Obesity, asthma prevalence and IL-4: Roles of inflammatory cytokines, adiponectin and neuropeptide Y

BackgroundObesity is associated with asthma risk and severity, but the underlying biological mechanisms are poorly understood. We hypothesized that cytokine markers of systemic inflammation, and adiponectin and neuropeptide Y (NPY) markers of immuno-modulating and neurohormonal regulation are involved in the obesity-asthma association. MethodsWe explored the relationships between body mass index (BMI), C-reactive protein (CRP), IL-6, TNF-, adiponectin and NPY with asthma prevalence and IL-4 levels in 70 youth with asthma and 69 age- and gender-matched healthy controls using cross-sectional and longitudinal data. ResultsMean BMI level was higher among patients with asthma than healthy controls (p<0.001). In logistic regression models controlling for potential confounders, independent associations with asthma prevalence were found for obesity (p=0.001), increasing tertiles of CRP (linear trend p<0.001), IL-6 (linear trend p<0.001) and lowest and highest tertiles of TNF- (quadratic trend p<0.05), increasing adiponectin (linear p=0.022) and decreasing tertiles of NPY (linear trend p=0.001). Among patients with asthma, NPY level was positively correlated with adiponectin (p<0.05) and TNF- (p<0.05), and levels of NPY and IL-6 were significantly associated with IL-4 level at baseline and 1-year follow-up. ConclusionsThe obesity-asthma association was not explained by systemic inflammation. Specifically, CRP, TNF-a, IL-6, NPY and adiponectin were independently associated with asthma prevalence. NPY and IL-6 were associated with IL-4 marker of allergic airway inflammation in asthma and should be further investigated as prognostic markers of asthma outcomes.