Fumonisin B1 (FB1) is a mycotoxin produced by a common fungal contaminant of corn. Ingestion of FB1-contaminated food during early pregnancy has recently been linked to increased risk for offspring with neural tube defects (NTDs) in global communities that rely on maize as a dietary staple. FB1 interferes with de novo sphingolipid biosynthesis, but the exact biochemical changes that contribute to abnormal morphogenesis are unknown. The objectives of the research plan are to identify biochemical and genetic biomarkers that predict FB1 exposures associated with increased risk for fetal malformations. In Guatemala, the occurrence of FB1 in maize is well documented, and the incidence of NTDs is often 6-10 times the global average for this type of birth defect. Preliminary exposure assessments have been conducted, and specific communities have been identified where FB1 in maize is frequently high. The proposed research will use information obtained from mouse studies to assess and validate biomarkers in human samples collected from women known to consume large amounts of FB1-contaminated maize. The project involves a collaborative effort between investigators at Creighton University, Duke University, USDA-ARS and CIENSA in Guatemala. Women in Guatemala will be asked to complete questionnaires intended to identify high and low consumers of maize, and enrolled subjects will provide urine and blood spots for further analysis. Parallel exposure studies will be done in mice in order to determine the dose-response threshold for FB1-induced alterations in sphingolipid metabolites in blood. Mouse models will also be used to identify the specific sphingolipid metabolites in maternal blood and embryonic neural tissue that correspond to increased risk for NTDs, and these biomarkers will be evaluated in human blood spots obtained from maize consumers exposed to high and low levels of FB1. In addition, mouse models will be used to further investigate the underlying signaling mechanisms involved that result in failure of neural tube closure. Additional studies will focus on the discovery and validation of gene expression profiles and genetic mutations in sphingolipid pathway genes that predict increased susceptibility. Candidate genes for analysis in human samples will be selected based on qPCR analyses of sphingolipid gene expression profiles in mice. Genes in sphingolipid metabolism and signaling pathways will be screened for mutations in human blood spots and in blood spots from susceptible vs. resistant mouse strains. Information from the proposed studies will form the basis for prospective and retrospective epidemiological studies to identify women at high risk for NTDs in maize-based cultures. In addition, mechanism-based biomarkers will provide a critical, and currently lacking, research tool for risk assessment, and aid in developing strategies for reducing the incidence of NTDs in global communities where consumption of FB1-contaminated maize is frequent.
Fumonisin (FB1) is a mycotoxin produced by a common fungal contaminant of maize. An association has recently been observed between ingestion of FB1-contaminated maize during early pregnancy and increased risk for having a child with a neural tube defect (NTD). The purpose of the application is to identify biomarkers of FB1 exposure in urine, and biochemical and genetic biomarkers in blood spots that are uniquely linked to increased risk for fetal malformations. FB1 exposure data, urine, and blood spots will be collected from human subjects in Guatemala who are consumers of maize. Mechanistic studies in mouse models that are susceptible or resistant to FB1-induced NTDs will enable the identification of sphingolipid metabolites, gene expression profiles, and genetic mutations that confer increased risk. The goal is the discovery and validation of biomarkers that can be used to predict risk in humans, such that we can prevent and/or reduce the incidence of NTDs in global populations that rely heavily on maize as a dietary staple.
