ApoE genotyping by DNA microarray assay and the relationship between ApoE allelic frequency and serum ApoE levels / 中华检验医学杂志

ABSTRACT

Objective To investigate the application value of apolipoprotein E (ApoE) genotyping by DNA microarray technology and the relationship between ApoE allelic frequency and serum ApoE levels in both healthy individuals and patients with Alzheimer ′s disease (AD).Methods This research is case-control study.DNA microarray was used to detect the ApoE genotypes of AD patients (n =280) and age-matched non-demented elderly control subjects ( n =230) .The cases and controls were collected in Guangzhou Huiai Hospital during July 2014 to September 2015.The accuracy of genotype results was verified by DNA sequencing.Serum ApoE levels were measured by immunoturbidimetric assay .The ApoE genotype distribution and the relationship between ApoE allelic frequency and serum ApoE levels were analyzed.The “t” test was used to compare the ApoE levels of AD patients and controls , variance analysis was used to analyze ApoE levels in the persons with different genotype .Results DNA microarray technology genotyping results were completely consistent with the results of DNA sequencing .In AD group, the ApoE genotype distribution were 2.9%(8 /280) for ε2ε3, 1.8% (5/280) for ε2ε4, 46.8% (131/280)for ε3ε3,45.4%(127 /280) for ε3ε4 and 3.1%(9 /280) for ε4ε4.While in the control group, the ApoE genotype distribution were 0.9%(2 /230) for ε2ε2, 12.6% (29/230)for ε2ε3, 1.3%(3 /230) forε2ε4, 70.0% (161 /230) for ε3ε3 and 15.2% (35 /230) for ε3ε4.The average serum concentrations of ApoE were (33.29 ±10.87)mg/L in AD patients and (41.28 ±10.95)mg/L in the controls.Among all participants, the average serum levels of ApoE were (50.86 ±6.21) mg/L for ε2 carriers, (38.78 ± 12.07)mg/L for ε3 carriers and (30.47 ±7.68)mg/L for ε4 carriers.In AD group,ApoE level of ε2, ε3,ε4 carriers is (50.31 ±9.08)mg/L, (38.30 ±7.60) mg/L and (32.86 ±5.93)mg/L respectively.In the control group, the ApoE level of ε2, ε3, ε4 carriers is (51.00 ±5.53)mg/L, (41.01 ±10.09)mg/L and (32.86 ±5.93)mg/L respectively.The ApoE levels of persons with different ApoE alleles are ε2 >ε3 >ε4. The difference is significant (F =89.6, P 0.05) .Conclusions DNA microarray technology possesses high efficiency and favorable accuracy.The ε2 allele is associated with a higher ApoE concentration , ε3 allele with a mediate concentration and ε4 allele with a lowest concentration.Serum concentrations of ApoE showed no significant difference between AD patients and the healthy groups who have the same genotype .The primary cause of the low serum ApoE levels in AD patients is that the ApoE ε4 allelic frequencies of them are higher than that of the healthy persons.