title: The role of leptin in human lipid and glucose metabolism: the effects of acute recombinant human leptin infusion in young healthy males.
abstract: BACKGROUND
  Obese and lean humans treated with leptin have not experienced convincing weight-loss results compared with the dramatic weight losses observed in obese rodents.
  
  
  OBJECTIVE
  We sought to investigate the effect of acutely elevating leptin to concentrations observed in obese individuals on muscle and adipose tissue metabolism and muscle signaling in healthy lean males.
  
  
  METHODS
  Healthy, lean, postabsorptive males were infused with either recombinant human leptin (rhleptin; n = 8) or saline (control; n = 8) for 4 h, which elicited leptin concentrations of ~ 20 and ~ 1 ng/mL, respectively. Systemic, skeletal muscle, and adipose tissue fat and glucose metabolism in vivo were assessed before, during, and 2 h after cessation of the infusion. Skeletal muscle biopsy specimens were obtained to quantify changes in signal transducers and activators of transcription-5'AMP-activated protein kinase (STAT-AMPK) signaling.
  
  
  RESULTS
  During the infusion of rhleptin, no differences in either systemic, skeletal muscle, or adipose tissue glucose or fat metabolism were observed. These observations were made despite increased activation of STAT (~ 17-fold) and AMPK (1.43-fold) after 1 h of rhleptin infusion. After the rhleptin infusion, an increase in systemic palmitate and fat oxidation was observed (P < 0.0003), which likely was caused by a concomitant increase in skeletal muscle palmitate oxidation (P < 0.02). This was observed despite lowered leptin concentrations and basal skeletal muscle STAT-AMPK signaling.
  
  
  CONCLUSIONS
  Elevating circulating leptin concentrations to concentrations comparable with those of obese individuals increases human in vivo skeletal muscle signaling through the AMPK pathway and causes an increase in skeletal muscle fatty acid oxidation. Abdominal adipose tissue was unaffected by the acute physiologic increase in leptin concentrations.
authors.affiliation: Centre of Inflammation and Metabolism, Department of Infectious Diseases, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Denmark. wolsk@dadlnet.dk
authors.forename: Emil
authors.initials: E
authors.lastname: Wolsk
authors.forename: Helene
authors.initials: H
authors.lastname: Mygind
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Grøndahl
authors.forename: Bente K
authors.initials: BK
authors.lastname: Pedersen
authors.forename: Gerrit
authors.initials: G
authors.lastname: van Hall
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D020738:Leptin / Q000494:pharmacology*; D050356:Lipid Metabolism / Q000187:drug effects*; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000097:blood; D011994:Recombinant Proteins / Q000494:pharmacology; D012016:Reference Values; D015398:Signal Transduction / Q000187:drug effects; D055815:Young Adult
chemical_list: D020738:Leptin; D011994:Recombinant Proteins; D019308:Palmitic Acid; D055372:AMP-Activated Protein Kinases; D005947:Glucose