Association of body mass index with the development of methacholine airway hyperresponsiveness in men: the Normative Aging Study

A clinician's guide to effects of obesity on childhood asthma and into adulthood

INTRODUCTION

Obesity, one of the most common chronic conditions affecting the human race globally, affects several organ systems, including the respiratory system, where it contributes to onset and high burden of asthma. Childhood onset of obesity-related asthma is associated with high persistent morbidity into adulthood.

AREAS COVERED

In this review, we discuss the disease burden in children and adults to highlight the overlap between symptoms and pulmonary function deficits associated with obesity-related asthma in both age ranges, and then discuss the potential role of three distinct mechanisms, that of mechanical fat load, immune perturbations, and of metabolic perturbations on the disease burden. We also discuss interventions, including medical interventions for weight loss such as diet modification, that of antibiotics and anti-inflammatory therapies, as well as that of surgical intervention on amelioration of burden of obesity-related asthma.

EXPERT OPINION

With increase in obesity-related asthma due to increasing burden of obesity, it is evident that it is a disease entity distinct from asthma among lean individuals. The time is ripe to investigate the underlying mechanisms, focusing on identifying novel therapeutic targets as well as consideration to repurpose medications effective for other obesity-mediated complications, such as insulin resistance, dyslipidemia and systemic inflammation.

Abnormal saturated fatty acids and sphingolipids metabolism in asthma

Recent advances in fatty acid analysis have highlighted the links between lipid disruption and disease development. Lipid abnormalities are well-established risk factors for many of the most common chronic illnesses, and their involvement in asthma is also becoming clear. Here, we review research demonstrating the role of abnormal lipid metabolism in asthma, with a focus on saturated fatty acids and sphingolipids. High levels of palmitic acid, the most abundant saturated fatty acid in the human body, have been found in the airways of asthmatic patients with obesity, and were shown to worsen eosinophilic airway inflammation in asthma model mice on a high-fat diet. Aside from being a building block of longer-chain fatty acids, palmitic acid is also the starting point for de novo synthesis of ceramides, a class of sphingolipids. We outline the three main pathways for the synthesis of ceramides, which have been linked to the severity of asthma and act as precursors for the dynamic lipid mediator sphingosine 1-phosphate (S1P). S1P signaling is involved in allergen-induced eosinophilic inflammation, airway hyperresponsiveness, and immune-cell trafficking. A recent study of mice with mutations for the elongation of very long-chain fatty acid family member 6 (Elovl6), an enzyme that elongates fatty acid chains, has highlighted the potential role of palmitic acid composition, and thus lipid balance, in the pathophysiology of allergic airway inflammation. Elovl6 may be a potential therapeutic target in severe asthma.

Association of Obesity and Severe Asthma in Adults

The incidence of obesity and asthma continues to enhance, significantly impacting global public health. Adipose tissue is an organ that secretes hormones and cytokines, causes meta-inflammation, and contributes to the intensification of bronchial hyperreactivity, oxidative stress, and consequently affects the different phenotypes of asthma in obese people. As body weight increases, the risk of severe asthma increases, as well as more frequent exacerbations requiring the use of glucocorticoids and hospitalization, which consequently leads to a deterioration of the quality of life. This review discusses the relationship between obesity and severe asthma, the underlying molecular mechanisms, changes in respiratory function tests in obese people, its impact on the occurrence of comorbidities, and consequently, a different response to conventional asthma treatment. The article also reviews research on possible future therapies for severe asthma. The manuscript is a narrative review of clinical trials in severe asthma and comorbid obesity. The articles were found in the PubMed database using the keywords asthma and obesity. Studies on severe asthma were then selected for inclusion in the article. The sections: 'The classification connected with asthma and obesity', 'Obesity-related changes in pulmonary functional tests', and 'Obesity and inflammation', include studies on subjects without asthma or non-severe asthma, which, according to the authors, familiarize the reader with the pathophysiology of obesity-related asthma.

The role of ACT score in mepolizumab discontinuation

BACKGROUND

Mepolizumab is a therapy for severe asthma. We have little knowledge of the characteristics of people in the US that discontinue mepolizumab in clinical care.

OBJECTIVE

To investigate the real-world efficacy and time to clinical discontinuation of mepolizumab, we evaluated individuals with asthma started on mepolizumab at the Cleveland Clinic. We hypothesized that individuals that discontinue mepolizumab have more severe and uncontrolled asthma at baseline.

METHODS

Between 2016 and 2022, patients who started on mepolizumab consented to be assessed over 18 months. At baseline, a questionnaire including demographic and medical history was collected. Laboratory findings such as ACT score, FENO (Fractional Excretion of Nitric Oxide), and spirometry were recorded. At the conclusion of the observation period, the participants were divided into two categories: Group A and Group B.

RESULTS

Group B [N = 28] discontinued mepolizumab (p < 0.05) at an average of 5.8 months (SD 4.2 months). Group A [N = 129] stayed on the therapy for at least 1 year. A participant with an ACT score less than 13 has an odds ratio of 6.64 (95% CI, 2.1 - 26.0) of discontinuing mepolizumab therapy. For a male, the odds of discontinuing mepolizumab therapy is 3.39 (95% CI, 1.1-11.2).

CONCLUSION

In this real-world study, we find that high eosinophil count may not be adequate in screening which individuals will benefit from mepolizumab. Up to 17% of patients fail therapy within 6 months, with male sex and low ACT score increasing risk of mepolizumab discontinuation at Cleveland Clinic.

Right place, no trace: A case report of postintubation bronchospasm

Evidence suggests obesity correlates with airway hyperreactivity, which can result in severe bronchospasm. This report presents a 31-year-old female with a high body mass index who presented for a laparoscopic hysterectomy and bilateral salpingo-oophorectomy. She had no past medical or atopic history. After induction of anaesthesia and intubation, O2 saturation fell with no CO2 trace, breathing sounds or chest rise. Despite confirming endotracheal tube position by video laryngoscopy, the CO2 trace remained flat and mechanical ventilation was difficult with high airway pressures. Blood pressure was stable with no mucocutaneous signs of anaphylaxis. Administration of 100% O2, bronchodilators and steroids improved ventilation and oxygenation with a return of a CO2 trace. The operation was postponed. Prior to her subsequent surgery, the patient was premedicated with inhaled steroids and long-acting beta agonist with an uneventful induction and intubation. Giving a rising obese population, this case report aims to educate anaesthetists and anaesthetic practitioners as to the presentation, risk factors, mechanisms and management of uncommon, life-threatening postintubation bronchospasm.

Atracurium-Induced Bronchospasm With Flat Capnograph at Induction of General Anaesthesia: A Case Report

Benzylisoquinolinium neuromuscular blocking agents can precipitate bronchospasm either through allergy/anaphylaxis or isolated stimulation of mast cell histamine release. This report presents a 75-year-old female who attended the day surgery unit for a rigid cystoscopy under general anaesthesia. She had a hyper-reactive airway history of mild historic asthma and sensitivity to aerosols. After administration of atracurium at induction of anaesthesia, ventilation became challenging with no chest rise and a flat CO2 trace. Repeat video laryngoscopy confirmed correct endotracheal tube position. The patient remained cardiovascularly stable with no mucocutaneous signs of anaphylaxis. Administration of high flow oxygen, sevoflurane, salbutamol and magnesium sulfate led to gradual improvement and normalisation of respiratory parameters. Surgery was postponed. This report highlights atracurium as an important trigger of bronchospasm at induction of anaesthesia, and illustrates that in rare cases a flat capnograph does not always indicate a mispositioned airway device. Several aspects of the anaesthetic plan for this patient were suboptimal given her respiratory history, namely, the choice of mode of anaesthesia and choice of neuromuscular blocking agent. These factors are discussed in the context of anaesthetic planning for patients presenting with features suggesting high bronchospastic risk.

High-fat Western diet alters crystalline silica-induced airway epithelium ion transport but not airway smooth muscle reactivity

OBJECTIVES

Silicosis is an irreversible occupational lung disease resulting from crystalline silica inhalation. Previously, we discovered that Western diet (HFWD)-consumption increases susceptibility to silica-induced pulmonary inflammation and fibrosis. This study investigated the potential of HFWD to alter silica-induced effects on airway epithelial ion transport and smooth muscle reactivity.

METHODS

Six-week-old male F344 rats were fed a HFWD or standard rat chow (STD) and exposed to silica (Min-U-Sil 5®, 15 mg/m3, 6 h/day, 5 days/week, for 39 d) or filtered air. Experimental endpoints were measured at 0, 4, and 8 weeks post-exposure. Transepithelial potential difference (Vt), short-circuit current (ISC) and transepithelial resistance (Rt) were measured in tracheal segments and ion transport inhibitors [amiloride, Na+ channel blocker; NPPB; Cl- channel blocker; ouabain, Na+, K+-pump blocker] identified changes in ion transport pathways. Changes in airway smooth muscle reactivity to methacholine (MCh) were investigated in the isolated perfused trachea preparation.

RESULTS

Silica reduced basal ISC at 4 weeks and HFWD reduced the ISC response to amiloride at 0 week compared to air control. HFWD + silica exposure induced changes in ion transport 0 and 4 weeks after treatment compared to silica or HFWD treatments alone. No effects on airway smooth muscle reactivity to MCh were observed.

Effect of overweight/obesity on relationship between fractional exhaled nitric oxide and airway hyperresponsiveness in Chinese elderly patients with asthma

Purpose: This retrospective study investigates the influence of overweight and obesity status on pulmonary function, airway inflammatory markers, and airway responsiveness in elderly asthma patients. Methods: Patients with asthma older than 65 years old who completed a bronchial provocation test (BPT) or bronchial dilation test (BDT) and a fractional exhaled nitric oxide (FeNO) test between December 2015 and June 2020 were identified retrospectively for this study. All of the patients were categorized into overweight/obesity and non-obesity groups based on their BMI. Pulmonary function test (PFT) and FeNO measurements were accomplished according to the 2014 recommendations of the Chinese National Guidelines of Pulmonary Function Test and American Thoracic Society/European Respiratory Society recommendations, respectively. Results: A total of 136 patients with an average age of 71.2 ± 5.40 years were identified. The average BMI was 23.8 ± 3.63, while the value of FeNO was 42.3 ± 38.4 parts per billion (ppb). In contrast to the non-obesity group, which had a value of 48.8 ± 43.1 ppb for FeNO, the overweight/obesity group had a significant lower value of 35.4 ± 31.4 ppb. There was no significant difference in the proportion of individuals with high airway hyperresponsiveness between the overweight/obesity and non-obesity groups (96 patients in total). Multiple linear regression analysis established an inverse correlation between FeNO and Provocation concentration causing a 20% fall in FEV1(PC20) but excluded significant relationships with age and BMI. The model's R is 0.289, and its p value is 0.045. Conclusion: The elderly Chinese Han asthmatics with overweight/obesity had lower FeNO levels than those with non-obese according to our findings. In addition, the FeNO level was inversely correlated between FeNO levels and PC20 in elderly asthmatics.

Bariatric surgery decreases the capacity of plasma from obese asthmatic subjects to augment airway epithelial cell proinflammatory cytokine production

Obesity is a risk factor for asthma. Individuals with asthma and obesity often have poor asthma control and do not respond as well to therapies such as inhaled corticosteroids and long-acting bronchodilators. Weight loss improves asthma control, with a 5%-10% loss in body mass necessary and sufficient to lead to clinically relevant improvements. Preclinical studies have demonstrated the pathogenic contribution of adipocytes from obese mice to the augmented production of proinflammatory cytokines from airway epithelial cells and the salutary effects of diet-induced weight loss to decrease these consequences. However, the effects of adipocyte-derived products on airway epithelial function in human obesity remain incompletely understood. We utilized samples collected from a 12-mo longitudinal study of subjects with obesity undergoing weight loss (bariatric) surgery including controls without asthma and subjects with allergic and nonallergic obese asthma. Visceral adipose tissue (VAT) samples were collected during bariatric surgery and from recruited normal weight controls without asthma undergoing elective abdominal surgery. Human bronchial epithelial (HBEC3-KT) cells were exposed to plasma or conditioned media from cultured VAT adipocytes with or without agonists. Human bronchial smooth muscle (HBSM) cells were similarly exposed to adipocyte-conditioned media. Proinflammatory cytokines were augmented in supernatants from HBEC3-KT cells exposed to plasma as compared with subsequent visits. Whereas exposure to obese adipocyte-conditioned media induced proinflammatory responses, there were no differences between groups in both HBEC3-KT and HBSM cells. These data show that bariatric surgery and subsequent weight loss beneficially change the circulating factors that augment human airway epithelial and bronchial smooth muscle cell proinflammatory responses.NEW & NOTEWORTHY This longitudinal study following subjects with asthma and obesity reveals that weight loss following bariatric surgery decreases the capacity for plasma to augment proinflammatory cytokine secretion by human bronchial epithelial cells, implicating that circulating but not adipocyte-derived factors are important modulators in obese asthma.

Prevalence of active and passive smoking among asthma and asthma-associated emergency admissions: a nationwide prevalence survey study

Asthma affects 7% of children and 8% of adults in the United States. There is a paucity of studies examining the association between passive smoking and an increased risk of asthma exacerbations that led the authors to examine the association between various modes of smoking and rates of asthma exacerbations. A retrospective cross-sectional/case-control study was conducted using the National Health and Nutrition Examination Survey dataset (2013-2018). Out of 312,979 respondents, 35,758 (11.43%) had a history of asthma, 9083 (2.9%) had asthma attacks in the past year, and 4731 (1.51%) had asthma-related emergency room admissions in the past year. Prevalence of asthma-related emergency admissions were higher among active cigarette smoking (46.25 vs 35.46%), e-cigarette smoking (26.63 vs 16.07%), and passive smoking at home (37.53 vs 25.67%), workplace passive smoking (14.35 vs 12.11%), in bar (32.38 vs 26.16%), and car (26.21 vs 14.44%) (p < 0.0001). In multivariate regression analysis, we found regular cigarette smoking (OR 1.13, 95% confidence interval (CI) 1.009-1.260, p = 0.0252), e-cigarette (OR 2.13, 95% CI 1.92-2.36, p = 0.0043), cigar use (OR 1.21, 95% CI 1.1-1.33, p < 0.001), ultra-long cigarette length (OR 4.85, 95% CI 3.33-7.06, p < 0.0001), and passive smoking (OR 5.25, 95% CI 3.43-8.06, p < 0.0001) were associated with increased rates of asthma exacerbations over last 12 months. The study shows increased odds of asthma exacerbations among those using ultra-long cigarettes, e-cigarettes, and cigars. Consequently, passive inhalation from even a single smoker in the home, workplace, bars and cars is associated with worsening outcomes in asthma patients.

Meta-omics profiling of the gut-lung axis illuminates metabolic networks and host-microbial interactions associated with elevated lung elastance in a murine model of obese allergic asthma

Obesity and associated changes to the gut microbiome worsen airway inflammation and hyperresponsiveness in asthma. Obesogenic host-microbial metabolomes have altered production of metabolites that may influence lung function and inflammatory responses in asthma. To understand the interplay of the gut microbiome, metabolism, and host inflammation in obesity-associated asthma, we used a multi-omics approach to profile the gut-lung axis in the setting of allergic airway disease and diet-induced obesity. We evaluated an immunomodulator, nitro-oleic acid (NO₂-OA), as a host- and microbial-targeted treatment intervention for obesity-associated allergic asthma. Allergic airway disease was induced using house dust mite and cholera toxin adjuvant in C57BL6/J mice with diet-induced obesity to model obesity-associated asthma. Lung function was measured by flexiVent following a week of NO₂-OA treatment and allergen challenge. 16S rRNA gene (from DNA, taxa presence) and 16S rRNA (from RNA, taxa activity) sequencing, metabolomics, and host gene expression were paired with a Treatment-Measured-Response model as a data integration framework for identifying latent/hidden relationships with linear regression among variables identified from high-dimensional meta-omics datasets. Targeting both the host and gut microbiota, NO₂-OA attenuated airway inflammation, improved lung elastance, and modified the gut microbiome. Meta-omics data integration and modeling determined that gut-associated inflammation, metabolites, and functionally active gut microbiota were linked to lung function outcomes. Using Treatment-Measured-Response modeling and meta-omics profiling of the gut-lung axis, we uncovered a previously hidden network of interactions between gut levels of amino acid metabolites involved in elastin and collagen synthesis, gut microbiota, NO₂-OA, and lung elastance. Further targeted metabolomics analyses revealed that obese mice with allergic airway disease had higher levels of proline and hydroxyproline in the lungs. NO₂-OA treatment reduced proline biosynthesis by downregulation of pyrroline-5-carboxylate reductase 1 (PYCR1) expression. These findings are relevant to human disease: adults with mild-moderate asthma and BMI ≥ 25 had higher plasma hydroxyproline levels. Our results suggest that changes to structural proteins in the lung airways and parenchyma may contribute to heightened lung elastance and serve as a potential therapeutic target for obese allergic asthma.

Fat mass index and airway hyperresponsiveness in Korean adults

OBJECTIVE

Airway hyperresponsiveness (AHR) is associated with asthma and obesity, which is defined as a high body mass index. Body mass mainly comprises fat mass (FM) and muscle mass (MM), which are independent of each other. We investigated the effect of changes in FM over time on the development of asymptomatic AHR in adults.

METHODS

This long-term longitudinal study included adults who were underwent health checkups at the Seoul National University Hospital Gangnam Center. The participants underwent two methacholine bronchial provocation tests with a follow-up period (between the first and second tests) of more than 3 years and bioelectrical impedance analysis (BIA) at all visits. FM index (FMI; FM normalized for height) and MM index (MMI; MM normalized for height) were calculated using BIA.

RESULTS

The study included 328 adult participants (61 women and 267 men). The mean number of BIA measurements was 6.96 and the follow-up duration was 6.69 years. In total, 13 participants showed a positive conversion of AHR. Multivariate analysis indicated that a high rate of change in FMI ([g/m²]/year), not MMI, was significantly associated with the risk of AHR development (P = 0.037) after adjustment for age, sex, smoking status, and FEV1 predicted.

CONCLUSION

A rapid gain of FM over time may be a risk factor for developing AHR in adults. Prospective studies are needed to confirm our results and evaluate the role of FM reduction in preventing AHR development in obese adults.

Effect of Obesity on Airway Mechanics

Background

Obesity is known to induce lung function impairment. Previous studies of decline in lung function associated with obesity are well established.

Materials and Methods

In this cross-sectional study, to evaluate the effects of different obesity indices on lung mechanics, healthy subjects (males-23 and females-22) were recruited. Anthropometric parameters like body mass index (BMI), waist circumference (WC), hip circumference (HC) and neck circumference (NC) were measured and waist-hip ratio (WHR) was derived. Spirometry, impulse oscillometry (IOS) and fractional exhaled nitric oxide (FeNO) measurements were performed to assess lung function. Subgroups were divided and analysed.

Results

In males, increased WHR is associated with increased total airway resistance (R5). BMI correlates positively with R5, R5% predicted, resistance at 20 Hz (R20) and R20% predicted; likewise, WHR shows a positive correlation with R5. In females, increased WHR has significantly higher R5, R5% predicted, R20, R20% predicted, area of reactance (Ax), resonant frequency (Fres) and decreased reactance at 5 Hz (X5), reactance at 20 Hz (X20), X20% predicted. The female group with higher WC shows significantly increased R5, R5% predicted, R20, R20% predicted, Ax, Fres and lower fixed ratio of forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC), X5, X20, X20% predicted. The group with higher NC has a lower FEV1/FVC ratio. WHR positively correlated with R5% predicted and Fres while WC correlated positively with R5, R5% predicted, Ax and Fres; same way, NC with X5% predicted.

Conclusion

Obesity/overweight causes significant changes in lung volumes, capacity and airway mechanics, Higher WC and WHR are associated with significant changes in lung mechanics, which are more prominent in females than in males. NC is not associated with changes in lung mechanics.

ELOVL6 deficiency aggravates allergic airway inflammation through the ceramide-S1P pathway in mice

BACKGROUND

Elongation of very-long-chain fatty acids protein 6 (ELOVL6), an enzyme regulating elongation of saturated and monounsaturated fatty acids with C12 to C16 to those with C18, has been recently indicated to affect various immune and inflammatory responses; however, the precise process by which ELOVL6-related lipid dysregulation affects allergic airway inflammation is unclear.

OBJECTIVES

This study sought to evaluate the biological roles of ELOVL6 in allergic airway responses and investigate whether regulating lipid composition in the airways could be an alternative treatment for asthma.

METHODS

Expressions of ELOVL6 and other isoforms were examined in the airways of patients who are severely asthmatic and in mouse models of asthma. Wild-type and ELOVL6-deficient (Elovl6^-/-) mice were analyzed for ovalbumin-induced, and also for house dust mite-induced, allergic airway inflammation by cell biological and biochemical approaches.

RESULTS

ELOVL6 expression was downregulated in the bronchial epithelium of patients who are severely asthmatic compared with controls. In asthmatic mice, ELOVL6 deficiency led to enhanced airway inflammation in which lymphocyte egress from lymph nodes was increased, and both type 2 and non-type 2 immune responses were upregulated. Lipidomic profiling revealed that the levels of palmitic acid, ceramides, and sphingosine-1-phosphate were higher in the lungs of ovalbumin-immunized Elovl6^-/- mice compared with those of wild-type mice, while the aggravated airway inflammation was ameliorated by treatment with fumonisin B1 or DL-threo-dihydrosphingosine, inhibitors of ceramide synthase and sphingosine kinase, respectively.

CONCLUSIONS

This study illustrates a crucial role for ELOVL6 in controlling allergic airway inflammation via regulation of fatty acid composition and ceramide-sphingosine-1-phosphate biosynthesis and indicates that ELOVL6 may be a novel therapeutic target for asthma.

Subgroup Analysis of a Randomized Trial of the Effects of Positive Messaging on Patient-Reported Outcomes with Asthma - Effect of Obesity

Objective

Asthma in obese patients represents a specific phenotype that is associated with increased symptoms, more frequent and severe exacerbations, reduced responsiveness to treatment, and decreased quality of life. Marketing and placebos have been shown to alter subjective responses to interventions in both asthma and obesity. We evaluated obesity as a potential treatment effect modifier of the effects enhanced drug messaging or placebos on subjective asthma outcomes.

Methods

We conducted a secondary analysis of a multicenter, randomized clinical trial that studied the effect of messaging and placebos on asthma outcomes. A total of 601 participants were randomized (1:1:1:1:1) to one of 5 groups: enhanced messaging with montelukast or placebo, neutral messaging with montelukast or placebo, or usual care and followed for 4 weeks after randomization. We compared baseline characteristics by obesity status for 600 participants with data on body weight. Obesity was evaluated as an effect modifier for enhanced messaging (versus neutral messaging) and on placebo effects (versus usual care) in 362 participants assigned to a placebo group or usual care for three asthma questionnaires: Asthma Control Questionnaire, Asthma Quality of Life Questionnaire and Asthma Symptoms Utility Index.

Results

Overall, 227 (37%) of participants were obese. Obese participants were older (mean age 41 vs 34), more likely female (82% vs 67%) and self-identified as Black (44% vs 25%) than non-obese participants. As previously published, enhanced messaging was associated with improvements in patient-reported asthma scores, but there was no evidence for a placebo effect. Obesity status did not influence the message effects nor did it modify responses to placebo.

Conclusion

Obesity has been shown to be an important factor associated with asthma outcomes and an effect modifier of drug treatment effects. We conducted a post hoc, subgroup analysis of data from a multicenter randomized trial of enhanced messaging and placebo associated with drug treatment on asthma outcomes. Our findings suggest that observed differences in treatment effects between obese and non-obese patients sometimes seen in trials of asthma treatments are unlikely to be due to different "placebo" effects of treatment and may reflect differential physiologic effects of active agents.

The Dual Pandemics of COVID-19 and Obesity: Bidirectional Impact

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for the COVID-19 pandemic, has been shown to disrupt many organ systems in the human body. Though several medical disorders have been affected by this infection, a few illnesses in addition may also play a role in determining the outcome of COVID-19. Obesity is one such disease which is not only affected by the occurrence of COVID-19 but can also result in a worse clinical outcome of COVID-19 infection. This manuscript summarizes the most recent evidence supporting the bidirectional impact of COVID-19 and obesity. It highlights how the presence of obesity can be detrimental to the outcome of COVID-19 in a given patient because of the mechanical limitations in lung compliance and also by the activation of several thrombo-inflammatory pathways. The sociodemographic changes brought about by the pandemic in turn have facilitated the already increasing prevalence of obesity. This manuscript highlights the importance of recognizing these pathways which may further help in policy changes that facilitate appropriate measures to prevent the further worsening of these two pandemics.

Asthma interactions between obesity and other risk factors

OBJECTIVE

To review and critically discuss published evidence on interactions between obesity and selected risk factors on asthma in children and adults, and to discuss potential future directions in this field.

DATA SOURCES

National Library of Medicine (via PubMed) STUDY SELECTION: A literature search was conducted for human studies on obesity and selected interactions (with sex, race and ethnicity, socioeconomic status, indoor and outdoor pollutants, depression, anxiety, and diet) on asthma. Studies that were published in English and contained a full text were considered for inclusion in this review.

RESULTS

Current evidence supports interactions between obesity and outdoor and indoor air pollutants (including second-hand smoke [SHS]) on enhancing asthma risk, although there are sparse data on the specific pollutants underlying such interactions. Limited evidence also suggests that obesity may modify the effects of depression or anxiety on asthma, whereas little is known about potential interactions between obesity and sex-hormone levels or dietary patterns.

CONCLUSION

Well-designed observational prospective studies (eg, for pollutants and sex hormones) and randomized clinical trials (eg, for the treatment of depression) should help establish the impact of modifying coexisting exposures to reduce the harmful effects of obesity on asthma. Such studies should be designed to have a sample size that is large enough to allow adequate testing of interactions between obesity and risk factors that are identified a priori and thus, well characterized, using objective measures and biomarkers (eg, urinary or serum cotinine for SHS, epigenetic marks of specific environmental exposures).

When Pandemics Collide: the Interplay of Obesity and COVID-19

PURPOSE OF REVIEW

The COVID-19 pandemic has been associated with significant morbidity and mortality worldwide. In addition to those with advanced age and co-morbidities such as heart disease or cancer, obese individuals have also had very high rates of hospitalization, critical illness, need for ventilator support, as well as mortality. A number of factors associated with obesity have led to devastating consequences as these two pandemics have interacted.

RECENT FINDINGS

Obese individuals through a combination of structural and cellular level changes have greater risk of ischemic heart disease, diabetes, cancer, and respiratory disease, which are themselves risk-factors for acquiring COVID-19 disease. These structural changes also result in increased intra-abdominal and intra-thoracic pressure as well as a restrictive lung physiology that leads to reduction in total lung capacity, functional residual capacity, and increase in airway hyper-reactivity. Adipose tissue is also impacted in obese individuals leading to local as well as systemic inflammation, which can contribute to increased release of free fatty acids and systemic insulin resistance. Additionally, angiotensin-converting enzyme 2 and dipeptidyl peptidase 4, which act as receptors for SARS-CoV-2 are also significantly increased in obese individuals. The present manuscript reviews these structural, immune, and molecular changes associated with obesity that make obese individuals more vulnerable to acquiring severe COVID-19 and more challenging to manage associated complications.

Paediatric obesity-related asthma: Disease burden and effects on pulmonary physiology

The prevalence of asthma and obesity in children has been steadily increasing globally over the past several decades, with increased concern in low and middle income countries. In this review, we summarize the current literature on these two parallel epidemics and explore the relationship between paediatric obesity and asthma in the paediatric population. Finally, we focus on the current literature as it relates to underlying physiologic alterations and changes in pulmonary function for children with obesity and asthma.

Childhood Obesity and Respiratory Diseases: Which Link?

Prevalence of childhood obesity is progressively increasing, reaching worldwide levels of 5.6% in girls and of 7.8% in boys. Several evidences showed that obesity is a major preventable risk factor and disease modifier of some respiratory conditions such as asthma and Obstructive Sleep Apnea Syndrome (OSAS). Co-occurrence of asthma and obesity may be due to common pathogenetic factors including exposure to air pollutants and tobacco smoking, Western diet, and low Vitamin D levels. Lung growth and dysanapsis phenomenon in asthmatic obese children play a role in impaired respiratory function which appears to be different than in adults. Genes involved in both asthma and obesity have been identified, though a gene-by-environment interaction has not been properly investigated yet. The identification of modifiable environmental factors influencing gene expression through epigenetic mechanisms may change the natural history of both diseases. Another important pediatric respiratory condition associated with obesity is Sleep-Disordered Breathing (SDB), especially Obstructive Sleep Apnea Syndrome (OSAS). OSAS and obesity are linked by a bidirectional causality, where the effects of one affect the other. The factors most involved in the association between OSAS and obesity are oxidative stress, systemic inflammation, and gut microbiota. In OSAS pathogenesis, obesity's role appears to be mainly due to mechanical factors leading to an increase of respiratory work at night-time. However, a causal link between obesity-related inflammatory state and OSAS pathogenesis still needs to be properly confirmed. To prevent obesity and its complications, family education and precocious lifestyle changes are critical. A healthy diet may lead to an improved quality of life in obese children suffering from respiratory diseases. The present review aimed to investigate the links between obesity, asthma and OSAS, focusing on the available evidence and looking for future research fields.

Association between obesity and lung function changes by sex and age in adults with asthma

OBJECTIVE

The lung function changes presenting before and after asthma treatment in obese people remain largely unknown. This study aimed to investigate the association between obesity and lung function changes before and after treatment in adults with asthma.

METHODS

We enrolled 937 newly diagnosed asthma patients from Cohort for Reality and Evolution of Adult Asthma in Korea cohort in 2015-2017, who performed follow-up spirometry after three months of asthma treatment. The percentage changes (Δ) between the spirometry results before and after treatment were calculated. Patients were categorized into four body mass index (BMI) groups; underweight (<18.5), normal (18.5-22.9), overweight (23.0-24.9), and obese (≥25.0). Association between percent change of pulmonary function and BMI was analyzed according to sex and/or age (< 45 yrs, 45-65 yrs, ≥ 65 yrs), which were statistically corrected for age, sex, smoking status, and medication history.

RESULTS

There was no consistent correlation between BMI and each lung function parameter. However, there were significant differences between BMI and ΔFEV₁/FVC before and after 3 months of controller treatment. The obese asthmatics showed significantly lower ΔFEV₁/FVC (6.0 ± 13.5%) than the underweight (12.6 ± 21.4%, P = 0.044) or normal weight (9.1 ± 14.6%, P = 0.031). Middle-aged women had higher BMI (24.11 ± 3.60 vs. 22.39 ± 3.52) and lower ΔFEV₁/FVC (5.7 ± 11.9% vs. 8.9 ± 14.3%, P = 0.012) than young women.

CONCLUSIONS

Obesity is negatively correlated with the ΔFEV₁/FVC before and after controller treatment. Sex and age differentially contribute to lung function changes in response to asthma medications in adult asthmatics, showing a significant decrease in the ΔFEV₁/FVC in middle-aged women.

A life course approach to elucidate the role of adiposity in asthma risk: evidence from a Mendelian randomisation study

BACKGROUND

Adiposity is associated with asthma although studies do not usually explore the inter-related role of childhood and adult adiposity in asthma risk using a life course perspective.

METHODS

We conducted a Mendelian randomisation (MR) study using genetic instruments for childhood body mass index (BMI) (n=47 541), childhood obesity (n=29 822) and adult BMI (n=681 725) applied to the UK Biobank (n=401 837), with validation in a genome-wide association study of asthma (GABRIEL, n=5616). We used inverse variance weighting and other sensitivity analyses to examine the relationship between adiposity and asthma risk. We assessed mediation using multivariable Mendelian randomisation (MVMR) analysis.

RESULTS

Childhood BMI was related to asthma in the UK Biobank (OR 1.10 per SD increase, 95% CI 0.99 to 1.22). Adult BMI was associated with asthma risk (OR 1.33 per SD increase, 95% CI 1.25 to 1.43). Analyses in GABRIEL gave directionally consistent results but with wide CI. The relationship between childhood obesity and asthma risk was less clear in both data sources. MVMR suggested the relation of childhood BMI with asthma risk was largely mediated via adult BMI.

CONCLUSION

Adiposity in childhood likely cause asthma, but the effect is primarily mediated via adult BMI.

Association between Body Mass Index and Prevalence of Asthma in Korean Adults

We evaluated the association between body mass index (BMI) and the prevalence of asthma. Using data from the 2015 Korean Community Health Survey, 214,971 participants aged between 19 and 106 years were included in this study. Asthma was defined based on the self-report of physician diagnosis. BMI was classified as underweight (<18.5 kg/m²), normal weight (18.5 kg/m²≤BMI<23.0 kg/m²), overweight (23.0 kg/m²≤ BMI<27.4 kg/m²), and obese (≥27.5 kg/m²) based on the BMI categories for Asians by the World Health Organization. Multiple logistic regression analysis was performed with sampling weights to evaluate the association between BMI and asthma after adjusting for age, educational level, income, type of residential area, smoking status, alcohol consumption, physical activity, hypertension, and diabetes. In men, BMI had an inverted J-shaped association with the prevalence of asthma, with an odds ratio of 1.88 (95% confidence interval [CI]: 1.89-2.24) for underweight and 1.12 (95% CIs: 0.97-1.29) for obesity. In women, BMI had a J-shaped association with the prevalence of asthma, with an odds ratio of 1.05 (95% CIs: 0.91-1.22) for underweight and 2.29 (95% CIs: 2.06-2.56) for obesity. In conclusion, in a nationally representative sample of Korean adults, the association between BMI and the prevalence of asthma varied between the sexes. This suggests that malnutrition and obesity are involved in the pathophysiology of asthma.

[Asthma and obesity in adults]

Asthma is a chronic inflammatory airway disorder characterized by a multitude of phenotypes. Epidemiological studies show an increase in asthma prevalence in obese patients regardless of age. The association of asthma and obesity is now considered as a phenotype with its own clinical, biological and functional characteristics. Regarding the pathophysiology of asthma and obesity, numerous factors such as nutrition, genetic predisposition, microbiome, ventilatory mechanics and the role of adipose tissue have been identified to explain the heterogeneous characteristics of patients with asthma and obesity. In adult patients with asthma and obesity, respiratory symptoms are particularly prominent and atopy and eosinophilic inflammation is uncommon compared to normal weight asthma patients. Obese asthma patients experience more hospitalizations and use more rescue medications than normal weight asthmatics. Management of asthma in obese patients is complex because these patients have less response to the usual anti-asthmatic treatments. Weight loss through caloric restriction combined with exercise is the main intervention to obtain improvement of asthma outcomes. Bariatric surgery is an invasive procedure with interesting results.

Sex differences in the association between asthma incidence and modifiable risk factors in Korean middle-aged and older adults: NHIS-HEALS 10-year cohort

Background

This study investigated the sex-specific incidence of asthma and the effects of modifiable risk factors, particularly obesity, on asthma incidence among middle-aged and older individuals in Korea.

Methods

We used data from the National Health Insurance Service-Health Screening Cohort (NHIS-HEALS), which includes health examinees aged 40–79 years in 2002–2003. In total, 459,529 participants with baseline anthropometric measurements were followed-up for 10 years and the development of asthma was evaluated (2004–2013). For subgroup analysis, 246,019 participants who had body mass index (BMI) and waist circumference (WC) measurements taken in 2008–2009 were included in the analysis of the asthma incidence for 2010–2013. Factors associated with asthma were analysed using Cox proportional hazard models.

Results

The cohort comprised 4,248,813 (men, 2,358,541; women, 1,890,272) person-years of follow-up for 2004–2013. The asthma incidence was 10.58 and 15.03 per 1000 person-years for men and women, respectively. Asthma incidence increased with age, notably so in men. Obesity based on the baseline BMI was significantly associated with asthma development in both sexes (men, HR = 1.23, 95% confidence interval (CI) = 1.13–1.34; women, HR = 1.40 95% CI = 1.32–1.48). High WC was also related to asthma incidence in both sexes with statistical significance (men, HR = 1.34, 95% CI = 1.16–1.57; women, HR = 1.19 95% CI = 1.03–1.37). Analysis of the combined effects of BMI and WC showed that men had a higher asthma risk in the group with both general obesity and abdominal obesity than in the group with non-abdominal obesity and normal BMI. However, obese women had a higher risk of asthma regardless of abdominal obesity. Similarly, smoking was associated with asthma in both sexes but drinking and physical activity showed different associations between the sexes.

Conclusions

Our results revealed that asthma incidence was substantially high at old age and lifestyle factors were associated with asthma development. Practical strategies including weight control and healthy lifestyle modification are required to prevent asthma in older people.

Pubertal BMI change and adult-onset asthma in men: Population-based cohort study in Sweden

BACKGROUND

The role of pubertal BMI change in adult-onset concomitant asthma and allergic rhinitis is unknown.

OBJECTIVE

We investigated the association of childhood and young adult BMI, and pubertal BMI changes with adult-onset asthma, allergic rhinitis, and concomitant asthma and rhinitis in Swedish men.

METHODS

The BMI Epidemiology Study in Gothenburg, Sweden, comprised of height and weight measures taken from school health records (6.5-9.5 years) and during military conscription (17.5-22 years) for all men born 1945-1961 (n = 37 652). Age-adjusted childhood BMI centred at 8 years and young adult BMI at 20 years were linked to high quality data on asthma and allergic rhinitis diagnoses from the Swedish National Patient Register.

FINDINGS

High BMI (4th quartile vs the two median quartiles) at 8 years was associated with increased risk of concomitant asthma and allergic rhinitis (HR 1.45; 95% CI 1.00-2.11). Overweight (HR 1.45; 95% CI 1.12-1.89) and obesity (HR 1.95; 95% CI 1.08-3.54) at 20 years were associated with increased risk of asthma without concomitant allergic rhinitis as main or auxiliary diagnosis. Pubertal BMI change showed a non-linear association, so that both low (1st quartile vs the two median quartiles) and high pubertal BMI changes were associated with increased risk of asthma (low: HR 1.36; 95% CI 1.11-1.68; high: HR 1.32; 95% CI 1.07-1.63) and asthma without concomitant allergic rhinitis (low: HR 1.33; 95% CI 1.04-1.69; high: HR 1.36; 95% CI 1.07-1.74) as a main diagnosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Both low and high pubertal BMI changes are predictors of adult-onset asthma in men, particularly asthma without concomitant allergic rhinitis. Primary prevention of adult-onset asthma requires monitoring of changes in BMI during puberty.

Obesity and childhood asthma in male schoolchildren in Saudi Arabia: Is there a role for leptin, interleukin-4, interleukin-5, and interleukin-21?

BACKGROUND

Adiposity is associated with high serum levels of adipokines and chemokines which are possibly implicated in a co-existence of obesity and asthma.

OBJECTIVES

Elucidate the possible roles of leptin, interleukin (IL)-4, IL-5 and IL-21 in linking obesity with childhood asthma.

DESIGN

Cross-sectional, analytical.

SETTING

Population of schoolchildren in a small Saudi city.

SUBJECTS AND METHODS

The study included a representative sample of Saudi schoolchildren grouped as obese asthmatics, non-obese asthmatics, or obese nonasthmatics, with nonobese nonasthmatics as a control group. An asthma control test was done for the asthmatic groups.

MAIN OUTCOME MEASURES

Serum levels of leptin, IL-4, IL-5, and IL-21.

SAMPLE SIZE

345 male schoolchildren with a mean (SD) age of 13.0 (2.3) years.

RESULTS

Median serum leptin concentrations in obese asthmatics were significantly higher than in nonobese asthmatics ( P<.001). Uncontrolled asthmatics also had significantly higher leptin levels than controlled asthmatic children ( P<.002). Leptin levels were weakly but significantly correlated with the cytokines IL-4, IL-5, and IL-21.

CONCLUSIONS

Leptin may contribute to a link between obesity and childhood asthma. Differences in IL-21 levels between nonobese and obese asthmatics suggest that the co-existence of asthma and obesity increased IL-21 levels. Leptin plus some proinflammatory cytokines especially IL-21 may be potential predictors for asthma control in children.

LIMITATIONS

Blood sampling at different stages of asthma might influence cytokine expression.

CONFLICT OF INTEREST

None.

Outcomes of Noninvasive Ventilation in Obese Patients With Acute Asthma Exacerbations

BACKGROUND

The role of noninvasive positive pressure ventilation (NIPPV) in acute asthma exacerbation is controversial. However, the outcome of NIPPV in obese patients with asthma during such exacerbation has not been well studied despite well-established relationship between obesity and asthma.

STUDY QUESTION

Does body mass index (BMI) play a role in the outcome of NIPPV during an acute exacerbation and does it predict of the success or failure of NIPPV?

STUDY DESIGN

The study was a retrospective analysis by design. The purpose of the study was to assess factors predicting the success or failure of NIPPV. The entire cohort was divided into 2 groups: patients who failed NIPPV and patients who did not. Univariate and multivariate regression analysis was used to predict the variables. Stepwise selection method was used to select variables for final regression model.

RESULTS

A total 96 patients were included in the study. Of those, 18 patients (18.9%) failed NIPPV and required endotracheal intubation (group 1). Rest (78.1%) did not fail NIPPV (group 2). Mean age of the study population was 48.8 years and 53% of patients were female. In the univariate analysis, the group that did not fail NIPPV (group 2) had significantly higher number of obese patients (47.9% versus 22.2%; P 0.013). Multivariate analysis showed significant association between BMI categories (BMI of 30 or more) and failure of NIPPV (odds ratio 0.26, 95% confidence interval, 0.08-0.85; P-value 0.017). Forced introduction of smoking status as a risk factor did not change the significance of association.

CONCLUSION

Despite the limitations of the study design and the sample size, our analysis showed that patients with high BMI (obese) fared well with NIPPV during acute asthma exacerbation. Because there are controversies on use of NIPPV during asthma exacerbation, larger-scale prospective studies are needed to better understand the role of NIPPV in obese patients with asthma during acute exacerbation.

BMI but not central obesity predisposes to airway closure during bronchoconstriction

BACKGROUND AND OBJECTIVE

Obesity produces restrictive effects on lung function. We previously reported that obese patients with asthma exhibit a propensity towards small airway closure during methacholine challenge which improved with weight loss. We hypothesized that increased abdominal adiposity, a key contributor to the restrictive effects of obesity on the lung, mediates this response. This study investigates the effect of body mass index (BMI) versus waist circumference (WC) on spirometric lung function, sensitivity to airway narrowing and closure, and airway closure during bronchoconstriction in patients with asthma.

METHODS

Participants underwent spirometry and methacholine challenge. Sensitivity to airway closure and narrowing was assessed from the dose-response slopes of the forced vital capacity (FVC) and the ratio of forced expiratory volume in 1 s (FEV₁ ) to FVC, respectively. Airway closure during bronchoconstriction (closing index) was computed as the percent reduction in FVC divided by the percent reduction in FEV₁ at maximal bronchoconstriction.

RESULTS

A total of 116 asthmatic patients (56 obese) underwent methacholine challenge. Spirometric lung function was inversely related to WC (P < 0.05), rather than BMI. Closing index increased significantly during bronchoconstriction in obese patients and was related to increasing BMI (P = 0.01), but not to WC. Sensitivity to airway closure and narrowing was not associated with BMI or WC.

CONCLUSION

Although WC is associated with restrictive effects on baseline lung function, increased BMI, rather than WC, predisposes to airway closure during bronchoconstriction. These findings suggest that obesity predisposes to airway closure during bronchoconstriction through mechanisms other than simple mass loading.

Non-eosinophilic asthma: current perspectives

Although non-eosinophilic asthma (NEA) is not the best known and most prevalent asthma phenotype, its importance cannot be underestimated. NEA is characterized by airway inflammation with the absence of eosinophils, subsequent to activation of non-predominant type 2 immunologic pathways. This phenotype, which possibly includes several not well-defined subphenotypes, is defined by an eosinophil count <2% in sputum. NEA has been associated with environmental and/or host factors, such as smoking cigarettes, pollution, work-related agents, infections, and obesity. These risk factors, alone or in conjunction, can activate specific cellular and molecular pathways leading to non-type 2 inflammation. The most relevant clinical trait of NEA is its poor response to standard asthma treatments, especially to inhaled corticosteroids, leading to a higher severity of disease and to difficult-to-control asthma. Indeed, NEA constitutes about 50% of severe asthma cases. Since most current and forthcoming biologic therapies specifically target type 2 asthma phenotypes, such as uncontrolled severe eosinophilic or allergic asthma, there is a dramatic lack of effective treatments for uncontrolled non-type 2 asthma. Research efforts are now focusing on elucidating the phenotypes underlying the non-type 2 asthma, and several studies are being conducted with new drugs and biologics aiming to develop effective strategies for this type of asthma, and various immunologic pathways are being scrutinized to optimize efficacy and to abolish possible adverse effects.

The asthma-obesity relationship: underlying mechanisms and treatment implications

PURPOSE OF REVIEW

Obesity is a worldwide epidemic with a prevalence that has tripled in the last two decades. Worldwide, more than 1.5 billion adults are overweight and more than 500 million obese. Obesity has been suggested to be a risk factor for the development of more difficult-to-control asthma. Although the mechanisms underlying the asthma-obesity relationship are not fully understood, several possible explanations have been put forward. These will be reviewed in this manuscript as well as the implications for the treatment of overweight and obese asthma patients.

RECENT FINDINGS

Insulin resistance is a possible factor contributing to the asthma-obesity relationship and the effect is independent of other components of the metabolic syndrome such as hypertriglyceridemia, hypertension, hyperglycemia, and systemic inflammation. Obesity has important effects on airway geometry, by especially reducing expiratory reserve volume causing obese asthmatics to breathe at low lung volumes. Furthermore, obesity affects the type of inflammation in asthma and is associated with reduced inhaled corticosteroids treatment responsiveness.

SUMMARY

Obesity induces the development of asthma with a difficult-to-control phenotype. Treatment targeting insulin resistance may be beneficial in obese asthma patients, especially when they have concomitant diabetes. Systemic corticosteroids should be avoided as much as possible as they are not very effective in obese asthma and associated with side-effects like diabetes, weight gain, and osteoporosis.

The effect of obesity on lung function

INTRODUCTION

There is a major epidemic of obesity, and many obese patients suffer with respiratory symptoms and disease. The overall impact of obesity on lung function is multifactorial, related to mechanical and inflammatory aspects of obesity. Areas covered: Obesity causes substantial changes to the mechanics of the lungs and chest wall, and these mechanical changes cause asthma and asthma-like symptoms such as dyspnea, wheeze, and airway hyperresponsiveness. Excess adiposity is also associated with increased production of inflammatory cytokines and immune cells that may also lead to disease. This article reviews the literature addressing the relationship between obesity and lung function, and studies addressing how the mechanical and inflammatory effects of obesity might lead to changes in lung mechanics and pulmonary function in obese adults and children. Expert commentary: Obesity has significant effects on respiratory function, which contribute significantly to the burden of respiratory disease. These mechanical effects are not readily quantified with conventional pulmonary function testing and measurement of body mass index. Changes in mediators produced by adipose tissue likely also contribute to altered lung function, though as of yet this is poorly understood.

Obesity and asthma

Obesity is a vast public health problem and both a major risk factor and disease modifier for asthma in children and adults. Obese subjects have increased asthma risk, and obese asthmatic patients have more symptoms, more frequent and severe exacerbations, reduced response to several asthma medications, and decreased quality of life. Obese asthma is a complex syndrome, including different phenotypes of disease that are just beginning to be understood. We examine the epidemiology and characteristics of this syndrome in children and adults, as well as the changes in lung function seen in each age group. We then discuss the better recognized factors and mechanisms involved in disease pathogenesis, focusing particularly on diet and nutrients, the microbiome, inflammatory and metabolic dysregulation, and the genetics/genomics of obese asthma. Finally, we describe current evidence on the effect of weight loss and mention some important future directions for research in the field.

A review of obesity and asthma across the life span

OBJECTIVE

This literature review aims to compare obese-asthmatic adults and children, and to characterize differences and similarities between the two subgroups from epidemiological, demographical, phenotypical, and physiological perspectives.

METHODS

Literature search was conducted using Pubmed database with "obesity," "asthma," "epidemiology," "cluster analysis," "demography," "mechanics," and ''FeNO'' as search terms.

METHODS

Articles investigating epidemiological, demographic, phenotypical variation, and mechanical aspects of breathing specifically in obese asthmatics were identified. The studies were then divided according to age: children (<18 years of age) and adults (>18 years of age).

RESULTS

Increase in asthma incidence and prevalence is observed in both obese-asthmatic children and adults. Asthma prevalence is greater in adult females regardless of ethnic background, and in men of African American and Hispanic ethnicities. Degree of weight gain and early onset of menarche appears to directly affect asthma severity in adolescent girls and females. Airway hyperresponsiveness and fractional exhaled nitric oxide do not have any positive correlation with high BMI in obese-asthmatic children and adults. Obesity also alters lung mechanics in asthmatics, but the impact is different for children and adults likely due to differential effect of obesity on central and peripheral airway.

CONCLUSION

Existing literature suggests both similarities and differences in obese-asthmatic children and adults. The most pertinent differences are related to gender, ethnicity, and lung functions.

High-fat-diet induces airway hyperresponsiveness partly through activating CD38 signaling pathway

CD38 is a plasma membrane bound multifunctional enzyme. It can be activated by inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-13, inducing calcium responses to agonist in airway smooth muscle cells (ASMC). Previous studies have found that high-fat-diet (HFD) induced obesity exhibited innate airway hyperresponsiveness (AHR). This study aimed to detect the effect of CD38 signaling pathway on the AHR of overweight/obese mice. The HFD-fed mice exhibited a significantly higher baseline airway resistance (Rn), and the increasing rates of Rn responded to increasing doses of methacholine compared with the LFD-fed mice. High-fat-diet increased CD38 expressions both in lung tissues and primary cultured ASMCs. Besides, preincubation with TNF-α led to a higher expression of CD38 protein and increased intracellular calcium in ASMC of the HFD-fed mice. Furthermore, CD38 gene knockdown through transfection of CD38 siRNA decreased the concentration of intracellular calcium. Additionally, the upregulations of CD38 protein and CD38 mRNA were also found in the lung tissues of HFD-fed mice challenged by ovalbumin (OVA). Collectively, our findings demonstrated a role of CD38 signaling pathway on the AHR of obesity and might be a potential therapeutic target for treating difficult-to-control obese asthma phenotype.

Overweight in childhood and adolescence: Does it lead to airway hyperresponsiveness in adulthood?

BACKGROUND

Obesity is increasing worldwide among children and adolescents, and has been associated with an increased incidence of asthma. However, the mechanisms underlying this association are incompletely understood.

OBJECTIVE

In this cohort study we aimed to investigate whether being overweight in childhood and adolescence is associated with an increased risk of airway hyperresponsiveness (AHR), a hallmark of asthma, in early adulthood.

METHODS

Of 527 subjects from a random population sample of children and adolescents (7-17 years) examined at baseline, a total of 184 subjects completed the follow-up visit 20 years later and were included in the present analysis. Both visits included assessment of height and weight, case history and spirometry. At both visits, bronchial provocation tests were performed using either histamine (baseline) or methacholine (follow-up). In addition, fractional exhaled nitric oxide (FeNO) was measured at follow-up.

RESULTS

No significant difference in the prevalence of AHR at follow-up was found between subjects who were overweight or obese at baseline visit (n = 26) (pediatric definition, body mass index ≥ 85%percentile) and normal weight subjects (n = 158) (positive bronchial provocation tests: 15.4% vs. 22.2%, respectively, p = 0.35). Likewise, follow-up FeNO levels did not differ significantly between subjects who were lean and those who were overweight or obese at baseline (geometric mean (95% confidence interval [CI]) 15.1 (13.7, 16.6) parts per billion (ppb) versus 13.0 (10.6, 15.9) ppb, p = 0.23).

CONCLUSION

In children and adolescents, being obese or overweight seems not to be associated with an increased risk of AHR or increased FeNO levels in early adulthood.

Co-morbidities and cognitive status in a cohort of teenagers with asthma

BACKGROUND

There is limited data regarding co-morbidities and cognitive status of asthma during childhood and adolescence. The aim of the current study was to explore the presence of co-morbidities and cognitive status in a large cohort of teenagers with asthma.

METHODS

The medical records of 314,897 consecutive 17-year-old males, undergoing comprehensive medical and cognitive evaluation prior to recruitment for military service, were reviewed. The prevalence of co-morbidities and a cognitive assessment in subjects with asthma were compared to those without asthma. Both a univariate and multivariate logistic regression analysis were performed.

RESULTS

Active asthma was documented in 21,728 (6.9%) subjects: 3.3% were diagnosed with mild intermittent asthma, and 3.6% with persistent asthma. A significant positive correlation between a higher cognitive score and prevalence of asthma was found (P < 0.001), with a 55% increased prevalence of asthma in the subjects with the highest cognitive score compared to those with the lowest score. The following co-morbidities were significantly more prevalent in asthmatics compared to non-asthmatics: chronic rhinitis (35% vs. 5%), atopic dermatitis (2% vs. 0.4%), urticaria (1% vs. 0.3%), anaphylaxis (0.4% vs. 0.1%), chronic sinusitis (0.4% vs. 0.1%), overweight with body mass index (BMI) above 25 kg/m(2) (20% vs. 17%) and underweight with BMI less than 17 kg/m(2) (3.2% vs. 2.8%), irritable bowel syndrome (IBS) (1% vs. 0.5%), and thyroid disorders(0.4% vs. 0.2%). Chronic rhinitis and sinusitis, atopic dermatitis, IBS, and thyroid disorders were all significantly more prevalent in persistent compared to intermittent asthma (P < 0.001).

CONCLUSIONS

In adolescence, a higher cognitive status was associated with a higher rate of asthma. Chronic rhinitis was the most prevalent co-morbidity and was found in one third of adolescent asthmatics. Other allergic diseases, chronic sinusitis, over and underweight, IBS, and thyroid disorders were also more prevalent in asthmatics. Pediatr Pulmonol. 2016; 51:901-907. © 2016 Wiley Periodicals, Inc.

Bronchospasm in obese patients undergoing elective laparoscopic surgery under general anesthesia

Background

Existing data suggest that obesity correlates with airway hyper-reactivity. However, the incidence of bronchospasm during bariatric surgery in obese patients has not been well studied.

Methods

This was a prospective observational study comparing 50 obese versus 50 non obese patients undergoing elective laparoscopic surgery over a 2 year period. Bronchospasm was detected clinically by auscultation and was confirmed by measuring peak airway pressure during mechanical ventilation. Blood gases were measured at predetermined time intervals intraoperatively. Categorical variables were analyzed using Fisher’s exact test, while numerical variables within and between groups were compared using repeated measures general linear model.

Results

The incidence of bronchospasm was significantly higher in obese compared to non obese patients (P = 0.027). Peak airway pressures and blood gases differed significantly when comparing non obese patients versus obese patients without bronchospasm versus obese patients with bronchospasm. Hypoventilation resulting in gradual increase of arterial PaCO₂ was noted in all groups during surgery.

Conclusion

The incidence of bronchospasm is higher in obese patients compared to non obese patients undergoing elective laparoscopic surgery. Airway pressures and blood gas values in obese patients are somewhere between values in non obese patients and values in patients with bronchospasm, thereby implying that obesity is associated with a state where bronchial smooth muscles are not fully relaxed. Consideration of increased airway reactivity in obese patients undergoing laparoscopic surgery is important for improved patient care and uneventful anesthetic course.

Adipokines and Cysteinyl Leukotrienes in the Pathogenesis of Asthma

Background. The prevalence of obesity has increased dramatically over the last decades, and its association with asthma is being increasingly recognized. Aims. Our hypothesis is that increased leptin and decreased adiponectin levels in obese subjects play a direct role in regulating inflammation in asthmatics. We wanted to examine the hypothesis that cysteinyl leukotrienes (cys-LT), inflammatory mediators that are regulated by adipokines, are involved in the pathogenesis of asthma. Methods. We studied a population of asthmatics and nonasthmatics, who in turn were divided into obese and nonobese categories. We examined leptin and its ratio to adiponectin, in asthmatics and nonasthmatics, with and without obesity. In addition, we measured cys-LT levels in exhaled breath condensate (EBC) and in peripheral blood monocytes (PBM) in these groups. Results. Leptin levels were increased in obese asthmatics compared to obese nonasthmatics. The leptin/adiponectin (L/A) ratio was higher in obese asthmatics compared to obese nonasthmatics. EBC cys-LT levels were elevated in asthmatics compared to nonasthmatics. Discussion. Proinflammatory adipokines, released from adipose tissue, may promote an asthma phenotype through enhanced cys-LT production that may result in more prevalent and difficult to control airway disease.

Sex difference in the association between obesity and asthma in U.S. adults: Findings from a national study

BACKGROUND

Obesity and asthma are both prevalent in the U.S. The a few studies that have examined the differences in association between obesity and asthma by sex provided mixed results. Reason for the sex differences is not well understood.

OBJECTIVE

Using U.S. nationally representative data we aimed to examine the association between obesity and asthma and potential sex differences.

METHODS

Data were obtained from the 2012 National Health Interview Survey (n = 33,153 adults, 4197 had asthma). Asthma was determined by a positive response to the question "Has a doctor or health care professional ever told you had asthma?" Obesity was determined as a Body Mass Index (BMI)≥30. Obese status was categorized as BMI = 30-34.9 (Class I obesity), BMI = 35-39.9 (Class II obesity), and BMI≥40 (Class III obesity).

RESULTS

The prevalence of asthma was 12.6% (11.0% in men, 14.2% in women), and was higher in the obese than non-obese individuals (16.6% vs. 11.1%, p < 0.0001). After controlling for potential confounders, Class I obesity (OR = 1.27, 95% CI = 1.11-1.44), Class II obesity (OR = 1.55, 95% CI = 1.31-1.84), Class III obesity (OR = 1.85, 95% CI = 1.54-2.21) were positively associated with asthma. The association between Class III obesity and asthma was stronger in women than men (2.11 (1.70-2.63) vs. 1.40 (1.01-1.96), p < 0.05), although the sex difference in the association between BMI and asthma was not significant. Positive associations between class II and class III obesity and asthma were observed among young and middle-aged women compared to young and middle-aged men. Stratified by allergic status, obesity remained being positively associated with asthma.

CONCLUSION

The prevalence of asthma was higher in women than men. Obesity (and BMI) was positively associated with asthma, overall or stratified by allergic status. The association between Class III obesity and asthma was stronger in women. Obesity and sex may be taken into consideration for the management of asthmatic patients.

Asthma and obesity: mechanisms and clinical implications

Obesity is the most common asthma co-morbidity; it has been associated with increased risk for asthma exacerbations, worse respiratory symptoms and poor control. The exact mechanisms remain elusive and are probably multifactorial, stemming from mechanical alterations of the airways and lung parenchyma, to systemic and airway inflammatory and metabolic dysregulation that adversely influences lung function and or response to therapy. However, the fact that not every obese asthmatic is equally affected by weight gain highlights the many challenges and complexities in understanding this association. The factors that determine susceptibility may not depend on being obese alone, but rather the interactions with other phenotypical characteristics, such as age of asthma onset, gender and race to name a few. Inability to account for asthma phenotypes that are differentially affected by increasing body mass index (BMI) may contribute to the lack of consistent results across studies. This review will provide a succinct summary of obesity-related mechanisms and the clinical impact on asthma including highlights on recent progress.

Optimizing respiratory function assessments to elucidate the impact of obesity on respiratory health

There is an increasing prevalence of obesity worldwide and its impact on respiratory health is of significant concern. Obesity affects the respiratory system by several mechanisms, including by direct mechanical changes due to fat deposition in the chest wall, abdomen and upper airway, as well as via systemic inflammation. The increased mechanical load in obese individuals leads to reduced chest wall and lung compliance and increased work of breathing. While there is generally minimal effect on spirometric values, as body mass index increases, the expiratory reserve volume, and hence functional residual capacity, reduces, often approaching residual volume in more severe obesity. The majority of evidence however suggests that obese individuals free from lung disease have relatively normal gas exchange. The link between asthma and obesity, while initially unclear, is now recognized as being a distinct asthma phenotype. While studies investigating objective markers of asthma have shown that there is no association between obesity and airway hyper-responsiveness, a recent working group identified obesity as a major risk factor for the development of asthma in all demographic groups. Although the temptation may be to attribute obesity as the cause of dyspnoea in symptomatic obese patients, accurate respiratory assessment of these individuals is necessary. Lung function tests can confirm that any altered physiology are the known respiratory consequences of obesity. However, given that obesity causes minimal changes in lung function, significant abnormalities warrant further investigation. An important consideration is the knowledge that many of the respiratory physiology consequences of obesity are reversible by weight loss.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Metabolic origins of childhood asthma

Childhood obesity and incidence of asthma are increasing globally. The parallel increase of the two suggests that obesity and asthma may be related and that abnormalities in the lipid and/or glucose metabolism may contribute to the pathogenesis of asthma. The clinical presentation of obese asthma is distinct from other asthma phenotypes and depending on age of onset of symptoms. Asthma in obese people tends to be more severe, not typically associated with allergy, and less responsive to standard anti-inflammatory therapy, including corticosteroids. Obesity and obesity-related comorbidities may lead to asthma via a number of mechanisms including changes in lung mechanics, the nitric oxide metabolism, and by causing inflammation. Furthermore, evidence suggests that nutrition during pregnancy contributes to intrauterine immune and metabolic programming in the offspring, which may have major influences on predisposition to cardiovascular, metabolic, and allergic diseases, including asthma, later in life. This review will highlight some suggested mechanistic links between obesity and diabetes with asthma.

Occupational asthma in a cable manufacturing company

Background:

During the past decade, incidence of asthma has increased, which might have been due to environmental exposures.

Objectives:

Considering the expansion of cable manufacturing industry in Iran, the present study was conducted to evaluate the prevalence of occupational asthma in a cable manufacturing company in Iran as well as its related factors.

Patients and Methods:

This study was conducted on employees of a cable manufacturing company in Yazd, Iran, in 2012. The workers were divided into two groups of exposure (to toluene diisocyanate, polyvinyl chloride, polyethylene or polypropylene) and without exposure. Diagnosis of occupational asthma was made based on the subjects’ medical history, spirometry and peak flowmetry, and its frequency was compared between the two groups.

Results:

The overall prevalence of occupational asthma was 9.7%. This rate was 13.8% in the exposed group. Logistic regression analysis showed that even after adjustment for confounding factors, a significant correlation existed between the frequency of occupational asthma and exposure to the produced dust particles (P < 0.05). In addition, age, work experience, body mass index, cigarette smoking and shift work had significant correlations with the prevalence of occupational asthma (P < 0.05).

Conclusions:

Considering the high prevalence of occupational asthma among cable manufacturing company workers in Iran, this issue needs to be addressed immediately in addition to reduction of exposure among subjects. Reduction in work shift duration, implementation of tobacco control and cessation programs for the personnel, and performing spirometry tests and respiratory examinations in shorter periods may be among effective measures for reducing the incidence of occupational asthma in this industry.

Asthma and body mass index in occupational setting

BACKGROUND

Asthma is the most common respiratory disease with an increasing prevalence. On the other hand, obesity is also a challenging disease compromising health in human communities. This study sought to assess the correlation of asthma and body mass index (BMI) in occupational setting.

METHODS

This study was conducted in a cable manufacturing company in 2012. A total of 551 workers from the production (exposed group) and non-production (unexposed group) units were studied. A questionnaire specifically designed for this purpose was filled out for study subjects and then all workers with respiratory symptoms suggestive of asthma thoroughly examined by a physician and medical history was taken from them. Complementary diagnostic tests were also carried out.

RESULTS

A total of 11.6% of our understudy subjects had asthma. The prevalence of asthma in exposed subjects with BMI≥25 kg/m(2) was found to be significantly higher than in exposed workers with BMI<25 kg/m(2) (p<0.01). However, no significant differences existed in prevalence of asthma between the two subgroups of BMI≥25 kg/m(2) and BMI<25 kg/m(2) in the unexposed group (p>0.05). After adjusting for confounding factors significant associations were observed between BMI and asthma at cut points of 30 kg/m(2) and 25 kg/m(2) (OR: 8.53 and 2.41, respectively).

CONCLUSION

Our study results showed that prevalence of asthma might be higher in workers with higher BMI who are exposed to occupational asthmogens. This finding highlights the necessity of offering weight loss recommendations in periodic examinations to workers with exposure to occupational asthmogens.

Heterogeneity of asthma in society

There has been an increased interest in studying other factors that affect asthma pathogenesis and cause heterogeneity in prevalence and incidence of asthma. The reason there are such varied expression patterns of disease in asthmatics is because of multiple variables that affect the pathogenesis of asthma. As an exemplar of an epidemiologic variable, we will discuss geographical location, obesity and vitamin D status of the individual, and their effects on asthma burden in humans. There is varying data regarding the prevalence or severity of asthma in urban versus rural setting which is likely related to the difference of the populations studied, complexity of causal variables involved, and local geographic factors. In addition to cross-sectional and cohort studies in humans, animal models and studies have established a link between asthma and obesity by investigating the mechanisms affecting both disease processes. The complicated interrelationship between obesity and asthma is an active area of epidemiological and experimental research with new insights being discovered at a rapid pace. Finally, vitamin D, an important immunomodulator thought to be important in pathogenesis of asthma, has both mechanistic and therapeutic implications in treatment of asthma. The influences of these factors on the clinical expression of asthma are discussed below.

Linking obesity and asthma

A growing body of literature suggests that obesity has a significant impact on asthma risk, phenotype, and prognosis. Epidemiological studies have clearly demonstrated that asthma is more likely to occur in obese patients, and health status is impaired in obese individuals with asthma, with obese asthmatics experiencing more symptoms, worse quality of life, increased healthcare use, and increased asthma severity. However, obesity has well-described effects on lung function and mechanics that can lead to symptoms of dyspnea without causing the pathophysiologic changes of asthma. Adding to the challenges of evaluating this association, some studies have failed to demonstrate a robust relationship between obesity and traditional biomarkers of airway inflammation in adult asthmatics, leading to the conclusion that obesity does not necessarily worsen airway inflammation in asthma. In this regard, emerging data suggest that nonatopic mechanisms may be relevant in obese asthmatics, and that these mechanisms may have a direct impact on the response of obese asthmatics to asthma therapies, most notably inhaled glucocorticoids. This article will review selected aspects of the contributions of obesity-related airway and systemic inflammation to asthma, with a focus on the impact of obesity as a modifier of risk, prognosis, and therapeutic response in asthma.