Abstract
Silent brain infarction (SBI) is often found with white matter hyperintensity (WMH). A recent genetic study on elderly twins indicated that the susceptibility to WMH was largely determined by genetic factors, implying the existence of genetic susceptibility for SBI as well. We therefore studied three genetic polymorphisms in SBI, the D/I polymorphism of angiotensin-converting enzyme (ACE) gene, the apolipoprotein (a) [apo (a)] phenotype and the T677C polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene, by a case-control study.
By MRI, 147 subjects with SBI [SBI group] and 214 without cerebral infarctions [Control group] were selected from participants of a health examination of the brain. Eighty-five patients with symptomatic subcortical infarction (SSI group) from the same area were also included in the study. In addition to the Control, two more reference populations were recruited.
Typing of the apo (a) phenotype was done by western blotting using an anti-apo (a) antibody. Genotypes of ACE and MTHFR were determined by PCR amplification of the genomic DNA and subsequent restriction enzyme digestion.
The ACE polymorphism was not associated either with SBI or with SSI. In contrast, the small-sized apo (a) was associated both with SSI and SBI. The MTHFR polymorphism was associated only with SSI. The association of MTHFR and apo (a) was greater in the younger subjects. Among the three genetic polymorphisms studied, only the apo (a) phenotype is a risk factor for SBI.
