METABOLISM OF CARBOHYDRATE IN THE BRAIN TISSUE

Carbohydrate metabolism in the brain was long thought of as being specific and different from liver carbohydrate metabolism. The present report tries to summarize current data and advances in our knowledge about carbohydrate metabolism. Glucose is brought to the brain by blood flowing through a special network of arteries and is quickly catabolized by the glycolytic and tricarboxylic acid cycle pathways to synthesis of numerous amino acids, nucleotides and NADPH. Glucose can be polymerized into glycogen in the brain, the nerve tissue is capable of synthesizing glucose-6-phosphate in the glucagonic pathway since the fructose-1, 6-bisphosphatase, the key enzyme believed to be absent is actually active and has been purified up to electrophoretic homogeneity. Moreover, the possibility of free glucose synthesis by astrocytes exists. Although the exact role of glycogen in the brain is not totally clear, it is known that the polysaccharide content generally decreases when the functioning of the brain is stimulated and increases in sedative state. This carbohydrate can therefore serve as an indicator for the level of brain activity. Through the administration of methionine sulfoxime, it is possible to increase the amount of glycogen in the brain massively and obtain particles similar to those found in the liver.