Attenuated insulin action on glucose uptake and transport in muscle following resistance exercise in rats

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Abstract
A previous study reported elevations of insulin-mediated muscle protein synthesis following four days of resistance exercise in rats (Fluckey et al. 1996. Am J Physiol270, E313–E319). The purpose of this study was to determine if insulin-stimulated muscle glucose uptake (a–v diff.) and 2-deoxyglucose (2-DG) transport were altered under similar conditions. The protocol consisted of squat-like exercises during four sessions with progressively increased weight (70–190 g). Each session consisted of 50 repetitions and sessions were separated by 48 h. Sixteen hours after the last exercise session, basal glucose uptake in perfused hindlimbs was not different (P > 0.05) between exercised (n=6) and non-exercised controls (n=6). However, there was a significant (P < 0.05) attenuation of insulin-stimulated (20 000 μU mL–1) glucose uptake in exercised vs. non-exercised rats (491 ± 31 vs. 664 ± 58 μmol glucose–1 g–1 [15-min insulin period]–1, respectively). Following resistance exercise, insulin-stimulated 2-DG transport, measured during the last 10 min of the perfusion period, was significantly reduced (P < 0.05) in the soleus, white gastrocnemius and extensor digitorum longus muscles. Additionally, GLUT-4 glucose transporter protein content was significantly reduced (P < 0.05) in white gastrocnemius and extensor digitorum longus muscles. These results demonstrate that insulin-stimulated glucose uptake and transport are reduced after resistance exercise. Furthermore, the applied resistance exercise protocol causes directionally opposite changes of insulin action in two major metabolic pathways, i.e. glucose transport and protein synthesis.