Bile acids and other anionic gut lumen solutes

Bile acids are steroid-based molecules synthesized from cholesterol in the liver and secreted into the duodenum to facilitate the emulsification and absorption of dietary lipids and fat-soluble vitamins. Beyond their detergent-like properties, they serve as critical signaling molecules that regulate metabolic pathways by activating receptors such as the Farnesoid X receptor (FXR) and the G protein-coupled bile acid receptor (TGR5). In the context of pharmacology, the bile acid pool in the gut lumen is targeted by sequestrants to interrupt enterohepatic circulation. This interruption is a primary therapeutic strategy for managing hypercholesterolemia, as it forces the liver to utilize systemic cholesterol for de novo bile acid synthesis. Additionally, sequestering these anionic solutes is effective in treating bile acid malabsorption and the pruritus associated with cholestatic liver diseases. While highly effective for lipid management, these interventions can interfere with the absorption of other anionic drugs and essential nutrients.

Other names

Bile saltsIntestinal bile acidsAnionic intestinal solutesConjugated bile acids

Bile acid sequestrants are non-absorbed, positively charged resins that bind to negatively charged bile acids and other anionic solutes in the intestinal lumen through ion exchange. This binding forms an insoluble complex that is excreted in the feces, preventing the reabsorption of bile acids via the enterohepatic circulation. The resulting depletion of the bile acid pool triggers the liver to upregulate the conversion of endogenous cholesterol into new bile acids, thereby lowering systemic LDL cholesterol levels.