The effect of a heavy exercise program on the distribution of pancreatic hormones in the streptozotocin-induced diabetic rat

Context: Exercise training has long been utilized as an adjunct to pharmacotherapy in the management of diabetes. Objectives: The effects of a heavy exercise training program on the distribution of insulin, glucagon, somatostatin and pancreatic polypeptide in pancreatic islet cells of diabetic rats was investigated. Animals: Forty male Wistar rats. Design: The animals were divided into 4 groups: control sedentary, diabetic sedentary, control heavy exercise, and diabetic heavy exercise. Intervention: Diabetes was induced with a single injection of streptozotocin (60 mg/kg i.p.). The exercise program included five 60-min sessions per week, speed 18 m/min with a running belt at a 5% incline and began 1 week after the streptozotocin treatment and continued for 12 weeks. Main outcome measure: Immunohistochemistry was used to label insulin, glucagon, somatostatin and pancreatic polypeptide in islet cells. Results: The percentage of insulin-positive cells was significantly lower in islets from diabetic rats (24.2±2.3%) as compared to the controls (87.5±2.0%). The percentage of glucagon-positive cells was significantly higher in islets from diabetic rats (44.0±1.7%) as compared to the controls (34.7±2.1%). The percentage of pancreatic polypeptide-positive cells was also significantly higher in islets from diabetic rats (20.8±1.6%) as compared to the controls (12.7±1.8%). The percentage of somatostatin-positive cells was not significantly altered in islets from diabetic rats (28.2±2.0%) as compared to the controls (21.9±2.7%). Heavy exercise did not significantly alter insulin, glucagon, pancreatic peptide or somatostatin labeling in either diabetic or control rats. Conclusions: Alterations in the distribution of pancreatic hormones in streptozotocin-induced diabetic rats, a model of type 1 diabetes, are not improved with heavy exercise.