Glucose transport in brain and retina: Implications in the management and complications of diabetes

Neural tissue is entirely dependent on glucose for normal metabolic activit y. Since glucose stores in the brain and retina are negligible compared to glucose demand, metabolism in these tissues is dependent upon adequate gluc ose delivery from the systemic circulation. In the brain, the critical inte rface for glucose transport is at the brain capillary endothelial cells whi ch comprise the blood-brain barrier (BBB). In the retina, transport occurs across the retinal capillary endothelial cells of the inner blood-retinal b arrier (BRB) and the retinal pigment epithelium of the outer BRB. Because g lucose transport across these barriers is mediated exclusively by the sodiu m-independent glucose transporter GLUT1, changes in endothelial glucose tra nsport and GLUT1 abundance in the barriers of the brain and retina may have profound consequences on glucose delivery to these tissues and major impli cations in the development of two major diabetic complications, namely insu lin-induced hypoglycemia and diabetic retinopathy. This review discusses th e regulation of brain and retinal glucose transport and glucose transporter expression and considers the role of changes in glucose transporter expres sion in the development of two of the most devastating complications of lon gstanding diabetes mellitus and its management. Copyright (C) 1999 John Wil ey & Sons, Ltd.