Astrocytic lipid dysregulation as an early driver of neurodegeneration.

Astrocytes have traditionally been cast as supportive glia, but they are increasingly recognized as metabolic hubs that regulate cholesterol synthesis, fatty acid detoxification, lipid droplet dynamics and redox homeostasis in the CNS. Neurons have a limited intrinsic capacity for lipid storage and detoxification and rely heavily on astrocytes to maintain a safe lipid environment. Emerging evidence indicates that dysregulation of astrocytic lipid homeostasis precedes overt neuronal degeneration in a range of neurodegenerative diseases, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, frontotemporal dementia and Huntington disease. Perturbations in astrocytic lipid handling can drive maladaptive reactive states, promote oxidative stress, impair lysosomal and mitochondrial function and disrupt neuron-glia lipid exchange, collectively creating an environment that leads to neurodegeneration. Therefore, lipid dysregulation within astrocytes could trigger or amplify neuronal vulnerability. In this Review, we assess evidence that astrocytic lipid metabolism is not solely protective or pathological but has instructive physiological roles and that astrocytic lipid dysregulation is an early driver of neurodegeneration. We critically evaluate disease-specific evidence, distinguishing correlative observations from causal mechanisms. We propose that targeting of astrocytic lipid homeostasis represents a promising strategy for preventing or minimizing neurodegeneration and opens new avenues for early detection and biomarker development.