Exercise Training Induced Cardioprotection with Moderate Hyperglycemia versus Sedentary Intensive Glycemic Control in Type 1 Diabetic Rats

Intensive insulin therapy (IIT; 4–7 mmol/L) is the preferred treatment for type 1 diabetes mellitus (T1DM) patients to reduce the risk of cardiovascular disease (CVD). However, this treatment strategy has been questioned as it is accompanied with a sedentary lifestyle leading to weight gain and insulin resistance. T1DM patients who partake in high-intensity aerobic training (AT(high)) to reduce CVD often utilize conventional insulin therapy (CIT; 9–15 mmol/L) to offset the risk of hypoglycemia. Moreover, exercise modalities incorporating resistance training (RT) have been shown to further reduce this risk. The purpose of this investigation was twofold: (1) to determine if CIT paired with AT(high) results in larger cardioprotection from an ischemia-reperfusion (I-R) injury than IIT and (2) to establish if the integration of RT with AT(high) (ART) results in similar cardioprotection as AT(high). Diabetic (D) male Sprague-Dawley rats were divided into D-IIT (n = 12), D-CIT (n = 12), D-AT(high) (n = 8), D-RT (n = 8), and D-ART (n = 8). T1DM was induced with streptozotocin, and blood glucose was adjusted with insulin. D-AT(high) occurred on a treadmill (27 m/min; 1 hr), D-RT performed weighted ladder climbs, and D-ART alternated daily between AT(high) and RT. Exercise occurred 5 days/wk for 12 wks. This investigation demonstrates that cardioprotection following an I-R injury was similar between D-AT(high) and D-IIT. This cardioprotection is not exercise-specific, and each provides unique advantages. D-AT(high) leads to improved glycemia while insulin sensitivity was enhanced following resistance exercises. Thus, exercise is an effective means to elicit cardioprotection in T1DM. However, in addition to glycemia, other factors should be considered when tailoring an exercise program for T1DM patients.