Answer:
Sodium regulates the absorption of glucose by the enterocytes.
There are two basic types of transport systems for glucose:
- Sodium dependent glucose transporters (SGLTs)
- Glucose transporters (GLUTs)
Sodium is transported into cells actively by SGLTs, and glucose is transported into cells passively. The co-transport system's energy source are the sodium ions. In addition to other tissues, the GI brush-border membrane contains a very high number of SGLTs.
There are as many as 6 more related proteins, mostly expressed in the kidney, and at least 3 SGLTs (SGLT1-3) have been described from different species. The extracellular side of the SGLTs has both N and C terminal ends, totaling up to 15 transmembrane domains.
The GLUTs enable the diffusion of glucose, and some of them can also move other hexose carbohydrates. Due to amino acid sequences in the four hydrophilic domains of the 12 transmembrane domains, certain GLUT proteins are tissue-specific.
