Muscle NT-3 levels increased by exercise training contribute to the improvement in caudal nerve conduction velocity in diabetic rats

The aim of the present study was to explore the role of exercise in diabetic peripheral neuropathy (DPN) and the mechanisms involved. For this purpose, 31 male Sprague-Dawley rats were used. The rats were assigned to 5 groups: diabetic rats subjected to exercise training (swimming) for 8 weeks (D-Ex1 group), diabetic rats subjected to exercise training for 4 weeks after 4 weeks of being sedentary (D-Ex2 group), diabetic rats which remained sedentary for 8 weeks (D-Sed group), control rats subjected to exercise training for 8 weeks (C-Ex1 group) and control rats which remained sedentary for 8 weeks (C-Sed group). Blood glucose levels and caudal nerve conduction velocity (NCV) were evaluated at 0 (baseline), 28 (4 weeks) and 56 days (8 weeks) after the induction of diabetes. The levels of neurotrophin-3 (NT-3) in skeletal muscle were measured by ELISA at the end of the experiment. Blood glucose levels in the D-Ex1 group rats decreased significantly after 8 weeks of exercise. The caudal NCV markedly decreased in all diabetic rats and significantly increased after 4 or 8 weeks of exercise training. Muscle NT-3 levels were significantly lower in the D-Sed compared to the 4 other groups. Muscle NT-3 levels positively correlated with caudal NCV. In conclusion, swimming training has a beneficial effect on DPN and muscle NT-3 levels, which could help improve caudal NCV in streptozotocin-induced diabetic rats.