Cytokine profile of obese asthma phenotype

Abstract

Background: The incidence of asthma and obesity is increasing worldwide. Understanding the causal directions between asthma and obesity could have important therapeutic implications. However, the mechanism connecting the two is not well defined.

Objective: This study was undertaken to compare pulmonary function tests (PFTs), C-reactive protein (CRP) and inflammatory cytokines in obesity and asthma in Egyptian adolescents and to investigate whether obese asthmatics have a specific inflammatory phenotype than lean asthmatics.

Methods: Fifty asthmatic and 30 control subjects were enrolled in the study and divided into 2 sub-groups: obese and non-obese. Serum levels of CRP, leptin, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-5, body mass index (BMI) and PFTs were done for asthmatics and controls.

Results: Serum levels of IL-6, TNF-α and leptin in obese individuals whether asthmatic or not showed significant increase compared to lean ones (P < 0.01). Body mass index (BMI) showed positive linear correlations with serum levels of IL-6, TNF-α, leptin and CRP. Serum IL-5 showed significantly higher levels in all asthmatics versus all controls (P < 0.01). Also serum IL-5 showed non-significant difference between lean and obese asthmatics and it showed significant negative correlations with FEV1/FVC % and PEF.

Conclusion: Serum levels ofIL-6, TNF-α and leptin could be considered surrogate markers for obesity, whereas serum IL-5 is considered a marker of airway inflammation in bronchial asthma. Thus obesity and asthma have been shown to coexist together but systemic and airway inflammation appears to operate independent of each other.

Keywords: Asthma, cytokines, obesity, phenotype