Activated factor XII levels are dependent on factor XII 46C/T genotypes and factor XII zymogen levels, and are associated with vascular risk factors in patients and healthy subjects.

Coagulation factor XII (FXII) is activated on contact with various biologic surfaces, including subendothelial tissues and lipoprotein particles. Thus, the plasma level of activated FXII (XIIa) might represent vascular lesions or be a marker of abnormal lipid metabolism. A 46C/T polymorphism was recently described in the FXII gene close to the ATG translation initiation codon, which was associated with inter-individual variation of plasma FXII zymogen levels. The present paper reports the association of the 46C/T polymorphism with plasma XIIa levels in apparently healthy subjects, and in patients with ischemic cerebrovascular disease (CVD) and arteriosclerosis obliterans (ASO). XIIa levels were not significantly different between patients and controls, but were strongly dependent on XII 46C/T genotypes (2.07 +/- 0.81, 1.65 +/- 0.63, and 0.93 +/- 0.41 ng/ml for C/C, C/T, and T/T genotypes, respectively; P < 0.0001). This association was evident for each group studied (P < 0.0001 for CVD and controls; P= 0.0007 for ASO). There were positive correlations between plasma FXII clotting activity and XIIa levels. In a univariate analysis, XIIa correlated with total cholesterol, triglycerides, plasminogen activator inhibitor-1, and C-reactive protein (CRP), although the presence of conventional cardiovascular risk factors (male sex, smoking, hypertension, hypercholesterolemia, diabetes) did not significantly increase XIIa. Stepwise regression analyses revealed that the XII clotting activity had the strongest association with XIIa. In conclusion, XIIa levels depended on XII 46C/T genotype and correlated with some cardiovascular risk factors. Thus, the FXII genotype should be taken into consideration for interpretation of plasma XIIa levels.