Obesity and asthma are associated, however the mechanism(s) are yet to be elucidated.
The aim of this study was to assess airway inflammation in relation to obesity and plasma fatty acids in males and females with and without asthma. Obese (n=68) and non-obese (n=47) adults with asthma, and obese (n=16) and non-obese (n=63) healthy controls had induced sputum and venous blood samples analysed for inflammatory markers.
There was a positive interaction between obesity and asthma on %sputum neutrophils (p=0.012) and CRP (p=0.003). Although sputum %eosinophils were elevated in asthma (p=0.001), there was no effect of obesity (p=0.16). Sputum %neutrophils were positively associated with BMI in asthmatic females (β[95%CI] =1.015[0.258,1.772], p=0.009) and neutrophilic asthma was present in a greater proportion of obese compared to non-obese females (42.9 vs 16.2%, p=0.017). In asthmatic males, sputum %neutrophils were positively associated with total plasma saturated fatty acids (β[95%CI] = 0.108[0.036,0.180], p=0.004) and negatively with monounsaturated fatty acids (β[95%CI] = -0.068[-0.131,-0.005], p=0.035).
This is the first study to demonstrate an increase in neutrophilic airway inflammation in obese asthma. This relationship was only significant in asthmatic females. In males, saturated and monounsaturated fatty acids were important predictors of neutrophilic airway inflammation in asthma.
