The effect of metabolic near-normalization, induced by continuous subcutaneous insulin infusion, on the exaggerated microalbuminuria of exercise was studied in eight insulin-dependent diabetic men selected for normal resting albuminuria. Patients were studied in randomized order during the ordinary glycemic control of conventional insulin treatment (CIT) and after 3 wk of “super-control” with continuous subcutaneous insulin infusion (CSII). Seven age-matched healthy men were used as controls. In the diabetics the albuminuric response to fixed-load bicycle exercise (600 kpm/min for 20 min) during CIT greatly exceeded that of the normal controls (P < 0.01). After 3 wk of optimal plasma glucose control, urinary albumin excretion rates in response to the same exercise load were significantly reduced (P < 0.02) in the diabetics and became statistically indistinguishable from that of the normal controls. The urinary excretion rate of β2-microglobulin, an index of tubular function, was not increased significantly by exercise either during CIT or CSII.
The plasma glucose fall after exercise was greater (P < 0.001) on CIT (8.5 ± 0.9 mmol/L) than on CSII (4.0 ± 0.6 mmol/L). The pulse rate acceleration in response to exercise was significantly reduced after 3 wk of CSII (P < 0.05). The exercise-induced systolic blood pressure rise was similar in controls and diabetics on both therapeutic regimens.
Thus, a period of metabolic near-normalization in the diabetic corrects the abnormal transglomerular passage of albumin induced by moderately strenuous muscular exercise and reduces the exercise tachycardia. Improved control with CSII appears to reduce greatly the risk of exercise-induced hypoglycemia, despite much tighter glycemic control.