ABSTRACT
Objective:To preliminarily explore the association between single nucleotide polymorphisms (SNP) of five candidate genes (APH1B, PRNP, HMGCR, SIRT1, ApoE) and Alzheimer′s disease (AD), and to analyze the methylation levels of BAX and ApoE promoters on the pathogenesis of AD.Methods:Seventeen cases who were admitted to the Department of Geriatrics of the First Affiliated Hospital of Xinjiang Medical University from 2014 to 2015 and diagnosed as likely to be AD by geriatrician and neurologists according to the AD diagnostic criteria in 4th Revised Edition of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association served AD group, with an age of (75.65±5.86) years, and 34 non-AD patients with matching baseline data such as age, gender, ethnicity, and education status among patients hospitalized during the same period were selected as control group, with an age of (77.59±7.41) years. Sanger sequencing method was used for SNP typing of candidate genes. Methylation-specific polymerase chain reaction was used to determine the DNA methylation level.Results:The distribution of ApoE ε4 allele was statistically different between the AD group and the control group (χ 2=9.718, P=0.002). Candidate genes (SIRT1 rs7895833, APH1B rs1047552, PRNP rs1799990, HMGCR rs3846662) SNP locus genotypes and alleles had no statistically significant differences in the distribution between the AD group and the control group ( P>0.05). After stratification according to whether they carried ApoE ε4, no statistically significant difference was found between the two groups ( P>0.05). The BAX promoter methylation level of the AD group (0.045±0.025) was lower than that of the control group (0.061±0.028) ( t=-2.078, P=0.045). After gender stratification, the BAX methylation level of the female AD group (0.044±0.021) was lower than that of the control group (0.065±0.275) ( t=-2.230, P=0.045). There was no statistically significant difference in the methylation level of ApoE promoter between the AD group and the control group ( P>0.05). After stratification according to whether they carry ApoE ε4 or not, the methylation level of AD patients with ApoE ε4 allele (1.553±0.291) was higher than that of non-carriers (1.221±0.261) ( t=2.480, P=0.025). Conclusions:ApoE ε4 allele may be a risk factor for the onset of AD. BAX promoter hypomethylation contributes to AD in the elderly in Xinjiang, especially in female. ApoE ε4 allele may cause AD through the interaction with ApoE methylation.