Fasting total homocysteine (tHcy) concentration and mortality in older Mexican Americans

Cystathionine β-synthase and methylenetetrahydrofolate reductase mutations in Mexican individuals with hyperhomocysteinemia

Background:

Hyperhomocysteinemia, a thrombotic risk factor, may have several causes. Among the genetic causes of hyperhomocysteinemia, there are polymorphisms in the enzymes methylenetetrahydrofolate reductase (C677T) and cystathionine β-synthase (C699T, C1080T, and 844ins68). Although the frequency of hyperhomocysteinemia in our country is high, there is no evidence about the frequencies of these polymorphisms.

Methods:

We analyzed 80 healthy individuals from several regions in our country. We evaluated the fasting and post-oral methionine load plasma Hcy and the genotypes in order to obtain the allele frequencies of the polymorphisms C677T of methylenetetrahydrofolate reductase and C699T, C1080T, and 844ins68 of the cystathionine β-synthase.

Results:

No individual had deficiency of folic acid, vitamins B12, or B6, but 80% had post-oral methionine load hyperhomocysteinemia. We found a significant increase in the Hcy plasma concentration associated with age and gender. Only the polymorphism C1080T was significantly associated with hyperhomocysteinemia.

Conclusion:

There is an association between fasting and post-oral methionine load plasma Hcy concentrations with the allelic frequencies of the polymorphisms C669T, 844ins68, and C1080T of the cystathionine β-synthase and C667T of the methylenetetrahydrofolate reductase in healthy Mexican individuals. As compared with individuals with normal fasting or post-oral methionine load Hcy plasma levels, only C1080T was significantly associated with hyperhomocysteinemia.

Elevated homocysteine levels and risk of cardiovascular and all-cause mortality: a meta-analysis of prospective studies

OBJECTIVE

To investigate whether elevated homocysteine levels were a predictor of subsequent coronary heart disease (CHD) mortality, cardiovascular mortality or all-cause mortality in the general population by a meta-analysis.

METHODS

In a systematic search conducted in the databases of PubMed and Embase prior to October 2013, we identified relevant prospective observational studies evaluating the association between baseline homocysteine levels and CHD mortality, cardiovascular or all-cause mortality in the general population. Pooled adjust risk ratio (RR) and corresponding 95% confidence interval (CI) were calculated separately for categorical risk estimates and continuous risk estimates.

RESULTS

Twelve studies with 23623 subjects were included in the meta-analysis. Comparing the highest to lowest homocysteine level categories, CHD mortality increased by 66% (RR 1.66; 95% CI 1.12-2.47; P=0.012), cardiovascular mortality increased by 68% (RR 1.68; 95% CI 1.04-2.70; P=0.033), and all-cause mortality increased by 93% (RR 1.93; 95% CI 1.54-2.43; P<0.001). Moreover, for each 5 μmol/L homocysteine increment, the pooled RR was 1.52 (95% CI 1.26-1.84; P<0.001) for CHD mortality, 1.32 (95% CI 1.08-1.61; P=0.006) for cardiovascular mortality, and 1.27 (95% CI 1.03-1.55; P=0.023) for all-cause mortality.

CONCLUSIONS

Elevated homocysteine levels are an independent predictor for subsequent cardiovascular mortality or all-cause mortality, and the risks were more pronounced among elderly persons.