ASBT

ASBT, or apical sodium-dependent bile acid transporter, also known as SLC10A2, is a membrane transporter in the solute carrier family 10. In humans, it is predominantly expressed on the apical surface of enterocytes in the distal ileum, where it mediates the uptake of bile acids from the intestinal lumen into the cell as part of the enterohepatic circulation. It is a sodium co-transporter; bile acids such as conjugated taurocholate and glycocholate are transported along with sodium across the apical membrane, while the bile acids exit the basolateral side to reach the portal vein via OST alpha/beta transporters.

ASBT function is essential for efficient reabsorption of bile acids, helping to conserve cholesterol and maintain the bile acid pool. Expression is highest in ileal enterocytes but lower levels may be found in other tissues, including the kidney. ASBT belongs to the SLC10 family; its activity is coupled to the sodium gradient maintained by the Na+/K+-ATPase.

Clinically, ASBT has drawn interest as a therapeutic target. Inhibiting ASBT (IBAT inhibitors) reduces intestinal bile acid reabsorption, increasing fecal bile acid excretion and altering cholesterol metabolism. Such inhibitors have been investigated in clinical trials for lowering LDL cholesterol and for metabolic liver diseases; they can cause gastrointestinal side effects such as diarrhea and abdominal discomfort, and their therapeutic use is under ongoing study.