Title : Placental transfer of essential micronutrients and toxic metals in occupationally exposed pregnant women - Implications in the pathogenesis of autism spectrum disorders
Abstract:
Background: Incidence of Autism Spectrum Disorders (ASD) in children as a neurodevelopmental abnormality is growing. Compounded by equivocal deductions from several genetic and environmental studies aimed at establishing its aetiology, it is becoming a global medical challenge. This work investigated placental transfer of some micronutrients (Cu, Zn, Ca, Mg, Se) and toxic (Cd, Pb) metals in occupationally vulnerable pregnant mothers as possible basis of neurodevelopmental abnormalities in children with ASD.
Method: 105 third trimester pregnant women comprising 50 occupationally exposed (cases) (27.68±5.57 years) and 55 non-occupationally exposed age-matched pregnant women (28.84±5.37 years) (controls) were recruited by convenient sampling method for this study. Blood (including cord blood) was collected from all participants. Trace and toxic elements levels were determined in the blood samples using Induction-Coupled Plasma-Mass Spectroscopy; anthropometric and sociodemographic data of the women along with the developmental milestone indices of the baby at infancy were also recorded.
Results: Levels of trace elements were 328.02±109.99mg/L, 370.82±192.97umol/L, 8.61±0.89mg/dl, 1.52±0.26mg/dl and 10.17±1.22mg/L; 348.27±150.61mg/L, 416.80±276.73umol/L, 8.61±0.86mg/dl, 1.46±0.35mg/dl and 8.96±1.15 mg/L for Cu, Zn, Ca, Mg and Se in cases and controls respectively. The differences were not significant. Less than 10% of participants samples (maternal and cord blood) had detectable toxic metal levels. However, cord blood trace elements concentrations were 125.07±24.66mg/l, 525.38±45.86umol/L, 8.44±0.15mg/dl, 1.51±0.31mg/dl and 7.02±0.72mg/dl in cases and 91.05±13.27mg/l, 591.22±44.62umol/l, 1.63±0.15mg/dl and 8.19±0.78mg/L in control for Cu, Zn, Ca, Mg and Se respectively. Only cord blood Mg level was significantly different (p=0.013). Baby weight and head circumferences also correlated significantly with cord Zn and Cu levels (r=0.293, p=0.039), (r=0.478, p=0.010) respectively.
Discussion: The observed downregulation of Mg and Se may have initiated a prooxidant reaction of the upregulated Cu in the foetus overwhelming the protective effects of Zn in scavenging the ROS produced by the combined effects of Cu and the toxic metals to which the cases were occupationally exposed. Our hypothesis is that given the role of Se, Cu and Mg in neurodevelopment, this may be the basis of the abnormal developmental milestones characteristic of ASD.
Conclusion: The need to monitor environmental exposure in pregnancy may be an imperative step in stemming the growing incidence of neurodevelopmental disorders in this environment.
Keywords: cord blood, pregnant women, occupational exposure, essential and toxic elements, neurodevelopmental disorders, autism spectrum disorder.
