Homocysteine and asymmetric dimethylarginine in relation to B vitamins in elderly people.

OBJECTIVE

Homocysteine is a cardiovascular risk factor, its metabolism is influenced by certain B vitamins and it is associated with endothelial dysfunction probably due to impaired bioavailability of NO caused by homocysteine-induced accumulation of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase. On this basis, we investigated the cardiovascular risk factors homocysteine and ADMA in relation to vitamins B(6), B(12) and folate in elderly people.

METHODS

A total of 102 subjects were recruited and divided into three groups according to age: A (70-74y, n = 48), B (75-79y, n = 35) and C (≥80y, n = 19). Plasma levels of vitamin B(6) were determined with HPLC, vitamin B(12) and folate by RIA. Plasma concentrations of homocysteine were analyzed with HPLC and levels of ADMA were measured by ELISA.

RESULTS

Plasma levels of vitamins B(6), B(12) and folate were found to be adequate in 93, 67 and 55% of participants, respectively. This study showed a significant age-associated decrease in vitamins B(6) (A > B, A > C: p < 0.05), B(12) and folate (A > C: p < 0.05) in parallel to a significant age-related increase in the cardiovascular risk factors homocysteine (A < C, B < C: p < 0.05) and ADMA (A < B: p < 0.05; A < C: p < 0.001). Moreover, homocysteine was significantly negatively (p < 0.01) related to vitamins B(6), B(12) and folate, and significantly positively (p < 0.01) correlated to ADMA.

CONCLUSIONS

The significant correlation between homocysteine and ADMA observed in this study may be an important mechanism decreasing NO bioavailability and so causing endothelial dysfunction. Due to the significant relation of vitamins B(6), B(12) and folate to plasma homocysteine, these vitamins may thus indirectly influence endothelial function and cardiovascular risk in elderly people.