Background: Asthma is a chronic inflammatory condition characterized by T-helper (TH) 2 polarization. In children, the prevalence of obesity is associated with an increased incidence of asthma. Notably, obesity is linked with TH1-mediated inflammation and has been identified as a major risk factor for asthma.
Objective: To investigate the impact of obesity on TH1 (tumor necrosis factor α, interferon gamma, interleukin (IL)-6, IL-8) and TH2 (IL-4, IL-5, IL-10, IL-13) immune responses in children with asthma.
Methods: We searched the MEDLINE and gray literature electronic databases for eligible studies from inception up until April 2020. The quality of included studies and evidence was independently assessed by 2 reviewers. The random-effects model was used in this meta-analysis, and outcomes were reported as standardized mean difference (SMD) and 95% confidence interval (CI).
Results: Overall, 5 studies comprising 482 participants met the inclusion criteria. The meta-analysis revealed an increased TH2-mediated immune response in lean people with asthma compared with controls without asthma (SMD: -1.15 [95% CI: -1.93, 0.36]; I2 = 93%; pH < .001). However, in obese people with asthma, there was polarization toward TH1 immune response compared with lean people with asthma (SMD: -0.43 [95% CI: -0.79, -0.08]; I2 = 88%, pH < .001).
Conclusion: This meta-analysis reveals that there are differences in immune responses mediated by T-helper cells in lean and obese children with asthma. Moreover, and not unique to asthma, obesity polarizes the immune response toward TH1 rather than the classical TH2. This could be an important aspect to understand to establish effective therapeutic targets for obese children with asthma.
Copyright © 2020 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.