Mixed muscle protein synthesis and breakdown after resistance exercise in humans

Abstract

Mixed muscle protein fractional synthesis rate (FSR) and fractional breakdown rate (FBR) were examined after an isolated bout of either concentric or eccentric resistance exercise. Subjects were eight untrained volunteers (4 males, 4 females). Mixed muscle protein FSR and FBR were determined using primed constant infusions of [2H5]phenylalanine and 15N-phenylalanine, respectively. Subjects were studied in the fasted state on four occasions: at rest and 3, 24, and 48 h after a resistance exercise bout. Exercise was eight sets of eight concentric or eccentric repetitions at 80% of each subject's concentric 1 repetition maximum. There was no significant difference between contraction types for either FSR, FBR, or net balance (FSR minus FBR). Exercise resulted in significant increases above rest in muscle FSR at all times: 3 h = 112%, 24 h = 65%, 48 h = 34% (P < 0.01). Muscle FBR was also increased by exercise at 3 h (31%; P < 0.05) and 24 h (18%; P < 0.05) postexercise but returned to resting levels by 48 h. Muscle net balance was significantly increased after exercise at all time points [(in %/h) rest = -0.0573 +/- 0.003 (SE), 3 h = -0.0298 +/- 0.003, 24 h = -0.0413 +/- 0.004, and 48 h = -0.0440 +/- 0.005], and was significantly different from zero at all time points (P < 0.05). There was also a significant correlation between FSR and FBR (r = 0.88, P < 0.001). We conclude that exercise resulted in an increase in muscle net protein balance that persisted for up to 48 h after the exercise bout and was unrelated to the type of muscle contraction performed.

Development of a Diagnostic Method for Detecting Increased Muscle Protein Degradation in Patients with Catabolic Conditions

“…In hemodialysis patients, we used different types of exercise to improve muscle function and the balance between muscle protein synthesis and breakdown (10,23,24). We found that endurance training reduced the level of the actin fragment in muscle of hemodialysis patients to values that were found in the muscle of normal adults (Table 2).…”

Heat shock response and autophagy—cooperation and control

“…Resistance exercise is important and well known in development of muscle mass (hypertrophy). In humans, resistance exercise increases protein synthesis [97][98][99][100][101][102][103][104][105][106] and improves protein balance during the recovery phase in the skeletal muscle, 8,107,108 but not during acute bouts of resistance exercise. 109 Similar to resistance exercise, low intensity aerobic training 110 causes a significant increase in fractional synthetic rate in the leg muscle.…”

“…8 Thus, exercise can be used to follow the cross-regulation of protein breakdown and rebuilding, including novel regulatory paths that might exist. We propose that there is such a novel, previously unappreciated regulated crosstalk between heat shock-governed protein synthesis and folding and the protein degradation state driven by autophagy.…”

Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt

“…This effect on protein synthesis appears to be shared with the anabolic effects of amino acids (particularly leucine) and insulin (10,11) . In addition, HMB attenuates the induction of the ubiquitin -proteosome proteolytic pathway caused by proteolysis-inducing factor, lipopolysaccharide and angiotensin II, resulting in a decrease in muscle protein breakdown (12 -14) .Human studies have shown a positive effect of resistance exercise on muscle protein synthesis as early as 1 -2 h postexercise and lasting up to 48 h (15,16) . Studies have also shown that the timing of nutrient availability is critical for maximal post-exercise stimulation of protein synthesis as well as blunting of protein breakdown (17) .…”