The SGLT-1 (Sodium-glucose linked transporter) is part of the SLC5 family of sodium-glucose transporters. This family has more than 220 members in human and bacterial cells and they are expressed in various tissues such as the gut, kidneys and the central nervous system. In human, these transporters are encoded by eleven genes¹. SGLT-1 plays a vital role in carbohydrate metabolism and is mainly located in the brush membrane of mature enterocytes in the small intestine. It absorbs D-galactose and D-glucose derived from ingested food².

SGLT-1 has 14 transmembrane α-helices with both the hydrophobic NH2 and hydrophilic COOH termini facing the extracellular side of the cell. SGLT-1 is a  symport type transporter carrying sodium and glucose from extracellular space into the cell’s cytoplasm. It is believed that sodium binds to the hydrophobic part of the protein and causes a conformational change that enables sugar to binds to the COOH terminal³. The transporter has a number of consensus sites for glycosylation but none are required for the transporter’s function.

The transporter’s regulation was found to be modulated by PKA and PKC. PKA increases vesicle exocytosis 100-fold. Interestingly, the activation of PKC inhibits rat and rabbit SGLT-1 while stimulates human SGLT-1.

Pathologies linked to SGLT-1 include the glucose-galactose mal-absorption (GGM) disease caused by a mutation in the transporter. In mice, SGLT-1 knockout causes an inability to survive on glucose containing diets and a decreased insulin and incretin response to glucose⁴. SGLT-1 is also related to the successful treatment of secretory diarrhea by oral rehydration.