Does maternal VDR FokI single nucleotide polymorphism have an effect on lead levels of placenta, maternal and cord bloods?

On-going consequences of in utero exposure of Pb: An epigenetic perspective

Epigenetic modifications by toxic heavy metals are one of the intensively investigated fields of modern genomic research. Among a diverse group of heavy metals, lead (Pb) is an extensively distributed toxicant causing an immense number of abnormalities in the developing fetus via a wide variety of epigenetic changes. As a divalent cation, Pb can readily cross the placental membrane and the fetal blood brain barrier leading to far-reaching alterations in DNA methylation patterns, histone protein modifications and micro-RNA expression. Over recent years, several human cohorts and animal model studies have documented hyper- and hypo-methylation of developmental genes along with altered DNA methyl-transferase expression by in utero Pb exposure in a dose-, duration- and sex-dependent manner. Modifications in the expression of specific histone acetyltransferase enzymes along with histone acetylation and methylation levels have been reported in rodent and murine models. Apart from these, down-regulation and up-regulation of certain microRNAs crucial for fetal development have been shown to be associated with in utero Pb exposure in human placenta samples. All these modifications in the developing fetus during the prenatal and perinatal stages reportedly caused severe abnormalities in early or adult age, such as - impaired growth, obesity, autism, diabetes, cardiovascular diseases, risks of cancer development and Alzheimer's disease. In this review, currently available information on Pb-mediated alterations in the fetal epigenome is summarized. Further research on Pb-induced epigenome modification will help to understand the mechanisms in detail and will enable us to formulate safety guidelines for pregnant women and developing children.

Vitamin D Receptor Is a Sepsis-Susceptibility Gene in Chinese Children

Background

We designed an association study among 267 cases of children with sepsis and 283 healthy controls, by genotyping 9 variants in the VDR gene.

Material/Methods

This was a hospital-based, case-control, genetic association study. In addition to 3 genetic modes of inheritance, haplotype and interaction analyses were employed to examine the prediction of VDR gene for pediatric sepsis. Effect-size estimates are expressed as odds ratio (OR) and 95% confidence interval (CI).

Results

Two variants in the VDR gene, rs2107301 and rs2189480, were found to play a leading role in susceptibility to sepsis in children. The mutant homozygotes of rs2107301 (CC) and rs2189480 (CC) were associated with a reduced risk of sepsis compared with the corresponding wild homozygotes (OR: 0.44 and 0.43, 95% CI: 0.21–0.92 and 0.23–0.81, p: 0.03 and 0.009, respectively). The mutations of rs2107301-C and rs2189480-C alleles were associated with reduced sepsis risk. Haplotype C-C-C-C-C-T-C-A-G in the VDR gene was significantly associated with a 0.59-fold decreased risk of sepsis (95% CI: 0.12–0.76, p: 0.02). In the haplotype–phenotype analysis, significant association was noted for high-density lipoprotein, even after simulation correction (p_sim <0.05).

Conclusions

Taken together, our findings indicate that the VDR gene may be a sepsis-susceptibility gene in Chinese Han children.

Lead Affects Vitamin D Metabolism in Rats

A negative association between blood lead and vitamin D concentrations has been reported, however, experimental data on the effect of lead (Pb) on vitamin D metabolism is scarce. We investigated the effects of Pb on serum vitamin D metabolites, vitamin D activating enzymes and vitamin D receptor (VDR) in rats. Newborn Wistar rat pups were exposed to 0.2% Pb-acetate via their dams’ drinking water from post-natal day (PND) 1 to 21 and directly in drinking water until PND30. Serum 25-hydroxyvitamin D was analyzed with LC-MS/MS and 1,25-dihydroxyvitamin D with an immunoassay. Tissue expression of vitamin D activating enzymes and VDR were measured by Western blot and immunohistochemistry. Serum 25-hydroxyvitamin D was significantly decreased at both PND21 and PND30, whereas 1,25-dihydroxyvitamin D was decreased (p < 0.05) only at PND21 in the Pb-exposed rats. Expression of renal 1-α-hydroxylase was decreased by Pb only at PND21 (p < 0.05) but the brain 1-α-hydroxylase was not affected. Hepatic 25-hydroxylase expression was significantly decreased at PND21 but significantly increased at PND30 by Pb exposure. VDR expression in the brain was increased at both PND21 and PND30 (p < 0.05). These results suggest that Pb interferes with vitamin D metabolism by affecting the expression of its metabolizing enzymes.

Vitamin D receptor gene TaqI single nucleotide polymorphism is not associated with lead levels in maternal and umbilical cord blood

PURPOSE

We aimed to investigate the association of vitamin D receptor (VDR) gene TaqI single nucleotide polymorphism (SNPs) with serum lead (Pb) levels in maternal and umbilical cord blood.

MATERIALS AND METHODS

Eighty-one patients who lived in Konya, Turkey for the last 3 years and had delivery at Başkent University Konya Hospital in 2016 were included in this study. Venous blood samples were drawn from each volunteer immediately before giving birth to determine the maternal Pb levels and VDR SNPs. Additionally, umbilical cord blood samples were collected from the umbilical vein into tube with EDTA as an anticoagulant immediately after birth to determine Pb levels of the fetus.

RESULTS

The median level of Pb in the maternal blood was 29.00 (Interquartile Range (IQR) = 16.35) μg/L and the median Pb level in the cord blood was 22.50 (IQR = 9.75) μg/L. Blood Pb level of women living in the urban area was significantly higher than in those living in the rural area (Z = 2.118; p = .034). There was a very strong positive correlation between the Pb levels in the maternal blood and in the umbilical cord blood (ρ = 0.825, p < .001, respectively). Regarding VDR SNPs, "TT", "TC", and "CC" VDR TaqI genotypes were observed in 28 (34.6%), 45 (55.5%), and eight samples (9.9%), respectively. Pb levels in maternal and cord blood were higher in women with the "CC" VDR TaqI genotype; however, there was no statistically significant difference (p > .05).

CONCLUSIONS

Although women with the "CC" VDR TaqI genotype had higher maternal and cord blood Pb levels, this was statistically insignificant and therefore, VDR TaqI SNPs did not significantly affect maternal and umbilical cord blood Pb levels.