Moderate-intensity exercise training exerts a protective effect on glycaemia and exercise capacity in NOD mice

Exercise has been recommended as part of the management of Type 1 diabetes mellitus (T1DM) for a long time, yet the adequate therapeutic doses of exercise in this disease remains to be defined. Here, we hypothesize that the non-obese diabetic (NOD) mouse might provide a useful model for the study of exercise in T1DM. Experiments were designed to test whether moderate-intensity exercise training could protect from deterioration of glycaemic profile seen in the progression of T1DM, maintaining a preserved exercise capacity and performance. 8 NOD mice (female, 12-wk old) underwent a 12-week training (30’ running at 12 m/min per day) interleaved by submaximal exercise test performed at week 0, 2 and 12. Control animals were rested during the training period. Fed plasma glucose was monitored every two weeks. Mice were accustomed on the treadmill 1 day apart the submaximal incremental test (protocol by Calvo et al. 2008). After 2 weeks of training, exercising-mice increased significantly maximal oxygen uptake (95±5.7 vs 69±1.9 ml/Kg0.75/min; P<.01, mean and SD), work (17.4±1.7 vs 10.2±1.7 m Kg; P<.01), maximal speed (48.5±3 vs 38±2.3 m/min; P<.01), run time (1424±116 vs 960±97 sec; P<.01), distance (751±94 vs 416±61 m; P<.01), compared with non-running mice. Upon completion of the training program, all the aforementioned muscular performance indicators were not improved with respect to the pre-training values, but they were higher than the non-running controls’. A significant glucose-lowering effect was registered after 6 weeks of training (17.45±1.21 vs 7.62±1.38 mmol/l, P<.05). Yet, after 12 weeks, plasma glucose was lower, even though not significantly, in the exercising animals compared to controls (26.07±0.66 vs 28.78±0.49 mmol/l, P=.07). Moreover, in the exercising group, not all animals resulted to be diabetic (2 out of 8) at the end of the training period. According to these preliminary indications, moderate-intensity exercise preserves functional and metabolic capacity from disease-induced deterioration and, ultimately, may be favourably intervening in the mechanisms involved in T1DM progression.