Dietary cholesterol and bile acids in intestinal lumen

Dietary cholesterol and bile acids in the intestinal lumen are central components of the body's lipid absorption and cholesterol homeostasis systems [1]. Bile acids are synthesized from cholesterol in the liver and secreted into the intestine to emulsify dietary fats and cholesterol into mixed micelles, which are then absorbed by enterocytes [2]. This process is primarily mediated by specific proteins such as Niemann-Pick C1-like 1 (NPC1L1) for cholesterol and the Apical Sodium-dependent Bile Acid Transporter (ASBT) for bile acids [1, 3]. High levels of luminal cholesterol and efficient bile acid recycling contribute to hypercholesterolemia, a major risk factor for atherosclerosis and cardiovascular disease [4]. Therapeutic strategies targeting these luminal components include bile acid sequestrants, which are non-absorbable resins that bind bile acids to prevent their reabsorption [2]. By interrupting the enterohepatic circulation, these drugs force the liver to deplete systemic cholesterol stores to synthesize new bile acids, thereby lowering LDL-C levels [2, 4]. Additionally, inhibitors like ezetimibe target the NPC1L1 transporter to block the entry of dietary and biliary cholesterol into the bloodstream [1]. Managing the concentration and transport of these molecules in the intestinal lumen remains a cornerstone of lipid-lowering therapy [4].

Other names

Intestinal sterols and bile saltsLuminal cholesterol and bile acidsEnterohepatic circulation components

Bile acid sequestrants are non-absorbable polymers that bind bile acids in the intestinal lumen through ionic and hydrophobic interactions, forming an insoluble complex excreted in feces [2]. This interrupts enterohepatic circulation, prompting the liver to upregulate LDL receptors to convert more systemic cholesterol into bile acids [2, 4]. Additionally, drugs like ezetimibe target the NPC1L1 transporter to specifically inhibit the uptake of dietary and biliary cholesterol from the lumen into enterocytes [1]. ASBT inhibitors further block the reabsorption of bile acids in the ileum, enhancing their excretion and lowering systemic cholesterol [3].