Association of polymorphism of DNA repair gene XRCC1 with sporadic late-onset Alzheimer's disease and age of onset in elderly Han Chinese

Alzheimer's disease (AD) is characterized by the presence of β-amyloid plaques, neurofibrillary tangles and extensive neuronal loss. There is evidence indicating that the increased DNA damages may contribute to neuronal loss in AD. Recently, it has been shown that the capacity of some types of DNA repair is impaired in the neurons of AD patients. A functional polymorphism (Arg194Trp) of X-ray repair cross-complementing group 1 (XRCC1) gene may be associated with the repair efficiency of DNA damage which may have a role in AD. Therefore, XRCC1 Arg194Trp polymorphism may be a good candidate for genetic risk analysis in AD. A case–control study from Turkey found that XRCC1 194Trp was associated with late-onset AD (LOAD). In order to determine whether the XRCC1 gene Arg194Trp polymorphism contributes to the risk for LOAD in elderly Han Chinese, we have investigated it in 212 sporadic LOAD patients and 203 healthy controls from Chinese. No significantly increased risk of LOAD in the carriers of XRCC1 194Trp allele (OR = 1.04, 95% CI 0.70–1.52, P = 0.860) was observed. As expected, Apolipoprotein (APOE) ε4 allele significantly increased the risk of LOAD (OR = 2.95, 95% CI 1.90–4.58, P < 0.001), while APOE ε2 allele significantly decreased the risk of LOAD (OR = 0.13, 95% CI 0.08–0.24, P < 0.001). After stratifying by APOE ε4 status, no increased LOAD risks associated with the XRCC1 194Trp allele carriers were observed. Our findings suggest that it is unlikely that the XRCC1 Arg194Trp polymorphism plays a major role in the pathogenesis of LOAD in elderly Han Chinese and does not support the previous findings that 194Trp allele confers an increased risk for LOAD.