Organ fuel selection: brain

摘要

Human brain tissue contains the enzymes necessary to metabolize a variety of substrates, and, in theory, has the biochemical capacity to metabolize glucose, ketones, lactate, fatty acids, glycerol and a variety of amino acids. Nevertheless, it has traditionally been considered that the brain uses glucose to fuel its metabolism and function, almost exclusively. Under normal circumstances this is largely true. In the resting, fasted state, the brain accounts for over 55% of the body's glucose consumption. Over 90% of all the glucose taken up by cerebral tissue is oxidized to CO_2 and water, the rest being metabolized through other means, either through the pentose phosphate pathway or through glycolysis to lactate and pyruvate. A negligible amount ofglucose is stored in the brain so that the brain has virtually no glucose reserves. Thus, brain metabolism and brain function are dependent on a continued supply of exogenous glucose in its circulation and if blood glucose falls, so too will the rate ofcerebral glucose metabolism.