Leucine-Enriched Amino Acid Ingestion After Resistance Exercise Prolongs Myofibrillar Protein Synthesis and Amino Acid Transporter Expression in Older Men
Sarcopenia, the loss of muscle mass and strength that occurs with aging, leaves older adults vulnerable to frailty, falls, mobility limitations, and mortality. Ingesting dietary protein or amino acids after engaging in resistance exercise has been identified and validated as an effective strategy for sustaining muscle and mitigating sarcopenia in the aging population. Scientists continue to investigate the specific nutritional factors that yield these muscle-building effects.
Acute metabolic study
Number of Subjects
70 - 74
Researchers examined the effects of increased leucine ingestion on skeletal muscle myofibrillar protein synthesis, mammalian/mechanistic target of rapamycin complex 1 signaling, and amino acid transporter mRNA expression in older men over a 24-hour period after resistance exercise.
One hour after performing resistance exercise, participants ingested 10 grams of essential amino acids made up of either 1.85 grams of leucine or 3.5 grams of leucine. Muscle biopsies were taken at rest, and 2, 5, and 24 hours after exercise.
While both groups increased muscle protein synthesis, the mRNA expression of select amino acid transporters, and the p70 S6 kinase 1 phosphorylation initiation factor for the mammalian target of rapamycin complex 1, only the group taking the essential amino acid mixture containing greater leucine content had elevated levels of muscle protein synthesis and mRNA expression at 24 hours after exercise. The enriched leucine also increased the initiation factor 4E binding protein 1 phosphorylation while the lower leucine dose of 1.85 grams did not.
Taking an essential amino acid supplement enriched with leucine after performing resistance exercise may lengthen the anabolic response and sensitivity to amino acids in older men.
The body’s response to muscle-building mechanisms becomes more subdued with age, which can lead to muscle wasting and a decline in functional status and quality of life. This study shows that an essential amino acid supplement with a high concentration of leucine can help make aging muscle more responsive to the muscle-building effects of exercise and rehabilitation programs when taken after resistance training.
Dickinson JM, Gundermann DM, Walker DK, et al. Leucine-enriched amino acid ingestion after resistance exercise prolongs myofibrillar protein synthesis and amino acid transporter expression in older men. J Nutr. 2014;144(11):1694-1702. doi:10.3945/jn.114.198671