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Metabolomics of Synovial Fluid and Infrapatellar Fat Pad in Patients with Osteoarthritis or Rheumatoid Arthritis. Inflammation 2022; 45:1101-1117. [PMID: 35041143 PMCID: PMC9095531 DOI: 10.1007/s10753-021-01604-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 11/17/2021] [Accepted: 11/19/2021] [Indexed: 12/13/2022]
Abstract
Osteoarthritis (OA) and autoimmune-driven rheumatoid arthritis (RA) are inflammatory joint diseases with complex and insufficiently understood pathogeneses. Our objective was to characterize the metabolic fingerprints of synovial fluid (SF) and its adjacent infrapatellar fat pad (IFP) obtained during the same surgical operation from OA and RA knees. Non-targeted metabolite profiling was performed for 5 non-inflammatory trauma controls, 10 primary OA (pOA) patients, and 10 seropositive RA patients with high-resolution mass spectrometry-based techniques, and metabolites were matched with known metabolite identities. Groupwise differences in metabolic features were analyzed with the univariate Welch’s t-test and the multivariate linear discriminant analysis (LDA) and principal component analysis (PCA). Significant discrimination of metabolite profiles was discovered by LDA for both SF and IFP and by PCA for SF based on diagnosis. In addition to a few drug-derived substances, there were 16 and 13 identified metabolites with significant differences between the diagnoses in SF and IFP, respectively. The pathways downregulated in RA included androgen, bile acid, amino acid, and histamine metabolism, and those upregulated included biotin metabolism in pOA and purine metabolism in RA and pOA. The RA-induced downregulation of androgen and bile acid metabolism was observed for both SF and IFP. The levels of 11 lipid metabolites, mostly glycerophospholipids and fatty acid amides, were also altered by these inflammatory conditions. The identified metabolic pathways could be utilized in the future to deepen our understanding of the pathogeneses of OA and RA and to develop not only biomarkers for their early diagnosis but also therapeutic targets.
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Roth K, Yang Z, Agarwal M, Liu W, Peng Z, Long Z, Birbeck J, Westrick J, Liu W, Petriello MC. Exposure to a mixture of legacy, alternative, and replacement per- and polyfluoroalkyl substances (PFAS) results in sex-dependent modulation of cholesterol metabolism and liver injury. ENVIRONMENT INTERNATIONAL 2021; 157:106843. [PMID: 34479135 PMCID: PMC8490327 DOI: 10.1016/j.envint.2021.106843] [Citation(s) in RCA: 175] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/22/2021] [Accepted: 08/19/2021] [Indexed: 05/22/2023]
Abstract
BACKGROUND Epidemiological studies have shown Per- and polyfluoroalkyl substances (PFAS) to be associated with diseases of dysregulated lipid and sterol homeostasis such as steatosis and cardiometabolic disorders. However, the majority of mechanistic studies rely on single chemical exposures instead of identifying mechanisms related to the toxicity of PFAS mixtures. OBJECTIVES The goal of the current study is to investigate mechanisms linking exposure to a PFAS mixture with alterations in lipid metabolism, including increased circulating cholesterol and bile acids. METHODS Male and female wild-type C57BL/6J mice were fed an atherogenic diet used in previous studies of pollutant-accelerated atherosclerosis and exposed to water containing a mixture of 5 PFAS representing legacy, replacement, and alternative subtypes (i.e., PFOA, PFOS, PFNA, PFHxS, and GenX), each at a concentration of 2 mg/L, for 12 weeks. Changes at the transcriptome and metabolome level were determined by RNA-seq and high-resolution mass spectrometry, respectively. RESULTS We observed increased circulating cholesterol, sterol metabolites, and bile acids due to PFAS exposure, with some sexual dimorphic effects. PFAS exposure increased hepatic injury, demonstrated by increased liver weight, hepatic inflammation, and plasma alanine aminotransferase levels. Females displayed increased lobular and portal inflammation compared to the male PFAS-exposed mice. Hepatic transcriptomics analysis revealed PFAS exposure modulated multiple metabolic pathways, including those related to sterols, bile acids, and acyl carnitines, with multiple sex-specific differences observed. Finally, we show that hepatic and circulating levels of PFOA were increased in exposed females compared to males, but this sexual dimorphism was not the same for other PFAS examined. DISCUSSION Exposure of mice to a mixture of PFAS results in PFAS-mediated modulation of cholesterol levels, possibly through disruption of enterohepatic circulation.
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Affiliation(s)
- Katherine Roth
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Zhao Yang
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Manisha Agarwal
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48202, USA; Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48202, USA
| | - Wendy Liu
- Department of Pathology, University Hospitals, Cleveland Medical Center, Cleveland, OH 44106, USA
| | - Zheyun Peng
- Department of Pharmaceutical Sciences, College of Pharmacy, Wayne State University, Detroit, MI 48202, USA
| | - Ze Long
- Department of Pharmaceutical Sciences, College of Pharmacy, Wayne State University, Detroit, MI 48202, USA
| | - Johnna Birbeck
- Department of Chemistry, Lumigen Instrumentation Center, Wayne State University, Detroit, MI 48202, USA
| | - Judy Westrick
- Department of Chemistry, Lumigen Instrumentation Center, Wayne State University, Detroit, MI 48202, USA
| | - Wanqing Liu
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48202, USA; Department of Pharmaceutical Sciences, College of Pharmacy, Wayne State University, Detroit, MI 48202, USA
| | - Michael C Petriello
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48202, USA; Department of Pharmacology, School of Medicine, Wayne State University, Detroit, MI 48202, USA.
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Sandri BJ, Lubach GR, Lock EF, Georgieff MK, Kling PJ, Coe CL, Rao RB. Early-Life Iron Deficiency and Its Natural Resolution Are Associated with Altered Serum Metabolomic Profiles in Infant Rhesus Monkeys. J Nutr 2020; 150:685-693. [PMID: 31722400 PMCID: PMC7138653 DOI: 10.1093/jn/nxz274] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 07/23/2019] [Accepted: 10/11/2019] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Iron deficiency is the most common nutrient deficiency in human infants aged 6 to 24 mo, and negatively affects many cellular metabolic processes, including energy production, electron transport, and oxidative degradation of toxins. There can be persistent influences on long-term metabolic health beyond its acute effects. OBJECTIVES The objective was to determine how iron deficiency in infancy alters the serum metabolomic profile and to test whether these effects persist after the resolution of iron deficiency in a nonhuman primate model of spontaneous iron deficiency. METHODS Blood was collected from naturally iron-sufficient (IS; n = 10) and iron-deficient (ID; n = 10) male and female infant rhesus monkeys (Macaca mulatta) at 6 mo of age. Iron deficiency resolved without intervention upon feeding of solid foods, and iron status was re-evaluated at 12 mo of age from the IS and formerly ID monkeys using hematological and other indices; sera were metabolically profiled using HPLC/MS and GC/MS with isobaric standards for identification and quantification at both time points. RESULTS A total of 413 metabolites were measured, with differences in 40 metabolites identified between IS and ID monkeys at 6 mo (P$\le $ 0.05). At 12 mo, iron-related hematological parameters had returned to normal, but the formerly ID infants remained metabolically distinct from the age-matched IS infants, with 48 metabolites differentially expressed between the groups. Metabolomic profiling indicated altered liver metabolites, differential fatty acid production, increased serum uridine release, and atypical bile acid production in the ID monkeys. CONCLUSIONS Pathway analyses of serum metabolites provided evidence of a hypometabolic state, altered liver function, differential essential fatty acid production, irregular uracil metabolism, and atypical bile acid production in ID infants. Many metabolites remained altered after the resolution of ID, suggesting long-term effects on metabolic health.
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Affiliation(s)
- Brian J Sandri
- Division of Neonatology, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA
| | - Gabriele R Lubach
- Harlow Center for Biological Psychology, University of Wisconsin, Madison, WI, USA
| | - Eric F Lock
- School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - Michael K Georgieff
- Division of Neonatology, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA,Center for Neurobehavioral Development, University of Minnesota, Minneapolis, MN, USA
| | - Pamela J Kling
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, WI, USA
| | - Christopher L Coe
- Harlow Center for Biological Psychology, University of Wisconsin, Madison, WI, USA
| | - Raghavendra B Rao
- Division of Neonatology, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA,Center for Neurobehavioral Development, University of Minnesota, Minneapolis, MN, USA,Address correspondence to RBR (e-mail: )
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Nørskov NP, Hedemann MS, Lærke HN, Knudsen KEB. Multicompartmental nontargeted LC-MS metabolomics: explorative study on the metabolic responses of rye fiber versus refined wheat fiber intake in plasma and urine of hypercholesterolemic pigs. J Proteome Res 2013; 12:2818-32. [PMID: 23596967 DOI: 10.1021/pr400164b] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A multicompartmental nontargeted LC-MS metabolomics approach was used to study the metabolic responses on plasma and urine of hypercholesterolemic pigs after consumption of diets with contrasting dietary fiber composition (whole grain rye with added rye bran versus refined wheat). To study the metabolic responses, we performed a supervised multivariate data analyses used for pattern recognition, which revealed marked effects of the diets on both plasma and urine metabolic profiles. Diverse pools of metabolites were responsible for the discrimination between the diets. Elevated levels of phenolic compounds and dicarboxylic acids were detected in urine of pigs after rye consumption compared to refined wheat. Furthermore, consumption of rye was characterized by lower levels of linoleic acid derived oxylipins and cholesterol in the plasma metabolic profiles. These results indicate that higher consumption of nonrefined dietary fiber is reflected in higher excretion of phenolic compounds and dicarboxylic acids in urine and lower levels of linoleic acid derived oxylipins and cholesterol in plasma, which can be linked to beneficial health effects of rye components. On the other hand, pro-inflammatory lipid mediators were detected in higher concentration after rye consumption compared to refined wheat, which is opposite to what would be expected. These may indicate that even though a positive lowering effect with respect to cholesterol and fatty acids was achieved, this effect of rye dietary fiber was not sufficient to prevent inflammation in pigs. Moreover, we performed an alignment of the metabolic profiles between the breads consumed by pigs, plasma, and urine with the purpose to follow the metabolic fate of the compounds and to identify their pathways. One metabolite was identified in all three compartments, 16 metabolites were similar between bread and plasma, 3 were similar between plasma and urine, and 2 were similar between bread and urine. The use of multicompartmental metabolomics offered higher order information, including intercompartment relationships, and provided novel targets for future research.
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Affiliation(s)
- Natalja P Nørskov
- Department of Animal Science, Aarhus University, AU-Foulum, Blichers Alle 20, PO Box 50, DK-8830 Tjele, Denmark
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Zhang Y, Hagedorn CH, Wang L. Role of nuclear receptor SHP in metabolism and cancer. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1812:893-908. [PMID: 20970497 PMCID: PMC3043166 DOI: 10.1016/j.bbadis.2010.10.006] [Citation(s) in RCA: 191] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/12/2010] [Accepted: 10/14/2010] [Indexed: 02/07/2023]
Abstract
Small heterodimer partner (SHP, NR0B2) is a unique member of the nuclear receptor (NR) superfamily that contains the dimerization and ligand-binding domain found in other family members, but lacks the conserved DNA-binding domain. The ability of SHP to bind directly to multiple NRs is crucial for its physiological function as a transcriptional inhibitor of gene expression. A wide variety of interacting partners for SHP have been identified, indicating the potential for SHP to regulate an array of genes in different biological pathways. In this review, we summarize studies concerning the structure and target genes of SHP and discuss recent progress in understanding the function of SHP in bile acid, cholesterol, triglyceride, glucose, and drug metabolism. In addition, we review the regulatory role of SHP in microRNA (miRNA) regulation, liver fibrosis and cancer progression. The fact that SHP controls a complex set of genes in multiple metabolic pathways suggests the intriguing possibility of developing new therapeutics for metabolic diseases, including fatty liver, dyslipidemia and obesity, by regulating SHP with small molecules. To achieve this goal, more progress regarding SHP ligands and protein structure will be required. Besides its metabolic regulatory function, studies by us and other groups provide strong evidence that SHP plays a critical role in the development of cancer, particularly liver and breast cancer. An increased understanding of the fundamental mechanisms by which SHP regulates the development of cancers will be critical in applying knowledge of SHP in diagnostic, therapeutic or preventive strategies for specific cancers. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.
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Affiliation(s)
- Yuxia Zhang
- Department of Medicine, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
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Griffiths WJ, Hornshaw M, Woffendin G, Baker SF, Lockhart A, Heidelberger S, Gustafsson M, Sjövall J, Wang Y. Discovering oxysterols in plasma: a window on the metabolome. J Proteome Res 2008; 7:3602-12. [PMID: 18605750 PMCID: PMC2567817 DOI: 10.1021/pr8001639] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
While the proteome defines the expressed gene products, the metabolome results from reactions controlled by such gene products. Plasma represents an accessible "window" to the metabolome both in regard of availability and content. The wide range of the plasma metabolome, in terms of molecular diversity and abundance, makes its comprehensive analysis challenging. Here we demonstrate an analytical method designed to target one region of the metabolome, that is, oxysterols. Since the discovery of their biological activity as ligands to nuclear receptors there has been a reawakening of interest in oxysterols and their analysis. In addition, the oxysterols, 24S- and 27-hydroxycholesterol, are currently under investigation as potential biomarkers associated with neurodegenerative disorders such as Alzheimer's disease and multiple sclerosis; widespread analysis of these lipids in clinical studies will require the development of robust, sensitive and rapid analytical techniques. In this communication we present results of an investigation of the oxysterols content of human plasma using a newly developed high-performance liquid chromatography-mass spectrometry (HPLC-MS) method incorporating charge-tagging and high-resolution MS. The method has allowed the identification in plasma of monohydroxylated cholesterol molecules, 7alpha-, 24S-, and 27-hydroxycholesterol; the cholestenetriol 7alpha,27-dihydroxycholesterol; and 3beta-hydroxycholest-5-en-27-oic acid and its metabolite 3beta,7alpha-dihydroxycholest-5-en-27-oic acid. The methodology described is also applicable for the analysis of other sterols in plasma, that is, cholesterol, 7-dehydrocholesterol, and desmosterol, as well as cholesterol 5,6- seco-sterols and steroid hormones. Although involving derivatization, sample preparation is straightforward and chromatographic analysis rapid (17 min), while the MS method offers high sensitivity (ng/mL of sterol in plasma, or pg on-column) and specificity. The methodology is suitable for targeted metabolomic analysis of sterols, oxysterols, and steroid hormones opening a "window" to view this region of the metabolome.
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Affiliation(s)
- William J Griffiths
- Institute of Mass Spectrometry, School of Medicine, Grove Building, Swansea University, Singleton Park, Swansea, UK.
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Maconi G, Di Sabatino A, Ardizzone S, Greco S, Colombo E, Russo A, Cassinotti A, Casini V, Corazza GR, Bianchi Porro G. Prevalence and clinical significance of sonographic detection of enlarged regional lymph nodes in Crohn's disease. Scand J Gastroenterol 2005; 40:1328-33. [PMID: 16243717 DOI: 10.1080/00365510510025746] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Reactive regional lymph node enlargement is a frequent ultrasonographic finding in patients with Crohn's disease. However, the prevalence of this condition and its clinical significance are unknown. This study assesses the prevalence of enlarged regional mesenteric lymph nodes and its clinical significance in Crohn's disease, and in particular whether there is a correlation between the sonographic detection of enlarged regional lymph nodes and the degree of clinical or biochemical activity of the disease. MATERIAL AND METHODS A total of 240 in- and outpatients with Crohn's disease underwent intestinal ultrasound to assess the presence of enlarged regional lymph nodes as well as the thickness and echopattern of the bowel wall, the site and extent of Crohn's disease and the presence of stenosis, fistulas and abscesses. Demographic, clinical and biochemical parameters were also collected for each patient. A multivariate model by means of multiple regression analysis was used to identify independent variables linked to regional lymph node enlargement. RESULTS Enlarged regional lymph nodes were detected ultrasonographically in 25.4% of Crohn's disease patients. The presence of regional lymph nodes showed a weak correlation with both clinical and biochemical Crohn's disease activity. Regional lymph nodes were found more frequently in young patients (50% of patients < 30 years, 18% of patients between 30 and 50 yrs, and 7% of patients > 50 yrs; p<0.0001) and in patients with a shorter disease duration. Enlarged regional lymph nodes were strongly correlated with internal fistulas and intra-abdominal abscesses. The multiple regression analysis showed that age, duration of disease and presence of internal fistulas were the best independent predictive factors linked to the presence of enlarged mesenteric lymph nodes. CONCLUSIONS The sonographic detection of enlarged regional lymph nodes is more frequent in young patients, which suggests an earlier phase of Crohn's disease and the presence of septic complications such as fistulas and abscesses, but this is of limited valued in assessing disease activity.
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Affiliation(s)
- Giovanni Maconi
- Department of Gastroenterology, L. Sacco University Hospital, Via G.B. Grassi 74, IT-20157 Milan, Italy.
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Abstract
Cholesterol and its metabolites, e.g., steroid hormones and bile acids, constitute a class of compounds of great biological importance. Their chemistry, biochemistry, and regulation in the body have been intensely studied for more than two centuries. The author has studied aspects of the biochemistry and clinical chemistry of steroids and bile acids for more than 50 years, and this paper, which is an extended version of the Schroepfer Medal Award lecture, reviews and discusses part of this work. Development and application of analytical methods based on chromatography and mass spectrometry (MS) have been a central part of many projects, aiming at detailed characterization and quantification of metabolic profiles of steroids and bile acids under different conditions. In present terminology, much of the work may be termed steroidomics and cholanoidomics. Topics discussed are bile acids in human bile and feces, bile acid production, bacterial dehydroxylation of bile acids and steroids during the enterohepatic circulation, profiles of steroid sulfates in plasma of humans and other primates, development of neutral and ion-exchanging lipophilic derivatives of Sephadex for sample preparation and group separation of steroid and bile acid conjugates, profiles of steroids and bile acids in human urine under different conditions, hydroxylation of bile acids in liver disease, effects of alcohol-induced redox changes on steroid synthesis and metabolism, alcohol-induced changes of bile acid biosynthesis, compartmentation of bile acid synthesis studied with 3H-labeled ethanol, formation and metabolism of sulfated metabolites of progesterone in human pregnancy, abnormal patterns of these in patients with intrahepatic cholestasis of pregnancy corrected by ursodeoxycholic acid, inherited and acquired defects of bile acid biosynthesis and their treatment, conjugation of bile acids and steroids with N-acetylglucosamine, sulfate-glucuronide double conjugates of hydroxycholesterols, extrahepatic 7alpha-hydroxylation and 3-dehydrogenation of hydroxycholesterols, and extrahepatic formation of C27 bile acids. The final part discusses analysis of free and sulfated steroids in brain tissue by capillary liquid chromatography-electrospray MS and suggests a need for reevaluation of the function of steroid sulfates in rat brain.
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Affiliation(s)
- Jan Sjövall
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77, Stockholm, Sweden.
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Wang L, Han Y, Kim CS, Lee YK, Moore DD. Resistance of SHP-null mice to bile acid-induced liver damage. J Biol Chem 2003; 278:44475-81. [PMID: 12933814 DOI: 10.1074/jbc.m305258200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The orphan nuclear hormone receptor SHP (gene designation NROB2) is an important component of a negative regulatory cascade by which high levels of bile acids repress bile acid biosynthesis. Short term studies in SHP null animals confirm this function and also reveal the existence of additional pathways for bile acid negative feedback regulation. We have used long term dietary treatments to test the role of SHP in response to chronic elevation of bile acids, cholesterol, or both. In contrast to the increased sensitivity predicted from the loss of negative feedback regulation, the SHP null mice were relatively resistant to the hepatotoxicity associated with a diet containing 0.5% cholic acid and the much more severe effects of a diet containing both 0.5% cholic acid and 2% cholesterol. This was associated with decreased hepatic accumulation of cholesterol and triglycerides in the SHP null mice. There were also alterations in the expression of a number of genes involved in cholesterol and bile acid homeostasis, notably cholesterol 12alpha-hydroxylase (CYP8B1), which was strongly reexpressed in the SHP null mice, but not the wild type mice fed either bile acid containing diet. This contrasts with the strong repression of CYP8B1 observed with short term bile acid feeding, as well as the effects of long term feeding on other bile acid biosynthetic enzymes such as cholesterol 7alpha-hydroxylase (CYP7A1). CYP8B1 expression could contribute to the decreased toxicity of the chronic bile acid treatment by increasing the hydrophilicity of the bile acid pool. These results identify an unexpected role for SHP in hepatotoxicity and suggest new approaches to modulating effects of chronically elevated bile acids in cholestasis.
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Affiliation(s)
- Li Wang
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Wang L, Lee YK, Bundman D, Han Y, Thevananther S, Kim CS, Chua SS, Wei P, Heyman RA, Karin M, Moore DD. Redundant pathways for negative feedback regulation of bile acid production. Dev Cell 2002; 2:721-31. [PMID: 12062085 DOI: 10.1016/s1534-5807(02)00187-9] [Citation(s) in RCA: 381] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The orphan nuclear hormone receptor SHP has been proposed to have a key role in the negative feedback regulation of bile acid production. Consistent with this, mice lacking the SHP gene exhibit mild defects in bile acid homeostasis and fail to repress cholesterol 7-alpha-hydroxylase expression in response to a specific agonist for the bile acid receptor FXR. However, this repression is retained in SHP null mice fed bile acids, demonstrating the existence of compensatory repression pathways of bile acid signaling. We provide evidence for two such pathways, based on activation of the xenobiotic receptor PXR or the c-Jun N-terminal kinase JNK. We conclude that redundant mechanisms regulate this critical aspect of cholesterol homeostasis.
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Affiliation(s)
- Li Wang
- Department of Molecular and Cellular Biology, Houston, TX 77030, USA
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Davis RA, Miyake JH, Hui TY, Spann NJ. Regulation of cholesterol-7α-hydroxylase: BAREly missing a SHP. J Lipid Res 2002. [DOI: 10.1016/s0022-2275(20)31482-6] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Abstract
Oxysterol 7 alpha-hydroxylase catalyzes hydroxylation of oxysterols and neurosterols and plays a role in the alternative bile acid synthesis pathway. This gene is widely expressed in many organs and peripheral tissues and may protect tissues from the toxicity of oxysterols. Mutation in CYP7B1 caused neonatal cholestasis. To examine the regulatory mechanisms governing CYP7B1 expression, the 5' flanking sequence of the CYP7B1 was analyzed and revealed a CpG island of about 1.2 kb. Transient transfection assays of deletion mutants of the CYP7B1 promoter-luciferase reporter gene in human liver-derived HepG2, fibroblast NT1088, and human embryonic kidney 293 cell lines revealed that the region from -291 to +189 was critical for gene transcription. Three GC box sequences located between -25 and +10 were essential for basal transcription because mutations of these sequences markedly reduced promoter activity. Sp1 and Sp3 bound to these sequences as demonstrated by DNase I footprinting assays and electrophoretic mobility shift assay. Thus, regulation of CYP7B1 transcription by Sp1 may play a pivotal role in regulating oxysterol levels, which regulate cholesterol metabolism.
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Affiliation(s)
- Z Wu
- Department of Biochemistry and Molecular Pathology, Northeastern Ohio Universities College of Medicine, P.O. Box 95, Rootstown, OH 44272, USA
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Abstract
7alpha-Hydroxy derivatives of oxysterols are of considerable interest because of their possible involvement in regulation of cholesterol metabolism. This paper describes stereoselective syntheses and complete characterization of the 7alpha-hydroxy derivatives of four key oxysterols: 25-hydroxycholesterol, 27-hydroxycholesterol, 24(S)-hydroxycholesterol, and 24(S), 25-epoxycholesterol.
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Affiliation(s)
- D Li
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA
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Abstract
Bile acids originate from the liver and are transported via bile to the intestines where they perform an important role in the absorption of lipids and lipid-soluble nutrients. Most of the bile acids are reclaimed from the terminal ileum and returned to the liver via portal blood for reuse. The transport of bile acids is vectorial in both liver and intestinal cells, originating and terminating at opposite poles. Bile acids enter through the basolateral pole in liver cells, and through the apical pole in intestinal cells. During the past decade, much has been learned about the mechanisms by which bile acids enter and exit liver and intestinal cells. By contrast, the mechanisms by which bile acids are transported across cells remain poorly understood. The current body of evidence suggests that bile acids do not traverse the cell by vesicular transport. Although a carrier-mediated mechanism is a likely alternative, only a handful of intracellular proteins capable of binding bile acids have been described. The significance of these proteins in the intracellular transport of bile acids remains to be tested.
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Affiliation(s)
- L B Agellon
- Department of Biochemistry, University of Alberta, Edmonton, Alta, Canada.
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Abstract
Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.
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Affiliation(s)
- G J Schroepfer
- Departments of Biochemistry, Rice University, Houston, Texas, USA.
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Wu Z, Martin K, Javitt N, Chiang J. Structure and functions of human oxysterol 7α-hydroxylase cDNAs and gene CYP7B1. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)32094-0] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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17
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Babiker A, Andersson O, Lindblom D, van der Linden J, Wiklund B, Lütjohann D, Diczfalusy U, Björkhem I. Elimination of cholesterol as cholestenoic acid in human lung by sterol 27-hydroxylase: evidence that most of this steroid in the circulation is of pulmonary origin. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33383-6] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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18
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Abstract
This article provides a review of the pathways through which cholesterol is degraded to bile acids. Regulation of key enzymes in the bile acid biosynthestic pathways is discussed. The important role of these pathways in the maintenance of cholesterol homeostasis and the possible therapeutic implications for the treatment of hypercholesterolemia are emphasized.
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Affiliation(s)
- Z R Vlahcevic
- Division of Gastroenterology, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA
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19
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Furster C. Hepatic and extrahepatic dehydrogenation/isomerization of 5-cholestene-3 beta,7 alpha-diol: localization of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase in pig tissues and subcellular fractions. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1436:343-53. [PMID: 9989265 DOI: 10.1016/s0005-2760(98)00126-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Conversion of 5-cholestene-3 beta,7 alpha-diol (7 alpha-hydroxycholesterol) into 7 alpha-hydroxy-4-cholesten-3-one was studied with microsomes from different pig tissues and with liver subcellular fractions. Dehydrogenase/isomerase activity was efficient in microsomes from liver, ovary and lung, but less efficient in microsomes from adrenal gland and kidney. Microsomes from these tissues, with the exception of lung, were also active in dehydrogenation/isomerization of dehydroepiandrosterone and pregnenolone. Inhibition studies were carried out with trilostane, a competitive inhibitor of 3 beta-hydroxysteroid dehydrogenases active in steroid hormone biosynthesis (C19/C21-dehydrogenases), and a monoclonal antibody raised against a purified hepatic 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase. The results showed that the C27-dehydrogenase activity in the tissues was not dependent on the C19/C21 dehydrogenases, but was dependent on the 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase. Liver mitochondria, cytosol and peroxisomes lacked dehydrogenase/isomerase activity towards 7 alpha-hydroxycholesterol when microsomal contamination was taken into account. Immunoblotting experiments with monoclonal antibodies raised against the 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase showed immunoreactivity only with protein in liver microsomes. Immunohistochemical studies showed localization of the 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase in the bile duct epithelium. It is concluded that 7 alpha-hydroxycholesterol is converted into 7 alpha-hydroxy-4-cholesten-3-one by the microsomal 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase in liver and extrahepatic tissues.
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Affiliation(s)
- C Furster
- Department of Pharmaceutical Biosciences, University of Uppsala, Sweden.
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20
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Abstract
The addition of a 7-hydroxyl group is an early and often rate-limiting step in the synthesis of bile acids. This reaction is catalysed by two cytochrome P450 enzymes known as cholesterol 7 alpha-hydroxylase and oxysterol 7 alpha-hydroxylase. cDNAs encoding these proteins have been isolated and used to define two evolutionarily conserved pathways that produce 7 alpha-hydroxylated bile acids.
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Affiliation(s)
- M Schwarz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235-9046, USA
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22
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Schwarz M, Lund EG, Lathe R, Björkhem I, Russell DW. Identification and characterization of a mouse oxysterol 7alpha-hydroxylase cDNA. J Biol Chem 1997; 272:23995-4001. [PMID: 9295351 DOI: 10.1074/jbc.272.38.23995] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The synthesis of essential 7alpha-hydroxylated bile acids in the liver is mediated by two pathways that involve distinct 7alpha-hydroxylases. One pathway is initiated in the endoplasmic reticulum by cholesterol 7alpha-hydroxylase, a well studied cytochrome P450 enzyme. A second pathway is initiated by a less well defined oxysterol 7alpha-hydroxylase. Here, we show that a mouse hepatic oxysterol 7alpha-hydroxylase is encoded by Cyp7b1, a cytochrome P450 cDNA originally isolated from the hippocampus. Expression of a Cyp7b1 cDNA in cultured cells produces an enzyme with the same biochemical and pharmacological properties as those of the hepatic oxysterol 7alpha-hydroxylase. Cyp7b1 mRNA and protein are induced in the third week of life commensurate with an increase in hepatic oxysterol 7alpha-hydroxylase activity. In the adult mouse, dietary cholesterol or colestipol induce cholesterol 7alpha-hydroxylase mRNA levels but do not affect oxysterol 7alpha-hydroxylase enzyme activity, mRNA, or protein levels. Cholesterol 7alpha-hydroxylase mRNA is reduced to undetectable levels in response to bile acids, whereas expression of oxysterol 7alpha-hydroxylase is modestly decreased. The liver thus maintains the capacity to synthesize 7alpha-hydroxylated bile acids regardless of dietary composition, underscoring the central role of 7alpha-hydroxylated bile acids in lipid metabolism.
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Affiliation(s)
- M Schwarz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9046, USA
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23
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Zhang J, Xue Y, Jondal M, Sjövall J. 7alpha-Hydroxylation and 3-dehydrogenation abolish the ability of 25-hydroxycholesterol and 27-hydroxycholesterol to induce apoptosis in thymocytes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:129-35. [PMID: 9249018 DOI: 10.1111/j.1432-1033.1997.00129.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Oxygenated derivatives of sterols (oxysterols), including 25-hydroxycholesterol and 27-hydroxycholesterol, have immunosuppressive effects. Oxysterols can directly induce apoptosis in immature thymocytes, cells which are inherently sensitive to induction of programmed cell death. For that reason, the metabolism of 25-hydroxycholesterol and 27-hydroxycholesterol in mouse thymus has been studied. When incubated with thymic tissue, both oxysterols were found to be 7alpha-hydroxylated with subsequent oxidation to 7alpha-hydroxy-3-oxo-delta4 steroids. A minor fraction of 27-hydroxycholesterol was also metabolised to 3beta-hydroxy-5-cholestenoic, 3beta,7alpha-dihydroxy-5-cholestenoic and 7alpha-hydroxy-3-oxo-4-cholestenoic acids. The 7alpha-hydroxylase was found to be localised to the thymic epithelial cells and the reaction was stimulated by interleukin-1beta and inhibited by metyrapone and RU486. In contrast to 25-hydroxycholesterol and 27-hydroxycholesterol, the 7alpha-hydroxylated metabolites, 7alpha,25-dihydroxycholesterol, 7alpha,25-dihydroxy-4-cholesten-3-one and 7alpha,27-dihydroxy-4-cholesten-3-one did not induce thymocyte apoptosis. The results suggest that 7alpha-hydroxylation may be of regulatory importance, possibly by protecting the developing thymocytes against toxic effects by oxysterols.
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Affiliation(s)
- J Zhang
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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24
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Rose KA, Stapleton G, Dott K, Kieny MP, Best R, Schwarz M, Russell DW, Björkhem I, Seckl J, Lathe R. Cyp7b, a novel brain cytochrome P450, catalyzes the synthesis of neurosteroids 7alpha-hydroxy dehydroepiandrosterone and 7alpha-hydroxy pregnenolone. Proc Natl Acad Sci U S A 1997; 94:4925-30. [PMID: 9144166 PMCID: PMC24607 DOI: 10.1073/pnas.94.10.4925] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/1997] [Accepted: 03/04/1997] [Indexed: 02/04/2023] Open
Abstract
Steroids produced locally in brain (neurosteroids), including dehydroepiandrosterone (DHEA), influence cognition and behavior. We previously described a novel cytochrome P450, Cyp7b, strongly expressed in rat and mouse brain, particularly in hippocampus. Cyp7b is most similar to steroidogenic P450s and potentially could play a role in neurosteroid metabolism. To examine the catalytic activity of the enzyme mouse Cyp7b cDNA was introduced into a vaccinia virus vector. Extracts from cells infected with the recombinant showed NADPH-dependent conversion of DHEA (Km, 13.6 microM) and pregnenolone (Km, 4.0 microM) to slower migrating forms on thin layer chromatography. The expressed enzyme was less active against 25-hydroxycholesterol, 17beta-estradiol and 5alpha-androstane-3beta,17beta-diol, with low to undetectable activity against progesterone, corticosterone, and testosterone. On gas chromatography and mass spectrometry of the Cyp7b metabolite of DHEA the retention time and fragmentation patterns were identical to those obtained with authentic 7alpha-hydroxy DHEA. The reaction product also comigrated on thin layer chromatography with 7alpha-hydroxy DHEA but not with 7beta-hydroxy DHEA; when [7alpha-3H]pregnenolone was incubated with Cyp7b extracts the extent of release of radioactivity into the medium suggested that hydroxylation was preferentially at the 7alpha position. Brain extracts also efficiently liberated tritium from [7alpha-3H]pregnenolone and converted DHEA to a product with a chromatographic mobility indistinguishable from 7alpha-hydroxy DHEA. We conclude that Cyp7b is a 7alpha-hydroxylase participating in the synthesis, in brain, of neurosteroids 7alpha-hydroxy DHEA, and 7alpha-hydroxy pregnenolone.
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Affiliation(s)
- K A Rose
- Centre for Genome Research and Centre for Neuroscience, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JQ, United Kingdom
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25
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Zeelen F. Chapter 22 Medicinal Chemistry of steroids. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2582(97)80047-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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26
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Furster C, Zhang J, Toll A. Purification of a 3beta-hydroxy-delta5-C27-steroid dehydrogenase from pig liver microsomes active in major and alternative pathways of bile acid biosynthesis. J Biol Chem 1996; 271:20903-7. [PMID: 8702847 DOI: 10.1074/jbc.271.34.20903] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A 3beta-hydroxy-Delta5-C27-steroid dehydrogenase active in bile acid biosynthesis was purified from pig liver microsomes by solubilization with sodium cholate and by chromatography on DEAE-Sepharose, aminohexyl-Sepharose, and blue Sepharose. The last step in the purification procedure was preparative isoelectric focusing in a Rotofor cell. The final enzyme preparation showed only one protein band upon SDS-polyacrylamide gel electrophoresis. The isoelectric point was estimated to about 7.0 and the apparent Mr was 36,000. The purified enzyme catalyzed the conversion of 7alpha-hydroxycholesterol, 7alpha,25-dihydroxycholesterol, 7alpha, 27-dihydroxycholesterol, and 3beta,7alpha-dihydroxy-5-cholestenoic acid into the corresponding 3-oxo-Delta4 compounds. The enzyme was inactive with C19 and C21 steroids as substrates. The enzyme was also inactive with C27 steroids having the 7-hydroxy group in beta- instead of alpha-position. The Km was found to be 0.30 and 0.32 microM with 7alpha-hydroxycholesterol and 7alpha, 27-dihydroxycholesterol as substrates, respectively. NAD+ was the preferred cofactor. A monoclonal antibody raised against the 3beta-hydroxy-delta5-C27-steroid dehydrogenase was prepared. After coupling to Sepharose, the antibody was able to bind the dehydrogenase and to decrease the conversion of 7alpha-hydroxycholesterol into 7alpha-hydroxy-4-cholest-3-one by more than 90%. The N-terminal amino acid sequence was determined and found to be similar but not identical with those of known 3beta-hydroxy-Delta5-steroid dehydrogenases active in steroid hormone biosynthesis. Thus, the purified enzyme active toward C27 steroids in bile acid biosynthesis appears to represent a novel type of 3beta-hydroxy-delta5-steroid dehydrogenase.
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Affiliation(s)
- C Furster
- Division of Biochemistry, Department of Pharmaceutical Biosciences, University of Uppsala, Uppsala, Sweden
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27
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Schwarz M, Lund EG, Setchell KDR, Kayden HJ, Zerwekh JE, Björkhem I, Herz J, Russell DW. Disruption of cholesterol 7alpha-hydroxylase gene in mice. II. Bile acid deficiency is overcome by induction of oxysterol 7alpha-hydroxylase. J Biol Chem 1996; 271:18024-31. [PMID: 8663430 PMCID: PMC4451191 DOI: 10.1074/jbc.271.30.18024] [Citation(s) in RCA: 194] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Past experiments and current paradigms of cholesterol homeostasis suggest that cholesterol 7alpha-hydroxylase plays a crucial role in sterol metabolism by controlling the conversion of cholesterol into bile acids. Consistent with this conclusion, we show in the accompanying paper that mice deficient in cholesterol 7alpha-hydroxylase (Cyp7-/- mice) exhibit a complex phenotype consisting of abnormal lipid excretion, skin pathologies, and behavioral irregularities (Ishibashi, S., Schwarz, M., Frykman, P. K. , Herz, J., and Russell, D. W.(1996) J. Biol. Chem. 261, 18017-18023). Aspects of lipid metabolism in the Cyp7-/- mice are characterized here to deduce the physiological basis of this phenotype. Serum lipid, cholesterol, and lipoprotein contents are indistinguishable between wild-type and Cyp7-/- mice. Vitamin D3 and E levels are low to undetectable in knockout animals. Stool fat content is significantly elevated in newborn Cyp7-/- mice and gradually declines to wild-type levels at 28 days of age. Several species of 7alpha-hydroxylated bile acids are detected in the bile and stool of adult Cyp7-/- animals. A hepatic oxysterol 7alpha-hydroxylase enzyme activity that may account for the 7alpha-hydroxylated bile acids is induced between days 21 and 30 in both wild-type and deficient mice. An anomalous oily coat in the Cyp7-/- animals is due to the presence of excess monoglyceride esters in the fur. These data show that 7alpha-hydroxylase and the pathway of bile acid synthesis initiated by this enzyme are essential for proper absorption of dietary lipids and fat-soluble vitamins in newborn mice, but not for the maintenance of serum cholesterol and lipid levels. In older animals, an alternate pathway of bile acid synthesis involving an inducible oxysterol 7alpha-hydroxylase plays a crucial role in lipid and bile acid metabolism.
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Affiliation(s)
- Margrit Schwarz
- Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9046
| | - Erik G. Lund
- Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9046
| | | | - Herbert J. Kayden
- Department of Medicine, New York University Medical Center, New York, New York 10016
| | - Joseph E. Zerwekh
- Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9046
| | - Ingemar Björkhem
- Department of Clinical Chemistry, Karolinska Institute, Huddinge Hospital, Huddinge S-14186, Sweden
| | - Joachim Herz
- Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9046
| | - David W. Russell
- Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9046
- To whom correspondence should be addressed: Dept. of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235-9046. Tel.: 214-648-2007; Fax: 214-648-7539;
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28
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Abstract
Material dealing with the chemistry, biochemistry, and biological activities of oxysterols is reviewed for the period 1987-1995. Particular attention is paid to the presence of oxysterols in tissues and foods and to their physiological relevance.
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Affiliation(s)
- L L Smith
- University of Texas Medical Branch, Galveston 77555-0653, USA
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29
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Sauter G, Fischer S, Pahernik S, Koebe HG, Paumgartner G. Formation of cholic acid and chenodeoxycholic acid from 7 alpha-hydroxycholesterol and 27-hydroxycholesterol by primary cultures of human hepatocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1300:25-9. [PMID: 8608157 DOI: 10.1016/0005-2760(95)00231-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
It has been suggested that chenodeoxycholic acid is preferentially formed by the alternative or 'acidic' pathway of bile acid biosynthesis starting with 27-hydroxylation of cholesterol, while cholic acid is derived from 7 alpha-hydroxycholesterol which initiates the 'neutral' pathway. We have studied bile acid formation from each of these precursors using human hepatocytes cultured in a novel sandwich collagen configuration. Culture supernatants were analyzed using capillary gas chromatography and gas chromatography-mass spectrometry. 27-Hydroxycholesterol and 7 alpha-hydroxycholesterol were both found to be efficiently converted to cholic acid as well as chenodeoxycholic acid. Analysis of acidic intermediates after addition of 7 alpha-hydroxycholesterol to the cultures revealed a significant increase of side-chain oxygenated C24- and C27-steroids with a 3-oxo-7 alpha-hydroxy-delta 4-ring structure. These data indicate that (i) the 'neutral' pathway is connected to the 'acidic' pathway by side-chain oxidation of C27-steroids with a 3-oxo-7 alpha-hydroxy-delta 4-ring structure and that (ii) the relative formation of cholic acid and chenodeoxycholic acid is regulated by metabolic events distal to the initial hydroxylation at either position 7 or position 27 of the cholesterol molecule.
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Affiliation(s)
- G Sauter
- Department of Medicine II, Klinikum Grosshadern, University of Munich, Germany
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30
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Tsankova V, Visentin M, Cantoni L, Carelli M, Tacconi MT. Peripheral benzodiazepine receptor ligands in rat liver mitochondria: effect on 27-hydroxylation of cholesterol. Eur J Pharmacol 1996; 299:197-203. [PMID: 8901023 DOI: 10.1016/0014-2999(95)00836-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effect of peripheral benzodiazepine receptor ligands: PK11195 (1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)isoquinoline-3-carboxamid e), Ro 5-4864 (4-chlorodiazepam), hemin, N-methyl protoporphyrin IX and protoporphyrin IX on liver mitochondrial 27-hydroxylation of cholesterol was studied by adding them together with [4-14C]cholesterol. N-Methyl protoporphyrin IX, PK11195 and protoporphyrin IX stimulated mitochondrial 27-hydroxylation of [4-14C] cholesterol in vitro, the first two being the most potent (2-3-fold increase). Ro 5-4864 and hemin were not active. 27-Hydroxylation of [4-14C]cholesterol was reduced to below control levels (respectively 40 and 56% decrease compared to control, P < 0.01) when PK11195, N-methyl protoporphyrin IX or protoporphyrin IX were allowed to equilibrate in vitro with mitochondria for 20 min at 37 degrees C. Hepatic protoporphyria was induced using 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) (100 mg/kg, i.p.) to study the effect of in vivo accumulation of large amounts of dicarboxylic porphyrins, i.e. endogenous peripheral benzodiazepine receptor ligands, on cholesterol 27-hydroxylation. DDC treatment caused an increase in total porphyrin content in liver homogenate (10-fold) and mitochondria (2-fold). Mitochondrial 27-hydroxylation of [4-14C]cholesterol was depressed after treatment (60% decrease, P < 0.01). We suggest that peripheral benzodiazepine receptor ligands act on liver mitochondrial 27-hydroxylation of cholesterol by a mechanism coupled to these receptors and that the time of exposure of peripheral benzodiazepine receptors to ligands is a major factor. The modulation of 27-hydroxycholesterol production may have a physiological role in liver and possibly in other tissues.
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Affiliation(s)
- V Tsankova
- Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy
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31
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Stravitz RT, Vlahcevic ZR, Russell TL, Heizer ML, Avadhani NG, Hylemon PB. Regulation of sterol 27-hydroxylase and an alternative pathway of bile acid biosynthesis in primary cultures of rat hepatocytes. J Steroid Biochem Mol Biol 1996; 57:337-47. [PMID: 8639470 DOI: 10.1016/0960-0760(95)00282-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In man, hepatic mitochondrial sterol 27-hydroxylase and microsomal cholesterol 7alpha-hydroxylase initiate distinct pathways of bile acid biosynthesis from cholesterol, the "acidic" and "neutral" pathways, respectively. A similar acidic pathway in the rat has been hypothesized, but its quantitative importance and ability to be regulated at the level of sterol 27-hydroxylase are uncertain. In this study, we explored the molecular regulation of sterol 27-hydroxylase and the acidic pathway of bile acid biosynthesis in primary cultures of adult rat hepatocytes. mRNA and protein turnover rates were approximately 10-fold slower for sterol 27-hydroxylase than for cholesterol 7alpha-hydroxylase. Sterol 27-hydroxylase mRNA was not spontaneously expressed in culture. The sole requirement for preserving sterol 27-hydroxylase mRNA at the level of freshly isolated hepatocytes (0 h) after 72 h was the addition of dexamethasone (0.1 microM; > 7-fold induction). Sterol 27-hydroxylase mRNA, mass and specific activity were not affected by thyroxine (1.0 microM), dibutyryl-cAMP (5O microM), nor squalestatin 1 (15O nM-1.0 microM), an inhibitor of cholesterol biosynthesis. Taurocholate (50 microM), however, repressed sterol 27-hydroxylase mRNA levels by 55%. Sterol 27-hydroxylase specific activity in isolated mitochondria was increased > 10-fold by the addition of 2-hydroxypropyl-beta-cyclodextrin. Under culture conditions designed to maximally repress cholesterol 7alpha-hydroxylase and bile acid synthesis from the neutral pathway but maintain sterol 27-hydroxylase mRNA and activity near 0 h levels, bile acid synthesis from [14C]cholesterol remained relatively high and consisted of beta-muricholate, the product of chenodeoxycholate in the rat. We conclude that rat liver harbors a quantitatively important alternative pathway of bile acid biosynthesis and that its initiating enzyme, sterol 27-hydroxylase, may be slowly regulated by glucocorticoids and bile acids.
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Affiliation(s)
- R T Stravitz
- Department of Medicine, Division of Gastroenterology, Medical College of Virginia, Richmond 23298, USA
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32
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The Regulation of Cholesterol Conversion to Bile Acids. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1569-2558(08)60347-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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33
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Lee C, Martin KO, Javitt NB. Bile acid synthesis: 7 alpha-hydroxylation of intermediates in the sterol 27-hydroxylase metabolic pathway. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)39165-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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34
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Payne DW, Shackleton C, Toms H, Ben-Shlomo I, Kol S, deMoura M, Strauss JF, Adashi EY. A novel nonhepatic hydroxycholesterol 7 alpha-hydroxylase that is markedly stimulated by interleukin-1 beta. Characterization in the immature rat ovary. J Biol Chem 1995; 270:18888-96. [PMID: 7642545 DOI: 10.1074/jbc.270.32.18888] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
During studies on the regulation of rat ovarian steroidogenic enzymes by interleukin-1 beta (IL-1 beta), we observed substantial metabolism of 25-hydroxycholesterol to two unusual polar products. This unexpected effect was observed both in isolated granulosa cells and in whole ovarian dispersates and was also induced by tumor necrosis factor alpha, but not by insulin-like growth factor I or follicle-stimulating hormone. The effect was dependent on time and the dose of IL-1 beta and was blocked by and IL-1 receptor antagonist. The formation of the polar metabolites was inhibited by ketoconazole and trilostane, but not by aminoglutethimide. Subsequent purification of these novel metabolites and analysis by gas chromatography/ mass spectrometry, NMR, and high performance liquid chromatography revealed them to be related 7 alpha-hydroxylated hydroxycholesterols (cholest-4-ene-7 alpha,25-diol-3-one and cholest-5-ene-3 beta,7 alpha,25-triol). IL-1 beta-stimulated ovarian 7 alpha-hydroxylase activity (3-10 pmol/min/mg of cellular protein) was nearly 4-fold that of control levels using 25-hydroxycholesterol as substrate. Activities at or below control levels were observed when IL-1 beta-treated cell sonicates were boiled or assayed in the presence of NADH (rather than NADPH), indicating that involvement of a nonenzymatic process was unlikely. IL-1 beta-stimulated 7 alpha-hydroxylase activity was inhibited to basal levels by a 10-fold excess of unlabeled 25- or 27-hydroxycholesterol, but not by cholesterol, pregnenolone, progesterone, testosterone, or dehydroepiandrosterone, suggesting that ovarian 7 alpha-hydroxylase is specific for hydroxycholesterols. Furthermore, when IL-1 beta-treated ovarian cultures were incubated with radiolabeled cholesterol or testosterone, no 7 alpha-hydroxylated products were observed. We were also unable to detect any mRNA transcripts for liver cholesterol 7 alpha-hydroxylase in IL-1 beta-stimulated ovarian cultures. This study describes an ovarian hydroxycholesterol 7 alpha-hydroxylase that differs from liver cholesterol 7 alpha-hydroxylase and from other nonhepatic progestin/ androgen 7 alpha-hydroxylases. The novel finding of the regulation of a 7 alpha-hydroxylase by IL-1 beta (and tumor necrosis factor alpha) suggests a unique role for cytokines in the regulation of cholesterol metabolism in the ovary and possibly other tissues.
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Affiliation(s)
- D W Payne
- Department of Obstetrics/Gynecology, University of Maryland Medical School, Baltimore 21201, USA
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35
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Zhang J, Larsson O, Sjövall J. 7 alpha-Hydroxylation of 25-hydroxycholesterol and 27-hydroxycholesterol in human fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1256:353-9. [PMID: 7786899 DOI: 10.1016/0005-2760(95)00045-e] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The metabolism of 27-hydroxycholesterol and 25-hydroxycholesterol was studied in cultures of human diploid fibroblasts. Both steroids underwent 7 alpha-hydroxylation with subsequent oxidation to 7 alpha-hydroxy-3-oxo-delta 4 steroids. A minor fraction of the 27-hydroxysteroids was oxidized to acids. Competition experiments indicated that both hydroxycholesterols were hydroxylated by the same enzyme, different from cholesterol 7 alpha-hydroxylase. 7 alpha,25-Dihydroxycholesterol suppressed the activity of HMG-CoA reductase at least as effectively as 25-hydroxycholesterol whereas 7 alpha,25-dihydroxy-4-cholesten-3-one was a less effective suppressor. The results suggest that cholesterol might be converted to 7 alpha-hydroxylated bile acid precursors in extrahepatic tissues in vivo and that the regulation of the activity of HMG-CoA reductase by oxysterols might be modulated by 7 alpha-hydroxylation and subsequent oxidation by 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase.
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Affiliation(s)
- J Zhang
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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36
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Axelson M, Larsson O, Zhang J, Shoda J, Sjövall J. Structural specificity in the suppression of HMG-CoA reductase in human fibroblasts by intermediates in bile acid biosynthesis. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)39905-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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37
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Toll A, Wikvall K, Sudjana-Sugiaman E, Kondo KH, Björkhem I. 7 alpha hydroxylation of 25-hydroxycholesterol in liver microsomes. Evidence that the enzyme involved is different from cholesterol 7 alpha-hydroxylase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 224:309-16. [PMID: 7925343 DOI: 10.1111/j.1432-1033.1994.00309.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Rat, pig and human liver microsomes were found to catalyze 7 alpha-hydroxylation of 25-hydroxycholesterol. In contrast to cholesterol 7 alpha-hydroxylase activity, the 7 alpha-hydroxylase activity towards 25-hydroxycholesterol in rat liver was not stimulated by cholestyramine treatment. After transfection with cDNA for human cholesterol 7 alpha-hydroxylase, COS cells showed a significant activity towards cholesterol but not towards 25-hydroxycholesterol. During purification of cholesterol 7 alpha-hydroxylase from pig liver microsomes, about 99% of the 7 alpha-hydroxylase activity towards 25-hydroxycholesterol and 27-hydroxycholesterol was clearly separated from 7 alpha-hydroxylase activity for cholesterol. The small amount of 25-hydroxycholesterol 7 alpha-hydroxylase activity retained in a partially purified preparation of cholesterol 7 alpha-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 7 alpha-hydroxylation of cholesterol and 7 alpha hydroxylation of side-chain-oxidized cholesterol in rat, pig and human liver. Inhibition experiments with a partially purified fraction of the oxysterol 7 alpha-hydroxylase from pig liver gave results consistent with the contention that the same enzyme is responsible for 7 alpha hydroxylation of both 25-hydroxycholesterol and 27-hydroxycholesterol. It has been suggested that cholesterol 7 alpha-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 7 alpha-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 7 alpha-hydroxylase.
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Affiliation(s)
- A Toll
- Department of Pharmaceutical Biosciences, University of Uppsala, Sweden
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38
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Shoda J, Axelson M, Sjövall J. Synthesis of potential C27-intermediates in bile acid biosynthesis and their deuterium-labeled analogs. Steroids 1993; 58:119-25. [PMID: 8475516 DOI: 10.1016/0039-128x(93)90048-r] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In connection with studies of alternative pathways in bile acid biosynthesis, potential intermediates in a pathway starting with 27-hydroxylation of cholesterol have been prepared in natural and deuterated forms. Established methods were used to prepare 27-hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid. Clemmensen reduction of kryptogenin in unlabeled and deuterated solvents yielded 27-hydroxy-cholesterol and 16-oxo-5-cholestene-3 beta,27-diol, which were separated by adsorption chromatography on Unisil. The labeled 27-hydroxycholesterol and 3 beta-hydroxy-5-cholestenoic acid derived from it consisted of molecules with seven (50%), six (20%), and eight (20%) deuterium atoms, and unlabeled molecules were not detected. The acetates of 27-hydroxycholesterol and methyl 3 beta-hydroxy-5-cholestenoate were 7 alpha-hydroxylated in a copper-catalyzed reaction with tert-butylperbenzoate, and the products were purified by chromatography on Unisil. The 7 beta-epimers were obtained as side products. Labeled 3 beta,7 alpha-dihydroxy-5-cholenoic acid was prepared in the same way from 3 beta-hydroxy-5-[2,2,4,4,23-2H5]-cholenoic acid. The 3-oxo-delta 4 analogs of the 3 beta-hydroxy-delta 5 compounds were prepared by oxidation with cholesterol oxidase. The labeled products had the same isotopic composition as the starting materials. Gas chromatographic retention indices and mass spectral characteristics of the trimethylsilyl ether derivatives of the neutral steroids and the methylated acids are given for all compounds.
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Affiliation(s)
- J Shoda
- Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden
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Dueland S, Trawick J, Nenseter M, MacPhee A, Davis R. Expression of 7 alpha-hydroxylase in non-hepatic cells results in liver phenotypic resistance of the low density lipoprotein receptor to cholesterol repression. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)50001-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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40
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Björkhem I, Nyberg B, Einarsson K. 7 alpha-hydroxylation of 27-hydroxycholesterol in human liver microsomes. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1128:73-6. [PMID: 1390879 DOI: 10.1016/0005-2760(92)90259-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Human liver microsomes were found to catalyze 7 alpha-hydroxylation of 27-hydroxycholesterol at a rate of up to about 0.2 nmol/mg protein per min. The product of the reaction, 5-cholestene-3 beta, 7 alpha, 27-triol, was identified by means of combined gas chromatography-mass spectrometry. Liver microsomes from two patients with an upregulated cholesterol 7 alpha-hydroxylase, did not have higher 7 alpha-hydroxylase activity towards 27-hydroxycholesterol than those from untreated patients, suggesting that the 7 alpha-hydroxylase active towards 27-hydroxycholesterol is not the same as that active towards cholesterol. The mitochondrial fraction of liver from untreated patients and patients treated with cholestyramine, had negligible 7 alpha-hydroxylase activity towards 27-hydroxycholesterol less than 0.01 nmol/mg protein per min). The results are in accord with the possibility that there is a pathway to bile acids in human liver in which the first step is a 27-hydroxylation of cholesterol.
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Affiliation(s)
- I Björkhem
- Department of Clinical Chemistry, Karolinska Institutet, Huddinge Hospital, Sweden
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Björkhem I. Mechanism of degradation of the steroid side chain in the formation of bile acids. J Lipid Res 1992. [DOI: 10.1016/s0022-2275(20)41612-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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