Complexity of asthma with obesity may involve airway microbiome

Published: December 23, 2022

Asthma is a complex chronic disease that can present in variable ways. Current evidence shows that the symptoms of asthma can result from more than one biological process. Asthma can range from mild to severe and be accompanied by other conditions that further complicate effective management. Obesity is another complex condition that can further complicate asthma management. Individuals with obesity may not exhibit the same biomarkers used to determine asthma phenotype and may have more severe disease that is more difficult to treat. Evidence shows that the interplay between the microbiome and the immune system, while not yet fully understood, is important.

In a recent issue of The Journal of Allergy and Clinical Immunology (JACI), Kozik et al report differences in the relationships between inflammatory mediators and airway bacterial microbiota associated with individuals who have both asthma and obesity compared to those with asthma alone. Using induced sputum samples, they identified airway bacterial and fungal microbiome profiles from adult participants with and without asthma and obesity (as defined by body mass index (BMI) at or above 30). They also measured levels of immune cells and inflammatory mediators (cytokines) in both induced sputum and peripheral blood. They then used correlation and network-based analyses to determine potentially important cytokine-cytokine and cytokine-microbe relationships in individuals with asthma and those with asthma and obesity.

Overall, the airways of adults with obesity were enriched in Prevotella, Gemella, and Streptococcus species. Among adults with asthma, those with obesity also exhibited higher airway fungal diversity, differences in the airway bacterial microbiota, and positive correlations between airway bacterial diversity and blood eosinophils. There were also higher levels of inflammatory mediators. Comparisons of cytokine-cytokine correlation patterns between adults with and without asthma and obesity revealed significant relationships between blood levels of the adipokine Plasminogen Activator Inhibitor 1 (PAI-1) and other cytokines in asthma, and further between PAI-1 and airway levels of cytokines only in asthma with obesity. Airway bacterial-cytokine networks showed differences between asthma and asthma with obesity, with many more bacterial-cytokine relationships identified in asthma with obesity. Along with these differences in airway microbial profiles and relationships, predictive functional analysis identified several microbial pathways associated with metabolism, fatty acid, and lipid synthesis enriched in adults with obesity and asthma.

This study provides evidence for altered airway microbial and microbial-immune relationships in non-severe obesity related asthma. Further work is needed to understand the clinical significance of these relationships, but they may be critical to the development of tailored diagnostic and therapeutic strategies for this complex clinical population.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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