Fig. 6.
The metabolism of C4 in cerebrotendinous xanthomatosis patients and rabbits provided a potential mechanism for bile acid 7-dehydroxylation by intestinal bacteria. Studies by Ingemar Björkhem in CTX patients with radiolabeled 7⍺-hydroxy-4-cholesten-3-one (C4) indicated that the C7⍺-hydroxyl group was highly labile and converted to cholesta-4,6-dien-3-one and then to cholestanol by intestinal bacteria. An analogy was made between 7⍺-dehydroxylation of C4 and the 7⍺-dehydroxylation of CA and CDCA by intestinal bacteria, in a mechanism distinct from that proposed in the Bergström-Samuelsson model, which did not include a 3-oxo-Δ4-steroid intermediate. CDCA, chenodeoxycholic acid; CTX, cerebrotendinous xanthomatosis.