Serum and urinary metabolites discriminate disease activity in ANCA associated glomerulonephritis in a pilot study

Renal biopsy is currently the gold standard for diagnosing active renal vasculitis. In this pilot study, metabolomics analysis was used to investigate the differences in metabolic profiles between paired patients' serum and urine samples collected during both the active and the remission phase of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV). Ten patients with AAV renal disease were included. Mean age was 61 years, with 6 patients each being male and Caucasian. Mean Birmingham Vasculitis Activity Score (BVAS) and mean glomerular filtration rate (GFR) were 17 and 28, respectively. We found that while the citric acid cycle intermediates citrate, iso-citrate and oxaloacetate had lower intensities in the active phase samples as compared to the remission phase samples. The intensities of other metabolites of carbohydrate metabolism, amino acid metabolism, and nucleotide synthesis were significantly higher in the active phase samples, indicating the upregulation of these pathways for the production of energy and other biomolecules such as proteins and nucleic acids during the active phase of AAV. This pilot study suggests that serum and urinary metabolomic profiling may be useful to monitor disease activity in renal AAV.