Cerebrospinal fluid steroidomics: are bioactive bile acids present in brain?
In this study we have profiled the free sterol content of cerebrospinal fluid by a combination of charge tagging and liquid chromatography-tandem mass spectrometry. Surprisingly, the most abundant cholesterol metabolites were found to be C(27) and C(24) intermediates of the bile acid biosynthetic pathways with structures corresponding to 7alpha-hydroxy-3-oxocholest-4-en-26-oic acid (7.170 +/- 2.826 ng/ml, mean +/- S.D., six subjects), 3beta-hydroxycholest-5-en-26-oic acid (0.416 +/- 0.193 ng/ml), 7alpha,x-dihydroxy-3-oxocholest-4-en-26-oic acid (1.330 +/- 0.543 ng/ml), and 7alpha-hydroxy-3-oxochol-4-en-24-oic acid (0.172 +/- 0.085 ng/ml), and the C(26) sterol 7alpha-hydroxy-26-norcholest-4-ene-3,x-dione (0.204 +/- 0.083 ng/ml), where x is an oxygen atom either on the CD rings or more likely on the C-17 side chain. The ability of intermediates of the bile acid biosynthetic pathways to activate the liver X receptors (LXRs) and the farnesoid X receptor was also evaluated. The acidic cholesterol metabolites 3beta-hydroxycholest-5-en-26-oic acid and 3beta,7alpha-dihydroxycholest-5-en-26-oic acid were found to activate LXR in a luciferase assay, but the major metabolite identified in this study, i.e. 7alpha-hydroxy-3-oxocholest-4-en-26-oic acid, was not an LXR ligand. 7Alpha-hydroxy-3-oxocholest-4-en-26-oic acid is formed from 3beta,7alpha-dihydroxycholest-5-en-26-oic acid in a reaction catalyzed by 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase (HSD3B7), which may thus represent a deactivation pathway of LXR ligands in brain. Significantly, LXR activation has been found to reduce the symptoms of Alzheimer disease (Fan, J., Donkin, J., and Wellington C. (2009) Biofactors 35, 239-248); thus, cholesterol metabolites may play an important role in the etiology of Alzheimer disease.
Ogundare
Michael
M
Institute of Mass Spectrometry, School of Medicine, Grove Building, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom.
Theofilopoulos
Spyridon
S
Lockhart
Andrew
A
Hall
Leslie J
LJ
Arenas
Ernest
E
Sjövall
Jan
J
Brenton
A Gareth
AG
Wang
Yuqin
Y
Griffiths
William J
WJ
D001647:Bile Acids and Salts / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002555:Cerebrospinal Fluid / Q000378:metabolism*; D002635:Chenodeoxycholic Acid / Q000031:analogs & derivatives; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D000071518:Liver X Receptors; D013058:Mass Spectrometry; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2 / Q000378:metabolism; D057093:Orphan Nuclear Receptors / Q000378:metabolism; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D047488:Retinoid X Receptors / Q000378:metabolism; D013261:Sterols / Q000378:metabolism*; D000099150:Receptor, Farnesoid X-Activated
D001647:Bile Acids and Salts; D002635:Chenodeoxycholic Acid; D000071518:Liver X Receptors; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D047488:Retinoid X Receptors; D013261:Sterols; D000099150:Receptor, Farnesoid X-Activated