Biology subjects

Yutuc, E.

Publications and source records attributed to Yutuc, E..

5 recordsLinked to original sources

bioRxiv2022

HSD3B1 is an Oxysterol 3β-Hydroxysteroid Dehydrogenase in Human Placenta

Most biologically active oxysterols have a 3{beta}-hydroxy-5-ene function in the ring system with an additional site of oxidation at C-7 or on the side-chain. In blood plasma oxysterols with a 7-hydroxy group are also observed with the alternative 3-oxo-4-ene function in the ring system formed by ubiquitously expressed 3{beta}-hydroxy-{Delta}5-C27-steroid oxidoreductase {Delta}5-isomerase, HSD3B7. However, oxysterols without a 7-hydroxy group are not substrates for HSD3B7 and are not usually observed with the 3-oxo-4-ene function. Here we report the unexpected identification of oxysterols in plasma derived from umbilical cord blood and blood from pregnant women taken before delivery at 37+ weeks of gestation, of side-chain oxysterols with a 3-oxo-4-ene function but no 7-hydroxy group. These 3-oxo-4-ene oxysterols were also identified in placenta, leading to the hypothesis that they may be formed by a previously unrecognised 3{beta}-hydroxy-{Delta}5-C27-steroid oxidoreductase {Delta}5-isomerase activity of HSD3B1, an enzyme which is highly expressed in placenta. Proof of principle experiments confirmed that HSD3B1 has this activity. We speculate that HSD3B1 in placenta is the source of the unexpected 3-oxo-4-ene oxysterols in cord and pregnant womens plasma and may have a role in controlling the abundance of biologically active oxysterols delivered to the fetus.

biochemistry↗

bioRxiv2022

Identification of Unusual Oxysterols Biosynthesised in Human Pregnancy by Charge-Tagging and Liquid Chromatography - Mass Spectrometry

The aim of this study was to identify sterols, oxysterols and any down-stream metabolites in placenta, umbilical cord blood plasma, maternal plasma and amniotic fluid to enhance our knowledge of the involvement of these molecules in pregnancy. We confirm the identification of 20S- hydroxycholesterol in human placenta, previously reported in a single publication, and propose a pathway from 22R-hydroxycholesterol to a C27 bile acid of probable structure 3{beta},20R,22R- trihydroxycholest-5-en-(25R)26-oic acid. The pathway is evident not only in placenta, but pathway intermediates are also found in umbilical cord plasma, maternal plasma and amniotic fluid but not non-pregnant women.

biochemistry↗

bioRxiv2020

Visualising Cholesterol in Brain by On-Tissue Derivatisation and Quantitative Mass Spectrometry Imaging

Despite being a critical molecule for neurobiology and brain health, mass spectrometry imaging (MSI) of cholesterol has been under reported compared to other lipids, due to the difficulty in ionising the sterol molecule. In the present work we have employed an on-tissue enzyme-assisted derivatisation strategy to improve detection of cholesterol in brain tissue sections. We report distribution and levels of cholesterol across specific brain structures of the mouse brain, in a model of Niemann-Pick type C1 (NPC1) disease, and during brain development. MSI revealed how cholesterol changes during development and that in the adult is highest in pons and medulla of the brain stem. Cholesterol was significantly reduced in the corpus callosum and other brain regions in the Npc1 null mouse, confirming hypomyelination at the molecular level. Our study demonstrates the potential of MSI to the study of sterols in neuroscience.

biochemistry↗

bioRxiv2018

Imaging Oxysterols in Mouse Brain by On-Tissue Derivatisation-Robotic Liquid Micro-Extraction Surface Analysis-Liquid Chromatography Mass Spectrometry

Dysregulated cholesterol metabolism is implicated in a number of neurological disorders. Many sterols, including cholesterol and its precursors and metabolites, are biologically active and important for proper brain function. However, spatial cholesterol metabolism in brain and the resulting sterol distributions are poorly defined. To better understand cholesterol metabolism in situ across the complex functional regions of brain, we have developed on-tissue enzyme-assisted derivatisation in combination with micro-liquid-extraction for surface analysis and liquid chromatography - mass spectrometry to image sterols in tissue slices (10 {micro}m) of mouse brain. The method provides sterolomic analysis at 400 {micro}m spot diameter with a limit of quantification of 0.01 ng/mm2. It overcomes the limitations of previous mass spectrometry imaging techniques in analysis of low abundance and difficult to ionise sterol molecules, allowing isomer differentiation and structure identification. Here we demonstrate the spatial distribution and quantification of multiple sterols involved in cholesterol metabolic pathways in wild type and cholesterol 24S-hydroxylase knock-out mouse brain. The technology described provides a powerful tool for future studies of spatial cholesterol metabolism in healthy and diseased tissues.\n\nSignificanceThe brain is a remarkably complex organ and cholesterol homeostasis underpins brain function. It is known that cholesterol is not evenly distributed across different brain regions, however, the precise map of cholesterol metabolism in the brain remains unclear. If cholesterol metabolism is to be correlated with brain function it is essential to generate such a map. Here we describe an advanced mass spectrometry imaging platform to reveal spatial cholesterol metabolism in situ at 400 {micro}m resolution on 10 {micro}m tissue slices from mouse brain. We mapped, not only cholesterol, but also other biologically active sterols arising from cholesterol turnover in both wild type and mice lacking cholesterol 24-hydroxylase (Cyp46a1), the major cholesterol metabolising enzyme.

neuroscience↗

bioRxiv2018

Bile Acid Biosynthesis Avoiding Cholesterol

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 investigated the bile acid content of plasma and urine from patients with a defect in cholesterol biosynthesis, i.e. Smith-Lemli-Opitz syndrome (SLOS), resulting in elevated levels of 7-dehydrocholesterol (7-DHC), an immediate precursor of cholesterol. Using liquid chromatography - mass spectrometry (LC-MS) we have identified a novel pathway of bile acid biosynthesis in SLOS avoiding cholesterol starting with 7-DHC. This pathway also proceeds to a minor extent in healthy individuals. Monitoring of the pathway products could provide a rapid diagnostic for SLOS while elevated levels of pathway intermediates could be responsible for some of the features of the disease. Importantly, intermediates in the pathway are modulators of the activity of Smoothened, an oncoprotein that mediates Hedgehog signalling during embryogenesis and regeneration of postembryonic tissue.

biochemistry↗