Combined treadmill running and insulin therapy favors the stabilization of glycemic metabolic parameters and avoids increased achilles tendon rigidity in diabetic rats

Abstract

Background. Hyperglycemia reduces tendon homeostasis. Effects of physical exercise on diabetic rats have been widely studied; however, the effects of a combined physical and insulin therapy on biomechanical properties of the Achilles tendon (AT) remain unclear. Therefore, the objective of this study was to evaluate the effects of the combi-nation of moderate-intensity exercise on a treadmill and insulin therapy on metabo-lism, physical conditioning, and biomechanics of AT in diabetic rats. Methods. Forty-eight Wistar rats were divided into six groups: Sedentary Control-SCG, Treadmill Control-TCG, Sedentary Diabetic-SDG, Sedentary Insulin Diabet-ic-SIDG, Treadmill Diabetic-TDG, and Treadmill Insulin Diabetic-TIDG. Diabetic animals were induced with streptozotocin diluted in sodium citrate buffer (50 mg/Kg; 10 mM; pH 4.5; intraperitoneally). All groups were subjected to the maximal effort test for pre (MET1) and post (MET2) maximal speed determination. The exercise protocol was administered for 5 weeks (1 h/day, 5 days/week). Blood glucose levels and biomechanical properties of AT (e.g., traction) were evaluated. Results. Increased glycemia was observed in SDG (p<0.001; p=0.003), SIDG (p=0.009; p=0.037), and TDG (p=0.002; p=0.009); however, compared with SCG and TCG, TIDG showed no significant differences. Maximal force was reduced in TIDG (p=0.009) and SIDG (p = 0.002) and increased in SCG and TDG compared with in SIDG (p=0.024). The elastic modulus was reduced in TCG compared with in SCG (p = 0.011) and increased in SDG (p<0.001), SIDG (p=0.019), and TDG (p=0.006) compared with in TCG. Conclusions. The combined physical exercise and insulin therapy favors the stabilization of glycemic metabolic parameters and avoids increased tendon rigidity in diabetic rats.