GPR17 and Alzheimer disease: Hence, in addition to resulting in dysregulation of OPC cellular metabolism, age-related changes in oligodendroglial P2X7R and GPR17 may have adverse effects on axonal metabolism, in particular under times of metabolic stress, which is a hallmark of brain ageing [50], and is postulated to play a key role in neuronal demise in AD [19] and MS [2].