PCSK9 Regulation of Lipid Metabolism in the Nervous System: Implications for Schwann Cell Function and Peripheral Neuropathy.

Neural function relies on tightly regulated lipid metabolism to sustain membrane integrity, synaptic signaling, and energy production. Myelinating glia, particularly Schwann cells, require continuous lipid flux to build and maintain myelin, rendering them vulnerable to imbalances between lipid entry and oxidative capacity. Proprotein convertase subtilisin/kexin type 9 (PCSK9), widely studied in hepatic cholesterol regulation, has emerging roles in the nervous system. In the central nervous system (CNS), local PCSK9 expression influences low-density lipoprotein receptor (LDLR) family abundance, neuronal survival pathways, and neuroinflammatory tone, although circulating PCSK9 has limited parenchymal access due to the blood-brain barrier (BBB). In the peripheral nervous system (PNS), recent evidence highlights a PCSK9-CD36 axis in Schwann cells; genetic Pcsk9 loss elevates CD36, increases fatty-acid influx, promotes lipid droplet expansion and acylcarnitine accumulation, and triggers mitochondrial stress that manifests as hypomyelination, C-fiber pathology, and selective small-fiber neuropathy. These findings suggest that PCSK9 normally restrains CD36-dependent transport to align lipid supply with metabolic demand. Clinically, PCSK9 inhibitors have demonstrated cardiovascular benefit without major neurocognitive signals, yet small-fiber outcomes have not been systematically assessed. This review integrates current evidence on PCSK9 biology across neural compartments, highlights mechanistic links to Schwann cell lipid handling, and outlines research priorities to resolve neural safety and therapeutic potential in lipid-driven neuropathies.