REN and diabetic kidney disease: The general concept of natural history of proteinuric diabetic kidney disease has been formed by the observational studies mostly done in patients with diabetes before the current era of recommended multidisciplinary treatment including intensive glycemic control, tight blood pressure control, and renoprotective therapy such as renin-angiotensin system blockades, glucagon-like peptide-1 receptor agonists or sodium-glucose transport protein 2 inhibitors [7].