title: The macrophage-specific serum marker, soluble CD163, is increased in obesity and reduced after dietary-induced weight loss.
abstract: OBJECTIVE
  Soluble CD163 (sCD163) is a new macrophage-specific serum marker elevated in inflammatory conditions. sCD163 is elevated in obesity and found to be a strong predictor of the development of type 2 diabetes. We investigated whether dietary intervention and moderate exercise was related to changes in sCD163 and how sCD163 is associated to insulin resistance in obesity.
  
  
  METHODS
  Ninety-six obese subjects were enrolled: 62 followed a very low energy diet (VLED) program for 8 weeks followed by 3-4 weeks of weight stabilization, 20 followed a moderate exercise program for 12 weeks, and 14 were included without any intervention. Fasting blood samples and anthropometric measures were taken at baseline and after intervention. Thirty-six lean subjects were included in a control group.
  
  
  RESULTS
  sCD163 was significantly higher in obese subjects (2.3 ± 1.0 mg/l) compared with lean (1.6 ± 0.4 mg/l, P < 0.001). Weight loss (11%) induced by VLED resulted in a reduction and partial normalization of sCD163 to 2.0 ± 0.9 mg/l (P < 0.001). Exercise for 12 weeks had no effect on sCD163. At baseline, sCD163 was significantly correlated with BMI (r = 0.46), waist circumference (r = 0.40), insulin resistance measured by the homeostasis model assessment (HOMA-IR; r = 0.41; all P < 0.001), and the leptin-to-adiponectin ratio (r = 0.28, P < 0.05). In a multivariate linear regression analysis with various inflammatory markers, sCD163 (β = 0.25), adiponectin (β = -0.24), and high sensitivity C-reactive protein (hs-CRP; β = 0.20) remained independently and significantly associated to HOMA-IR (all P < 0.05). After further adjustment for waist circumference, only sCD163 was associated with HOMA-IR (P < 0.05).
  
  
  CONCLUSIONS
  The macrophage-specific serum marker sCD163 is increased in obesity and partially normalized by dietary-induced weight loss but not by moderate exercise. Furthermore, we confirm that sCD163 is a good marker for obesity-related insulin resistance.
authors.affiliation: Department of Medicine and Endocrinology (MEA), Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Karen
authors.initials: K
authors.lastname: Fjeldborg
authors.forename: Tore
authors.initials: T
authors.lastname: Christiansen
authors.forename: Marianne
authors.initials: M
authors.lastname: Bennetzen
authors.forename: Holger
authors.initials: H
authors.lastname: J Møller
authors.forename: Steen B
authors.initials: SB
authors.lastname: Pedersen
authors.forename: Bjørn
authors.initials: B
authors.lastname: Richelsen
mesh_terms: D052242:Adiponectin / Q000097:blood; D000328:Adult; D015703:Antigens, CD / Q000097:blood*; D015214:Antigens, Differentiation, Myelomonocytic / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism; D031204:Caloric Restriction; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000175:diagnosis; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood; D016014:Linear Models; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000097:blood / Q000178:diet therapy*; D016032:Randomized Controlled Trials as Topic; D011956:Receptors, Cell Surface / Q000097:blood*; D055105:Waist Circumference; D015431:Weight Loss; D000098902:CD163 Antigen
chemical_list: D052242:Adiponectin; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D015415:Biomarkers; D000098902:CD163 Antigen; D020738:Leptin; D011956:Receptors, Cell Surface; D002097:C-Reactive Protein