protein for the transport and function of vitamin D. We also found suggestive cross-associated loci for neonatal and maternal vitamin D near immune genes, such as CXCL6-IL8 and ACKR1 We found no interactions with ASD. However, when including a set of cases with intellectual disability but not ASD (N = 179), we observed a suggestive interaction between decreased levels of neonatal vitamin D and a specific maternal genotype near the PKN2 gene. Our results suggest that genetic variation influences total vitamin D levels during pregnancy and at birth via proteins in the vitamin D pathway, but also potentially via distinct mechanisms involving loci with known roles in immune function that might be involved in vitamin D pathophysiology in pregnancy.

New aspects of vitamin D metabolism and action - addressing the skin as source and target

Vitamin D has a key role in stimulating calcium absorption from the gut and promoting skeletal health, as well as many other important physiological functions. Vitamin D is produced in the skin. It is subsequently metabolized to its hormonally active form, 1,25-dihydroxyvitamin D (1,25(OH)₂D), by the 1-hydroxylase and catabolized by the 24-hydroxylase. In this Review, we pay special attention to the effect of mutations in these enzymes and their clinical manifestations. We then discuss the role of vitamin D binding protein in transporting vitamin D and its metabolites from their source to their targets, the free hormone hypothesis for cell entry and HSP70 for intracellular transport. This is followed by discussion of the vitamin D receptor (VDR) that mediates the cellular actions of 1,25(OH)₂D. Cell-specific recruitment of co-regulatory complexes by liganded VDR leads to changes in gene expression that result in distinct physiological actions by 1,25(OH)₂D, which are disrupted by mutations in the VDR. We then discuss the epidermis and hair follicle, to provide a non-skeletal example of a tissue that expresses VDR that not only makes vitamin D but also can metabolize it to its hormonally active form. This enables vitamin D to regulate epidermal differentiation and hair follicle cycling and, in so doing, to promote barrier function, wound healing and hair growth, while limiting cancer development.

Significance of Vitamin D Binding Protein in Assessing Vitamin D Status Among Under-Five Children

Despite ample sunshine, 50-90% Indian children have Vitamin D deficiency (VDD). This enigma of widespread VDD needs exploration especially among under-fives as physiological variations in Vitamin D Binding Protein (VDBP) levels could be potential confounders in the interpretation of total 25-hydroxyvitamin D [25(OH)D]. However, there is scarce information about relevance of VDBP levels in under-five age group. We therefore, explored association of VDBP levels among 1-5 year old children with VDD. Serum levels of 25(OH)D, VDBP, calcium, parathyroid hormone (PTH) and alkaline phosphatase were estimated in 210 apparently healthy children in the age group of 1-5 years. VDD was defined as serum 25(OH)D levels < 20 ng/ml as per the IOM classification. VDBP levels were classified as low if levels were < 168 μg/ml as per the kit. The prevalence of VDD was 79.5% (n = 167) and VDBP levels were low in 48.6% (n = 102) of children. 25(OH)D levels correlated positively with VDBP (r = 0.298, p = 0.0001). A significant number of children (52.7%) with VDD had low VDBP (p = 0.015). and despite adequate sun exposure, 43% of children showed VDD and 56.6% had low VDPB levels. The low VDBP levels largely explain low 25OHD levels without necessarily implying VDD. It may add a new dimension for better understanding of widespread VDD among under-five children. It thus, points towards the need for redefining cut offs and complete evaluation of vitamin D status among under-fives including VDBP.

Identification and analysis of 35 genes associated with vitamin D deficiency: A systematic review to identify genetic variants

Vitamin D deficiency is a public health concern associated with, but not limited to, skeletal anomalies, chronic diseases, immune conditions, and cancer, among others. Hypovitaminosis D is mainly associated with environmental and lifestyle factors that affect sunlight exposure. However, genetic factors also influence 25-hydroxyvitamin D (25[OH]D) serum concentration. Although there is available information of genes with clear biological relevance or markers identified by Genome-Wide Association Studies, an overall view and screening tool to identify known genetic causes of altered serum levels of 25(OH)D is lacking. Moreover, there are no studies including the total genetic evidence associated with abnormal serum concentration of 25(OH)D. Therefore, we conducted a de-novo systematic literature review to propose a set of genes comprehensive of all genetic variants reported to be associated with deficiency of vitamin D. Abstracts retrieved from PubMed search were organized by gene and curated one-by-one using the PubTerm web tool. The genes identified were classified according to the type of genetic evidence associated with serum 25(OH)D levels and were also compared with the few commonly screened genes related to vitamin D status. This strategy allowed the identification of 35 genes associated with serum 25(OH)D concentrations, 27 (75%) of which are not commercially available and are not, therefore, analyzed in clinical practice for genetic counseling, nor are they sufficiently studied for research purposes. Functional analysis of the genes identified confirmed their role in vitamin D pathways and diseases. Thus, the list of genes is an important source to understand the genetic determinants of 25(OH)D levels. To further support our findings, we provide a map of the reported functional variants and SNPs not included in ClinVar, minor allelic frequencies, SNP effect sizes, associated diseases, and an integrated overview of the biological role of the genes. In conclusion, we identified a comprehensive candidate list of genes associated with serum 25(OH)D concentrations, most of which are not commercially available, but would prove of importance in clinical practice in screening for patients that should respond to supplementation because of alterations in absorption, patients that would have little benefit because alterations in the downstream metabolism of vitamin D, and to study non-responsiveness to supplementation with vitamin D.

Genetic, environmental and biomarker considerations delineating the regulatory effects of vitamin D on central nervous system function

Studies show that vitamin D (vit-D) (25(OH)D), the bioactive metabolite (1,25(OH)2D3) and vit-D receptors (vit-D receptor; protein disulphide isomerase, family A member 3) are expressed throughout the brain, particularly in regions pivotal to learning and memory. This has led to the paradigm that avoiding vit-D deficiency is important to preserve cognitive function. However, presently, it is not clear if the common clinical measure of serum 25(OH)D serves as a robust surrogate marker for central nervous system (CNS) homeostasis or function. Indeed, recent studies report CNS biosynthesis of endogenous 25(OH)D, the CNS expression of the CYP group of enzymes which catalyse conversion to 1,25(OH)2D3 and thereafter, deactivation. Moreover, in the periphery, there is significant ethnic/genetic heterogeneity in vit-D conversion to 1,25(OH)2D3 and there is a paucity of studies which have actually investigated vit-D kinetics across the cerebrovasculature. Compared with peripheral organs, the CNS also has differential expression of receptors that trigger cellular response to 1,25(OH)2D3 metabolites. To holistically consider the putative association of peripheral (blood) abundance of 25(OH)D on cognitive function, herein, we have reviewed population and genetic studies, pre-clinical and clinical intervention studies and moreover have considered potential confounders of vit-D analysis.

Vitamin D Deficiency in Middle Childhood Is Related to Behavior Problems in Adolescence

BACKGROUND

Vitamin D deficiency (VDD) is associated with depression and schizophrenia in adults. The effect of VDD in childhood on behavioral development is unknown.

OBJECTIVES

We aimed to study the associations of VDD and vitamin D binding protein (DBP) in middle childhood with behavior problems in adolescence.

METHODS

We quantified plasma total 25-hydroxyvitamin D [25(OH)D] and DBP in 273 schoolchildren aged 5-12 y at recruitment into a cohort study in Bogota, Colombia. Externalizing and internalizing behavior problems were assessed after a median 6-y follow-up by parental report [Child Behavior Checklist (CBCL)] and self-report [Youth Self-Report (YSR)]. We estimated mean problem score differences with 95% CIs between exposure categories using multivariable linear regression. We also compared the prevalence of clinical behavior problems (score >63) between exposure groups. We assessed whether the associations between DBP and behavior problems were mediated through VDD.

RESULTS

Mean ± SD CBCL and YSR externalizing problems scores were 56.5 ± 9.3 and 53.2 ± 9.5, respectively. Internalizing problems scores averaged 57.1 ± 9.8 and 53.7 ± 9.8, respectively. VDD [25(OH)D <50 nmol/L] prevalence was 10.3%. VDD was associated with an adjusted 6.0 (95% CI: 3.0, 9.0) and 3.4 (95% CI: 0.1, 6.6) units higher CBCL and YSR externalizing problems scores, respectively, and an adjusted 3.6 (95% CI: 0.3, 6.9) units higher CBCL internalizing problems scores. The prevalence of clinical total externalizing problems was 1.8 (95% CI: 1.1, 3.1) times higher in children with VDD than that in children without VDD. DBP concentration below the population median was related to higher YSR aggressive behavior and anxious/depressed subscale scores and to higher prevalence of clinical total externalizing problems. The associations between DBP and behavior problems were not mediated through VDD.

CONCLUSIONS

VDD and low DBP in middle childhood are related to behavior problems in adolescence.

Prevalence of vitamin D deficiency in women from southern Brazil and association with vitamin D-binding protein levels and GC-DBP gene polymorphisms

Vitamin D deficiency is highly prevalent worldwide, and vitamin D-binding protein (DBP) a major regulator of serum vitamin D levels. The rs4588 and rs7041 polymorphisms of the GC gene constitute the genetic basis of the three major isoforms of circulating DBP (GC1s, GC1f, and GC2), while the rs2282679 variant is located in an important regulatory region of the GC gene. The aim of this study was to assess the prevalence of 25-hydroxyvitamin D [25(OH)D] deficiency and to ascertain whether it is associated with DBP levels and with GC gene variants. Biorepository samples of 443 women aged 20 to 72 years, with no evidence of clinical disease, were analyzed. Circulating levels of 25(OH)D were considered sufficient if ≥20 ng/mL and deficient if <20 ng/mL. Genotype analysis was performed by RT-PCR. Mean age was 53.4±9.4 years; mean BMI was 27.8±5.8 kg/m2. The overall sample had mean 25(OH)D levels of 22.8±8.3 ng/mL; 39.7% of participants had deficient circulating 25(OH)D levels. Higher prevalence ratios (PR) of 25(OH)D deficiency were found for the CC genotype of rs2282679 (PR 1.74; 95%CI 1.30 to 2.24; p<0.001), GC2 isoform (PR 1.66; 95%CI 1.17 to 2.38; p = 0.005), time since menopause (PR 1.02; 95%CI 1.003 to 1.03, p = 0.016), and HOMA-IR (PR 1.02; 95%CI 1.01 to 1.03, p = 0.004). DBP levels (per 30 μg/mL increase in DBP) were associated with lower PR for 25(OH)D deficiency (PR 0.89; 95%CI 0.80;0.99; p = 0.027). Except for HOMA-IR, these prevalence ratios remained significant after adjustment for age and BMI. In conclusion, the rs2282679 polymorphism and the GC2 isoform of DBP were associated with lower serum DBP levels and with susceptibility to 25(OH)D deficiency in Brazilian women with no evidence of clinical disease.

Genetic Variation of the Vitamin D Binding Protein Affects Vitamin D Status and Response to Supplementation in Infants

CONTEXT

Single nucleotide polymorphisms (SNPs) of the vitamin D binding protein encoding the GC (group component) gene affect 25-hydroxyvitamin D (25OHD) concentrations, but their influence on vitamin D status and response to vitamin D supplementation in infants is unknown.

OBJECTIVE

To study GC genotype-related differences in 25OHD concentrations and the response to supplementation during a vitamin D intervention study in infants.

DESIGN

In this randomized controlled trial, healthy term infants received vitamin D3 (10 or 30 μg/d) from 2 weeks to 24 months of age. GC SNPs rs2282679, rs4588, rs7041, and rs1155563 were genotyped. rs4588/7041 diplotype and haplotypes of rs2282679, rs4588, and rs7041 (Haplo3SNP) and of all four SNPs (Haplo4SNP) were determined.

MAIN OUTCOME MEASURES

25OHD measured in cord blood at birth and at 12 and 24 months during intervention.

RESULTS

A total of 913 infants were included. Minor allele homozygosity of all studied GC SNPs, their combined haplotypes, and rs4588/rs7041 diplotype 2/2 were associated with lower 25OHD concentrations at all time points in one or both intervention groups [analysis of covariance (ANCOVA) P < 0.043], with the exception of rs7041, which did not affect 25OHD at birth. In the high-dose supplementation group receiving 30 μg/d vitamin D3, but not in those receiving 10 µg/d, genotype of rs2282679, rs4588, and rs7041; diplotype; and Haplo3SNP significantly affected intervention response (repeated measurement ANCOVA Pinteraction < 0.019). Minor allele homozygotes had lower 25OHD concentrations and smaller increases in 25OHD throughout the intervention.

CONCLUSIONS

In infants, vitamin D binding protein genotype affects 25OHD concentration and efficiency of high-dose vitamin D3 supplementation.

Environmental and Genetic Determinants of Serum 25(OH)-Vitamin D Levels during Pregnancy and Early Childhood

Vitamin D insufficiency has become a common health problem worldwide, particularly among pregnant women and young children. Therefore, we sought to identify environmental, dietary, and genetic determinants of serum 25(OH)-vitamin D (25(OH)D) levels during pregnancy and early childhood. 25(OH)D was measured in women at 24-weeks of gestation (n = 738) and one-week postpartum (n = 284) in the population-based Danish COPSAC₂₀₁₀ mother–child cohort; and in cord blood (n = 257) and age 4 years (n = 298) in children from the at-risk COPSAC₂₀₀₀ mother–child cohort. Environmental, dietary, and genetic variables were tested for association with 25(OH)D using linear regression analyses. After adjusting for season of blood sampling, determinants of lower 25(OH)D levels during pregnancy in the women were higher pre-pregnancy BMI, lower age at birth, lower genetic vitamin D score, lower dietary vitamin D intake, and lower social circumstances. In children, the determinants were lower maternal age at birth, higher pre-pregnancy BMI, lower genetic vitamin D score, older siblings, exposure to tobacco smoking, and female sex. Genetics was an important determinant at all time points, alone explaining 2%–11% of the variance in 25(OH)D. Important determinants of circulating 25(OH)D levels during pregnancy and early childhood include environmental factors, diet, and to a large extent genetics.

Proteomic analysis of gingival crevicular fluid for novel biomarkers of pubertal growth peak

Background

Detection of pubertal growth peak is vital in orthodontic treatment timing and planning. Gingival crevicular fluid (GCF) contains abundant proteins from different sources and is an ideal source of biomarkers. The aim of this research is to detect candidate GCF biomarkers of pubertal growth by tandem mass tags (TMT) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to help diagnosis and treatment planning of functional treatment.

Methods

Forty subjects were recruited and were divided into pubertal and post-pubertal groups according to cervical vertebral maturation method. GCF samples were collected by paper points. GCF proteome of pubertal and post-pubertal subjects was compared by TMT labelling coupled with LC-MS/MS.

Results

A total of 537 proteins were detected in GCF samples, with 183 proteins detected in GCF for the first time. These proteins were involved in processes of immune response, ion transport, and signal transduction. The GCF concentration of vitamin D binding protein (DBP) and seroserotransferrin (Tf) was significantly higher in pubertal than that in post-pubertal subjects. DBP and Tf, therefore, were considered to be candidate biomarkers of pubertal growth. This result was validated using GCF samples from new subjects (P < 0.05).

Conclusion

Our results indicate that TMT labelling coupled with LC-MS/MS were proved to be a useful method for proteomic analysis of GCF with high accuracy. The expression of DBP and Tf was increased in children at circumpubertal stage and can be considered candidate biomarkers of pubertal growth.

Influence of Vitamin D in Advanced Non-Small Cell Lung Cancer Patients Treated with Nivolumab

Nivolumab is one of the most commonly used monoclonal antibodies for advanced non-small cell lung cancer treatment, to the extent that the presence of its anti-antibody is considered a negative prognostic factor. Vitamin D (VD) modulates expression of the genes involved in drug metabolism and elimination. Immune system regulation and immunodeficiency is frequent in non-small cell lung cancer patients. To date, no data have been reported about the relationship between nivolumab and VD. The aim of this study was to quantify plasma 25-hydroxyVD (25-VD) and 1,25-VD, nivolumab, and its anti-antibody before starting treatment (baseline) and at 15, 45 and 60 days of therapy. VD-pathway-associated gene single nucleotide polymorphisms (SNPs) were also evaluated. Molecules were quantified through enzyme-linked immunosorbent assay, and SNPs through real-time PCR. Forty-five patients were enrolled. Median nivolumab concentrations were 12.5 μg/mL, 22.3 μg/mL and 27.1 μg/mL at 15, 45 and 60 days respectively. No anti-nivolumab antibodies were found. Correlations were observed between nivolumab concentrations and 25-VD levels. Nivolumab concentrations were affected by VD-pathway-related gene SNPs. VDBP AC/CC genotype and baseline 25-VD < 10 ng/mL predicted a nivolumab concentration cut-off value of <18.7 μg/mL at 15 days, which was associated with tumor progression. This is the first study showing VD marker predictors of nivolumab concentrations in a real-life context of non-small cell lung cancer treatment.

The effect of vitamin D pathway genes and deferasirox pharmacogenetics on liver iron in thalassaemia major patients

Monitoring and treating iron overload is crucial in transfusion-dependent thalassaemia patients. Liver stiffness measurement by transient elastography and T2* magnetic resonance imaging represent non-invasive ways to evaluate the adequacy of the iron chelation treatment. We explored the role of single nucleotide polymorphisms involved in vitamin D metabolism, transport and activity, and in deferasirox metabolism on liver iron burden parameters. One-hundred and five beta-thalassaemia patients, treated with deferasirox, have been enrolled. Drug plasma C_trough and AUC were measured by a HPLC-UV method. Allelic discrimination was performed by real-time PCR. Age, UGT1A1-364 CT/TT and CYP27B1 -1260 GT/TT positively predicted liver stiffness values. Deferasirox dose and serum ferritin negatively predicted T2* data, whereas age and CYP2D6 1457 GG genotype positively influenced these values. The discoveries of this research may be useful for personalized medicine and the proposed method could be applied in patients with hereditary hemochromatosis and myelodysplastic syndromes.

Interactions between vitamin D binding protein variants and major dietary patterns on the odds of metabolic syndrome and its components in apparently healthy adults

BACKGROUND

Recent studies have shown that the risks of chronic diseases resulting from high-risk alleles, such as cardiovascular diseases and metabolic syndrome (MetS), can be affected by various dietary patterns. Among the genes affected by environmental factors are those associated with vitamin D binding protein (DBP).

METHODS

This cross-sectional study was conducted on a random sample of 265 apparently healthy adults aged 18-50. MetS was defined according to the adult treatment panel III criteria. Major dietary patterns were determined using factor analysis on 24 food groups, using a valid and reliable 147-item food frequency questionnaire (FFQ). DBP genotypes were determined by polymerase chain reactions-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

After adjustment for confounder factors, results demonstrated strong interactions between, on the one hand, a high intake of healthy pattern and DBP haplotype (rs7041/rs4588 major alleles) and on the other, low MetS odds (OR = 0.64, 95% CI 0.47-0.87, P ≤ 0.001), serum triglyceride levels (OR = 0.72, 95% CI 0.56-0.93, P = 0.01) and fasting blood glucose (OR = 0.36, 95% CI 0.14-0.96, P = 0.04). Also, individuals with a higher adherence to traditional dietary patterns demonstrated reduced odds of high waist circumference among the major allele (low-risk allele) carriers of rs7041/rs4588 (OR = 0.69, 95% CI 0.55-0.88, P = 0. 003). Interactions were also seen between high traditional pattern intake and DBP haplotype elevated blood pressure odds (OR = 1.31, 95% CI 1.02-1.68, P = 0.02).

CONCLUSIONS

The present evidence indicates that interactions between healthy dietary patterns with DBP haplotypes (Gc 1F, Gc 1S and Gc 2) and traditional dietary patterns with DBP haplotypes may be effective in reducing the odds of MetS and some of its components through consuming healthy food groups and inherited low risk alleles.

Vitamin D Binding Protein, Total and Free Vitamin D Levels in Different Physiological and Pathophysiological Conditions

This review focuses on the biologic importance of the vitamin D binding protein (DBP) with emphasis on its regulation of total and free vitamin D metabolite levels in various clinical conditions. Nearly all DBP is produced in the liver, where its regulation is influenced by estrogen, glucocorticoids and inflammatory cytokines but not by vitamin D itself. DBP is the most polymorphic protein known, and different DBP alleles can have substantial impact on its biologic functions. The three most common alleles-Gc1f, Gc1s, Gc2-differ in their affinity with the vitamin D metabolites and have been variably associated with a number of clinical conditions. Although DBP has a number of biologic functions independent of vitamin D, its major biologic function is that of regulating circulating free and total levels of vitamin D metabolites. 25 hydroxyvitamin D (25(OH)D) is the best studied form of vitamin D as it provides the best measure of vitamin D status. In a normal non-pregnant individual, approximately 0.03% of 25(OH)D is free; 85% is bound to DBP, 15% is bound to albumin. The free hormone hypothesis postulates that only free 25(OH)D can enter cells. This hypothesis is supported by the observation that mice lacking DBP, and therefore with essentially undetectable 25(OH)D levels, do not show signs of vitamin D deficiency unless put on a vitamin D deficient diet. Similar observations have recently been described in a family with a DBP mutation. This hypothesis also applies to other protein bound lipophilic hormones including glucocorticoids, sex steroids, and thyroid hormone. However, tissues expressing the megalin/cubilin complex, such as the kidney, have the capability of taking up 25(OH)D still bound to DBP, but most tissues rely on the free level. Attempts to calculate the free level using affinity constants generated in a normal individual along with measurement of DBP and total 25(OH)D have not accurately reflected directly measured free levels in a number of clinical conditions. In this review, we examine the impact of different clinical conditions as well as different DBP alleles on the relationship between total and free 25(OH)D, using only data in which the free 25(OH)D level was directly measured. The major conclusion is that a number of clinical conditions alter this relationship, raising the question whether measuring just total 25(OH)D might be misleading regarding the assessment of vitamin D status, and such assessment might be improved by measuring free 25(OH)D instead of or in addition to total 25(OH)D.

Vitamin D-binding protein is inversely associated with the incidence of gastrointestinal and ear infections in school-age children

Circulating 25-hydroxy vitamin D (25(OH)D) is related to decreased rates of gastrointestinal and ear infections in school-age children. Vitamin D-binding protein (DBP) transports 25(OH)D and exerts immunological functions; however, it is unknown whether DBP is associated with infectious morbidity in children. We quantified plasma DBP concentrations in 540 school-age children at the time of recruitment into a cohort study in Bogotá, Colombia and obtained daily information on infectious morbidity symptoms and doctor visits during the school year. We compared the incidence rates of gastrointestinal and respiratory symptoms across quartiles of DBP concentration by estimating adjusted incidence rate ratios (IRRs) with 95% confidence interval (CI). We also estimated the per cent of the associations between DBP and morbidity that were mediated through 25(OH)D using a counterfactual frame. Mean ± s.d. DBP concentration was 2650 ± 1145 nmol/l. DBP was inversely associated with the rates of diarrhoea with vomiting (IRR for quartiles 2-4 vs. 1 = 0.48; 95% CI 0.25-0.92; P = 0.03) and earache/ear discharge with fever (IRR for quartiles 2-4 vs. 1 = 0.29; 95% CI 0.12-0.71; P = 0.006). The DBP-morbidity associations were not mediated through 25(OH)D. We conclude that plasma DBP predicts lower incidence of gastrointestinal and ear infections in school-age children independent of 25(OH)D.

In the search for reliable biomarkers for the early diagnosis of autism spectrum disorder: the role of vitamin D

Autism spectrum disorder (ASD) affects about 1% of the world's population. Vitamin D is thought to be essential for normal brain development and modulation of the immune system. Worldwide about 1 billion people are affected by vitamin D deficiency. High-sensitivity C-reactive protein (hs-CRP), cytochrome P450 2E1 (CYP2E1) and 8-hydroxy-2'-deoxyguanosine (8-OH-dG) are biomarkers related to inflammation and oxidative stress. In the present study, these biomarkers were together with serum 25-hydroxyvitamin D (25(OH)D₃) analyzed in 28 (mean age seven years) Saudi male patients with ASD. The study was conducted to determine if there is any relationship between vitamin D levels, the tested biomarkers and the presence and severity of ASD. The hope was to identify if these biomarkers may be useful for early ASD diagnosis. The Childhood Autism Rating Scale (CARS) and the Social Responsiveness Scale (SRS) were used to measure autism severity. The results of the ASD children were compared with 27 age and gender-matched neurotypical controls. The data indicated that Saudi patients with ASD have significantly lower plasma levels of 25(OH)D₃ than neurotypical controls (38 ng/ml compared to 56 ng/ml, respectively; [P = 0.001]). Surprisingly, the levels of CYP2E1 were lower in the children with ASD than the neurotypical controls (0.48 ± 0.08 vs. 69 ± 0.07 ng/ml, respectively; P = 0.001). The ASD children also had significantly higher levels of hs-CRP (0.79 ± 0.09 vs. 0.59 ± 0.09 ng/ml, respectively; P = 0.001) and 8-OH-dG (8.17 ± 1.04 vs. 4.13 ± 1.01 ng/ml, respectively; P = 0.001, compared to neurotypical age and gender-matched controls. The values for hs-CRP and 8-OH-dG did not correlate [P < 0.001] with autism severity. There was found a relationship between autism severity on the CARS scale and the levels of 25(OH)D₃ and CYP1B1. But this was not found for SRS. All four biomarkers seemed to have good sensitivity and specificity, but the sample size of the present study was too small to determine clinical usefulness. The findings also indicate that inadequate levels of vitamin D play a role in the etiology and severity of autism. Furthermore, the results of the present study suggest the possibility of using 25(OH)D₃, CYP1B1, hs-CRP and 8-OH-dG, preferably in combination, as biomarkers for the early diagnosis of ASD. However, further research is needed to evaluate this hypothesis.

Risk factors for vitamin D deficiency in sickle cell disease

Vitamin D deficiency (VDD), 25-OHD levels <20 ng/ml, is prevalent among patients with sickle cell disease (SCD) and is linked to acute and chronic pain and bone fracture in this population. There is limited literature regarding VDD-associated risk factors for SCD. We examined potential clinical and genomic parameters associated with VDD in 335 adults with SCD in a cross-sectional study. VDD was present in 65% of adult SCD patients, and 25-OHD levels independently and positively correlated with older age (P < 0·001) and vitamin D supplementation (P < 0·001). 25-OHD levels were higher in SCD patients over 40 years of age compared to the general African-American population. Both lower 25-OHD levels and increased pain frequency were associated with increased expression of SLC6A5 encoding glycine transporter-2 (GlyT2), a protein involved in neuronal pain pathways. Lower 25-OHD levels were also associated with increased expression of CYP3A4, and with decreased expression of GC (also termed DBP) and VDR, three genes involved in vitamin D metabolism. We conclude that vitamin D supplementation should be an almost universal feature of the care of young adults with SCD, and that further research is warranted into genomic factors that regulate vitamin D metabolism in SCD.

Genetic and Racial Differences in the Vitamin D Endocrine System

Twin studies indicate that genetic factors may explain about 50% of the variation of serum 25-hydroxyvitamin D (25OHD). Polymorphisms of 3 genes, delta-7-sterol-reductase, CYP2R1, and DBP/GC (and maybe CYP24A1) combined, can explain about 5% to 10% of the variation in serum 25OHD. These polymorphisms are found in nearly all populations. The variation in serum 25OHD found in different areas and populations in the world is mainly due to environmental and lifestyle factors, not truly dependent on racial differences. One genetic variant of DBP, (GC2), is associated with a modest (∼10%) decrease in serum DBP and 25OHD concentrations for unexplained reasons.

A lack of association between vitamin D-binding protein and 25-hydroxyvitamin D concentrations in pediatric type 1 diabetes without microalbuminuria

PURPOSE

Vitamin D deficiency is reported to be more common in type 1 diabetes patients and might be associated with the increased urinary loss of vitamin D binding protein (VDBP) consequent to impaired 25-hydroxyvitamin D (25(OH)D) circulation. We aimed to evaluate the possible increased urinary loss of VDBP, a correlation between VDBP and circulating 25(OH)D level, and risk factors influencing low vitamin D level in pediatric type 1 diabetes patients without microalbuminuria.

METHODS

This is a cross-sectional study of subjects who visited Seoul National University Children's Hospital between January and March 2013. Forty-two type 1 diabetes patients and 29 healthy controls were included. Biochemical parameters including serum and urine VDBP concentrations were analyzed.

RESULTS

There was no significant difference in the frequency of vitamin D deficiency or serum 25(OH)D level between the 2 groups. The serum and urine VDBP concentrations did not show any difference between the 2 groups. Serum 25(OH) D level did not correlate with serum or urine VDBP. Multivariate regression analysis revealed that daylight outdoor hours (β=2.948, P=0.003) and vitamin D intake (β=2.865, P=0.003) affected the 25(OH)D level; the presence of type 1 diabetes or urinary VDBP excretion was not significant.

CONCLUSIONS

In pediatric type 1 diabetes patients, urinary VDBP excretion did not contribute to low serum 25(OH)D level in the setting of normoalbuminuria. The factors associated with 25(OH)D level during winter periods were daylight outdoor hours and vitamin D intake. Further studies including both micro- and macroalbuminuria patients with type 1 diabetes are warranted.

Role of CYP24A1, VDR and GC gene polymorphisms on deferasirox pharmacokinetics and clinical outcomes

β-Thalassemia patients develop deficiency in vitamin D absorption and liver hydroxylation, resulting in extremely low calcitriol levels. We explored the role of single-nucleotide polymorphisms (SNPs) involved in vitamin D metabolism, transport and activity on deferasirox pharmacokinetics and outcomes (effectiveness trough levels (C_trough) and the area under the curve (AUC) cutoffs of 20 μg ml^-1 and 360 μg ml^-1 h^-1, respectively; nonresponse AUC limit of 250 μg ml^-1 h^-1). Ninety-nine β-thalassemic patients were enrolled. Drug plasma C_trough and AUC were measured by the high-performance liquid chromatography system coupled with an ultraviolet determination method. Allelic discrimination for VDR, CYP24A1, CYP27B1 and GC gene SNPs was performed by real-time PCR. CYP24A1 22776 TT significantly influenced C_min and negatively predicted it in regression analysis. CYP24A1 3999 CC was associated with C_trough and C_min and was a negative predictor of T_max, whereas CYP24A1 8620 GG seemed to have a role in C_trough, AUC, t_1/2 and C_min, and was an AUC negative predictor factor. Considering treatment outcome, Cdx2 and GC 1296 were retained in regression analysis as AUC efficacy cutoff negative predictors.

Nutritional Rickets and Osteomalacia in the Twenty-first Century: Revised Concepts, Public Health, and Prevention Strategies

PURPOSE OF REVIEW

Nutritional rickets and osteomalacia are common in dark-skinned and migrant populations. Their global incidence is rising due to changing population demographics, failing prevention policies and missing implementation strategies. The calcium deprivation spectrum has hypocalcaemic (seizures, tetany and dilated cardiomyopathy) and late hypophosphataemic (rickets, osteomalacia and muscle weakness) complications. This article reviews sustainable prevention strategies and identifies areas for future research.

RECENT FINDINGS

The global rickets consensus recognises the equal contribution of vitamin D and dietary calcium in the causation of calcium deprivation and provides a three stage categorisation for sufficiency, insufficiency and deficiency. For rickets prevention, 400 IU daily is recommended for all infants from birth and 600 IU in pregnancy, alongside monitoring in antenatal and child health surveillance programmes. High-risk populations require lifelong supplementation and food fortification with vitamin D or calcium. Future research should identify the true prevalence of rickets and osteomalacia, their role in bone fragility and infant mortality, and best screening and public health prevention tools.

Acute Homeostatic Changes Following Vitamin D2 Supplementation

Context:

Changes in vitamin D binding protein (DBP) concentrations and catabolism of 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D (24,25D) after vitamin D2 supplementation may alter concentrations and bioavailability of circulating 25-hydroxyvitamin D (25D).

Objective:

Examine acute changes in vitamin D metabolism and bioavailability after vitamin D2 supplementation.

Methods:

Study design was secondary analysis of a single-arm interventional study. Thirty consenting volunteers were treated with five 50,000 IU oral doses of ergocalciferol over 2 weeks. Main outcome measures included concentrations of DBP, vitamin D metabolites, and bioavailable 25-hydroxyvitamin D (25D) in pre- and posttreatment serum samples.

Results:

After supplementation, 25D₂ (mean ± standard deviation) increased from 1.4 ± 0.9 ng/mL to 45.3 ± 16.5 ng/mL (P < 0.0001), and 25D₃ levels decreased from 26.8 ± 9.9 ng/mL to 19.7 ± 8.2 ng/mL (P < 0.0001). Total 25D (25D₂ plus 25D₃) increased from 28.2 ± 10.0 ng/mL to 65.0 ± 21.1 ng/mL (152.2% ± 102.5%; P < 0.0001). DBP and total 24,25D concentrations increased 39.1% ± 39.4% (165.6 ± 53.8 µg/mL to 222.0 ± 61.1 µg/mL; P < 0.0001) and 31.3% ± 48.9% (3.9 ± 2.0 ng/mL to 4.7 ± 2.1 ng/mL; P = 0.0147), respectively. In contrast to total 25D, bioavailable 25D increased by 104.4% ± 99.6% (from 5.0 ± 2.0 ng/mL to 8.7 ± 2.7 ng/mL; P < 0.001), and 1,25D increased by 32.3% ± 38.8% (from 45.5 ± 10.7 pg/mL to 58.1 ± 13.0 pg/mL; P = 0.0006). There were no changes in calcium or parathyroid hormone (P > 0.05 for both).

Conclusion:

Changes after vitamin D2 supplementation involve acute rise in serum DBP and 24,25D, both of which may attenuate the rise in bioavailable 25D and 1,25D.

Associations between serum 25(OH)D concentrations and prevalent asthma among children living in communities with differing levels of urbanization: a cross-sectional study

Background

Prior evidence suggests that vitamin D deficiency may increase the risk of asthma and atopy and impair pulmonary function in children.

Methods

In this cross-sectional analysis nested in a case-control study, we analyzed serum 25(OH)D concentrations in 413 children with asthma and 471 children without asthma living in two geographically adjacent study communities (Pampas and Villa El Salvador). We measured total and antigen-specific IgE levels, pulmonary function, asthma control, and exhaled nitric oxide.

Results

Mean 25(OH)D concentrations were 25.2 ng/mL (SD 10.1) in children with asthma and 26.1 ng/mL (SD 13.7) in children without asthma (p = 0.28). Vitamin D deficiency (25(OH)D < 20 ng/ml) was more common in Pampas than in Villa El Salvador (52.7% vs. 10.5%; p < 0.001). In the overall study population, a 10 ng/ml decrease in serum 25(OH)D concentrations was not significantly associated with odds of asthma (OR 1.09, 95% CI: 0.94 to 1.25). However, vitamin D deficiency was associated with a 1.6-fold increase in odds of asthma in the overall cohort (95% CI: 1.14 to 2.25). After stratifying by site, a 10 ng/mL decrease in serum 25(OH)D concentrations was associated with 18% higher odds of having asthma in Pampas (OR = 1.18, 95% CI 1.02 to 1.38), whereas there was no significant association between 25(OH)D concentrations and asthma in Villa El Salvador (OR = 0.95, 95% CI 0.87 to 1.05). Combined data from these geographically adjacent populations suggests a possible threshold for the relationship between 25(OH)D levels and asthma at approximately 27.5 ng/ml. Serum 25(OH)D concentrations were not clearly associated with asthma control, total serum IgE, atopy, or airway inflammation.

Conclusion

Serum 25(OH)D concentrations were inversely associated with asthma in one study community with a high prevalence of deficiency. Studies are needed to investigate a possible threshold 25(OH)D concentration after which higher vitamin D levels show no further benefit for asthma.

Electronic supplementary material

The online version of this article (doi:10.1186/s40733-017-0033-2) contains supplementary material, which is available to authorized users.

Efficacy and safety of early supplementation with 800 IU of vitamin D in very preterm infants followed by underlying levels of vitamin D at birth

Background

To determine the efficacy and safety of early supplementation with 800 IU of vitamin D in very low birth weight (VLBW) infants.

Methods

Sixty-six infants with a birth weight less than 1500 g admitted to the Neonatal Intensive Care Unit. Of these, 52 infants were eligible and received 800 IU/day vitamin D from 2 weeks of age. We examined 25-hydroxyvitamin-D (25[OH]D) levels from cord blood at birth and serum at 32 and 36 weeks of postmenstrual age.

Results

The study infants were divided by cord-blood levels of 25(OH)D at birth into 25(OH)D concentrations < 10 ng/mL (n = 20) or ≥ 10 ng/mL (n = 29). Vitamin D intake of 800 IU/day safely achieved an 88% probability of vitamin D sufficiency at 36 weeks postmenstrual age in VLBW infants with cord-blood levels of 25(OH)D ≥ 10 ng/mL, and 65% probability of vitamin D sufficiency was observed in infants with 25 OHD concentrations < 10 ng/mL at birth.

Conclusion

Considering the efficacy and safety of vitamin D supplementation in this study, vitamin D intake of 800 IU/day may enhance vitamin D status during early hospitalization in VLBW infants with 25 OHD concentrations < 10 ng/mL at birth. The clinical significance of optimal vitamin D intake in VLBW infants needs to be studied in larger controlled studies.

Genetic variant in vitamin D-binding protein is associated with metabolic syndrome and lower 25-hydroxyvitamin D levels in polycystic ovary syndrome: A cross-sectional study

Vitamin D deficiency has been related to metabolic syndrome (MetS) in polycystic ovary syndrome (PCOS). The vitamin D-binding protein (DBP) is the main protein involved in vitamin D transport. Two single-nucleotide polymorphisms (SNPs) of the DBP gene, rs4588 and rs7041, have been associated with low circulating levels of 25-hydroxyvitamin D [25(OH)D] in various populations, but not in women with PCOS. Therefore, we determined the genotype and haplotype distribution of DBP gene polymorphisms and investigated the associations between these genetic variants and their haplotypes with PCOS, MetS, and 25(OH)D levels in women with PCOS and controls from the South of Brazil. The sample included 291 women (191 with PCOS and 100 controls). All participants were genotyped for polymorphisms rs2282679, rs4588, and rs7041. Serum 25(OH)D levels were determined in a subset of 102 participants. Women with PCOS were younger and had significantly higher body mass index, blood pressure, and insulin resistance than the control group (p<0.05). The prevalence of MetS in PCOS and controls was 26.5% and 4.8% respectively. Levels of 25(OH)D were lower in PCOS women with MetS, even after adjustment for age (p = 0.033). No associations were observed between PCOS and the polymorphisms or their haplotypes. A higher frequency of genotype TT of rs7041 was found in PCOS participants with MetS (OR: 2.21, 95%CI:1.08–4.52; p = 0.027). This same genotype was associated with lower 25(OH)D levels in both PCOS and control women (OR: 4.40, 95%CI:1.62–12.00; p = 0.002). In conclusion, these findings indicate that DBP gene polymorphisms and their haplotypes are not directly associated with PCOS. In contrast, the TT genotype of SNP rs7041 was associated with MetS in PCOS women, and with lower 25(OH)D levels in both PCOS and control groups.