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

Abstract

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 (AThigh) 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 AThigh results in larger cardioprotection from an ischemia-reperfusion (I-R) injury than IIT and (2) to establish if the integration of RT with AThigh (ART) results in similar cardioprotection as AThigh. Diabetic (D) male Sprague-Dawley rats were divided into D-IIT (n = 12), D-CIT (n = 12), D-AThigh (n = 8), D-RT (n = 8), and D-ART (n = 8). T1DM was induced with streptozotocin, and blood glucose was adjusted with insulin. D-AThigh occurred on a treadmill (27 m/min; 1 hr), D-RT performed weighted ladder climbs, and D-ART alternated daily between AThigh and RT. Exercise occurred 5 days/wk for 12 wks. This investigation demonstrates that cardioprotection following an I-R injury was similar between D-AThigh and D-IIT. This cardioprotection is not exercise-specific, and each provides unique advantages. D-AThigh 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.

Influence of exercise training on diabetic kidney disease: A brief physiological approach

“…111 In agreement with these findings, the resistance exercise also attenuated the risk of exercise-induced hypoglycemia in rats with T1DM. 112…”

Sexual dimorphism in response to repetitive bouts of acute aerobic exercise in rodents with type 1 diabetes mellitus

“…While both T1DM and non-T1DM females demonstrated significantly higher β-oxidation activity in skeletal muscle immediately after exercise compared to males; we found no differences between the sexes in glycogen content in these tissues (Fig 4). The only significant factor in liver glycogen content was diabetes, which was to be expected in males based on previous literature from our laboratory [26,32,39]. The absence of a glycogen sparing effect in females contrasts with data showing lower glycogen usage in healthy exercising women in the LP [15] due to the higher E2 levels.…”

“…Successive days of exercise have demonstrated to produce a marked reduction and utilization of muscle glycogen content [40]. Indeed, muscle glycogen content on day 4 post-exercise ranged from approximately 0.25-0.64 g/100g which is substantially lower than previously reported muscle glycogen content post-exercise [26,39]. Moreover, post-exercise muscle glycogen stores can take greater than 24 hours for complete restoration to near preexercise levels [41].…”

An Exercise Mimetic Approach to Reduce Poststroke Deconditioning and Enhance Stroke Recovery

“…Aerobic exercise was conducted on a motorized treadmill for 45 minutes at 70% to 80% of each rat's peak oxygen consumption (VO 2 peak; measured 10 days and 4 weeks poststroke), in accordance with physical activity and exercise recommendations for stroke survivors. 25 For resistance exercise (see Supplemental Material for detailed protocol 26,27 ), rats climbed a vertical ladder with 50%, 75%, 90%, and 100% of their maximal lifting capacity for the first 4 climbs, followed by 100% of their maximal lifting capacity until exhaustion (~8-12 climbs).…”