Sphingolipid classes and the interrelationship with pediatric asthma and asthma risk factors

BACKGROUND

While dysregulated sphingolipid metabolism has been associated with risk of childhood asthma, the specific sphingolipid classes and/or mechanisms driving this relationship remain unclear. We aimed to understand the multifaceted role between sphingolipids and other established asthma risk factors that complicate this relationship.

METHODS

We performed targeted LC-MS/MS-based quantification of 77 sphingolipids in plasma from 997 children aged 6 years from two independent cohorts (VDAART and COPSAC2010 ). We examined associations of circulatory sphingolipids with childhood asthma, lung function, and three asthma risk factors: functional SNPs in ORMDL3, low vitamin D levels, and reduced gut microbial maturity. Given racial differences between these cohorts, association analyses were performed separately and then meta-analyzed together.

RESULTS

We observed elevations in circulatory sphingolipids with asthma phenotypes and risk factors; however, there were differential associations of sphingolipid classes with clinical outcomes and/or risk factors. While elevations from metabolites involved in ceramide recycling and catabolic pathways were associated with asthma and worse lung function [meta p-value range: 1.863E-04 to 2.24E-3], increased ceramide levels were associated with asthma risk factors [meta p-value range: 7.75E-5 to .013], but not asthma. Further investigation identified that some ceramides acted as mediators while some interacted with risk factors in the associations with asthma outcomes.

CONCLUSION

This study demonstrates the differential role that sphingolipid subclasses may play in asthma and its risk factors. While overall elevations in sphingolipids appeared to be deleterious overall; elevations in ceramides were uniquely associated with increases in asthma risk factors only; while elevations in asthma phenotypes were associated with recycling sphingolipids. Modification of asthma risk factors may play an important role in regulating sphingolipid homeostasis via ceramides to affect asthma. Further function work may validate the observed associations.

The relationship of fetal sex and maternal race and ethnicity with early and late pregnancy C-reactive protein and interleukin-8

PROBLEM

Promotion of a healthy pregnancy is dependent on a coordinated immune response that minimizes inflammation at the maternal-fetal interface. Few studies investigated the effect of fetal sex on proinflammatory biomarkers during pregnancy and whether maternal race could impact this association. We aimed to examine whether fetal sex could, independently of maternal race/ethnicity and the condition of pregnancy (normal vs. complicated), impact inflammatory markers (C-reactive protein [CRP] and interleukin-8 [IL-8] levels) in early and late pregnancy.

METHODS OF STUDY

This study was a cohort analysis using prospectively collected data from pregnant women who participated in the Vitamin Antenatal Asthma Reduction Trial (VDAART, N = 816). Maternal serum CRP and IL-8 levels were measured in early and late pregnancy (10-18 and 32-38 weeks of gestation, respectively). Five hundred and twenty-eight out of 816 pregnant women who participated in the trial had available CRP and IL-8 measurements at both study time points. We examined the association of fetal sex with early and late CRP and IL-8 levels and their paired sample difference. We further investigated whether maternal race/ethnicity, pregnancy complications (i.e., preeclampsia and gestational diabetes), and early pregnancy body mass index (BMI) could affect the association between these two biomarkers and fetal sex adjusting for potential confounders. For this purpose, we used generalized linear and logistic regression models on log-normalized early and late CRP and IL-8 levels as well as their split at median to form high and low groups.

RESULTS

Women pregnant with male fetuses (266/528 = 56.5%) had higher CRP levels in early to mid-pregnancy (β = .18: 95% confidence interval [CI]: CI = 0.03-0.32; p = .02). Twenty-seven percent (143/528) of the study subjects were Hispanic. Hispanic African American [AA] women and women of races other than White and AA had higher levels of CRP at early to mid-pregnancy compared with White women (β = .57; 95% CI: 0.17-0.97; p < .01 and β = .27; 95% CI: 0.05-0.48; p = .02, respectively). IL-8 levels were not associated with fetal sex in early and late pregnancy (p's > .05). Other factors such as gestational diabetes and early pregnancy BMI were associated with higher CRP levels and higher CRP and IL-8 levels, respectively. Dichotomizing log-normalized cytokine levels at the median in a sensitivity analysis, women with male fetuses had lower odds of high (above-median) IL-8 levels at early pregnancy. Also, women with races other than AA and White carrying male fetuses had higher odds of having high (above-median) late-pregnancy CRP and early-pregnancy IL-8 levels (adjusted odds ratio [aOR] = 3.80, 95% CI: 0.24-1.23; p = .02 and aOR = 3.57; 95% CI: 0.23-1.03; p = .02, respectively). Of the pregnancy complications, women with gestational diabetes mellitus had a higher paired difference of early and late pregnancy CRP levels (β = .38; 95% CI: 0.09-0.68; p = .01), but no difference in IL-8 levels (p's > .05). No associations between the inflammatory markers and preeclampsia were found.

CONCLUSION

Fetal sex is associated with CRP in early pregnancy and an association with IL-8 in early pregnancy is implied. Our study further indicates that maternal race/ethnicity could be a contributing factor in the relationship between fetal sex and inflammatory responses during pregnancy. However, the specificity and level of the contribution might vary by type of cytokine, pregnancy stage, and other confounding factors such as BMI that may impact these associations.

Omega-3 Fatty Acids Interact with DPP10 Region Genotype in Association with Childhood Atopy

Associations of omega-3 fatty acids (n-3) with allergic diseases are inconsistent, perhaps in part due to genetic variation. We sought to identify and validate genetic variants that modify associations of n-3 with childhood asthma or atopy in participants in the Vitamin D Antenatal Asthma Reduction Trial (VDAART) and the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC). Dietary n-3 was derived from food frequency questionnaires and plasma n-3 was measured via untargeted mass spectrometry in early childhood and children aged 6 years old. Interactions of genotype with n-3 in association with asthma or atopy at age 6 years were sought for six candidate genes/gene regions and genome-wide. Two SNPs in the region of DPP10 (rs958457 and rs1516311) interacted with plasma n-3 at age 3 years in VDAART (p = 0.007 and 0.003, respectively) and with plasma n-3 at age 18 months in COPSAC (p = 0.01 and 0.02, respectively) in associationwith atopy. Another DPP10 region SNP, rs1367180, interacted with dietary n-3 at age 6 years in VDAART (p = 0.009) and with plasma n-3 at age 6 years in COPSAC (p = 0.004) in association with atopy. No replicated interactions were identified for asthma. The effect of n-3 on reducing childhood allergic disease may differ by individual factors, including genetic variation in the DPP10 region.

Changes in Body Mass Index Among School-Aged Youths Following Implementation of the Healthy, Hunger-Free Kids Act of 2010

Importance

The prevalence of obesity among youths 2 to 19 years of age in the US from 2017 to 2018 was 19.3%; previous studies suggested that school lunch consumption was associated with increased obesity. The Healthy, Hunger-Free Kids Act of 2010 (HHFKA) strengthened nutritional standards of school-based meals.

Objective

To evaluate the association between the HHFKA and youth body mass index (BMI).

Design, Setting, and Participants

This cohort study was conducted using data from the Environmental Influences on Child Health Outcomes program, a nationwide consortium of child cohort studies, between January 2005 and March 2020. Cohorts in the US of youths aged 5 to 18 years with reported height and weight measurements were included.

Exposures

Full implementation of the HHFKA.

Main Outcomes and Measures

The main outcome was annual BMI z-score (BMIz) trends before (January 2005 to August 2016) and after (September 2016 to March 2020) implementation of the HHFKA, adjusted for self-reported race, ethnicity, maternal education, and cohort group. An interrupted time-series analysis design was used to fit generalized estimating equation regression models.

Results

A total of 14 121 school-aged youths (7237 [51.3%] male; mean [SD] age at first measurement, 8.8 [3.6] years) contributing 26 205 BMI measurements were included in the study. Overall, a significant decrease was observed in the annual BMIz in the period following implementation of the HHFKA compared with prior to implementation (-0.041; 95% CI, -0.066 to -0.016). In interaction models to evaluate subgroup associations, similar trends were observed among youths 12 to 18 years of age (-0.045; 95% CI, -0.071 to -0.018) and among youths living in households with a lower annual income (-0.038; 95% CI, -0.063 to -0.013).

Conclusions and Relevance

In this cohort study, HHFKA implementation was associated with a significant decrease in BMIz among school-aged youths in the US. The findings suggest that school meal programs represent a key opportunity for interventions to combat the childhood obesity epidemic given the high rates of program participation and the proportion of total calories consumed through school-based meals.

Predicting metabolomic profiles from microbial composition through neural ordinary differential equations

Characterizing the metabolic profile of a microbial community is crucial for understanding its biological function and its impact on the host or environment. Metabolomics experiments directly measuring these profiles are difficult and expensive, while sequencing methods quantifying the species composition of microbial communities are well-developed and relatively cost-effective. Computational methods that are capable of predicting metabolomic profiles from microbial compositions can save considerable efforts needed for metabolomic profiling experimentally. Yet, despite existing efforts, we still lack a computational method with high prediction power, general applicability, and great interpretability. Here we develop a method - mNODE (Metabolomic profile predictor using Neural Ordinary Differential Equations), based on a state-of-the-art family of deep neural network models. We show compelling evidence that mNODE outperforms existing methods in predicting the metabolomic profiles of human microbiomes and several environmental microbiomes. Moreover, in the case of human gut microbiomes, mNODE can naturally incorporate dietary information to further enhance the prediction of metabolomic profiles. Besides, susceptibility analysis of mNODE enables us to reveal microbe-metabolite interactions, which can be validated using both synthetic and real data. The presented results demonstrate that mNODE is a powerful tool to investigate the microbiome-diet-metabolome relationship, facilitating future research on precision nutrition.

Early-life fecal metabolomics of food allergy

BACKGROUND

Intestinal microenvironmental perturbations may increase food allergy risk. We hypothesize that children with clinical food allergy, those with food sensitization, and healthy children can be differentiated by intestinal metabolites in the first years of life.

METHODS

In this ancillary analysis of the Vitamin D Antenatal Asthma Reduction Trial (VDAART), we performed untargeted metabolomic profiling in 824 stool samples collected at ages 3-6 months, 1 year and 3 years. Subjects included 23 with clinical food allergy at age 3 and/or 6 years, 151 with food sensitization but no clinical food allergy, and 220 controls. We identified modules of correlated, functionally related metabolites and sought associations of metabolite modules and individual metabolites with food allergy/sensitization using regression models.

RESULTS

Several modules of functionally related intestinal metabolites were reduced among subjects with food allergy, including bile acids at ages 3-6 months and 1 year, amino acids at age 3-6 months, steroid hormones at 1 year, and sphingolipids at age 3 years. One module primarily containing diacylglycerols was increased in those with food allergy at age 3-6 months. Fecal caffeine metabolites at age 3-6 months, likely derived from breast milk, were increased in those with food allergy and/or sensitization (beta = 5.9, 95% CI 1.0-10.8, p = .02) and were inversely correlated with fecal bile acids and bilirubin metabolites, though maternal plasma caffeine levels were not associated with food allergy and/or sensitization.

CONCLUSIONS

Several classes of bioactive fecal metabolites are associated with food allergy and/or sensitization including bile acids, steroid hormones, sphingolipids, and caffeine metabolites.

The maternal prenatal and offspring early-life gut microbiome of childhood asthma phenotypes

BACKGROUND

The infant fecal microbiome is known to impact subsequent asthma risk, but the environmental exposures impacting this association, the role of the maternal microbiome, and how the microbiome impacts different childhood asthma phenotypes are unknown.

METHODS

Our objective was to identify associations between features of the prenatal and early-life fecal microbiomes and child asthma phenotypes. We analyzed fecal 16 s rRNA microbiome profiling and fecal metabolomic profiling from stool samples collected from mothers during the third trimester of pregnancy (n = 120) and offspring at ages 3-6 months (n = 265), 1 (n = 436) and 3 years (n = 506) in a total of 657 mother-child pairs participating in the Vitamin D Antenatal Asthma Reduction Trial. We used clinical data from birth to age 6 years to characterize subjects with asthma as having early, transient or active asthma phenotypes. In addition to identifying specific genera that were robustly associated with asthma phenotypes in multiple covariate-adjusted models, we clustered subjects by their longitudinal microbiome composition and sought associations between fecal metabolites and relevant microbiome and clinical features.

RESULTS

Seven maternal and two infant fecal microbial taxa were robustly associated with at least one asthma phenotype, and a longitudinal gut microenvironment profile was associated with early asthma (Fisher exact test p = .03). Though mode of delivery was not directly associated with asthma, we found substantial evidence for a pathway whereby cesarean section reduces fecal Bacteroides and microbial sphingolipids, increasing susceptibility to early asthma.

CONCLUSION

Overall, our results suggest that the early-life, including prenatal, fecal microbiome modifies risk of asthma, especially asthma with onset by age 3 years.

The Association of Prenatal C-Reactive Protein and Interleukin-8 Levels with Maternal Characteristics and Preterm Birth

OBJECTIVE

 The determinants of preterm birth remain unknown. Excessive maternal inflammation during pregnancy may play an important role in the pathogenesis of preterm birth. Our objective was to describe the association of prenatal levels of proinflammatory C-reactive protein (CRP) and interleukin-8 (IL-8) with preterm birth in participants of the Vitamin D Antenatal Asthma Reduction Trial.

STUDY DESIGN

 Five hundred and twenty-eight patients with available samples of both first- and third-trimester plasma were included in this analysis. CRP and IL-8 were measured from maternal prenatal samples. We examined the association between prenatal CRP and IL-8 with maternal health characteristics and the outcome of preterm birth. We also described the patterns of change in CRP and IL-8 from first to third trimester and their association with preterm birth. A subgroup analysis comparing only those with a spontaneous preterm birth phenotype to those with term birth was also performed.

RESULTS

 Maternal characteristics including lower educational attainment, higher prepregnancy body mass index, gestational diabetes, lower vitamin D, and an unhealthy diet were associated with elevated levels of prenatal CRP and IL-8. Higher third trimester CRP and an increase in CRP from first to third trimester were associated with an increased odds of preterm birth when compared to lower levels of CRP (adjusted odds ratio [aOR] = 1.49, 95% confidence interval: 1.02, 2.23, p = 0.04) or a decrease in CRP over pregnancy (aOR = 3.06, 95% CI = 1.31,7.55, p = 0.01), after adjusting for potential confounders. These associations were strengthened when comparing only patients with spontaneous preterm birth (n = 22) to those with term births.

CONCLUSION

 Higher levels of the proinflammatory markers CRP and IL-8 are associated with indicators of poor maternal health and preterm birth. Prenatal CRP levels may reflect maternal prenatal health status and serve as a predictor of preterm birth, especially among those with spontaneous preterm birth.

KEY POINTS

· Elevated prenatal CRP is associated with poor maternal health.. · High prenatal CRP may predict premature birth, especially spontaneous premature birth phenotypes.. · Vitamin D insufficiency may be a modifiable risk factor for prenatal inflammation..

The Association of Prenatal C-Reactive Protein Levels With Childhood Asthma and Atopy

BACKGROUND

The pathogenesis of childhood asthma is complex, and determinants of risk may begin in utero.

OBJECTIVE

To describe the association of systemic prenatal inflammation, measured by plasma C-reactive protein (CRP), with childhood asthma, eczema, and allergic rhinitis.

METHODS

A total of 522 maternal-offspring pairs from the Vitamin D Antenatal Asthma Reduction Trial were included. Prenatal plasma CRP level was measured between 10 and 18 weeks of gestation and between 32 and 38 weeks of gestation. Offspring asthma, eczema, and allergic rhinitis were assessed quarterly between birth and age 6 years. We performed mediation analyses of prenatal CRP on the association between several maternal characteristics and offspring asthma.

RESULTS

Elevated early and late prenatal CRP and an increase in CRP from early to late pregnancy were associated with asthma by age 6 years (early: adjusted odds ratio [aOR], 1.76, 95% CI, 1.12-2.82, P = .02; late: aOR, 2.45, 95% CI, 1.47-4.18, P < .001; CRP increase: aOR, 2.06, 95% CI, 1.26-3.39, P < .004). Prenatal CRP and childhood asthma associations were strengthened among offspring with atopic asthma (early: aOR, 3.78, 95% CI, 1.49-10.64, P = .008; late: aOR, 4.84, 95% CI, 1.68-15.50, P = .005; CRP increase: aOR, 3.01, 95% CI, 1.06-9.16, P = .04). Early and late prenatal CRP mediated 96% and 86% of the association between maternal prepregnancy body mass index and offspring asthma, respectively.

CONCLUSIONS

Higher prenatal CRP and an increase in CRP from early to late pregnancy are associated with childhood asthma. Systemic inflammation during pregnancy associated with modifiable maternal characteristics may be an important determinant of childhood asthma risk.

The Association of Prenatal Vitamin D Sufficiency With Aeroallergen Sensitization and Allergic Rhinitis in Early Childhood

BACKGROUND

The role of prenatal vitamin D sufficiency and supplementation in the development of childhood aeroallergen sensitization and allergic rhinitis remains uncertain.

OBJECTIVE

To describe the association of prenatal vitamin D sufficiency with childhood allergic outcomes in participants of the Vitamin D Antenatal Asthma Reduction Trial, a randomized controlled trial of prenatal vitamin D supplementation.

METHODS

We included 414 mother-offspring pairs with offspring aeroallergen sensitization data available at age 6 years in this analysis. We examined the association between prenatal vitamin D sufficiency status, based on vitamin D levels measured in the first and third trimesters, or vitamin D supplementation treatment assignment with the outcomes of aeroallergen sensitization, parent-reported clinical allergic rhinitis, parent-reported clinical allergic rhinitis with aeroallergen sensitization, food sensitization, any sensitization, eczema, and total IgE at ages 3 and 6 years.

RESULTS

Compared with early and late insufficiency, early prenatal vitamin D insufficiency with late sufficiency was associated with reduced development of clinical allergic rhinitis with aeroallergen sensitization at 3 years (adjusted odds ratio [aOR] = 0.34; 95% confidence interval [CI], 0.13-0.82; P = .02) and 6 years (aOR = 0.54; 95% CI, 0.29-0.98; P = .05). At 6 years, clinical allergic rhinitis with sensitization was significantly decreased in offspring whose mothers received high-dose vitamin D (aOR = 0.54; 95% CI, 0.32-0.91; P = .02) compared with offspring whose mothers who received low-dose vitamin D. Associations of prenatal vitamin D with aeroallergen sensitization were strengthened among children who also developed asthma or who had a maternal history of atopy.

CONCLUSIONS

Among mothers with first-trimester vitamin D insufficiency, we detected a protective effect of third-trimester prenatal vitamin D sufficiency on the development of clinical allergic rhinitis with aeroallergen sensitization at ages 3 and 6 years.

Characteristics and Mechanisms of a Sphingolipid-associated Childhood Asthma Endotype

Rationale: A link among sphingolipids, 17q21 genetic variants, and childhood asthma has been suggested, but the underlying mechanisms and characteristics of such an asthma endotype remain to be elucidated.Objectives: To study the sphingolipid-associated childhood asthma endotype using multiomic data.Methods: We used untargeted liquid chromatography-mass spectrometry plasma metabolomic profiles at the ages of 6 months and 6 years from more than 500 children in the COPSAC₂₀₁₀ (Copenhagen Prospective Studies on Asthma in Childhood) birth cohort focusing on sphingolipids, and we integrated the 17q21 genotype and nasal gene expression of SPT (serine palmitoyl-CoA transferase) (i.e., the rate-limiting enzyme in de novo sphingolipid synthesis) in relation to asthma development and lung function traits from infancy until the age 6 years. Replication was sought in the independent VDAART (Vitamin D Antenatal Asthma Reduction Trial) cohort.Measurements and Main Results: Lower concentrations of ceramides and sphingomyelins at the age of 6 months were associated with an increased risk of developing asthma before age 3, which was also observed in VDAART. At the age of 6 years, lower concentrations of key phosphosphingolipids (e.g., sphinganine-1-phosphate) were associated with increased airway resistance. This relationship was dependent on the 17q21 genotype and nasal SPT gene expression, with significant interactions occurring between the genotype and the phosphosphingolipid concentrations and between the genotype and SPT expression, in which lower phosphosphingolipid concentrations and reduced SPT expression were associated with increasing numbers of at-risk alleles. However, the findings did not pass the false discovery rate threshold of <0.05.Conclusions: This exploratory study suggests the existence of a childhood asthma endotype with early onset and increased airway resistance that is characterized by reduced sphingolipid concentrations, which are associated with 17q21 genetic variants and expression of the SPT enzyme.

Metabolome-Microbiome Crosstalk and Human Disease

In this review, we discuss the growing literature demonstrating robust and pervasive associations between the microbiome and metabolome. We focus on the gut microbiome, which harbors the taxonomically most diverse and the largest collection of microorganisms in the human body. Methods for integrative analysis of these "omics" are under active investigation and we discuss the advances and challenges in the combined use of metabolomics and microbiome data. Findings from large consortia, including the Human Microbiome Project and Metagenomics of the Human Intestinal Tract (MetaHIT) and others demonstrate the impact of microbiome-metabolome interactions on human health. Mechanisms whereby the microbes residing in the human body interact with metabolites to impact disease risk are beginning to be elucidated, and discoveries in this area will likely be harnessed to develop preventive and treatment strategies for complex diseases.

Fish-oil supplementation in pregnancy, child metabolomics and asthma risk

Background

We recently demonstrated that maternal dietary supplementation with fish oil-derived n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs) during pregnancy reduces the risk of asthma in the offspring but the mechanisms involved are unknown.

Methods

Here we investigated potential metabolic mechanisms using untargeted liquid chromatography-mass spectrometry-based metabolomics on 577 plasma samples collected at age 6 months in the offspring of mothers participating in the n-3 LCPUFA randomized controlled trial. First, associations between the n-3 LCPUFA supplementation groups and child metabolite levels were investigated using univariate regression models and data-driven partial least square discriminant analyses (PLS-DA). Second, we analyzed the association between the n-3 LCPUFA metabolomic profile and asthma development using Cox-regression. Third, we conducted mediation analyses to investigate whether the protective effect of n-3 LCPUFA on asthma was mediated via the metabolome.

Findings

The univariate analyses and the PLS-DA showed that maternal fish oil supplementation affected the child's metabolome, especially with lower levels of the n-6 LCPUFA pathway-related metabolites and saturated and monounsaturated long-chain fatty acids-containing compounds, lower levels of metabolites of the tryptophan pathway, and higher levels of metabolites in the tyrosine and glutamic acid pathway. This fish oil-related metabolic profile at age 6 months was significantly associated with a reduced risk of asthma by age 5 and the metabolic profile explained 24% of the observed asthma-protective effect in the mediation analysis.

Interpretation

Several of the observed pathways may be involved in the asthma-protective effect of maternal n-3 LCPUFA supplementation and act as mediators between the intervention and disease development.

Funding

COPSAC is funded by private and public research funds all listed on www.copsac.com.

Integrative analysis of the intestinal metabolome of childhood asthma

BACKGROUND

The intestinal metabolome reflects the biological consequences of diverse exposures and might provide insight into asthma pathophysiology.

OBJECTIVE

We sought to perform an untargeted integrative analysis of the intestinal metabolome of childhood asthma in this ancillary study of the Vitamin D Antenatal Asthma Reduction Trial.

METHODS

Metabolomic profiling was performed by using mass spectrometry on fecal samples collected from 361 three-year-old subjects. Adjusted logistic regression analyses identified metabolites and modules of highly correlated metabolites associated with asthma diagnosis by age 3 years. Sparse canonical correlation analysis identified associations relevant to asthma between the intestinal metabolome and other "omics": the intestinal microbiome as measured by using 16S rRNA sequencing, the plasma metabolome as measured by using mass spectrometry, and diet as measured by using food frequency questionnaires.

RESULTS

Several intestinal metabolites were associated with asthma at age 3 years, including inverse associations between asthma and polyunsaturated fatty acids (adjusted logistic regression β = -6.3; 95% CI, -11.3 to -1.4; P = .01) and other lipids. Asthma-associated intestinal metabolites were significant mediators of the inverse relationship between exclusive breast-feeding for the first 4 months of life and asthma (P for indirect association = .04) and the positive association between a diet rich in meats and asthma (P = .03). Specific intestinal bacterial taxa, including the family Christensenellaceae, and plasma metabolites, including γ-tocopherol/β-tocopherol, were positively associated with asthma and asthma-associated intestinal metabolites.

CONCLUSION

Integrative analyses revealed significant interrelationships between the intestinal metabolome and the intestinal microbiome, plasma metabolome, and diet in association with childhood asthma. These findings require replication in future studies.

Diet during Pregnancy and Infancy and the Infant Intestinal Microbiome

OBJECTIVES

To determine the association between diet during pregnancy and infancy, including breastfeeding vs formula feeding, solid food introduction, and the infant intestinal microbiome.

STUDY DESIGN

Infants participating in the Vitamin D Antenatal Asthma Reduction Trial were included in this study (n = 323). Maternal and infant diets were assessed by questionnaire. Infant stool samples were collected at age 3-6 months. Stool sequencing was performed using the Roche 454 platform. Analyses were stratified by race/ethnicity.

RESULTS

Breastfeeding, compared with formula feeding, was independently associated with infant intestinal microbial diversity. Breastfeeding also had the most consistent associations with individual taxa that have been previously linked to early-life diet and health outcomes (eg, Bifidobacterium). Maternal diet during pregnancy and solid food introduction were less associated with the infant gut microbiome than breastfeeding status. We found evidence of a possible interaction between breastfeeding and child race/ethnicity on microbial composition.

CONCLUSIONS

Breastfeeding vs formula feeding is the dietary factor that is most consistently independently associated with the infant intestinal microbiome. The relationship between breastfeeding status and intestinal microbiome composition varies by child race/ethnicity. Future studies will need to investigate factors, including genomic factors, which may influence the response of the microbiome to diet.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00920621.

Partial Least Squares Discriminant Analysis and Bayesian Networks for Metabolomic Prediction of Childhood Asthma

To explore novel methods for the analysis of metabolomics data, we compared the ability of Partial Least Squares Discriminant Analysis (PLS-DA) and Bayesian networks (BN) to build predictive plasma metabolite models of age three asthma status in 411 three year olds (n = 59 cases and 352 controls) from the Vitamin D Antenatal Asthma Reduction Trial (VDAART) study. The standard PLS-DA approach had impressive accuracy for the prediction of age three asthma with an Area Under the Curve Convex Hull (AUCCH) of 81%. However, a permutation test indicated the possibility of overfitting. In contrast, a predictive Bayesian network including 42 metabolites had a significantly higher AUCCH of 92.1% (p for difference < 0.001), with no evidence that this accuracy was due to overfitting. Both models provided biologically informative insights into asthma; in particular, a role for dysregulated arginine metabolism and several exogenous metabolites that deserve further investigation as potential causative agents. As the BN model outperformed the PLS-DA model in both accuracy and decreased risk of overfitting, it may therefore represent a viable alternative to typical analytical approaches for the investigation of metabolomics data.

Meta-analysis of effects of exclusive breastfeeding on infant gut microbiota across populations

Previous studies on the differences in gut microbiota between exclusively breastfed (EBF) and non-EBF infants have provided highly variable results. Here we perform a meta-analysis of seven microbiome studies (1825 stool samples from 684 infants) to compare the gut microbiota of non-EBF and EBF infants across populations. In the first 6 months of life, gut bacterial diversity, microbiota age, relative abundances of Bacteroidetes and Firmicutes, and predicted microbial pathways related to carbohydrate metabolism are consistently higher in non-EBF than in EBF infants, whereas relative abundances of pathways related to lipid metabolism, vitamin metabolism, and detoxification are lower. Variation in predicted microbial pathways associated with non-EBF infants is larger among infants born by Caesarian section than among those vaginally delivered. Longer duration of exclusive breastfeeding is associated with reduced diarrhea-related gut microbiota dysbiosis. Furthermore, differences in gut microbiota between EBF and non-EBF infants persist after 6 months of age. Our findings elucidate some mechanisms of short and long-term benefits of exclusive breastfeeding across different populations.

A prospective microbiome-wide association study of food sensitization and food allergy in early childhood

BACKGROUND

Alterations in the intestinal microbiome are prospectively associated with the development of asthma; less is known regarding the role of microbiome alterations in food allergy development.

METHODS

Intestinal microbiome samples were collected at age 3-6 months in children participating in the follow-up phase of an interventional trial of high-dose vitamin D given during pregnancy. At age 3, sensitization to foods (milk, egg, peanut, soy, wheat, walnut) was assessed. Food allergy was defined as caretaker report of healthcare provider-diagnosed allergy to the above foods prior to age 3 with evidence of IgE sensitization. Analysis was performed using Phyloseq and DESeq2; P-values were adjusted for multiple comparisons.

RESULTS

Complete data were available for 225 children; there were 87 cases of food sensitization and 14 cases of food allergy. Microbial diversity measures did not differ between food sensitization and food allergy cases and controls. The genera Haemophilus (log2 fold change -2.15, P=.003), Dialister (log2 fold change -2.22, P=.009), Dorea (log2 fold change -1.65, P=.02), and Clostridium (log2 fold change -1.47, P=.002) were underrepresented among subjects with food sensitization. The genera Citrobacter (log2 fold change -3.41, P=.03), Oscillospira (log2 fold change -2.80, P=.03), Lactococcus (log2 fold change -3.19, P=.05), and Dorea (log2 fold change -3.00, P=.05) were underrepresented among subjects with food allergy.

CONCLUSIONS

The temporal association between bacterial colonization and food sensitization and allergy suggests that the microbiome may have a causal role in the development of food allergy. Our findings have therapeutic implications for the prevention and treatment of food allergy.

Association between prehospital vitamin D status and incident acute respiratory failure in critically ill patients: a retrospective cohort study

Objective

We hypothesise that low 25-hydroxyvitamin D (25(OH)D) levels before hospitalisation are associated with increased risk of acute respiratory failure.

Design

Retrospective cohort study.

Setting

Medical and Surgical Intensive care units of two Boston teaching hospitals.

Patients

1985 critically ill adults admitted between 1998 and 2011.

Interventions

None.

Measurements and main results

The exposure of interest was prehospital serum 25(OH)D categorised as ≤10 ng/mL, 11–19.9 ng/mL, 20–29.9 ng/mL and ≥30 ng/mL. The primary outcome was acute respiratory failure excluding congestive heart failure determined by International Classification of Diseases Ninth Edition (ICD-9) coding and validated against the Berlin Definition of acute respiratory sistress syndrome. Association between 25(OH)D and acute respiratory failure was assessed using logistic regression, while adjusting for age, race, sex, Deyo-Charlson Index and patient type (medical vs surgical).

In the cohort, the mean age was 63 years, 45% were male and 80% were white; 25(OH)D was ≤10 ng/mL in 8% of patients, 11–19.9 ng/mL in 24%, 20–29.9 ng/mL in 24% and ≥30 ng/mL in 44% of patients. Eighteen per cent (n=351) were diagnosed with acute respiratory failure. Compared to patients with 25(OH)D ≥30 ng/mL, patients with lower 25(OH)D levels had significantly higher adjusted odds of acute respiratory failure (≤10 ng/mL, OR=1.84 (95% CI 1.22 to 2.77); 11–19.9 ng/mL, OR=1.60 (95% CI 1.19 to 2.15); 20–29.9 ng/mL, OR=1.37 (95% CI 1.01 to 1.86)).

Conclusions

Prehospital 25(OH)D was associated with the risk of acute respiratory failure in our critically ill patient cohort.