Household environmental microbiota influences early-life eczema development.

Exposure to a diverse microbial environment during pregnancy and early postnatal period is important in determining predisposition towards allergy. However, the effect of environmental microbiota exposure during preconception, pregnancy and postnatal life on development of allergy in the child has not been investigated so far. In the S-PRESTO (Singapore PREconception Study of long Term maternal and child Outcomes) cohort, we collected house dust during all three critical window periods and analysed microbial composition using 16S rRNA gene sequencing. At 6 and 18 months, the child was assessed for eczema by clinicians. In the eczema group, household environmental microbiota was characterized by presence of human-associated bacteria Actinomyces, Anaerococcus, Finegoldia, Micrococcus, Prevotella and Propionibacterium at all time points, suggesting their possible contributions to regulating host immunity and increasing the susceptibility to eczema. In the home environment of the control group, putative protective effect of an environmental microbe Planomicrobium (Planococcaceae family) was observed to be significantly higher than that in the eczema group. Network correlation analysis demonstrated inverse relationships between beneficial Planomicrobium and human-associated bacteria (Actinomyces, Anaerococcus, Finegoldia, Micrococcus, Prevotella and Propionibacterium). Exposure to natural environmental microbiota may be beneficial to modulate shed human-associated microbiota in an indoor environment.

Role of maternal tryptophan metabolism in allergic diseases in the offspring.

BACKGROUND: Nicotinamide (vitamin B3) is a metabolite of tryptophan and dietary precursor of enzymes involved in many regulatory processes, which may influence fetal immune development. OBJECTIVE: We examined whether maternal plasma concentrations of nicotinamide, tryptophan or nine related tryptophan metabolites during pregnancy were associated with the risk of development of infant eczema, wheeze, rhinitis or allergic sensitization. METHODS: In the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study, we analysed the associations between maternal plasma levels of nicotinamide, tryptophan and tryptophan metabolites at 26-28 weeks of gestation and allergic outcomes collected through interviewer-administered questionnaires at multiple time-points and skin prick testing to egg, milk, peanut and mites at age 18 months. Multivariate analysis was undertaken adjusting for all metabolites measured and separately adjusting for relevant demographic and environmental exposures. Analyses were also adjusted for multiple comparisons using the false discovery method. RESULTS: Tryptophan metabolites were evaluated in 976/1247 (78%) women enrolled in GUSTO. In multivariate analysis including all metabolites, maternal plasma 3-hydrokynurenine was associated with increased allergic sensitization at 18 months (AdjRR 2.6, 95% CI 1.3-5.2 for highest quartile) but the association with nicotinamide was not significant (AdjRR 1.8, 95% CI 0.9-3.6). In analysis adjusting for other exposures, both 3-hydrokynurenine and nicotinamide were associated with increased allergic sensitization (AdjRR 2.0, 95% CI 1.1-3.6 for both metabolites). High maternal plasma nicotinamide was associated with increased infant eczema diagnosis by 6 and 12 months, which was not significant when adjusting for all metabolites measured, but was significant when adjusting for relevant environmental and demographic exposures. Other metabolites measured were not associated with allergic sensitization or eczema, and maternal tryptophan metabolites were not associated with offspring rhinitis and wheeze. CONCLUSIONS AND CLINICAL RELEVANCE: Maternal tryptophan metabolism during pregnancy may influence the development of allergic sensitization and eczema in infants.

Developmental Origins of Health and Disease: Impact of environmental dust exposure in modulating microbiome and its association with non-communicable diseases.

Non-communicable diseases (NCDs) including obesity, diabetes, and allergy are chronic, multi-factorial conditions that are affected by both genetic and environmental factors. Over the last decade, the microbiome has emerged as a possible contributor to the pathogenesis of NCDs. Microbiome profiles were altered in patients with NCDs, and shift in microbial communities was associated with improvement in these health conditions. Since the genetic component of these diseases cannot be altered, the ability to manipulate the microbiome holds great promise for design of novel therapies in the prevention and treatment of NCDs. Together, the Developmental Origins of Health and Disease concept and the microbial hypothesis propose that early life exposure to environmental stimuli will alter the development and composition of the human microbiome, resulting in health consequences. Recent studies indicated that the environment we are exposed to in early life is instrumental in shaping robust immune development, possibly through modulation of the human microbiome (skin, airway, and gut). Despite much research into human microbiome, the origin of their constituent microbiota remains unclear. Dust (also known as particulate matter) is a key determinant of poor air quality in the modern urban environment. It is ubiquitous and serves as a major source and reservoir of microbial communities that modulates the human microbiome, contributing to health and disease. There are evidence that reported significant associations between environmental dust and NCDs. In this review, we will focus on the impact of dust exposure in shaping the human microbiome and its possible contribution to the development of NCDs.