On the mechanism of biosynthesis of cholestanol from 7 alpha-hydroxycholesterol

In a patient with cerebrotendinous xanthomatosis (CTX), a small part of i.v. administered [7 beta-3H]-7 alpha-hydroxycholesterol was converted into cholestanol. Traces of 3H were also found in plasma cholesterol, but its specific radioactivity was only about 1% of that of cholestanol. When [7 beta-3H]-7 alpha-hydroxycholesterol was given orally to rabbits, significant amounts of 3H were found in cholestanol in different organs. Much less 3H was found in cholesterol. Our results support the conclusion that the pathway from 7 alpha-hydroxycholesterol to cholestanol does not involve cholesterol, but 7 alpha-hydroxy-4-cholesten-3-one and cholesta-4,6-dien-3-one as intermediates.