| Summary: | The natural history and factors affecting the progression of nephropathy in non-insulin-dependent diabetes mellitus are poorly understood. The hypothesis that glomerular filtration declines at a similar rate in NIDDM and IDDM was examined in a cohort of 87 subjects (55 NIDDM and 32 IDDM). The rate of decline of calculated GFR (Cockcroft-Gault) was significantly slower in IDDM compared to NIDDM (0.29 vs 0.43 ml.min.<SUP>-1</SUP> month<SUP>-1</SUP>;p<0.05), in subjects with a baseline glomerular filtration rate (GFR) of ≤ 80 ml.min<SUP>-1</SUP> followed for a median of 6.4 years. The rate of decline of GFR was more rapid in Caucasian than in Afro-Caribbean NIDDM subjects. For all individuals, 24-hour protein excretion proved the most significant variable associated with the decline of GFR. Together with diastolic blood pressure these factors accounted for 34% of the variation of the data. For the NIDDM group, blood pressure treatment at the outset replaced diastolic blood pressure as a significant associate of decline of GFR. The effect of percutaneous renal artery angioplasty was examined in nine subjects with NIDDM, nephropathy and renal artery stenosis to determine if this procedure influences the progression of nephropathy. No benefit was demonstrated. Twenty-six NIDDM individuals from the above cohort were prospectively studied over a two-year period. The rate of decline of GFR was 0.48 ml.min<SUP>-1</SUP>month<SUP>-1</SUP>. Blood pressure, serum cholesterol and 24-hour protein were all associated with GFR decline, with 38% of the variation in the data accounted for by the first two factors. EDTA clearance was compared to calculated GFR and creatinine clearance for 72 patient episodes to determine the clinical value of these surrogate markers of GFR in NIDDM subjects. Calculated GFR underestimated true GFR by 4%, on average, with significant differences for the Afro-Caribbean, but not Caucasian or Asian, group, Endogenous creatinine clearance may have a role in monitoring disease progression in obese subjects.
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