Macrophage activation, age and sex effects of immunometabolism in obese asthma.

Obese asthma is characterised by infiltration of adipose tissue by activated macrophages and mast cells. The aim of this study was to examine the age and sex effects of immunometabolism in obese asthma. Obese and non-obese asthmatic children and adults underwent spirometry, body composition assessment by dual energy X-ray absorptiometry and measurement of serum soluble CD163 (sCD163), tryptase, C-reactive protein (CRP) and other adipocytokines. Plasma CRP (p<0.01) and leptin (p<0.01) were elevated in obese asthmatic adults, and sCD163 (p=0.003) was elevated in obese asthmatic children. We observed significantly higher sCD163 in obese female children compared to obese female adults and male children, and higher CRP in obese female adults compared to obese male children and adults. Serum tryptase concentrations were not significantly different across age groups. sCD163 positively correlated with the proportion of android fat in obese female children (r=0.70, p=0.003) and obese female adults (r=0.65, p=0.003). In obese female children, sCD163 was inversely associated with forced expiratory volume in 1 s % predicted (r=-0.55, p=0.02) and was positively associated with the Asthma Control Questionnaire (r=0.57, p=0.02). Obese children with asthma have sex-specific macrophage activation, which may contribute to worse asthma control and lung function. The heterogeneous systemic inflammatory profile across age and sex suggests the existence of sub-phenotypes in obese asthma at the molecular level.