! Dietary changes have been shown to affect nervous system function as well as influence animal behavior as best exhibited by diet-based treatments for neurological disorders. Ketogenic diets are used to treat individuals suffering from epileptic seizures while caloric restriction is known to influence circadian rhythm, foraging behavior, and anxiety-like behaviors in rodents. To enact changes in cognition and behavior, transcriptional programs must exist in the brain that lead to downstream changes in nervous system structure and function in response to changes in peripheral metabolites. Diet-specific transcriptional programs in the brain, however, are not well characterized. Ethanolamine phosphate phospholyase (ETNPPL) is a PLP-dependent enzyme capable of irreversibly degrading the phospholipid precursor ethanolamine phosphate to acetaldehyde, ammonium, and inorganic phosphate. Etnppl is enriched in mature astrocytes within the central nervous system. Interestingly, there is an 8-fold increase in relative Etnppl mRNA after an 18-hour fasting period in hippocampal astrocytes isolated from mice. In humans, Etnppl mRNA is increased 2-fold in brains of schizophrenics and decreased 72% in depressed individuals. The manner and purpose of this diet-induced transcriptional control is not known nor are ETNPPL?s implications in neurological diseases. The central hypothesis of this proposal is that ETNPPL plays a role in regulating metabolic homeostasis within the central nervous system which may influence nervous system function and structure as well as influence animal behavior. We will study the contribution of ETNPPL in the nervous system using a constitutive knockout mouse to address the following specific aims:
Specific Aim I : Characterization of ETNPPL and determination of the mechanism(s) of fasting-regulated Etnppl expression. 1A. Characterize Etnppl gene and protein expression, subcellular localization, and activity. 1B. Determine the molecular mechanism of fasting transcriptional control on Etnppl expression upon altered lipid homeostasis Specific Aim II: Determine the functional role of ETNPPL on murine metabolic physiology in vivo. 2A. Determine the importance of PEtN-degradation on flux of lipid species using Etnppl-/- mice. 2B. Determine the effect of ETNPPL on metabolic profile using steady-state metabolomics 2C. Determine the role(s) of fasting enrichment of Etnppl on the flux of oxidative substrates using Etnppl-/- mice. We expect that contributions from this proposal will provide a greater understanding of transcriptional programs specific to the brain that are regulated by diet. ! ! ! !
! Diet composition can affect CNS structure and function by altering transcriptional programs. Using an unbiased screen for actively translating mRNAs we compared mice subjected to different dietary states, we observed an 8-fold enrichment in the ethanolamine phosphate (PEtN) phospholyase, Etnppl in murine hippocampal astrocytes from mice that were fasted overnight. Etnppl protein irreversibly degrades PEtN which is used in metabolic pathways of multiple lipid classes, and Etnppl has among the most highly differentiated mRNA expression patterns in individuals with mood disorders (72% decrease) and schizophrenia (2-fold increase). The understanding of the role of Etnppl in the CNS will aid in the understanding of diet-controlled transcriptional programs in the brain and metabolic aspects of neurological disorders. !
