Interaction between SNCA gene polymorphisms and T2DM with Parkinson's disease

To investigate the association of several single nucleotide polymorphisms (SNPs) within alpha-synuclein (SNCA) gene and additional gene-environment interaction with Parkinson's disease (PD) risk.

Hardy-Weinberg equilibrium (HWE) is tested for controls using SNPstats (http://bioinfo.iconcologia.net/SNPstats). Logistic regression is used to calculate the ORs (95% CI) for relations between the four SNPs and PD risk. The generalized multifactor dimensionality reduction (GMDR) model is used to evaluate the synergy between gene and environment.

A total of 1161 people were included in this study, including 386 cases of PD and 775 normal controls. In this study, the genotype frequency of the control group was consistent with HWE distribution. Rs356219-G allele frequency was 30.0% in patients and 19.8% in control group. The rs356221-T allele frequency was 29.7% in the patients and 20.8% in the control group. Rs356219-G and rs356221-T alleles were associated with increased PD risk, with adjusted ORs (95% CI) of 1.92 (1.28-2.52) and 1.52 (1.05-2.02), respectively. We also found no significant correlation between rs2301134 and rs2301135 and susceptibility to PD. The best gene-environment interaction models were determined by GMDR analysis, which shown a significant gene-T2DM interaction combinations, but the gene-alcohol drinking interaction combinations were all not significant. We also conducted stratified analysis for interaction effect using logistic regression. We found that T2DM patients with rs356221-AT/ TT genotype have the highest PD risk, compared to subjects with rs356219-AA genotype, OR (95%CI) = 2.67 (1.83-3.46).

The rs356219-G and rs356221-T, gene-environment interaction between rs356221 and T2DM were all associated with increased PD risk.