Differences in hepatic levels of intermediates in bile acid biosynthesis between Cyp27(-/-) mice and CTX.
Cerebrotendinous xanthomatosis (CTX) is a rare, recessively inherited lipid storage disease characterized by a markedly reduced production of chenodeoxycholic acid and an increased formation of 25-hydroxylated bile alcohols and cholestanol. Patients with this disease are known to have mutations in the sterol 27-hydroxylase (Cyp27) gene. However, one study showed that mice with a disrupted Cyp27 gene did not have any CTX-related clinical or biochemical abnormalities. To explore the reason, hepatic cholesterol, cholestanol, and 12 intermediates in bile acid biosynthetic pathways were quantified in 10 Cyp27(-/-) and 7 Cyp27(+/+) mice, two CTX patients (untreated and treated with chenodeoxycholic acid), and four human control subjects by high resolution gas chromatography-mass spectrometry. Mitochondrial 27-hydroxycholesterol and 5beta-cholestane-3alpha,7alpha,12alpha,27-tetrol were virtually absent in both Cyp27(-/-) mice and CTX patients. In Cyp27(-/-) mice, microsomal concentrations of intermediates in the early bile acid biosynthetic pathway (7alpha-hydroxycholesterol, 7alpha-hydroxy-4-cholesten-3-one, 7alpha,12alpha-dihydroxy-4-cholesten-3-one, and 5beta-cholestane-3alpha,7alpha,12alpha-triol), 25-hydroxylated bile alcohols (5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol, 5beta-cholestane-3alpha,7alpha,12alpha,23R,25-pentol, and 5beta-cholestane-3alpha,7alpha,12alpha,24R, 25-pentol), and cholestanol were all significantly elevated compared with those in Cyp27(+/+) mice, although the levels were lower than those in untreated CTX patients. The intermediate levels in early bile acid biosynthesis were more elevated in male (16;-86% of CTX) than in female Cyp27(-/-) mice (7-30% of CTX). In contrast, 25-hydroxylated bile alcohol concentrations were not significantly different between male and female Cyp27(-/-) mice and were considerably lower (less than 14%) than those in CTX patients.These results suggest that 1) in Cyp27(-/-) mice, especially in females, classic bile acid biosynthesis via 7alpha-hydroxycholesterol is not stimulated as much as in CTX patients; and 2) formed 25-hydroxylated bile alcohols are more efficiently metabolized in Cyp27(-/-) mice than in CTX patients.
Honda
A
A
Department of Gastroenterology, University of Tsukuba, Tsukuba City 305-8575, Japan.
Salen
G
G
Matsuzaki
Y
Y
Batta
A K
AK
Xu
G
G
Leitersdorf
E
E
Tint
G S
GS
Erickson
S K
SK
Tanaka
N
N
Shefer
S
S
D000328:Adult; D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D053493:Cholestanetriol 26-Monooxygenase; D002784:Cholesterol / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D013250:Steroid Hydroxylases / Q000235:genetics / Q000502:physiology*; D019294:Xanthomatosis, Cerebrotendinous / Q000235:genetics / Q000378:metabolism*
D001647:Bile Acids and Salts; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol; D013250:Steroid Hydroxylases; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase; C506832:Cyp27a1 protein, mouse