M Yan, Y Zhao, C X Cao, J Song and Y L Lim^,,

National Heart Centre of Singapore and Singapore General Hospital

The endothelial cell nitric oxide (NO) is synthesized by endothelial nitric oxide synthase (eNOS) encoded by the NOS 3 gene on chromosome 7. NO plays a key role in the regulation of vascular tone, and reduced NO synthesis has been implicated in the development of atherosclerosis, which has a heritable component. A missense Glu²⁹⁸ŽAsp variant in exon 7 of the eNOS gene was found to be a major risk factor for coronary artery disease in UK and Japan.   Therefore, this study is to identify whether the common variant of the eNOS (Glu²⁹⁸ŽAsp) is associated with the acute myocardial infarction in Singapore.

We are conducting a case-control study for patients with acute myocardial infarction (AMI) and control subjects in National Heart Centre of Singapore. Approval to use the blood samples was given by Ethics Committee of Singapore General Hospital. Genomic DNA was prepared from samples of whole blood by QIAmp DNA blood mini kit (QIAGEN, Germany). Oligonucleotide primers for polymerase chain reaction (PCR) were used by the published sequence of human NOS 3 gene. Genotyping of the polymorphism was performed by PCR amplification of exon 7 with the flanking intronic primers followed by MboI restriction endonuclease digestion for 16 hours at 37°C and resolution by electrophoresis on 2% agarose gel.

The results show that the 206 bp PCR products is cleaved into 119 bp and 87 bp fragments in the presence of a T mutation at nucleotide 894 (which corresponds to Asp²⁹⁸) in 14 patients. The mutation was confirmed by gene sequencing. The frequency of missense Glu²⁹⁸ŽAsp variant was significantly higher in AMI group (70%).

Our preliminary results show that a common variant of the eNOS  (Glu²⁹⁸ŽAsp) is a major risk factor for AMI in Singapore. The disease-maker for AMI will be found by using the gene testing of eNOS 3 to prevent coronary artery disease.

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