Homocysteine influences blood clot properties alone and in combination with total fibrinogen but not with fibrinogen γ' in Africans.

Simultaneously increased fibrinogen and homocysteine (Hcy) in blood are believed to elevate the risk of cardiovascular disease mortality. However, the pathophysiological mechanisms involved are unknown. We sought to determine whether Hcy or its genetic determinants influence blood clot properties alone or in combination with fibrinogen. In addition, we investigated, for the first time, the gamma prime (γ') isoform of fibrinogen with Hcy in relation to clot architecture and lysis. Single-nucleotide polymorphisms, Hcy and hemostatic variables, including clot lysis, determined with a global fibrinolytic assay [giving lag time, slope, maximum absorbance and clot lysis time (CLT)], were measured in 1867 healthy black South Africans and cross-sectionally analyzed. Increasing Hcy did not affect fiber cross-sectional area (maximum absorbance). However, it decreased the time needed to initiate the coagulation cascade and for fibrin fibers to grow (lag time), it increased the tempo of lateral aggregation (slope) and reduced CLT. None of the single-nucleotide polymorphisms measured had effects on clot properties. Combined effects were observed between Hcy and total fibrinogen in predicting CLT. Fibrinogen γ', which affected markers of the fibrinolytic assay, did not have conjoint effects with Hcy. We believe that there is value in recognizing the combined effects of Hcy and fibrinogen, but not its γ' isoform in relation to clot structure and lysis. The enhanced fibrinolysis rate observed in patients with low fibrinogen and high Hcy may have adverse consequences for health if it disturbs hemostasis and results in a bleeding tendency.