Background and Purpose-Elevated plasma levels of homocysteine are associated with an increased risk of deep-vein thrombosis. Through a case-control study, we examined the potential association among homocysteine, folate and vitamin B 12 levels, and the common C6773 T mutation in the methylene tetrahydrofolate reductase (MTHFR) gene in patients with cerebral venous thrombosis (CVT). Methods-Forty-five patients with CVT and 90 control subjects were studied. Plasma levels of homocysteine (fasting and after methionine load), folate, and vitamin B 12 were measured. Genotyping of the MTHFR gene was also performed. The estimated risk of CVT associated with hyperhomocysteinemia, low vitamin levels, and MTHFR mutation were expressed as odds ratio (OR) and its 95% CI (crude and after adjusting by other independent variables). Results-The adjusted OR for CVT associated with high (Ͼ90th percentile) fasting levels of homocysteine was 4.6 (1.6 to 12.8). The association between low plasma folate values (Ͻ10th percentile) and presence of CVT was 3.5 (1.2 to 10.0) after adjustment for confounding factors. There was a higher frequency of MTHFR mutation in patients with CVT (22% versus 10%), but it was not statistically significant (Pϭ0.098). Patients with MTHFR mutation and low folate levels presented the highest homocysteine levels. Conclusions-High plasma concentrations of homocysteine and low plasma folate levels were associated with an increased risk of CVT in this population in which low socioeconomic conditions and deficient nutritional status may contribute to its relatively high incidence.

Background and Purpose: Elevated homocysteine (Hcy) plasma levels are associated with an increased risk of spontaneous cervical artery dissection (sCAD). We examined the potential association between Hcy, folate, vitamin B₁₂ levels and 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms in patients with cerebral infarct caused by sCAD. Patients and Methods: 39 patients who survived a cerebral infarct caused by sCAD [20 (51%) women; 24 (61.5%) vertebral and 15 (38.5%) internal carotid arteries], and 76 healthy control subjects were included. Hcy plasma levels (fasting and after methionine load), folate and vitamin B₁₂ levels were measured. We also performed polymorphisms of MTHFR. Hcy, vitamin B₁₂, folates and polymorphisms of MTHFR were assessed and any associations were analyzed using multivariate statistics. Results: Mean plasma fasting Hcy level was 9.81 µmol/l for cases and 6.38 for controls (p = 0.001). The occurrence of sCAD was associated with elevated fasting Hcy levels (>95th percentile over the control group) with an adjusted odds ratio of 7.9 (95% CI 1.66–35). The association between low plasma folate values (<5th percentile) and the presence of CAD was 7.9 (95% CI 1.6–31) after adjusting for confounding variables. The distribution of the MTHFR genotype showed a higher TT mutant frequency among CAD patients (p = 0.034). Conclusions: High plasma concentrations of Hcy and low plasma levels of folate were associated with an increased risk of sCAD in the sample studied. We conclude that deficiencies in nutritional status may contribute to the relatively high incidence of CAD in Mexico.

La homocisteína es un aminoácido que se sintetiza en el organismo a partir de otro: la metionina. La única fuente de metionina es la ingesta, a partir principalmente de proteínas animales. El metabolismo de la homocisteína está muy relacionado con las vitaminas B 6 , B 12 y ácido fólico. La metionina que proviene de la ingesta se metaboliza, principalmente en el hígado, en homocisteína (Figura 1). A partir de aquí, la homocisteína puede seguir dos vías: a) Remetilación: transformarse de nuevo en metionina, mediante un proceso catalizado por la enzima metionina sintasa y dependiente de la vitamina B 12 y del N 5-metil-tetrahidro-folato (que actúan como cofactor y como dador de metilo). b) Transulfuración: unirse a la serina y transformarse en cisteína, que se elimina por la orina. Esta segunda vía depende de la enzima cistationina β-sintasa, que tiene a la vitamina B 6 como cofactor (88). LA HOMOCISTINURIA Las extremidades longilíneas, aracnodactilia, genu valgo, pie plano e hiperlaxitud articular conforman un fenotipo denominado marfanoide. Éste no es exclusivo de la enfermedad de Marfan, sino que se observa también en otra enfermedad hereditaria: la homocistinuria.

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