Metabolic profiling reveals new serum biomarkers of lupus nephritis.

Metabolomics has been applied to explore altered metabolite profiles in disease and identify unique metabolic signatures specific to certain pathologies. The aim of the current study is to characterize the metabolic profile of patients diagnosed with lupus nephritis (LN) and explore new insights into underlying disease processes. A metabolomic approach using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS) was developed in serum samples from 32 LN patients, 30 idiopathic nephrotic syndrome (INS) patients and 28 healthy controls (HCs). Potential biomarkers were screened from orthogonal projection to latent structures discriminate analysis (OPLS-DA) and further evaluated by receiver operating characteristic analysis (ROC). A total of 14 potential biomarkers were screened and tentatively identified for LN patients compared to HCs. Compared to HCs and INS patients, the LN patients had increased serum levels of sorbitol and glycocholic acid metabolites and decreased levels of cortisol, creatinine and L-aspartyl-L-phenylalanine. A panel of three metabolomics (theophylline, oxidized glutathione and capric acid) was identified as biomarkers of LN with a sensitivity of 87.50% and a specificity of 67.86% using ROC analysis. Our results suggest that UPLC-HRMS based quantification of circulating metabolites was a useful tool for identification of biomarkers with the ability to segregate LN patients from INS patients and HCs. The potential biomarkers indicated that the LN metabolic disturbance may be closely associated with inflammation injury, oxidative stress and phospholipid metabolism.