Two gene families are responsible for glucose transport in humans. SLC2 (encoding GLUTs) and SLC5 (encoding SGLTs) families mediate glucose absorption in the small intestine, glucose reabsorption in the kidney, glucose uptake by the brain across the blood-brain barrier and glucose release by all cells in the body.
Glucose is the main energy source used by cells to make energy. Im mammals, blood glucose levels are tightly controlled and glucose is taken up from interstitial fluid by a passive, facilitative transport driven by the diffusion gradient of glucose (and other sugars) across the plasma membrane. This process is mediated by a family of Na+-independent, facilitative glucose transporters (GLUTs) encoded by the SLC2A gene family (Zhao FQ and Keating AF, 2007; Wood IS and Trayhurn P, 2003). There are 14 members belonging to this family (GLUT1-12, 14 and HMIT (H+/myo-inositol symporter)). The GLUT family can be subdivided into three subclasses (I-III) based on sequence similarity and characteristic sequence motifs (Joost HG and Thorens B, 2001).