Alzheimer"s Imaging Biomarkers in Obesity

High body fat at midlife, as evidenced by overweight or obese body mass index (BMI), is increasingly understood as a risk factor for Alzheimer's disease. However, the underlying processes and mechanisms that may underlie this risk remains unknown. With this project, the Investigator proposes to create a new cohort of cognitively normal 120 midlife individuals, age 40-60 years. The investigator and research staff will characterize the participant's overweight or obese status using metabolic tests including, an oral glucose tolerance test, fasting plasma insulin, fasting plasma glucose, and hemoglobin A1c measurements. This testing will generate categories of metabolically abnormal overweight and obese (MAOO), metabolically normal overweight and obese (MNOO), and metabolically normal lean participants (MNLP). Research staff will evaluate differences between these groups on neuroimaging with the newer classification framework of Alzheimer's biomarkers with amyloid (A), tau (T), and neurodegeneration (N), or ATN. Neurodegeneration will be assessed by atrophy on brain MRI as reflected by regional volumes on Freesurfer. Staff will also evaluate MR neuroimaging markers for neuroinflammation using a newer method called diffusion basis spectrum imaging (DBSI), developed at the Mallinckrodt Institute of Radiology at Washington University in St. Louis in collaboration with The Charles F. and Joanne Knight Alzheimer's Disease Research Center (Knight ADRC).