Urinary proteome was analyzed and quantified by Tandem Mass Tag (TMT) labeling followed by bioinformatics analysis to study DN pathophysiology and to identify biomarkers of clinical outcome. We included type 2 diabetic normotensive non-obese males with and without incipient DN (microalbuminuria). Sample collection included blood and urine at baseline (control and DN-basal) and, in DN patients, after 3 months of losartan treatment (DN-treated). Urinary proteome analysis identified 166 differentially abundant proteins between controls and DN patients, 27 comparing DN-treated and DN-basal patients, and 182 between DN-treated patients and controls. Mathematical modeling analysis identified 80 key proteins involved in DN pathophysiology, 15 in losartan effect and 7 of these 95 are essential in both processes. VCAM-1 and neprilysin are the only ones that are differentially expressed in the urinary proteome. We observed an increase of VCAM-1 urine levels in DN-basal patients compared to diabetic controls and an increase of urinary neprilysin in DN-treated patients with persistent albuminuria, the latter confirmed by ELISA . Our results point to neprilysin and VCAM-1 as potential candidates in DN pathology and treatment.