Renoprotection in diabetes. With special reference to insulin-dependent patients

Diabetic patients developing nephropathy go through several stages of renal disease, moving from normo- to micro- to macroalbuminuria. Microalbuminuria is defined as urinary albumin excretion between 20-200 micrograms/min; lower values are designated normoalbuminuria and higher values macroalbuminuria. Only with macroalbuminuria does glomerular filtration rate (GFR) fall consistently. The main intermediary end-points are reduction or prevention of micro-/macroalbuminuria, prevention or reduction of fall in GFR (stronger end-point), with postponement of end-stage renal disease as a final end-point. Good metabolic control can prevent or postpone the development of microalbuminuria, the earliest sign of diabetic renal disease. The ideal therapeutic window may be HbA1C between 7 and 8.5% (mean reference value 5.5%). Thus, efforts should focus on obtaining the best possible control before the onset of microalbuminuria without disturbing hypoglycemia. In patients with microalbuminuria, blood pressure starts to increase and early antihypertensive treatment becomes important. Good glycemic control may be difficult to achieve. With overt nephropathy, defined as clinical proteinuria, a relentless decline in GFR occurs, unless patients are carefully treated with antihypertensive agents and good metabolic control is still important. Fall rate in GFR may be reduced from 12-->3 ml/min/year. Protein restriction may also be of interest, but a clear beneficial effect of optimized diabetes care is more difficult to document in clinical trials. However HbA1C of less than 8% is associated with slow regression. Early screening is recommended, with emphasis on testing for albuminuria, including microalbuminuria, along with careful control of glycemia and blood pressure.