Abstract
Levodopa is administered with dopa decarboxylase inhibitors (DDI) to prevent its peripheral degradation. This increases conversion of levodopa to 3-O-methyldopa (3-OMD) by catechol-O-methyltransferase (COMT). S-adenosylmethionine (SAM), which is synthesized from adenosine triphosphate and methionine (MET), serves as methyl donor for this O-metabolisation of levodopa with resulting conversion of SAM to total homocysteine (tHcy) via S-adenosylhomocysteine (SAH). Previous studies showed augmented plasma levels of tHcy in long-term levodopa/DDI-treated patients with Parkinson's disease (PP). Objective of this study was to compare MET, SAM, levodopa, 3-OMD, tHcy and SAH in plasma of 20 levodopa/DDI treated PP and corresponding controls. A significant decrease of MET respectively SAM and an increase of tHcy appeared in PP. SAH with its short half-life did not differ. Levodopa/DDI long-term treatment contributes to altered levels of substrates of the O-methylation cycle in PP.
MeSH terms
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Aged
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Aged, 80 and over
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Antiparkinson Agents / administration & dosage
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Antiparkinson Agents / adverse effects*
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Antiparkinson Agents / pharmacokinetics
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Aromatic Amino Acid Decarboxylase Inhibitors
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Cardiovascular Diseases / chemically induced
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Cardiovascular Diseases / metabolism
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Cardiovascular Diseases / physiopathology
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Dopa Decarboxylase / metabolism
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Down-Regulation / drug effects
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Down-Regulation / physiology
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Drug Interactions / physiology
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Enzyme Inhibitors / administration & dosage
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Enzyme Inhibitors / adverse effects*
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Female
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Homocysteine / blood*
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Humans
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Levodopa / administration & dosage
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Levodopa / adverse effects
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Levodopa / pharmacokinetics
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Male
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Methionine / blood*
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Middle Aged
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Parkinson Disease / blood
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Parkinson Disease / drug therapy*
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Parkinson Disease / physiopathology
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S-Adenosylmethionine / blood*
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Up-Regulation / drug effects
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Up-Regulation / physiology
Substances
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Antiparkinson Agents
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Aromatic Amino Acid Decarboxylase Inhibitors
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Enzyme Inhibitors
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Homocysteine
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Levodopa
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S-Adenosylmethionine
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Methionine
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Dopa Decarboxylase