Prenatal lead exposure is associated with decreased cord blood DNA methylation of the glycoprotein VI gene involved in platelet activation and thrombus formation

Early-life lead exposure impairs neurodevelopment and later exposure affects the cardiovascular system. Lead has been associated with reduced global 5-methylcytosine DNA methylation, suggesting that lead toxicity acts through epigenetic mechanisms. The objective of this study is to clarify how early-life lead exposure alters DNA methylation of specific genes, using an epigenomic approach. We measured lead concentrations in urine [gestational week (GW), 8] and erythrocytes (GW 14), using inductively coupled plasma mass spectrometry, for 127 pregnant mothers recruited in the MINIMat food and supplementation cohort in rural Bangladesh. Cord blood DNA methylation was analyzed with the Infinium HumanMethylation450K BeadChip, and top sites were validated by methylation-sensitive high-resolution melt curve analysis. Maternal urinary lead concentrations (divided into quartiles) showed significant (after adjustment for false discovery rate) inverse associations with methylation at nine CpGs. Three of these sites were in the 5'-end, including the promoter, of glycoprotein IV (GP6); cg18355337 (q = 0.029, β = -0.30), cg25818583 (q = 0.041, β = -0.18), and cg23796967 (q = 0.047, β = -0.17). The methylation in another CpG site in GP6 was close to significant (cg05374025, q = 0.057, β = - 0.23). The erythrocyte lead concentrations (divided into quartiles) were also inversely associated with CpG methylation in GP6, although this was not statistically significant after false discovery rate adjustments. Eight CpG sites in GP6 constituted a differentially methylated region in relation to urinary lead (P = 0.005, q = 0.48) and erythrocyte lead (P = 0.007, q = 0.46). In conclusion, we found that moderate prenatal lead exposure appears to epigenetically affect GP6, a key component of platelet aggregation and thrombus formation, suggesting a novel link between early lead exposure and cardiovascular disease later in life.

Urinary iodine concentrations of pregnant women in rural Bangladesh: a longitudinal study

Iodine is an essential dietary element required for normal fetal growth and development. We aimed to explore intraindividual and interindividual variations in iodine intake in pregnant women and whether non-dietary factors might influence the intake. Iodine intake was assessed in 271 women, residing in Matlab, rural Bangladesh, by measuring their urinary iodine concentration (UIC) at gestational week (GW) 8, 14, 19, and 30 with inductively coupled plasma mass spectrometry. The women's UIC increased significantly during pregnancy (median 241 (GW8) and 300 μg/l (GW30)). About 6% of the women had insufficient iodine intake (UIC<150 μg/l) and 10% had excessive iodine intake (UIC≥500 μg/l) at all of their four sampling occasions. The women's UIC were dependent on their education, socio-economic status, and BMI, as well as the season of sampling and iodine concentrations in drinking water. Supplementation with a multi-micronutrient capsule, including 150 μg potassium iodine, increased the UIC in women with the lowest UIC (10th percentile) at GW30 but decreased the UIC in women with the highest UIC (90th percentile) at GW30. In conclusion, median UIC throughout pregnancy indicated adequate intake of iodine among pregnant women in Matlab, but, notably, consistently insufficient and excessive intake was also prevalent.

Maternal urinary iodine concentration up to 1.0 mg/L is positively associated with birth weight, length, and head circumference of male offspring

Adequate iodine status in early life is crucial for neurodevelopment. However, little is known about the effects of maternal iodine status during pregnancy on fetal growth. The present study investigated the potential impact of maternal iodine status during pregnancy on offspring birth size. This large prospective cohort study was nested in a Bangladeshi population-based randomized supplementation trial in pregnant women [MINIMat (Maternal and Infant Nutrition Interventions in Matlab)]. Urine samples obtained at 8 wk of gestation from 1617 women were analyzed for iodine and other elements, such as arsenic and cadmium, using inductively coupled plasma mass spectrometry. Anthropometric measurements at birth included weight, length, and head and chest circumference. Maternal urinary iodine concentrations (UICs) ranged from 0.020 to 10 mg/L, with a median of 0.30 mg/L. Below ∼1.0 mg/L, UIC was significantly positively associated with birth weight and length. Birth weight and length increased by 9.3 g (95% CI: 2.9, 16) and 0.042 cm (95% CI: 0.0066, 0.076), respectively, for each 0.1-mg/L increase in maternal UIC. No associations were observed between UIC and head or chest circumference. When we stratified the analyses by newborn sex, the positive associations between maternal UIC (<1 mg/L) and measurements of size at birth were restricted to boys, with no evidence in girls. Among boys, the mean weight, length, and head circumference increased by 70 g (P = 0.019), 0.41 cm (P = 0.013), and 0.28 cm (P = 0.031) for every 0.5-mg/L increase in maternal UIC. Maternal iodine status was positively associated with weight, length, and head circumference in boys up to ∼1 mg/L, which is well above the recommended maximum concentration of 0.5 mg/L. The associations leveled off at UIC ≥ 1 mg/L. Our findings support previous conclusions that the advantages of correcting potential iodine deficiency outweigh the risks of excess exposure.