PROJECT SUMMARY A longitudinal multi-omics examination of beta amyloid deposition (A), pathologic tau (T), neurodegeneration (N), and cognitive decline in the years prior to Alzheimer’s disease (AD) diagnosis is critical to better understand, predict, prevent, diagnose, and treat the disease. Gaps in knowledge include the timing, trajectory, and etiology of metabolite changes in the disease process. This renewal application augments two existing longitudinal cohort studies of preclinical and clinical AD, the Wisconsin Registry for Alzheimer’s Prevention and the Wisconsin Alz- heimer’s Disease Research Center, with rich phenotypic data from blood, cerebrospinal fluid (CSF), imaging, lifestyle questionnaires, and neuropsychological testing. The overall objective is to measure plasma and CSF metabolomics in additional longitudinal samples and use sophisticated data analysis approaches to establish the timing, trajectory, and etiology of metabolite changes in the disease process. The central hypothesis is that changes in metabolites are influenced by genetics and lifestyle and occur at distinct stages of AD pathology. The rationale for the proposed research is that a better understanding of the timing, trajectory, and etiology of AD- related metabolomic changes is critical to prevent (e.g., lifestyle interventions), diagnose (metabolomic bi- omarkers), and treat (new therapeutic targets) the disease. The central hypothesis will be tested by executing the following specific aims: 1) determine the timing and trajectory of plasma and CSF metabolites throughout the AD process using sophisticated longitudinal modeling approaches, 2) integrate genomics and metabolomics to determine which AD-associated metabolites are in the causal pathway to AD using Mendelian randomization analyses, and 3) determine which AD-associated plasma and CSF metabolites mediate the relationships be- tween AD-associated lifestyle factors and AD-related outcomes. At the conclusion of this project, expected out- comes include: 1) identification of metabolites/pathways that are precursors to AD pathologic changes and may be therapeutic targets versus those that change in the early stages and can be used as early biomarkers versus diagnostic/prognostic metabolites that are markers of more advanced disease, 2) identification of metabolites that are in the causal pathway and may inform therapeutic targets, 3) a better understanding of mechanisms linking metabolic and vascular disease processes with AD, and 3) identification of metabolites linking lifestyle factors to AD risk that can inform future intervention trials and clinical practice by identifying more specific be- havior changes and providing biomarkers of biologic change to monitor the effectiveness of interventions with a shorter period of follow up.