Distribution characteristics of the apolipoprotein E gene and the effects of its polymorphism on blood lipid and cognitive dysfunction in the middle-aged and elderly population in Northwest China

AIM To investigate the distribution characteristic of the apolipoprotein (Apo)E gene and the effects of its polymorphism on blood lipids in a middle-aged and elderly population with mild cognitive impairment (MCI) and Alzheimer’s disease (AD) in Northwest China. METHODS According to MCI and AD diagnostic criteria, the present investigation enrolled 120 patients with MCI and 64 patients with AD from Shaanxi, Gansu, Qinghai and other regions treated in the Geriatric Department and Neurology Department of Xijing Hospital, the Fourth Military Medical University along with 65 healthy people who served as a control group and received physical examination in the hospital during the same period. Blood samples of the subjects were collected and serum lipid levels and ApoE gene types were measured. RESULTS Among all subjects, six kinds of genotypes in the population were identified. ApoE allele frequencies and genotype frequencies of the AD patient group, MCI patient group, and the control group were all in line with H-W genetic equilibrium. Among those identified, ApoE E3/E3 had the highest genotype rate (72.3%), and the least was E2/E2 (1.5%). Other genotype frequencies included E3/E4 18.8%, E2/E3 8.4%, E2/E4 9.23%, and E4/E4 6.7%. Genoptype frequencies of ApoE E3/E4 and E4/E4 in the AD and MCI groups were higher when compared to the normal control group (P<0.05) and E2/E3 was lower than the control group (P<0.05). The difference of allele frequency between the MCI and AD groups were not significant. In addition, total cholesterol (TC) and low density lipoprotein-C (LDL-C) in the AD group were higher than those in the normal control group (P<0.05); however, the ε4 carriers had a higher TC level than the ε2 carriers (P<0.05). CONCLUSION The distribution of ApoE gene in middle-aged and elderly population in Northwest China has certain geographical characteristics. The prevalence of MCI and AD in the population is related, in part, to the polymorphism of the apolipoprotein E gene and serum lipid levels.