Bile salt–cholesterol mixed micelle

Bile salt–cholesterol mixed micelles are supramolecular lipid assemblies formed in the small intestine to facilitate the absorption of dietary and biliary lipids. Composed of bile salts, phospholipids (primarily lecithin), fatty acids, and monoglycerides, these micelles create a hydrophobic core that solubilizes cholesterol and fat-soluble vitamins (A, D, E, and K), allowing them to pass through the unstirred water layer to the enterocyte brush border (Hofmann, 1999). This process is essential for lipid homeostasis but also contributes to the development of hypercholesterolemia and atherosclerosis when cholesterol uptake is excessive (Phan et al., 2018). Therapeutic intervention often targets these micelles to lower plasma LDL cholesterol levels; for instance, bile acid sequestrants disrupt micelle formation by binding bile salts, while plant sterols competitively displace cholesterol from the micelle, effectively reducing its bioavailability for intestinal transporters like NPC1L1 (Gylling et al., 2014; StatPearls, 2023).

Other names

Intestinal mixed micelleBile acid-cholesterol micelleBile salt-phospholipid-cholesterol aggregateBile salt-lipid mixed micelle

Bile acid sequestrants (e.g., cholestyramine) bind to bile acids within the intestinal lumen, preventing the formation of mixed micelles and increasing fecal excretion of bile salts (StatPearls, 2023). Plant sterols and stanols competitively displace cholesterol from the micellar core due to their higher affinity, thereby reducing the amount of cholesterol available for absorption by NPC1L1 (Gylling et al., 2014). Additionally, lipase inhibitors like orlistat prevent the hydrolysis of triglycerides into monoglycerides and fatty acids, which are necessary components for stable mixed micelle formation (Phan et al., 2018).