Influence of the vitamin D-binding protein on the serum concentration of 1,25-dihydroxyvitamin D3. Significance of the free 1,25-dihydroxyvitamin D3 concentration

Unmeasurable low vitamin D levels caused by a novel, homozygote loss-of-function variant in the group-specific component gene

A 29-year-old female, born to consanguineous parents, was found with unmeasurable levels of vitamin D (<10 nmol/L) after routine biochemical screening during her first pregnancy. She did not respond to either oral or intramuscular vitamin D supplementation and was an otherwise healthy young woman, with no signs of rickets, osteomalacia, osteoporosis, or secondary hyperparathyroidism. Western blot analysis revealed total lack of vitamin D binding protein, and next generation sequencing confirmed a novel, pathogenic homozygote loss-of-function mutation in exon 13 of the group-specific component gene, that encodes the poly A tail for vitamin D binding protein. She was therefore diagnosed with hereditary DBP deficiency, and vitamin D supplementation was diminished to life-long regular vitamin D supplementation (25 μg per day). This case is extremely interesting, as it expands our knowledge of vitamin D physiology and supports the free hormone hypothesis, given that the patient was asymptomatic despite no measurable levels of vitamin D.

The impact of genetic variants related to vitamin D and autoimmunity: A systematic review

Over the past few years, there has been a notable increment in scientific literature aimed at unraveling the genetic foundations of vitamin D signaling and its implications for susceptibility to autoimmunity, however, most of them address isolated diseases. Here, we conducted a systematic review of genetic variants related to vitamin D and autoimmune diseases and we discussed the current landscape of susceptibility and outcomes. Of 65 studies analyzed, most variants cited are in vitamin D binding protein (VDBP; rs2282679 GC gene), 25-hydroxylase (rs10751657 CYP2R1), 1α-hydroxylase (rs10877012, CYP27B1) and the nuclear hormone receptor superfamily [FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) in VDR gene]. Therefore, our findings confirmed the associations of several genetic variants of vitamin D signaling with a broad spectrum of autoimmune diseases/traits. In addition, given the low number of papers found with functional analysis, further studies to elucidate the real effect that the variants exert on Vitamin D signaling are recommended.

The Association of Vitamin D during Pregnancy and mRNA Expression Levels of Inflammatory Factors with Preterm Birth and Prelabor Rupture of Membranes

The aim of this study was to elucidate the association between vitamin D (VD) and the risk for preterm birth (PTB) and prelabor rupture of membranes (PROM). This study included two parts, with a cohort study and a case-control study. Plasma 25-hydroxyvitamin vitamin D [25(OH)D] levels in three trimesters in the cohort study and maternal 25(OH)D before delivery in the case-control study were measured. Quantitative real-time PCR was used to detect relative mRNA expression levels of the inflammatory factors associated with pyroptosis in peripheral blood mononuclear cell (PBMC), placenta and fetal membranes. Multinomial logistic regression and the Wilcoxon test were applied to analyze the associations. In the cohort study, 6381 pregnant women were included. We found that VD deficiency in T3 (PTB without PROM: OR = 1.90, 95% CI: 1.02-3.55, Term PROM (TPROM): OR = 0.76, 95% CI: 0.59-0.98) and less change of 25(OH)D between T1 and T3 (PTB without PROM: OR = 2.32, 95% CI: 1.07-5.06, TPROM: OR = 0.73, 95% CI: 0.56-0.96) were associated with the increased risk of PTB without PROM, while there was a decreased risk of TPROM. Neither VD, nor the increase of VD during pregnancy was associated with the premature rupture of membranes preterm delivery (PPROM). In the case-control study, there were no associations between VD during delivery and PTB or PROM (TPROM: OR = 1.33, 95% CI: 0.52-3.44); PTB without PROM: OR = 1.66, 95% CI: 0.33-8.19; PPROM: OR = 1.19, 95% CI: 0.42-3.40). The mRNA expression of NLRP1 (NOD-like receptor thermal protein domain associated protein 1) (p = 0.0165) in PBMC in the TPROM group was higher than that in the term group, and IL-18 (p = 0.0064) was lower than that in the term group. Plasma 25(OH)D in T3 and the increase of 25(OH)D between T1 and T3 were associated with a lower risk for PTB without PROM but a higher risk for TPROM. Further studies are warranted to clarify the association between VD and PTB and PROM and its mechanism.

Associations between serum vitamin D biomarkers and tumor expression of Ki67, p53, and COX-2 in colorectal cancer cases from the Southern Community Cohort Study

Higher 25-hydroxyvitamin D is associated with lower colorectal cancer (CRC) risk, with limited data from African Americans (AAs), who have greater risk for CRC and 25-hydroxyvitamin D deficiency. In a predominantly AA sample of CRC cases from the Southern Community Cohort Study (SCCS), we report associations between vitamin D biomarkers and tumor expression of proteins implicated in vitamin D's anti-tumorigenic pathways (e.g. proliferation and inflammation) and CRC prognosis. SCCS participants with incident CRC were identified via state cancer registries. Serum 25-hydroxyvitamin D and vitamin D binding protein (VDBP) were measured at enrollment. 'Free' 25-hydroxyvitamin D was calculated via standard equation. Cellular Ki67, p53, and COX-2 were measured from tumor samples and categorized using literature-defined cut-points related to survival. Generalized linear models were used to measure associations between vitamin D exposures, tumor biomarkers, and stage. In total, 104 cases (40-79 years) were analyzed. 25-hydroxyvitamin D was not associated with high Ki67 (odds ratio (OR) per 1-standard deviation (SD) increase [95% confidence interval] 1.35[0.86-2.11]), p53 (0.75[0.47-1.20]), or COX-2 expression (1.25[0.78-2.01]), or metastatic disease (1.04[0.59-1.81]). Mean biomarker expression was unrelated to 25-hydroxyvitamin D (p-trend ≥.09). Null associations were observed for VDBP and free 25-hydroxyvitamin D. In AAs (n = 70), higher VDBP was associated with lower odds of high Ki67 expression (0.53[0.28-0.98], p-trend =.04). In conclusion, we observed no associations between 25-hydroxyvitamin D and prognostic marker expression in CRC. An inverse association between VDBP and tumor Ki67 in AAs is consistent with reports showing relationships with reduced CRC mortality.

Sex-Specific Variations in Vitamin D and Vitamin D Binding Protein (Vdbp) and Flipped Pattern of their Association in Preeclamptic Women with Dyslipidemia

BACKGROUND

Women with preeclampsia frequently have disorders of calcium metabolism during their pregnancies, including hypocalciuria and low vitamin D levels. The link between fetal sex and vitamin D and vitamin D binding protein levels in pregnancy and preeclampsia is not clear.

AIM

Present study was designed to explore sex-specific variations in vitamin D and vitamin D binding protein levels in maternal and umbilical cord blood samples for age and gestation matched 20 primigravida normotensive and 20 primigravida with preeclampsia with a singleton pregnancy.

METHODS

Routine investigations, vitamin D binding protein (VDBP), and serum vitamin D in both maternal serum and cord blood were measured in both groups. Association between maternal and cord blood vitamin D levels was highly positive in both cases and control with babies of either sex.

RESULTS

This association exhibited sexual dimorphism between cord blood vitamin D and vitamin D binding protein (VDBP) suggesting that the occurrence of pregnancy complications differs according to fetal sex with a higher cardiovascular and metabolic load for the mother in the presence of a male fetus.

CONCLUSION

Vitamin D binding protein (VDBP) measurement along with vitamin D level should be advised in clinical practice for early detection and screening.

Megalin and Vitamin D Metabolism—Implications in Non-Renal Tissues and Kidney Disease

Megalin is an endocytic receptor abundantly expressed in proximal tubular epithelial cells and other calciotropic extrarenal cells expressing vitamin D metabolizing enzymes, such as bone and parathyroid cells. The receptor functions in the uptake of the vitamin D-binding protein (DBP) complexed to 25 hydroxyvitamin D3 (25(OH)D3), facilitating the intracellular conversion of precursor 25(OH)D3 to the active 1,25 dihydroxyvitamin D3 (1,25(OH)2D3). The significance of renal megalin-mediated reabsorption of 25(OH)D3 and 1,25(OH)2D3 has been well established experimentally, and other studies have demonstrated relevant roles of extrarenal megalin in regulating vitamin D homeostasis in mammary cells, fat, muscle, bone, and mesenchymal stem cells. Parathyroid gland megalin may regulate calcium signaling, suggesting intriguing possibilities for megalin-mediated cross-talk between calcium and vitamin D regulation in the parathyroid; however, parathyroid megalin functionality has not been assessed in the context of vitamin D. Within various models of chronic kidney disease (CKD), megalin expression appears to be downregulated; however, contradictory results have been observed between human and rodent models. This review aims to provide an overview of the current knowledge of megalin function in the context of vitamin D metabolism, with an emphasis on extrarenal megalin, an area that clearly requires further investigation.

Vitamin D Signaling in Psoriasis: Pathogenesis and Therapy

Psoriasis is a systemic, chronic, immune-mediated disease that affects approximately 2–3% of the world’s population. The etiology and pathophysiology of psoriasis are still unknown, but the activation of the adaptive immune system with the main role of T-cells is key in psoriasis pathogenesis. The modulation of the local neuroendocrine system with the downregulation of pro-inflammatory and the upregulation of anti-inflammatory messengers represent a promising adjuvant treatment in psoriasis therapies. Vitamin D receptors and vitamin D-mediated signaling pathways function in the skin and are essential in maintaining the skin homeostasis. The active forms of vitamin D act as powerful immunomodulators of clinical response in psoriatic patients and represent the effective and safe adjuvant treatments for psoriasis, even when high doses of vitamin D are administered. The phototherapy of psoriasis, especially UVB-based, changes the serum level of 25(OH)D, but the correlation of 25(OH)D changes and psoriasis improvement need more clinical trials, since contradictory data have been published. Vitamin D derivatives can improve the efficacy of psoriasis phototherapy without inducing adverse side effects. The anti-psoriatic treatment could include non-calcemic CYP11A1-derived vitamin D hydroxyderivatives that would act on the VDR or as inverse agonists on RORs or activate alternative nuclear receptors including AhR and LXRs. In conclusion, vitamin D signaling can play an important role in the natural history of psoriasis. Selective targeting of proper nuclear receptors could represent potential treatment options in psoriasis.

Maternal and Fetal Genetic Variation in Vitamin D Metabolism and Umbilical Cord Blood 25-Hydroxyvitamin D

CONTEXT

Single nucleotide polymorphisms (SNPs) in vitamin D metabolism pathway genes are associated with circulating 25-hydroxyvitamin D (25(OH)D) in adults. Less is known about the relationships between mother and offspring SNPs and umbilical cord blood 25(OH)D.

OBJECTIVE

(1) To undertake a meta-analysis of the relationships of maternal and offspring SNPs in the vitamin D metabolism pathway and cord blood 25(OH)D in pregnant women including novel data; and (2) to examine these relationships in women who received antenatal cholecalciferol supplementation in a clinical trial.

METHODS

Novel data analysis from an observational mother-offspring cohort study (Southampton Women's Survey) and the MAVIDOS double-blind, randomized, placebo-controlled trial of 1000 IU/day cholecalciferol supplementation in pregnancy, and an electronic literature search of published studies in PubMed up to 31 July 2021. Studies reporting associations between rs12785878 (DHCR7), rs10741657 (CYP2R1), rs6013897 (CYP24A1), or rs2282679 (GC) and cord blood 25(OH)D. One published study was included in addition to the novel data analysis. Associations between both maternal and offspring SNPs at rs2282679 (GC) and rs12785878 (DHCR7), and cord blood 25(OH)D were identified. When maternal genotype was adjusted for offspring genotype, and vice versa, there was persisting evidence for associations with maternal rs12785878 (β [95% CI] 1.6 nmol/L [0.3, 2.8] per common allele), and offspring rs2282679 (β 3.1 nmol/L ]2.0, 4.4] per common allele). Maternal and offspring SNPs at rs1074657 and rs613897 were not associated with cord blood 25(OH)D.

RESULT

Associations between both maternal and offspring SNPs at rs2282679 (GC) and rs12785878 (DHCR7), and cord blood 25(OH)D were identified. When maternal genotype was adjusted for offspring genotype, and vice versa, there was persisting evidence for associations with maternal rs12785878 (β [95% CI] 1.6 nmol/L [0.3, 2.8] per common allele), and offspring rs2282679 (β 3.1 nmol/L ]2.0, 4.4] per common allele). Maternal and offspring SNPs at rs1074657 and rs613897 were not associated with cord blood 25(OH)D.

CONCLUSION

Common genetic variation in the vitamin D metabolism pathway is associated with umbilical cord blood 25(OH)D.

Alterations in circulating levels of vitamin D binding protein, total and bioavailability of vitamin D in diabetic retinopathy patients

AIMS

This study aimed to investigate the association between circulating levels of vitamin D binding protein (VDBP) and its genotypes and diabetic retinopathy risk.

METHODS

This case-control study recruited 154 patients with type 2 diabetes mellitus; 62 with diabetic retinopathy (DR) and 92 without DR and diabetic nephropathy (DN). Circulating levels of 25-hydroxyvitamin D3 and VDBP levels were measured in the patients. The genotype and phenotype of VDBP were evaluated based on two common VDBP variations; rs7041 and rs4588.

RESULTS

Serum levels of VDBP were significantly lower in patients with DR than in patients without DR and/or DN (Ln-VDBP (μg/ml): 6.14 ± 0.92 vs. 6.73 ± 1.45, p = 0.001) even after adjustment for age, sex, body mass index, disease duration, estimated glomerular filtration rate (eGFR), HbA1C, insulin therapy profile, and serum levels of 25(OH)D. The distribution of VDBP phenotypes and genotypes in the two studied groups were nearly the same, and the distribution was similar to that of the general population.

CONCLUSIONS

In this study, we found the association between lower circulating levels of VDBP and risk of DR. However, the precise mechanism linking these two remains unknown. Further and more in-depth research is needed to find out the underlying causes of the relationship.

Free Vitamin D3 Index and Vitamin D-binding protein in multiple sclerosis - a presymptomatic case-control study

Background and purpose

High levels of 25‐hydroxyvitamin D₃ (25[OH]D₃) are associated with a lower risk for multiple sclerosis (MS). The bioavailability of 25(OH)D₃ is regulated by its main plasma carrier, vitamin D‐binding protein (DBP). Free 25(OH)D₃ can be estimated by also measuring DBP concentration. In addition, DBP has immunomodulatory functions that may independently affect MS pathogenesis. No previous studies have assessed free 25(OH)D₃ or DBP in presymptomatically collected samples. This study was undertaken to assess free 25(OH)D₃ and DBP as risk factors for MS.

Methods

A nested case–control study was performed with presymptomatic serum samples identified through cross‐linkage of MS registries and Swedish biobanks. Concentration of 25(OH)D₃ was measured with liquid chromatography and DBP levels with sandwich immunoassay. Free 25(OH)D₃ was approximated as free vitamin D₃ index: (25[OH]D₃/DBP) × 10³. MS risk was analyzed by conditional logistic regression, calculating odds ratios (ORs) with 95% confidence intervals (CIs).

Results

Serum samples from 660 pairs of matched cases and controls were included.

At <20 years of age, high levels of free vitamin D₃ index were associated with a lower risk of MS (highest vs. lowest quintile: OR = 0.37, 95% CI = 0.15–0.91, p for trend across quintiles = 0.04). At age 30–39 years, high levels of DBP were associated with a lower MS risk (highest vs. lowest quintile: OR = 0.36, 95% CI = 0.15–0.85, p for trend = 0.02).

Conclusions

These findings support the hypothesis that high levels of free 25(OH)D₃ at a young age reduce the risk of MS later in life. They also implicate a role for DBP in MS etiology.

The association of free vitamin D₃ index, vitamin D‐binding protein, and the risk of developing multiple sclerosis was assessed in a case–control study of presymptomatically collected samples. High free vitamin D₃ index before the age of 20 years was associated with a lower risk of developing multiple sclerosis later in life. High levels of vitamin D binding protein after the age of 30 years were associated with a lower risk of developing multiple sclerosis.

Placental uptake and metabolism of 25(OH)vitamin D determine its activity within the fetoplacental unit

Pregnancy 25-hydroxyvitamin D [25(OH)D] concentrations are associated with maternal and fetal health outcomes. Using physiological human placental perfusion and villous explants, we investigate the role of the placenta in regulating the relationships between maternal 25(OH)D and fetal physiology. We demonstrate active placental uptake of 25(OH)D3 by endocytosis, placental metabolism of 25(OH)D3 into 24,25-dihydroxyvitamin D3 and active 1,25-dihydroxyvitamin D [1,25(OH)2D3], with subsequent release of these metabolites into both the maternal and fetal circulations. Active placental transport of 25(OH)D3 and synthesis of 1,25(OH)2D3 demonstrate that fetal supply is dependent on placental function rather than simply the availability of maternal 25(OH)D3. We demonstrate that 25(OH)D3 exposure induces rapid effects on the placental transcriptome and proteome. These map to multiple pathways central to placental function and thereby fetal development, independent of vitamin D transfer. Our data suggest that the underlying epigenetic landscape helps dictate the transcriptional response to vitamin D treatment. This is the first quantitative study demonstrating vitamin D transfer and metabolism by the human placenta, with widespread effects on the placenta itself. These data demonstrate a complex interplay between vitamin D and the placenta and will inform future interventions using vitamin D to support fetal development and maternal adaptations to pregnancy.

Aging Men With Insufficient Vitamin D Have a Higher Mortality Risk: No Added Value of its Free Fractions or Active Form

CONTEXT

Low total 25-hydroxyvitamin D (25(OH)D) has been associated with mortality. Whether vitamin D in its free form or 1,25-dihydroxyvitamin D (1,25(OH)2D), provide any additional information is unclear.

OBJECTIVE

To determine what level of 25(OH)D is predictive for mortality and if free 25(OH)D or 1,25(OH) 2 D concentrations have any added value.

METHODS

This prospective cohort comprised 1915 community-dwelling men, aged 40 to 79 years. Intervention included determination of association of total and free 25(OH)D and 1,25(OH) 2 D concentrations with survival status. Vitamin D results were grouped into quintiles. For total 25(OH)D, specific cutoff values were also applied. Cox proportional hazard models were used adjusted for center, body mass index, smoking, alcohol, physical activity, season of blood sample, kidney function, and number of comorbidities.

RESULTS

A total of 469 (23.5%) men died during a mean follow-up of 12.3 ± 3.4 years. Compared to those with normal vitamin D values (> 30 µg/L), men with a total 25(OH)D of less than 20 µg/L had an increased mortality (hazard ratio [HR] 2.03 [95% CI, 1.39-2.96]; P < .001). Likewise, men in the lowest 3 free 25(OH)D quintiles (< 4.43 ng/L) had a higher mortality risk compared to the highest quintile (HR 2.09 [95% CI, 1.34-3.25]; P < .01). Mortality risks were similar across all 1,25(OH)2D and vitamin D binding protein quintiles.

CONCLUSION

Aging men with vitamin D deficiency have a 2-fold increased mortality risk. Determinations of either the free fractions of vitamin D or measurement of its active form offer no additional information on mortality risks.

Vitamin D kinetics in nonpregnant and pregnant women after a single oral dose of trideuterated vitamin D3

The plasma pool of the hormone 1,25-dihydroxyvitamin D (1,25(OH)₂D) is increased throughout most of human pregnancy. Mechanisms behind this adaptation are unclear, in part due to limited data on vitamin D kinetics during pregnancy. Stable isotopes make it possible to study vitamin D kinetics in vulnerable study populations like pregnant women. We conducted a pilot study of vitamin D kinetics in nonpregnant and pregnant women. We evaluated a clinical protocol and developed analytical methods to assess the serum appearance and disappearance of trideuterated vitamin D₃ (d3-vitamin D₃) and trideuterated 25-hydroxyvitamin D₃ (d3-25(OH)D₃) after a single oral dose of 25 μg of [6,19,19-²H]-vitamin D₃ (d3-vitamin D₃). Blood was collected at baseline and 2, 4, 6, 24, 168, 264, and 456 hours post-dosing. We then described the serum kinetic profiles of d3-vitamin D₃ and d3-25(OH)D₃ in nonpregnant and pregnant women. Serum kinetic profiles of d3-vitamin D₃ and d3-25(OH)D₃ followed a time course in line with previous pharmacokinetic studies. There was marked variability between participants in the area under the concentration-time curve (AUC) of d3-25(OH)D₃ over the 20-day study period. This AUC of d3-25(OH)D₃ was positively correlated with the serum vitamin D binding protein (DBP) concentration, which was higher in pregnant compared with nonpregnant women. The mean serum half-life of 25(OH)D₃ was longer but not significantly different in pregnant women (18.8 days) compared with nonpregnant women (13.6 days). Our pilot study demonstrated that a single oral dose of 25 μg of d3-vitamin D₃ can be used to study vitamin D kinetics. Serum DBP concentration is an important predictor of vitamin D kinetics, and more research is needed to fully understand the significance of elevated DBP concentration during pregnancy.

Analysis of plasma proteins using 2D gels and novel fluorescent probes: in search of blood based biomarkers for Alzheimer's disease

BACKGROUND

The Australian Imaging and Biomarker Lifestyle (AIBL) study of aging is designed to aid the discovery of biomarkers. The current study aimed to discover differentially expressed plasma proteins that could yield a blood-based screening tool for Alzheimer's disease.

METHODS

The concentration of proteins in plasma covers a vast range of 12 orders of magnitude. Therefore, to search for medium to low abundant biomarkers and elucidate mechanisms of AD, we immuno-depleted the most abundant plasma proteins and pre-fractionated the remaining proteins by HPLC, prior to two-dimensional gel electrophoresis. The relative levels of approximately 3400 protein species resolved on the 2D gels were compared using in-gel differential analysis with spectrally resolved fluorescent protein detection dyes (Zdyes™). Here we report on analysis of pooled plasma samples from an initial screen of a sex-matched cohort of 72 probable AD patients and 72 healthy controls from the baseline time point of AIBL.

RESULTS

We report significant changes in variants of apolipoprotein E, haptoglobin, α1 anti-trypsin, inter-α trypsin inhibitor, histidine-rich glycoprotein, and a protein of unknown identity. α1 anti-trypsin and α1 anti-chymotrypsin demonstrated plasma concentrations that were dependent on APOE ε4 allele dose. Our analysis also identified an association with the level of Vitamin D binding protein fragments and complement factor I with sex. We then conducted a preliminary validation study, on unique individual samples compared to the discovery cohort, using a targeted LC-MS/MS assay on a subset of discovered biomarkers. We found that targets that displayed a high degree of isoform specific changes in the 2D gels were not changed in the targeted MS assay which reports on the total level of the biomarker.

CONCLUSIONS

This demonstrates that further development of mass spectrometry assays is needed to capture the isoform complexity that exists in theses biological samples. However, this study indicates that a peripheral protein signature has potential to aid in the characterization of AD.

Evaluation of Maternal and Infantile Levels of Vitamin D in Preterm Infants

INTRODUCTION

Vitamin D deficiency is highly prevalent during pregnancy and in premature infants. This study was done to investigate the maternal and infantile levels of vitamin D in preterm infants.

METHODS

Using available sampling during 2018-2020, the maternal and umbilical cord serum levels of vitamin D were measured in 294 premature infants in Ghaem Hospital, Mashhad, Iran. A researcher- made questionnaire consisting of neonatal demographic and clinical characteristics was used as the data collection tool. Both maternal and placental vitamin D levels were categorized into four classes: severe deficiency (vitamin D<10 ng/ml), moderate deficiency (10.1≤vitamin D≤20 ng/ml), mild deficiency (20.1≤vitamin D≤30 ng/ml) and normal (vitamin D >30.1ng ml).

RESULTS

Vitamin D deficiency was seen in 89% of premature infants (46.6% severe, 30.6% moderate, and 11.9% mild). Serum levels of vitamin D were 18.28±13.94 ng/ml and 14.10±9.70 ng/ml in mothers and infants, respectively. The infants below and above 32 weeks exhibited vitamin D values of 10.97±6.31 ng/ml and 18.05±11.64 ng/ml, respectively. The difference in vitamin D levels between boys (12.59±8.40 ng/ml) and girls (16.05±11.45 ng/ml) was found to be significant (P=0.009). Moderate and severe vitamin D deficiency was more common at earlier pregnancy ages (P=0.001).

CONCLUSION

Vitamin D deficiency is more common and severe in preterm infants and their mothers. Controlling vitamin D levels during pregnancy, especially in women at risk of preterm labor and preterm infants, may help reduce prematurity problems.

Investigating the Role of Functional Polymorphism of Maternal and Neonatal Vitamin D Binding Protein in the Context of 25-Hydroxyvitamin D Cutoffs as Determinants of Maternal-Neonatal Vitamin D Status Profiles in a Sunny Mediterranean Region

Recent results indicate that dysregulation of vitamin D-binding protein (VDBP) could be involved in the development of hypovitaminosis D, and it comprises a risk factor for adverse fetal, maternal and neonatal outcomes. Until recently, there was a paucity of results regarding the effect of maternal and neonatal VDBP polymorphisms on vitamin D status during pregnancy in the Mediterranean region, with a high prevalence of hypovitaminosis D. We aimed to evaluate the combined effect of maternal and neonatal VDBP polymorphisms and different maternal and neonatal 25-hydroxyvitamin D (25(OH)D) cut-offs on maternal and neonatal vitamin D profile. Blood samples were obtained from a cohort of 66 mother–child pairs at birth. Our results revealed that: (i) Maternal VDBP polymorphisms do not affect neonatal vitamin D status at birth, in any given internationally adopted maternal or neonatal cut-off for 25(OH)D concentrations; (ii) neonatal VDBP polymorphisms are not implicated in the regulation of neonatal vitamin D status at birth; (iii) comparing the distributions of maternal VDBP polymorphisms and maternal 25(OH)D concentrations, with cut-offs at birth, revealed that mothers with a CC genotype for rs2298850 and a CC genotype for rs4588 tended to demonstrate higher 25(OH)D (≥75 nmol/L) during delivery (p = 0.05 and p = 0.04, respectively), after adjustments for biofactors that affect vitamin D equilibrium, including UVB, BMI and weeks of gestation. In conclusion, this study from Southern Europe indicates that maternal and neonatal VDBP polymorphisms do not affect neonatal vitamin D status at birth, whereas mothers with CC genotype for rs2298850 and CC genotype for rs4588 demonstrate higher 25(OH)D concentrations. Future larger studies are required to establish a causative effect of these specific polymorphisms in the attainment of an adequate (≥75 nmol/L) maternal vitamin D status during pregnancy.

Association of vitamin D and gene variants in the vitamin D metabolic pathway with preterm birth

OBJECTIVES

The aim of this study was to explore the association of vitamin D (VitD) levels during pregnancy and its metabolic pathway genes with the risk for preterm birth (PTB) among pregnant women in southeast China.

METHODS

This study was conducted in Zhoushan Maternal and Child Health Hospital, Zhejiang, from August 2011 to May 2018. Plasma 25-hydroxyvitamin vitamin D [25(OH)D] levels in three trimesters and single-nucleotide morphisms in the VitD metabolic pathway were measured. Relevant information was collected using questionnaires and an electronic medical recorder system. Multiple statistical methods including linear regression, logistic regression, and crossover analysis were applied.

RESULTS

The prospective cohort study included 3465 pregnant women, of which 202 were PTB (week of gestation at delivery: 33.38 ± 4.05), accounting for 5.8%. After adjusting for potential confounders, VitD sufficiency (≥30 ng/mL) in the second and third trimesters was associated with longer gestational age at delivery compared with VitD deficiency (<20 ng/mL). However, no significant association was found between VitD with the risk for PTB. rs7041, rs10210408, and rs2228171 were associated with gestational week and the risk for PTB. Significant associations were found of rs10210408, rs2209314, rs1155563, rs2544381 and the status of VitD in the second and third trimester with the gestational week. We also found that rs7041 and VitD in the second trimester might exert interaction on gestational week and the risk for PTB (P_inter = 0.038; P_inter = 0.019); rs16846876 and VitD in the second trimester might exert interaction on gestational week (P_inter = 0.024); rs4334089 and VitD in the third trimester might exert interaction on gestational week (P_inter = 0.024). Similar results were found when we tested pregnant women's plasma 25(OH)D in the first and second trimesters.

CONCLUSIONS

Women with VitD deficiency were associated with shorter gestational weeks. Single-nucleotide morphisms in VitD metabolic pathway genes were significantly associated with gestation week and the risk for PTB, mainly in vitamin D-binding protein (GC) and low-density lipoprotein-related protein 2 (LRP2)genes. Additionally, maternal VitD with GC gene and maternal VitD with vitamin D receptor (VDR) gene might exert interactions on the risk for PTB.

The effect of umbilical cord blood spexin, free 25(OH) vitamin D3 and adipocytokine levels on intrauterine growth and anthropometric measurements in newborns

Spexin is a newly described peptide and is known to reduce the uptake of long-chain fatty acids into adipocytes. The serum spexin levels of obese children between the ages of 12-18 are lower. The effect of serum spexin and free 25(OH) vitamin D3 levels on intrauterine development in newborns is unknown. Our aims is to evaluate the effects of spexin and adipocytokin levels in the cord blood of term newborn babies on the weight of the baby according to the gestation age (GA) and anthropometric measurement results. Babies who were born in our hospital and whose GA was ≥37 weeks were evaluated in three groups as appropriate for GA (AGA), small for GA (SGA) and large for GA (LGA). A total of 84 babies, including an equal number of infants in AGA, SGA and LGA groups, were included in the study. Spexin, leptin, active ghrelin, free 25(OH) vitamin D3, glucose, and insulin levels in the cord blood of infants were examined at birth. The results were compared according to GA and birth weight (BW). There was no statistically significant difference between groups in terms of mean spexin, active ghrelin, free 25(OH) vitamin D3, and insulin levels. The mean leptin level was significantly higher in LGA group than SGA and AGA groups (p 0.004). The mean spexin and leptin levels were higher in girls than in boys (respectively p value 0.029, 0.003). Although there is a significant positive correlation between BW, head circumference, height, umbilical circumference, umbilical circumference/height ratio and the mean leptin levels (p < 0.001), there was no significant correlation between mean spexin, active ghrelin, free 25 (OH) vitamin D3, insulin, and glucose levels. This study suggests that spexin may not have an effect on intrauterine development.

Vitamin D and Reproductive Hormones Across the Menstrual Cycle

STUDY QUESTION

How do the calciotropic hormones (25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and intact parathyroid hormone (iPTH)) vary across the menstrual cycle and do cyclic patterns of reproductive hormones (estradiol, progesterone, LH, FSH) differ by vitamin D status?

SUMMARY ANSWER

Calciotropic hormones vary minimally across the menstrual cycle; however, women with 25-hydroxyvitamin D below 30 ng/ml have lower mean estradiol across the menstrual cycle.

WHAT IS KNOWN ALREADY

Prior human studies suggest that vitamin D status is associated with fecundability, but the mechanism is unknown. Exogenous estrogens and prolonged changes in endogenous estradiol (pregnancy or menopause) influence concentrations of 25-hydroxyvitamin D. In vitro, treatment with 1,25-dihydroxyvitamin D increases steroidogenesis in ovarian granulosa cells. There are little data about changes in calciotropic hormones across the menstrual cycle or cyclic patterns of reproductive hormones by categories of vitamin D status.

STUDY DESIGN, SIZE, DURATION

A prospective cohort study of 89 self-identified white women aged 18-44, across two menstrual cycles. Participants were a subset of the BioCycle Study, a community-based study conducted at the University of Buffalo, 2005-2007.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Eligible participants had self-reported regular menstrual cycles between 21 and 35 days and were not using hormonal contraception or vitamins. Early morning fasting blood samples were drawn at up to eight study visits per cycle. Visits were timed to capture information in all cycle phases. Serum samples for 89 women (N = 163 menstrual cycles) were analyzed for estradiol, progesterone, LH, FSH and 25-hydroxyvitamin D (25(OH)D). Variability in calciotropic hormones within and across menstrual cycles was assessed using intraclass correlation coefficients and non-linear mixed models. Given the relative stability of the calciotropic hormones across the menstrual cycle, non-linear mixed models were used to examine differences in the cyclic patterns of estradiol, progesterone, LH and FSH by categories of each calciotropic hormone (split at the median). These models were conducted for all ovulatory cycles (N = 142 ovulatory menstrual cycles) and were adjusted for age, BMI (measured in clinic) and self-reported physical activity.

MAIN RESULTS AND THE ROLE OF CHANCE

Median 25(OH)D concentration was 29.5 ng/ml (SD 8.4), and only 6% of women had vitamin D deficiency (<20 ng/ml). The mean concentration of 25(OH)D did not differ between the luteal and follicular phase; however, both 1,25(OH)2D and iPTH showed small fluctuations across the menstrual cycle with the highest 1,25(OH)2D (and lowest iPTH) in the luteal phase. Compared with women who had mean 25(OH)D ≥30 ng/ml, women with lower 25(OH)D had 13.8% lower mean estradiol (95% confidence interval: -22.0, -4.7) and 10.8% lower free estradiol (95% CI: -0.07, -0.004). Additionally, compared to women with iPTH ≤36 pg/ml, women with higher concentrations of iPTH had 12.7% lower mean estradiol (95% CI: -18.7, -6.3) and 7.3% lower progesterone (95% CI: -13.3, -0.9). No differences in the cyclic pattern of any of the reproductive hormones were observed comparing cycles with higher and lower 1,25(OH)2D.

LIMITATIONS, REASONS FOR CAUTION

Women included in this study had self-reported 'regular' menstrual cycles and very few were found to have 25(OH)D deficiency. This limits our ability to examine cycle characteristics, anovulation and the effects of concentrations of the calciotropic hormones found in deficient individuals. Additionally, the results may not be generalizable to women with irregular cycles, other races, or populations with a higher prevalence of vitamin D deficiency.

WIDER IMPLICATIONS OF THE FINDINGS

These findings support current clinical practice that does not time testing for vitamin D deficiency to the menstrual cycle phase. We find that women with lower vitamin D status (lower 25(OH)D or higher iPTH) have lower mean concentrations of estradiol across the menstrual cycle. Although this study cannot identify a mechanism of action, further in vitro work or clinical trials may help elucidate the biologic mechanisms linking calciotropic and reproductive hormones.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (contract numbers: HHSN275200403394C, HHSN275201100002I and Task 1 HHSN27500001) and the National Institute of Environmental Health Sciences. There are no competing interests.

Recommendations on the measurement and the clinical use of vitamin D metabolites and vitamin D binding protein - A position paper from the IFCC Committee on bone metabolism

Vitamin D, an important hormone with a central role in calcium and phosphate homeostasis, is required for bone and muscle development as well as preservation of musculoskeletal function. The most abundant vitamin D metabolite is 25-hydroxyvitamin D [25(OH)D], which is currently considered the best marker to evaluate overall vitamin D status. 25(OH)D is therefore the most commonly measured metabolite in clinical practice. However, several other metabolites, although not broadly measured, are useful in certain clinical situations. Vitamin D and all its metabolites are circulating in blood bound to vitamin D binding protein, (VDBP). This highly polymorphic protein is not only the major transport protein which, along with albumin, binds over 99% of the circulating vitamin D metabolites, but also participates in the transport of the 25(OH)D into the cell via a megalin/cubilin complex. The accurate measurement of 25(OH)D has proved a difficult task. Although a reference method and standardization program are available for 25(OH)D, the other vitamin D metabolites still lack this. Interpretation of results, creation of clinical supplementation, and generation of therapeutic guidelines require not only accurate measurements of vitamin D metabolites, but also the accurate measurements of several other "molecules" related with bone metabolism. IFCC understood this priority and a committee has been established with the task to support and continue the standardization processes of vitamin D metabolites along with other bone-related biomarkers. In this review, we present the position of this IFCC Committee on Bone Metabolism on the latest developments concerning the measurement and standardization of vitamin D metabolites and its binding protein, as well as clinical indications for their measurement and interpretation of the results.

Associations between maternal vitamin D status during three trimesters and cord blood 25(OH)D concentrations in newborns: a prospective Shanghai birth cohort study

PURPOSE

Prenatal vitamin D (VitD) deficiency influences children's health in later life. We aimed to test the associations between maternal VitD status in each of the three trimesters of pregnancy and cord blood 25(OH)D concentrations in newborns.

METHODS

Participants were pregnant women recruited from the Shanghai Birth Cohort (SBC) (n = 1100). Of all the participants, 946 completed the collection of venous blood at early (< 16 weeks, T1), mid- (24-28 weeks, T2), and late (32-34 weeks, T3) pregnancy as well as the corresponding cord blood in the newborns. Maternal serum 25(OH)D concentrations were measured by LC-MS/MS, and the information on confounding factors was obtained through a standardized questionnaire.

RESULTS

The mean 25(OH)D concentrations at time points T1, T2, T3 in maternal blood and cord blood of the newborns were 26.31 ng/mL, 31.92 ng/mL, 35.62 ng/mL, and 19.77 ng/mL, respectively. Neonatal 25(OH)D level in cord blood was positively correlated with maternal serum 25(OH)D levels at each trimester, and the strongest correlation was found at time point T3.

CONCLUSION

Maternal 25(OH)D concentrations at each trimester were positively associated with neonatal VitD status in cord blood, and the strongest correlation was found in the late stage of pregnancy, which could be considered as a sensitive time window. Attention should be paid to the nutritional status of VitD during pregnancy to better prevent the VitD deficiency in neonates.

Total, Bioavailable, and Free 25(OH)D Relationship with Indices of Bone Health in Elderly: A Randomized Controlled Trial

CONTEXT

Questions regarding the superiority of free and bioavailable 25-hydroxyvitamin D [25(OH)D] in predicting health outcomes remain unresolved.

OBJECTIVE

This study investigates the impact of vitamin D variables-total, bioavailable, or free 25(OH)D-on indices of bone and mineral metabolism, at baseline and in response to 2 vitamin D doses.

DESIGN

Our objectives are implemented as exploratory analyses on data collected in a 1-year, double-blind, randomized controlled trial completed in July 2014.

SETTING

Participants were recruited from 3 major hospitals in an ambulatory setting.

PARTICIPANTS

Participants were >65 years of age, overweight, and had a baseline serum 25(OH)D between 10 and 30 ng/mL. A total of 221 participants completed the study.

INTERVENTION

Subjects were randomized to receive calcium and oral vitamin D3 (600 IU/day or 3750 IU/day) supplementation.

RESULTS

Participants who received the higher vitamin D dose had levels that were 1.3- to 1.4-fold higher than those taking the lower dose, for all variables (P value < 0.001). Serum values of bioavailable and free 25(OH)D were associated with total 25(OH)D, with r values of 0.942 and 0.943, respectively (P value < 0.001). Parathyroid hormone (PTH) was negatively associated with all vitamin D variables, with correlation coefficients ranging from -0.22 to -0.25, while calcium and bone turnover markers (carboxy-terminal collagen crosslinks and osteocalcin) did not. Only total 25(OH)D had a positive relationship with % change bone mineral density (BMD) at the femoral neck at 12 months, while only free and bioavailable 25(OH) had a positive relationship with % change total body BMD at 12 months.

CONCLUSION

Calculated free and bioavailable 25(OH)D do not appear to be superior to total 25(OH)D in predicting indices of bone health in an elderly population.

Opposite correlation of 25-hydroxy-vitamin D- and 1,25-dihydroxy-vitamin D-metabolites with gestational age, bone- and lipid-biomarkers in pregnant women

25-Hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) need to be bound to carrier proteins to be transported to their target cells. The majority of either 25OHD or 1,25(OH)₂D is bound to vitamin D-binding protein (DBP), a smaller fraction is bound to albumin and only very small amounts of 25OHD or 1,25(OH)₂D are free. Albumin-bound 25OHD or 1,25(OH)₂D is relatively easily available after dissociation from albumin. Thus, the sum of free and albumin-bound forms is called bioavailable 25OHD and bioavailable 1,25(OH)₂D. Total 25OHD and 1,25(OH)₂D are defined as the sum of free, albumin-bound and DBP-bound 25OHD and 1,25(OH)₂D, respectively. This cross-sectional study in 427 pregnant women compared the correlation of the six vitamin D compounds with biomarkers of bone health, lipid metabolism, kidney function, endocrine parameters, and group B water-soluble vitamins. Among the 25OHD metabolites analysed, total 1,25(OH)₂D showed clearly the best correlation with calcium, bone-specific alkaline phosphatase, adiponectin, LDL, HDL, urea, thyroxine, and group B water-soluble vitamins. When comparing the three 25OHD metabolites, both free 25OHD and bioavailable 25OHD showed overall good correlations with calcium, bone-specific alkaline phosphatase, adiponectin, LDL, HDL, urea, thyroxine, triiodothyronine, and group B water-soluble vitamins, The correlations of 1,25(OH)₂D and 25OHD metabolites went always in opposite directions. Only PTH correlates always inversely with all six vitamin D compounds. In conclusion, free 25(OH)D and bioavailable 25(OH)D are more precise determinants of the vitamin D status than total 25(OH)D in normal pregnancy, whereas total 1,25(OH)₂D is superior to free and bioavailable 1,25(OH)₂D. Except for PTH, correlations of 25(OH)D and 1,25(OH)₂D metabolites with typical clinical chemistry readouts go in opposite directions.

The Association between Maternal Serum Vitamin D Levels and Gestational Diabetes Mellitus among Filipino Patients: A Cross-Sectional Study

Objectives

To determine the association between low maternal serum vitamin D and gestational diabetes mellitus (GDM) among Filipino women in St. Luke’s Medical Center, Quezon City.

Methodology

A cross-sectional study involving pregnant women at outpatient clinics in a tertiary hospital in the Philippines. Simultaneous testing for fasting blood sugar, 75g oral glucose tolerance test and serum vitamin D was done. Participants were classified as GDM versus non-GDM, and normal versus low serum vitamin D. Univariate and multivariate statistics were done to determine relationship between vitamin D and GDM.

Results

Of 211 included women, 198 (93.8%) had low vitamin D levels, and 56 (26.5%) had GDM. Vitamin D was significantly higher in the GDM group (21.0±8.1 vs 18.8±5.3 ng/mL, p=0.0189). The proportion of women with low vitamin D levels was significantly higher among those without GDM (96.1% vs 87.5%, OR=0.28, p=0.029]. After adjusting for age, parity, history of GDM and pre-pregnancy BMI, no significant association was observed (adjusted OR=0.66, p=0.522). No correlation was seen between vitamin D and FBS (r=0.28, p=0.095), 1-hour post-75 g OGTT (r=0.26, p=0.643), and 2-hour post-75 g OGTT (r=0.28, p=0.113).

Conclusion

There was an association found between maternal serum vitamin D level and GDM in the univariate analysis, but none was evident after adjusting for possible confounders. The unanticipated high prevalence of low vitamin D levels among pregnant Filipinos needs to be verified in future studies.

MLL1 Inhibition and Vitamin D Signaling Cooperate to Facilitate the Expanded Pluripotency State

Dynamic establishment of histone modifications in early development coincides with programed cell fate restriction and loss of totipotency beyond the early blastocyst stage. Causal function of histone-modifying enzymes in this process remains to be defined. Here we show that inhibiting histone methyltransferase MLL1 reprograms naive embryonic stem cells (ESCs) to expanded pluripotent stem cells (EPSCs), with differentiation potential toward both embryonic and extraembryonic lineages in vitro and in vivo. MLL1 inhibition or deletion upregulates gene signatures of early blastomere development. The function of MLL1 in restricting induction of EPSCs is mediated partly by Gc, which regulates cellular response to vitamin D signaling. Combined treatment of MLL1 inhibitor and 1α,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃) cooperatively enhanced functionality of EPSCs, triggering an extended 2C-like state in vitro and robust totipotent-like property in vivo. Our study sheds light on interplay between epigenetics and vitamin D pathway in cell fate determination.

Relationships between Total, Free and Bioavailable Vitamin D and Vitamin D Binding Protein in Early Pregnancy with Neonatal Outcomes: A Retrospective Cohort Study

Maternal vitamin D deficiency has been associated with adverse neonatal outcomes, however, existing results are inconsistent. Current data focus on total 25-hydroxyvitamin D (25(OH)D) as the common measure of vitamin D status, while additional measures including vitamin D-binding protein (VDBP) and free and bioavailable metabolites have not been explored in relation to neonatal outcomes. We examined whether VDBP and total, free, and bioavailable vitamin D metabolites in early pregnancy are associated with subsequent neonatal outcomes. In this retrospective analysis of 304 women in early pregnancy (<20 weeks gestation), demographic and anthropometric data were collected and total 25(OH)D (chemiluminescent assay), VDBP (polyclonal enzyme-linked immunosorbent assay (ELISA)) and albumin (automated colorimetry) were measured in bio-banked samples. Free and bioavailable 25(OH)D were calculated using validated formulae. Neonatal outcomes were derived from a medical record database. Higher maternal total and free 25(OH)D concentrations were associated with higher neonatal birthweight (β = 5.05, p = 0.002 and β = 18.06, p = 0.02, respectively), including after adjustment for maternal covariates including age, body mass index (BMI) and ethnicity (all p ≤ 0.04). Higher total 25(OH)D and VDBP concentrations were associated with a lower likelihood of neonatal jaundice (odds ratio [OR] [95%CI] = 0.997 [0.994, 1.000], p = 0.04 and 0.98 [0.96, 0.99], p = 0.03, respectively), but these were attenuated after adjustment for the above maternal covariates (both p = 0.09). Our findings suggest a novel association between free 25(OH)D and neonatal birthweight. Total 25(OH)D concentrations were also associated with birthweight, and both total 25(OH)D and VDBP were associated with jaundice, but the latter were not significant after adjustment. These results suggest a potential link between these metabolites and neonatal outcomes; however, further large-scale prospective studies are warranted.

Validation and Determination of 25(OH) Vitamin D and 3-Epi25(OH)D3 in Breastmilk and Maternal- and Infant Plasma during Breastfeeding

Vitamin D deficiency in pregnant women and their offspring may result in unfavorable health outcomes for both mother and infant. A 25hydroxyvitamin D (25(OH)D) level of at least 75 nmol/L is recommended by the Endocrine Society. Validated, automated sample preparation and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were used to determine the vitamin D metabolites status in mother-infant pairs. Detection of 3-Epi25(OH)D3 prevented overestimation of 25(OH)D3 and misclassification of vitamin D status. Sixty-three percent of maternal 25(OH)D plasma levels were less than the recommended level of 25(OH)D at 3 months. Additionally, breastmilk levels of 25(OH)D decreased from 60.1 nmol/L to 50.0 nmol/L between six weeks and three months (p < 0.01). Furthermore, there was a positive correlation between mother and infant plasma levels (p < 0.01, r = 0.56) at 3 months. Accordingly, 31% of the infants were categorized as vitamin D deficient (25(OH)D < 50 nmol/L) compared to 25% if 3-Epi25(OH)D3 was not distinguished from 25(OH)D3. This study highlights the importance of accurate quantification of 25(OH)D. Monitoring vitamin D metabolites in infant, maternal plasma, and breastmilk may be needed to ensure adequate levels in both mother and infant in the first 6 months of infant life.

Early Pregnancy Vitamin D Binding Protein Is Independently Associated with the Development of Gestational Diabetes: A Retrospective Cohort Study

BACKGROUND

Vitamin D-binding protein (VDBP) has been implicated in several adverse pregnancy outcomes either directly or indirectly via influencing the concentrations of biologically active vitamin D metabolites. However, human studies exploring these metabolites in pregnancy remain sparse. Here, we examine whether VDBP and total, free, and bioavailable 25-hydroxyvitamin D (25(OH)D) metabolites in early pregnancy are associated with subsequent adverse pregnancy outcomes.

METHODS

We conducted a retrospective analysis of 304 pregnant women in early pregnancy (<20 weeks gestation). The demographic characteristics, anthropometric data, and total 25(OH)D were measured and plasma or serum samples were collected and bio-banked. Using these samples, we measured VDBP (polyclonal ELISA) and albumin (automated colorimetry), and calculated free and bioavailable 25(OH)D using validated formulae. Pregnancy outcomes were derived from scanned medical records. Regression models were used to analyse the relationships between vitamin D metabolites in early pregnancy and subsequent pregnancy outcomes (gestational diabetes mellitus (GDM), pre-eclampsia, preterm birth), with adjustment for predetermined clinically relevant maternal factors including age, body mass index (BMI), and ethnicity.

RESULTS

Lower VDBP concentrations were associated with higher glucose levels and a greater likelihood of developing GDM at 26-28 weeks gestation (odds ratio [OR] (95% CI) = 0.98 (0.97,0.99), p = 0.015). This finding remained significant after adjustment for maternal covariates including age, BMI, and ethnicity (β = -0.003, p = 0.03). Lower total, free and bioavailable 25(OH)D, but not VDBP, were associated with a shorter length of gestation, but only the relationship with total 25(OH)D remained significant after adjustment for the above maternal covariates (β = 0.02, p = 0.006).

CONCLUSIONS

This is the first study to examine VDBP, and total, free and bioavailable 25(OH)D in relation to pregnancy outcomes in a well characterised multi-ethnic cohort of pregnant women. Our findings show that VDBP and total 25(OH)D are associated with GDM and length of gestation, respectively; however, further investigations using large-scale prospective studies are needed to confirm our findings.

The measurement of vitamin D metabolites part II-the measurement of the various vitamin D metabolites

Today, the possibility exists to measure a number of different vitamin D metabolites with accurate and precise methods. The most abundant vitamin D metabolite, 25(OH)D, is considered the best marker for estimating vitamin D status and is therefore the most commonly measured in clinical practice. There is no consensus on the added value of measuring other metabolites beyond 25-hydroxyvitamin D, although, in some special clinical scenarios and complicated cases, these metabolites may provide just the information needed for an accurate diagnosis. The problem this review addresses is which metabolite to measure and when and how to measure it.

Free vitamin D correlate better with bone mineral density and thoracolumbar junction osteoporotic vertebral fractures than serum vitamin D

Background

Vitamin D deficiency has long been studied as a risk factor for osteoporosis. However, the association between serum vitamin D status, bone mineral density (BMD) and the incidence of vertebral fractures (OVFs) remain controversial. It is believed that free portion of the circulating vitamin D carries the metabolic activities of vitamin D. Therefore, the aim of the present study is to analyse if free vitamin D correlates with BMD and osteoporotic fragile vertebral fractures in the elderly population.

Methods

A total of 90 consecutive patients, including 81 female and 9 male patients, aged > 48 years, were included in this cross sectional study between March and July of 2018. Total vitamin D (total 25(OH)D), free vitamin D (free 25(OH)D), calcium and phosphorus were measured. BMD was measured using dual energy X-ray absorptiometry (DEXA) and osteoporotic vertebral fracture was assessed using plain radiograph. Multiple linear regression was performed to find out the association between total vitamin D, free vitamin D and BMD at various sites. To evaluate the association with osteoporotic vertebral multivariate logistic regression model was used.

Results

The mean total vitamin D and free vitamin D were 25.1 ± 10.2 and 6.1 ± 1.7 respectively. Free vitamin D had a linear correlation with total vitamin D (R² = 0.69). While free vitamin D had a positive correlation with lumbar BMD roles (p < 0.05), total vitamin D didn’t have any association with BMD at any site. Of the total patients, 62 patients (68.9%) had thoracolumbar junction OVFs. Free vitamin D level correlated with the prevalence of OVFs as well as lumbar osteoporosis (p < 0.05). However, there was no statistical correlation between serum vitamin D status and the OVFs.

Conclusions

Free vitamin D was significantly related to the occurrence of thoracolumbar junction OVFs and lumbar BMD, which assumed to be a positive predictor for fracture and osteoporosis prevention. However, total serum vitamin D levels did not have any association with BMD at different sites as well as fragile vertebral fracture.

Trial registration

The study is registered at clinicaltrials.gov NCT03605173.

Vitamin D, and Maternal and Child Health

Vitamin D has important roles in calcium metabolism and in the prevention of rickets and osteomalacia; low levels of 25-hydroxyvitamin D are common in the general population and amongst pregnant women. Whilst there is a wealth of observational evidence linking vitamin D deficiency to a wide range of disease outcomes, there are currently few high-quality randomised controlled trials to confirm any causal associations, although many are currently in progress. Furthermore, currently, the vast majority of published guidelines recommend standard supplemental vitamin D doses for children and pregnant women, yet there is increasing recognition that individual characteristics and genetic factors may influence the response to supplementation. As such, future research needs to concentrate on documenting definite beneficial clinical outcomes of vitamin D supplementation, and establishing personalised dosing schedules and demonstrating effective approaches to optimising initiation and adherence.

The Role of Skeletal Muscle in Maintaining Vitamin D Status in Winter

The status of vitamin D is determined mainly by its formation in skin by the photochemical action of solar UVB light (wavelength 290-320 nm) on the precursor 7-dehydrocholesterol. Because of seasonal variation in intensity of solar UV light, vitamin D status falls in winter and rises in summer. It has been presumed that there is no functional store of vitamin D. Thus, to avoid deficiency, a nutritional supply would be required in winter. However, there is now evidence that the main circulating metabolite of vitamin D, 25-hydroxyvitamin D, accumulates in skeletal muscle cells, which provide a functional store during the winter months. The mechanism is mediated by muscle cell uptake of circulating vitamin D-binding protein (DBP) through a megalin-cubilin membrane transport process. DBP then binds to cytoplasmic actin to provide an array of high-affinity binding sites for 25-hydroxyvitamin D [25(OH)D]. The repeated passage of 25(OH)D into and out of muscle cells would account for its long residence time in blood.

Relationship between Vitamin D Level and Serum TNF-α Concentration on the Severity of Chronic Obstructive Pulmonary Disease

BACKGROUND

Chronic Obstructive Pulmonary Disease (COPD) is a chronic inflammatory disease and disturbed bacterial clearance. Vitamin D deficiency is sometimes observed in COPD patients and as significant roles in increasing inflammation of airway obstruction and systemic obstruction, increasing pro-inflammatory cytokine including TNF-α, reduction of bacterial clearance and increase exacerbation risk due to infection. Also, vitamin D plays significant roles in the metabolism of calcium and mineralisation of bones and regulation system of immune. TNF-α also has essential roles in pathogenesis and inflammation of COPD. Several studies that investigate the relationship between vitamin D level and serum TNF-α concentration in COPD patients are relatively uncommon, including in Indonesia.

AIM

This study aimed to assess the relationship between vitamin D level and TNF-α concentration in patients on the severity of the chronic obstructive pulmonary disease.

METHODS

This study was a hospital-based descriptive cross-sectional study. Total samples were 50 COPD patients with the average age of older than 60 years during their enrollments at the Department of Pulmonology and Respiratory Medicine of the Dr Wahidin Sudirohusodo General Hospital Makassar in September 2018-January 2019. All procedures of the present study were reviewed and approved by the Research Ethics Committee of Medicine Faculty of Hasanuddin University. The severity of COPD was assessed according to the combination of COPD assessment stages that referred to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) Guideline 2015 that consisted of the combination of scoring COPD Assessment Test (CAT), the modified Medical Research Council (mMRC) questionnaire and results of the spirometry measurement. Assessment of airway obstruction levels referred to the GOLD spirometry criteria. Determination of thoracic photographs was conducted to verify the COPD diagnosis of the severity of COPD. Determination of serum TNF-α concentration and vitamin D3 [1,25(OH)2D3] level used the ELISA method.

RESULTS

The majority of COPD patients were observed in the category of older than 60 years old accounted for 34 COPD patients (68%), and the majority of COPD patients were males accounted for 47 males with COPD (94%). The majority of COPD patients were observed in the group of D (38%). All the study subjects observed in this study were smokers, and 82% of them were in the category of heavy smokers. 21 study subjects had higher concentration of serum TNF-α (tertile 3 = 0.21-1.83 pg/dl), 20 study subjects and lower level of vitamin D (tertile 1 = 182.1-364.5 pg/dl). The majority of the study subjects (38%) were in the category of severe COPD (category D of the severity of COPD at the tertile 3) according to the GOLD Combine Assessment. Given the relationship between vitamin D level and serum TNF-α concentration on the airway obstruction, there were significant positive correlations between the increase of vitamin D levels and the increase of serum TNF-α concentrations on airway obstruction. Given the relationship between vitamin D level and serum TNF-α concentration on the severity of COPD, there were significant positive correlations between the increase of vitamin D levels (tertiles 1, 2 and 3) and the increase of serum TNF-α concentrations on the severity of COPD at p-value < 0.05. Overall, there were non-linear relationships between vitamin D level and serum TNF-α concentration on the severity of COPD.

CONCLUSIONS

Serum TNF-α concentration was positively associated with airway obstruction level and severity of COPD. Low level of vitamin D was negatively associated with airway obstruction level and severity of COPD. Vitamin D3 level (1,25(OH)2D) was negatively associated with serum TNF-α concentration and airway obstruction level and severity of COPD.

Changes of Vitamin D-Binding Protein, and Total, Bioavailable, and Free 25-Hydroxyvitamin D in Transgender People

CONTEXT

Total 25-hydroxyvitamin D [25(OH)D] is mainly bound to vitamin d-binding protein (DBP). Bioavailable 25(OH)D consists of albumin-bound and free 25(OH)D and is available for metabolic processes. As sex steroids influence DBP, hormonal treatment (HT) in transgender people might affect DBP and consequently the available 25(OH)D. Total 25(OH)D might therefore not well represent bioavailable and free 25(OH)D.

OBJECTIVE

To investigate the effects of HT on DBP, and total, bioavailable, and free 25(OH)D, and to assess whether total 25(OH)D well represents bioavailable and free 25(OH)D.

DESIGN

A prospective study.

SETTING

A university hospital.

PARTICIPANTS

Twenty-nine transwomen and 30 transmen.

INTERVENTION

Estradiol and cyproterone acetate in transwomen, and testosterone in transmen.

MAIN OUTCOME MEASURES

DBP, total 25(OH)D, free 25(OH)D, and albumin were measured at baseline and after 3 months of HT, and deseasonalized total 25(OH)D and bioavailable 25(OH)D were calculated.

RESULTS

DBP changed with +5% (95% CI, -0% to 10%; P = 0.06) in transwomen and with -3% (95% CI: -9% to 3%; P = 0.34) in transmen. No significant changes were found in total 25(OH)D, free, and bioavailable 25(OH)D concentrations. Total 25(OH)D was well correlated with bioavailable (R2, 0.75) and free (R2, 0.76) 25(OH)D.

CONCLUSIONS

DBP tended to increase in transwomen, but did not change in transmen. HT did not influence free 25(OH)D, total 25(OH)D, and bioavailable 25(OH)D concentrations in transwomen and transmen. As total 25(OH)D represents bioavailable and free 25(OH)D well, HT in transgender people does not interfere with the assessment of vitamin D status.

Seasonal variation of serum 25-hydroxyvitamin D and parameters of bone and mineral disorder in dialysis patients

BACKGROUND

Vitamin D deficiency is common among dialysis patients and may impact blood concentrations of calcium, phosphorus, intact parathyroid hormone (iPTH), and alkaline phosphatase (ALP). Seasonal variation of serum 25-hydroxyvitamin D [25(OH)D] concentrations has been well established for the general population; however, less is known about circannual variation in 25(OH)D as well as other parameters of mineral and bone disorder among dialysis patients.

METHOD

Based on 57,500 serum 25(OH)D measurements collected over two years from January 2009 to December 2010 among 25,025 dialysis patients, we evaluated the circannual variations in serum concentrations of 25(OH)D, calcium, phosphorus, iPTH, and ALP by a linear regression model with a cosinor function for the time period (month). We adjusted for potential confounders including case-mix variables, and ultraviolet index.

RESULTS

Serum 25(OH)D concentrations showed significant circannual variation and mean serum 25(OH)D was 3.2 ng/mL higher in summer than in winter. Furthermore, 25(OH)D concentration increased steadily by 1.3 ng/mL per year. While serum calcium concentrations showed statistically significant but clinically negligible seasonal variation (0.02 mg/dL in peak-trough difference), serum phosphorus did not follow such a pattern. Serum iPTH concentrations also showed a modest seasonal variation with 9% higher values in winter than in summer. Concordantly, ALP concentrations in the winter were 2% higher than in the summer time. Seasonal variation of 25(OH)D was greater in male (vs. female), African-American (vs. non-African-American), and younger (vs. older) dialysis patients.

CONCLUSION

Serum 25(OH)D and iPTH concentrations show seasonal variation among dialysis patients while the variation in other parameters of mineral and bone disorder was clinically irrelevant, if any. Serum 25(OH)D also showed a gradual increase over time. Clinicians and researchers should be aware of these changes when interpreting laboratory results in dialysis patients.

Serum cortisol and vitamin D status are independently associated with blood pressure in pregnancy

The aim was to study if serum cortisol during pregnancy was associated with blood pressure and development of gestational hypertensive disorders. Additionally, associations between 25-hydroxyvitamin D (25OHD) and cortisol, including confounding effects and interactions in their relation to blood pressure were investigated. In total, 1413 pregnant women from the prospective Swedish GraviD cohort were included. Serum was collected in the first (T1) and third trimester (T3) and analyzed for 25OHD by liquid chromatography mass spectrometry and cortisol using an electro-chemiluminescence immunoassay. The main outcome measures were T1 blood pressure and development of gestational hypertensive disorders (gestational hypertension or preeclampsia). Gestational hypertensive disorders were defined as new onset hypertension, with or without proteinuria, after gestational week 20. Mean ± SD cortisol increased significantly from T1 to T3 (312 ± 123 vs. 659 ± 201 nmol/L, p < 0.001) and this increase was influenced by ethnicity. Serum concentrations of cortisol and 25OHD correlated in both T1 (B = 0.35, p < 0.001) and T3 (B = 0.30, p < 0.001). Cortisol and 25OHD were positively associated with T1 blood pressure, and there were non-significant trends for associations with gestational hypertensive disorders. Cortisol and 25OHD did not display any confounding effect or effect modification in their relationships with blood pressure. In conclusion, there was a positive correlation between serum cortisol and 25OHD in both early and late pregnancy. Both cortisol and 25OHD were positively associated with early pregnancy blood pressure. These results imply that the two hormones might be on different paths in their relationship with blood pressure.

Vitamin D-binding protein deficiency in mice decreases systemic and select tissue levels of inflammatory cytokines in a murine model of acute muscle injury

BACKGROUND

Severe acute muscle injury results in massive cell damage, causing the release of actin into extracellular fluids where it complexes with the vitamin D-binding protein (DBP). We hypothesized that a systemic DBP deficiency would result in a less proinflammatory phenotype.

METHODS

C57BL/6 wild-type (WT) and DBP-deficient (DBP-/-) mice received intramuscular injections of either 50% glycerol or phosphate-buffered saline into thigh muscles. Muscle injury was assessed by histology. Cytokine levels were measured in plasma, muscle, kidney, and lung.

RESULTS

All animals survived the procedure, but glycerol injection in both strains of mice showed lysis of skeletal myocytes and inflammatory cell infiltrate. The muscle inflammatory cell infiltrate in DBP-deficient mice had remarkably few neutrophils as compared with WT mice. The neutrophil chemoattractant CXCL1 was significantly reduced in muscle tissue from DBP-/- mice. However, there were no other significant differences in muscle cytokine levels. In contrast, plasma obtained 48 hours after glycerol injection revealed that DBP-deficient mice had significantly lower levels of systemic cytokines interleukin 6, CCL2, CXCL1, and granulocyte colony-stimulating factor. Lung tissue from DBP-/- mice showed significantly decreased amounts of CCL2 and CXCL1 as compared with glycerol-treated WT mice. Several chemokines in kidney homogenates following glycerol-induced injury were significantly reduced in DBP-/- mice: CCL2, CCL5, CXCL1, and CXCL2.

CONCLUSIONS

Acute muscle injury triggered a systemic proinflammatory response as noted by elevated plasma cytokine levels. However, mice with a systemic DBP deficiency demonstrated a change in their cytokine profile 48 hours after muscle injury to a less proinflammatory phenotype.

Serum and synovial fluid vitamin D metabolites and rheumatoid arthritis

Vitamin D-deficiency has been linked to inflammatory diseases including rheumatoid arthritis (RA). Studies to date have focused on the impact of serum 25-hydroxyvitamin D3 (25(OH)D3), an inactive form of vitamin D, on RA disease activity and progression. However, anti-inflammatory actions of vitamin D are likely to be mediated at sites of RA disease, namely the inflamed joint, and may involve other vitamin D metabolites notably the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). In the current study serum and synovial fluid samples from n = 20 patients with persistent RA and n = 7 patients with reactive arthritis (ReA) were analysed for multiple vitamin D metabolites. Serum data for RA and ReA patients were compared to healthy controls (HC). There was no significant difference between RA or ReA patients relative to HC for 25(OH)D3, 24,25(OH)2D3, 1,25(OH)2D3 or 25(OH)D2. However, 3-epi-25(OH)D3 was significantly lower in RA and ReA patients compared to HC (p < 0.05). All vitamin D metabolites, apart from 25(OH)D2, were lower in SF compared to serum, and SF 1,25(OH)2D3 was unquantifiable in 13/20 RA and 4/7 ReA samples. SF 25(OH)D3, 3-epi-25(OH)D3 and DBP correlated inversely with swollen joint score, and serum 25(OH)D2 and SF DBP correlated directly with C-reactive protein levels. These data indicate that serum 25(OH)D3 provides only limited insight into the role of vitamin D in RA. Alternative serum metabolites such as 3-epi-25(OH)2D3, and SF metabolites, notably lack of SF 1,25(OH)2D3, may be more closely linked to RA disease severity and progress.

Longitudinal changes in serum vitamin D binding protein and free 25-hydroxyvitamin D in a multiracial cohort of pregnant adolescents

Serum free 25-hydroxyvitamin D (25(OH)D) rather than total 25(OH)D may better indicate vitamin D status during pregnancy given the pregnancy-associated increase in serum vitamin D binding protein (DBP) concentration. Our aims were to assess changes in DBP and free 25(OH)D across gestation and to determine whether free compared with total 25(OH)D more strongly correlates with markers of vitamin D and calcium metabolism during pregnancy. This ancillary study included 58 pregnant adolescents (53% African American, 47% White) who completed a vitamin D3 supplementation study in Rochester, NY. Blood was collected at entry, mid-study, and delivery (median 17, 29, and 40 weeks' gestation). Mixed-effects regression was used to test for differences in DBP, directly measured free 25(OH)D, and other serum markers by study visit and race. Free and total 25(OH)D were evaluated in relation to serum PTH, 1,25(OH)2D, 24,25(OH)2D, and calcium. The mean DBP concentration was above nonpregnant reference values at entry and increased across gestation (P < 0.0001). Total 25(OH)D explained most of the variance in free 25(OH)D (r ≥ 0.67; P < 0.0001). Holding total 25(OH)D constant, each 100 mg/L increase in DBP was associated with a 0.4 pg/mL decrease in free 25(OH)D (P < 0.01). The percent free 25(OH)D was inversely related to both DBP and total 25(OH)D at each visit. Regardless of race or visit, total 25(OH)D was a stronger correlate of PTH, 1,25(OH)2D, and 24,25(OH)2D, and neither total nor free 25(OH)D was related to serum calcium. African Americans had lower total 25(OH)D (P <  0.0001), but free 25(OH)D did not significantly differ by race (P =  0.2). In pregnant adolescents, DBP concentration was elevated and inversely associated with percent free 25(OH)D, but measured free 25(OH)D provided no advantage over total 25(OH)D as a predictor of PTH, 1,25(OH)2D, 24,25(OH)2D, or calcium. The clinical relevance of the small racial difference in percent free 25(OH)D requires further investigation.

The GC2 haplotype of the vitamin D binding protein is a risk factor for a low plasma 25-hydroxyvitamin D concentration in a Han Chinese population

Background

The GC haplotype of the vitamin D binding protein (encoded by the GC gene) might be a risk factor to the vitamin D (VD) nutritional status for many populations, while evidences from the Chinese Han population are sparse. We test the association between vitamin D binding protein genotypes and VD status as well as the metabolic parameters of glucose and lipids in a Han Chinese population.

Methods

In a cross-sectional study conducted at a health examination centre (registered in ClinicalTrials.gov as QLS2013), 2641 adults were included and grouped according to their plasma 25-hydroxyvitamin D (25OHD) concentrations as VD deficient (VDD), insufficient (VDI), or sufficient (VDS). The rs7041 and rs4588 genotypes were analysed with a molecular beacon-based qPCR method using blood samples.

Results

Plasma 25OHD concentrations were lower in the GC2/2, rs7041T/T, and rs4588A/A genotypes than the GC1f/1s, rs7041G/T, and rs4588C/C genotypes (P <  0.05). After adjusting for confounders, the GC2 haplotype increased the risk of low VD status (P <  0.05) in both genders. More genotypic models revealed the negative contributions of rs4588A than rs7041T to low VD status (P <  0.05). The combined rates of VDD and VDI were 80.2% in males and 86.1% in females. Compared with VDI, VDS, or both, VDD showed higher plasma concentrations of fasting blood glucose, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides in males (P <  0.05); however, no significant differences were found with regard to these parameters between the subgroups defined by the GC genotypes (P > 0.05).

Conclusions

In a Han Chinese population, the GC2 haplotype or more exactly rs4588A is a risk factor for low VD status but is not associated with glucose and lipid metabolic disorders, which are inversely correlated with the circulating 25OHD concentration in males.

Trial registration

The study was retrospectively registered in January 2018 as NCT03406234 in the ClinicalTrials.gov online system.

Electronic supplementary material

The online version of this article (10.1186/s12986-019-0332-0) contains supplementary material, which is available to authorized users.

Vitamin D Binding Protein: A Historic Overview

Vitamin D and all its metabolites are bound to a specific vitamin D binding protein, DBP. This protein was originally first discovered by its worldwide polymorphism and called Group-specific Component (GC). We now know that DBP and GC are the same protein and appeared early in the evolution of vertebrates. DBP is genetically the oldest member of the albuminoid family (including albumin, α-fetoprotein and afamin, all involved in transport of fatty acids or hormones). DBP has a single binding site for all vitamin D metabolites and has a high affinity for 25OHD and 1,25(OH)2D, thereby creating a large pool of circulating 25OHD, which prevents rapid vitamin D deficiency. DBP of higher vertebrates (not amphibians or reptiles) binds with very high affinity actin, thereby preventing the formation of polymeric actin fibrils in the circulation after tissue damage. Megalin is a cargo receptor and is together with cubilin needed to reabsorb DBP or the DBP-25OHD complex, thereby preventing the urinary loss of these proteins and 25OHD. The total concentrations of 25OHD and 1,25(OH)2D in DBP null mice or humans are extremely low but calcium and bone homeostasis remain normal. This is the strongest argument for claiming that the "free hormone hypothesis" also applies to the vitamin D hormone, 1,25(OH)2D. DBP also transports fatty acids, and can play a role in the immune system. DBP is genetically very polymorphic with three frequent alleles (DBP/GC 1f, 1s, and 2) but in total more than 120 different variants but its health consequences, if any, are not understood. A standardization of DBP assays is essential to further explore the role of DBP in physiology and diseases.

The Role of Vitamin D Binding Protein, Total and Free 25-Hydroxyvitamin D in Diabetes

Vitamin D is important for bone health, but may also have extra-skeletal effects. Vitamin D and its binding protein DBP have immunological effects and may therefore be important in the development of type 1 diabetes (T1DM), and low serum levels of 25-hydroxyvitamin D (25(OH)D) are associated with later development of type 2 diabetes (T2DM). However, it has so far been difficult to convincingly show an effect of vitamin D supplementation on prevention or treatment of diabetes. The serum level of 25(OH)D has traditionally been used as a marker of a subject's vitamin D status. This measurement includes both 25(OH)D bound to DBP and albumin as well as the free from of 25(OH)D. However, according to the free hormone hypothesis, the free form is the biologically active. Previously the free form of 25(OH)D had to be calculated based on measurements of 25(OH)D, DBP, and albumin, but recently a method for direct measurement of free 25(OH)D has become commercially available. This is important in clinical conditions where the amount of DBP is affected, and has caused a renewed interest in which vitamin D metabolite to measure in clinical situations. In the present review the relations between DBP, total and free 25(OH)D in T1DM and T2DM are described.

Impact of Vitamin D Status in Chronic Liver Disease

BACKGROUND

Vitamin D deficiency is extremely common in chronic liver disease (CLD) patients. Up to 93% of these patients have some degree of vitamin D insufficiency. Liver plays an important role in the metabolism and pleiotropic functions of vitamin D. Vitamin D deficiency has been associated with increased mortality, bacterial infections, portal hypertension complications, and fibrosis severity. We aimed to determine the impact of vitamin D level in CLD.

METHODS

One hundred fifty individuals consisting of 75 cirrhotic patients (cases) and 75 respective attendants (controls) were enrolled between July 2015 and July 2017. A detailed clinical and laboratory evaluation was done along with estimation of vitamin D level. Unpaired t-test and analysis of variance was used to compare difference in the level of continuous variables between different groups. Linear regression analysis was performed to analyze the correlation between vitamin D deficiency and severity of liver disease.

RESULTS

The age of patients ranged from 18 years to 69 years with mean of 48.85 ± 13.6 years in the case group and 46.57 ± 17.24 years in the control group. Out of 75 CLD patients, vitamin D deficiency (<20 ng/dl) was found in 31 (41.4%) patients, out of which 14(18.7%) suffered from severe vitamin D deficiency (<10 ng/ml). On applying analysis of variance test, there was significant difference in vitamin D level and serum albumin and serum bilirubin (P < 0.05). On linear regression, vitamin D level showed significant negative correlation with Child-Pugh score (r = -0.7379, P < 0.0001) and Model For End-Stage Liver Disease score (r = -0.6671, P < 0.0001).

CONCLUSION

Our study concluded that CLD is associated with a significantly low level of vitamin D, which was independent to patient's gender, body mass index, residence, and education level. The findings of our study suggest that awareness of serum vitamin D level in patients with CLD is important. Further studies are required to validate the importance of vitamin D levels and impact of vitamin D supplementation on CLD.

The Vitamin D Binding Protein and Inflammatory Injury: A Mediator or Sentinel of Tissue Damage?

Neutrophils are the most abundant type of white blood cell in most mammals including humans. The primary role of these cells is host defense against microbes and clearance of tissue debris in order to facilitate wound healing and tissue regeneration. The recruitment of neutrophils from blood into tissues is a key step in this process and is mediated by numerous different chemoattractants. The neutrophil migratory response is essential for host defense and survival, but excessive tissue accumulation of neutrophils is observed in many inflammatory disorders and strongly correlates with disease pathology. The vitamin D binding protein (DBP) is a circulating multifunctional plasma protein that can significantly enhance the chemotactic activity of neutrophil chemoattractants both in vitro and in vivo. Recent in vivo studies using DBP deficient mice showed that DBP plays a larger and more central role during inflammation since it induces selective recruitment of neutrophils, and this cofactor function is not restricted to C5a, as prior in vitro studies indicated, but can enhance chemotaxis to many chemoattractants. DBP also is an extracellular scavenger for actin released from damaged/dead cells and formation of DBP-actin complexes is an immediate host response to tissue injury. Recent in vitro evidence indicates that DBP bound to G-actin, and not free DBP, functions as an indirect but essential cofactor for neutrophil migration. DBP-actin complexes always will be formed regardless of what initiated an inflammation, since release of actin from damaged cells is a common feature in all types of injury and DBP is abundant and ubiquitous in all extracellular fluids. Indeed, these complexes have been detected in blood and tissue fluids from both humans and experimental animals following various forms of injury. The published data strongly supports the premise that DBP-actin complexes are the functional neutrophil chemotactic cofactor that enhances neutrophil chemotaxis in vitro and augments neutrophilic inflammation in vivo. This review will assess the fundamental role of DBP in neutrophilic inflammation and injury.

Immunomodulatory Effect of Vitamin D and Its Potential Role in the Prevention and Treatment of Type 1 Diabetes Mellitus-A Narrative Review

Type 1 diabetes mellitus is a chronic autoimmune disease associated with degeneration of pancreatic β-cells that results in an inability to produce insulin and the need for exogenous insulin administration. It is a significant global health problem as the incidence of this disorder is increasing worldwide. The causes are still poorly understood, although it certainly has genetic and environmental origins. Vitamin D formed profusely in the skin upon exposure to sunlight, as well as from dietary sources, exhibits an immunomodulatory effect based on gene transcription control. Indeed, vitamin D can downregulate mechanisms connected with adaptive immunity, induce immunological tolerance and decrease auto-aggression-related inflammation. These properties provide the basis for a preventive and therapeutic role of vitamin D. As many studies have demonstrated, appropriate supplementation with vitamin D reduces the risk of autoimmune diseases, including type 1 diabetes mellitus, and alleviates disease symptoms in patients. The aim of this narrative review is to present the molecular mechanisms for the vitamin D immunomodulatory effect as well as review human clinical studies on the use of vitamin D as adjuvant therapy in type 1 diabetes mellitus.

Vitamin D assays and the definition of hypovitaminosis D: results from the First International Conference on Controversies in Vitamin D

The First International Conference on Controversies in Vitamin D was held in Pisa, Italy, 14-16 June 2017. The meeting's purpose was to address controversies in vitamin D research, review the data available, to help resolve them, and suggest a research agenda to clarify areas of uncertainty. The serum 25-hydroxyvitamin D [25(OH)D] concentration [i.e. the sum of 25(OH)D3 and 25(OH)D2 ] remains the critical measurement for defining vitamin D status. Assay variation for 25(OH)D has contributed to the current chaos surrounding efforts to define hypovitaminosis D. An essential requirement to develop a consensus on vitamin D status is that measurement of 25(OH)D and, in the future, other potential vitamin D biomarkers [e.g. 1α,25(OH)2 D3 , 3-epi-25(OH)D, 24,25(OH)2 D3, vitamin D-binding protein, free/bioavailable 25(OH)D and parathyroid hormone] be standardized/harmonized, to allow pooling of research data. Vitamin D Standardization Program tools are described and recommended for standardizing 25(OH)D measurement in research. In the future, similar methodology, based on National Institute for Standards and Technology standard reference materials, must be developed for other candidate markers of vitamin D status. Failure to standardize/harmonize vitamin D metabolite measurements is destined to promulgate continued chaos. At this time, 25(OH)D values below 12 ng ml-1 (30 nmol l-1 ) should be considered to be associated with an increased risk of rickets/osteomalacia, whereas 25(OH)D concentrations between 20 ng ml-1 and 50 ng ml-1 (50-125 nmol l-1 ) appear to be safe and sufficient in the general population for skeletal health. In an effort to bridge knowledge gaps in defining hypovitaminosis D, an international study on rickets as a multifactorial disease is proposed.

Vitamin D in individuals before onset of rheumatoid arthritis - relation to vitamin D binding protein and its associated genetic variants

Background

Vitamin D has been implicated as being involved in the aetio-pathogenesis of several autoimmune diseases including rheumatoid arthritis (RA). Previous studies present contradictory results. Vitamin D binding protein (DBP), the major transport protein, is also involved in various inflammatory processes. The aim of this study was to investigate the relationship between circulating levels of 25-hydroxyvitamin D [25(OH) D], DBP and polymorphisms in group-specific component (GC) in pre-symptomatic individuals and matched controls within prospective cohorts of the Northern Sweden.

Methods

Blood samples donated to the Medical Biobank prior to the onset of symptoms of RA (n = 515, mean [SD] time before the onset of symptoms 6.2 [9.3] years) and from matched (2:1) population-based controls (n = 267) were used. Plasma 25(OH) vitamin D levels were analyzed using liquid chromatography tandem-mass spectrometry and DBP levels were analyzed using enzyme-linked immunosorbent assay. GC polymorphisms (rs4588 and rs7041) were analyzed with TaqMan assays (Applied Biosystems).

Results

Levels of 25(OH) D or DBP were not statistically different between pre-symptomatic individuals and controls in a crude, or a multiple-adjusted logistic regression model. However, an increased risk for future RA was found in females of DBP (OR 1.014 [95%CI 1.001-1.028]) per 10 mg/L adjusted for carriage of the minor allele of rs4588, in a multiple-adjusted model (p < 0.05).

Conclusions

This study indicated that vitamin D is not associated with the future risk of RA although increasing levels of DBP were however, associated with an increased risk of disease in females carrying the minor allele of a DBP encoding SNP.

Determination of Free 25(OH)D Concentrations and Their Relationships to Total 25(OH)D in Multiple Clinical Populations

CONTEXT

The optimal measure of vitamin D status is unknown.

OBJECTIVE

To directly measure circulating free 25-hydroxyvitamin D [25(OH)D] concentrations and relationships to total 25(OH)D in a clinically diverse sample of humans.

DESIGN

Cross-sectional analysis.

SETTING

Seven academic sites.

PATIENTS

A total of 1661 adults: healthy (n = 279), prediabetic (n = 479), outpatients (n = 714), cirrhotic (n = 90), pregnant (n = 20), nursing home resident (n = 79).

INTERVENTIONS

Merge research data on circulating free 25(OH)D (directly-measured immunoassay), total 25(OH)D (liquid chromatography/tandem mass spectrometry), D-binding protein [DBP; by radial (polyclonal) immunodiffusion assay], albumin, creatinine, intact parathyroid hormone, and DBP haplotype.

MAIN OUTCOME MEASURES

Distribution of free 25(OH)D (ANOVA with Bonferroni correction for post hoc comparisons) and relationships between free and total 25(OH)D (mixed-effects modeling incorporating clinical condition, DBP haplotype with sex, race, estimated glomerular filtration rate (eGFR), body mass index (BMI), and other covariates).

RESULTS

Free 25(OH)D was 4.7 ± 1.8 pg/mL (mean ± SD) in healthy persons and 4.3 ± 1.9 pg/mL in outpatients, with levels of 0.5 to 8.1 pg/mL and 0.9 to 8.1 pg/mL encompassing 95% of healthy persons and outpatients, respectively. Free 25(OH)D was higher in patients with cirrhosis (7.1 ± 3.0 pg/mL; P < 0.0033) and nursing home residents (7.9 ± 2.1 pg/mL; P < 0.0033) than in other groups and differed between whites and blacks (P < 0.0033) and between DBP haplotypes (P < 0.0001). Mixed-effects modeling of relationships between free and total 25(OH)D identified clinical conditions (patients with cirrhosis > nursing home residents > patients with prediabetes > outpatients > pregnant women) and BMI (lesser effect) as covariates affecting relationships but not eGFR, sex, race, or DBP haplotype.

CONCLUSIONS

Total 25(OH)D, health condition, race, and DBP haplotype affected free 25(OH)D, but only health conditions and BMI affected relationships between total and free 25(OH)D. Clinical importance of free 25(OH)D needs to be established in studies assessing outcomes.