Urinary corticosterone and normetanephrine levels after voluntary wheel and forced treadmill running in the db/db mouse

Exercise is recommended for the treatment of type 2 diabetes because of its benefits on body weight and glycemic control. Our recent work using the db/db mouse, a model that mimics the phenotype of type 2 diabetes, demonstrated that forced treadmill training exerted detrimental effects on obesity, hyperglycemia and insulin resistance. We investigated whether this response is explained by increased corticosterone and norepinephrine secretion, measured as urinary byproducts, since these hormones are known to alter glucose homeostasis. Male db/db mice and lean littermates serving as controls, were assigned to sedentary, voluntary wheel, and forced treadmill training groups for a period of 5 weeks. After 5 weeks of treadmill running, db/db mice remained hyperglycemic compared to sedentary db/db mice and were hyperinsulinemic compared to db/db voluntary runners. Urine glucose and corticosterone levels were also highest in db/db treadmill runners compared to all groups. Urine normetanephrine levels, although lower in db/db mice compared to control mice, were increased after treadmill running. Our results indicate that treadmill running leads to perturbations in plasma levels of hormones associated with glucose homeostasis. A greater stress response may be invoked by treadmill training, worsening glycemic control in this model of type 2 diabetes.