Sugar Transport Across Epithelia

The transport of d-glucose, d-galactose, and d-fructose across epithelial cells is mediated by SGLTs, GLUT5, and GLUT2 in the apical and/or basolateral membrane. The SGLTs (sodium–glucose cotransporters) are responsible for active glucose transport, while the GLUTs (facilitative glucose transporters) are responsible for passive glucose and fructose transport. The structure and function of each of these transport proteins are summarized, and then we highlight the similarities and differences between these two classes of membrane transporters. We next discuss their roles in sugar absorption in the intestine and glucose reabsorption from the glomerular filtrate in the kidney. Reference is made to genetic disorders of glucose transport in the intestine, Glucose–Galactose Malabsorption, and in the kidney, Familial Renal Glucosuria, and the Fanconi–Bickel syndrome, and the use of specific SGLT2 inhibitors to treat Type II Diabetes Mellitus.