Taurodeoxycholic

Taurodeoxycholic acid, abbreviated TDCA, is a taurine conjugate of the secondary bile acid deoxycholic acid. It is formed in the liver by conjugating deoxycholic acid with the amino sulfonic acid taurine and is then secreted into bile as part of the bile acid pool. Conjugation with taurine increases the water solubility of bile acids and reduces passive diffusion, aiding their excretion into the bile.

Biological role and metabolism: Like other bile acids, TDCA is involved in the emulsification and digestion of dietary fats by helping to form micelles that solubilize lipids. TDCA participates in the enterohepatic circulation, being reabsorbed from the intestine and returned to the liver. In the gut, bacterial processes can deconjugate TDCA, regenerating deoxycholic acid, which can then be reconjugated in the liver or further metabolized.

Formation and distribution: Primary bile acids such as cholic and chenodeoxycholic acids are secreted by the liver, and gut bacteria can convert some into deoxycholic acid. In the liver, deoxycholic acid is conjugated with taurine via the enzyme BAAT (bile acid-CoA:amino acid N-acyltransferase) to form TDCA. TDCA is present in bile and, to a lesser extent, in systemic circulation or urine as part of bile acid profiles studied in clinical and research settings.

Clinical relevance: Alterations in bile acid composition, including TDCA levels, can be associated with liver or biliary disorders and changes in gut microbiota. TDCA is often measured in studies evaluating hepatic function and enterohepatic circulation, contributing to broader bile acid profiling.