L-Dopa therapy increases homocysteine concentration in cerebrospinal fluid from patients with Parkinson's disease

To investigate the effect of L-3,4-dihydroxyphenylalanine (L-dopa) therapy on homocysteine (HC) concentration in patients with Parkinson's disease (PD), the concentrations in cerebrospinal fluid (CSF) of total HC and methionine (Met) were compared between 18 patients with PD before and after treatment with L-dopa and 16 neurologically normal control patients. Concentrations of total HC in patients with PD were significantly higher following L-dopa therapy (169+/-27 nM) than before treatment (111+/-22 nM) and than in controls (85+/-25 nM) (patients with PD before L-dopa treatment vs. controls, p<0.005; patients with PD after L-dopa treatment vs. before treatment, p<0.0001). Conversely, concentrations of total Met in patients with PD were significantly lower after L-dopa therapy (5.3+/-1.7 microM) than before L-dopa therapy (6.8+/-1.9 microM) (p<0.001). These findings in patients with PD suggest that L-dopa therapy enhances intracerebral methylation and elevates concentration of HC.