Effect of L-Dopa administration on blood homocysteine concentration in Parkinson's patients

J. W. Miller, C. A. Thomas, M. R. Nadeau, L. Brattstrom, R. G. Feldman, P. A. Wolf, J. Selhub

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L-Dopa reuses a significant elevation of blood homocysteine (HCY) concentration in rats. This results from the O-methylation of L-Dopa and its metabolic product dopamine. In O-methylation, S-adenosylmethionine donates a methyl group producing S-adenosylhomocysteine which is then hydrolyzed to form HCY. The synthesis of HCY then exceeds cellular metabolic capacity leading to HCY overflow into the blood. In the present study, we determined if L-Dopa administration also causes an increase of blood HCY in humans. Blood samples were collected from 40 Parkinson's patients: 20 on L-Dopa therapy. 20 L-Dopa naive. Plasma HCY concentrations were then determined, along with plasma levels of the B vitamin folate. B12, and B6. The mean plasma HCY concentration in the L-Dopa group was greater than that of the naive group (11.6 ± 4.1 vs 8.8 ± 3.7 microM, respectively; p = 0.03). Furthermore, while no significant differences in mean plasma levels of any of the B vitamins were observed between the two groups, low normal or mildly deficient levels of one or more of the B vitamins were associated with elevated HCY only in the L-Dopa group. This suggests that the B vitamin requirement necessary to maintain normal blood HCY concentrations in patients treated with L-Dopa is higher than in L-Dopa naive patients. Since an elevated blood HCY level is associated with increased risk for vascular disease, B vitamin supplements may be warranted for Parkinson's patients on chronic, high dose L-Dopa therapy.

Original languageEnglish (US)
JournalFASEB Journal
Issue number3
StatePublished - 1997
Externally publishedYes

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology


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