The glucoregulatory response to high-intensity aerobic exercise following training in rats with insulin-treated type 1 diabetes mellitus

© 2016, National Research Council of Canada. All rights reserved. An acute bout of exercise elicits a rapid, potentially deleterious, reduction in blood glucose in patients with type 1 diabetes mellitus (T1DM). In the current study, we examined whether a 10-week aerobic training program could alleviate the rapid exercise-associated reduction in blood glucose through changes in the glucoregulatory hormonal response or increased hepatic glycogen storage in an insulin-treated rat model of T1DM. Thirty-two male Sprague-Dawley rats were divided evenly into 4 groups: non-T1DM sedentary (C) (n = 8), non-T1DM exercised (CX) (n = 8), T1DM sedentary (D) (n = 8), and T1DM exercised (DX) (n = 8). Exercise training consisted of treadmill running for 5 days/week (1 h, 27 m/min, 6% grade) for 10 weeks. T1DM was induced by multiple streptozotocin injections (20 mg/kg) followed by implantation of subcutaneous insulin pellets. At week 1, an acute exercise bout led to a significant reduction in blood glucose in DX (p \u3c 0.05), whereas CX exhibited an increase in blood glucose (p \u3c 0.05). During acute exercise, serum epinephrine was increased in both DX and CX (p \u3c 0.05), whereas serum glucagon was increased during recovery only in CX (p \u3c 0.01). Following aerobic training in DX, the exercise-mediated reduction in blood glucose remained; however, serum glucagon increased to the same extent as in CX (p \u3c 0.05). DX exhibited significantly less hepatic glycogen (p \u3c 0.001) despite elevations in glycogenic proteins in the liver (p \u3c 0.05). Elevated serum epinephrine and decreased hepatic adrenergic receptor expression were also evident in DX (p \u3c 0.05). In summary, despite aerobic training in DX, abrupt blood glucose reductions and hepatic glycogen deficiencies were evident. These data suggest that sympathetic overactivity may contribute to deficiencies in hepatic glycogen storage