BMI trajectory in childhood is associated with asthma incidence at young adulthood mediated by DNA methylation

Childhood body mass index trajectories and asthma and allergies: A systematic review

BACKGROUND

Previous systematic reviews have focused on associations between single time point measures of Body Mass Index (BMI) and asthma and allergic diseases. As BMI changes dynamically during childhood, examination of associations between longitudinal trajectories in BMI and allergic diseases is needed to fully understand the nature of these relationships.

OBJECTIVE

To systematically synthesise the association between BMI trajectories in childhood (0-18 years) and allergic diseases (asthma, eczema, allergic rhinitis, or food allergies outcomes).

DESIGN

We conducted a systematic review following the PRISMA guidelines, and two independent reviewers assessed the study quality using the ROBINS-E and GRADE tools. A narrative synthesis was performed as the statistical heterogeneity did not allow a meta-analysis.

DATA SOURCES

A search was performed on PubMed and EMBASE databases on 4th January 2023.

ELIGIBILITY CRITERIA

Longitudinal cohort studies assessing the associations between childhood BMI trajectories and allergic diseases were included.

RESULTS

Eleven studies met the inclusion criteria with a total of 37,690 participants between 0 and 53 years of age. Ten studies examined asthma outcomes, three assessed association with allergic rhinitis, two assessed eczema, and one assessed food allergy. High heterogeneity and high risk of bias were observed. Overall, the quality of evidence was very low. Nevertheless, two consistent findings were identified: (1) a persistently high BMI between 6 and 10 years of age may be associated with an increased risk of asthma at 18 years and (2) a rapid increase in BMI in the first 2 years of life may be associated with subsequent asthma.

CONCLUSIONS

Maintaining a normal BMI trajectory during childhood may reduce the risk of asthma. Future research that adequately addresses confounding and includes longer-term follow-up is needed. Moreover, additional studies examining potential associations with eczema, food allergies, and allergic rhinitis outcomes are needed.

Asthma, obesity, and microbiota: A complex immunological interaction

Obesity and allergic asthma are inflammatory chronic diseases mediated by distinct immunological features, obesity presents a Th1/Th17 profile, asthma is commonly associated with Th2 response. However, when combined, they result in more severe asthma symptoms, greater frequency of exacerbation episodes, and lower therapy responsiveness. These features lead to decreased life quality, associated with higher morbidity/mortality rates.  In addition, obesity prompts specific asthma phenotypes, which can be dependent on atopic status, age, and gender. In adults, obesity is associated with neutrophilic/Th17 profile, while in children, the outcome is diverse, in some cases children with obesity present aggravation of atopy, and Th2 inflammation, and in others an association with a Th1 profile, with reduced IgE levels and eosinophilia. These alterations occur due to a complex group of factors among which the microbiome has been recently explored. Particularly, evidence shows its important role in susceptibility or resistance to asthma development, via gut-lung-axis, and demonstrates its relevance to the immune pathogenesis of the syndrome. Few studies address the relevance of the lung microbiome in shaping the immune response, locally. However, specific bacteria, like Moraxella catarrhalis, Haemophilus influenza, and Streptococcus pneumoniae, correlate with important features of the obese-asthmatic phenotype. Although maternal obesity is known to increase asthma risk in offspring, the impact on lung colonization is unknown. This review details the main key immune mechanisms involved in obesity-aggravated asthma, featuring the effect of maternal obesity in the establishment of gut and lung microbiota of the offspring, acting as potential childhood asthma inducer.

Duration of exposure to epidural anesthesia at delivery, DNA methylation in umbilical cord blood and their association with offspring asthma in Non-Hispanic Black women

Epidural anesthesia is an effective pain relief modality, widely used for labor analgesia. Childhood asthma is one of the commonest chronic medical illnesses in the USA which places a significant burden on the health-care system. We recently demonstrated a negative association between the duration of epidural anesthesia and the development of childhood asthma; however, the underlying molecular mechanisms still remain unclear. In this study of 127 mother-child pairs comprised of 75 Non-Hispanic Black (NHB) and 52 Non-Hispanic White (NHW) from the Newborn Epigenetic Study, we tested the hypothesis that umbilical cord blood DNA methylation mediates the association between the duration of exposure to epidural anesthesia at delivery and the development of childhood asthma and whether this differed by race/ethnicity. In the mother-child pairs of NHB ancestry, the duration of exposure to epidural anesthesia was associated with a marginally lower risk of asthma (odds ratio = 0.88, 95% confidence interval = 0.76-1.01) for each 1-h increase in exposure to epidural anesthesia. Of the 20 CpGs in the NHB population showing the strongest mediation effect, 50% demonstrated an average mediation proportion of 52%, with directional consistency of direct and indirect effects. These top 20 CpGs mapped to 21 genes enriched for pathways engaged in antigen processing, antigen presentation, protein ubiquitination and regulatory networks related to the Major Histocompatibility Complex (MHC) class I complex and Nuclear Factor Kappa-B (NFkB) complex. Our findings suggest that DNA methylation in immune-related pathways contributes to the effects of the duration of exposure to epidural anesthesia on childhood asthma risk in NHB offspring.

DNA methylation and aeroallergen sensitization: The chicken or the egg?

Background

DNA methylation (DNAm) is considered a plausible pathway through which genetic and environmental factors may influence the development of allergies. However, causality has yet to be determined as it is unknown whether DNAm is rather a cause or consequence of allergic sensitization. Here, we investigated the direction of the observed associations between well-known environmental and genetic determinants of allergy, DNAm, and aeroallergen sensitization using a combination of high-dimensional and causal mediation analyses.

Methods

Using prospectively collected data from the German LISA birth cohort from two time windows (6–10 years: N = 234; 10–15 years: N = 167), we tested whether DNAm is a cause or a consequence of aeroallergen sensitization (specific immunoglobulin E > 0.35kU/l) by conducting mediation analyses for both effect directions using maternal smoking during pregnancy, family history of allergies, and a polygenic risk score (PRS) for any allergic disease as exposure variables. We evaluated individual CpG sites (EPIC BeadChip) and allergy-related methylation risk scores (MRS) as potential mediators in the mediation analyses. We applied three high-dimensional mediation approaches (HIMA, DACT, gHMA) and validated results using causal mediation analyses. A replication of results was attempted in the Swedish BAMSE cohort.

Results

Using high-dimensional methods, we identified five CpGs as mediators of prenatal exposures to sensitization with significant (adjusted p < 0.05) indirect effects in the causal mediation analysis (maternal smoking: two CpGs, family history: one, PRS: two). None of these CpGs could be replicated in BAMSE. The effect of family history on allergy-related MRS was significantly mediated by aeroallergen sensitization (proportions mediated: 33.7–49.6%), suggesting changes in DNAm occurred post-sensitization.

Conclusion

The results indicate that DNAm may be a cause or consequence of aeroallergen sensitization depending on genomic location. Allergy-related MRS, identified as a potential cause of sensitization, can be considered as a cross-sectional biomarker of disease. Differential DNAm in individual CpGs, identified as mediators of the development of sensitization, could be used as clinical predictors of disease development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01332-5.

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.

Association of childhood BMI trajectory with post-adolescent and adult lung function is mediated by pre-adolescent DNA methylation

Background

Body mass index (BMI) has been shown to be associated with lung function. Recent findings showed that DNA methylation (DNAm) variation is likely to be a consequence of changes in BMI. However, whether DNAm mediates the association of BMI with lung function is unknown. We examined the mediating role of DNAm on the association of pre-adolescent BMI trajectories with post-adolescent and adulthood lung function (forced expiratory volume (FEV₁), forced vital capacity (FVC), and FEV₁/FVC).

Methods

Analyses were undertaken in the Isle of Wight birth cohort (IOWBC). Group-based trajectory modelling was applied to infer latent BMI trajectories from age 1 to 10 years. An R package, ttscreening, was applied to identify CpGs at 10 years potentially associated with BMI trajectories for each sex. Linear regressions were implemented to further screen CpGs for their association with lung function at 18 years. Path analysis, stratified by sex, was applied to each screened CpG to assess its role of mediation. Internal validation was applied to further examine the mediation consistency of the detected CpGs based on lung function at 26 years. Mendelian randomization (MR-base) was used to test possible causal effects of the identified CpGs.

Results

Two BMI trajectories (high vs. low) were identified. Of the 442,475 CpG sites, 18 CpGs in males and 33 in females passed screening. Eight CpGs in males and 16 CpGs in females (none overlapping) were identified as mediators. For subjects with high BMI trajectory, high DNAm at all CpGs in males were associated with decreased lung function, while 8 CpGs in females were associated with increased lung function at 18 years. At 26 years, 6 CpGs in males and 14 CpGs in females showed the same direction of indirect effects as those at 18 years. DNAm at CpGs cg19088553 (GRIK2) and cg00612625 (HPSE2) showed a potential causal effect on FEV₁.

Conclusions

The effects of BMI trajectory in early childhood on post-adolescence lung function were likely to be mediated by pre-adolescence DNAm in both males and females, but such mediation effects were likely to diminish over time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02089-4.

DNA Methylation and Asthma Acquisition during Adolescence and Post-Adolescence, an Epigenome-Wide Longitudinal Study

The role of epigenetics in the pathogenesis of asthma acquisition in adolescence and post-adolescence has been unknown. We carried out a longitudinal epigenome-wide association study, using data from the Isle of Wight Birth Cohort (IOWBC). To improve statistical power, we first screened CpGs based on associations of DNA methylation (DNAm) at an age of 10 years (pre-adolescence) with asthma acquisition at 10-18 years (during adolescence). A logistic regression with repeated measures was applied to CpGs that passed screening to examine the associations of pre-adolescence DNAm with asthma acquisition from 10-18 years and 18-26 years, with an interaction term to evaluate transition period specificity. Findings were further tested in an independent birth cohort, ALSPAC. In total, 205 CpGs (with 150 being females) showed associations with asthma acquisition (main or interaction effects) at FDR = 0.05 in IOWBC, of which 112 (90 being females) showed consistent associations in the ALSPAC. Genes that the identified CpGs were mapped to, e.g., AKAP1 and ENO1, have been shown to be associated with the risk of asthma. Our findings indicated that DNAm at specific CpGs was associated with asthma acquisition. CpGs showing such associations were likely to be different between males and females and, at certain CpGs, were unique to a specific transition period.

The Burden of Childhood Asthma by Age Group, 1990-2019: A Systematic Analysis of Global Burden of Disease 2019 Data

BACKGROUND

Asthma is a common respiratory disease in children. We aimed to update information about the incidence and mortality and disability-adjusted life years (DALYs) of childhood asthma and provide evidence-based recommendations for childhood asthma prevention.

METHODS

Data were obtained from the Global Burden of Disease (GBD) study, which was conducted from 1990 to 2019 in 204 countries. First, we estimated incidence, mortality and DALY rates of childhood asthma using a Bayesian meta-regression model. Second, we analyzed the relationship between the sociodemographic index (SDI) and DALYs in different age groups. Third, we studied changes in trends of the age-standardized DALY rate between 1990 and 2019 based on age group, SDI, and risk factors.

RESULTS

Globally, the number of deaths due to childhood asthma and the incidence and DALY rates were 12.9 thousand (95% UI 10.6 to 15.7), 22 million (95% UI 15 to 31), and 5.1 million (95% UI 3.4 to 7.5) in 2019, decreasing by 65.1% (95% UI 47.6 to 72.4), 5.3% (95% UI 2.6 to 8.8) and 30% (95% UI 18 to 41) from those in 1990, respectively. With the exception of high-SDI regions, the age-standardized DALY rate in all age groups in all SDI regions declined. In 2019, the age-standardized DALY rate in 1- to 4-year-old individuals was highest in low-SDI regions and that of 5- to 19-year-old individuals was highest in high-SDI regions. In contrast to low-SDI regions, individuals in high-SDI regions had a higher risk of DALYs due to asthma, except in those aged 1 to 4 years. A high body mass index (BMI) was a stronger risk factor than occupational asthmagens for childhood asthma.

CONCLUSION

Our findings provide insight into asthma prevention and treatment through the identification of key factors related to childhood asthma. Based on the data available, different risk factors according to age group and region/country suggest different prevention strategies, which is key for preventing childhood asthma.