REN and diabetes mellitus: CKD, chronic kidney disease; CKD-EPI, Chronic Kidney Disease Epidemiology Collaboration; GFR, glomerular filtration rate; HbA1c, glycated hemoglobin; KIM-1, kidney injury molecule-1; NIDDK, National Institute of Diabetes and Digestive and Kidney Diseases; NGAL, neutrophil gelatinase-associated lipocalin; NR, not reported; RAAS, renin-angiotensin-aldosterone system; T2DM, type 2 diabetes mellitus; UMIN, University Hospital Medical Information Network; USA, United States of America; jRCT, Japan Registry of Clinical Trials; TGF-β1, transforming growth factor beta 1