A co-ordinated transcriptional programme in the maternal liver supplies LC-PUFAs to the conceptus using phospholipids

Essential fatty acids (EFAs) and their derivatives, the long and very long chain polyunsaturated fatty acids (LC-PUFAs), are preferentially transported by the mother to the fetus. Failure to supply EFAs is strongly linked with stillbirth, fetal growth restriction, and impaired neurodevelopmental outcomes. However, dietary supplementation during pregnancy is unable to simply reverse these outcomes, suggesting imperfectly understood interactions between dietary EFA intake and the molecular mechanisms of maternal supply. Here we combine untargeted lipidomics with transcriptional profiling of healthy and genetically-manipulated murine models to understand the maternal adaptations required to provide LC-PUFAs to the developing fetus. We discovered a late pregnancy-specific, selective activation of the Liver X Receptor signalling pathway which dramatically increases maternal supply of LC-PUFAs within circulating phospholipids. Crucially, genetic ablation of this pathway in the mother reduced LC-PUFA accumulation by the fetus. Overall our work suggests new molecular strategies for improving maternal-fetal transfer of these important lipids.