Serum and urinary Galectin-3 binding protein (G3BP) as novel biomarkers in lupus nephritis

Abstract Background One potentially fatal complication of systemic lupus erythematosus (SLE) is lupus nephritis (LN) which requires invasive renal biopsy for diagnosis and monitoring. Non-invasive biomarkers are needed. Galectin-3 binding protein (G3BP) has shown potential in autoimmune diseases. Aim The aim of the work was to evaluate serum and urinary G3BP levels as novel biomarkers in LN patients and how they relate to lab-based indicators of disease activity and renal histopathological changes. Methods Ninety-three participants (SLE with LN, SLE without LN, and healthy controls) in this case–control study had serum and urinary G3BP measured by ELISA; LN patients also had renal biopsies. Results Serum G3BP levels were significantly higher in the LN group (26.27 ± 38.23 ng/ml) compared to SLE without LN (16.27 ± 23.07 ng/ml) and controls (9.36 ± 12.59 ng/ml) ( p < 0.001). Serum G3BP varied significantly across LN classes, with Class IV showing the highest levels (21 ± 6.18 ng/ml, p = 0.001). Also, urinary G3BP levels were significantly higher in the LN group (38.24 ± 22.47 ng/ml) compared to SLE without LN (24.99 ± 16.96 ng/ml) and controls (15.73 ± 9.55 ng/ml) ( p < 0.001). Urinary G3BP varied significantly across LN classes, with Class IV showing the highest levels (33.9 ± 4.42 ng/ml, p = 0.001). Urinary G3BP correlated with serum G3BP (Rs = 0.719, p < 0.001), disease duration, and urinary albumin-to-creatinine ratio (UACR). Conclusion Serum and urinary G3BP levels show promise as non-invasive biomarkers for reflecting disease activity and histological severity in LN, with urinary G3BP levels demonstrating superior diagnostic performance.