title: Soluble leptin receptor and soluble receptor-bound fraction of leptin in the metabolic syndrome.
abstract: OBJECTIVE
  In obesity, plasma leptin is high and soluble leptin receptor (sOb-R) levels are low, resulting in a low fraction of bound leptin. The aim of this study was to investigate the influence of insulin resistance (IR) and the metabolic syndrome (MS) on sOb-R concentration and the bound-free ratio of leptin.
  
  
  METHODS
  sOb-R, leptin levels, and homeostasis model assessment (HOMA) index for IR were determined in 76 middle-aged obese or overweight men.
  
  
  RESULTS
  Concentration of sOb-R and soluble receptor-bound fraction of leptin were lowest in the highest tertile of HOMA-IR. sOb-R and the bound-free ratio of leptin correlated with HOMA-IR, leptin concentration, and waist-to-hip ratio independently of age, BMI, and fat mass. Leptin and waist-to-hip ratio were the sole independent determinants of sOb-R concentration, and BMI, HOMA-IR, and visceral adipose tissue were independent determinants of the bound fractin of leptin. sOb-R concentration and the bound fraction of leptin decreased with increasing numbers of components of the MS, resulting in lower sOb-R concentration and a lower fraction of bound leptin in men with the MS.
  
  
  CONCLUSIONS
  IR and abdominal obesity are associated with low sOb-R concentration and low bound-free ratio of leptin independent of fat mass. Low sOb-R concentration and low bound-free ratio of leptin segregate with components of the MS. We suggest that low sOb-R levels and a low fraction of specifically bound leptin are markers of leptin resistance, which is independently associated with IR and abdominal obesity and may constitute an additional component of the MS.
authors.affiliation: Department of Medicine, University of Innsbruck, Innsbruck, Austria.
authors.forename: Anton
authors.initials: A
authors.lastname: Sandhofer
authors.forename: Markus
authors.initials: M
authors.lastname: Laimer
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Ebenbichler
authors.forename: Susanne
authors.initials: S
authors.lastname: Kaser
authors.forename: Bernhard
authors.initials: B
authors.lastname: Paulweber
authors.forename: Josef R
authors.initials: JR
authors.lastname: Patsch
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D001794:Blood Pressure; D001823:Body Composition; D001824:Body Constitution; D015992:Body Mass Index; D005215:Fasting; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood*; D016014:Linear Models; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood*; D008875:Middle Aged; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000097:blood*; D054411:Receptors, Leptin
chemical_list: D007328:Insulin; C515448:LEPR protein, human; D020738:Leptin; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin