Myelin as energy store

Brain myelin as an energy source

We recently found by magnetic resonance imaging that marathon runners undergo widespread myelin water fraction (MWF) decrease at completion of the effort. This reduction involves white and gray matter regions including primary motor and sensory cortical areas and pathways, as well as the corpus callosum and internal capsule. Notably, MWF levels recover within two months after the marathon. These results suggest that myelin use and replenishment is an unprecedented form of metabolic plasticity aimed at maintaining brain function during extreme conditions.

These findings challenge the commonly held view that neuronal function relies exclusively on glucose and oxygen supply, as the brain has no obvious energy stores, except for limited astrocyte glycogen. In addition, these data reveal that myelin consumption and replenishment may be a novel form of metabolic plasticity aimed at maintaining brain function during energy scarcity. Mechanistic details of how myelin lipids contribute to brain energy demand remains unknown and difficult to grasp. We are currently investigating how and under which circumstances may support brain energy demands.

Obtaining this knowledge may also help understanding brain function decline during ageing and neurodegenerative diseases, as waning glial support leading to synaptic, axonal and neuronal malfunctions may cause fuel shortage and metabolic deficits leading to nervous tissue damage.

Reference

• Ramos-Cabrer, P. et al. Widespread Drastic Reduction of Brain Myelin Content upon Prolonged Endurance Exercise.

• http://biorxiv.org/lookup/doi/10.1101/2023.10.10.561303 (2023).