Negative correlation between serum IL-6 level and cardiorespiratory fitness in 10- to 11-year-old boys with increased BMI

Abstract

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. 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. 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. 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.