Effect of sports activity on carnitine metabolism Measurement of free carnitine, γ-butyrobetaine and acylcarnitines by tandem mass spectrometry

Abstract The effects of sports activity on carnitine metabolism were studied using mass spectrometry. Serum levels of free carnitine, acylcarnitines (acetylcarnitine, propionylcarnitine, C4-, C5- and C8-acylcarnitine) and γ-butyrobetaine, a carnitine precursor, were determined by tandem mass spectrometry in liquid secondary ion mass ionization mode. The coefficients of variation at three different concentrations were 2.8∼7.9% for γ-butyrobetaine, and 1.2∼6.7% for free carnitine. The recoveries added to serum were 109.1% for γ-butyrobetaine, 89.3% for free carnitine. Sports activity caused increased serum levels of γ-butyrobetaine, acetylcarnitine, C4- and C8-acylcarnitines and decreased serum levels of free carnitine. This method requires a small amount of sample volume (20 μl of serum) and short total instrumental time for the analysis (1 h for preparation, 2 min per sample for mass spectrometric analysis). Therefore, this method can be applied to study carnitine metabolism under various conditions that affect fatty acid oxidation.