Figure 1.

Identification of acylcarnitines as serum biomarkers of APAP toxicity through metabolomic analysis of 24-h serum samples from wild-type and Cyp2e1-null mice treated with 200 and 400 mg/kg APAP. A, Scores scatter plot of an PLS-DA model on the APAP-elicited dose-dependent influence on the serum metabolome. Details of data processing and model construction were described in the Experimental procedures. A two-component PLS-DA model was constructed to characterize the relationship among six mouse groups (n=7 or 8 mice/group), including wild-type mice (control: ■; 200 mg/kg APAP: ▲; 400 mg/kg APAP: •) and Cyp2e1-null mice (control: □; 200 mg/kg APAP: Δ; 400 mg/kg APAP: ○). The t[1] and t[2] values represent the scores of each sample in principal component 1 and 2, respectively. Fitness (R²) and prediction power (Q²) of this PLS-DA model are 0.486 and 0.429, respectively. The model was validated through the recalculation of R² and Q² values after the permutation of sample identities. B, Loadings scatter plot representing the correlation between individual serum ion (w*) and each sample group (c) in the 1^st and 2nd components of the PLS-DA model. Data points representing palmitoylcarnitine (I), myristoylcarnitine (II), oleoylcarnitine (III) and palmitoleoylcarnitine (IV) were labeled in the plot. C, MS² fragmentation of palmitoylcarnitine (I). Major fragment ions were interpreted in the inlaid structural diagrams. D, Influence of APAP treatment on serum palmitoylcarnitine level (mean ± SD) in wild-type and Cyp2e1-null mice (n=4; *, p < 0.05 and **, p < 0.01). Palmitoylcarnitine level in serum (mean ± SD) was measured using the multiple reactions monitoring mode in LC-MS. [²H₃]palmitoylcarnitine was used as internal standard.