Sequence Variants of Toll Like Receptor 4 and Late-Onset Alzheimer's Disease

Background: Toll like receptor 4 (TLR4) has been related to inflammation and beta-amyloid deposition in Alzheimer's disease (AD) brain. No study has explored the association between haplotype-tagging single nucleotide polymorphisms (htSNPs) of TLR4 and AD risk previously and ApoE e4 status alone showed low sensitivity in identifying late-onset AD (LOAD) patients. Methods: A total of 269 LOAD patients were recruited from three hospitals in northern Taiwan (2007-2010). Controls (n = 449) were recruited from elderly health checkup and volunteers of the hospital during the same period of time. Five common (frequency >= 5%) TLR4 htSNPs were selected to assess the association between TLR4 polymorphisms and the risk of LOAD in the Chinese ethnic population. Results: Homozygosity of TLR4 rs1927907 was significantly associated with an increased risk of LOAD [ TT vs. CC: adjusted odds ratio (AOR) = 2.45, 95% confidence interval (CI) = 1.30-4.64]. After stratification, the association increased further in ApoE e4 non-carriers (AOR = 3.07) and in hypertensive patients (AOR = 3.60). Haplotype GACGG was associated with a decreased risk of LOAD (1 vs. 0 copies: AOR = 0.59, 95% CI = 0.36-0.96; 2 vs. 0 copies: AOR = 0.31, 95% CI = 0.14-0.67) in ApoE e4 non-carriers. ApoE e4 status significantly modified this association (p(interaction) = 0.01). These associations remained significant after correction for multiple tests. Conclusions: Sequence variants of TLR4 were associated with an increased risk of LOAD, especially in ApoE e4 non-carriers and in hypertensive patients. The combination of TLR4 rs1927907 and ApoE e4 significantly increased the screening sensitivity in identifying LOAD patients from 0.4 to 0.7.