Predictors of renal morphological changes in the early stage of microalbuminuria in adolescents with IDDM.

OBJECTIVE

To evaluate the impact of glycemic control, blood pressure, lipid levels, glomerular filtration rate (GFR), age, and duration of IDDM on the degree of structural glomerular changes in the transitional stage of microalbuminuria.

RESEARCH DESIGN AND METHODS

Fifteen adolescents (seven boys and eight girls) with > 5 years of duration of IDDM and with low-grade microalbuminuria (15-30 micrograms/min) participated. Seventeen living kidney donors served as healthy control subjects. Five-year mean HbA1c; 5-year mean systolic and diastolic blood pressure; GFR, cholesterol, and triglycerides 2-5 years before renal biopsy; age; and duration of IDDM were investigated and related to basement membrane thickness (BMT), mesangial and matrix volume fractions, and the overall glomerulopathy index [(BMT/10 + mat/glom, %) + matrix star volume].

RESULTS

BMT and the overall diabetic glomerulopathy were increased in diabetic patients as compared with control subjects (P < 0.001), whereas matrix volume fraction, but not mesangial volume fraction, tended to be increased (P = 0.11). In multivariate analysis, BMT was predicted by 5-year mean HbA1c, diabetes duration, and previous GFR (R2 = 0.71, P = 0.003). With matrix volume fraction as the dependent variable, BMT and diabetes duration were the only significant determinants (R2 = 0.63, P = 0.003). Diabetes duration, 5-year mean HbA1c, and GFR were the variables with an independent influence on the overall diabetic glomerulopathy index (R2 = 0.72, P = 0.003). Preceding blood pressure and lipid levels or age had no significant independent influence on these morphometric measures.

CONCLUSIONS

In the very early stage of microalbuminuria in IDDM adolescents, a high percentage of the variation in BMT and overall severity of glomerulopathy is explained by prolonged hyperglycemia and diabetes duration. Previous glomerular hyperfiltration may also add to the prediction of these morphological changes.