Weight supported quadrupedal treadmill exercise improves insulin sensitivity in a rat model of spinal cord injury and diabetes

Abstract

Previous studies have shown exercise is a simple and economical therapeutic modality that effectively benefits patients with type 2 diabetes. Spinal cord injured (SCI) individuals have a high risk for developing type 2 diabetes. However, there have been no studies that have examined the effects of treadmill exercise in individuals with SCI and type 2 diabetes. We examined the effects of imposing quadrupedal body weight supported treadmill exercise in a rodent model of SCI and type 2 diabetes. Seventeen rats received a severe spinal cord contusion (T10). One day after the contusion, the rats were placed on a high energy diet (10% fat, 20% sucrose, and 70% rodent chow) and 40 days later, a low dose of streptozotocin (STZ; 30 mg/kg, i.p.) was administered. The rats were assigned to an exercise (n=8) or non‐exercise group (n=9). Exercise consisted of weight supported, quadrupedal treadmill walking (23 cm/s) for 1 hr/day, 5 days/week for 6 weeks. Insulin tolerance tests were performed, hemodynamic measurements were recorded, and heart and hindlimb muscle tissue was harvested after the rats were killed. Based on fasting blood glucose, the high energy diet and STZ treatment was successful in inducing diabetes in the rats (i.e. >140 mg/dL; exercise: 202±50 mg/dL; non‐exercise: 146±29 mg/dL). Fasting blood glucose levels were not significantly different between the groups. However, insulin sensitivity was improved by exercise based on insulin tolerance test. We found significant differences in glucose levels 45 and 60 min after insulin injection indicating a greater insulin sensitivity in the exercised group. Exercise also significantly increased tibialis anterior, gastrocnemius and soleus muscle weights by 7%, 20%, 31% respectively indicating the exercise was effective in activating hindlimb activity in the SCI rats. These findings suggest for the first time that weight supported treadmill exercise can reduce metabolic abnormalities that occur after SCI.Support or Funding InformationNIH grant R15NS082711 to R. de Leon