An Association Study Between Cystatin C, APOE Polymorphism, And Sporadic Alzheimer' Disease

Abstract Objective To determine whether the polymorphism of apolipoprotein E gene (APOE) and Cystatin C gene (CST3) are associated with Sporadic Alzheimer's Disease(AD), to detect the influences of CST3B,APOEε4 Allele and lipids, apolipoprotein on Sporadic AD. Methods CST3 of patients with Sporadic AD was genotyped by using nested polymerase chain reaction of genomic DNA and restriction enzyme digestion with SacⅡ(KspⅠ) and compared with those of non-demented (ND) control subjects. APOE was genotyped by using Multi Allele-specific primer PCR; Mini-Mental State Examination (MMSE) scores for both patients with Sporadic AD and ND subjects. In addition, the concentration of serum TC, TG, HDL-C, LDL-C, apoE, apoA, apoB and Cystatin C were measured in fasting blood samples. Results (1) Genotype frequencies of AA,AB and BB were 81．8%, 14．3% and 3．9% in patients with Sporadic AD, and 76．6%, 20．9% and 2．5% in ND control subjects. The B Allele frequency was 11 % in patients with Sporadic AD and 1% in ND control subjects. There were no statistical difference either in genotype or in Allele frequency between Sporadic AD and ND subjects (χ~2=0．835, P=0．361;χ~2=0．359, P=0．549) . (2) APOEε4 genotype frequency was 20．8% in patients with Sporadic AD and 9．5% in ND control subjects. There were statistically significant differences in APOEε4 genotype frequency between AD and ND subjects (χ~2=5．785, P=0．016, OR=2．501, 95% CI 1．163～5．376) . Allele frequency of APOEε4 was 11．7% in patients with Sporadic AD and 5．1%in ND control subjects. APOEε4 allele frequencies in AD was significantly higher than in ND subjects (χ~2=6．772, P =0．009) . (3) The concentration of serum TC, HDL-C, LDL-C, apoE and apoB in AD subjects were significant lower than in ND subjects (all P=0．000) . The concentration of TG, apoA, and Cystatin C were not statistical difference between AD and ND subjects (all P>0．05) . The concentration of serum TC,LDL-C and HDL-C were statistically significant differences in the subjects with APOEε2,ε3 andε4 (all P<0．05) . APOEε4 allele had been associated with high TC, LDL-C levels and with a decreased level of HDL-C relative toε3 allele, but the APOEε2 allele had opposite effect. Our data suggested APOE genotypes probably regulated lipid metabolism. (4) Combined analysis of CST3 and APOE genotype showed the CST3B-/APOEε4+ genotype was a risk factor of Sporadic AD(P=0．03, OR=2．471, 95% CI 1．069-5．172) . Controlling age and gender, Logistic regression analysis showed that APOEε4 Allele was a risk factor (OR=4．541, 95% CI 1．365-15．101, P=0．014) , TC and HDL-C were protection factors (OR=0．193, 95% CI 0．039-0．945, P=0．042; OR=0．192, 95% CI 0．093-0．397, P＝0．000) of Sporadic AD. There were no interaction effect between APOE s4 genotype and TC, HDL-C.(TC* genotypeP=0．475; HDL-C* genotype P=0．596) . Conclusion (1) Our data suggest that the polymorphism of CST3 and APOE are to be present in the population of our study. The CST3 gene polymorphism is not associated with order of severity of dementia and age of onset of Sporadic AD. The CST3 gene polymorphism is not associated with Sporadic AD and might not be a major risk factor of Sporadic AD. The APOEε4 Allele is significant associated with Sporadic AD. APOEε4 might be a risk factor in the onset of Sporadic AD. TC and HDL-C might be a protection factor in the onset of Sporadic AD. The results suggest that APOEε4, TC and HDL-C can be used as biomarkers of Sporadic AD.