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Ronnebaum TA, Gupta K, Christianson DW. Higher-order oligomerization of a chimeric αβγ bifunctional diterpene synthase with prenyltransferase and class II cyclase activities is concentration-dependent. J Struct Biol 2020; 210:107463. [PMID: 31978464 DOI: 10.1016/j.jsb.2020.107463] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 01/03/2020] [Accepted: 01/15/2020] [Indexed: 12/11/2022]
Abstract
The unusual diterpene (C20) synthase copalyl diphosphate synthase from Penicillium verruculosum (PvCPS) is the first bifunctional terpene synthase identified with both prenyltransferase and class II cyclase activities in a single polypeptide chain with αβγ domain architecture. The C-terminal prenyltransferase α domain generates geranylgeranyl diphosphate which is then cyclized to form copalyl diphosphate at the N-terminal βγ domain interface. We now demonstrate that PvCPS exists as a hexamer at high concentrations - a unique quaternary structure for known αβγ terpene synthases. Hexamer assembly is corroborated by a 2.41 Å-resolution crystal structure of the α domain prenyltransferase obtained from limited proteolysis of full-length PvCPS, as well as the ab initio model of full-length PvCPS derived from small-angle X-ray scattering data. Hexamerization of the prenyltransferase α domain appears to drive the hexamerization of full-length PvCPS. The PvCPS hexamer dissociates into lower-order species at lower concentrations, as evidenced by size-exclusion chromatography in-line with multiangle light scattering, sedimentation velocity analytical ultracentrifugation, and native polyacrylamide gel electrophoresis experiments, suggesting that oligomerization is concentration dependent. Even so, PvCPS oligomer assembly does not affect prenyltransferase activity in vitro.
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Affiliation(s)
- Trey A Ronnebaum
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
| | - Kushol Gupta
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David W Christianson
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
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2
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Trenin AS. [Microbial metabolites that inhibit sterol biosynthesis, their chemical diversity and characteristics of mode of action]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2015; 39:633-57. [PMID: 25696927 DOI: 10.1134/s1068162013060095] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Inhibitors of sterol biosynthesis (ISB) are widespread in nature and characterized by appreciable diversity both in their chemical structure and mode of action. Many of these inhibitors express noticeable biological activity and approved themselves in development of various pharmaceuticals. In this review there is a detailed description of biologically active microbial metabolites with revealed chemical structure that have ability to inhibit sterol biosynthesis. Inhibitors of mevalonate pathway in fungous and mammalian cells, exhibiting hypolipidemic or antifungal activity, as well as inhibitors of alternative non-mevalonate (pyruvate gliceraldehyde phosphate) isoprenoid pathway, which are promising in the development of affective antimicrobial or antiparasitic drugs, are under consideration in this review. Chemical formulas of the main natural inhibitors and their semi-synthetic derivatives are represented. Mechanism of their action at cellular and biochemical level is discussed. Special attention is given to inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase (group of lovastatin) and inhibitors of acyl-CoA-cholesterol-acyl transferase (ACAT) that possess hypolipidemic activity and could be affective in the treatment of atherosclerosis. In case of inhibitors of late stages of sterol biosynthesis (after squalene formation) special attention is paid to compounds possessing evident antifungal and antitumoral activity. Explanation of mechanism of anticancer and antiviral action of microbial ISB, as well as the description of their ability to induce apoptosis is given.
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Focken T, Hanessian S. Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules. Beilstein J Org Chem 2014; 10:1848-77. [PMID: 25246946 PMCID: PMC4168934 DOI: 10.3762/bjoc.10.195] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/26/2014] [Indexed: 12/12/2022] Open
Abstract
A review of the synthesis of natural products and bioactive compounds adopting phosphonamide anion technology is presented highlighting the utility of phosphonamide reagents in stereocontrolled bond-forming reactions. Methodologies utilizing phosphonamide anions in asymmetric alkylations, Michael additions, olefinations, and cyclopropanations will be summarized, as well as an overview of the synthesis of the employed phosphonamide reagents.
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Affiliation(s)
- Thilo Focken
- Xenon Pharmaceuticals Inc., 3650 Gilmore Way, Burnaby, BC V5G 4W8, Canada
| | - Stephen Hanessian
- Department of Chemistry, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada
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Park J, Matralis AN, Berghuis AM, Tsantrizos YS. Human isoprenoid synthase enzymes as therapeutic targets. Front Chem 2014; 2:50. [PMID: 25101260 PMCID: PMC4106277 DOI: 10.3389/fchem.2014.00050] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Accepted: 06/25/2014] [Indexed: 12/14/2022] Open
Abstract
In the human body, the complex biochemical network known as the mevalonate pathway is responsible for the biosynthesis of all isoprenoids, which consists of a vast array of metabolites that are vital for proper cellular functions. Two key isoprenoids, farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) are responsible for the post-translational prenylation of small GTP-binding proteins, and serve as the biosynthetic precursors to numerous other biomolecules. The down-stream metabolite of FPP and GGPP is squalene, the precursor to steroids, bile acids, lipoproteins, and vitamin D. In the past, interest in prenyl synthase inhibitors focused mainly on the role of the FPP in lytic bone diseases. More recently pre-clinical and clinical studies have strongly implicated high levels of protein prenylation in a plethora of human diseases, including non-skeletal cancers, the progression of neurodegenerative diseases and cardiovascular diseases. In this review, we focus mainly on the potential therapeutic value of down-regulating the biosynthesis of FPP, GGPP, and squalene. We summarize the most recent drug discovery efforts and the structural data available that support the current on-going studies.
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Affiliation(s)
- Jaeok Park
- Department of Biochemistry, McGill University Montreal, QC, Canada
| | | | - Albert M Berghuis
- Department of Biochemistry, McGill University Montreal, QC, Canada ; Department of Microbiology and Immunology, McGill University Montreal, QC, Canada
| | - Youla S Tsantrizos
- Department of Biochemistry, McGill University Montreal, QC, Canada ; Department of Chemistry, McGill University Montreal, QC, Canada
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Deglycosylation of stilbene glucoside compounds improves inhibition of 3-hydroxy-3-methylglutaryl coenzyme a reductase and squalene synthase activities. Food Sci Biotechnol 2014. [DOI: 10.1007/s10068-014-0088-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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6
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Vega-Pérez JM, Periñán I, Argandoña M, Vega-Holm M, Palo-Nieto C, Burgos-Morón E, López-Lázaro M, Vargas C, Nieto JJ, Iglesias-Guerra F. Isoprenyl-thiourea and urea derivatives as new farnesyl diphosphate analogues: synthesis and in vitro antimicrobial and cytotoxic activities. Eur J Med Chem 2012; 58:591-612. [PMID: 23174318 DOI: 10.1016/j.ejmech.2012.10.042] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 10/22/2012] [Accepted: 10/24/2012] [Indexed: 01/07/2023]
Abstract
A series of new isoprenyl-thiourea and urea derivatives were synthesized by the reaction of alkyl or aryl isothiocyanate or isocyanate and primary amines. The structures of the compounds were established by (1)H NMR, (13)C NMR, MS, HRMS and elemental analysis. The new compounds were screened for in vitro antimicrobial activity against seven strains representing different types of gram-positive and gram-negative bacteria. More than a third of the synthesized compounds showed variable inhibition activities against the tested strains. Best antimicrobial activities were found for those thiourea analogues with 3-methyl-2-butenyl, isobutyl or isopentyl groups and aromatic rings possessing electron withdrawing substituents. The new compounds were also subjected to a preliminary screening for antitumoral activity. The presence of a highly lipophilic group and an electron withdrawing group in the aromatic rings enhanced anticancer activity of the synthesized compounds, showing in most cases more activity than that of the controls.
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Affiliation(s)
- José M Vega-Pérez
- Departamento de Química Orgánica y Farmacéutica, Facultad de Farmacia, Universidad de Sevilla, 41071 Sevilla, Spain.
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Kahlon AK, Roy S, Sharma A. Molecular Docking Studies to Map the Binding Site of Squalene Synthase Inhibitors on Dehydrosqualene Synthase ofStaphylococcus Aureus. J Biomol Struct Dyn 2010; 28:201-10. [DOI: 10.1080/07391102.2010.10507353] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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8
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Urbina JA. Ergosterol biosynthesis and drug development for Chagas disease. Mem Inst Oswaldo Cruz 2010; 104 Suppl 1:311-8. [PMID: 19753490 DOI: 10.1590/s0074-02762009000900041] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 05/18/2009] [Indexed: 12/13/2022] Open
Abstract
This article presents an overview of the currently available drugs nifurtimox (NFX) and benznidazole (BZN) used against Trypanosoma cruzi, the aetiological agent of Chagas disease; herein we discuss their limitations along with potential alternatives with a focus on ergosterol biosynthesis inhibitors (EBI). These compounds are currently the most advanced candidates for new anti-T. cruzi agents given that they block de novo production of 24-alkyl-sterols, which are essential for parasite survival and cannot be replaced by a host's own cholesterol. Among these compounds, new triazole derivatives that inhibit the parasite's C14alpha sterol demethylase are the most promising, as they have been shown to have curative activity in murine models of acute and chronic Chagas disease and are active against NFX and BZN-resistant T. cruzi strains; among this class of compounds, posaconazole (Schering-Plough Research Institute) and ravuconazole (Eisai Company) are poised for clinical trials in Chagas disease patients in the short term. Other T. cruzi-specific EBI, with in vitro and in vivo potency, include squalene synthase, lanosterol synthase and squalene epoxidase-inhibitors as well as compounds with dual mechanisms of action (ergosterol biosynthesis inhibition and free radical generation), but they are less advanced in their development process. The main putative advantages of EBI over currently available therapies include their higher potency and selectivity in both acute and chronic infections, activity against NFX and BZN-resistant T. cruzi strains, and much better tolerability and safety profiles. Limitations may include complexity and cost of manufacture of the new compounds. As for any new drug, such compounds will require extensive clinical testing before being introduced for clinical use, and the complexity of such studies, particularly in chronic patients, will be compounded by the current limitations in the verification of true parasitological cures for T. cruzi infections.
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Affiliation(s)
- Julio A Urbina
- Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela.
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Calo F, Bondke A, Richardson J, White AJ, Barrett AG. Total synthesis and determination of the absolute stereochemistry of the squalene synthase inhibitors CJ-13,981 and CJ-13,982. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.02.121] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Combined gas chromatographic/mass spectrometric analysis of cholesterol precursors and plant sterols in cultured cells. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 877:2081-6. [PMID: 19525158 DOI: 10.1016/j.jchromb.2009.05.050] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 04/20/2009] [Accepted: 05/21/2009] [Indexed: 11/20/2022]
Abstract
We developed a powerful gas chromatographic/mass spectrometric method allowing quantitative analysis of 11 structurally similar cholesterol precursors and plant sterols (squalene, desmosterol, 7-dehydrocholesterol, lathosterol, zymosterol, dihydro-lanosterol, lanosterol, FF-MAS, T-MAS, campesterol, sitosterol) from cultured human hepatocytes in a single chromatographic run. Deuterium labelled cholesterol, sitosterol and lathosterol were used as internal standards. Care was taken to select ions for the detection that gave the most appropriate discrimination in the assay. Replicate analyses gave a coefficient of variation less than 6%. Recovery experiments were satisfactory for 7-dehydrocholesterol, campesterol, desmosterol, lathosterol, zymosterol and cholesterol with less than 7% difference between expected and found levels. For other sterols, the difference between expected and found levels varied between 10 and 16%. It is concluded that this method is suitable for studies on the effect of different inhibitors and stimulators of cholesterol synthesis in cultured cells. Additionally, the method is relevant also for clinical applications since abnormally increased late cholesterol intermediates in patients are representations of the inherited disorders linked to different enzyme defects in the post-squalene cholesterol biosynthesis.
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Viturro E, Koenning M, Kroemer A, Schlamberger G, Wiedemann S, Kaske M, Meyer HHD. Cholesterol synthesis in the lactating cow: Induced expression of candidate genes. J Steroid Biochem Mol Biol 2009; 115:62-7. [PMID: 19429461 DOI: 10.1016/j.jsbmb.2009.02.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 02/18/2009] [Indexed: 11/21/2022]
Abstract
Despite the extensive knowledge for other species, cholesterol metabolism in ruminants is nowadays still not clear. Huge differences in milk cholesterol concentration are observed between breeds, managing strategies, individuals and moment of the lactating cycle, but the genetic actors working in the process of cholesterol secretion into milk have not been identified. As ruminant diet contains no cholesterol, understanding the mechanisms and regulation of synthesis, transport and secretion into milk is crucial when trying to reduce the amount of this metabolite in dairy products. The present work aims to study the expression of candidate genes for these processes in the liver of Bos taurus during the lactating cycle. Liver biopsies were obtained from 16 adult brown Swiss cows at different time points (2 weeks pre-partum and 0, 2, 4 and 8 weeks post-partum). After RNA extraction and reverse transcription, gene expression of candidate genes was studied using quantitative RT-PCR. Key enzymes of the cholesterol synthesis (3-hydroxy-methyglutaryl-coenzyme-A (HMG-CoA) synthase, HMG-CoA reductase and farnesyldiphosphat-farnesyltransferase (FDFT)) and gene expression feed-back regulators involved in lipid metabolism (sterol regulatory element binding proteins (SREBP1and 2) SREBP-cleavage activating protein (Scap) were selected as candidate genes. HMG-CoA-reductase and FDFT showed a huge expression increase until week 2 post-partum (p<0.01), most probably in response to the new requirements in the mammary gland. As well, and as a possible explanation for such modifications, an increase in the expression of the regulators SREBP1 and Scap was observed (p<0.01 and p<0.05 respectively). Most important, the whole synthesis machinery showed a coordinated regulation, as highly significant positive correlations were found between the expression levels of the above mentioned enzymes (p<0.01). The increase of milk and blood cholesterol levels in B. taurus after parturition might be the result of a coordinated induction in the expression of key liver enzymes and their regulating factors.
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Affiliation(s)
- Enrique Viturro
- Physiology Weihenstephan, Technische Universitaet Muenchen, Weihenstephaner Berg, Freising, Germany.
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Do R, Kiss RS, Gaudet D, Engert JC. Squalene synthase: a critical enzyme in the cholesterol biosynthesis pathway. Clin Genet 2009; 75:19-29. [DOI: 10.1111/j.1399-0004.2008.01099.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Tavridou A, Kaklamanis L, Megaritis G, Kourounakis AP, Papalois A, Roukounas D, Rekka EA, Kourounakis PN, Charalambous A, Manolopoulos VG. Pharmacological characterization in vitro of EP2306 and EP2302, potent inhibitors of squalene synthase and lipid biosynthesis. Eur J Pharmacol 2006; 535:34-42. [PMID: 16545796 DOI: 10.1016/j.ejphar.2006.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 01/26/2006] [Accepted: 02/07/2006] [Indexed: 11/21/2022]
Abstract
We investigated the effects of EP2306 and EP2302, two novel 2-biphenylmorpholine derivatives, on squalene synthase activity in rabbit and human liver microsomes, lipid biosynthesis, low-density lipoprotein (LDL) receptor expression and LDL protein uptake as well as apoB secretion in HepG2 cells. Both EP2306 and EP2302 inhibited squalene synthase activity dose-dependently. In rabbit liver microsomes, the IC50 values were 33 microM for EP2306 and 0.6 microM for EP2302 whereas in human liver microsomes, they were 63 microM for EP2306 and 1 microM for EP2302. Both EP2300 compounds inhibited cholesterol production by HepG2 cells dose dependently with IC50 values of 13.3 microM for EP2306 and 3 microM for EP2302. Furthermore, both EP2300 compounds and simvastatin significantly reduced triglyceride synthesis and apoB secretion and increased LDL receptor expression and LDL uptake in HepG2 cells. In summary, we have shown that EP2300 compounds are potent inhibitors of squalene synthase activity in rabbit and human liver microsomes and also they are effective inhibitors of cholesterol and triglyceride biosynthesis in HepG2 cells. These results suggest that EP2306 and EP2302 might prove to be useful for lipid-lowering and treatment of atherosclerosis in vivo.
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Affiliation(s)
- Anna Tavridou
- ELPEN Pharmaceutical Co Inc., 95 Marathonos Av.,19009 Pikermi, Greece
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Burnett JR, Watts GF. New therapies for familial hypercholesterolemia. Expert Opin Ther Pat 2006. [DOI: 10.1517/13543776.16.3.349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Ishikawa M, Namiki A, Kubota T, Yajima S, Fukazawa M, Moroi M, Sugi K. Effect of pravastatin and atorvastatin on glucose metabolism in nondiabetic patients with hypercholesterolemia. Intern Med 2006; 45:51-5. [PMID: 16484739 DOI: 10.2169/internalmedicine.45.1476] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVE The aim of this study was to assess the effects of hydrophilic pravastatin and lipophilic atorvastatin on glucose metabolism and lipid metabolism in non-diabetic patients with hypercholesterolemia. METHODS Fasting plasma glucose (FPG), hemoglobin A(1c) (HbA(1c)), total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), high-density lipoprotein cholesterol (HDLC), and triglyceride (TG) levels were determined before and after statin treatment. PATIENTS A total of 44 nondiabetic patients (FPG < or =125 mg/mL; HbA(1c) <5.8%) undergoing treatment with either pravastatin (n=21) or atorvastatin (n=23) for hypercholesterolemia were investigated. RESULTS FPG level in the pravastatin but not atorvastatin group was significantly lowered after vs before treatment. Accordingly, the HbA(1c) level in the atorvastatin but not in the pravastatin group was significantly increased. As expected, both TC and LDL-C levels were significantly lowered in both groups. In particular, the TC level in the atorvastatin group was more remarkably and significantly improved than in the pravastatin group. On the other hand, the HDL-C level in the pravastatin group but not in the atorvastatin group was significantly increased after the administration period. The TG level was unaffected in both groups. CONCLUSION Pravastatin was suggested to act favorably, while atorvastatin adversely, regarding it's effects on glucose metabolism in nondiabetic hypercholesterolemic patients, although atorvastatin exerted more potent cholesterol-lowering effects compared with pravastatin.
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Affiliation(s)
- Michiro Ishikawa
- Division of Cardiovascular Medicine, Toho University Ohashi Medical Center, Tokyo
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Urbina JA, Concepcion JL, Caldera A, Payares G, Sanoja C, Otomo T, Hiyoshi H. In vitro and in vivo activities of E5700 and ER-119884, two novel orally active squalene synthase inhibitors, against Trypanosoma cruzi. Antimicrob Agents Chemother 2004; 48:2379-87. [PMID: 15215084 PMCID: PMC434216 DOI: 10.1128/aac.48.7.2379-2387.2004] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2003] [Revised: 01/15/2004] [Accepted: 03/02/2004] [Indexed: 11/20/2022] Open
Abstract
Chagas' disease is a serious public health problem in Latin America, and no treatment is available for the prevalent chronic stage. Its causative agent, Trypanosoma cruzi, requires specific endogenous sterols for survival, and we have recently demonstrated that squalene synthase (SQS) is a promising target for antiparasitic chemotherapy. E5700 and ER-119884 are quinuclidine-based inhibitors of mammalian SQS that are currently in development as cholesterol- and triglyceride-lowering agents in humans. These compounds were found to be potent noncompetitive or mixed-type inhibitors of T. cruzi SQS with K(i) values in the low nanomolar to subnanomolar range in the absence or presence of 20 microM inorganic pyrophosphate. The antiproliferative 50% inhibitory concentrations of the compounds against extracellular epimastigotes and intracellular amastigotes were ca. 10 nM and 0.4 to 1.6 nM, respectively, with no effects on host cells. When treated with these compounds at the MIC, all of the parasite's sterols disappeared from the parasite cells. In vivo studies indicated that E5700 was able to provide full protection against death and completely arrested the development of parasitemia when given at a concentration of 50 mg/kg of body weight/day for 30 days, while ER-119884 provided only partial protection. This is the first report of an orally active SQS inhibitor that is capable of providing complete protection against fulminant, acute Chagas' disease.
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Affiliation(s)
- Julio A Urbina
- Instituto Venezolano de Investigaciones, Centro de Bioquimica y Biofisica, Altos de Pipe, Caracas 1020, Venezuela.
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