Muscle capillary basement-membrane thickness and long-term glycemia in type I diabetes mellitus.

We explored the relation between the thickness of the quadriceps-muscle capillary basement membrane and the glycemia level in 102 young patients with Type I diabetes (median age, 17 years; range, 12 to 29). Membrane thickness was measured in serial biopsy specimens obtained after two consecutive 2 1/2-year observation periods, and glycemia was assessed in terms of glycosylated hemoglobin and fasting blood glucose levels determined at eight-week intervals. An association between membrane thickness and glycemia level was apparent in both cross-sectional and longitudinal analysis. Cross-sectional analysis of data on 39 postpubertal patients (growth less than 1.0 cm during the five years) showed a positive association of membrane thickness to glycosylated hemoglobin (r = 0.53, P = 0.0002) and blood glucose values (r = 0.37, P = 0.01) averaged over the antecedent 2 1/2-year period. By contrast, in 32 pubertal patients (growth greater than 7.5 cm) there was a significant negative association of membrane thickness to both glycosylated hemoglobin (r = -0.40, P = 0.01) and blood glucose (r = -0.42, P = 0.009). In longitudinal analysis, there was no correlation between changes in membrane thickness and average glycemia levels during the two follow-up periods in 32 pubertal patients (for glycosylated hemoglobin, r = 0.11; P = 0.25), but in the postpubertal group (n = 20) there was a significant positive covariation (r = 0.57, P = 0.0004). The data indicate that in postpubertal diabetic patients, the thickness of the muscle capillary basement membrane is positively related to the level of glycemia, but this relation does not obtain in the pubertal state.