title: Prolonged erythropoietin treatment does not impact gene expression in human skeletal muscle.
abstract: BACKGROUND
  We tested for the presence of erythropoietin receptor (Epo-R) in human skeletal muscle and alterations in gene expression after prolonged use of an erythropoiesis-stimulating agent (ESA).
  
  
  METHODS
  Nine healthy men were treated with ESA for 10 weeks (darbepoietin alfa). Muscle biopsies were collected before and after treatment. Alterations in gene expression were evaluated by gene array. Western blot and PCR analysis were used to test for Epo-R presence in human skeletal muscle.
  
  
  RESULTS
  Very low Epo-R mRNA levels were found, but a new and sensitive antibody did not identify Epo-R protein in human skeletal muscle. The between-subject variation in skeletal muscle gene expression was greater than that observed in response to prolonged ESA treatment.
  
  
  CONCLUSIONS
  Erythropoietin is unlikely to exert direct effects in human skeletal muscle due to a lack of Epo-R protein. Furthermore, prolonged ESA treatment does not seem to exert either direct or indirect effects on skeletal muscle gene expression.
authors.affiliation: Department of Endocrinology and Internal Medicine, NBG/THG, Aarhus University Hospital, Aarhus, Denmark; Medical Research Laboratories, Aarhus University, Aarhus, Denmark; Section of Sports Sciences, Institute of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Britt
authors.initials: B
authors.lastname: Christensen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Nellemann
authors.forename: Kasper
authors.initials: K
authors.lastname: Thorsen
authors.forename: Morten Muhlig
authors.initials: MM
authors.lastname: Nielsen
authors.forename: Steen B
authors.initials: SB
authors.lastname: Pedersen
authors.forename: Marie Juul
authors.initials: MJ
authors.lastname: Ornstrup
authors.forename: Jens Otto L
authors.initials: JO
authors.lastname: JØrgensen
authors.forename: Niels
authors.initials: N
authors.lastname: Jessen
mesh_terms: D000328:Adult; D004921:Erythropoietin / Q000008:administration & dosage / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D055815:Young Adult
chemical_list: D012333:RNA, Messenger; D017467:Receptors, Erythropoietin; D004921:Erythropoietin
keywords: A82; Western blotting; erythropoiesis-stimulating agent; erythropoietin receptor; gene array