Effects of folic acid fortification and multivitamin therapy on homocysteine and vitamin b12 status in cardiac transplant recipients

Prevalence of MTHFR C677T and MS A2756G polymorphisms in major depressive disorder, and their impact on response to fluoxetine treatment

OBJECTIVE

To examine the prevalence of the C677T polymorphism of the methylene tetrahydrofolate reductase (MTHFR) gene and the A2756G polymorphism of methionine synthase (MS), and their impact on antidepressant response.

METHODS

We screened 224 subjects (52% female, mean age 39 ± 11 years) with SCID-diagnosed major depressive disorder (MDD), and obtained 194 genetic samples. 49 subjects (49% female, mean age 36 ± 11 years) participated in a 12-week open clinical trial of fluoxetine 20-60 mg/day. Association between clinical response and C677T and A2756G polymorphisms, folate, B12, and homocysteine was examined.

RESULTS

Prevalence of the C677T and A2756G polymorphisms was consistent with previous reports (C/C = 41%, C/T = 47%, T/T = 11%, A/A = 66%, A/G = 29%, G/G = 4%). In the fluoxetine-treated subsample (n = 49), intent-to-treat (ITT) response rates were 47% for C/C subjects and 46% for pooled C/T and T/T subjects (nonsignificant). ITT response rates were 38% for A/A subjects and 60% for A/G subjects (nonsignificant), with no subjects exhibiting the G/G homozygote. Mean baseline plasma B12 was significantly lower in A/G subjects compared to A/A, but folate and homocysteine levels were not affected by genetic status. Plasma folate was negatively associated with treatment response.

CONCLUSION

The C677T and A2756G polymorphisms did not significantly affect antidepressant response. These preliminary findings require replication in larger samples.

Improvement in stroke mortality in Canada and the United States, 1990 to 2002

BACKGROUND

In the United States and Canada, folic acid fortification of enriched grain products was fully implemented by 1998. The resulting population-wide reduction in blood homocysteine concentrations might be expected to reduce stroke mortality if high homocysteine levels are an independent risk factor for stroke.

METHODS AND RESULTS

In this population-based cohort study with quasi-experimental intervention, we used segmented log-linear regression to evaluate trends in stroke-related mortality before and after folic acid fortification in the United States and Canada and, as a comparison, during the same period in England and Wales, where fortification is not required. Average blood folate concentrations increased and homocysteine concentrations decreased in the United States after fortification. The ongoing decline in stroke mortality observed in the United States between 1990 and 1997 accelerated in 1998 to 2002 in nearly all population strata, with an overall change from -0.3% (95% CI, -0.7 to 0.08) to -2.9 (95% CI, -3.5 to -2.3) per year (P=0.0005). Sensitivity analyses indicate that changes in other major recognized risk factors are unlikely to account for the reduced number of stroke-related deaths in the United States. The fall in stroke mortality in Canada averaged -1.0% (95% CI, -1.4 to -0.6) per year from 1990 to 1997 and accelerated to -5.4% (95% CI, -6.0 to -4.7) per year in 1998 to 2002 (P< or =0.0001). In contrast, the decline in stroke mortality in England and Wales did not change significantly between 1990 and 2002.

CONCLUSIONS

The improvement in stroke mortality observed after folic acid fortification in the United States and Canada but not in England and Wales is consistent with the hypothesis that folic acid fortification helps to reduce deaths from stroke.

Genetic polymorphisms predisposing to hyperhomocysteinemia in cardiac transplant patients

Genetic determinants for high homocysteine (Hcy) levels are now well known. We studied several single nucleotide polymorphisms (SNP) in Hcy-regulating genes [methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C; methionine synthase (MS) A2756G; methionine synthase reductase (MTRR) A66G] in relation to total plasma Hcy levels, transplant coronary artery disease and thromboembolic episodes in 84 heart transplant patients, and we compared the incidence of these polymorphisms with those in a healthy adult controls. At least one copy of the G allele of the MTRR A66G SNP was found in a significantly greater proportion of cardiac transplant (CTX) recipients compared with controls (94.0% vs. 79.9% respectively). None of the SNP analyzed were correlated with total Hcy plasma levels or the presence of transplant coronary artery disease. However, MS A2756G was significantly associated with cobalamin levels (AA genotype: 290 +/- 122 pmol/l; AG: 381 +/- 151 pmol/l and GG: 415 +/- 100 pmol/l), as was MTRR A66G (AA: 478 +/- 219 pmol/l, AG: 306 +/- 124 pmol/l and GG: 306 +/- 123 pmol/l). MTRR A66G was also correlated with serum folate. No association was found with thromboembolic events. In conclusion, there was a significant difference in the frequency of the G allele genotype of the MTRR A66G in CTX patients versus controls. Differences in cobalamin and folate levels with the MTRR A66G and MS A2756G polymorphisms were noted. Thus, SNP in Hcy-regulating genes may be important determinants of vitamin metabolism in CTX, raising the question of increased vitamin requirements to minimize increased plasma Hcy in this high-risk group.