Natural course of kidney function in Type 2 diabetic patients with diabetic nephropathy

Aims To determine the natural course of kidney function and to evaluate the impact of putative progression promoters in Caucasian Type 2 diabetes mellitus (DM) patients with diabetic nephropathy who had never received any antihypertensive treatment. Methods A long-term observational study of 13 normotensive to borderline hypertensive Type 2 DM patients with diabetic nephropathy. Glomerular filtration rate (GFR) was measured approximately every year (Cr-51-EDTA plasma clearance technique). Albuminuria, blood pressure (BP) and haemoglobin A(1c) (HbA(1c)) was determined 2-4 times per year and serum cholesterol every second year. Results The patients (12 males/one female), age 56 +/- 9 (mean +/- SD) years, with a known duration of diabetes of 10 +/- 6 years, were followed for 55 (24-105) (median (range)) months. GFR decreased from 104 (50-126) to 80 (39-112) ml.min(-1).1.73 m(-2) (P = 0.002) with a median rate of decline of 4.5 (-0.4 to 12) ml.mid(-1).year(-1). During follow-up, albuminuria rose from 494 (301-1868) to 908 (108-2169) mg/24h (P=0.25), while BP, HbA(1c), and serum cholesterol remained essentially unchanged. In univariate analysis the rate of decline in GFR did not correlate significantly with neither baseline nor mean values during followup of BP, albuminuria, HbA(1c), and serum cholesterol. Conclusions Our study suggests that normotensive to borderline hypertensive Type 2 DM patients with diabetic nephropathy have a rather slow decline in kidney function, but we did not unravel the putative progression promoters responsible for the variation in rate of decline in GFR.