Using
isotope dilution-mass spectrometry, it was shown that human bile contains significant amount of
7 alpha-hydroxy-4-cholesten-3-one, an intermediate in the major pathway for
bile acid biosynthesis. In bile from 14 healthy subjects, the concentration was 0.14 +/- 0.01 micrograms/ml (mean +/- S.E.). Four bile samples collected from two patients with
cerebrotendinous xanthomatosis contained considerably higher amounts of this
steroid, 0.47-1.32 micrograms/ml. After
oral administration of [4-14C]
7 alpha-hydroxy-4-cholesten-3-one to rabbits, 14C-labeled
cholestanol could be isolated from the intestinal wall, liver, and blood after 24 h. The label incorporated into the intestinal wall was about 10% of that obtained with [4-14C]cholesta-4,6-dien-3-one or [4-14C]4-cholesten-3-one as precursors. Labeled cholesta-4,6-dien-3-one and
4-cholesten-3-one could be isolated from the intestinal contents 12 h after feeding [4-14C]
7 alpha-hydroxy-4-cholesten-3-one to rabbits. It is proposed that cholesta-4,6-dien-3-one and
4-cholesten-3-one are formed from
7 alpha-hydroxy-4-cholesten-3-one by the same mechanism as that involved in 7 alpha-dehydroxylation of primary
bile acids. We suggest that biliary
7 alpha-hydroxy-4-cholesten-3-one may be a physiological precursor to
cholestanol. The possibility is discussed that part of the increased formation of
cholestanol in patients with
cerebrotendinous xanthomatosis is due to excess biliary
7 alpha-hydroxy-4-cholesten-3-one or some metabolite of this
steroid.