L-Carnitine protects plasma components against oxidative alterations.
OBJECTIVE
L-Carnitine as a dietary supplement has been reported to have a beneficial effect on several cardiovascular risk parameters and exercise capacity, but the biological relevance of its activity is poorly understood. Dietary supplements (including L-carnitine) are often used to foster exercise performance; however, these may affect some pathways of human body metabolism. The aim of this study in vitro was to determine antioxidative properties of L-carnitine (0.1-100 μM) added to plasma and to assess if L-carnitine might protect plasma proteins and lipids against oxidative/nitrative damage (determined by levels of protein carbonyl groups, thiols, 3-nitrotyrosine formation and thiobarbituric-acid reactive substances generation) caused by 100 μM peroxynitrite (ONOO(-)), a strong physiologic oxidative/nitrative agent.


METHODS
The level of carbonyl group generation was measured by a colorimetric method. For the estimation of 3-nitrotyrosine formation, a competition enzyme-linked immunosorbent assay was performed. Plasma lipid peroxidation was measured spectrophotometrically as the production of thiobarbituric-acid reactive substances. High-performance liquid chromatography was used to analyze total free thiol groups of plasma proteins and low-molecular-weight thiols (glutathione, cysteine, and homocysteine) in plasma.


RESULTS
The L-carnitine added to plasma inhibited in vitro ONOO(-)-induced oxidation and nitration of blood plasma proteins. Incubation of plasma with peroxynitrite resulted in the decrease of protein thiols. L-Carnitine had a protective effect on peroxynitrite-induced decreased -SH level in plasma proteins. The presence of L-carnitine also prevented the decrease of low-molecular-weight thiols (glutathione, cysteine, and homocysteine) in plasma caused by peroxynitrite and protected plasma lipids against peroxidation induced by peroxynitrite.


CONCLUSIONS
These results demonstrated that L-carnitine possesses antioxidative activity.
Kolodziejczyk
Joanna
J
Department of General Biochemistry, University of Lodz, Lodz, Poland.
Saluk-Juszczak
Joanna
J
Wachowicz
Barbara
B
D000328:Adult; D000975:Antioxidants / Q000737:chemistry*; D001798:Blood Proteins / Q000737:chemistry*; D002331:Carnitine / Q000737:chemistry*; D003545:Cysteine / Q000097:blood; D019587:Dietary Supplements; D005978:Glutathione / Q000097:blood; D006710:Homocysteine / Q000097:blood; D006801:Humans; D008054:Lipid Peroxides / Q000097:blood*; D008055:Lipids / Q000097:blood / Q000737:chemistry*; D008297:Male; D009994:Osmolar Concentration; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D030421:Peroxynitrous Acid / Q000737:chemistry; D050050:Protein Carbonylation; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D014443:Tyrosine / Q000031:analogs & derivatives / Q000097:blood; D055815:Young Adult
D000975:Antioxidants; D001798:Blood Proteins; D008054:Lipid Peroxides; D008055:Lipids; D016877:Oxidants; D017392:Thiobarbituric Acid Reactive Substances; D006710:Homocysteine; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D005978:Glutathione; D003545:Cysteine; D002331:Carnitine