Loss of epigenetic adaptation to a high-fat diet in alpha-synuclein transgenic mice

Introduction: In humans, a high-fat diet and obesity are associated with a higher risk and accelerated progression of Parkinson's disease (PD). Similarly, in animal models a high-fat diet exacerbates PD-related phenotypes, including dopaminergic neurodegeneration, and alpha-synuclein aggregation. We previously demonstrated that transgenic mice overexpressing human, mutated A30P alpha-synuclein failed to transcriptionally adapt to metabolic stress which could be a potential explanation for the high-fat diet-dependent aggravation of PD pathology. However, the underlying epigenetic mechanisms that might regulate this impaired response remained unknown. Methods: Here, we profiled genome-wide DNA methylation and hydroxymethylation in brainstem and hippocampus of wild type and transgenic mice exposed to a long-term standard or high-fat diet. Results: Wild type mice displayed pronounced diet-dependent adaptations that were largely missing in transgenic mice. In the brainstem, a high-fat diet increased the epigenetic age and induced a loss of DNA methylation of neuronal genes involved in protein degradation and mitochondrial metabolism-changes that were largely driven by DNA hydroxymethylation and absent in transgenic mice. Integration of methylation and gene expression data further revealed shared, and brain region-specific interaction networks implicated in metabolism, proteostatis, and neuronal pathways showing molecular adaptation specifically in wild type mice upon high-fat diet. Discussion: Together, these findings point to failure of high-fat diet-induced epigenetic adaptability under alpha-synuclein overexpression, suggesting that altered DNA methylation and DNA hydroxymethylation might contribute to diet-dependent acceleration of PD pathology.