Aging differentially affects human skeletal muscle amino acid transporter expression when essential amino acids are ingested after exercise

Jared M. Dickinson, Micah J. Drummond, Jennifer R. Coben, Elena Volpi, Blake B. Rasmussen

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Background & aims: Amino acid transporters have been proposed as regulators of protein synthesis. The primary aim of this study was to determine whether amino acid transporter expression is increased in human muscle following resistance exercise (RE) coupled with essential amino acid (EAA) ingestion, and whether a differential response occurs with aging. Secondly, we aimed to compare this response to a previous study examining RE alone. Methods: Young (n = 7, 30 ± 2 yr) and older men (n = 6, 70 ± 2 yr) ingested EAA 1 h after RE. Muscle biopsies were obtained at rest and 3 and 6 h post exercise to examine amino acid transporter mRNA and protein expression. Results: In both age groups, RE + EAA increased mRNA of L-type amino acid transporter 1 (LAT1)/solute linked carrier (SLC)7A5, sodium-coupled neutral amino acid transporter 2 (SNAT2)/SLC38A2, and cationic amino acid transporter 1/SLC7A1 (p < 0.05). SNAT2 protein increased in young at 3 and 6 h (p < 0.05), whereas old maintained higher LAT1 protein (p < 0.05). Compared to RE alone, RE + EAA enhanced amino acid transporter expression only in young (p < 0.05). Conclusions: RE increases muscle amino acid transporter expression in young and older adults, however, post exercise EAA ingestion enhances amino acid transporter expression only in young indicating that aging may influence the function of specific amino acid transporters.

Original languageEnglish (US)
Pages (from-to)273-280
Number of pages8
JournalClinical Nutrition
Volume32
Issue number2
DOIs
StatePublished - Apr 2013

Keywords

  • MTORC1 signaling
  • Muscle protein synthesis
  • Nutrition
  • Resistance exercise
  • Sarcopenia

ASJC Scopus subject areas

  • Nutrition and Dietetics
  • Critical Care and Intensive Care Medicine

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