Lowering Microglial Lipid Burden via PLIN2 Modulation in Alzheimer's Disease

Abstract Microglial dysfunction is a hallmark of Alzheimer’s disease (AD), coupling impaired amyloid-β clearance with chronic inflammatory and metabolic stress. A defining feature of this stress is lipid droplet accumulation; PLIN2, a canonical droplet-coat protein, stabilizes neutral lipids and restricts their turnover, potentially locking microglia into a maladaptive, lipid-laden state. We hypothesize that reducing PLIN2 in microglia relieves lipid stress, re-engages phagolysosome and mitochondrial programs, and improves AD-relevant pathology and behavior, with parallel rescue in human APOE4 microglia. We will test this using an integrated in vivo/in vitro strategy. In 5xFAD mice with microglia-specific Plin2 deletion (Cx3cr1-CreERT2;Plin2^fl/fl;5xFAD), we will quantify amyloid burden, plaque-proximal gliosis, lipid-droplet load, and cognition (Barnes maze, novel object recognition). To define mechanism, we will map PLIN2-dependent microglial states via single-cell RNA-seq and Xenium spatial transcriptomics, integrated with targeted lipidomics and metabolomics from the same cohorts, assessing shifts in sterol/lipid synthesis modules, phagolysosome competence, and mitochondrial resilience. Human relevance will be established by CRISPR PLIN2 knockout in APOE3/3 and APOE4/4 iPSC-derived microglia, measuring lipid droplet burden, Aβ phagocytosis, bioenergetics, lysosomal function, cytokine output, and transcriptomic state transitions. Preliminary data show that PLIN2 loss reduces lipid droplets and enhances phagocytosis under lipid and Aβ stress, supporting feasibility and the causal framing. Targeting a droplet coat protein to unlock turnover, rather than modulating biogenesis alone, represents a distinct therapeutic axis, and the tight coupling of spatial single-cell state mapping with lipid/metabolic phenotyping plus cross-species validation yields a robust translational bridge. The expected outcome is to establish PLIN2 as a microglial lipid-stress switch and to deliver a biomarker framework for future therapeutic development in AD.