Treadmill exercise training fails to reverse defects in glucose, insulin and muscle GLUT4 content in the db/db mouse...

Regular exercise is recommended for the treatment of type 2 diabetes because of the benefits on body weight and glycemic control. The present study was designed to compare the impact of voluntary wheel and forced treadmill running on the metabolic state in the db/db mouse model of type 2 diabetes. Our hypothesis is that voluntary exercise training reduces body weight, blood glucose and insulin levels and restores GLUT4 levels in skeletal muscle, whereas forced exercise training produces a greater effect.

Male diabetic db/db mice were assigned to sedentary (DS), voluntary wheel running (DV), and forced treadmill running (DT) groups for 12 weeks. Nondiabetic heterozygote littermates served as control (CN).

Over the 12-week period, DV and DT mice ran a total of 4.24+/-0.18km and 11.8km, respectively. At week 12, fasting plasma glucose was decreased in DV mice compared to DS mice and occurred in the absence weight loss. In DT mice, body weight and fasting plasma glucose were not improved with exercise when compared to DS mice and were actually higher compared to DV mice. After training, fasting plasma insulin was increased in DS mice compared to CN mice and training failed to normalize plasma insulin levels. Gastrocnemius GLUT4 content was reduced in DS mice compared to CN mice and training had no effect in preventing this depression from occurring.

The results of this study indicate that while voluntary exercise improved only blood glucose, forced treadmill exercise training failed to restore body weight, blood glucose and insulin, and muscle GLUT4 content.