Correlation between MCP-1-2518A/G polymorphism and the risk of Alzheimer's disease

The -2518A/G polymorphism in monocyte chemotactic protein-1 (MCP-1) has been extensively investigated for association with Alzheimer's disease (AD); however, the results from different studies are inconsistent. The aim of this study was to draw an accurate conclusion of the association. All eligible case-control studies were searched in PubMed, Embase, Chinese National Knowledge Infrastructure, China Biological Medicine Databases, and Wanfang Databases. Eight case-control studies with a total of 2370 cases and 2413 controls were eligible to be included in this meta-analysis. The association was evaluated by calculating the odds ratios (ORs) with the corresponding 95% confidence intervals (CIs). Overall, there was no significant association between MCP-1-2518A/G polymorphism and AD risk in all genetic models (the allele model G vs. A: OR = 1.15, 95% CI 0.92-1.45, p = 0.22; the co-dominant model GG vs. AA: OR = 1.38, 95% CI 0.80-2.36, p = 0.25; the dominant model AG + GG vs. AA: OR = 1.14, 95% CI 0.89-1.46, p = 0.31; the recessive model GG vs. AG + AA: OR = 1.35, 95% CI 0.87-2.09, p = 0.18). In subgroup analysis by ethnicity, a significant difference was not detected in both Caucasians and Asians. In allele model (G vs. A), the required sample size of 31858 was calculated by applying trial sequential analysis. Cumulative z curve is always below the trial sequential monitoring boundary and is nominally statistically significant (Z = 1.96). A consistent result was obtained in other genetic models. In summary, the present meta-analysis suggests that MCP-1-2518A/G polymorphism may not be associated with genetic susceptibility of AD in general population, but the association remains indeterminate due to the insufficient evidence.