MTOR and type 2 diabetes mellitus: It is significant, therefore, that GPR17 and P2X7R regulate whole-body metabolism and are implicated in type-2 diabetes [17, 61] and regulate mTOR and AMPK [8, 62], which also contribute to type-2 diabetes [39], since dysregulation of these pathways are central to age-related changes in OPCs and targeting these pathways rejuvenates ageing OPC stemness [56, 63].