title: Elevated plasma homocysteine levels in patients treated with levodopa: association with vascular disease.
abstract: BACKGROUND
  Hyperhomocysteinemia is a risk factor for vascular disease and potentially for dementia and depression. The most common cause of elevated homocysteine levels is deficiency of folate or vitamin B(12). However, patients with Parkinson disease (PD) may have elevated homocysteine levels resulting from methylation of levodopa and dopamine by catechol O-methyltransferase, an enzyme that uses S-adenosylmethionine as a methyl donor and yields S-adenosylhomocysteine. Since S-adenosylhomocysteine is rapidly converted to homocysteine, levodopa therapy may put patients at increased risk for vascular disease by raising homocysteine levels.
  
  
  OBJECTIVE
  To determine whether elevations in plasma homocysteine levels caused by levodopa use are associated with increased prevalence of coronary artery disease (CAD), and to determine what role folate and vitamin B(12) have in levodopa-induced hyperhomocysteinemia.
  
  
  METHODS
  Subjects included 235 patients with PD followed up in a movement disorders clinic. Of these, 201 had been treated with levodopa, and 34 had not. Blood samples were collected for the measurement of homocysteine, folate, cobalamin, and methylmalonic acid levels. A history of CAD (prior myocardial infarctions, coronary artery bypass grafting, or coronary angioplasty procedures) was prospectively elicited. We analyzed parametric data by means of 1-way analysis of variance or the t test, and categorical data by means of the Fisher exact test or chi(2) test.
  
  
  RESULTS
  Mean +/- SD plasma homocysteine levels were significantly higher in patients treated with levodopa (16.1 +/- 6.2 micro mol/L), compared with levodopa-naïve patients (12.2 +/- 4.2 micro mol/L; P<.001). We found no difference in the plasma concentration of folate, cobalamin, or methylmalonic acid between the 2 groups. Patients whose homocysteine levels were in the higher quartile (>or=17.7 micro mol/L) had increased prevalence of CAD (relative risk, 1.75; 95% confidence interval, 1.08-2.70;P=.04).
  
  
  CONCLUSIONS
  Levodopa therapy, rather than PD, is a cause of hyperhomocysteinemia in patients with PD. Deficiency of folate or vitamin B(12) levels does not explain the elevated homocysteine levels in these patients. To our knowledge, this is the first report that levodopa-related hyperhomocysteinemia is associated with increased risk for CAD. These findings have implications for the treatment of PD in patients at risk for vascular disease, and potentially for those at risk for dementia and depression.
authors.affiliation: Yarmen Center for Parkinson's Disease, Department of Neurology, Beth Israel Medical Center, New York, NY, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Rogers
authors.forename: Anna
authors.initials: A
authors.lastname: Sanchez-Saffon
authors.forename: Alan B
authors.initials: AB
authors.lastname: Frol
authors.forename: Ramon
authors.initials: R
authors.lastname: Diaz-Arrastia
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000978:Antiparkinson Agents / Q000009:adverse effects*; D003324:Coronary Artery Disease / Q000097:blood / Q000453:epidemiology; D005260:Female; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000139:chemically induced*; D007980:Levodopa / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy*; D012307:Risk Factors; D014805:Vitamin B 12 / Q000097:blood
chemical_list: D000978:Antiparkinson Agents; D006710:Homocysteine; D007980:Levodopa; D005492:Folic Acid; D014805:Vitamin B 12