Association of the Polymorphisms and Plasma Level of CHI3L1 with Alzheimer's Disease in the Chinese Han Population: A Case-Control Study

Objective: To investigate whether the polymorphisms and plasma level of chitinase-3-like protein 1 (CHI3L1) are associated with Alzheimer's disease (AD) in the Chinese Han population. Methods: A total of 166 patients who were initially diagnosed with AD were enrolled as the case group, and 184 healthy subjects were recruited as the healthy controls. TaqMan (R) SNP genotyping assays were applied for the genotyping of rs4950928, rs10399931 and rs6691378. The plasma level of CHI3L1 was determined by enzyme-linked immunosorbent assay. Results: The CG+GG genotype of rs4950928 C>G is a protective factor for AD and could effectively reduce the severity of AD. Patients with the CT+TT genotype of rs10399931 C>T had a significantly increased risk of AD, and it apparently aggravated the severity of AD. Moreover, the plasma CHI3L1 level in AD patients was significantly higher than that in healthy controls, which was increased with the severity of AD. A Kaplan-Meier survival curve showed that significant differences in 5-year survival rates were found in AD patients in different genotypes of CHI3L1 rs4950928 C>G and rs10399931 C>T. The AD patients and healthy controls who carried the CG+GG genotype of rs4950928 C>G had lower plasma CHI3L1 levels than CC genotype carriers. However, the CT+TT genotype of rs10399931 in the AD patients had an elevated plasma level of CHI3L1 as compared with the CC genotype. Binary logistic regression analysis showed that the plasma level of CHI3L1, the CC genotype of rs4950928 C>G and the CT+TT genotype of rs10399931 C>T were risk factors for AD. Conclusion: Polymorphisms of the CHI3L1 gene (rs4950928 C>G and rs10399931 C>T) are associated with the risk and prognosis of AD and can affect the expression of CHI3L1 in plasma.