Intermittent clinical proteinuria and renal function in diabetes: evolution and the effect of glycaemic control.

The evolution of renal disease was studied in 12 insulin dependent diabetics selected for intermittent clinical proteinuria. After a run in period during which patients were studied three monthly for at least 12 months members of pairs of patients matched for age and duration of diabetes were allocated either to receive continuous subcutaneous insulin infusion or to continue with their usual conventional insulin injection therapy (controls) and studied three monthly for a further year. Mean (SEM) plasma glucose concentration and glycosylated haemoglobin (HbA1) value improved significantly in the insulin infusion group (glucose 10.1 (1.0) v 5.3 (0.3) mmol/l (182 (18) v 95 (5) mg/100 ml); HbA1 9.6 (0.8) v 7.6 (0.5)%; p less than 0.001 and p less than 0.005, run in v experimental periods) but not in the control group. Blood pressure was kept normal throughout. Glomerular filtration rate fell significantly in the insulin infusion and control groups throughout the study, from mean (SEM) baseline values of 114 (16) and 119 (15) ml/min/1.73 m2 to final values of 92 (15) and 95 (13) ml/min/1.73 m2 respectively (p less than 0.05 and p less than 0.01). The mean rate of decline in glomerular filtration rate did not change significantly in either group (run in v experimental periods: insulin infusion group 1.0 v 0.8 ml/min/month; controls 0.8 v 0.9 ml/min/month). Mean (SEM) plasma creatinine concentration rose slightly in the insulin infusion group only (93 (5) to 109 (11) mumol/l (1.1 (0.06) to 1.2 (0.1) mg/100 ml), 0.1 greater than p greater than 0.05; controls 94 (6) to 96 (6) mumol/l (1.1 (0.07) and 1.1 (0.07) mg/100 ml]. The urinary excretion rate of albumin varied widely and unpredictably throughout, while beta 2 microglobulin excretion remained normal and unchanged in both groups. Thus a at the stage of intermittent clinical proteinuria when albumin excretion rate is unpredictably variable (breaking through the "clinically positive" threshold only episodically) renal function, though still in the "normal" range, is already declining progressively; and the study failed to show that sustained improvement in mean glycaemia exerts a significant effect on this early deterioration of renal function.