Glucose and Energy Metabolism in the Brain

Abstract

Of all the nutrients used by the mammalian system, only glucose is able to satisfactorily maintain the metabolism of cerebral tissue. Although mannose and other sugars can also be metabolized, they must first be converted into glucose. On the other hand, fructose, another simple sugar, is capable of being utilized without conversion, but the process is a relatively slow one. And while the brain can additionally make use of ketone bodies, such as 2-hydroxybutyric acid, their low transport rate across the blood-brain barrier restricts their contribution to the production of energy (Hawkins and Biebuyck, 1979). Other substrates that support brain function are converted into glucose elsewhere in the body. Gluconeogenesis, the formation of new molecules of glucose from other components, is absent in the brain.