PROJECT SUMMARY Phospholipids, the fundamental components of cell membranes, play a crucial role in brain function. Research indicates that changes in membrane lipid composition and fluidity may be contributing to the development of Alzheimer’s disease (AD). By studying the distribution and alteration of membrane lipids in response to Aβ exposure, new insights into the biology of AD and potential biomarkers for the disease may be uncovered. Despite numerous studies on the role of membrane lipids in AD, research has been restricted to ex-vivo tissues, and has not been utilized for diagnosis due to the absence of non-invasive imaging techniques. This project aims to bridge this gap by developing an innovative MRI imaging technique to assess membrane lipid properties in AD. The technique uses a nuclear Overhauser enhancement (NOE) saturation transfer method. Our preliminary studies strongly suggest that the NOE signal primarily originates from phospholipids and changes significantly in AD on animal models. The NOE signal relies on both the underlying pool concentration and the NOE coupling rate. Moreover, according to NOE theory, the NOE coupling rate depends on the molecular motional properties, which may serve as an indicator of lipid fluidity as they likely share similar physical properties. Based on these preliminary findings and analysis, we hypothesize that the NOE pool concentration could reflect membrane lipid content, and the NOE coupling rate could represent lipid fluidity regulated by membrane composition. The project is divided into three aims: 1) verifying the dependency of the NOE signal on lipid properties on reconstituted phospholipid samples and cultured cells with varied lipid composition; 2) confirming the origin of the NOE imaging in AD by correlating it with phospholipid species maps determined by imaging mass spectrometry on animal AD models; and 3) evaluating the potential of NOE for early detection of AD by comparing it with other traditional imaging methods in a longitudinal study. The ultimate goal of this project is to provide a groundbreaking tool for AD research and diagnosis, enabling the non-invasive study of membrane lipids in live brains. This could significantly improve our understanding of AD pathology, potentially leading to new treatment strategies and early diagnosis.