Myelin Lipid Reserves as a Conditional Metabolic Buffer: Implications for Alzheimer's Disease and Ischemic Stroke.

Brain energetics rely on a distributed partnership among cell types and fuel sources. Beyond astrocytic glycogen, the brain has limited conventional energy reserves. Emerging evidence broadens this view by positioning myelin and oligodendrocytes as active stabilizers of metabolic homeostasis. They align substrate delivery with demand and directly sustain axonal ATP production. This review highlights current understanding that myelin lipid stores function as a conditional metabolic buffer that can be mobilized when glycolytic supply wanes. Firstly, we outline the protective repertoire of myelin (e.g., adaptive myelination, antioxidant defense, and metabolic coupling) and then summarize myelin lipid metabolism, spanning de novo synthesis and β-oxidation. We next demonstrate disease contexts marked by energetic failure. Specifically, Alzheimer’s disease exhibits a chronic metabolic downshift, whereas ischemic stroke produces an acute collapse of energy production. Both states may recruit the proposed buffer. However, leveraging lipid-derived fuels is not without risk. Reactive oxygen species, acidosis, and iron handling must be tightly regulated to avoid collateral injury. Finally, we highlight methodological priorities that can resolve mechanism in vivo, including white matter-resolved fluxomics, myelin specific imaging paired with proteo-lipidomics, and lineage-restricted perturbations of β-oxidation and autophagy. On the translational front, we propose stage specific strategies. In summary, defining when and how to mobilize and supplement myelin lipid reserves could transform a conceptual buffer into a practical lever for disease modification in hypometabolic brain disorders.