Urine levels decrease significantly in animal models of AKI, including gentamicin [221] and I/R-induced AKI rats [217], while studies have reported that AQP5 levels are significantly upregulated in the collecting ducts of patients with diabetic nephropathy (DN) [207,222,223], suggesting that urine levels of these AQPs might be novel noninvasive biomarkers to diagnose DN. The gene discussed is AQP5; the disease is acute kidney injury.