The Effect of Leucine-Enriched Essential Amino Acid Supplementation on Anabolic and Catabolic Signaling in Human Skeletal Muscle after Acute Resistance Exercise: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Comparison Trial

• Published in: Nutrients Vol. 12; no. 8; p. 2421
• Main Authors: Takegaki, Junya, Sase, Kohei, Yasuda, Jun, Shindo, Daichi, Kato, Hiroyuki, Toyoda, Sakiko, Yamada, Toshiyuki, Shinohara, Yasushi, Fujita, Satoshi
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 12.08.2020
• Subjects: Amino Acids, Essential - pharmacology; Cytokines - metabolism; Dietary Supplements; dosage; Double-Blind Method; essential amino acids; Exercise - physiology; gene expression; Healthy Volunteers; Humans; Interleukin-1beta - metabolism; interleukin-6; Interleukin-6 - metabolism; Leucine - pharmacology; Male; males; Mechanistic Target of Rapamycin Complex 1 - metabolism; Muscle Proteins - metabolism; Muscle, Skeletal - metabolism; muscles; phosphorylation; Phosphorylation - drug effects; placebos; rapamycin; Resistance Training; RNA, Messenger - metabolism; Signal Transduction - drug effects; skeletal muscle; SKP Cullin F-Box Protein Ligases - metabolism; strength training; Tripartite Motif Proteins - metabolism; Ubiquitin-Protein Ligases - metabolism; whey protein; Young Adult; resistance exercise; LEAAs; inflammation; mTORC1; ubiquitin
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu12082421

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.