title: Methylenetetrahydrofolate reductase C677T polymorphism and type 2 diabetes mellitus in Chinese population: a meta-analysis of 29 case-control studies.
abstract: BACKGROUND
  Methylenetetrahydrofolate reductase (MTHFR), a key enzyme in folate metabolism, had significant effects on the homocysteine levels. The common functional MTHFR C677T polymorphism had been extensively researched. Several studies had evaluated the relationship between MTHFR C677T polymorphism and type 2 diabetes mellitus (T2DM), but the results were still controversial in the Chinese Han population. This meta-analysis was conducted to evaluate the relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population.
  
  
  METHODS
  We searched the relevant studies in multiple electronic databases, which published up to December 2013. We reviewed and extracted data from all the included studies on the relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population. The odds ratios (ORs) and their 95% confidence intervals (95%CIs) were used to evaluate the relationship. Fixed-effects and random-effects meta-analysis were used to pool ORs by the heterogeneity. Publication bias and sensitivity analysis were also examined.
  
  
  RESULTS
  29 studies were finally included in our meta-analysis, which contained 4656 individuals with T2DM and 2127 healthy controls. There was a significant relationship between MTHFR C677T polymorphism and T2DM under dominant (OR: 1.70, 95% CI: 1.42-2.02), recessive (OR: 1.48, 95% CI: 1.21-1.80), homozygous (OR: 1.89, 95% CI: 1.47-2.42), heterozygous (OR: 1.58, 95% CI: 1.33-1.87), and additive (OR: 1.46, 95% CI: 1.28-1.68) genetic model in a random-effects model. Subgroup analysis also reached similar results. Sensitivity analysis indicated that the overall result were dependable.
  
  
  CONCLUSIONS
  There was a significant relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population. The results of our meta-analysis suggested that MTHFR 677T allele might be a risk genetic factor of T2DM in the Chinese Han population.
authors.affiliation: Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, People's Republic of China; Liaoning Academy of Safety Science, Shenyang, People's Republic of China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhu
authors.affiliation: Department of Clinical Epidemiology and Evidence Medicine, The First Hospital of China Medical University, Shenyang, People's Republic of China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, People's Republic of China.
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Zhi
authors.affiliation: Key Laboratory of Endocrine diseases in Liaoning Province, The First Hospital of China Medical University, Shenyang, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, People's Republic of China.
authors.forename: Quanmei
authors.initials: Q
authors.lastname: Zheng
authors.affiliation: Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, People's Republic of China.
authors.forename: Guifan
authors.initials: G
authors.lastname: Sun
mesh_terms: D000483:Alleles; D044466:Asian People / Q000235:genetics; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D006801:Humans; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide
chemical_list: D042965:Methylenetetrahydrofolate Reductase (NADPH2)