Time Course of Metabolic Alterations Associated with the Progression of Systemic Lupus Erythematosus in MRL/lpr Mice Based on GC/MS
Serum metabolomics based on gas chromatography/mass spectrometry (GC/MS) was employed to investigate the metabolic alterations at different stages of SLE using lupus-prone mice (MRL/lpr) and age-matched C57BL/6 mice at 9, 11 and 13 weeks of age.
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Mice were sacrificed at 9, 11 and 13 weeks of age (n =5 per MRL/lpr group and n =5 per C57BL/6 group). Blood was collected by cardiac puncture and mice were euthanized by cervical dislocation. Serum was separated by centrifugation at 3000 g. Serum samples were prepared as follows: after thawing at 4 °C, 30 μL of serum was mixed with 60 μL of cold acetonitrile (containing 20 μg/mL of tridecanoic acid as internal standard), and then centrifuged (4 °C 12000 g × 10 min) to precipitate protein. The supernatant was concentrated in a centrifugal concentrator. Quality control (QC) samples were obtained by taking and mixing 30 μL of each sample, and the QC sample was treated in the same manner as the sample. Oximation and silanization were carried out before analysis. First, the extract was dissolved in 30 μL of methoxyamine pyridine (20 mg/mL), and incubated in a 40 °C water bath for 90 min. After adding 30 μL of MSTFA, the sample continued to incubate for 60 min. Derivative products were centrifuged at 12,000 g for removal of precipitation, and then the supernatant was transferred to a glass vial.