Glucose is the principal cerebral metabolic substrate under normal circumstances. Glucose provides energy (adenosine triphosphate) to neural cells and carbon for neurotransmitter production, one of the numerous biosynthetic reactions that the brain carries out, via glycolysis and the tricarboxylic acid (TCA) cycle.
1 However, glucose metabolism also fulfills other, less-acknowledged cerebral biosynthetic requirements, which are no less important from a clinical standpoint when they remain unmet,
2 such as anaplerosis (ie, the replenishment of intermediates that are normally lost from the TCA pool). Thus, a myriad of cerebral energetic and carbon fluxes, many of which are poorly understood quantitatively,
3 stem from brain glucose availability. This is, in turn, contingent on the activity of the facilitative membrane glucose transporter type I (GLUT1), which permits glucose to cross the blood-brain barrier and subsequently transit into, and probably through, astrocytes.