Novel Essential Amino Acid Supplements Following Resistance Exercise Induce Aminoacidemia and Enhance Anabolic Signaling Irrespective of Age: A Proof-of-Concept Trial

Abstract

We investigated the effects of ingesting a leucine-enriched essential amino acid (EAA) gel alone or combined with resistance exercise (RE) versus RE alone (control) on plasma aminoacidemia and intramyocellular anabolic signaling in healthy younger (28 ± 4 years) and older (71 ± 3 years) adults. Blood samples were obtained throughout the three trials, while muscle biopsies were collected in the postabsorptive state and 2 h following RE, following the consumption of two 50 mL EAA gels (40% leucine, 15 g total EAA), and following RE with EAA (combination (COM)). Protein content and the phosphorylation status of key anabolic signaling proteins were determined via immunoblotting. Irrespective of age, during EAA and COM peak leucinemia (younger: 454 ± 32 µM and 537 ± 111 µM; older: 417 ± 99 µM and 553 ± 136 µM) occurred ~60–120 min post-ingestion (younger: 66 ± 6 min and 120 ± 60 min; older: 90 ± 13 min and 78 ± 12 min). In the pooled sample, the area under the curve for plasma leucine and the sum of branched-chain amino acids was significantly greater in EAA and COM compared with RE. For intramyocellular signaling, significant main effects were found for condition (mTOR (Ser2481), rpS6 (Ser235/236)) and age (S6K1 (Thr421/Ser424), 4E-BP1 (Thr37/46)) in age group analyses. The phosphorylation of rpS6 was of similar magnitude (~8-fold) in pooled and age group data 2 h following COM. Our findings suggest that a gel-based, leucine-enriched EAA supplement is associated with aminoacidemia and a muscle anabolic signaling response, thus representing an effective means of stimulating muscle protein anabolism in younger and older adults following EAA and COM.

The efficacy of essential amino acid supplementation for augmenting dietary protein intake in older adults: implications for skeletal muscle mass, strength and function

“…In contrast, other studies have observed a blunting of the mTORC1 pathway (124) , when EAA were ingested following resistance exercise. A comparable profile of aminoacidaemia, mTORC1 signalling, and/or MPS has also been documented, irrespective of age (39,(125)(126)(127) . Therefore, it has been suggested that optimising both anabolic stimuli (i.e.…”

“…However, when combining the anabolic stimuli of protein supplementation and resistance exercise training, findings are more consistent in demonstrating improvements in outcome measurements of muscle health in older adults. The capacity of resistance exercise to sensitise muscle to the anabolic potential of dietary protein is primarily achieved through a timely supply of EAA (34,39,40) . Accordingly, a meta-analysis by Cermak et al (37) revealed that gains in lean tissue mass were of greater magnitude in both younger and older adults when combining resistance training with protein supplementation v. resistance training alone.…”

“…Hence, on a per meal basis, the consumption of adequate, high-quality protein sources that comprise the full complement of EAA represents an intuitive strategy for the management of sarcopenia. Moreover, there is extensive evidence that combining protein supplementation with resistance exercise training exhibits a synergistic effect on skeletal muscle mass, strength and functional outcomes in older adults (37,38) , with exercise sensitising skeletal muscle to the anabolic action of EAA (34,39,40) . On this basis, lifestyle strategies designed to combat sarcopenia and promote skeletal muscle health in older adults require a holistic approach encompassing both exercise and protein nutrition interventions (Fig.…”

Myofibrillar Protein Synthesis and Acute Intracellular Signaling with Elastic Band Resistance Exercise in Young and Older Men

“…By contrast, despite a blunted iMyoPS response to EB-RET in OM, we report no differences in the expression of key AA transporters/sensors, LAT-1, SNAT-2, or Sestrin-2 with age or 1 h after EB-RET and whey protein ingestion, similar to recent work from others in YM after combined RET and EAA ingestion (30). Although Sestrin-2 has been reported to be a key leucine sensor in vitro , there is conflicting evidence around the response of Sestrin-2 to aging, acute RET, and protein feeding (31). Our data add to the conflicting evidence of AA transporters/sensors and their putative role in exercise and feeding-induced muscle anabolism.…”