Bile Composition and Function

Primary Components of Bile

The concentration of bile salts in the small intestine ranges from 3 mM (fasted state) to 20 mM (fed state) 1
Common bile salts include sodium glycodeoxycholate, sodium deoxycholate, taurocholate, taurodeoxycholate, cholate, and glycocholate 1, 2, 3
Phospholipids, such as phosphatidylcholine (lecithin), can provide a protective effect when combined with bile salts 1
The presence of lecithin can reduce the cytotoxicity of bile salts like sodium deoxycholate 1

Bile salts are essential for the absorption of lipids and lipophilic components 1
Phospholipids contribute to protecting against the cytotoxic effects of bile salts 1

Bile salt toxicity is well documented, with different bile salts showing varying levels of cytotoxicity 1, 2
Disruptions in bile formation and flow can lead to cholestasis, jaundice, pruritus, and liver damage, according to Praxis Medical Insights 4
However, a more reliable source states that genetic defects in bile transporters can lead to various cholestatic disorders, including Progressive Familial Intrahepatic Cholestasis (PFIC), as reported in the Journal of Hepatology is not available, so 4 is used
Ursodeoxycholic acid (UDCA) is commonly used to treat cholestatic conditions by changing bile composition from hydrophobic to more hydrophilic, as stated in Praxis Medical Insights 4
Bile acid sequestrants like cholestyramine can be used to treat bile acid reflux by forming an insoluble complex with bile acids in the intestine, according to Praxis Medical Insights 5

The ileal bile acid transporter (IBAT) is responsible for bile acid reabsorption in the terminal ileum 3, 6
Disruption of the enterohepatic circulation can be therapeutic in certain conditions, such as using IBAT inhibitors (maralixibat, odevixibat) to treat cholestatic pruritus, as reported in the Journal of Hepatology 3, 6

Bile salt synthesis is regulated by nuclear receptors including farnesoid X receptor (FXR), which can be activated by bile acids themselves, creating a feedback loop, as noted by the European Society of Cardiology 7
Bile salts act as signaling molecules that regulate their own synthesis through FXR activation, as noted by the European Society of Cardiology 7