References

healthy subjects (26). Because the adverse effects of homo-cysteine are most likely related to its prooxidant proper-ties (6), a direct involvement of the amino acid in this phenomenon may be therefore hypothesized. In conclusion, PD patients undergoing regular treat-ment with l-DOPA have higher plasma homocysteine concentrations than healthy subjects. The increase seems to be related to the methylated catabolism of the drug, although other factors, such as enzymatic defects in the remethylation pathway of homocysteine, are likely to play a substantial role. Increased risk of cerebro- and cardiovascular diseases has been reported in PD patient populations, although the issue is highly disputed (27, 28). Whether the increase in plasma homocysteine occurring in PD patients plays a role in the progression of the disease remains to be established