title: The effects of exercise and adipose tissue lipolysis on plasma adiponectin concentration and adiponectin receptor expression in human skeletal muscle.
abstract: OBJECTIVE
  It has been suggested that adiponectin regulates plasma free fatty acid (FFA) clearance by stimulating FFA uptake and/or oxidation in muscle. We aimed to determine changes in plasma adiponectin concentration and adiponectin receptor 1 and 2 mRNA expression in skeletal muscle during and after prolonged exercise under normal, fasting conditions (high FFA trial; HFA) and following pharmacological inhibition of adipose tissue lipolysis (low FFA trial; LFA). Furthermore, we aimed to detect and locate adiponectin in skeletal muscle tissue.
  
  
  METHODS
  Ten subjects performed two exercise trials (120 min at 50% VO(2max)). Indirect calorimetry was used to determine total fat oxidation rate. Plasma samples were collected at rest, during exercise and during post-exercise recovery to determine adiponectin, FFA and glycerol concentrations. Muscle biopsies were taken to determine adiponectin protein and adiponectin receptor 1 and 2 mRNA expression and to localise intramyocellular adiponectin.
  
  
  RESULTS
  Basal plasma adiponectin concentrations averaged 6.57+/-0.7 and 6.63+/-0.8 mg/l in the HFA and LFA trials respectively, and did not change significantly during or after exercise. In the LFA trial, plasma FFA concentrations and total fat oxidation rates were substantially reduced. However, plasma adiponectin and muscle adiponectin receptor 1 and 2 mRNA expression did not differ between trials. Immunohistochemical staining of muscle cross-sections showed the presence of adiponectin in the sarcolemma of individual muscle fibres and within the interfibrillar arterioles.
  
  
  CONCLUSIONS
  Plasma adiponectin concentrations and adiponectin receptor 1 and 2 mRNA expression in muscle are not acutely regulated by changes in adipose tissue lipolysis and/or plasma FFA concentrations. Adiponectin is abundantly expressed in muscle, and, for the first time, it has been shown to be present in/on the sarcolemma of individual muscle fibres.
authors.affiliation: Department of Pathology, Research Institute GROW, Maastricht University, Maastricht, The Netherlands.
authors.forename: Chamindie
authors.initials: C
authors.lastname: Punyadeera
authors.forename: Antoine H G
authors.initials: AH
authors.lastname: Zorenc
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: McAinch
authors.forename: Egbert
authors.initials: E
authors.lastname: Smit
authors.forename: Ralph
authors.initials: R
authors.lastname: Manders
authors.forename: Hans A
authors.initials: HA
authors.lastname: Keizer
authors.forename: David
authors.initials: D
authors.lastname: Cameron-Smith
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D052242:Adiponectin; D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001160:Arterioles; D002153:Calorimetry, Indirect; D015444:Exercise / Q000502:physiology*; D005215:Fasting / Q000097:blood / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006801:Humans; D000960:Hypolipidemic Agents / Q000494:pharmacology; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood*; D008066:Lipolysis; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D009994:Osmolar Concentration; D011719:Pyrazines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D054419:Receptors, Adiponectin; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D012508:Sarcolemma / Q000378:metabolism
chemical_list: C475418:ADIPOR1 protein, human; C475420:ADIPOR2 protein, human; D052242:Adiponectin; D005230:Fatty Acids, Nonesterified; D000960:Hypolipidemic Agents; D036341:Intercellular Signaling Peptides and Proteins; D011719:Pyrazines; D012333:RNA, Messenger; D054419:Receptors, Adiponectin; D011956:Receptors, Cell Surface; C027696:acipimox