Obese Asthmatics are Characterised by Altered Adipose Tissue Macrophage Activation

Abstract

Adipose tissue-derived inflammation is linked to obesity-related co-morbidities. This study aimed to quantify and immuno-phenotype adipose tissue macrophages (ATMs) from obese asthmatics and obese non-asthmatics, and to examine associations between adipose tissue, systemic and airway inflammation.

Visceral (VAT) and sub-cutaneous (SAT) adipose tissue were collected from obese adults undergoing bariatric surgery and processed to obtain the stromovascular fraction. Pro- (M1) and anti-inflammatory (M2) macrophages were quantified by flow cytometry. Cytospins of induced sputum were stained for differential cell counts. Plasma C reactive protein (CRP) and CD163 were measured by ELISA.

VAT contained a higher number of ATMs compared to SAT. A higher percentage of M1 ATMs was observed in VAT of obese asthmatics compared to obese non-asthmatics. The M1:M2 ratio in VAT was negatively associated with FEV₁%. Sputum macrophage count was correlated positively with M1 ATMs and negatively with M2 ATMs in VAT. In obese asthmatics, CRP was positively associated with M1:M2 ratio in VAT. There were no associations with CD163. An elevated ratio of M1:M2 ATMs was observed in VAT of obese asthmatics with increased disease severity.

VAT inflammation with increased pro-inflammatory macrophages (M1) occurs in obese asthma and may be a determinant of systemic inflammation and asthma severity.

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