الفهرس 
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Abstract
Glucose is a major energy source for the adult human brain. In brain, glucose is almost entirely oxidized through sequential glycolysis and the tricarboxylic cycle (TCA) to produce metabolic intermediaries and ATP accompanied by oxidative phosphorylation. Glucose can be oxidized through an alternative pathway which is the pentose phosphate pathway (PPP). Glucose oxidation through PPP supplies 5-carbon monosaccharides for nucleic acid synthesis and NADPH for reductive biosynthetic processes and for maintenance of the redox balance in the cell. Glucose can also be stored as glycogen (Beltrán et al., 2012). Glucose is not only an excellent energetic fuel; it is also a remarkably versatile precursor supplying metabolic intermediaries for biosynthetic reactions. In brain most of these intermediaries used to synthesize neurotransmitters and gliotransmitters. Neuronal metabolic processes in the brain depend on the activity of astrocytes, which produce lactate and activate glycolysis and glycogen metabolism (Falkowska et al., 2015) In the adult brain, glycogen is found in astrocytes. The end-feet of the astrocytes contain GLUT1 type glucose transporters which are sites of glucose uptake. Brain glycogen is metabolized by enzymes found in astrocytes, such as glycogen phosphorylase (GP) and glycogen synthase (GYS). The brain isoform of GP is found mainly in astrocytes. GYS is also found in neurons and is mainly expressed in the hippocampus, cerebellum and olfactory bulbs. GYS occurs in both inactive phosphorylated (GYSb) and active dephosphorylated (GYSa) forms, which allows a precise regulation of glycogen metabolism (Guglielmi et al., 2003.