Clin Chem Lab Med 2004;42(12):1370–1376  2004 by Walter de Gruyter • Berlin • New York. DOI 10.1515/CCLM.2004.256 Methylenetetrahydrofolate reductase gene A222V polymorphism and risk of ischemic stroke Larry Baum 1, *, Ka Sing Wong 1 , Ho Keung Ng 2 , Brian Tomlinson 1 , Timothy Hudson Rainer 3 , Daniel Kam Yin Chan 4 , G. Neil Thomas 5 , Xiangyan Chen 2 , Peter Poon 1 , Wing Sze Cheung 2 and Kam Sang Woo 1 1 Department of Medicine and Therapeutics, 2 Department of Anatomical and Cellular Pathology, 3 Accident and Emergency Medicine Academic Unit, Chinese University of Hong Kong, Shatin, Hong Kong, PR China 4 Department of Age Care and Rehabilitation, Bankstown Health Service, (University of New South Wales), New South Wales, Australia 5 Department of Community Medicine, University of Hong Kong, Pokfulam, Hong Kong, PR China Abstract The 5,10-methylenetetrahydrofolate reductase (MTHFR) gene 677C™T polymorphism causes an A222V amino acid change which affects MTHFR enzyme activity and can increase homocysteine, a vascular disease risk factor. This polymorphism was examined for association with stroke. In a case-con- trolstudyof241ischemicstrokepatientsand304con- trols in Hong Kong, the V allele increased in stroke w28% vs. 20%, odds ratio (OR) 1.5, ps0.003x.Alackof significance for the increase in the VV genotype(7.5% vs. 4.6%, OR 1.7, ps0.16) may be due to its rarity in this region. V-allele carriers had more severe strokes (according to the NIH stroke scale). The association of the V allele with stroke occurred mostly in women or older subjects and was due to decreasing V allele fre- quency with age, as seen in other studies. This V fre- quency decline with age might be due to a loss of V-carrying controls from a higher risk of cancer, vas- cular disease, bone fracture, and kidney failure when folate is sparse. Examination of previous studies revealed that the association of VV genotype with stroke appeared stronger in Japan than elsewhere, possibly due to dietary differences. Perhaps folate supplementation for stroke prevention would partic- ularly benefit VV individualsinsuchhigh-riskregions. Keywords: elderly; folate; methylenetetrahydrofolate reductase (MTHFR); mutation; polymorphism; stroke. *Corresponding author: Larry Baum, Department of Medicine and Therapeutics, Chinese University of Hong Kong, Shatin, Hong Kong, PR China Phone: q852-26323146, Fax: q852-26373852, E-mail: lwbaum@cuhk.edu.hk Introduction 5,10-Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that converts 5,10-methylenetetrahydro- folate to 5-methyltetrahydrofolate, which donates a methyl group in the conversion of homocysteine to methionine (1–3). A common polymorphism in MTHFR, 677C™T, leads to an amino acid change, A222V, that reduces the enzyme’s stability and activ- ity, which can cause an accumulation of homocys- teine when the folate level is low (1–3). Increased blood homocysteine level is a risk factor for athero- sclerotic diseases (1–9). For this reason, numerous studies have examined the association of this poly- morphism with ischemic heart disease and stroke (1–6, 9–25). Meta-analyses have shown either no effect or a small increased risk with the VV genotype (5, 9, 14). Materials and methods To explore the possible association of the MTHFR A222V polymorphism with stroke, we carried out a case–control study of 241 ischemic stroke and 304 age-matched control subjects in Hong Kong. Following admission to the acute stroke unit of a general regional hospital, Prince of Wales Hospital, Shatin, Hong Kong, from January 2002 to Novem- ber 2003, 227 Chinese patients with acute ischemic stroke or transient ischaemic attack (TIA) were recruited. TIA is defined as a neurological deficit lasting less than 24 h that is attributed to focal cerebral or retinal ischaemia. Research with humans was carried out according to the principles of the Declaration of Helsinki; informed consent was obtained, and the hospital’s institutional review board approved the study. Patients were hospitalized because of acute cerebral infarction within 7 days of symptom onset. Brain computed tomography (CT) was performed within 24 h of admission. Patients with past history or CT features of intracerebral hemorrhage were excluded. Magnetic resonance imaging, including T1, T2-weighted and magnetic resonance angiog- raphy (MRA), was performed for most of the patients (90%), except those who were contraindicated for MRI because of a pacemaker in situ, refusal, claustrophobia, or an unstable medical condition. Ultrasound carotid duplex, extracranial and transcranial Doppler (TCD) ultrasound, and electrocar- diography were performed routinely for cerebral infarction patients at this hospital. Allpatientsunderwentadetailedclinicalanalysis.Age,sex and vascular risk factors, including hypertension, diabetes mellitus and smoking habit, were collected during acute admission for all the patients. Current smokers were defined as subjects now smoking regularly. Subjects were defined as hypertensive if their systolic blood pressure (SBP) was )140 mmHg or diastolic blood pressure (DBP) )90 mmHg on at least two occasions, or if they were receiving blood pressure-loweringmedication.Patientswereconsidereddia- betic if the fasting plasma glucose was )7.8 mmol/l (26). A