EARLY GLOMERULOPATHY IS PRESENT IN YOUNG, TYPE-1 (INSULIN-DEPENDENT) DIABETIC-PATIENTS WITH MICROALBUMINURIA

Increased urinary albumin excretion, microalbuminuria, may be the firs t sign of early diabetic nephropathy. We examined glomeruli by morphom etric methods in 17 patients with Type 1 (insulin-dependent) diabetes mellitus and microalbuminuria. The median age was 19 (range 18-29) yea rs, duration of diabetes 12 (8-15) years, mean blood pressure 93 (87-1 15) mm Hg, glomerular filtration rate 132 (101-209) ml . min-1 . 1.73 m2-2, albumin excretion rate (mean over 1 year) 32 (15-194) mug/min. R eference data were obtained from 11 healthy kidney donors. Mesangial v olume estimates were obtained by serial sectioning in three total prof iles in each of three glomeruli in diabetic patients. Basement membran e thickness and matrix volume fraction were estimated from one level p er glomerulus. Two matrix parameters, matrix star volume and matrix th ickness, were estimated. Interstitial volume fraction in cortex was me asured by light microscopy. The morphological parameters were signific antly increased in the diabetic group compared to the control group, b asement membrane thickness (mean with 95% confidence intervals) was 59 5 nm (549-641 nm) vs 305 nm (287-325 nm), p = 0.0001; mesangial volume fraction 0.22 (0.21-0.23) vs 0.19 (0.18-0.21), p = 0.04, and matrix v olume fraction 0.13 (0.12-0.13 vs 0.09 (0.08-0.10), p = 0.001. Also ma trix star volume and thickness, interstitial volume fraction and mean capillary diameter were significantly increased. The intra-individual variation among glomeruli expressed as coefficient of variation was 7. 4% vs 9% (basement membrane thickness) and 11.7% vs 25% (mesangial vol ume fraction) in the diabetic and the control group, respectively. Inc rement of basement membrane thickness and matrix volume fraction per y ear were significantly correlated with mean 1-year HbA1c (r = 0.55 and r = 0.51, respectively). We conclude that microalbuminuria in Type 1 diabetes is associated with increased basement membrane thickness and also mesangial matrix expansion. This increment seems to correlate wit h glycaemic control.