General and Organ Fat Assessed by Magnetic Resonance Imaging and Respiratory Outcomes in Childhood

Association between visceral adipose tissue and asthma based on the NHANES and Mendelian randomization study

BACKGROUND

Obesity is a crucial risk factor for asthma. Observational studies have examined the association between abdominal obesity and asthma symptoms. This study aimed to investigate the causal relationship between visceral adipose tissue (VAT) and asthma and its potential as an independent indicator.

METHODS

This study utilized data from the National Health and Nutrition Examination Survey spanning 2011-8. Multivariable logistic regression and stratified variable selection were employed to identify associations between asthma and VAT. Moreover, a two-sample Mendelian randomization analysis, using 221 genetic variants as instrumental variables, was conducted to assess this relationship further.

RESULTS

Our findings indicated that individuals with higher VAT levels were more likely to develop asthma. Visceral obesity remained a significant risk factor for asthma after adjusting for demographic characteristics. Genetic predictions suggest a positive association between VAT and an elevated risk of asthma (odds ratio [OR] = 1.393, 95% confidence interval [CI]: 1.266-1.534, and P = 1.43E-11). No significant polymorphisms were detected using the Mendelian randomization-Egger intercept test.

CONCLUSIONS

This study presents potential evidence supporting the causal role of VAT in asthma development. Furthermore, the findings from the Mendelian randomization analysis further reinforce the relationship between VAT and asthma risk.

Physical activity and body mass related to catch-up lung function growth in childhood: a population-based accelerated cohort study

OBJECTIVE

The existence of catch-up lung function growth and its predictors is uncertain. We aimed to identify lung function trajectories and their predictors in a population-based birth cohort.

METHODS

We applied group-based trajectory modelling to z-scores of forced expiratory volume in 1 second (zFEV1) and z-scores of forced vital capacity (zFVC) from 1151 children assessed at around 4, 7, 9, 10, 11, 14 and 18 years. Multinomial logistic regression models were used to test whether potential prenatal and postnatal predictors were associated with lung function trajectories.

RESULTS

We identified four lung function trajectories: a low (19% and 19% of the sample for zFEV1 and zFVC, respectively), normal (62% and 63%), and high trajectory (16% and 13%) running in parallel, and a catch-up trajectory (2% and 5%) with catch-up occurring between 4 and 10 years. Fewer child allergic diseases and higher body mass index z-score (zBMI) at 4 years were associated with the high and normal compared with the low trajectories, both for zFEV1 and zFVC. Increased children's physical activity during early childhood and higher zBMI at 4 years were associated with the catch-up compared with the low zFEV1 trajectory (relative risk ratios: 1.59 per physical activity category (1.03-2.46) and 1.47 per zBMI (0.97-2.23), respectively). No predictors were identified for zFVC catch-up growth.

CONCLUSION

We found three parallel-running and one catch-up zFEV1 and zFVC trajectories, and identified physical activity and body mass at 4 years as predictors of zFEV1 but not zFVC catch-up growth.

Body composition and respiratory outcomes in children: a population-based prospective cohort study

BACKGROUND

Body composition might influence lung function and asthma in children, but its longitudinal relations are unclear. We aimed to identify critical periods for body composition changes during childhood and adolescence in relation to respiratory outcomes in adolescents.

METHODS

In a population-based prospective cohort study, we measured body mass index, fat mass index (FMI), lean mass index (LMI) and the ratio of android fat mass divided by gynoid fat mass (A/G ratio) by dual-energy X-ray absorptiometry at 6, 10 and 13 years. At 13 years, lung function was measured by spirometry, and current asthma was assessed by questionnaire.

RESULTS

Most prominently and consistently, higher FMI and A/G ratio at age 13 years were associated with lower forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) and forced expiratory flow after exhaling 75% of FVC (FEF75) (range Z-score difference -0.13 (95% CI -0.16 to -0.10) to -0.08 (95% CI -0.11 to -0.05) per SD score increase), and higher LMI at all ages was associated with higher FEF75 (range Z-score difference 0.05 (95% CI 0.01 to 0.08) to 0.09 (95% CI 0.06 to 0.13)). Between the ages of 6 and 13 years, normal to high FMI and A/G ratio were associated with lower FEV1/FVC and FEF75 (range Z-score difference -0.20 (95% CI -0.30 to -0.10) to -0.17 (95% CI -0.28 to -0.06)) and high to high LMI with higher FEF75 (range Z-score difference0.32 (95% CI 0.23 to 0.41)). Body composition changes were not associated with asthma.

CONCLUSION

Adolescents with higher total and abdominal fat indices may have impaired lung function, while those with a higher lean mass during childhood and adolescence may have better small airway function. Public health measures should focus on a healthy body composition in adolescents to minimise respiratory morbidity.

The effect of body compartments on lung function in childhood and adolescence

BACKGROUND

There is an association between body composition and lung function, assessed by spirometry, but the effects of body compartments on static lung volumes and its changes during lung growth remain to be explored. We aimed to investigate the association of appendicular lean mass, reflecting skeletal muscle mass, and fat mass on forced and static lung function measures in childhood and adolescence.

METHODS

In total, 1489 children and adolescents (6-18 years) of the observational, longitudinal (first and second visit within 4 years), general population-based LEAD study have been investigated. The association of appendicular lean mass and fat mass indices (ALMI and FMI; assessed by dual-energy X-ray absorptiometry) on lung function by spirometry (FEV1, FVC) and body plethysmography (TLC, RV, FRC) was investigated cross-sectionally. Longitudinal associations between lung function and body compartment changes between the two visits were analyzed.

FINDINGS

The ALMI is positively associated with FEV1, FVC, and TLC. Contrary, FMI is inversely associated with lung function measures including FRC and RV. During the phase of lung growth, higher gain in muscle mass is associated with higher increases of FVC and TLC.

INTERPRETATION

This study demonstrates the different effects of muscle and fat mass on forced expiratory and static lung volumes. Achieving and maintaining muscle mass in childhood and adolescence might become an important preventive strategy for lung health in adulthood.

Impact of obesity in asthma: Possible future therapies

Obesity is one of the factors associated with the severity of asthma. Obesity is associated with aggravation of the pathophysiology of asthma, including exacerbations, airway inflammation, decreased pulmonary function, and airway hyperresponsiveness. The present review addresses the characteristics of asthma with obesity, focusing especially on the heterogeneity caused by the degree of type 2 inflammation, sex differences, the onset of asthma, and race differences. To understand the severity mechanisms in asthma and obesity, such as corticosteroid resistance, fatty acids, gut microbiome, and cytokines, several basic research studies are evaluated. Finally, possible future therapies, including weight reduction, microbiome-targeted therapies, and other molecular targeted therapies are addressed. We believe that the present review will contribute to better understanding of the severity mechanisms and the establishment of novel treatments for severe asthma patients with obesity.

Pediatric obesity and severe asthma: Targeting pathways driving inflammation

Asthma affects more than 300 million people of all ages worldwide, including about 10-15% of school-aged children, and its prevalence is increasing. Severe asthma (SA) is a particular and rare phenotype requiring treatment with high-dose inhaled corticosteroids plus a second controller and/or systemic glucocorticoid courses to achieve symptom control or remaining "uncontrolled" despite this therapy. In SA, other diagnoses have been excluded, and potential exacerbating factors have been addressed. Notably, obese asthmatics are at higher risk of developing SA. Obesity is both a major risk factor and a disease modifier of asthma in children and adults: two main "obese asthma" phenotypes have been described in childhood with high or low levels of Type 2 inflammation biomarkers, respectively, the former characterized by early onset and eosinophilic inflammation and the latter by neutrophilic inflammation and late-onset. Nevertheless, the interplay between obesity and asthma is far more complex and includes obese tissue-driven inflammatory pathways, mechanical factors, comorbidities, and poor response to corticosteroids. This review outlines the most recent findings on SA in obese children, particularly focusing on inflammatory pathways, which are becoming of pivotal importance in order to identify selective targets for specific treatments, such as biological agents.

From Beneath the Skin to the Airway Wall: Understanding the Pathological Role of Adipose Tissue in Comorbid Asthma-Obesity

This article provides a contemporary report on the role of adipose tissue in respiratory dysfunction. Adipose tissue is distributed throughout the body, accumulating beneath the skin (subcutaneous), around organs (visceral), and importantly in the context of respiratory disease, has recently been shown to accumulate within the airway wall: "airway-associated adipose tissue." Excessive adipose tissue deposition compromises respiratory function and increases the severity of diseases such as asthma. The mechanisms of respiratory impairment are inflammatory, structural, and mechanical in nature, vary depending on the anatomical site of deposition and adipose tissue subtype, and likely contribute to different phenotypes of comorbid asthma-obesity. An understanding of adipose tissue-driven pathophysiology provides an opportunity for diagnostic advancement and patient-specific treatment. As an exemplar, the potential impact of airway-associated adipose tissue is highlighted, and how this may change the management of a patient with asthma who is also obese. © 2023 American Physiological Society. Compr Physiol 13:4321-4353, 2023.

Mid-childhood fat mass and airflow limitation at 15 years: The mediating role of insulin resistance and C-reactive protein

BACKGROUND

We previously reported an association of high fat mass levels from age 9 to 15 years with lower forced expiratory flow in 1 s (FEV₁ )/forced vital capacity (FVC) ratio (i.e., increased risk of airflow limitation) at 15 years. Here, we aimed to assess whether insulin resistance and C-reactive protein (CRP) at 15 years partially mediate this association.

METHODS

We included 2263 children from the UK Avon Longitudinal Study of Parents and Children population-based cohort (ALSPAC). Four fat mass index (FMI) trajectories ("low," "medium-low," "medium-high," "high") from 9 to 15 years were previously identified using Group-Based Trajectory Modeling. Data on CRP, glucose, insulin, and post-bronchodilator FEV₁ /FVC were available at 15 years. We defined insulin resistance by the homeostasis model assessment-estimated insulin resistance index (HOMA-IR). We used adjusted linear regression models and a causal mediation analysis to assess the mediating role of HOMA-IR and CRP.

RESULTS

Compared to children in the "low" FMI trajectory, children in the "medium-high" and "high" FMI trajectories had lower FEV₁ /FVC at 15 years. The percentage of the total effect explained by HOMA-IR was 19.8% [-114.1 to 170.0] and 20.4% [1.6 to 69.0] for the "medium-high" and "high" trajectories, respectively. In contrast, there was little evidence for a mediating role of CRP.

CONCLUSION

The association between mid-childhood fat mass and FEV₁ /FVC ratio at 15 years may be partially mediated by insulin resistance.

Risk Factors Affecting Development and Persistence of Preschool Wheezing: Consensus Document of the Emilia-Romagna Asthma (ERA) Study Group

Wheezing at preschool age (i.e., before the age of six) is common, occurring in about 30% of children before the age of three. In terms of health care burden, preschool children with wheeze show double the rate of access to the emergency department and five times the rate of hospital admissions compared with school-age asthmatics. The consensus document aims to analyse the underlying mechanisms involved in the pathogenesis of preschool wheezing and define the risk factors (i.e., allergy, atopy, infection, bronchiolitis, genetics, indoor and outdoor pollution, tobacco smoke exposure, obesity, prematurity) and the protective factors (i.e., probiotics, breastfeeding, vitamin D, influenza vaccination, non-specific immunomodulators) associated with the development of the disease in the young child. A multidisciplinary panel of experts from the Emilia-Romagna Region, Italy, addressed twelve key questions regarding managing preschool wheezing. Clinical questions have been formulated by the expert panel using the PICO format (Patients, Intervention, Comparison, Outcomes). Systematic reviews have been conducted on PubMed to answer these specific questions and formulate recommendations. The GRADE approach has been used for each selected paper to assess the quality of the evidence and the degree of recommendations. Based on a panel of experts and extensive updated literature, this consensus document provides insight into the pathogenesis, risk and protective factors associated with the development and persistence of preschool wheezing. Undoubtedly, more research is needed to improve our understanding of the disease and confirm the associations between certain factors and the risk of wheezing in early life. In addition, preventive strategies must be promoted to avoid children's exposure to risk factors that may permanently affect respiratory health.

Obesity-related asthma in children and adolescents

There is substantial epidemiological and experimental evidence of an obesity-related asthma phenotype. Compared to children of healthy weight, children with obesity are at higher risk of asthma. Children with obesity who have asthma have greater severity and poorer control of their asthma symptoms, more frequent asthma exacerbations, and overall lower asthma-related quality of life than children with asthma who have a healthy weight. In this Review, we examine some of the latest evidence on the characteristics of this phenotype and its main underlying mechanisms, including genetics and genomics, changes in airway mechanics and lung function, sex hormone differences, alterations in immune responses, systemic and airway inflammation, metabolic dysregulation, and modifications in the microbiome. We also review current recommendations for the treatment of these children, including in the management of their asthma, and current evidence for weight loss interventions. We then discuss initial evidence for potential novel therapeutic approaches, such as dietary modifications and supplements, antidiabetic medications, and statins. Finally, we identify knowledge gaps and future directions to improve our understanding of asthma in children with obesity, and to improve outcomes in these susceptible children. We highlight important needs, such as designing paediatric-specific studies, implementing large multicentric trials with standardised interventions and outcomes, and including racial and ethnic groups along with other under-represented populations that are particularly affected by obesity and asthma.

Spirometric phenotypes from early childhood to young adulthood: a Chronic Airway Disease Early Stratification study

Background

The prevalences of obstructive and restrictive spirometric phenotypes, and their relation to early-life risk factors from childhood to young adulthood remain poorly understood. The aim was to explore these phenotypes and associations with well-known respiratory risk factors across ages and populations in European cohorts.

Methods

We studied 49 334 participants from 14 population-based cohorts in different age groups (≤10, >10–15, >15–20, >20–25 years, and overall, 5–25 years). The obstructive phenotype was defined as forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) z-score less than the lower limit of normal (LLN), whereas the restrictive phenotype was defined as FEV₁/FVC z-score ≥LLN, and FVC z-score <LLN.

Results

The prevalence of obstructive and restrictive phenotypes varied from 3.2–10.9% and 1.8–7.7%, respectively, without clear age trends. A diagnosis of asthma (adjusted odds ratio (aOR=2.55, 95% CI 2.14–3.04), preterm birth (aOR=1.84, 1.27–2.66), maternal smoking during pregnancy (aOR=1.16, 95% CI 1.01–1.35) and family history of asthma (aOR=1.44, 95% CI 1.25–1.66) were associated with a higher prevalence of obstructive, but not restrictive, phenotype across ages (5–25 years). A higher current body mass index (BMI was more often observed in those with the obstructive phenotype but less in those with the restrictive phenotype (aOR=1.05, 95% CI 1.03–1.06 and aOR=0.81, 95% CI 0.78–0.85, per kg·m⁻² increase in BMI, respectively). Current smoking was associated with the obstructive phenotype in participants older than 10 years (aOR=1.24, 95% CI 1.05–1.46).

Conclusion

Obstructive and restrictive phenotypes were found to be relatively prevalent during childhood, which supports the early origins concept. Several well-known respiratory risk factors were associated with the obstructive phenotype, whereas only low BMI was associated with the restrictive phenotype, suggesting different underlying pathobiology of these two phenotypes.

Obstructive and restrictive phenotypes are present from childhood to adulthood but without age trends. Established risk factors for airway disease are associated with the obstructive phenotype, whereas low BMI is associated with the restrictive.https://bit.ly/3BMoMtI

Trajectories of adiposity indicators and association with asthma and lung function in urban minority children

BACKGROUND

A relationship between adiposity and asthma has been described in some cohort studies, but little is known about trajectories of adiposity throughout early childhood among children at high risk for developing asthma in urban United States cities. Moreover, early life trajectories of adipokines that have metabolic and immunologic properties have not been comprehensively investigated.

OBJECTIVE

Our objective was to characterize trajectories of adiposity in a longitudinal birth cohort of predominately Black and Latinx children (n = 418) using several different repeated measures including body mass index (BMI) z score, bioimpedance analysis, leptin, and adiponectin in the first 10 years of life.

METHODS

In a longitudinal birth cohort of predominately Black and Latinx children, we used repeated annual measures of BMI, bioimpedance analysis (ie, percentage of body fat), leptin, and adiponectin to create trajectories across the first 10 years of life. Across those trajectories, we compared asthma diagnosis and multiple lung function outcomes, including spirometry, impulse oscillometry, and methacholine response.

RESULTS

Three trajectories were observed for BMI z score, bioimpedance analysis, and leptin and 2 for adiponectin. There was no association between trajectories of BMI, percentage of body fat, leptin, or adipokine and asthma diagnosis or lung function (P > .05).

CONCLUSIONS

Trajectories of adiposity were not associated with asthma or lung function in children at high risk for developing asthma. Risk factors related to geography as well as social and demographic factors unique to specific populations could explain the lack of association and should be considered in obesity and asthma studies.

Nutrition, Obesity and Asthma Inception in Children. The Role of Lung Function

Obesity is an important public health problem. WHO estimates that about 39 million children younger than 5 years of age are overweighted or obese. On the other hand, asthma is the most prevalent chronic disease in childhood, and thus, many children share those two conditions. In the present paper we review the epidemiology of children with asthma and obesity, as well as the consequences of being obese on the respiratory system. On the one hand obesity produces an underlying T-helper 2 (TH2) low inflammation state in which numerous cytokines, which could have an impact in the respiratory system play, a role. On the other hand, some respiratory changes have been described in obese children and, specially, the development of the so called “dysanapsis” (the disproportionate scaling of airway dimensions to lung volume) which seems to be common during the first stages of life, probably related to the early development of this condition. Finally, this review deals with the role of adipokines and insulin resistance in the inception and worsening of asthma in the obese child.

Childhood Adiposity Associated With Expanded Effector Memory CD8+ and Vδ2+Vγ9+ T Cells

CONTEXT

Adult obesity is associated with chronic low-grade inflammation and may give rise to future chronic disease. However, it is unclear whether adiposity-related inflammation is already apparent in childhood.

OBJECTIVE

To study associations between child adiposity measures with circulating monocytes and naive and memory subsets in CD4, CD8, and γδ T cell lineages.

METHODS

Ten-year-old children (n = 890) from the Generation R Cohort underwent dual-energy x-ray absorptiometry and magnetic resonance imaging for body composition (body mass index [BMI], fat mass index [FMI], android-to-gynoid fat mass ratio, visceral fat index, liver fat fraction). Blood samples were taken for detailed immunophenotyping of leukocytes by 11-color flow cytometry.

RESULTS

Several statistically significant associations were observed. A 1-SD increase in total FMI was associated with +8.4% (95% CI 2.0, 15.2) Vδ2+Vγ9+ and +7.4% (95% CI 2.4, 12.5) CD8+TEMRO cell numbers. A 1-SD increase in visceral fat index was associated with +10.7% (95% CI 3.3, 18.7) Vδ2+Vγ9+ and +8.3% (95% CI 2.6, 14.4) CD8+TEMRO cell numbers. Higher android-to-gynoid fat mass ratio was only associated with higher Vδ2+Vγ9+ T cells. Liver fat was associated with higher CD8+TEMRO cells but not with Vδ2+Vγ9+ T cells. Only liver fat was associated with lower Th17 cell numbers: a 1-SD increase was associated with -8.9% (95% CI -13.7, -3.7) Th17 cells. No associations for total CD8+, CD4+ T cells, or monocytes were observed. BMI was not associated with immune cells.

CONCLUSION

Higher Vδ2+Vγ9+ and CD8+TEMRO cell numbers in children with higher visceral fat index could reflect presence of adiposity-related inflammation in children with adiposity of a general population.

Cardio-metabolic risk factors during childhood in relation to lung function and asthma

BACKGROUND

Cardio-metabolic risk factors might have an adverse effect on respiratory outcomes, but associations in children are unknown. We aimed to study the longitudinal associations of cardio-metabolic risk factors with lung function and asthma at school age. We also examined whether any association was explained by child's body mass index (BMI).

METHODS

In a population-based cohort study among 4988 children, cardio-metabolic risk factors were measured at 6 and 10 years and included blood pressure, cholesterol, triglycerides, insulin, and C-reactive protein (CRP) concentrations. At age 10 years, lung function was measured by spirometry and current physician-diagnosed asthma was assessed by questionnaire.

RESULTS

After adjustment for confounders, child's BMI, and multiple testing, we observed that a higher diastolic blood pressure at the age of 6 years was associated with a higher forced vital capacity (FVC) at the age of 10 years (Z-score difference (95% CI): 0.05 (0.01, 0.08), per SDS increase in diastolic blood pressure). Also, child's CRP concentrations above the 75th percentile at both ages 6 and 10 years were related to a lower FVC as compared to CRP concentrations below the 75th percentile at both ages (Z-score difference (95% CI) -0.21 (-0.36, -0.06)). No consistent associations of other cardio-metabolic risk factors with respiratory outcomes were observed.

CONCLUSION

Blood pressure and CRP, but not lipids and insulin, were associated with lower lung function but not with asthma. The underlying mechanisms and long-term effects of these associations require further investigation.

The impact of obesity on immune function in pediatric asthma

PURPOSE OF REVIEW

Pediatric obese asthma is a complex disease that remains poorly understood. The increasing worldwide incidence of both asthma and obesity over the last few decades, their current high prevalence and the challenges in treating obese asthmatic patients all highlight the importance of a better understanding of the pathophysiological mechanisms in obese asthma. While it is well established that patients with obesity are at an increased risk of developing asthma, the mechanisms by which obesity drives the onset of asthma, and modifies existing asthma, remain unclear. Here, we will focus on mechanisms by which obesity alters immune function in asthma.

RECENT FINDINGS

Lung parenchyma has an altered structure in some pediatric obese asthmatics, known as dysanapsis. Central adiposity is linked to reduced pulmonary function and a better predictor of asthma risk in children than BMI. Obesity in young children is associated with an increased risk of developing asthma, as well as early puberty, and hormonal alterations are implicated in obese asthma. Obesity and asthma each yield immunometabolic dysregulation separately and we are learning more about alterations in these pathways in pediatric obese asthma and the potential impact of bariatric surgery on those processes.

SUMMARY

The recent progress in clarifying the connections between childhood obesity and asthma and their combined impacts on immune function moves us closer to the goals of improved understanding of the pathophysiological mechanisms underpinning obese asthma and improved therapeutic target selection. However, this common inflammatory disease remains understudied, especially in children, and much remains to be learned.

The effect of catch-up growth in the first year of life on later wheezing phenotypes

Although wheezing phenotypes have previously been accurately described using well-defined cohorts reporting longitudinal wheezing, early-life factors which lead to development of each wheezing phenotype remain uncertain [1, 2]. Birth weight and catch-up growth affect later respiratory outcomes [3], but the influence of weight gain on specific wheezing phenotypes in term-born children has not been described. Rapid weight gain in early-life is associated with increased rates of childhood wheeze and lower lung function [4, 5]. In one meta-analysis rapid infant weight gain was linked to pre-school wheeze and school-aged asthma; and to increased childhood respiratory symptoms in another meta-analysis [6, 7]. Effect of weight gain in early-life in term-born children on wheezing in early-life is less well reported [8]. In contrast, rapid increase in body mass index in infancy is associated with increased risk of asthma at school-age in preterm-born infants [9].

This study shows that catch-up growth in infancy is associated with increased early wheeze in childhood, so care is needed to not to excessively feed in early infancyhttps://bit.ly/2YPxtBw

ERS International Congress 2019: highlights from Best Abstract awardees

#ERSCongress 2019: highlights from Best Abstract awardees http://bit.ly/2XWlD7Y.