Document Detail

Dynamic regulation of MTHFR mRNA expression and C677T genotype modulate mortality in coronary artery disease patients after revascularization.
MedLine Citation:
PMID:  17604826     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: A large body of evidence links plasma homocysteine (Hcy) concentrations and cardiovascular disease. A common MTHFR polymorphism (C677T) leads to a variant with reduced activity and associated with increased Hcy levels. Coronary surgery precipitates a significant and sustained increase in the blood concentrations of Hcy and elevated levels of plasma Hcy have been associated to saphenous vein (SV) graft disease after CABG. However, the effects of MTHFR genotypes in the incidence of cardiovascular events after CABG have not been investigated prospectively. Here, we investigate whether MTHFR gene variants are associated with an increased cardiovascular risk in individuals submitted to CABG. We also propose a molecular mechanism to explain our findings. METHODS: We performed MTHFR C677T genotypes in 558 patients with two or three vessel-disease and normal left ventricular function prospectively followed in the MASS II Trial, a randomized study to compare treatments for multivessel CAD and preserved left ventricle function. Follow-up time was 5 years. Survival curves were calculated with the Kaplan-Meier method, and evaluated with the log-rank statistic. We assessed the relationship between baseline variables and the composite end-point of death, myocardial infarction and refractory angina using a Cox proportional hazards survival model. Finally, using an ex-vivo organ culture we have reproduced the arterialization of SV implants by culturing human SV either under venous hemodynamic condition (flow: 5 mL/min; no pressure) or arterial hemodynamic condition (flow: 50 mL/min; pressure: 80 mm Hg) for 1 day. MTHFR gene expression was quantified by real time RT-PCR in 15 SV from different individuals in both experimental conditions. RESULTS: There were no significant differences among individuals within each genotype group for baseline clinical characteristics. A statistically significant association between the TT genotype, associated with increased serum levels of Hcy, and cardiovascular mortality after 5 years was verified (p=0.007) in individuals submitted to CABG surgery. In addition, MTHFR TT genotype was still significantly associated with a 4.4 fold increased risk in cardiovascular outcomes (p=0.01) even after adjustment of a Cox multivariate model for age, sex, hypertension, diabetes, LDL, HDL, triglycerides, and number of diseased vessels in this population. Finally, a significant reduction in MTHFR gene expression was demonstrated in human SV when submitted to an arterial hemodynamic condition (p=0.02). CONCLUSIONS: There is a dynamic regulation of MTHFR gene expression during the arterialization process of human saphenous vein grafts resulting in lower levels of gene expression when in an arterial hemodynamic condition. In addition, the C677T MTHFR functional variant is associated with a worse outcome in individuals submitted to CABG. Taken together, these data suggest an important role of Hcy metabolism in individuals after CABG.
Alexandre C Pereira; Ayumi A Miyakawa; Neuza H M Lopes; Paulo R Soares; Sergio A de Oliveira; Luiz A M Cesar; Jose F Ramires; Whady Hueb; Jose Eduardo Krieger
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Publication Detail:
Type:  Journal Article     Date:  2007-07-02
Journal Detail:
Title:  Thrombosis research     Volume:  121     ISSN:  0049-3848     ISO Abbreviation:  Thromb. Res.     Publication Date:  2007  
Date Detail:
Created Date:  2007-11-06     Completed Date:  2008-03-03     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0326377     Medline TA:  Thromb Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  25-32     Citation Subset:  IM    
Heart Institute, University of São Paulo Medical School, São Paulo, Brazil.
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MeSH Terms
Cardiovascular Diseases / genetics,  mortality
Coronary Artery Bypass / adverse effects
Coronary Artery Disease / genetics*,  mortality
Data Collection
Gene Expression Regulation, Enzymologic*
Homocystine / blood,  metabolism
Methylenetetrahydrofolate Reductase (NADPH2) / genetics*
Middle Aged
Myocardial Revascularization / mortality*
Polymorphism, Single Nucleotide*
Postoperative Complications / mortality
RNA, Messenger / analysis
Saphenous Vein / surgery
Reg. No./Substance:
0/RNA, Messenger; 462-10-2/Homocystine; EC Reductase (NADPH2)

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