title: Negative correlation between serum IL-6 level and cardiorespiratory fitness in 10- to 11-year-old boys with increased BMI.
abstract: OBJECTIVE
  Some markers of inflammation have been found to be associated with cardiorespiratory fitness levels, but only few studies have studied this in overweight children. The aim of this study was to investigate associations between markers of inflammation and the fitness levels measured by peak oxygen consumption (VO(2peak) and VO(2peak)/kg) in boys with increased body mass index (BMI) and with normal BMI.
  
  
  METHODS
  Subjects were 38 boys with BMI above 85th percentile (OWB) and 38 boys with normal BMI (NWB) at the age of 10 to 11 years. Serum concentrations of IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFNγ, TNF-α, IL-1α, IL-1β, MCP-1, EGF, CRP and associations with measured cardiorespiratory fitness levels were studied. High-sensitive chips were used to measure 13 markers of inflammation.
  
  
  RESULTS
  Mean VO(2peak) was significantly higher (2.1±0.3 vs. 1.8±0.3 L/min; p<0.05) and mean VO(2peak)/kg significantly lower (33.7±4.7 vs. 48.9±6.4 mL/min/kg; p<0.05) in OWB than in NWB group. Out of 13 measured biochemical markers IL-6 correlated with VO(2peak)/kg (r=-0.37; p<0.05) and TNF-α with VO(2peak) (r=0.41; p<0.01) in OWB. BMI and IL-6 together explained 44.5% of the variability of VO(2peak)/kg in the OWB group.
  
  
  CONCLUSIONS
  Overweight boys had lower cardiorespiratory fitness level measured by VO(2peak)/kg and this was negatively correlated with serum IL-6 level. Measurement of serum IL-6 level in overweight boys may help to identify subjects who need specific exercise formats to achieve maximal beneficial health effects and to reduce their risk for the development of type 2 diabetes and atherosclerosis later in life.
authors.affiliation: Faculty of Exercise and Sport Sciences, University of Tartu, 50090, Tartu, Estonia. liina.utsal@ut.ee
authors.forename: Liina
authors.initials: L
authors.lastname: Utsal
authors.forename: Vallo
authors.initials: V
authors.lastname: Tillmann
authors.forename: Mihkel
authors.initials: M
authors.lastname: Zilmer
authors.forename: Jarek
authors.initials: J
authors.lastname: Mäestu
authors.forename: Priit
authors.initials: P
authors.lastname: Purge
authors.forename: Meeli
authors.initials: M
authors.lastname: Saar
authors.forename: Evelin
authors.initials: E
authors.lastname: Lätt
authors.forename: Katre
authors.initials: K
authors.lastname: Maasalu
authors.forename: Toivo
authors.initials: T
authors.lastname: Jürimäe
authors.forename: Jaak
authors.initials: J
authors.lastname: Jürimäe
mesh_terms: D050197:Atherosclerosis / Q000453:epidemiology; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002648:Child; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology; D005080:Exercise Test; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D050177:Overweight / Q000453:epidemiology / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012307:Risk Factors
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6