Not just lost, but used as an energy reserve? A 2012 study in mice found glial-produced myelin supplying energy to neurons as lactate after mitochondrial respi

Not just lost, but used as an energy reserve? A 2012 study in mice found glial-produced myelin supplying energy to neurons as lactate after mitochondrial respiration was inhibited (like an proposed astro-glial shuttle for some glutamatergic neurons). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3613737/ once myelination has occurred, reduced mitochondrial functions do not perturb oligodendrocyte survival, myelin maintenance or axonal integrity. We proposed that oligodendrocytes survive by enhanced glycolysis, and predicted to see in vivo an increase in the brain lactate concentration using localized proton magnetic resonance spectroscopy (MRS). As expected, Cox10 mutants showed a more strongly increased lactate resonance lactate is not cleared by drainage, but is locally metabolized the monocarboxylate transporter MCT2 localizes to myelinated axons. This strongly suggests that lactate generated in oligodendrocytes is released and reaches the axonal compartment Our model of axon–oligodendrocyte metabolic coupling is reminiscent of the astroglial ‘lactate shuttle’, which is thought to support the energy metabolism of glutamatergic synapses in the cortex So wow - myelin lipids used as an energy reserve if not buffer. It makes a lot of sense that glial cells hard at work building structure and metabolites for neurons might also provide energy. Indeed, perhaps the energy benefit was the initial evolutionary advantage, and then insulation enabling longer neuron runs (and lower energy use) would permit other adaptations. (Also, for those extolling fatigue hallucinations or psycho-active breath-holding, please remember that's toxic to neurons, and neuronal regeneration is ... limited.)