Effect of Insulin Pump Treatment for One Year on Renal Function and Retinal Morphology in Patients with IDDM

The effect of strict metabolic control for 1 yr on renal function and retinal morphology was estimated in 24 insulin-dependent diabetic individuals (age 29 ± 8 yr, diabetes duration 10 ± 6 yr) with Albustix negative urine and minimal or no background retinopathy before the study. They were randomized to conventional insulin treatment (CIT) or continuous subcutaneous insulin infusion (CSII) with a portable pump. During CSII treatment the metabolic status was significantly improved and glomerular filtration rates (GFR) were found to decline (from 130 ± 18 to 116 ± 15 ml/min/1.73 m², P < 0.01). The mean value of urinary albumin excretion (UAE) was not statistically significantly reduced (from 15.3 ± 24.1 to 6.8 ± 1.5 mg/24 h, P > 0.1). In the CIT group both GFR and UAE values were unchanged. In all subjects before treatment we found a positive correlation between the metabolic status, estimated by the HbA_1c values, and GFR as well as UAE values, respectively (r = 0.64, P < 0.01 and r = 0.42, P < 0.05). We conclude that elevated GFR values can be reduced toward normal level by insulin pump treatment for 1 yr. Retinal morphology was found to deteriorate in four of 12 CIT subjects and in three of 12 CSII subjects. However, the progression was mild and in most individuals only due to a slight increase in the number of microaneurysms. Pump treatment did not induce proliferation and “cotton-wool” exudates were not detectable in any pump subject after 1 yr of treatment. We conclude that CSII treatment for 1 yr was unable to stop the progression of retinopathy in individuals with minimal or no retinopathy on entering the study. On the other hand, pump treatment did not induce cotton-wool exudates or proliferation in these subjects as previously reported in subjects with more severe retinopathy before CSII treatment.