Interplay between methylenetetrahydrofolate reductase gene polymorphism 677C-->T and serum folate levels in determining hyperhomocysteinemia in heart transplant recipients.

BACKGROUND: Homocysteine metabolism is often impaired in heart transplant recipients, and increased total homocysteine plasma levels may constitute a risk factor for the development of heart allograft vascular disease. Although 677C-->T transition in methylenetetrahydrofolate reductase (MTHFR) is associated with increased homocysteine levels in the general population, it is unclear whether MTHFR polymorphism influences homocysteine metabolism after heart transplant. METHODS: Homocysteine, serum folate, renal function, concentrations of cyclosporine and its metabolites, and MTHFR genotype were determined in 57 heart transplant recipients (age, 55 +/- 11 yr; 21% women; time from transplant, 48 +/- 42 months). RESULTS: Forty nine percent of the study population presented with hyperhomocysteinemia. Homocysteine was 17.1 +/- 5.9 micromol/liter, 19.4 +/- 4.9 micromol/liter, and 26.3 +/- 14.2 micromol/liter for genotypes CC, CT, and TT, respectively (p = 0.028, Kruskal-Wallis test). At multivariate analysis, MTHFR genotype was independently associated with homocysteine (p = 0.005). When the study population was divided into 2 groups accordingly to serum folate levels (above/below the median value of 6.1 ng/ml), MTHFR genotype remained a significant predictor of homocysteine only in patients with low serum folate (p = 0.048). CONCLUSIONS: This study demonstrates that hyperhomocysteinemia is frequent in heart transplant recipients and that the 677C-->T transition in the MTHFR gene independently and unfavorably influences homocysteine metabolism in this group of patients. Adequate folate intake may overcome genetic predisposition to hyperhomocysteinemia.