Association between late-onset Alzheimer's disease and microsatellite polymorphisms in intron II of the human toll-like receptor 2 gene

Abstract

The amyloid beta protein (Aβ) deposits in the brains of patients with Alzheimer's disease (AD) are closely associated with innate immune responses that were assumed to play a pivotal role in the pathogenesis of AD. Toll-like receptor 2 (TLR2) is thought to contribute to Aβ clearance. Studies have reported the presence and functional implications of guanine-thymine (GT) repeat microsatellite polymorphisms in intron II of the human TLR2 gene. The present study evaluated the association of the microsatellite polymorphism and sporadic late-onset AD (LOAD) in the Han Chinese population. The numbers of (GT) repeats were counted in 137 AD patients and in 137 non-AD control subjects, using polymerase chain reaction and genescan analysis. The alleles were divided into three subclasses: (GT)16 or less as the S allele, (GT)17 to (GT)22 as the M allele, and (GT)23 or more as the L allele. Patients with AD had more S alleles (P<0.001; odds ratio (OR)=2.32; 95% confidence interval (CI)=1.57-3.42) and fewer L alleles (P=0.02; OR=0.66; 95% CI=0.46-0.93) than did healthy controls. Genotypes SS and SM were more common, whereas ML and SL were less common in patients with AD. In subgroup analyses, the genotypes including S alleles were associated with an increased risk of LOAD (OR=2.05, 95% CI=1.26-3.34), and this association was influenced by the presence of APOE ɛ4 alleles. This study demonstrates an association of microsatellite polymorphisms in intron II of the human TLR2 gene with risk for LOAD in Han Chinese.