Differential effects of resistance and endurance exercise in the fed state on signalling molecule phosphorylation and protein synthesis in human muscle

Abstract

Resistance (RE) and endurance (EE) exercise stimulate mixed skeletal muscle protein synthesis. The phenotypes induced by RE (myofibrillar protein accretion) and EE (mitochondrial expansion) training must result from differential stimulation of myofibrillar and mitochondrial protein synthesis. We measured the synthetic rates of myofibrillar and mitochondrial proteins and the activation of signalling proteins (Akt-mTOR-p70S6K) at rest and after an acute bout of RE or EE in the untrained state and after 10 weeks of RE or EE training in young healthy men. While untrained, RE stimulated both myofibrillar and mitochondrial protein synthesis, 67% and 69% (P < 0.02), respectively. After training, only myofibrillar protein synthesis increased with RE (36%, P = 0.05). EE stimulated mitochondrial protein synthesis in both the untrained, 154%, and trained, 105% (both P < 0.05), but not myofibrillar protein synthesis. Acute RE and EE increased the phosphorylation of proteins in the Akt-mTOR-p70S6K pathway with comparatively minor differences between two exercise stimuli. Phosphorylation of Akt-mTOR-p70S6K proteins was increased after 10 weeks of RE training but not by EE training. Chronic RE or EE training modifies the protein synthetic response of functional protein fractions, with a shift toward exercise phenotype-specific responses, without an obvious explanatory change in the phosphorylation of regulatory signalling pathway proteins.

Figure 1

Infusion trial protocol

Figure 2

A, plasma glucose (mm) and insulin (IU ml⁻¹) concentrations. B, whole-blood venous total amino acid concentration (mm). Values are means ±s.e.m.*Significantly different from values in untrained, letters depict a significant effect of time, P < 0.05.

Figure 3

Myofibrillar (A) and mitochondrial enriched (B) FSR at rest and for the 4 h period after single-leg cycling (endurance) or single leg knee extension exercise (resistance) in the fed state Values are means ±s.e.m. as percentage per hour. *Training effect: significantly different from untrained values with same leg at same time; +leg effect: significantly different from endurance values, same training state and at same time; #time effect: significantly different from values at rest with same leg at same time and from those with same training state, P < 0.05.

Figure 4

Examples of analysis of protein Western blots Representative blots for all signalling proteins measured, in all conditions, in this study. All bands for a particular antibody were obtained from a single Western blot.

Figure 5

Ratio of phosphorylated to total Akt (Ser⁴⁷³) (A), GSK3β (Ser⁹) (B), mTOR (Ser²⁴⁴⁸) (C), p70S6Kinase (Thr³⁸⁹) (D) at rest, immediately after (0 h) and 4 h (4 h) after single-leg knee extension (resistance) or cycling (endurance) in the fed state prior to and after 10 weeks of unilateral resistance or endurance training Values are means ±s.e.m. in arbitrary units. *Training effect: significantly different from untrained values with same leg at same time; +leg effect: significantly different from endurance values, same training state and at same time; time effect: letters depict a significant effect of time (lower case represent untrained and upper case represent trained), P < 0.05.

Figure 6

Ratio of phosphorylated to total rpS6 (Ser^235/236) (A) and eIF4E (Ser²⁰⁹) (B) at rest, immediately after (0 h) and 4 h after single-leg knee extension (resistance) or cycling (endurance) in the fed state before and after 10 weeks of unilateral resistance or endurance training Values are means ±s.e.m. in arbitrary units. *Training effect: significantly different from untrained values with same leg at same time; +leg effect: significantly different from endurance values, same training state and at same time; time effect: letters depict a significant effect of time (lower case represent untrained and upper case represent trained), P < 0.05.

Figure 7

Ratio of phosphorylated to total AMPKα (Thr¹⁷²) (A) and FAK (Tyr^576/577) (B) at rest, immediately after (0 h) and 4 h after single-leg knee extension (resistance) or cycling (endurance) in the fed state prior to and after 10 week of unilateral resistance or endurance training Values are means ±s.e.m. in arbitrary units. *Training effect: significantly different from untrained with same leg at same time; +leg effect: significantly different from endurance same training state and at same time; time effect: letters depict a significant effect of time (lower case represent untrained and upper case represent trained), P < 0.05.