BACKGROUND: Numerous studies have examined whether vitamin D is associated with gestational diabetes mellitus (GDM). Nevertheless, it is still challenging to determine the causality, due to a number of shortcomings in observational research and randomized controlled trials.
OBJECTIVE: Mendelian randomization (MR) with two samples was conducted to investigate the potential causative association between 25-hydroxyvitamin D (25(OH)D), vitamin D binding protein (VDBP) and GDM risk.
METHODS: Publicly accessible summary data from independent cohorts were used for two-sample MR. For 25(OH)D, we obtained data from UK Biobank, IEU and EBI, then performed a meta-analysis to enhance the statistical power (via METAL); for VDBP, data were obtained from the INTERVAL study; for GDM, data were obtained from FinnGen. The inverse variance weighted (IVW) approach was performed as the main analysis, together with several sensitivity analyses, such as MR-Egger, maximum likelihood, weighted median, and weighted mode.
RESULTS: The IVW results revealed a weak negative causal connection between 25(OH)D and GDM risk [OR (95% CI) = 0.71 (0.50, 0.99), p = 0.046]. However, the causal association was unstable according to sensitivity analyses, and Cochran\'s Q test revealed significant heterogeneity. After removing BMI-related IVs, the causal association between 25(OH)D and GDM disappeared [OR (95% CI) = 0.76 (0.55, 1.06), p = 0.101]. In addition, our study found no proof to support the assumption that VDBP level was related to GDM risk causally [OR (95% CI) = 0.98 (0.93, 1.03), p = 0.408].
CONCLUSIONS: According to this study, a weak negative causal association between 25(OH)D and GDM risk was found, while we had little proof to support the link between VDBP and GDM. To further explore whether total or free 25(OH)D levels and GDM are causally related, GWAS data with an emphasis on women of reproductive age and other ethnic groups are required.

Atopic diseases, including atopic dermatitis (AD) and allergic asthma (AA), are characterized by complex immune responses involving various T cells subsets and their cytokine profiles. It is assumed that single nucleotide polymorphisms (SNPs) in the Vitamin D receptor (VDR) gene and the Vitamin D-binding protein (GC) gene are related to the action of Vitamin D and, consequently, play a role in regulating the immune response. However, there is not enough data to unequivocally support the hypothesis about the relationship between T cells profile and VDR or GC SNPs. Two hundred sixty-six subjects (aged > 18 years) were involved in the study: 100 patients with mild or moderate AD, 85 patients with mild or moderate AA, and 81 healthy individuals. Blood cell counts were determined by standard methods. Flow cytometric analysis was used to evaluate CD4+ T-helper (Th) cell subtypes: Th2, Th1, Th17, and T regulatory (Treg) cells in peripheral blood. Measurements of cytokines, total immunoglobulin E (IgE), and Vitamin D levels in serum were evaluated by ELISA. Significantly higher levels of Th1, Th2, and Th17 cells, along with lower levels of Tregs, were found in patients with atopic diseases compared to healthy individuals. Additionally, higher serum levels of interleukin (IL) 5, IL-17A, and transforming growth factor-β1 (TGF-β1), as well as lower levels of IL-10, were observed in patients with atopic diseases than in control. The study established associations between VDR SNPs and immune profiles: the AA genotype of rs731236 was associated with increased Th2 and Th17 cells and a higher Th1/Th2 ratio; the GG genotype of rs731236 was linked to decreased serum IL-10 and TGF-β1 levels; and the TT genotype of rs11168293 was associated with increased IL-10 levels. Additionally, the GG genotype of GC gene SNP rs4588 was associated with reduced Th2 and Th17 lymphocytes, while the TT genotype of rs4588 was linked to decreased IL-10 levels. Furthermore, the CC genotype of rs7041 was associated with higher levels of Th2, Th17, IL-10, and IL-35, as well as reduced levels of TGF-β1, while the GG genotype of rs3733359 was associated with reduced IL-10 levels. In conclusion, our study demonstrates that the Vitamin D receptor gene single nucleotide polymorphisms rs731236 and rs11168293, along with polymorphisms in the Vitamin D-binding protein gene (rs4588, rs7041, rs3733359), are significantly associated with variations in T cell profiles in atopy. These variations may play a crucial role in promoting inflammation and provide insight into the genetic factors contributing to the pathogenesis of atopy.

Vitamin D plays a role in inflammatory skin disease, but the exact mechanisms and the clinical significance remain unclear. According to the free hormone hypothesis, it is the free concentration of 25-hydroxy vitamin D (25(OH)D) that is biologically active. Vitamin D-binding protein (DBP) acts as the major transporter of vitamin D in the circulation, and DBP concentration defines the free 25(OH)D levels. DBP levels are elevated in various inflammatory conditions, including psoriasis. Narrowband-ultraviolet B (NB-UVB) is the most widely used phototherapy and is an established first-line treatment for psoriasis and atopic dermatitis (AD), often used before proceeding to systemic treatment. The aim of this study was to investigate the influence of NB-UVB phototherapy on DBP and high-sensitivity C-reactive protein (hsCRP) levels, as markers of systemic inflammation, in inflammatory skin disease. Thirty adults (psoriasis (n = 20) and AD (n = 10)) were treated with NB-UVB. Serum DBP, hsCRP, total and free 25(OH)D, and 1,25-dihydroxy vitamin D (1,25(OH)2D) were measured before and after NB-UVB. Disease severity was assessed with Psoriasis Area and Severity Index (PASI), SCORing Atopic Dermatitis (SCORAD), and Visual Analogue Scale (VAS). DBP decreased in psoriasis patients and varied with no clear trend in AD patients. HsCRP decreased in both groups, but this did not reach statistical significance. PASI, SCORAD, and VAS improved, and vitamin D levels increased after NB-UVB. Sub-analysis indicated a better response to NB-UVB for patients with vitamin D deficiency and insufficiency compared to vitamin D-sufficient patients. The decrease in DBP after NB-UVB in psoriasis patients suggests a potential systemic anti-inflammatory effect of phototherapy. Measurement of vitamin D levels may potentially serve as a tool to identify patients who would derive the greatest benefit from NB-UVB phototherapy.

The severity of autism spectrum disorder (ASD) shows wide variations, though the reason remains unclear. Vitamin D (VitD) deficiency is considered a risk factor for ASD and its supplementation was reported to reduce symptom severity. Since VitD, either synthesized in the skin or absorbed from the food, is transported to the liver by the vitamin D binding protein (DBP), we have analyzed DBP genetic polymorphisms [rs7041 (A/C), rs4588 (G/T), and rs3755967 (C/T)] affecting DBP function [Case = 411; Control = 397], levels of plasma 25(OH)D and DBP [Case = 25; Control = 26], and DBP mRNA expression [Case = 74; Control = 44] in a group of Indo-Caucasoid ASD probands and neurotypical subjects. ASD probands with rs7041\'CC\', rs4588 \'TT\', and rs3755967 \'TT\' genotypes exhibited higher scores for a few traits. Scores for Imitation and Listening response were also higher in the presence of the \"A-T\" haplotype (rs7041-rs4588). Plasma 25(OH)D and DBP levels as well as DBP mRNA expressions were significantly lower in the ASD probands as compared to the neurotypical subjects. We infer that DBP deficiency, in the presence of risk genetic variants, could be one of the reasons for the reported 25(OH)D deficiency of the ASD probands.

Bevezetés: A krónikus vesebetegség gyakran jár együtt súlyos D-vitamin-hiánnyal. Kimutatása a szérum 25-hidroxi-D-vitamin-szintjének mérése alapján történik, amelyhez a rutinban főként az immunoassay-t alkalmazzák. Ennek hátránya, hogy az eredmény függ a minta D-vitaminkötő és egyéb fehérjéinek szintjétől is. Célkitűzés: Egyes szérumfehérjék és a D-vitamin-ellátottság közötti kapcsolat tanulmányozása D3-vitamin-naiv, krónikus vesebetegekben. Módszerek: 103 beteg (30 nem dializált, 36 peritonealis dializált és 37 hemodializált) szérumában mértük meg az összes 25-hidroxivitamin-D, a kalcium, az összfehérje, az albumin, a D-vitaminkötő fehérje és az elektroforetikus fehérjefrakciók szintjét. Az intakt parathormon koncentrációt 2. és 3. generációs módszerrel is meghatároztuk. Eredmények: Elégséges D-vitamin-ellátottságot egy esetben sem igazoltunk. A nem dializáltak 87%-a, a hemodializáltak 86%-a, a peritonealisan dializált betegek mindegyike D-vitamin-hiányos volt. A dializáltakban a referenciatartományon kívül eső alfa-1- (18%), béta- (22%) globulin és az albumin/globulin hányados (19%) szignifikánsan ritkábban fordult elő, mint a dialízisben nem részesülő esetekben, szemben a D-vitaminkötő fehérjével (37%). A peritonealisan kezeltekben szignifikánsan alacsonyabbnak bizonyult az összes 25-hidroxivitamin-D, kalcium és összfehérje, gamma-globulin, albumin/globulin hányados értéke és szignifikánsan magasabbnak az alfa-1,2-globulin és a D-vitaminkötő fehérje szintje. Csak a peritonealisan dializált betegekben igazolódott az összes 25-hidroxivitamin-D és az intakt parathormon között szignifikáns negatív korreláció mindkét módszerrel mérve, míg ez a hemodializált betegek esetében csak 3. generációs módszerrel igazolódott. Következtetés: Krónikus vesebetegekben a gyakori D-vitamin-hiány súlyosbodik a dialízis után, különösen a peritonealisan dializáltakban, ezért nekik nagyobb dózis D3-vitamin adása szükséges. A magas alfa-1-globulin-szint D-vitamin-hiánnyal jár együtt mind a dializált, mind a nem dializált esetekben. A peritonealisan dializáltakban a D-vitaminkötő fehérje és az egyéb szérumfehérjék szintjei gyakrabban eltérnek a referenciatartománytól, mint a hemodializáltakban. A szekunder hyperparathyreosis kezelésében a natív D-vitamin adásának is jelentősége van. Ez a peritonealis dialízisben mindkét intaktparathormon-módszerrel, de hemodialízisben csak a 3. generációs módszerrel igazolódott, ezért hemodialízisben ennek a módszernek a használata javasolt. Orv Hetil. 2024; 165(30): 1154–1165.

OBJECTIVE: Vitamin D deficiency and variations in the vitamin D binding protein (VDBP) gene may play a role in the development of Polycystic ovary syndrome (PCOS). This study aims to investigate the association of the rs4588 polymorphism with PCOS in Iranian women, as well as its association with infertility and recurrent pregnancy loss (RPL) in these patients.
RESULTS: The analysis revealed statistically significant differences in the distributions of genotypes and alleles of the rs4588 polymorphism among the three groups (p < 0.0001). The AC genotype and A allele showed an association with an elevated risk of PCOS and infertility. In this study, no association was found between genotypes and alleles of the rs4588 polymorphism and the risk of RPL in women with PCOS. Subjects with the AA or AC genotype exhibited significantly higher levels of LDL compared to those with the CC genotype.

Vitamin D (vitD) deficiency (25-hydroxy-vitamin D < 50 nmol/L) is common in pregnancy and associated with an increased risk of adverse pregnancy outcomes. High-dose vitD supplementation is suggested to improve pregnancy health, but there is limited knowledge about the effects on placental vitD transport and metabolism and the vitD status of newborns. Comparing the current standard maternal supplementation, 10 µg/day to a 90 µg vitD supplement, we investigated placental gene expression, maternal vitD transport and neonatal vitD status. Biological material was obtained from pregnant women randomized to 10 µg or 90 µg vitD supplements from week 11-16 onwards. Possible associations between maternal exposure, neonatal vitD status and placental expression of the vitD receptor (VDR), the transporters (Cubilin, CUBN and Megalin, LRP2) and the vitD-activating and -degrading enzymes (CYP24A1, CYP27B1) were investigated. Maternal vitD-binding protein (VDBP) was determined before and after supplementation. Overall, 51% of neonates in the 10 µg vitD group were vitD-deficient in contrast to 11% in the 90 µg group. High-dose vitD supplementation did not significantly affect VDBP or placental gene expression. However, the descriptive analyses indicate that maternal obesity may lead to the differential expression of CUBN, CYP24A1 and CYP27B1 and a changed VDBP response. High-dose vitD improves neonatal vitD status without affecting placental vitD regulation.

Vitamin D-binding protein (DBP), also known as Gc-globulin, is a protein that affects several physiological processes, including the transport and regulation of vitamin D metabolites. Genetic polymorphisms in the DBP gene have a significant impact on vitamin D levels and may have implications for disease risk. DBP polymorphisms are linked to differential immune responses, which could influence the onset of juvenile diseases. This narrative review examines the various roles of DBP, with a focus on bone health, immunological regulation, and lipid metabolism in children. Chronic disorders affected by DBP polymorphisms include bone abnormalities, autoimmune diseases, cardiovascular issues, childhood asthma, allergies, cystic fibrosis, acute liver failure, celiac disease, inflammatory bowel disease, and chronic kidney disease. Future research should focus on identifying the processes that underpin the many roles that DBP plays and developing customized therapeutics to improve health outcomes in the juvenile population.

UNASSIGNED: Vitamin D binding protein (DBP) might increase substantially after ovarian stimulation and hence could be associated with IVF/ICSI outcomes because it determines the fraction of free bioavailable 25(OH) vitamin D. In this study, we aim to determine whether DBP is associated with E2 level after ovarian stimulation and IVF/ICSI outcomes.
UNASSIGNED: Post-hoc analysis of a prospective observational cohort.
UNASSIGNED: Single-center study.
UNASSIGNED: 2569 women receiving embryo transfer.
UNASSIGNED: None.
UNASSIGNED: The main outcomes were oocyte and embryo quality as well as pregnancy outcomes.
UNASSIGNED: DBP concentration correlates with E2 on hCG day (=day of inducing ovulation with hCG; correlation coefficient r = 0.118, P<0.001) and E2 x-fold change to baseline level (r = 0.108, P<0.001). DBP is also positively correlated with total 25(OH)D (r = 0.689, R2 = 0.475, P<0.001) and inversely with free 25(OH)D (r=-0.424, R2=0.179, P<0.001), meaning that E2-stimulated DBP synthesis results in a decrease of free 25(OH)D during ovarian stimulation. However, such alteration does not affect IVF/ICSI outcomes when considering confounding factors, such as the number and quality of oocytes nor embryo quality as well as pregnancy outcomes.
UNASSIGNED: DBP concentration correlates with the degree of E2 increase after ovarian stimulation. DBP is also positively correlated with total 25(OH)D and inversely with free 25(OH)D, suggesting that the proportion of free 25(OH)D decreases during ovarian stimulation caused by E2-stimulated DBP synthesis. However, such alteration does not affect clinical IVF/ICSI outcomes.

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.