An Acceptable Exercise Test to Study Microalbuminuria in Type 1 Diabetes

Abstract

A modified test for studying the response of urinary albumin excretion (UAV) to exercise in diabetic patients is described. It is designed to produce a standardized increase in pulse rate (by 90-110%) rather than a standardized workload. Thirty-three normotensive Type 1 diabetic patients with normal pre-exercise UAV (less than 10 micrograms min-1) on the day of the test were compared with 25 non-diabetic subjects matched for age and sex. The patients developed a significantly greater increase in the median UAV (p less than 0.05) and systolic blood pressure (p less than 0.01) during exercise, despite the use of lower workloads (p less than 0.05). During exercise, the albumin excretion in the patients was not related to their heart rate, blood pressure, workload or fall in blood glucose; nor was it related to duration of diabetes, glycosylated haemoglobin or insulin dose. An exercise UAV greater than 15 micrograms min-1 was found in 10 of the 33 patients; it was significantly correlated (p less than 0.01) with the frequency of previous overnight microalbuminuria (greater than 10 micrograms min-1), and was associated with a greater progression of microalbuminuria (p less than 0.05) over a mean period of 24 months. Retinol-binding protein excretion rate was also measured as an indicator of proximal tubular function and did not increase in either group.