C677T methylenetetrahydrofolate reductase polymorphism interferes with the effects of folic acid and zinc sulfate on sperm concentration.

Objective: To determine the frequency of C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism in fertile and subfertile males, and the MTHFR-dependent response of sperm concentration after folic acid and/or zinc sulfate intervention.

Design: Double-blind, placebo-controlled intervention study. Two outpatient fertility clinics and nine midwifery practices in The Netherlands.

Homocysteine metabolism and B-vitamins in schizophrenic patients: low plasma folate as a possible independent risk factor for schizophrenia.

Two apparently unrelated disorders, neural tube defects (NTD) and schizophrenia showed increased risks in birth cohorts exposed to famine during early gestation. NTD is associated with impaired folate metabolism. We investigated whether schizophrenia is also linked with a dysfunctional folate metabolism.

Effect of the methylenetetrahydrofolate reductase 677C-->T mutation on the relations among folate intake and plasma folate and homocysteine concentrations in a general population sample.

Background: Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate and homocysteine metabolism. The common MTHFR 677C-->T polymorphism decreases the enzyme's activity.

Objective: The objective of the study was to assess the effect of the polymorphism on the relations among folate intake, plasma folate concentration, and total plasma homocysteine (tHcy) concentration.

Single nucleotide polymorphisms in the transcobalamin gene: relationship with transcobalamin concentrations and risk for neural tube defects.

Homocysteine levels are elevated in mothers of neural tube defect (NTD) children, which may be due to a disturbed folate or vitamin B12 metabolism. Vitamin B12 is transported to the tissues by transcobalamin (TC). We previously showed that a low holo-TC/total-TC ratio is a risk factor for NTD, possibly due to an impaired binding of vitamin B12 to TC.