Effect of obesity on airway and systemic inflammation in adults with asthma: a systematic review and meta-analysis.

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.

Endotyping pediatric obesity-related asthma: Contribution of anthropometrics, metabolism, nutrients, and CD4+ lymphocytes to pulmonary function.

BACKGROUND: Obesity-related complications including visceral fat, metabolic abnormalities, nutrient deficiencies, and immune perturbations are interdependent but have been individually associated with childhood asthma. OBJECTIVE: We sought to endotype childhood obesity-related asthma by quantifying contributions of obesity-related complications to symptoms and pulmonary function. METHODS: Multiomics analysis using Similarity Network Fusion followed by mediation analysis were performed to quantify prediction of obese asthma phenotype by different combinations of anthropometric, metabolic, nutrient, and TH-cell transcriptome and DNA methylome data sets. RESULTS: Two clusters (n = 28 and 26) distinct in their anthropometric (neck and midarm circumference, waist to hip ratio [WHR], and body mass index [BMI] z score), metabolic, nutrient, and TH-cell transcriptome and DNA methylome footprint predicted 5 or more pulmonary function indices across 7 different data set combinations. Metabolic measures attenuated the association of neck, WHR, and BMI z score with FEV1/forced vital capacity (FVC) ratio and expiratory reserve volume (ERV), of neck, midarm, and BMI z score with functional residual capacity, but only of WHR with inspiratory capacity. Nutrient levels attenuated the association of neck, midarm circumference, and BMI z score with functional residual capacity, and of WHR with FEV1/FVC ratio, ERV, and inspiratory capacity. TH-cell transcriptome attenuated the association of all 4 anthropometric measures with FEV1/FVC ratio, but only of WHR with ERV and inspiratory capacity. The DNA methylome attenuated the association of all 4 anthropometric measures with FEV1/FVC ratio and ERV, but only of WHR with inspiratory capacity. CONCLUSIONS: Anthropometric, metabolic, nutrient, and immune perturbations have individual but interdependent contributions to obese asthma phenotype, with the most consistent effect of WHR, highlighting the role of truncal adiposity in endotyping childhood obesity-related asthma.

Increasing physical activity in severe asthma: a systematic review and meta-analysis.

INTRODUCTION: Physical inactivity is common in asthma and is recognised as an important modifiable risk for poor clinical outcomes such as impaired asthma control and health-related quality of life (HRQoL). Despite evidence supporting the role of physical activity in reducing the risk of these outcomes, little is known about optimal interventions for increasing physical activity in those with severe disease. This systematic review and meta-analysis evaluates the effectiveness of interventions in increasing physical activity in severe asthma. METHODS: MEDLINE, the Cumulative Index to Nursing and Allied Health Literature, Embase, PubMed, Informit, SPORTDiscus and Cochrane databases were searched up to September 2021 for physical activity-based intervention studies that assessed physical activity outcomes (e.g. steps per day, time spent undertaking physical activity) in adults with severe asthma. Data on asthma-related (e.g. asthma control) and health-related outcomes (e.g. HRQoL) were assessed as secondary outcomes. The revised Cochrane Risk of Bias tool was used to assess risk of bias. Random-effects meta-analyses synthesised data where possible. RESULTS: Four randomised controlled trials (all 12 weeks in duration) including 176 adults with moderate-to-severe asthma were included. An increase in physical activity was reported with a moderate-vigorous intensity aerobic and resistance training intervention (steps per day and time spent undertaking physical activity), and an unsupervised pedometer-based intervention (steps per day). Meta-analyses showed that physical activity interventions had an overall positive effect on steps per day (mean difference (MD) 1588, 95% CI 399-2778; p=0.009, I2=23), asthma control (MD -0.65, 95% CI -0.95--0.35; p<0.0001, I2=0%) and HRQoL (MD 0.56, 95% CI 0.10-1.01; p=0.02, I2=16%) compared to control. CONCLUSION: While there is some evidence supporting the effectiveness of interventions in improving physical activity in adults with severe asthma, higher-quality, large-scale studies of longer duration are needed to determine the optimal intervention.

The effects of increasing fruit and vegetable intake in children with asthma: A randomized controlled trial.

BACKGROUND: A high fruit and vegetable (F&V) diet reduces asthma exacerbations in adults; this has not been examined in children to date. OBJECTIVE: To investigate the effect of a 6-month, high F&V diet on the time to first asthma exacerbation in children with asthma, in a parallel-group, randomized, controlled trial. METHODS: Children (aged 3-11 years) with asthma, history of exacerbations and usual low F&V intake (≤3 serves/day) were randomized to the intervention (high F&V diet) or control group (usual diet) for 6 months. The primary outcome was time to first exacerbation requiring medical intervention. Secondary outcomes included exacerbation rate, lung function, plasma TNF-α, CRP, and IL-6, faecal microbiota and peripheral blood mononuclear cell (PBMC) histone deacetylase (HDAC) activity and G-protein coupled receptor (GPR) 41/43 and HDAC (1-11) expression. RESULTS: 67 children were randomized between September 2015 and July 2018. F&V intake (difference in change (∆): 3.5 serves/day, 95% CI: [2.6, 4.4] p < 0.001) and plasma total carotenoids (∆: 0.44 µg/ml [0.19, 0.70] p = 0.001) increased after 6 months (intervention vs control). Time to first exacerbation (HR: 0.81, 95% CI: [0.38, 1.69], p = 0.569; control vs. intervention) and exacerbation rate (IRR: 0.84, [0.47, 1.49], p = 0.553; control vs. intervention) were similar between groups. In per-protocol analysis, airway reactance z-scores increased in the intervention versus control group (X5 ∆: 0.76 [0.04, 1.48] p = 0.038, X20 ∆: 0.93 [0.23, 1.64] p = 0.009) and changes in faecal microbiota were observed though there was no difference between groups in systemic inflammation or molecular mechanisms. In the control group, CRP and HDAC enzyme activity increased, while GPR41 expression decreased. No adverse events attributable to the interventions were observed. CONCLUSION & CLINICAL RELEVANCE: A high F&V diet did not affect asthma exacerbations over the 6-month intervention, though warrants further investigation as a strategy for improving lung function and protecting against systemic inflammation in children with asthma.

Weight loss in obese children with asthma - is it important?

Obesity is a significant public health problem worldwide, and it has been identified as an independent risk factor for asthma in both adults and children. Not only does obesity increase asthma risk, but it is also associated with decreased asthma-related quality of life, worsened symptoms and asthma control, increased frequency and severity of asthma exacerbations and reduced response to asthma medications. In this review we examine the epidemiology and implications of obesity in both children and adults with asthma, and how the obesogenic "western" diet contributes to asthma prevalence and progression. Finally, we summarise the current evidence on the impact of weight loss on asthma outcomes in both adults and children, highlighting the need for further research to be conducted in the paediatric population.

Effects of Moderate- versus Vigorous-Intensity Exercise Training on Asthma Outcomes in Adults.

BACKGROUND: The therapeutic effects of exercise has prompted calls for it to be embedded into standard asthma care, but evidence informing the optimal exercise intensity is lacking. OBJECTIVE: This study aimed to compare the effects of moderate- and vigorous-intensity aerobic exercise training on asthma outcomes and inflammation. METHODS: This was a 12-week randomised controlled trial in 46 adults with asthma randomised to either 1) 45min moderate-intensity exercise training three times/week, 2) 30min vigorous-intensity exercise training three times/week, or 3) control group. Asthma-related quality of life (AQLQ), asthma control (ACQ), cardiorespiratory fitness, body composition, and airway and systemic inflammation were assessed pre- and post-intervention. RESULTS: Forty-one participants completed the study (89% retention). The moderate-intensity group had a statistically and clinically significant improvement in AQLQ [0.63 (0.33 to 0.93) p<0.001) and ACQ [-0.51 (-0.83 to -0.19), p=0.003] relative to control. The vigorous-intensity group had a statistically, but not clinically, significant improvement in AQLQ [0.46 (0.14 to 0.80, p=0.007] and ACQ [-0.36 (-0.69 to -0.02, p=0.040] relative to control. Following moderate-intensity training, there was a reduction in sputum macrophage [-1341 (-2491 to -191)x104/mL, p=0.024] and lymphocyte [-114 (-220 to -8)x104/mL, p=0.036] counts relative to control. A reduction in android fat mass, but not a change in fitness, was associated with improved AQLQ (rs=-0.341, p=0.030) and reduced sputum IL-6 (rs=0.422, p=0.013). CONCLUSION: Our findings suggest that both moderate-intensity and vigorous-intensity aerobic exercise training are associated with improvements in clinical asthma outcomes, and therefore both intensities could be recommended as an adjuvant asthma therapy.

Using a knowledge translation framework to identify health care professionals' perceived barriers and enablers for personalised severe asthma care.

BACKGROUND: Whilst multidimensional assessment enables the detection of treatable traits in severe asthma and has the potential to improve patient outcomes, healthcare disparities exist, and little is known about the factors influencing optimal management in severe asthma. This study aimed to explore perceived barriers, and enablers to implementing personalised care in severe asthma, from the healthcare professionals' perspective. METHODS: A descriptive, qualitative study involving a single focus group (n = 7) and semi-structured interviews (n = 33) with multidisciplinary healthcare professionals involved in severe asthma care was conducted. A hybrid thematic and content analysis was undertaken to identify themes, which were then deductively mapped to the Theoretical Domains Framework (TDF). RESULTS: Overall, three emergent themes were identified: (1) Barriers- (2) Enablers- to optimal management; (3) Desired model of care. Across all TDF domains, 6 constructs influenced development and implementation of optimal care: (1) belief about consequences, (2) environmental context and resources, (3) belief about capabilities, (4) social/professional role and identity, (5) goals and (6) knowledge. CONCLUSION: Implementation of personalised care in severe asthma is complex and non-linear. The use of a theory-based approach effectively demonstrated how a variety of behaviours could be targeted to optimise and promote personalised care in different clinical setting.

The Effects of Increasing Fruit and Vegetable Intake in Children with Asthma on the Modulation of Innate Immune Responses.

Children with asthma are at risk of acute exacerbations triggered mainly by viral infections. A diet high in fruit and vegetables (F&V), a rich source of carotenoids, may improve innate immune responses in children with asthma. Children with asthma (3−11 years) with a history of exacerbations and low F&V intake (≤3 serves/d) were randomly assigned to a high F&V diet or control (usual diet) for 6 months. Outcomes included respiratory-related adverse events and in-vitro cytokine production in peripheral blood mononuclear cells (PBMCs), treated with rhinovirus-1B (RV1B), house dust mite (HDM) and lipopolysaccharide (LPS). During the trial, there were fewer subjects with ≥2 asthma exacerbations in the high F&V diet group (n = 22) compared to the control group (n = 25) (63.6% vs. 88.0%, p = 0.049). Duration and severity of exacerbations were similar between groups. LPS-induced interferon (IFN)-γ and IFN-λ production showed a small but significant increase in the high F&V group after 3 months compared to baseline (p < 0.05). Additionally, RV1B-induced IFN-λ production in PBMCs was positively associated with the change in plasma lycopene at 6 months (rs = 0.35, p = 0.015). A high F&V diet reduced asthma-related illness and modulated in vitro PBMC cytokine production in young children with asthma. Improving diet quality by increasing F&V intake could be an effective non-pharmacological strategy for preventing asthma-related illness by enhancing children's innate immune responses.

The Management of Extrapulmonary Comorbidities and Treatable Traits; Obesity, Physical Inactivity, Anxiety, and Depression, in Adults With Asthma.

Asthma is a complex and heterogenous disease characterized by variability in disease expression and severity. Multiple extrapulmonary comorbidities and treatable traits are common in people with asthma, and there is an increasing appreciation of how these may complicate asthma management. This review will discuss the prevalence and impact of extrapulmonary comorbidities/risk factors or "traits," which have been found to co-exist in asthma (obesity, symptoms of depression and/or anxiety and physical inactivity), the impact these traits have on future outcomes (including exacerbation risk and quality of life) and asthma management, and how we should target treatment in asthma when these extrapulmonary traits are present.

The use of treatable traits to address COPD complexity and heterogeneity and to inform the care.

COPD is complex and heterogeneous with respect to its aetiology, clinical presentation, phenotypes and biological mechanisms. Despite this, COPD is still diagnosed and treated according to simple clinical measures, including airflow limitation, symptoms and exacerbation frequency, leading to failure to recognise the disease's heterogeneity and/or to provide targeted interventions. COPD continues to have a very large burden of disease with suboptimal outcomes for people with the disease, including frequent hospitalisation with exacerbations, rapid lung function decline, multimorbidity and death from respiratory failure. In light of this, there have been increasing calls for a renewed taxonomy with better characterisation of COPD phenotypes and endotypes. This would allow the unravelling of COPD's complexity and heterogeneity, the implementation of targeted interventions and improved patient outcomes. The treatable traits strategy is a proposed vehicle for the implementation of precision medicine in chronic airway diseases. In this review, in addition to summarising the key knowledge on the heterogeneity of COPD, we refer to the existing evidence pertaining to the treatable traits strategy as applied in COPD and discuss implementation in different settings.

Children With Asthma Have Impaired Innate Immunity and Increased Numbers of Type 2 Innate Lymphoid Cells Compared With Healthy Controls.

Background: Asthma is the most frequent cause of hospitalisation among children; however, little is known regarding the effects of asthma on immune responses in children. Objective: The present study aimed to evaluate cytokine responses of peripheral blood mononuclear cells (PBMCs), PBMC composition and lung function in children with and without asthma. Methods: Using a case-control design, we compared 48 children with asthma aged 3-11 years with 14 age-matched healthy controls. PBMC composition and cytokine production including interferon (IFN)-γ, interleukin (IL)-1ß, IL-5 and lL-6 following stimulation with rhinovirus-1B (RV1B), house dust mite (HDM) and lipopolysaccharide (LPS) were measured. Lung function was assessed using impulse oscillometry and nitrogen multiple breath washout. Results: The frequency of group 2 innate lymphoid cells were significantly higher in asthmatics and PBMCs from asthmatics had deficient IFN-γ production in response to both RV1B and LPS compared with controls (P<0.01). RV1B-induced IL-1ß response and HDM-stimulated IL-5 production was higher in asthmatics than controls (P<0.05). In contrast, IL-1ß and IL-6 were significantly reduced in response to HDM and LPS in asthmatics compared to controls (P<0.05). Children with asthma also had reduced pulmonary function, indicated by lower respiratory reactance as well as higher area of-reactance and lung clearance index values compared with controls (P<0.05). Conclusion: Our study indicates that children with asthma have a reduced lung function in concert with impaired immune responses and altered immune cell subsets. Improving our understanding of immune responses to viral and bacterial infection in childhood asthma can help to tailor management of the disease.

Short-chain fatty acids, prebiotics, synbiotics, and systemic inflammation: a systematic review and meta-analysis.

BACKGROUND: Prebiotic soluble fibers are fermented by beneficial bacteria in the colon to produce short-chain fatty acids (SCFAs), which are proposed to have systemic anti-inflammatory effects. OBJECTIVE: This review examines the effect of SCFAs, prebiotics, and pre- and probiotic combinations (synbiotics) on systemic inflammation. DESIGN: Relevant English language studies from 1947 to May 2017 were identified with the use of online databases. Studies were considered eligible if they examined the effects of SCFAs, prebiotics, or synbiotics; were delivered orally, intravenously, or per rectum; were on biomarkers of systemic inflammation in humans; and performed meta-analysis where possible. RESULTS: Sixty-eight studies were included. Fourteen of 29 prebiotic studies and 13 of 26 synbiotic studies reported a significant decrease in ≥1 marker of systemic inflammation. Eight studies compared prebiotic and synbiotic supplementation, 2 of which reported a decrease in inflammation with synbiotics only, with 1 reporting a greater anti-inflammatory effect with synbiotics than with prebiotics alone. Meta-analyses indicated that prebiotics reduce C-reactive protein (CRP) [standardized mean difference (SMD): -0.60; 95% CI: -0.98, -0.23], and synbiotics reduce CRP (SMD: -0.40; 95% CI: -0.73, -0.06) and tumor necrosis factor-α (SMD -0.90; 95% CI: -1.50, -0.30). CONCLUSIONS: There is significant heterogeneity of outcomes in studies examining the effect of prebiotics and synbiotics on systemic inflammation. Approximately 50% of included studies reported a decrease in ≥1 inflammatory biomarker. The inconsistency in reported outcomes may be due to heterogeneity in study design, supplement formulation, dosage, duration, and subject population. Nonetheless, meta-analyses provide evidence to support the systemic anti-inflammatory effects of prebiotic and synbiotic supplementation.

The Impact of a Weight Loss Intervention on Diet Quality and Eating Behaviours in People with Obesity and COPD.

There is a paucity of evidence to guide clinicians about appropriate management strategies for people with obesity and Chronic Obstructive Pulmonary Disease (COPD). We have recently published results from the first weight loss intervention in adults (>18 years) with obesity (body mass index; BMI ≥ 30 kg/m²) and COPD, using a low-calorie diet coupled with a partial meal replacement plan and resistance exercise training, which resulted in a 6.4% reduction in weight while maintaining skeletal muscle mass and improving health status. This sub-study aims to evaluate the intervention by (a) examining changes in dietary intake and nutritional biomarkers and (b) examining predictors of weight loss. Dietary intake was evaluated using four-day food diaries, and analysis of plasma fatty acids and plasma carotenoids as biomarkers of dietary fat intake and fruit and vegetable intake, respectively. Twenty-eight obese COPD subjects (n = 17 males, n = 11 females) with a mean (standard deviation; SD) age of 67.6 (6.3) years completed the 12-week weight loss intervention. Pre-intervention, mean (SD) BMI was 36.3 (4.6) kg/m². Micronutrient intake improved from pre- to post-intervention, with the percentage of subjects meeting the Nutrient Reference Values increased for all micronutrients. Post-intervention, significant decreases in total (p = 0.009) and saturated fat intake (p = 0.037), and corresponding decreases in total (p = 0.007) and saturated plasma fatty acids (p = 0.003) were observed. There was a trend towards higher total carotenoids post-intervention (p = 0.078). Older age (p = 0.025), higher pre-intervention uncontrolled eating (p < 0.001) and plasma carotenoids (p = 0.009) predicted weight loss. This demonstrates the efficacy of a weight loss intervention in improving diet quality of obese COPD adults.