title: Association of MTHFR C677T with total homocysteine plasma levels and susceptibility to Parkinson's disease: a meta-analysis.
abstract: The C677T single-nucleotide polymorphism in the methylenetetrahydrofolate reductase gene (MTHFR) may elevate homocysteine (Hcy) levels and increase the risk of Parkinson's disease (PD); however, results are conflicting. Our aim was to resolve contradictions in the literature and to determine whether MTHFR C677T has a significant role in regulating Hcy levels and/or is a significant risk factor for PD. MEDLINE, EMBASE, the Cochrane Library, China Biological Medicine Database and Google Scholar were searched until May 2014. Strict selection and exclusion criteria were determined, and odds ratios (ORs)/weighted mean differences (WMDs) with 95 % confidence intervals (CIs) were used to assess the strength of associations. Statistical analyses were performed using STATA 12.0. Fifteen studies that together assessed 2690 PD cases and 8465 controls were included. Meta-analysis showed that no significant difference in the distribution of MTHFR C677T between PD cases and controls was found. While stratifying for ethnicity, significant association was revealed in Europeans (T vs. C, OR = 1.17, 95 % CIs 1.04-1.31) but not in Asians. Significant association between the T allele and increased Hcy levels was found in PD cases and controls; Hcy levels were higher in PD cases and controls carrying the MTHFR T677 allele than in non-carriers (TT vs. CC, PD WMD = 6.50, 95 % CIs 6.20-6.80; controls WMD = 4.52, 95 % CIs 4.24-4.80). Other within-group comparisons showed similar results. This meta-analysis suggests that MTHFR C667T may confer PD susceptibility in Europeans. The T allele may be an independent risk factor for elevated Hcy levels in PD patients.
authors.affiliation: Department of Neurology, The First Hospital, China Medical University, NO. 155 Nanjing Bei Street, Heping District, 110001, Shenyang, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhu
authors.forename: Rui-Xia
authors.initials: RX
authors.lastname: Zhu
authors.forename: Zhi-Yi
authors.initials: ZY
authors.lastname: He
authors.forename: Xu
authors.initials: X
authors.lastname: Liu
authors.forename: He-Nan
authors.initials: HN
authors.lastname: Liu
mesh_terms: D044466:Asian People / Q000235:genetics; D002681:China; D020022:Genetic Predisposition to Disease; D006710:Homocysteine / Q000097:blood; D006801:Humans; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D010300:Parkinson Disease / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D012307:Risk Factors; D044465:White People / Q000235:genetics
chemical_list: D006710:Homocysteine; C573423:MTHFR protein, human; D042965:Methylenetetrahydrofolate Reductase (NADPH2)