Infants' MTHFR polymorphisms and nonsyndromic orofacial clefts susceptibility: a meta-analysis based on 17 case-control studies.

Methylenetetrahydrofolate reductase (MTHFR), an important enzyme in folate metabolism, is thought to be involved in the development of nonsyndromic orofacial clefts (NSOC). However, conflicting results have been achieved when evaluating the associations between infants' MTHFR C677T and A1298C polymorphisms and the risk of NSOC. To obtain more precise estimations of these associations, a meta-analysis recruiting 17 case-control studies was performed. Among Asians we found that CT heterozygote, TT homozygote, and CT/TT of infants' MTHFR C677T variant could contribute to elevated risks of NSOC, compared with CC wild-type homozygote (OR = 1.741, 95% CI = 1.043-2.907 for CT vs. CC, OR = 2.311, 95% CI = 1.313-4.041 for TT vs. CC, and OR = 1.740, 95% CI = 1.051-2.882 for CT/TT vs. CC, respectively). Similar effect was also observed on MTHFR 677T T allele, when using C allele as a reference in Asians (OR = 1.420, 95% CI = 1.191-1.693, for T allele vs. C allele). Furthermore, in stratified analysis by types of disease, CT/CC was suggested to confer decreased susceptibility to CL/P under recessive genetic model (OR = 0.854, 95% CI = 0.730-1.000). For MTHFR A1298C, the MTHFR 1298C allele in the case group of Caucasians was significantly lower than that in the control group, suggesting a protective effect against NSOC in Caucasian populations (OR = 0.711, 95% CI = 0.641-0.790, for C allele vs. A allele). In conclusion, the meta-analysis provided confirmative evidences that infants' MTHFR C677T and A1298C polymorphisms were involved in the development of NSOC. (C) 2012 Wiley Periodicals, Inc.