27-Hydroxycholesterol

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Ingemar Björkhem - One of the best experts on this subject based on the ideXlab platform.

  • marked accumulation of 27 hydroxycholesterol in spg5 patients with hereditary spastic paresis
    Journal of Lipid Research, 2010
    Co-Authors: Rebecca Schule, Ludger Schols, Teepu Siddique, Han Xiang Deng, Yi Yang, Sandra Donkervoort, Magnus Hansson, Ricardo E Madrid, Nailah Siddique, Ingemar Björkhem
    Abstract:

    Patients with a recessively inherited “pure” hereditary spastic paresis (SPG5) have mutations in the gene coding for the oxysterol 7 α hydroxylase (CYP7B1). One of the expected metabolic consequences of such mutations is accumulation of oxysterol substrates due to decreased enzyme activity. In accordance with this, we demonstrate here that four patients with the SPG5 disease have 6- to 9-fold increased plasma levels of 27-Hydroxycholesterol. A much higher increase, 30- to 50-fold, was found in cerebrospinal fluid. The plasma levels of 25-hydroxycholesterol were increased about 100-fold. There were no measurable levels of this oxysterol in cerebrospinal fluid. The pattern of bile acids in serum was normal, suggesting a normal bile acid synthesis. The findings are discussed in relation to two transgenic mouse models with increased levels of 27-hydroxy cholesterol in the circulation but without neurological symptoms: the cyp27a1 transgenic mouse and the cyp7b1 knockout mouse. The absolute plasma levels of 27-Hydroxycholesterol in the latter models are, however, only about 20% of those in the SPG5 patients. If the accumulation of 27-Hydroxycholesterol is an important pathogenetic factor, a reduction of its levels may reduce or prevent the neurological symptoms. A possible strategy to achieve this is discussed.

  • changes in the levels of cerebral and extracerebral sterols in the brain of patients with alzheimer s disease
    Journal of Lipid Research, 2004
    Co-Authors: Maura Heverin, Ulf Diczfalusy, Dieter Lutjohann, Nenad Bogdanovic, Thomas A Bayer, Irina A Pikuleva, Lionel Bretillon, Bengt Winblad, Ingemar Björkhem
    Abstract:

    : 24S-hydroxycholesterol is a side-chain oxidized oxysterol formed in the brain that is continuously crossing the blood-brain barrier to reach the circulation. There may be an opposite flux of 27-Hydroxycholesterol, which is formed to a lower extent in the brain than in most other organs. Here we measured cholesterol, lathosterol, 24S- and 27-Hydroxycholesterol, and plant sterols in four different brain areas of deceased Alzheimer's disease (AD) patients and controls. 24S-hydroxycholesterol was decreased and 27-Hydroxycholesterol increased in all the brain samples from the AD patients. The difference was statistically significant in four of the eight comparisons. The ratio of 27-Hydroxycholesterol to 24S-hydroxycholesterol was significantly increased in all brain areas of the AD patients and also in the brains of aged mice expressing the Swedish Alzheimer mutation APP751. Cholesterol 24S-hydroxylase and 27-hydroxylase protein was not significantly different between AD patients and controls. A high correlation was observed between the levels of 24S-hydroxycholesterol and lathosterol in the frontal cortex of the AD patients but not in the controls. Most probably the high levels of 27-Hydroxycholesterol are due to increased influx of this steroid over the blood-brain barrier and the lower levels of 24S-hydroxycholesterol to decreased production. The high correlation between lathosterol and 24-hydroxycholesterol is consistent with a close coupling between synthesis and metabolism of cholesterol in the frontal cortex of the AD brain.

  • on the substrate specificity of human cyp27a1 implications for bile acid and cholestanol formation
    Journal of Lipid Research, 2003
    Co-Authors: Maria Norlin, Ingemar Björkhem, Sara Von Bahr, Kjell Wikvall
    Abstract:

    The mitochondrial sterol 27-hydroxylase (CYP27A1) is required for degradation of the C27-sterol side chain in bile acid biosynthesis. CYP27A1 seems, however, to have roles beyond this, as illustrated by patients with a deficient sterol 27-hydroxylase due to mutations of the CYP27A1 gene [cerebrotendinous xanthomatosis (CTX)]. These subjects have symptoms ranging from accumulation of bile alcohols and cholestanol to accelerated atherosclerosis and progressive neurologic impairment. The present work describes a detailed investigation on the substrate specificity of recombinant human CYP27A1. In accordance with some previous work with rat liver mitochondria, the activity in general increased with the polarity of the substrate. An obvious example was the finding that cholesterol was 27-hydroxylated more efficiently than cholesterol oleate but less efficiently than cholesterol sulfate. The oxysterols 24S-hydroxycholesterol and 25-hydroxycholesterol were 27-hydroxylated less efficiently than cholesterol, possibly due to steric hindrance. Surprisingly, sterols with a 3-oxo-Delta4 structure were found to be hydroxylated at a much higher rate than the corresponding sterols with a 3beta-hydroxy-Delta5 structure. The rates of hydroxylation of the sterols were: 7alpha-hydroxy-4-cholesten-3-one>4-cholesten-3-one>7alpha-hydroxycholesterol>24-hydroxy-4-cholesten-3-one> cholesterol>25-hydroxy-4-cholesten-3-one>24-hydroxycholesterol>or=25-hydroxycholesterol. The possibility is discussed that the findings may have implications for oxysterol-mediated regulation of gene expression. The very high activity of CYP27A1 towards the cholestanol precursor 4-cholesten-3-one may be of importance in connection with the accumulation of cholestanol in patients with CTX.

  • side chain oxidized oxysterols in cerebrospinal fluid and the integrity of blood brain and blood cerebrospinal fluid barriers
    Journal of Lipid Research, 2003
    Co-Authors: Ulf Diczfalusy, Valerio Leoni, Steve Meaney, Thomas Masterman, Pria Patel, Ingemar Björkhem
    Abstract:

    The side chain oxidized oxysterol 24S-hydroxycholesterol (24-OH-chol) is formed almost exclusively in the brain, and there is a continuous passage of this oxysterol through the circulation to the liver. 27-Hydroxycholesterol (27-OH-chol) is produced in most organs and is also taken up by the liver. The 27-OH-chol-24-OH-chol ratio is about 0.1 in the brain and about 2 in the circulation. This ratio was found to be about 0.4 in cerebrospinal fluid (CSF) of asymptomatic patients, consistent with a major contribution from the circulation in the case of 27-OH-chol. In accordance with this, we demonstrated a significant flux of deuterium labeled 27-OH-chol from plasma to the CSF in a healthy volunteer. Patients with a defective blood-brain barrier were found to have markedly increased absolute levels (up to 10-fold) of both 27-OH-chol and 24-OH-chol in CSF, with a ratio between the two sterols reaching up to 2. There was a significant positive correlation between the levels of both oxysterols in CSF and the albuminCSF-albuminplasma ratio. The 27-OH-cholCSF-24-OH-cholCSF ratio was found to be about normal in patients with active multiple sclerosis and significantly increased in patients with meningitis, polyneuropathy, or hemorrhages. Results are discussed in relation to the possible use of 24-OH-cholCSF as a surrogate marker of central nervous system demyelination and/or neuronal death.

  • on the rate of translocation in vitro and kinetics in vivo of the major oxysterols in human circulation critical importance of the position of the oxygen function
    Journal of Lipid Research, 2002
    Co-Authors: Steve Meaney, Ulf Diczfalusy, Karl Bodin, Ingemar Björkhem
    Abstract:

    Oxysterols possess powerful biological activities. Some of their effects on the regulation of key enzymes are similar to those of cholesterol, but are much more potent. One of the critical properties of oxysterols is their ability to pass lipophilic membranes at a high rate. Transfer of unesterified 25-hydroxycholesterol from red blood cells to plasma has been reported to occur more than 1,000 times faster than cholesterol. Here we have measured the relative rate of such translocation of the three major oxysterols in human circulation: 27-Hydroxycholesterol, 24S-hydroxycholesterol, and 4β-hydroxycholesterol. The distance from the 3β-hydroxyl group to the additional hydroxyl group is the greatest possible in 27-Hydroxycholesterol and the least possible in 4β-hydroxycholesterol. The rate of exchange between erythrocytes and plasma was found to be high for 27-Hydroxycholesterol and 24S-hydroxycholesterol, and hardly possible to measure for 4β-hydroxycholesterol and cholesterol. When injected intravenously into humans, deuterium labeled 24- and 27-Hydroxycholesterol caused an immediate high enrichment of the corresponding plasma sterols followed by a decay. After injection of labeled 4β-hydroxycholesterol, the maximum deuterium enrichment occurred after 2–3 h, when secretion of the oxysterol from the liver is likely to be the limiting factor. When radiolabeled cholesterol was injected under the same conditions, maximum appearance of label occurred after about 2 days. The results illustrate the importance of the position of the additional oxygen in oxysterols and are discussed in relation to the rate of metabolism and biological effects of these oxysterols.

Ulf Diczfalusy - One of the best experts on this subject based on the ideXlab platform.

  • comparison of endogenous 4β hydroxycholesterol with midazolam as markers for cyp3a4 induction by rifampicin
    Drug Metabolism and Disposition, 2013
    Co-Authors: Linda Bjorkhembergman, Leif Bertilsson, Eva Bredberg, Tommy B Andersson, Tobias Backstrom, Hanna Nylen, Yuko Ronquistnii, Ulf Diczfalusy
    Abstract:

    CYP3A4, considered the most important enzyme in drug metabolism, is often involved in drug-drug interactions. When developing new drugs, appropriate markers for detecting CYP3A4 induction are needed. Our study compared endogenously formed 4 β -hydroxycholesterol with the midazolam clearance in plasma and the 6 β -hydroxycortisol/cortisol ratio in urine as markers for CYP3A4 induction. To this end, we performed a clinical trial in which 24 healthy subjects were randomized to 10, 20, or 100 mg daily doses of rifampicin for 14 days ( n = 8 in each group) to achieve a low and moderate CYP3A4 induction. The CYP3A4 induction could be detected even at the lowest dose of rifampicin (10 mg) via the estimated midazolam clearance, the 4 β -hydroxycholesterol ratio (both P β -hydroxycortisol ratio ( P β -hydroxycholesterol/cholesterol ratio; and 1.7, 2.9, and 3.1 for the 6 β -hydroxycortisol/cortisol ratio. In conclusion, the 4 β -hydroxycholesterol ratio is comparable to midazolam clearance as a marker of CYP3A4 induction, and each may be used to evaluate CYP3A4 induction in clinical trials evaluating drug-drug interactions for new drugs.

  • serum levels of 25 hydroxyvitamin d and the cyp3a biomarker 4β hydroxycholesterol in a high dose vitamin d supplementation study
    Drug Metabolism and Disposition, 2013
    Co-Authors: Linda Bjorkhembergman, Hanna Nylen, Annacarin Norlin, Jonatan D Lindh, Lena Ekstrom, Erik Eliasson, Peter Bergman, Ulf Diczfalusy
    Abstract:

    The primary aim was to study the relationship between individual serum levels of 25-hydroxyvitamin D and 4 β -hydroxycholesterol, which is an endogenous biomarker of the drug-metabolizing CYP3A enzymes. In addition, the relationship between this biomarker and inflammation, measured as C-reactive protein (CRP), was investigated. Serum samples were used from a recently performed clinical trial in patients with antibody deficiency or increased susceptibility to respiratory tract infections that were randomized to either placebo or high-dose (4000 IU/day) vitamin D for 12 months. One hundred sixteen patients were included in the final analyses, and serum samples collected 6 months after study start were analyzed. At this time point, 25-hydroxyvitamin D levels were found to range between 10 and 284 nM. Individual levels of 25-hydroxyvitamin D as well as CRP were compared with 4 β -hydroxycholesterol levels. In addition, all participants were genotyped for two polymorphisms (Taq1 and Foq1) in the vitamin D receptor gene. There was no significant correlation between individual serum levels of 25-hydroxyvitamin D and 4 β -hydroxycholesterol. However, a moderate, but statistically significant, negative correlation between CRP and 4 β -hydroxycholesterol levels was observed. This study in patients with highly variable serum levels of 25-hydroxyvitamin D could not reveal any relationship between vitamin D and 4 β -hydroxycholesterol, an endogenous biomarker of CYP3A activity. However, the negative correlation between CRP and 4 β -hydroxycholesterol supports earlier experimental results that inflammation may suppress hepatic CYP3A activity, a finding of potentially high clinical relevance that warrants further exploration.

  • on the formation and possible biological role of 25 hydroxycholesterol
    Biochimie, 2013
    Co-Authors: Ulf Diczfalusy
    Abstract:

    Abstract The oxysterol 25-hydroxycholesterol is a widely used compound displaying an array of pharmacological actions in in vitro systems and cell based experimental systems. In spite of the frequent use of this compound over the last few decades and a large number of studies in vitro and in vivo, its mechanism of formation in vivo is still not well understood. Cholesterol autoxidation does not seem to be an important contributor to in vivo formation of 25-hydroxycholesterol. A number of different cytochrome P450 enzymes such as CYP27A1 and CYP3A4 have been reported to catalyze the conversion of cholesterol to 25-hydroxycholesterol in vitro, but the importance of these reactions in vivo remains unclear. The dioxygenase enzyme cholesterol 25-hydroxylase has been shown to generate 25-hydroxycholesterol, but in cholesterol 25-hydroxylase knockout mice there are still significant levels of 25-hydroxycholesterol in several tissues. This suggests that cholesterol 25-hydroxylase is not the sole producer of 25-hydroxycholesterol. The relative importance of different mechanisms of formation of 25-hydroxycholesterol in vivo have still to be elucidated. The maintenance of cholesterol homeostasis is of great importance to supply tissues with the appropriate amount of cholesterol and prevent accumulation that may affect health. Numerous articles mention 25-hydroxycholesterol as an important regulator of cholesterol metabolism. However, mice with a disruption of the cholesterol 25-hydroxylase gene regulate cholesterol metabolism normally and patients with highly elevated levels of 25-hydroxycholesterol also display normal cholesterol and bile acid levels. These reports challenge the hypothesis that 25-hydroxycholesterol is an important regulator of cholesterol metabolism. Recent reports suggest that 25-hydroxycholesterol and one of its metabolites may have functions in regulation of humoral immunity. Thus, 25-hydroxycholesterol may be more important as a regulator of immunity than as a regulator of cholesterol metabolism.

  • 4β hydroxycholesterol as an endogenous marker for cyp3a4 5 activity stability and half life of elimination after induction with rifampicin
    British Journal of Clinical Pharmacology, 2009
    Co-Authors: Ulf Diczfalusy, Kajsa P Kanebratt, Eva Bredberg, Tommy B Andersson, Ylva Bottiger, Leif Bertilsson
    Abstract:

    WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • We have suggested that 4β-hydroxycholesterol may be used as an endogenous marker of CYP3A activity. • Recently, we found unexpectedly that the plasma concentration of 4β-hydroxycholesterol continued to increase for several weeks after complete induction of CYP3A4/5 by carbamazepine. • In the present study we investigated the time course of elimination of 4β-hydroxycholesterol from the circulation following CYP3A induction with rifampicin. WHAT THIS STUDY ADDS • 4β-Hydroxycholesterol is eliminated very slowly from the circulation with an apparent half-life of 17 days. • The long half-life results in a low variation in plasma concentration with time, but excludes 4β-hydroxycholesterol as a marker for rapid changes in CYP3A activity. AIMS The oxysterol 4β-hydroxycholesterol has been suggested as a marker for CYP3A4/5 activity. We have previously shown that plasma 4β-hydroxycholesterol continues to increase for several weeks after maximal induction of CYP3A4/5 by carbamazepine at the dose given. In the present study we aimed to determine the time course of the decrease in plasma 4β-hydroxycholesterol after termination of induction of CYP3A4/5 by rifampicin. An additional aim was to determine the variation in plasma level of 4β-hydroxycholesterol with time in 12 untreated healthy volunteers. METHODS Twenty-four healthy subjects were allocated into three study groups of equal sizes. The volunteers were treated with rifampicin (either 20 mg day–1, 100 mg day–1 or 500 mg day–1) for 2 weeks. Blood samples were taken before, during and after rifampicin treatment. In another group of 12 untreated volunteers blood samples were collected at different time points in order to determine the intraindividual variations in plasma 4β-hydroxycholesterol concentrations. Plasma levels of 4β-hydroxycholesterol were determined by isotope-dilution gas chromatography–mass spectrometry. RESULTS Rifampicin treatment increased plasma 4β-hydroxycholesterol levels. After termination of rifampicin treatment plasma levels of 4β-hydroxycholesterol decreased slowly with an apparent half-life of 17 days. The intraindividual variation in plasma levels of 4β-hydroxycholesterol in untreated subjects was low, with coefficients of variation of between 4.8 and 13.2% over a period of 3 months. CONCLUSIONS After termination of induction of CYP3A4/5, plasma 4β-hydroxycholesterol levels decreased slowly during 8 weeks. The half-life of elimination (17 days) resembled that of cholesterol rather than other oxysterols. The long half-life results in stable plasma concentrations with time.

  • changes in the levels of cerebral and extracerebral sterols in the brain of patients with alzheimer s disease
    Journal of Lipid Research, 2004
    Co-Authors: Maura Heverin, Ulf Diczfalusy, Dieter Lutjohann, Nenad Bogdanovic, Thomas A Bayer, Irina A Pikuleva, Lionel Bretillon, Bengt Winblad, Ingemar Björkhem
    Abstract:

    : 24S-hydroxycholesterol is a side-chain oxidized oxysterol formed in the brain that is continuously crossing the blood-brain barrier to reach the circulation. There may be an opposite flux of 27-Hydroxycholesterol, which is formed to a lower extent in the brain than in most other organs. Here we measured cholesterol, lathosterol, 24S- and 27-Hydroxycholesterol, and plant sterols in four different brain areas of deceased Alzheimer's disease (AD) patients and controls. 24S-hydroxycholesterol was decreased and 27-Hydroxycholesterol increased in all the brain samples from the AD patients. The difference was statistically significant in four of the eight comparisons. The ratio of 27-Hydroxycholesterol to 24S-hydroxycholesterol was significantly increased in all brain areas of the AD patients and also in the brains of aged mice expressing the Swedish Alzheimer mutation APP751. Cholesterol 24S-hydroxylase and 27-hydroxylase protein was not significantly different between AD patients and controls. A high correlation was observed between the levels of 24S-hydroxycholesterol and lathosterol in the frontal cortex of the AD patients but not in the controls. Most probably the high levels of 27-Hydroxycholesterol are due to increased influx of this steroid over the blood-brain barrier and the lower levels of 24S-hydroxycholesterol to decreased production. The high correlation between lathosterol and 24-hydroxycholesterol is consistent with a close coupling between synthesis and metabolism of cholesterol in the frontal cortex of the AD brain.

Kjell Wikvall - One of the best experts on this subject based on the ideXlab platform.

  • on the substrate specificity of human cyp27a1 implications for bile acid and cholestanol formation
    Journal of Lipid Research, 2003
    Co-Authors: Maria Norlin, Ingemar Björkhem, Sara Von Bahr, Kjell Wikvall
    Abstract:

    The mitochondrial sterol 27-hydroxylase (CYP27A1) is required for degradation of the C27-sterol side chain in bile acid biosynthesis. CYP27A1 seems, however, to have roles beyond this, as illustrated by patients with a deficient sterol 27-hydroxylase due to mutations of the CYP27A1 gene [cerebrotendinous xanthomatosis (CTX)]. These subjects have symptoms ranging from accumulation of bile alcohols and cholestanol to accelerated atherosclerosis and progressive neurologic impairment. The present work describes a detailed investigation on the substrate specificity of recombinant human CYP27A1. In accordance with some previous work with rat liver mitochondria, the activity in general increased with the polarity of the substrate. An obvious example was the finding that cholesterol was 27-hydroxylated more efficiently than cholesterol oleate but less efficiently than cholesterol sulfate. The oxysterols 24S-hydroxycholesterol and 25-hydroxycholesterol were 27-hydroxylated less efficiently than cholesterol, possibly due to steric hindrance. Surprisingly, sterols with a 3-oxo-Delta4 structure were found to be hydroxylated at a much higher rate than the corresponding sterols with a 3beta-hydroxy-Delta5 structure. The rates of hydroxylation of the sterols were: 7alpha-hydroxy-4-cholesten-3-one>4-cholesten-3-one>7alpha-hydroxycholesterol>24-hydroxy-4-cholesten-3-one> cholesterol>25-hydroxy-4-cholesten-3-one>24-hydroxycholesterol>or=25-hydroxycholesterol. The possibility is discussed that the findings may have implications for oxysterol-mediated regulation of gene expression. The very high activity of CYP27A1 towards the cholestanol precursor 4-cholesten-3-one may be of importance in connection with the accumulation of cholestanol in patients with CTX.

  • 7α hydroxylation of 25 hydroxycholesterol in liver microsomes
    FEBS Journal, 1994
    Co-Authors: Anders Toll, Kjell Wikvall, Elly Sudjanasugiaman, Kazuhiro Kondo, Ingemar Björkhem
    Abstract:

    Rat, pig and human liver microsomes were found to catalyze 7α-hydroxylation of 25-hydroxycholesterol. In contrast to cholesterol 7α-hydroxylase activity, the 7α-hydroxylase activity towards 25-hydroxycholesterol in rat liver was not stimulated by cholestyramine treatment. After transfection with cDNA for human cholesterol 7α-hydroxylase, COS cells showed a significant activity towards cholesterol but not towards 25-hydroxycholesterol. During purification of cholesterol 7α-hydroxylase from pig liver microsomes, about 99% of the 7α-hydroxylase activity towards 25-hydroxycholesterol and 27-Hydroxycholesterol was clearly separated from 7α-hydroxylase activity for cholesterol. The small amount of 25-hydroxycholesterol 7α-hydroxylase activity retained in a partially purified preparation of cholesterol 7α-hydroxylase was not inhibited by addition of cholesterol, indicating that the oxysterol binding site is different from the cholesterol binding site, presumely due to the presence of two different enzymes. It is concluded that different enzymes are involved in 7α-hydroxylation of cholesterol and 7α hydroxylation of side-chain-oxidized cholesterol in rat, pig and human liver. Inhibition experiments with a partially purified fraction of the oxysterol 7α-hydroxylase from pig liver gave results consistent with the contention that the same enzyme is responsible for 7α hydroxylation of both 25-hydroxycholesterol and 27-Hydroxycholesterol. It has been suggested that cholesterol 7α-hydroxylase can preferentially use oxysterols, in particular 25-hydroxycholesterol, as substrates and by this means inactivate important physiological regulators of cholesterol homeostasis. Such a mechanism would explain the unique property of the liver to resist down-regulation of the low-density-lipoprotein receptor [Dueland, S., Trawick, J. D., & Davies, R. A. (1993) J. Biol. Chem. 267, 22695–22698]. The present results do not support the contention that the important coupling between cholesterol 7α-hydroxylase activity, the low-density-lipoprotein receptor activity and hydroxymethylglutaryl coenzyme A reductase activity in liver cells is due to inactivation of 25-hydroxycholesterol or 27-Hydroxycholesterol by the action of cholesterol 7α-hydroxylase.

  • 24 25 and 27 hydroxylation of cholesterol by a purified preparation of 27 hydroxylase from pig liver
    Biochimica et Biophysica Acta, 1993
    Co-Authors: Kjell Wikvall, Erik G. Lund, Ingemar Björkhem, Catrin Furster
    Abstract:

    Abstract Pig liver mitochondria were found to catalyze 27-, 25- and 24-hydroxylation of cholesterol at relative rates of about 1:0.2:0.04. An apparently homogeneous preparation of pig liver mitochondrial cytochrome P-450-27 was found to catalyze the same three hydroxylations at about the same relative rates when reconstituted with adrenodoxin and adrenodoxin reductase. The 24-hydroxycholesterol formed was shown to consist of one of the two possible stereoisomers. When using specifically deuteriumlabeled substrates a significant isotope effect was observed in the case of 24-hydroxylation(KH/KD ⪢ 10), but not 25-hydroxylation (KH/KD = 1.1), or 27-hydroxylation (KH/KD = 1.1). The difference between the 24-hydroxylation and the other two hydroxylations may be due to different interactions between cholesterol and the same enzyme, with a resulting difference with respect to the rate-limiting step in the reaction. The physiological significance of the mitochondrial 24-hydroxylation is discussed.

  • 7α hydroxylation of 26 hydroxycholesterol 3β hydroxy 5 cholestenoic acid and 3β hydroxy 5 cholenoic acid by cytochrome p 450 in pig liver microsomes
    FEBS Letters, 1992
    Co-Authors: Anders Toll, Jan Sjövall, Junichi Shoda, Magnus Axelson, Kjell Wikvall
    Abstract:

    Pig liver microsomes were found to catalyze the 7α-hydroxylation of several potential bile acid precursors besides cholesterol. 26-Hydroxycholesterol, 3β-hydroxy-5-cholestenoic acid and 3β-hydroxy-5-cholenoic acid were all efficiently converted into the 7α-hydroxylated products. Two cytochrome P-450 fractions showing 7α-hydroxylase activity could be isolated. One fraction catalyzed 7α-hydroxylation of 26-hydroxycholesterol. 3β-hydroxy-5-cholestenoic acid and 3β-hydroxy-5-cholenoic acid but was inactive towards cholesterol. The other fraction catalyzed 7α-hydroxylation of cholesterol in addition to the other substrates. 26-Hydroxycholesterol in equimolar concentration did not inhibit the cholesterol 7α-hydroxylase activity of this fraction. It is concluded that liver microsomes contain a cytochrome P-450 catalyzing 7α-hydroxylation of 26-hydroxycholesterol, 3β-hydroxy-5-cholestenoic acid and 3β-hydroxy-5-cholenoic acid. The results indicate that this cytochrome P-450 is different from that catalyzing 7α-hydroxylation of cholesterol.

Jonas Alex Morales Saute - One of the best experts on this subject based on the ideXlab platform.

  • hereditary spastic paraplegia type 5 natural history biomarkers and a randomized controlled trial
    Brain, 2017
    Co-Authors: Ludger Schols, Tim W Rattay, Imma Fischer, Christine Jagle, Matthew J Fraidakis, Jonathan Baets, Christoph Meisner, Peter Martus, Andrea Martinuzzi, Jonas Alex Morales Saute
    Abstract:

    SPG5 is a rare subtype of Hereditary Spastic Paraplegia caused by mutations in the oxysterol-7 alpha-hydroxylase gene CYP7B1. Schols et al. study properties of lipid biomarkers in SPG5 and evaluate a treatment strategy targeting oxysterol accumulation in a randomized controlled trial (STOP-SPG5).Spastic paraplegia type 5 (SPG5) is a rare subtype of hereditary spastic paraplegia, a highly heterogeneous group of neurodegenerative disorders defined by progressive neurodegeneration of the corticospinal tract motor neurons. SPG5 is caused by recessive mutations in the gene CYP7B1 encoding oxysterol-7 alpha-hydroxylase. This enzyme is involved in the degradation of cholesterol into primary bile acids. CYP7B1 deficiency has been shown to lead to accumulation of neurotoxic oxysterols. In this multicentre study, we have performed detailed clinical and biochemical analysis in 34 genetically confirmed SPG5 cases from 28 families, studied dose-dependent neurotoxicity of oxysterols in human cortical neurons and performed a randomized placebo-controlled double blind interventional trial targeting oxysterol accumulation in serum of SPG5 patients. Clinically, SPG5 manifested in childhood or adolescence (median 13 years). Gait ataxia was a common feature. SPG5 patients lost the ability to walk independently after a median disease duration of 23 years and became wheelchair dependent after a median 33 years. The overall cross-sectional progression rate of 0.56 points on the Spastic Paraplegia Rating Scale per year was slightly lower than the longitudinal progression rate of 0.80 points per year. Biochemically, marked accumulation of CYP7B1 substrates including 27-Hydroxycholesterol was confirmed in serum (n = 19) and cerebrospinal fluid (n = 17) of SPG5 patients. Moreover, 27-Hydroxycholesterol levels in serum correlated with disease severity and disease duration. Oxysterols were found to impair metabolic activity and viability of human cortical neurons at concentrations found in SPG5 patients, indicating that elevated levels of oxysterols might be key pathogenic factors in SPG5. We thus performed a randomized placebo-controlled trial (EudraCT 2015-000978-35) with atorvastatin 40 mg/day for 9 weeks in 14 SPG5 patients with 27-Hydroxycholesterol levels in serum as the primary outcome measure. Atorvastatin, but not placebo, reduced serum 27-Hydroxycholesterol from 853 ng/ml [interquartile range (IQR) 683-1113] to 641 (IQR 507-694) (-31.5%, P = 0.001, Mann-Whitney U-test). Similarly, 25-hydroxycholesterol levels in serum were reduced. In cerebrospinal fluid 27-Hydroxycholesterol was reduced by 8.4% but this did not significantly differ from placebo. As expected, no effects were seen on clinical outcome parameters in this short-term trial. In this study, we define the mutational and phenotypic spectrum of SPG5, examine the correlation of disease severity and progression with oxysterol concentrations, and demonstrate in a randomized controlled trial that atorvastatin treatment can effectively lower 27-Hydroxycholesterol levels in serum of SPG5 patients. We thus demonstrate the first causal treatment strategy in hereditary spastic paraplegia.

  • hereditary spastic paraplegia type 5 natural history biomarkers and a randomized controlled trial
    Brain, 2017
    Co-Authors: Ludger Schols, Tim W Rattay, Imma Fischer, Christine Jagle, Matthew J Fraidakis, Jonathan Baets, Christoph Meisner, Peter Martus, Andrea Martinuzzi, Jonas Alex Morales Saute
    Abstract:

    Spastic paraplegia type 5 (SPG5) is a rare subtype of hereditary spastic paraplegia, a highly heterogeneous group of neurodegenerative disorders defined by progressive neurodegeneration of the corticospinal tract motor neurons. SPG5 is caused by recessive mutations in the gene CYP7B1 encoding oxysterol-7α-hydroxylase. This enzyme is involved in the degradation of cholesterol into primary bile acids. CYP7B1 deficiency has been shown to lead to accumulation of neurotoxic oxysterols. In this multicentre study, we have performed detailed clinical and biochemical analysis in 34 genetically confirmed SPG5 cases from 28 families, studied dose-dependent neurotoxicity of oxysterols in human cortical neurons and performed a randomized placebo-controlled double blind interventional trial targeting oxysterol accumulation in serum of SPG5 patients. Clinically, SPG5 manifested in childhood or adolescence (median 13 years). Gait ataxia was a common feature. SPG5 patients lost the ability to walk independently after a median disease duration of 23 years and became wheelchair dependent after a median 33 years. The overall cross-sectional progression rate of 0.56 points on the Spastic Paraplegia Rating Scale per year was slightly lower than the longitudinal progression rate of 0.80 points per year. Biochemically, marked accumulation of CYP7B1 substrates including 27-Hydroxycholesterol was confirmed in serum (n = 19) and cerebrospinal fluid (n = 17) of SPG5 patients. Moreover, 27-Hydroxycholesterol levels in serum correlated with disease severity and disease duration. Oxysterols were found to impair metabolic activity and viability of human cortical neurons at concentrations found in SPG5 patients, indicating that elevated levels of oxysterols might be key pathogenic factors in SPG5. We thus performed a randomized placebo-controlled trial (EudraCT 2015-000978-35) with atorvastatin 40 mg/day for 9 weeks in 14 SPG5 patients with 27-Hydroxycholesterol levels in serum as the primary outcome measure. Atorvastatin, but not placebo, reduced serum 27-Hydroxycholesterol from 853 ng/ml [interquartile range (IQR) 683-1113] to 641 (IQR 507-694) (-31.5%, P = 0.001, Mann-Whitney U-test). Similarly, 25-hydroxycholesterol levels in serum were reduced. In cerebrospinal fluid 27-Hydroxycholesterol was reduced by 8.4% but this did not significantly differ from placebo. As expected, no effects were seen on clinical outcome parameters in this short-term trial. In this study, we define the mutational and phenotypic spectrum of SPG5, examine the correlation of disease severity and progression with oxysterol concentrations, and demonstrate in a randomized controlled trial that atorvastatin treatment can effectively lower 27-Hydroxycholesterol levels in serum of SPG5 patients. We thus demonstrate the first causal treatment strategy in hereditary spastic paraplegia.

Erik G. Lund - One of the best experts on this subject based on the ideXlab platform.

  • expression cloning of an oxysterol 7α hydroxylase selective for 24 hydroxycholesterol
    Journal of Biological Chemistry, 2000
    Co-Authors: Jia Lihawkins, Erik G. Lund, Amy D Bronson
    Abstract:

    Abstract The synthesis of 7α-hydroxylated bile acids from oxysterols requires an oxysterol 7α-hydroxylase encoded by theCyp7b1 locus. As expected, mice deficient in this enzyme have elevated plasma and tissue levels of 25- and 27-Hydroxycholesterol; however, levels of another major oxysterol, 24-hydroxycholesterol, are not increased in these mice, suggesting the presence of another oxysterol 7α-hydroxylase. Here, we describe the cloning and characterization of murine and human cDNAs and genes that encode a second oxysterol 7α-hydroxylase. The genes contain 12 exons and are located on chromosome 6 in the human (CYP39A1locus) and in a syntenic position on chromosome 17 in the mouse (Cyp39a1 locus). CYP39A1 is a microsomal cytochrome P450 enzyme that has preference for 24-hydroxycholesterol and is expressed in the liver. The levels of hepatic CYP39A1 mRNA do not change in response to dietary cholesterol, bile acids, or a bile acid-binding resin, unlike those encoding other sterol 7α-hydroxylases. Hepatic CYP39A1 expression is sexually dimorphic (female > male), which is opposite that of CYP7B1 (male > female). We conclude that oxysterol 7α-hydroxylases with different substrate specificities exist in mice and humans and that sexually dimorphic expression patterns of these enzymes in the mouse may underlie differences in bile acid metabolism between the sexes.

  • cdna cloning of cholesterol 24 hydroxylase a mediator of cholesterol homeostasis in the brain
    Proceedings of the National Academy of Sciences of the United States of America, 1999
    Co-Authors: Erik G. Lund, Joseph M Guileyardo, David W. Russell
    Abstract:

    The turnover of cholesterol in the brain is thought to occur via conversion of excess cholesterol into 24S-hydroxycholesterol, an oxysterol that is readily secreted from the central nervous system into the plasma. To gain molecular insight into this pathway of cholesterol metabolism, we used expression cloning to isolate cDNAs that encode murine and human cholesterol 24-hydroxylases. DNA sequence analysis indicates that both proteins are localized to the endoplasmic reticulum, share 95% identity, and represent a new cytochrome P450 subfamily (CYP46). When transfected into cultured cells, the cDNAs produce an enzymatic activity that converts cholesterol into 24S-hydroxycholesterol, and to a lesser extent, 25-hydroxycholesterol. The cholesterol 24-hydroxylase gene contains 15 exons and is located on human chromosome 14q32.1. Cholesterol 24-hydroxylase is expressed predominantly in the brain as judged by RNA and protein blotting. In situ mRNA hybridization and immunohistochemistry localize the expression of this P450 to neurons in multiple subregions of the brain. The concentrations of 24S-hydroxycholesterol in serum are low in newborn mice, reach a peak between postnatal days 12 and 15, and thereafter decline to baseline levels. In contrast, cholesterol 24-hydroxylase protein is first detected in the brain of mice at birth and continues to accumulate with age. We conclude that the cloned cDNAs encode cholesterol 24-hydroxylases that synthesize oxysterols in neurons of the brain and that secretion of 24S-hydroxycholesterol from this tissue in the mouse is developmentally regulated.

  • elimination of cholesterol in macrophages and endothelial cells by the sterol 27 hydroxylase mechanism comparison with high density lipoprotein mediated reverse cholesterol transport
    Journal of Biological Chemistry, 1997
    Co-Authors: Amir Babiker, Erik G. Lund, Ulf Diczfalusy, Olof Andersson, Samir Deeb, Ayeleth Reshef, E Leitersdorf, Ingemar Björkhem
    Abstract:

    Abstract Cultured macrophages and endothelial cells have been reported to secrete 27-oxygenated metabolites of cholesterol. This mechanism was compared with the classical high density lipoprotein (HDL)-dependent reverse cholesterol transport. Under standard conditions, macrophage preparations had considerably higher capacity to secrete 27-Hydroxycholesterol and 3β-hydroxy-5-cholestenoic acid than had endothelial cells and fibroblasts. Western blotting showed that lung macrophages contained the most sterol 27-hydroxylase protein of the cells tested. The relative amounts of 3β-hydroxy-5-cholestenoic acid produced by the macrophages were also highest. Macrophages derived from monocytes of patients with sterol 27-hydroxylase deficiency did not secrete 27-oxygenated products, demonstrating that sterol 27-hydroxylase is the critical enzyme for the conversion of cholesterol into the 27-oxygenated steroids. That sterol 27-hydroxylase is responsible not only for 27-hydroxylation of cholesterol but also for the further oxidation of this steroid into 3β-hydroxy-5-cholestenoic acid was shown with use of tritium-labeled 27-Hydroxycholesterol and an inhibitor of sterol 27-hydroxylase. Secretion of 27-oxygenated products by the cultured macrophages as well as the ratio between the alcohol and the acid appeared to be dependent upon total 27-hydroxylase activity, the availability of substrate cholesterol, and the presence of an acceptor for 27-Hydroxycholesterol in the medium. With albumin as extracellular acceptor, the major secreted product was 3β-hydroxy-5-cholestenoic acid. Under such conditions, secretion of labeled 27-oxygenated products was higher than that of labeled cholesterol from lung alveolar macrophages preloaded with [4-14C]cholesterol. With HDL as acceptor, 27-Hydroxycholesterol was the major secreted product, and the total secretion of labeled 27-oxygenated products was only about 10% of that of labeled cholesterol. Thus, 27-Hydroxycholesterol and cholesterol may compete for HDL-mediated efflux from the cells. The results support the contention that the sterol 27-hydroxylase-mediated elimination of cholesterol is more important in macrophages than in endothelial cells. This mechanism may be an alternative and/or a complement to the classical HDL-mediated reverse cholesterol transport in macrophages, in particular when the concentration of HDL is low.

  • determination of cholesterol oxidation products in human plasma by isotope dilution mass spectrometry
    Analytical Biochemistry, 1995
    Co-Authors: Susanna Dzeletovic, Erik G. Lund, Olof Breuer, Ulf Diczfalusy
    Abstract:

    Abstract A method based on isotope dilution-mass spectrometry was developed for the determination of nine cholesterol oxidation products in human plasma. The cholesterol oxidation products determined were cholest-5-ene-3 β,7 α-diol, cholest-5-ene-3 β,7β-diol (7α- and 7β-hydroxycholesterol, respectively), 3β-hydroxycholest-5-en-7-one (7-oxocholesterol), 5,6α-epoxy-5α-cholestan-3β-ol (cholesterol-5α,6α-epoxide), 5,6β-epoxy- 5β-cholestan-3β-ol (cholesterol-5β,6β-epoxide), cholestane-3β,5α,6β-triol, cholest-5-ene-3β,24-diol (24-hydroxycholesterol), cholest-5-ene-3β,25-diol (25-hydroxycholesterol), and cholest-5-ene-3β,27-diol (27-Hydroxycholesterol). A corresponding deuterium-labeled internal standard, containing 3 to 6 deuterium atoms, was synthesized for each cholesterol oxidation product except 5β,6β-epoxycholesterol which was determined using the internal standard for 5α,6α-epoxycholesterol. Plasma from 31 healthy volunteers was analyzed by the new method and 27-, 24-, and 7α-hydroxycholesterol were the most abundant cholesterol oxidation products (mean values 154, 64, and 43 ng/ml, respectively). The other oxysterols determined were present in concentrations lower than 30 ng/ml. Males had higher 27-Hydroxycholesterol concentrations in plasma than females. The 5,6-oxygenated products were present mainly unesterified while the other oxidation products were mostly in esterified form.

  • atherosclerosis and sterol 27 hydroxylase evidence for a role of this enzyme in elimination of cholesterol from human macrophages
    Proceedings of the National Academy of Sciences of the United States of America, 1994
    Co-Authors: Ingemar Björkhem, Ulf Diczfalusy, Olof Andersson, Bo Sevastik, Chonggao Duan, Erik G. Lund
    Abstract:

    Abstract 27-Hydroxycholesterol was found in surprisingly high amounts in atherosclerotic human femoral arteries. When human macrophages were cultured in a medium containing serum, there was a significant transfer of 27-hydroxy-cholesterol and 3 beta-hydroxy-5-cholestenoic acid from the cells into the medium. Sterol 27-hydroxylase (EC 1.14.13.15) is likely to be responsible for formation of the two products as shown by use of immunoblotting, a specific inhibitor, and the 18O-labeling technique. Sterol 27-hydroxylase has the unusual ability to hydroxylate the same methyl group three times to give a carboxylic acid; thus, 3 beta-hydroxy-5-cholestenoic acid is likely to be a direct product of the enzyme. The production of these steroids increased after addition of cholesterol to the culture medium. By using deuterium-labeled cholesterol, it was ascertained that most of the oxidized products were formed from exogenous cholesterol taken up by the cells. 27-Hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid are present in the circulation and are efficiently converted into bile acids in human liver. It is suggested that conversion of cholesterol into 27-Hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid represents a general defence mechanism for macrophages and possibly also other peripheral cells exposed to cholesterol. Absence of this defence mechanism may contribute to the premature atherosclerosis known to occur in patients with sterol 27-hydroxylase deficiency (cerebrotendinous xanthomatosis).