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Effect of Cyp27A1 gene dosage on atherosclerosis development in ApoE-knockout mice.
FASEB J.
PUBLISHED: 12-10-2013
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In humans, sterol 27-hydroxylase (CYP27A1) deficiency leads to cholesterol deposition in tendons and vasculature. Thus, in addition to its role in bile acid synthesis, where it converts cholesterol to 27-hydroxycholesterol (27-OHC), CYP27A1 may also be atheroprotective. Cyp27A1-deficient (Cyp27A1(-/-)) mice were crossed with apolipoprotein E (apoE)-deficient mice. Cyp27A1(+/+)/apoE(-/-) [ApoE-knockout (KO)], Cyp27A1(+/-)/apoE(-/-) heterozygous (het), and Cyp27A1(-/-)/apoE(-/-) [double-knockout (DKO)] mice were challenged with a Western diet (WD) for 3 and 6 mo. ApoE-KO mice fed a chow diet or a WD were used as the control. The severity of atherosclerosis in DKO mice was reduced 10-fold. Compared with the control, the DKO mice had no 27-OHC, total plasma cholesterol and low-density lipoprotein and very low density lipoprotein (LDL/VLDL) concentrations were reduced 2-fold, and HDL was elevated 2-fold. Expression of hepatic CYP7A1, CYP3A, and CYP8B1 were 5- to 10-fold higher. 3-Hydroxy-3-methyl-glutaryl-CoA reductase (HMGR) activity increased 4-fold. Fecal cholesterol was increased. In contrast, het mice fed a WD developed accelerated atherosclerosis and severe skin lesions, possibly because of reduced reverse cholesterol transport due to diminished 27-OHC production. CYP27A1 activity is involved in the control of cholesterol homeostasis and development of atherosclerosis with a distinct gene dose-dependent effect.-Zurkinden, L., Solcà, C., Vögeli, I. A., Vogt, B., Ackermann, D., Erickson, S. K., Frey, F. J., Sviridov, D., Escher, G. Effect of Cyp27A1 gene dosage on atherosclerosis development in ApoE-knockout mice.
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Evidence for a role of sterol 27-hydroxylase in glucocorticoid metabolism in vivo.
J. Endocrinol.
PUBLISHED: 01-01-2013
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The intracellular availability of glucocorticoids is regulated by the enzymes 11?-hydroxysteroid dehydrogenase 1 (HSD11B1) and 11?-hydroxysteroid dehydrogenase 2 (HSD11B2). The activity of HSD11B1 is measured in the urine based on the (tetrahydrocortisol+5?-tetrahydrocortisol)/tetrahydrocortisone ((THF+5?-THF)/THE) ratio in humans and the (tetrahydrocorticosterone+5?-tetrahydrocorticosterone)/tetrahydrodehydrocorticosterone ((THB+5?-THB)/THA) ratio in mice. The cortisol/cortisone (F/E) ratio in humans and the corticosterone/11-dehydrocorticosterone (B/A) ratio in mice are markers of the activity of HSD11B2. In vitro agonist treatment of liver X receptor (LXR) down-regulates the activity of HSD11B1. Sterol 27-hydroxylase (CYP27A1) catalyses the first step in the alternative pathway of bile acid synthesis by hydroxylating cholesterol to 27-hydroxycholesterol (27-OHC). Since 27-OHC is a natural ligand for LXR, we hypothesised that CYP27A1 deficiency may up-regulate the activity of HSD11B1. In a patient with cerebrotendinous xanthomatosis carrying a loss-of-function mutation in CYP27A1, the plasma concentrations of 27-OHC were dramatically reduced (3.8 vs 90-140?ng/ml in healthy controls) and the urinary ratios of (THF+5?-THF)/THE and F/E were increased, demonstrating enhanced HSD11B1 and diminished HSD11B2 activities. Similarly, in Cyp27a1 knockout (KO) mice, the plasma concentrations of 27-OHC were undetectable (<1 vs 25-120?ng/ml in Cyp27a1 WT mice). The urinary ratio of (THB+5?-THB)/THA was fourfold and that of B/A was twofold higher in KO mice than in their WT littermates. The (THB+5?-THB)/THA ratio was also significantly increased in the plasma, liver and kidney of KO mice. In the liver of these mice, the increase in the concentrations of active glucocorticoids was due to increased liver weight as a consequence of Cyp27a1 deficiency. In vitro, 27-OHC acts as an inhibitor of the activity of HSD11B1. Our studies suggest that the expression of CYP27A1 modulates the concentrations of active glucocorticoids in both humans and mice and in vitro.
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Glucose and insulin induction of bile acid synthesis: mechanisms and implication in diabetes and obesity.
J. Biol. Chem.
PUBLISHED: 12-05-2011
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Bile acids facilitate postprandial absorption of nutrients. Bile acids also activate the farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5 and play a major role in regulating lipid, glucose, and energy metabolism. Transgenic expression of cholesterol 7?-hydroxylase (CYP7A1) prevented high fat diet-induced diabetes and obesity in mice. In this study, we investigated the nutrient effects on bile acid synthesis. Refeeding of a chow diet to fasted mice increased CYP7A1 expression, bile acid pool size, and serum bile acids in wild type and humanized CYP7A1-transgenic mice. Chromatin immunoprecipitation assays showed that glucose increased histone acetylation and decreased histone methylation on the CYP7A1 gene promoter. Refeeding also induced CYP7A1 in fxr-deficient mice, indicating that FXR signaling did not play a role in postprandial regulation of bile acid synthesis. In streptozocin-induced type I diabetic mice and genetically obese type II diabetic ob/ob mice, hyperglycemia increased histone acetylation status on the CYP7A1 gene promoter, leading to elevated basal Cyp7a1 expression and an enlarged bile acid pool with altered bile acid composition. However, refeeding did not further increase CYP7A1 expression in diabetic mice. In summary, this study demonstrates that glucose and insulin are major postprandial factors that induce CYP7A1 gene expression and bile acid synthesis. Glucose induces CYP7A1 gene expression mainly by epigenetic mechanisms. In diabetic mice, CYP7A1 chromatin is hyperacetylated, and fasting to refeeding response is impaired and may exacerbate metabolic disorders in diabetes.
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Profiling sterols in cerebrotendinous xanthomatosis: utility of Girard derivatization and high resolution exact mass LC-ESI-MS(n) analysis.
J. Chromatogr. B Analyt. Technol. Biomed. Life Sci.
PUBLISHED: 08-21-2010
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In this study we profile free 3-oxo sterols present in plasma from patients affected with the neurodegenerative disorder of sterol and bile acid metabolism cerebrotendinous xanthomatosis (CTX), utilizing a combination of charge-tagging and LC-ESI-MS(n) performed with an LTQ-Orbitrap Discovery instrument. In addition, we profile sterols in plasma from 24-month-old cyp27A1 gene knockout mice lacking the enzyme defective in CTX. Charge-tagging was accomplished by reaction with cationic Girards P (GP) reagent 1-(carboxymethyl) pyridinium chloride hydrazide, an approach uniquely suited to studying the 3-oxo sterols that accumulate in CTX, as Girards reagent reacts with the sterol oxo moiety to form charged hydrazone derivatives. The ability to selectively generate GP-tagged 3-oxo-4-ene and 3-oxo-5(H) saturated plasma sterols enabled ESI-MS(n) analysis of these sterols in the presence of a large excess (3 orders of magnitude) of cholesterol. Often cholesterol detected in biological samples makes it challenging to quantify minor sterols, with cholesterol frequently removed prior to analysis. We derivatized plasma (10 ?l) without SPE removal of cholesterol to ensure detection of all sterols present in plasma. We were able to measure 4-cholesten-3-one in plasma from untreated CTX patients (1207±302 ng/ml, mean±SD, n=4), as well as other intermediates in a proposed pathway to 5?-cholestanol. In addition, a number of bile acid precursors were identified in plasma using this technique. GP-tagged sterols were identified utilizing high resolution exact mass spectra (±5 ppm), as well as MS(2) ([M](+)?) spectra that possessed characteristic neutral loss of 79Da (pyridine) fragment ions, and MS(3) ([M](+)?[M-79](+)?) spectra that provided additional structurally informative fragment ions.
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Mice with null mutation of Ceacam I develop nonalcoholic steatohepatitis.
Hepat Med
PUBLISHED: 05-01-2010
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Transgenic liver-specific inactivation of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM1) impairs hepatic insulin clearance and causes hyperinsuline-mia, insulin resistance, elevation in hepatic and serum triglyceride levels, and visceral obesity. It also predisposes to nonalchoholic steatohepatitis (NASH) in response to a high-fat diet. To discern whether this phenotype reflects a physiological function of CEACAM1 rather than the effect of the dominant-negative transgene, we investigated whether Ceacam1 (gene encoding CEACAM1 protein) null mice with impaired insulin clearance also develop a NASH-like phenotype on a prolonged high-fat diet. Three-month-old male null and wild-type mice were fed a high-fat diet for 3 months and their NASH phenotype was examined. While high-fat feeding elevated hepatic triglyceride content in both strains of mice, it exacerbated macrosteatosis and caused NASH-characteristic fibrogenic changes and inflammatory responses more intensely in the null mouse. This demonstrates that CEACAM1-dependent insulin clearance pathways are linked with NASH pathogenesis.
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Role of CYP27A1 in progesterone metabolism in vitro and in vivo.
Am. J. Physiol. Endocrinol. Metab.
PUBLISHED: 08-11-2009
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In the kidney, progesterone is inactivated to 20alpha-dihydro-progesterone (20alpha-DH-progesterone) to protect the mineralocorticoid receptor from progesterone excess. In an attempt to clone the enzyme with 20alpha-hydroxysteroid activity using expression cloning in CHOP cells and a human kidney expression library, serendipitously cDNA encoding CYP27A1 was isolated. Overexpression of CYP27A1 in CHOP cells decreased progesterone conversion to 20alpha-DH-progesterone in a dose-dependent manner, an effect enhanced by cotransfection with adrenodoxin and adrenodoxin reductase. Incubation of CHOP cells with 27-hydroxycholesterol, a product of CYP27A1, increased the ratio of progesterone to 20alpha-DH-progesterone in a concentration-dependent manner, indicating that the effect of CYP27A1 overexpression was mediated by 27-hydroxycholesterol. To analyze whether these observations are relevant in vivo, progesterone and 20alpha-DH-progesterone were measured by gas chromatography-mass spectometry in 24-h urine of CYP27A1 gene knockout (ko) mice and their control wild-type and heterozygote littermates. In CYP27A1 ko mice, urinary progesterone concentrations were decreased, 20alpha-DH-progesterone increased, and the progesterone-to-20alpha-DH-progesterone ratio decreased threefold (P < 0.001). Thus CYP27A1 modulates progesterone concentrations. The underlying mechanism is inhibition of 20alpha-hydroxysteroid dehydrogenase by 27-hydroxycholesterol.
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Nonalcoholic fatty liver disease.
J. Lipid Res.
PUBLISHED: 06-06-2009
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Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the United States and, indeed, worldwide. It has become a global public health issue. In the United States, the prevalence in the general population is estimated at approximately 20%, while that in the morbidly obese population at approximately 75-92% and in the pediatric population at approximately 13-14%. The progressive form of NAFLD, nonalcoholic steatohepatitis, is estimated at approximately 3-5%, with approximately 3-5% of these having progressed to cirrhosis. Thus, the numbers of individuals at risk for end-stage liver disease and development of primary liver cancer is large. NAFLD is an independent risk factor for cardiovascular disease, leads to increased all-cause mortality, and to increased liver-related mortality. This review focuses on recent advances in our understanding of the NAFLD disease spectrum, including etiology, diagnosis, treatment, and genetic and environmental risk factors and suggests future directions for research in this important area.
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