Inflammatory cytokines and metabolic risk factors during growth and maturation: influence of physical activity.

Cytokines influence tissue and cell physiology in positive and negative ways. Our aim in this chapter is to briefly present on select cytokines and their relationship to disease, metabolic risk factors, and physical activity in youth. We discuss the association of adiponectin, interleukin-6 (IL-6), resistin, tumor necrosis factor-α (TNF-α), and C-reactive protein (CRP) with metabolic risk factors in youth, and whether circulating concentrations of these cytokines are different based on being physically active or engaging in exercise training. Results from several studies show that adiponectin concentrations are reduced with increased adiposity, while others show that TNF-α, IL-6, resistin and CRP concentrations may be elevated with increased adiposity. Results from studies link decreased adiponectin with increased insulin resistance, while some evidence links increased TNF-α and resistin with increased insulin resistance. Several studies relate higher blood pressures to decreased adiponectin, increased TNF-α, and CRP concentrations. The only lipids associated with the cytokines appear to be triglycerides and HDL cholesterol. Higher levels of habitual physical activity are associated with higher adiponectin and perhaps decreased TNF-α and resistin concentrations. Exercise training also appears to positively influence the concentrations of these cytokines. In conclusion, the role of these cytokines is still somewhat unclear as is their associations with metabolic risk factors. However, the available evidence indicates that chronic inflammatory states such as obesity in childhood are associated with a pro-inflammatory profile and the presence of increased risk factors for disease while physical activity or exercise training elicit a protective role relative to this profile.