Vitamin D binding protein is lower in infertile patients compared to fertile controls: a case control study

Vitamin D binding protein correlate with estrogen increase after administration of human chorionic gonadotropin but do not affect ovulation, embryo, or pregnancy outcomes

Background

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.

Design

Post-hoc analysis of a prospective observational cohort.

Setting

Single-center study.

Participants

2569 women receiving embryo transfer.

Intervention

None.

Main outcome measures

The main outcomes were oocyte and embryo quality as well as pregnancy outcomes.

Results

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.

Conclusion

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.

Identification of a Single Nucleotide Polymorphism of Vitamin D Receptor (VDR) and Vitamin D Binding Protein (VDBP) Gene and Its Dysregulated Pathway Through VDR-VDBP Interaction Network Analysis in Vitamin D-Deficient Infertile Females

INTRODUCTION

The prevalence of female infertility in Pakistan is currently estimated at 22%, and emerging research suggests that vitamin D (VD) deficiency (VDD) may play a significant role in influencing female fertility. The focus of this study was to investigate the single nucleotide polymorphism (SNP) patterns within the VD binding protein (VDBP). The study aimed to explore dysregulated pathways and gene enrichment through an interaction network analysis, specifically focusing on the interplay between the VD receptor (VDR) and VDBP in females experiencing unexplained infertility (UI) coupled with VDD.

METHODS

A cross-sectional study was conducted on VD-deficient, fertile, and UI female subjects. VDBP and VDR were assessed by enzyme-linked immunoassay and genotyping performed. FunRich (version 3.1.3; http://funrich.org/index.html) was employed for analysis of the identified proteins: VDR and VDBP and with their mapped gene datasets, gene enrichment, and protein-protein interaction (PPI) network.

RESULTS

The mean VD and VDR values of infertile females were significantly lower than those of fertile females. VDBP in infertile females (median (IQR)): 296.05 (232.58-420.23)) was lower than that of fertile females (469.9 (269.57-875.55), (p=0.01)). On sequence analysis, a mutation rs 4588 SNP (Thr 436 Lys) was found in exon 11 of the VDBP gene of UI females, but no mutation in exons 8 and 9 of the VDR gene, with some insignificant intronic variants, was observed. The proteins such as plasma membrane estrogen receptor signaling pathway (p < 0.001), VDR, SMAD3, NCOR1, CREBBP, NCOA1, STAT1, GRB2, PPP2CA, TP53, and NCOA2 were enriched after biological pathway grouping when VDR was made the focused gene and directly interacting with VDBP.

CONCLUSION

The females with UI exhibited significantly low VD, VDBP, and VDR. The plasma membrane estrogen receptor signaling pathway was enriched in VDD infertile females.

Investigation of the Changes in Concentrations of Vitamin D-Binding Protein and Lactoferin in Plasma and Peritoneal Fluid of Patients with Endometriosis

An evaluation of the association between the concentrations of vitamin D-binding protein and lactoferrin in the plasma and peritoneal fluid may facilitate the elucidation of molecular mechanisms in endometriosis. Vitamin D-binding protein and lactoferrin concentrations were measured by ELISA in plasma and peritoneal fluid samples from 95 women with suspected endometriosis as classified by laparoscopy into groups with (n = 59) and without endometriosis (n = 36). There were no differences (p > 0.05) in the plasma and peritoneal fluid concentrations of vitamin D-binding protein and lactoferrin between women with and without endometriosis. In women with endometriosis, there was a significant correlation between plasma and peritoneal fluid vitamin D-binding protein concentrations (r = 0.821; p = 0.000), but there was no correlation between lactoferrin concentrations in those compartments (r = 0.049; p > 0.05). Furthermore, in endometriosis, lactoferrin was found to correlate poorly with vitamin D-binding protein (r= -0.236; p > 0.05) in plasma, while in the peritoneal fluid, the correlation between those proteins was significant (r = 0.399; p = 0.002). The characteristic properties of vitamin D-binding protein and lactoferrin and the associations between their plasma and peritoneal fluid concentrations found in women with endometriosis may provide a novel panel of markers to identify high-risk patients in need of further diagnostic measures.

Total and free vitamin D status among apparently healthy adults living in Duhok Governorate

Serum total 25‐OHD is a main marker of vitamin D which represents the intake and sunlight exposure. Free form of 25‐OHD, the small fraction not bound to a transporter protein has been incorporated as a new marker. This cross-sectional study aimed to evaluate the impact of several factors on total and free vitamin D levels in healthy subjects and to find out if the free form of vitamin D could be a better representative of the body’s vitamin D status. Total and free 25‐OHD were analyzed by ELISA method in a blood sample collected from 391 apparently healthy volunteers (219 female and 172 Male) from Duhok Governorate/Iraq population. Total and free 25‐OHD levels were increased proportionally to BMI with lower values seen in the underweight group, also a significant gender differences in total D3 level with higher values in males (23.90 ± 16.41) ng/ml than females (21.24 ± 15.65) ng/ml was observed. Total and Free 25‐OHD levels were significantly associated with ages, their deficiency most frequent occurs in the younger ages between (16–25) years old. Smokers had higher level of Total 25‐OHD (26.95 ± 19.01) ng/ml and Free 25‐OHD (9.47 ± 4.94) pg/ml than nonsmokers (22.14 ± 14.59) ng/ml and (7.87 ± 4.32) pg/ml respectively. A significant increase in Free 25‐OHD level in the veiled women (9.12 ± 4.64) ng/ml than unveiled (6.16 ± 3.73) ng/ml with a significant positive correlation between Free 25‐OHD level and dress style was also seen. 30% and 33% of the participants whom their daily exposure to sunlight for 30 min and > 1 h respectively were severe deficient in total 25‐OHD. 95% of the participants who had Abnormally low level of free D were exposed for ≥ 30 min to sunlight. Daily exposure to sunlight was negatively associated with Free 25‐OHD level.

Does the Serum Vitamin D Status and its Possible Effect on Serum Anti-Müllerian Hormone Levels Predict Fertility in Premenopausal Women?

Context:

Evidence suggests that serum Vitamin D level influences female reproduction. However, clinical studies have reported conflicting evidence on the effect of serum Vitamin D levels on serum Anti-Müllerian hormone (AMH), with little evidence in African women.

Aim:

The study aimed to compare the relationship between serum Vitamin D and serum AMH among infertile and fertile women.

Settings and Design:

This comparative cross-sectional study analyzed data from 170 premenopausal women; 81 infertile, and 89 fertile women attending a Nigerian tertiary hospital between March and June 2019.

Materials and Methods:

Serum AMH and 25-hydroxyvitamin D (25(OH) Vitamin D) concentrations were analysed using enzyme-linked immunosorbent assay.

Statistical Analysis:

Statistical analysis was done using SPSS version 25 for windows. Categorical variables were summarized in frequencies and proportions while continuous variables were summarized in means ± standard deviation and median (interquartile range). The association was explored using linear regression. The level of significance was set at 0.05.

Results:

The prevalence of Vitamin D deficiency (<20 ng/ml) in infertile women and fertile women was 16% and 18%, respectively. There was no difference in serum Vitamin D levels between infertile and fertile women in this study after controlling for age and body mass index (BMI) (P = 0.186). There was no association between serum 25(OH) Vitamin D and serum AMH in infertile (B = 0.002; P = 0.474) and fertile women (B = ‒0.002; P = 0.522) after adjusting for age and BMI.

Conclusion:

Infertile and fertile women had similar serum Vitamin D levels and there was no relationship between serum Vitamin D and serum AMH in both infertile and fertile women.

Vitamin D-Binding Protein in Pregnancy and Reproductive Health

Vitamin D-binding protein (VDBP), the main carrier of vitamin D, has recently been implicated in reproductive health and pregnancy outcomes including endometriosis, polycystic ovary syndrome (PCOS), pre-eclampsia, and gestational diabetes mellitus (GDM). Improved methods for measuring VDBP and an increased understanding of its role in biological processes have led to a number of newly published studies exploring VDBP in the context of pregnancy. Here, we synthesize the available evidence regarding the role of VDBP in reproductive health and pregnancy, and we highlight areas requiring further study. Overall, low levels of maternal serum VDBP concentrations have been associated with infertility, endometriosis, PCOS and spontaneous miscarriage, as well as adverse pregnancy outcomes including GDM, pre-eclampsia, preterm birth and fetal growth restriction. However, increased VDBP concentration in cervicovaginal fluid has been linked to unexplained recurrent pregnancy loss and premature rupture of membranes. Some genetic variants of VDBP have also been associated with these adverse outcomes. Further studies using more accurate VDBP assays and accounting for ethnic variation and potential confounders are needed to clarify whether VDBP is associated with reproductive health and pregnancy outcomes, and the mechanisms underlying these relationships.

Vitamin D and metabolic disturbances in polycystic ovary syndrome (PCOS): A cross-sectional study

OBJECTIVE

To compare vitamin D status in women with PCOS versus fertile women and subsequently evaluate the association between vitamin D status and metabolic disturbances in PCOS women.

METHODS

We conducted a cross-sectional comparison study of 639 women with PCOS and 449 fertile women. Serum 25-hydroxyvitamin D (25(OH)D) was stratified into a severe deficient (< 25 nmol/l), insufficient (25-50 nmol/l), moderate (50-75 nmol/l) and adequate (> 75 nmol/l) status. The main outcome measures were the difference in vitamin D status between PCOS and fertile women, and the association between serum 25(OH)D and metabolic disturbances in PCOS women only.

RESULTS

Serum 25(OH)D was significantly lower in PCOS women compared to fertile controls (mean 25(OH)D of 49.0 nmol/l versus 64.5 nmol/l). An adjusted significant difference was seen between serum 25(OH)D and homeostasis model assessment (HOMA-IR) (β = 0.76; 95% CI: 0.63-0.91; p < 0.01), HDL-cholesterol (β = 0.20; 95% CI: 0.05-0.60, p < 0.01) and apolipoprotein A1 (β = 26.2; 95% CI: 7.5-45.0, p < 0.01) between the highest vitamin D group compared to the lowest vitamin D group.

CONCLUSIONS

This study demonstrates that women with PCOS have a significantly lower serum 25(OH)D compared to fertile controls. A compromised vitamin D status in PCOS women is associated with a higher HOMA-IR and an unfavourable lipid profile. Large randomized controlled trials are necessary to explore the causality of this linkage.

Deconvoluting the Biological Roles of Vitamin D-Binding Protein During Pregnancy: A Both Clinical and Theoretical Challenge

The teleological purpose of an ongoing pregnancy is to fulfill its fundamental role of a successful, uncomplicated delivery, in conjunction with an optimal intrauterine environment for the developing fetus. Vitamin D metabolism is adapted to meet both these demands during pregnancy; first by stimulation of calcium absorption for adequate intrauterine bone mineral accrual of the fetus, and second, by enhancing systemic and local maternal tolerance to paternal and fetal alloantigens. Vitamin D-binding protein (VDBP) is one of the key biomolecules that optimize vitamin D homeostasis and also contributes as an immune regulator for a healthy, ongoing pregnancy. In this regard, recent results indicate that dysregulation of VDBP equilibrium could be a risk factor for adverse fetal, maternal, and neonatal outcomes, including preeclampsia, preterm birth, and gestational diabetes. Moreover, it has been hypothesized to be also implicated in the interpretation of vitamin D status in the pregnant state. The aim of this review is to assess available literature regarding the association of VDBP with clinical outcomes during pregnancy, as a potential biomarker for future clinical practice, with a discourse on current knowledge gaps and future research agenda.