Metal Mixtures, MicroRNAs and Metabolomics in Extracellular Vesicles, and Early-life Programming of Childhood Sleep Patterns: A Longitudinal Study

SUMMARY Sleep is an essential component of children’s development. Disrupted sleep in early life may cause short-term and lifelong cognitive, behavioral, and metabolic disorders. Prenatal and early-life exposures to neurotoxic metals have been linked to the sleep disruption in animal models. However, human studies supporting this link are scarce, evaluated metals individually rather than mixtures as occurs in real-life settings, and characterized neither the susceptible developmental time windows nor the underlying molecular mechanisms. We will study how metal exposure during pregnancy and early life affects children’s sleep and sleep disruption during childhood and investigate the underlying molecular mechanisms. We will leverage the unique resources of the PROGRESS birth cohort from Mexico City, known to have a high metal exposure, with biobanked blood specimens, and objective and longitudinal actigraphy-derived sleep measures at 4–5, 6–7, 8–9, and 10–12 years of age. In PROGRESS children, we used a breakthrough approach developed by our team to precisely quantify the time course of metal exposures by measuring metals trapped in teeth layers that recapitulate longitudinal weekly exposures from the second trimester of pregnancy to the first year after birth, and cumulative exposures up until teeth shedding in childhood. To assess potential molecular mechanisms, we will build on novel evidence implicating circulating extracellular vesicles (EVs) in sleep biology. EVs, tiny vesicles secreted by sleep relevant cells such as the brain, suprachiasmatic nucleus, and circulatory system, are highly sensitive to metal exposures and are a critical signaling system regulating child sleep and circadian rhythms. EVs transport microRNAs (EV- miRNA transcriptome) and metabolites (EV-metabolome) that affect the functions of distant recipient cells and regulate child’s sleep. However, the roles of the EV-miRNA transcriptome and metabolome in metal exposures and children’s sleep have not been studied. The study will be enabled by a team of excellent investigators with complementary expertise. In Aim 1, we will determine the impact of metal exposures during pregnancy, infancy and childhood on children’s sleep and markers of circadian rhythms longitudinally over 12 years, determining windows of susceptibility and metal mixture effects (N=600). We will then identify circadian rhythm-related EV- miRNA transcriptome (Aim 2) or neurotransmitter EV-metabolome (Aim 3) profiles measured across two study visits (4-5 and 6-7 years; N=550) linking metal exposures during pregnancy and early life to children’s sleep disruption through age 12. In both Aims 2 and 3, we will apply statistical causal modeling and pathway analysis to characterize pathways linking metal exposures, the EV-miRNA transcriptome/metabolome, and children’s actigraphy-derived sleep metrics. We will replicate our findings in an US-based cohort (N=100). If successful, we will discover new, underappreciated environmental causes and mechanisms of sleep disruption that will lead to stricter metals regulations and the implementation of interventions that help millions of children and prevent lifelong changes associated with metal-induced sleep abnormalities.