| Research backgroundCerebrovascular disease (CVD) is one of the diseases with high prevalence, mortality and morbidity, of which ischemic cerebrovascular disease (ICVD) holds a large proportion. There is a series of damage cascade after cerebral ischemia, including calcium steady-state imbalances, oxidative stress damage, toxic effect of excitatory amino acids, dysfunction of mitochondria, activation of protease, changes of gene expression, and so on. The consequence of the damage cascade is cell apoptosis and death. Epigenetics refers to changes of gene expression with the same gene sequence, influenced by environment, including DNA methylation, histone modification, chromatin remodeling, regulation of non-coding RNA, and so on. Superoxide dismutase (SOD) is one of the antioxidants, and plays an important role in the anti-oxidative stress damage. Resent studies revealed that SOD was reduced in the patients suffering cerebral infarction. The methylation status of sod gene could affect its expression. However, there are no related reports about human peripheral blood EC-SOD methylation status and cerebral infarction at the moment. Thus, the study is designed to investigate the relationship of methylation status of EC-SOD and cerebral infarction, in order to illustrate the epigenetic mechanism in the diagnosis of cerebral infarction.Research objectiveTo evaluate the relationship of methylation status of EC-SOD and cerebral infarction using case-control study method. Subjects and methodsWe used the case-control method in the study. The case group contained 83 patients (45 males and 38 females, with average age of 61.60±9.73 year), recruited from September,2010 to February,2011 in the Second Hospital of Shandong University, China. All of the case group patients accorded with cerebrovascular disease diagnosis standard of the 4th cerebrovascular disease meeting in 1995, were confirmed for cerebral infarction by MRI or CT without consciousness disturbance, could cooperate with the physical examination. Those with severe diseases of liver and kidney, endocrine and metabolic diseases, connective tissue disease and cancer, unstable vital signs, other nerve system diseases and atrial fibrillation were not included in the study. As the control group, we recruited 94 health persons (52 males,42 females, with average age of 61.67±6.98 year) from the annual heath examination in Qing-he community hospital, with age and gender matched with the case group.Evaluate the relationship of methylation status of EC-SOD and cerebral infarction using methylation-specific PCR (MSP) methods.Results1. The case group contained 83 cases, while the control group contained 94, and they matched on both age and gender. Factors having no correlation with case group contained body mass index (BMI), diastolic pressure and fasting blood-glucose (FBG). Factors having positive correlation with case group, including:smoking proportion, drinking proportion, the proportion of meat-lovers, waistline, history of hypertension, history of diabetes mellitus, systolic pressure, heart rate and triglyceride. Total cholesterol and the amount of exercise had negative correlation with case group.2. There were 3 methylation patterns detected in the EC-SOD gene in the peripheral blood genome, including full-methylation, half-methylation and none-methylation. In the 83 patients of the case group, there were 4 cases with full-methylation,21 cases with half-methylation; therefore the methylation frequence was 30.12%. In contrast, there were 9 cases with full-methylation,41 half-methylation in the 94 cases of control group, so the methylation frequence was 53.19%. The methylation status of case group was lower than the control group (P<0.05).3. The patients were divided based on infarct size. There were 94 persons in the control group,58 ones in the small-size cerebral infarction group, and 25 ones in the large-size cerebral infarction group.There were 50 cases with methylation,44 non-methylation in the 94 cases of the control group, so the methylation frequence was 53.19%. There were 25 cases with methylation,33 non-methylation in the 58 cases of the small-size cerebral infarction group, so the methylation frequence was 43.10%. In the 25 patients of the large-size cerebral infarction group, there were 0 cases with methylation,25 cases with non-methylation; therefore the methylation frequence was 0%.The methylation status of the large-size cerebral infarction group was lower than the small-size cerebral infarction group (P<0.05). Compared with the control group, the methylation status of the large-size cerebral infarction group was lower(P<0.05). However, there was no difference between the control group and the small-size cerebral infarction group(P>0.05).4. The relationship was analyzed between the EC-SOD methylation status and cerebral related factors.(1) Both cerebral infarction group and control group were divided into 2 groups based on age.In the control group, there were 49 cases in the older group and 45 ones in the younger group. The older group contained 16 non-methylation ones,28 half-methylation ones and 5 full-methylation ones, so the frequence of methylation was 67.34%. In contrast, there were 28 non-methylation ones,13 half-methylation ones and 4 full-methylation ones, so the frequence of methylation was 37.78%. The methylation status of the older group was higher than the younger group (P<0.05). In the cerebral infarction group, there were 41 cases in the older group and 42 ones in the younger group. The older group contained 22 non-methylation ones,16 half-methylation ones and 3 full-methylation ones, so the frequence of methylation was 46.34%. In contrast, there were 36 non-methylation ones,5 half-methylation ones and 1 full-methylation ones, so the frequence of methylation was 14.28%. The EC-SOD methylation status of the older group was higher than the younger group (P<0.05).(2) There was no relationship between sex, AS, metabolic syndrome, Hcy and EC-SOD methylation status (P>0.05)5. NIHSS scores of non-methylation group, half-methylation group and full-methylation group were 2.95±3.38,1.05±1.43,0.75±0.50 (P<0.05). Barthel Index of the three groups were 84.91±20.91,94.05±11.25,96.25±4.78 (P>0.05).Conclusion1. The EC-SOD methylation status of case group was lower than the control group. Therefore, it is presumed that EC-SOD methylation status is related to cerebral infarction.2. Compared with the small-size cerebral infaction group and control group, the methylation status of the large-size cerebral infarction group was lower. There was no significant difference between small-size cerebral infaction group and control group. It is presumed the status of EC-SOD methylation is related to the size of infarction.3. The methylation status of EC-SOD was related to age. The frequence of methylation is presumed to grow with age. There was no relationship between sex, AS, metabolic syndrome, Hcy and status of EC-SOD methylation.4. NIHSS scores showed significant difference among non-methylation group, half-methylation group and full-methylation group, which refered the relation between the methylation staus and neural function defect after infarction. |
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