What is the process called by which microbiota convert primary bile acids to secondary bile acids?

• A. Deconjugation
• B. 7β-hydroxylation
• C. 7α-dehydroxylation
• D. Sulfation

Answer: (C)

Microbiota modify bile acids by removing the 7α-hydroxyl group, a process called 7α-dehydroxylation. Primary bile acids made in the liver—cholic acid and chenodeoxycholic acid—are secreted (often after conjugation with glycine or taurine) into the intestine. Certain gut bacteria carry out 7α-dehydroxylation, producing the secondary bile acids deoxycholic acid from cholic acid and lithocholic acid from chenodeoxycholic acid. This step is distinct from deconjugation, which simply removes the glycine or taurine conjugate; it is also different from 7β-hydroxylation and from sulfation, which are not the pathways that generate these secondary bile acids.