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Scott HA, Ng SH, McLoughlin RF, Valkenborghs SR, Nair P, Brown AC, Carroll OR, Horvat JC, Wood LG. Effect of obesity on airway and systemic inflammation in adults with asthma: a systematic review and meta-analysis. Thorax 2023; 78:957-965. [PMID: 36948588 DOI: 10.1136/thorax-2022-219268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 02/25/2023] [Indexed: 03/24/2023]
Abstract
BACKGROUND Obesity is associated with more severe asthma, however, the mechanisms responsible are poorly understood. Obesity is also associated with low-grade systemic inflammation; it is possible that this inflammation extends to the airways of adults with asthma, contributing to worse asthma outcomes. Accordingly, the aim of this review was to examine whether obesity is associated with increased airway and systemic inflammation and adipokines, in adults with asthma. METHODS Medline, Embase, CINAHL, Scopus and Current Contents were searched till 11 August 2021. Studies reporting measures of airway inflammation, systemic inflammation and/or adipokines in obese versus non-obese adults with asthma were assessed. We conducted random effects meta-analyses. We assessed heterogeneity using the I2 statistic and publication bias using funnel plots. RESULTS We included 40 studies in the meta-analysis. Sputum neutrophils were 5% higher in obese versus non-obese asthmatics (mean difference (MD)=5.0%, 95% CI: 1.2 to 8.9, n=2297, p=0.01, I2=42%). Blood neutrophil count was also higher in obesity. There was no difference in sputum %eosinophils; however, bronchial submucosal eosinophil count (standardised mean difference (SMD)=0.58, 95% CI=0.25 to 0.91, p<0.001, n=181, I2=0%) and sputum interleukin 5 (IL-5) (SMD=0.46, 95% CI=0.17 to 0.75, p<0.002, n=198, I2=0%) were higher in obesity. Conversely, fractional exhaled nitric oxide was 4.5 ppb lower in obesity (MD=-4.5 ppb, 95% CI=-7.1 ppb to -1.8 ppb, p<0.001, n=2601, I2=40%). Blood C reactive protein, IL-6 and leptin were also higher in obesity. CONCLUSIONS Obese asthmatics have a different pattern of inflammation to non-obese asthmatics. Mechanistic studies examining the pattern of inflammation in obese asthmatics are warranted. Studies should also investigate the clinical relevance of this altered inflammatory response. PROSPERO REGISTERATION NUMBER CRD42021254525.
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Affiliation(s)
- Hayley A Scott
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, New South Wales, Australia
- Immune Health Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
| | - Shawn Hm Ng
- School of Medicine and Public Health, The University of Newcastle, Callaghan, New South Wales, Australia
| | - Rebecca F McLoughlin
- School of Nursing and Midwifery, The University of Newcastle, Callaghan, New South Wales, Australia
- National Health and Medical Research Council, Centre of Excellence in Treatable Traits, New Lambton Heights, New South Wales, Australia
- Asthma and Breathing Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
| | - Sarah R Valkenborghs
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, New South Wales, Australia
- Active Living Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
| | - Parameswaran Nair
- Division of Respirology, McMaster University and St Joseph's Healthcare, Hamilton, Ontario, Canada
| | - Alexandra C Brown
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, New South Wales, Australia
- Immune Health Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
| | - Olivia R Carroll
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, New South Wales, Australia
- Immune Health Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
| | - Jay C Horvat
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, New South Wales, Australia
- Immune Health Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
| | - Lisa G Wood
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, New South Wales, Australia
- Immune Health Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
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Abstract
BACKGROUND It is thought that airway inflammation is more common in obese asthmatic patients because inflammation is harder to control and does not respond well to glucocorticoid treatment. OBJECTIVE This study's aim was to investigate the effect of obesity on airway and systemic inflammation in children with asthma and to identify the biomarkers that play a role in this inflammation. METHODS The study included patients aged 6-16 years who were diagnosed with asthma in the paediatric allergy outpatient clinic of Bagcilar Training and Research Hospital in Turkey. Complete blood count parameters were compared between three groups: obese asthmatic (n=43), obese non-asthmatic (n=45), and non-obese non-asthmatic (control group, n=30). Levels of high-sensitive CRP (hs-CRP), neutrophil gelatinase-associated lipocalin (NGAL), osteopontin (OPN), and matrix metalloproteinase-9 (MMP-9), and 25(OH)-vitamin D were compared between the groups. RESULTS No statistically significant differences were observed in 25(OH)-vitamin D, NGAL, OPN, hs-CRP, and MMP-9 levels between groups. There was a statistically significant negative correlation between FEV1/FVC and NGAL and MMP-9. CONCLUSION This is the first study to investigate levels of hs-CRP, NGAL, OPN, MMP-9, and 25(OH)-vitamin D in obese asthmatic children. Larger studies with sputum and BAL examinations are required to determine the potential of biomarkers for identifying inflammation in obese asthmatic children.
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