Abstract
Resistance exercise transiently activates anabolic and catabolic systems in skeletal muscle. Leucine-enriched essential amino acids (LEAAs) are reported to stimulate the muscle anabolic response at a lower dose than whey protein. However, little is known regarding the effect of LEAA supplementation on the resistance exercise-induced responses of the anabolic and catabolic systems. Here, we conducted a randomized, double-blind, placebo-controlled, parallel-group comparison trial to investigate the effect of LEAA supplementation on mechanistic target of rapamycin complex 1 (mTORC1), the ubiquitin–proteasome system and inflammatory cytokines after a single bout of resistance exercise in young men. A total of 20 healthy young male subjects were supplemented with either 5 g of LEAA or placebo, and then they performed 10 reps in three sets of leg extensions and leg curls (70% one-repetition maximum). LEAA supplementation augmented the phosphorylation of mTORSer2448 (+77.1%, p < 0.05), p70S6KThr389 (+1067.4%, p < 0.05), rpS6Ser240/244 (+171.3%, p < 0.05) and 4EBP1Thr37/46 (+33.4%, p < 0.05) after resistance exercise. However, LEAA supplementation did not change the response of the ubiquitinated proteins, MuRF-1 and Atrogin-1 expression. Additionally, the mRNA expression of IL-1β and IL-6 did not change. These data indicated that LEAA supplementation augments the effect of resistance exercise by enhancing mTORC1 signal activation after exercise.
Highlights
Skeletal muscle mass is a major determinant of physical performance in humans
We investigated the effect of Leucine-enriched essential amino acids (LEAAs) supplementation on mechanistic target of rapamycin complex 1 (mTORC1), the ubiquitin–proteasome system and inflammatory cytokines after a single bout of resistance exercise in young men
We investigated the effect of LEAA supplementation on the acute response to resistance exercise
Summary
Skeletal muscle mass is a major determinant of physical performance in humans. Resistance training effectively increases skeletal muscle mass, and numerous nutritional interventions can be used to augment the effect of exercise training [1,2,3,4]. One type of nutritional intervention is supplementation with essential amino acids (EAAs, in particular, leucine). EAAs have a stimulatory effect on muscle anabolism [5,6]. Several previous animal studies have reported that leucine supplementation effectively attenuates skeletal muscle atrophy and/or muscle protein degradation induced by inflammation, Nutrients 2020, 12, 2421; doi:10.3390/nu12082421 www.mdpi.com/journal/nutrients. Nutrients 2020, 12, 2421 disuse, and other factors [7,8]. EAAs can positively affect muscle anabolism and muscle catabolism
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