TNF and acute kidney injury: Differential excretion of collagen alpha chain‐derived peptide fragments was already described in a number of other proteomic studies on CKD and AKI 19, 27, 37, 38 and is indicative for alterations in extracellular matrix turnover 39, 40, i.e. via tumor necrosis factor alpha‐induced activation of matrix‐degrading proteases 41, 42.