Homocysteine thiolactone contributes to the prognostic value of fibrin clot structure/function in coronary artery disease

Abstract

Fibrin clot structure/function contributes to cardiovascular disease. We examined sulfur-containing metabolites as determinants of fibrin clot lysis time (CLT) and maximum absorbance (Absmax) in relation to outcomes in coronary artery disease (CAD) patients. Effects of B-vitamin/folate therapy on CLT and Absmax were studied. Plasma samples were collected from 1,952 CAD patients randomized in a 2 x 2 factorial design to (i) folic acid, vitamins B12, B6; (ii) folic acid, vitamin B12; (iii) vitamin B6; (iv) placebo for 3.8 years in the Western Norway B-Vitamin Intervention Trial. Clot lysis time (CLT) and maximum absorbance (Absmax) were determined using a validated turbidimetric assay. Acute myocardial infarction (AMI) and mortality were assessed during a 7-year follow-up. Data were analyzed using bivariate and multiple regression. Survival free of events was studied using Kaplan Mayer plots. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models. Baseline urinary homocysteine (uHcy)-thiolactone and plasma cysteine (Cys) were significantly associated with CLT while plasma total Hcy was significantly associated with Absmax, independently of fibrinogen, triglycerides, vitamin E, glomerular filtration rate, body mass index, age, sex plasma creatinine, CRP, HDL-C, ApoA1, and previous diseases. B-vitamins/folate did not affect CLT and Absmax. Kaplan-Meier analysis showed associations of increased baseline CLT and Absmax with worse outcomes. In Cox regression analysis, baseline CLT and Absmax (>cutoff) predicted AMI (CLT: HR 1.58, 95% CI 1.10–2.28; P = 0.013. Absmax: HR 3.22, CI 1.19–8.69; P = 0.021) and mortality (CLT: HR 2.54, 95% CI 1.40–4.63; P = 0.002. Absmax: 2.39, 95% CI 1.17–4.92; P = 0.017). After adjustments for other prognostic biomarkers these associations remained significant. Cys and uHcy-thiolactone, but not tHcy, were significant predictors of AMI in Cox regression models that included CLT. Conclusions uHcy-thiolactone and plasma Cys are novel determinants of CLT, an important predictor of adverse CAD outcomes. CLT and Absmax were not affected by B-vitamin/folate therapy, which could account for the lack of efficacy of such therapy in CAD. Trial registration: URL: http://clinicaltrials.gov. Identifier: NCT00354081.