Israel Medical Association Journal

Abstract

Background: Hyperhomocysteinemia is associated with increased cardiovascular risk, but treatment with folic acid has no effect on outcome in unselected patient populations.

Objectives: To confirm previous observations on the association of homozygosity for the TT MTHFR genotype with B12 deficiency and endothelial dysfunction, and to investigate whether patients with B12 deficiency should be tested for 677MTHFR genotype.

Methods: We enrolled 100 individuals with B12 deficiency, tested them for the MTHFR C677T polymorphism and measured their homocysteine levels. Forearm endothelial function was checked in 23 B12-deficient individuals (13 with TT MTHFR genotype and 10 with CT or CC genotypes). Flow-mediated dilatation (FMD) was tested after short-term treatment with B12 and folic acid in 12 TT MTHFR homozygotes.

Results: Frequency of the TT MTHFR genotype was 28/100 (28%), compared with 47/313 (15%) in a previously published cohort of individuals with normal B12 levels (P = 0.005). Mean homocysteine level was 21.2 ± 16 mM among TT homozygotes as compared to 12.3 ± 5.6 mM in individuals with the CC or CT genotype (P = 0.008). FMD was abnormal (£ 6%) in 9/13 TT individuals with B12 deficiency (69%), and was still abnormal in 7/12 of those tested 6 weeks after B12 and folic treatment (58%).

Conclusions: Among individuals with B12 deficiency, the frequency of the TT MTHFR genotype was particularly high. The TT polymorphism was associated with endothelial dysfunction even after 6 weeks of treatment with B12 and folic acid. Based on our findings we suggest that B12 deficiency should be tested for MTHFR polymorphism to identify potential vascular abnormalities and increased cardiovascular risk. 

Background: The etiology of chest pain with normal epicardial coronary arteries (cardiac syndrome X) seems to be related to endothelial cell dysfunction. Multiple factors are implicated in the pathophysiology, including evelated levels of homocysteine in the blood. Mutations in the MTHFR gene are associated with evelated levels of homocysteine.

Objectives: To test whether abnormal homocysteine metabolism is associated with syndrome X.

Methods: Forty-two women with chest pain, positive stress test and normal coronary arteries (syndrome X) and 100 asymptomatic women (controls) were studied for the C677T mutation. Vitamin B12, folic acid, and plasma levels of homocysteine were also measured. Endothelial cell function was studied in 10 patients with syndrome X and homozygosity for C677T mutation, and in 10 matched healthy controls. Folic acid (5 mg daily) was prescribed to syndrome X patients after initial measurements of ECF[1]. Following 13 weeks of treatment, ECF and blood tests were repeated and compared to baseline measurements.

Results: Homozygosity for C677T mutation was doubled in syndrome X vs. control (33%, 14/42 vs. 16%, 16/100, P < 0.02), and homocysteine levels were increased (9.16 ± 2.4 vs. 8.06 ± 2.6 μmol/L, P = 0.02). In the 10 homozygous patients, homocysteine levels decreased significantly after treatment with 5 mg/day folic acid (10 ± 3.3 vs. 5.4 ± 1.1 µmol/L, P = 0.004). Abnormal baseline ECF improved after treatment with folic acid: flow-mediated dilatation was greater (11.3 ± 7.9% vs. 0.7 ± 4.5%, P < 0.002), as was nitroglycerin-mediated dilatation (15.2 ± 9.0% vs. 5.6 ± 6.4%, P < 0.003). Frequency of chest pain episodes was significantly reduced after 13 weeks of folic acid treatment.

Conclusion: Our findings establish the association between the C677T mutation, endothelial cell dysfunction and cardiac syndrome X, and provide a novel and simple therapy for a subset of patients with syndrome X and homozygosity for the C677T mutation.