Glomerular filtration rate, urinary albumin excretion rate, and blood pressure changes in normoalbuminuric normotensive type 1 diabetic patients - An8-year follow-up study

OBJECTIVE - To analyze the changes in glomerular filtration rate (GFR), uri nary albumin excretion rate (UAER), and blood pressure (BP) levels in a coh ort of normoalbuminuric and normotensive type 1 diabetic patients. RESEARCH DESIGN AND METHODS - This is an 8.4 +/- 2.1-year prospective study of 33 normotensive normoalbuminuric (24-h UAER <20 mu g/min) type 1 diabet ic patients. UAER (radioimmunoassay), GFR (Cr-51-EDTA single-injection tech nique), and GHb (ion-exchange chromatography) were measured at baseline and at 1- to 2-year intervals. RESULTS - The GFR decreased (137.6 +/- 16.5 to 116.4 +/- 21.3 ml.min(-1).1. 73 m(-2) P < 0.05) during the follow-up period. GFR reduction (-0.20 +/- 0. 29 ml.min(-1).month(-1); P < 0.05) was associated with baseline GFR and mea n GHb (R-2 = 0.30, beta = 0.072, F = 6.54, P = 0.004). UAER was higher at t he end of the study (3.7-7.1 mu g/min: P = 0.017). Microalbuminuria was obs erved in two patients, while macroalbuminuria was observed in one. No chang es in UAER were observed when these three patients were excluded from the a nalysis. Mean blood pressure (MBP) increased during the study (85.8 +/- 9.7 to 99.6 +/- 11.6 mmHg, P <0.001). MBP at the end of the study was associat ed with age and GFR at baseline (R-2 = 0.39; beta = 0.074, F = 9.64; P = 0. 001). CONCLUSIONS - In this cohort of normoalbuminuric normotensive type I diabet ic patients, GFR decreased and BP levels increased during the follow-up per iod. The predictors for the GFR change were baseline GFR level and metaboli c control. For end-of-study MBP, the predictor was baseline GFR level.