Exercise as a provocative test in early renal disease in Type 1 (insulin-dependent) diabetes: albuminuric, systemic and renal haemodynamic responses

Publisher Website
Google Scholar
Abstract
The value of exercise as a provocative test for early renal disease in Type 1 (insulin-dependent) diabetes was reevaluated. Three carefully characterized groups of males were studied: 10 non-diabetic controls, 16 diabetic patients (group 1) with normal urinary albumin excretion (< 15 μg/min) and 14 Albustix-negative diabetics (group 2) with increased urinary albumin excretion (15–122 μg/min). Assignment to a study group was made on the basis of three 24-h urine collections, and the groups were well matched for age, weight, height, and serum creatinine concentration. The two diabetic groups were similar with regard to duration of disease (13±6 versus 16±3 years), metabolic control (HbA1c: 8.4±1.4 versus 8.7±1.3%) and degree of diabetic complications (beat-to-beat variation and retinopathy). An exercise protocol of 450 and 600 kpm/min workloads was employed. In the resting state group 2 patients had elevated systolic blood pressure compared with the normal subjects (132±13 versus 119±9 mmHg), and their glomerular filtration rate was significantly reduced compared with group 1 (123±19 versus 138±15ml/min per 1.73m2, p < 0.05). During exercise the urinary albumin excretion rate increased significantly in all three groups (normal subjects: 6±0.7 to 8±1.3 (μg/min); group 1: 6±0.6 to 9±1 μg/min and group 2: 48±10 to 113±23 μg/min), the relative increase being higher in group 2 (p < 0.01). The changes in systemic haemodynamics were similar in all three groups in spite of a reduced maximum working capacity in group 2 (949±249 versus group 1:1163±200 and normal subjects 1267±264 kpm/min (p < 0.05). The renal haemodynamic changes were qualitatively similar for the three groups, but the filtration fraction during exercise increased in groups 1 and 2 to almost identical values and were significantly higher than in normal subjects (group 1 + group 2: 0.29±0.02 versus normal subjects: 0.26±0.03, p < 0.02). These findings suggest that an elevated transcapillary pressure gradient, as obtained during moderate exercise, will not cause an abnormal increase in albumin excretion per se. A functional glomerular lesion, already recognisable at rest (elevated albumin excretion) must also be present.