Time Course of In Vivo Insulin Sensitivity after a Single Bout of Exercise in Rats

Abstract

After a single bout of treadmill running (20 m·min ^-1 hour), the time course of the in vivo insulin sensitivity was determined in previously untrained rats. The glucose infusion rate (GIR, mg·kg^-1 · min˜^-1 as an index of insulin sensitivity was assessed by the euglycemic insulin clamp technique 1 (lh-post-Ex group), 3 (3h-post-Ex), 6 (6h-post-Ex) and 24 hours after exercise (24h-post-Ex), n = 8 in each group. GIRs increased with time from 5.72 ± 1.02 (lh-post-Ex), to 7.58 ± 1.07 (3h-post-Ex), 10.31 ± 1.52 (6h-post-Ex) and 10.23 ± 1.62 (24h-post-Ex) vs control (5.51 ± 0.63); the GIR in the 6h-post-Ex and the 24h-post-Ex were significantly higher than those in the control and the lh-post-Ex groups (p < 0.05). The rate of increase was equivalent to that observed after long-term training in our previous study. GIR of α-adrenergic blockade infused 1 hour after exercise (lh-post-Exα) significantly increased (8.32 ± 0.96) compared to the control and no exercise α-blocker-infused control (Cα) (p < 0.05). But no significant difference was shown between 1h-post-Ex and lh-post-Exα groups. In the ß-blocker-infused group, GIR did not show a significant increase. These results indicate that an increase in the in vivo insulin sensitivity after a single bout of exercise is not evident until 6 hours post-exercise. The delay in the sensitivity might partly be explained by the suppression caused by catecholamines via the α-mechanism.

Key words

insulin sensitivity - exercise - rat - adrenergic blockade