High frequency of vitamin B12 deficiency in asymptomatic individuals homozygous to MTHFR C677T mutation is associated with endothelial dysfunction and homocysteinemia

Departments of 1 Cardiovascular Medicine and 2 Molecular Hematology, Lady Davis Carmel Medical Center, and the 3 Ruth and Bruce Rappaport Faculty of Medicine, Technion IIT, Haifa, Israel Submitted 30 October 2006 ; accepted in final form 11 April 2007 The aim of this study was to examine the association of homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation and vitamin B12 deficiency in 360 asymptomatic individuals and to investigate forearm endothelial function in C677T homozygotes. MTHFR C677T mutation and levels of vitamin B12, folic acid, and homocysteine were measured in study participants. Frequency of homozygosity for the C677T mutation was 67/360 (18.6%). Homocysteine levels were elevated in homozygous compared with heterozygous subjects or those without the mutation (20.6 ± 18.8 vs. 9.4 ± 3.2 µmol/l; P < 0.0001). The number of subjects with vitamin B12 deficiency (