Resistance training enhances components of the insulin signaling cascade in normal and high-fat-fed rodent skeletal muscle

Abstract

Our laboratory recently reported that chronic resistance training (RT) improved insulin-stimulated glucose transport in normal rodent skeletal muscle, owing, in part, to increased GLUT-4 protein concentration (Yaspelkis BB III, Singh MK, Trevino B, Krisan AD, and Collins DE. Acta Physiol Scand 175: 315-323, 2002). However, it remained to be determined whether these improvements resulted from alterations in the insulin signaling cascade as well. In addition, the possibility existed that RT might improve skeletal muscle insulin resistance. Thirty-two male Sprague-Dawley rats were assigned to four groups: control diet (Con)-sedentary (Sed); Con-RT; high-fat diet (HF)-Sed; and HF-RT. Animals consumed their respective diets for 9 wk; then RT animals performed 12 wk of training (3 sets, 10 repetitions at 75% one-repetition maximum, 3x/wk). Animals remained on their dietary treatments over the 12-wk period. After the training period, animals were subjected to hindlimb perfusions. Insulin-stimulated insulin receptor substrate-1-associated phosphatidylinositol-3 kinase activity was enhanced in the red gastrocnemius and quadriceps of Con-RT and HF-RT animals. Atypical PKC-zeta/lambda and Akt activities were reduced in HF-Sed and normalized in HF-RT animals. Resistance training increased GLUT-4 protein concentration in red gastrocnemius and quadriceps of Con-RT and HF-RT animals. No differences were observed in total protein concentrations of insulin receptor substrate-1, Akt, atypical PKC-zeta/lambda, or phosphorylation of Akt. Collectively, these findings suggest that resistance training increases insulin-stimulated carbohydrate metabolism in normal skeletal muscle and reverses high-fat diet-induced skeletal muscle insulin resistance by altering components of both the insulin signaling cascade and glucose transporter effector system.

Effects of Endurance Exercise Training on Insulin Signaling in Human Skeletal Muscle

“…8). This reduction could not be attributed to changes in protein content of either IRS-1 or the p85 regulatory subunit of PI3-K and seems to be contradictory to the finding of improved PI3-K signaling after training in rodent muscle (13,14,40,41). However, the existing data in human skeletal muscle are not equivocal.…”

The Molecular Bases of Training Adaptation

“…Moreover, in vivo contraction after running and resistance training in rodents has also produced conflicting findings where AKT has been reported to increase (Bolster et al 2003b;Sakamoto et al 2003;Reynolds et al 2004) or remain unchanged Nader and Esser 2001;Krisan et al 2004;Eliasson et al 2006;Williamson et al 2006b) in response to exercise (Table 1.2). Notably, Bolster et al (2004) and Thorell and coworkers (1999) has shown that moderate duration (30-60 min) low-(~70% VO 2max ) and highintensity (~125% VO 2max ) cycling exercise is sufficient to increase AKT phosphorylation in humans.…”

“…Given the proposed role for AKT in compensatory hypertrophy (Bodine et al 2001b;Lai et al 2004) the original hypothesis was that a cumulative increase in the phosphorylation of AKT ser473 would occur following high-frequency resistance training. Nevertheless, AKT activity has previously been shown to both increase (Nader and Esser 2001;Bolster et al 2003b;Sakamoto et al 2004a;Creer et al 2005) or remain unchanged (Widegren et al 1998;Krisan et al 2004) in response to a variety of contractile stimuli. There are a number of possible explanations for the dephosphorylation of AKT in response to stacked resistance training bouts.…”

mTOR signaling response to resistance exercise is altered by chronic resistance training and detraining in skeletal muscle

“…Similarly, the rat squat training model has also been used as an animal resistance exercise model, which results in increased anabolic signaling activity (4,11,25). However, a previous study using this model reported that p70S6K phosphorylation was elevated for up to 12 h after exercise but returned to preexercise levels by 24 h after exercise (7,11,21), and it has not been reported to alter muscle weight as a result of repeated bouts of exercise, probably because insufficient exercise load or volume was added to muscle (14,24). In contrast, certain signaling proteins show relatively prolonged changes in their activated or elevated phosphorylation state during a recovery period (27,32,34), and in agreement with these data, we observed elevated phosphorylation of p70S6K, p90RSK, and rpS6 24 h after the initial training session.…”