|
pubmed:abstractText |
Bile acid production in cerebrotendinous xanthomatosis (CTX) is subnormal, yet the activity of cholesterol 7alpha-hydroxylase, the rate-determining enzyme of bile acid synthesis, is elevated. To explain this discrepancy, bile acid precursors were sought in bile and feces of three CTX subjects. Over 10% of the total sterols excreted in bile and feces consisted of compounds more polar than cholesterol. Chromatographic analysis of the polar fractions in conjunction with gasliquid chromatography (GLC)-mass spectrometry indicated two major constituents, 5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol and 5beta-cholestane-3alpha,7alpha,12alpha,24xi,25-pentol. After i.v. injection of [4-(14)C]cholesterol both bile alcohols were radioactive proving that they were derived from cholesterol. The accumulation of alcohols hydroxylated at C-25 and C-24,25 suggests that decreased bile acid synthesis in CTX results from impaired oxidation of the cholesterol side chain. This finding and the virtual absence of intermediates hydroxylated at C-26 indicate that current views of the major pathway of bile acid synthesis may require revision.
|
