title: Leptin signaling in skeletal muscle after bed rest in healthy humans.
abstract: OBJECTIVE
  This study aimed at determining the effects of bed rest on the skeletal muscle leptin signaling system.
  
  
  METHODS
  Deltoid and vastus lateralis muscle biopsies and blood samples were obtained from 12 healthy young men (mean ± SD, BMI 22.8 ± 2.7 kg/m(2)) before and after 7 days of bed rest. Leptin receptor isoforms (OB-Rs), suppressor of cytokine signaling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) protein expression and signal transducer and activator of transcription 3 (STAT3) phosphorylation were analyzed by Western blot.
  
  
  RESULTS
  After bed rest basal insulin concentration was increased by 53% (P < 0.05), the homeostasis model assessment (HOMA) by 40% (P < 0.05), and serum leptin concentration by 35% (P < 0.05) with no changes in body fat mass. Although the soluble isoform of the leptin receptor (s-OBR) remained unchanged, the molar excess of leptin over sOB-R was increased by 1.4-fold after bed rest (P < 0.05). OB-Rs and SOCS3 protein expression, and STAT3 phosphorylation level remained unaffected in deltoid and vastus lateralis by bed rest, as PTP1B in the deltoid. PTP1B was increased by 90% with bed rest in the vastus lateralis (P < 0.05). There was a linear relationship between the increase in vastus lateralis PTP1B and the increase in both basal insulin concentrations (r = 0.66, P < 0.05) and HOMA (r = 0.68, P < 0.05) with bed rest.
  
  
  CONCLUSIONS
  One week of bed rest is associated with increased leptin levels without augmenting STAT3 phosphorylation indicating some degree of leptin resistance in skeletal muscle, which can be explained, at least in part, by an elevation of PTP1B protein content in the vastus lateralis muscle.
authors.affiliation: Departamento de Educación Física, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017, Las Palmas de Gran Canaria, Canary Island, Spain, borja.guerra@gmail.com.
authors.forename: Borja
authors.initials: B
authors.lastname: Guerra
authors.forename: Jesus Gustavo
authors.initials: JG
authors.lastname: Ponce-González
authors.forename: David
authors.initials: D
authors.lastname: Morales-Alamo
authors.forename: Amelia
authors.initials: A
authors.lastname: Guadalupe-Grau
authors.forename: Kristian
authors.initials: K
authors.lastname: Kiilerich
authors.forename: Teresa
authors.initials: T
authors.lastname: Fuentes
authors.forename: Stine
authors.initials: S
authors.lastname: Ringholm
authors.forename: Rasmus Sjørup
authors.initials: RS
authors.lastname: Biensø
authors.forename: Alfredo
authors.initials: A
authors.lastname: Santana
authors.forename: Carsten
authors.initials: C
authors.lastname: Lundby
authors.forename: Henriette
authors.initials: H
authors.lastname: Pilegaard
authors.forename: José A L
authors.initials: JA
authors.lastname: Calbet
mesh_terms: D000328:Adult; D001510:Bed Rest; D016022:Case-Control Studies; D006801:Humans; D020738:Leptin / Q000097:blood / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D010766:Phosphorylation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics / Q000378:metabolism; D054411:Receptors, Leptin / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C515448:LEPR protein, human; D020738:Leptin; D020033:Protein Isoforms; D054411:Receptors, Leptin; C106644:SOCS3 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1