Effects of aerobic exercise on microalbuminuria and enzymuria in type 2 diabetic patients

Increased urinary albumin excretion is a strong predictor for the development of overt diabetic nephropathy and overall cardiovascular morbidity and mortality in patients with type 2 diabetes. In a previous study, regular aerobic physical activity in overweight/obese patients with type 2 diabetes mellitus was found to have significant beneficial effects on glycemic control, insulin resistance, cardiovascular risk factors, and oxidative stress. The aim of the present study was to investigate the effects of aerobic exercise in the same cohort of type 2 diabetic patients on urinary albumin excretion, serum levels and urinary excretion of enzymes, tubular damage, and metabolic control markers in type 2 diabetic patients. Changes from baseline to 3 and 6 months of aerobic exercise were assessed for urinary albumin excretion, serum activities, and urinary excretion of N-acetyl-beta-D-glucosaminidase (NAGA), plasma cell glycoprotein 1 (PC-1) and aminopeptidase N (APN), as well as their association with insulin resistance, cardiovascular risk factors, and oxidative stress parameters in 30 male type 2 diabetic patients (aged 54.8 +/- 7.3 years, with a mean BMI of 30.8 +/- 3.0 kg/m2). Microalbuminuria was found in six (20%) diabetic patients at baseline, three of them (10%) after three months, and only one patient (3.33%) at the end of the study period. A significant correlation was found for urinary albumin excretion at baseline both with sulfhydryl-groups and catalase, but not for urinary albumin excretion with MDA and glutathione. The prevalence of microalbuminuria tended to decrease after six months of aerobic exercise in type 2 diabetic patients, independently of any improvement in insulin resistance and oxidative stress parameters. Neither between-group nor within-group changes were found for urinary PC-1, APN, and NAGA activity. Serum NAGA was significantly increased (p < 0.05) over the control level in diabetic patients at baseline, but it decreased to the normal level after six months of exercise. This study has shown that a six-month aerobic exercise, without any change in the medication, tended to decrease microalbuminuria without changing enzymuria. However, further studies are needed not only to confirm those findings, but to elucidate potential mechanisms that would clarify the beneficial effects of exercise.