The following is a summary of “Urinary beta-2 microglobulin increases whereas TIMP-2 and IGFBP7 decline after unilateral nephrectomy in healthy kidney donors,” published in the June 2024 issue of Nephrology by de Rooij et al.

Urinary markers such as beta-2 microglobulin (B2M), tissue inhibitor of metalloproteinases-2 (TIMP-2), insulin-like growth factor-binding protein 7 (IGFBP7), kidney injury molecule-1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) detect early kidney injury. 

Researchers conducted a retrospective study to assess the relationship between baseline biomarker concentrations and kidney function 1-year post-nephrectomy. 

They compared the levels of B2M, TIMP-2, IGFBP7, KIM-1, and NGAL in the urine of living kidney donors 24 hours before and after nephrectomy. The data from 38 living kidney donors was examined using the Renal Protection Against Ischaemia-Reperfusion in transplantation study. To assess the association between baseline biomarker levels and kidney function 1-year post-nephrectomy, linear regression analysis was utilized.

The results showed that 24 hours before nephrectomy, median levels of urinary creatinine and creatinine standardized B2M, TIMP-2, IGFBP7, KIM-1, NGAL, and albumin 24 h, 9.4 mmol/L, 14 µg/mmol, 16 pmol/mmol, 99 pmol/mmol, 63 ng/mmol, 1390 ng/mmol and 0.7,g/mmol, with 24 h later differences in nephrectomy of -0.9, +1906, -7.1, -38.3, -6.9, +2378 and +1.2, respectively. The change in donor eGFR after 12 months per SD increment for B2M, TIMP-2, IGFBP7, KIM-1, and NGAL was -1.1, -2.3, -0.7, -1.6, and -2.8, respectively. Urinary TIMP-2 and IGFBP7 excretion halved after nephrectomy, similar to urinary creatinine, suggesting these markers predominantly reflect glomerular filtration. B2M and NGAL excretion increased significantly, like albumin, indicating decreased proximal tubular reabsorption following nephrectomy. KIM-1 did not change considerably after nephrectomy.

Investigators concluded that no biomarkers showed a significant correlation with long-term donor eGFR. However, the results provide insight into the pathophysiology of these urinary biomarkers. 

Source: nature.com/articles/s41598-024-62246-1#auth-Esther_N__M_-Rooij-Aff1-Aff2