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 (51Cr-EDTA plasma clearance technique). Albuminuria, blood pressure (BP) and haemoglobin A1c (HbA1c) 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 x min(-1) x 1.73 m(-2) (P = 0.002) with a median rate of decline of 4.5 (-0.4 to 12) ml x min(-1) x year(-1). During follow-up, albuminuria rose from 494 (301-1868) to 908 (108-2169) mg/24 h (P = 0.25), while BP, HbA1c 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 follow-up of BP, albuminuria, HbA1c 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.