Structural basis of diabetic nephropathy in microalbuminuric NIDDM patients: a light microscopy study

The objective of the study was to evaluate early structural changes occurring in patients with non-insulin-dependent diabetes mellitus (NIDDM) and microalbuminuria by light microscopy. Basal renal biopsy was performed in patients who were subsequently randomized to different antihypertensive treatments. Fourteen NIDDM patients aged 36-65 years (duration of diabetes 9 +/- 7 years) with microalbuminuria (mean urinary albumin excretion 66 +/- 49 micrograms/min) underwent percutaneous renal biopsy. Control biopsies were obtained from five patients of similar age undergoing nephrectomy for renal neoplasia with normal renal function and no history of renal disease. Control and diabetic biopsies were processed by light microscopy and stained with haematoxylin and eosin, periodic acid Schiff, Masson's trichrome and silver methenamine. The percentage of globally sclerotic glomeruli was evaluated. Glomerular volume was determined using perimeter analysis. A semiquantitative assessment (range 0 to 3+) was made of mesangial sclerosis, interstitial fibrosis, tubular atrophy, arteriosclerosis and arteriolar hyalinosis. Glomerular volume was significantly increased in diabetic as compared to control glomeruli (3.2 +/- 8 vs 1.8 +/- 7, p < 0.01). Mesangial sclerosis (0.9 vs 0, p < 0.0001) and arteriolar hyalinosis (0.91 vs 0.2, p < 0.022) were significantly higher in diabetic compared to control subjects. No significant differences between diabetic and control subjects were found in the percentage of globally sclerotic glomeruli or in the extent of interstitial fibrosis, tubular atrophy and arteriosclerosis. Thus NIDDM patients with microalbuminuria show histological findings consistent with diabetic nephropathy characterized by glomerular hypertrophy, mesangial sclerosis and arteriolar hyalinosis. However, the renal histological changes are mild and appear less marked than in insulin-dependent diabetic patients.