Nicotinamide-N-methyltransferase (NNMT) in schizophrenia: genetic association and decreased frontal cortex mRNA levels.

Emerging evidence suggests impaired one-carbon metabolism in schizophrenia. Homocysteine is one of the key components of one-carbon metabolism. Elevated plasma homocysteine levels were reported in schizophrenia.

Hyperhomocysteinemia does not affect global DNA methylation and nicotinamide N-methyltransferase expression in mice.

DNA methylation is coupled with one-carbon metabolism involving homocysteine/methionine interconversion. Correlation between plasma homocysteine levels and leukocyte global DNA methylation was reported but not always replicated. Nicotinamide N-methyltransferase (NNMT) is a determinant of plasma homocysteine levels.