Gas chromatography time-of-flight mass spectrometry based metabolomic approach to evaluating toxicity of triptolide

Metabolomics allows high-throughput analysis of low-molecular-weight compounds in biofluids that reflect the physiological status and biochemical metabolism of living systems. Hence it has the potential to evaluate toxicity and clarifies the metabolism-related toxic mechanisms. In this study a promising candidate drug parent, triptolide, was given to Sprague-Dawley rats as a model toxicant at a single dose of 0.6, or 2.4 mg/kg, i.g. Both routine biochemical assays and histopathological inspection showed time-dependent hepatic toxicity at the higher dose, but no obvious toxicity at the lower dose. Meanwhile, serum metabolome was profiled using the non-targeted metabolomic tool, gas chromatography time-of-flight mass spectrometry. Based on the acquired metabolomic data, mathematical models were calculated and the metabolic patterns of serum were evaluated using projection to latent structure-discriminant analysis. The relative distance of each treated group from the normal control was calculated to provide a measure of toxicity. Treatment with triptolide at either the higher or lower dose caused deviations in the metabolic pattern and resulted in perturbation of taurine, creatinine, free fatty acids, beta-hydroxybutyrate, tricarboxylic acid cycle intermediates, and amino acids. This finding indicates the dysfunction of beta-oxidation of free fatty acids and impairment of the mitochondria and confirms the hepatic toxicity of triptolide. The identified toxic markers and the calculated relative distance values quantitatively demonstrated dose- and time-dependent toxicity, whereas the scores plot of the model provided the qualitative information. The metabolomic approach was non-invasive and more sensitive than routine toxic assessment, and the results of both methods correlated well.