Department of General Biochemistry, University of Lodz, Lodz, Poland.
Nutrition. 2011 Jun;27(6):693-9. doi: 10.1016/j.nut.2010.06.009. Epub 2010 Sep 24.
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.
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.
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.
These results demonstrated that L-carnitine possesses antioxidative activity.
左旋肉碱作为膳食补充剂，据报道对多种心血管风险参数和运动能力有有益影响，但对其活性的生物学相关性知之甚少。膳食补充剂（包括左旋肉碱）常被用于促进运动表现；然而，这些可能会影响人体代谢的某些途径。本体外研究的目的是确定添加到血浆中的左旋肉碱（0.1-100μM）的抗氧化特性，并评估左旋肉碱是否可能保护血浆蛋白和脂质免受 100μM 过氧亚硝酸盐（ONOO（-））引起的氧化/硝化损伤（通过蛋白质羰基、巯基、3-硝基酪氨酸形成和硫代巴比妥酸反应物质生成的水平来确定），过氧亚硝酸盐（ONOO（-））是一种强生理氧化/硝化剂。
通过比色法测量羰基生成水平。为了估计 3-硝基酪氨酸的形成，进行了竞争性酶联免疫吸附测定。通过分光光度法测量血浆脂质过氧化，作为硫代巴比妥酸反应物质的产生。高效液相色谱法用于分析血浆蛋白质的总游离巯基和低分子量巯基（谷胱甘肽、半胱氨酸和同型半胱氨酸）。
添加到血浆中的左旋肉碱抑制了体外 ONOO（-）诱导的血浆蛋白质氧化和硝化。血浆与过氧亚硝酸盐孵育导致蛋白质巯基减少。左旋肉碱对过氧亚硝酸盐诱导的血浆蛋白质 -SH 水平降低具有保护作用。左旋肉碱的存在还可以防止过氧亚硝酸盐引起的血浆中低分子量巯基（谷胱甘肽、半胱氨酸和同型半胱氨酸）减少，并保护血浆脂质免受过氧亚硝酸盐诱导的过氧化。
这些结果表明，左旋肉碱具有抗氧化活性。
