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D'Alessandro A, Lukens JR, Zimring JC. The role of PIMT in Alzheimer's disease pathogenesis: A novel hypothesis. Alzheimers Dement 2023; 19:5296-5302. [PMID: 37157118 DOI: 10.1002/alz.13115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 04/11/2023] [Indexed: 05/10/2023]
Abstract
There are multiple theories of Alzheimer's disease pathogenesis. One major theory is that oxidation of amyloid beta (Aβ) promotes plaque deposition that directly contributes to pathology. A competing theory is that hypomethylation of DNA (due to altered one carbon metabolism) results in pathology through altered gene regulation. Herein, we propose a novel hypothesis involving L-isoaspartyl methyltransferase (PIMT) that unifies the Aβ and DNA hypomethylation hypotheses into a single model. Importantly, the proposed model allows bidirectional regulation of Aβ oxidation and DNA hypomethylation. The proposed hypothesis does not exclude simultaneous contributions by other mechanisms (e.g., neurofibrillary tangles). The new hypothesis is formulated to encompass oxidative stress, fibrillation, DNA hypomethylation, and metabolic perturbations in one carbon metabolism (i.e., methionine and folate cycles). In addition, deductive predictions of the hypothesis are presented both to guide empirical testing of the hypothesis and to provide candidate strategies for therapeutic intervention and/or nutritional modification. HIGHLIGHTS: PIMT repairs L-isoaspartyl groups on amyloid beta and decreases fibrillation. SAM is a common methyl donor for PIMT and DNA methyltransferases. Increased PIMT activity competes with DNA methylation and vice versa. The PIMT hypothesis bridges a gap between plaque and DNA methylation hypotheses.
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Affiliation(s)
- Angelo D'Alessandro
- University of Colorado Denver-Anschutz Medical Campus, Aurora, Colorado, USA
| | - John R Lukens
- Carter Immunology Center and Center for Brain Immunology and Glia, University of Virginia Departments of Pathology and Neuroscience, Charlottesville, Virginia, USA
| | - James C Zimring
- Carter Immunology Center and Center for Brain Immunology and Glia, University of Virginia Departments of Pathology and Neuroscience, Charlottesville, Virginia, USA
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Shih YL, Shih CC, Chen JY. Elevated homocysteine level as an indicator for chronic kidney disease in community-dwelling middle-aged and elderly populations in Taiwan: A community-based cross-sectional study. Front Med (Lausanne) 2022; 9:964101. [PMID: 36004372 PMCID: PMC9393293 DOI: 10.3389/fmed.2022.964101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 07/18/2022] [Indexed: 11/17/2022] Open
Abstract
Background Hyperhomocysteinemia is an important factor for endothelial cell damage and a risk factor for cardiovascular diseases. Chronic kidney disease (CKD) is recognized as a leading burden in Taiwan’s healthcare system. This study aimed to investigate the association between homocysteine levels and CKD in middle-aged and elderly adults from a community in northern Taiwan. Methods A total of 396 middle-aged and elderly Taiwanese adults were enrolled and completed the health survey. We divided participants according to tertiles of homocysteine levels as first group (homocysteine level ≤ 11.1 μmol/L), second group (homocysteine level 11.2∼14.3 μmol/L), and third group (homocysteine level > 14.3 μmol/L). CKD was defined as estimated glomerular filtration rate (eGFR) < 60 (mL/min/1.73 m2) or urine albumin to creatinine ratio > 30 (mg/g). Pearson correlation was calculated between eGFR and other related risk factors after adjustment for age. The risk of CKD in the second and third groups compared to that in the first group was assessed by multivariate logistic regression after adjustment for age, sex, smoking, hypertension (HTN), diabetes mellitus (DM), body mass index (BMI), dyslipidemia, and uric acid. The Youden index and receiver operating characteristic (ROC) curve were calculated for the optimized cutoff value. Results Elevated plasma homocysteine levels were more likely to lower the eGFR and increase the prevalence of CKD. Pearson correlation showed a positive correlation between eGFR and high-density lipoprotein cholesterol, while a negative correlation was observed between homocysteine levels, waist circumference, systolic blood pressure, uric acid levels and BMI (all p < 0.05). In the logistic regression analysis, the prevalence of CKD increased, as well as the homocysteine level. The odds ratio of CKD under 95% confidence interval was 2.655 (1.284–5.490) for the third group compared with the first group after adjusting for age, sex, smoking, DM, HTN, dyslipidemia, uric acid, and BMI (p = 0.008). The area under the ROC curve was 0.662, and a cutoff value of 15.15 μmol/L for the homocysteine level was obtained for detecting subjects with CKD. Conclusion Our study findings revealed that elevated homocysteine levels were significantly associated with CKD and could be used as an indicator of CKD among the middle-aged and elderly populations in Taiwan.
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Affiliation(s)
- Yu-Lin Shih
- Department of Family Medicine, Chang-Gung Memorial Hospital, Linkou Branch, Taoyuan City, Taiwan
| | - Chin-Chuan Shih
- General Administrative Department, United Safety Medical Group, New Taipei City, Taiwan
| | - Jau-Yuan Chen
- Department of Family Medicine, Chang-Gung Memorial Hospital, Linkou Branch, Taoyuan City, Taiwan
- College of Medicine, Chang Gung University, Taoyuan City, Taiwan
- *Correspondence: Jau-Yuan Chen,
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Vanholder R, Pletinck A, Schepers E, Glorieux G. Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update. Toxins (Basel) 2018; 10:toxins10010033. [PMID: 29316724 PMCID: PMC5793120 DOI: 10.3390/toxins10010033] [Citation(s) in RCA: 191] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 12/21/2017] [Accepted: 12/23/2017] [Indexed: 02/07/2023] Open
Abstract
In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β2-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.
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Affiliation(s)
- Raymond Vanholder
- Nephrology Section, Department of Internal Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.
| | - Anneleen Pletinck
- Nephrology Section, Department of Internal Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.
| | - Eva Schepers
- Nephrology Section, Department of Internal Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.
| | - Griet Glorieux
- Nephrology Section, Department of Internal Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.
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4
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Long Y, Nie J. Homocysteine in Renal Injury. KIDNEY DISEASES 2016; 2:80-7. [PMID: 27536696 DOI: 10.1159/000444900] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 02/23/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND Homocysteine (Hcy) is an intermediate of methionine metabolism. Hyperhomocysteinemia (HHcy) can result from a deficiency in the enzymes or vitamin cofactors required for Hcy metabolism. Patients with renal disease tend to be hyperhomocysteinemic, particularly as renal function declines, although the underlying cause of HHcy in renal disease is not entirely understood. SUMMARY HHcy is considered a risk or pathogenic factor in the progression of chronic kidney disease (CKD) as well as the cardiovascular complications. KEY MESSAGES In this review, we summarize both clinical and experimental findings that reveal the contribution of Hcy as a pathogenic factor to the development of CKD. In addition, we discuss several important mechanisms mediating the pathogenic action of Hcy in the kidney, such as local oxidative stress, endoplasmic reticulum stress, inflammation and hypomethylation.
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Affiliation(s)
- Yanjun Long
- State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Division of Nephrology, Nanfang Hospital, Southern Medical University, Guangzhou, Guiyang, PR China; Division of Nephrology, Guizhou Provincial People's Hospital, Guizhou Provincial Institute of Nephritic and Urinary Disease, Guiyang, PR China
| | - Jing Nie
- State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Division of Nephrology, Nanfang Hospital, Southern Medical University, Guangzhou, Guiyang, PR China
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Strauss KA, Ferreira C, Bottiglieri T, Zhao X, Arning E, Zhang S, Zeisel SH, Escolar ML, Presnick N, Puffenberger EG, Vugrek O, Kovacevic L, Wagner C, Mazariegos GV, Mudd SH, Soltys K. Liver transplantation for treatment of severe S-adenosylhomocysteine hydrolase deficiency. Mol Genet Metab 2015; 116:44-52. [PMID: 26095522 DOI: 10.1016/j.ymgme.2015.06.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Accepted: 06/13/2015] [Indexed: 12/12/2022]
Abstract
A child with severe S-adenosylhomocysteine hydrolase (AHCY) deficiency (AHCY c.428A>G, p.Tyr143Cys; c.982T>G, p.Tyr328Asp) presented at 8 months of age with growth failure, microcephaly, global developmental delay, myopathy, hepatopathy, and factor VII deficiency. Plasma methionine, S-adenosylmethionine (AdoMet), and S-adenosylhomocysteine (AdoHcy) were markedly elevated and the molar concentration ratio of AdoMet:AdoHcy, believed to regulate a myriad of methyltransferase reactions, was 15% of the control mean. Dietary therapy failed to normalize biochemical markers or alter the AdoMet to AdoHcy molar concentration ratio. At 40 months of age, the proband received a liver segment from a healthy, unrelated living donor. Mean AdoHcy decreased 96% and the AdoMet:AdoHcy concentration ratio improved from 0.52±0.19 to 1.48±0.79 mol:mol (control 4.10±2.11 mol:mol). Blood methionine and AdoMet were normal and stable during 6 months of follow-up on an unrestricted diet. Average calculated tissue methyltransferase activity increased from 43±26% to 60±22%, accompanied by signs of increased transmethylation in vivo. Factor VII activity increased from 12% to 100%. During 6 postoperative months, head growth accelerated 4-fold and the patient made promising gains in gross motor, language, and social skills.
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Affiliation(s)
- Kevin A Strauss
- Clinic for Special Children, Strasburg, PA, USA; Franklin and Marshall College, Lancaster, PA, USA; Lancaster General Hospital, Lancaster, PA, USA.
| | - Carlos Ferreira
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Teodoro Bottiglieri
- Center of Metabolomics, Institute of Metabolic Disease, Baylor Research Institute, Dallas, TX, USA
| | - Xueqing Zhao
- Nutrition Research Institute, University of North Carolina at Chapel Hill, Kannapolis, NC, USA
| | - Erland Arning
- Center of Metabolomics, Institute of Metabolic Disease, Baylor Research Institute, Dallas, TX, USA
| | - Shucha Zhang
- Nutrition Research Institute, University of North Carolina at Chapel Hill, Kannapolis, NC, USA
| | - Steven H Zeisel
- Nutrition Research Institute, University of North Carolina at Chapel Hill, Kannapolis, NC, USA
| | - Maria L Escolar
- Program for the Study of Neurodevelopment in Rare Disorders and Center for Rare Disease Therapy, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | | | - Erik G Puffenberger
- Clinic for Special Children, Strasburg, PA, USA; Franklin and Marshall College, Lancaster, PA, USA
| | - Oliver Vugrek
- Translational Medicine Group, Ruđer Bošković Institute, Zagreb, Croatia
| | - Lucija Kovacevic
- Translational Medicine Group, Ruđer Bošković Institute, Zagreb, Croatia
| | - Conrad Wagner
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - George V Mazariegos
- Hillman Center for Pediatric Transplantation, Thomas E. Starzl Transplant Institute and Center for Rare Disease Therapy, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA
| | - S Harvey Mudd
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD, USA
| | - Kyle Soltys
- Hillman Center for Pediatric Transplantation, Thomas E. Starzl Transplant Institute and Center for Rare Disease Therapy, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA
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Abstract
Hyperhomocysteinemia occurs in chronic- and end-stage kidney disease at the time when dialysis or transplant becomes indispensable for survival. Excessive accumulation of homocysteine (Hcy) aggravates conditions associated with imbalanced homeostasis and cellular redox thereby resulting in severe oxidative stress leading to oxidation of reduced free and protein-bound thiols. Thiol modifications such as N-homocysteinylation, sulfination, cysteinylation, glutathionylation, and sulfhydration control cellular responses that direct complex metabolic pathways. Although cysteinyl modifications are kept low, under Hcy-induced stress, thiol modifications persist thus surpassing cellular proteostasis. Here, we review mechanisms of redox regulation and show how cysteinyl modifications triggered by excess Hcy contribute development and progression of chronic kidney disease. We discuss different signaling events resulting from aberrant cysteinyl modification with a focus on transsulfuration.
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Paul R, Borah A. The potential physiological crosstalk and interrelationship between two sovereign endogenous amines, melatonin and homocysteine. Life Sci 2015; 139:97-107. [PMID: 26281918 DOI: 10.1016/j.lfs.2015.07.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 07/07/2015] [Accepted: 07/31/2015] [Indexed: 12/13/2022]
Abstract
The antioxidant melatonin and the non-proteinogenic excitotoxic amino acid homocysteine (Hcy) are very distinct but related reciprocally to each other in their mode of action. The elevated Hcy level has been implicated in several disease pathologies ranging from cardio- and cerebro-vascular diseases to neurodegeneration owing largely to its free radical generating potency. Interestingly, melatonin administration potentially normalizes the elevated Hcy level, thereby protecting the cells from the undesired Hcy-induced excitotoxicity and cell death. However, the exact mechanism and between them remain obscure. Through literature survey we have found an indistinct but a vital link between melatonin and Hcy i.e., the existence of reciprocal regulation between them, and this aspect has been thoroughly described herein. In this review, we focus on all the possibilities of co-regulation of melatonin and Hcy at the level of their production and metabolism both in basal and in pathological conditions, and appraised the potential of melatonin in ameliorating homocysteinemia-induced cellular stresses. Also, we have summarized the differential mode of action of melatonin and Hcy on health and disease states.
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Affiliation(s)
- Rajib Paul
- Cellular and Molecular Neurobiology Laboratory, Department of Life Science and Bioinformatics, Assam University, Silchar, Assam, India
| | - Anupom Borah
- Cellular and Molecular Neurobiology Laboratory, Department of Life Science and Bioinformatics, Assam University, Silchar, Assam, India.
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The potential role of homocysteine mediated DNA methylation and associated epigenetic changes in abdominal aortic aneurysm formation. Atherosclerosis 2013; 228:295-305. [PMID: 23497786 DOI: 10.1016/j.atherosclerosis.2013.02.019] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 02/08/2013] [Accepted: 02/08/2013] [Indexed: 12/26/2022]
Abstract
Previous studies have suggested that homocysteine (Hcy) has wide-ranging biological effects, including accelerating atherosclerosis, impairing post injury endothelial repair and function, deregulating lipid metabolism and inducing thrombosis. However, the biochemical basis by which hyperhomocysteinemia (HHcy) contributes to cardiovascular diseases (CVDs) remains largely unknown. Several case-control studies have reported an association between HHcy and the presence of abdominal aortic aneurysms (AAA) and there are supportive data from animal models. Genotypic data concerning the association between variants of genes involved in the methionine cycle and AAA are conflicting probably due to problems such as reverse causality and confounding. The multifactorial nature of AAA suggests the involvement of additional epigenetic factors in disease formation. Elevated Hcy levels have been previously linked to altered DNA methylation levels in various diseases. Folate or vitamin B12 based methods of lowering Hcy have had disappointingly limited effects in reducing CVD events. One possible reason for the limited efficacy of such therapy is that they have failed to reverse epigenetic changes induced by HHcy. It is possible that individuals with HHcy have an "Hcy memory effect" due to epigenetic alterations which continue to promote progression of cardiovascular complications even after Hcy levels are lowered. It is possible that deleterious effect of prior, extended exposure to elevated Hcy concentrations have long-lasting effects on target organs and genes, hence underestimating the benefit of Hcy lowering therapies in CVD patients. Therapies targeting the epigenetic machinery as well as lowering circulating Hcy concentrations may have a more efficacious effect in reducing the incidence of cardiovascular complications.
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Perna AF, Ingrosso D. Low hydrogen sulphide and chronic kidney disease: a dangerous liaison. Nephrol Dial Transplant 2012; 27:486-93. [PMID: 22323660 DOI: 10.1093/ndt/gfr737] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Hydrogen sulphide, H(2)S, is a gaseous compound involved in a number of biological responses, e.g. blood pressure, vascular function and energy metabolism. In particular, H(2)S is able to lower blood pressure, protect from injury in models of ischaemia-reperfusion and induce a hypometabolic state. In chronic kidney disease (CKD), low plasma hydrogen sulphide levels have been established in humans and in animal models. The enzymes involved in its production are cystathionine β-synthase, cystathionine γ-lyase and 3-mercaptopyruvate sulphurtransferase. The mechanisms for H(2)S decrease in CKD are related to the reduced gene expression (demonstrated in uraemic patient blood cells) and decreased protein levels (in tissues such as liver, kidney, brain in a CKD rat model). In the present Nephrol Dial Transplant issue, in fact, Aminzadeh and Vaziri document that the alterations in this pathway complicate the uraemic state and are linked to CKD progression. They furnish a time frame in CKD and record enzyme tissue distribution. It remains to be established if low H(2)S is causally linked to CKD progression and if interventions aimed to restore the status quo ante are able to modify this picture.
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Perna AF, Luciano MG, Ingrosso D, Raiola I, Pulzella P, Sepe I, Lanza D, Violetti E, Capasso R, Lombardi C, De Santo NG. Hydrogen sulfide, the third gaseous signaling molecule with cardiovascular properties, is decreased in hemodialysis patients. J Ren Nutr 2011; 20:S11-4. [PMID: 20797558 DOI: 10.1053/j.jrn.2010.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Hydrogen sulfide, H(2)S, is the third endogenous gas with cardiovascular properties, after nitric oxide and carbon monoxide. H(2)S is a potent vasorelaxant, and its deficiency is implicated in the pathogenesis of hypertension and atherosclerosis. Cystathionine beta-synthase, cystathionine gamma-lyase, and 3-mercaptopyruvate sulfurtransferase catalyze H(2)S formation. Chronic kidney disease is characterized by high prevalence of hyperhomocysteinemia, hypertension, and high cardiovascular mortality, especially in hemodialysis patients. H(2)S levels are decreased in hemodialysis patients through transcriptional deregulation of genes encoding for the H(2)S-producing enzymes. Potential implications relate to the pathogenesis of the manifestations of the uremic syndrome, such as hypertension and atherosclerosis.
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Affiliation(s)
- Alessandra F Perna
- First Division of Nephrology, Department of Clinical and Experimental Internal Medicine, Second University of Medicine, Naples, Italy.
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Fang P, Li X, Wang J, Xing L, Gao Y, Niu L, Teng M. Crystal Structure of the Protein l-Isoaspartyl Methyltransferase from Escherichia coli. Cell Biochem Biophys 2010; 58:163-7. [DOI: 10.1007/s12013-010-9103-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Pengfei Fang
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui, People's Republic of China
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Chen NC, Yang F, Capecci LM, Gu Z, Schafer AI, Durante W, Yang XF, Wang H. Regulation of homocysteine metabolism and methylation in human and mouse tissues. FASEB J 2010; 24:2804-17. [PMID: 20305127 DOI: 10.1096/fj.09-143651] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hyperhomocysteinemia is an independent risk factor for cardiovascular disease. Homocysteine (Hcy) metabolism involves multiple enzymes; however, tissue Hcy metabolism and its relevance to methylation remain unknown. Here, we established gene expression profiles of 8 Hcy metabolic and 12 methylation enzymes in 20 human and 19 mouse tissues through bioinformatic analysis using expression sequence tag clone counts in tissue cDNA libraries. We analyzed correlations between gene expression, Hcy, S-adenosylhomocysteine (SAH), and S-adenosylmethionine (SAM) levels, and SAM/SAH ratios in mouse tissues. Hcy metabolic and methylation enzymes were classified into two types. The expression of Type 1 enzymes positively correlated with tissue Hcy and SAH levels. These include cystathionine beta-synthase, cystathionine-gamma-lyase, paraxonase 1, 5,10-methylenetetrahydrofolate reductase, betaine:homocysteine methyltransferase, methionine adenosyltransferase, phosphatidylethanolamine N-methyltransferases and glycine N-methyltransferase. Type 2 enzyme expressions correlate with neither tissue Hcy nor SAH levels. These include SAH hydrolase, methionyl-tRNA synthase, 5-methyltetrahydrofolate:Hcy methyltransferase, S-adenosylmethionine decarboxylase, DNA methyltransferase 1/3a, isoprenylcysteine carboxyl methyltransferases, and histone-lysine N-methyltransferase. SAH is the only Hcy metabolite significantly correlated with Hcy levels and methylation enzyme expression. We established equations expressing combined effects of methylation enzymes on tissue SAH, SAM, and SAM/SAH ratios. Our study is the first to provide panoramic tissue gene expression profiles and mathematical models of tissue methylation regulation.
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Affiliation(s)
- Natalie C Chen
- Department of Pharmacology, Temple University School of Medicine, 3420 North Broad St., MRB, Philadelphia, PA 19140, USA
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13
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Perna AF, Luciano MG, Ingrosso D, Pulzella P, Sepe I, Lanza D, Violetti E, Capasso R, Lombardi C, De Santo NG. Hydrogen sulphide-generating pathways in haemodialysis patients: a study on relevant metabolites and transcriptional regulation of genes encoding for key enzymes. Nephrol Dial Transplant 2009; 24:3756-63. [PMID: 19654230 DOI: 10.1093/ndt/gfp378] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Hydrogen sulphide, H(2)S, is the third endogenous gas with putative cardiovascular properties, after nitric oxide and carbon monoxide. H(2)S is a vasorelaxant, while H(2)S deficiency is implicated in the pathogenesis of hypertension and atherosclerosis. Cystathionine beta-synthase (CBS), cystathionine gamma-lyase (CSE) and 3-mercaptopyruvate sulphurtransferase (MPS) catalyze H(2)S formation, with different relative efficiencies. Chronic kidney disease (CKD) is characterized by elevation of both plasma homocysteine and cysteine, which are substrates of these enzymes, and by a high prevalence of hypertension and cardiovascular mortality, particularly in the haemodialysis stage. It is possible that the H(2)S-generating pathways are altered as well in this patient population. METHODS Plasma H(2)S levels were measured with a common spectrophotometric method. This method detects various forms of H(2)S, protein-bound and non-protein-bound. Blood sulphaemoglobin, a marker of chronic exposure to H(2)S, was also measured, as well as related sulphur amino acids, vitamins and transcriptional levels of relevant genes, in haemodialysis patients and compared to healthy controls. RESULTS Applying the above-mentioned methodology, H(2)S levels were found to be decreased in patients. Sulphaemoglobin levels were significantly lower as well. Plasma homocysteine and cysteine were significantly higher; vitamin B(6), a cofactor in H(2)S biosynthesis, was not different. H(2)S correlated negatively with cysteine levels. CSE expression was significantly downregulated in haemodialysis patients. CONCLUSIONS Transcriptional deregulation of genes encoding for H(2)S-producing enzymes is present in uraemia. Although the specificity of the method employed for H(2)S detection is low, the finding that H(2)S is decreased is complemented by the lower sulphhaemoglobin levels. Potential implications of this study relate to the pathogenesis of the uraemic syndrome manifestations, such as hypertension and atherosclerosis.
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Affiliation(s)
- Alessandra F Perna
- First Division of Nephrology, Department of Clinical and Experimental Internal Medicine, via Pansini 5, Second University of Medicine, 80138 Naples, Italy.
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Effect of 40% restriction of dietary amino acids (except methionine) on mitochondrial oxidative stress and biogenesis, AIF and SIRT1 in rat liver. Biogerontology 2008; 10:579-92. [PMID: 19039676 DOI: 10.1007/s10522-008-9200-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Accepted: 11/11/2008] [Indexed: 01/20/2023]
Abstract
Previous studies have shown that the decrease in mitochondrial reactive oxygen species (mitROS) generation and oxidative damage to mitochondrial DNA (mtDNA) that occurs during life extending dietary restriction also occurs during protein or methionine restriction, whereas it does not take place during carbohydrate or lipid restriction. In order to study the possible effects of other amino acids, in this investigation all the dietary amino acids, except methionine, were restricted by 40% in male Wistar rats (RESTAAS group). After 6-7 weeks, experimental parameters were measured in the liver. Amino acid restriction did not change the levels of the methionine metabolites S-adenosylmethionine and S-adenosylhomocysteine, mitochondrial oxygen consumption and ROS generation, oxidative damage to mtDNA, amounts of the respiratory complexes I-IV, and the mitochondrial biogenesis factors PGC-1alpha and NRF-2. On the other hand, adenylate energy charge, mitochondrial protein oxidation, lipooxidation and glycooxidation, the degree of mitochondrial fatty acid unsaturation, and the amount of the apoptosis inducing factor (AIF) were decreased in the RESTAAS group. Amino acid restriction also increased SIRT1 protein. These results, together with previous ones, strongly suggest that the decrease in mitROS generation and oxidative damage to mtDNA that occurs during dietary restriction is due to restriction of a single aminoacid: methionine. They also show for the first time that restriction of dietary amino acids different from methionine decreases mitochondrial protein oxidative modification and AIF, and increases SIRT1, in rat liver.
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Stopper H, Treutlein AT, Bahner U, Schupp N, Schmid U, Brink A, Perna A, Heidland A. Reduction of the genomic damage level in haemodialysis patients by folic acid and vitamin B12 supplementation. Nephrol Dial Transplant 2008; 23:3272-9. [DOI: 10.1093/ndt/gfn254] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Fink K, Brink A, Vienken J, Heidland A, Stopper H. Homocysteine exerts genotoxic and antioxidative effects in vitro. Toxicol In Vitro 2007; 21:1402-8. [PMID: 17590309 DOI: 10.1016/j.tiv.2007.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 05/05/2007] [Accepted: 05/08/2007] [Indexed: 12/26/2022]
Abstract
INTRODUCTION Patients with end-stage renal disease suffer from increased genomic damage and cancer incidence. One possible reason is the accumulation of uremic toxins such as homocysteine (Hcy). Elevated Hcy levels--usually indicative of cardiovascular events--correlated with the genomic damage in cross-sectional studies. Therefore we investigated the genotoxic effects of Hcy in vitro. METHODS To analyse the genomic damage, micronucleus tests and the comet-assay were performed in L5178Y and HL60 cells. Additionally, the influence of Hcy on cell cycle progression, DNA-cytosine-methylation, oxidative stress levels and on the cellular glutathione content were determined. RESULTS Low millimolar concentrations of Hcy-induced micronuclei in both cell lines but did not enhance the DNA damage observed with the comet-assay. Cell cycle progression was inhibited in S-phase, while DNA-cytosine-methylation remained unchanged. Furthermore, Hcy protected cells challenged with H(2)O(2) from oxidative stress. This was accompanied by an increased cellular glutathione level. CONCLUSION Since the genotoxic effect was limited to high Hcy concentrations, a contribution of Hcy to the enhanced genomic damage in end-stage renal disease patients would only be conceivable upon local Hcy accumulation. Whether the detected antioxidant capacity of Hcy is relevant for any situation in patients remains to be elucidated.
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Affiliation(s)
- K Fink
- Institute of Pharmacology and Toxicology, University of Wuerzburg, Versbacherstrasse 9, 97078 Wuerzburg, Germany.
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18
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Yi F, Li PL. Mechanisms of homocysteine-induced glomerular injury and sclerosis. Am J Nephrol 2007; 28:254-64. [PMID: 17989498 DOI: 10.1159/000110876] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 09/13/2007] [Indexed: 12/25/2022]
Abstract
Hyperhomocysteinemia (hHcys) has been recognized as a critical risk or pathogenic factor in the progression of end-stage renal disease (ESRD) and in the development of cardiovascular complications related to ESRD. Recently, evidence is accumulating that hHcys may directly act on glomerular cells to induce glomerular dysfunction and consequent glomerular sclerosis, leading to ESRD. In this review, we summarize recent findings that reveal the contribution of homocysteine as a pathogenic factor to the development of glomerular sclerosis or ESRD. In addition, we discuss several important mechanisms mediating the pathogenic action of homocysteine in the glomeruli or in the kidney, such as local oxidative stress, endoplasmic reticulum stress, homocysteinylation, and hypomethylation. Understanding these mechanisms may help design new approaches to develop therapeutic strategies for treatment of hHcys-associated end-organ damage and for prevention of deterioration of kidney function and ultimate ESRD in patients with hypertension and diabetes mellitus or even in aged people with hHcys.
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Affiliation(s)
- Fan Yi
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA
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19
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Lin PY, Yang TH, Lin HG, Hu ML. Synergistic effects of S-adenosylhomocysteine and homocysteine on DNA damage in a murine microglial cell line. Clin Chim Acta 2007; 379:139-44. [PMID: 17300772 DOI: 10.1016/j.cca.2007.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Revised: 01/05/2007] [Accepted: 01/07/2007] [Indexed: 11/23/2022]
Abstract
BACKGROUND Homocysteine (Hcy) and S-adenosylhomocysteine (SAH) are 2 major metabolites of methionine. However, little is known about their interactions in human diseases. METHODS We determined the interaction of Hcy with SAH on DNA damage (measured as comet formation) and DNA hypomethylation (assayed as 5-methyldeoxycytidine, 5-mdc) in BV-2 cells (immortalized murine microglia). RESULTS Hcy at 100 micromol/l and SAH at 4 micromol/l alone caused little DNA strand breaks, whereas 100 micromol/l Hcy in combination with 0.5 to 4 micromol/l SAH led to marked DNA damage and uracil misincorporation. The combination of 100 micromol/l Hcy with 4 micromol/l SAH (SAH+Hcy) significantly increased intracellular H(2)O(2), and the DNA damage induced by SAH+Hcy was strongly inhibited by addition of superoxide dismutase, catalase or desferrioxamine, suggesting the involvement of reactive oxygen species. DNA damage induced by SAH+Hcy may also involve DNA hypomethylation (i.e., decreased %5-mdc) because of the high correlation between them. The effects induced by SAH+Hcy were specific to SAH but not to Hcy because they were markedly decreased by replacing SAH with adenosine (4.0 micromol/l) but was not affected by replacing Hcy with cysteine (100 micromol/l). CONCLUSION SAH in combination with Hcy can cause synergistic DNA damage in BV-2 cells. It remains to be seen whether some of the Hcy-related diseases may be caused by a collaborative action of Hcy with SAH.
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Affiliation(s)
- Pei-Ying Lin
- Department of Food Science and Biotechnology, National Chung-Hsing University, 250 Kuo-Kuang Road, Taichung, 402, Taiwan, ROC
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20
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Hermes M, Osswald H, Kloor D. Role of S-adenosylhomocysteine hydrolase in adenosine-induced apoptosis in HepG2 cells. Exp Cell Res 2007; 313:264-83. [PMID: 17097637 DOI: 10.1016/j.yexcr.2006.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 10/06/2006] [Accepted: 10/10/2006] [Indexed: 12/18/2022]
Abstract
Adenosine has been shown to initiate apoptosis through different mechanisms: (i) activation of adenosine receptors, (ii) intracellular conversion to AMP and stimulation of AMP-activated kinase, (iii) conversion to S-adenosylhomocysteine (AdoHcy), which is an inhibitor of S-adenosylmethionine (AdoMet)-dependent methyltransferases. Since the pathways involved are still not completely understood, we further investigated the role of AdoHcy hydrolase in adenosine-induced apoptosis. In HepG2 cells, adenosine induced caspase-like activity and DNA fragmentation, a marker of apoptosis. These effects were potentiated by co-incubation with homocysteine or adenosine deaminase inhibitor, pentostatin, and were mimicked by inhibition of AdoHcy hydrolase by adenosine-2',3'-dialdehyde (Adox). Adenosine-induced effects were significantly inhibited by dipyridamole, an inhibitor of adenosine transporter, whereas inhibitors of adenosine kinase did not affect adenosine-induced changes. Various adenosine receptor agonists and AICAR, an activator of AMP-activated kinase, did not mimic the effect of adenosine. Thus, adenosine-induced apoptosis is likely due to intracellular action of AdoHcy and independent of AMP-activated kinase and adenosine receptors. Because elevated AdoHcy levels are associated with reduced mRNA methylation, we studied mRNA expression in Adox-treated cells by microarray analysis. Since several p53-target genes and other apoptosis-related genes were up-regulated by Adox, we conclude that AdoHcy is involved in adenosine-induced apoptosis by altering gene expression.
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Affiliation(s)
- Marina Hermes
- Department of Pharmacology and Toxicology, Faculty of Medicine, University of Tuebingen, Wilhelmstrasse 56, D-72074 Tuebingen, Germany
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21
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Perna AF, Satta E, Acanfora F, Lombardi C, Ingrosso D, De Santo NG. Increased plasma protein homocysteinylation in hemodialysis patients. Kidney Int 2006; 69:869-76. [PMID: 16395265 DOI: 10.1038/sj.ki.5000070] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hyperhomocysteinemia, an independent cardiovascular risk factor, is present in the majority of hemodialysis patients. Among the postulated mechanisms of toxicity, protein homocysteinylation is potentially able to cause significant alterations in protein function. Protein homocysteinylation occurs through various mechanisms, among which is the post-translational acylation of free amino groups (protein-N-homocysteinylation, mediated by homocysteine (Hcy) thiolactone). Another type of protein homocysteinylation occurs through the formation of a covalent -S-S- bond, found primarily with cysteine residues (protein-S-homocysteinylation). Scant data are available in the literature regarding the extent to which alterations in protein homocysteinylation are present in uremic patients on hemodialysis, and the effects of folate treatment are not known. Protein homocysteinylation was measured in a group of hemodialysis patients (n=28) compared to controls (n=14), with a new method combining protein reduction, gel filtration and Hcy derivatization. Chemical hydrolysis was performed, followed by high-pressure liquid chromatography separation. The effects of folate treatment on protein homocysteinylation, as well as in vitro binding characteristics were evaluated. Plasma Hcy, protein-N-homocysteinylation and protein-S-homocysteinylation were significantly higher in patients vs controls. Plasma Hcy and protein-S-homocysteinylation were significantly correlated. After 2 months of oral folate treatment, protein-N-homocysteinylation was normalized, and protein-S-homocysteinylation was significantly reduced. Studies on albumin-binding capacity after in vitro homocysteinylation show that homocysteinylated albumin is significantly altered at the diazepam-binding site. In conclusion, increased protein homocysteinylation is present in hemodialysis patients, with possible consequences in terms of protein function. This alteration can be partially reversed after folate treatment.
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Affiliation(s)
- A F Perna
- Division of Nephrology, Department of Biochemistry and Biophysics, F Cedrangolo and Cardiovascular Research Center, School of Medicine, Second University of Naples, Via Pansini 5, Ed. 17, 80131 Naples, Italy.
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22
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Tickoo SK, dePeralta-Venturina MN, Harik LR, Worcester HD, Salama ME, Young AN, Moch H, Amin MB. Spectrum of epithelial neoplasms in end-stage renal disease: an experience from 66 tumor-bearing kidneys with emphasis on histologic patterns distinct from those in sporadic adult renal neoplasia. Am J Surg Pathol 2006; 30:141-53. [PMID: 16434887 DOI: 10.1097/01.pas.0000185382.80844.b1] [Citation(s) in RCA: 298] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Most (up to 71%) of renal cell neoplasms occurring in patients with end-stage renal disease (ESRD), particularly with acquired cystic disease of the kidney (ACDK), have been reported to be papillary renal cell carcinoma (RCC). Our initial experience with tumors in such a setting indicated that many tumors were histologically difficult to classify into the known subtypes of RCC or had features that were different from those in sporadically occurring RCCs. In this study on 66 ESRD kidneys (52 of which showed features of ACDK) removed because tumors were detected in them, we found two major groups of RCC. Overall, there were 261 grossly identified tumors in these kidneys, and many additional tumors were observed on microscopic evaluation in some. Of the two major groups of RCCs, one consisted of tumors similar to those seen in sporadic settings (ie, clear-cell, papillary, and chromophobe RCC), and these formed the dominant mass in 12 (18%), 10 (15%), and 5 (8%) of the 66 kidneys, respectively. The other group consisted of two subtypes of RCC that appear quite unique to ESRD. The more common tumor that we have designated as "acquired cystic disease-associated RCC" was seen as the dominant mass in 24 (36%) of 66 of the kidneys, and it formed the most common tumor type among the smaller nondominant masses, as well. It was characterized by a typical microcystic architecture, eosinophilic cytoplasm with Fuhrman's grade 3 nuclei, and frequent association with intratumoral oxalate crystals. Additionally, these tumors frequently, but usually focally, exhibited papillary architecture, and clear cytoplasm. These tumors occurred only in kidneys with ACDK, and not in noncystic ESRD. The other category was "clear-cell papillary RCC of the end-stage kidneys," present as the dominant mass in 15 (23%) of the 66 kidneys and occurring in both the ACDK and noncystic ESRD. These predominantly cystic tumors showed prominent papillary architecture with purely clear-cell cytology. Immunohistochemical studies in tumors with histology similar to the known subtypes of sporadic RCC showed immunoprofiles similar to that reported in sporadically occurring tumors. The two subtypes of RCC unique to ESRD had distinctive immunoprofiles supporting their separate morphologic subcategorization. Only the acquired cystic disease-associated RCC showed lymph node metastases in 2 cases and sarcomatoid features in 2 more cases. One of the latter 2 died with widespread metastatic disease within 34 months of nephrectomy. Thus, a broad spectrum of renal cell tumors exist in ESRD, only some of which resemble the sporadic RCCs. Acquired cystic disease-associated RCC is the commonest tumor subtype in ESRD, and biologically it appears to be more aggressive than the other tumor subtypes in ESRD.
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Affiliation(s)
- Satish K Tickoo
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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23
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Souto JC, Soria JM. Plasma homocysteine and the genetics of cardiovascular disease. Future Cardiol 2006; 2:169-78. [PMID: 19804073 DOI: 10.2217/14796678.2.2.169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cardiovascular disease (CVD) is extremely complex. It results from the interaction of many genetic and environmental factors. Several studies have demonstrated its genetic basis, estimating a heritability of approximately 60%. In the last 5 years, at least 19 genome-wide explorations for genes related to CVD have been undertaken, but none has yet unequivocally demonstrated a causal relationship with the disease. One method that can be used to find the causative genes is analyzing intermediate genetic phenotypes or risk factors, such as plasma homocysteine (Hcy). A recent genome-wide quantitative-trait-linkage analysis of Hcy plasma levels has found a previously unsuspected gene as the major genetic determinant of this risk factor. It codes for the enzyme nicotinamide N-methyltransferase, and this gene is now a candidate gene that explains a portion of the genetic basis of CVD. If confirmed, this finding will probably influence future research on the mechanisms underlying atherosclerosis and CVD, as well as other complex diseases related to plasma Hcy levels, such as Alzheimer's disease and osteoporosis.
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Affiliation(s)
- Juan Carlos Souto
- Unitat d'Hemostàsia i Trombosi, Hospital de la Santa Creu i Sant Pau, Sant Antoni M feminine Claret 167, 08025 Barcelona, Spain.
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24
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Huijberts MSP, Becker A, Stehouwer CDA. Homocysteine and vascular disease in diabetes: a double hit? Clin Chem Lab Med 2005; 43:993-1000. [PMID: 16197287 DOI: 10.1515/cclm.2005.174] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cardiovascular disease is a major problem in diabetes, and risk factors presumably unrelated to diabetes, such as hyperhomocysteinaemia, may be related to the development of cardiovascular complications in diabetic individuals. Plasma homocysteine levels are usually normal in diabetes, although both lower and higher levels have been reported. Homocysteine levels in diabetes are modulated by hyperfiltration and renal dysfunction, as well as low folate status. Insulin resistance does not appear to be a major determinant of plasma homocysteine level. Hyperhomocysteinaemia has been associated with microalbuminuria and retinopathy in type 1 and type 2 diabetes. In patients with type 2 diabetes, plasma homocysteine concentration is a significant predictor of cardiovascular events and death. This relation seems to be stronger in subjects with diabetes than without. The underlying pathophysiological mechanism of this increased vascular risk remains unexplained, but may be related to worsening of endothelial dysfunction and/or structural vessel properties induced by oxidative stress. Because homocysteine and diabetes have apparent synergistic detrimental vascular effects, patients with diabetes are candidates for screening and treatment with folic acid until the results of ongoing clinical trials are available.
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Affiliation(s)
- Maya S P Huijberts
- Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands
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25
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Fux R, Kloor D, Hermes M, Röck T, Proksch B, Grenz A, Delabar U, Bücheler R, Igel S, Mörike K, Gleiter CH, Osswald H. Effect of acute hyperhomocysteinemia on methylation potential of erythrocytes and on DNA methylation of lymphocytes in healthy male volunteers. Am J Physiol Renal Physiol 2005; 289:F786-92. [PMID: 15855656 DOI: 10.1152/ajprenal.00465.2004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Homocysteine is a precursor of S-adenosylmethionine (AdoMet) and a metabolite of S-adenosylhomocysteine (AdoHcy). The ratio of AdoMet to AdoHcy, defined as the methylation potential (MP), indicates the flow of methyl groups within the cells. Chronic elevations of total homocysteine (tHcy) in plasma correlate with increased AdoHcy concentrations, decreased MP, and impaired DNA methylation. However, the influence of acute hyperhomocysteinemia on MP is unknown. We induced acute hyperhomocysteinemia in 14 healthy volunteers by oral administration of l-homocysteine (65.1 μmol/kg body wt) in an open, randomized, placebo-controlled two-period crossover study. The kinetics of tHcy in blood and urine, MP in blood, and global DNA methylation in lymphocytes were studied systematically during 48 h. Plasma tHcy concentrations reached a peak at 34 ± 11 min after an oral load with l-homocysteine and decreased with a half-life of 257 ± 41 min (means ± SD). Only 2.3% of the homocysteine dose were recovered in urine. AdoHcy concentrations and MP in whole blood and erythrocytes were not affected by the oral homocysteine load. Furthermore, global DNA methylation in lymphocytes did not change under these conditions. We found no difference between the genotypes of 5,10-methylenetetrahydrofolate reductase in response to the homocysteine load. However, AdoMet content in erythrocytes was significantly higher in the C677T carriers (CT; n = 7) compared with the CC genotype ( n = 7). Although chronic elevation of tHcy has been shown to affect MP and DNA methylation, acute elevation of plasma tHcy above 20 μmol/l for 8 h is not sufficient to change MP and to induce DNA hypomethylation in lymphocytes.
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Affiliation(s)
- R Fux
- Dept. of Pharmacology and Toxicology, Div. of Experimental Pharmacology, Univ. Hospital Tübingen, Wilhelmstr. 56, D-72074 Tübingen, Germany.
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26
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Molino D, De Lucia D, Marotta R, Perna A, Lombardi C, Cirillo M, De Santo NG. In uremia, plasma levels of anti-protein C and anti-protein S antibodies are associated with thrombosis. Kidney Int 2005; 68:1223-9. [PMID: 16105054 DOI: 10.1111/j.1523-1755.2005.00515.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Vascular access thrombosis is an important cause of morbidity in patients with end-stage renal failure on maintenance hemodialysis (MHD). However, little is known about its risk factors. The present study was undertaken to evaluate the role of coagulation factors, fibrinolytic factors, and anti-phospholipid antibodies (aPL). In particular, we have evaluated the role of anti-protein C and anti-protein S antibodies in patients on MHD with and without thrombosis because no data are available in the literature. METHODS The study group comprised 30 patients with thrombotic complications (TC), 40 patients matched for age, sex, and dialytic age with no thrombotic complications (NTC) and 400 controls. We have measured: anti-protein C antibodies, anti-protein S antibodies, anticardiolipin antibodies (ACA), anti-beta2-glycoprotein antibodies (beta2-GPI), and anti-prothrombin antibodies (aPT), along with prothrombin time, fibrinogen, plasminogen, protein C, protein S, anti-thrombin III, APC-resistance test, D-dimer, tissue-type plasminogen's activator, plasminogen activator inhibitor-1 (PAI-1), prothrombin fragment 1+2, factors of the intrinsic and extrinsic pathway, C-reactive protein, and homocysteine. RESULTS There were no significant differences between groups for prothrombin time, fibrinogen, plasminogen, protein C, protein S, anti-thrombin III, activated protein C (APC) resistance, D-dimer, tPA, C-reactive protein, Factors II, X, and VII. The anti-beta2-GP1 and aPT were elevated in both TC and NTC patients, compared to the control group. Significant differences between TC and NTC groups were found for anti-protein C and anti-protein S antibodies, ACA-IgM, PAI-1, Factor VIII, prothrombin fragments 1+2, and homocysteine. CONCLUSION The most novel finding was a significant elevation of anti-protein C antibodies and anti-protein S antibodies in the TC group (i.e., in patients on MHD with thrombosis of vascular access). It indicates that other pathogenetic mechanisms in addition to endothelial damage may cause hypercoagulability in uremia.
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Affiliation(s)
- Daniela Molino
- First Division of Nephrology, Second University of Naples, Naples, Italy
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27
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Fragedaki E, Nebel M, Schupp N, Sebekova K, Völkel W, Klassen A, Pischetsrieder M, Frischmann M, Niwa T, Vienken J, Heidland A, Stopper H. Genomic damage and circulating AGE levels in patients undergoing daily versus standard haemodialysis. Nephrol Dial Transplant 2005; 20:1936-43. [PMID: 15919695 DOI: 10.1093/ndt/gfh898] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Patients with end-stage renal failure, whether on conservative or haemodialysis therapy, have a high incidence of DNA damage. It is not known if improved control of the uraemic state by daily haemodialysis (DHD) reduces DNA lesions. METHODS DNA damage in peripheral blood lymphocytes (PBLs) was evaluated in a cross-sectional study of 13 patients on DHD (2-3 h, 6 times/week), 12 patients on standard haemodialysis (SHD) therapy (4-5 h, 3 times/week) and 12 healthy age-matched volunteer controls. The biomarker of DNA damage used was micronucleus frequency. The assessed plasma parameters of microinflammation and oxidative stress were C-reactive protein (CRP), interleukin-6 (IL-6), neopterin, advanced oxidation protein products (AOPP), and homocysteine. We also measured plasma concentrations of the circulating advanced glycation end products (AGEs) MGI (methylglyoxal-derived imidazolinone), CML (carboxymethyllysine), imidazolone A (3-deoxyglucosone-derived imidazolinone) and AGE-associated fluorescence. RESULTS Compared to SHD, DHD was associated with significantly lower DNA damage, approaching the normal range. Micronuclei (MN) frequency averaged 29.1 MN+/-5.9/1000 binucleated (BN) cells in the SHD group, which is significantly elevated (P<0.01), 14.8 MN+/-4.0/1000 BN cells in the DHD group, and 13.2 MN+/-3.04/1000 BN cells in the controls. CRP and AOPP were in the normal range (and similar between the dialysis groups). In contrast, IL-6 and neopterin were significantly elevated, with lower values associated with DHD as compared with SHD. The increased levels of AGEs tended to be lower in the DHD group, reaching significance for CML and imidazolone A. CONCLUSIONS Overall, it was found that genomic damage in PBLs is lower in patients on DHD than in those on SHD. Lower plasma concentrations of uraemic toxins, including circulating AGEs, may account for the differences. To confirm these data, prospective clinical trials need to be performed.
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Affiliation(s)
- Evangelia Fragedaki
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacherstr. 9, D-97080 Würzburg, Germany
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D'Angelo S, Ingrosso D, Migliardi V, Sorrentino A, Donnarumma G, Baroni A, Masella L, Tufano MA, Zappia M, Galletti P. Hydroxytyrosol, a natural antioxidant from olive oil, prevents protein damage induced by long-wave ultraviolet radiation in melanoma cells. Free Radic Biol Med 2005; 38:908-19. [PMID: 15749387 DOI: 10.1016/j.freeradbiomed.2004.12.015] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2004] [Revised: 11/09/2004] [Accepted: 12/10/2004] [Indexed: 11/20/2022]
Abstract
Previous studies showed that long-wave ultraviolet (UVA) radiation induces severe skin damage through the generation of reactive oxygen species and the depletion of endogenous antioxidant systems. Recent results from our laboratory indicate a dramatic increase of both lipid peroxidation products (TBARS) and abnormal L-isoaspartyl residues, marker of protein damage, in UVA-irradiated human melanoma cells. In this study, the effects of hydroxytyrosol (DOPET), the major antioxidant compound present in olive oil, on UVA-induced cell damages, have been investigated, using a human melanoma cell line (M14) as a model system. In UVA-irradiated M14 cells, a protective effect of DOPET in preventing the uprise of typical markers of oxidative stress, such as TBARS and 2'7'-dichlorofluorescein (DCF) fluorescence intensity, was observed. In addition, DOPET prevents the increase of altered L-isoAsp residues induced by UVA irradiation. These protective effects are dose dependent, reaching the maximum at 400 microM DOPET. At higher concentrations, DOPET causes an arrest of M14 cell proliferation and acts as a proapoptotic stimulus by activating caspase-3 activity. In the investigated model system, DOPET is quantitatively converted into its methylated derivative, endowed with a radical scavenging ability comparable to that of its parent compound. These findings are in line with the hypothesis that the oxidative stress plays a major role in mediating the UVA-induced protein damage. Results suggest that DOPET may exerts differential effects on melanoma cells according to the dose employed and this must always be taken into account when olive oil-derived large consumer products, including cosmetics and functional foods, are employed.
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Affiliation(s)
- Stefania D'Angelo
- Department of Biochemistry and Biophysics "F. Cedrangolo," Medical School, Second University of Naples, Naples, Italy
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Bodamer OA, Sahoo T, Beaudet AL, O'Brien WE, Bottiglieri T, Stöckler-Ipsiroglu S, Wagner C, Scaglia F. Creatine metabolism in combined methylmalonic aciduria and homocystinuria. Ann Neurol 2005; 57:557-60. [PMID: 15786446 DOI: 10.1002/ana.20419] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Methylation is an important aspect of many fundamental biological processes including creatine biosynthesis. We studied five patients with an inborn error of cobalamin metabolism to characterize the relation between homocysteine and creatine metabolism. Plasma guanidinoacetate concentrations were increased, 14.9 +/- 4.8 micromol/L (p < 0.0001), whereas plasma creatine concentrations were in the low reference range, 43.8 +/- 20.7 micromol/L (p = not significant). Individuals with combined methylmalonic aciduria and homocystinuria have a functional impairment of the creatine synthetic pathway probably secondary to a relative depletion of labile methyl groups. The neurotoxic effects of guanidinoacetate may be partly responsible for the observed neurological phenotype.
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Affiliation(s)
- Olaf A Bodamer
- Unit of Biochemical Genetics, Department of Pediatrics, University of Vienna Children's Hospital, Vienna, Austria.
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30
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Riksen NP, Rongen GA, Boers GHJ, Blom HJ, van den Broek PHH, Smits P. Enhanced Cellular Adenosine Uptake Limits Adenosine Receptor Stimulation in Patients With Hyperhomocysteinemia. Arterioscler Thromb Vasc Biol 2005; 25:109-14. [PMID: 15539618 DOI: 10.1161/01.atv.0000150651.85907.69] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective—
Endogenous adenosine has several cardioprotective effects. We postulate that in patients with hyperhomocysteinemia increased intracellular formation of S-adenosylhomocysteine decreases free intracellular adenosine. Subsequently, facilitated diffusion of extracellular adenosine into cells through dipyridamole-sensitive transporters is enhanced, limiting adenosine receptor stimulation. We tested this hypothesis in patients with classical homocystinuria (n=9, plasma homocysteine 93.1±24.7 μmol/L) and matched controls (n=8, homocysteine 9.1±1.0).
Methods and Results—
Infusion of adenosine (0.5, 1.5, 5.0, and 15.0 μg/min/dL forearm) into the brachial artery increased forearm blood flow, as measured with venous occlusion plethysmography, to 2.9±0.4, 4.3±0.5, 5.6±1.1, and 9.6±2.1 in the patients and to 2.8±0.6, 4.4±1.0, 9.0±1.7, and 17.0±3.1 mL/min/dL in controls (
P
<0.05). However, adenosine-induced vasodilation in the presence of dipyridamole (100 μg/min/dL) was similar in both groups (
P
=0.9). Additionally, in isolated erythrocytes, adenosine uptake was accelerated by incubation with homocysteine (half-time 6.4±0.3 versus 8.1±0.5 minutes,
P
<0.001) associated with increased intracellular formation of S-adenosylhomocysteine (
P
<0.0001).
Conclusions—
In hyperhomocysteinemia, adenosine-induced vasodilation is impaired but is restored by dipyridamole. Accelerated cellular adenosine uptake probably accounts for these observations. These impaired actions of adenosine could well contribute to the cardiovascular complications of hyperhomocysteinemia.
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Affiliation(s)
- Niels P Riksen
- Department of Pharmacology-Toxicology 233, University Medical Centre Nijmegen, Geert Grooteplein 21, 6525 EZ Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
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31
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Perna AF, Capasso R, Lombardi C, Acanfora F, Satta E, Ingrosso D. Hyperhomocysteinemia and macromolecule modifications in uremic patients. Clin Chem Lab Med 2005; 43:1032-8. [PMID: 16197294 DOI: 10.1515/cclm.2005.181] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractHyperhomocysteinemia is present in the majority of well-nourished chronic renal failure and uremic patients. Most observations reported in the literature come from studies carried out in end-stage renal disease patients treated with hemodialysis. The underlying mechanisms of the toxic effects of homocysteine in uremia related to cardiovascular disease and other disturbances are still under scrutiny. As a consequence, macromolecules (i.e., proteins and DNA) have been found to be altered to various extents. One of the mechanisms of homocysteine toxicity is related to the action of its metabolic precursor, S-adenosylhomocysteine, a powerful methyltransferase competitive inhibitor. Disruption of DNA methylation has been demonstrated to occur as a result of hyperhomocysteinemia, and/or is associated with vascular damage. DNA hypomethylation has been found in the mononuclear cell fraction of uremic patients with hyperhomocysteinemia. Proteins are also targets of homocysteine-dependent molecular damage. The formation of oxidative products with free cysteinyl residue thiol groups has been demonstrated to occur in blood. The latter also represents a mechanism for the transport of homocysteine in plasma. In addition, homocysteine thiolactone has been shown to react with free amino groups in proteins to form isopeptide bonds, in particular at the lysine residue level. Another type of isopeptide bond in proteins may result from the deamidation and isomerization of asparaginyl residues, yielding abnormal isoaspartyl residues, which have been demonstrated to be increased in uremic patients. Folate treatment exerts a partial, but significant, homocysteine-lowering effect in uremic patients and has been shown to improve the changes in macromolecules induced by high homocysteine levels. In conclusion, both DNA and proteins are structurally modified in uremia as a consequence of high homocysteine levels. The role of these macromolecule changes in inducing the clinical complications of hyperhomocysteinemia in these patients, although still conjectural in some respects, is at present sustained by several pieces of evidence.
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Affiliation(s)
- Alessandra F Perna
- First Division of Nephrology, School of Medicine, Second University of Naples, Naples, Italy.
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33
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Perna AF, Acanfora F, Satta E, Lombardi C, Ingrosso D, De Santo NG. Hyperhomocysteinemia and cardiovascular disease in uremia: The newest evidence in epidemiology and mechanisms of action. Semin Nephrol 2004; 24:426-30. [PMID: 15490404 DOI: 10.1016/j.semnephrol.2004.06.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In the general population, hyperhomocysteinemia is an independent risk factor for cardiovascular disease (ischemic disease, such as stroke and myocardial infarction, and arterial and venous thrombosis). We can presume that the association is causal, based on the example of homocystinuria, and on the evidence put forward by several basic science and epidemiologic studies. However, the results of large intervention trials, which may grant further support to this hypothesis, are not yet available. In chronic renal failure and in uremia, the evidence that is offered by carefully performed prospective studies also indicate the presence of an association, although some studies suggest reverse epidemiology. The mechanisms underlying the association, and able to explain the several toxic effects of homocysteine, related or not to cardiovascular disease, are unclear. Oxidation, nitrosylation, and hypomethylation are among the postulated mechanisms. In uremia, protein hypomethylation interferes with protein repair; DNA hypomethylation impairs regulation of gene expression, whereas folate treatment reverts such alterations. Acylation, another structural modification able to impair protein function, is a possible mediator of homocysteine toxicity.
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Affiliation(s)
- Alessandra F Perna
- First Division of Nephrology, Department of Pediatrics, Second University of Naples, Naples, Italy.
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34
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Abstract
Hyperhomocysteinemia, a new cardiovascular risk factor, occurs in 85-100% of patients with end-stage renal disease. The exact mechanism by which renal function is linked to plasma homocysteine has not been definitively established. There is reasonably good clinical evidence that hyperhomocysteinemia in itself does not cause renal insufficiency. Two, not mutually exclusive, hypotheses are that in renal failure: i) homocysteine disposal is impaired in the kidneys themselves and ii) extra-renal homocysteine metabolism is defective, possibly due to uremic toxins. Several methods have been applied to investigate kidney and whole-body sulfur amino acid metabolism in healthy subjects and in patients with different degrees of renal failure. Arteriovenous extraction studies have not found a significant homocysteine disposal in the human kidney. Methods to study whole-body homocysteine metabolism have included measurement of plasma metabolites, calculation of plasma homocysteine elimination after oral loading and the use of stable isotope techniques with methionine tracers. The results implicate a decreased homocysteine clearance instead of an increased production as the cause of hyperhomocysteinemia in renal failure, but the exact site of the impaired clearance remains controversial.
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Affiliation(s)
- Coen van Guldener
- Department of Internal Medicine, Institute for Cardiovascular Research, Vrije Universiteit Medical Centre, Amsterdam, The Netherlands.
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35
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Altintas E, Sezgin O. S-adenosylhomocysteine hydrolase, S-adenosylmethionine, S-adenosylhomocysteine: correlations with ribavirin induced anemia. Med Hypotheses 2004; 63:834-7. [PMID: 15488656 DOI: 10.1016/j.mehy.2004.03.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2004] [Accepted: 03/05/2004] [Indexed: 11/23/2022]
Abstract
Objective is to speculate on the ribavirin induced anemia by inhibiting S-adenosylhomocysteine (SAH)-hydrolase activity. The major toxicity associated with the use of ribavirin is hemolytic anemia. This adverse effect has been ascribed to the accumulation of ribavirin triphosphate in the erythrocyte, which interferes with erythrocyte function. Ribavirin has been found to inhibit SAH-hydrolase activity in erythrocyte. SAH is further hydrolyzed to adenosine and homocysteine by SAH-hydrolase. The formation of S-adenosylmethionine (SAM) is then demethylated to SAH. SAH, the metabolite of SAM, on the other hand is a powerful inhibitor of methyltransferase enzymes, competing for the SAM binding site. A concurrent decrease in SAM and an increase in SAH levels would inhibit methylation of many tissue components including proteins, DNA, RNA, phospholipids and other small molecules. The enzyme protein carboxyl methyltransferase type II has been recently shown to play a crucial role in the repair of damaged proteins. SAM is the methyl donor of the reaction, and its demethylated product, SAH is the natural inhibitor of this reaction, as well as of most SAM-dependent methylations. The biological function of this transmethylation reaction is related to the repair or degradation of age-damaged proteins. Methyl ester formation in erythrocyte membrane proteins has been used as a marker reaction to tag these abnormal residues and to monitor their increase associated with erythrocyte ageing diseases. Liver disease is complicated by cholesterol deposition in hepatic and extrahepatic membranes. Erythrocyte membrane fluidity has been improved with the administration of SAM and correlated with the cholesterol/phospholipid ratio of the membranes. The levels of SAH-hydrolase activity were also found to undergo a sharp decrease with red cell ageing. The similarity of these alterations with certain morphofunctional characteristics of erythrocyte in some conditions as chronic renal failure, liver disease and hereditary spherocytosis makes it possible to hypothesize that the inhibition of SAH-hydrolase could constitute at least a part of ribavirin induced hemolytic anemia.
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Affiliation(s)
- Engin Altintas
- Division of Gastroenterology, School of Medicine, Mersin University, Zeytinli Bahce Cad. Eski Otogar Yani, 33079 Mersin, Turkey.
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36
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Perna AF, Ingrosso D, Satta E, Lombardi C, Acanfora F, De Santo NG. Homocysteine metabolism in renal failure. Curr Opin Clin Nutr Metab Care 2004; 7:53-7. [PMID: 15090904 DOI: 10.1097/00075197-200401000-00010] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE OF REVIEW This review focuses on recent findings (June 2002-July 2003) on the topic of homocysteine, a sulfur amino acid associated with cardiovascular disease, and its metabolism in renal failure, a condition with a high prevalence of both hyperhomocysteinemia and cardiovascular disease. RECENT FINDINGS A large meta-analysis of prospective studies in the general population established that hyperhomocysteinemia is a risk factor for cardiovascular disease. The results of intervention trials, once available, will also have to be tested in a meta-analysis, because of predicted problems with their statistical power. In kidney patients, intervention trials, still in the recruiting stage, target transplant patients, because of their unique characteristics related to folate responsiveness. As for the cause of hyperhomocysteinemia, new findings show that in humans, renal metabolic extraction depends on renal plasma flow in the post-absorptive state. Folate absorption or interconversion seems not to be affected. Riboflavin is a determinant of plasma homocysteine levels in uraemia. The consequences of hyperhomocysteinemia in uraemia are DNA hypomethylation and altered gene expression. SUMMARY The causes of hyperhomocysteinemia in renal failure are still not clear. However, the possibilities include defective renal or extrarenal metabolism as a result of uraemic toxicity. Renal plasma flow is important in homocysteine renal metabolism. Among the consequences of hyperhomocysteinemia in renal failure are impaired protein and DNA methylation, with an alteration in the allelic expression of genes regulated through methylation. Intervention trials are under way to test whether hyperhomocysteinemia is causally related to cardiovascular disease in this patient population.
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Affiliation(s)
- Alessandra F Perna
- First Division of Nephrology/Department of Pediatrics, School of Medicine, Second University of Naples, Naples, Italy.
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37
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Becker A, Henry RMA, Kostense PJ, Jakobs C, Teerlink T, Zweegman S, Dekker JM, Nijpels G, Heine RJ, Bouter LM, Smulders YM, Stehouwer CDA. Plasma homocysteine and S-adenosylmethionine in erythrocytes as determinants of carotid intima-media thickness: different effects in diabetic and non-diabetic individuals. The Hoorn Study. Atherosclerosis 2003; 169:323-30. [PMID: 12921985 DOI: 10.1016/s0021-9150(03)00199-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE Hyperhomocysteinemia is a risk factor for atherothrombosis. Through unknown mechanisms, individuals with type 2 diabetes appear particularly susceptible. We determined whether components of homocysteine metabolism are associated with intima-media thickness in individuals with and without type 2 diabetes. METHODS AND RESULTS In a cross-sectional design, we studied 231 Caucasian individuals, 60.6% having type 2 diabetes. We measured fasting homocysteine, vitamin B6 and vitamin B12 in plasma, and folate, S-adenosylmethionine and S-adenosylhomocysteine in plasma and erythrocytes. A homocysteine concentration >12 micromol/l was associated with a greater intima-media thickness of +0.07 mm (95% CI, +0.01 to +0.13; P=0.03) among diabetic individuals and of -0.004 mm (95%CI, -0.08 to +0.07; P=0.92) among non-diabetic individuals. An erythrocyte S-adenosylmethionine concentration above >4000 nmol/l was associated with a smaller intima-media thickness of -0.04 mm (95%CI, -0.10 to +0.02; P=0.17) for diabetic individuals versus -0.12 mm (95%CI, -0.20 to -0.36; P=0.005) for non-diabetic individuals. CONCLUSIONS With regard to carotid intima-media thickness, individuals with diabetes appear more susceptible to the detrimental effects of homocysteine than non-diabetic individuals. In addition, diabetic individuals may lack the protective effect on the vascular wall conferred by high concentrations of S-adenosylmethionine. These findings may help explain why hyperhomocysteinemia is an especially strong risk factor for atherothrombosis among individuals with type 2 diabetes.
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Affiliation(s)
- A Becker
- Institute for Research in Extramural Medicine, VU University Medical Center, Amsterdam, Netherlands
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38
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Becker A, Smulders YM, van Guldener C, Stehouwer CDA. Epidemiology of Homocysteine as a Risk Factor in Diabetes. Metab Syndr Relat Disord 2003; 1:105-20. [DOI: 10.1089/154041903322294434] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- A. Becker
- Institute for Research in Extramural Medicine, VU University Medical Center,Amsterdam, The Netherlands
| | - Y. M. Smulders
- Department of Internal Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - C. van Guldener
- Department of Internal Medicine, and Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - C. D. A. Stehouwer
- Department of Internal Medicine, and Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
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39
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40
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Perna AF, Ingrosso D, Lombardi C, Cesare CM, Acantora F, Satta E, De Santo NG. Homocysteine in uremia. Am J Kidney Dis 2003; 41:S123-6. [PMID: 12612968 DOI: 10.1053/ajkd.2003.50100] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Hyperhomocysteinemia is an independent cardiovascular risk factor that possibly accounts for about one of 5 cardiovascular deaths. It is conceivable that the importance of hyperhomocysteinemia will increase when other risk factors, such as hypertension or hypercholesterolemia, will become less prevalent in the general population. In chronic renal failure (CRF), high plasma homocysteine levels are a common finding and in uremia almost the rule. However, a small subset of patients remains normohomocysteinemic. The cause of hyperhomocysteinemia in CRF, whether it lies in an impaired renal or extrarenal metabolism or through uremic retention toxins, is still under intensive scrutiny. As for the consequences of high homocysteine levels in the general population and in patients with CRF, these are many-fold and linked to the mechanism of homocysteine toxic action. In fact, homocysteine can be harmful to cells because (1) it evokes oxidative stress (through the production of reactive oxygen species), (2) binds to nitric oxide, (3) produces homocysteinylated proteins, or (4) leads to the accumulation of its precursor, S-adenosylhomocysteine, a potent inhibitor of biological transmethylations. Macromolecule hypomethylation is a common feature in CRF and uremia with possible functional consequences. Nutritional or pharmacologic interventions have been proposed in the treatment of hyperhomocysteinemia, while the results of large clinical trials designed to assess if lowering homocysteine levels is effective in reducing cardiovascular risk, are pending.
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Affiliation(s)
- Alessandra F Perna
- First Division of Nephrology/Department of Pediatrics, School of Medicine, Second University of Naples (SUN), Naples, Italy.
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41
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Becker A, Smulders YM, Teerlink T, Struys EA, de Meer K, Kostense PJ, Jakobs C, Dekker JM, Nijpels G, Heine RJ, Bouter LM, Stehouwer CDA. S-adenosylhomocysteine and the ratio of S-adenosylmethionine to S-adenosylhomocysteine are not related to folate, cobalamin and vitamin B6 concentrations. Eur J Clin Invest 2003; 33:17-25. [PMID: 12492448 DOI: 10.1046/j.1365-2362.2003.01104.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND It is unclear whether homocysteine itself is causal in the pathogenesis of cardiovascular disease. Alternatively or additionally, the association between homocysteine and cardiovascular disease may be because of its metabolic precursor, S-adenosylhomocysteine, or of the ratio of S-adenosylmethionine to S-adenosylhomocysteine. Therefore, it is relevant to know how these moieties are interrelated, and whether, as is the case for homocysteine, they are influenced by blood levels of folate, cobalamin or vitamin B6. DESIGN We cross-sectionally studied a population-based cohort of 97 Caucasian subjects aged 60-85 years. Concentrations of homocysteine, S-adenosylhomocysteine, S-adenosylmethionine, folate, cobalamin and vitamin B6 were measured in fasting blood samples. RESULTS In multiple regression analysis, homocysteine was associated with vitamin B12 (per 50 pmol L-1 increase of cobalamin, change in homocysteine, -0.70 mmol L-1; 95% CI, -1.30 to -0.10 mmol L-1) and folate (per 100 nmol L-1 increase in erythrocyte folate, change in homocysteine, -0.68 mmol L-1; 95% CI -1.28 to -0.08 mmol L-1). S-adenosylhomocysteine, S-adenosylmethionine and the ratio of S-adenosylmethionine to S-adenosylhomocysteine were not associated with serum folate, cobalamin or vitamin B6, nor with erythrocyte folate. Furthermore, plasma homocysteine showed a negative correlation with the ratio of S-adenosylmethionine to S-adenosylhomocysteine in plasma (r = -0.27; P < 0.01) but not in erythrocytes. CONCLUSIONS In contrast to homocysteine, the plasma concentrations of S-adenosylhomocysteine and the ratio of S-adenosylmethionine to S-adenosylhomocysteine were not associated with the folate, cobalamin and vitamin B6 concentrations in the present study. If these precursors in part explain why homocysteine is associated with cardiovascular disease, homocysteine-lowering treatment with B vitamins may be less effective than currently expected, at least in an elderly population.
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Affiliation(s)
- A Becker
- Department of Internal Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, the Netherlands
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42
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Huang JW, Yen CJ, Pai MF, Wu KD, Tsai TJ, Hsieh BS. Association between serum aspartate transaminase and homocysteine levels in hemodialysis patients. Am J Kidney Dis 2002; 40:1195-201. [PMID: 12460038 DOI: 10.1053/ajkd.2002.36948b] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Hyperhomocysteinemia is a common metabolic abnormality in patients undergoing hemodialysis (HD). An impairment of remethylation of homocysteine (Hcy) is seen in these patients but cannot account completely for hyperhomocysteinemia. Homocysteine is derived from transmethylation of methionine that can be metabolized through transamination pathway alternatively. However, the significance of transamination in the metabolism of Hcy in HD patients is not studied. METHODS A total of 145 patients undergoing HD for more than 3 months were enrolled in the study. Vitamins B were not prescribed routinely to these patients. Among them, 49 patients had positive test results for hepatitis B surface antigen or antihepatitis C virus antibody. Serum Hcy, folic acid, vitamin B12, pyridoxal 5' -phosphate, methionine, and transaminase were measured, and parameters of dialysis adequacy were calculated. Multiple linear regression model was used to analyze the factors determining Hcy levels. RESULTS All patients had higher Hcy levels (40.3 +/- 28.3 micromol/L) than the upper limit of reference range 15 micromole/L. The levels of vitamin B(12) were all higher than 160 pg/mL (118 pmol/L). Only 9 patients had serum folic acid lower than 3 ng/mL (6.8 nmol/L). The predialysis Hcy levels were correlated with age, HD duration, folic acid, vitamin B12, and aspartate transaminase (AST) levels among all patients or the subgroup of hepatitis noncarriers with linear multiple regression analysis. In hepatitis carriers, AST levels were not associated with Hcy. A cutoff value of AST less than 14 U/L predicted a predialysis Hcy level higher than 27 micromol/L in noncarriers, with a sensitivity of 83.9% and a specificity of 50.2%. CONCLUSION In addition to vitamin B12 and folic acid, the serum AST levels correlated inversely with predialytic Hcy levels independently in hepatitis noncarrier HD patients. The results suggest that transamination may play an important role in the development of hyperhomocysteinemia when impaired transmethylation is encountered in uremic patients.
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Affiliation(s)
- Jenq-Wen Huang
- Department of Internal Medicine, National Taiwan University Hospital and Far Eastern Memorial Hospital, Taipei, Taiwan
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43
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Castro R, Struys EA, Jansen EEW, Blom HJ, de Almeida IT, Jakobs C. Quantification of plasma S-adenosylmethionine and S-adenosylhomocysteine as their fluorescent 1,N(6)-etheno derivatives: an adaptation of previously described methodology. J Pharm Biomed Anal 2002; 29:963-8. [PMID: 12093531 DOI: 10.1016/s0731-7085(02)00121-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A simplified reversed phase HPLC system for the detection of fluorescent 1,N(6)-etheno derivatives of SAM (S-adenosylmethionine) and S-adenosylhomocysteine (SAH) is described. The most important changes from the previously reported method are a shorter derivatization reaction time, the use of a solid-phase extraction resulting in an increase of the method's sensitivity, and the use of only one chromatographic system to separate SAM and SAH (in which the use of an ion-pairing reagent in the mobile phase is avoided). The linearity of the method was established, and the intra-assay coefficients of variation were 10.4 and 4.7% for SAM and SAH, respectively. Normal plasma values (n=8), evaluated with the present methodology, were, for SAM and SAH, respectively, 57+/-12 and 28+/-3 nM (mean+/-SD).
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Affiliation(s)
- Rita Castro
- Department of Clinical Chemistry, Free University Hospital, Amsterdam, The Netherlands
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44
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Cyclin A transcriptional suppression is the major mechanism mediating homocysteine-induced endothelial cell growth inhibition. Blood 2002. [DOI: 10.1182/blood.v99.3.939.h80302000939_939_945] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, it was reported that homocysteine (Hcy) specifically inhibits the growth of endothelial cells (ECs), suppresses Ras/mitogen-activated protein (MAP) signaling, and arrests cell growth at the G1/S transition of the cell cycle. The present study investigated the molecular mechanisms underlying this cell-cycle effect. Results showed that clinically relevant concentrations (50 μM) of Hcy significantly inhibited the expression of cyclin A messenger RNA (mRNA) in ECs in a dose- and time-dependent manner. G1/S-associated molecules that might account for this block were not changed, because Hcy did not affect mRNA and protein expression of cyclin D1 and cyclin E. Cyclin D1- and E-associated kinase activities were unchanged. In contrast, cyclin A–associated kinase activity and CDK2 kinase activity were markedly suppressed. Nuclear run-on assay demonstrated that Hcy decreased the transcription rate of the cyclin A gene but had no effect on the half-life of cyclin A mRNA. In transient transfection experiments, Hcy significantly inhibited cyclin A promoter activity in endothelial cells, but not in vascular smooth muscle cells. Finally, adenovirus-transduced cyclin A expression restored EC growth inhibition and overcame the S phase block imposed by Hcy. Taken together, these findings indicate that cyclin A is a critical functional target of Hcy-mediated EC growth inhibition.
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45
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Cyclin A transcriptional suppression is the major mechanism mediating homocysteine-induced endothelial cell growth inhibition. Blood 2002. [DOI: 10.1182/blood.v99.3.939] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Previously, it was reported that homocysteine (Hcy) specifically inhibits the growth of endothelial cells (ECs), suppresses Ras/mitogen-activated protein (MAP) signaling, and arrests cell growth at the G1/S transition of the cell cycle. The present study investigated the molecular mechanisms underlying this cell-cycle effect. Results showed that clinically relevant concentrations (50 μM) of Hcy significantly inhibited the expression of cyclin A messenger RNA (mRNA) in ECs in a dose- and time-dependent manner. G1/S-associated molecules that might account for this block were not changed, because Hcy did not affect mRNA and protein expression of cyclin D1 and cyclin E. Cyclin D1- and E-associated kinase activities were unchanged. In contrast, cyclin A–associated kinase activity and CDK2 kinase activity were markedly suppressed. Nuclear run-on assay demonstrated that Hcy decreased the transcription rate of the cyclin A gene but had no effect on the half-life of cyclin A mRNA. In transient transfection experiments, Hcy significantly inhibited cyclin A promoter activity in endothelial cells, but not in vascular smooth muscle cells. Finally, adenovirus-transduced cyclin A expression restored EC growth inhibition and overcame the S phase block imposed by Hcy. Taken together, these findings indicate that cyclin A is a critical functional target of Hcy-mediated EC growth inhibition.
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46
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Bostom AG, Culleton B. Hyperhomocysteinemia in Chronic Renal Disease: Potential Relevance to Arteriosclerosis. Semin Dial 2002. [DOI: 10.1046/j.1525-139x.1999.00012.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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47
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Perna AF, Ingrosso D, Satta E, Romano M, Cimmino A, Galletti P, Zappia V, De Santo NG. Metabolic consequences of hyperhomocysteinemia in uremia. Am J Kidney Dis 2001; 38:S85-90. [PMID: 11576929 DOI: 10.1053/ajkd.2001.27411] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
An elevated blood level of homocysteine (Hcy), a sulfur amino acid, is associated with increased cardiovascular risk. Hcy is generated from S-adenosylhomocysteine (AdoHcy), the demethylated product of S-adenosylmethionine (AdoMet) in transmethylation reactions. AdoHcy is a competitive inhibitor of AdoMet-dependent methyltransferases. AdoHcy accumulation is prevented by rapid metabolism of its products. Chronic renal failure (CRF) is almost constantly associated with hyperhomocysteinemia. It has been shown that: (1) AdoHcy concentration is significantly increased and the AdoMet-AdoHcy ratio is reduced in erythrocytes of patients with CRF; (2) erythrocyte membrane protein methyl esterification, catalyzed by the enzyme protein L-isoaspartyl O-methyltransferase (PCMT; EC 2.1.1.77), is reduced in CRF; PCMT catalyzes a repair reaction involved in the conversion of an isopeptide bond (detrimental to protein structure and function) into a normal peptide bond; (3) D-aspartate residues, a side product of protein methylation and repair, are significantly reduced in erythrocyte membrane proteins of patients with CRF; and (4) folate treatment significantly reduces plasma Hcy levels and improves AdoMet-AdoHcy ratios. Stable isotope studies recently confirmed that the rate of methyl transfer reactions is significantly reduced in uremia. Additional evidence, obtained by independent groups, is consistent with this interpretation. We recently found increased isoaspartyl content of circulating plasma protein levels, particularly albumin, which was only partially reduced after folate treatment, in uremia. This kind of molecular damage possibly is caused by protein increased intrinsic instability as a result of interference with the uremic milieu. In conclusion, Hcy is an uremic toxin involved in protein molecular damage through the inhibition of methylation reactions and protein PCMT-mediated repair.
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Affiliation(s)
- A F Perna
- Department of Pediatrics, Division of Nephrology, and Department of Biochemistry and Biophysics, School of Medicine, Second University of Naples, Naples, Italy.
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Nonaka H, Tsujino T, Watari Y, Emoto N, Yokoyama M. Taurine prevents the decrease in expression and secretion of extracellular superoxide dismutase induced by homocysteine: amelioration of homocysteine-induced endoplasmic reticulum stress by taurine. Circulation 2001; 104:1165-70. [PMID: 11535574 DOI: 10.1161/hc3601.093976] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Hyperhomocysteinemia is an independent risk factor for atherosclerosis. Homocysteine has been shown to induce endoplasmic reticulum (ER) stress in vascular endothelial cells. ER stress is a condition in which glycoprotein trafficking is disrupted and unfolded proteins accumulate in the ER. ER molecular chaperons, such as GRP78, are induced and an ER resident kinase, PERK, is activated when cells are subjected to ER stress. Conversely, taurine is reported to have antiatherogenic effects by unknown mechanisms. To elucidate the mechanisms by which homocysteine induces atherosclerosis and taurine prevents it, we examined whether homocysteine and taurine affect the expression and secretion of extracellular superoxide dismutase (EC-SOD), a glycoprotein secreted from vascular smooth muscle cells (VSMCs) that protects the vascular wall from oxidative stress. METHODS AND RESULTS We assessed the expression of EC-SOD and GRP78 mRNA in cultured rat VSMCs by Northern blot analysis. The EC-SOD protein secreted into the culture medium was examined by Western blot analysis. Homocysteine (5 mmol/L) and other ER stress inducers, including A23187, were found to decrease EC-SOD mRNA expression and protein secretion. Furthermore, they upregulated GRP78 mRNA expression and activated PERK. Taurine (0.5 to 10 mmol/L), conversely, prevented these actions induced by homocysteine. CONCLUSIONS Homocysteine induces ER stress and reduces the secretion and expression of EC-SOD in VSMCs, leading to increased oxidative stress in the vascular wall. Taurine restores the secretion and expression of EC-SOD by ameliorating ER stress induced by homocysteine.
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MESH Headings
- Animals
- Calcimycin/pharmacology
- Cells, Cultured
- Dose-Response Relationship, Drug
- Endoplasmic Reticulum/drug effects
- Endoplasmic Reticulum/metabolism
- Enzyme Activation/drug effects
- Gene Expression Regulation/drug effects
- HSP70 Heat-Shock Proteins/genetics
- Homocysteine/pharmacology
- Membrane Proteins/genetics
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Superoxide Dismutase/drug effects
- Superoxide Dismutase/genetics
- Superoxide Dismutase/metabolism
- Taurine/pharmacology
- Time Factors
- eIF-2 Kinase/drug effects
- eIF-2 Kinase/metabolism
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Affiliation(s)
- H Nonaka
- Division of Cardiovascular and Respiratory Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
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Suliman ME, Lindholm B, Bárány P, Bergström J. Hyperhomocysteinemia in chronic renal failure patients: relation to nutritional status and cardiovascular disease. Clin Chem Lab Med 2001; 39:734-8. [PMID: 11592443 DOI: 10.1515/cclm.2001.122] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A moderate increase in plasma total homocysteine (tHcy) is considered to be an independent risk factor for cardiovascular disease (CVD) in the general population. Almost all chronic renal failure (CRF) patients have plasma concentration of tHcy that is elevated 3 to 4 times above normal. The prevalence of CVD, diabetes mellitus, malnutrition and hypoalbuminemia is high in CRF patients. Previous investigations have focused on the role of vitamin status on plasma tHcy in CRF patients, but little information exists on the influence of nutritional status and hypoalbuminemia on plasma tHcy in CRF, although a substantial fraction of tHcy (>70%) is protein-bound, mainly to albumin. Our study in patients with end-stage renal disease showed that more than 90% of the patients had elevated plasma tHcy levels, which were higher in patients with normal nutritional status than in malnourished patients. Moreover, plasma tHcy was inversely correlated with subjective global nutritional assessment (high values denote malnutrition) and positively correlated with serum albumin and protein intake. Hence, it seems likely that serum-albumin is a strong determinant of plasma tHcy in CRF patients and this may contribute to the lower tHcy levels in malnourished patients. Patients with diabetes mellitus had lower serum-albumin and plasma tHcy than non-diabetic patients, irrespective whether they were malnourished or not. Patients with CVD had lower (although still elevated) plasma tHcy levels than those without CVD. An explanation may be that the prevalence of diabetes mellitus, malnutrition and hypoalbuminema, i.e. factors that decrease tHcy, was higher in patients with CVD, which may explain why they had less elevated values. Assuming that hyperhomocysteinemia carries an independent risk of CVD, this implies that almost all CRF patients are exposed to this risk. CRF patients with CVD had a higher prevalence of malnutrition, hypoalbuminemia and diabetes mellitus, which was associated with a lower plasma Hcy level. This may explain why plasma tHcy was lower (although still abnormally high) in patients with CVD than in patients without CVD. The lower tHcy levels in CVD patients do not contradict the assumption that hyperhomocysteinemia is a risk factor for CVD since almost all patients are exposed to this risk, and other factors might be present that confound the relationship between the absolute tHcy levels and CVD. Our findings imply that nutritional status and serum albumin, as well as the presence of diabetes mellitus, should be taken into consideration when evaluating tHcy as a risk factor for CVD in CRF patients.
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Affiliation(s)
- M E Suliman
- Department of Clinical Science, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden
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50
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Anwar W, Guéant JL, Abdelmouttaleb I, Adjalla C, Gérard P, Lemoel G, Erraess N, Moutabarrek A, Namour F. Hyperhomocysteinemia is related to residual glomerular filtration and folate, but not to methylenetetrahydrofolate-reductase and methionine synthase polymorphisms, in supplemented end-stage renal disease patients undergoing hemodialysis. Clin Chem Lab Med 2001; 39:747-52. [PMID: 11592445 DOI: 10.1515/cclm.2001.124] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Glomerular filtration is one of the major determinants of plasma total homocysteine (tHcy). To evaluate the respective roles of residual glomerular filtration (by measuring a specific protein marker, cystatin C), genetic polymorphisms and nutritional status in tHcy blood levels in end-stage renal disease patients (ESRD) under hemodialysis and supplemented with folate, we measured tHcy, folate, vitamin B12 (B12), creatinine, cystatin C, albumin and C-reactive protein and determined the polymorphism of methylenetetrahydrofolate reductase (MTHFR) (C677T and A1289C) and of methionine synthase (MS) (A2756G) in 114 ESRD patients before hemodialysis and 76 control subjects. All patients received a folate supplementation of 700 microg/day. Hyperhomocysteinemia was observed in all patients and exceeded the upper normal limit by 2-fold in 52.4% of the patients. Serum folate was significantly increased and the B12 level was not different from controls. Folate, Cystatin C and creatinine were significantly correlated to tHcy, while no correlation was found between tHcy, albumin and C-reactive protein. No difference in genotype frequency between ESRD patients and controls was found for MTHFR A1289C and MS A2756G. The MTHFR 677TT genotype was less frequent and was associated with a significantly higher tHcy level in patients. Folate and residual glomerular filtration estimated by cystatin C and creatinine levels were two independent determinants of tHcy in ESRD patients. These data suggest that hyperhomocysteinemia is a consequence as well as a complicating factor of renal failure.
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Affiliation(s)
- W Anwar
- Laboratoire de Pathologie Cellulaire et Moléculaire en Nutrition--EMI INSERM 0014 et URM IFREMER 20, Faculté de Médecine, Vandoeuvre, France
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