title: Erythropoietin Does Not Enhance Skeletal Muscle Protein Synthesis Following Exercise in Young and Older Adults.
abstract: OBJECTIVE
  Erythropoietin (EPO) is a renal cytokine that is primarily involved in hematopoiesis while also playing a role in non-hematopoietic tissues expressing the EPO-receptor (EPOR). The EPOR is present in human skeletal muscle. In mouse skeletal muscle, EPO stimulation can activate the AKT serine/threonine kinase 1 (AKT) signaling pathway, the main positive regulator of muscle protein synthesis. We hypothesized that a single intravenous EPO injection combined with acute resistance exercise would have a synergistic effect on skeletal muscle protein synthesis via activation of the AKT pathway.
  
  
  METHODS
  Ten young (24.2 ± 0.9 years) and 10 older (66.6 ± 1.1 years) healthy subjects received a primed, constant infusion of [ring-13C(6)] L-phenylalanine and a single injection of 10,000 IU epoetin-beta or placebo in a double-blind randomized, cross-over design. 2 h after the injection, the subjects completed an acute bout of leg extension resistance exercise to stimulate skeletal muscle protein synthesis.
  
  
  RESULTS
  Significant interaction effects in the phosphorylation levels of the members of the AKT signaling pathway indicated a differential activation of protein synthesis signaling in older subjects when compared to young subjects. However, EPO offered no synergistic effect on vastus lateralis mixed muscle protein synthesis rate in young or older subjects.
  
  
  CONCLUSIONS
  Despite its ability to activate the AKT pathway in skeletal muscle, an acute EPO injection had no additive or synergistic effect on the exercise-induced activation of muscle protein synthesis or muscle protein synthesis signaling pathways.
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Séverine
authors.initials: S
authors.lastname: Lamon
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Zacharewicz
authors.affiliation: Department of Nutrition and Metabolism, University of Texas Medical Branch Galveston, TX, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Arentson-Lantz
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Paul A Della
authors.initials: PA
authors.lastname: Gatta
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Lobna
authors.initials: L
authors.lastname: Ghobrial
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Frederico
authors.initials: F
authors.lastname: Gerlinger-Romero
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Garnham
authors.affiliation: Department of Nutrition and Metabolism, University of Texas Medical Branch Galveston, TX, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Paddon-Jones
authors.affiliation: Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Geelong, VIC, Australia.
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Russell
keywords: aging; anabolic signaling; erythropoietin; muscle protein synthesis; resistance exercise