Exercise-induced oxidative stress and antioxidant enzyme activity in type 2 diabetic patients with and without diastolic dysfunction and hypertension

INTRODUCTION: Antioxidant systems are important factors affecting the oxidation of lipoproteins and thereby the progression of atherosclerotic disease. It has been suggested that physical activity might maintain and promote the antioxidant defence capacity against the oxidative stress. Left ventricular dysfunction (LVDD) and hypertension are more common in subjects with diabetes mellitus (DM) type 2.

OBJECTIVE: To evaluate the oxidative stress in patients with DM type 2, particularly with LVDD and hypertension and to determine the influence of acute exercise training on the investigated parameters.

METHODS: To assess the oxidative stress of patients, we determined the following antioxidative parameters: triglycerides (TG), total cholesterol, low density cholesterol, OxLDL cholesterol, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), plasminogen activator-type 1 (PAI-1) which were measured at rest and immediately after the acute bout of the cardiopulmonary exercise cycle ergometer test.

RESULTS: In basal conditions, diabetic patients had a significant increase of TG (3.12 +/- 1.09 vs 1.74 +/- 0.9 mmol/l; p < 0.01), OxLDL cholesterol (84.73 +/- 16.9 vs 79.00 +/- 29.26 mmol/l; p < 0.05) and SOD enzyme activity (913.38 +/- 120.36 vs 877.14 +/- 153.18; p < 0.05) compared to controls. During the acute exercise test, there were significantly greater levels of OxLDL (84.73 +/- 16.90 vs 92.33 +/- 23.29 mmol/l; p < 0.05) in study patients. SOD significantly increased in both groups during exercise, in diabetic patients (913.38 +/- 120.36 vs 921.50 +/- 130.03 U/g Hb; p < 0.05) and in controls (877.14 +/- 153.18 vs 895.00 +/- 193.49 U/g Hb; p < 0.05). GSH-Px significantly increased only in diabetic patients after acute exercise (45.04 +/- 11.19 vs 51.81 +/- 15.07 U/g Hb; p < 0.01), but not in controls. PAI significantly decreased during the exercise test only in healthy subjects (2.60 +/- 0.35 vs 2.22 +/- 0.65; p < 0.05). Type 2 diabetic patients with cardiovascular complications (LVDD and hypertension) had a significant increase of GSH-Px activity (47.10 +/- 7.37 vs 54.52 +/- 11.97 U/g Hb; p < 0.01).

CONCLUSION: Elevated enzyme levels are associated with exercise in type 2 diabetic patients. We suggest that it could be a compensatory mechanism to prevent free radical tissue damage. We hypothesize that a physical training programme induces the enhancement of muscular and liver antioxidant enzymes and reduces the oxidative stress.