Abstract
Objective Glycoprotein acetylation (GlycA) is a novel biomarker for chronic inflammation, associated to cardiovascular risk. Serum GlycA levels are increased in several inflammatory diseases, including systemic lupus erythematosus (SLE). We investigated the relevance of serum GlycA measurement in SLE and lupus nephritis (LN).
Methods GlycA was measured by NMR in 194 serum samples from patients and controls. Comparisons were performed between groups. Clinical and biological parameters were tested for correlation with GlycA levels. The predictive value of GlycA to differentiate proliferative from non-proliferative LN was determined using logistic regression models.
Results GlycA was correlated to C-reactive protein (CRP), neutrophil count, proteinuria and the SLE disease activity index (SLEDAI), and inversely with serum albumin. GlycA was higher in active (n=105) than in quiescent (n=39) SLE patients, in healthy controls (n=29), and in patients with non-lupus nephritis (n=21), despite a more altered renal function in the latter. In patients with biopsy-proven active LN, GlycA was higher in proliferative (n=32) than non-proliferative (n=11) LN, independent of renal function and proteinuria level. Logistic regression models showed that, in univariate models, GlycA outperforms traditional biomarkers. A bivariate model using GlycA and BMI better predicted the proliferative status of LN than a model comprising CRP, renal function (eGFR), serum albumin, proteinuria, C3 consumption and the presence of anti-dsDNA antibodies.
Conclusion Serum GlycA is elevated in SLE, and correlates with disease activity and LN. Serum GlycA, which summarizes different inflammatory processes, could be a valuable biomarker to discriminate proliferative from non-proliferative LN and should be tested in large, prospective cohorts.
