Electronic Thesis and Dissertation Repository


Doctor of Philosophy




Dr. Jamie Melling


Type 1 diabetes mellitus (T1DM) is associated with compromised glycemic control and a heightened risk for cardiovascular disease. The common treatment of T1DM with strict glycemic control through intensive insulin therapy can be problematic (weight gain, insulin resistance, hypoglycemia). Regular exercise is known to improve cardiovascular health, yet most individuals with T1DM remain sedentary, and identify the risk of exercise-induced hypoglycemia as a significant barrier. The investigation into the use of different forms of exercise (higher intensity, resistance) for preventing exercise-induced hypoglycemia in populations with T1DM has been promising, however, little work has investigated their cardiovascular benefit or whether the risk of exercise-induced hypoglycemia changes over the course of exercise training. As such, using a novel insulin-treated rat model of T1DM the objectives of this dissertation were: (1) to determine whether the risk of hypoglycemia in response to different exercise modalities changes over the course of training in T1DM, (2) to characterize which exercise modality provides the largest amount of cardiovascular protection (as determined by recovery from an ischemia-reperfusion injury and fine-wire vascular myography), while assessing risk for exercise-induced hypoglycemia, and (3) to explore whether exercise training, when paired with modest glycemic control, results in larger cardiovascular protection than stringent glycemic control alone. The main findings of these collective studies were as follows; (1) the magnitude of the abrupt decline in blood glucose in response to different exercise modalities remains consistent after exercise training and infrequently reaches hypoglycemic concentrations if blood glucose concentrations are elevated prior to exercise in T1DM rats, (2) both exercise-induced fluctuations in blood glucose and the amount of cardiovascular protection obtained from regular exercise training appears to be modality-specific; however, results suggest that high intensity aerobic exercise provides the largest amount of cardiovascular protection (increased recovery from ischemia-reperfusion injury, vascular insulin sensitivity, and glycemic control), and (3) maintaining more modest glycemic control may provide similar cardiovascular benefits as stricter glycemic control when combined with regular exercise. Overall, less of a reliance on strict glycemic could allow for exercise to be performed safely (and providing cardiovascular benefits), while preventing complications associated with intensive insulin therapy.