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Bile acid biosynthesis in Smith-Lemli-Opitz syndrome bypassing cholesterol: Potential importance of pathway intermediates

Jonas Abdel-Khalik, Tom Hearn Orcid Logo, Alison Dickson, Peter Crick, Eylan Yutuc Orcid Logo, Karl Austin-Muttitt, Brian W. Bigger, Andrew A. Morris, Cedric H. Shackleton, Peter T. Clayton, Takashi Iida, Ria Sircar, Rajat Rohatgi, Hanns-Ulrich Marschall, Jan Sjövall, Ingemar Björkhem, Jonathan Mullins Orcid Logo, William Griffiths Orcid Logo, Yuqin Wang Orcid Logo

The Journal of Steroid Biochemistry and Molecular Biology, Volume: 206, Start page: 105794

Swansea University Authors: Jonas Abdel-Khalik, Tom Hearn Orcid Logo, Alison Dickson, Peter Crick, Eylan Yutuc Orcid Logo, Karl Austin-Muttitt, Jonathan Mullins Orcid Logo, William Griffiths Orcid Logo, Yuqin Wang Orcid Logo

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Abstract

Bile acids are the end products of cholesterol metabolism secreted into bile. They are essential for the absorption of lipids and lipid soluble compounds from the intestine. Here we have identified a series of unusual Δ5-unsaturated bile acids in plasma and urine of patients with Smith-Lemli-Opitz s...

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Published in: The Journal of Steroid Biochemistry and Molecular Biology
ISSN: 0960-0760
Published: Elsevier BV 2021
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa55690
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Abstract: Bile acids are the end products of cholesterol metabolism secreted into bile. They are essential for the absorption of lipids and lipid soluble compounds from the intestine. Here we have identified a series of unusual Δ5-unsaturated bile acids in plasma and urine of patients with Smith-Lemli-Opitz syndrome (SLOS), a defect in cholesterol biosynthesis resulting in elevated levels of 7-dehydrocholesterol (7-DHC), an immediate precursor of cholesterol. Using liquid chromatography – mass spectrometry (LC-MS) we have uncovered a pathway of bile acid biosynthesis in SLOS avoiding cholesterol starting with 7-DHC and proceeding through 7-oxo and 7β-hydroxy intermediates. This pathway also occurs to a minor extent in healthy humans, but elevated levels of pathway intermediates could be responsible for some of the features SLOS. The pathway is also active in SLOS affected pregnancies as revealed by analysis of amniotic fluid. Importantly, intermediates in the pathway, 25-hydroxy-7-oxocholesterol, (25R)26-hydroxy-7-oxocholesterol, 3β-hydroxy-7-oxocholest-5-en-(25R)26-oic acid and the analogous 7β-hydroxysterols are modulators of the activity of Smoothened (Smo), an oncoprotein that mediates Hedgehog (Hh) signalling across membranes during embryogenesis and in the regeneration of postembryonic tissue. Computational docking of the 7-oxo and 7β-hydroxy compounds to the extracellular cysteine rich domain of Smo reveals that they bind in the same groove as both 20S-hydroxycholesterol and cholesterol, known activators of the Hh pathway.
Keywords: sterol; oxysterol; bile acid7-dehydrocholesterol; Smith-Lemli-Opitz syndrome; high-performance liquid chromatography; mass spectrometry; Hedgehog signalling pathway
College: Faculty of Medicine, Health and Life Sciences
Funders: UKRI, BB/N015932/1
Start Page: 105794