AQP5 and diabetic kidney disease: Zubiri et al. suggested the use of urinary bikunin precursor and histone-lysine N-methylthransferase (KHMT) as biomarkers for DKD patients [31], whereas Rossi et al. [32] found that urinary EV-derived AQP2 and AQP5 could be used as biomarkers for DKD patients.