B-group vitamins, MTHFR C677T polymorphism and carotid intima-media thickness in clinically healthy subjects

Objective: Plasma B-group vitamins and age may affect the carotid intima-media thickness (IMT) in subjects with different 677TT genotype of the methylenetetrahydrofolate reductase ( MTHFR) gene. Design: A hospital-based cross-study. Setting: Genomic and Vascular Center, Changhua Christian Hospital, Changhua, Taiwan. Subjects: Five hundred and forty-one clinically healthy subjects. Intervention: Fasting plasma, homocysteine (Hcy), vitamin B-6, vitamin B-12, folate and B-mode carotid ultrasound. Results: MTHFR genotype, plasma concentrations of folate, vitamin B-6 and vitamin B-12 and age were significantly correlated to the plasma Hcy concentration. MTHFR 677TT carriers had higher concentrations of Hcy than did subjects with the CC and CT genotypes. Age, sex, body mass index and plasma Hcy were independent contributors to increase carotid IMT. However, with stratification by mean value of age and B-group vitamins concentrations, we found that at advanced age, lower plasma folate and vitamin B-12 were three risk factors involved in the enhancing effect of the MTHFR 677TT genotype on the increase of plasma Hcy and carotid IMT. Conclusion: MTHFR 677TT-related carotid atherosclerosis was only identified in healthy elderly subjects with lower level of plasma folate and vitamin B-12.