The methylene tetrahydrofolate reductase (MTHFR) gene codes for an essential enzyme in folate metabolism. There is evidence of increased risk of autism spectrum disorders (ASD) associated with common mutations affecting the folate/methylation cycle. It is thought that these associations, by themselves, may provide a partial explanation for a subgroup of children genomically at risk for ASD.
Increased folinic acid during pregnancy and early development may offset the genomic risk factors. Since folate-dependent methylation, provides, in part, the methyl group for inactivation of monoamine neurotransmitters via Catecholamine -O- Methyltransferase (COMT) system, this may help to further differentiate subtypes within the broad phenotypes of ASD.
In a 2014 study undertaken by researchers at the Ain Shams University, Egypt (Faculty of Medicine), the homozygote mutant 677T genotype (MTHFR) was found to be present in 15 percent of the autistic population studied, whereas, the heterozygous 677CT genotype occurred in 50 percent of the autistic children. It is important to note that the homozygosity of 677T of the MTHFR gene is more prevalent in the ASD population. Previous findings have revealed that the homozygote mutant 677T is present in up to 23 percent of children diagnosed ASD. An interesting point to note is that there is an ethnic variability in the frequency of the mutation with those of Mediterranean descent presenting with a higher frequency than that of Caucasians. Moreover, it has been confirmed that Caucasians experience a higher frequency than that of African/African American descent. In this most recent study, researchers reported an approximate 50 percent decrease in MTHFR enzyme activity, and interestingly, a 30 percent decrease in MTHFR enzyme activity for children diagnosed with autism presenting as heterozygous.
So what has come out of this study?
MTHFR C677T polymorphism (mutation) contributes to increased ASD risk, and periconceptional folic acid may reduce ASD risk in those with MTHFR 677C>T polymorphism. However, it is very important to remain mindful that this association alone is sufficient to produce the complex array of symptoms associated with ASD. Perhaps just one piece of a puzzle.
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