Glomerular structure and function in proteinuric Type 2 (non-insulin-dependent) diabetic patients

Glomerular ultrastructure was examined in a series of 20 Type 2 (non-insulin-dependent) diabetic patients with proteinuria. Reference was made to data previously obtained in non-diabetic kidney donors and in Type 1 (insulin-dependent) diabetic patients with similar degrees of proteinuria. The Type 2 diabetic patients demonstrated the changes which characterize the diabetic glomerulopathy seen in Type 1 diabetic patients: basement membrane thickening, and increase in the mesangium and mesangial matrix expressed as fraction of the glomerular volume. Among the Type 2 diabetic patients there was more variation than among the Type 1 diabetic patients, as this group included subjects with normal parameters. The group means and coefficients of variation (= SD/mean) of the glomerulopathy parameters combined in the glomerulopathy index = basement membrane thickness/10+ Vv(matrix/glom).100 were 81 (0.30) and 92 (0.15) in the two diabetic groups, clearly different from the non-diabetic index, 42 (0.16). All Type 2 diabetic patients who also had retinopathy had a glomerulopathy index above the normal range. Similar changes in glomerular composition were seen in the two diabetic groups: with increasing glomerulopathy the volume of matrix dominated over the peripheral basement membrane, and a shift in the ratio of interfaces was seen: mesangial surface towards capillary lumen increased relative to the urinary surface, and peripheral capillary surface comprised less of the total capillary surface. Data indicated marked glomerular hypertrophy, which correlated with the mesangial volume fraction, thus encompassing preserved filtration surface per glomerulus.